Prakash Periakaruppan

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.

Direct electrochemistry of glucose oxidase and sensing of glucose at a glassy carbon electrode modified with a reduced graphene oxide/fullerene-C60 composite

In the present work, a glucose biosensor was fabricated based on the direct electrochemistry of glucose oxidase at glassy carbon modified with a reduced graphene oxide (RGO) and fullerene-C60 (C60) composite. The reduced graphene oxide/fullerene (RGO–C60) composite was prepared by electrochemical reduction of a graphene oxide (GO) and C60 composite at −1.4 V for 200 s in pH 5 solution; while the GO–C60 composite was prepared by a simple sonication of C60 in GO solution for 6 hours at 45 °C. A well-defined and enhanced reversible redox peak of GOx was observed at RGO–C60 composite compared with other modified electrodes. The heterogeneous electron transfer rate constant (Ks) and the surface coverage concentration of GOx at RGO–C60/GOx modified electrode were calculated to be 2.92 s−1 and 1.19 × 10−10 mol cm−2, respectively. Under optimum conditions, the amperometry response of the biosensor was linear against the concentration of glucose from 0.1 to 12.5 mM with a response time of 3 s. The limit of detection was estimated to be 35 μM based on S/N = 3 with a high sensitivity of 55.97 μA mM−1 cm−2. In addition, the fabricated biosensor showed a good practical ability for the detection of glucose in human blood serum samples.

Simultaneous and selective electrochemical determination of dihydroxybenzene isomers at a reduced graphene oxide and copper nanoparticles composite modified glassy carbon electrode

Herein, we have demonstrated the simultaneous and selective electrochemical determination of dihydroxybenzene isomers at a reduced graphene oxide (RGO) and copper nanoparticles (Cu-NPs) composite modified electrode. The RGO/Cu-NPs composite was prepared by a single-step electrochemical reduction method. The synthesized RGO/Cu-NPs composite was characterized using scanning electron microscopy and elemental analysis. Linear sweep voltammetry was employed for the simultaneous determination of hydroquinone (HQ), catechol (CC) and resorcinol (RC). A well defined and more enhanced oxidation peak response is observed for HQ, CC and RC at the RGO/Cu-NPs composite electrode compared to other modified electrodes, which indicates fast electron transfer from dihydroxybenzene isomers at the RGO/Cu-NPs composite electrode. The composite modified electrode shows high electrocatalytic activity towards the oxidation of HQ, CC and RC. The electrochemical sensor shows a wide linear response in the concentration range of 3 μM to 350 μM, 3 to 350 μM and 12 μM to 200 μM for HQ, CC and RC respectively with a detection limit of 0.032 μM, 0.025 μM and 0.088 μM (S/N = 3). In addition, the proposed sensor shows good selectivity and stability along with good precision and consistency. The obtained results clearly demonstrate that the RGO/Cu-NPs composite can be an advanced electrode material for the real time sensing of dihydroxybenzene isomers.

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 simple electrochemical platform for detection of nitrobenzene in water samples using an alumina polished glassy carbon electrode.

In this work, we report a selective electrochemical sensing of nitrobenzene (NB) using an alumina (γ-Al2O3) polished glassy carbon electrode (GCE) for the first time. The scanning electron microscopy studies confirm the presence of alumina particles on the GCE surface. X-ray photoelectron spectroscopy studies reveal that the utilized alumina is γ-Al2O3. The alumina polished GCE shows an enhanced sensitivity and lower overpotential toward the reduction of NB compared to unpolished GCE. The differential pulse voltammetry response was used for the determination of NB and it shows that the reduction peak current of NB is linearly proportional to the concentrations of NB ranging from 0.5 to 145.5μM. The limit of detection is found to be 0.15μM based on 3σ. The fabricated electrode exhibits its appropriate selectivity towards NB in the presence of a range of nitro compounds and metal ions. The good practicality of the sensor in various water samples reveals that it can be a promising electrode material for practical applications. In addition, the proposed NB sensor is simple and cost effective one when compared with previously reported NB sensors in the literature.