Spatiotemporally Super-resolved Volumetric Traction Force Microscopy

Quantification of mechanical forces is a major challenge across biomedical sciences. Yet such measurements are essential to understanding the role of biomechanics in cell regulation and function. Traction force microscopy remains the most broadly applied force probing technology but typically restricts itself to single-plane two-dimensional quantifications with limited spatiotemporal resolution. Here, we introduce an enhanced force measurement technique combining 3D super-resolution fluorescence structural illumination microscopy and traction force microscopy (3D-SIMTFM) offering increased spatiotemporal resolution, openingup unprecedented insights into physiological three-dimensional force production in living cells

Enhanced Lifetime Of Excitons In Nonepitaxial Au/cds Core/shell Nanocrystals

The ability of metal nanoparticles to capture light through plasmon excitations offers an opportunity for enhancing the optical absorption of plasmon-coupled semiconductor materials via energy transfer. This process, however, requires that the semiconductor component is electrically insulated to prevent a backward charge flow into metal and interfacial states, which causes a premature dissociation of excitons. Here we demonstrate that such an energy exchange can be achieved on the nanoscale by using nonepitaxial Au/CdS core/shell nanocomposites. These materials are fabricated via a multistep cation exchange reaction, which decouples metal and semiconductor phases leading to fewer interfacial defects. Ultrafast transient absorption measurements confirm that the lifetime of excitons in the CdS shell (tau approximate to 300 ps) is much longer than lifetimes of excitons in conventional, reduction-grown Au/CdS heteronanostructures. As a result, the energy of metal nanoparticles can be efficiently utilized by the semiconductor component without undergoing significant nonradiative energy losses, an important property for catalytic or photovoltaic applications. The reduced rate of exciton dissociation in the CdS domain of Au/CdS nanocomposites was attributed to the nonepitaxial nature of Au/CdS interfaces associated with low defect density and a high potential barrier of the interstitial phase

Label-Free Pump–Probe Nanoscopy

In the last few decades fluorescence microscopy has been the most widely used microscopy technique and much effort has been put into the development of advanced super-resolution fluorescence microscopy techniques to circumvent the diffraction limit. Despite their well-established benefits, these techniques have to rely on the photo-physical properties of fluorescent molecules to obtain the desired contrast and spatial resolution. The labeling procedure may cause unwanted alterations in the sample. With the advent of ultrashort-pulsed laser sources, it became possible to better explore novel non-fluorescent-based contrast mechanisms that rely solely on intrinsic properties of the molecules of interest and which led to the development of label-free microscopy approaches. In this chapter, the imaging capabilities of absorption-based pump\u2013probe microscopy are presented. This technique explores the ultrafast dynamic properties of the sample with high spatial and temporal resolution, as well as high sensitivity and chemical specificity. Two pulses, a pump and a probe, with a proper spatial and temporal overlap are used. The pump is absorbed, inducing a measurable change in the sample carrier population, which is then monitored by a delayed probe pulse. The development of new label-free approaches also represents a key challenge for the exploration of super-resolution approaches in non-fluorescence-based methods