A hydroquinone mediated PVA-H 2 SO 4 gel electrolyte (PHHQ) and activated carbon from bio-waste were prepared for supercapacitor fabrication. PHHQ delivered a higher capacitance (941 F g 21 at 1 mA cm 22 ) and energy density (20 Wh kg 21 at 0.33 W g 21 ) than the PVA-H 2 SO 4 gel electrolyte (425 F g 21 at 1 mA cm 22 , 9 Wh kg 21 at 0.33 W g 21 ).

Electric double layer capacitors (EDLCs) were fabricated using biomass derived porous activated carbon as electrode material with 1 M H 2 SO 4 and VOSO 4 added 1 M H 2 SO 4 as electrolytes. Here, VOSO 4 was used as redox additive to improve the overall performance of EDLC. As expected, the VOSO 4 electrolyte showed $43% of improved specific capacitance of 630.6 F g À1 at 1 mA cm À2 compared to pristine 1 M H 2 SO 4 (440.6 F g À1 ) due to the contribution of VO 2+ /VO 2 + redox reaction at the electrode-electrolyte interface. Possible redox reaction mechanism of VO 2+ /VO 2 + pair is also briefly illustrated. The good cycling performance of 97.57% capacitance retention was observed even after 4000 cycles. For comparison, the polymer gel electrolyte (PVA/VOSO 4 /H 2 SO 4 ) was also prepared and then the performance of the fabricated EDLCs was studied. Overall, these findings could open up a simple and cost effective way to improve the performance of EDLCs significantly.

In the present work, perovskite LaFeO 3 thin films with unique morphology were obtained on silicon substrate using radio frequency magnetron sputtering technique. The effect of thickness and temperature on the morphological and structural properties of LaFeO 3 films was systematically studied. The X-ray diffraction pattern explored the highly oriented orthorhombic perovskite phase of the prepared thin films along [121]. Electron micrograph images exposed the network and nanocube surface morphology of LaFeO 3 thin films with average sizes of ∼90 and 70 nm, respectively. The developed LaFeO 3 thin films not only possess unique morphology, but also influence the gas-sensing performance toward NO 2 . Among the two morphologies, nanocubes exhibited high sensitivity, good selectivity, fast response−recovery time, and excellent repeatability for 1 ppm level of NO 2 gas at room temperature. The response time for nanocubes was 24−11 s with a recovery duration of 35−15 s less than the network structure. The sensitivity toward NO 2 detection was found to be in the range 29.60−157.89. The enhancement in gassensing properties is attributed to their porous structure, surface morphology, numerous surface active sites, and the oxygen vacancies. The gas-sensing measurements demonstrate that the LaFeO 3 sensing material is an outstanding candidate for NO 2 detection.

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This study examines the use of a conductive carbon fiber to construct a flexible biosensing platform for monitoring biomarkers in sweat. Cortisol was chosen as a model analyte. Functionalization of the conductive carbon yarn (CCY) with ellipsoidal Fe2O3 has been performed to immobilize the antibodies specific to cortisol. 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-Hydroxysuccinimide (NHS) chemistry has been used to immobilize the antibodies onto the Fe2O3 modified CCY. Crystallinity, structure, morphology, flexibility, surface area, and elemental analysis were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FE-SEM/EDS) and Brunauer–Emmett–Teller (BET) analysis. Mechanical properties of the fiber such as tensile strength, young’s modulus have also been investigated. Under optimal parameters, the fabric sensor exhibited a good linearity (r2 = 0.998) for wide a linear range from 1 fg to 1 μg with a detection limit of 0.005 fg/mL for the sensitive detection of cortisol. Repeatability, reliability, reproducibility, and anti-interference properties of the current sensor have been investigated. Detection of cortisol levels in human sweat samples has also been investigated and the results were validated with commercial chemiluminescence immunoassay (CLIA) method.

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Sensors fabricated on fabrics provide an elevated ease of use for wearable sensors. Such sensors will play a critical role in detecting the elevations in the concentrations of biochemical markers in human sweat. The ability of making such measurements is becoming an important tool for non-invasive and real-time health monitoring. We present a yarn-based flexible and superwettable electrochemical immunosensing strategy for highly selective and sensitive detection of cortisol in sweat. ZnO nanorods (ZnONRs)-coated flexible carbon yarns were prepared by using a hydrothermal method for immobilizing specific anti-cortisol antibodies and used as an immunosensing platform for detecting sweat cortisol levels. The morphology, elemental composition, crystallinity, and specific surface area were analyzed by using analytical techniques such as transmission electron microscopy (TEM), field emission scanning electron microscopy coupled energy-dispersive X-ray analysis (FE-SEM/EDS), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The ZnONRs integrated carbon yarns showed excellent mechanical stability and superwettable properties. The immunosensor exhibited a wide linear detection range from 1 fg/mL to 1 μg/mL. The detection limits of the immunosensor were calculated to be between 0.45 and 0.098 fg/mL by using CV and DPV techniques, respectively. Additionally, cell viability studies were performed to investigate the biocompatibility and cytotoxicity of this carbon yarn ZnO sensing platform. The immunosensor was applied to measure the cortisol concentration in human sweat samples, and the outcomes were validated by using a chemiluminescent immunoassay system.

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