Water/oil nanoemulsion-based synthesis of BixSn6-2xSy (0.33 ≤ × ≤ 2.95) semiconductor QDs for efficient photocatalytic degradation of MB dye

Mosaad Negem; David Miller; John Irvine; Fakiha El-Taib Heakal

doi:10.1007/s11356-023-26596-z

Water/oil nanoemulsion-based synthesis of Bi_xSn_6-2xS_y (0.33 ≤ × ≤ 2.95) semiconductor QDs for efficient photocatalytic degradation of MB dye

Environ Sci Pollut Res Int. 2023 Apr;30(20):58998-59012. doi: 10.1007/s11356-023-26596-z. Epub 2023 Mar 31.

Authors

Mosaad Negem¹, David Miller², John Irvine², Fakiha El-Taib Heakal³

Affiliations

¹ Chemistry Department, Faculty of Science, Fayoum University, Fayoum, Egypt.
² School of Chemistry, EaSTChem, University of St Andrews, St Andrews, Fife, KY16 9ST, UK.
³ Chemistry Department, Faculty of Science, Cairo University, Giza, 12613, Egypt. hfakiha@cu.edu.eg.

PMID: 37000392
DOI: 10.1007/s11356-023-26596-z

Abstract

The development of efficient photocatalysts for the photodegradation of organic dyes in wastewater is highly worthwhile. Herein, the nanoemulsion tactic was utilized to synthesize Bi_xSn₆_-2xS_y (0.33 ≤ x ≤ 2.95) photocatalysts with morphological structures that changed from nanowhiskers to quantum dots (QDs). The optical properties of these materials were examined by UV-visible absorbance spectroscopy and photoluminescence, while Mott-Schottky analysis was utilized to study their electronic properties. Bi_xSn_6-2xS_y materials exhibit appreciable absorption in the UV-visible light range with a direct band gap that increases from 1.23 to 1.46 eV. Both crystal structure and composition greatly affect the photocatalytic activity of Bi_xSn_6-2xS_y semiconductors. Among the various synthesized photocatalysts, BiSn₄S_4.5 can efficiently photodegrade methylene blue dye (MB) in the shortest time under UV-visible light. The photocatalytic activity is positively affected by the change of crystal structure from orthorhombic to cubic symmetry. Based on the Mott-Schottky plots, the flat band potential (E_fb) and the semiconductor behavior of the fabricated Bi_xSn_6-2xS_y nanomaterials were determined. The obtained E_fb values for SnS, Bi_0.33Sn_5.34S_5.8, BiSn₄S_5.5, and Bi_2.14Sn_1.71S_4.7 are -0.18 V, -0.42 V, -0.53 V, and -0.51 V (vs. Ag/AgCl), respectively. The E_fb value is clearly shifted towards more negative potential values with increasing the Bi molar ratio (x). However, Bi_2.95Sn_0.1S_4.5 semiconductor was found to be of n-type character, having a positive E_fb value of +0.66 V (vs. Ag/AgCl). Photocurrent and EIS responses confirm the high stability and photocatalytic activity of BiSn₄S_5.5, which also achieves the lowest charge transfer resistance. The modified electronic properties of the Bi_xSn_6-2xS_y semiconductors significantly improve their photocatalytic activity, rendering them to be promising absorbers for sunlight harvesting applications.

Keywords: Direct band gap; MB photodegradation; Metal chalcogenides; Mott-Schottky plots; Nanoemulsion tactic; Semiconductor quantum dots.

MeSH terms

Catalysis
Methylene Blue / chemistry
Quantum Dots*
Semiconductors
Water

Substances

Water
Methylene Blue