Pitchaimani Veerakumar

Highly dispersed silica-supported nanocopper as an efficient heterogeneous catalyst : application in the synthesis of 1,2,3-triazoles and thioethers

In this paper, we report the synthesis of amine modified SiNPs (silica nanoparticles) by a sol–gel method and the role of synthesized SiO2 as a solid support for the nanocatalyst CuNPs (copper nanoparticles). The nanocatalyst is characterized by XRD, HRTEM, BET, AFM, SEM, EDX, UV-vis, FT-IR and TGA techniques. The Cu/SiO2 (catalyst A) serves as an efficient heterogeneous nanocatalyst exhibiting high catalytic activity for the synthesis of a series of 1,4-disubstituted-1,2,3-triazoles and thioethers. The catalyst A can be recycled and reused several times without any significant loss of catalytic activity as proved by XRD and HRTEM techniques.

Palladium Nanoparticle Incorporated Porous Activated Carbon: Electrochemical Detection of Toxic Metal Ions

A facile method has been developed for fabricating selective and sensitive electrochemical sensors for the detection of toxic metal ions, which invokes incorporation of palladium nanoparticles (Pd NPs) on porous activated carbons (PACs). The PACs, which were derived from waste biomass feedstock (fruit peels), possess desirable textural properties and porosities favorable for dispersion of Pd NPs (ca. 3-4 nm) on the graphitic PAC substrate. The Pd/PAC composite materials so fabricated were characterized by a variety of different techniques, such as X-ray diffraction, field-emission transmission electron microscopy, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. The Pd/PAC-modified glassy carbon electrodes (GCEs) were exploited as electrochemical sensors for the detection of toxic heavy metal ions, viz., Cd(2+), Pb(2+), Cu(2+), and Hg(2+), which showed superior performances for both individual as well as simultaneous detections. For simultaneous detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+), a linear response in the ion concentration range of 0.5-5.5, 0.5-8.9, 0.5-5.0, and 0.24-7.5 μM, with sensitivity of 66.7, 53.8, 41.1, and 50.3 μA μM(-1) cm(-2), and detection limit of 41, 50, 66, and 54 nM, respectively, was observed. Moreover, the Pd/PAC-modified GCEs also show perspective applications in detection of metal ions in real samples, as illustrated in this study for a milk sample.

Highly stable and active palladium nanoparticles supported on porous carbon for practical catalytic applications

Carbon porous materials (CPMs) containing highly dispersed palladium nanoparticles (PdNPs) with an average size of ca. 5 nm were synthesized by microwave (MW) irradiation procedure, during which the Pd2+ ions were effectively reduced to the Pd0 form and highly dispersed on the carbon support. The Pd/CPM samples were characterized by a variety of analytical and spectroscopy techniques, viz. N2 adsorption/desorption isotherm measurements, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning and field emission transmission electron microscopy (SEM/FETEM), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. The Pd/CPM composites were employed as heterogeneous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in aqueous media. The reaction was monitored by UV-Visible spectroscopy, yielding a pseudo-first-order rate constant (k) of 6.87 × 10−2 s−1. Moreover, the catalysts were exploited for C–C coupling reactions using the microwave (MW) method. In addition, a novel electrochemical sensor for the detection of 4-NP was developed based on a Pd/CPM-modified glassy carbon electrode (GCE) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The 4-NP sensor was found to exhibit excellent sensitivity, lower detection limit, reliability, and durability surpassing the reported modified electrodes, rendering practical industrial applications.

Nickel Nanoparticle-Decorated Porous Carbons for Highly Active Catalytic Reduction of Organic Dyes and Sensitive Detection of Hg(II) Ions.

High surface area carbon porous materials (CPMs) synthesized by the direct template method via self-assembly of polymerized phloroglucinol-formaldehyde resol around a triblock copolymer template were used as supports for nickel nanoparticles (Ni NPs). The Ni/CPM materials fabricated through a microwave-assisted heating procedure have been characterized by various analytical and spectroscopic techniques, such as X-ray diffraction, field emission transmission electron microscopy, vibrating sample magnetometry, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. Results obtained from ultraviolet-visible (UV-vis) spectroscopy demonstrated that the supported Ni/CPM catalysts exhibit superior activity for catalytic reduction of organic dyes, such as methylene blue (MB) and rhodamine B (RhB). Further electrochemical measurements by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) also revealed that the Ni/CPM-modified electrodes showed excellent sensitivity (59.6 μA μM(-1) cm(-2)) and a relatively low detection limit (2.1 nM) toward the detection of Hg(II) ion. The system has also been successfully applied for the detection of mercuric ion in real sea fish samples. The Ni/CPM nanocomposite represents a robust, user-friendly, and highly effective system with prospective practical applications for catalytic reduction of organic dyes as well as trace level detection of heavy metals.

Electrochemical detection of 4-nitrophenol based on biomass derived activated carbons

A novel method for detecting an environmental pollutant, 4-nitrophenol (4-NP), by exploiting biomass-derived activated carbon (AC) is reported. The electrochemical performances of the 4-NP sensor were assessed by cyclic and linear sweep voltammetries. The presence of oxygen surface functional groups and heteroatoms (72.6% C, 6.1% H, 6.5% N, and 7.5% S) in the biomass-derived AC with high surface area (1555 m2 g−1) are found to be responsible for the excellent catalytic activities and reversible redox behaviors observed during the detection of 4-NP. The effects of pH of the electrolyte buffer solution, accumulated potential and duration as well as the analyte concentration on the electrocatalytic performance of the sensor were investigated. Consequently, a linear correlation between the cathodic reduction peak current with 4-NP concentration up to 500 μM with a detection limit and sensitivity of 0.16 μM and 5.810 μA μM−1 cm−2, respectively, were observed over the AC-modified GCE in 0.05 M acetate buffer solution (pH 5.0), surpassing the existing modified electrodes in the literature. The facile 4-NP sensor thus implemented is also advantageous for its simplicity, stability, reliability, durability, and low cost, rendering practical applications for real sample systems.

