Balakumar Vellaichamy

Ag nanoshell catalyzed dedying of industrial effluents

A rapid way to dedye industrial effluents is reported herein using silver nanoshells (Ag-NSs) as a green catalyst. Ag-NSs were synthesized using Crataeva religiosa leaf extract as both a reducing and stabilizing agent, and they were characterized by UV-visible spectroscopy, FT-IR spectroscopy, XRD, HR-TEM and EDX analysis. The green synthesized Ag-NSs catalyze in a minute the degradation of organic dye pollutants such as (1) methylene blue, (2) rhodamine-B, (3) safranin, (4) methyl orange, (5) eosin yellow, (6) rose bengal, (7) methyl red, (8) rhodamine-6G, (9) indigo, (10) crystal violet, (11) malachite green and (12) victoria blue from an aqueous environment using NaBH4. Ag-NSs are able to be conveniently separated from an aqueous environment after catalytic dedying and reusable even after five cycles. The formation of Ag-NSs and dedying mechanism have also been investigated and discussed.

A facile, one-pot and eco-friendly synthesis of gold/silver nanobimetallics smartened rGO for enhanced catalytic reduction of hexavalent chromium

A one-pot synthesis of rGO, AgNPs, rGO/AgNPs, AuNPs, rGO/AuNPs, Ag-AuNPs and rGO/Ag-AuNPs using Albizia saman leaf extract as a reducing and stabilizing agent is reported herein. The obtained nanomaterials were characterized by UV-Vis, FT-IR, XRD, TEM and EDX analyses, and were involved as innovative catalysts in the conversion of toxic Cr6+ to benign Cr3+, using formic acid as a reducing agent. The green synthesized rGO/Ag-AuNPs show superior catalytic activity, stability and reusability, due to the synergistic effect of rGO and Ag-AuNPs, compared to rGO, AgNPs, rGO/AgNPs, AuNPs, rGO/AuNPs and Ag-AuNPs. The kinetics, efficiency and mechanism of catalytic depollution process have been investigated and discussed. Hybrid materials of this kind are easy to prepare and can be used in the environmental remediation process.

Catalytic hydrogenation performance of an in situ assembled Au@g-C3N4–PANI nanoblend: synergistic inter-constituent interactions boost the catalysis

A novel gold–graphitic carbon nitride–polyaniline (Au@g-C3N4–PANI) nanoblend was synthesized via in situ oxidative polymerization of aniline using auric acid as an oxidant in the presence of g-C3N4. The structure and morphology of the nanoblend was characterized by UV-Vis, FT-IR, XRD, Raman, TGA, HR-TEM and SEM mapping analysis and the results demonstrate that Au nanoparticles with an average size of 10 nm are well-dispersed on the surface of g-C3N4–PANI. A systematic investigation of this new star Au@g-C3N4–PANI nanohybrid material shows an excellent catalytic performance in the hydrogenation of benzaldehyde (BZ) to benzyl alcohol (BA) in aqueous solution. The sustainable catalyst Au@g-C3N4–PANI has relatively high catalytic activity, stability and reusability compared to the sole and binary components, g-C3N4 and g-C3N4–PANI, under similar conditions. Au@g-C3N4–PANI exhibits a remarkable conversion percentage (99.9%), rate constant (0.5034 min−1) and turnover frequency (0.1666 mM mg−1 min−1) for the reduction of BZ. Its enhanced catalytic activity is attributed to a strong synergistic effect arising due to inter-constituent interactions between the Au nanoparticles and the covalently grafted PANI on the g-C3N4. The rate of BZ hydrogenation is found to be dependent on the concentrations of catalyst, substrate and reductant and the type of solvents. The stability and reusability of the catalyst and the catalysis mechanism are investigated and discussed.

Silver-nanospheres as a green catalyst for the decontamination of hazardous pollutants

The development of efficient green chemistry routes for the synthesis of metal nanoparticles has become a major focus for researchers. The present paper reports a facile, green and one-pot synthesis of silver-nanospheres (Ag-NSs) with a high yield and a uniform size of 7 nm using Simarouba glauca leaf extract (SGLE). The Ag-NSs have been characterized for their morphology, crystallinity and structure using TEM, EDX, XRD, and FT-IR and their formation mechanism has been discussed. In addition, the decontamination of hazardous pollutants, 4-hydroxynitrobenzene (4-HNB) and 4-nitrophenylamine (4-NPA) with the addition of an excess amount of ice cold NaBH4 solution using the Ag-NSs as an excellent green catalyst has also been investigated spectrometrically. The reusability of the catalyst was achieved for the reaction even after five cycles.

Evaluation of a New Biosensor Based on in Situ Synthesized PPy-Ag-PVP Nanohybrid for Selective Detection of Dopamine

In the present work, in situ synthesis of polypyrrole-silver-polyvinylpyrrolidone (PPy-Ag-PVP) nanohybrid using AgNO3 as an oxidant and polyvinylpyrrolidone (PVP) as a stabilizer and surfactant is demonstrated. The obtained ternary PPy-Ag-PVP nanohybrid was characterized by UV-vis, FT-IR, XRD, Raman, TGA, SEM, and HR-TEM analysis. Further the synthesized PPy-Ag-PVP has been investigated for its selective and sensitive sensing of dopamine (DA). The PPy-Ag-PVP modified glassy carbon electrode shows a reversible electrochemical behavior with superior response for DA. The limit of detection and limit of quantification are found to be 0.0126 and 0.042 μM (S/N = 3 and 10), respectively, with remarkable sensitivity (7.26 μA mM-1 cm-2). The practical application of the present modified electrode has been validated by determining the concentration of DA in human urine samples of different age group.

