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Robust Nanostructured Silver and Copper Fabrics with Localized Surface Plasmon Resonance Property for Effective Visible Light Induced Reductive Catalysis
Advanced Materials Interfaces
Abstract
Inspired by high porosity, absorbency, wettability, and hierarchical ordering on the micrometer and nanometer scale of cotton fabrics, a facile strategy is developed to coat visible light active metal nanostructures of copper and silver on cotton fabric substrates. The fabrication of nanostructured Ag and Cu onto interwoven threads of a cotton fabric by electroless deposition creates metal nanostructures that show a localized surface plasmon resonance (LSPR) effect. The micro/nanoscale hierarchical ordering of the cotton fabrics allows access to catalytically active sites to participate in heterogeneous catalysis with high efficiency. The ability of metals to absorb visible light through LSPR further enhances the catalytic reaction rates under photoexcitation conditions. Understanding the modes of electron transfer during visible light illumination in Ag@Cotton and Cu@Cotton through electrochemical measurements provides mechanistic evidence on the influence of light in promoting electron transfer during heterogeneous catalysis for the first time. The outcomes presented in this work will be helpful in designing new multifunctional fabrics with the ability to absorb visible light and thereby enhance light-activated catalytic processes.
... One simple strategy to increase the NanoZyme concentration without potential interference is to immobilize nanoparticles on supporting templates. Our previous work has shown the benefits of high porosity, absorbency, and hierarchical structuring in cotton-based templates [3,40,42,[57][58][59] in allowing exposure to a large number of catalytically active sites for applications in catalysis [57,58], sensors, and electronics [40,42,60]. By loading Ag nanoparticles on cotton textiles, we recently showed the potential of Ag@Fabric to directly detect millimolar level of glucose in urine samples with high accuracy [3]. ...
... One simple strategy to increase the NanoZyme concentration without potential interference is to immobilize nanoparticles on supporting templates. Our previous work has shown the benefits of high porosity, absorbency, and hierarchical structuring in cotton-based templates [3,40,42,[57][58][59] in allowing exposure to a large number of catalytically active sites for applications in catalysis [57,58], sensors, and electronics [40,42,60]. By loading Ag nanoparticles on cotton textiles, we recently showed the potential of Ag@Fabric to directly detect millimolar level of glucose in urine samples with high accuracy [3]. ...
... By loading Ag nanoparticles on cotton textiles, we recently showed the potential of Ag@Fabric to directly detect millimolar level of glucose in urine samples with high accuracy [3]. Our ongoing efforts in the field of NanoZyme technologies have shown that copper is one of the most promising NanoZymes with outstanding catalytic efficiencies [15,20,57,58,61]. ...
Renal complications are long-term effect of diabetes mellitus where glucose is excreted in urine. Therefore, reliable glucose detection in urine is critical. While commercial urine strips offer a simple way to detect urine sugar, poor sensitivity and low reliability limit their use. A hybrid glucose oxidase (GOx)/horseradish peroxidase (HRP) assay remains the gold standard for pathological detection of glucose. A key restriction is poor stability of HRP and its suicidal inactivation by hydrogen peroxide, a key intermediate of the GOx-driven reaction. An alternative is to replace HRP with a robust inorganic enzyme-mimic or NanoZyme. While colloidal NanoZymes show promise in glucose sensing, they detect low concentrations of glucose, while urine has high (mM) glucose concentration. In this study, a free-standing copper NanoZyme is used for the colorimetric detection of glucose in human urine. The sensor could operate in a biologically relevant dynamic linear range of 0.5–15 mM, while showing minimal sample matrix effect such that glucose could be detected in urine without significant sample processing or dilution. This ability could be attributed to the Cu NanoZyme that for the first time showed an ability to promote the oxidation of a TMB substrate to its double oxidation diimine product rather than the charge-transfer complex product commonly observed. Additionally, the sensor could operate at a single pH without the need to use different pH conditions as used during the gold standard assay. These outcomes outline the high robustness of the NanoZyme sensing system for direct detection of glucose in human urine.
Graphical abstract
... The bimetallic Ag-M (M = Au, Pd, or Pt) nanozyme fabrics were synthesised by first creating the parent Ag fabric via an electroless deposition technique, as described in our previous work [22,45]. The method involved sensitisation of cotton fabric in an acidic solution using tin chloride, followed by seeded growth of Pd 0 nuclei, which acted as a catalyst for the subsequent deposition of silver nanoparticles onto the fabric via reduction of the diamine silver (I) complex [45]. ...
... The bimetallic Ag-M (M = Au, Pd, or Pt) nanozyme fabrics were synthesised by first creating the parent Ag fabric via an electroless deposition technique, as described in our previous work [22,45]. The method involved sensitisation of cotton fabric in an acidic solution using tin chloride, followed by seeded growth of Pd 0 nuclei, which acted as a catalyst for the subsequent deposition of silver nanoparticles onto the fabric via reduction of the diamine silver (I) complex [45]. These Ag fabrics were converted into bimetallic Ag-M fabrics by exposing the 1 × 1 cm 2 Ag fabric to aqueous solutions of HAuCl 4 , PdCl 2 , or H 2 PtCl 6 . ...
The enhanced catalytic properties of bimetallic nanoparticles have been extensively investigated. In this study, bimetallic Ag-M (M = Au, Pt, or Pd) cotton fabrics were fabricated using a combination of electroless deposition and galvanic replacement reactions, and improvement in their peroxidase-mimicking catalytic activity compared to that of the parent Ag fabric was studied. The Ag-Pt bimetallic nanozyme fabric, which showed the highest catalytic activity and ability to simultaneously generate hydroxyl (•OH) and superoxide (O 2 •− ) radicals, was assessed as a urine glucose sensor. This nanozyme fabric sensor could directly detect urinary glucose in the pathophysiologically relevant high millimolar range without requiring sample predilution. The sensor could achieve performance on par with that of the current clinical gold standard assay. These features of the Ag-Pt nanozyme sensor, particularly its ability to avoid interference effects from complex urinary matrices, position it as a viable candidate for point-of-care urinary glucose monitoring.
Graphical Abstract
... Hybrid materials, where several metal species are present in a complex material are of great interest as they combine the functionalities of each independent component thereby facilitating a fine control or tunability over the properties of the hybrid material [20,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. Over the past two decades, galvanic replacement reactions (GRR) have emerged as a versatile tool to create hybrid systems with controllable material composition [30,32,33,37,43,[47][48][49][50]. ...
... This observation is consistent with previous reports where the catalytic performance was found to be influenced by optimal metal loading on the surface of the CuTCNQ crystals [9,13,14,36]. Additionally, the hybrid material formed with 500 μM concentration may also show optimal performance due to the efficient accumulation of charge due to the injection of electrons from thiosulfate to the catalyst surface and the subsequent transfer of this charge to the ferricyanide ions [12,27,31,32]. Therefore, we can say that the optimal concentration of the addition species, better access of the reactants to the interface and an optimal charge accumulation/charge transfer at the interface may all play a role in improving the catalytic rate. ...
Galvanic replacement reactions (GRRs) are spontaneous electroless reactions that proceed due to the favorable difference in the electrochemical potentials of the two chemical species participating in the reaction. To date, the reacting species in GRRs almost exclusively have been limited to a metal cation. In this work, for the first time, we provide a rare example of a redox mediated GRR where an anion in the original template is replaced by another anion. Extensive use of spectroscopies, microscopies and electrochemical techniques reveals that the exposure of metal-organic semiconductor of CuTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) to neutral TCNQF4⁰ (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) dissolved in acetonitrile results in the spontaneous oxidation of the TCNQ¹– anion in CuTCNQ along with the concomitant reduction of the TCNQF4⁰ to TCNQF4¹⁻ anion. In this case, the exposure of phase I CuTCNQ grown on a Cu foil (Cu(foil)│CuTCNQ(solid)) to TCNQF4⁰ in acetonitrile results in a hybrid material containing Cu(foil)│CuTCNQx(TCNQF4)y(solid), where x + y = 1. The favorable difference in the redox potentials of the TCNQF41−/0 and TCNQ1−/0 processes in acetonitrile provides a strong driving force to facilitate the GRR between TCNQ⁻ and TCNQF4. The resulting hybrids show superior redox catalytic behavior in the reduction of [Fe(CN)6]³⁻ to [Fe(CN)6]⁴⁻ by S2O3²⁻ in comparison to CuTCNQ and CuTCNQF4 where the TCNQF4 content in the hybrid plays an important role in enhancing the catalytic rate. Mechanistic details related to the role of the Cu(foil)|CuTCNQ(F4) interface, and differences in the solubility of CuTCNQ and CuTCNQF4 in acetonitrile are presented.
... Khorsand et al. fabricated an excellent hydrophobic Ni film with the micro-nano network by electrodeposition technique and superhydrophobic surface also showed outstanding lasting durability in 3.5 wt.% sodium chloride solution [66]. Anderson et al. developed revolutionary research in nanotechnology which is based on a new inexpensive and high-quality technique to synthesize distinctive nanostructures which can degrade organic matter when getting in contact with light, and directly onto textiles [64]. Based on such research, it is being made possible to replace the washing machines with a little bit of sunshine. ...
... D) (a1-a3) SEM images of copper@Cotton, a4) EDX spectrum acquired from scanning area shown in (a1, and a5) layered map image acquired from EDX comprising element mapping of copper and oxygen. (b1-b3) SEM pictures of silver@Cotton, b4) EDX spectrum acquired from scanning area shown in (b1, and b5) layered map picture acquired from EDX comprising element mapping of silver and oxygen, (these images are reproduced from ref. [64] copyright 2016, John Wiley and Sons, Inc. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) ...
Self-cleaning concept has achieved significant attention because of their distinct features and inclusive range of probable applications in various fields. Inspired from the lotus effect; the self-cleaning properties showed by the leaves due to the micro and nanoscopic design which reduces the water droplets adhesion to the surface, self-cleaning technology (SCT) plays a significant role in the current time in various applications. One of its special features is its ability to keep the surface clean and maintain the self-cleaning property stable under severe environmental conditions over an intended period of time. This review introduces an overview of the fabrication techniques for superhydrophobic coating and self-cleaning (SC) applications in various fields. The SCT has applications in areas such as textiles, cotton-fabrics garments, buildings construction, lavatories, domestic-automobiles windows, architectural heritage, and photovoltaic and solar cells. As SCT has wide range of applications , there is a need for a deeper understanding of the resilience and preparation of SC surfaces. Therefore, we have discussed the major applications of SCT in building, toilet, mineral paints for architectural heritage, photovoltaic devices or solar cell, fabrics or textile industry in this review. Apart from this, we have also added information regarding the techniques of SC superhydrophobic surfaces and flexible self-cleaning materials and their applications. SCT naturally suffers from great issues in their durability and stability. As the durability of SCT is significant in daily human life, it is intensively reflected in this literature survey. Furthermore, the ongoing progress and potential efforts in the recent innovative applications of SCT along with the critical conclusions , forthcoming views, and obstacles on the field of the durability of SCT are discussed in the presented survey.
... Other clothing characteristics that could be achieved with nanotechnology include self-cleaning fabrics, water-repelling textiles, and clothing that can reduce odors by chemically changing the compounds that cause bad odor. These innovations would take advantage of nano-specific properties, particularly the high surface area per volume ratio of nano-sized materials that increase the exposure of active surfaces to the surrounding environment (Anderson et al., 2016;izzifortiz;Smith). ...
Metal nanoparticles (MNPs) are an important subgroup of the nanomaterial family. They form a market of high commercial value covering a broad spectrum of applications and markets including the agricultural, biomedical, food, and textile
industries and drug delivery, anticancer, antimicrobial, imaging, sensors, batteries, solar cells and catalytic actions.
