Jiale Xie

Graphene quantum-dot-doped polypyrrole counter electrode for high-performance dye-sensitized solar cells.

Herein graphene quantum dot (GQD), a graphene material with lateral dimension less than 100 nm, is explored to dope PPy on F-doped tin oxide glass as an efficient counter electrode for high-performance dye-sensitized solar cells (DSSCs). The GQDs-doped PPy film has a porous structure in comparison to the densely structured plain PPy, and displays higher catalytic current density and lower charge transfer resistance than the latter toward I3(-)/I(-) redox reaction. The highest power conversion efficiency (5.27%) for DSSCs is achieved with PPy doped with10% GQDs, which is comparable to that of Pt counter electrode-based DSSCs. This work provides an inexpensive alternative to replace platinum for DSSCs.

Solvent-mediated directionally self-assembling MoS2 nanosheets into a novel worm-like structure and its application in sodium batteries

Ultralong worm-like MoS2 nanostructures were assembled with a solvent-mediated solvothermal process by controlling the composition ratio of the miscible precursors in solution. The formation mechanism of worm-like MoS2 nanostructures was proposed and the as-prepared materials as anodes in sodium ion batteries delivered a good discharge–charge capacity, superior cycling stability and excellent coulombic efficiency. This work provides an efficient and economic approach to tailor the nanostructure of layered transition metal oxides and transition-metal dichalcogenides simply by controlling the chemical composition and physical properties in a solvothermal process.

Au Nanoparticles–3D Graphene Hydrogel Nanocomposite To Boost Synergistically in Situ Detection Sensitivity toward Cell-Released Nitric Oxide

In situ detection of nitric oxide (NO) released from living cells has become very important in studies of some critical physiological and pathological processes, but it is still very challenging due to the low concentration and fast decay of NO. A nanocomposite of Au nanoparticles deposited on three-dimensional graphene hydrogel (Au NPs-3DGH) was prepared through a facile one-step approach by in situ reduction of Au(3+) on 3DGH to build a unique sensing film for a strong synergistic effect, in which the highly porous 3DGH offers a large surface area while Au NPs uniformly deposited on 3DGH efficiently catalyze the electrochemical oxidation of NO for sensitive detection of NO with excellent selectivity, fast response, and low detection limit. The sensor was further used to in situ detect NO released from living cells under drug stimulation, showing significant difference between normal and tumor cells under drug stimulation.

A new class of fluorescent-dots: long luminescent lifetime bio-dots self-assembled from DNA at low temperatures

Quantum-dots (QDs) have fuelled up intensive research efforts over the past two decades. Nevertheless, currently developed two classes of fluorescent QDs, colloidal semiconductor QDs and carbonaceous QDs suffer from either toxicity or short luminescence lifetime. Here, we report a new class of fluorescent bio-dots that are derived from DNA via self-assembly at low temperatures down to 80°C, which has an optical bandgap of 3.4 eV, and in particular possesses strong photoluminescence with a much longer luminescence lifetime (τ1 = 10.44 ns) than the carbonaceous QDs (τ1 < 0.5 ns). It is discovered that it is the interactions of base pair cytosines with each other to form sp2 carbon–like centers as luminescence centers or chromophores for the photoluminescence. The use of bio-dots in cell imaging with strong photoluminescence signal and good biocompatibility demonstrates great potentials of broad biological and optoelectronic applications.

Polymer-Mediated Self-Assembly of TiO2@Cu2O Core-Shell Nanowire Array for Highly Efficient Photoelectrochemical Water Oxidation.

Phototoelectrochemical (PEC) water splitting represents a highly promising strategy to convert solar energy to chemical energy in the form of hydrogen, but its performance is severely limited by the water oxidation reaction. We conformally grew an ultrathin and continuous coating of Cu2O on TiO2 nanowire array (NWA) to form a truly core-shell TiO2@Cu2O NWA via a new facile, economical, and scalable polymer-mediated self-assembly approach, in which the polymer serves as a stabilizer, reductant, and linker simultaneously. This heteronanostructure was subsequently directly used as a photoanode for PEC water splitting, showing a photocurrent density of 4.66 mA cm(-2) at 1.23 V vs RHE in 0.5 M Na2SO4 solution and a maximum photoconversion efficiency of 0.71%, both of which are the highest reported for TiO2-based photoanodes measured under the same conditions (neutral conditions and without any sacrificial agent). The superior PEC performance of the TiO2@Cu2O NWA toward water oxidation is primarily due to much enhanced visible light collection and charge separation for high charge carrier density as well as greatly facilitated charge transfer and transport. This work not only offers a novel TiO2@Cu2O core-shell NWA photoanode for highly efficient PEC water oxidation and investigate its enhancement mechanism but also provides scientific insights into the mechanism of the polymer-mediated self-assembly, which can be further extended to fabricate various other core-shell nanoarchitectures for broad applications.

Au@CdS Core-Shell Nanoparticles-Modified ZnO Nanowires Photoanode for Efficient Photoelectrochemical Water Splitting.

