AgNO3 Concentration Research Articles

A Facile Method for the Fabrication of Silver Nanoparticles Surface Decorated Polyvinyl Alcohol Electrospun Nanofibers and Controllable Antibacterial Activities.

Polyvinyl alcohol (PVA) electrospun nanofibers (NFs) are ideal carriers for loading silver nanoparticles (Ag NPs) serving as antibacterial materials. However, it is still a challenge to adjust the particles size, distribution, and loading density via a convenient and facile method in order to obtain tunable structure and antimicrobial activities. In this study, Ag NPs surface decorated PVA composite nanofibers (Ag/PVA CNFs) were fabricated by the solvothermal method in ethylene glycol, which plays the roles of both reductant and solvent. The morphology and structure of the as-fabricated Ag/PVA CNFs were characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, UV-visible spectroscopy, and Fourier transform infrared spectroscopy. Ag NPs had an average diameter of 30 nm, the narrowest size distribution and the highest loading density were successfully decorated on the surfaces of PVA NFs, at the AgNO3 concentration of 0.066 mol/L. The antibacterial properties were evaluated by the methods of absorption, turbidity, and growth curves. The as-fabricated Ag/PVA hybrid CNFs exhibit excellent antimicrobial activities with antibacterial rates over 98%, especially for the sample prepared with AgNO3 concentration of 0.066 mol/L. Meanwhile, the antibacterial effects are more significant in the Gram-positive bacteria of Staphylococcus aureus (S. aureus) than the Gram-negative bacteria of Escherichia coli (E. coli), since PVA is more susceptive to S. aureus. In summary, the most important contribution of this paper is the discovery that the particles size, distribution, and loading density of Ag NPs on PVA NFs can be easily controlled by adjusting AgNO3 concentrations, which has a significant impact on the antibacterial activities of Ag/PVA CNFs.

A rapid microwave-assisted synthesis of silver nanoparticles using Ziziphus jujuba Mill fruit extract and their catalytic and antimicrobial properties

An eco-friendly and sustainable approach was developed for the synthesis of silver nanoparticles (AgNPs) of Ziziphus jujuba Mill (ZJM) fruit extract by a microwave-assisted technique. The developed method was simple, economically viable, sustainable, and eco-friendly. Concentrations of AgNO3 and ZJM fruit extract and reaction time were optimized for the final properties of synthesized AgNPs. The prepared AgNPs were characterized by UV-visible and FTIR spectrophotometers, powder XRD, TEM, and DLS. XRD results showed a face-centered cubic structure for the prepared AgNPs. The obtained size of AgNPs was 8 ± 1 nm with spherical shape. The FTIR spectrum indicates that ZJM is a good capping agent to stabilize AgNPs. A negative zeta potentials value of − 21.2 mV indicates the stability of AgNPs. The AgNPs has good stability over a wide range of pH and ionic strength. The role and efficacy of AgNPs in the catalytic degradation of methylene blue (MB) and Congo red (CR) dye were studied, and the reduction reaction rate constants were found to be 0.033 s−1 (180 s) and 0.025 s−1 (200 s) respectively. The synthesized AgNPs showed rapid and excellent catalytic reduction of MB and CR dyes. The rapid catalytic reduction reactions followed pseudo-order kinetics. The ZJM fruit extract-capped AgNPs showed good antimicrobial activity against tested bacterial and fungal cultures.

