Surpassing the Diffraction Limit in Label-Free Optical Microscopy.

Super-resolution optical microscopy has enhanced our ability to visualize biological structures on the nanoscale. Fluorescence-based techniques are today irreplaceable in exploring the structure and dynamics of biological matter with high specificity and resolution. However, the fluorescence labeling concept narrows the range of observed interactions and fundamentally limits the spatiotemporal resolution.

Fast Leaps between Millisecond Confinements Govern Ase1 Diffusion along Microtubules.

Diffusion is the most fundamental mode of protein translocation within cells. Confined diffusion of proteins along the electrostatic potential constituted by the surface of microtubules, although modeled meticulously in molecular dynamics simulations, has not been experimentally observed in real-time. Here, interferometric scattering microscopy is used to directly visualize the movement of the microtubule-associated protein Ase1 along the microtubule surface at nanometer and microsecond resolution.

Nanoscopic Structural Fluctuations of Disassembling Microtubules Revealed by Label-Free Super-Resolution Microscopy.

Microtubules are cytoskeletal polymers of tubulin dimers assembled into protofilaments that constitute nanotubes undergoing periods of assembly and disassembly. Static electron micrographs suggest a structural transition of straight protofilaments into curved ones occurring at the tips of disassembling microtubules. However, these structural transitions have never been observed and the process of microtubule disassembly thus remains unclear.

Fast photothermal spatial light modulation for quantitative phase imaging at the nanoscale.

Spatial light modulators have become an essential tool for advanced microscopy, enabling breakthroughs in 3D, phase, and super-resolution imaging. However, continuous spatial-light modulation that is capable of capturing sub-millisecond microscopic motion without diffraction artifacts and polarization dependence is challenging. Here we present a photothermal spatial light modulator (PT-SLM) enabling fast phase imaging for nanoscopic 3D reconstruction.

Influence of Zn on the photoluminescence of colloidal (AgIn)ZnS nanocrystals.

We study the effect of Zn on the photophysical properties of a family of group I-III-VI nanocrystals (NCs), namely in solid solutions of (AgIn)ZnS (ZAIS). We focus on the comparison of the photoluminescence (PL) properties of ZAIS NCs of comparable sizes and different amounts of Zn. This approach helps us to decouple the effects of size and varying chemical composition of the NCs which both influence the PL properties.

Selective turn-on and modulation of resonant energy transfer in single plasmonic hybrid nanostructures.

Förster resonant energy transfer (FRET) is a nonradiative process by which the energy of light absorbed by a donor molecule is transferred to an acceptor molecule over a distance of several nanometers. FRET plays a crucial role in photosynthesis and nature-inspired artificial light-harvesting systems that are being explored for use in energy conversion applications. Localized plasmons of metal nanoparticles can potentially lead to a significant increase of FRET efficiency and effective donor-acceptor distance.

Single-particle spectroscopy of I-III-VI semiconductor nanocrystals: spectral diffusion and suppression of blinking by two-color excitation.

Ternary I-III-VI semiconductor nanocrystals have been explored as non-toxic alternatives to II-VI semiconductors for optoelectronic and sensing applications, but large photoluminescence spectral width and moderate brightness restrict their practical use. Here, using single-particle photoluminescence spectroscopy on nanocrystals of (AgIn)xZn2(1-x)S2 we show that the photoluminescence band is inhomogeneously broadened and that size distribution is the dominant factor in the broadening. The residual homogeneous linewidth of individual nanocrystals reaches up to 75% of the ensemble spectral width.

New insight into singlet oxygen generation at surface modified nanocrystalline TiO2--the effect of near-infrared irradiation.

The generation of singlet oxygen in aqueous colloids of nanocrystalline TiO2 (anatase) modified by organic chelating ligands forming surface Ti(IV) complexes was studied. Detailed studies revealed a plausible and to date unappreciated influence of near-infrared irradiation on singlet oxygen generation at the surface of TiO2. To detect (1)O2, direct and indirect methods have been applied: a photon counting technique enabling time-resolved measurements of (1)O2 phosphorescence, and fluorescence measurements of a product of singlet oxygen interaction with Singlet Oxygen Sensor Green (SOSG).

Plasmonic molecular nanohybrids-spectral dependence of fluorescence quenching.

We demonstrate strong spectral dependence of the efficiency of fluorescence quenching in molecular systems composed of organic dyes and gold nanoparticles. In order to probe the coupling with metallic nanoparticles we use dyes with varied spectral overlap between the plasmon resonance and their absorption. Hybrid molecular structures were obtained via conjugation of metallic nanoparticles with the dyes using biotin-streptavidin linkage.