Hexagonal Te/TeOx Nanosheets for Anticancer, Photothermal, and NO2 Gas Sensing Applications

Abstract

Herein, we present a highly rapid one-pot synthesis of Te/TeO_x nanosheets via high-energy electron beam irradiation. No external reducing agent was used as in situ generated solvated electrons reduced the precursors. Remarkably, the nanosheet formation was completed within seconds. UV–vis absorption spectra delineated a characteristic allowed direct transition from the valence band (p-bonding triplet) to the conduction band (p-antibonding triplet) at ∼275 nm, accompanied by a broad absorption band spanning 480–750 nm. X-ray photoelectron spectroscopy confirmed the nanomaterial composition as Te and TeO_x, corroborated by complementary X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy studies. Imaging techniques revealed the predominant formation of hexagon-shaped nanosheets, originating from the aggregation of initially formed one-dimensional (1D) nanostructures. Extensive pulse radiolysis investigations provided insights into the formation mechanism of Te-based nanomaterials. Further kinetic studies, involving variations in pH, absorbed dose, and water content in the nanoreactor, offered a profound understanding of the decay behavior of Te-based intermediate species. A notable aspect of this work is the exceptional anticancer efficacy (>80%) demonstrated by Te/TeO_x nanosheets against A549 lung cancer cells while exhibiting negligible cytotoxicity toward normal WI38 cells. This finding has been explained based on the cellular uptake of the nanosheets and reactive oxygen species generation, as evidenced by atomic absorption spectrometry and the 2,7-dichlorodihydro fluorescein-diacetate fluorimetry assay, respectively. Further, Te/TeO_x nanosheets were explored as gas sensors, displaying outstanding sensitivity and selectivity toward NO₂, with a detection threshold as low as ≤1 ppm at ambient temperature. Additionally, these nanosheets exhibited significant photothermal conversion efficiency under NIR light irradiation. Reusability tests highlighted their remarkable stability and sustained heating efficacy, underscoring the immense potential of Te/TeO_x nanosheets as versatile photothermal nanoagents.