Production of extracellular silver nanoparticles by radiation-resistant Deinococcus wulumuqiensis R12 and its mechanism perspective

Recently, rapid progress has been made in the utilization of microbes for green synthesis of metal nanoparticles. We found that the cell-free supernatant of the extremophile Deinococcus wulumuqiensis R12 contains silver nanoparticles (AgNPs) when grown in media with different concentrations of AgNO3. The microbially synthesized AgNPs were then systematically characterized by UV/Vis spectroscopy (UV/Vis), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), dynamic light scattering (DLS) and zeta potential measurements. The microbial AgNPs had an absorption peak at 430 nm and had a face-centered cubic structure. They were spherical with a uniform size of 5–16 nm, which was smaller than most reported AgNPs. The mechanism of nanoparticle synthesis by D. wulumuqiensis R12 was then briefly investigated. A previously unknown NADPH-dependent oxidoreductase of 28.29 kDa was identified, which might play the main role in the biosynthesis of AgNPs by strain R12. The concentration of the oxidoreductase in the supernatant increased 4-fold after the addition of AgNO3. Furthermore, the addition of NADPH significantly improved the production of AgNPs.

COMPARATIVE STUDY ON BIOSYNTHESIS OF VALUABLE ANTIMICROBIAL AND ANTITUMOR NANO-SILVER USING FRESH WATER GREEN AND BLUE-GREEN MICROALGAE

Two levels Plackett-Burman experimental design was employed to screen the main factors that significantly affect the synthesis of bioactive silver nanoparticles. Scenedesmus obliquus ethanol extract, Scenedesmus obliquus dried algal powder and Spirulina platensis aqueous extract were the most favorable reducing and capping agents. Also the high pH value (10), rpm (150), high concentration of AgNO3 (4 mM) and dark conditions had the highest significant influence on biosynthesis of active nanoparticles. Characterizations of the formed AgNPs were approved by UV–Visible Spectroscopy, Transmission Electron Microscopy and Fourier Transform Infrared spectroscopy. The nanoparticles were varied in sizes and shape that ranged between 2.83 and 27.17nm, depending on the organism used and the method of biosynthesis. Valuable inhibitory effects were showed by all bio-synthesized nanoparticles against four tested Gram- positive and Gram- negative bacteria, except that formed by Spirulina platensis powder. Moreover, the nanoparticles exhibited wide range of antifungal activities. AgNPs prepared from ethanol extract of Spirulina platensis was the most active against HepG2 and MCF-7 cell lines, with IC50values 62.1 and 56.2 ug/mL, respectively. The obtained results, indicated the advantages of AgNPs from microalgae and possible industrial applications as a source of antifungal, antibacterial, and antitumor formulation.

Bioaccumulation of silver and its effects on biochemical parameters and histological alterations in an Indian major carp Labeo rohita

Extensive usage of silver in several applications may contaminate the freshwater compartment and affects the health status of aquatic organisms. In the present investigation, fingerlings of Indian major carp Labeo rohita were exposed (35 days) to sublethal concentrations of silver nitrate (AgNO3) and bioaccumulation pattern, biochemical and histological alterations were evaluated. Initially, the median lethal concentration (LC 50) of silver nitrate to the fish Labeo rohita for 96 h was calculated and it was found to be 0.035 mg L−1. To assess the toxicity of ionic silver two sublethal concentrations (0.0035 mg L−1: 1/10th of LC 50 and 0.007 mg L−1; 1/5th of LC 50) were selected and the experiment was conducted for a period of 35 days. A considerable quantity of AgNO3 was accumulated in the gill, liver and kidney tissues of Labeo rohita. Accumulation of AgNO3 was high in liver tissue compared to other organs/tissue. Membrane-bound enzyme (Na+/K+/-ATPase) activity was inhibited in both the concentrations when compared with the control group. Likewise, plasma electrolytes (Na+, K+ and Cl−) level were significantly decreased when compared with untreated groups. On the other hand, a noticeably increased level of glucose was observed in fish exposed to 0.0035 and 0.007 mg L−1 of AgNO3. Moreover, declining protein level was assessed during the initial days (7 and 14 days), and the level was increased in the rest of the exposure period. Extensive histopathological abnormalities were noticed in gill (hyperplasia, epithelial lifting, curling of lamellae) and liver (degeneration of hepatic nucleus, vacuolization, hepatic necrosis) of fish treated with silver nitrate when compared to control groups. The results obtained in the present study revealed that the bioaccumulation pattern, alterations in membrane-bound gill-ATPase activity, plasma electrolytes, biochemical and histological parameters of fish can be useful for biomonitoring the changes in the environment and health condition of fish in freshwater ecosystem contaminated with silver. Highlights •The fingerlings of Labeo rohita were exposed to sublethal concentrations of AgNO3 for 35 days.

