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The green synthesis of silver nanoparticles (AgNPs) has been attractive in biomedical applications due to its nontoxic and eco-friendly approach. This study presents the facile, rapid, and cost-effective synthesis of AgNPs by photoassisted chemical reduction using Riceberry (RB) rice extract as a reducing agent. The effects of reaction parameters including photoirradiation, irradiation time, the volume ratio of silver nitrate (AgNO3) to RB extract, and pH condition on the AgNP formation were also investigated. The characterization of AgNPs was determined by UV–visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy. For antibacterial application, the synthesized AgNPs were studied by disc diffusion method against Escherichia coli and Staphylococcus aureus. The results indicated that light irradiation was an important factor to accelerate the formation of AgNPs. The synthesis parameters including volume of RB extract and pH condition significantly affected the particle size and crystallinity of AgNPs. The volume ratio of AgNO3 to RB extract 1 : 12.5 at pH 2.5 under photoirradiation was the successful condition to form nanometer-sized crystalline particles (average particle size of 59.48 ± 0.37 nm) within 30 min with a rate constant of 0.210 min–1. The FT-IR measurement also suggested that the phytochemical constituents in RB extract were served as reducing and stabilizing agents for the synthesis of AgNPs. Additionally, the obtained AgNPs from various conditions demonstrated the antibacterial activity against both strains. Therefore, this study proposes an effective integration technique to synthesize AgNPs within a short time for antibacterial application. [ABSTRACT FROM AUTHOR]

According to the literature data, metal nanoparticles can be synthesized by various methods but the chemical reduction methods are mostly applied getting more advantageous comparing with the other methods. This work emphasizes also that the combination of synthetized methods could lead to the spectacular results depending on the application. Among the chemical methods, this work analyzed the polyol method, radiolytic process, microemulsion method, solvo-thermal method, microwave-assisted synthesis, and electrochemical synthesis. It also presents the main application of metal nanoparticles in biomedical fields, empathizing on their antimicrobial potential. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of the aqueous solutions of silver nanoparticles (Ag NPs) prepared by chemical reduction method are analyzed using femtosecond and picosecond pulses at different wavelengths. In the case of 800 and 400 nm, the growths of nonlinear absorption and nonlinear refraction with the increase of Ag NP concentration, as well as a change at the signs of nonlinear optical processes, are determined. The nonlinear absorption coefficient and nonlinear refractive index of Ag NP solutions measured using picosecond pulses were a few orders of magnitude larger than those in the case of femtosecond probe pulses. We also demonstrate the optical limiting properties of Ag NPs using 800 nm, 60 fs pulses. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) were synthesized by chemical reduction of Ag+ ions (from silver nitrate AgNO3), using aqueous or ethanolic Aloe vera extracts as reducing, stabilizing, and size control agent. The nanoparticles’ sizes were between 2 and 7 nm for ethanolic extract and between 3 and 14 nm for aqueous extract, as measured by High-Resolution Transmission Electron Microscope (HRTEM). The antibacterial activity against a mesophilic microorganism, Kocuria varians, a Gram-positive coccus, was measured by counting bacterial colonies in agar plate for both extracts. We found that 4% effective concentration is the lowest concentration that completely inhibited visible growth. Mercury removal was investigated by Atomic Absorption Spectroscopy (AAS) measurements, where it was shown that it is not necessary to use high concentrations of nanoparticles for effective removal of mercury inasmuch as with a 20% V/V concentration of both extracts; the Hg(II) removal percentage was above 95%. These results show that the mercury remaining unremoved from the different essays is below the level allowed by World Health Organization (WHO) and the Environmental Protection Agency (EPA). [ABSTRACT FROM AUTHOR]

