Article

Corrigendum to “Integrated miniature fluorescent probe to leverage the sensing potential of ZnO quantum dots for the detection of copper (II) ions” [Talanta 116 (2013) 514–519]

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Abstract

Quantum dots are fluorescent semiconductor nanoparticles that can be utilised for sensing applications. This paper evaluates the ability to leverage their analytical potential using an integrated fluorescent sensing probe that is portable, cost effective and simple to handle. ZnO quantum dots were prepared using the simple sol-gel hydrolysis method at ambient conditions and found to be significantly and specifically quenched by copper (II) ions. This ZnO quantum dots system has been incorporated into an in-house developed miniature fluorescent probe for the detection of copper (II) ions in aqueous medium. The probe was developed using a low power handheld black light as excitation source and three photo-detectors as sensor. The sensing chamber placed between the light source and detectors was made of 4-sided clear quartz windows. The chamber was housed within a dark compartment to avoid stray light interference. The probe was operated using a microcontroller (Arduino Uno Revision 3) that has been programmed with the analytical response and the working algorithm of the electronics. The probe was sourced with a 12V rechargeable battery pack and the analytical readouts were given directly using a LCD display panel. Analytical optimisations of the ZnO quantum dots system and the probe have been performed and further described. The probe was found to have a linear response range up to 0.45mM (R(2)=0.9930) towards copper (II) ion with a limit of detection of 7.68×10(-7)M. The probe has high repeatable and reliable performance.

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... Equal concentrations of various metal ions were added to the ZCGQDs composite sample to obtain a 50 µM colloidal solution of different metal ions and allowed to stand for 15 min [49]. The changes in the fluorescence intensity of the ZCGQDs complexes before and after the addition of Cu 2+ were measured. ...
... The stepwise dilution method was used to obtain the Cu 2+ solutions of different con centrations, which were added to the ZCGQDs composite samples, mixed, and shaken to obtain the colloidal solutions of copper ions, and the solutions were allowed to stand for 10 min [48,49]. The changes in the fluorescence intensity of the ZCGQDs complexes before and after the addition of Cu 2+ were measured. ...
... The stepwise dilution method was used to obtain the Cu 2+ solutions of different concentrations, which were added to the ZCGQDs composite samples, mixed, and shaken to obtain the colloidal solutions of copper ions, and the solutions were allowed to stand for 10 min [48,49]. The changes in the fluorescence intensity of the ZCGQDs complexes before and after the addition of Cu 2+ were measured. ...
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In this paper, the fluorescence properties of ZnOQD-GO-g-C3N4 composite materials (ZCGQDs) were studied. Firstly, the addition of a silane coupling agent (APTES) in the synthesis process was explored, and it was found that the addition of 0.04 g·mL−1 APTES had the largest relative fluorescence intensity and the highest quenching efficiency. The selectivity of ZCGQDs for metal ions was also investigated, and it was found that ZCGQDs showed good selectivity for Cu2+. ZCGQDs were optimally mixed with Cu2+ for 15 min. ZCGQDs also had good anti-interference capability toward Cu2+. There was a linear relationship between the concentration of Cu2+ and the fluorescence intensity of ZCGQDs in the range of 1~100 µM. The regression equation was found to be F0/F = 0.9687 + 0.12343C. The detection limit of Cu2+ was about 1.74 μM. The quenching mechanism was also analyzed.
... The interest is concerned in the nanometric-sized particles that exhibit special traits as excellent physical and chemical properties distinct and superior to those of the bulk ZnO solids [97][98][99][100][101]. This difference is associated with quantum confinement effects and increased surface atoms of the solid materials at the level of the nano-scale [102]. ...
... In addition, the ZnO phase displayed the same structure for all the samples. Precisely, the five observed diffraction peaks after annealing including (100), (002), (101), (102) and (110), match well the wurtzite hexagonal structure of the ZnO NPs, having predominantly (101) preferred orientation as a result of minimizing the internal stress and surface energy through this plane [74]. After raising the annealing temperatures beyond 150°C, no peaks corresponding to impurities were observed in the patterns, confirming the high phase purity of the samples due to the deduction of chemical residues and impurities. ...
... However, ZnO is an effective alternative due to its comparative band gap energy and lower cost of fabrication [100,101]. In addition, ZnO is considered higher photoactive than TiO2 as reported by several scientist [102][103][104][105]. The higher photoactivity is referred to the higher efficiency to provoke the formation of photoexcited charge carriers [100,106]. ...
Thesis
Hybrid heterojunctions composed of semiconductors and metallic nanostructures have perceived as a sustainable technology, due to their perfect effectiveness in improving, renovating, and enriching the properties of the integrated components. The cooperative coupling results in the variation of the system’s functional properties, by which the metal-generated surface plasmon resonance can enhance the charge separation, light absorption, as well as luminescence of the semiconductor. This phenomenon enables strong interactions with other photonic elements such as quantum emitters. These multifaceted functionalities arise from the synergic exciton-plasmon interaction between the linked units. Thereby, hybrid systems become suitable for various applications including: solar energy conversion, optoelectronic devices, light-emitting diodes (LED), photocatalysis, biomedical sensing, etc. Au-ZnO nanostructures have received growing interest in these applications, where the deposition of gold nanoparticles (GNPs) promotes the system’s response towards the visible region of the light spectrum through their surface plasmon resonance (SPR). Based on a specific size and purity of ZnO nanostructures, as well as the GNPs, and a definite inter-distance between the nanoparticles, the properties of the ZnO nanostructures are varied, especially the photoemission and photocatalytic ones. In this context, we have focused on the construction of size-tunable ZnO nanocrystals (NCs), then incorporated into GNPs solutions using a simple chemical way. This work is divided into two parts: the first is to perform synthesis of pure ZnO NCs having excellent UV photoluminescence. This was achieved through a low-temperature aqueous synthesis, resulting in rough and amorphous structures. The synthesis was followed by a post-thermal treatment in order to crystallize the obtained particles. The synthesis was followed by structural and optical studies (SEM, TEM, XRD, photoluminescence). The photocatalytic activities of ZnO NCs were studied through tailoring their ability to degrade the methylene blue (MB) dye. In addition, the relationship between ZnO structures, luminescence, and photocatalytic properties was explored in details. In the second step, the obtained ZnO NCs were added to gold nanoparticles of various sizes and volume fractions. The effective role of GNPs concerning their size, amount, and their capping molecule on the photoemission of the ZnO nanostructures was emphasized through the charge and/or energy transfer between the constituents in the hybrid system. In the same way, the systems photocatalytic activities were examined after coupling ZnO to GNPs. Further advancement in the integration of the ZnO NCs into PMMA polymer layers was featured in order to obtain large area template of homogenous ZnO properties. The PMMA-assembled ZnO nanoparticles could be promising substrates as catalysts for growing ZnO nanowires, metallic nanoparticles and hybrid nanomaterials.
... Cu 2+ is known as a common environmental toxin, but it is used as a trace component in biological systems. Luminescent ZnO nanopar ticles are used as Cu 2+ sensors thanks to their luminescence quenching [55]. ...
Article
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Metal nanoparticles are currently one of the most researched materials in the field of science and technology. These materials are up to one hundred nanometers in size and differ from ordinary metals in their unique physical and chemical properties. The use of metal nanoparticles in biomedicine is one of the most promising areas of theire application. For example, gold nanoparticles can be used to diagnose and treat cancer. Gold nanoparticles can be coated with various molecules that can target and interact with cancer cells, allowing cancer to be detected and staged. Silver nanoparticles can be used as antimicrobial agents, since silver has a high activity against bacteria and fungi. Also, silver nanoparticles can be used to treat wounds, as they promote rapid healing and prevent infections. Metal nanoparticles are also applied in other industries e.g. to produce electronics, improve the properties of materials, manufacture catalysts, and many other things that are used both in everyday life and in the production and improvement of technological processes. This article discusses the use of metal nanoparticles of silver (AgNPs), zinc (ZnNPs), titanium oxide (TiO2NPs), and gold (AuNPs) in biomedicine and other fields.