Light Sensors Based on Silicon Nanowires

The article deals with the synthesis of silicon nanowires by the method of metal-assisted chemical etching (MACE). The purpose of this work is to use in light sensors silicon nanowires that synthesized by the MACE. To achieve this goal, it was necessary to synthesize silicon nanowires by the MACE and to study their structural features, to obtain diode structures based on silicon nanowires and to study their sensitivity to visible radiation, to establish the influence of technological parameters of the MSHT process on the sensitivity of photo sensors and sensors. Today, nanostructures are obtained by the method of reactive ion etching, electrochemical etching and plasma implantation. However, most of these methods require sophisticated process equipment. Metal-assisted chemical etching (MACE) method is very promising for nanostructures creation. Two-stage MACE was used to make the samples. In the first stage, silver nanoparticles were deposited on the surface of single crystalline silicon. In the second stage, the samples were etched in a solution of water, hydrogen peroxide and hydrofluoric acid and, as a consequence, a structured surface was obtained. It should be noted that the samples were treated at different times of each of the stages of MACE. Based on the obtained samples, diode light sensors with different photoelectric parameters were synthesized. For the sensors obtained, the sensitivity was calculated in the photodiode and photogenerator modes, and the volt-ampere, luxury-ampere characteristics and dependences of the current density on the illumination density were constructed. structured silicon has a mesh-like appearance, where the dark regions are gaps (pores) and the light ones are silicon (pore walls, nanowires). First, compare the samples with different deposition times. It is seen that as the deposition time of the particles increases from 10 to 40 s, a more developed silicon surface is formed. Also, with the duration of deposition 40s on the silicon surface there are needle-like formations, which according to the results in the work are silver dendrites. All the above characteristics were analyzed for the effect of the deposition time of silver particles t1 and etching time t2 on them. Studies have shown that the optimum technological conditions of metal assisted chemical etching of silicon for using in light sensors are the following conditions: the deposition time of silver particles 40c, etching time 30 min, the content of hydrogen peroxide in the second solution of 0.8 ml. This mode of synthesis of the structuring of silicon substrates provides maximum photosensitivity ratios both in the photodiode (1.53 mA / lmV) and in the photogenerator (304 mA / W) modes. The influence of the concentration of H2O2 used in the second stage is crucial only for the photocurrent, which is not critical, and the influence of the AgNO3 concentration in the first stage of MACE does not have a significant effect on the parameters.

Optimization of synthesizing silver nanoparticles from Trichoderma strains for inhibition of Fusarium oxysporum

With the popularity of green concepts, the use of biological method to synthesize metal nanoparticles is a favored method. Silver nanoparticles (AgNPs) have attracted more and more attention in the control of agricultural diseases, because of their strong antifungal activity and not easy inducing resistance for pathogens. In this study, Trichoderma citrinoviride and Trichoderma velutinous were used to study the most suitable synthesis conditions for AgNPs, and their antifungal activity against Fusarium oxysporum. The silver nanoparticles had an absorbance peak at 400-500 nm, the most suitable synthesis conditions were at standing and light with CL method (mycelium filtrate), AgNO₃ concentration of 2.0 mmol/L, pH of 7, and reaction temperature of 45 °C. AgNPs synthesized by T. citrinoviride and T. velutinous inhibited F. oxysporum, the inhibition effect was better with the increase of silver nanoparticle concentration. When the concentration of AgNPs was 200 mg/L, the antifungal rate from T. citrinoviride and T. velutinous was 33.75% and 36.08%, respectively.

Synthesis of silver nanoparticles (AgNPs) using culinary banana peel extract for the detection of melamine in milk.

