Experimental High-Resolution Observation of the Truncated Double-Icosahedron Structure: A Stable Twinned Shell in Alloyed Au-Ag Core@Shell Nanoparticles.

Given the binary nature of nanoalloy systems, their properties are dependent on their size, shape, structure, composition, and chemical ordering. When energy and entropic factors for shapes and structure variations are considered in nanoparticle growth, the spectra of shapes become so vast that even metastable arrangements have been reported under ambient conditions. Experimental and theoretical variations of multiply twinned particles have been observed, from the Ino and Marks decahedra to polyicosahedra and polydecahedra with comparable energetic stability among them. Herein, we report the experimental production of a stable doubly truncated double-icosahedron structure (TdIh) in Au-Ag nanoparticles, in which a twinned Ag-rich alloyed shell is reconstructed on a Au-Ag alloyed Ino-decahedral core. The structure, chemical composition, and growth pathway are proposed on the basis of high-angle annular dark-field scanning transmission electron microscopy analysis and excess energy calculations, while its structural stability is estimated by large-scale atomic molecular dynamics simulations. This novel nanostructure differs from other structures previously reported.

Plasmonic effect of metal nanoparticles on the photocatalytic properties of TiO2/rGO composite.

A comparative study of the plasmon effect of Ag and Au nanoparticles on TiO2/rGO nanocomposite was carried out. The synthesis of Au and Ag nanoparticles was carried out by laser ablation. The morphology and structure of the nanocomposites were studied by EDA, HRTEM, XRD and Raman spectroscopy. It was shown that the absorption capacity of the nanocomposite material was increased in the visible range of the spectrum when Ag and Au nanoparticles were added to TiO2/rGO. This leads to an increase in their photocatalytic activity. The photocurrent generated by NC/Au 10-11films is in 3.8 times and NC/Ag 10-12is in 2 times higher compared to pure TiO2/rGO film. Similar results were obtained from experimental data on the dyes photodegradation. In the presence of plasmon nanoparticles a significant enhancement in the electrical properties of the TiO2/rGO nanocomposite was recorded. The charge carrier transfer resistance in nanocomposites was decreased by almost ∼7 times for NC/Au,10-11and ∼4 times for NC/Ag,10-12films compared to pure TiO2/rGO. In addition, for nanocomposites with Ag or Au nanoparticles, a decrease in the effective electron lifetime was observed. The data obtained allow us to conclude that plasmonic NPs have a synergistic effect in TiO2/rGO nanocomposites, which consists in modifying both their light-harvesting properties and charge-transport characteristics. The results obtained can be used for the design of materials with improved photocatalytic and optoelectronic characteristics.

Highly luminescent, fast switching electro-optical device based on core-shell bimetallic nanoparticles/ ferroelectric liquid crystal composites.

Owing to the passive nature of liquid crystal (LC) materials, achieving luminous displays using pure LC materials is challenging. In addition, it is difficult to achieve a fast switching time using pristine ferroelectric LC devices without compromising their cell thickness. Herein, we have developed a fast switching and highly luminescent electro-optical device by dispersing a minute concentration of bimetallic nanoparticles (Au@Ag NPs) having a spherical gold core and a silver shell within a ferroelectric liquid crystal (FLC) host matrix, ZLI3654. Au@Ag core-shell NPs having synergic attributes of both counterparts were successfully synthesized by a facile seed-mediated route. The Au core helps to tune the shape of the Ag shell and provides enhanced electron density as well as improved stability against oxidation. Introducing nanoparticles induces little structural modifications to the host FLC, resulting in an improvement in the mesogenic alignment. Interestingly, ∼29-fold enhancement in the photoluminescence (PL) intensity is observed on dispersing 0.25 wt% of Au@Ag NPs into the FLC host matrix. The enhanced electromagnetic field in the FLC-nanocomposite is attributed to the Localized Surface Plasmon Resonance of Au@Ag NPs, which strengthens the photon absorption rates by the FLC molecules, culminating in the massive enrichment of the PL intensity. In addition, the improved localized electric field inside the FLC device led to a noticeable enhancement in the spontaneous polarization, dielectric permittivity, and, most interestingly, ∼53% fastening in the switching time at an optimum concentration (0.25 wt%) of Au@Ag NPs. The improved electro-optical parameters of the Au@Ag NPs/FLC composite have been compared with the performance of both pristine Au NPs/FLC and Ag NPs/FLC composites, respectively, for the comprehensiveness of the study. The present study paves a systematic way to develop FLC-based advanced electro-optical devices with faster switching and higher luminescence properties.