... It has been taken note that the photoactivity may be changed through differing the surface area lattice position and also the surface area of photocatalysts (Jimenez-Cadena, Comini, Ferroni, Vomiero, & Sberveglieri, 2010). As an example, topping solutions have been efficiently utilized to affect the morphology of zinc oxide NPs (Ng, Wong, Phung, & Chua, 2013). In a study done on ZnO nanosheets has revealed that the velocity of forerunner (sodium hydroxide) being incorporated to the zinc acetate remedy can result in various growth devices of ZnO nanostructures (Xu, Qin, Mishra, Gu, & Zhu, 2010). ...
Article
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Zinc oxide (ZnO) nanostructures have been revealed to be a photocatalytic prospect owing to the truth that they are cost-effective. Titanium dioxide (TiO2) and ZnO nanoparticles (NPs) are commonly utilized in sunscreens as inorganic physical sun blockers. However, ZnO is more operative in UVA (315-400 nm) range and TiO2 in the UVB (280-315 nm) range. The combination of these particles assures a broad-band UV protection. However, to solve the cosmetic drawback of these opaque sunscreens, micro-sized TiO2 and ZnO have been increasingly replaced by TiO2 and ZnO NPs. In many cases ZnO NPs can be counted as an effective replacement of TiO2 NPs, however, the former has a lower cost. This review is firstly focusing on the photo-degradation procedures using ZnO NPs. Secondly, there are numerous methods that have been used to enhance the photo-response of zinc oxide nano-structures. Additionally, with the high efficiency of the photocatalytic response of ZnO NPs, it has been shown that it can be obtained with the appropriate choice of the required nanostructures regarding the synthesis technique and also the correct photocatalytic system. ZnO NPs is a vital material for numerous industrial usages. ZnO has been found to be effective in various strains of microorganisms, and numerous research articles on this area are evidence of its potential as antimicrobial agent.
... Examples of 3D structures of ZnO contain dandelion, coniferous, flower, urchin-like, etc. [47]. Due to their high stability, high electron mobility, and strong mechanical power, with many applications such as Nano-lasers, solar cells, photodetectors, photocatalytic, photovoltaics, and electronic processes [48]. The 3D nanostructures are extremely valuable for chemical sensors for dye-sensitized solar cells and photocatalysis also makes it possible to bear mass in substances based on their large specific surface area [49]. ...
Article
Photodetection has been gained a lot of attention in last years biased on military wide range and civil application. With essential properties of Zno which has the wide band gap, strong radiation hardness, low cost and good chemical stabilities. ZnO are considered as the most successful candidate for UV photodetector. The study of our report is to review photodetectors based on doped Zno nanostructures and the new advances in ZnO nanostructured generation technique including adjustment and doping methods with modifications of ZnO photodetector. Final part of this review is about literature reviews were reported in recent years about optoelectrical property of Zno nanostructures, due to the fact that Zinc oxide is an important semiconductor material for optoelectronic and industrial applications, such solar cell, photosensors and photodetectors.
... They require a light source, and LEDs were more extensively used due to their easy integration with the Arduino, stable monochromatic illumination, low power and low voltages requirements, develop little heat, and are small in size. These papers describe integrated fluorescence detection systems that uses LED, 47 digital camera, 48 photodiode, 51,53 light sensor 49,50 and RGB sensors 52,54 as detectors. RGB sensors have a white LED, responsible for ambient lighting. ...
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Sustainable analytical methods are highly demanded in the modern society. Within the green principles, novel procedures that attend the sustainable development goals have been proposed and the internet of things (IoT) can play key role to achieve this goal. The association of IoT with analytical chemistry enables the real-time obtaining of analytical data to control industrial processes as well as for monitoring different environmental scenarios and human health by accessing remotely analytical information. In this context, this review presents the main IoT technologies used for analytical chemistry as well as a tutorial for beginners in the field.
... In addition to the above applications, luminescent ZnO nanoparticles were employed for cell imaging [10]. Luminescent ZnO nanoparticles have also been employed in the detection of metal ions such as copper (Cu 2+ ) [11] and cobalt (Co 2+ ) [12], organic molecules such as dopamine (DA) [13], picric acid (PA) [14], and bisphenol A (BPA) [15] and proteins such as carbohydrate antigen [16] in the biological system. Detection of such ions, organic molecules, and biomolecules by the luminescent nanoparticles is based on the quenching of their luminescence which enables the early diagnosis of various diseases, neurological disorders and cancers, thus ZnO nanoparticles have been considered as promising candidates for bioimaging applications. ...
Article
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Zinc oxide (ZnO) nanoparticles have received growing attention for several biomedical applications. Nanoparticles proposed for these applications possess the potential to interact with biological components such as the blood, cells/ tissues following their administration into the body. Hence we carried out in vivo investigations in Swiss Albino Mice to understand the interaction of ZnO nanorods with the biological components following intravenous and oral routes of administration to assess nanoparticles safety. Intravenously injected ZnO nanorods were found to induce the significant reduction in the red blood cells and platelet counts. Elevated levels of serum enzymes such as serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase were observed following intravenous and oral administration. Also, increased levels (p<0.05) of oxidative stress markers such as glutathione in the liver of intravenous treated mice and liver, spleen of oral treated mice; and lipid peroxidation in the spleen of intravenous treated mice compared to untreated mice. Significant DNA damage was observed in liver, spleen, and kidney of mice treated intravenously; liver and kidney of mice treated orally compared to untreated mice. Histology revealed focal venous congestion in the liver of intravenous and oral treated mice; more red pulp congestion in the spleen of oral treated mice compared to the intravenous treated group; pulmonary vascular congestion in intravenous (mild) and oral treated mice (moderate). In conclusion differences in the histology of the organs tested could be due to the differences in the distributed concentrations of nanoparticles. These findings can be considered helpful for the development of biocompatible nanoparticles for biomedical applications.
... The competence of the prepared sensor was fairly high in real water samples from different sources. Ng and co-workers [102] produced a turn-off luminescent sensor for Cu 2+ ions by using ZnO nanomaterials. The developed sensor showed good control over the selectivity and sensitivity for the metal ions under study, with the limit of detection (LOD) of~7.68 × 10 −7 M. The biocomposites of ZnO with ZnS nanostructures have the potential for the estimation of Cu 2+ ions in aqueous media ( Figure 15). ...
Article
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Recent advancement in nanoscience and nanotechnology has witnessed numerous triumphs of zinc oxide (ZnO) nanomaterials due to their various exotic and multifunctional properties and wide applications. As a remarkable and functional material, ZnO has attracted extensive scientific and technological attention, as it combines different properties such as high specific surface area, biocompatibility, electrochemical activities, chemical and photochemical stability, high-electron communicating features, non-toxicity, ease of syntheses, and so on. Because of its various interesting properties, ZnO nanomaterials have been used for various applications ranging from electronics to optoelectronics, sensing to biomedical and environmental applications. Further, due to the high electrochemical activities and electron communication features, ZnO nanomaterials are considered as excellent candidates for electrochemical sensors. The present review meticulously introduces the current advancements of ZnO nanomaterial-based chemical sensors. Various operational factors such as the effect of size, morphologies, compositions and their respective working mechanisms along with the selectivity, sensitivity, detection limit, stability, etc., are discussed in this article.
... It gradually comes to a general consensus that decorating imine-linked receptors is unavoidable to fabricate selective ZnO fluorescent probes. Conversely, Ng reported that the unmodified ZnO nanoparticles can be used as "turn-off" fluorescent probe for effective detection of Cu 2+ , which is more convenient and economical [37]. Choosing a mature probe is able to reduce the difficulty in the investigation of the compatibility. ...
Article
This work uses ZnO nanoparticles as the probe and a case, proving that the grey level can replace fluorescent intensity to realize a quantitative detection function of paper-based Cu²⁺ sensor. Portable Cu²⁺ test papers were obtained through dipping filter papers in as-prepared ZnO sol possessing the Cu²⁺ quenching property. Based on grey level which is obtained through ordinary digital camera and computer, the detection function of the fabricated Cu²⁺ test paper is extended from qualitative detection relied on naked eyes to quantitative detection whose detection range is calculated to be 10-1000μM. The fabricated test papers also could resist the interruption of some competing ions and is a potential candidate for portable Cu²⁺ detection device with quantitative function. Since the strategy of replacing fluorescence intensity by grey level is based on the map relationship between the fluorescence intensity and the digital signal (grey level), it is promising to be applied to other fluorescent test papers to gain quantitative test papers aimed at corresponding chemicals. At the same time, the mechanism of Cu²⁺-induced fluorescence quenching was also investigated by fluorescence lifetime, UV-vis spectra, and photoluminescence spectra. And a static quenching mechanism based on the non-fluorescence complex formed by Cu²⁺ and Ox- is brought up.
