Yujie Liang

A room temperature chemical route for large scale synthesis of sub-15 nm ultralong CuO nanowires with strong size effect and enhanced photocatalytic activity

We describe a facile room temperature solution-phase chemical approach for large scale synthesis of sub-15 nm ultralong crystalline CuO nanowires with an average diameter of about 8 nm and lengths of up to several tens of micrometers. The results indicated that Cu(OH)2 nanowires were first formed and subsequently served as template to direct the formation of CuO nanowires. XRD, TEM, SAED and HRTEM were used to systemically investigate the chemical compositions, morphology, size and microstructure features of the as-prepared nanowires. The Raman study of the as-prepared CuO nanowires indicates that the Raman scattering peaks are broadened and red-shifted about 20 cm−1 compared with values of bulk CuO crystals, showing that the as-prepared CuO nanowires exhibit strong quantum size confinement effects. A rational interpretation for the red-shifted and broaden of Raman peaks is given according to phonon confinement model of an infinite crystal. The band gap energy estimated from the UV-vis absorption spectrum of the nanowires was about 3.48 eV, which is apparently much larger than the value of bulk CuO crystals. Thus, UV-vis optical absorption property further confirms the strong quantum size confinement effects of the nanowires. The photocatalytic activity of the as-prepared CuO nanowires was further investigated by evaluating the photo-degradation of a model pollutant rhodamine B (RhB). The results indicated that CuO nanowires have enhanced photocatalytic performance with 97.2% decomposition of RhB after 12 h reaction under UV light irradiation, which was much higher than that of commercial CuO powders (37.6%).

Conversion of hexagonal Sb2Te3 nanoplates into nanorings driven by growth temperature.

We describe a novel route for the conversion of hexagonal Sb(2)Te(3) nanoplates into nanorings driven by growth temperature in a simple solvothermal process. The transmission electron microscopy was employed to investigate systemically the morphology, size, crystallinity, and microstructure of the as-prepared products. The experiments indicated that the growth temperature had a great effect on the morphology of antimony telluride nanostructures. When the experiments were conducted at 200 °C, the hexagonal antimony telluride nanoplates were obtained. However, if the experiments were carried out at higher temperature of 230 °C, the hexagonal antimony telluride nanorings were achieved by dissolution of the inner part with a higher density of defects of the hexagonal nanoplates for the first time. A possible formation mechanism was proposed on the basis of experimental results and analysis. This work may open a new rational route for the synthesis of the hexagonal antimony telluride nanorings, which may have scientific and technological applications in various functional devices.

Morphology-controlled synthesis and growth mechanism of ZnO nanostructures via the NaCl nonaqueous ionic liquid route

An environmentally friendly NaCl nonaqueous ionic liquid route has been developed to synthesize ZnO nanostructures including nanowires and nanoplates for the first time. ZnO nanostructures were prepared by decomposing precursor Zn5(CO3)2(OH)6 nanoparticles in NaCl nonaqueous ionic liquid, in which the precursor Zn5(CO3)2(OH)6 nanoparticles were first prepared by a facile one-step, solid-state reaction and ground with both NaCl and NP-9 or only in NaCl, then heated at 850 °C for 2 h. XRD, TEM and HRTEM techniques were used to investigate chemical composition, morphology, size, and microstructure features of the as-prepared ZnO nanostructures. The comparative experiments have been conducted systematically to investigate the growth mechanism of ZnO nanostructures, and the roles of salt NaCl nonaqueous ionic liquid and surfactant nonyl pheyl ether (9) (NP-9) on the formation of ZnO nanostructures. The experimental results demonstrated that ZnO nanowires were achieved by decomposing precursor Zn5(CO3)2(OH)6 nanoparticles in NaCl nonaqueous ionic liquid, in which the precursor Zn5(CO3)2(OH)6 nanoparticles were firstly ground with NaCl and NP-9, while ZnO nanoplates were obtained by decomposing precursor Zn5(CO3)2(OH)6 nanoparticles in NaCl nonaqueous ionic liquid, in which the precursor Zn5(CO3)2(OH)6 nanoparticles were firstly ground with NaCl in absence of NP-9. A rational interpretation has been given for the growth of ZnO nanowires and nanoplates.

Hierarchical three-dimensional flower-like Co 3 O 4 architectures with a mesocrystal structure as high capacity anode materials for long-lived lithium-ion batteries

In this work, we rationally design a high-capacity electrode based on three-dimensional (3D) hierarchical Co3O4 flower-like architectures with a mesocrystal nanostructure. The specific combination of the micro-sized 3D hierarchical architecture and the mesocrystal structure with a high porosity and single crystal-like nature can address the capacity fading and cycling stability as presented in many conversion electrodes for lithium-ion batteries. The hierarchical 3D flower-like Co3O4 architecture accommodates the volume change and mitigates mechanical stress during the lithiation–delithiation processes, and the mesocrystal structure provides extra lithium-ion storage and electron/ion transport paths. The achieved hierarchical 3D Co3O4 flower-like architectures with a mesocrystal nanostructure exhibit a high reversible capacity of 920 mA·h·g−1 after 800 cycles at 1.12 C (1 C = 890 mA·h·g−1), improved rate performance, and cycling stability. The finding in this work offers a new perspective for designing advanced and long-lived lithium-ion batteries.

