A binary flow of a Ar/Zn mixture has been used in simulations as well as in physical growth experiments for ZnO nanowire growth by vapor phase deposition. Systematic investigations of the gas transport and the chemical behavior under controlled vacuum and flow conditions revealed that the gases emerging from carbothermal reduction, namely, CO (g) and CO 2(g) , are not enough to stimulate a controlled ZnO nanowire growth. An optimum O 2 concentration is crucial to promote nanowire growth, while CO (g) and CO 2(g) enhance the tendency to grow a film. Importantly, the here presented simulations can be used to predict and tailor the region of nanowire growth under appropriate assumptions for any tube furnace.

The controlled reversible switching between vapor-solid (VS) and vapor-liquid-solid (VLS) growth of ZnO nanowires (NWs) mediated by organic solvents, namely, ionic liquids (ILs), is demonstrated. Suppression or enhancement of the VLS mechanism is achieved by the control of Zn oxidation and ZnO reduction by the abundant IL pyrolyzates working as an additional carbon source. A new model called reactiVe VLS mode based on the Zn-Au alloy and the immediate oxidation of the out-sourced Zn is suggested. Cleaning the tube with concentrated HCl completely reverses the growth from the VLS back to the VS mechanism. The VLS NWs show a strong band-gap luminescence, whereas in the case of VS NWs, the defect luminescence is enhanced. Our results clarify, for the first time, the reason for the different roles of Au, that is, acting as surface defects or as a catalyst in VS and VLS growth modes, respectively. In addition, our results demonstrate the possibility of changing not only the growth mode and extending the growth region but also the NWs' crystal quality using ILs as an additional carbon source.

Fluorescence techniques dominate the field of live-cell microscopy, but bleaching and motion blur from too long integration times limit dynamic investigations of small objects. High contrast, label-free life-cell imaging of thousands of acquisitions at 160 nm resolution and 100 Hz is possible by Rotating Coherent Scattering (ROCS) microscopy, where intensity speckle patterns from all azimuthal illumination directions are added up within 10 ms. In combination with fluorescence, we demonstrate the performance of improved Total Internal Reflection (TIR)-ROCS with variable illumination including timescale decomposition and activity mapping at five different examples: millisecond reorganization of macrophage actin cortex structures, fast degranulation and pore opening in mast cells, nanotube dynamics between cardiomyocytes and fibroblasts, thermal noise driven binding behavior of virus-sized particles at cells, and, bacterial lectin dynamics at the cortex of lung cells. Using analysis methods we present here, we decipher how motion blur hides cellular structures and how slow structure motions cover decisive fast motions.

Living cells are highly dynamic systems responding to a large variety of biochemical and mechanical stimuli over minutes, which are well controlled by e.g. optical tweezers. However, live cell investigation through fluorescence microscopy is usually limited not only by the spatial and temporal imaging resolution but also by fluorophore bleaching. Therefore, we designed a miniature light-sheet illumination system that is implemented in a conventional inverted microscope equipped with optical tweezers and interferometric tracking to capture 3D images of living macrophages at reduced bleaching. The horizontal light-sheet is generated with a 0.12 mm small cantilevered mirror placed at 45° to the detection axis. The objective launched illumination beam is reflected by the micro-mirror and illuminates the sample perpendicular to the detection axis. Lateral and axial scanning of both Gaussian and Bessel beams, together with an electrically tunable lens for fast focusing, enables rapid 3D image capture without moving the sample or the objective lens. Using scanned Bessel beams and line-confocal detection, an average axial resolution of 0.8 µm together with a 10-15 fold improved image contrast is achieved.