... Furthermore, composite fibers reinforced with clay nanoparticles exhibit properties such as flame retardance and ultraviolet protection due to their thermal and chemical resistance (OECD, 2004). A significant advancement in this field is the creation of self-cleaning fabrics; studies have shown that textiles treated with copper and silver-based nanoparticles can autonomously clean themselves when exposed to light (Anderson et al., 2016). Additionally, innovative lightweight filaments capable of generating and storing solar energy are being integrated into textile applications ( Figure 5C). ...
... Other clothing characteristics that could be achieved with nanotechnology include self-cleaning fabrics, water-repelling textiles, and clothing that can reduce odors by chemically changing the compounds that cause bad odor. These innovations would take advantage of nano-specific properties, particularly the high surface area per volume ratio of nano-sized materials that increase the exposure of active surfaces to the surrounding environment (Anderson et al., 2016;izzifortiz;Smith). ...
... The UV-Vis spectra of AgNPs commonly exhibit a characteristic peak at 420 nm due to their strong surface plasmon resonance (SPR) effect. [27][28][29][30][31][32] The absorption and scattering characteristics of AgNPs can be altered by varying the particle size, shape, or refractive index near their surface. A noticeable blue shift compared with AgNPs absorption maxima is credited to C-shelling and a decrease in particle size, while a sharp peak intensity is attributed to the stability of nanoparticles. ...
Background
The precise detection and quantification of organophosphorus pesticides are highly required to ensure food safety. The non‐enzymatic nanosensor technology has appeared as an efficient method to replace conventional analytical techniques of pesticide detection. The utilization of carbon‐based nanomaterials and metal nanoparticles has shown great potential to develop non‐enzymatic nanosensors for the sensitive and selective sensing of food contaminants.
Results
In this study, bifunctional carbon shell silver nanoparticles (Ag@C NPs) having oxidase‐like properties and advanced optical activities were used as nanozymes for visual detection of highly toxic organophosphorus pesticide (OP), Chlorpyrifos. The as‐prepared nanomaterial was characterized for its structural and morphological features. The nanosensor was fabricated by immobilizing Ag@C NPs in the network of sodium alginate gel over a cellulosic paper disc. The detection was based on the inhibition of oxidase‐like activity of Ag@C NPs by the adsorption of pesticide which blocks the accessibility of substrate to produce the blue‐colored product. Under the optimized conditions, the fabricated sensor showed potential analytical response for Chlorpyrifos providing a dynamic linear range from 0–350 ng/mL with a limit of detection, of 0.097 ng/mL and limit of quantification, of 0.293 ng/mL. In addition, the devised sensor was able to recover Chlorpyrifos from spiked wheat, apple, and water samples with excellent recovery percentages. Further, the constructed nanosensor exhibited excellent selectivity and specificity to Chlorpyrifos.
Conclusion
The fabricated surface provides a rapid, selective, low cost and portable detection method for the real‐time detection of OP traces from food and environmental samples.
... In plasmonic photocatalysis, noble metal nanoparticles are often combined with certain compounds that expose relatively high surface area as well as active sites. Although Pd and Pt are highly active catalysts, metal NPs based on Cu and Ag have tremendous advantages over their more noble counterparts in the context of cost and in that they exhibit intense absorbance properties in the visible region due to localized surface plasmon resonance (LSPR) (Anderson et al. 2016). ...
The synthesis of silica gel nanostructures and loading it with copper specie via a hydrothermal process were performed. The sample is treated with an amino-functional reagent 3-aminopropyl triethoxysilane (APTES). The products were characterized by X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), TGA/DSC measurements, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the nanostructures were studied for degradation of methylene blue dye (as a classic dye contaminant) in aqueous solution utilizing visible light source. The results displayed that the sample treated with APTES is much more effective in photocatalytic degradation of methylene blue. This modified catalyst could eliminate methylene blue dye (50 mL, 18 µg mL⁻¹) within 60 min under visible light. The degradation efficiency was increased by shortening the degradation time to 30 min in the alkaline medium. The pseudo-first-order model well describes the kinetics of the reaction.
... It has been reported that Ag/Cu hybrid coating showed good antibacterial and antifungal activity against E. coli, S. aureus, MRSA, A. baumanii, P. aeruginosa, P. vulgaris and C. albicans (Paszkiewicz et al. 2016;Slamborova et al. 2013). Ag/Cu nanoparticles on cotton fabric possessed a localized surface plasmon resonance (Anderson et al. 2016), and bimetallic coating with low concentration of Ag/Cu (0.015 * 0.13 wt%) had antimicrobial properties against a wide range of multidrug-resistant bacteria and fungi (Eremenko et al. 2016). Ag/Cu coated cotton showed higher adsorption rate of tryptophan than Ag coated cotton, but the complexation of tryptophan and Ag/Cu NPs did not reduce their bactericidal capability against a number of microorganisms (Petrik et al. 2020). ...
Cotton is one of the most important cellulose fibers, but the absence of antimicrobial capacity along with the self-cleaning, UV protection and electric conductivity often frustrates its wider applications in many fields. Nanotechnology has provided new insights into the development of functional nanomaterials with unique chemical and physical properties. Silver has been effectively incorporated into the cotton fabrics as the antimicrobial agents due to the strong inhibitory and antimicrobial effects on a broad spectrum of bacteria, fungi and virus with low toxicity to human being. In this review, a variety of strategies have been summarized to load silver on cotton fabrics in situ or ex situ and to fabricate high performance value-added cotton fabrics with self-cleaning, UV protection, electric conductivity and antimicrobial capability depending on the synthesis of silver coating or silver-based nanocomposite coating.
Graphic abstract
... The sensor system showed an inverse relationship between the catalytic activity of the gold nanorods and malathion concentration with a sensitivity of 1.78 μg/mL and the ability to detect malathion in water samples. The authors further improved the sensitivity of the sensor system by creating bimetallic nanomaterials (Singh et al. 2017b;Anderson et al. 2016Anderson et al. , 2019. The bimetallic palladium-gold nanorods sensor system used in this case showed an improvement in sensitivity that was two orders of magnitude higher than the monometallic system (1.78 μg/mL with the Au nanorods to 60 ng/mL in the bimetallic Pd-Au nanorods). ...
Detection of pesticides in food and environmental samples is critical as pesticide residues compromise with human and animal health. The residual pesticides are also of significant environmental concern as they continue to accumulate in soil and water leading to change in the natural flora and fauna. Owing to these effects, several strategies have been proposed to detect and monitor their presence. Traditional strategies involve the use of expensive analytical tools that cannot be directly used on-site, require technical expertise, face high operating cost, and are time intensive. This has led to the recent interest in alternative strategies for more efficient pesticide detection.
... The sensor system showed an inverse relationship between the catalytic activity of the gold nanorods and malathion concentration with a sensitivity of 1.78 μg/mL and the ability to detect malathion in water samples. The authors further improved the sensitivity of the sensor system by creating bimetallic nanomaterials (Singh et al. 2017b;Anderson et al. 2016Anderson et al. , 2019. The bimetallic palladium-gold nanorods sensor system used in this case showed an improvement in sensitivity that was two orders of magnitude higher than the monometallic system (1.78 μg/mL with the Au nanorods to 60 ng/mL in the bimetallic Pd-Au nanorods). ...
Since magnetic Fe3O4 nanoparticles were discovered to show intrinsic peroxidase-like catalytic activity in 2007, nanoscale materials with enzyme-mimicking characteristics (nanozymes) have attracted considerable interest from the academic and industrial communities. Unlike vulnerable natural enzymes that need complicated separation and purification processes at high cost, nanozymes with better robustness against harsh environments can be massively produced with lower cost. These merits have endowed them with promising applications in catalysis, sensing, biomedicine, and environmental engineering. Particularly, their catalytic properties can be easily tuned by foreign species like some ions, making it possible to employ them to design new methods for the determination of these species. In this book chapter, we aim at summarizing nanozymes used as emerging nanomaterials to detect toxic ions. Typically, detection of inorganic Hg²⁺, Ag⁺, arsenate/arsenite, Pb²⁺, [Cr2O7]²⁻, halide ions, phosphates and S-containing species based on the modulation of nanozyme activity is reviewed, and the underlying sensing mechanisms and strategies explored are comprehensively classified. Their opportunities and challenges in future toxic ion analysis for environmental monitoring are also discussed.
... Crosslinkers in cotton cellulose exist in two categories, firstly, the self-polymerizing and/or cross-linking cellulose chains formed using agents like polycarboxylic acids [51], to create threedimensional polymers. Secondly, those known as cellulose reactants that cross-link cellulose to various agents by reaction via the hydroxyl groups of cellulose to form covalent bonds [ [69], in-situ synthesis [70,71], foam techniques, spraying, direct addition to the fiber spin dope, weaving metal wires with fibers, layer-by-layer (LbL) assembly technique [72][73][74][75], copolymerization or grafting, micro-encapsulation technique [76,77], vapor deposition [78,79], dropcasting method, UV irradiation, corona discharge treatment, [80][81][82][83]. They may also require a variation of pH, temperature, and use of catalysts in the form of nanoparticles such as TiO 2 [84]. ...
... Light-absorbing characteristics of nanomaterials have created salient opportunities in applying light to activate nanomaterials for control of biological processes. In particular, combining the use of light as a trigger with the nanozyme activity of nanomaterials offers remarkable potential to control the antibacterial property [165,166]. Karim's group showed the ability of visible light to work as an external trigger for controlling the antibacterial property of semiconducting CuO nanorods (NRs) [167]. In visible light illumination, the apparent binding affinity of CuO NRs to H 2 O 2 increased by over four times in comparation with non-illuminated conditions, (Fig. 23IV). ...
With the rapid advancement and progress of nanotechnology, nanomaterials with enzyme-like catalytic activity have fascinated the remarkable attention of researchers, due to their low cost, high operational stability, adjustable catalytic activity, and ease of recycling and reuse. Nanozymes can catalyze the same reactions as performed by enzymes in nature. In contrast the intrinsic shortcomings of natural enzymes such as high manufacturing cost, low operational stability, production complexity, harsh catalytic conditions and difficulties of recycling, did not limit their wide applications. The broad interest in enzymatic nanomaterial relies on their outstanding properties such as stability, high activity, and rigidity to harsh environments, long-term storage and easy preparation, which make them a convenient substitute instead of the native enzyme. These abilities make the nanozymes suitable for multiple applications in sensing and imaging, tissue engineering, environmental protection, satisfactory tumor diagnostic and therapeutic, because of distinguished properties compared with other artificial enzymes such as high biocompatibility, low toxicity, size dependent catalytic activities, large surface area for further bioconjugation or modification and also smart response to external stimuli. This review summarizes and highlights latest progress in applications of metal and metal oxide nanomaterials with enzyme/multienzyme mimicking activities. We cover the applications of sensing, cancer therapy, water treatment and anti-bacterial efficacy. We also put forward the current challenges and prospects in this research area, hoping to extension of this emerging field. In addition to therapeutic potential of nanozymes for disease prevention, their practical effects in diagnostics, to monitor the presence of SARS-CoV-2 and related biomarkers for future pandemics will be predicted.
... The light absorption properties of nanomaterials make it possible to use light to control the biological activity of nanozymes without additional operations [99][100][101]. ...
