Characterization of natural thin layer deposits on rocks: Exploring structural, morphological, and optical properties at the nanoscale

Four rock samples were collected from the region of Hanuman Tekdi Parvati Nagar in Aurangabad. These samples underwent X-ray diffraction (XRD) spectroscopy analysis to ascertain their mineral composition. The investigation revealed that the samples exhibited a polycrystalline nature and contained diverse minerals, with variations observed between samples. Notable minerals detected in the samples included copper (Cu), silicon (Si), zinc oxide (ZnO), calcium oxide (CaO), magnetite (Fe3O4), titanium dioxide (TiO2), nickel oxide (NiO), and others. The FTIR spectra exhibited absorption peaks corresponding to several functional groups and metal oxides throughout the 400-1000 cm−1 wavelength range. These functional groups included NCS and O–H, while the metals seen were CuO, Au6, Au8, Fe–O, Zn–O, and Ti–O, among others. The field emission scanning electron microscopy (FE-SEM) images revealed the presence of agglomerated nanoparticles exhibiting diverse surface morphologies in size and shape. Additionally, the samples showed varying amounts of different elemental components. The UV‒VIS spectrophotometric analysis reveals that all samples (a, b, c, d) exhibit a prominent absorption peak at 240 nm, albeit with varying intensities. The nanoparticles' band-gap energy (Eg) is determined for each of the aforementioned samples (a, b, c, d). The energy values for samples (a, b) were determined to be 4.30 eV and 3.75 eV, while samples (c, d) exhibited energy values of 2.34 eV and 3.71 eV, respectively. •Nanoscale nature.•FE-SEM.•Band-gap energy.•Surface morphologies.•Polycrystalline.