Interfacial molecular regulation of TiO2 for enhanced and stable cocatalyst-free photocatalytic hydrogen production.

On the basis of the inherent property limitations of commercial P25-TiO2, many surface interface modification methods have attracted substantial attention for further improving the photocatalytic properties. However, current strategies for designing and modifying efficient photocatalysts (which exhibit complicated manufacturing processes and harsh conditions) are not efficient for production that is low cost, is nontoxic, and exhibits good stability; and therefore restrict practical applications. Herein, a facile and reliable method is reported for in situ amine-containing silane coupling agent functionalization of commercial P25-TiO2 by covalent surface modification for constructing a highly efficient photocatalyst. As a consequence, a high efficiency of H2 evolution was achieved for TiO2-SDA with 0.95 mmol h-1 g-1 (AQE ∼45.6 % at 365 nm) under solar light irradiation without a co-catalyst. The amination modification broadens the light absorption range of the photocatalyst, inhibits the binding of photogenerated carriers, and improves the photocatalytic efficiency; which was verified by photochemical properties and DFT theoretical calculations. This covalent modification method ensures the stability of the photocatalytic reaction. This work provides an approach for molecularly modified photocatalysts to improve photocatalytic performance by covalently modifying small molecules containing amine groups on the photocatalyst surface.

Diffusion-Freezing-Induced Microphase Separation for Constructing Large-Area Multiscale Structures on Hydrogel Surfaces.

Hydrogels with multiscale structured surface have attracted significant attention for their valuable applications in diverse areas. However, current strategies for the design and fabrication of structured hydrogel surfaces, which suffer from complicated manufacturing processes and specific material modeling, are not efficient to produce structured hydrogel surfaces in large area, and therefore restrict their practical applications. To address this problem, a general and reliable method is reported, which relies on the interplay between polymer chain diffusion and the subsequent freezing-induced gelation and microphase separation processes. The basic idea is systematically analyzed and further exploited to manufacture gel surfaces with gradient structures and patterns through the introduction of temperature gradient and shape control of the contact area. Moreover, the formed micro/nanostructured surfaces are exemplified to work as capillary systems and thus can uplift the liquid spontaneously indicating the potential application for anti-dehydration. It is believed that the proposed facile and large-area fabrication method can inspire the design of materials with various functionalized surfaces.

Conductive Hydrogels as Smart Materials for Flexible Electronic Devices.

Flexible conductive materials have gained considerable research interest in recent years because of their potential applications in flexible energy storage devices, sensors, touch panels, electronic skins, etc. With excellent flexibility, outstanding electric properties and tunable mechanical properties, conductive hydrogels as conductive materials offer plentiful insights and opportunities for flexible electronic devices. Numerous synthetic strategies have been developed to obtain various conductive hydrogels, and high-performance flexible electronic devices based on these conductive hydrogels have been realized. This review provides a comprehensive overview of conductive-hydrogel-based flexible electronics, ranging from conductive hydrogels synthesis to several important flexible devices applications, including touch panels, sensors and energy storage. Finally, we provide new future research directions and perspectives for conductive-hydrogel-based flexible and portable electronic devices.

General Strategy to Fabricate Highly Filled Microcomposite Hydrogels with High Mechanical Strength and Stiffness.

Conventional synthetic hydrogels are intrinsically soft and brittle, which severely limits the scope of their applications. A variety of approaches have been proposed to improve the mechanical strength of hydrogels. However, a facile and ubiquitous strategy to prepare hydrogels with high mechanical strength and stiffness is still a challenge. Here, we report a general strategy to prepare highly filled microcomposite hydrogels with high mechanical performance using an ultrasonic assisted strategy. The microparticles were dispersed in the polymer network evenly, resulting in homogeneous and closely packed structures. The as-prepared hydrogels with extraordinary mechanical performance can endure compressive stress up to 20 MPa (at 75% strain) and exhibit high stiffness (elastic modulus is around 18 MPa). By using our comprehensive strategy, different hydrogels can enhance their mechanical strength and stiffness by doping various microparticles, leading to a much wider variety of applications.

High-speed transport of liquid droplets in magnetic tubular microactuators.