Melamine adulteration in milk is a serious health concern for the consumers. A reliable and sensitive technique using silver nanoparticle (AgNPs) was developed for the detection of melamine in milk sample. The AgNPs was synthesized using culinary banana peel extract (BPE) where pH, temperature, theamount of concentration of BPE and concentration of AgNO3 was standardized. The effect of the parameters used for the synthesis of AgNPs was analyzed by observing the colour of reaction mixture and surface plasmon resonance. The AgNPs synthesized under optimum conditions were characterized by SEM-EDX, TEM and FTIR. FTIR studies reveal the effective conjugation between AgNPs and bioactive components of BPE and formation of spherical and regular shaped AgNPs were confirmed by TEM images. Presence of Ag as a dominating metal in AgNPs confirmed the formation of AgNPs. The level of melamine above 0.5mg/L in milk could easily be detected through theinterference synthesis of AgNPs.

Optimization of mycobiosynthesis of silver nanoparticles by using Fusarium 4F1 and Trichoderma TRS isolates

Silver nanoparticles (Ag-NPs) by mixing silver nitrate (AgNO3) with cell-free filtrate (CFF) of the two fungal isolates viz., Fusarium 4F1 and Trichoderma TrS were synthesized. pH, substrate concentration and incubation period for the production of better quality and quantity of Ag-NPs was optimized. The Ag-NPs by UV-vis spectroscopy were characterized. Between the two fungal isolates, pH levels, AgNO3 concentrations and incubation periods studied, the highest number of spherical shaped, monodispersed and stable Ag-NPs were recorded from Fusarium 4F1 at pH 9, 2 mM AgNO3 and 72 hrs of incubation.

Rapid and ultrasensitive surface enhanced Raman scattering detection of hexavalent chromium using magnetic Fe3O4/ZrO2/Ag composite microsphere substrates

It is greatly significant to sense hexavalent chromium (Cr (VI)) in water because Cr (VI) is one of the most toxic heavy metals and is extremely harmful for human health and environment. In this study, we explored sensitive surface-enhanced Raman scattering (SERS) substrates for rapid detection of Cr (VI) using magnetic Fe3O4/ZrO2/Ag composite microspheres. We firstly coated uniform zirconium dioxide layer around Fe3O4 cores to achieve Fe3O4/ZrO2 microspheres and then deposited silver nanoparticles onto their surface via controlled reduction of AgNO3 by n-butylamine. The SERS sensitivity of Fe3O4/ZrO2/Ag composite microspheres were easily tailored via facilely changing the concentration of AgNO3 to tune the coverage of silver nanoparticles on the Fe3O4/ZrO2/Ag. We used 4-mercaptobenzoic acid (4-MBA) as a Raman molecule to evaluate the SERS activity of Fe3O4/ZrO2/Ag. They illustrated excellent SERS property as well as magnetic responsibility. The optimized Fe3O4/ZrO2/Ag were employed to quantitatively detect Cr (VI) in aqueous solution. The results showed good linear relationship between SERS intensities and logarithm concentrations of Cr (VI) (R2 = 0.98) with a detection limit of low down to 10−7 M, which is much lower than the safety value (1 μM) in drinking water of United States Environmental Protection Agency. Moreover, the highly uniform and robust Fe3O4/ZrO2/Ag composite microspheres display outstanding signal reproducibility (RSD = 8.34 %) and good storage stability. These results indicate that the prepared Fe3O4/ZrO2/Ag composite microspheres have promising application prospect for SERS analysis of environmental pollutants.