... In the development of a low-cost and field-serviceable instrument, an Arduino Uno, from the Arduino family of off-the-shelf development kits that have been receiving increasing interest since their release in 2012, can be a suitable microprocessor to handle signal capture and A/D conversion. Recent work has shown Arduino platforms integrated into optical sensing systems, for instance for Copper (II) ions [4] and Volatile Organic Compounds in seawater [5]. Another advantage to these platforms is that the device can be flashed with firmware allowing the device to function without the need for external control software from e.g. a laptop computer. ...
Article
Humanitarian demining requires a broad range of methodologies and instrumentation for reliable identification of landmines, antipersonnel mines, and other explosive remnants of war (ERWs). Optical sensing methods are ideal for this purpose due to advantages in sensitivity, time-of-response and small form factor. In this work we present a portable photoluminescence-based sensor for nitroaromatic vapours based on the conjugated polymer Super Yellow integrated into an instrument comprising an excitation LED, photodiode, Arduino microprocessor and pumping mechanics for vapour delivery. The instrument was shown to be sensitive to few-ppb concentrations of explosive vapours under laboratory conditions, and responds to simulated buried landmine vapour. The results indicate that a lightweight, easy-to-operate, low-cost and highly-sensitive optical sensor can be readily constructed for landmine and ERW detection in the field, with potential to aid worldwide efforts in landmine mitigation.
... Luminescent ZnO NPs have been employed as Cu 2+ sensors based on the quenching of their luminescence. Ng et al. [55] found this novel, turn-off luminescent assay for Cu 2+ ions had highly repeatable and reliable performances, and the limit of detection (LOD) was measured to be 7.68 × 10 −7 M. Note: limit of detection (LOD); photoluminescence (PL); (3-aminopropyl) triethoxysilane (APTES). ...
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During the past decades, numerous achievements concerning luminescent zinc oxide nanoparticles (ZnO NPs) have been reported due to their improved luminescence and good biocompatibility. The photoluminescence of ZnO NPs usually contains two parts, the exciton-related ultraviolet (UV) emission and the defect-related visible emission. With respect to the visible emission, many routes have been developed to synthesize and functionalize ZnO NPs for the applications in detecting metal ions and biomolecules, biological fluorescence imaging, nonlinear multiphoton imaging, and fluorescence lifetime imaging. As the biological applications of ZnO NPs develop rapidly, the toxicity of ZnO NPs has attracted more and more attention because ZnO can produce the reactive oxygen species (ROS) and release Zn2+ ions. Just as a coin has two sides, both the drug delivery and the antibacterial effects of ZnO NPs become attractive at the same time. Hence, in this review, we will focus on the progress in the synthetic methods, luminescent properties, and biological applications of ZnO NPs.
... It takes advantage of an open-source software development kit (mbed), a compatible universal microcontroller, and a simple feedback control algorithm. In fact, universal electronic modules provide many opportunities for the development of low-cost and versatile analytical platforms [9][10][11][12][13][14] . ...
Article
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In order to ascertain optimum conditions for biocatalytic processes carried out in vitro, we have designed a bio-opto-electronic system which ensures real-time compensation for depletion of adenosine triphosphate (ATP) in reactions involving transfer of phosphate groups. The system covers ATP concentration range of 2-48 μM. The report demonstrates feasibility of the device operation using apyrase as the ATP-depleting enzyme.
... Moreover, the reactivation of FL intensity in the CdTe@Cys sample was done easily Generally, quantum dots (QDs) are referred to as the zero- 42 dimensional colloidal crystals that possesses strong size depen- 43 dence and multi-colored luminescence properties [1,2] along with 44 its intrinsic features, such as the sharp and symmetric emission, 45 photostability and high quantum yields. Owing to these inherent 46 inimitable properties, QDs play a vital role in various avenues 47 namely the identification of the chemical moieties [3], clinical 48 diagnostics [4][5][6][7][8][9], optoelectronics [10,11], bio-imaging and bio-49 sensing [12][13][14][15][16][17][18][19]. 50 QDs are chemically unstable and have poor solubility in water 51 and due to these deficits it was not preferred for biomedical appli-52 cations. ...
Article
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l-Cysteine (Cys) capped CdTe quantum dots (CdTe@Cys QDs) were successfully synthesized in an aqueous medium. The synthesized CdTe@Cys samples were analyzed using Fourier transform infrared (FT-IR) spectroscopy, fluorescence (FL) spectroscopy, transmission electron microscopy (TEM), confocal microscopy and subsequently subjected to the antibacterial test. Systematic investigations were carried out for the determination of optimal conditions namely the ratios of Cd:Te, CdTe:Cys, pH value and the chemical stability of CdTe@Cys. Moreover, the reactivation of FL intensity in the CdTe@Cys sample was done easily by the addendum of Cys. The introduction of additional cysteine to the CdTe@Cys QDs sample showed an enhancement in terms of the FL intensity and stability along with the reduced antibacterial activity. This was further confirmed through Thiazolyl blue tetrazolium bromide (MTT) assays. Both the result of the bio-stability tests namely the antibacterial test and MTT assay displayed similarities between the externally added Cys and cytotoxicity of the bacteria and human HeLa cancer cell lines. Confocal microscopic images were captured for the CdTe@Cys conjugated Escherichia coli.
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Metal-oxide nanomaterials, especially transition metal-oxide nanomaterials, bring the possibility of diversified applications due to their unique chemical and structural properties. They possess a high surface area as well as exceptional optoelectronic, magnetic, and thermal stability properties. These materials have been used as a potential matrix in large-scale applications such as catalysis, photocatalysis, sensing and biosensing, supercapacitors, energy storage devices, and biomedical field due to their natural abundance, the potential for recycling, low toxicity, cost-efficiency, and easy synthetic route. Because of the advantageous features like simplicity, high sensitivity, and selectivity of chromogenic- and fluorogenic-based sensors, the optically active metal-oxide nanomaterials are also applied for the sensing of various analytes like metal ions, anions, biomolecules, etc. This chapter summarized the different aspects such as synthesis and characterization of metal-oxide nanoparticles, and their potential applications in sensing and biosensing.
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Open source hardware such as microcontroller prototyping boards has made it possible to interface classical laboratory instruments with computers. A wide selection of sensors is available for improving the sensitivity of the instruments. Laboratory automation is possible as these microcontroller boards can be programmed via compiler. In the present study, a light emitting diode (LED) based detector for filter fluorimeter was designed and fabricated. The detector signals were acquired and processed with an open source microcontroller boards. The signal was then interfaced with laptop computer. A filter program ensured noise reduction. The results were more sensitive and coherent than otherwise possible with the inbuilt detector system of the old filter fluorimeter. The experiment is useful is demonstration of laboratory automation. Keywords: Microcontroller boards, open source, fluorimeter, undergraduate experiment, fluorimeter, Arduino
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One of the strategies to overcome the drawbacks of fast charge recombination of a photocatalyst is to develop semiconductor heterostructures. Herein, we report a two-step precipitation-hydrothermal process to create CuFeO2-ZnO heterostructures with different weight percentages of CuFeO2 (0.5, 1, 5, and 10%). Though X-ray diffraction detected the presence of CuFeO2 on ZnO above 5%, Raman spectroscopy could reveal the presence of CuFeO2 phase as low as 0.5 wt%. For all of the compositions, the bandgap of ZnO did not vary (3.15 eV) on forming heterostructures with CuFeO2. The oxidation of methylene blue under sunlight was used to determine the photocatalytic performance of the heterostructures. In comparison to pure ZnO and CuFeO2, CuFeO2-ZnO heterostructures exhibited a better photocatalytic efficiency. Overall, 5 wt% CuFeO2 on ZnO showed 100% degradation with a rate constant of 0.272 ± 0.002 min⁻¹, which is 16 times faster than ZnO. Time-resolved photoluminescence analysis indicated a higher lifespan of charge carriers in the 5wt% CuFeO2-ZnO heterostructure (32.3 ns) than that of CuFeO2 (0.85 ns) and ZnO (27.6 ns). The Mott–Schottky flat band potentials of ZnO and CuFeO2 was determined to be -0.82 and 1.17 eV, respectively, revealing the presence of Type I heterostructures. The heterostructures also showed outstanding recyclability, with a degradation rate of 97% even after four cycles. The current study shows the significance of forming p-type CuFeO2 and n-type ZnO heterostructures for enhanced photocatalysis.
