Fluorescent sensors from salicylaldimine derivatives for metal ions

Abstract

An in-situ forming and sensing was developed as a high-throughput screening of fluorescent chemosensors for metal ions. The 45 salicylaldimines, formed in-situ from the condensation between 5 salicylaldehydes and 9 amines, in 96 well-plates were photographed under black light along with the 5 salicylaldehydes in the absence and presence of 18 metal ions. The library of fluorescence response images of these 50 chemosensors were processed into RGB values. The PCA of theΔRGB, the differences between those of images with and without the metal ions, showed 9 sensors with normalized loading value over 70%. The sensor array constructed from these 9 sensors could classify 15 non-alkali metal ions with 99% accuracy based on a leave-one-out cross-validation. The cross-validation of the data from all possible combinations of 2-9 sensors revealed that certain pairs of sensors could also classify the metal ions without any loss of accuracy. This in-situ forming-sensing technique was also applied to identify a new selective sensor for Al3+ from 10 hydrazones generated from 5 salicylaldehyde and 2 dihydrazides. However, the response time of the hydrazone sensor is relatively slow and further investigation is needed to understand the sensing mechanism.