Bacterial infection-related diseases have been growing year-by-year rapidly and raising health problems globally. The exploitation of novel, high efficiency, and bacteria-binding antibacterial agents are extremely need. As far as now, the most extensive treatment is restricted to antibiotics, which may be overused and misused, leading to increased multidrug resistance. Antibiotics abuse, as well as antibiotic-resistance of bacteria, is a global challenge in the current situation. It is highly recommended and necessary to develop novel bactericide to kill the bacteria effectively without causing further resistance development and biosafety issues. Nanozymes, inorganic nanostructures with intrinsic enzymatic activities, have attracted more and more interest from the researchers owing to their exceptional advantages. Compared to natural enzymes, nanozymes can destroy many Gram-positive, Gram-negative bacteria, which builds an important bridge between biology and nanotechnology. As the potent nanoantibiotics, nanozymes have exciting broad-spectrum antimicrobial properties and negligible biotoxicities. And we summarized and highlighted the recent advances on nanozymes including its antibacterial mechanism and applications. Finally, challenges and limitations for the further improvement of the antibacterial activity are covered to provide future directions for the use of engineered nanozymes with enhanced antibacterial function.
... Bimetallic nanoparticles are of great interest due to their wide applications in catalysis [1][2][3], sensors [4], optics [5], electronics [6], biomedicine [7], magnetics [8], etc. To date, bimetallic catalysts are typically prepared by electrodeposition [9], thermal deposition [10], the self-assembly approach [11], and galvanic replacement reaction [12]. However, these techniques are inevitably time-consuming with the introduction of environmentally hazardous species (such as oleic acid, ammonia, etc). ...
The atmospheric microplasma in the gas-liquid phase technique serves as a new potential efficient and green catalyst preparation technique to fabricate nanomaterials. Due to the presence of diverse reactive species, this technique can promote rapid complex reactions in solutions, which are typically sluggish in traditional chemical processes. Here, atmospheric microplasma induced liquid chemistry (AMILC) is applied to fabricate three-dimensional (3D) binary Pt3Co nanoflowers. Nano-architectures of Pt3Co bimetals (2D nanosheets and 3D nanoflowers) can be formed by tuning the initial cobalt molar concentration in the solution. 3D nanoflowers show a ‘nano-bouquet’ like nanostructure with Co-oxide forming leaves and Pt3Co forming waxberries. 3D nanoflowers show promising electrocatalytic behavior towards ethanol and glucose sensing in alkaline condition. Additionally, AMILC takes less synthesis duration (~10 min) without hazardous chemicals for Pt3Co bimetal nanostructure preparation compared to conventional chemical approaches (>2 h), indicating that AMILC is a potential candidate with better energy efficiency, lower carbon footprint and green plasma chemistry process for 3D nanostructure material synthesis in catalyst applications.
... Cu-Ag bimetallic systems have been well investigated in the previous works [9][10][11][12][13]. However, in most of these cases, the reports describe only one structure or interface under an implicit equilibrium condition [14][15][16][17]. Here, we use galvanic exchange method, which produce two structural configurations: Cu@Ag core-shell and Cu-Ag nano-corn-cob (NC) liked (as tiny-sized Ag loaded onto the surface of Cu). ...
... The electron-hole pairs can then undergo further reactions with dissolved oxygen and water to form reactive radical species such as ·O 2 and ·OH, and this process is often represented schematically for the degradation of a pollutant [27][28][29]. It is well known that Ag NPs are good biocidal agents, and their antimicrobial activity is enhanced when they are incorporated into TiO 2 photocatalysts [2,10,27,[30][31][32][33]. Therefore, a lot of researches of preparation method and properties of Ag NPs deposited on TiO 2 have been published [28,[34][35][36]. ...
The continuous increase in the concentration of carbon dioxide (CO 2 ) in the atmosphere is a wake‐up call for global environmental problems. In recent years, more and more electrochemical, photochemical, thermochemical, and other means have been applied to the use of converting CO 2 into value‐added chemicals or fuels, leveraging the characteristics of material nanostructures to catalyze the reduction of CO 2 , reduce the concentration of CO 2 in the atmosphere, facilitate a balanced carbon‐neutral energy cycle, and generate renewable energy for human use. Among the options available, copper‐based materials have been established as the sole category capable of converting CO 2 into a variety of reduction products, including 16 hydrocarbons, such as carbon monoxide (CO) and hydrocarbons, as well as widely used alcohols. This paper outlines various synthesis approaches for copper‐based nanostructured catalysts and explores their applications in the electrocatalytic, photocatalytic, and thermocatalytic reduction of CO 2 . Finally, it discusses the current challenges and summarizes potential solutions and strategies for the future advancement of CO 2 conversion technology.
So far, it is still extremely challenging to develop an efficient catalyst for deep oxidation of methanol at low temperature. Herein, we report the construction of the highly dispersed CuAg alloy on the surface of Ce0.90In0.10Oδ nanorods support for catalyzing methanol deep oxidation. The composition, structure and properties of catalysts were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet‐visible (UV‐vis) spectroscopy and X‐ray photoelectron spectroscopy (XPS). The results show that the CuxAg100‐x/Ce0.90In0.10Oδ alloy catalysts exhibit superior catalytic activity and stability compared to pure Ag/Ce0.90In0.10Oδ, with the highest activity observed for Cu40Ag60/Ce0.90In0.10Oδ, accompanied by the light‐off temperature (T50) and full conversion temperature (T90) of 115 and 145 °C, respectively. This is attributed to the synergistic effect of CuAg alloy, which results in electron transfer, generating more Ag⁰, and enhanced interaction between CuAg alloy and the support, leading to increased Ce³⁺ content and higher oxygen vacancy concentration. This work successfully applies CuAg alloy catalysts in thermo‐catalytic reaction, offering promising prospects for CuAg alloy catalysts in the methanol deep oxidation.
The expanding use of nanoparticles in a wide range of applications has brought to light the need to adopt an integrated approach regarding their synthesis, use, recovery and handling.
This book covers the intense research field of nanoparticle utilization as remediation agents for toxic pollutants, and pays special attention to their post-application recovery, the monitoring of their fate when released, and life cycle analysis. The reader may therefore evaluate the prospects and limitations of these technologies through the prism of sustainability demands.
Several chapters summarize successful applications of single or multi-phase nanoparticles for drinking water purification, wastewater and gas-stream treatment and soil consolidation. Importantly, they evaluate the potential scale-up for real-world applications that need to compete with traditional treatment methods.
However, the risk of uncontrolled release into the environment can be a significant drawback to the extended use of nanoparticles. For this reason, a detailed analysis is given to aspects of their post-use recycling and regeneration, determination of release pathways, risk assessment methods and life cycle evaluation studies, highlighting the importance of preventing the unintended release of nanoparticles into the environment.
This book will be a valuable resource for anyone looking at the development of nanoparticles with a view to environmental remediation strategies.
With the growing concerns about the conservation of the environment and the minimal consumption of water, the self-cleaning approach for textile materials is gaining much popularity and interest day-by-day. There are various approaches for producing self-cleaning textiles surfaces, of which the application of nanoparticles is more effective. The self-cleaning property can be achieved by either creating super-hydrophobic surfaces or applying photocatalyst materials. Super-hydrophobic self-cleaning surface follows the principle of the behavior of liquid on surface roughness. On the contrary, under the exposure of light radiation, the photocatalytic self-cleaning surface follows the chemical redox reaction mechanisms to degrade the organic materials including microorganisms or stains. Several previous studies were done to implement self-cleaning functionality to textile materials. Hierarchical surface roughness using nano-whisker or nano-spherical structure using SiO2, carbon nanotubes or ZnO nanoflower produces super-hydrophobic self-cleaning surface with excellent water contact angle whereas different semiconductor nanoparticles including TiO2, ZnO, SnO2 exhibit photocatalytic properties. There are various suggested methods of synthesis and fabrication methods to impart nanoparticles on textile materials. In this review paper, the progress and technological advances in the field of nanoparticles impregnated self-cleaning textiles materials are discussed with different fabrication methods and nanoparticles. Apart from various challenges and limitations, nanoparticles coated self-cleaning textile materials have a wide range of applications in different fields.
Copper has been reclusive with regard to its plasmonic investigations among the founding plasmonic metals. With the advent of technology and the associated improvements in understanding of plasmonics, copper has been able to make a stand for itself among its peers and even outshine them in a few aspects such as dielectric loss, cost, and a more intricate and facile tuning of the near and far field intensities of the plasmon-enhanced distributions. This review is aimed at highlighting the different classes of plasmonic copper (PC), ranging from its pristine version to the array of composited and alloyed compositions. The focus is on an all-encompassing review of PC with regard to its shortcomings and merits, its exploration for plasmonic applications, and emerging phenomena discovered due to the plasmonic virtue. We aim to bring about a comprehensive treatise of the investigations on PC, where the major discussions are on the topics of a generic treatise on surface plasmons (both localized and propagating), pristine copper and its potential for different applications, the almost inescapable phenomenon of oxidation, and the associations that copper has been made to form in order to be exploited for multiple uses such as chalcogenides, silicides, alloys, and other metamaterial architectures. Specific outcomes of the changes to the near and far-field distributions of PC in various conditions such as oxidized/alloyed/composited and stabilized have been discussed, highlighting the changes to PC in lieu of these modifications. The concluding sections highlight some fascinating compositions including multi-elemental copper and its atomic clusters and cursorily studied compositions which are among the few materials that could offer untapped capabilities which will be made evident from brief glimpses of their plasmonic character. The outlook for plasmonic copper has never been more promising, ranging from the need for comprehensive investigations of emerging material compositions and configurations (of both pristine and composited copper) to the realm of commercialization. Copper has, thus, been projected to be a viable alternative to existing options including the poster children of plasmonics, namely, silver and gold.
Graphical Abstract
Metamaterials are promising candidates for broadband light absorbers, but complex manufacturing procedures with expensive instruments have limited their practical applications. Herein, this work develops an all‐solution‐processed three‐dimensional (3D) metamaterial—based on a gold nanocage (GNC)/silk fibroin (SF) nanocomposite thin film—that achieves near‐unity (>94%) and broadband (350–2000 nm) light absorption. At a low particle density, the film exhibits a typical signal for localized surface plasmon resonance (LSPR) absorption at 856 nm, originating from its hollow geometrical shape of GNCs. In contrast, at high particle densities the films display ultrahigh broadband absorption, even in the non‐LSPR regions. This work attributes this behavior to the highly dense GNCs dispersed uniformly in the SF matrix acting optically as extremely fragmented metallic films, thereby retaining the highly absorptive nature of the metal while strongly suppressing its highly reflective properties. Moreover, the metamaterial absorber displays a desirable broadband‐light‐induced photothermal effect when illuminated with a halogen lamp. Finally, investigations into the photothermal electronic properties of this metamaterial combined with an Al/Si Schottky diode reveal an excellent photoresponse and photostability. The as‐designed systems can function at telecommunication wavelengths longer than the typical operation wavelengths of Si‐based devices. Such 3D metamaterial absorbers can be efficient platforms for various photothermal applications.
The past few decades have witnessed the flourish of creating metal oxides for biocatalytic therapeutics due to their structural diversities, feasible modifications, tunable catalytic sites, and low cost when compared to their natural enzyme counterparts. Here, in this timely review, the most recent progress and future trends in engineering tunable structured metal oxides and decoding their structure‐reactivity relationships for biocatalytic therapeutics is comprehensively summarized. At first, the fundamental activities, evaluations, and mechanisms of metal oxide‐based biocatalysts are carefully disclosed. Subsequently, the merits, design methods, and state‐of‐art achievements of different types of nanostructured and biofunctionalized metal oxides are thoroughly discussed. Thereafter, it provides detailed comments on the catalytic center modulation strategies to engineer metal oxides for efficient reactive oxygen species (ROS)‐catalysis, including atomic catalytic site engineering, heterostructures, and support effects. Furthermore, the representative applications of these ROS‐catalytic metal oxides have been systematically summarized, such as catalytic disinfections, cancer therapies, ROS scavenging and anti‐inflammations, biocatalytic sensors, as well as corresponding toxicities. Finally, current challenges and future perspectives are also highlighted. It is believed that this review can provide cutting‐edge and multidisciplinary instruction for the future design of ROS‐catalytic metal oxides and stimulate their widespread utilization in broad therapeutic applications.