Size, concentration, coating, and exposure time effects of silver nanoparticles on the activities of selected soil enzymes

Silver nanoparticles (AgNPs) have a wide variety of applications in consumer products and can directly or indirectly leak into environmental compartments such as soil. The environmental risks associated with AgNPs must be assessed to assist in the development of regulatory guidelines. Because they are linked to numerous soil ecosystem functions, soil enzyme activities are very sensitive to any changes in soil management caused by environmental or human factors. Therefore, changes in soil enzymatic activities upon exposure to AgNPs can serve as early indicators of any adverse effect that these particles might have on soil quality. The objective of this study was to investigate the effect of the concentration of AgNPs (1, 10, and 100 mg kg−1 soil), size of particles (30, 80, and 200 nm), nanoparticle coatings (citrate, lipoic acid, and polyvinylpyrrolidone), and contact time between nanoparticles and soil (3 h, 3 d, and 30 d) on two soil enzymes, phenol oxidase and arylamidase, in a silt loam soil. Soil samples were treated with silver ions with similar treatments, and enzyme assays were performed to understand how the enzyme activities differed under the influence of ionic silver and nano-silver. The results revealed that the effect of AgNPs and silver ions on the soil enzymatic activities depended on the Ag dose and length of exposure more than on the particle size and coating. Soil arylamidase and phenol oxidase activities were generally inhibited in the presence of a high concentration of AgNPs and AgNO3 (100 mg kg−1 soil), though in low Ag concentrations, there was no significant inhibition. The levels of inhibition varied notably in relation to the enzyme type, wherein the arylamidase activity was affected severely compared to phenol oxidase. The effect of silver ions dissolved from AgNPs was not significant, indicating that the adverse effects on enzyme functioning was caused by the AgNPs themselves.

The Efficacy of AgNO3 Nanoparticles Alone and Conjugated with Imipenem for Combating Extensively Drug-Resistant Pseudomonas aeruginosa.

IntroductionThe extensive drug-resistant (XDR) Pseudomonas aeruginosa (P. aeruginosa) causes a range of infections with high mortality rate, which inflicts additional costs on treatment. The use of nano-biotechnology-based methods in medicine has opened a new perspective against drug-resistant bacteria. The aim of this study was to evaluate the effectiveness of the AgNO3 nanoparticles alone and conjugated with imipenem (IMI) to combat extensively drug-resistant P. aeruginosa.MethodsAntibiotic susceptibility was carried out using disc diffusion method. Detection of different resistant genes was performed using standard polymerase chain reaction (PCR). The chemically synthesized AgNO3 particles were characterized using scanning electron microscope (SEM), dynamic light scattering (DLS) and X-ray diffraction (XRD) methods. Fourier transform infrared spectroscopy (FTIR) was accomplished to confirm the binding of AgNO3 with IMI. The microdilution broth method was used to obtain minimum inhibitory concentration (MIC) of AgNO3 and IMI-conjugated AgNO3. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was carried out on L929 cell line to study the cytotoxicity of nanoparticles. The data were analyzed by Eta correlation ratio and chi-square (X2) test.ResultsAnalysis of the antibiotic resistance pattern showed that 12 (24%) isolates were XDR, and MIC values of IMI were between 64 and 128 μg/mL. Frequency of SHV, TEM, CTX M, IMP, VIM, OPR, SIM, SPM, GIM, NDM, VEB, PER, KPC, OXA, intI, intII, and intIII genes were 29 (58%), 26 (52%), 26 (52%), 32 (64%), 23 (46%), 43 (86%), 3 (6%), 6 (12%), 3 (6%), 4 (8%), 7 (14%), 6 (12%), 18 (36%), 4 (8%), 19 (38%), 16 (32%), and 2 (4%), respectively. The XRD, SEM, DLS, and FTIR analysis confirmed the synthesis of AgNO3 nanoparticles and their conjugation with IMI. The AgNO3 nanoparticles had antimicrobial activity, and their conjugation with IMI showed enhanced effectiveness against XDR isolates. The synthesized AgNO3 showed no cytotoxic effects.ConclusionThe results suggest that IMI-conjugated AgNO3 has a strong potency as a powerful antibacterial agent against XDR P. aeruginosa.