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p-Nitrophenol (p-NP) is a nitroaromatic compound that causes a serious threat to humans and the environment due to its carcinogenic, mutagenic, cyto, and embryonic toxicity even at low concentration. Thus, selective and sensitive detection of p-NP is highly desirable for human health and environmental monitoring. The effectiveness of (3-Aminopropyl) triethoxysilane (APTES) coated zinc oxide (ZnO) ([email protected]) quantum dots (QDs) as a fluorescent material was studied for detection of p-NP under various reaction conditions. The concentration of p-NP can sense by the depth of [email protected] QDs fluorescence quenching. Under the optimum reaction conditions, a linear relationship was observed between a relative fluorescence quenching intensity of [email protected] QDs and concentration of the p-NP over the range of 1.0–80 μM. The lower detection limit of [email protected] towards p-NP is 0.089 μM, which is below the allowable drinking water standard as per US-EPA. Thus, a sensitive and selective fluorescence-based method is developed to detect p-NP on account of the partially inner filter effect (IFE) and electron transfer process.
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Histamine, one of the most important biogenic amines (BAs) is considered as food hazard and therefore various agencies have fixed threshold in different food and beverages. In this manuscript, two novel fluorescent turn-on probes were developed for the instantaneous detection of histamine. The β-cyclodextrin (β-CD) capped ZnO quantum dots (QDs) were decorated with the vitamin B6 cofactors like pyridoxal 5’-phosphate (PLP) and pyridoxal (Py) by forming host-guest inclusion complexation between the capped β-CD and PLP/Py. The cofactors decorated QDs ([email protected] and [email protected]) were applied for the sensing of BAs. Addition of histamine to the [email protected] and [email protected] solution resulted selective fluorescence enhancement at 473 nm and 460 nm, respectively. Without any interference from the other tested BAs, the fluorescence response of the probes [email protected] and [email protected] showed good linearity to histidine concentration from 2.49-24.4 μM and 7.44-47.6 μM with the detection limit down to 0.59 μM and 0.97 μM, respectively.
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Nanoparticle-based therapies are found to be effective due to the unique mechanisms-of-action to engineered nanoparticles. These nanoparticles are programmed to be target specific and they can hold drugs along with imaging agents for simultaneous diagnostic and therapeutic purposes. They are making their way into the clinical realm. In this work we propose to develop Cadmium sulphide (CdS) nanoparticles with reduced toxicity that could function as a theranostic nanoparticle for bio- imaging applications. The work focuses on the toxicological investigation of surface modified cadmium sulphide nanoparticles. Uncoated and Chitosan coated CdS nanoparticles were synthesized by wet chemical method. The physico-chemical properties of the nanoparticles were characterized by X-ray diffraction, UV–Vis absorption, Fourier transform infrared, photoluminescence, X-ray photoelectron spectroscopy, dynamic light scattering, zeta potential and transmission electron microscopy. MTT assay was performed for toxicity profiling of the synthesized CdS nanoparticles in Human Jurkat cell and erythrocytes cell lines. The results showed a significant reduction in toxicity when the CdS nanoparticles surface was modified with Chitosan. Flow cytometer studies were performed to assess the incorporation of the synthesized nanoparticles into the cells. Photoluminescence studies showed that the surface modified CdS nanoparticles retained their fluorescence intensity regardless of their surface modification with Chitosan. Chitosan modified surface of the nanoparticles served as an effective barricade against the degradation of cadmium core. Surface modification with Chitosan, reduced the toxicity of cadmium sulphide nanoparticles retaining their fluorescent property in the cells. Thus by intentionally attaching bio-conjugates can be efficiently used for drug delivery to target specific cells as well as enable the imaging for cells.
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Here, we demonstrate for the first time a strategy to self-assemble ZnO nanoparticles (NP) on a large area by a facile one-step process. First, rough and random ZnO nanocrystals (NC), were produced by free-stabilizing aqueous synthesis. Therefore, a post thermal treatment at various temperatures ranging from 80 to 800 °C was necessary to obtain size-tunable and photoluminescent crystalline NP. The fabricated NP had both efficient UV photoluminescence and photocatalytic activity by photo-degradation of Methylene Blue (MB) dye. The annealed NP showed an absorption blue shift in the UV region with decreasing size. This shift was attributed to high quantum confinement effect since ZnO NP diameter reached values lower than the Bohr radius of ZnO (~2.7 nm). The photocatalytic activity displayed dependency on the particle’s size, number, and crystallinity. Subsequently, the NP were self-assembled inside poly(methyl methacrylate) (PMMA) nanoholes. Subsequently, large area substrate of homogenous properties ZnO NP was obtained. Moreover, the synthesis facility, photoemission and photocatalytic properties of ZnO NP could be a new insight into the realization of high performance and low cost UV laser devices.
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In this study, a novel quenched electrochemiluminscence (ECL) sensor was constructed based on the integration of ZnO and g-C3N4 for determination of fipronil. The [email protected]3N4 composites were shaped on the glassy carbon electrode by one-step electrodeposition, which showed strong ECL signals compared to the pure g-C3N4. With the presence of low concentration of fipronil, a remarkable decrease of ECL signal was observed due to the quenching effect of fipronil on ECL emission. The results showed the quenched ECL intensity responded linearly to the logarithm of fipronil concentration in the range of 5–1000 nmol L⁻¹ with a low detection limit of 1.5 nmol L⁻¹ (S/N = 3). The developed ECL sensor exhibited high sensitivity and specificity for the determination of fipronil, which provides a potential application to fipronil analysis in real egg samples.
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Encryption is of vital importance in both military and civil fields. Although there have been a few attempts to information encryption and anti-counterfeiting employing functional materials, it is still urgently needed to develop advanced encryption routes that cannot be cracked easily. This paper presents a simple strategy for advanced encryption based on the fluorescence quenching of ZnO nanoparticles (NPs) by acid and copper ions. In this strategy, certain patterns are printed onto a ZnO NPs pre-coated paper using the CuCl2 aqueous solution as ink, to produce an invisible latent image which is only visible under ultraviolet (UV) irradiation. For encryption, the patterns can be perfectly concealed by exposing to vinegar vapour due to the dissolution of the ZnO NPs in acidic conditions; and the decryption can be performed via neutralizing in soda vapour ambient and succedent uniformly re-coating of ZnO NPs. An additional matrix of pixels with encoded grey levels by tuning the dose of the CuCl2 is demonstrated to further enhance the anti-counterfeiting capability. A 4×4 micron-sized matrix with a totally combination of 1.67×108 codes has been enciphered in the latent patterns for demonstration, which makes a huge barrier for counterfeiting. The results reported in this paper provide a simple strategy for advanced encryption, and may inspire versatile applications in the fields of information security and anti-counterfeiting.
Chapter
The two aspects of the further progress in the development of biosensors are in the consideration of this chapter; one of them is connected with the application of nanoparticles or nanostructured materials as transducer surface, and the second one is concerned with the use of artificial selective materials for increasing stability, simplicity, and cheapness of the analytical devices. The main attention is focused on optical devices based on photoluminescence (PhL) and photoconductivity measurements in nanostructured porous silicon, AgO, ZnO, TiO2, In2O3, and WO3 nanoparticles, carbon, Si and SiO2 nanotubes as well as other nanomaterials. The structural and optical properties of nanostructured transducers have been characterized using atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), and other optical analytical approaches. The abilities of all analyzed biosensor complex are demonstrated at the determination of numerous chemical substances (T2 mycotoxin, aflatoxin, patulin, zearelenone, etc.) and diagnosis of retroviral bovine leucosis, salmonellosis, and others. In all cases, the results obtained with nanostructured biosensors are compared with data obtained by standard analytical methods. The most important results are achieved for biosensors based on surface plasmon resonance (SPR) or total internal enhanced ellipsometry (TIRE). A special attention is paid to the results reported by the authors of the chapter.