Preparation of silver nanoparticles was carried out by semicontinuous reduction of Ag+ ions at low temperatures. Silver nitrate was used as the Ag0 precursor, the carboxymethyl cellulose (CMC) as stabilizer and primary reducing agent, and sodium borohydride as reducing agent. Weight ratios of 1 : 1 and 1 : 2 of AgNO3 : CMC were used for carrying out the reactions. Silver nanoparticles were characterized by UV-VIS spectroscopy, transmission electronic microscopy (TEM), and X-ray diffraction (XRD). The formation of silver nanoparticles was confirmed by XRD spectroscopy and by the presence of an absorption peak around 400 nm in the UV-visible spectrum. Unimodal size distributions of spheroidal nanoparticles were observed by TEM. Greater productivities than those reported by other authors were obtained with the advantage of using a lower temperature and minor reaction times. By using a higher CMC/AgNO3 weight ratio or a higher concentration of AgNO3, AgNPs with larger average size were produced. Antibacterial activity of AgNPs against S. aureus and E. coli was determined by the agar disk diffusion method. The higher the AgNPs concentration, the larger the inhibition zone. The minimum inhibitory concentration (MIC) of AgNPs against S. aureus and E. coli was 5 μg/disk. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) were rapidly synthesized using an exopolysaccharide from Arthrobacter sp. B4 (B4-EPS). The optimum condition for AgNPs synthesis was under the concentration of 5 g/L B4-EPS and 1 mM AgNO3 at 80°C between pH 7.0 and 8.0. The resulting AgNPs displayed a face-centred-cubic structure with the size range from 9 nm to 72 nm. Further analysis showed that flocculation and reduction of B4-EPS played a pivotal role in the formation of AgNPs. Furthermore, these nanoparticles exhibited great stability, excellent antimicrobial activity, and low phytotoxicity. The aforementioned data provide a feasible and efficient approach for green synthesis of AgNPs using microbial polysaccharides with flocculation and reduction activity, which will be promising in medical filed. [ABSTRACT FROM AUTHOR]

The objective of this study is to evaluate the structural, thermal, and electrical properties of multiwalled carbon nanotubes (MWNT) hybridized with silver nanoparticles (AgNP) obtained via chemical reduction of aqueous silver salt assisted with sodium dodecyl sulphate (SDS) as stabilizing agent. Transmission electron microscopy (TEM) reveals microstructural analysis of the MWNT-Ag hybrids. The Fourier transform infrared (FTIR) spectra prove the interactions between the AgNP and carboxyl groups of the MWNT. Raman spectra reveal that the D- to G-band intensity ratios ID/IG and ID′/IG increase upon the deposition of AgNP onto the surface of the MWNT. Thermogravimetric analysis (TGA) shows that the MWNT-Ag hybrids decompose at a much faster rate and the weight loss decreased considerably due to the presence of AgNP. Nonlinearity of current-voltage (I-V) curves indicates that electrical transport of pristine MWNT is enhanced when AgNP is induced as charge carriers in the MWNT-Ag hybrids. The threshold voltage Vth value for the MWNT doped with a maximum of 70 vol% of AgNP was substantially reduced by 65% relative to the pristine MWNT. The MWNT-Ag hybrids have a favourable electrical characteristic with a low threshold voltage that shows enhancement mode for field-effect transistor (FET) applications. [ABSTRACT FROM AUTHOR]

In the present research, a nonenzymatic glucose biosensor was fabricated by depositing Ag nanoparticles (Ag-NPs) using in situ chemical reduction method on TiO2 nanotubes which were synthesized by anodic oxidation process. The structure, morphology, and mechanical behaviors of electrode were examined by scanning electron microscopy and nanoindentation. It was found that Ag-NPs remained both inside and outside of TiO2 nanotubes whose length and diameter were about 1.2 μm and 120 nm. The composition was constructed as an electrode of nonenzymatic biosensor for glucose oxidation. The electrocatalytic properties of the prepared electrodes for glucose oxidation were investigated by cyclic voltammetry (CVs) and differential pulse voltammetry (DPV). Compared with bare TiO2 and Ag-fresh TiO2 nanotube, Ag-TiO2/(500°C) nanotube exhibited the best electrochemical properties from cyclic voltammetry (CVs) results. Differential pulse voltammetry (DPV) results showed that, at +0.03 V, the sensitivity of the electrode to glucose oxidation was 3.69 mA⁎cm-2⁎mM-1 with a linear range from 20 mM to 190 mM and detection limit of 24 μM (signal-to-voice ratio of 3). In addition the nonenzymatic glucose sensors exhibited excellent selectivity, stability, and repeatability. [ABSTRACT FROM AUTHOR]

