Noble metal nanoparticles growth-based colorimetric strategies: From monocolorimetric to multicolorimetric sensors

Noble metal nanoparticles as color labels and signal generators have been widely accepted for the fabrication of colorimetric assays and sensors due to their simplicity and practicality. In the past, organic dye probes and interparticle distance-dependent nanocolorimetric sensors have witnessed great progress in chem/biosensing and recognition events. However, they often suffer from a low color resolution due to the inherent low extinction coefficients of organic dyes probes and the monocolor change-based signal readout. Currently, target-dependent in situ growth of noble metal nanoparticles provides a general means to follow naked-eye-detectable color readouts with high resolution, further allowing great advances in the development of monocolorimetric and multicolorimetric sensors for different target analytes in various detection areas, such as modern bioanalysis, environmental monitoring, food analysis and clinical diagnosis. However, reviews exploring the color readout classifications, signal generation and amplification mechanisms, as well as providing guidance on the progress of such noble metal nanoparticle growth-based colorimetric assays have rarely been reported. To highlight the significant advances in this newly-developing noble metal nanoparticle morphology/size-dependent colorimetric assays field, we herein exclusively summarise the sensing fundamentals, development evolution and cutting-edge applications of this emerging field. Finally, we provide general guidance on how to design such assays on the basis of their current challenges and future perspectives. (C) 2019 Elsevier B.V. All rights reserved.