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In this work, the fluorescent β-cyclodextrin-capped ZnO quantum dots (β-CD@ZnO QDs) with a good water-solubility have been synthesized via a facile method. And the synthesized β-CD@ZnO QDs with a diameter ∼3.64 nm and a yellow fluorescence have been characterized by high resolution transmission electron microscope, UV-visible absorption, photoluminescence, and Fourier transform infrared spectroscopy. The β-CD@ZnO QDs were used as a fluorescent sensor for the detection of p-nitrophenol. A linear relationship to the concentration of the p-nitrophenol over the range of 1.0–40 μM with the detection limit of 0.34 μM was obtained. The sensing property of the β-CD-capped ZnO QDs has been successfully examined in real water samples. And the quenching mechanism was proposed, which showed that the quenching effect may be caused by the inclusion complexation between β-CD and p-nitrophenol and electron transfer.
Article
Based on the perturbation treatments for a tetragonally distorted tetrahedral 3d 9 cluster, the g factors and local angular distortions are calculated for ZnO:Cu2+ nanocrystals with various Cu2+ concentrations in different systems I and II under dissimilar experimental conditions. Because of the dynamic Jahn–Teller effect, the bond angles θ between the four equivalent Cu2+–O2– bonds and the C4 axis are about 1.5o larger than that (θ0 ≈ 54.736o) of an ideal tetrahedron. Consequently, the original slightly trigonally distorted oxygen tetrahedron of the host Zn2+ site is transformed into a tetragonally compressed one. The isotropy of g factors may be attributed to the appropriate angular distortions Δθ = θ – θ0 due to the dynamic Jahn-Teller effect. The slightly increasing (or decreasing) g factors with concentration x can be illustrated as the delicate increases (or decreases) of the angular distortions (Δθ) and the covalency factors (N) for system I (or II), respectively, under almost equivalent crystal-fi eld strengths (Dq).
Article
A visual detection method for trace Cu(2+) in aqueous solutions using triangular silver nanoplates (abbreviated as TAgNPs) as the probe was developed. The method is based on that TAgNPs could be corroded in sodium thiosulfate (Na2S2O3) solutions. The absorption spectrum of TAgNPs solution changed when it is corroded by Na2S2O3. The reaction of oxygen with ascorbic acid (Vc) in the presence of a low concentration of Cu(2+) generates hydrogen peroxide that reacts with Na2S2O3, which leads the concentration of Na2S2O3 in the solution to be decreased. Therefore, the reaction between TAgNPs and the reacted mixture of Na2S2O3/Vc/Cu(2+) was prevented efficiently. When the Na2S2O3 concentration and reaction time are constant, the decrease in the concentration of Na2S2O3 is directly proportional to the Cu(2+) concentration. Thus, morphology, color, and maximum absorption wavelength of TAgNPs changed with the change of Cu(2+) concentration. The changed maximum absorption wavelength of TAgNPs (Δλ) is proportional to Cu(2+) concentration in the range from 7.5×10(-9) to 5.0×10(-7)M with a correlation coefficient of r=0.9956. Moreover, color change of TAgNP solution was observed clearly over a Cu(2+) concentration range from 7.5×10(-8) to 5.0×10(-7)M. This method has been used to detect the Cu(2+) content of a human hair sample, and the result is in agreement with that obtained by the atomic absorption spectroscopy (AAS) method. Copyright © 2015. Published by Elsevier B.V.
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This review summarizes the recent progress in quantum dot (QD) based sensors used for the photoluminescent detection of a variety of species in vitro and in vivo. New trends in using these nanomaterials for sensing applications are highlighted.
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Heteroatom doping enables graphene with novel properties and thus may broaden the potential of graphene-based materials. In this paper, novel ZnO nanocrystals decorated nitrogen-doped graphene (N-GR) composites were prepared through a one-step thermal-treatment route using glycine as the nitrogen source. ZnO nanocrystals with a size about 8 nm were well-dispersed and tightly anchored on the N-GR sheet. Compared with ZnO nanocrystals decorated undoped graphene, the ZnO/N-GR nanocomposites could not only enhance the electrochemiluminescence (ECL) intensity by 4.3-fold, but also moved the ECL onset potential positively for ~200 mV. All these results could be ascribed to the presence of nitrogen in graphene which decreased the barrier of ZnO nanocrystals reduction. Furthermore, the ECL sensor based on ZnO/N-GR nanocomposites was fabricated for the ultrasensitive detection of pentachlorophenol (PCP). This recyclable and eco-friendly sensor have excellent performances including wide linear range (0.5 pM ~ 61.1 nM), low detection limit (0.16 pM, S/N = 3), good selectivity and stability, which is a promising sensor for the practical application in the environment analysis.
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A tetraphenylethylene (TPE) Schiff base macrocycle with an aggregation-induced emission (AIE) effect was synthesized by the condensation reaction of the TPE dialdehyde and 1,2-benzenediamine. The macrocycle could aggregate into nanofibers in an aqueous solution to give a stable and fluorescent suspension. The fluorescent nanofibers showed a highly selective response to copper ions in an aqueous solution with the detection sensitivity up to a nanomolar level. Meanwhile, the emission of the nanofibers displayed a very large Stokes shift up to 260 nm because of the AIE effect, which brought the emission into the red area and avoided background interference. Therefore, the macrocycle probe showed great potential for the detection of Cu(II) in real water samples including pork juice-containing water. In addition, the macrocycle reacted with Cu(II) to give a color change and so the copper ion can be detected at the 10 μM level by the naked eye.
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The presence of surfactants (Hexamine, tetraethylammonium bromide (TEAB), cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB) and PVP) on the surface of zinc oxide (ZnO) nanoparticles resulted variation in their optical properties. The optical properties of each surfactant-capped zinc oxide nanoparticles were investigated using UV–visible absorption and fluorescence techniques. The particle size of these nanoparticles were calculated from their absorption edge, and found to be in the quantum confinement range. The absorption spectra and fluorescent emission spectra showed a significant blue shift compared to that of the bulk zinc oxide. Large reduction in the intensity of visible emission of zinc oxide/surfactant was observed and these emissions were vanished more quickly, with the decrease in excitation energy, for the smaller nanoparticles. Out of the four surfactants (other than PVP), CTAB-capped zinc oxide has smallest particle size of 2.4 nm, as calculated from the absorption spectrum. Thus the presence of surfactant on the surface of zinc oxide plays a significant role in reducing defect emissions. Furthermore, ZnO/PVP nanoparticles showed no separate UV emission peak; however, the excitonic UV emission and the visible emission at 420 nm overlap to form a single broad band around 420 nm.
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Copper is an essential element, however, this heavy metal is an inhibitor of microbial activity at relatively low concentrations. The objective of this study was to evaluate the inhibitory effect of copper(II) towards various microbial trophic groups responsible for the removal of organic constituents and nutrients in wastewater treatment processes. The results of the batch bioassays indicated that copper(II) caused severe inhibition of key microbial populations in wastewater treatment systems. Denitrifying bacteria were found to be very sensitive to the presence of copper(II). The concentrations of copper(II) causing 50% inhibition (IC(50)) on the metabolic activity of denitrifiers was 0.95 mg L(-1). Copper was also inhibitory to fermentative bacteria, aerobic glucose-degrading heterotrophs, and nitrifying bacteria (IC(50) values=3.5, 4.6 and 26.5 mg L(-1), respectively). Nonetheless, denitrifying and nitrifying bacteria showed considerable recovery of their metabolic activity after only several days of exposure to high copper levels (up to 25 and 100mg Cu(II) L(-1) for denitrification and nitrification, respectively). The recovery could be due to attenuation of soluble copper or to microbial adaptation.
Article
We report that fluorescent carbon nanodots (C-dots) can act as an optical probe for quantifying Sn(II) ions in aqueous solution. C-dots are synthesized by carbonization and surface oxidation of preformed sago starch nanoparticles. Their fluorescence is significantly quenched by Sn(II) ions, and the effect can be used to determine Sn(II) ions. The highest fluorescence intensity is obtained at a concentration of 1.75 mM of C-dots in aqueous solution. The probe is highly selective and hardly interfered by other ions. The quenching mechanism appears to be predominantly of the static (rather than dynamic) type. Under optimum conditions, there is a linear relationship between fluorescence intensity and Sn(II) ions concentration up to 4 mM, and with a detection limit of 0.36 μM. Figure Highly fluorescent carbon nanodots (CDs) were synthesized from preformed starch nanoparticles via a green synthetic method. The potential application of these CDs as a sensing probe for Sn(II) ions were evaluated. Our studies showed that CDs are highly sensitive and selective towards Sn(II) detection in aqueous system.
