Electrochemical synthesis of silver nanoparticles-coated gold nanoporous film electrode and its application to amperometric detection for trace Cr(VI)

A simple mechanical polishing treatment of commercial solid-gold electrodes (SGEs) can renew the active gold surface, reduce manufacturing-related grooves, and markedly improve the repeatability of geometric-area estimation and the analytical performance in stripping voltammetry. The work focuses on the accurate determination of the geometric area of a SGE by two voltammetric techniques. Cyclic voltammetry (CV) at different scan rates, referred to as the Randles–Ševčik equation, and voltage scans at different electrode rotation rates, based on the Levich equation, were performed. The geometric area of the SGE was also evaluated by scanning electron microscopy (SEM). Commercial SGEs show grooves on their surface, derived from the fabrication processes. The effects of these grooves on the voltammetric response were investigated. The measurements were carried out on the SGE both as received from the manufacturer and after a reduction in the grooves height by a drastic mechanical treatment. After the treatment, the estimated area values were lower and more precise (3.05 ± 0.02 mm2). Moreover, the reduction in the grooves’ height affected the area estimations in contrast with the meaning of the geometric area, as intended by the Randles–Ševčik and Levich equations. Furthermore, the gold exposed surface was measured by CV in sulphuric acid. Finally, the SGE was tested for the detection of Hg in a NaCl solution by anodic stripping voltammetry: the repeatability of the response improved after the mechanical treatment, confirming the usefulness of this step before electrode usage.

A simple procedure for field fish sample pretreatment was developed. This treatment in combination with square wave anodic stripping voltammetry (SW-ASV) with solid gold electrodes (SGE) and gold nanoparticle-modified glassy carbon electrodes (AuNPs-GCE) was applied for the determination of total mercury content. A certified reference material (CRM, Tuna Fish BCR 463), ten freeze-dried samples of canned tuna and two fresh fish samples were analysed both with a bench-top voltammetric analyser after microwave digestion and with a portable potentiostat after mild eating using a small commercial food warmer. The results obtained by the two SW-ASV approaches and by a Direct Mercury Analyser (DMA), the official method for mercury determination, were in very good agreement. In particular, (i) the results obtained with in field procedure are consistent with those obtained with the conventional microwave digestion; (ii) the presence of gold nanoparticles on the active electrode surface permits an improvement of the analytical performance in comparison to the SGE: the Limit of Quantification (LOQ) for mercury in fish-matrix was 0.1 μg L−1 (Hg cell concentration), corresponding to 0.06 mg kg−1 wet fish, which is a performance comparable to that of DMA. The pretreatment proposed in this study is very easy and applicable to fresh fish; in combination with a portable potentiostat, it proved to be an interesting procedure for on-site mercury determination.

Arsenic (As) contamination in one of the most serious water quality concern due to its toxic effects and worldwide availability. To avoid its poisoning effects, especially in the form of As(V), it is important to develop new techniques for its treatment. The current study was conducted to investigate the As(V) removal from aqueous systems using silver (Ag) nanoparticles (NPs). The Ag NPs were synthesized through a simple method by using Vernonia Anthelmintica (L.) plant extract and characterized by using UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Energy dispersive X-ray (EDX) spectroscopy and Scanning electron microscopy (SEM). The removal of As(V) was tested with respect to time, optimum dose, effect of light and pH, treatment with ultra-sonication and continuous flow process. The results showed that Ag NPs can effectively remove As(V) from aqueous systems in the presence of sunlight (100%), ultra-sonication process (100%), neutral pH (100%), and continuous flow (71.6%). While the same NPs could not show effective removal of As(V) with respect to low dose (15%), darkness (38.9%), low pH of 3.4 (21.4%) and high pH of 11 (11.1%). Using Ag NPs can reduce As(V) to the permissible limits set by World health organization (WHO). Moreover, the Ag NPs work efficiently in sunlight and in the neutral pH range, therefore adjustment of pH is not required to activate these NPs.

A new method is reported for detecting heavy metal ions by using the self assembled monolayer (SAM) technique and surface enhanced Raman spectroscopy (SERS). The p‐mercaptobenzoic acid (MBA) served as the SERS readout molecule and the modified tag to attach on the smooth gold substrate as well as the tag of nanoparticles by the SAM method. Two carboxyl groups from MBA molecules which were attached respectively to gold substrate and gold nanoparticles were linked through the heavy metal ions (Cu2+, Pb2+ and Zn2+) as bridge, and thus sandwich structure of ‘MBA modified gold substrate/heavy metal ions/MBA modified gold nanoparticles’ was built for detection. The observation of the oxidation peak of metal nanoparticles from cyclic voltammetry (CV) curve, gold nanoparticles from scanning electron microscopy (SEM) images and SERS signal of MBA from the sandwich structure indicated the existence of heavy metal ions. The difference in the wavenumbers of vibrational modes from MBA in the sandwich structure constructed by different could be used to identify different heavy metal ions. The assembled structure was rinsed by strong chelator of EDTA solution to remove the heavy metal ions from the sandwich structure and thus to obtain a fresh gold substrate modified with MBA for the cyclic detection. Copyright © 2007 John Wiley & Sons, Ltd.

