Publikationen

The development of simple and effective tools for selective ratiometric detection of hypochlorite (ClO−) is one of the most important goals for elucidating the biofunction of ClO− in associated diseases. However, most developmental probes suffer from the notorious aggregation-caused quenching (ACQ) effect that greatly limits their applications. Herein, we report on novel aggregation-induced emission dots (AIED) for ratiometric detection of ClO− via a co-precipitation strategy. The AIED nanoprobe displayed a ratiometric signal output, which was more promising to minimize the bad environmental factors and simultaneously avoided the ACQ effect. Notably, amphiphilic block copolymer endowed the nanoprobe with stable water dispersibility and easy modification. The as-prepared AIED probe exhibited high sensitivity (~ 89 nM), high selectivity, outstanding photostability, and prominent long-term fluorescence stability. Furthermore, the as-prepared AIED was applied for the visualized fluorescence detection of ClO− and further utilized to detect ClO− in real samples. We expect the nanoprobe to be an outstanding tool to understand ClO−-associated diseases.

Selective crystallization represents one of the most economical and convenient methods to provide large-scale optically pure chiral compounds. Although significant development has been achieved since Pasteur’s separation of sodium ammonium tartrate in 1848, this method is still fundamentally low efficient (low transformation ratio or high labor). Herein, we describe an enantiomer-selective-magnetization strategy for quantitatively separating the crystals of conglomerates by using a kind of magnetic nano-splitters. These nano-splitters would be selectively wrapped into the S-crystals, leading to the formation of the crystals with different physical properties from that of R-crystals. As a result of efficient separation under magnetic field, high purity chiral compounds (99.2 ee% for R-crystals, 95.0 ee% for S-crystals) can be obtained in a simple one-step crystallization process with a high separation yield (95.1%). Moreover, the nano-splitters show expandability and excellent recyclability. We foresee their great potential in developing chiral separation methods used on different scales.

Abstract Controllable stabilization of liquids on interfaces is emerging as a novel method to mediate surface properties. Here, the fast, stimuli-responsive liquid release from dynamic polymer coatings is described to mediate surface slipperiness and optical performance. These polymer coatings consist of a slippery liquid-locked rough surface and a liquid-supplied bottom layer storing the liquid in embedded droplets. They are prepared by a simple one-pot casting of a solution of cross-linkable polymer and silicone oil in tetrahydrofuran. It is demonstrated that upon mechano-, solvent-, or thermo-stimulation, the liquid stored in the bottom layer is released altering both surface slipperiness and optical properties of the coatings.

The break-up of a nanowire with an organic ligand shell into discrete droplets is analysed in terms of the Rayleigh-Plateau instability. Explicit account is taken of the effect of the organic ligand shell upon the energetics and kinetics of surface diffusion in the wire. Both an initial perturbation analysis and a full numerical analysis of the evolution in wire morphology are conducted, and the governing non-dimensional groups are identified. The perturbation analysis is remarkably accurate in obtaining the main features of the instability, including the pinch-off time and the resulting diameter of the droplets. It is conjectured that the surface energy of the wire and surrounding organic shell depends upon both the mean and deviatoric invariants of the curvature tensor. Such a behaviour allows for the possibility of a stable nanowire such that the Rayleigh-Plateau instability is not energetically favourable. A stability map illustrates this. Maps are also constructed for the final droplet size and pinch-off time as a function of two non-dimensional groups that characterise the energetics and kinetics of diffusion in the presence of the organic shell. These maps can guide future experimental activity on the stabilisation of nanowires by organic ligand shells.

We studied the concentration-dependent agglomeration of apolar nanoparticles in different solvents. Octanethiol-stabilized gold nanoparticles (AuNPs) in evaporating liquid droplets were observed in situ using small-angle X-ray scattering. Concurrent analysis of liquid volume and particle agglomeration provided time-dependent absolute concentrations of free and agglomerated particles. All dispersions underwent an initial stage where the particle concentration increased but no agglomerates formed. Subsequently, agglomeration started at concentrations that varied by several orders of magnitude for different solvents. While agglomerates grew, the concentration of the dispersed particles remained at a constant “colloidal solubility” in most solvents. We consistently found that the colloidal stability of AuNPs decreased as cyclohexane > heptane > nonane > decane > toluene and suggest that details of the molecular interactions between solvent and ligand shell set this order.