Hydrogen production from water splitting using solar energy based on photoelectrochemical (PEC) cells has attracted increasing attention because it leaves less of a carbon footprint and has economic superiority of solar and hydrogen energy. Oxide semiconductors such as ZnO possessing high stability against photocorrosion in hole scavenger systems have been widely used to build photoanodes of PEC cells but under visible light their conversion efficiencies with respect to incident‐photon‐to‐current conversion efficiency (IPCE) measured without external bias are still not satisfied. An innovative way is presented here to significantly improve the conversion efficiency of PEC cells by constructing a core–shell structure‐based photoanode comprising Au@CdS core–shell nanoparticles on ZnO nanowires (Au@CdS‐ZnO). The Au core offers strong electronic interactions with both CdS and ZnO resulting in a unique nanojunction to facilitate charge transfer. The Au@CdS‐ZnO PEC cell under 400 nm light irradiation without any applied bias provides an IPCE of 14.8%. Under AM1.5 light illumination with a bias of 0.4 V, the Au@CdS‐ZnO PEC cell produces H2 at a constant rate of 11.5 μmol h−1 as long as 10 h. This work provides a fundamental insight to improve the conversion efficiency for visible light in water splitting.

Modification of a thin layer of α-Fe2O3 onto a largely voided TiO2 nanorod array as a photoanode to significantly improve the photoelectrochemical performance toward water oxidation

A largely voided TiO2 nanorod array was synthesized and further modified with a thin layer of α-Fe2O3 (Fe2O3@TiO2), by the pyrolysis of an FeCl3 ethanol solution, as a photoanode toward water oxidation, showing significantly improved photoelectrochemical performance over a TiO2 nanorod array. Among all of the Fe2O3 decorated TiO2-based photoanodes, the optimal voided Fe2O3@TiO2 nanorod array photoanode delivered the largest photocurrent density of 3.39 mA cm−2 at 1.23 V (vs. RHE) and the highest applied bias photon-to-current efficiency (ABPE) (1.153%) under 100 mW cm−2 UV-vis light illumination. In particular, the ABPE for the as-prepared photoanode was ∼3.3 times higher than that of the plain TiO2 nanorod array (0.35%), ∼11.3 times higher than that of the Fe2O3-modified randomly arranged TiO2 nanorods and ∼6.2 times higher than that of a Fe2O3-modified densely arranged TiO2 nanotube array. The significant enhancement mainly originates from the large voids in the nanorod array allowing a thin layer of Fe2O3 to fully modify the TiO2 nanorods, which improves the absorption of UV light, boosts the charge interface transfer rate, reduces the charge diffusion length and suppresses the charge recombination process. This work demonstrates a feasible route to improving the photoelectrochemical catalytic performance of TiO2 semiconductors toward water splitting.

Hierarchically porous graphitic carbon nitride: large-scale facile synthesis and its application toward photocatalytic dye degradation

For the first time we develop a novel strategy toward large-scale facile synthesis of hierarchically porous graphitic carbon nitride (hp-g-CN) by polymerization of melamine monomers using ammonium persulfate as an oxidant, followed by paralyzing the resulting microstructures under Ar. Then we use it as an efficient photocatalyst toward degradation of methyl orange dye under visible light irradiation.

Fluffy-ball-shaped carbon nanotube–TiO2 nanorod nanocomposites for photocatalytic degradation of methylene blue

One dimensional TiO2 nanomaterials have attracted tremendous attention due to their excellent photocatalytic properties. However, the synthesis of spherical-shaped carbon nanotubes (CNTs)–TiO2 nanorod composites for photocatalytic degradation of water pollutants has not been reported. In the present study we fabricated fluffy-ball-shaped multiwalled CNT–TiO2 nanorod composites via a facile hydrothermal approach. By using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it is found that morphologies of the nanocomposites could be controlled by changing the reaction duration, CNT amount and Ti source concentration. TEM images and X-ray powder diffraction (XRD) results show the excellent crystalline structure and the rutile phase of the TiO2 nanorods in the nanocomposites. Based on the results, a possible mechanism for the growth of the nanocomposites was proposed. Great potentials of the composited microspheres in water treatment were demonstrated through the photocatalytic degradation of methylene blue, in which a degradation efficiency as high as 93% could be reached. This study provides not only a new approach to developing CNT–TiO2 nanorod composites, but also a very promising photocatalyst for potential applications in waste water treatment.

Tailoring Co(OH)2 hollow nanostructures via Cu2O template etching for high performance supercapacitors

Co(OH)2 hollow nanostructures including cube, octahedron and flower are delicately tailored via a simple and fast one-step Cu2O template etching method. The as-prepared materials were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscope (FESEM), N2 adsorption-desorption and electrochemical methods and X-ray photoelectron spectroscopy (XPS). In particular, the supercapacitive behaviors of the as-prepared materials were investigated to explore relation of capacitance versus nanostructure. Results indicate that the as-prepared Co(OH)2 samples inherit the size and shape of the Cu2O templates but with an inside hollow, and the differently nanostructured Co(OH)2 exhibits different capacitive behaviors. Among various morphologies, the flower Co(OH)2 has the largest specific capacitance of 1350 F/g, while octahedron Co(OH)2 has the smallest one of 986.4 F/g. This is mainly because the flower Co(OH)2 not only has the largest available surface area, but also offers the fast interfacial electron transfer for higher pseudocapacitance and enhanced electrolyte ion diffusion rate for high power density, which is supported by both theoretical calculation, measured BET data and ac impedance measurements. This work may provide a vivid example to rationally design a nanostructure and further explore its fundamental insights for high performance supercapacitors.