Solar-light Driven Cu_xO-TiO₂ Hybrid Photocatalyst for the Reduction of CO₂ into CH₄; A Sustainable Approach

( Vinoth Kumar ),인수일 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Photocatalytic CO₂ conversion to fuel offers an exciting prospect for solar energy storage and transportation thereof. Several photocatalysts have been employed for CO₂ photoreduction; the challenge of realizing a low-cost, readily synthesized photocorrosion-stable material that absorbs and utilizes a broad portion of the solar light. Herein, a mesoporous p-n heterojunction material, Cu_xO-TiO₂ (x = 1, 2), is synthesized via annealing of Cu and Ti precursors. Such an experimental approach in which two materials of diverse bandgaps are coupled provides a simultaneous opportunity for greater light absorption and rapid charge separation due to the intrinsic p-n heterojunction nature. The developed photocatalyst demonstrates an improved photocatalytic activity with the CO₂ reduction of our optimal sample (augmented light absorption, efficacious charge separation and mesoporosity) that utilizes no metal cocatalysts, a remarkable CH₄ yield of 221.63 ppm·g^-1·h^-1 is achieved.

Experimental investigation and parametric optimization of stir casting process parameters for aluminium metal matrix composite

Vinothkumar S,Senthilkumar P 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4

Metal matrix composite (MMC) is a composite material with a dispersed phase in a metallic matrix. In this work, the stircasting process is employed to fabricate aluminium MMC. The process parameters selected for this work are squeezepressure, squeeze time, die preheating temperature and stirring speed. The optimization of the process parameters arecarried out with an objective of the maximization of the tensile strength, compressive strength and hardness. Thealuminium scrap particles are used as the matrix material and alumina powder is used as the reinforcing material and itis mixed with this matrix material after preheating the same in the fabrication of the MMC. Regression equation for theresponses, ANOVA analysis and grey relational coefficient are analysed and the Grey relational grade is determined byintegrating the grey relational coefficient of the response variable and ranking is done. The analysis of variance isperformed for the tensile strength, compressive strength and hardness and the R-square value are found to be 92.7%,94.89% and 98.98% respectively.

Structure dependent luminescence, peroxidase mimetic and hydrogen peroxide sensing of samarium doped cerium phosphate nanorods

Vinothkumar, G.,I. L., Arun,Arunkumar, P.,Ahmed, Waseem,Ryu, Sangbong,Cha, Suk Won,Babu, K. Suresh The Royal Society of Chemistry 2018 Journal of Materials Chemistry B Vol.6 No.41

<P>Rare earth phosphates have been used extensively in luminescent phosphors, bio-imaging, catalysis, and sensors. However, there is a need to correlate the structural-chemical changes associated with stability and performance. In the present work, hydrothermally synthesized CePO4:Smx (<I>x</I> = 0, 5 and 10 mol%) nanorods were annealed at different temperatures to understand the modulations in structure as well as optical and enzyme mimetic properties. As prepared samarium doped cerium phosphate (SCP) nanorods crystallized in a hydrated hexagonal structure transformed into an anhydrous hexagonal and a monoclinic structure on annealing at 400 °C and 800 °C, respectively. Though temperature did not affect the rod-like morphology of the SCP, the lattice strain changed from compressive to tensile. Monoclinic SCP exhibited excellent emission until 5% Sm<SUP>3+</SUP> doping while the quenching effect dominated at 10% Sm<SUP>3+</SUP>. Monoclinic SCP samples demonstrated higher peroxidase-like enzymatic activity in comparison to natural enzyme HRP and hexagonal SCP. A mechanism for the enhanced peroxidase-like activity of the monoclinic structure was proposed based on the fluorescence property of terephthalic acid and the surface peroxo complex using Raman spectroscopy. Fluorimetric detection based on the luminescent quenching effect of the monoclinic SCP nanorods treated with different concentrations of hydrogen peroxide showed a linear response from 0 to150 μM concentration with a detection limit (LOD) of 3.17 μM H2O2. Our results demonstrate the importance of structure for enzyme mimetic activity.</P>

Efficient Catalytic Regeneration of NADH using Water Soluble Rh(III)NHC Complex

( Vinothkumar Ganesan ),윤성호 한국공업화학회 2023 한국공업화학회 연구논문 초록집 Vol.2023 No.0

Ionic Radii and Concentration Dependency of RE³⁺ (Eu³⁺, Nd³⁺, Pr³⁺, and La³⁺)-Doped Cerium Oxide Nanoparticles for Enhanced Multienzyme-Mimetic and Hydroxyl Radical Scavenging Activity

Vinothkumar, G.,Rengaraj, S.,Arunkumar, P.,Cha, Suk Won,Suresh Babu, K. American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol. No.