Silver nanoparticles with average diameter of 22.4nm were prepared by aqueous reduction method for low-temperature sintering bonding application.The reaction temperature and PVP concentration, which are the influential factors of nanoparticle characteristics, were investigated during reduction process. In our research, monodispersity of nanoparticles was remarkably improved while unfavorable agglomeration was avoided with the AgNO3/PVPmass ratio of 1 :4 at the reaction temperature 30°C. Besides, copper padswere successfully bonded using sintering pasteemploying fresh silver nanoparticleswith diameter of 20~35 nm at 200°C. In addition, after morphology of the bonding joint was analysed by scanning electron microscope (SEM), the porous sintering characteristics were confirmed. [ABSTRACT FROM AUTHOR]

An AgNPs solution was synthesized by chemical reduction, characterized, and tested against Candida glabrata, Candida tropicalis, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus (MRSA). Minimum inhibitory (MICs) and minimum fungicidal/bactericidal concentrations (MFC/MBC) were determined on planktonic cells. Also, total biofilm mass was determined by crystal violet (CV) staining and morphological changes by scanning electron microscope (SEM). MICs for C. glabrata, C. tropicalis, S. aureus, and MRSA were 15.63, 3.91, 1.95, and 1.95 μg/mL, respectively. MFC for C. glabrata was 62.5 μg/mL and for C. tropicalis 15.63 μg/mL The same MBC (3.91 μg/mL) was observed for S. aureus and MRSA. CV assay showed that the AgNPs (1000 μg/mL) promoted reductions in biofilm mass of ~60% for C. glabrata and ~35% for C. tropicalis. A reduction of ~20% in C. tropicalis biomass was also observed at the concentration of 3.91 μg/mL. No significant effect on total biomass was found for S. aureus and MRSA. SEM images revealed that C. glabrata and C. tropicalis biofilm cells, exposed to the AgNPs (1000 μg/mL), had an irregular and shriveled appearance. AgNPs solution exhibited considerable antimicrobial activity against important fungal and bacterial pathogens, associated with several oral and systemic diseases, and has potential as an antimicrobial agent. [ABSTRACT FROM AUTHOR]

We demonstrate that silver nanoparticles undergo an interaction with Hg2+ found in traces. The PEG-PVP-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with surface plasmon resonance UV/Vis spectroscopy. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ ion. A linear and inversely proportional relationship was found between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ ion over the range from 10 ppm to 1 ppm at absorption on 411 nm. The detection limit for Hg2+ ions in homogeneous aqueous solutions is estimated to be 1 ppm. This system shows excellent selectivity for Hg2+. The results found have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions. The proposed method was successfully applied to quantify the amount of mercury in seafood. [ABSTRACT FROM AUTHOR]

The electrochemical properties of silver nanoparticle (d ∼ 5 nm) synthesized within aminosilica film from spontaneous reduction reaction were examined using cyclic voltammetry and the results show that the nanocomposite film exhibits similar redox property as solution-synthesized silver nanoparticles whenmeasuring in phosphate buffer solution and its redox potentials were found to be sensitive to the presence of chloride ions. It also shows that silver nanoparticles and hydrolyzed aminosilica increase the electron diffusivity of the aminosilica film. Both results confirm that an accurate reference electrode suitable for microfluidic devices can be created simply by treating an aminosilica-coated electrode with a silver nitrate solution. Furthermore, a humidity sensor based on silver-silica nanocomposite film has also been demonstrated. [ABSTRACT FROM AUTHOR]