No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Synthesis of silver nanoparticles by γ-ray irradiation in acetic water solution containing chitosan
Abstract
Silver nanoparticles were synthesized by gamma-ray irradiation of acetic water solutions containing AgNO3 and chitosan. The resulting particles with the average diameter of 4 5 nm were densely dispersed in the solution due to the protection of chitosan chains. UV vis spectra showed that the irradiation dose would affect the size distribution of nanoparticles.
... Moreover, Sun et al. [56] found that chitosan chains break in an acidic aqueous solution, which may lessen chitosan's ability to stabilize metallic particles to some extent. A number of investigations have been conducted recently on the γ-irradiation method of generating AgNPs in chitosan solution [57][58][59]; however, the impact of pH has not yet been examined. ...
... The special properties of the AgNPs were verified using TEM with our current technique. Nanomaterials 2024, 14,1018 A number of investigations have been conducted recently on the γ-irradiation me generating AgNPs in chitosan solution [57][58][59]; however, the impact of pH has been examined. Nonetheless, research has been carried out on how pH affect stabilizers. ...
Silver nanoparticles (AgNPs) can be produced safely and greenly using water hyacinth, an invasive aquatic plant, as a reducing agent. This study aimed to optimize the UV-irradiation parameters for the synthesis of AgNPs from water hyacinth leaf extract. The study varied the reaction time and pH levels and added a stabilizing agent to the mixture. The synthesized AgNPs were characterized using UV-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The findings revealed that the optimal conditions for synthesizing AgNPs were achieved by adjusting the pH level to 8.5, adding starch as a stabilizing agent, and exposing the mixture to UV-A radiation for one hour. These conditions resulted in the smallest size and highest quantity of AgNPs. Furthermore, the synthesized AgNP colloids remained stable for up to six months. This study highlights the potential of utilizing water hyacinth as a sustainable and cost-effective reducing agent for AgNP synthesis, with potential applications in pharmaceuticals, drug development, catalysis, and sensing detection.
... There are many developed approaches such as chemical [7], electrochemical [8] and decreasing photochemical [9], ultrasound [10], microwave [11], and irradiations of both gamma [12] and electron to [13][14][15][16][17][18][19] synthesize Ag-NPs by various stabilizers [20][21][22][23]. Ag-NPs depending on sizes and forms utilized in biosensors materials, cosmetics, antimicrobial uses, conducting materials and electrical constituents. ...
... Salleh et al. [23] to form AgNPs by the reduction of AgNO3. Peng Chen Briefly reported photo-induced fragmenting Ag-NPs [19,59]: ...
In this paper we demonstrate physical method (Gamma irradiation technique) for synthesizing Ag-NPs when there is no reduction agent or heat treatment as useful in antimicrobial applications and medical devices. As a strong support, stabilizer, and silver precursor, Chitosan (CS) and AgNO3 were utilized. Ag/Cs characteristics were investigated as a function of gamma dose and-irradiation periods in recent published paper. For conducting the research in Ag-CS-Isopropanol (IPA) by gamma Irradiation method, here we used UV-vis spectroscopy for examining energy gap and Plasmon resonance of surface (SPR) of the produced silver nanoparticles (Ag-NPs). Manufactured Ag-NP UV-vis spectroscopy revealed as the gamma dose increased, the highest wavelength intensity of the plasmon peaks rose. and with energy gap in rang (2.1-2.4) eV. The effect of Ag/CS-APA solutions has examined due on human blood properties and antibacterial activity to water samples selected from local riverbank in Iraq. Overall, the optical characteristic of Ag-CS-APA nanocomposite solution make them promising material for optical thin films and as antibacterial agent in health sector.
... The use of gamma irradiation in the presence of chitosan to decrease ions of silver in the solution has been previously documented [29,30] among the numerous methods utilized for silver and chitosan nanocomposites production. However, we believe that there are no studies on employing gamma irradiation to produce silver nanoparticles for antimicrobial applications (silver nanoparticles/(CM chitosan-isopropanol)). ...
... Referred to the reports of the researchers Chen et al. [30] and Nhien et al. [32] the irradiation-reduction procedure to fabricate silver particles is the following: ...
The present study demonstrates a green process for the synthesis of spherical-shaped and stabilized silver nanoparticles Ag NPs using gamma irradiated conditions. This method has certain advantages over conventional methods since it can manage the particle size and structure and generates totally reduced and extremely pure nanoparticles free from by-products or chemical reducing agents. Silver nanoparticles composite (Ag NPs / CM) is prepared from an aqueous solution of silver nitrate, chitosan and isopropanol, at room temperature using gamma irradiation doses to induce reduction and cross-linking to formation in situ Ag NPs/ CM-chitosan-isopropanol solutions. The production and homogenous distribution of silver nanoparticles in the hydrogel matrix were characterized using transmission electron microscopy, XRD, Zeta potential and UV-Vis spectrophotometer analysis. The silver/ CM-chitosan-isopropanol matrixes possessed different gamma doses using a Co- 60 gamma source. Through the comprehensive results of IR- Ag NPs /(CM- chitosan isopropanol solutions due to antibacterial activity test, the results show the prepared Ag NPs /CM-chitosan-isopropanol could be used as an antibacterial agent. The obtained Ag nanoparticles were stable for over 3 months at room temperature. the analysis outcomes indicate that the colloidal Solution (silver nanoparticles / (CM chitosan - isopropanol)) has a promising ability to be used in antibacterial applications in the future.
... Xác định hoạt tính kháng ôxy hóa: Hoạt tính kháng ôxy hóa dựa vào khả năng bắt gốc ABTS + của SeNPs/β-glucan theo phương pháp của P. Chen và cs (2007) [16] sử dụng mẫu blank là nước cất và mẫu đối chứng là β-glucan tan nước 2%. Hoạt tính bắt gốc tự do được tính theo công thức: H (%) = (1 -A/A o ) x 100. ...
... Chiếu xạ là phương pháp hữu hiệu để khử các ion kim loại như bạc (Ag + ), đồng (Cu 2+ ), vàng (Au 3+ ) trở về đạng dạng nano kim loại (Ag 0 , Cu 0 , Au 0 ), trong đó e-aq, H • và OH • sinh ra trong quá trình chiếu xạ sẽ khử Se 4+ thành Se 0 [12,16]. S. Remita và cs (2005) [17] cho rằng, liều xạ tối thiểu để khử 1 mM kim loại hoá trị I từ dạng ion về dạng bão hoà điện tích là ~1,67 kGy, tuy nhiên giá trị này có thể tăng lên khi trong dung dịch phản ứng có chứa các hợp chất có khả năng phản ứng với gốc tự do e aq , H • và OH • như linoleic acid, chitosan... Cho đến nay có rất ít nghiên cứu ứng dụng bức xạ để chế tạo SeNPs được công bố, đặc biệt là chế tạo SeNPs ổn định trong β-glucan hầu như chưa được nghiên cứu. ...
The colloidal solutions of selenium nanoparticles (SeNPs) stabilised in water-soluble β-glucan were successfully prepared by the gamma ray (Co-60) irradiation method. The saturation dose for complete reduction of solutions contained 40, 60, 80, 100, and 120 ppm Se4+ were determined at 4, 6, 8, 10, and 12 kGy, respectively. The structural characteristic and particle size were analysed by Fourier transform infrared spectrophotometer (FTIR) and Dynamic light scattering (DLS). The obtained results showed that the increase of β-glucan concentration from 1 to 4% or pH of sample from 5 to 10 caused a slight change of particle size but strongly affected the particle size distribution in the product. The particle size of the product was almost unchanged after 60 days stored at 0 and 4oC conditions, but a slight increase was observed in the sample stored at room temperature after 30 days. In addition, the antioxidant activity of SeNPs/β-glucan was much higher than that of vitamin C at the same tested concentration and this activity was increased by the increase of reaction time. The smaller particles size in the product displayed the higher antioxidant activity. These results indicated that SeNPs/β-glucan prepared by irradiation method is a very promising product for application in the fields of cosmetic and functional food.
... The XRD patterns of the chitosan-AgNPs and chitosan-AuNPs are shown in Figure 3. The XRD pattern of the chitosan-AgNPs exhibited a strong characteristic peak for chitosan at about 20 • (Figure 4a), while the XRD showed another peak at about 64 • and 77 • corresponding to Ag nanoparticles in addition to the chitosan at 20 • [23][24][25]. Additionally, the XRD pattern for chitosan-AuNPs showed a characteristic peak at about 20 • , and for gold nanoparticles at 38 • , and 66 • . ...
... Several reports have mentioned that silver nanoparticles have a stronger antimicrobial activity than gold nanoparticles; this may be due to a stronger plasmon resonance in the silver nanoparticle. chitosan at about 20° (Figure 4a), while the XRD showed another peak at about 64° and 77° corresponding to Ag nanoparticles in addition to the chitosan at 20° [23][24][25]. Additionally, the XRD pattern for chitosan-AuNPs showed a characteristic peak at about 20°, and for gold nanoparticles at 38°, and 66°. Figure 4 illustrates the FTIR spectra of chitosan, chitosan-AgNPs, and chitosan-AuNP conjugates synthesized with Aspergillus sp. ...