<P>The antioxidant activity of cerium oxide nanoparticles (CNPs) depends on the concentration of oxygen vacancies and Ce<SUP>3+</SUP> active sites. In the present work, we report the impact of 5 mol % trivalent rare-earth-doped (RE<SUP>3+</SUP> = Eu<SUP>3+</SUP>, Nd<SUP>3+</SUP>, Pr<SUP>3+</SUP>, and La<SUP>3+</SUP>) CNPs on the oxidation state modulation and antioxidant property with respect to ionic radii. An increase in the lattice parameter, strain, and oxygen vacancy concentration was observed as a function of ionic radii. Among the various dopants in CNPs, La<SUP>3+</SUP> with higher ionic radii having smaller crystallite size (7.9 nm) and higher vacancy displayed better peroxidase, oxidase, and hydroxyl radical (HO<SUP>•</SUP>) scavenging activities. The kinetic parameters for the peroxidase and oxidase activities were found to be superior with <I>K</I><SUB>m</SUB> = 0.217 and 0.261 mM, respectively, for 5 mol % La<SUP>3+</SUP>-doped CNPs. To divulge the role of dopant concentration on the structural properties, we also explored using 10 and 20 mol % La<SUP>3+</SUP> doping in CNPs. Because of the smaller crystallite size (6.7 nm) and higher defect level (3.12 × 10<SUP>21</SUP> cm<SUP>-3</SUP>), 20% La<SUP>3+</SUP> doping showed superior peroxidase and oxidase activities, as shown by the low <I>K</I><SUB>m</SUB> values. CNPs exhibit both peroxidase and oxidase activities in a concentration-dependent manner. Moreover, CNPs exhibit concentration-dependent peroxidase and oxidase activities that can be selectively activated for various theranostic applications. Thus, our results demonstrate the crucial role of ionic radii and the concentration of RE<SUP>3+</SUP> dopants on defect formation in CNPs for improved antioxidant properties of ceria.</P> [FIG OMISSION]</BR>

Experimental investigation and machinability behavior on synthesized titanium composite

R. Vinothkumar,J. Maniraj,V.S. Thangarasu 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.3

The current study aims to describe the experimental examination and ultrasonic machinability behavior of the titaniumcomposite, which is synthesized by a casting technique. Tungsten carbide (WC) works as reinforcing particles and adds 6%of the titanium alloy's weight. Material properties, characterization, and alloy composition are examined by mechanicaltesting, scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDAX), respectively. Rate of metal removal(RMR) and surface finish (SF) are evaluated by the variation of ultrasonic machining (USM) input constraints such as powerrating, slurry concentration, and grit size. Ultrasonic machining parameters and desired responses are optimized using theTaguchi technique. The ultrasonically machined surface and its microstructural analysis are investigated using atomic forcemicroscopy (AFM). The desirable RMR was attained at a power rating of 450 W, a 20% slurry concentration, and a grit sizeof 400. Surface finish was reached at a power rating of 150 W, 15% slurry concentration, and grit size of 400.

