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BiVO4 is one of the promising photoanodes for water oxidation, while its efficiency is much lower than the theoretical value because of the rapid recombination rate and low activity for the oxygen evolution reaction (OER). Herein, a BiVO4/Au/NiFeOOH sandwich structure is constructed for enhanced PEC water oxidation. In comparison with BiVO4/NiFeOOH, the incorporation of Au nanoparticles (NPs) can further enhance the PEC performance toward water oxidation. The BiVO4/Au/NiFeOOH photoanode exhibits a photocurrent density of 5.3 mA cm−2 at 1.23 V, which is 3.47 times that of BiVO4. Systematic experimental and theoretical studies indicate that Au NPs enhance the PEC water oxidation through the generation of hot holes through an interband transition, improving the photocarrier separation, and enhancing the water oxidation activity of NiFeOOH. This work not only provides a new way for the fabrication of highly efficient photoanodes for water oxidation, but also deepens the understanding of the role of Au NPs in promoting PEC water splitting. [ABSTRACT FROM AUTHOR]

The rapid development of electronic devices requires high power storage batteries. However, reported 3D carbon-based materials are semiconductors or metals and are used in Li- or Na-ion batteries with low capacities. Thus, it is of interest to discover whether there is a universal semi-metallic material for use in high performance Li-, Na-, and K-ion batteries. Inspired by the recent synthesis of 3D carbon-based materials, in the research reported here, a 3D regular porous structure (bct-C56) is designed using graphene sheets. The porous carbon-based material has mechanical, dynamic, thermal, and mechanical stabilities. Interestingly, bct-C56 exhibits semi-metallic features with two Dirac nodal surfaces with mirror symmetry, as well as high Fermi velocities, indicating high electron-transport abilities. More excitingly, its theoretical capacities are 743.8, 478.2, and 425.0 mA h g−1, with diffusion barriers of 0.05–0.12, 0.07–0.12, and 0.03–0.05 eV, average OCVs of 0.31, 0.45, and 0.59 V, and volume expansion levels of 1.2%, 0.02%, and 3.1%, in Li-, Na-, and K-ion batteries, respectively. All these excellent characteristics suggest that semi-metallic bct-C56 is a universal anode material for use in metal-ion batteries with a fast charge–discharge rate. In this research, not only was a new material with a Dirac nodal surface feature designed, but it also offers an approach for the creation of high performance and universal metal-ion battery anodes with 3D porous carbon materials. [ABSTRACT FROM AUTHOR]

A superhydrophobic copper foam (CF) with excellent robustness and durability was successfully fabricated by using an in situ growth method combined with surface hexadecanethiol (HDT) modification of HKUST-1/CF. The wettability mechanism for the conversion of the superhydrophilic to superhydrophobic states was clarified and explored via density functional theory (DFT). The as-prepared HKUST-1/HDT/CF surface possessed good superhydrophobicity under the optimal conditions including the mass ratio of copper nitrate trihydrate (Cu(NO3)2·3H2O) to 1,3,5-benzenetricarboxylicacid (H3BTC), HDT immersion time, in situ growth time and hydrothermal reaction temperature. The superhydrophobic surface can maintain a desirable hydrophobic state after immersing in different pH solutions, abrasion of weight, and continuous ultrasonic testing. The highest water contact angle (WCA) value of the obtained samples was 162.9° under the aforementioned harsh conditions. Additionally, the superhydrophobic CF has a bright future in the field of oil/water separation due to the obtained HKUST-1/HDT/CF surface with excellent water-repellent performance. [ABSTRACT FROM AUTHOR]

Lysosome visualization is very important for accurate diagnosis of human diseases. However, currently developed lysosome imaging probes usually have poor specificity and are easily quenched, leading to a low signal to noise ratio in lysosome labeling. To resolve this problem, herein, metal–organic framework-based probes of copper–terephthalic acid (CuBDC) are investigated, which show sensitivity to pH and hydrogen peroxide (H2O2), simultaneously. By self-assembling under the template effect of soluble starch, the particle size of CuBDC can be well controlled for entering into cells and locating lysosomes. Based on the Fenton-like reaction, CuBDC can catalyze the decomposition of H2O2 into ˙OH, which in turn reacts with CuBDC to generate a stable fluorescent substance. Meanwhile, Cu2+ can be released from CuBDC under acidic conditions for reacting with H2O2 more thoroughly. And the synthesized CuBDC has a similar attraction to the electrophilic ˙OH at different pH values owing to the residual soluble starch in the particles. The above properties cause CuBDC to have a stable fluorescence signal with low pH values and high H2O2 concentration, simultaneously. The fluorescence imaging experiments in HeLa cells demonstrate that CuBDC acting as a pH/H2O2 responsive fluorescent probe holds great promise for lysosome-specific imaging. [ABSTRACT FROM AUTHOR]