Nanotechnology is emerging as a new technology with encouraging innovations. Global antibiotic use has grown enormously, with antibiotic resistance increasing by about 80 percent. In view of this alarming situation, intensive research has been carried out into biogenic nanoparticles and their antibacterial, antifungal, and antitumor activities. Many methods are available to enhance stability and dispersion via peroration of conjugate with a polymer, such as chitosan, and other bioactive natural products. Two marine fungi were isolated and identified as Aspergillus sp. and Alternaria sp. via sequencing of the 16S rRNA gene. In this work, these strains were used to form the conjugation of biogenic silver nanoparticles (AgNPs) from Aspergillus sp. Silv2 extract and gold nanoparticles (AuNPs) from Alternaria sp. Gol2 extracts with chitosan to prepare chitosan–AgNPs and chitosan–AuNP conjugates. A variety of imaging and analytical methods, such as UV–vis, X-ray powder diffraction (XRD), FTIR spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were utilized to characterize biogenic nanoparticles and conjugates. The biosynthesized Ag and Au nanoparticles along with the prepared conjugates were evaluated for their antimicrobial effects on Gram-negative and Gram-positive bacterial isolates, including Escherichia coli and Staphylococcus aureus. Both chitosan–AgNP and AuNP showed powerful antimicrobial activities compared to the control. On the other hand, chitosan–AgNP conjugation had better antibacterial ctivity than chitosan–AuNPs, which exhibited moderate activity against S. aureus and very low activity against E. coli. Furthermore, the antibiofilm potentials of the prepared conjugates were tested against four biofilm-forming bacteria, including P. aeruginosa, B. subtilis, E. coli, and S. aureus. The obtained results indicate that the chitosan–AgNP showed a promising anti-biofilm activities on all strains, especially S. aureus, while chitosan–AuNP conjugates showed moderate anti-biofilm against B. subtilis and weak activities against the other three strains. These results showed the superiority of chitosan–AgNP as a promising antibacterial as well as biofilm formation inhibitors.
... In addition, multilayer scaffolds facilitate layer-by-layer cell proliferation, migration, ECM deposition, and mineralization [14]. Chitosan (Chi) is one of the most plentiful natural polysaccharides and a copolymer of glucosamine and N-acetylglucosamine units connected by 1,4glucosidic bonds [15]. The presence of free amino groups at a pH lower than 2.6 has turned Chi into a polyelectrolyte polymer with a positive charge [16]. ...
The combining of therapeutic agents with electrospun nanofibers boosts their regeneration potential; therefore, Researchers have increasingly turned towards the development of electrospun nanofiber scaffolds to encapsulate or surface-adsorb biological payloads, such as cytokines, exosomes, peptides, nucleic acids, and enzymes. Due to their high surface-to-volume ratio, ease of manufacturing, and drug-loading capacity, electrospun nanofibers are hopeful in tissue engineering and scaffold fabrication. Electrospun multilayer scaffolds offer a promising construction for preserving the integrity and bioactivity of therapeutic factors while permitting the controlled and prolonged release of biomolecules into the environment. The present study aimed to evaluate the mechanism of controlled release of electrospun exosomes from a three-layer nanofiber scaffold and its effect on the expression of DDR2 and VEGF genes in fibroblast cells in vitro. Adipose-derived mesenchymal stem cells were obtained and isolated from liposuction surgery samples, and their intrinsic nature was confirmed using flow cytometry. After the exosomes were separated from the cell supernatant, their size, shape, and index markers were identified. The cytotoxicity, biocompatibility, and mechanical characteristics of scaffolds were evaluated. The qRT-PCR results showed the upregulation of DDR2 and VEGF genes in the three-layer scaffold containing the exosomes was 2.04 and 1.47-fold compared to the control group. The design and construction of multi-layered electrospun nanofibers loaded with bioactive substances and favorable mechanical and biological properties for controlled and sustained release will be promising and effective scaffolds for therapeutic purposes.
... This is why, these metallic nanopartilces are now cureently a subject of research and further downstream as its potential therapeutic applications (Chalopka et al, 2010; Prov et al, 2011; Dankovich et al, 2011). Furthermore, these nanoparticles display several structural-dependent properties that are now a concern for their applications ranging from catalysts and, pharmaceuticals properties (Park et al, 2008;Chen et al, 2007). In consequence of this fact, the antibacterial activity of several metal nanoparticles especially the silver nanoparticles (AgNPs) is firmly related to their structural properties; the smaller the metal nuclei, the higher the biological activity. ...
Metal nanoparticles (NPs) have attracted the interest of scientific community due to their fascinating applications in the field of biology, material science and medicine. Silver nanoparticles have attracted particular interest, compared with other NPs, as their useful properties are achievable due to biocompatibility. The use of plant extract for the green synthesis of nanoparticles is valuable due to the ease of scale-up and less biohazardous nature. The synthesis of NPs by biological method involving green-chemistry, eco-friendly based approach, make use of the active compounds of plants, bacteria, fungi, actinomycetes, yeast and algae. Endophytes are microorganisms that colonize inside the plant parts without causing any negative impact on the host and form an important component in the plant-micro ecosystem. Endophytes are becoming a promising source of novel biomolecules with wide therapeutic applications. Metabolites isolated from endophytes have shown potential use in agriculture, industries and modern medicine such as antibiotics, antimycotics, immunosuppressant and anticancer compounds. The identification of such endophytic fungi is considered beneficial as it helps conserve the plant biodiversity. The objective of the present study is to explore the anti-cancer potential of silver nanoparticles obtained by green synthesis using the endophytic fungus isolated from the medicinal plant Abutilon indicum against AtT 20 Mouse pituitary cell lines. The synthesized nanoparticles will be characterized using UV, FTIR and TEM. Further, to identify the potential therapeutic effect of AgNPs in AtT 20 cells, preliminary MTT assay will be carried out identify the cytotoxic effect. Further cell cycle analysis and apoptotic assays will be carried out using flow cytometry. The result from these studies should provide novel insight leading to development of potential AgNPs based therapeutics against cancers.
... This is possible thanks to the synthesis method. Synthesis of AgNPs can be carried out by different methods: chemical reduction [15][16][17], photochemical reduction [18], gamma [19], electron beam [20,21], microwave [22,23], laser [24], ultra violet [25], electrochemistry [26], sonochemistry [27], and synthesis ultrasound [28][29][30]. ...
Plaque control is especially important during orthodontic treatment because areas of the teeth near brackets and wires are difficult to clean with a toothbrush, resulting in debris buildup of food or dental plaque, thus causing caries and periodontal disease. The objective of this study was to evaluate the antimicrobial properties of silver nanoparticles (AgNPs), titanium dioxide nanoparticles (TiO2NPs), and silver/titanium dioxide nanoparticles (Ag/TiO2NPs), synthesized on the surface of α-alumina ceramic brackets. The AgNPs and TiO2NPs were synthesized by a simple chemical method, and these were characterized by XRD, SEM, and XPS TEM; the antimicrobial activity was tested against Staphylococcus aureus and Escherichia coli by diffusion test. The results of this study demonstrated that by this simple chemical method, silver and titanium dioxide nanoparticles can be synthesized on the surface of α-alumina esthetic brackets, and these NPs possess good antimicrobial activity and the possibility of reducing dental caries, periodontal disease, and white spot generated during orthodontic treatment.
... Currently, silver nanomaterials are synthesized by various physical and chemical methods, such as photochemical reduction [14], chemical reduction [15], using gamma radiation ...
Synthesis of silver nanoparticles (AgNPs) using plant extracts extracted from Ganoderma lucidum in the buffer zone of Bach Ma National Park, Vietnam is a simple, convenient, economical, and environmentally friendly method. This study describes the biosynthesis of silver nanoparticles in both cases with and without ultrasonic assistance using Ganoderma lucidum extract as a reducing and protective agent. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the as-synthesized AgNPs. Compared to the heating reflux method, the proposed ultrasonic wave assisted heating reflux method produced AgNPs had higher efficiency, smaller and more uniform particle size 6.08 ± 1.80 nm of nm in a short synthesis time period. The antibacterial and antifungal properties of ultrasonically synthesized silver nanomaterials (US-AgNPs) were also investigated. US-AgNPs are important nanomaterials that can find many good applications in practice.
... The physical methods include laser ablation [11], spark discharge [12], and pyrolysis [13]. The chemical methods are electrochemical reaction [14], Reduction of chemicals [15], solution irradiation [16] and others. The foremost process involved in chemical blend is the reduction of Cu + ions to Cu NPs. ...
The usage of copper nanoparticles (CuNPs) is now acknowledged as a promising therapeutic agent in the detection and treatment of cancer. This study aimed to develop a sustainable method for synthesizing CuNPs using Pedalium murex L. and characterization by SEM, FTIR, XRD & UV-Vis methods. The produced CuNPs were primarily spherical and varied in shape, and the average dimension ranged between 20 and 50 nm. The aqueous fruit juice of Pedalium murex L. contained biomolecules that serve as capping and reducing agents for the production of CuNPs, according to the findings of FTIR analysis. Various assays were used to determine the fruit extract’s in vitro antioxidant activity. CuNPs exhibited dose-dependent cytotoxicity and apoptosis promotion in A549 cells. The findings demonstrated that biosynthesized CuNPs using Pedalium murex L. fruit juice have anti-cancer properties and can be used in lung cancer treatment, particularly for early-stage intervention.
... Due to the increasing applications of silver nanoparticles in various areas, there are different methods for the production, each of which has advantages and disadvantages, including vapor-phase synthesis of nanoparticles, photolysis or gamma-ray method, electrochemical method, synthesis of silver nanoparticles through chemical methods, use of microwaves and lasers and production of nanoparticles using biotechnology [9][10][11][12][13][14][15][16]. ...
One of the methods of synthesis of nanomaterials is the use of plant extract in synthesis. The aim of this study was to investigate the effect of the T-Consciousness Bond Field in the synthesis of green silver nanoparticles using plant extract. Taheri Consciousness Fields (TCFs), as new Fields, have been founded and introduced by Mohammad Ali Taheri about four decades ago. These Fields are non material and non-energetic, so it has no quantity. However, it has a direct influence on both matter and energy. In other words, although TCFs cannot be directly measured, their effects can be indirectly studied by using various controlled experiments. In this experiment, the extract was prepared for 10 samples together. Five samples were considered the control and the names of the other 5 samples were declared to the person in charge of establishing the Consciousness Bond Field. The XRD results showed that the percentage of crystallization was lower in the control samples. The percentage of silver chloride phase formation on average was higher in the samples under the influence of TCF. The silver phase crystallite size on average was smaller on average under TCF. DLS showed that the particles size means in the samples under TCF was higher than in the control samples. Studying Zeta potential showed that the average of the obtained values regardless of the electric charge in the samples under TCF were higher than the control. TEM test showed that the samples under TCF had on average larger particle sizes than the control. The largest particle size in the control was 34.27 nm and, in the samples, under the TCF it was 54.72 nm. In the samples under the TCF, the average, particle size distribution was more uniform. It was found that the mean of particles with medium size in the group under the TCF was 29% larger than the control group. Therefore, Consciousness Bond Field can be used as a method to resize nanoparticles.