Surfaces with surface-bound ligand molecules generally attract each other when immersed in poor solvents but repel each other in good solvents. While this common wisdom holds, for example, for oleylamine-ligated ultrathin nanowires in the poor solvent ethanol, the same nanowires were recently observed experimentally to bundle even when immersed in the good solvent n-hexane. To elucidate the respective binding mechanisms, we simulate both systems using molecular dynamics. In the case of ethanol, the solvent is completely depleted at the interface between two ligand shells so that their binding occurs, as expected, via direct interactions between ligands. In the case of n-hexane, ligands attached to different nanowires do not touch. The binding occurs because solvent molecules penetrating the shells preferentially orient their backbone normal to the wire, whereby they lose entropy. This entropy does not have to be summoned a second time when the molecules penetrate another nanowire. For the mechanism to be effective, the ligand density appears to best be intermediate, that is, small enough to allow solvent molecules to penetrate, but not so small that ligands do not possess a clear preferred orientation at the interface to the solvent. At the same time, solvent molecules may be neither too large nor too small for similar reasons. Experiments complementing the simulations confirm the predicted trends.

We introduce a new method for the characterization of particles extracted from steels. Microalloyed steels were dissolved to extract niobium and titanium carbonitride particles, which are of critical importance for the mechanical properties of the steel. The size distribution and chemical composition of the particles were analyzed by single-particle inductively coupled plasma mass spectrometry and compared to results from electron microscopy. Mass spectrometry rapidly provided data on a large number of particles (>2000 in 1 min) and indicated two particle populations that differed in size and composition: smaller particles contained only niobium, whereas larger particles contained both niobium and titanium. Electron microscopy of a much smaller number of particles confirmed the results and indicated that the larger particles had complex, overgrown structures. The combination of single-particle mass spectrometry and electron microscopy enables a better understanding of the precipitation processes that form the particles during steel production at different stages of the thermomechanical-rolling process. A better understanding of the processes helps to improve the rolling process in order to exploit the alloying elements optimally.

The chemical extraction of niobium and titanium carbonitride precipitates from microalloyed steels was studied. Steel samples and chemically synthesized reference nanoparticles were subjected to commonly used extraction protocols, and conditions were systematically varied. High acid concentrations led to particle etching with losses above 10%; long extraction times and small etchant volumes led to the formation of dense SiOx networks that engulfed the extracted particles. The addition of surfactants was found to reduce agglomeration and limit etching. We developed an optimized extraction protocol that can extract and retain particles with diameters below 10 nm with reduced etching and negligible network formation. The resulting particle dispersions are suitable both for efficient electron microscopy of large particle numbers in a single run and colloidal analysis of large numbers of particles in dispersion.

The change from organic solvents to aqueous solvents for safe and robust battery electrolytes is desirable for electrochemical energy storage. Thermodynamically, water has an electrochemical stability window of 1.23 V, and pure water freezes at 0 °C. Such properties clearly restrict the high-voltage applications and temperature adaptability of aqueous electrolytes. Herein, we report an aqueous supporting electrolyte containing imidazolium chloride, showing unprecedented large temperature and electrochemical windows. Thermal analysis over −80 to 80 °C shows such an aqueous electrolyte to be free of transition events of icing and phase changes. X-ray scattering results of these aqueous solutions in the presence of active materials reveal the pivotal role of imidazolium chloride to preserve the liquid phase at rather low temperatures. Metal phthalocyanines with electroactive organic ligand rings and multi-electron-transfer reactions at low negative potentials (−0.2 to −1.6 V vs Ag) are demonstrated in water-based anolytes for redox flow batteries for the first time over a broad temperature range.

Soft robotic systems are increasingly emerging as robust alternatives to conventional robotics. Here, we demonstrate the development of programmable soft actuators based on volume expansion/retraction accompanying liquid–vapor phase transition of a phase-change material confined within an elastomer matrix. The combination of a soft matrix (a silicone-based elastomer) and an embedded ethanol-impregnated polyacrylonitrile nanofiber (PAN NF) mat makes it possible to form a sealed compound device that can be operated by changing the actuator temperature above/below the boiling point of ethanol. The thermo-responsive actuators based on this principle demonstrate excellent bending ability at a sufficiently high temperature (>90 °C) – comparable with compressed air-based soft actuators. The actuator using the mechanism presented here is easy to manufacture and automate and is recyclable. Finally, the actuation mechanism can be incorporated into a wide variety of shapes and configurations, making it possible to obtain tunable and programmable soft robots that could have a wide variety of industrial applications. ER