In many areas of non-invasive optical imaging, particularly in biology and materials science, the use of conventional fluorescence-based microscopy techniques is constrained by a number of factors, including the need for molecular labels and the occurrence of photobleaching. Optical scattering methods provide a powerful alternative that can overcome these limitations by detecting the inherent light-scattering properties of a sample. One such technique, interferometric scattering (iSCAT) microscopy, is a highly sensitive, label-free method that enables the detection of subwavelength entities, such as nanoparticles and single molecules, by using optical interference to translate a weak scattering signal into a strong, detectable intensity change. Because it is a label-free technique, it avoids issues like photobleaching and allows for the precise determination of a nanoparticle’s properties, such as size and mass. It is also highly effective for 3D tracking and quantifying ultrafast diffusion in solids.
STROBE contributed to an important review article in Nature Reviews Methods Primers that provides a comprehensive overview of iSCAT microscopy, its theoretical underpinning, practical implementation, and applications. In particular, STROBE’s contribution focuses on the Center’s development of stroboSCAT, an advanced, time-resolved variant of iSCAT. This innovative technique was created to address a critical challenge in materials science: the difficulty of quantitatively separating different physical phenomena, such as the generation of electronic charge carriers (excitons) and unwanted heat, which have overlapping optical signatures.
stroboSCAT employs a unique pump-probe and multi-wavelength strategy to quantitatively separate and map these contributions with exceptional spatiotemporal precision. This enables accurate observation and characterization of electronic, thermal, and mass transport in a wide range of materials at the nanoscale both separately and also in combination. This methodological advancement represents a significant step forward for fundamental research in optoelectronics and materials science, given the complexities of energy transport and conversion in next-generation functional materials.
For example, stroboSCAT is specifically applied to simultaneously map heat and exciton populations in materials like few-layer molybdenum disulfide (MoS₂). By enabling the quantitative separation of these signals, stroboSCAT transforms iSCAT from a general imaging platform into a powerful analytical instrument for resolving ultrafast energy transport and transduction at the nanoscale.