Fabrics are an indispensable part of our everyday life. They provide us with protection, offer privacy, and form an intimate expression of ourselves through their aesthetics. Imparting functionality at the fiber level represents an intriguing path toward innovative fabrics with a hitherto unparalleled functionality and value. The fiber technology based on thermal drawing of a perform, which is identical in its materials and geometry to the final fiber, has emerged as a powerful platform for the production of exquisite fibers with prerequisite composition, geometric complexity, and control over feature size. A ‘Moore's law’ for fibers is emerging, delivering higher forms of function that are important for a broad spectrum of practical applications in healthcare, sports, robotics, space exploration, etc. In this Review, we survey progress in thermally-drawn fibers and devices and discuss their relevance to ‘smart’ fabrics. A new generation of fabrics that can see, hear and speak, sense, communicate, harvest and store energy, as well as store and process data is anticipated. We conclude with a critical analysis of existing challenges and opportunities currently faced by thermally-drawn fibers and fabrics that are expected to become sophisticated platforms delivering value-added services for our society.
The ability to detect glucose concentrations in human urine offers a non-invasive approach to monitor kidney health and vascular complications associated with diabetes. We show the potential of employing catalytically active nanoparticles directly grown on textiles to produce a colorimetric sensor for glucose. We use a galvanic replacement (GR) reaction for the synthesis of bimetallic nanoparticles. Here, Cu nanoparticles act as a sacrificial template that undergoes a spontaneous electroless GR reaction when exposed to metal ions of gold, silver, platinum, and palladium to form bimetallic Cu-M nanoparticles (M = Au, Ag, Pt, or Pd). The evaluation of their intrinsic peroxidase-mimicking catalytic activity (“nanozyme”) in comparison to that of the Cu nanozyme revealed that the bimetallic systems show a higher catalytic rate with the Cu–Pt nanozyme showing the highest catalytic efficiency. This property of the Cu–Pt nanozyme was then utilized to detect glucose in human urine using the glucose oxidase enzyme as a molecular recognition element. A key outcome from our study is the ability to detect urine glucose without requiring sample dilution which is an advantage over the gold standard GOx-POx method and significantly more reliable performance over commercial urine glucose dipsticks. The difference in the intensity of the colorimetric response between different glucose concentrations further allowed this sensor system to be combined with digital imaging tools for multivariate analysis.
This work presents a synergistic approach to boost plasmon- or surface-enhanced Raman scattering (SERS) by combining molecular and electrical modulators that fine-tune the electronic structure of metal−molecule interfaces, especially the...
Nanozymes are fundamentally interesting catalysts that are investigated as alternatives to fragile protein‐enzymes for applications in biotechnology, for prodrug activation, and use in biomedicine, as well as the catalysts that contributed to the Origin of Life. However, until now, nanozymes mostly have been documented to exhibit activity as red/ox catalysts, whereas examples of activity outside this broad class of reactions are very few. Herein, activity of nanozymes on glucuronide prodrugs is investigated, specifically focusing on the mechanism of prodrug conversion reactions. The main finding of this work is that nanozymes exhibit glucuronide‐like activity, but also catalyze prodrug conversion via esterase‐like mechanism and facilitate group transfer reactions.
Cotton and its derivate are widely studied and used as a medical and biomedical product in the “Health care textile” aria. The cotton-based materials have been used in external (surgical clothing, surgical covers, and beddings) and internal (traditional and advanced wound dressing, tissue engineering, drug delivery, surgical area, and dental applications) application. For the use in the internal application, the biomaterials have to pass many in vitro and in vivo tests due to the final application. Cotton is used to cover the wound as a barrier for bacterial penetrate and keep the wound aria warm since 19 century. Due to different medical demands, the modification of cotton has been developed to meet the diverse requirements with different biomaterial applications. The cotton has unique properties such as high surface area, favorable mechanical property, gas permeability, cellulose fibers, etc. which makes it a good candidate for use in medical and biomedical applications. Nowadays, due to innovations, novel and ultra-modern biomaterials are available. The researchers are developing new functional cotton base biomaterials at an incredible rate. The health care textile aims to bring comfort and better treatment for patients in their painful days. The huge study has been physically and chemically modified the structure of cotton gauze. Chemical modifications such as etherification, oxidation, and phosphorylation of cotton gauze have been studied to develop wound dressing for different kinds of wounds. Cotton has the capability to deliver the drug in the wound area, which can be stimulation responsive or non-stimulation responsive. In the surgical application, the cotton is used as surgical sutures and cotton rolls. It has been widely used in tissue engineering and dental application also. This study aims to summarize the development of the biomedical use of cotton and its derivatives.
Cotton is one of themost widely used and comfortable fiber for textile and
apparel. Among the different parameters that determine the quality of cotton, cotton
contamination is one key factor that also determines its price. This chapter includes
what cotton contamination is and constitutes, the origins and kinds of cotton contaminants,
effects of contaminants on cotton processing, and the different methods used to
detect cotton contaminants. Cotton contamination is that the presence of an impurity,
or another undesirable component that spoils, corrupts, infects, makes unfit, ormakes
inferior a product. Therefore, detecting and eliminating cotton contaminations as
timely as possible before processing or within the process is essential. The different
techniques of detecting contaminants are discussed in detail. The methods used
for detecting cotton contaminations are generally classified as manual, gravimetric,
electro-optical, and machine vision methods.
The textile industry delivers two types of wastes during production,
namely hard waste and soft waste. These are used as a raw material in Blow Room
mixing with virgin cotton with limited volume. Besides, the sector also releases a
large amount of used garment/cloth and remnants (solidwaste),which causes landfill
and pollution. Recycling of used clothes and remnants was started in the late 1980s to
reduce such an impact on the environment. Recycling also helps to reduce raw material
costs in mélange yarn manufacturing. The used clothes, as well as the garment
wastes, are collected and supplied to the factories. Before the processing, they are
sorted depending on their color and fabric type. These fabrics are converted into
fibers called “reclaimed/regenerated fibers” by a serious of machines, i.e., cleaning,
cutting, conditioning, shoddying/tearing, and baling. The reclaimed fibers are mixed
with virgin cotton in preset volume according to the desired end product. Mainly
mixing/blending in factories is practical at Blow Room and Draw Frame. Sometimes
it is done at Speed Frame. The conventional spinning types of machinery with
different settings are used to process reclaimed fibers. But there are also supplementary
processes. In this chapter, the fiber preparation methods, mixing types, spinning
are discussed. Also, the advantages, disadvantages, and application areas of mélange
yarn are discussed.
The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h⁻¹. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
Single-atom and single-particle catalysis is an area of considerable topical interest due to their potential in explaining important fundamental processes and applications across several areas. An interesting avenue in single-particle catalysis is spatial control of chemical reactivity within the particle by employing light as an external stimulus. To demonstrate this concept, we report galvanic replacement reactions (GRRs) as a spatial marker of subparticle chemical reactivity of a silver nanoprism with AuCl4
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ions under optical excitation. The location of a GRR within a single Ag nanoprism can be spatially controlled depending on the plasmon mode excited. This leads to chemomorphological transformation of Ag nanoprisms into interesting Ag-Au structures. This spatial biasing effect is attributed to localized hot electron injection from the tips and edges of the silver nanoprisms to the adjacent reactants that correlate with excitation of different surface plasmon modes. The study also employs low-energy-loss EELS mapping to additionally probe the spatially confined redox reaction within a silver nanoprism. The findings presented here allow the visualization of a plasmon-driven subparticle chemical transformation with high resolution. The selective optical excitation of surface plasmon eigenmodes of anisotropic nanoparticles offers opportunities to spatially modulate chemical transformations mediated by hot electron transfer.
The tremendous impact of UV radiation on every individual has resulted in massive interest in development of new sensor technologies to effectively monitor the solar exposure. However, there is no comprehensive review that critically discusses the advances made in the field of wearable UV sensor technologies and to position them as next‐generation mass‐deployable wearable devices. Herein, this gap is addressed by first classifying UV detection technologies into photoelectric and photochromic systems and summarizing their unique strengths and drawbacks. This is followed by a discussion on the integration of novel materials and design concepts with these technologies to develop wearable UV sensors. Then, the commercially available wearable UV sensors are examined thoroughly together with their limitations. Toward the end, a highly critical future outlook is provided, wherein the role of technological and regulatory interventions in assisting the development and integration of wearable UV sensors in the day‐to‐day activities is discussed. More importantly, the purpose of this review is not only to provide an in‐depth understanding of the underlying UV detection mechanism, design principles, and wearable technologies but also to act as a roadmap for those interested in the development and regulation of commercially deployable wearable UV sensors.
Nanostructured materials can now be engineered with great precision and complexity as a result of advances in design and fabrication, and offer distinct advantages in many biosensing and biomedical applications. The materials most widely used in this field are semiconductors and noble metals. Each offers multiple length scales of nanostructuring that program their physicochemical properties for different biosensing applications. Here, nanostructured materials and their applications are reviewed together with semiconductors and noble metals, as well as hybrid materials that unite these two classes—all with the goal of linking performance characteristics to applications in biomedicine. Nanostructured materials are now ubiquitous functional elements in biomolecular sensors. Herein, semiconductor and noble metal nanomaterials used successfully to develop new biomolecular detection capabilities for in vitro, in vivo, intracellular, and extracellular sensing are reviewed. Structural characteristics that can be directly linked with performance enhancements are highlighted to showcase the rationale for using nanomaterials in biomedical applications.
Controlled integration of plasmonic nanoparticles with metal-organic frameworks (MOFs) creates a class of multifunctional nanomaterials that powerful for various applications, especially in the field of photocatalysis and photoelectrocatalysis -which recently have been witnessed a vast interest in the exploration of localized surface plasmon resonance of plasmonic NPs to improve the efficiency of catalysis processes. This perspective highlights and summarizes recent significant progress in the field of catalysis, focusing on integration strategies and considerations and several possible plasmonic enhancement mechanisms involved. Brief overviews of optical and electronics properties of plasmonic NPs is also introduced, and finally the development prospect of the field is briefly discussed.
With growing environmental and health concerns over persistent organic compounds such as organophosphates, regulatory bodies have imposed strict regulations for their use and monitoring in water bodies. Although conventional analytical tools exist for the detection of organophosphorus pesticides, new strategies need to be developed to fulfil the ASSURED (affordable, sensitive, specific, user-friendly, rapid, equipment-free and deliverable to end users) criteria of the World Health Organisation. One such strategy is to employ the ability of certain nanoparticles to mimic the enzymatic activity of natural enzymes to develop optical sensors. We show that the intrinsic peroxidase-mimic NanoZyme activity of tyrosine-capped silver nanoparticles (Ag-NanoZyme) can be exploited for highly specific and rapid detection of chlorpyrifos, an organophosphorus pesticide. The underlying working principle of the proposed aptasensor is based on the dynamic non-covalent interaction of the chlorpyrifos specific aptamer (Chl) with the NanoZyme (sensor probe) vs. the pesticide target (analyte). The incorporation of the Chl aptamer ensures high specificity leading to a colorimetric response specifically in the presence of chlorpyrifos, while the sensor remains unresponsive to other pesticides from organophosphate and non-organophosphate groups. The robustness of the sensor to work directly in environmental samples was established by evaluating its ability to detect chlorpyrifos in river water samples. The excellent recovery rates demonstrate the sensor robustness, while the simplicity, and rapid sensor response (2 min) to detect the presence of chlorpyrifos highlights the capabilities of the proposed colorimetric sensing system.
