Scientific publications

Gallium hydride stabilized by the base quinonuclidine reacts with acetone under addition of the Ga-H function to the carbon–oxygen double bond yielding (HGa)5(OiPr)8O (1) as isolable compound. (HGa)5(OiPr)8O may be formally split in to four entities of HGa(OiPr)2 and one entity HGaO. The inner atomic skeleton of 1 is a novel Ga5O9 heterocluster with gallium atoms occupying the corners of a distorted trigonal bi-pyramid, an oxygen atom in the center and the remaining alcoholate oxygen atoms bridging eight of the nine edges of the bi-pyramid (X-ray diffraction analysis). Potassium indium alkoxide KIn(OtBu)4 has been used to synthesize several new compounds like In4(OtBu)8(C5H4)2 (2), (py)2CuIn(OtBu)4 (3), and [CuIn(OtBu)4]2 (4) by reaction with TiCl2cp2 (2) and CuCl (3, 4). All compounds were characterized by spectroscopic means and by X-ray structure analyses revealing novel polycyclic structures.

Hydrogels are normally isotropic and weak, in contrast to their natural analogs that possess hierarchically oriented structure and excellent mechanical properties. Inspired by the unique structure of natural materials, we develop an approach for preparing highly anisotropic hydrogels with programmable oriented polymer structure and extraordinary mechanical properties. Our method is based on a novel welding technique for stretched cellulose hydrogel films, in which interfacial reconfiguration occurs, allowing full integration without compromising the highly aligned polymer orientation. We demonstrate the versatility of this method by fabricating four types of anisotropic tough multilayer hydrogels with differently oriented hierarchies: parallel lamination (‖), orthogonal lamination (⊥), axial rolling, and concentric rolling. These high-water-content hydrogels (∼68 wt%) exhibit extremely high anisotropy (birefringence ≥0.006, the highest reported for hydrogels) and superior mechanical properties (Young's modulus of ∼140 MPa, tensile strength of ∼47 MPa, and work of extension of ∼20 MJ m−3). Moreover, these hydrogels also show interesting anisotropic electrical conductivity and asymmetric shape deformation. Because this method is easy to apply and offers flexibility in designing complex hierarchical hydrogel structures, our work opens a new window to designing novel hydrogel materials for engineering and biomedical applications.

The mechanical properties (e.g., modulus and strength) of conventional tough hydrogels are considerably inferior to those required for practical load-bearing applications. However, developing hydrogels with a combination of superior mechanical properties such as stiffness, strength, and toughness is very challenging. Herein, we propose a new design strategy based on the synergistic effect of hydrophobic/hydrophilic components to fabricate novel hydrogels with superior mechanical properties. Both hydrophobic and hydrophilic monomers were integrated into hydrogels using a simple two-step fabrication process, which led to the formation of a randomly distributed interconnected 3D structure of hard-phase and soft-phase regions comprising hydrophobic-rich and hydrophilic-rich components, respectively. The 3D structure of hard-phase regions imparted exceptional stiffness and strength, whereas soft-phase regions provided sacrificial bonds to achieve stretchability and toughness. Different hydrophobic monomers with widely variable extents of hydrophobicity were used. The obtained results indicated that hydrogels based on benzene-containing hydrophobic monomers and exhibiting a higher-than-ambient glass transition temperature can show superior mechanical properties. Highly water-stable physical hydrogels with water contents of 50–60 wt.% and exceptionally high Young’s modulus (150–280 MPa), tensile strength (7–17 MPa), and fracture energy (6680–7450 J/m2) were developed; these values are far superior to those of single-component hydrogels and tough hydrogels reported to date. This combination of superior properties, reported here for the first time, is expected to significantly broaden the application of hydrogels. The proposed strategy is quite general and offers further opportunities to develop diverse ultra-stiff, strong, and tough functional hydrogels using suitable monomer combinations.

The handling of droplets in a controlled manner is essential to numerous technological and scientific applications. In this work, we present a new open-surface platform for droplet manipulation based on an array of bendable nozzles that are dynamically controlled by a magnetic field. The actuation of these nozzles is possible thanks to the magnetically responsive elastomeric composite which forms the tips of the nozzles; this is fabricated with Fe3O4 microparticles embedded in a polydimethylsiloxane matrix. The transport, mixing, and splitting of droplets can be controlled by bringing together and separating the tips of these nozzles under the action of a magnet. Additionally, the characteristic configuration for droplet mixing in this platform harnesses the kinetic energy from the feeding streams; this provided a remarkable reduction of 80% in the mixing time between drops of liquids about eight times more viscous than water, i.e., 6.5 mPa/s, when compared against the mixing between sessile drops of the same fluids

Conductive hydrogels are attracting increasing attention owing to their great potential for applications in flexible devices. For practical use, these high-water-content materials should not only show good conductivity but also be strong, stretchable, tough, and elastic. Herein, we describe a class of novel conductive tough hydrogels based on strong staggered Fe3+-carboxyl coordinating interactions. They are made from copolymers of acrylamide and N-acryloyl glutamic acid, a bidentate-based comonomer. The design of the staggered structure of Fe3+ and bidentate units is expected to enable energy dissipation and also results in a synergetic effect of two binding sites for fast self-recovery. We demonstrate that the equilibrated hydrogels with a water content of 53 wt % exhibit superior mechanical properties (e.g., highest tensile strength, 12.1 MPa; Young’s modulus, 36.1 MPa; work of extension, 42.1 MJ m–3; fracture energy, 10,691 J m–2; compressive strength, 65.1 MPa at 98% strain without a macroscopic fracture) compared to the ion-coordinated hydrogels reported to date, including elasticity at small strain, fast self-recoverability at room temperature (∼25 °C), a high dielectric constant (k = 341–1395 at 100 kHz), and good electrical conductivity (0.0018–0.024 S cm–1). Given their extraordinary overall characteristics, we envision their potential applications in flexible electronic devices.

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.