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Silver nanoparticles with reduced graphene oxide for surface-enhanced vibrational spectroscopy of DNA constituents
摘要： Composite of silver nanoparticles with reduced graphene oxide flakes is proposed for surface enhanced vibrational spectroscopy, particularly for detection of adenine and thymine as constituents of deoxyribonucleic acid. Composite was formed by original method implying simultaneous reduction of silver ions and graphene oxide by discharge plasma at the gas–liquid interface. Combination of nanosized silver with reduced graphene oxide provided greater enhancement of Raman light scattering and infrared light absorption in comparison with separately used components. Addition of the composite to water solutions of adenine and thymine allowed detection of these analytes at micromolar concentrations. Composite of nano-silver with reduced graphene oxide can be prospective for surface enhanced spectroscopy as an alternative to the expensive lithographically prepared noble metal substrates.
关键词： Adenine,Surface Enhanced InfraRed Absorption (SEIRA),Thymine,Reduced graphene oxide,Discharge plasma,Silver nanoparticles,Surface Enhanced Raman Scattering (SERS)
更新于2025-09-23 15:23:52
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A Study on the Solvent Vapor Induced Film Formation of PS/AgNPs Composites
摘要： In this study, pyrene (P) tagged polystyrene (PS) latex dispersions and silver nanoparticles (AgNPs) were mixed at various weight fractions in the range between 0 and 50 wt%. The prepared mixtures were dropped on the glass substrates by considering drop casting method and were dried at the room temperature. The resultant powder films were then exposed to solvent vapor to monitor how film formation and morphological behaviors of PS/AgNPs composites are altered. Film formation behavior of composites was assessed via fast transient fluorescence (FTRF) which measures the ?uorescence lifetimes of P from its decay traces during vapor exposure process. It was observed that pyrene lifetimes decreased as vapor exposure time, t increased. A Stern–Volmer kinetic analysis was used for low quenching ef?ciencies to interpret the decrease in pyrene lifetimes. UV-Vis (UVV) technique was employed to monitor optical transparency of the films. In the range of 0-20 wt% of AgNPs content, smooth and transparent films were obtained. However, above this range, the films were seen that they have low transparency and poor film formation since the increment in AgNPs content was lead to aggregations. The Prager–Tirrel model was employed to the FTRF data to obtain back-and-forth frequencies, ν, of the reptating PS chains during vapor induced ?lm formation process. SEM images of the samples were taken after film formation process is completed and were found to be consistent with optical and fluorescence quenching data.
关键词： Polystyrene latex,film formation,reptation frequency,fluorescence lifetime,nanocomposites,crossing-density,Silver nanoparticles,vapor-induced
更新于2025-09-23 15:23:52
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Utility of surface plasmon resonance response of silver nanoparticles for assay of Teicoplanin in human plasma using spectrofluorimetric technique
摘要： Teicoplanin (TEIC) is a glycopeptide antimicrobial medication for management of several bacterial infectious diseases caused by gram-positive bacteria including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. Novel, very simple, fast and cost-effective two spectrofluorimetric methods were developed for the ultra-trace determination of TEIC in pharmaceutical vials and human plasma. The investigated methods based on measuring the fluorescence of TEIC in methanol (method A) and enhancing its fluorescence by 10 folds using silver nanoparticles (AgNPs) without any solvent extraction (method B). The fluorescence of TEIC was investigated at 385nm (excitation at 335 nm) with calibration ranged from 1 to 25 ng mL?1 and from 0.6 to 30 ng mL?1 with Limit of detection (LOD) of 280 and 160 pg mL?1 for method A and B respectively. The established methods were optimized, validated and bio-analytically validated via ICH and US-FDA guidelines. The performed methods were used to determine TEIC in human plasma with high percentage recovery of 98.8 ± 1.75. Further, the proposed methods were applied to study the stability of TEIC after exposure to various degradation stress conditions and kinetic degradations.
