Schiff base stabilized gold nanoparticles: Synthesis, characterization, catalytic reduction of nitroaromatic compounds, fluorometric sensing, and biological activities

Abstract

Currently, the controllable fabrication of ultra-small, highly dispersed, stable, and functionalized metal nanoparticles (MNPs) by is crucial for the industrially applicable applications. The simple fabrication of Schiff base stabilized gold nanoparticles (AuNPs) does not require stringent experimental conditions, and thus, a straight forward, rapid, and efficient method for the fabrication of highly active catalysts for treating environmental pollutants. Here, we demonstrate the facile fabrication of AuNPs in aqueous solutions via the reduction of hydrogen tetrachloroaurate(III) trihydrate (HAuCl4⋅3H2O) by the Schiff base ligand ((1-((E)-(4-(trifluoromethoxy)phenylimino)methyl)naphthalen-2-ol)) with ultra-small size (<5 nm), high dispersion, and excellent stability. The synthesized Schiff base stabilized AuNPs were characterized by UV–vis absorption, photoluminescence, FTIR, powder XRD, SEM, and TEM techniques. The Schiff base stabilized AuNPs were utilized for the catalytic reduction of nitroaromatic compounds (4-nitrophenol (4-NP) and 4-nitroaniline (4-NA)) in the liquid phase reaction. The maximum reduction efficiency up to 82 % and 94 % was achieved in the presence of NaBH4 for the conversion of 4-NP and 4-NA within 16 min reaction, respectively. In addition, the synthesized AuNPs have exhibited selective sensing detection of Pb2+ metal ions in nano-molar range of concentration by spectrofluorometrically with the limit of detection (LOD) is 0.0325 nM and limit of quantification (LOQ) is 0.0694 nM. The synthesized AuNPs revealed comparable results of antibacterial, antifungal, and antioxidant activities with comparable standard drugs.

Keywords

• Schiff base
• AuNPs
• Surface plasmon resonance
• Nitroaromatics reduction
• Detection of Pb(II)
• Biological activity