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Over-Stretching Tolerant Conductors on Rubber Films by Inkjet-Printing Silver Nanoparticles for Wearables
摘要： The necessity to place sensors far away from the processing unit in smart clothes or artificial skins for robots may require conductive wirings on stretchable materials at very low-cost. In this work, we present an easy method to produce wires using only commercially available materials. A consumer grade inkjet printer was used to print a wire of silver nanoparticles with a sheet resistance below 1 Ω/sq. on a non-pre-strained sheet of elastic silicone. This wire was stretched more than 10,000 times and was still conductive afterwards. The viscoelastic behavior of the substrate results in a temporarily increased resistance that decreases to almost the original value. After over-stretching, the wire is conductive within less than a second. We analyze the swelling of the silicone due to the ink’s solvent and the nanoparticle film on top by microscope and SEM images. Finally, a 60 mm long stretchable conductor was integrated onto wearables, and showed that it can bear strains of up to 300% and recover to a conductivity that allows the operation of an assembled LED assembled at only 1.8 V. These self-healing wires can serve as wiring and binary strain or pressure sensors in sportswear, compression underwear, and in robotic applications.
关键词： silver nanoparticles,stretchable,printed electronics,wearables,inkjet printing
更新于2025-09-23 15:22:29
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Enhanced NLO activity of organic 2-methyl-5-nitroaniline crystal: Experimental and computational investigation with and without silver addition
摘要： The nonlinear optical (NLO) material, 2-methyl-5-nitroaniline (M5NA), is synthesized and the crystals are grown by slow evaporation technique. The theoretical vibrational spectral analyses are done for the first time for M5NA using B3LYP computational method with the basis set cc-pVTZ. Natural Bond Orbital (NBO) and Atoms In Molecules (AIM) analyses are carried out for obtaining the charge transfer interactions and the Hirshfeld surface analysis with the fingerprint plot is performed for finding out the intermolecular interaction sites of the molecule. Using the theoretical and experimental IR and Raman spectra, the vibrations of M5NA are estimated. Changes in the linear and nonlinear optical properties with the addition of silver nanoparticles are studied from the UV–vis absorption spectra and the Z-Scan curves. A comparison of the hyperpolarizability values is done with pure and silver-added M5NA.
关键词： NLO,HOMO-LUMO,DFT,Vibrational spectroscopy,Silver nanoparticles
更新于2025-09-23 15:22:29
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Detection of the conformational changes of <i>Discosoma</i> red fluorescent proteins adhered on silver nanoparticles-based nanocomposites <i>via</i> surface-enhanced Raman scattering
摘要： Description of the relationship between protein structure and function remains a primary focus in molecular biology, biochemistry, protein engineering and bioelectronics. Regardless the targeted application, the current strategies on revealing the relationship between protein structure and function lead to exposure and interaction of proteins with non-biological organic and inorganic solid surfaces. Proper description of the underlying mechanisms will certainly unveil the fundamental protein-adsorption problem and add value to the effort of record and quantification of the conformational changes of the protein native state when interacting with solid surfaces. To that end the application of physics-based diagnostic methods is suitable and highly demanded. Raman spectroscopy appears the most frequently used method for the study of biomolecule recognition, and ultra-sensitive analysis, down to a single molecule. However, to tackle the sensitivity limitations of Raman spectroscopy imposed by the small Raman cross sections, the biological systems should be coupled with metallic nanostructures. The scattering efficiency can be thus increased by several orders of magnitude due to the activation of localized surface plasmon resonance (LSPR) that induces strong enhancement of the electromagnetic (EM) field in the vicinity of the metallic surface. This enables to largely extend the application of Raman spectroscopy in molecular spectroscopy, biomolecule recognition, and ultra-sensitive analysis, down to a single molecule. Besides the sensing properties, the strong EM enhancement can be exploited to probe protein conformational changes under photoexcitation, including real-time monitoring. Therefore, since its discovery in the late 70s, the Surface-Enhanced Raman Scattering (SERS) has proven to be a very powerful and reliable analytical tool for chemo- and bio-sensing, due to the strong enhancement of the vibrational signatures of analytes in different chemical environments. In this context, a lot of resources and time have been employed in the effort to develop plasmonic substrates based on metallic nanostructures aiming at a further increase of the EM enhancement for the realization of noninvasive, highly-sensitive, and large-scale optical sensors. A large variety of metallic nanostructure morphologies and arrangements (nanosphere, nanotriangles, nanodisks, nanorods, nanocubes, etc.) and different coupling geometries (dimers, trimers, arrays, etc.) have been developed up to date for SERS platforms. However, their conversion to macroscopic plasmonic substrates relies generally on the NPs volunteer arrangement on dielectric surfaces (mainly through applying chemical methods), thus often resulting in non-uniform distribution on large areas, without a well-defined control of the spacing between the metallic nanostructures and the probed molecules, high point-to-point variability, scarce reproducibility and stability under irradiation conditions (due to photothermal and photodegradation processes). To overcome the limitations in producing solid SERS substrates various physical approaches, like thermal evaporation, combined nanoimprint lithography-shadow evaporation, gas aggregation source (GAS), pulsed laser deposition (PLD), low-energy ion beam synthesis (LE-IBS), and plasma-based deposition processes, have been proposed in the literature. It is generally acknowledged that the silver nanoparticles (AgNPs) realize the best nanoscale antenna in the visible range for amplifying local electronic and vibrational signals, thus providing unique molecular information in the optical far-field regime. Indeed, compared to gold nanoparticles, the AgNPs offer the advantage of stronger plasmonic enhancement because of lower interference between intraband and interband electronic transitions. Moreover, the use of AgNPs covers another aspect of the relationship between protein structure and function which concerns the biological activity of the AgNPs. Because of their antimicrobial properties, the AgNPs have the potential to impact human health and environment. The biological activity of AgNPs goes both ways, through the activity of ionic silver (Ag+) and through direct contact with the AgNPs resulting in protein denaturation at different cell locations; specifically sensible are those enzymes of the respiratory chain and transport channels. Therefore, there exists a recognized need to address the relationship between protein structure and function from two distinctly different vantage points: (i) quantification of the conformational changes of proteins by using the antenna effect of AgNPs and (ii) analysis of the conformational changes of proteins induced by the AgNPs extreme chemical and biological activities. The intent of this work is to bring additional insight into the mechanisms of adsorption of proteins on solid surfaces through quantification of the conformational changes of proteins adhered on AgNPs-based nanocomposites via SERS. We focus on the wild-type Discosoma recombinant red fluorescent protein (DsRed), belonging to the family of naturally fluorescent proteins (FPs). The strong interest toward the FP family originates from their application in molecular biology as reporters of gene expression, as noninvasive markers in molecular biology and other singular events of cell activity. Potential use of the FPs extends toward therapeutics, tissue regeneration, bioelectronics and protein engineering. The most widely characterized member of this family is the green fluorescent protein (GFP). The lately cloned from reef coral Discosoma sp. DsRed protein possesses the longest yet reported, for a wild-type spontaneously fluorescent protein, excitation and emission maxima at 558 nm and 583 nm, respectively. Owing to its high fluorescence yield the red fluorescent DsRed protein has become important both as a model for understanding fluorescent proteins and as a tool for biomedical research. The DsRed protein and its engineered derivatives have found broad use in cell and molecular biology including fluorescence microscopy as a marker, fluorescence correlation spectroscopy (FCS) and fluorescence activated cell sorting (FACS). Recently, the DsRed was found suitable for rational design of ultra-stable and reversible photoswitches for super-resolution imaging. Moreover, it has been hypothesized that FPs from reef-building corals operate as part of an adaptive mechanism to optically interact and to regulate the symbiotic relationship between corals and photosynthetic algae. Structural rearrangements near the chromophore influence the maturation speed and brightness of the DsRed variants. It is therefore essential to examine the conformational transitions that affect the protein’s ability to transfer optical excitation energy. Studies of the conformational changes of DsRed protein have been reported in the literature but the DsRed Raman fingerprints were investigated only by recurring to chemically synthesized model chromophores. However, the later differ from the wild-type DsRed protein for the absence of the α-helix and β-sheets that naturally surround the chromophore and for the different extensions of the conjugated π-system. The choice of chemically synthesized model chromophores is explained by the complications brought by the presence of immature green species in the solution created as a photoproduct of the red ones, thus often resulting in an unclear or incomplete band assignment. The novelty of this work lays down the point that we work with the wild-type DsRed protein in its native state and not with DsRed model chromophore. All reported experimental studies in the literature were performed in solution. No information on the DsRed protein structural and conformational changes can be found when the DsRed protein is adhered on a solid substrate and irradiated by light. The lack of information on the above discussed issues motivated this study focusing on the investigation of the interaction of wild-type DsRed proteins with AgNPs-based plasmonic substrates. Our approach involves analysis of dehydrated DsRed protein layers in link with natural conditions during drying. To perform the SERS study on the conformational changes of DsRed proteins adhered on AgNPs-based nanocomposites we have elaborated, by plasma process, highly uniform and reproducible plasmonic substrates composed of a single layer of AgNPs coated by a silica layer. Focus was made on the possibility to well control, on a large scale, the AgNPs size distribution and interparticle distances. The resulting uniformity of hot-spot distribution guarantees the reproducibility and stability of this plasmonic sensor. Subsequently, we show how the enhanced EM field in the vicinity of the AgNPs could be employed to detect the presence and identify the conformational changes of proteins, adsorbed and adhered to the plasmonic substrate, during optical irradiation. The achieved enhancement of the electromagnetic field in the vicinity of the AgNPs is as high as 105. This very strong enhancement factor allowed detecting Raman signals from discontinuous layers of DsRed issued from solution with protein concentration of only 80 nM. Three different conformations of the DsRed proteins after adhesion and dehydration on the plasmonic substrates were identified. It was found that the DsRed chromophore structure of the adsorbed proteins undergoes optically assisted chemical transformations when interacting with the optical beam, which leads to reversible transitions between the three different conformations. The proposed time-evolution scenario endorses the dynamical character of the relationship between protein structure and function. It also confirms that the conformational changes of proteins with strong internal coherence, like DsRed proteins, are reversible.