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We report synthesis and spectroscopic characterization of sol–gel derived zinc oxide (ZnO) quantum dots (Qdots) of 3–8 nm size. The Qdots exhibited a broad and strong visible emission peak centered near 520 nm with a quantum efficiency of approximately 5%. A weak ultraviolet (UV) emission peak was also observed near the band gap at 370 nm. The integrated area under the curve for the visible emission band was 35 times greater than that of the band-edge UV emission band of ZnO Qdots at room temperature. The photophysical characteristics (luminescence wavelength and intensity) of ethanol-dispersed Qdots were greatly affected over time (aging), suggesting the continuation of particle growth. In contrast, no such spectroscopic changes were noticed for air-dried ZnO Qdots. Time-resolved emission spectra of Qdots recorded at 520 nm emission were fitted with two sequential exponential decay curves with lifetimes of 14 ns and 77 ns. Visible photoluminescence of ZnO at low temperature (80 K) exhibited 150% higher intensity than that at room temperature. This was discussed based on the standard model of competitive radiative and non-radiative relaxation processes at various temperatures.
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This review discusses the application of quantum dots (QDs) to chemical and biological detection, for which they have excellent features, particularly size-dependent optical properties.We can summarize the main areas discussed in this review as follows:(1) QDs associated with enzyme-linked immunosorbent assay (ELISA), chip detection and capillary electrophoresis (CE) enhance the sensitivity and the speed of detection of residues;(2) QDs are applied with other techniques, including polymerase chain reaction (PCR), fluorescence resonance-energy transfer (FRET) analysis, fluorescence in-situ hybridization (FISH) and western blot analysis; and,(3) QDs combined with the above techniques can successfully detect DNA and protein.We also cover perspectives and challenges in analytical applications of QDs.
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Cyanine and related polymethine dyes have been widely used as fluorescent and phosphorescent dyes for biological investigations. But the mechanism of this kind of cyanine dye as pH sensor is still not clear. In this paper, two groups of cyanine dyes were designed and synthesized, each including two asymmetry cyanine dyes and one symmetry dye. The UV–vis and fluorescent spectra of compounds Ia–b and IIa–b were recorded in phosphate buffers with different pH value. It was found that these compounds could be used as a kind of pH sensors with high pKa value. The calculation on structures or conformations of compounds Ia–b, IIa–b and Ic before and after protonation revealed that the planar conjugations were different between non-protonic and protonic forms. It implied that the change from PET to ICT system was possible in the process of binding between polymethine cyanine dyes and proton.
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Fluorescent potential-sensitive dyes (PSDs) were screened for use in potassium-sensitive optical sensor membranes. A potassium-sensitive plasticized PVC layer containing valinomycin as an ion carrier, lipophilic borate salt as an anionic additive, and a PSD was chosen as a model for evaluating the applicability of PSDs. A commercial carbocyanine dye (3,3′-dihexadecyloxacarbocyanine perchlorate) was found to exhibit the best properties in terms of signal changes, photostability and operational life-time. The sensor membrane responds reversibly to potassium ion, with fluorescence intensity changes exceeding 50% and response times being of the order of 1 min. The response to potassium is slightly pH dependent. Typically, an 8% change in intensity is observed over the range pH 5–8. The new sensor membrane exhibits significantly improved signal changes compared to previous optodes based on related sensing schemes. We also report the effects of different plasticizers and lipophilic additives on the response of the layers. The response mechanism is discussed with respect to morphology of the membrane.
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To get a real understanding on the complexity of origin and mechanism of visible emission for ZnO quantum dots (QDs), we systematically property of visible emission of ZnO QDs with tunable diameters in a range of 2.2−7.8 nm synthesized via a sol−gel route using self-made zinc−oleate complex as a precursor. It is indicated that the visible emission of ZnO QDs can be ascribed to singly ionized oxygen vacancies, which is associated with the paramagnetic centers with electron paramagnetic resonance (EPR) value of g = 2.0056. The visible emission property of the ZnO QDs displays highly size-dependent behavior. With ZnO QDs size decreasing, the visible emission peaks blue-shift to the positions with shorter wavelength due to quantum size effect, however, is different from that of band gap. Quantitative investigation shows that the visible emission can correspond to a transition of holes from the valence band to the preexisting deep donor energy level, which is different from the well-known conclusion that the visible emission is due to the transition of an electron from the conduction band to a deep trap. Two important points can be obtained: the defects of singly ionized oxygen vacancies determine the origin and intensity of visible emission of ZnO QDs; and the visible emission peak position of ZnO QDs is decided by their size, and a transition of holes from the valence band to the preexisting deep donor energy level is responsible for the visible emission of the ZnO QDs.
Article
ZnO nanoparticles in the size range from 2 to 7 nm were prepared by addition of LiOH to an ethanolic zinc acetate solution. This method [Spanhel, L.; Anderson, M. A. J. Am. Chem. Soc. 1991, 113, 2826] was modified and extended at several points. The synthesis of very small ZnO nuclei was simplified. It was found that aging of particles was governed by temperature, the water content, and the presence of reaction products. Water and acetate induced considerably accelerated particle growth. Growth could almost be stopped by removal of these species ("washing"). Washing consisted of repeated precipitation of ZnO by addition of alkanes such as heptane, removal of the supernatant, and redispersion in ethanol. The aging characteristics are interpreted in terms of the concentration of dissolved Zn II species and reactions well-known in sol-gel chemistry. These findings present a better-defined and more versatile procedure for production of clean ZnO sols of readily adjustable particle size. Such sols are of particular interest for studies of electrical and optical properties of ZnO nanoparticle films. For example, films exhibiting >99% transparency in the visible region could only be obtained by deposition from a washed sol.
Article
Colloidal semiconductor nanocrystals or quantum dots (QDs) are one of the most relevant developments in the fast-growing world of nanotechnology. Initially proposed as luminescent biological labels, they are finding new important fields of application in analytical chemistry, where their photoluminescent properties have been exploited in environmental monitoring, pharmaceutical and clinical analysis and food quality control. Despite the enormous variety of applications that have been developed, the automation of QDs-based analytical methodologies by resorting to automation tools such as continuous flow analysis and related techniques, which would allow to take advantage of particular features of the nanocrystals such as the versatile surface chemistry and ligand binding ability, the aptitude to generate reactive species, the possibility of encapsulation in different materials while retaining native luminescence providing the means for the implementation of renewable chemosensors or even the utilisation of more drastic and even stability impairing reaction conditions, is hitherto very limited. In this review, we provide insights into the analytical potential of quantum dots focusing on prospects of their utilisation in automated flow-based and flow-related approaches and the future outlook of QDs applications in chemical analysis.
Article
A near-infrared-emitting CdTe/CdS core/shell quantum dots (QDs)-based photoluminescence (PL) sensor was designed and applied for highly selective and sensitive detection of Cd(2+). This sensor was based on a PL "OFF-ON" mode. First, the addition of ammonium pyrrolidine dithiocarbamate (APDC) led to remarked PL quenching of QDs. Second, PL of APDC surface modified QDs (QDs-APDC) was gradually restored with the each increment of Cd(2+) concentration. Experimental results showed that PL of QDs-APDC was near proportional upon the addition of Cd(2+) in the range from 0.1 to 2 μM with a good correlation coefficient of 0.9989. The limit of detection of this proposed method was 6 nM. Interferential experiments confirmed that this sensor of Cd(2+) was highly selective over other metal ions. To further investigate perfect analysis performance, this sensor was favorably utilized to determine Cd(2+) in tap water, river water and liposome solutions.