Colloidal lithography (CL) has evolved as an alternative to conventional photo‐ and electron‐beam lithography to pattern surfaces with nanometer range resolution. As CL offers substrate‐independent precise positioning and patterning of nanomaterials as long‐range ordered crystals, this has seen new opportunities in optoelectronics. Herein, the scope of CL is expanded to fabricate for the first time, 3D organic–inorganic heterojunction photocatalysts with well‐controlled spacing and coverage density. To achieve this, monodisperse polystyrene (PS) beads of different sizes are used as colloidal masks on a ZnO substrate. Electron beam assisted silver deposition onto these PS masks, and subsequent removal of PS lead to the formation of patterns of silver nanostars on the ZnO thin film. The solid–vapor reaction of silver nanostars with a metal‐coordinating charge‐transfer complex of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) allows spontaneous conversion of Ag nanostars to the large aspect ratio nanowires of metal–organic AgTCNQ semiconductors. This strategy, combining the strengths of CL with high electron affinity of TCNQ molecules allows facile fabrication of long‐range patterns of the heterojunctions of organic (AgTCNQ) and inorganic (ZnO) semiconductors. These surface‐supported 3D heterojunctions act as outstanding photocatalysts through their ability to efficiently separate the electron–hole pairs and thus increasing the electron–hole life times.
A simple galvanic replacement (GR) reaction‐based strategy to create copper‐based bimetallic fabrics for photoreductive catalysis is reported. It is shown that a nanostructured Cu@Fabric can be easily converted into bimetallic Cu‐Au@Fabric and Cu‐Ag@Fabric through a spontaneous electroless process that involves simple exposure of copper fabrics to the aqueous solutions of gold and silver ions. The nanoscale hierarchical ordering of cotton fabrics combined with their high porosity and wettability make them outstanding supports for catalyst recovery and reusability. The deposition of miniscule quantities of expensive noble metals on readily available Cu not only reduces the overall catalyst cost, but also plays a major role in improving the catalyst stability and reusability over several cycles through minimizing Cu oxidation. The synergistic effects of the localized surface plasmon resonance (LSPR) properties of Cu, Au, and Ag allow these bimetallic fabrics into highly active visible light photocatalysts. Mechanistic investigation of the photocatalytic activity provides in‐depth information on the electron transfer processes occurring at the catalyst/ reactant interface, revealing electron transport as the rate‐limiting step, which could be overcome under visible light photoillumination conditions. The outcomes enhance the understanding of template‐supported bimetallic nanostructures for LSPR‐induced photocatalysis applications, offering new potential to design multifunctional fabrics for various applications.
Besides aspect ratio (AR) and localized surface plasmon resonance (LSPR) peak wavelength, the cross-section shape of individual Au nanorod sensors is also crucial factors controlling their plasmon sensitivities. These three effects have not been investigated simultaneously till now. In this paper, we numerically investigate nanorods’ cross-section-dependent responses both of refractive index sensitivity factor S and corresponding figure of merit FOM to their AR and LSPR peak wavelengths by discrete dipole approximation. The cross-section shapes are demonstrated to affect the values of S and FOM although it does not destroy the overall response tendency of S/FOM to LSPR peak wavelengths and AR. Their optimal LSPR spectral regions and AR are unveiled, which are revealed to be cross-section shape-dependent and independent, respectively. The triangular Au nanocolumn is revealed to provide good candidate for Au LSPR-based biological sensing and detection, whose optimal LSPR peak wavelength falls in the second near-infrared window.
Human norovirus (NoV) remains the most common cause of viral gastroenteritis and the leading cause of viral foodborne outbreaks globally. NoV is highly pathogenic with an estimated median viral infective dose (ID50) ranging from 18 to 1,015 genome copies. For NoV detection, the only reliable and sensitive method available for detection and quantification is RTqPCR. NoV detection in food is particularly challenging, requiring matrix specific concentration of the virus and removal of inhibitory compounds to detection assays. Hence, the RTqPCR method poses some challenges for rapid in-field or point-of-care diagnostic applications. We propose a new colorimetric NanoZyme aptasensor strategy for rapid (10 min) and ultrasensitive (calculated LoD of 3 viruses per assay equivalent to 30 viruses/mL of sample and experimentally-demonstrated LoD of 20 viruses per assay equivalent to 200 viruses/mL) detection of the infective murine norovirus (MNV), a readily-cultivable surrogate for NoV. Our approach combines the enzyme-mimic catalytic activity of gold nanoparticles with high target specificity of an MNV aptamer to create sensor probes that produce a blue colour in the presence of this norovirus, such that the colour intensity provides the virus concentrations. Overall, our strategy offers the most sensitive detection of norovirus or a norovirus surrogate achieved to date using a biosensor approach, enabling for the first time, the detection of MNV virion corresponding to the lower end of the ID50 for NoV. We further demonstrate the robustness of the norovirus NanoZyme aptasensor by testing its performance in the presence of other non-target microorganisms, human serum and shellfish homogenate, supporting the potential of detecting norovirus in complex matrices. This new assay format can, therefore, be of significant importance as it allows ultrasensitive norovirus detection rapidly within minutes, while also offering the simplicity of use and need for non-specialized laboratory infrastructure.
In the present study, catalytically active Ag nanoparticles were biosynthesized by the extract of Ginkgo biloba leaves through a facile and green manner. Well-dispersed Ag nanoparticles in spherical shape with size of 20–40 nm were obtained. Catalyzing the reduction of four typical pollutants, 4-nitrophenol, congo red, methyl orange, and rhodamine B, were achieved using the synthesized Ag nanoparticles, with the full conversion in 15–100 min. The pseudo-first order rate constant was calculated to be 0.0452 min⁻¹, 0.0568 min⁻¹, 0.0805 min⁻¹, and 0.285 min⁻¹ for 4-nitrophenol, congo red, methyl orange, and rhodamine B, respectively. Furthermore, the catalytic activity can be preserved for 5 successive cycles. Wide applications in selective reduction reactions for pollutants treatment and fine chemical synthesis can be expected using the obtained catalytically active and recyclable Ag nanoparticles.
The development of new catalytic transformations with easy separation and recyclability is essential in chemical synthesis. An efficient heterogeneous catalytic system composed of a conducting polymer, polypyrrole (PPy), deposited on cotton fabric support, and decorated with silver nanoparticles is described. Such ternary composites can be used in environmental issues, such as water-pollution treatment. The model reduction of p-nitrophenol to p-aminophenol with sodium borohydride was investigated by means of UV–visible spectroscopy. The reaction was catalyzed even by PPy alone and the catalytic effect was strongly enhanced by silver nanoparticles. It obeys the first-order kinetics. The catalytic effect increases with the catalyst dose due to increased number of catalytic sites. This also applies to the increased content of silver. The elevated temperature as well as the reduced polarity of the reaction medium have negative effect on the catalyst performance. The catalysts can be reused several times while maintaining good efficiency. The ternary composites are thus good candidates for the catalytic reductive removal of toxic compounds from water.
N-aryl imidazoles play an important role as structural and functional units in many natural products and biologically active compounds. Herein, we report a photocatalytic route for the C-N cross-coupling reactions over a Cu/graphene catalyst, which can effectively catalyze N-arylation of imidazole and phenylboronic acid, and achieve a turnover frequency of 25.4 h(-1) at 25 (o)C and the irradiation of visible light. The enhanced catalytic activity of the Cu/graphene under the light irradiation results from the localized surface plasmon resonance of copper nanoparticles. The Cu/graphene photocatalyst has a general applicability for photocatalytic C-N, C-O and C-S cross-coupling of arylboronic acids with imidazoles, phenols and thiophenols. This study provides a green photocatalytic route for the production of N-aryl imidazoles.
Inspired by the hierarchical structure of the mastoid on the micrometer and nanometer scale and the waxy crystals of the mastoid on natural lotus surfaces, a facile one-step hydrothermal strategy is developed to coat flower-like hierarchical TiO2 micro/nanoparticles onto cotton fabric substrates (TiO2@Cotton). Furthermore, robust superhydrophobic TiO2@Cotton surfaces are constructed by the combination of hierarchical structure creation and low surface energy material modification, which allows versatility for self-cleaning, laundering durability, and oil/water separation. Compared with hydrophobic cotton fabric, the TiO2@Cotton exhibits a superior antiwetting and self-cleaning property with a contact angle (CA) lager than 160° and a sliding angle lower than 5°. The superhydrophobic TiO2@Cotton shows excellent laundering durability against mechanical abrasion without an apparent reduction of the water contact angle. Moreover, the micro/nanoscale hierarchical structured cotton fabrics with special wettability are demonstrated to selectively collect oil from oil/water mixtures efficiently under various conditions (e.g., floating oil layer or underwater oil droplet or even oil/water mixtures). In addition, it is expected that this facile strategy can be widely used to construct multifunctional fabrics with excellent self-cleaning, laundering durability, and oil/water separation. The work would also be helpful to design and develop new underwater superoleophobic/superoleophilic materials and microfluidic management devices.
We report a robust and recyclable "dip-catalyst" based on a gold nanoparticle (Au NP)-loaded filter paper composite, prepared by a simple dip-coating process using concentrated Au NP suspensions in toluene. While acting as catalysts, the composites display excellent surface enhanced Raman scattering (SERS) efficiency, allowing the real-time monitoring of chemical reactions.
n the last years the antimicrobial nanofinishing of biomedical textiles has become a very active, high growth research field, assuming a great importance among all available material surface modifications in textile industry. This review offers the opportunity to update and critically discuss the latest advances and applications in this field. The survey suggests an emerging new paradigm in the production and distribution of nanoparticles for biomedical textile applications based on non-toxic renewable biopolymers such as chitosan, alginate and starch. Moreover a relationship among metal and metal oxide nanoparticle size, its concentration on the fabric and the antimicrobial activity exists, allowing the optimization of antimicrobial functionality.
Reductive amination of cyclohexanol/cyclohexanone was studied over copper catalysts supported on zirconia. The effect of copper loading and dispersion was studied on the activity and selectivity of the reaction. A series of zirconia supported copper catalysts with varying copper loadings (1–15wt%) were prepared by incipient wet impregnation method. The catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). Copper dispersion and metal area were determined by N2O decomposition by passivation method. X-ray diffraction patterns indicate the presence of crystalline CuO phase from 4.0wt% Cu on zirconia. TPR patterns reveal the presence of highly dispersed copper oxide at lower temperatures and bulk CuO at higher temperatures. The acid–base properties of catalysts were investigated by means of a model reaction cyclohexanol dehydrogenation to cyclohexanone and compare with the results of TPD of ammonia, which allows to measure the acid–base properties of the support and to investigate the changes in surface acidity or basicity, resulting from the metal impregnation.
a The synthesis of organic semiconducting materials based on silver and copper-TCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) and their fluorinated analogues has received a significant amount of attention due to their potential use in organic electronic applications. However, there is a scarcity in the identification of different applications for which these interesting materials may be suitable candidates. In this work, we address this by investigating the catalytic properties of such materials for the electron transfer reaction between ferricyanide and thiosulphate ions in aqueous solution, which to date has been almost solely limited to metallic nanomaterials. Significantly it was found that all the materials investigated, namely CuTCNQ, AgTCNQ, CuTCNQF 4 and AgTCNQF 4 , were catalytically active and, interestingly, the fluorinated analogues were superior. AgTCNQF 4 demonstrated the highest activity and was tested for its stability and re-usability for up to 50 cycles without degradation in performance. The catalytic reaction was monitored via UV-vis spectroscopy and open circuit potential versus time measurements, as well as an investigation of the transport properties of the films via electrochemical impedance spectroscopy. It is suggested that morphology and bulk conductivity are not the limiting factors, but rather the balance between the accumulated surface charge from electron injection via thiosulphate ions on the catalyst surface and transfer to the ferricyanide ions which controls the reaction rate. The facile fabrication of re-usable surface confined organic materials that are catalytically active may have important uses for many more electron transfer reactions.