关键词： plasmonic substrate,protein conformation,surface-enhanced Raman scattering,plasma deposition process,Discosoma red-fluorescent protein DsRed,Silver nanoparticles
更新于2025-09-23 15:22:29
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Speciation and Determination of Ionic and Trace-Level Colloidal Silver in Selected Personal Care Products by Thermal Lens Spectrometry
摘要： The collinear dual beam thermal lens spectrometric (TLS) detection in batch mode (BM), as well as combined with the flow injection analysis (FIA), was applied to determine the colloidal silver in personal care products available in the public pharmacies and declared by producers to contain nanosilver at the level of 5-30 μg ml-1. It was found, that the examined samples contain mainly ionic silver (99% or more), whereas the colloidal form of silver is at the level of less than 1 μg ml-1. The TLS methods were confirmed to be fast, precise, highly accurate and highly sensitive with limits of quantitation of 0.30 ng ml-1 and 1.50 ng ml-1 and relative standard deviations not higher than 1.2% and 6.0% for BM- and FIA-TLS configuration, respectively. The developed TLS methods have nearly 60 times lower LOQ values concerning the colloidal silver determination than the classical spectrophotometric method. To verify the obtained results of the real sample analysis the total amount of ionic silver was determined by the use of ICP-OES technique.
关键词： Thermal lens spectrometric determination,Personal care products,Flow injection analysis,Silver nanoparticles,Colloidal silver
更新于2025-09-23 15:21:21
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Effects of reaction conditions on light-dependent silver nanoparticle biosynthesis mediated by cell extract of green alga Neochloris oleoabundans
摘要： Silver nanoparticles (AgNPs) were synthesized by incubating the mixture of AgNO3 solution and whole-cell aqueous extracts (WCAEs) of Neochloris oleoabundans under light conditions. By conducting single-factor and multi-factor optimization, the effects of parameters including AgNO3 concentration, pH, and extraction time were quantitatively evaluated. The optimal conditions in terms of AgNP yield were found to be 0.8 mM AgNO3, pH 5, and 9-h extraction. The AgNPs thus synthesized were quasi-spherical with a mean particle diameter of 16.63 nm and exhibited decent uniformity as well as antibacterial activities, which may facilitate AgNP biosynthesis’s application in the near future.
关键词： Extraction time,Biosynthesis,Silver nanoparticles,Light-dependent reaction,AgNO3 concentration,pH,Microalgae
更新于2025-09-23 15:21:21
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Ecofriendly synthesis of monodispersed silver nanoparticles using Andean Morti?o berry as reductant and its photocatalytic activity
摘要： Morti?o (Vaccinium floribundum Kunth) berry is an endemic fruit from the Andes region and rich in vitamins, polyphenolic and anthocyanin compounds. The present report describes the Morti?o berry extract mediated biosynthesis of silver nanoparticles and their photocatalytic evaluations. The conditions for the synthesis of silver nanoparticles were optimised by adjusting amount of berry extract, pH, and time. Biosynthesis of silver nanoparticles was primarily identified by the appearance of yellow colour and confirmed by measurements of UV-visible spectroscopy. Particle size distribution, morphology and crystalline nature of silver nanoparticles were characterised by transmission electron microscopy, dynamic light scattering, and X-ray diffraction techniques. All characterisation technique reveals that the generated silver nanoparticles were stable, non-aggregated, monodispersed, spherical shape with an average size of 20.5 ± 1.5 nm and face centred cubic in nature. In order to evaluate photocatalytic activity, degradation of methylene blue dye by silver nanoparticles under sunlight was used as model system. It showed photocatalytic activity against methylene blue dye (5 mg/L, k= 0.00707788 min-1), efficiently. This ecofriendly approach highlighted the importance of Morti?o berry in green nanotechnology and generates a new scope of other Andean fruits in engineering applications.
