Highly Sensitive and Selective Spiropyran-Based Sensor for Copper(II) Quantification

• Published in: ACS omega Vol. 6; no. 16; pp. 10776 - 10789
• Main Authors: Trevino, Kimberly M, Tautges, Brandon K, Kapre, Rohan, Franco Jr, Francisco C, Or, Victor W, Balmond, Edward I, Shaw, Jared T, Garcia, Joel, Louie, Angelique Y
• Format: Journal Article
• Language: English
• Published: American Chemical Society 27.04.2021
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.1c00392

The metal-binding capabilities of the spiropyran family of molecular switches have been explored for several purposes from sensing to optical circuits. Metal-selective sensing has been of great interest for applications ranging from environmental assays to industrial quality control, but sensitive metal detection for field-based assays has been elusive. In this work, we demonstrate colorimetric copper sensing at low micromolar levels. Dimethylamine-functionalized spiropyran (SP1) was synthesized and its metal-sensing properties were investigated using UV–vis spectrophotometry. The formation of a metal complex between SP1 and Cu2+ was associated with a color change that can be observed by the naked eye as low as ≈6 μM and the limit of detection was found to be 0.11 μM via UV–vis spectrometry. Colorimetric data showed linearity of response in a physiologically relevant range (0–20 μM Cu2+) with high selectivity for Cu2+ ions over biologically and environmentally relevant metals such as Na+, K+, Mn2+, Ca2+, Zn2+, Co2+, Mg2+, Ni2+, Fe3+, Cd2+, and Pb2+. Since the color change accompanying SP1–Cu2+ complex formation could be detected at low micromolar concentrations, SP1 could be viable for field testing of trace Cu2+ ions.