Ag nanoparticles capped by a nontoxic polymer: Electrochemical and spectroscopic characterization of a novel nanomaterial for glucose detection

Modified electrodes with metal or metal oxides nanoparticles are particularly appealing to improve sensor performances and fabricate miniaturized devices, as required also in glucose detection. A Pt electrode modified by drop casting of a novel nanostructured film based on silver nanoparticles (Ag-NPs) capped in a commercial nontoxic polyvinyl alcohol (PVA) matrix is proposed here as a valid alternative to classical glucose (bio)sensors. The extensive electrochemical and spectroscopic characterization by X-ray Photoelectron Spectroscopy (XPS) of this advanced nanomaterial is presented to study its response to glucose and to investigate the chemical nature of deposited Ag.     

Surface enhanced Raman scattering on SiO2/Ag nanoparticles aggregate and preparation of nitrogen-doped carbon dots by pyrolysis of Co(2,2′-bipyridine)2(dicyanamide)2

Co(2,2'-bipyridine)₂(dicyanamide)₂, Co(bpy)₂(N(CN)₂)₂, was synthesised by solution crystallisation method. The ‘external’ lattice modes of Co(bpy)₂(N(CN)₂)₂ crystal have been determined by use of the method of nuclear site group analysis. Based on the surface enhanced Raman scattering (SERS) activity of silver nanoparticles (Ag-NPs), a SiO₂/Ag-NPs/Co(bpy)₂(N(CN)₂)₂ aggregate was prepared in order to better analyse the adsorption orientation of the cobalt complex on the surface of Ag-NPs. The result of the SERS measurement indicates that the molecular plane presents a tilted orientation with respect to the Ag-NPs surface. The system described here could serve as the basis for a study of accurate and available SERS sensor. The pyrolysis products at 553 and 593 K, respectively, in air have been investigated. The results showed that nitrogen-doped carbon dots were obtained from the pyrolysis products of Co(bpy)₂(N(CN)₂)₂ calcined at 553 K. This process can be exploited as a simple and effective path for the synthesis of nitrogen-doped carbon dots by using nitrogen-containing metal organic complex as precursors.     

Influence of silver nanoparticles on the fabrics functions prepared by in-situ technique

The development of multifunctional fabrics is an important purpose for their application in many fields. This study provided a simple approach for innovative textile design by applying the optical properties of Plasmonic noble metal nanoparticles. The utilization of feasible technique to functionalize both semi-synthetic and synthetic fabrics namely viscose and acrylic fabric has been accomplished. Where, fabrics functions have been developed by in situ synthesis of silver nanoparticles (Ag NPs) into their surface using trisodium citrate as multifunctional agent (reductant, stabilizer, and linker). The silver NPs incorporated into fabrics has been characterized by UV–visible spectroscopy, scanning electron microscopy, energy dispersive X-ray, and X-ray photoelectron spectroscopy. The mechanism of assembling Ag NPs in situ incorporated fabric matrix has been discussed. The influence of silver nanoparticles on the coloration, UV-protection, and antibacterial properties of the fabrics has also been examined. The overall results indicated that, the in situ Ag NPs-incorporated into fabrics has been applied as a colorant for both viscose and acrylic fabrics effectively beside the improvement for UV-blocking and anti-bacterial properties.     

Effects of silver nanoparticles on wastewater biofilms

The goal of this research is to understand the potential antibacterial effect of silver nanoparticles (Ag-NPs) on biological wastewater treatment processes. It was found that original wastewater biofilms are highly tolerant to the Ag-NP treatment. With an application of 200 mg Ag/L Ag-NPs, the reduction of biofilm bacteria measured by heterotrophic plate counts was insignificant after 24 h. After the removal of loosely bound extracellular polymeric substances (EPS), the viability of wastewater biofilms was reduced when treated under the same conditions. By contrast, when treated as planktonic pure culture, bacteria isolated from the wastewater biofilms were highly vulnerable to Ag-NPs. With a similar initial cell density, most bacteria died within 1 h with the application of 1 mg Ag/L Ag-NPs. The results obtained here indicate that EPS and microbial community interactions in the biofilms play important roles in controlling the antimicrobial effects of Ag-NPs. In addition, slow growth rates may enhance the tolerance of certain bacteria to Ag-NPs. The effects of Ag-NPs on the entire microbial community in wastewater biofilms were analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis, PCR-DGGE. The studies showed that the microbial susceptibility to Ag-NPs is different for each microorganism. For instance, Thiotrichales is more sensitive to Ag-NPs than other biofilm bacteria.