... Standard method for the synthesis of metal NPs (MNPs) involves the use of chemical (i.e., chemical reduction using a reducing agent), physical (e.g., irradiation, photochemical treatment) or mechanical processes (e.g., ultra-sonication). However, they have limitations, such as low yield, high cost, use of toxic chemicals, and high energy requirements (Chen et al., 2007;Khaydarov et al., 2009;Liu et al., 2017;Naikoo et al., 2021). Alternatively, more sustainable approaches are currently being explored to reduce the environmental impact of MNPs production methods, while improving their efficacy as pharmaceuticals and antiviral/antimicrobial nanomaterials (Lahiri et al., 2021). ...
Gold nanoparticles (AuNPs) have been explored for their use in medicine. Here, we report a sustainable, and cost-effective method to produce AuNPs using a bacterial strain such as Pseudomonas mendocina CH50 which is also known to be a polyhydroxyalkanoate (PHA) producer. A cell-free bacterial supernatant, which is typically discarded after PHA extraction, was used to produce spherical AuNPs of 3.5 ± 1.5 nm in size as determined by Transmission Electron Microscopy (TEM) analysis. The AuNPs/PHA composite coating demonstrated antibacterial activity against Staphylococcus aureus 6538P, and antiviral activity, with a 75% reduction in viral infectivity against SARS-CoV-2 pseudotype virus.
... This point to silver's intrinsic potential in the natural world. Conventionally AgNPs are prepared via physio-chemical methods such as chemical reduction [2,3], gamma-ray radiation [4], microemulsion [5], electrochemical method [6], laser ablation [7], autoclave [8], microwave [2,3] and photochemical reduction [9], which makes the use of toxic chemicals and high energy needs to provide with an effective yield. Plants are viewed as a reservoir of biological components that can be used to produce AgNPs in the green. ...
Silver being the auspicious metal on earth with immense potentialities have paved a way towards its biosynthesis from counterparts of plants as nanoparticles, which has opened up a new spectrum of applications in this scientific era. This study carves out an eco-friendly perspective towards the nanoparticles industry via inculcating green synthesis method for AgNP production from Wrightia arborea leaf extract. Once formed these biogenic AgNPs were characterized via UV–VIS, FTIR and XRD respectively. The UV–VIS spectrum showed maximum absorbance peak of AgNPs at 417 nm. FTIR spectra depicted the role of phytochemicals as stabilizing and capping agents. By using XRD diffractogram and Scherrer equation, the size of biosynthesized AgNPs were found to be 22.4 nm respectively. Based on these data, it was assumed that these biosynthesized AgNPs are spherical in shape. The present study investigates the cytogenetic and genotoxic effects of these biogenic silver nanoparticles on meristematic cells of Allium cepa root tips. In this study, onion root tips were treated with silver nanoparticle solutions of different concentrations (1, 5 and 10 mg /ml) along with control. Effects on cell division and chromosomes were observed at time periods of 1 and 24 h respectively. These biogenic AgNPs have the potential to be cytotoxic by inducing disturbances to A. cepa mitotic phases. These resulted chromosomal abnormalities showcase its potential towards genotoxicity. AgNPs, thus demonstrated a clear mito-depressive effect culminating in growth inhibition of the A. cepa roots. Mitotic inhibition and abnormality indices were recorded. The data demonstrated that these biosynthesized AgNPs exhibit both clastogenic and aneugenic activity. In a nutshell, it can be stated that, creating a proper awareness of potential genetic damage caused by biogenic AgNPs is crucial for testing its safety in environmental and related applications.
... Silver nanoparticles (AgNPs) have widely been used for the disinfection of medical and household devices, in cosmetology, wound dressing, treatment of water, as catalytic agents, and in the pharmaceutical and textile industries. Different methods have been used for the preparation of silver (Ag) NPs, i.e. photoreduction [8], sequential injection method [9], chemical reduction [10], photochemical reduction [11], electrochemical reduction [6], biosynthesis [12], lithography [13] and physical methods [14]. The size, shape, and chemical environment of AgNPs affect the optical, electrical, magnetic, and catalytic properties. ...
... The physical methods include laser ablation [21], spark discharging [22], and pyrolysis [23]. The chemical methods are electrochemical reduction [24], chemical reduction [25], solution irradiation [26], etc. The major process involved in chemical synthesis is the reduction of Ag + ions to AgNPs. ...
This article presents a simple, eco-friendly, and green method for the synthesis of silver nanoparticles (AgNPs) from AgNO3 solution utilizing an aqueous extract of Callisia fragrans leaf. The effects of C. fragrans leaf extraction conditions were evaluated. Parameters affecting the synthesis of AgNPs, such as the volume of extract, pH, temperature, and reaction time were investigated and optimized. The obtained AgNPs were analyzed by UV–Vis spectroscopy, X-ray diffraction pattern, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), and FTIR techniques. TEM and DLS analyses have shown that the synthesized AgNPs were predominantly spherical in shape with an average size of 48 nm. The zeta potential of the colloidal solution of AgNPs is −27 mV, indicating the dispersion ability of AgNPs. The results of GC–MS and FTIR analyses show the presence of biomolecules in the aqueous extract of C. fragrans leaf that acts as reducing and capping agents for the biosynthesis of AgNPs. The synthesized AgNPs demonstrate anticancer activity against MCF-7, HepG2, KB, LU-1, and MKN-7 cell lines, with inhibitory concentrations at 50% (IC50 values) of 2.41, 2.31, 2.65, 3.26, and 2.40 µg·mL⁻¹, respectively. The obtained results in the study show that the biosynthesized AgNP from C. fragrans leaf extract can be further exploited as a potential candidate for anticancer agents.
... With strong antibacterial activity, AgNPs have been used for effective regeneration and treatment in biomedical applications [12][13][14]. AgNPs have been fabricated using various techniques, including chemical reduction, gamma irradiation, microemulsion, electrochemical procedures, microwaves, and laser ablation [15][16][17]. Although these techniques produce AgNPs with good yields, there are limitations such as the use of toxic chemicals, high operating costs, and high energy requirements that need to be addressed [16,18]. ...
(1) Background: Infections of pathogenic microorganisms can be life-threatening due to delayed healing or even worsening conditions in tissue engineering and regenerative medicine. The excessive presence of reactive oxygen species in damaged and infected tissues causes a negative inflammatory response, resulting in failed healing. Thus, the development of hydrogels with antibacterial and antioxidant abilities for the treatment of infectious tissues is in high demand. (2) Methods: We herein describe the development of green-synthesized silver-composited polydopamine nanoparticles (AgNPs), which are fabricated by the self-assembly of dopamine as a reducing and antioxidant agent in the presence of silver ions. (3) Results: The facile and green-synthesized AgNPs have a nanoscale diameter with mostly spherical shapes, with various shapes coexisting. The particles are stable in an aqueous solution for up to 4 weeks. In addition, remarkable antibacterial activity against Gram-positive and -negative bacterial strains and antioxidant capabilities were evaluated by in vitro assays. When incorporated into biomaterial hydrogels at concentrations above 2 mg L−1, the hydrogels produced powerful antibacterial effects. (4) Conclusions: This study describes a biocompatible hydrogel with antibacterial and antioxidant activities from the introduction of facile and green-synthesized AgNPs as a safer tool for the treatment of damaged tissues.
... Therefore, to accelerate the modification reaction of MMT, microwave irradiation has been considered as an alternative method, due to its various benefits such as rapid heating to the reaction temperature, enhanced reaction rates, and formation of novel phases [180]. Taking into account the biological toxicity and the environmental hazard of the residual reducing agent, reduction by different approaches (i.e., UV irradiation [181], and γ-ray irradiation [182], it has been proposed as an alternative way to eliminate the use of toxic reductant and purification steps. Moreover, controlled NP size, with uniform distribution and improved antibacterial activity, is achievable by microwave irradiation method [183,184]. ...
One of the crucial challenges of our time is to effectively use metal and metal oxide nanoparticles (NPs) as an alternative way to combat drug-resistant infections. Metal and metal oxide NPs such as Ag, Ag2O, Cu, Cu2O, CuO, and ZnO have found their way against antimicrobial resistance. However, they also suffer from several limitations ranging from toxicity issues to resistance mechanisms by complex structures of bacterial communities, so-called biofilms. In this regard, scientists are urgently looking for convenient approaches to develop heterostructure synergistic nanocomposites which could overcome toxicity issues, enhance antimicrobial activity, improve thermal and mechanical stability, and increase shelf life. These nanocomposites provide a controlled release of bioactive substances into the surrounding medium, are cost effective, reproducible, and scalable for real life applications such as food additives, nanoantimicrobial coating in food technology, food preservation, optical limiters, the bio medical field, and wastewater treatment application. Naturally abundant and non-toxic Montmorillonite (MMT) is a novel support to accommodate NPs, due to its negative surface charge and control release of NPs and ions. At the time of this review, around 250 articles have been published focusing on the incorporation of Ag-, Cu-, and ZnO-based NPs into MMT support and thus furthering their introduction into polymer matrix composites dominantly used for antimicrobial application. Therefore, it is highly relevant to report a comprehensive review of Ag-, Cu-, and ZnO-modified MMT. This review provides a comprehensive overview of MMT-based nanoantimicrobials, particularly dealing with preparation methods, materials characterization, and mechanisms of action, antimicrobial activity on different bacterial strains, real life applications, and environmental and toxicity issues.
... The resulting image is an amorphous structure. However, it is seen in the literature that the severe broad peak between 20 and 30 thetas is attributed to chitosan (Chen et al., 2007;Akmaz et al., 2013). Additionally, the peaks of AgN are unfortunately not visible. ...