Enhanced photoelectrochemical water splitting and photocatalytic water oxidation of Cu2O nanocube-loaded BiVO4 nanocrystal heterostructures

Reducing the fast recombination of photogenerated electron-hole pairs of semiconductor photocatalyst is very important to improve its photocatalysis. In this paper we fabricate Cu2O nanocube-decorated BiVO4 nanocrystal (denoted as BiVO4@Cu2O nanocrystal@nanocube) heterostructure photocatalyst by coupling n-type BiVO4 with p-type Cu2O. The BiVO4@Cu2O nanocrystal@nanocube photocatalysts show superior photocatalytic activities in photoelectrochemical (PEC) activity and photocatalytic water oxidation to BiVO4 photocatalysts under visible light illumination. The BiVO4@Cu2O nanocrystal@nanocube heterostructure electrode achieves the highest photocurrent density of ∼ 10 μA cm−2 at 0 V versus Ag/AgCl, 5 times higher than that of BiVO4 nanocrystal electrode (∼ 2 μA cm−2). The light induced evolution rate of O2 generation for BiVO4@Cu2O nanocrystal@nanocube heterostructures is as high as 150 μmol h−1100 mg cat−1, more than 3 times higher than that (48 μmol h−1100 mg cat−1) of BiVO4 nanocrystals. The enhanced photocatalysis activities of the BiVO4@Cu2O nanocrystal@nanocube photocatalysts are attributed to the efficient separation of the photoexcited electron-hole pairs caused by inner electronic field (IEF) of p-n junction. This study opens up new opportunities in designing photoactive materials with highly enhanced performance for solar energy conversion.

Heterogeneous p–n Junction CdS/Cu2O Nanorod Arrays: Synthesis and Superior Visible-Light-Driven Photoelectrochemical Performance for Hydrogen Evolution

Heterogeneous p-n junction CdS/Cu2O nanorod arrays have been fabricated by using a facile successive ionic-layer adsorption and reaction process to grow Cu2O nanoparticles on the surface of ordered CdS nanorod arrays. The heterogeneous p-n junction nanorod arrays exhibit superior photoelectrochemical performance for hydrogen (H2) generation and high stability under visible-light irradiation. The highest photocurrent density achieved by heterogeneous nanorod array photoelectrode is 4.2 mA cm-2 in a sacrificial Na2S and Na2SO3 mixture electrolyte solution at 0 V versus Ag/AgCl, which is 4 times higher than that of a pure CdS nanorod array photoelectrode. In addition, the heterogeneous nanorod array photoelectrode achieves an incident photon conversion efficiency value of 40.5% at 470 nm. The photocatalytic hydrogen generation rate of the heterogeneous nanorod array photoelectrode reaches up to 161.2 μmol h-1, around 3-fold increase compared to that of a bare CdS photoelectrode. Furthermore, the heterogeneous p-n junction CdS/Cu2O nanorod arrays show an excellent stability under long light illumination of 7200 s. The improved photoelectrochemical performance, photocatalytic activity, and excellent stability of the heterogeneous nanorod array photoelectrode resulted from the efficient separation of photoinduced electron-hole pairs, which is achieved by the synergistic effects of CdS, Cu2O, p-n junction, and an inner electric field in the photoelectrode. The present work provides a new strategy to fabricate a heterogeneous photoelectrode. This facile strategy is expected to be utilized to fabricate electrodes of other materials for highly efficient solar-driven water splitting application.

Sensitive surface-enhanced Raman scattering of TiO2/Ag nanowires induced by photogenerated charge transfer

In this work, the semiconductor TiO2 nanowires were successfully coupled with plasmonic metal Ag nanoparticles to fabricate hybrid nanostructures with enhanced sensitive Raman substrate. The SERS activities of fabricated hybrid nanostructures were evaluated by detecting the Raman signals of R6G molecules. The fabricated TiO2/Ag nanowire/nanoparticle hybrid nanostructures show sensitive detection ability for R6G molecules. Based on the band structures of Ag nanoparticle, TiO2 nanowire and R6G molecule, the enhanced sensitive SERS activities of hybrid nanostructures is ascribed to an efficient charge transfer process, in which the photogenerated electrons transfer to the conduction band of TiO2 nanowires from metal Ag nanoparticles, and then to LUMO level of R6G molecules, leading to enhanced SERS activities. This efficient charge transfer process is achieved by the synergistic effects of plasmonic metal Ag nanoparticle, semiconductor TiO2 nanowire and R6G molecule. Furthermore, the transfer process of photoexcited electrons from metal Ag nanoparticle to conduction band of TiO2 nanowire is evidently confirmed by the photoresponse properties of hybrid nanostructures under illumination only with visible light (λ>420nm). The findings achieved in this work demonstrate that efficient turning the charge transfer in plasmonic metal nanoparticle/semiconductor/molecule hybrid nanostructure can significantly enhance its SERS activity.