Photo-oxidase nanozymes are emerging enzyme-mimicking materials that produce reactive oxygen species (ROS) upon light illumination and subsequently catalyze the oxidation of the substrate. Carbon dots are promising photo-oxidase nanozymes due to their biocompatibility and straightforward synthesis. Carbon dot-based photo-oxidase nanozymes become active for ROS generation under UV or blue light illumination. In this work, sulfur and nitrogen doped carbon dots (S,N-CDs) were synthesized by solvent-free, microwave assisted technique. We demonstrated that sulfur, nitrogen doping of carbon dots (band gap of 2.11 eV) has enabled photo-oxidation of 3,3,5,5'tetramethylbenzidine (TMB) with extended visible light (up to 525 nm) excitation at pH 4. The photo-oxidase activities by S,N-CDs produce Michaelis-Menten constant (K m ) of 1.18 mM and the maximum initial velocity (V max ) as 4.66 × 10 À 8 Ms À 1 , under 525 nm illumination. Furthermore, visible light illumination can also induce bactericidal activities with growth inhibition of Escherichia coli (E. coli). These results demonstrate that S,N-CDs can increase intracellular ROS in the presence of LED light illumination.

Recently, ferroelectric and antiferroelectric ceramic materials have gained a lot of interest for the development of environment-friendly highly-efficient electrocaloric refrigeration and energy-storage devices. In this work, lead-free Ba 1−x Li x TiO 3 ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05 were synthesized by the conventional solid-state reaction method, and the effect of Li doping on dielectric, leakage current, ferroelectric, electrocaloric, and energy storage properties of BaTiO 3 ceramics was systematically investigated. The XRD and Raman studies confirmed that the structure of Ba 1−x Li x TiO 3 remains tetragonal as for BaTiO 3 . The Li substitution shifted the phase transition (T C ) of BaTiO 3 slightly towards the lower temperature side. Significant drop in leakage current was observed with an addition of Li content. The maximum values of the electrocaloric effect (ΔT), electrocaloric responsivity, and coefficient of performance were found to be 1.44 K, 0.24 × 10 −6 K m/V, and 5.75, respectively, for x = 0.04 at an applied field of 60 kV/cm near the Curie temperature. The maximal value of energy storage density was found to be 0.42 J/cm 3 with an energy storage efficiency of 60% for x = 0.05. Our results suggested that lead-free Ba 1−x Li x TiO 3 ceramic material is a promising candidate for potential applications in solid-state refrigeration technology and high-efficiency energy storage devices.

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