Diabetes-related wounds are a significant problem with serious consequences for both patients and health care systems. The aim of this study is to produce healing films that will expedite the healing of diabetic wounds in order to minimize the negative effects experienced by diabetic patients. For this purpose, films were produced by combining chitosan, which possesses the ability to accelerate wound healing, silver nanoparticles, well-known for their superior properties such as preventing the occurrence of microbiological activity and providing thermal stability, and ascorbic acid, also referred to as vitamin C, which the body requires during the treatment process. The films were evaluated by applying a series of characterization analyzes (XRD, FTIR, Transmission Electron Microscopy, DSC-TGA) to the produced films. In addition, the films were subjected to microbiological tests. Following that, the films’ swelling and ascorbic acid release behaviors were investigated in deionized water and a phosphate buffered saline solution with pH 7.4, respectively.
... Zinc nanoparticles have wide application; various synthetic methods have been employed to produce ZnNps [6] . Zinc nanoparticles can produced from zinc oxide and zinc sulphate. ...
Soil borne diseases which are caused to various plants include a wide variety of soil microbes like fungi and bacteria, among which Fusarium wilt is one such disease caused by Fusarium oxysporum cubense in banana plants. Wilt disease or the panama disease of plant is among the most destructive disease of banana in the tropics and even the control methods like field sanitation, soil treatments and crop rotations have not been a long term control for this disease. An alternative method of treating Fusarium oxysporum was adopted by using various natural plant leaves of Glycosmis pentaphylla and Azadirachta indica. Nanoparticles are small particles with a dimension of 10-9 and 10-10. Green synthesis is a new method developed for the synthesis of nanoparticles which is small in size, large surface area and eco- friendly. Leaf extracts of these plants were used for synthesis of copper and zinc nanoparticles, as nanoparticles are powerful antimicrobial agents. The extract is prepared with a stock solution of 100mM copper sulphate and 100mM zinc sulphate. The leaf extracts were prepared with 5 solvents (Distilled water, Propane, Hexane, Acetone and Methanol). The action of plant leaves were observed by the zone of inhibition obtained with a concentration of 50, 100 and 150µl respectively. The result was more in copper nanoparticles of leaf extract as compared to the zinc nanoparticles of particular leaf extracts but the zinc particles with methanol and propane showed good result with particular leaves. In dried condition of leaves copper nanoparticles with propane as solvent exhibited a greater zone of inhibition. Moreover the solvent, methanol showed good results with both zinc and copper nanoparticles. The synthesized nanoparticle were characterized by UV-VIS spectrophotometry to confirm the formation of nanoparticles. Green synthesis is used namely because of low cost, simple, use of less toxic materials, most important is eco-friendly.
... The silver nitrate dosimeter features a linear response and good measurements reproducibility [22]. The influence of γ-rays on AgNO 3 solution had been examined [29][30][31][32][33][34]. A liquid detector based on silver nitrate and 1% sodium citrate is introduced, where the ionizing radiation induces the formation of spherical AgNPs as recognized by the appearance of a sharp peak around 410 nm in the absorbance spectrum of the colloidal solution [35]. ...
The dosimetric characteristics of hydrogel dosimeters based on polyacrylamide (PAC) as a capping agent incorporating silver nitrate as a radiation-sensitive material are investigated using UV-Vis spectrophotometry within the dose range 0–100 Gy. Glycerol was used in the hydrogel matrix to promote the dosimetric response and increase the radiation sensitivity. Upon exposing the PAC hydrogel to γ-ray, it exhibits a Surface Plasmon Resonance (SPR) band at 453 nm, and its intensity increases linearly with absorbed doses up to 100 Gy. The results are compared with the silver nitrate gel dosimeter. Glycerol of 15% in the hydrogel matrix enhances the radiation sensitivity by about 30%. PAC hydrogel dosimeter can be considered a near water equivalent material in the 400 keV–20 MeV photon energy range. At doses less than 15 Gy, the PAC hydrogel dosimeter retains higher radiation sensitivity than the gel dosimeter. The total uncertainty (2σ) of the dose estimated using this hydrogel is about 4%. These results may support the validity of using this hydrogel as a dosimeter to verify radiotherapy techniques and dose monitoring during blood irradiation.
The surfaces of the works of art are one of their most important parts since they interact directly with the observer's perception. On the other hand, they are also in direct contact with physical, chemical and biological agents that can induce degradation and signs of aging. Dust deposits, stains and aged layers of protection can degrade, causing irreversible damage to works of art. In this way, the removal of undesirable materials from artistic surfaces is essential to preserve cultural heritage articles. The aim of this work was to develop silver nanoparticles-based hydrogels and to study the behavior regarding solvent concentration, stability and ability to clean dirt samples based on paper and canvas. The hydrogels were synthesized (reticulated) by gamma rays having the simultaneous formation of silver nanoparticles (AgNP) in the same process. The samples were characterized by swelling tests, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and optical microscopy (OM). The results showed the removal of dirt from the paper samples, as well as the softening of the dirt from the canvas, without leaving residues and without affecting the integrity of the art works submitted to treatment.
Recent surge in the occurrence of antimicrobial resistance genes among pathogenic
microbes has been a course of concern globally. Antimicrobial resistance is one of
the major threats to human health warranting research for more potent antimicrobial
agents. Nanoparticles are among the most promising novel therapeutic agents that
could be used against pathogens that exhibit diverse resistance to antibiotics. In
particular, silver nanoparticles were shown to exhibit great antimicrobial potency. In
contrast to chemical synthesis, plant extracts synthesized silver nanoparticles have no
known setbacks. The extracts caused the reduction of the metallic silver, formulation
and stabilization of the nanoparticles. This review has described that nanoparticles
structure, particle size and its zeta (ζ) potential are among the major factor that
influence its antimicrobial activity. In fact, as particle size decreases, the surface area�to-volume ratio greatly increases thus effecting maximum efficacy. The review has
presented in details on the biogenic synthesis of silver nanoparticles while extensively
exploring the mechanisms behind such antimicrobial potency. It is hope the review
will provide a reference information to both students and researchers as well as served
as a guide for policy makers in decision making regarding the possibility of using
silver nanoparticles as antimicrobial agents.
Recent surge in the occurrence of antimicrobial resistance genes among pathogenic
microbes has been a course of concern globally. Antimicrobial resistance is one of
the major threats to human health warranting research for more potent antimicrobial
agents. Nanoparticles are among the most promising novel therapeutic agents that
could be used against pathogens that exhibit diverse resistance to antibiotics. In
particular, silver nanoparticles were shown to exhibit great antimicrobial potency. In
contrast to chemical synthesis, plant extracts synthesized silver nanoparticles have no
known setbacks. The extracts caused the reduction of the metallic silver, formulation
and stabilization of the nanoparticles. This review has described that nanoparticles
structure, particle size and its zeta (ζ) potential are among the major factor that
influence its antimicrobial activity. In fact, as particle size decreases, the surface area�to-volume ratio greatly increases thus effecting maximum efficacy. The review has
presented in details on the biogenic synthesis of silver nanoparticles while extensively
exploring the mechanisms behind such antimicrobial potency. It is hope the review
will provide a reference information to both students and researchers as well as served
as a guide for policy makers in decision making regarding the possibility of using
silver nanoparticles as antimicrobial agents.
Poly(N-vinyl pyrrolidone/chitosan/Ag nanoparticles) Poly (NVP/CS/AgNPs) nanocomposite was prepared by using gamma radiation. Silver nitrate was reduced to AgNPs by using gamma radiation to create highly stable, and evenly dispersed AgNPs within the nanocomposite network. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis are used to identify the characteristics of the prepared nanocomposite. The newly biocompatible Poly (NVP/CS/AgNPs) nanocomposite prepared by the gamma radiation is used as a model for an anticancer drug. Regarding its application on cancer cells, the results of the outcome demonstrate that the Poly (NVP/CS/AgNPs) nanocomposite significantly decreased the HepG2 cell viability from 100% to 1.5% after 72 hours using the concentration of 30 µg/ml, and the IC50 recorded 10.024 µg/ml at 72 hours of treatment. Moreover, the treatment with the Poly (NVP/CS/AgNPs) nanocomposite increases the cytotoxicity against cancer cells at different concentrations 30 µg/ml and 3.75 µg/ml at different time intervals of 24, 48, and 72 hours. The percent change of MDA, and H 2 O 2 increased in treated cells, and was recorded at 127%, and 69%, respectively, but the CAT activity decreased by 47% in comparison with untreated cells. Relative gene expression was performed in the control, and treated group. The gene expression revealed that the Bcl-2 gene expression as the anti-apoptotic gene was downregulated in the treated group. In contrast, the apoptotic gene BAX was upregulated, and reached 7383-fold in the group treated. The Bax/ Bcl2 ratio reached 625.19 which is an excellent indicator of apoptosis. Using western blot, the protein expression increased for Caspse-3 and P53 recorded at 203% and 109%, respectively. In conclusion, Poly (NVP/CS/AgNPs) nanocomposite has a potent effect on killing cancer cells.
Green synthesis of silver nanoparticles was carried out using leaf extract from Calluna vulgaris. The formation of nanoparticles was confirmed through the emergence of a surface plasmon resonance band in ultraviolet-visible spectroscopy. The characterization conducted using various microscopic techniques revealed that the nanoparticles mostly ranged in size from approximately 20 to 70 nm. Analysis, including Fourier transform infrared spectrometry, X-ray diffraction, and energy-dispersive X-ray spectroscopy, confirmed the chemical, crystalline structure, and presence of silver, respectively. The synthesized nanoparticles exhibited notable stability with an average zeta potential of -23.1 ± 0.6 mV. Evaluation of their antibacterial activity against Staphylococcus aureus and Escherichia coli demonstrated significant efficacy with diameters of inhibition zones measuring 10.23 ± 0.54 mm and 15.38 ± 0.32 mm, respectively. Additionally, the nanoparticles displayed a remarkable inhibition of approximately 88% against E. coli biofilm formation at a concentration of 100 μg/mL. They also exhibited unique photocatalytic performances. This research contributes to the literature in this field by producing new silver nanoparticles with cost-effectiveness, stability, antibacterial, antioxidant, antibiofilm, and photocatalytic properties, while using a previously untapped plant extract for this purpose.