Etching of Ag nanoparticles triggered bidirectional regulation for electrochemiluminescence ratiometric immunoassay.

A highly efficient ratiometric electrochemiluminescence (ECL) immunoassay was explored by bidirectionally regulating the ECL intensity of two luminophors. The immunoassay was conducted in a split-type mode consisting of an ECL detection procedure and a sandwich immunoreaction. The ECL detection was executed using a dual-disk glassy carbon electrode modified with two potential-resolved luminophors (g-C3N4-Ag and Ru-MOF-Ag nanocomposites), and the sandwich immunoreaction using glucose oxidase (GOx)-modified SiO2 nanospheres as labels was carried out in a 96-well plate. The Ag nanoparticles (NPs) acted as bifunctional units both for triggering the resonance energy transfer (RET) with g-C3N4 and for accelerating the electron transfer rate of the Ru-MOF-Ag ECL reaction. When the H2O2 catalyzed by GOx in the 96-well plate was transferred to the dual-disk glass carbon electrode, the doped Ag NPs in the two luminophors could be etched, thus destroying the RET between C3N4 and the accelerated reaction to Ru-MOF, resulting in an opposite trend in the ECL signal outputted from the dual disks. Using the ratio of the two signals for quantification, the constructed immunosensor for a model target, i.e. myoglobin, exhibited a low detection limit of 4.7 × 10-14 g/mL. The ingenious combination of ECL ratiometry, bifunctional Ag NPs, and a split-type strategy effectively reduces environmental and human errors, offering a more precise and sensitive analysis for complex samples.

Unveiling the remarkable simultaneous adsorption-photocatalytic potential of Ag nanoparticles-anchored phosphotungestic acid loaded ZIF-8 for Congo red removal.

This research paper presents a direct approach to synthesize AgNPs deposited on polyoxometalate/ZIF-8 on-site (referred to as AgNPS@PW@ZIF-8) to develop a highly efficient photocatalyst in the water treatment. Phosphotungestic acid (PW) serves a multi-purpose in this context: it acts as a bridge layer between AgNPs and Zeolitic Imidazolate Framework-8 (ZIF-8), a local reducing agent, and a catalyst for electron transfer during the photocatalysis process. A comprehensive characterization of the resulting nanostructure was performed utilizing an array of techniques, such as XRD, FTIR, EDX, TEM, BET, Raman, and TGA. The nanostructure that was created exhibited effective removal of Congo red at different pH levels via a combination of simultaneous adsorption and photocatalysis. After 60 min at pH 7, the dye molecules were completely eliminated in the presence of 0.5 g/L AgNPS@PW@ZIF-8 at room temperature. The charge transfer can be facilitated by the PW bridge layer connecting AgNPs and ZIF-8, owing to the photoactive characteristics and strong electron transfer capabilities of PW molecules. Strong electron transferability of PW between Ag nanoparticles and ZIF-8 facilitates charge transfer and significantly improves the photocatalytic performance of ZIF-8. Moreover, the nanostructure demonstrated great structural stability and recyclability, sustaining a high efficiency of removal throughout five consecutive cycles through the implementation of a simple procedure. Widespread applications of the developed nanostructure in aquatic environments for adsorption and photocatalytic reactions are possible.

Prunus persica leaves aqueous extract mediated biosynthesis of Ag nanoparticles and assessment of its anti-quorum sensing potential against Hafnia species.

