In the current work, Al ³⁺ and Er ³⁺ -substituted nickel-copper spinel ferrites Ni _0.2 Cu _0.8 Al _x Er _x Fe _{2−2 x} O ₄ ( x = 0, 0.04, 0.08, 0.12, 0.16) are prepared using the sol–gel method.

Neurotransmitters are essential chemical messengers required for proper brain function, and any changes in their concentrations can lead to neuronal diseases. Therefore, sensitive and selective detection is crucial. This study presents a fast and simple colorimetric method for dopamine detection using three reagent solutions: AgNP and MPA, Ag/Au nanocomposite, and mercaptophenylacetic acid. TEM images showed a narrow distribution of Ag and Au nanoparticles with average sizes of 20 nm and 13 nm, respectively, with gold nanoparticles bound to the edges of silver nanoparticles. A paper-based biosensor was created using manual wax printing for the colorimetric detection of dopamine. Visual detection onsite showed color changes with both the silver nanoparticles and mercaptophenylacetic acid mixture and the silver–gold nanoparticle composite. Electrochemical detection using a glassy carbon electrode modified with 8 mM mercaptophenylacetic acid demonstrated high selectivity and sensitivity towards dopamine, with a peak in the range of 0.7–0.9 V. Interferences were minimized, ensuring high sensitivity and selective detection of dopamine.

Layered double hydroxides (LDHs) have attracted a lot of interest because of their tunable layered structure, high surface area, and redox activity, which lead to good electrochemical energy storage performance. The electrochemical performance of carbonate-intercalated Ce-doped NiCoAl LDH, synthesized by a simple hydrothermal route followed by anion exchange, was investigated in this work. The structural and morphological characterizations confirmed the effective doping and intercalation, which enhanced the electrochemical properties. Electrochemical studies showed that carbonate-intercalated Ce-doped NiCoAl LDH had the highest specific capacitance of about 2500 F g⁻¹ at 10 mV s⁻¹, which delivered both high rate capability and outstanding long-term cycling stability of about 88.4% after 10 000 cycles. These results show that carbonate-intercalated Ce-doped NiCoAl LDH is a promising candidate for high-performance energy storage.

Supercapacitors are a family of energy storage devices that have attracted significant attention because of their high power density, quick charge and discharge times, and extended cycle life. For the development of high-performance supercapacitors, electrodes with high specific capacitance values along with good structural stability are essential. In this context, we report the synthesis of a surface oxygen-modified CoAlFe LDH@Fe₃O₄ heterostructure using a simple hydrothermal route followed by post modification using hydrogen peroxide. High crystallinity and phase purity were confirmed by structural studies employing X-ray diffraction (XRD), and functional groups essential to electrochemical performance were revealed by Fourier-transform infrared spectroscopy (FTIR). XRD and FTIR results confirmed the formation of the heterostructure with the presence of magnetic Fe₃O₄. In addition, the surface oxygen coordination was found to be significantly improved. Excellent retention, low internal resistance, and better capacitive behavior were demonstrated by electrochemical studies. For the electrochemical evaluation of the heterostructure, a 1 M KOH electrolyte was used. A remarkable specific capacitance value of 1709.6 F g⁻¹ at a current density of 1 A g⁻¹ was achieved. In addition, the heterostructure exhibited excellent durability with 89.39% capacity retention after 10 000 consecutive charge–discharge cycles. A low charge transfer resistance value was confirmed using electrochemical impedance spectroscopy. A scalable and efficient method for creating high-performance supercapacitor electrodes is presented in this study. Additionally, the relationship between surface chemistry and structural order in affecting electrochemical performance is thoroughly examined, providing a fresh perspective on the future of innovative energy materials.