关键词： Spectrofluorimetry,Teicoplanin,Silver nanoparticles,Metal-enhanced fluorescence,Human plasma analysis
更新于2025-09-23 15:23:52
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Quantification of Glucose via in situ Growth of Cu2O/Ag Nanoparticles
摘要： The monitoring of glucose levels in blood is extremely important for the effective control of diabetes. Nanomaterial-based approaches for the quantification of glucose typically require two steps: material preparation and the actual glucose measurement. Herein, we report a single-step method that combines these functions via the in situ growth of Cu2O/Ag nanoparticles (NPs). Mechanistically, we use glucose itself to reduce Cu2+ and Ag+ ions that are stabilized with 3-mercaptopropionic acid (3-MPA) and bovine serum albumin (BSA) under alkaline conditions to form Cu2O/Ag NPs and produce a color change in solution due to plasmonic resonance at 400 nm, which can be related back to the concentration of glucose. We study several factors in this reaction, including the molar ratios of the metal ions and 3-MPA, the reaction time, and the temperature to control the synthesis of the Cu2O/Ag NPs and thus their sensitivity toward glucose. Introducing BSA into the system is a key factor for the quantification of glucose in blood without pretreatment, improving the probe’s limit of detection and reducing the sample volumes to 1 μL. This colorimetric assay based on Cu2O/Ag NPs exhibits excellent sensitivity and specificity toward glucose, and a linear relationship with glucose concentrations ranging from 15 to 300 μM and a limit of detection of 9.2 μM. As proof of concept, we demonstrated that the Cu2O/Ag NP probes could successfully detect glucose in two representative blood samples by neglecting interferences from various common species, demonstrating the potential of this technique in point-of-care analysis.
关键词： plasmonic resonance,3-mercaptopropionic acid,bovine serum albumin,silver nanoparticles,glucose quantification,Cu2O
更新于2025-09-23 15:23:52
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Facile synthesis of silver-polypyrrole nanocomposites: Use of ionic liquid as solvent and template
摘要： In this study we show a facile method to synthesize nanocomposites of PPY and silver from the direct oxidation of pyrrole by silver cations from silver bis(trifluoromethanesulfonyl)imide (AgTf2N), using 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMImTf2N) as solvent and template to the hybrid material formation. Some synthesis parameters, such as initial concentration of the oxidant agent (C) and oxidant-to-monomer molar ratio (K) were varied in order to evaluate their influence on the final product. The black powders obtained, according to the characterization results, contain doped polypyrrole and silver nanoparticles amounts ranged from 26 to 36 wt%, depending on the C and K parameters utilized in the syntheses. The measured electrical conductivity values of the samples were in the order of 10-2 S cm-1, which classify the hybrid materials as semiconductor. By adding the HTf2N acid to the synthesis, a sample with more elevated electrical conductivity (0.12 S cm-1) was obtained, caused by the higher protonation degree of the oxidized units in the polymer.
关键词： Polypyrrole,Nanocomposite,Ionic liquids,Silver nanoparticles
更新于2025-09-23 15:23:52
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Surface-Enhanced Raman Scattering (SERS) With Silver Nano Substrates Synthesized by Microwave for Rapid Detection of Foodborne Pathogens
摘要： Rapid and sensitive methods have been developed to detect foodborne pathogens, a development that is important for food safety. The aim of this study is to explore Surface-enhanced Raman scattering (SERS) with silver nano substrates to detect and identify the following three foodborne pathogens: Escherichia coli O157: H7, Staphylococcus aureus and Salmonella. All the cells were resuspended with 10 mL silver colloidal nanoparticles, making a concentration of 107 CFU/mL, and were then exposed to 785 nm laser excitation. In this study, the results showed that all the bacteria can be sensitively and reproducibly detected directly by SERS. The distinctive differences can be observed in the SERS spectral data of the three food-borne pathogens, and the silver colloidal nanoparticles can be used as highly sensitive SERS-active substrates. In addition, the assay time required only a few minutes, which indicated that SERS coupled with the silver colloidal nanoparticles is a promising method for the detection and characterization of food-borne pathogens. At the same time, principle component analysis (PCA) and hierarchical cluster analysis (HCA) made the different bacterial strains clearly differentiated based on the barcode spectral data reduction. Therefore, the SERS methods hold great promise for the detection and identification of food-borne pathogens and even for applications in food safety.