Silicon-based two-dimensional (2D) materials have unique properties and extraordinary engineering applications. However, penta-silicene is unstable. Herein, by employing first-principles calculations, we provide a facile surface chemistry method, i.e. functionalization, to acquire and reconfigure stable penta-silicene for use in flexible lithium-ion batteries. Our results of density functional theory calculations showed that the reconfigured penta-silicene nanosheets possess a broad range of properties, including semiconductors with an indirect bandgap, semiconductors with a direct bandgap, semimetals and metals. For fluorinated penta-silicene, a fluorine-concentration-induced transition from a semiconductor to a metal is found. For fully fluorinated penta-silicene, a mechanically induced transition from a semiconductor with an indirect bandgap to a semiconductor with a direct bandgap is obtained. Our calculation results showed the reconfigured penta-silicene is a high-performance anode for use in flexible lithium (Li)-ion batteries. A transition from a semiconductor to a metal with adsorption of Li atoms indicates a high electrical conductivity. It possesses low Li diffusion barriers (0.08–0.28 eV), demonstrating a high mobility of Li ions. The metallic feature and low Li diffusion barriers reveal that it has an ultrafast charge/discharge rate. This work suggests that surface chemistry reconfiguration provides new stable materials with excellent mechanical properties and tunable electronic properties for their promising applications in flexible metal-ion batteries and solar batteries as well as nanoelectronics devices. [ABSTRACT FROM AUTHOR]

Auxetic materials have numerous promising engineering applications such as fracture resistance and energy storage due to their negative Poisson's ratios (NPRs). However, compared to materials possessing positive Poisson's ratios (PPRs), auxetic materials are rare. In this paper, by employing first principles calculations, we found a high NPR two-dimensional (2D) material, tungsten carbide (W2C), in the transition metal carbides (MXenes). Our results of the relatively moderate Young's modulus and fracture strength as well as the critical strain showed that the 2D monolayer W2C is an extraordinary flexible material. Our DFT results also demonstrated that W2C possesses high NPRs while Hf2C and Ta2C have PPRs. Furthermore, the mechanically induced deformation mechanism and the NPR formation mechanism of W2C have been proposed. Such an intrinsic NPR in W2C is attributed to the strong coupling between the C-p and W-d orbitals in the pyramid structural unit. The mechanically induced deformation mechanism and the PPR formation mechanism of Hf2C have also been determined. The intrinsic NPR for W2C transforms to PPR upon the surface functionalization induced. The behavior occurs due to the W–C interaction weakening. The excellent NPR in the 2D MXene material combined with other outstanding properties such as the metallic state would bring about its promising engineering prospects, ranging from the metal-ion battery, to automobiles and aircraft. [ABSTRACT FROM AUTHOR]