Hafnia sp. was one of the specific spoilage bacteria in aquatic products, and the aim of the study was to investigate the inhibition ability of the silver nanoparticles (AgNPs) biosynthesis by an aqueous extract of Prunus persica leaves toward the spoilage-related virulence factors of Hafnia sp. The synthesized P-AgNPs were spherical, with a mean particle size of 36.3 nm and zeta potential of 21.8 ± 1.33 mV. In addition, the inhibition effects of P-AgNPs on the growth of two Hafnia sp. strains and their quorum sensing regulated virulence factors, such as the formation of biofilm, secretion of N-acetyl-homoserine lactone (AHLs), proteases, and exopolysaccharides, as well as their swarming and swimming motilities were evaluated. P-AgNPs had a minimum inhibitory concentration (MIC) of 64 µg ml-1 against the two Hafnia sp. strains. When the concentration of P-AgNPs was below MIC, it could inhibit the formation of biofilms by Hafnia sp at 8-32 µg ml-1, but it promoted the formation of biofilms by Hafnia sp at 0.5-4 µg ml-1. P-AgNPs exhibited diverse inhibiting effects on AHLs and protease production, swimming, and swarming motilities at various concentrations.

Development of a SERS aptasensor for the determination of L-theanine using a noble metal nanoparticle-magnetic nanospheres composite.

An ultrasensitive surface-enhanced Raman spectroscopy (SERS) aptamer sensor (aptasensor) using a noble metal nanoparticle-magnetic nanospheres composite was developed for L-theanine detection. It makes use of Fe3O4@Au MNPs and Au@Ag NPs embedded with the Raman reporter 4-mercaptobenzoic acid (4MBA). Au@4MBA@Ag NPs modified by aptamer and Fe3O4@Au MNPs modified by cDNA created the aptasensor with the strongest Raman signal of 4MBA through the specific binding of the aptamer. With the preferred binding of L-theanine aptamer to L-theanine, Au@4MBA@Ag NPs were released from Fe3O4@Au MNPs, causing a linear decrease in SERS intensity to achieve the SERS detection of the L-theanine. The SERS peak of 4MBA at 1078 cm-1 was used for quantitative determination. SERS intensity showed a good log-linear relationship within the range 10-10 to 10-6 M of L-theanine. The aptasensor has a high selectivity for L-theanine compared with other twelve tested analytes. Hence, this aptasensor is a promising analytical tool for L-theanine detection. The developed method was applied to the analysis of real samples, demonstrating excellent performance. The comparison with the standard liquid chromatography mass spectrometry method showed an error within 20%.

SERS biosensors based on catalytic hairpin self-assembly and hybridization chain reaction cascade signal amplification strategies for ultrasensitive microRNA-21 detection.

A highly sensitive surface-enhanced Raman scattering (SERS) biosensor has been developed for the detection of microRNA-21 (miR-21) using an isothermal enzyme-free cascade amplification method involving catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR). The CHA reaction is triggered by the target miR-21, which causes hairpin DNA (C1 and C2) to self-assemble into CHA products. After AgNPs@Capture captures the resulting CHA product, the HCR reaction is started, forming long-stranded DNA on the surface of AgNPs. A strong SERS signal is generated due to the presence of a large amount of the Raman reporter methylene blue (MB) in the vicinity of the SERS "hot spot" on the surface of AgNPs. The monitoring of the SERS signal changes of MB allows for the highly sensitive and specific detection of miR-21. In optimal conditions, the biosensor exhibits a satisfactory linear range and a low detection limit for miR-21 of 42.3 fM. Additionally, this SERS biosensor shows outstanding selectivity and reproducibility. The application of this methodology to clinical blood samples allows for the differentiation of cancer patients from healthy controls. As a result, the CHA-HCR amplification strategy used in this SERS biosensor could be a useful tool for miRNA detection and early cancer screening.

Plant-Assisted Synthesis of Ag-Based Nanoparticles on Cotton: Antimicrobial and Cytotoxicity Studies.

