A. Suganthi

Synthesis, characterization and study of photocatalytic activity of surface modified ZnO nanoparticles by PEG capping

Nanoparticles of bare and PEG (Polyethylene glycol) capped zinc oxide (ZnO) were synthesized by precipitation method. The photocatalytic activity of bare and modified ZnO nanoparticles was studied by monitoring the degradation of Rhodamine B (RhB). The results show that PEG capped ZnO nanoparticles has reduced photocatalytic activity than the bare ZnO nanoparticles. The reduction in the chemical oxygen demand (COD) and total organic carbon (TOC) results also revealed the reduced photocatalytic activity of PEG capped ZnO. The UV-shielding property was evaluated by measuring the transmittance which shows that both bare and PEG capped ZnO nanoparticles possess good UV-shielding ability.

Fabrication of g-C 3 N 4 /NiO heterostructured nanocomposite modified glassy carbon electrode for quercetin biosensor

Herein, we report a one-pot synthesis of structurally uniform and electrochemically active graphitic carbon nitride/nickel oxide (g-C3N4/NiO) nanocomposite and an investigation on the electrocatalytic oxidation of quercetin (QR). The synthesized g-C3N4/NiO nanocomposite has uniform surface distribution, which was characterized with scanning electron microscopy (SEM). Moreover, the composition of synthesized g-C3N4/NiO nanocomposite was characterized by UV-vis-spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR spectra), BET, SEM and HRTEM. The g-C3N4/NiO was electrochemically treated in 0.1 MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with QR concentration from 0.010 μM to 250 µM with a fast response time of less than 2 s and a detection limit of 0.002 μM. To further evaluate the feasibility of using this sensor for real sample analysis, QR content in various real samples including green tea, green apple, honey suckle were determined and satisfactory results were achieved.

Ultrasonic assisted synthesis with enhanced visible-light photocatalytic activity of NiO/Ag 3 VO 4 nanocomposite and its antibacterial activity

The NiO/Ag3VO4 nanocomposite photocatalysts were developed by ultrasonic assisted preparation method to study the photocatalytic activity under visible light irradiation. The samples were characterized by UV-DRS, XRD, FT-IR, XPS, SEM, EDX, TEM, EIS and BET analysis. The photocatalytic activity of NiO/Ag3VO4 nanocomposite for the photodegradation of 4-Nitro Phenol (4-NP) and Rose Bengal (RB) under visible light irradiation was studied and it is observed that the activity has been much higher than that of the pure Ag3VO4. DRS spectrum shows the absorption edge of NiO-Ag3VO4 in visible region of spectrum. The formation of cubic structured NiO and orthorhombic structured Ag3VO4 was confirmed by powder X-ray diffraction analysis. The results of XPS analysis confirmed the coexistence of NiO and Ag3VO4 in the NiO/Ag3VO4 composite. The specific surface area and pore structure of the prepared samples were measured by BET. Enhanced charge separation efficiency was confirmed by electrochemical impedance spectroscopy (EIS) measurements. The kinetics of the NiO/Ag3VO4 nanocomposite was proposed to investigate the intervened effects of NiO to Ag3VO4 on the promotion of photocatalytic property. NiO/Ag3VO4 was found to be stable and reusable without appreciable loss of catalytic activity up to four consecutive cycles. A possible electron-hole transfer mechanism at the NiO/Ag3VO4 interface is proposed. It also showed effective and efficient bactericidal activities against Staphylococcus aureus, Streptococcus, Proteus and Escherichia coli bacteria. Our results provide some new insights on the performance of visible light photocatalysts on environmental remediation.