Functional porous carbon/nickel oxide nanocomposites as binder-free electrodes for supercapacitors.

High-surface-area, guava-leaf-derived, heteroatom-containing activated carbon (GHAC) materials were synthesized by means of a facile chemical activation method with KOH as activating agent and exploited as catalyst supports to disperse nickel oxide (NiO) nanocrystals (average size (2.0±0.1) nm) through a hydrothermal process. The textural and structural properties of these GHAC/NiO nanocomposites were characterized by various physicochemical techniques, namely, field-emission SEM, high-resolution TEM, elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The as-synthesized GHAC/NiO nanocomposites were employed as binder-free electrodes, which exhibited high specific capacitance (up to 461 F g(-1) at a current density of 2.3 A g(-1)) and remarkable cycling stability, which may be attributed to the unique properties of GHAC and excellent electrochemical activity of the highly dispersed NiO nanocrystals.

Ruthenium nanoparticles decorated curl-like porous carbons for high performance supercapacitors.

The synthesis of highly dispersed and stable ruthenium nanoparticles (RuNPs; ca. 2–3 nm) on porous activated carbons derived from Moringa Oleifera fruit shells (MOC) is reported and were exploited for supercapacitor applications. The Ru/MOC composites so fabricated using the biowaste carbon source and ruthenium acetylacetonate as the co-feeding metal precursors were activated at elevated temperatures (600–900 oC) in the presence of ZnCl2 as the pore generating and chemical activating agent. The as-prepared MOC carbonized at 900 oC was found to possess a high specific surface area (2522 m2 g−1) and co-existing micro- and mesoporosities. Upon incorporating RuNPs, the Ru/MOC nanocomposites loaded with modest amount of metallic Ru (1.0–1.5 wt%) exhibit remarkable electrochemical and capacitive properties, achiving a maximum capacitance of 291 F g−1 at a current density of 1 A g−1 in 1.0 M H2SO4 electrolyte. These highly stable and durable Ru/MOC electrodes, which can be facily fabricated by the eco-friendly and cost-effective route, should have great potentials for practical applications in energy storage, biosensing, and catalysis.

Ru/Al2O3 catalyzed N-oxidation of tertiary amines by using H2O2

Synthesis of several aromatic heterocyclic N-oxides using nanoruthenium (Ru(PVP)/γ-Al2O3, catalyst I) in the presence of 30% H2O2 as the oxidant is presented. Catalyst I shows good catalytic activity in N-oxidation reactions. Aqueous H2O2 as a cheap and clean oxidant with active catalyst I has been developed to minimize waste production and meet the requirements of green chemistry. A variety of aromatic tertiary nitrogen compounds have been efficiently oxidized to their corresponding N-oxides in excellent yields.

Cajeput tree bark derived activated carbon for the practical electrochemical detection of vanillin

Cajeput tree bark derived activated carbon (TBAC) has been prepared and exploited for the electrochemical detection of vanillin (VAN). The physicochemical properties of the TBACs graphitized at different temperatures were characterized using a variety of analytical and spectroscopic techniques, which include X-ray diffraction, field emission-scanning/transmission electron microscopy (FE-SEM/TEM), N2 adsorption/desorption isotherm measurements, and thermogravimetric analysis (TGA). Utilized as VAN sensors, the electrochemical activities of various TBAC modified electrodes were assessed using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The observed superior electrocatalytic activity for the oxidation of VAN is attributed to the high surface area and desirable porosities possessed by TBAC. The VAN sensor exhibited a wide linear range (5–1150 μM), low detection limit (0.68 μM), and excellent sensitivity (0.32 μA mM−1 cm−2), which surpass the existing carbon-based electrodes reported in the literature. The facile VAN sensor subsequently realized is also advantaged by its simplicity, stability, reliability, durability, and low cost, which render real sample analysis and practical industrial applications.

Highly stable ruthenium nanoparticles on 3D mesoporous carbon: an excellent opportunity for reduction reactions

Carbon mesoporous materials (CPMs) have great potential in the field of heterogeneous catalysis. Highly dispersed ruthenium nanoparticles (RuNPs) embedded in three dimensional (3D) CPMs as catalysts with a high surface area (1474 m2 g−1) were prepared by microwave-thermal reduction processes. Characterization technologies including X-ray diffraction (XRD), N2 adsorption/desorption isotherm measurements, field emission transmission electron microscopy (FE-TEM), thermogravimetric analysis (TGA), hydrogen temperature-programmed reduction (H2-TPR), Raman spectroscopy and 13C solid state cross polarization and magic angle spinning (13C CP/MAS) NMR spectroscopy were utilized to scrutinize the catalysts. It was revealed that the Ru/CPM catalysts exhibited a highly ordered 3D mesoporous structure and a large surface area and were widely used as catalysts for reduction reactions. Reduction of p-nitroaniline (p-NA) and crystal violet (CV) using NaBH4 with the use of this catalyst was studied by means of UV-vis spectroscopy. Here, NaBH4 acts as a hydrogen donor. This catalyst shows an excellent catalytic activity towards reduction of p-NA and CV dye at room temperature. Due to the promising properties of CPMs, they can be utilized to fabricate 3D carbon-based materials for a variety of novel applications.