The syntheses of Ag-based nanoparticles (NPs) with the assistance of plant extracts have been shown to be environmentally benign and cost-effective alternatives to conventional chemical syntheses. This study discusses the application of Paliurus spina-christi, Juglans regia, Humulus lupulus, and Sambucus nigra leaf extracts for in situ synthesis of Ag-based NPs on cotton fabric modified with citric acid. The presence of NPs with an average size ranging from 57 to 99 nm on the fiber surface was confirmed by FESEM. XPS analysis indicated that metallic (Ag0) and/or ionic silver (Ag2O and AgO) appeared on the surface of the modified cotton. The chemical composition, size, shape, and amounts of synthesized NPs were strongly dependent on the applied plant extract. All fabricated nanocomposites exhibited excellent antifungal activity against yeast Candida albicans. Antibacterial activity was significantly stronger against Gram-positive bacteria Staphylococcus aureus than Gram-negative bacteria Escherichia coli. In addition, 99% of silver was retained on the samples after 24 h of contact with physiological saline solution, implying a high stability of nanoparticles. Cytotoxic activity towards HaCaT and MRC5 cells was only observed for the sample synthetized in the presence of H. lupulus extract. Excellent antimicrobial activity and non-cytotoxicity make the developed composites efficient candidates for medicinal applications.

Plasmon-Driven Photochemical Reduction Reaction on Silver Nanostructures for Green Fabrication of Superhydrophobic Surface.

Green fabrication of superhydrophobic surface by water-based processing is still challenging, because introduction of the substances with hydrophilic moieties compromises its superhydrophobicity. Herein, a plasmon-driven photochemical reduction reaction under ultraviolet light (UVA) irradiation is first discovered and is applied to deoxygenation of hydrophilic organic adsorbates on rough nano-Ag coating for the formation of stable superhydrophobic surface. A nano-Ag coating with strong localized surface plasmon resonance in the UVA region is prepared by a water-based silver mirror reaction and results in a unique chemical reduction reaction on its surface. Consequently, the low residual hydrophilic functionalities and the formed cross-linked structure of the adsorbate on Ag nanoparticles (NPs) enables the coating to exhibit stable superhydrophobicity against to both air and water. The superhydrophobic Ag NP-coated sandpaper can also be used as a surface-enhanced Raman scattering (SERS) substrate to concentrate aqueous analytes for trace detection.

Isoniazide modified Ag nanoparticles triggered photothermal immunoassay for carcinoembryonic antigen detection.

As the most well-known analytical tool, the thermometer has been extended to the field of biological analysis based on the photothermal effect. Herein, isoniazide modified Ag nanoparticles were prepared as nanolabels to build an immunoassay. The nanoparticles were characterized by transmission electron microscope (TEM), dynamic laser scattering (DLS), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR). When the target protein was present, the sandwich immunoassay was developed and the photothermal reaction was triggered by isoniazide modified Ag nanoparticles. As a reducing agent, isoniazide is used to transform phosphomolybdic acid hydrate into molybdenum blue solution. And molybdenum blue had good photothermal stability and high photothermal conversion efficiency. The temperature variation of molybdenum blue solution showed a positive correlation with the concentration of carcinoembryonic antigen (CEA). Thus, the target protein of CEA was quantitative detection by thermometer. The linear response range is 0.1 ng mL-1 to 40 ng mL-1, and the detection limit is 0.08 ng mL-1. Moreover, the proposed protocol had satisfactory selectivity, accuracy, and reproducibility.

A ZnIn2S4/Ag2CO3 Z-scheme heterostructure-based photoelectrochemical biosensor for neuron-specific enolase.