Article
Nano-crystalline ZnO particles were synthesized using alcoholic solutions of zinc acetate dihydrate through a colloidal process. Five types of capping agents: 3-aminopropyl trimethoxysilane (Am), tetraethyl orthosilicate (TEOS), mercaptosuccinic acid (Ms), 3-mercaptopropyl trimethoxysilane (Mp) and polyvinylpyrrolidone (Pv) were added at the first ZnO precipitation time (first PPT) to limit the particle growth. The first three capping agents effectively capped the ZnO nanoparticles and limited the growth of the particles, while the last two capping agents caused agglomeration or larger clusters in the solutions. Particles synthesized were in the size range of 10–30 nm after capping, and grew to 60 and 100 nm in 3 and 6 weeks, respectively, during storage at ambient conditions. Refluxing time was found to only affect the first PPT time. Washing by ethanol and slow drying were very important in converting Zn(OH)2 into ZnO. XRD analyses revealed single phase ZnO Wurtzite crystal structure. Photoluminescence (PL) spectra showed high-intensity in UV emission and very low intensity in the visible emission, which indicates a good surface morphology of the ZnO nanoparticles with little surface defects. Optical absorption spectra showed a blue shift by the capped ZnO due to the quantum confinement effect by the single crystal size of 5–6 nm as analysed by TEM. Capping effectiveness of each agent is discussed through possible capping mechanism and chemical reaction of each capping agent. This synthesis process is a low cost, high purity, easy to control method using only bio-compatible materials.
Article
This paper describes the investigation of surface modified quantum dots (QDs) as a sensing receptor for Cu2+ ion detection by optical approach. Water-soluble l-cysteine-capped ZnS QDs have been synthesised in aqueous medium. These functionalised nanoparticles were used as a fluorescence sensor for Cu (II) ion, involved in the fluorescence quenching. The optimum fluorescence intensity was found to be at pH 5.0 with a nanoparticle concentration of 2.5 mg L−1. The effect of foreign ions on the intensity of ZnS QDs showed a low interference response towards other metal ions except Ag+ and Fe3+ ions. The quenching mechanism was studied and the results show the existence of both static and dynamic quenching processes. However, static quenching is more prominent of the two. The limit of detection of this system was found to be 7.1 × 10−6 M. When compared with single organic fluorophores, l-cysteine-capped ZnS QDs are brighter and more stable against photobleaching. This method is not only simple, sensitive and low cost, but also reliable for practical applications.
Article
A DNA fluorescence probe system based on fluorescence resonance energy transfer (FRET) from CdTe quantum dot (QD) donors to Au nanoparticle (AuNP) acceptors is presented. CdTe QDs, 2.5nm in diameter, as energy donors, were prepared in water. Au nanoparticles, 16nm in diameter, as energy acceptors, were prepared from gold chloride by reduction. CdTe QDs were linked to 5'-NH2-DNA through 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride (EDC) as a linker, and the 3'-SH-DNA was self-assembled onto the surface of AuNPs. The hybridization of complementary double stranded DNA (dsDNA) bound to the QDs and AuNPs (CdTe-dsDNA-Au) determined the FRET distance of CdTe QDs and Au nanoparticles. Compared to the fluorescence of CdTe-DNA, the fluorescence of CdTe-DNA-Au conjugates decreased extremely, which indicated that the FRET occurred between CdTe QDs and Au nanoparticles. The fluorescence change of this conjugate depended on the ratio of Au-DNA to CdTe-DNA. When the AuNPs-DNA to QD-DNA ratio was 10:1, the FRET efficiency reached a maximum. The probe system would have a certain degree of fluorescence recovery when a complementary single stranded DNA was introduced into this system, which showed that the distance between CdTe QDs and Au nanoparticles was increased.
Article
Four different generation of thiol-DAB dendrimers were synthesized, S-DAB-G(x) (x=1, 2, 3 and 5), and coupled with CdSe quantum dots, to obtain fluorescent nanocomposites as metal ions sensing. Cd(II) and Pb(II) showed the higher enhancement and quenching effects respectively towards the fluorescence of S-DAB-G(5)-CdSe nanocomposite. The fluorescence enhancement provoked by Cd(II) can be linearized using a Henderson-Hasselbalch type equation and the quenching provoked by Pb(II) can be linearized by a Stern-Volmer equation. The sensor responds to Cd(II) ion in the 0.05-0.7μM concentration range and to Pb(II) ion in the 0.01-0.15mM concentration range with a LOD of 0.06mM. The sensor has selectivity limitations but its dendrimer configuration has analytical advantages.
Article
We have developed a new analytical method to detect multiple DNA simultaneously based on the biobarcoded CdSe/ZnS quantum dot (QD) and magnetic microparticle (MMP). It was demonstrated by using oligonucleotide sequences of 64 bases associated with human papillomavirus 16 and 18 L1 genes (HPV-16 and HPV-18) as model systems. This analytical system involves three types of probes, a MMP probe and two streptavidin-modified QD probes. The MMPs are functionalized with HPV-16 and HPV-18 captures DNA to form MMP probes. The QDs are conjugated with HPV-16 or HPV-18 probe DNA along with FAM- or Rox-labeled random DNA to form HPV-16 and HPV-18 QD probes, respectively. A one-step hybridization reaction was performed by mixing the MMP probes, HPV-16 and HPV-18 target DNA (T-16 and T-18), HPV-16 and HPV-18 QD probes. Afterwards, the hybrid-conjugated microparticles were separated by a magnet and heated to remove the MMPs. Finally, the detections of T-16 and T-18 were done by measuring fluorescence signals of FAM and Rox, respectively. Under the optimum conditions, the fluorescence intensity exhibited a good linear dependence on target DNA concentration in the range from 8 × 10⁻¹¹ to 8 × 10⁻⁹ M. The detection limit of T-16 is up to 7 × 10⁻¹¹ M (3σ), and that of T-18 is 6 × 10⁻¹¹ M. Compared with other biobarcode assay methods, the proposed method that QDs were used as the solid support has some advantages including shorter preparation time of QD probes, faster binding kinetics and shorter analytical time. Besides, it is simple and accurate.
Article
Currently HPLC/MS is the state of the art tool for environmental/drinking water perfluorooctane sulfonate (PFOS) monitoring. PFOS can bind to peroxisomal proliferator-activated receptor-alpha (PPARα), which forms heterodimers with retinoid X receptors (RXRs) and binds to PPAR response elements. In this bioassay free PFOS in water samples competes with immobilized PFOS in ELISA plates for a given amount of PPARα-RXRα. It can be determined indirectly by immobilizing PPARα-RXRα-PFOS complex to another plate coated with PPARα antibody and subsequent measuring the level of PPARα-RXRα by using biotin-modified PPARα-RXRα probes-quantum dots-streptavidin detection system. The rapid and high-throughput bioassay demonstrated a detection limit of 2.5 ng L(-1) with linear range between 2.5 ng L(-1) and 75 ng L(-1). Detection results of environmental water samples were highly consistent between the bioassay and HPLC/MS.
Article
CdTe quantum dots (QDs) were used as a highly selective probe for the detection of prion protein. Orange-emitting precipitates appeared within 30s of the addition of recombination prion protein (rPrP) to a solution of green-emitting CdTe QDs. This allowed colorimetric qualitative and semi-quantitative detection of rPrP. The decrease in fluorescence intensity of the supernatant could be used for quantitative detection of rPrP. The fluorescence intensity of the supernatant was inversely proportional to the rPrP concentration from 8 to 200 nmol L(-1) (R(2)=0.9897). Transmission electron microscopy results showed that fibrils existed in the precipitates and these were partly transformed to amyloid plaques after the addition of rPrP.
Article
Quantum dots (QDs) are novel photostable semiconductor nanocrystals possessing wide excitation spectra and narrow, symmetrical emission spectra and can be conjugated to a wide range of biological targets, including proteins, antibodies and nucleic acid probes. These characteristics have provoked considerable interest in their use for bioimaging. Much investigation has been performed into their use for multiplex immunohistochemistry and in situ hybridisation which, when combined with multispectral imaging, has enabled quantitation and colocalisation of gene expression in clinical tissue. Many advances have recently been made using QDs for live cell and in vivo imaging, in which QD-labelled molecules can be tracked and visualised in 3-D. This review aims to outline the beneficial properties presented by QDs along with important advances in their biological application.