We present a facile and low temperature approach for the fabrication of flexible organic electronic devices by growing high aspect ratio nanorod arrays of potassium 7,7,8,8-tetracyanoquinodimethane (KTCNQ), a crystalline organic semiconductor with charge transfer capabilities, on cotton threads interwoven within the three-dimensional (3-D) matrix of a cotton textile. We demonstrate the capability of this material in developing optoelectronic switches and gas sensors. The ability to grow KTCNQ nanorod arrays in a radial symmetry directly on textiles as a versatile 3-D microtemplate can be extended to the synthesis of a variety of metal-organic charge transfer complexes onto different flexible substrates that can find applications in electronics, catalysis and sensing.
Studies of the optical properties and catalytic capabilities of noble metal nanoparticles (NPs), such as gold (Au) and silver (Ag), have formed the basis for the very recent fast expansion of the field of green photocatalysis: photocatalysis utilizing visible and ultraviolet light, a major part of the solar spectrum. The reason for this growth is the recognition that the localised surface plasmon resonance (LSPR) effect of Au NPs and Ag NPs can couple the light flux to the conduction electrons of metal NPs, and the excited electrons and enhanced electric fields in close proximity to the NPs can contribute to converting the solar energy to chemical energy by photon-driven photocatalytic reactions. Previously the LSPR effect of noble metal NPs was utilized almost exclusively to improve the performance of semiconductor photocatalysts (for example, TiO2 and Ag halides), but recently, a conceptual breakthrough was made: studies on light driven reactions catalysed by NPs of Au or Ag on photocatalytically inactive supports (insulating solids with a very wide band gap) have demonstrated that these materials are a class of efficient photocatalysts working by mechanisms distinct from those of semiconducting photocatalysts. There are several reasons for the significant photocatalytic activity of Au and Ag NPs. (1) The conduction electrons of the particles gain the irradiation energy, resulting in high energy electrons at the NP surface which is desirable for activating molecules on the particles for chemical reactions. (2) In such a photocatalysis system, both light harvesting and the catalysing reaction take place on the nanoparticle, and so charge transfer between the NPs and support is not a prerequisite. (3) The density of the conduction electrons at the NP surface is much higher than that at the surface of any semiconductor, and these electrons can drive the reactions on the catalysts. (4) The metal NPs have much better affinity than semiconductors to many reactants, especially organic molecules. Recent progress in photocatalysis using Au and Ag NPs on insulator supports is reviewed. We focus on the mechanism differences between insulator and semiconductor-supported Au and Ag NPs when applied in photocatalytic processes, and the influence of important factors, light intensity and wavelength, in particular estimations of light irradiation contribution, by calculating the apparent activation energies of photo reactions and thermal reactions.
We demonstrate aqueous phase biosynthesis of phase-pure metallic copper nanoparticles (CuNPs) using a silver resistant bacterium Morganella morganii. This is particularly important considering that there has been no report that demonstrates biosynthesis and stabilization of pure copper nanoparticles in the aqueous phase. Electrochemical analysis of bacterial cells exposed to Cu(2+) ions provides new insights into the mechanistic aspect of Cu(2+) ion reduction within the bacterial cell and indicates a strong link between the silver and copper resistance machinery of bacteria in the context of metal ion reduction. The outcomes of this study take us a step closer towards designing rational strategies for biosynthesis of different metal nanoparticles using microorganisms.
Catalysis by metallic nanoparticles is certainly among the most intensely studied problems in modern nanoscience. However, reliable tests for catalytic performance of such nanoparticles are often poorly defined, which makes comparison and benchmarking rather difficult. We tackle in this tutorial review a subset of well-studied reactions that take place in aqueous phase and for which a comprehensive kinetic analysis is available. Two of these catalytic model reactions are under consideration here, namely the reduction of (i) p-nitrophenol and (ii) hexacyanoferrate (iii), both by borohydride ions. Both reactions take place at the surface of noble metal nanoparticles at room temperature and can be accurately monitored by UV-vis spectroscopy. Moreover, the total surface area of the nanoparticles in solution can be known with high precision and thus can be directly used for the kinetic analysis. Hence, these model reactions represent cases of heterogeneous catalysis that can be modelled with the accuracy typically available for homogeneous catalysis. Both model reactions allow us to discuss a number of important concepts and questions, namely the dependence of catalytic activity on the size of the nanoparticles, electrochemistry of nanoparticles, surface restructuring, the use of carrier systems and the role of diffusion control.
Diatoms produce diverse three-dimensional regular silica structures with nanometer to micrometer dimensions and hold considerable promise for biological or biomimetic fabrication of nanostructured materials and devices. In this paper, a simple procedure for fabrication of gold nanostructures with complex morphologies using porous diatom frustules as templates is described. The gold nanostructures are formed by means of thermal evaporation of gold onto porous frustules. Nanostructured gold films were obtained upon release from the diatom templates and were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Vis spectrophotometry. Three centric diatom species, Coscinodiscus sp., Thalassiosira eccentrica and one unidentified species cultured in our laboratory, were used as templates. The prepared gold replicas come in a variety of forms and shapes including arrays of nanoscale pillars, dots and more complex three-dimensional structures, depending on which porous surface of the diatom was used for replication. In all cases, gold nanostructures closely follow the organization and distribution of pores of the frustule template. Spectrophotometric characterisation shows that the templated nanostructured gold films exhibit localized surface plasmon resonance (LSPR) effects. © the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
In this paper, electrochemical behavior of a diphtheria immunosensor modified with nano-size conductor and semiconductor, as a mode of silica/gold/silver nanoparticles, has been investigated. Potentiometric immunosensor, cyclic voltammetry, and electrochemical impedance techniques were used to investigate the immobilization of diphtheria antibody on silica/gold/silver colloids. In the impedance spectroscopic study, an obvious difference of the electron transfer resistance between the silica-colloid modified electrode and the gold/silver-colloid modified electrodes was observed. The cyclic voltammogram tends to be more irreversible on silica colloids. Subsequently, using the silica colloid-modified immunosensor by potentiometry as a mode, it is found that the resulting immunosensor exhibited fast potentiometric response (<3 min), high sensitivity and good reproducibility. Moreover, analytical results of several specimens obtained using the silica colloid-modified immunosensor are in satisfactory agreement with those given by the ELISA method, implying a promising alternative approach for detecting diphtheria antigen in the clinical diagnosis.
The electrochemical and electrocatalytic behaviour of silver nanoprisms, nanospheres and nanocubes of comparable size in an alkaline medium have been investigated to ascertain the shape dependent behaviour of silver nanoparticles, which are an extensively studied nanomaterial. The nanomaterials were synthesised using chemical methods and characterised with UV-visible spectroscopy, transmission electron microscopy and X-ray diffraction. The nanomaterials were immobilised on a substrate glassy carbon electrode and characterised by cyclic voltammetry for their surface oxide electrochemistry. The electrocatalytic oxidation of hydrazine and formaldehyde and the reduction of hydrogen peroxide were studied by performing cyclic voltammetric and chronoamperometric experiments for both the nanomaterials and a smooth polycrystalline macrosized silver electrode. In all cases the nanomaterials showed enhanced electrocatalytic activity over the macro-silver electrode. Significantly, the silver nanoprisms that are rich in hcp lamellar defects showed greater activity than nanospheres and nanocubes for all reactions studied. © 2010 The Royal Society of Chemistry.
Silver nanoparticles were synthesized and deposited on different types of fabrics using ultrasound irradiation. The structure of silver-fabric composites was studied by physico-chemical methods. The mechanism of the strong adhesion of silver nanoparticles to the fibers is discussed. The excellent antibacterial activity of the Ag-fabric composite against Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) cultures was demonstrated.
Chemical plating techniques have been used in silicon processing for many years for junction delineation and ohmic contact formation. In recent years, interest in this area has been renewed because of the potential use of electroless copper deposition for ultra-large-scale integration (ULSI) metallization and for the formation of thin metal etch masks for deep-ultraviolet lithography. Good deposition selectivity, low operating temperature, high copper purity, good filling characteristics, and planar topography have been among the many advantageous attributes reported from early investigations.
In the June 1993 issue of the MRS Bulletin on Copper Metallization, Cho et al. gave an exposition on the use of electroless copper for VLSI. More comprehensive reviews of the electrochemical fundamentals can be found in References 8,9, and 10. This article summarizes the current understanding of various chemical and material aspects of this deposition method in an attempt to give an overview of the film growth characteristics for thin film applications. Because of length limitations, only selected topics are included. The emphasis is on the initiation conditions and the resultant microstructure and properties obtained. We also discuss special considerations for fine pattern formation.
The information presented here applies primarily to electroless copper deposition on metals and metal silicides since these are the typical substrate surfaces for metallization in contact vias of ULSI circuits. Strictly speaking, metallization of upper-level interconnects occurs mostly on a dielectric base. However, since copper systems usually require a diffusion barrier to shield the copper from diffusing into the silicon, we can treat the deposition process startingfrom this layer onward.
The use of membranes for gas permeation and phase separation offers many distinct advantages over other more energy dependent processes. The operational efficiencies of these membranes rely heavily on high gas permeability. Here, we report membranes with significantly increased permeability without a considerable decrease in mechanical strength or selectivity, synthesized from a polymer nanocomposite that incorporates graphene and polydimethylsiloxane (PDMS). These graphene-PDMS nanocomposite membranes were able to enhance the gas permeation of N2, CO2, Ar and CH4 in reference to pristine PDMS membranes. This is achieved by creating interfacial voids between the graphene flakes and polymer chains, which increases the fractional free volume within the nanocomposites giving rise to an increase in permeation. An optimal loading of graphene was found to be 0.25 wt%, while greater loading created agglomeration of the graphene flakes hence reducing the effective surface area. We present the enhancements that the membranes can provide to sensing and phase separation applications. We show that these nanocomposites are near transparent to CO2 gas molecules in sensing measurements. This study offers a new area of research for graphene-based nanocomposites.
We present a novel strategy based on the immobilization of palladium nanoparticles (Pd NPs) on filter paper for development of a catalytic system with high efficiency and recyclability. Oleylamine-capped Pd nanoparticles, dispersed in an organic solvent, strongly adsorb on cellulose filter paper, which shows a great ability to wick fluids due to its microfiber structure. Strong van der Waals forces and hydrophobic interactions between the particles and the substrate lead to nanoparticle immobilization, with no desorption upon further immersion in any solvent. The prepared Pd NP-loaded paper substrates were tested for several model reactions such as the oxidative homocoupling of arylboronic acids, the Suzuki cross-coupling reaction, and nitro to amine reduction, and they display efficient catalytic activity and excellent recyclability and reusability. This approach of using NP-loaded paper substrates as reusable catalysts is expected to open doors for new type of catalytic support for practical applications
A generalized low temperature approach for fabricating high aspect ratio nanorod arrays of alkali metal-TCNQ (7,7,8,8-tetracyanoquinodimethane) charge transfer complexes at 140 °C is demonstrated. This facile approach overcomes the current limitation associated with fabrication of alkali metal-TCNQ complexes that are based on physical vapor deposition processes and typically require an excess of 800 °C. The compatibility of soft substrates with the proposed low temperature route allows direct fabrication of NaTCNQ and LiTCNQ nanoarrays on individual cotton threads interwoven within the 3D matrix of textiles. The applicability of these textile-supported TCNQ-based organic charge transfer complexes towards optoelectronics and gas sensing applications is established.