An efficient photo-to-electrical signal is pivotal to photoelectrochemical (PEC) biosensors. In our work, a novel PEC biosensor was fabricated for the detection of neuron-specific enolase (NSE) based on a ZnIn2S4/Ag2CO3 Z-scheme heterostructure. Due to the overlapping band potentials of the ZnIn2S4 and Ag2CO3, the formed Z-scheme heterostructure can promote the charge separation and photoelectric conversion efficiency. And the concomitant Ag nanoparticles in Ag2CO3 provided multiple functions to enhance the PEC response of the Z-scheme heterostructure. It acts not only as a bridge for the transfer of carriers between ZnIn2S4 and Ag2CO3, promoting the constructed Z-scheme heterostructure, but also as electron mediators to accelerate the transfer of photogenerated carriers and improve the capture of visible light of the Z-scheme heterostructure by surface plasmon resonance (SPR). Compared with single Ag2CO3 and ZnIn2S4, the photocurrent of the designed Z-scheme heterostructure increased more than 20 and 60 times respectively. The fabricated PEC biosensor based on a ZnIn2S4/Ag2CO3 Z-scheme heterostructure exhibits sensitive detection to NSE, and presents a linear range of 50 fg·mL-1 ~ 200 ng·mL-1 with a limit of detection of 4.86 fg·mL-1. The proposed PEC biosensor provides a potential approach for clinical diagnosis.

Ag/g-C3N4 nanocomposite: Green fabrication and its application as a catalyst in the synthesis of new series of depsipeptides as biologically active compounds and investigation on their anti-breast cancer activity.

In this study, we bring forward a green and novel eco-friendly strategy for the fabrication of Ag/g-C3N4 nanocomposite via a fast in-situ generation method using Ferula Gummosa extracts as both stabilizer and reducing agent. Ag/g-C3N4 nanocomposite was analyzed by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX-MAP), and transmission electron microscopy (TEM). After procurement and characterization, the catalytic activity of the prepared reagent was surveyed in the synthesis of a new series of depsipeptides using aspirin/ketoprofen, cyclohexyl isocyanide, and aryl aldehydes at ambient temperature in EtOH/H2O as a green media. Taking into account the economic and environmental facets, the method bestows some advantages such as using plant extracts as green media for the preparation of Ag nanoparticles, simple work-up procedure, mild reaction conditions, short reaction times, and high yields of the products. Additionally, the Ag/g-C3N4 nanocomposite catalyst can be recycled effectually and reused several times without a substantial loss in reactivity.

Application of Ag nanoparticles decorated on graphene nanosheets for electrochemical sensing of CEA as an important cancer biomarker.

In this research, a novel biosensing platform is described based on graphene nano-sheets decorated with Ag nano-particles (GNSs@Ag NPs). The designed electrochemical aptasensor was employed to determine carcinoembryonic antigen (CEA), an important cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity for CEA tumor marker because of the high specific surface area and excellent conductivity of the prepared GNSs@Ag NPs composite. The established assay demonstrated a wide linear range from 0.001 pg/mL to 10 pg/mL with a correlation coefficient of 0.9958 and low detection limit (DL) of 0.5 fg/mL based on S/N = 3 protocol. The derived biosensor illustrated acceptable selectivity towards common interfering species including HER2, VEGF, IgG, MUC1 and CFP10. In addition, the aptsensor showed good reproducibility and fast response time. The applicability of the suggested strategy in human serum samples was also examined and compared to the commercial enzyme-linked immunosorbent assay (ELISA). Based on the experimental data, it was found that the discussed sensing platform can be exerted in the monitoring of CEA in different cancers for early diagnosis.

Ag nanocomposite hydrogels with immune and regenerative microenvironment regulation promote scarless healing of infected wounds.