Radiation chemistry enables the synthesis of colloidal nanoparticles without chemical reducing agents, yielding metal nanoparticles via simple and direct processes. Aliphatic alcohols are widely used to promote the formation of nanoparticles in radiolytic synthesis by inhibiting the reoxidation of these metal nanoparticles by scavenging hydroxyl radicals. However, the role of the scavenger has been limited to simply accelerating the formation of the nanoparticles without altering their nature. Herein, the role of radical scavengers is investigated in determining the type of metal nanoparticles formed, with the scavenger concentration playing a crucial role. It is found that the addition of isopropyl alcohol controls the formation of hexagonal close‐packed (hcp) palladium hydride (PdHx) nanoparticles that are previously synthesized for the first time via radiation chemistry by increasing the concentrations of hydrated electrons and hydrogen radicals. This discovery reveals a more active role for radical scavengers in radiolytic syntheses, and this strategy can be used for the cost‐effective mass production of hcp PdHx nanoparticles.
The application of nanomaterials in different fields totally depends on their characteristics. Considering the impact of the synthesis method on the final product’s characteristics such as size and morphology, selection of the proper method is critical. In general, the nanomaterial synthesis methods can be classified into two main categories: top-down and bottom-up. In the top-down methods, bulk materials are converted into nanomaterials using specific techniques such as mechanical milling. In the bottom-up methods, following the selection of a suitable precursor and creation of adequate conditions, atoms and molecules will lie next to each other and make nanomaterials consequently. Although most of the top-down synthesis methods are capable of mass production of nanomaterials, the diversity and ease of the bottom-up synthesis methods have made this category more interesting. Different types of nanomaterials can be used as carriers for cancer therapy, including zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) nanomaterials. This chapter investigates the most important synthesis methods for the abovementioned nanomaterials and evaluates the corresponding effective parameters.
Recently, there has been a growing interest in silver nanoparticles (AgNPs) and their biomedical applications. Nevertheless, the clinical translation of such a promising technology into the global healthcare market encounters multiple obstacles. In the current chapter, we put some light on the market status and clinical profile of AgNPs as well as the technical, industrial, and regulatory challenges hampering their translation from the bench to the bedside. Then, some promising advancements that enable the clinical translation of AgNPs are highlighted, including the innovative high-throughput production technologies and the recruitment of AgNPs into the battle against the emerging infectious diseases and pandemics. Furthermore, AgNPs are compared versus other competitive nanotechnologies from a technical and clinical perspective. Lastly, we inspire the key aspects that should be considered for the successful translation of this area of endeavor into the clinics and the healthcare market.
Zinc oxide nanoparticles (ZnO NPs) are attracting the interest of researchers due to their potential applications in cancer treatment. It was recently shown that ZnO NPs specifically destroy cancer cells. However, the underlying molecular processes that drive ZnO NPs' anticancer activity are unclear. Radical polymerization was used for synthesizing zinc oxide nanoparticles using gamma radiation. Polyvinylpyrrolidone (PVP) was employed as a stabilizer in the production of zinc oxide nanoparticles using zinc nitrate. PVP@ZnO nanostructures were characterized using a number of techniques, including high‐resolution transmission electron microscopy (HRTEM) and UV–visible spectroscopy. Fourier‐transform infrared spectroscopy (FTIR) was used to study the functional groups of the produced nanostructures. Moreover, the surface morphology of prepared zinc oxide nanoparticles (ZnO NPs) and PVP@ZnO nanostructures was shown using SEM. In addition, the crystalline structure of the aforementioned samples was identified and investigated via XRD. The current work examined the anticancer effect of ZnO nanocomposite against rat hepatocellular carcinoma (HCC). The results demonstrated that ZnO nanocomposite exert distinct effects on apoptosis and PGC‐1α pathways in hepatocellular carcinoma in rats. mRNA levels of tumor suppressor gene p53 and antiapoptotic gene BCL‐2 were downregulated, while the apoptotic gene Bax was upregulated and Caspase‐3 activity increased in diethylnitrosamine (DEN) + ZnO nanocomposite‐treated rats in comparison with DEN‐treated rats. ZnO nanocomposite were also found to have an effect on liver function (ALT, AST, ALP, and GGT) and total antioxidant capacity (TAC). Treatment with DEN manifested a significant decrease in the expression of mtTFA and PGC‐1α (mtTFA: 0.54 fold and PGC‐1α: 0.31 fold in respect to the normal control), while ZnO nanocomposite treatment induced a remarkable increase in their expression. In conclusion, the present data demonstrated that ZnO nanocomposite showed anticancer activity via induction of apoptosis and PGC‐1α pathways. In addition, improvements in liver function and antioxidant capacity.
Chitosan and bauxite as natural compounds were applied for the synthesis of chitosan/bauxite (CS/B) as heterogeneous catalyst and this novel catalyst was characterized using several techniques such as FTIR, XRD, FESEM, EDX, TEM, BET and TGA analysis. The as-synthesized catalyst showed more stability and specific surface area compared to those of starting materials. The CS/B catalyst was tested in the Knoevenagel condensation under various condition and the best yield was achieved in ethanol at room temperature. The advantage of CS/B is ecofriendly, thermal stability, low-cost preparation and simple work-up. Further, the as-synthesized catalyst can be recycled for four times and it can suggest benefit heterogeneous catalyst with high yield for the organic reaction. It is notable that the components of CS/B are completely natural materials, and this catalyst is the combination of organic and inorganic compounds with high advantages.
Silver being the auspicious metal on earth with immense potentialities have paved a way towards its biosynthesis from counterparts of plants as nanoparticles, which has opened up a new spectrum of applications in this scientific era. This study carves out an eco-friendly perspective towards the nanoparticles industry via inculcating green synthesis method for AgNP production from Wrightia arborea leaf extract. Once formed these biogenic AgNPs were characterized via UV–VIS, FTIR and XRD respectively. The UV–VIS spectrum showed maximum absorbance peak of AgNPs at 417 nm. FTIR spectra depicted the role of phytochemicals as stabilizing and capping agents. By using XRD diffractogram and Scherrer equation, the size of biosynthesized AgNPs were found to be 22.4 nm respectively. Based on these data, it was assumed that these biosynthesized AgNPs are spherical in shape. The present study investigates the cytogenetic and genotoxic effects of these biogenic silver nanoparticles on meristematic cells of Allium cepa root tips. In this study, onion root tips were treated with silver nanoparticle solutions of different concentrations (1, 5 and 10 mg /ml) along with control. Effects on cell division and chromosomes were observed at time periods of 1 and 24 h respectively. These biogenic AgNPs have the potential to be cytotoxic by inducing disturbances to A. cepa mitotic phases. These resulted chromosomal abnormalities showcase its potential towards genotoxicity. AgNPs, thus demonstrated a clear mito-depressive effect culminating in growth inhibition of the A. cepa roots. Mitotic inhibition and abnormality indices were recorded. The data demonstrated that these biosynthesized AgNPs exhibit both clastogenic and aneugenic activity. In a nutshell, it can be stated that, creating a proper awareness of potential genetic damage caused by biogenic AgNPs is crucial for testing its safety in environmental and related applications.
A flexible nanocomposite film based on polyvinyl alcohol (PVA), silver nanoparticles, and calcium titanate (CaTiO3) was synthesized using gamma radiation induced-reduction. Temperature-dependent structural, optical, DC electrical conductivity, electric modulus, and dielectric properties of PVA/Ag/CaTiO3 nanocomposite film were investigated. The XRD pattern proved the successful preparation of the nanocomposite film. Also, as the temperature increases, the average crystallite sizes of CaTiO3 and Ag nanoparticles decrease from 19.8 to 9.7 nm and 25 to 14.8 nm, respectively. Further, the optical band gap increased from 5.75 to 5.84 eV with increasing temperature. The thermal stability is improved, and the semiconductor behavior for PVA/Ag/CaTiO3 nanocomposite film is confirmed by thermal activation energy ΔE with values in the 0.11–0.8 eV range. Furthermore, the maximum barrier Wm value was found of 0.29 eV. PVA/Ag/CaTiO3 nanocomposite film exhibits a semicircular arc originating from the material’s grain boundary contributions for all temperatures. The optical, DC electrical conductivity, and dielectric properties of the PVA/Ag/CaTiO3 nanocomposite film can be suitable for flexible electronic devices such as electronic chips, optoelectronics, and energy storage applications.
Ag and ZnO nanoparticles (NPs) were synthesized by a green synthesis from a Pinus latteri tree extraction. Characterizations of the as-prepared Ag and ZnO NPs were determined by DSC/TGA analyses, XRD patterns, and FE-SEM images. The average particles of the as-prepared materials, including Ag NPs and ZnO NPs, are approximately 25 nm and 45 nm, respectively. The XRD patterns confirmed the presence of the Ag metal and ZnO wurtzite crystalline phases. In addition, an agar-well diffusion method was used to evaluate the Escherichia coli (E. coli) antibacterial activity of as-prepared materials. Results show that Ag NPs and ZnO NPs have a high inhibitory ability against E. coli bacteria. Specially, E. coli antibacterial activity of Ag NPs is higher than ZnO NPs under the same conditions.
