Vijayanagara Sri Krishnadevaraya University

In the current study, the synthesis of tetra-4-(2-methoxyphenoxy) carboxamide cobalt(II) amide-bridged phthalocyanine (CoTMePhCAPc) is described, as well as its characterization by Fourier transform infrared (FT-IR), UV-visible, and mass spectroscopy; powder X-ray diffraction (PXRD); thermogravimetric analysis (TGA); scanning electron microscopy (SEM); and electrochemistry. Sensing of nitrite (NO2-) and hydrogen peroxide (H2O2) simultaneously was done on CoTMePhCAPc with the composite multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (CoTMePhCAPc/MWCNT/GCE) in the range of linear absorption (NO2- and H2O2: CV 50-750, differential pulse voltammetry (DPV) 50-750, CA 50-500 nmol L-1), lower detection limit (NO2- and H2O2: CV 10.5 and 12.5, DPV 10.5 and 11.2, CA 6.0 and 5.5 nmol L-1), and sensitivity (NO2- and H2O2: CV 0.379 and 0.529, DPV 0.043 and 0.049, CA 0.033 and 0.040 μA nM-1 cm-2). The composite electrode exhibits improved electrocatalytic behavior compared to modified electrodes for nitrite and H2O2. The CoTMePhCAPc/MWCNT/GCE sensor displays good selectivity even in the presence of an excess of interfering metal ions and biomolecules at the applied potentials of +400 mV (nitrite) and -400 mV (H2O2). Moreover, the fabricated sensor was studied with various phosphate-buffered saline (PBS) (pH 5-9) electrolyte solutions. The unknown H2O2 concentration in blood samples and apple juice and nitrite concentration in drinking water and butter leaf lettuce were all measured using the usual addition method. Docking analysis clearly indicates that the ligand shows excellent inhibition activity toward the three subjected protein molecules.

Improving the thermohydraulic performance of solar thermal receivers is essential for enhancing the efficiency of concentrated solar energy systems. This study experimentally and numerically investigates the heat transfer and flow characteristics of a parabolic trough collector equipped with a triangular absorber tube using ZnO/water nanofluids as the working fluid. A total of 320 operating conditions were evaluated by varying the nanoparticle volume concentration (0-0.4 vol.%) and Reynolds number (3500-7000) to assess their combined influence on heat transfer enhancement, pressure drop, and overall performance. The results show that the incorporation of ZnO nanoparticles significantly enhances thermal performance. At a volume concentration of 0.4 vol.% and a Reynolds number of 7000, the Nusselt number increases by 94.4% compared with deionized water, while the pressure drops increase by 88.9%. Despite the rise in hydraulic losses, the performance evaluation criterion improves by 158.7%, indicating that the heat transfer enhancement outweighs the additional pumping power requirement. The triangular absorber geometry further intensifies turbulence and boundary-layer disruption, contributing to improved convective heat transfer. To complement the experimental analysis, machine learning models, including linear regression, multivariate adaptive regression splines, Gaussian process regression, and random forest, were developed to predict thermohydraulic performance. Among these, Gaussian process regression demonstrated the highest predictive accuracy across the investigated parameter range. The findings highlight the combined benefits of nanofluid application, geometric modification, and data-driven modeling for improving the efficiency and operational reliability of parabolic trough solar collectors.

Metal-organic framework (MOF)-based composites are emerging as promising candidates for advanced energy storage and conversion technologies. In this work, a new MOF containing octa-benzimidazole-substituted cobalt phthalocyanine (CoBPc) is synthesized, and its composite with multiwalled carbon nanotubes (MWCNTs) is engineered to evaluate its dual functionality toward supercapacitor performance and hydrogen evolution reaction (HER). The integration of redox-active CoBPc with conductive MWCNTs promotes strong pi-pi interactions, enhances electron transport, and increases the accessible surface area, collectively improving catalytic behavior. The CoBPc-MWCNT composite exhibits excellent supercapacitive performance, delivering a capacitance of 25 mF, a specific capacity of 500 Fg1-, a current density of 35.2 mA cm-2, an energy density of 69.4 Wh kg-1, and a power density of 844 Wg1-, along with remarkable cycling stability over 4000 cycles and 46.5 h long-term durability in 0.5 M H2SO4. For HER, the hybrid electrode demonstrated a low overpotential of 153 mV at -10 mA cm-2, approaching the performance of standard Pt/C, and a Tafel slope of 39 mV dec-1, indicating fast reaction kinetics. The impedance and ECSA results of the composite substantiate the reduced overpotential, highlighting the influence of enhanced conductivity and abundant active sites. The superior dual performance is attributed to the nitrogen-rich phthalocyanine framework and the conductive carbon network, enabling strong pi-pi interactions, optimized electron density, and efficient charge transport.

Hybrid nanofluids are opening new frontiers in thermal systems, revolutionizing drug delivery, and offering fresh hope in cancer therapy, precision in technological and medical fields. With this motive, we performed a computational study to explore the impact of non-uniform heat source on MHD flow of ZnO+ZrO2-EG hybrid nanofluid over a horizontally moving thin needle with variable thickness. The prime novelty of this work is to examine the enhanced thermal conductivity of the hybrid nanofluid by using Maxwell/Xue nanomodels in the presence of Bongiorno’s slip mechanism. The established governing flow equations were computed utilizing the bvp5c package of MATLAB software. Subsequently, we studied and visualized the effects of key variables on fluid behavior, focusing on temperature, velocity, and concentration profiles. The findings demonstrate that augmenting the nanoparticle volume fraction substantially develops the fluid's heat performance. It is shown that the dynamic relationship among thermal radiation, needle thickness, and volume fraction results in a remarkable boost in heat transfer phenomenon. Notably, the Xue nanomodel shows better heat and mass transfer capacity than the Maxwell nanomodel. Validation against prior theoretical work ensures the reliability of the current findings. The major applicability of this work can be found in production of small measuring instruments of aerodynamical systems.

The main focus of past research on cilia-driven transport and nanofluid flow has been on planar or circular channels, without accounting for realistic duct geometries, variable fluid properties, or magnetic-field effects. Within these constraints, the present work aims to develop a complete mathematical model of magnetohydrodynamic Carreau-Buongiorno nanofluid flow in an elliptical converging duct driven by metachronal ciliary motion. The nonlinear governing equations, including variable viscosity and thermal conductivity, Brownian motion, thermophoresis, viscous dissipation, and Lorentz force effects, are reduced into a wave frame and simplified through the lubrication approximation. The Homotopy Perturbation Method is used to obtain semi-analytical solutions. The findings indicate that momentum redistribution in variable viscosity decreases the axial velocity along the major axis and increases core flow in the minor axis. The magnetic fields increase flow along the major axis by transferring momentum via the Lorentz force, but they reduce motion along the minor axis in the core region. Increased thermal conductivity improves heat diffusion, whereas thermophoresis and Brownian motion play important roles in the transport and thermal mixing of nanoparticles. The novelty of this study is that the combined modelling of cilia-driven propulsion, non-Newtonian nanofluid interactions, magnetic control, and converging geometry (elliptical) is performed. The results are useful in focused drug delivery, microfluidic cooling, and the bio-inspired pump design.