Baodan Liu - Cochemist

Morphology-controlled syntheses of α-MnO2 for electrochemical energy storage

Co-reporter:Weidong He, Wenjin Yang, Chenggang Wang, Xiaolong Deng, Baodan Liu and Xijin Xu

Physical Chemistry Chemical Physics 2016 vol. 18(Issue 22) pp:15235-15243

Publication Date(Web):10 May 2016

DOI:10.1039/C6CP02548J

Manganese dioxide (MnO2) nanoarchitectures including microspheres assembled by nanosheets and hollow urchins assembled by nanorods have been successfully synthesized using a facile and efficient hydrothermal method at 150 °C. The effects of concentrations of the reactants and reaction time on the structures and morphologies of MnO2 were systematically investigated. The experimental results showed that the morphologies of MnO2 transformed into nanosheet-assembled microspheres (10 min) from nanorod-assembled hollow urchins (5 min) by tuning the suitable reaction time. The nanorod-assembled hollow urchins experienced the morphology transformation cycle from urchin to a disordered structure to urchin with the extension of the reaction time. Furthermore, the nanorods with different diameters and lengths were formed with different concentrations of reactants at the same reaction time (8 h). The MnO2 nanorods fabricated with 0.59 g KMnO4 showed a maximum specific capacitance (198 F g−1) with a good rate capability and excellent cycling stability (maintained 94% after 2000 cycles). Furthermore, the nanosheet-assembled microspheres exhibited the higher specific capacitance of 131 F g−1 at 1 A g−1 with a long-term cycling stability for the samples at different reaction times. These results indicated their promising applications as high-performance supercapacitor electrodes and provided a generic guideline in developing different nanostructured electrode materials for electrochemical energy storage.

Pseudobinary Solid-Solution: An Alternative Way for the Bandgap Engineering of Semiconductor Nanowires in the Case of GaPZnSe

Co-reporter:Wenjin Yang;Bing Yang;Jianyu Wang;Takashi Sekiguchi;Staedler Thorsten;Xin Jiang

Advanced Functional Materials 2015 Volume 25( Issue 17) pp:2543-2551

Publication Date(Web):

DOI:10.1002/adfm.201404523

Bandgap engineering of semiconductor nanostructures is of significant importance either for the optical property tailoring or for the integration of functional optoelectronic devices. Here, an efficient way to control the bandgap and emission wavelength is reported for a binary compound semiconductor through alloying with another binary compound. Taking GaP-ZnSe system as an example, the bandgap of quaternary GaP-ZnSe solid-solution nanowires can be selectively tailored in the range of 1.95–2.2 eV by controlling the solubility of ZnSe dopants in GaP host. High-resolution transmission electron microscopy measurement and chemical analyses using an X-ray energy dispersive spectrometer (EDS) demonstrate the solid-solution feature of GaP-ZnSe semiconductor alloy, while X-ray photoelectron spectroscopy (XPS) characterization verifies the formation of some new chemical bonds corresponding to Zn-P and Ga-S bonds in GaP-ZnSe nanowires. The strategy to tailor the optoelectronic property of semiconductor nanostructures through the solid-solution of two different binary compounds represents a general routine to the property modification of all pseudobinary systems and will open more opportunity for their applications in electronics, optics and optoelectronics.

Dislocation-Induced Nanoparticle Decoration on a GaN Nanowire

Co-reporter:Bing Yang, Fang Yuan, Qingyun Liu, Nan Huang, Jianhang Qiu, Thorsten Staedler, Baodan Liu, and Xin Jiang

ACS Applied Materials & Interfaces 2015 Volume 7(Issue 4) pp:2790

Publication Date(Web):January 6, 2015

DOI:10.1021/am5079896

GaN nanowires with homoepitaxial decorated GaN nanoparticles on their surface along the radial direction have been synthesized by means of a chemical vapor deposition method. The growth of GaN nanowires is catalyzed by Au particles via the vapor–liquid–solid (VLS) mechanism. Screw dislocations are generated along the radial direction of the nanowires under slight Zn doping. In contrast to the metal-catalyst-assisted VLS growth, GaN nanoparticles are found to prefer to nucleate and grow at these dislocation sites. High-resolution transmission electron microscopy (HRTEM) analysis demonstrates that the GaN nanoparticles possess two types of epitaxial orientation with respect to the corresponding GaN nanowire: (I) [1̅21̅0]np//[1̅21̅0]nw, (0001)np//(0001)nw; (II) [1̅21̅3]np//[12̅10]nw, (101̅0)np//(101̅0)nw. An increased Ga signal in the energy-dispersive spectroscopy (EDS) profile lines of the nanowires suggests GaN nanoparticle growth at the edge surface of the wires. All the crystallographic results confirm the importance of the dislocations with respect to the homoepitaxial growth of the GaN nanoparticles. Here, screw dislocations situated on the (0001) plane provide the self-step source to enable nucleation of the GaN nanoparticles.Keywords: dislocation; GaN; growth; nanostructures; nucleation