Herein, a gamma irradiation cell consist of a borated polyethylene (BPE) cylinder with a cadmium inner wall was designed and constructed at Isfahan miniature neutron source reactor (MNSR) for synthesize of metal nanoparticles. The cell is placed in a dry channel irradiation site near the reactor core. The performance of this irradiation cell with appropriate shape and size was evaluated and the neutron flux (φ) and the neutron and gamma dose rates (Dn and Dg) inside it are calculated using MCNP code. The results showed that the designed cell could deliver appropriate gamma dose rate to samples and reduce the thermal neutron flux from 5.82×1010 to 6.28×107 n.cm-2.s-1, i.e. over 99.89% attenuation. Also, the gamma dose rate inside the designed neutron shield is calculated to be 3.83 kSv.h-1. To evaluate the designed and constructed cell, synthesis of Pd and Ag nanoparticles (NPs) on SiO2 supporter was done. Prepared nanocomposites were characterized by using XRD, FE-SEM, and EDXA techniques. Observed results showed metallic Pd and Ag NPs were produced successfully by means of a designed gamma irradiation cell at the reactor via gamma assisted route in nanometer sizes for the first time.
Nanocomposite hydrogels were prepared by gamma-radiation copolymerization of poly (vinyl pyrrolidone) (PVP)/sodium alginate (AG) in the presence of silver nanoparticles (Ag NPs). The effect of irradiation dose and Ag NPs content on the gel content and swelling characters of PVP/AG/Ag NPs copolymers was investigated. In addition, the structure-property behavior of the copolymers was characterized by IR spectroscopy, thermogravimetric analysis (TGA) and x-ray diffraction (XRD). The drug uptake-release characters of PVP/AG/silver NPs copolymers, taking Prednisolone as a model drug, were studied. The study showed that the appropriate dose of gamma irradiation to achieve homogeneous nanocomposites hydrogel films and the highest swelling in water was 30 kGy, regardless of composition. The introduction of Ag NPs up to 5 wt% improved the physical properties and enhanced the drug uptake-release characters.
Nowadays, hybrid silver nanoparticles showed high surface active properties, cost-effective synthesis, and rapidly fabricated nanocomposites. The enormous novel behavior of silver nanoparticles widens its application area in various fields. This chapter summarizes the synthesis of silver nanoparticles, the different spectroscopic tools required, the role of doping, and the applications of silver nanoparticles. Here, we discuss different techniques for the removal of pollutants via photocatalysis, adsorption, oxidation, reaction mechanism, and reduction process with silver nanomaterials and also focus on the importance of green synthesized nanoparticles. The morphological distribution of silver nanoparticles affects its electromagnetic, catalytic, and optical properties by changing the stabilizers and artificial methods and reducing pollutants. This includes the methods of fabrication of silver nanomaterials with their applications and doped and modified nanocomposites with the upsurge of their surface activity. This research gap is also discussed in the form of future scope
Nanotechnology is an emerging field of science with increased applications in diverse area for the development of new materials at nanoscale levels. Synthesis of nanoparticles using biological methods is referred as greener synthesis of nanoparticles. Pulses exudates of seven different legumes; Fenugreek (Trigonellafoenum-graecum), Green peas (Pisum sativum L.) and Peanut (Arachis hypogaea L.) were used for the synthesis of silver, copper, and zinc nanoparticles and determine the antibacterial properties of these nanoparticles against Escherichia coli (E. coli), Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Klebsiella pneumoniae. Nanoparticles prepared from these seed extracts have antibacterial activity. Synthesized nanoparticles were characterized by UV-VIS Spectrophotometry. Silver nanoparticles shows maximum peak at 385 nm. Copper nanoparticles shows maximum peak at 680 nm. Zinc nanoparticles shows maximum peak at 350 nm. Synthesized silver, copper and zinc nanoparticles shows antibacterial activity against the selected bacterial species. Antimicrobial assay was performed by agar well diffusion method using Muller Hinton agar media. When antibacterial activity of silver, copper and zinc nanoparticles from 3 different concentrations were observed, nanoparticles have 150 μl concentration shows maximum activity against these microbes. Silver, Copper and Zinc nanoparticles showed greater antibacterial activity compared to silver nitrate, copper sulphate and zinc sulphate solution. This green synthesis method is alternative to chemical method, since it is cheap, pollutant free and eco-friendly.
Nanotechnology is an emerging field of science with increased applications in diverse area for the development of new materials at nanoscale levels. Synthesis of nanoparticles using biological methods is referred as greener synthesis of nanoparticles. Pulses exudates of two different legumes; Chick pea (Cicer arietinum L.) and Black gram (Vigna mungo (L.) Hepper)were used for the synthesis of silver, copper, and zinc nanoparticles anddetermine the antibacterial properties of these nanoparticles against Escherichia coli (E. coli), Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Klebsiella pneumoniae. Nanoparticles prepared from these seed extracts have antibacterial activity. Synthesized nanoparticles were characterized by UV-VIS Spectrophotometry. Silver nanoparticles shows maximum peak at 385 nm. Copper nanoparticles shows maximum peak at 680 nm. Zinc nanoparticles shows maximum peak at 350 nm. Synthesized silver, copper and zinc nanoparticles shows antibacterial activity against the selected bacterial species. Antimicrobial assay was performed by agar well diffusion method using Muller Hinton agar media. when antibacterial activity of silver, copper and zinc nanoparticles from 3 different concentrations were observed, nanoparticles have 150 μl
concentration shows maximum activity against these microbes. Silver, Copper and Zinc nanoparticles showed greater antibacterial activity compared to silver nitrate, copper sulphate and zinc sulphate solution. This green synthesis method is alternative to chemical method, since it is cheap, pollutant free and eco-friendly.
Nanotechnology is an emerging field of science with increased applications in diverse area for the development of new materials at nanoscale levels. Synthesis of nanoparticles using biological methods is referred as greener synthesis of nanoparticles. Pulses exudates of two different legumes; Mung bean (Vigna radiata), Cowpea (Vigna unguiculata)were used for the synthesis of silver, copper, and zinc nanoparticles anddetermine the antibacterial properties of these nanoparticles against Escherichia coli (E. coli), Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Klebsiella pneumoniae. Nanoparticles prepared from these seed extracts have antibacterial activity. Synthesized nanoparticles were characterized by UV-VIS Spectrophotometry. Silver nanoparticles shows maximum peak at 385 nm. Copper nanoparticles shows maximum peak at 680 nm. Zinc nanoparticles shows maximum peak at 350 nm. Synthesized silver, copper and zinc nanoparticles shows antibacterial activity against the selected bacterial species. Antimicrobial assay was performed by agar well diffusion method using Muller Hinton agar media. When antibacterial activity of silver, copper and zinc nanoparticles from 3 different concentrations were observed, nanoparticles have 150 μl concentration shows
maximum activity against these microbes. Silver, Copper and Zinc nanoparticles showed greater antibacterial activity compared to silver nitrate, copper sulphate and zinc sulphate solution. This green synthesis method is alternative to chemical method, since it is cheap, pollutant free and eco-friendly.
This chapter briefly discusses immense research on chitosan-based nanomaterials as well as also highlights the current developments and their utility in different applications majorly focusing on the biomedical field. Chitosan is a well-known nontoxic, biocompatible, and biodegradable polymer possessing enormous possibilities for structural modification either by chemical or mechanical pathways, thereby generating novel polymeric designs with enhanced properties and functions, particularly in biology. Chitosan has been used as a fascinating biomaterial in developing different types of drug delivery techniques, as regenerative medicine in the area of health science or pharmacy. Tremendous use of agrochemicals for increasing crop production and their protection causes significant health and environmental concerns; therefore, chitosan-based nanomaterials such as nanoparticles, hydrogels, and nanocomposites have been applied in agriculture due to their unique antimicrobial and plant growth-promoting properties. These special properties endorse chitosan with promising potentialities for development in biomedicine fields like drug delivery, gene delivery, cell and molecular imaging, development of different sensors, and the treatment and diagnosis of some diseases like cancer, neurodegenerative diseases, etc. In contrast to the native chitosan, the chitosan-based nanomaterials are known to exhibit improved chemical, mechanical, and physical properties like higher surface area, tensile strength, porosity, conductivity, photo-luminescence, etc. This chapter focuses on the current research aspects of chitosan-based nanomaterials by highlighting their properties and potentialities in different domains.
Antibacterial resistance is by far one of the greatest challenges to global health. Many pharmaceutical or material strategies have been explored to overcome this dilemma. Of these, silver nanoparticles (AgNPs) are known to have a non-specific antibacterial mechanism that renders it difficult to engender silver-resistant bacteria, enabling them to be more powerful antibacterial agents than conventional antibiotics. AgNPs have shown promising antibacterial effects in both Gram-positive and Gram-negative bacteria. The aim of this review is to summarize the green synthesis of AgNPs as antibacterial agents, while other AgNPs-related insights (e.g., antibacterial mechanisms, potential toxicity, and medical applications) are also reviewed.
Soil borne diseases which are caused to various plants include a wide variety of soil microbes like fungi and bacteria, among which Fusarium wilt is one such disease caused by Fusarium oxysporum cubense in banana plants. Wilt disease or the panama disease of plant is among the most destructive disease of banana in the tropics and even the control methods like field sanitation, soil treatments and crop rotations have not been a long term control for this disease. An alternative method of treating Fusarium oxysporum was adopted by using various natural plant leaves of Ocimum tenuiflorum and Tabernaemontana divaricate. Nanoparticles are small particles with a dimension of 10-9 and 10-10. Green synthesis is a new method developed for the synthesis of nanoparticles which is small in size, large surface area and eco- friendly. Leaf extracts of these plants were used for synthesis of copper and zinc nanoparticles, as nanoparticles are powerful antimicrobial agents. The extract is prepared with a stock solution of 100mM copper sulphate and 100mM zinc sulphate. The leaf extracts were prepared with 5 solvents (Distilled water, Propane, Hexane, Acetone and Methanol). The action of plant leaves were observed by the zone of inhibition obtained with a concentration of 50, 100 and 150µl respectively. The result was more in copper nanoparticles of leaf extract as compared to the zinc nanoparticles of particular leaf extracts but the zinc particles with methanol and propane showed good result with particular leaves. In dried condition of leaves copper nanoparticles with propane as solvent exhibited a greater zone of inhibition. Moreover the solvent, methanol showed good results with both zinc and copper nanoparticles. The synthesized nanoparticle were characterized by UV-VIS spectrophotometry to confirm the formation of nanoparticles. Green synthesis is used namely because of low cost, simple, use of less toxic materials, most important is eco-friendly.
