Solution-based nanosensors for in-field detection with the naked eye

Nanomaterials are revolutionising analytical applications with low-cost tests that enable detecting a target molecule in a few steps and with the naked eye. With this approach, non-experts can perform analyses on-site and without utilising electronic readers. This is advantageous in point-of-care diagnostics, in-field measurements and analyses performed in resource-constrained settings. Here we review the main strategies adopted for detecting analytes with the naked eye and at the point of need using plasmonic nanosensors, catalytic nanoparticles and fluorescent nanomaterials. Examples of the detection of ions, glucose, small molecules, peptides and proteins with the nanosensors are explained in detail.