Correlation between the Structure and Catalytic Activity of [Cp*Rh(Substituted Bipyridine)] Complexes for NADH Regeneration

Ganesan, Vinothkumar,Sivanesan, Dharmalingam,Yoon, Sungho American Chemical Society 2017 Inorganic Chemistry Vol.56 No.3

<P>A series of water-soluble half-sandwich [Cp*Rh-III(N<^>N)Cl](+) (Cp* = pentamethylcyclopentadiene, N<^>N-substituted 2,2'-bipyridine) complexes containing electron-donating substituents around the 2,2'-bipyridyl ligand were synthesized and fully characterized for the regioselective reduction of nicotinamide coenzyme (NAD(+)). The influence of the positional effect of the substituents on the structural, electrochemical, and catalytic properties of the catalyst was systematically studied in detail. The catalytic efficiency of the substituted bipyridine Cp*RhIII complexes are inversely correlated with their redox potentials. The 5,5'-substituted bipyridine Cp*RhIII complex, which had the lowest reduction potential, most effectively regenerated NADH with a turnover frequency of 1100 h(-1). Detailed kinetic studies on the generation of intermediate(s) provide valuable mechanistic insight into this catalytic cycle and help to direct the future design strategy of corresponding catalysts.</P>

Optimization of Fermentation Parameters for Enhanced Production of Naringinase by Soil Isolate Aspergillus niger VB07

Vaidyanathan VinothKumar,Periasamy Kayambu Subash RevathiBabu 한국식품과학회 2010 Food Science and Biotechnology Vol.19 No.3

Aspergillus niger VB07 was isolated from the soil of citrus fruit market used to produce extracellular naringinase in a liquid medium. Various parameters of fermentation have been examined in order to improve overall enzyme yield. Naringinase yield of 17.28 IU/mL in an optimized medium containing naringin (0.1%), rhamnose (0.5%), peptone (0.25%), glycine (10 mM), and pH 4.5 at 28℃ for 7 days has been obtained at shake flask level. Compared to the initial medium, the highest naringinase yield observed is approximately increased by 1.8 times under the optimized conditions. Amino acids mediated naringinase synthesis was reported.

Carbonylative ring expansion of oxetane into γ-butyrolactone using bimetallic cobaltate catalysts: Insight into the deactivation mechanism

Ganesan Vinothkumar,윤성호 대한화학회 2023 Bulletin of the Korean Chemical Society Vol.44 No.12

γ-butyrolactones and their derivatives serve as the fundamental building blocks for a wide range of biologically significant and synthetically challenging natural products, which find extensive applications in various high-demand chemicals. In this study, we have successfully established a facile and atom-efficient synthesis of γ-butyrolactones through the carbonylative ring expansion of oxetanes. We employed both homogeneous and heterogenized bimetallic catalysts ([HCP-TPPM][Co(CO)4], where HCP refers to hyper cross-linked polymer and TPP denotes tetraphenylporphyrin, with M = Cr3+ and Al3+). While the homogeneous catalysts exhibited remarkable activity, the heterogeneous catalysts offered the distinct advantages of facilitating product separation and enabling catalyst recycling. Notably, during the catalyst recycling studies, we observed a decrease in catalytic activity attributed to cobaltate leaching. The hypothesis of cobaltate leaching through β-hydrogen elimination was validated by comparative studies using substrates with and without β-hydrogen in both batch and continuous flow catalytic processes.

A facile development of rare earth neodymium nickelate nanoparticles for selective electrochemical determination of antipsychotic drug prochlorperazine

Venkatachalam Vinothkumar,Chelliah Koventhan,Shen-Ming Chen,Yu-Feng Huang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.109 No.-

In this study, the synthesis of neodymium nickelate (Nd2NiO4, NNO) nanoparticles with diverse temperatureswere developed by the simple coprecipitation method. The successfully prepared NNO was characterizedwith various spectroscopic instruments. The surface morphology, size, shape, composition,crystallinity, functionality, bonding, and the presence of elements of the nanoparticles were analyzedby suitable characterization techniques. The electrochemical features were investigated by electrochemicalimpedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry (EIS, CV, and DPV)methods. As results expected, the modified NNO-500/SPCE sensor displays low electron transfer resistance(Rct), high active surface area, and excellent electrocatalytic activity for the detection of prochlorperazine(PCP) rather than other electrodes. Under optimized electrochemical detections, the DPV studyrevealed a low limit of detection (LoD), and limit of quantification (LoQ) of 4 nM, and 14 nM with widelinearity of 0.025–1220 mM for PCP at the NNO-500 sensor. In addition, high selectivity, stability, precision,and satisfactory recoveries in biological samples for PCP detection. Thus, our study provides a simplisticbut effective method for constructing perovskite-type materials with excellent electrochemicalperformance.