A novel graphitized porous carbon nanosphere (GPCNS) material obtained by a convenient simultaneous activation and graphitization route, which was realized by heating resorcinol–formaldehyde (RF) resin nanospheres immersed with ZnCl2 and FeCl3 in an inert atmosphere, has been reported. A high graphitization level was achieved through the catalytic graphitization by reduced Fe metal, and the hierarchically micro/mesoporous structure was produced in a controlled fashion by tuning the mass ratio of the activating agent ZnCl2 and a carbon precursor. An optimal sample of GPCNS-2 was prepared with a FeCl3/ZnCl2/RF mass ratio of 0.5 : 2 : 1, exhibiting a highly graphitized framework and uniform spherical morphology with an average diameter of ∼500 nm, as well as well-interconnected micro/mesoporous structure with a large surface area of 1664.8 m2 g−1. Acting as an electrode material for a supercapacitor application in 6 M KOH electrolyte, GPCNS-2 displayed excellent electrochemical performance with a high specific capacitance of 402.5 F g−1 at a current density of 1 A g−1. Moreover, an electrochemical impedance spectroscopy test demonstrated that the low internal electrical resistance of GPCNS-2 contributed a superior rate capability of above 75% retention rate even at 50 A g−1. Furthermore, the GPCNS-2 electrode possessed an outstanding cycling stability, and about 96% of its initial specific capacitance at 5 A g−1 was maintained after 5000 cycles. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) represent an important class of luminescent quantum dots owing to their low toxicity and superior biocompatibility. Chemical functionalization of GQDs and subsequent combination with other materials further provide attractive techniques for advanced bioapplications. Herein, we report the facile fabrication of fluorescent organosilane-functionalized graphene quantum dots (Si-GQDs) and their embedding into mesoporous hollow silica spheres as a biolabel for the first time. Well-proportioned Si-GQDs with bright and excitation dependent tunable emissions in the visible region were obtained via a simple and economical solvothermal route adopting graphite oxide as a carbon source and 3-(2-aminoethylamino)-propyltrimethoxysilane as a surface modifier. The as-synthesized Si-GQDs can be well dispersed and stored in organic solvents, easily manufactured into transparent film and bulk form, and particularly provide great potential to be combined with other materials. As a proof-of-principle experiment, we demonstrate the successful incorporation of Si-GQDs into hollow mesoporous silica spheres and conduct preliminary cellular imaging experiments. Interestingly, the Si-GQDs not only serve as fluorescent chromophores in the composite material, but also play a crucial role in the formation of mesoporous hollow silica spheres with a distinctive bi-layer architecture. The layer thickness and optical properties can be precisely controlled by simply adjusting the silane coupling agent addition procedure in the preparation process. Our demonstration of low-cost Si-GQDs and their encapsulation into multifunctional composites may expand the applications of carbon-based nanomaterials for future biomedical imaging and other optoelectronic applications. [ABSTRACT FROM AUTHOR]

Large micropore surface area, superior electrical conductivity and suitable pore size are simultaneously desired characteristics for high-performance capacitive carbons. However, these desired features tend to be mutually competing, and are generally difficult to integrate into a single carbon. Considering this challenge, we developed a sustainable, less time-demanding, pollution-free strategy to construct highly graphitized porous carbon (GPC) by one-step heat-treatment. This approach achieves the need of the abovementioned characteristics for capacitive carbons, wherein potassium ferrate works as both an activating agent and graphitization catalyst to achieve synchronous hierarchical porosity and graphitization of wasted natural wood, and the resultant carbon materials possess a large micropore surface area of 870.4 m 2 g -1 , a highly graphitic carbon skeleton and a well-interconnected micro-meso-macropore structure. The assembled GPC-based symmetrical capacitors exhibited a satisfactory capacitive performance in different aqueous electrolytes (H 2 SO 4 , KOH and Na 2 SO 4 ), including high specific capacitance, prominent rate capability, satisfactory energy density and good cycle stability. Meanwhile, we compared the contributions of porosity and the graphitized structure to capacitive performance, and porosity was dominant in determining capacitance and the graphitized skeleton had a positive effect in enhancing the capacitive performance. In addition, we established the relationship between the structure of GPC and electrochemical capacitive performance in different aqueous electrolytes, providing a valuable reference for GPC-based supercapacitors in different practical applications. More importantly, this strategy holds great promise to sustainably convert biowaste to high-added-value capacitive carbons for advanced energy storage applications in the future., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Lysosome visualization is very important for accurate diagnosis of human diseases. However, currently developed lysosome imaging probes usually have poor specificity and are easily quenched, leading to a low signal to noise ratio in lysosome labeling. To resolve this problem, herein, metal-organic framework-based probes of copper-terephthalic acid (CuBDC) are investigated, which show sensitivity to pH and hydrogen peroxide (H 2 O 2 ), simultaneously. By self-assembling under the template effect of soluble starch, the particle size of CuBDC can be well controlled for entering into cells and locating lysosomes. Based on the Fenton-like reaction, CuBDC can catalyze the decomposition of H 2 O 2 into ˙OH, which in turn reacts with CuBDC to generate a stable fluorescent substance. Meanwhile, Cu 2+ can be released from CuBDC under acidic conditions for reacting with H 2 O 2 more thoroughly. And the synthesized CuBDC has a similar attraction to the electrophilic ˙OH at different pH values owing to the residual soluble starch in the particles. The above properties cause CuBDC to have a stable fluorescence signal with low pH values and high H 2 O 2 concentration, simultaneously. The fluorescence imaging experiments in HeLa cells demonstrate that CuBDC acting as a pH/H 2 O 2 responsive fluorescent probe holds great promise for lysosome-specific imaging.