Magnetic field-induced droplet actuation has attracted substantial research interest in recent years. However, current magnetic-controlled liquids depend primarily on magnetic particles added to a droplet, which serves as the actuator on an open surface. These liquids inevitably suffer from droplet splitting with the magnetic particles or disengaging with the magnet, possibly leading to sample contamination, which severely limits their transport speed and practical applications. Here, we report a simple and additive-free method to fabricate magnetic tubular microactuators for manipulating liquid droplets by magnetism-induced asymmetric deformation, which generates an adjustable capillary force to propel liquids. These magnetic tubular microactuators can drive various liquid droplets with controllable velocity and direction. A speed of 10 cm s-1 can be achieved, representing the highest speed of liquid motion driven by an external stimulus-induced capillary force in a closed tube found so far.

Anti-freezing, Conductive Self-healing Organohydrogels with Stable Strain-Sensitivity at Subzero Temperatures.

Conductive hydrogels are a class of stretchable conductive materials that are important for various applications. However, water-based conductive hydrogels inevitably lose elasticity and conductivity at subzero temperatures, which severely limits their applications at low temperatures. Herein we report anti-freezing conductive organohydrogels by using an H2 O/ethylene glycol binary solvent as dispersion medium. Owing to the freezing tolerance of the binary solvent, our organohydrogels exhibit stable flexibility and strain-sensitivity in the temperature range from -55.0 to 44.6 °C. Meanwhile, the solvent molecules could form hydrogen bonds with polyvinyl alcohol (PVA) chains and induce the crystallization of PVA, greatly improving the mechanical strength of the organohydrogels. Furthermore, the non-covalent crosslinks endow the conductive organohydrogels with intriguing remoldability and self-healing capability, which are important for practical applications.

Covalent tethering of photo-responsive superficial layers on hydrogel surfaces for photo-controlled release.

The diffusion and transport of substances between a hydrogel and its environment have received tremendous research interest, due to the wide range of applications of hydrogel materials in fields related to drug carriers and drug delivery vehicles. To date, much research has been done to tailor the diffusion and transport of substances through hydrogels, where most efforts were focused on tuning the 3D network properties of the hydrogel including loop size, hydrophobicity of building blocks and the stimuli-responsive properties of backbones. These conventional strategies, however, usually suffer from complicated fabrication procedures and result in a homogeneous increase in hydrophobicity of the hydrogel network, leading to low efficiency control over the diffusion of substances through the hydrogel. Herein, a facile strategy that can functionalize the surfaces of hydrogels, while keeping the interior network unchanged, was reported, and is realized by quaternization reaction confined to the hydrogel/oil interface. Owing to the introduction of the photo-responsive molecule IBSP as a modifier, the surface wettability of the resulting hydrogel can be controlled by light both in air and underwater environments. Consequently, the diffusion rate of a substance through this modified hydrogel can be regulated by light, which brings convenience to the controlled release of hydrogels and other hydrogel-related fields.

Poly(aryl ether) Dendrons with Monopyrrolotetrathiafulvalene Unit-Based Organogels exhibiting Gel-Induced Enhanced Emission (GIEE).

A series of poly(aryl ether) dendrons with a monopyrrolo-tetrathiafulvalene unit linked through an acyl hydrazone linkage were designed and synthesized as low molecular mass organogelators (LMOGs). Two of the dendrons could gelate the aromatic solvents and some solvent mixtures, but the others could not gel all solvents tested except for n-pentanol. A subtle change on the molecular structure produces a great influence on the gelation behavior. Note that the dendrons could form the stable gel in the DMSO/water mixture without thermal treatment and could also form the binary gel with fullerene (C60 ) in toluene. The formed gels undergo a reversible gel-sol phase transition upon exposure to external stimuli, such as temperature and chemical oxidation/reduction. A number of experiments (SEM, FTIR spectroscopy, (1) H NMR spectroscopy, and UV/Vis absorption spectroscopy, and XRD) revealed that these dendritic molecules self-assembled into elastically interpenetrating one-dimensional fibrillar aggregates and maintain rectangular molecular-packing mode in organogels. The hydrogen bonding, π-π, and donor-acceptor interactions were found to be the main driving forces for formation of the gels. Moreover, the gel system exhibited gel-induced enhanced emission (GIEE) property in the visible region in spite of the absence of a conventional fluorophore unit and the fluorescence was effectively quenched by introduction of C60 .