A general strategy toward the rational synthesis of metal tungstate nanostructures using plasma electrolytic oxidation method

Co-reporter:Yanan Jiang, Baodan Liu, Zhaofeng Zhai, Xiaoyuan Liu, Bing Yang, Lusheng Liu, Xin Jiang

Applied Surface Science 2015 Volume 356() pp:273-281

Publication Date(Web):30 November 2015

DOI:10.1016/j.apsusc.2015.08.080

Highlights

•: Plasma electrolyte oxidation (PEO) method has been used for the rational synthesis of tungstate nanostructures.
•: ZnWO₄ nanoplates have strong mechanical adhesion with porous TiO₂ film substrate.
•: The morphology and dimensional size of ZnWO₄ nanostructures can be selectively tailored by controlling the annealing temperature and growth time.
•: The PEO method can be widely applied to the growth of various metal oxides.

Local defect-induced red-shift of cathodoluminescence in individual ZnS nanobelts

Co-reporter:B. D. Liu, B. Yang, B. Dierre, T. Sekiguchi and X. Jiang

Nanoscale 2014 vol. 6(Issue 21) pp:12414-12420

Publication Date(Web):02 Sep 2014

DOI:10.1039/C4NR04464A

The luminescence of semiconductor nanostructures is strongly dependent on their size, dimensions, morphology, composition, or defects, and their band emissions can be properly and selectively tailored through the rational manipulation of these parameters during material growth. Using spatially-resolved cathodoluminescence spectroscopy, monochromatic contrast maps and high-resolution transmission electron microscopy, an obvious red-shift of the near-band-edge emission of wurtzite ZnS nanobelts, resulting from a strip of stacking faults or a zinc-blende phase with tens of atomic layers in width, has been observed and its related mechanism has been discussed. This finding is not specific to the defect-dependent optical properties tailoring of ZnS nanostructures and represents a general validity for clarifying the mechanism of peak-shift (band-gap expansion or shrinking) of a wide range of semiconductor nanostructures with various defects. In addition, the general formation mechanism of the belt-like nanostructure was proposed based on precise microstructure analyses on a ZnS nanobelt with atomic terrace growth fronts.

Origin of Yellow-Band Emission in Epitaxially Grown GaN Nanowire Arrays

Co-reporter:Baodan Liu, Fang Yuan, Benjamin Dierre, Takashi Sekiguchi, Song Zhang, Yongkuan Xu, and Xin Jiang

ACS Applied Materials & Interfaces 2014 Volume 6(Issue 16) pp:14159

Publication Date(Web):July 24, 2014

DOI:10.1021/am5034878

Here, we report the origin of the yellow-band emission in epitaxial GaN nanowire arrays grown under carbon-free conditions. GaN nanowires directly grown on [0001]-oriented sapphire substrate exhibit an obvious and broad yellow-band in the visible range 400–800 nm, whereas the insertion of Al/Au layers in GaN–sapphire interface significantly depresses the visible emission, and only a sharp peak in the UV range (369 nm) can be observed. The persuasive differences in cathodoluminescence provide direct evidence for demonstrating that the origin of the yellow-band emission in GaN nanowire arrays arises from dislocation threading. The idea using buffering/barrier layers to isolate the dislocation threading in epitaxially grown GaN nanowires can be extended to the rational synthesis and structural defect controlling of a wide range of semiconductor films and nanostructures with superior crystal quality and excellent luminescence property.Keywords: epitaxial growth; GaN; interface; nanowire arrays; yellow-band emission

Synthesis and cathodoluminescence of Sb/P co-doped GaN nanowires

Co-reporter:Zaien Wang, Baodan Liu, Fang Yuan, Tao Hu, Guifeng Zhang, Benjamin Dierre, Naoto Hirosaki, Takashi Sekiguchi, Xin Jiang

