Colorimetric detection of trace toxic metals in water based on gold nanoparticles (AuNPs) has been well demonstrated. However, almost all the available assays focus on free metal ions instead of metal-organic complexes, which are ubiquitous in real waters and more challenging for decontamination. Therefore, the specific analysis of metal-organic complexes has become an essential prerequisite for propelling the application of gold nanoparticles form laboratory study to real contaminated environment. In this study, we developed a novel colorimetric nanoprobe strategy for complexed Cr(III) species based on the analyte-induced aggregation of gold nanoparticles (AuNPs), as coated by a cationic surfactant tributylhexadecylphosphonium bromide (THPB) instead of traditional carboxyl modifiers. At alkaline pHs (pH=11), the unique hydrolysis and extremely slow decomplexation of Cr(III) is believed to form the specific interaction between Cr(III)-citrate and THPB-AuNPs and thereafter enhance the NPs aggregation, as verified by XPS, UV-Vis and Zeta potential. Such detection system could be realized via both naked eye and/or UV-Vis spectroscopy with the detection limit of 8.0 and 0.29 μM respectively, much lower than the total Cr toxic level regulated by Chinese environmental protection agency (EPA) (1.5 mg/L, ~30 μM). The proposed detection system also exhibits high selectivity against various interfering substances including free ions, small organic molecules and other metal-citrate complexes. Also, the THPB-AuNPs could be stored at room temperature for 30 days with the constant detection performance. Moreover, the quantitative detection of Cr(III)-organic complexes with the background of various real water samples agreed well with that based on ICP-AES, making it an attractive alternative for on-site detection of authentic samples containing Cr(III)-organic species.

Specifically and visually detect aqueous Cr(III)-organic complexes based on cationic surfactant-modified Au nanoprobe

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.