A sensitive chemosensor for nitro-containing compounds based on Au nanoclusters/Ba2+ co-assembly system: The crucial role of ligands to metal charge transfer

Abstract

Gold nanoclusters (AuNCs) are a class of promising inorganic-organic hybrid nanomaterials with exceptional photoluminescent properties. The understanding of their photoluminescent mechanism is important for developing functional AuNCs-based materials. In this work, thiobarbituric acid-modified AuNCs (TBA-AuNCs) was prepared and its photoluminescent property was modulated through co-assembly with Ba2+. The emission intensity was sharply enhanced with the formation of TBA-AuNCs/Ba2+ complex. Structural characterization including transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the hybridization of TBA-AuNCs with Ba2+. The pH-dependent photoluminescence as well as zeta potential measurements demonstrated that the ligand to metal charge transfer (LMCT) is crucial for the regulation of emission property of the TBA-AuNCs/Ba2+. Based on this special photoluminescent mechanism, the TBA-AuNCs/Ba2+ complex was employed as a chemical sensor for nitro-substituted aromatic compounds. The emission intensity of TBA-AuNCs/Ba2+ selectively displayed sharp quenching in response to 2-methyl-4-nitroimidazole among various imidazole derivatives. Simultaneously, the complex also showed high sensitivity toward p-nitroaniline and 2-nitrophenol. Therefore, the developed TBA-AuNCs/Ba2+ assemblies are potential in detecting the nitro-containing compounds, which will find applications in pharmaceutical analysis, environmental protection and other related fields.