The Ever-Expanding Optics of Single-Molecules and Nanoparticles

Our traditional approach of understanding the properties of an individual object is often based on an extrapolation from the properties of an ensemble. This approach naturally arises from the ease to access ensembles in an experiment. With new experimental developments this extrapolation appeared to be an oversimplification and with the advent of single-molecule optics around 1990, this idea of homogeneity and isotropy at the smallest scales finally disappeared. The world has become more interesting at the smallest scales and better understood since then and the field of single-molecule optics has rapidly evolved. In the early 1990s pioneering experiments still targeted single molecules as objects of interest themselves. This seemingly small step has revolutionized biology, sparked a new era for optical microscopy and quantum optics and provided an indispensable tool for materials science and physics. The ability to optically image, study and therefore also to manipulate single molecules created new opportunities for uncovering previously unknown phenomena. In the 2000s this field has spread out to many other systems and nanoscale objects, that can now be accessed at the single-particle level exploring new physical principles directly on the most fundamental, single-object level.

This virtual special issue attempts to attract a collection of works that will represent an adequate sampling snapshot for the expanding creativity that shares a single conceptual spark made possible by the pioneering experiments some three decades ago: think single-molecule.

To represent the developments, we suggest contributions from the following fields:

1. Photothermal phenomena
2. Quantum optics
3. Plasmonics
4. Single-molecule spectroscopy
5. Single-particle spectroscopy
6. Single-molecule biophysics and enzymology
7. Laser tweezers
8. Molecular imaging