In this study, cupric oxide–polyaniline (CuO–PANI) composite was prepared by two-step methodology. First step was involved in the synthesis of PANI by the chemical oxidative polymerization of aniline in the presence of (NH$_4)_2$S$_2$O$_8$ as an oxidizing agent. In the second step, 25 mg of PANI was used as template for making a composite with CuO by hydrothermal method. The crystalline phase, morphology and composition of composite material were investigated by the powder X-ray diffraction and scanning electron microscopy techniques. The composite material contained the monoclinic phase of CuO and some poor diffraction patterns of PANI. The composite material exhibits a flower-like morphology. The CuO–PANI composite was deposited on the glassy carbon electrode and used for the electrochemical determination of hydrochlorothiazide (HCT) in Britton–Robinson (B–R) buffer pH 4.0 by the cyclic voltammetry. The HCT has shown a well resolved anodic peak at 1.20 V against Ag/AgCl reference electrode. The electrode kinetics was diffusion controlled and irreversible in nature. The CuO–PANI composite possessed a linear from 8 to 52 ${\mu}$M HCT concentration with a regression coefficient of 0.99. The limit of detection of the CuO–PANI composite was obtained as 0.8 ${\mu}$M for the HCT. The CuO–PANI composite is highly selective, stable and sensitive for the HCT. Therefore, we believe that the newly prepared CuO–PANI composite material can be useful for the different electrochemical applications.

In this study, we report enzyme-free glucose sensors based on palladium (Pd) nanoparticles deposited onto Co$_3$O$_4$ nanostructures. A simple, low-temperature aqueous method was used for the fabrication of Co$_3$O$_4$ nanostructures.Then, Pd nanoparticles were decorated onto Co$_3$O$_4$ nanostructures using the ultraviolet reduction method. Morphology, elemental composition and crystalline features of the proposed composite nanostructures were investigated by powderX-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. Cyclic voltammetry and linear sweep voltammetry were used to investigate the electrochemical behaviour of Pd–Co$_3$O$_4$ nanostructures during glucose sensing. The proposed nanostructures showed excellent electrochemical activity for the quantitative detection of glucose at a potential of 0.6 V vs. Ag/AgCl. Importantly, the fabricated enzyme-free glucose sensor shows a linear response over the range of 1–6.0 mM glucose, with a limit of detection of 0.01 mM. The interference study was also carried out to probe the selectivity of Pd–Co$_3$O$_4$ nanostructures towards glucose detection in the presence of differentinterfering substances. The combined results attest that the as-synthesized Pd–Co$_3$O$_4$ nanostructures are highly stable and selective for the detection of glucose, suggesting their great potential for the quantitative determination of glucose in different biological fluids.