Silver nanoparticle-embedded RGO-nanosponge for superior catalytic activity towards 4-nitrophenol reduction

The present work highlights a bio-inspired synthesis of uniform 2 nm sized plasmonic silver nanospheres (Ag-NSs) embedded in reduced graphene oxide nanosponge (RGONS) using Tabebuia berteroi leaf extract. The green reduced RGONS/Ag-NSs is very clean and displays a fabulous catalytic activity towards the reduction of 4-nitrophenol (4-NP) in the presence of ice cold NaBH4 solution. Various analytical techniques were adopted to confirm the composition and structure of the crystalline nanocatalyst materials, including UV-visible absorption spectroscopy, FT-IR, XRD, Raman spectroscopy, HR-TEM and EDX. The formation of Ag-NSs, RGONS and RGONS/Ag-NSs, catalytic mechanism, stability and reusability of the catalyst were also investigated. The catalytic activity of RGONS/Ag-NSs is found to be superior to that ever reported.

Green synthesized nanospherical silver for selective and sensitive sensing of Cd2+ colorimetrically

We report here a facile, green and one-pot synthesis of nano-spherical silver (NSS) using Bombax ceiba leaf extract (BCLE) as both a reducing and stabilizing agent. The synthesized NSS has been characterized using UV-visible, FT-IR, XRD, HR-TEM, EDX, SEM and EDX mapping analysis and the formation and stabilization mechanism are discussed. The green synthesized NSS was tested for selective and sensitive sensing of Cd2+ colorimetrically in the presence of interfering metal ions. The limit of detection (LOD) for Cd2+ is found to be 1.5 × 10−9 mol L−1. This proposed method can be successfully applied to determine the concentration of Cd2+ in water samples at the nano-molar level.

A new analytical device incorporating a nitrogen doped lanthanum metal oxide with reduced graphene oxide sheets for paracetamol sensing

The novel N-CeO2 nanoparticles decorated on reduced graphene oxide (N-CeO2@rGO) composite has been synthesized by sonochemical method. The characterization of as prepared nanocomposite was intensely performed by UV-Vis, FT-IR, EDX, FE-SEM, HR-TEM, XRD, and TGA analysis. The synthesized nanomaterial was further investigated for its selective and sensitive sensing of paracetamol (PM) based on a N-CeO2@rGO modified glassy carbon electrode. A distinct and improved reversible redox peak of PM is obtained at N-CeO2@rGO nanocomposite compared to the electrodes modified with N-CeO2 and rGO. It displays a very good performance with a wide linear range of 0.05-0.600 μM, a very low detection limit of 0.0098 μM (S/N = 3), a high sensitivity of 268 μA µM-1 cm-2 and short response time (<3 s). Also, the fabricated sensor shows a good sensibleness for the detection of PM in various tablet samples.

Efficacious separation of electron–hole pairs in CeO 2 -Al 2 O 3 nanoparticles embedded GO heterojunction for robust visible-light driven dye degradation

Herein, we have developed a facile and one pot synthesis of ternary CeO2-Al2O3@GO nanocomposite via wet chemical method. The structural and morphological characteristics of the synthesized nanocomposite was investigated using UV-DRS, FT-IR, XRD, FE-SEM, HR-TEM, EDX and TGA analysis. The CeO2-Al2O3@GO composite was tested for its ability to photocatalytically degrade Rhodamine B (RhB) under visible light illumination. The influence of various operational parameters such as pH, catalyst dosage and initial dye concentration on the photo degradation was investigated in detail. The synthesized CeO2-Al2O3@GO composite shows greater photocatalytic degradation of RhB (99.0%) under visible light irradiation than the raw CeO2, Al2O3, and GO catalysts and any other reported nanocomposite materials. The recyclability results also demonstrate the excellent stability and reusability of the CeO2-Al2O3@GO nanocomposite. This work will be beneficial in the field of industrial and engineering applications in the degradation of organic pollutants. Also, a study of this kind will definitely stimulate many researches in the recently emerging field of solar-driven water splitting.

New Electrochemical Sensor Based on a Silver-Doped Iron Oxide Nanocomposite Coupled with Polyaniline and Its Sensing Application for Picomolar-Level Detection of Uric Acid in Human Blood and Urine Samples

A simple and very sensitive electrochemical sensor for the detection of uric acid (UA) has been developed based on polyaniline (PANI) merged into a silver-doped iron oxide (Ag-Fe2O3) nanocomposite-modified glassy carbon electrode. The synthesized ternary composite material (Ag-Fe2O3@PANI) was characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray, High-resolution transmission electron microscopy, X-ray diffraction, and thermo gravimetric analysis analyses. The nanocomposite-modified electrode shows an exceptional electrocatalytic activity and reversibility to the oxidation of UA in a 0.1 M phosphate buffer solution (pH 7.0) compared to those in PANI and Ag-Fe2O3. The detection limit of UA is found to be 102 pM with a linear dynamic range of 0.001-0.900 μM. The fabricated UA sensor also exhibits good selectivity, reproducibility, and long-time stability. The limit of detection and linear range attained for the synthesized composite are much greater compared to those of any other composite materials reported in the literature. The proposed method has been successfully applied for the selective detection of UA in various real samples such as human serum and urine with good recoveries. This platform that assimilates such electrocatalytic ternary nanocomposite with high performance can be widely employed for fabricating diverse sensors.