Structural refinement and electrochemical properties of one dimensional (ZnO NRs)1-x(CNs)x functional hybrids for serotonin sensing studies.

Herein, the efficient serotonin (5-HT) sensing studies have been conducted using the (ZnO NRs)1-x(CNs)x nanocomposites (NCs) having appropriate structural and electrochemical properties. Initially, the different compositions of ZnO nanorods (NRs), with varying content of carbon nanostructures (CNs=MWCNTs and RGO), are prepared using simple in-situ wet chemical method and thereafter these NCs have been characterized for physico-chemical properties in correlation to the 5-HT sensing activity. XRD Rietveld refinement studies reveal the hexagonal Wurtzite ZnO NRs oriented in (101) direction with space group 'P63mc' and both orientation as well as phase of ZnO NRs are also retained in the NCs due to the small content of CNs. The interconnectivity between the ZnO NRs with CNs through different functional moieties is also studied using FTIR analysis; while phases of the constituents are confirmed through Raman analysis. FESEM images of the bare/NCs show hexagonal shaped rods with higher aspect ratio (4.87) to that of others. BET analysis and EIS measurements reveal the higher surface area (97.895 m2/g), lower charge transfer resistance (16.2 kΩ) for the ZCNT 0.1 NCs to that of other NCs or bare material. Thereafter, the prepared NCs are deposited on the screen printed carbon electrode (SPCE) using chitosan as cross-linked agent for 5-HT sensing studies; conducted through cyclic voltammetry (CV) and square wave voltammetry (SWV) measurements. Among the various composites, ZCNT0.1 NCs based electrodes exhibit higher sensing activity towards 5-HT in accordance to its higher surface area, lower particle size and lower charge transfer resistance. SWV measurements provide a wide linear response range (7.5-300 µM); lower limit of detection (0.66 µM), excellent limit of quantification (2.19 µM) and good reproducibility to ZCNT 0.1 NCs as compared to others for 5-HT sensing studies.

Interfacially Interactive Ternary Silver-Supported Polyaniline/Multiwalled Carbon Nanotube Nanocomposites for Catalytic and Antibacterial Activity.

Herein, a protocol strategy has been designed for the preparation of ternary silver nanoparticles-supported polyaniline multiwalled carbon nanotube (Ag NPs-PANI/MWCNT) nanocomposites with a chemical interaction for catalytic and antibacterial activity. The morphological study confirmed that Ag NPs were immobilized on the surface of PANI, and afterward, Ag NPs-PANI were mixed with the MWCNTs. The X-ray diffraction technique revealed the face-centered cubic structure of Ag NPs, and the X-ray photoelectron spectroscopy study revealed the chemical constituent and signature of π-π* and C-N interactions in the nanocomposites. The ternary Ag NPs-PANI/MWCNTs nanocomposites have the apparent rate of reaction (K app) as 5.4 × 10-3 s-1, higher than binary nanocomposites for catalytic reduction of 4-nitrophenol to 4-aminophenol at room temperature. Antibacterial activity of Ag NPs-PANI/MWCNT nanocomposites is higher against pathogenic bacteria. Thereafter, because of multifold applications of ternary nanocomposites, they have a broad scope in the field of environmental and healthcare sectors.

Synthesis of Ni2+ ion doped ZnO-MWCNTs nanocomposites using an in situ sol-gel method: an ultra sensitive non-enzymatic uric acid sensing electrode material.

Nickel (Ni2+) ion doped zinc oxide-multi-wall carbon nanotubes (NZC) with different composition ratios of MWCNTs (from 0.01 to 0.1 wt%) are synthesized through an in situ sol-gel method. The synthesized NZC nanocomposites (NCs) are used as electrode materials with glassy carbon electrodes (GCEs) for electrochemical detection of uric acid (UA). The cyclic voltammogram of the representative NZC 0.1 modified GCE (NZC 0.1/GCE) revealed the highest electrochemical sensing activity towards the oxidation of UA at 0.37 V in 0.2 M phosphate buffer solution (PBS) having pH 7.4 ± 0.02. The limit of detection (LOD) and limit of quantification (LOQ) for the NZC 0.1/GCE are determined to be 5.72 nM and 19.00 nM (S/N = 3) respectively, which is the lowest compared to the literature values reported for enzymatic and non-enzymatic detection techniques. The synergistic effect of NZC 0.1 NCs is proposed as one of the factors for the enhanced electrochemical oxidation of UA complemented by the phase, lattice parameters, functional groups, morphology, elemental compositions, types of bonding and specific surface area with pore size ascertained using various techniques. The synthesized NZC 0.1 NCs are further proposed as selective electrode materials for the electrochemical detection of UA as authenticated further by performing interference tests with other metabolites such as ascorbic acid (AA), dopamine (DA) and d-glucose. The optimized electrochemical studies are further adopted for sensing of UA from human excretion samples using NZC 0.1 NCs.

Ag Nanoparticles Connected to the Surface of TiO2 Electrostatically for Antibacterial Photoinactivation Studies.

Supported silver nanoparticles (Ag NPs) were prepared by chemical reduction method with a sol-gel method. The structure, morphology, and interconnectivity of Ag/TiO2 nanocomposites (NCs) were analyzed using different instrumental techniques. Transmission electron microscopy reveals the Ag NPs have uniformly distributed and anchored on the surface of TiO2 . The reduction in electron-hole recombination was measured by Photoluminescence measurements lead, to an increased photocatalytic inactivation of bacteria. Increase in the amount of Ag NPs on TiO2 resulted in a slight decrease in optical band gap energy of TiO2 . The effect of Ag NPs content on the photocatalytic properties of TiO2 for inhibition of bacteria in visible light irradiation was studied. Furthermore, the antibacterial activity of Ag/TiO2 NCs in the presence of UVA light was studied against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacterial strain by plate count method. Lower values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the catalysts were observed and used to determine the tolerance factor which is shown bactericidal nature of the NCs. Subsequently, time-killing assay of Ag/TiO2 NCs was shown dynamics of antimicrobial activity. These multifold antibacterial studies exhibited potent antibacterial nature of the NCs and employed in the wider range of biomedical fields.