Facet-Engineered Surfaces of Two-Dimensional Layered BiOI and Au–BiOI Substrates for Tuning the Surface-Enhanced Raman Scattering and Visible Light Photodetector Response

A simple and facile solution phase synthesis of two-dimensional (2D) layered BiOI single-crystalline square sheets at tunable reaction conditions yielded dominant exposed (001) facets. The bismuth oxyiodide (BiOI) structures analyzed by scanning electron microscopy and atomic force microscopy (AFM) reveal screw-dislocation-driven growth of spiral pyramid-like layer-by-layer (LBL) stacking of ultrathin BiOI sheet of about 2.5 nm. Vertically aligned, oriented Au nanotriangles (Au NTs) allow more analyte molecules to access their sharp tips to form hot-spots thereby enabling development of ultrasensitive plasmonic sensors. Injection of plasmonic hot carriers into the semiconductor at the plasmonic metal–semiconductor interface (Au–BiOI) fabricated under optimal conditions with Au NTs form tunable surface enhanced Raman scattering substrate with maximum enhancement factor on the order of 106 and 27 nanomol as a limit of detection. Electrical transport measurements on BiOI and Au–BiOI LBL 2D square sheet materials under applied pressure using conducting-AFM established the use of these nanosheets as a nanoscale pressure sensor. Photodetector studies show good photoresposnsivity, reproducibility, and fast photoresponse time indicating that the materials is a promising candidate for visible light-photodetector using 454 and 535 nm led lights.