Ag nanoparticles decorated Ag@ZrO2 composite nanospheres as highly active SERS substrates for quantitative detection of hexavalent chromium in waste water

A novel highly active surface enhanced Raman scattering (SERS) substrate of Ag nanoparticles decorated Ag@ZrO2 composite nanosphere was prepared and characterized. A uniform ZrO2 shell was firstly coated over Ag cores by sol-gel process using zirconium butoxide as Zr precursor to achieve Ag@ZrO2 nanospheres and then Ag nanoparticles were in situ deposited on the Ag@ZrO2 through the reduction of AgNO3 to produce Ag@ZrO2@Ag composite nanospheres. The cover density of Ag nanoparticles on Ag@ZrO2@Ag nanospheres could be controlled by changing the concentration of AgNO3. TEM, FE-SEM, EDX, UV–vis and XRD analyses were used to characterize their morphology, structure and composition. The SERS property of Ag@ZrO2@Ag was evaluated using 4-mercaptobenzoic acid (4-MBA) as Raman probe molecules. The experimental results showed Ag@ZrO2@Ag nanospheres presented remarkably SERS activity, high signal reproducibility (RSD = 6.39%) and exceptional storing stability. Subsequently, the Ag@ZrO2@Ag nanospheres acted as SERS substrates to sense Cr (VI) in water at various concentrations, and the SERS results showed great linear correlation between SERS intensities and the concentration of Cr (VI) (R2 = 0.97) with the detection limit of 0.5 μM, which is below the safety level (1 μM) in drinking water of United States Environmental Protection Agency. The Ag@ZrO2@Ag nanospheres were also successfully used to confirm the concentration of Cr (VI) in real industrial wastewater. These results demonstrated the extraordinary potential of Ag@ZrO2@Ag composite nanospheres serving as SERS substrates for trace and quantitative determination of Cr (VI) in environmental field.

Síntese verde de nanopartículas de prata intermediada por fungo anamórfico e eficácia antibacteriana e antifúngica

O objetivo deste estudo foi investigar o efeito do pH, da temperatura e da concentração de nitrato de prata (AgNO3) na síntese de nanopartículas de prata (AgNPs) por Aspergillus flavo-furcatis e avaliar o respectivo potencial antimicrobiano. Um experimento fatorial 2³ foi realizado para avaliar o efeito das condições físico-químicas na síntese de AgNPs. A caracterização das AgNPs foi realizada em espectroscopia UV-Vis e ICP-MS. A atividade antimicrobiana foi avaliada por difusão em ágar por poço e microdiluição em caldo. O pH e a concentração de AgNO3 tiveram efeitos significativos na síntese de AgNPs nas condições experimentais. As AgNPs sintetizadas em pH 9,0 e concentração de AgNO3 de 1,5 mM apresentaram maior eficácia contra Staphylococcus aureus (3,17 µg/mL), Escherichia coli (6,35 µg/mL) e Candida albicans (0,79 µg/mL). Os dados mostraram que a síntese de AgNPs por A. flavo-furcatis é influenciada pelo pH e pela concentração de AgNO3, indicando que as AgNPs sintetizadas possuem atividade antimicrobiana contra S. aureus, E. coli e C. albicans.

Facile and Green Route to Silver Nanoparticles Using Aqueous Plant Extract, and their Photocatalytic and Antibacterial Studies

