Facile sintering-based synthesis and characterization of high-quality crystalline borophene quantum dots

Borophene Quantum Dots (BPQDs) have been shown to exhibit unique properties that make them suitable as zero-dimensional nanomaterials. These properties include optical, structural, electrical, mechanical, photophysical, and magnetic characteristics, particularly their ferromagnetic behavior. Ultra-stable crystalline semiconductor BPQDs can be synthesized by thermally degrading (using the sintering method) sodium borohydride (NaBH 4 ) in normal atmospheric air, employing a scalable method. The synthesis process involves controlled heating and cooling cycles for the processing of borophene. Under ambient atmospheric conditions, oxygen can act as an active site for ferromagnetic behavior. Various characterization techniques, such as Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, Energy Dispersive X-ray, Raman spectroscopy, X-ray Diffraction, Vibrating Sample Magnetometer, Fourier-transform infrared spectroscopy, Photoluminescence (PL) spectroscopy, and Ultraviolet–visible (UV-Vis) spectroscopy, have revealed that the interaction between oxygen and boron-hydride functionalities influences the optical, emission, electrical, and ferromagnetic behavior of BPQDs. Oxygen functionality enhances light absorption and emission properties in UV-Vis and PL spectroscopy through recombination/fusion processes in defects, thereby controlling the optical, electrical, and ferromagnetic properties of BPQDs for applications in optoelectronics, biosensing, bio-imaging, spintronics, radiation shielding, nanomedicine, energy storage, and hydrogen storage. A memory device based on BPQDs exhibits an enhanced ON/OFF current ratio, with a sensitivity of 5 × 10 4 , and operates at a low voltage of less than 2V for stability. These properties make BPQDs valuable for use in electronic and memory devices. • The lattice spacing of 0.28 nm in the HRTEM image corresponds to the β-borophene structure. • The XRD pattern of BPQDs shows a strong peak at around 23.4° corresponding to the (018) lattice of borophene. • The most prominent peak at 762 cm −1 is identified as the E g vibrational mode of the B–B cluster. • The Tauc plot indicates that the bandgap of the BPQDs is calculated to be 3.55 eV, suggesting a semiconducting structure. • When excited at 300 nm (4.13 eV), the BPQDs emit near the blue, with a peak at 475 nm (2.61 eV).