Soil borne diseases which are caused to various plants include a wide variety of soil microbes like fungi and bacteria, among which Fusarium wilt is one such disease caused by Fusarium oxysporum cubense in banana plants. Wilt disease or the panama disease of plant is among the most destructive disease of banana in the tropics and even the control methods like field sanitation, soil treatments and crop rotations have not been a long term control for this disease. An alternative method of treating Fusarium oxysporum was adopted by using various natural plant leaves of Gliricidia sepium and Piper nigrum. Nanoparticles are small particles with a dimension of 10-9 and 10-10. Green synthesis is a new method developed for the synthesis of nanoparticles which is small in size, large surface area and eco- friendly. Leaf extracts of these plants were used for synthesis of copper and zinc nanoparticles, as nanoparticles are powerful antimicrobial agents. The extract is prepared with a stock solution of 100mM copper sulphate and 100mM zinc sulphate. The leaf extracts were prepared with 5 solvents (Distilled water, Propane, Hexane, Acetone and Methanol). The action of plant leaves were observed by the zone of inhibition obtained with a concentration of 50, 100 and 150µl respectively. The result was more in copper nanoparticles of leaf extract as compared to the zinc nanoparticles of particular leaf extracts but the zinc particles with methanol and propane showed good result with particular leaves. In dried condition of leaves copper nanoparticles with propane as solvent exhibited a greater zone of inhibition. Moreover the solvent, methanol showed good results with both zinc and copper nanoparticles. The synthesized nanoparticle were characterized by UV-VIS spectrophotometry to confirm the formation of nanoparticles. Green synthesis is used namely because of low cost, simple, use of less toxic materials, most important is eco-friendly.
In this project, a bio-based heterogeneous catalyst is synthesized via multi steps process. First, nano-rod hydroxyapatite modified by silica compound is prepared, functionalized with of some nitrogen sources linkages such as, 4-aminoacetanilide and consequent immobilization of Ag nanoparticles by Sorbus aucuparia extract. The as-prepared catalyst, [email protected]@SiO2-TAA, was successfully characterized by using FTIR, XRD, BET, SEM/EDX, TGA, TEM, ICP-AES and elemental mapping analysis. Furthermore, metal-ligand interactions in [email protected]@SiO2-TAA complex models were assessed to interpret the immobilization behavior of Ag-NPs on the surface of nano-rod hydroxyapatite through quantum chemistry computations. The catalytic activity of the [email protected]@SiO2-TAA was investigated in multi-component Hantzcsh reactions under mild conditions to furnish the corresponding products in high yields and short reaction times. Moreover, the recyclability study and Ag leaching of the [email protected]@SiO2-TAA verified that the catalyst could be easily recovered and also recycled up to six runs with only slight loss of activity.
We present a simple method for the optical manipulation and spectroscopy of colloidal silver nanoparticles in aqueous solution using optical tweezers combined with dark-field microscopy. Because of their localized plasmon resonances, single trapped metal nanoparticles can be used as efficient near-field optical probes, with potential applicability in surface-enhanced spectroscopy, near-field microscopy, and biochemical sensing schemes. As a proof of principle, we study the near-field optical interaction between a trapped and an immobilized Ag nanoparticle.
Several differently prepared silver sols and a gold sol were examined using electron microscopy optical absorption and microelectrophoresis techniques. The effects of 4-dimethyl-amino-pyridine and pyridine addition to the sols were also studied. In all cases of amine adsorption onto the sol particles, an accompanying decrease in the magnitude of the electrophoretic mobility of the particles was observed, and a long wavelength (>500 nm) absorption band was formed. The solution species responsible for these changes is an aggregate composed of the primary sol.
The nanocomposites of stable nanosilver particles embedded in polyacrylonitrile matrix were synthesized by /gamma-irradiation, in which the monomer acrylonitrile was polymerized and the silver ions were reduced simultaneously by /gamma-irradiation to form composites in situ. The strong interactions between silver ions with -CN groups of polyacrylonitrile are found, which were confirmed by X-ray powder diffraction, IR spectrum and absorption spectra.
Poly(acrylic acid)–metal nanocomposites were synthesized by irradiating the solutions of metal ions (Ag+, Cu2+, Ni2+) in acrylic acid monomer with γ-ray. The products are characterized by XRD and TEM. It was found that the nanometer metal particles are well dispersed in poly(acrylic acid) with a narrow-size distribution.
Polyacrylamide–silver nanocomposites with a silver particle size
distribution ranging from 2 to 20 nm in a polyacrylamide matrix are
synthesized by γ-irradiation at room temperature.
Electron-transfer processes between simple 1-hydroxyalkyl, 1-ethoxyethyl, and 2-hydroxycyclohexadienyl radicals and metal ions at the surface of colloidal silver are described. C6H6OH radicals are oxidized by Ag+ to yield phenol. In the absence of Ag+, no electron exchange between C6H6OH and the silver particles takes place. When the silver particles carry a tiny deposit of thallium metal, the C6H6OH radicals are reduced. Cu+ (and Cu2+) ions adsorbed on the silver particles oxidize C6H6OH radicals. However, reduction of C6H6OH by Cu+ occurs, if the silver particles are covered with copper metal. 1-Hydroxyalkyl and 2-ethoxyethyl radicals reduce Tl+ ions in the presence of colloidal silver, but oxidize Tl atoms in homogeneous solution. Water can be decomposed to yield H2 by 1-hydroxy-1-methyl and 1-hydroxyethyl, but not by 1-hydroxymethyl, 1-ethoxyethyl, and 2-hydroxycyclohexadienyl radicals. These findings are discussed in terms of standard potentials for the oxidation and reduction of the radicals and in terms of distributions of occupied and unoccupied electronic redox levels in the radicals and the colloidal metal. In these experiments γ radiolysis was used to produce the radicals at a controlled rate.
Ag+ ions, in aqueous polyvinyl alcohol (PVA) solution and in PVA hydrogel matrix have been gamma radiolytically reduced to produce Ag clusters. UV-visible absorption spectral characteristics of Ag clusters obtained under different gamma dose, Ag+ concentration, PVA concentration and crosslinking density of the gel used have been studied. The effect of Ag+ ions on the radiation crosslinking of the PVA chains, have also been investigated by viscosity measurements. The radiation-induced Ag+ ion reduction was followed by crosslinking of the PVA chains. PVA was found to be a very efficient stabilizer to prevent aggregation of Ag clusters. The clusters produced in the hydrogel matrix were expected to be smaller than the pore size (∼2–20nm) of the gels used in the study. These Ag clusters were unable to reduce methyl viologen (MV2+) chloride and were stable in air.
A report on the structure of trimer silver crystal Ag32+ was presented in the article. During the growth of small colloidal silver clusters in aqueous solution, the trimer silver ion exhibits a remarkable behavior in that this species represents the changeover from pseudo-first-order reaction mechanisms to second-order mechanisms. This model explained experimental observations such as the relative stability of trimer clusters and also the formation of silver clusters of a specific number of atoms i.e., the 'magic' clusters.
The nanocomposites of stable nanosilver particles embedded in polyacrylonitrile matrix were synthesized by γ-irradiation, in which the monomer acrylonitrile was polymerized and the silver ions were reduced simultaneously by γ-irradiation to form composites in situ. The strong interactions between silver ions with –CN groups of polyacrylonitrile are found, which were confirmed by X-ray powder diffraction, IR spectrum and absorption spectra.
Colloidal silver has been formed either by irradiation with 253.7 nm light or by chemical reduction of AgClO4 in the presence of protective agents such as poly(vinylpyrrolidone), carboxy methyl cellulose, and gelatin. The particles were characterized by their absorption maximum and transmission electron micrographs. Peptization effect was observed in the presence of photosensitive benzophenone. Surface modification studies of silver particles in the presence of various complexing agents, viz., N-(hydoxyethyl)ethylenediaminetriacetic acid, iminodiacetic acid, nitrilotriacetic acid, 2-mercaptobenzimidazole, benzotriazole, 5-aminotetrazole, imidazole, and sanazole were carried out and it was shown that the reactivity of silver particles increases in their presence. However, in the presence of stabilizers, due to competitve reactions, partial recovery of the surface plasmon absorption band was observed. The Fermi potential of surface modified silver particles seems to lie in the range of −0.40 ± 0.05 V.
Ag(CN)2- is reduced at a low rate by radiolytically generated hydroxymethyl radicals. The reduction occurs on tiny nuclei in solution formed by hydrolysis. When colloidal silver seed particles are present in the solution, the reduction of Ag(CN)2- is much faster, and larger silver particles with a narrow size distribution are produced. A mechanism is proposed, in which the •CH2OH radicals transfer electrons to the seed particles, and the stored electrons finally reduce Ag(CN)2- directly on the surface of the seeds. The limitations of this kind of radiolytic particle enlargement are discussed. In the presence of colloidal platinum, Ag(CN)2- is also rapidly reduced by the organic radicals. Bimetallic particles of the PtcoreAgshell type with a rather nonsymmetric shape of the shell are formed; despite this irregular structure, the optical spectra agree fairly well with literature spectra calculated for symmetric bimetallic particles.
Organic free radicals of high negative redox potential such as ..cap alpha..-alcohol radicals were found to transfer electrons to colloidal silver particles stabilized by sodium dodecyl sulfate in aqueous solution. The colloidal particles thus became a pool of stored electrons that could reduce water to form hydrogen or react with suitable acceptors in solution. The organic radicals were produced by irradiation, using suitable scavengers for the primary radicals from the radiolysis of the aqueous solvent. The solutions initially contained silver ions at 1 x 10â»â´ - 2 x 10â»Â³ M. At doses below 10âµ rd, the silver ions were completely reduced to form the colloidal catalyst. In this dose range, the corresponding hydrogen yield amounted to 1 molecule per 100 eV. It increased steeply at higher doses up to 3 molecules per 100 eV. The Hâ yield decreased with increasing dose rate and with increasing pH in alkaline solutions. It was highest at a concentration of sodium dodecyl sulfate of 1 x 10â»Â³ M, i.e., far below the critical micelle concentration of this surfactant. Changes in the absorption spectrum of the colloid are attributed to changes in the size of the silver particles upon charging up with electrons. The competition of radical-colloid reactions with radical-radical deactivation in the bulk of solution or at the surface of the colloidal particles is also discussed. 11 figures.