Article
A comprehensive review of the development of assays, bioprobes, and biosensors using quantum dots (QDs) as integrated components is presented. In contrast to a QD that is selectively introduced as a label, an integrated QD is one that is present in a system throughout a bioanalysis, and simultaneously has a role in transduction and as a scaffold for biorecognition. Through a diverse array of coatings and bioconjugation strategies, it is possible to use QDs as a scaffold for biorecognition events. The modulation of QD luminescence provides the opportunity for the transduction of these events via fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), charge transfer quenching, and electrochemiluminescence (ECL). An overview of the basic concepts and principles underlying the use of QDs with each of these transduction methods is provided, along with many examples of their application in biological sensing. The latter include: the detection of small molecules using enzyme-linked methods, or using aptamers as affinity probes; the detection of proteins via immunoassays or aptamers; nucleic acid hybridization assays; and assays for protease or nuclease activity. Strategies for multiplexed detection are highlighted among these examples. Although the majority of developments to date have been in vitro, QD-based methods for ex vivo biological sensing are emerging. Some special attention is given to the development of solid-phase assays, which offer certain advantages over their solution-phase counterparts.
Article
We have synthesized ZnO nanoparticles by precipitation from zinc acetate in a series of n-alkanols from ethanol to 1-hexanol as a function of temperature. In this system, nucleation and growth are relatively fast and, at longer times, the average particle size continues to increase due to diffusion-limited coarsening. During coarsening, the particle volume increases linearly with time, in agreement with the Lifshitz-Slyozov-Wagner (LSW) model. The coarsening rate increases with increasing temperature for all solvents and increases with alkanol chain length. We show that the rate constant for coarsening is determined by the solvent viscosity, surface energy, and the bulk solubility of ZnO in the solvent.
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Nanocrystals (quantum dots) and other nanoparticles (gold colloids, magnetic bars, nanobars, dendrimers and nanoshells) have been receiving a lot of attention recently with their unique properties for potential use in drug discovery, bioengineering and therapeutics. In this review, structural, optical and biological assets of nanocrystals are summarized and their applications to drug discovery studies are discussed. Unique properties of these nanoparticles can offer new advancements in drug discovery.
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It is generally accepted that copper toxicity is a consequence of the generation of reactive oxygen species (ROS) by copper ions via Fenton or Haber-Weiss reactions. Copper ions display high affinity for thiol and amino groups occurring in proteins. Thus, specialized proteins containing clusters of these groups transport and store copper ions, hampering their potential toxicity. This mechanism, however, may be overwhelmed under copper overloading conditions, in which copper ions may bind to thiol groups occurring in proteins non-related to copper metabolism. In this study, we propose that indiscriminate copper binding may lead to damaging consequences to protein structure, modifying their biological functions. Therefore, we treated liver subcellular membrane fractions, including microsomes, with Cu2+ ions either alone or in the presence of ascorbate (Cu2+/ascorbate); we then assayed both copper-binding to membranes, and microsomal cytochrome P450 oxidative system and GSH-transferase activities. All assayed sub-cellular membrane fractions treated with Cu2+ alone displayed Cu2+-binding, which was significantly increased in the presence of Zn2+, Hg2+, Cd2+, Ag+1 and As3+. Treatment of microsomes with Cu2+ in the microM range decreased the microsomal thiol content; in the presence of ascorbate, Cu2+ added in the nM concentrations range induced a significant microsomal lipoperoxidation; noteworthy, increasing Cu2+ concentration to > or =50 microM led to non-detectable lipoperoxidation levels. On the other hand, microM Cu2+ led to the inhibition of the enzymatic activities tested to the same extent in either presence or absence of ascorbate. We discuss the possible significance of indiscriminate copper binding to thiol proteins as a possible mechanism underlying copper-induced toxicity.
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Quantum dot materials are increasingly used in cellular assays, and offer a powerful and enabling complement to existing methods of labeling proteins, such as green fluorescent protein. These materials give researchers the ability to study specificity and functional responses in cellular systems, in a highly multiplexed manner, at either a molecular or cellular level. The recent literature bears witness to the increasing use of quantum dots for the investigation of chemicals on biological systems, and paves the way to the use of these assays for high-throughput analysis of functional responses in relevant models at scales including molecular, cellular and whole animal.
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The use of quantum dots for biological and biomedical applications is one of the fastest moving fields of nanotechnology today. The unique optical properties of these nanometer-sized semiconductor crystals make them an exciting fluorescent tool for in-vivo and in-vitro imaging as well as for sensoric applications. To apply them in biological fluids or aqueous environment it is essential to modulate the chemical nature of quantum dot surfaces to alter their solubility and add additional chemical functionalities. By employing different coating technologies they cannot only be rendered water soluble but also functionalized to fulfill different tasks, like receptor targeting or sensing of low molecular weight substances. To achieve this goal different polymeric coatings are applied to provide solubility in water and additional functional groups for attachment. Taken together the versatile modifications described in this review make quantum dots a promising alternative to conventional fluorescent dyes and may offer possibilities for new future developments.
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Quantum dots (QDs) are among the most promising items in the nanomedicine toolbox. These nanocrystal fluorophores have several potential medical applications including nanodiagnostics, imaging, targeted drug delivery, and photodynamic therapy. The diverse potential applications of QDs are attributed to their unique optical properties including broad-range excitation, size-tunable narrow emission spectra, and high photostability. The size and composition of QDs can be varied to obtain the desired emission properties a makes them amenable for simultaneous detection of multiple targets. Also, numerous surface functionalizations can be used to adapt QDs to the needed application. Recent reports have shown successful use of QDs in various medical applications. With respect to in vivo applications, caution must be exercised with QDs due to their toxic components. Development of appropriate health and safety regulations and resolution of intellectual property issues are necessary for commercialization. In light of these obstacles however, QDs appear to be too valuable to nanomedicine to dismiss, and will eventually come into routine practical use.
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Quantum dots show strong fluorescence emission and long stability compared with classical organic fluorescent dyes; therefore, quantum dots take the place of other dyes in Western blot, immunostaining and bioimaging. Since macrophage plays crucial roles in many pathophysiological processes, tracking macrophage migration, homing and fate is important for understanding the complex roles of macrophages in disease or developing disease diagnosis. Because of the high expression of mannose receptor on macrophage, mannosylation is an attractive strategy to label macrophage. In this study, using polyethylene-glycol (PEG) (M.W. 2,000; PEG(2,000))-coated quantum dots, we prepared mannosylated PEG(2,000) (Man-PEG(2,000)) quantum dots for labeling macrophage. The uptake characteristics of Man-PEG(2,000) quantum dots were investigated by primary cultured peritoneal macrophages. The uptake of Man-PEG(2,000) quantum dots was inhibited by an excess amount of mannose, suggesting mannose receptor-mediated uptake of Man-PEG(2,000) quantum dots. The result of MTT assay suggested the extremely low cytotoxicity of Man-PEG(2,000) quantum dots. In conclusion, the Man-PEG(2,000) synthesized is safe and is taken up by macrophage mannose receptor recognition.
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Quantum dots (QDs), nanometer-sized fluorescent probes with unique optical and electronic properties, offer a promising and powerful tool for cancer imaging and diagnostics. For the past few years, QDs were actively developed for biomolecular profiling of cancer biomarkers, in vivo tumor imaging, and even targeted drug delivery. These emerging applications are currently being improved and integrated into clinical practice. In this article, we describe the development of multifunctional QDs and their potential applications in oncology, with a particular emphasis on the diagnosis, prognosis, and treatment of urologic cancers.
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Semiconductor quantum dots (QDs) are tiny light-emitting particles on the nanometer scale, and are emerging as a new class of fluorescent labels for biology and medicine. In comparison with organic dyes and fluorescent proteins, they have unique optical and electronic properties, with size-tunable light emission, superior signal brightness, resistance to photobleaching, and broad absorption spectra for simultaneous excitation of multiple fluorescence colors. QDs also provide a versatile nanoscale scaffold for designing multifunctional nanoparticles with both imaging and therapeutic functions. When linked with targeting ligands such as antibodies, peptides or small molecules, QDs can be used to target tumor biomarkers as well as tumor vasculatures with high affinity and specificity. Here we discuss the synthesis and development of state-of-the-art QD probes and their use for molecular and cellular imaging. We also examine key issues for in vivo imaging and therapy, such as nanoparticle biodistribution, pharmacokinetics, and toxicology.