关键词： silver nanoparticles,rapid detection,food safety,Surface-enhanced Raman scattering,foodborne pathogens,bioanalysis
更新于2025-09-23 15:22:29
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Long-Term Stability of Two Thermoplastic Polymers Modified with Silver Nanoparticles
摘要： The aim of this study was to investigate the mechanical properties of polymeric composites prepared via extrusion and injection moulding. Four stable thermoplastic polymers were used as composites matrices (two kinds of polymethyl methacrylate and two kinds of co-polymer acrylonitrile-butadiene-styrene). Silver nanoparticles AgNPs were used as a modifying phase. Mechanical properties of testes materials were determined during the uniaxial stretching. Surface properties such as roughness and contact angle were also evaluated. The materials’ stability was assessed using scanning electron microscopy and non-destructive ultrasonic testing. All measurements were carried out at time intervals, determining both the initial parameters and after 6 and 12 months of incubation in deionized water. The obtained results proved that neither the preparation technology nor the amount of the modi?er adversely affect the mechanical properties of the tested composites. The incorporated modi?er does not change the surface properties signi?cantly. The studies conducted after the materials’ incubation in water indicate their stability.
关键词： biomaterials,silver nanoparticles,biostable polymers
更新于2025-09-23 15:22:29
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Ternary Ag nanoparticles/natural-magnetic SiO2-nanowires/reduced graphene oxide nanocomposites with highly visible photocatalytic activity for 4-nitrophenol reduction
摘要： Agglomerate and reuse limit the promising application of silver nanoparticles (AgNPs) as catalyst. To eliminate those disadvantages, herein, Fe-containing silica nanowires (SiO2NWs) and reduced graphene oxide (RGO) are used as suitable substrates to prepare AgNPs/SiO2NWs/RGO nanocomposite via self-assembly approach. The nanocomposite mostly assembled with each other via intermolecular hydrogen bond and electrostatic adsorption to form a three-dimensional network structure. The AgNPs/SiO2NWs/RGO nanocomposite exhibit excellent photocatalytic activity for 4-nitrophenol reduction by NaBH4, originating from that the nearly mono-dispersed AgNPs are adhered on the surface of the SiO2NWs and RGO, allowing the effective contact of reactants with catalyst and facilitating the electron transfer between them in the reaction. The obtained nanocomposites exhibit the superior stability and can be easily recovered with their fully catalytic activities due to the hydrophobic and magnetic properties of the nanocomposites. It shows the great prospect for the 4-NP reduction in practice and is promising for wide applications in visible light catalytic reaction.
关键词： SiO2 nanowires,Photo-catalytic activity,Reduced graphene oxide,Silver nanoparticles,4-Nitrophenol reduction
更新于2025-09-23 15:22:29
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‘Planetary’ silver nanoparticles originating from a magnetron sputter plasma
摘要： In a gas aggregation cluster source, nanoparticles are formed by aggregation of single atoms to particles as well as by agglomeration of smaller particles to form larger particles. Because the small particles are often electrically charged, it is possible that particles are mutually attracted or repelled by electric forces. In this work we report the observation of bound multi-nanoparticle systems which are the result of the electrical and centrifugal forces acting on nanoparticles in a magnetron sputtering cluster source. Transmission electron microscopy analysis of the deposited ‘planetary’ nanoparticle systems exhibits characteristic inter-particle distances and sizes, consistent with different charge states of the particles. Simulations confirm the presence of metastable bound nanoparticle systems up to at least 7/8 satellites. The discovery of such ‘planetary’ nanoparticle systems inside a cluster source opens up possibilities for more research into their properties and how they can be further controlled and explored.
关键词： planetary,silver nanoparticles,particle orbits,satellites,gas aggregation cluster source,magnetron sputtering
更新于2025-09-23 15:22:29
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Kinetics of Ag <sub/>300</sub> nanoclusters formation: The catalytically effective nucleus via a steady-state approach
摘要： The kinetics of formation of silver nanoparticles consisting of nearly 300 metal atoms is investigated, which were prepared by reduction of silver nitrate with hydrazine in ethylene glycol at 25?C without any stabilizer other than the glycol solvent. The resulting sigmoidal kinetic curves are analyzed by using the 1997 Finke–Watzky two-step mechanism of slow continuous nucleation with subsequent fast autocatalytic surface growth. The kinetics of homogeneous nucleation of metal nanoparticles was analyzed using the assumption about the stepwise adjunction of precursor and the quasi steady-state approximation. The equations were proposed to calculate the concentration of the formed metal nanoparticles and their mean size from the experimentally determined values of the Finke–Watzky rate constants. It is shown that a stepwise nucleation process can be described in the terms of the catalytically effective nucleus concept and that the number of atoms in the catalytically effective nucleus can be estimated.
关键词： silver nanoparticles,homogeneous nucleation,kinetics,catalytically effective nucleus concept
更新于2025-09-23 15:22:29