BACKGROUND: Bacterial infection, complex wound microenvironment and persistent inflammation cause delayed wound healing and scar formation, thereby disrupting the normal function and appearance of skin tissue, which is one of the most problematic clinical issues. Although Ag NPs have a strong antibacterial effect, they tend to oxidize and form aggregates in aqueous solution, which reduces their antibacterial efficacy and increases their toxicity to tissues and organs. Current research on scar treatment is limited and mainly relies on growth factors and drugs to reduce inflammation and scar tissue formation. Therefore, there is a need to develop methods that effectively combine drug delivery, antimicrobial and anti-inflammatory agents to modulate the wound microenvironment, promote wound healing, and prevent skin scarring. RESULTS: Herein, we developed an innovative Ag nanocomposite hydrogel (Ag NCH) by incorporating Ag nanoparticles (Ag NPs) into a matrix formed by linking catechol-modified hyaluronic acid (HA-CA) with 4-arm PEG-SH. The Ag NPs serve dual functions: they act as reservoirs for releasing Ag/Ag+ at the wound site to combat bacterial infections, and they also function as cross-linkers to ensure the sustained release of basic fibroblast growth factor (bFGF). The potent antibacterial effect of the Ag NPs embedded in the hydrogel against S.aureus was validated through comprehensive in vitro and in vivo analyses. The microstructural analysis of the hydrogels and the in vitro release studies confirmed that the Ag NCH possesses smaller pore sizes and facilitates a slower, more sustained release of bFGF. When applied to acute and infected wound sites, the Ag NCH demonstrated remarkable capabilities in reshaping the immune and regenerative microenvironment. It induced a shift from M1 to M2 macrophage polarization, down-regulated the expression of pro-inflammatory factors such as IL-6 and TNF-α, and up-regulated the expression of anti-inflammatory IL-10. Furthermore, the Ag NCH played a crucial role in regulating collagen deposition and alignment, promoting the formation of mature blood vessels, and significantly enhancing tissue reconstruction and scarless wound healing processes. CONCLUSIONS: We think the designed Ag NCH can provide a promising therapeutic strategy for clinical applications in scarless wound healing and antibacterial therapy.

Synthesis of a capillary surface-enhanced Raman scattering substrate integrating sampling and detection based on meniscus self-assembled technology.

A method is proposed to fabricate a novel capillary surface-enhanced Raman scattering (SERS) substrate integrating sampling and detection based on meniscus evaporation self-assembled technology, named Meniscus@AgNPs@Capillary substrate. Ag nanoparticles (AgNPs) were arranged in the inner wall of the capillary through meniscus evaporation. The parameters which might affect the deposition of AgNPs during evaporation were investigated, including the evaporation temperature, self-assembly time, the ratio of silver sol to ethanol, and capillary length. The enhancement effect of SERS under different fabrication conditions was investigated using rhodamine 6G (R6G) as a Raman probe. Moreover, the optimal fabricated Meniscus@AgNPs@Capillary substrate was applied to the detection of several environmental pollutants such as polystyrene nanoplastics (PSNPs) and various antibiotics, with limits of detection (LOD) of 10 µg/L and 1 µg/L, respectively. The Meniscus@AgNPs@Capillary substrate presented the advantages of time and effort saving, high sensitivity, and on-site sampling and testing.

PVP-capped silver nanoparticles for efficient SERS detection of adenine based on the stabilizing and enrichment roles of PVP.

A polyvinylpyrrolidone-capped (PVP-capped) strategy is reported to synthesize Ag NPs on silicon wafers via galvanic replacement reaction for SERS detection of adenine, where PVP acts as stabilizing agent in synthesis and efficient enrichment in detection. The morphologies of Ag NPs are optimized with uniform particle size by adjusting synthesis conditions, which hold excellent SERS performances like a high enhancement factor of 1.42 × 106, good uniform, reproducibility, and transferable nature. With the protection of the capped PVP, the Ag NPs keep excellent SERS properties even against harsh conditions of high temperature (100 ℃) and strong acid and base for 24 h. Utilizing the structural feature of PVP with abundant carbonyl groups, the PVP-capped Ag NPs achieve efficient enrichment of adenine through hydrogen bonding and π-interactions, which is analyzed by density functional theory. Quantitative detection of adenine is performed with a wide linear range from 10-4 to 10-8 M and a low limit of detection of 1 nM. Detection of adenine in human urine samples is achieved with a recovery of 99.1-103.4% and an RSD of less than 5%.

Role of PGPR and silver nanoparticles on the physiology of Momordica charantia L. irrigated with polluted water comprising high Fe and Mn.