A novel highly selective and sensitive detection of serotonin based on Ag/polypyrrole/Cu 2 O nanocomposite modified glassy carbon electrode

A silver/polypyrrole/copper oxide (Ag/PPy/Cu2O) ternary nanocomposite was prepared by sonochemical and oxidative polymerization simple way, in which Cu2O was decorated with Ag nanoparticles, and covered by polyprrole (PPy) layer. The as prepared materials was characterized by UV-vis-spectroscopy (UV-vis), FT-IR, X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) with EDX, high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Sensing of serotonin (5HT) was evaluated electrocatalyst using polypyrrole/glassy carbon electrode (PPy/GCE), polypyrrole/copper oxide/glassy carbon electrode (PPy/Cu2O/GCE) and silver/polypyrrole/copper oxide/glassy carbon electrode (Ag/PPy/Cu2O/GCE). The Ag/PPy/Cu2O/GCE was electrochemically treated in 0.1MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with 5-HT concentration from 0.01 to 250 µmol L-1 and the detection limit was found to be 0.0124 μmol L-1. It exhibits high electrocatalytic activity, satisfactory repeatability, stability, fast response and good selectivity against potentially interfering species, which suggests its potential in the development of sensitive, selective, easy-operation and low-cost serotonin sensor for practical routine analyses. The proposed method is potential to expand the possible applied range of the nanocomposite material for detection of various concerned electro active substances.

Facile sonochemical synthesis of Zn 2 SnO 4 -V 2 O 5 nanocomposite as an effective photocatalyst for degradation of Eosin Yellow

This study presents a novel method for the preparation of Zn2SnO4/V2O5 nanocomposites via a sonochemical aqueous route. This method is mild, convenient, cheap and efficient. The as prepared samples were characterized by XRD, SEM, EDAX, TEM, BET, FT-IR and UV-DRS spectra. DRS spectrum shows the adsorption edge of Zn2SnO4-V2O5 in visible region of spectrum. The structural and morphological features of the as synthesized Zn2SnO4-V2O5 nanocomposites have been observed using both scanning and transmission electron microscopy. BET surface area analysis inferred that the prepared hetero-junctions are meso-porous in nature. The photocatalytic activity of Zn2SnO4-V2O5 nanocomposites for the degradation of Eosin Yellow (EY) dye under visible light was investigated in detail. 3% Zn2SnO4-V2O5 nanocomposite exhibited the highest photocatalytic performance (92% of EY degradation) when compared with 2% Zn2SnO4-V2O5 and 5% Zn2SnO4-V2O5. The adsorption of Eosin Yellow followed the pseudo-first order kinetic model. Simultaneously, high stability of the sample was also investigated by four successive photodegradation of EY under visible light. The relationship between photocatalytic activity and the structure of 3% Zn2SnO4-V2O5 nanocomposite is discussed, and possible reaction mechanisms are also proposed. Therefore, the facile sonochemical preparation process provides some insight into the application of Zn2SnO4-V2O5 nanocomposites in photocatalytic degradation of organic pollutants.

A simple sonochemical approach to fabricate a urea biosensor based on zinc phthalocyanine/graphene oxide/urease bioelectrode

A novel zinc phthalocyanine/graphene oxide (ZnPh/GO) nanocomposite modified glassy carbon electrode (GCE) was prepared by using sonochemical approach and simple drop casting method. Urease (Urs) was used as the specific enzyme for urea detection and was physically immobilized onto the surface of ZnPh/GO nanocomposite. The fabricated ZnPh/GO/Urs matrix was successfully characterized by UV-vis-spectroscopy, FT-IR spectroscopy, scanning electron microscopy (SEM), raman spectrum, thermogravimetric analysis, cyclic voltammetric (CV) and amperometric techniques. The electrocatalytic performance of the ZnPh/GO/Urs electrode was investigated by urea biosensor. Our results demonstrate that the modified electrode has excellent electrocatalytic activity towards the sensing of urea in 0.1 M phosphate buffer solution (PBS, pH 7.2). The biosensor tolerated a wide linear concentration range for urea from 0.4 to 22 μM (R2 = 0.991), with a detection limit of 0.034 µM (S/N = 3). The ZnPh/GO/Urs bioectrode has several excellent properties, including a fast response time, high reproducibility and stability.