Combinatorial Scanning\nKelvin Probe and Density Functional\nTheory Studies on Selective <i>n</i>‑Butanol Adsorption\nProperties of pH-Dependent Bi<sub>2</sub>WO<sub>6</sub> Nanostructures

Fast and effective detection of volatile organic compounds\n(VOCs)\nis a crucial criterion for developing stable and room-temperature\noperable gas sensors. In this work, we have synthesized Bi<sub>2</sub>WO<sub>6</sub> (BW) nanostructures using the hydrothermal method\nat pH 1 (BW-1), pH-3 (BW-3), pH 5 (BW-5), pH 7 (BW-7), and pH 9 (BW-9)\nto study their room-temperature VOC adsorption properties. X-ray diffraction\nstudy confirms that both internal strain and crystallite size increase\nwith the pH. Field-emission scanning electron microscope results showed\na change in the morphology of BW nanostructures from flakes to sheets.\nThe results obtained from the surface photovoltage, photoluminescence\nspectra, Raman spectra, and X-ray photoelectron spectroscopy revealed\nthat the defects and oxygen vacancies in the nanostructures increase\nwith the pH. Further, the gas adsorption properties are examined using\nthe scanning Kelvin probe system through contact potential difference\nmeasurements in both dark and visible light conditions in air and\nvarious VOCs like <i>n</i>-butanol, benzene, triethylamine,\nand acetone. The BW-9 sample has exhibited ∼40% enhanced photoresponse\nunder an <i>n</i>-butanol atmosphere compared with BW-1.\nThe chemiresistive gas sensing performance of BW-9 between 50 and\n400 ppm exhibits a sensitivity value of 0.00816 ± 0.0007 ppm<sup>–1</sup>. Computational investigations using density functional\ntheory have confirmed that surface-adsorbed oxygen on BW shows a higher\naffinity for <i>n</i>-butanol with a higher adsorption energy\nof −0.877 eV among other VOCs. Overall, these combined experimental\nand computational studies have demonstrated the selective adsorption\nbehavior of BW nanostructures toward <i>n</i>-butanol, a\npotential industrial pollutant.