Excitation Polarization Sensitivity of Plasmon-Mediated Silver Nanotriangle Growth on a Surface

In this contribution, we report an effective and relatively simple route to grow triangular flat-top silver nanoparticles (NPs) directly on a solid substrate from smaller NPs through a wet photochemical synthesis. The method consists of fixing small, preformed nanotriangles (NTs) on a substrate and subsequently irradiating them with light in a silver seed solution. Furthermore, the use of linearly polarized light allows for exerting control on the growth direction of the silver nanotriangles on the substrate. Evidence for the role of surface plasmon resonances in governing the growth of the NTs is obtained by employing linear polarized light. Thus, this study demonstrates that light-induced, directional synthesis of nanoparticles on solid substrates is in reach, which is of utmost importance for plasmonic applications

Super-resolution Localization and Defocused Fluorescence Microscopy on Resonantly Coupled Single-Molecule, Single-Nanorod Hybrids

Optical antennas made of metallic nanostructures dramatically enhance single-molecule fluorescence to boost the detection sensitivity. Moreover, emission properties detected at the optical far field are dictated by the antenna. Here we study the emission from molecule–antenna hybrids by means of super-resolution localization and defocused imaging. Whereas gold nanorods make single-crystal violet molecules in the tip’s vicinity visible in fluorescence, super-resolution localization on the enhanced molecular fluorescence reveals geometrical centers of the nanorod antenna instead. Furthermore, emission angular distributions of dyes linked to the nanorod surface resemble that of nanorods in defocused imaging. The experimental observations are consistent with numerical calculations using the finite-difference time-domain method

Shear-Stress-Induced Conformational Changes of von Willebrand Factor in a Water–Glycerol Mixture Observed with Single Molecule Microscopy

The von Willebrand factor (VWF) is a human plasma protein that plays a key role in the initiation of the formation of thrombi under high shear stress in both normal and pathological situations. It is believed that VWF undergoes a conformational transition from a compacted, globular to an extended form at high shear stress. In this paper, we develop and employ an approach to visualize the large-scale conformation of VWF in a (pressure-driven) Poiseuille flow of water–glycerol buffers with wide-field single molecule fluorescence microscopy as a function of shear stress. Comparison of the imaging results for VWF with the results of a control with λ-phage double-stranded DNA shows that the detection of individual VWF multimers in flow is feasible. A small fraction of VWF multimers are observed as visibly extended along one axis up to lengths of 2.0 μm at high applied shear stresses. The size of this fraction of molecules seems to exhibit an apparent dependency on shear stress. We further demonstrate that the obtained results are independent of the charge of the fluorophore used to label VWF. The obtained results support the hypothesis of the conformational extension of VWF in shear flow

Effets de l'ordonnance d'expropriation sur les baux ruraux

Important cellular events such as division require drastic changes in the shape of the membrane. These remodeling processes can be triggered by the binding of specific proteins or by changes in membrane composition and are linked to phospholipid metabolism for which dedicated enzymes, named phospholipases, are responsible. Here wide-field fluorescence microscopy is used to visualize shape changes induced by the action of phospholipase A1 on dye-labeled supported membranes of POPC (1-palmitoyl-2-oleoly-<i>sn</i>-glycero-3-phosphocholine). Time-lapse imaging demonstrates that layers either shrink and disappear or fold and collapse into vesicles. These vesicles can undergo further transformations such as budding, tubulation, and pearling within 5 min of formation. Using dye-labeled phospholipases, we can monitor the presence of the enzyme at specific positions on the membrane as the shape transformations occur. Furthermore, incorporating the products of hydrolysis into POPC membranes is shown to induce transformations similar to those observed for enzyme action. The results suggest that phospholipase-mediated hydrolysis plays an important role in membrane transformations by altering the membrane composition, and a model is proposed for membrane curvature based on the presence and shape of hydrolysis products

Accelerating the Phase Separation in Aqueous Poly(<i>N</i>‑isopropylacrylamide) Solutions by Slight Modification of the Polymer Stereoregularity: A Single Molecule Fluorescence Study

We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model

Field-Controlled Charge Separation in a Conductive Matrix at the Single-Molecule Level: Toward Controlling Single-Molecule Fluorescence Intermittency

The fluorescence intermittency or “blinking” of single molecules of ATTO647N (ATTO) in the conductive matrix polyvinylcarbazole (PVK) is described in the presence of an external applied electric field. It is shown that due to the energy distribution of the highest occupied molecular orbital (HOMO) level of PVK, which is energetically close to the HOMO of ATTO, sporadic electron transfer occurs. As a result, the on/off dynamics of blinking can be influenced by the electric field. This field will, depending on the respective position and orientation of the dye/polymer system with respect to those of the electrodes, either enhance or suppress electron transfer from PVK to ATTO as well as the back electron transfer from reduced ATTO to PVK. After the charge-transfer step, the applied field will pull the hole in PVK away from the dye, increasing the overall time the dye resides in a dark state

Accelerating the Phase Separation in Aqueous Poly(<i>N</i>‑isopropylacrylamide) Solutions by Slight Modification of the Polymer Stereoregularity: A Single Molecule Fluorescence Study

We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model

Accelerating the Phase Separation in Aqueous Poly(<i>N</i>‑isopropylacrylamide) Solutions by Slight Modification of the Polymer Stereoregularity: A Single Molecule Fluorescence Study

We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model

Accelerating the Phase Separation in Aqueous Poly(<i>N</i>‑isopropylacrylamide) Solutions by Slight Modification of the Polymer Stereoregularity: A Single Molecule Fluorescence Study

We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model

Accelerating the Phase Separation in Aqueous Poly(<i>N</i>‑isopropylacrylamide) Solutions by Slight Modification of the Polymer Stereoregularity: A Single Molecule Fluorescence Study

We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model