Silver nanoparticles were prepared through an environmental friendly and cost-effective plant-mediated technique, using crude extracts of Welsh onion plant. The synthesized nanoparticles were characterized using UV-vis spectrophotometer, powdered X-ray diffractometer (p-XRD), Fourier transform infra-red (FTIR) spectrophotometer, and transmission electron microscope (TEM). Silver nanoparticles of different sizes and morphologies were obtained by varying some synthesis parameters such as concentrations of AgNO3 (1, 2 and 5 mM) and ratio of the volume of the plant extract to AgNO3 (1:5 and 1:10) at constant reaction temperature of 80 °C. The difference in the reaction conditions showed significant effects on silver nanoparticles obtained. The surface plasmon resonance (SPR) varied with change in concentration of AgNO3 and the ratio of the AgNO3 to the plant extracts. The lowest SPR appeared around 412 nm (2 mM; 1:10), while the largest was achieved around 427 nm (5 mM; 1:10). FTIR results revealed the presence of different characteristic functional groups responsible for the bioreduction of silver ions in Welsh onion extract. Transmission electron microscopy (TEM) showed that the lowest average particle size of the silver nanoparticles was 3.74 nm (2 mM; 1:10), while the highest was 15.72 nm (1 mM; 1:5). Monodispersed spherical shaped nanoparticles were obtained from the 2 mM concentration of the AgNO3, while particles with some degree of agglomeration were obtained from 1 and 5 mM concentration. The p-XRD studies revealed face centred cubic structures. The nanoparticles obtained from 1 and 5 mM (1:5) gave moderate photo-catalytic potentials in the degradation of methyl red dye. However, the photocatalytic property increased with increase in the concentration of the precursor salt (AgNO3) from 1 to 5 mM. Gram positive Staphylococcus aureus and Bacillus cereus and Gram negative Klebsiela pneumonia and Escherichia coli bacteria strains were susceptible to the silver nanoparticles (2 mM). The nanoparticles were most active against E. coli with a minimum inhibitory concentration (MIC) below 0.05 mg/mL. The silver nanoparticles could become potential compounds in the future antibiotic research.

Environmentally Benign and Large-Scale Synthesis of Monodisperse Oleate-Protected Silver Nanoparticles in Ethanol

An environmentally benign solvothermal process was introduced to synthesize monodisperse silver nanoparticles (Ag NPs). Silver nitrate (AgNO3) was reduced by ethanol which was also used for recyclable solvent. The as-synthesized Ag NPs were stabilized by oleate. Effects of reaction temperature, reaction time, AgNO3 concentration as well as molar ratio of sodium oleate and AgNO3 on the formation and surface plasmon resonance (SPR) were determined by means of UV–Vis spectrophotometer. TEM and XRD were used to characterize the size, morphology and crystalline structure of Ag NPs. The excessive AgNO3 over sodium oleate and high concentration of AgNO3 are favorable for the synthesis of monodisperse Ag NPs in large scale. The characteristic SPR absorption of Ag NPs centers at ca. 430 nm despite of reaction temperature, reaction time and even AgNO3 concentration. The nucleation and growth of Ag NPs completed in a very short period of time, showing the high efficiency of our synthetic route for the synthesis of uniform Ag NPs.

PVP‐mediated galvanic replacement growth of AgNPs on copper foil for SERS sensing

Herein, the authors present a simple and cost-effective silver nanoparticles (AgNPs)-based surface-enhanced Raman scattering (SERS) sensor based on galvanic displacement reaction using AgNO3 and copper foil as precursors. With the mediation of polyvinyl pyrrolidone (PVP), AgNPs grow in-situ on the surface of copper foil at room temperature. AgNPs-based SERS sensor was prepared with optimised AgNO3 concentration of 50 mM, the mass ratio of AgNO3 to PVP of 2:1 and characterised using scanning electron microscopy and X-ray diffraction. As-fabricated SERS sensor exhibited a high Raman signal enhancement factor of 3.5 × 105 in the detection of Rhodamine 6G (R6G). Furthermore, a decent linear relationship for methyl parathion sensing was obtained in the range from 1 × 10−6 to 1 × 10−4 M, with an actual detection limit of 1 × 10−6 M. Recoveries of methyl parathion-spiked lake water samples ranging from 93.64 to 106.16% were obtained, suggesting the feasibility of the SERS sensor. These features demonstrated that the AgNPs-based SERS sensor can potentially be used in sensing a trace amount of chemicals in surface water for environmental protection.

