Fluorescence-based sensors as an emerging tool for anion detection: mechanism, sensory materials and applications

Abstract

Negatively charged ions are an integral part of our ecosystem, where at certain concentrations (fixed by the Environmental Protection Agency (EPA) and World Health Organization (WHO)), they are non-toxic. However, with an increase or decrease in their concentration due to pollution, industrialization, etc., anions show harmful effects. Therefore, the detection of anions with high sensitivity and selectivity is necessary, which is challenging. In the past few years, various fluorescence-based sensory materials have been developed to detect anions in the solution, solid, and vapor phases through various mechanisms. Significant undertakings are in progress to develop fluorescent materials with high sensitivity, selectivity, and fast response time. This review article starts with the various sensing mechanisms for fluorescence-based anion detection. Subsequently, the fluorescent sensory materials for anion detection are widely and efficiently summarized, focusing on the last 10 years of investigation. The focus of this review is to present a broad scope of fluorescent materials, for example, supramolecular systems, polymeric chemosensors, small molecules, metal–organic frameworks (MOFs), and aggregation-induced emissive materials, and their associated mechanisms and applications. Also, an outline of the reported fluorescent materials and their mechanism, anion detection, low detection limit (LOD), and applications are presented in a table format.