The translation of a technology from the laboratory into the real world should meet the demand of economic viability and operational simplicity. Inspired by recent advances in conductive ink pens for electronic devices on paper, we present a “pen-on-paper” approach for making surface enhanced Raman scattering (SERS) substrates. Through this approach, no professional training is required to create SERS arrays on paper using an ordinary fountain pen filled with plasmonic inks comprising metal nanoparticles of arbitrary shape and size. We demonstrate the use of plasmonic inks made of gold nanospheres, silver nanospheres and gold nanorods, to write SERS arrays that can be used with various excitation wavelengths. The strong SERS activity of these features allowed us to reach detection limits down to 10 attomoles of dye molecules in a sample volume of 10 μL, depending on the excitation wavelength, dye molecule and type of nanoparticles. Furthermore, such simple substrates were applied to pesticide detection down to 20 ppb. This universal approach offers portable, cost effective fabrication of efficient SERS substrates at the point of care. This approach should bring SERS closer to the real world through ink cartridges to be fixed to a pen to create plasmonic sensors at will.
Copper is a low-cost plasmonic metal. Efficient photocatalysts of copper nanoparticles on graphene support are successfully developed for controllably catalyzing the coupling reactions of aromatic nitro compounds to the corresponding azoxy or azo compounds under visible-light irradiation. The coupling of nitrobenzene produces azoxybenzene with a yield of 90 % at 60 °C, but azobenzene with a yield of 96 % at 90 °C. When irradiated with natural sunlight (mean light intensity of 0.044 W cm(-2) ) at about 35 °C, 70 % of the nitrobenzene is converted and 57 % of the product is azobenzene. The electrons of the copper nanoparticles gain the energy of the incident light through a localized surface plasmon resonance effect and photoexcitation of the bound electrons. The excited energetic electrons at the surface of the copper nanoparticles facilitate the cleavage of the NO bonds in the aromatic nitro compounds. Hence, the catalyzed coupling reaction can proceed under light irradiation and moderate conditions. This study provides a green photocatalytic route for the production of azo compounds and highlights a potential application for graphene.
Paper and textiles have been used ubiquitously in our everyday lives, such as books and newspapers for propagating information, clothing and packaging. In this perspective, we will summarize our recent efforts in exploring these old materials for emerging energy and environmental applications. The motivations and challenges of using paper and textiles for device applications will be discussed. Various types of energy and environmental devices have been demonstrated including supercapacitors, Li-ion batteries, microbial fuel cells and water filters. Due to their unique morphologies, paper and textile-based devices not only can be fabricated with simple processing, but also show outstanding device performance. Being renewable and earth-abundant materials, paper and textiles could play significant roles in addressing future energy and environmental challenges.
A complex between Cu(II) and a polyampholyte synthesized from methacrylic acid, imidazole and ethyleneglycol diglycidyl ether was used as a heterogeneous catalyst for hydrogen peroxide activation and degradation of chlorophenols. The material was characterized by XPS and by measurements of the zeta potential. The isoelectric point determined experimentally was 8.0, differing from that obtained by titration (6.4), which indicated the presence of fixed positive charges in disubstituted imidazole units. The XPS N 1s signal for pyridinic nitrogen in the imidazole units, and the O 1s signals from the carbonyl, hydroxyl and carboxylate groups shifted to higher binding energies after copper uptake, proving the chemical nature of Cu(II) adsorption on the polyampholyte. The XPS spectrum of the complex showed a Cu 2p3/2 peak at 934.7eV and the characteristic shake-up satellite of Cu(II). When the complex was used as a heterogeneous catalyst for H2O2 activation, Cu(I) was proved to be a probable intermediate species and contributed to elucidate the mechanism. The Auger CuLMM spectrum supports the presence of Cu(I) with a kinetic energy value of 914.8eV. The complex was applied in the oxidation of chlorinated phenols in aqueous solution at room temperature without any loss in efficiency.
Recent progress in nano-optics has paved the route toward the development of highly sensitive and label-free optical transducers using the localized surface plasmon resonance (LSPR) of metal nanostructures. In this review we describe the basis behind LSPR sensing and summarize the latest progress regarding nanostructure fabrication techniques and biosensing applications. Direct colorimetric assays reaching sensitivities in the zeptomolar range, or miniaturized multiplexed sensors constitute cutting-edge research in the LSPR biosensing field. We finally discuss the challenges that LSPR biosensors should face in order to be used in the near-future as commercial devices.
With the increasing popularity of the galvanic replacement approach towards the development of bimetallic nanocatalysts, special emphasis has been focused on minimizing the use of expensive metal (e.g. Pt), in the finally formed nanomaterials (e.g. Ag/Pt system as a possible catalyst for fuel cells). However, the complete removal of the less active sacrificial template is generally not achieved during galvanic replacement, and its residual presence may significantly impact on the electrocatalytic properties of the final material. Here, we investigate the hydrogen evolution reaction (HER) activity of Ag nanocubes replaced with different amounts of Pt, and demonstrate how the bimetallic composition significantly affects the activity of the alloyed nanomaterial.
Plasmonic nanostructures have played a significant role in the field of nanotechnology due to their unprecedented ability to concentrate light at the nanometre scale, which renders them precious for various sensing applications. The adsorption of plasmonic nanoparticles and nanostructures onto solid substrates in a controlled manner is a crucial process for the fabrication of nanoplasmonic devices, in which the nanoparticles amplify the electromagnetic fields for enhanced device performance. In this perspective article we summarize recent developments in the fabrication of flexible nanoplasmonic devices for sensing applications based on surface enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR) shifts. We introduce different types of flexible substrates such as filter paper, free-standing nanofibres, elastomers, plastics, carbon nanotubes and graphene, for the fabrication of low-cost flexible nanoplasmonic devices. Various techniques are described that allow impregnation of such flexible substrates with plasmonic nanoparticles, including solution processes, physical vapour deposition and lithographic techniques. From the discussion in this Perspective, it is clear that highly sensitive and reproducible flexible plasmonic devices can currently be fabricated on a large scale at relatively low-cost, toward real-world applications in diagnostics and detection.
There is increasing interest in developing artificial systems that can mimic natural photosynthesis to directly harvest and convert solar energy into usable or storable energy resources. Photocatalysis, in which solar photons are used to drive redox reactions to produce chemical fuel, is the central process to achieve this goal. Despite significant efforts to date, a practically viable photocatalyst with sufficient efficiency, stability and low cost is yet to be demonstrated. It is often difficult to simultaneously achieve these different performance metrics with a single material component. The heterogeneous photocatalysts with multiple integrated functional components could combine the advantages of different components to overcome the drawbacks of single component photocatalysts. A wide range of heterostructures, including metal/semiconductor, semiconductor/semiconductor, molecule/semiconductor and multi-heteronanostructures, have been explored for improved photocatalysts by increasing the light absorption, promoting the charge separation and transportation, enhancing the redox catalytic activity and prolonging the functional life-time. The present review gives a concise overview of heterogeneous photocatalysts with a focus on the relationship between the structural architecture and the photocatalytic activity and stability.
A new method was developed for the homogeneous deposition of silver nanoparticles on colloid silica spheres. The method does not make use of an external electron source, but of a chemical moiety adsorbed on the surface, which can easily get oxidized. The process is mainly performed in two steps: a first step in which the adsorption of Sn2+ ions occurs on the surface of the silica particles and a second step comprising the addition of Ag+ ions, which are reduced and simultaneously adsorbed on the surface, while Sn2+ oxidizes to Sn4+. The whole process can be repeated to obtain a denser coating on the surface.
We present the employment of the Keggin ion 12-phosphotungstic acid as a UV-switchable reducing agent for the decoration of Au, Ag, Pt, and Cu nanoparticles onto the surface of TiO(2) nanotubes synthesized by electrochemical anodization. The synthesized composites were studied using SEM, GADDS XRD, and EDX, and the photocatalytic activity of the composites was examined by measuring the photodegradation of the organic dye "Congo red" under simulated solar light. Decoration with metal nanoparticles was observed to enhance the activity of the photocatalytic process by upward of 100% with respect to unmodified TiO(2) nanotubes.
The dynamics of the charge transfer process that transpires during the chemisorption of thiol-derived monolayers on gold electrodes have been examined by monitoring the temporal evolution of the open circuit potential (OCP). As a consequence of adlayer formation, the OCP shifts negatively. This shift is attributed to the accumulation of negative charge on the electrode through the donation of electron density from sulfur to gold. The magnitude of the shift, however, is much less than that estimated for a one-electron chemisorption process at an interface modeled simply as a parallel plate capacitor. Based on the findings of these and other experiments, we propose that the formation process involves both the oxidative deposition of the adlayer and the reduction of the sulfhydryl proton to hydrogen. Evidence consistent with these conclusions is presented.
This paper deals with the antibacterial efficacy of nanosized silver colloidal solution on the cellulosic and synthetic fabrics. Two kinds of Bacteria; Gram-positive and Gram-negative, were used. TEM observation of silver nanoparticles showed their shape, and size distribution. The particles were very small (2–5 nm) and had narrow distribution. SEM images of treated fabrics indicated silver nanoparticles were well dispersed on the surfaces of specimens. WAXS patterns did not show any peak of silver as the fabric had very small quantity of silver particles. However, ICP-MS informed the residual concentration of silver particles on fabrics before/after laundering. The antibacterial treatment of the textile fabrics was easily achieved by padding them with nanosized silver colloidal solution. The antibacterial efficacy of the fabrics was maintained after many times laundering.
This study has shown that Pt/K-βAl2O3 electrochemical catalyst can reach high catalytic activity for the selective reduction of N2O by C3H6. In addition it was also demonstrated that Electrochemical Promotion could be a solution to reduce the adverse effects of
poisons (O2 and H2O) on the catalytic activity. For instance, in the presence of O2 (1%) and H2O (3%) in the reactive stream, electrochemical pumping of potassium ions to the Pt catalyst increased the N2O reduction rate by a factor of 7.4 at 400°C. We have also demonstrated that the wet impregnation procedure led to a very
stable Pt film, with very good resistance to thermal sintering under real operation conditions. Therefore, the use of Pt impregnated
films deposited on K-βAl2O3 solid electrolytes is a feasible solution for the treatment of automotive exhaust gases.
Silicon, in its various forms, finds widespread use in electronic, optical, and Structural materials. Research on uses of silicon and silica has been intense for decades, raising the question of how much diversity is left for innovation with this element. Shape variation is particularly well examined. Here, we review the principles revealed by diatom frustules, the porous silica shells of diatoms, microscopic, unicellular algae. The frustules have nanometer-scale detail, and the almost 100 000 species with unique frustule morphologies suggest nuanced structural and optical functions well beyond the current ranges used in advanced materials. The unique frustule morphologies have arisen through tens of millions of years of evolutionary selection, and so are likely to reflect optimized design and function. Performing the structural and optical equivalent of data mining, and understanding and adopting these designs, affords a new paradigm in materials science, an alternative to combinatorial materials synthesis approaches in spurring the development of new material and more nuanced materials. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.