Natural latex-capped silver nanoparticles for two-way electrochemical displacement sensing of Eriochrome black T

A novel electrochemical displacement sensor has been reported for the first time standing on the oxidation behavior of the modifier and displacer. The electrochemical displacement sensor based on glassy carbon electrode (GC) modified with natural latex-capped silver nanoparticles (NL-AgNPs) has been conducted for the Eriochrome Black T (EBT) assessment. NL-AgNPs have been synthesized by direct chemical reduction under different reaction conditions such as NL and AgNO3 concentration, temperature and pH for optimizing the size, and stability of nanoparticles before modifying the GC electrode. Under the optimized conditions, NL-AgNPs have been characterized with UV–VIS spectroscopy, fluorescence emission spectroscopy (FL), transmission electron microscope (TEM), zeta potential analyzer and cyclic voltammetry (CV). Under optimized electrolytic and voltammetric conditions, EBT has been detected at NL-AgNPs/GC based on modifier (NL-AgNPs) and displacer (EBT) oxidation. Both displacer and modifier-based sensor (two-way sensor) have shown a linear range of 2–96 µg/L and detection limits of 2.92 and 7.01 µg/L, respectively. A high selectivity for EBT detection in river water with 110 and 107.5 recovery values has been shown for both modifier- and displacer-based sensor, respectively.

One pot synthesis of nano Ag in calcium alginate beads and its catalytic application in p‐Nitrophenol reduction with kinetic parameter estimation and model fitting

AbstractIn this work, one step process of synthesis of silver nanoparticles (Agnp) embedded in insitu formed calcium alginate (CA) beads is stated. CA, formed from the reaction between sodium alginate and calcium hydroxide, acts as reducing and stabilizing agent as well as support for nanoparticles. The reaction mechanism for the formation and stabilization of Agnp is proposed where the vicinal dihydroxy groups of alginate are assumed to act as the reducing agent for Ag+ to Ag°. Transmission electron microscopy (TEM), x‐ray diffraction (XRD), UV‐vis spectroscopy, field emission scanning electron microscopy (FESEM), and atomic absorption spectroscopy (AAS) were used to characterize the Agnp. The formation of spherical nanoparticles with average size range of 4‐5 nm was confirmed by TEM. Catalytic activity of this nano silver‐calcium alginate (Agnp‐CA) composite was evaluated in the reduction of p‐nitrophenol. Concentrations of sodium alginate, calcium hydroxide, and AgNO3 are found to be the parameters that critically affect the synthesis of Agnp. The efficacy of the catalyst is expressed on the basis of suitable reaction parameters. Both pseudo‐homogeneous and heterogeneous kinetic models are proposed for the reaction to find the best model and the Eley‐Riedel model is found to fit well with the experimental data. The novelty of this work is that the tandem process of CA bead formation, Agnp formation, and Agnp entrapment in CA have been transformed into a single‐step process. Moreover, elaborations of each step of the ionic mechanisms of Agnp formation and p‐NP reduction with Agnp and the establishment of a heterogeneous kinetic model for the reaction are reported for the first time here.

Highly stable silver nanoparticles containing guar gum modified dual network hydrogel for catalytic and biomedical applications

Although many preparation methods have been reported till date, it is still a great challenge to prepare silver nanoparticles (AgNPs) that simultaneously possess high stability and enhanced applicability. We report a rapid and efficient synthesis of AgNPs containing polyvinyl alcohol (PVA)-guar gum (GG) smart hydrogel composite, which exhibited pH-dependent swelling and enhanced mechanical strength. The AgNPs were synthesized in situ in the PVA-GG hydrogel from various concentrations of the AgNO3 precursor solution in the presence of NaBH4. Stable AgNPs (90 days) of 10−20 nm uniformly dispersed in PVA-GG hydrogel was obtained. Simultaneously, at the optimum concentration of AgNO3 (0.01 M), the tensile strength and elongation at break were enhanced by 74 % and 11 %, and swelling capacity was increased by 18 % as compared to PVA-GG hydrogel (control). The PVA-GG-AgNPs hydrogel composite exhibited excellent catalytic activity and antibacterial property, which makes them a suitable candidate for industrial applications.