关键词： Photocatalysis,Ecofriendly,Phytochemicals,Morti?o berry,Transmission Electron Microscopy,Silver nanoparticles
更新于2025-09-23 15:21:21
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Sensitive surface-enhanced Raman scattering substrates based on anti-pyramidal gold architectures decorated with silver nanoparticles
摘要： A micro-structured gold surface, consisting of a periodic square–based anti–pyramidal array (Klarite) with a smooth boundary surface on which silver nanoparticles (diameter: 60 nm) were deposited, produced an active surface enhanced Raman scattering substrate. With p-aminothiophenol as a probe molecule, the Raman activity of the micro–structured surface was compared before and after deposition of the silver nanoparticles. Experimental results show that the Raman spectra on the silver/p-aminothiophenol/Klarite structure is stronger than that on the silver/p-aminothiophenol/gold film and the Raman spectra on the silver/p-aminothiophenol/gold film is stronger than that on silver/p-aminothiophenol, p-aminothiophenol/Klarite structure, p-aminothiophenol/gold film, which is confirmed by numerical simulations. A similar result is obtained with crystal violet as test molecule.
关键词： Anti-pyramidal architectures,surface enhanced Raman scattering,p-aminothiophenol,silver nanoparticles
更新于2025-09-23 15:21:21
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GREEN SYNTHESIS OF SILVER NANOPARTICLES FROM AQUEOUS STEM EXTRACT OF CERIOPS TAGAL
摘要： Biosynthesis of reliable and eco-friendly nanoparticles is an important branch of green nanotechnology. Ceriops tagal, a mangrove plant has various medicinal properties. Synthesis of C.tagal mediated nanoparticles may further enhance its medicinal potency. The aqueous stem extract of C.tagal was used as a bio-reducing agent for synthesis of silver nanoparticles Reduction of metal ions was confirmed by Ultraviolet-visible absorption spectroscopy, transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. Before and after bio-reduction changes in functional groups of plant extract was recorded by FTIR spectra. The kinetics of particle formation was dependent on time, temperature and metal salt concentration. UV-Visible spectroscopy demonstrated peak at 455 nm. TEM and XRD results revealed shapes, size and structure of synthesized nanoparticles. These results have indicated the formation of silver nanoparticles.
关键词： Mangroves,silver nanoparticles,aqueous extract,Ceriops tagal
更新于2025-09-23 15:21:21
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Controlled synthesis of AgNPs@ZIF-8 composite: Efficient heterogeneous photocatalyst for degradation of methylene blue and congo red
摘要： Photocatalytic degradation of organic dyes using novel metal based composite materials is one of the most intriguing and sustainable ways to reduce water pollution. Herein, facile synthesis of AgNPs@ZIF-8 via in situ generation of AgNPs and ZIF-8 (Zeolitic Imidazolate Framework) was demonstrated, and composites with different Ag contents (abbreviated as SZ, SZ1, SZ2 SZ3) were well characterized by powder X-ray diffraction (PXRD) pattern, X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red (FT-IR) spectroscopy. Encapsulation/decoration of AgNPs (particle size: 96 nm in SZ and 17.32 ± 2.35 nm in SZ1 to SZ3) in ZIF-8 matrix has been ensured by TEM and EDX analysis. Brunauer-Emmett-Teller (BET) adsorption-desorption studies indicate that the surface area of SZ (982 m2 g?1) is less than those of SZ1 to SZ3 (due to the encapsulation of large amount of Ag nanoparticles in SZ). The synthesized composites are thermally stable up to 400 °C in air and nitrogen atmosphere. AgNPs@ZIF-8 exhibited excellent photocatalytic efficiency to degrade organic dyes compared to ZIF-8 due to its large surface area, highly porous and unique synergistic properties. SZ2 degrades off 97.25 % methylene blue (MB) and 100 % congo red (CR) at pH ≥ 7. Further, degraded fragments were analysed by GC–MS and plausible degradation mechanism was discussed.
关键词： Silver nanoparticles,Organic pollutants,Photocatalyst,Heterogeneous catalysis,Composite materials
更新于2025-09-23 15:21:01
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Optical sensors based on silver nanoparticles for determination of pharmaceuticals: An overview of advances in the last decade
摘要： This review focuses on optical nanosensors based on silver nanoparticles (Ag NPs) and demonstrates their applications in the determination of pharmaceutical compounds in the last decade. Such optical sensors have received high attention in the analytical field owing to their low cost and simplicity since they do not require any complex or expensive instrumentation. This article reviews Ag NP-based optical methods for the determination of pharmaceutical compounds from 2010 to 2020. The reported optical methods are classified into four types: spectrophotometry, spectrofluorimetry, scattering and chemiluminescence. Ag NPs play different roles in the different sensing platforms used by these methods, the details of which are carefully explained in this review. Moreover, the relevant analytical parameters of the developed methods are categorized by role and tabulated. It is hoped that this review will stimulate further research in this field with similar nanostructures.
关键词： Silver nanoparticles,Optical sensors,Pharmaceutical compounds
更新于2025-09-23 15:21:01