Antimicrobial silver nanoparticles were immobilized on nylon and silk fibers by following the layer-by-layer deposition method. The sequential dipping of nylon or silk fibers in dilute solutions of poly(diallyldimethylammonium chloride) (PDADMAC) and silver nanoparticles capped with poly(methacrylic acid) (PMA) led to the formation of a colored thin film possessing antimicrobial properties. The layer-by-layer deposition was monitored by measuring the K/S value, which is the ratio between the sorption coefficient (K) and the scattering (S) of the coated fibers, with a reflectance spectrophotometer. The K/S values for both silk and nylon fibers were found to increase as a function of the number of deposited layers. Although the film growth was observed on both fibers, the K/S value of the nylon fiber was significantly lower than silk fibers. Scanning electron microscopy studies of both fibers confirmed that the layer-by-layer coating on the nylon fibers was not as uniform as on the silk fibers. Antimicrobial tests against Staphylococcus aureus bacteria were performed and antimicrobial activity was demonstrated for both coated fibers. The deposition of 20 PDADMAC/PMAcapAg layers onto the fibers resulted in 80% bacteria reduction for the silk fiber and 50% for the nylon fiber. Although the film growth was more efficient on the silk fibers, these results suggest that this technique could be used in the design of new synthetic or natural technical fibers where antimicrobial properties are required.
Copper oxide nanoparticles were synthesized and subsequently deposited on the surface of cotton fabrics using ultrasound irradiation. Optimization of the process resulted in a homogeneous distribution of CuO nanocrystals, 15 nm in size, on the fabric surface. The antibacterial activities of the CuO–fabric composite were tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures. A significant bactericidal effect, even in a 1% coated fabric (%wt.), was demonstrated.
The nanoporous copper foam was prepared by electrochemical reduction of copper ion at the copper substrate. The as-prepared substrate was used as three-dimensional templates for preparation of Pt coated nanostructured Cu-foam by galvanic replacement of Cu with platinum by simply immersing the prepared nanoporous copper foam in a K2PtCl6 aqueous solution. The structure and nature of the fabricated Pt coated nanostructured Cu-foam was characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Pt coated nanostructured Cu-foam modified copper electrode exhibited remarkable electrocatalytic activity for the hydrogen evolution reaction. The effect of electrodeposition time during Cu-foam formation on the kinetic constants for hydrogen evolution reaction was comparatively investigated.
A study was conducted to investigate the galvanic replacement reactions to prepare nanoscale porosity in metal foils. The study also investigated the reaction of Cu2+ ions with nickel foil in a Cu-Ni nanoporous surface. The study used scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Auger microscopy, and X-ray photoemission spectroscopy (XPS) analysis to determine the characteristics of the Cu-Ni based nanoporous materials. It was also observed that the highly porous Cu on nickel foil can be used for many application including the catalytic wet air oxidation (CWAO) of ferulic acid. The study also found that a nonoporous Cu-Ni catalyst can oxidize ferulic acid by using mild conditions. The study also provide a method for prepare a nanoscale porosity in bulk surfaces.
We demonstrate a facile localized reduction approach to synthesizing a Au nanoparticle-decorated Keggin ion/TiO(2) photococatalyst for improved solar light photocatalysis application. This has been achieved by exploiting the ability of TiO(2)-bound Keggin ions to act as a UV-switchable, highly localized reducing agent. Notably, the approach proposed here does not lead to contamination of the resultant cocatalyst with free metal nanoparticles during aqueous solution-based synthesis. The study shows that for Keggin ions (phosphotungstic acid, PTA), being photoactive molecules, the presence of both Au nanoparticles and PTA on the TiO(2) surface in a cocatalytic system can have a dramatic effect on increasing the photocatalytic performance of the composite system, as opposed to a TiO(2) surface directly decorated with metal nanoparticles without a sandwiched PTA layer. The remarkable increase in the photocatalytic performance of these materials toward the degradation of a model organic Congo red dye correlates to an increase of 2.7-fold over that of anatase TiO(2) after adding Au to it and 4.3-fold after introducing PTA along with Au to it. The generalized localized reduction approach to preparing TiO(2)-PTA-Au cocatalysts reported here can be further extended to other similar systems, wherein a range of metal nanoparticles in the presence of different Keggin ions can be utilized. The composites reported here may have wide potential implications toward the degradation of organic species and solar cell applications.
In this study, the reaction of semiconductor microrods of phase I copper 7,7,8,8-tetracyanoquinodimethane (CuTCNQ) with KAuBr(4) in acetonitrile is reported. It was found that the reaction is redox in nature and proceeds via a galvanic replacement mechanism in which the surface of CuTCNQ is replaced with metallic gold nanoparticles. Given the slight solubility of CuTCNQ in acetonitrile, two competing reactions, namely CuTCNQ dissolution and the redox reaction with KAuBr(4), were found to operate in parallel. An increase in the surface coverage of CuTCNQ microrods with gold nanoparticles occurred with an increased KAuBr(4) concentration in acetonitrile, which also inhibited CuTCNQ dissolution. The reaction progress with time was monitored using UV-visible, FT-IR, and Raman spectroscopy as well as XRD and EDX analysis, and SEM imaging. The CuTCNQ/Au nanocomposites were investigated for their photocatalytic properties, wherein the destruction of Congo red, an organic dye, by simulated solar light was found dependent on the surface coverage of gold nanoparticles on the CuTCNQ microrods. This method of decorating CuTCNQ may open the possibility of modifying this and other metal-TCNQ charge transfer complexes with a host of other metals which may have significant applications.
We show for the first time that by controlling the growth kinetics of Morganella psychrotolerans, a silver-resistant psychrophilic bacterium, the shape anisotropy of silver nanoparticles can be achieved. This is particularly important considering that there has been no report that demonstrates a control over shape of Ag nanoparticles by controlling the growth kinetics of bacteria during biological synthesis. Additionally, we have for the first time performed electrochemistry experiments on bacterial cells after exposing them to Ag(+) ions, which provide significant new insights about mechanistic aspects of Ag reduction by bacteria. The possibility to achieve nanoparticle shape control by using a "green" biosynthesis approach is expected to open up new exciting avenues for eco-friendly, large-scale, and economically viable shape-controlled synthesis of nanomaterials.
Metal nanoparticles hold great promise for heterogeneous catalysis due to their high dispersion, large concentration of highly undercoordinated surface sites, and the presence of quantum confinement effects, which can drastically alter their reactivity. However, the poor thermal stability of nano-sized particles limits their use to low temperature conditions and constitutes one of the key hurdles towards industrial application. The present perspective paper briefly reviews the mechanisms underlying nanoparticle sintering, and then gives an overview of emerging approaches towards stabilizing metal nanoparticles for heterogeneous catalysis. We conclude by highlighting the current needs for further developments in the field.
This review describes recent advances in electrochemical impedance spectroscopy (EIS) with an emphasis on its novel applications to various electrochemistry-related problems. Section 1 discusses the development of new EIS techniques to reduce measurement time. For this purpose, various forms of multisine EIS techniques were first developed via a noise signal synthesized by mixing ac waves of various frequencies, followed by fast Fourier transform of the signal and the resulting current. Subsequently, an entirely new concept was introduced in which true white noise was used as an excitation source, followed by Fourier transform of both excitation and response signals. Section 2 describes novel applications of the newly developed techniques to time-resolved impedance measurements as well as to impedance imaging. Section 3 is devoted to recent applications of EIS techniques, specifically traditional measurements in various fields with a special emphasis on biosensor detections.
Recently there is strong interest in lightweight, flexible, and wearable electronics to meet the technological demands of modern society. Integrated energy storage devices of this type are a key area that is still significantly underdeveloped. Here, we describe wearable power devices using everyday textiles as the platform. With an extremely simple "dipping and drying" process using single-walled carbon nanotube (SWNT) ink, we produced highly conductive textiles with conductivity of 125 S cm(-1) and sheet resistance less than 1 Omega/sq. Such conductive textiles show outstanding flexibility and stretchability and demonstrate strong adhesion between the SWNTs and the textiles of interest. Supercapacitors made from these conductive textiles show high areal capacitance, up to 0.48F/cm(2), and high specific energy. We demonstrate the loading of pseudocapacitor materials into these conductive textiles that leads to a 24-fold increase of the areal capacitance of the device. These highly conductive textiles can provide new design opportunities for wearable electronics and energy storage applications.
The reaction of gold substrates with p-nitrobenzene diazonium tetrafluoroborate (NBD) in 0.1 M H(2)SO(4) at open-circuit potential (OCP) is demonstrated to proceed by electron transfer from gold to the NBD cation. Electrochemical, atomic force microscopy, and X-ray photoelectron spectroscopy analyses reveal the formation of multilayer films with the same composition as electrografted films. The film growth characteristics (surface concentration and film thickness vs time) also follow those observed during electrografting, consistent with electron transfer from the substrate to the diazonium cation. The OCP of the gold substrate increases during the period of film growth ( approximately 60 min) and then decreases to close to its initial value. The increase corresponds to accumulation of positive charge as electrons are transferred to NBD; the discharge process is tentatively attributed to slow oxidation of adventitious impurities in the reaction solution. Films formed at OCP or by electrografting from aqueous acid solution are markedly less stable to sonication in acetonitrile than are those electrografted from acetonitrile. Increased amounts of physisorbed material in films prepared in aqueous media or bonding of aryl groups to different gold sites in the two media are tentatively proposed to account for the different stabilities.
A new, efficient and ligand-free cross-coupling reaction of aryl halides and diaryl diselenides using a catalytic amount of nanocrystalline CuO as a recyclable catalyst with KOH as the base in DMSO at 110 degrees C is reported. This protocol has been utilized for the synthesis of a variety of aryl selenides in excellent yields from the readily available aryl halides and diaryl diselenides.
The development of synthetic catalysts is inspired by nature's use of enzymes to achieve high reaction rates and 100% selectivity. These natural catalysts often contain inorganic nanoclusters at the active site, and it is an understanding of the activity and selectivity of these nanoclusters and their interaction with the surrounding protein, which can aid in the design of synthetic catalysts. Since natural and synthetic catalysts are composed of these nanoclusters, the fields of catalysis and nanoscience are inextricably linked.
While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape of the colloidal nanocatalyst on the catalytic activity as well as the effect of the catalytic process on the shape and size of the colloidal transition metal nanocatalysts and their recycling potential. These studies provide important clues on the mechanism of the reactions we studied and also can be very useful in the process of designing better catalysts in the future.
Despite recent exciting progress in catalysis by supported gold nanoparticles, there remains the formidable challenge of preparing supported gold catalysts that collectively incorporate precise control over factors such as size and size-distribution of the gold nanoparticles, homogeneous dispersion of the particles on the support, and the ability to utilize a wide range of supports that profoundly affect catalytic performance. Here, we describe a synthetic methodology that achieves these goals. In this strategy, weak interface interactions evenly deposit presynthesized organic-capped metal nanoparticles on oxide supports. The homogeneous dispersion of nanoparticles on oxides is then locked in place, without aggregation, through careful calcination. The approach takes advantage of recent advances in the synthesis of metal and oxide nanomaterials and helps to bring together these two classes of materials for catalysis applications. An important feature is that the strategy allows metal nanoparticles to be well dispersed on a variety of oxides with few restrictions on their physical and chemical properties. Following this synthetic procedure, we have successfully developed efficient gold catalysts for green chemistry processes, such as the production of ethyl acetate from the selective oxidation of ethanol by oxygen at 100 degrees C.
- R Narayanan
- M A El-Sayed
R. Narayanan, M. A. El-Sayed, J. Phys. Chem. B. 2005, 109, 12663.