The Effect of Ag nanoparticles on electrochemical properties of Titanate nanotubes electrode materials

Synthesis and superconductivity of (Ag)x/CuTl-1223 composites

Synthesis and characterisation of cobalt oxide nanoparticles decorated graphene oxide and its electrocatalytic behaviour

The present study evaluates in vitro cytotoxic effects and the mode of interaction of biologically synthesized Ag and Au nanoparticles (NPs) using Brassica oleracea L. var. capitata f. rubra (BOL) against HT-1080 cancer cells and bacterial cells as well as their wound healing efficacy using a mouse model. UV-visible spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray analysis have ascertained the formation of nano-sized Ag and Au particles. Fourier transform infrared analysis has confirmed that polyphenol and amide groups in BOL act as capping as well as reducing agents. The free radical scavenging activity under in vitro conditions is found to be higher for the Ag NPs when compared to the Au NPs. Acridine orange-ethidium bromide dual staining and comet assay have indicated that the cytotoxic effects are mediated through nuclear morphological changes and DNA damage. The intracellular localization of Ag and Au NPs in HT-1080 cells and their subsequent effect on apoptosis and necrosis were analyzed by flow cytometry while the mode of interaction was established by scanning electron microscopy under field emission mode and by bio-transmission electron microscopy. These methods of analysis clearly revealed that the Ag and Au NPs have easily entered and accumulated into the cytosol and nucleus, resulting in activation of inflammatory and apoptosis pathways, which in turn cause damage in DNA. Further, mRNA and protein expression of caspase-3 and caspase-7, TNF-α, and NF-κB have provided sufficient clues for induction of intrinsic and extrinsic apoptosis and inflammatory pathways in Ag NP- and Au NP-treated cells. Evaluation of wound healing properties of Ag and Au NPs using a mouse model indicates rapid healing of wounds. In addition, no clear toxic effects and no nuclear abnormalities in peripheral blood cells are observed. Ag NPs appear to be a better anticancer therapeutic agent than Au NPs. Nonetheless, both Ag NPs and Au NPs show potential for promoting topical wound healing without any toxic effects. Graphical abstract Schematic representation of biological synthesis of Ag and Au NPs and its application on cancer and wound healing.

Influence of the support material and the resulting particle distribution on the deposition of Ag nanoparticles for the electrocatalytic activity of benzyl bromide reduction

Ternary nanocomposite of cobalt oxide nanograins and silver nanoparticles grown on reduced graphene oxide conducting platform for high-performance supercapattery electrode material

Metallic nanoparticles (NPs), in general, are able, due to the high surface area per unit volume, to absorb the maximum incoming light flux through the vicinity of plasmonic structures and then provide local heating. Thus, silver (Ag) NPs have been used to generate heat and increase the temperature of water from solar radiation energy. The optimal plasmonic heating generation can be obtained as soon as the wavelength of the light source is close to the plasmonic resonance wavelength of Ag NPs. Ag NPs have been fabricated through a straightforward, cheap, as well as environmentally friendly approach. In this study, Salix babylonica L., weeping willow leaf extract has been utilized as a reducing, capping, and stabilizing agent, without using any other toxic materials. The importance of this study lies in the generation of hot electrons, which can be obtained by collecting the solar spectrum near the infrared and infrared regions, which cannot be obtained by conventional photocatalytic devices. Numerous characterization techniques such as; UV-Vis, FT-IR spectroscopy, X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis were used to study the optical, chemical, structural, morphological, properties of the Ag NPs. The impact of pH on the properties of Ag NPs and their performance to generate heat during solar irradiation have been investigated intensively. This study showed that the synthesized Ag NPs with pH value 12 is the optimum condition and can increase the temperature of water dramatically. An evaluation of the current patents displays that the field of green synthesis Ag NPs utilizing plant extracts is a vital field and produces rather stable, safe and effective Ag NPs. The novelty of this patent is that Ag NPs can be synthesized from a one-pot reaction without using any exterior stabilizing and reducing agent, which is not conceivable by means of the existing processes. This study, also, is rare and distinctive, and it demonstrates that even a slight quantity of the Ag NPs is significantly raising the temperature of water effectively.

A novel disposable sensor based on gold digital versatile disc chip modified with graphene oxide decorated with Ag nanoparticles/β-cyclodextrin for voltammetric measurement of naproxen

This paper reports the green synthesis of Ag, Cu and AgCu nanoparticles at room temperature using palm leaves extract. The purpose of this study is to eliminate the use of chemicals in the synthesis of nanoparticles and evaluate the efficiency of the palm leaves extract as the reducing and stabilizing agents. The palm leaves extract was added to metal salt solution and continuously stirred until reaction completed. The produced nanoparticles were analyzed using atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analyses revealed that palm leaves extract has efficiently reduced the silver ions, but not the copper ions. During synthesis of AgCu nanoparticles, simultaneous reduction was occurred leading to formation of alloyed nanoparticles. Biomolecules from the palm leaves extract adsorbed on the surface of nanoparticles forming a capping layer thus stabilized the nanoparticles. The produced Ag and Cu nanoparticles were predominantly spherical with the particle size of Cu nanoparticles were larger than Ag nanoparticles. The AgCu nanoparticles closely resembled the Ag nanoparticles due to high Ag content with average size of 13nm. Therefore, palm leaves extract has a potential to be a good reducing and stabilizing agents.

Electrodeposition preparation of Ag nanoparticles loaded TiO2 nanotube arrays with enhanced photocatalytic performance

AGNES at vibrated gold microwire electrode for the direct quantification of free copper concentrations