Label‐Free Optical Single‐Molecule Micro‐ and Nanosensors

Abstract

Label-free optical sensor systems have emerged that exhibit extraordinary sensitivity for detecting physical, chemical, and biological entities at the micro/nanoscale. Particularly exciting is the detection and analysis of molecules, on miniature optical devices that have many possible applications in health, environment, and security. These micro- and nanosensors have now reached a sensitivity level that allows for the detection and analysis of even single molecules. Their small size enables an exceedingly high sensitivity, and the application of quantum optical measurement techniques can allow the classical limits of detection to be approached or surpassed. The new class of label-free micro- and nanosensors allows dynamic processes at the single-molecule level to be observed directly with light. By virtue of their small interaction length, these micro- and nanosensors probe light-matter interactions over a dynamic range often inaccessible by other optical techniques. For researchers entering this rapidly advancing field of single-molecule micro- and nanosensors, there is an urgent need for a timely review that covers the most recent developments and that identifies the most exciting opportunities. The focus here is to provide a summary of the recent techniques that have either demonstrated label-free single-molecule detection or claim single-molecule sensitivity.

Silicon‐Based Integrated Label‐Free Optofluidic Biosensors: Latest Advances and Roadmap

“…In particular, single‐molecule detection has been achieved based on techniques such as surface‐enhanced Raman scattering (SERS), [ 23,24 ] localized surface plasmon resonance (LSPR), [ 25,26 ] and ultra‐high Q optical microcavities. [ 27,28 ]…”

Functional Mid‐Infrared Polaritonics in van der Waals Crystals

“…Second, most molecules have their characteristic vibrational and rotational modes in the mid‐infrared. By detecting these strong and unique spectral fingerprints from light–molecule interactions, it is possible to achieve efficient bioimaging and chemical sensing that overcomes the limitations of Raman scattering‐based chemical detection . Third, the thermal radiation of objects with moderate temperatures (from room temperature to 1000 °C) peaks in the mid‐infrared region.…”

“…

scattering-based chemical detection. [1,2] Third, the thermal radiation of objects with moderate temperatures (from room temperature to 1000 °C) peaks in the midinfrared region. Therefore, by acquiring the ability to modulate the mid-infrared radiation of materials, it becomes possible to control the thermal emission properties of a heated object without altering its temperature.

…”

Photocontrolled Healable Structural Color Hydrogels

“…Attracted and inspired by these natural examples, scientists have focused on the fabrication of structural color materials and devoted to promoting their applications . Structural color hydrogels, regarded as the significant applications, have been extensively studied in biochemical field and applied in development of optical devices, molecular detection, force sensing, wearable devices, etc . However, most current strategies for repairing the structural color hydrogels that were broken during use require complex dynamic covalent reaction components to heal the scratches or cuts .…”

“…DOI: 10.1002/smll.201903104 optical devices, molecular detection, force sensing, wearable devices, etc. [8][9][10][11][12][13][14][15][16] However, most current strategies for repairing the structural color hydrogels that were broken during use require complex dynamic covalent reaction components to heal the scratches or cuts. [17,18] In addition, these healing processes usually require specific operation or inevitable chemical procedure to trigger.…”