Ag+ ions are reduced in aqueous solutions by a short pulse of high-energy radiation. At the low radiation dose applied, second-order reactions of the early intermediates are negligible. Three elementary processes occur during microseconds after the pulse, in each of which Ag+ is a reactant: e(aq)(-) + Ag+ --> Ag-0 (k = 4.8 x 10(10) M(-1) s(-1)); Ag-0 + Ag+ --> Ag-2(+) (k = 8.5 x 10(9) M(-1) s(-1)); Ag-2(+) + Ag+ --> Ag-3(2+) (k = 2.0 X 10(9) M(-1) s(-1)). The reactions overlap temporally. Computer simulation is used to obtain the rate constants and the absorption spectra of the three species involved. Ag-3(2+) has not yet been detected in water at ambient temperature; it was known to exist only in zeolite cages and frozen organic glasses.
Silver nanoparticles were synthesized by irradiating solutions, prepared by mixing AgNO3 and poly-vinyl alcohol (PVA), with 6 MeV electrons. The electron-irradiated solutions and the thin coatings cast from them were characterized using the ultraviolet–visible (UV–vis), x-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. During electron irradiation, the process of formation of the silver nanoparticles appeared to be initiated at an electron fluence of ~2 × 1013 e cm−2. This was evidenced from the solution, which turned yellow and exhibited the characteristic plasmon absorption peak around 455 nm. Silver nanoparticles of different sizes in the range 60–10 nm, with a narrow size distribution, could be synthesized by varying the electron fluence from 2 × 1013 to 3 × 1015 e cm−2. Silver nanoparticles of sizes in the range 100–200 nm were also synthesized by irradiating an aqueous AgNO3 solution with 6 MeV electrons.
Ag/cross-linked poly(vinyl alcohol) (PVA) cable-like nanostructures
were synthesized with control in an aqueous solution of a hydrolysable
amphiphilic block polymer, poly(vinyl acetone) (PVKA) (ketalization degree
DH = 0.533)
under γ-ray irradiation, via one-step in situ reduction of
Ag+
and cross-linking of alcohol units. In the present approach, we try to control the speed of
the cross-linking reaction of PVA chains (alcohol units), which are yielded from the
hydrolysed PVKA, utilizing the low hydrolysis rate of the PVKA in dilute acidic solution.
Ag nanoparticles were synthetized in the interlamellar space of a layered kaolinite clay mineral. Disaggregation of the lamellae of non-swelling kaolinite was achieved by intercalation of dimethyl sulfoxide. The kaolinite was suspended in aqueous AgNO3 solution and, after adsorption of Ag+, the ions were reduced with NaBH4. The interlamellar space limits particle growth (dave=3.8–4.2 nm); however, larger silver particles may be formed on the exterior surface of kaolinite with dave=5.6–10.5 nm diameter. The diameter of the particles prepared in this way is depending on the initial AgNO3 concentration. The silver nanoparticles prepared were characterized by UV–vis spectroscopy, X-ray diffraction (XRD), Small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM).
The elucidation of the long range distance dependence of the localized surface plasmon resonance (LSPR) of surface-confined noble metal nanoparticles is the aim of this work. It was suspected that the linear distance dependence found in CH 3 (CH 2) x SH self-assembled monolayer (SAM) formation was the thin shell limit of a longer range, nonlinear dependence. To verify this, multilayer SAM shells based on the interaction of HOOC-(CH 2) 10 SH and Cu 2+ were assembled onto surface-confined noble metal nanoparticles and were monitored using UV-visible spectroscopy. Measurement of the LSPR extinction peak shift versus number of layers and adsorbate thickness is nonlinear and has a sensing range that is dependent on the composition, shape, in-plane width, and out-of-plane height of the nanoparticles. Theoretical calculations based on an accurate electrodynamics description of the metal nanoparticle plus surrounding layered material indicate plasmon resonance wavelength shifts that are in excellent agreement with the measurements. The calculations show that the sensing range is determined by falloff of the average induced electric field around the nanoparticle. This detailed set of experiments coupled with an excellent theory versus experiment comparison prove that the sensing capabilities of noble metal nanoparticles can be size tuned to match the dimensions of biological and chemical analytes by adjusting the aforementioned properties. The optimization of the LSPR nanosensor for a specific analyte will significantly improve an already sensitive nanoparticle-based sensor.
Silver and gold nanotriangles were fabricated by nanosphere lithography (NSL) and their localized surface plasmon resonance (LSPR) spectra were measured by UV-vis extinction spectroscopy. It is demonstrated that the short range (viz., 0-2 nm) distance dependence of the electromagnetic fields that surround these nanoparticles when resonantly excited can be systematically tuned by changing their size, structure, and composition. This is accomplished by measuring the shift in the peak wavelength, λ max , of their LSPR spectra caused by the adsorption of hexadecanethiol as a function of nanoparticle size (in-plane width, out-of-plane height, and aspect ratio), shape (truncated tetrahedron versus hemisphere), and composition (silver versus gold). We find that the hexadecanethiol-induced LSPR shift for Ag triangles decreases when in-plane width is increased at fixed out-of-plane height or when height is increased at fixed width. These trends are the opposite to what was seen in an earlier study of the long range distance dependence in which 30 nm thick layers were examined (Haes et al. J. Phys. Chem. B 2004, 108, 109), but both the long and short range results are confirmed by a theoretical analysis based on finite element electrodynamics. The theory results also indicate that the short range results are primarily sensitive to hot spots (regions of high induced electric field) near the tips of the triangles, so this provides an example where enhanced local fields play an important role in extinction spectra. Our measurements further show that the hexadecanethiol-induced LSPR peak shift is larger for nanotriangles than for hemispheres with equal volumes and is larger for Ag nanotriangles than for Au nanotriangles with the same in-plane widths and out-of-plane heights. The dependence of the alkanethiol-induced LSPR peak shift on chain length for Ag nanotriangles is approximately size-independent. We anticipate that the improved understanding of the short range dependence of the adsorbate-induced LSPR peak shift on nanoparticle structure and composition reported here will translate to significant improvements in the sensitivity of refractive-index-based nanoparticle nanosensors.
Gamma radiolysis method was used to prepare polyvinyl alcohol (PVA) capped silver nanoparticles by optimizing various conditions like metal ion concentration and polymer (PVA) of different molecular weights. The role of different scavengers was also studied. The decrease in particle size was observed with increase in the molecular weight of capping agent. γ-radiolytic method provides silver nanoparticles in fully reduced and highly pure state. XRD (X-ray diffraction) technique confirmed the zero valent state of silver. Optical studies were done using UV-visible spectrophotometer to see the variation of electronic structure of the metal sol. Transmission Electron Microscopic (TEM) studies reveal the fcc geometry. The TEM show clearly split Debye-Scherrer rings. The d values calculated from the diffraction ring pattern are in perfect agreement with the ASTM data. Ag particles less than 10 nm are spherical in shape, whereas the particles above 30 nm have structure of pentagonal biprisms or decahedra, referred to as multiply twinned particles.
The labeling of biological species using dyes has become common practice to aid in their detection, and immediate positive identification of specific dyes in high dilution is a key requirement. Here the detection by surface-enhanced resonance Raman scattering (SERRS) of eight commercially available dye labels (ROX, rhodamine 6G, HEX, FAM, TET, Cy3, Cy5, TAMRA) attached to oligonucleotide strands is reported. Each of the eight labels was easily detected by using the SERRS from silver nanoparticles to produce a unique, molecularly specific spectrum. The conditions were optimized to obtain the best signal enhancement, and linear concentration graphs at low oligonucleotide concentrations were obtained. At higher concentrations (above approximately 10(-)(8) mol dm(-)(3)), curvature was introduced into the concentration graphs with the exception of rhodamine 6G, TET, and FAM, which gave linearity over the entire concentration range studied. Detection limits as low as 0.5 fmol were obtained, with lower possible if a smaller sample was analyzed. Investigation was also carried out into the effect of a Tris-HCl buffer containing the surfactant Tween 20 to aid in the prevention of surface adhesion of the oligonucleotides to the sample vessels at ultralow concentrations. The Tween 20 allowed lower detection limits to be obtained for each of the labels studied. This study shows that the different dyes commonly used with oligonucleotides can give quantitative SERRS at concentration levels not possible when the same dyes are used with fluorescence detection.
Silver nanoparticles were prepared by using polyvinyl pyrrolidone (PVP) as a stabilizer and gamma-irradiation. Transmission electron microscopy (TEM) results showed that both the amount and the molecular weight of PVP in the irradiated solution considerably affect the average size of the silver nanoparticles. The average size of the silver nanoparticles decreases with increasing the amount of PVP in the solution, but increases with increasing its molecular weight. Further, TEM showed that the silver nanoparticles become disassembled into smaller nanoparticles after dilution with distilled water and sonication. Since the processes of dilution and sonication are not expected to result in chemical reactions or to split the silver nanoparticles, we conclude that each silver nanoparticle prepared by [Formula: see text] -irradiation consists of several smaller nanoparticles surrounded by PVP. Thus, based on these observations, we propose a three-step mechanism for the growth of the silver nanoparticles under the conditions considered here. In the first step, the silver ions interact with PVP, then in the second step the silver ions that are exposed to gamma-irradiation are reduced to silver atoms; nearby silver atoms then aggregate at close range. These aggregates are the primary nanoparticles. Finally, these primary nanoparticles coalesce with other nearby primary nanoparticles or interact with PVP to form larger aggregates which are the secondary (final) nanoparticles.