The current investigation designed to estimate the bioremediation potential of plant growth-promoting rhizobacteria (PGPR) and Ag-nanoparticles. Tube well and HIT water comprising Mn and Fe above recommended values were used as treatments while tap water irrigation was treated as control. The HIT water showed 24, 200, and 64.11% higher content of Na, K Ca over control. Seeds were sterilized in 95% ethanol and soaked for 3 h before sowing in 73 h old culture of Pseudomonas stutzeri (Kx574858) @ 108 cells/ml. Phytotoxic effect of Fe and Mn reduce plant biomass and suppress photosynthetic activity indicates. The carotenoids, proline, and proline activity were 366, 450, and 678% higher in tube well water with combined PGPR and Ag-nanoparticles treatments. Pseudomonas stutzeri was more effective than Ag-nanoparticles to reduce oxidative stress with higher production of carotenoids, flavonoids, proline content, and enzyme SOD and CAT activities in HIT water. It is contingent that the high Mn and Fe bearing waste water enhance PGPR bioremediation potential to reduce metal stress in plants with synergistic action of PGPR and organic matter to alleviate oxidative stresses under metal stress. The residual effect of P. stutzeri on organic matter content of the rhizosphere soil and germination rate was higher for Momordica charantia L.

This is the first statement indicating that Ag-nanoparticles oxidize Mn and Fe efficiently to reduce COD and organic matter works synergistically with PGPR and Ag-nanoparticles to enhance ROS production that increase proline, carotenoids, flavonoids, phenolics, and enzymes SOD, POD, PAL, and CAT activities to reduce oxidative stress in cucurbits.

Blending Approach Preparation of PVA-g-PMA Films with Embedded "Green" Synthesized Silver Nanoparticles for Acetone Optical Detection.

The blending approach (also known as the ex-situ approach) was used for the deposition of thin composite films comprising poly(vinyl alcohol-graft-methyl acrylate) (PVA-g-PMA) and silver nanoparticles (AgNPs). Firstly, the copolymer aqueous dispersion was synthesized through the redox polymerization of methyl acrylate (MA) on poly(vinyl alcohol) (PVA) using ammonium cerium (IV) nitrate as the initiator. Then, AgNPs were synthesized through a "green" method using the water extract of lavender based on by-products of the essential oil industry, and then they were blended with the polymer. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine nanoparticle size, along with their stability over time in suspension, during the 30-day period. Thin films of the PVA-g-PMA copolymer, with different AgNP volume fractions varying between 0.008 and 0.260%, were deposited via the spin-coating method on Si substrates, and their optical properties were explored. UV-VIS-NIR spectroscopy and non-linear curve fitting were used for the determination of the refractive index, extinction coefficient, and thickness of the films, while photoluminescence measurements at room temperature were conducted for studying the emission of the films. The concentration dependence of film thickness was observed and showed that thickness increased linearly from 31 nm to 75 nm when the nanoparticles' weight content increased from 0.3 wt% to 2.3 wt%. The sensing properties toward acetone vapors were tested in a controlled atmosphere by measuring reflectance spectra before and during exposure to the analyte molecules in the same film spot; the swelling degree of films was calculated and compared to the corresponding undoped samples. It was shown that the concentration of AgNPs of 1.2 wt% in the films is optimal for the enhancement of the sensing response toward acetone. The influence of AgNPs on the films' properties was revealed and discussed.

Micropattern of Silver/Polyaniline Core-Shell Nanocomposite Achieved by Maskless Optical Projection Lithography.

With the development of device miniaturization, a flexible and fast preparation method is in demand for achieving microstructures with desired patterns. We develop a novel photoreduction-polymerization method for preparing conductive metal-polymer patterns. Ag/polyaniline (PANI) nanocomposites have been successfully synthesized by maskless optical projection lithography (MOPL) technology, which is based on multiphoton absorption and the localized surface plasmon resonance (LSPR) effect. The individualized design and synthesis of the nanocomposite patterns at the micro-nano scale are flexibly realized on a variety of substrates. The surface-enhanced Raman scattering (SERS) effect of Rhodamine 6G (R6G) is demonstrated on the microstructure of a square maze-shaped Ag/PANI nanocomposite. The electrical conductivity of the as-prepared nanocomposite is obtained. The preparation protocol proposed in this study opens up new avenues for the fabrication of micro-nano devices such as sensors and detectors.