NiS Nanosheets Decorated on Hollow Carbon Spheres from Liquefied Wood for Supercapacitors.

Carbon-based supercapacitors with high performance have a wide foreground among various energy storage devices. In this work, wood-based hollow carbon spheres (WHCS) were prepared from liquefied wood through the processes of emulsification, curing, carbonization, and activation. Then, the hydrodeposition method was used to introduce nickel sulfide (NiS) to the surface of the microspheres, obtaining NiS/WHCS as the supercapacitor electrode. The results show that NiS/WHCS microspheres exhibited a core-shell structure and flower-like morphology with a specific surface (307.55 m2 g-1) and a large total pore volume (0.14 cm3 g-1). Also, the capacitance could be up to 1533.6 F g-1 at a current density of 1 A g-1. In addition, after 1000 charge/discharge cycles, the specific capacitance remained at 72.8% at the initial current density of 5 A g-1. Hence, NiS/WHCS with excellent durability and high specific capacitance is a potential candidate for electrode materials.

Vacancy-Modified Porous g-C3N4 Nanosheets Controlled by Physical Activation for Highly Efficient Visible-Light-Driven Hydrogen Evolution and Organics Degradation.

As a promising photocatalyst material, g-C3N4 has great application potential in energy production and environmental improvement. In this work, surface-modified g-C3N4 nanosheets with excellent stability and high photocatalytic activity were successfully synthesized by physical steam activation. The charge transfer rate of carbon nitride was improved due to the synergistic effect of nitrogen defect and oxygen doping caused by steam activation. Meanwhile, the specific surface area and pore volume of the optimized sample reached 124.3 m2 g-1 and 0.42 cm3 g-1, respectively, which increased the exposed reaction sites of reactants, enhancing the photocatalytic activity of g-C3N4. In addition, this novel g-C3N4 displayed a great H2 evolution rate of 5889.39 µmol h-1 g-1 with a methylene blue degradation rate up to 6.52 × 10-3 min-1, which was 3.7 and 2.1 times of original g-C3N4, respectively. This study provided a simple and economical method to develop a highly efficient g-C3N4 photocatalyst for solar energy conversion.

Titanium Carbide MXene Quantum Dots-Modified Hydroxyapatite Hollow Microspheres as pH/Near-Infrared Dual-Response Drug Carriers.

Titanium carbide MXene quantum dots (MQDs) possess intrinsic regulatory properties and selective toxicity to cancer cells. Here, MDQs were selected for the modification of hydroxyapatite (HA) microspheres, and MXene quantum dots-modified hydroxyapatite (MQDs-HA) hollow microspheres with controllable shapes and sizes were prepared as bone drug carriers. The results show that the prepared MQDs-HA hollow microspheres had a large BET surface area (231.2 m2/g), good fluorescence, and low toxicity. In addition, MQDs-HA showed a mild storage-release behavior and good responsiveness of pH and near-infrared (NIR). Thus, the MQDs-HA hollow microspheres have broad application prospects in the field of drug delivery and photothermal therapy.

CaCO3 Crystals with Unique Morphologies Controlled by the Hydrogen-Bonded Supramolecular Assemblies of Ureido-Pyrimidinone-Amino Acid Derivatives.

Biomineral materials such as nacre of shells exhibit high mechanical strength and toughness on account of their unique "brick-mortar" multilayer structure. 2-Ureido-4[1H]-pyrimidinone (UPy) derivatives with different types of end groups, due to the self-complementary quadruple hydrogen bonds and abundant Ca2+ binding sites, can easily self-assemble into supramolecular aggregates and act as templates and skeleton in the process of inducing mineral crystallization. In this work, UPy derivatives were used as templates to induce the mineralization and growth of CaCO3 through a CO2 diffusion method. The morphology of CaCO3 crystals was modulated and analyzed by adjusting the synthesizing parameters including Ca2+ concentration, pH, and end groups. The results showed that, by the regulatory role of the mineralization template, it was easier to realize the multilayer crystal structure at a lower concentration of Ca2+ (less than 0.01 mol L-1). Under alkaline regulation, the quadruple hydrogen bonds would be destroyed, and the template's regulation effect on the morphology of CaCO3 crystals would be weakened. Moreover, by comparing different types of end groups, it was proven that the UPy derivatives with carboxylic acid groups (-COOH) played a crucial role in the process of CaCO3 crystallization with unique morphologies.

Ag-thiolate interactions to enable an ultrasensitive and stretchable MXene strain sensor with high temporospatial resolution.

High-sensitivity strain sensing elements with a wide strain range, fast response, high stability, and small sensing areas are desirable for constructing strain sensor arrays with high temporospatial resolution. However, current strain sensors rely on crack-based conductive materials having an inherent tradeoff between their sensing area and performance. Here, we present a molecular-level crack modulation strategy in which we use layer-by-layer assembly to introduce strong, dynamic, and reversible coordination bonds in an MXene and silver nanowire-matrixed conductive film. We use this approach to fabricate a crack-based stretchable strain sensor with a very small sensing area (0.25 mm2). It also exhibits an ultrawide working strain range (0.001-37%), high sensitivity (gauge factor ~500 at 0.001% and >150,000 at 35%), fast response time, low hysteresis, and excellent long-term stability. Based on this high-performance sensing element and facile assembly process, a stretchable strain sensor array with a device density of 100 sensors per cm2 is realized. We demonstrate the practical use of the high-density strain sensor array as a multichannel pulse sensing system for monitoring pulses in terms of their spatiotemporal resolution.