Nanomaterial-based enzyme mimetics (nanozymes) is an emerging field of research that promises to produce alternatives to natural enzymes for a variety of applications. The search for the most cost-effective and efficient inorganic nanomaterials, such as metal oxides, cannot be won by pristine CuO. However, unlike CuO, the Zn-doped CuO (Zn-CuO) nanoparticles reported in this paper reveal superior peroxidase-like enzyme activity. This places Zn-CuO in a good position to participate in a range of activities aimed at developing diverse enzyme applications. The peroxidase-like activity was tested and confirmed against various chromogenic substrates in the presence of H2O2 and obeyed the Michaelis-Menten enzymatic pathway. The mechanism of enhanced enzymatic activity was proved by employing terephthalic acid as a fluorescence probe and by electron spin resonance. The nanozyme, when tested for the detection of glucose, showed a substantial enhancement in the detection selectivity. The limit of detection (LOD) was also decreased reaching a limit as low as 0.27 ppm. Such a low LOD has not been reported so far for the metal oxides without any surface modifications. Moreover, the nanozyme (Zn-CuO) was utilized to detect the three antioxidants tannic acid, tartaric acid, and ascorbic acid and the relative strength of their antioxidant capacity was compared.

The study of graphene-based antivirals is still at a nascent stage and the photothermal antiviral properties of graphene have yet to be studied. Here, we design and synthesize sulfonated magnetic nanoparticles functionalized with reduced graphene oxide (SMRGO) to capture and photothermally destroy herpes simplex virus type 1 (HSV-1). Graphene sheets were uniformly anchored with spherical magnetic nanoparticles (MNPs) of varying size between ∼5 and 25 nm. Fourier-transform infrared spectroscopy (FT-IR) confirmed the sulfonation and anchoring of MNPs on the graphene sheets. Upon irradiation of the composite with near-infrared light (NIR, 808 nm, 7 min), SMRGO (100 ppm) demonstrated superior (∼99.99%) photothermal antiviral activity. This was probably due to the capture efficiency, unique sheet-like structure, high surface area, and excellent photothermal properties of graphene. In addition, electrostatic interactions of MNPs with viral particles appear to play a vital role in the inhibition of viral infection. These results suggest that graphene composites may help to combat viral infections including, but not only, HSV-1.

The carbon dot initiated polypyrrole (PPY) and CuO composite were synthesized into PPY@CuO using a simple one-step sonochemical approach. The synthesized PPY and the PPY@CuO were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, 13C-solid-state nuclear magnetic resonance (NMR) spectroscopy, UV–visible spectroscopy, and scanning electron microscopy. A strong interaction was demonstrated between the PPY chains and CuO. This interaction led to changes in the backbone chain of the PPY@CuO composite when compared to the carbon dot initiated PPY. The antibacterial activity against Escherichia coli and Staphylococcus aureus of the carbon dot initiated synthesis of PPY and the sonochemically prepared PPY@CuO composite materials was revealed. The results indicate the biocidal efficacy of PPY@CuO on both Gram-positive and Gram-negative bacteria. The PPY@CuO composite exhibited an enhanced antibacterial performance in comparison with the carbon dot initiated PPY and CuO. This is a first report on the sonochemical synthesis of a polymer composite composed of PPY and CuO, demonstrating the efficacy of its antibacterial action at a concentration of 1 mg/mL of the composite involving 0.234 mg/mL of CuO.

One of the limitations in the applications and commercialization of metal oxides in diverse fields is their inferior colloidal stability.