Molecular Amplification as an Affordable Strategy for Trace‐Level Detection of Ionic Analytes with Fluorimetric or Colorimetric Readout

Abstract

AbstractNaked‐eye detection of an analyte at an ultralow concentration in a complex mixture is the ultimate goal of an analytical chemist. Over the years, with a wide range of sophisticated analytical techniques based on, for example, various microscopies (TEM, SEM, AFM), surface plasmon resonance (SPR) and surface‐enhanced Raman spectroscopy (SERS), one can achieve as low as single‐molecule detection. Despite their excellent sensitivities, these methods are often found to be unsuitable for on‐location analysis of real‐life samples due to limitations such as the requirement for advanced instrumental facilities and skilled technicians, high‐cost maintenance, and multi‐step sample preparation procedures. On the other hand, using the concept of molecular amplification a similar level of sensitivity can be achieved with changes in color or fluorescence as the output response. Unlike previous related reviews, in this work we chose not to focus on the different kinds of amplification strategies (target, label, signal, or receptor amplification) nor on the species responsible for generating reporter molecules (catalysts, macromolecules, metal surfaces, and supramolecular aggregates). Instead, herein we have attempted to discuss how the concept of molecular amplification has helped in the trace‐level detection of ionic analytes (for example, anions, heavy metal pollutants and charged biological molecules).