Journal of Luminescence 2014 Volume 145() pp:208-212

Publication Date(Web):January 2014

DOI:10.1016/j.jlumin.2013.07.038

•Sb/P co-doped GaN nanowires were synthesized through a well-designed multi-channel chemical vapor deposition (CVD) process.•Sb/P co-doping leads to the crystallinity deterioration of GaN nanowires.•Sb/P co-doping caused the red-shift of GaN nanowires band-gap in UV range.•Compared with Sb doping, P atoms are more easy to incorporate into the GaN lattice.Sb/P co-doped Gallium Nitride (GaN) nanowires were synthesized via a simple chemical vapor deposition (CVD) process by heating Ga2O3 and Sb powders in NH3 atmosphere. Scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS) measurements confirmed the as-synthesized products were Sb/P co-doped GaN nanowires with rough morphology and hexagonal wurtzite structure. Room temperature cathodoluminescence (CL) demonstrated that an obvious band shift of GaN nanowires can be observed due to Sb/P co-doping. Possible explanation for the growth and luminescence mechanism of Sb/P co-doped GaN nanowires was discussed.

Solid–Solution Semiconductor Nanowires in Pseudobinary Systems

Co-reporter:Baodan Liu, Yoshio Bando, Lizhao Liu, Jijun Zhao, Mitome Masanori, Xin Jiang, and Dmitri Golberg

Nano Letters 2013 Volume 13(Issue 1) pp:85-90

Publication Date(Web):December 3, 2012

DOI:10.1021/nl303501t

Pseudobinary solid–solution semiconductor nanowires made of (GaP)1–x(ZnS)x, (ZnS)1–x(GaP)x and (GaN)1–x(ZnO)x were synthesized based on an elaborative compositional, structural, and synthetic designs. Using analytical high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS), we confirmed that the structure uniformity and a lattice match between the two constituting binary components play the key roles in the formation of quaternary solid–solution nanostructures. Electrical transport measurements on individual GaP and (GaP)1–x(ZnS)x nanowires indicated that a slight invasion of ZnS in the GaP host could lead to the abrupt resistance increase, resulting in the semiconductor-to-insulator transition. The method proposed here may be extended to the rational synthesis of many other multicomponent nanosystems with tunable and intriguing optoelectronic properties for specific applications.

Synthesis, Microstructure, and Cathodoluminescence of [0001]-Oriented GaN Nanorods Grown on Conductive Graphite Substrate

Co-reporter:Fang Yuan, Baodan Liu, Zaien Wang, Bing Yang, Yao Yin, Benjamin Dierre, Takashi Sekiguchi, Guifeng Zhang, and Xin Jiang

ACS Applied Materials & Interfaces 2013 Volume 5(Issue 22) pp:12066

Publication Date(Web):October 28, 2013

DOI:10.1021/am403876e

One-dimensional GaN nanorods with corrugated morphology have been synthesized on graphite substrate without the assistance of any metal catalyst through a feasible thermal evaporation process. The morphologies and microstructures of GaN nanorods were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results from HRTEM analysis indicate that the GaN nanorods are well-crystallized and exhibit a preferential orientation along the [0001] direction with Ga3+-terminated (101̅1) and N3–-terminated (101̅1̅) as side facets, finally leading to the corrugated morphology surface. The stabilization of the electrostatic surface energy of {101̅1} polar surface in a wurtzite-type hexagonal structure plays a key role in the formation of GaN nanorods with corrugated morphology. Room-temperature cathodoluminescence (CL) measurements show a near-band-edge emission (NBE) in the ultraviolet range and a broad deep level emission (DLE) in the visible range. The crystallography and the optical emissions of GaN nanorods are discussed.Keywords: cathodoluminescence; crystallography; GaN; graphite; nanorods;

Solid Solution, Phase Separation, and Cathodoluminescence of GaP–ZnS Nanostructures

Co-reporter:Baodan Liu, Yoshio Bando, Benjamin Dierre, Takashi Sekiguchi, Dmitri Golberg, and Xin Jiang

ACS Applied Materials & Interfaces 2013 Volume 5(Issue 18) pp:9199

Publication Date(Web):August 27, 2013

DOI:10.1021/am4027949

Quaternary solid-solution nanowires made of GaP and ZnS have been synthesized through well-designed synthetic routines. The as-synthesized GaP–ZnS solid-solution nanowires exhibit decent crystallinity with the GaP phase as the host, while a large amount of twin structural defects are observed in ZnS-rich nanowires. Cathodoluminescence studies showed that GaP-rich solid-solution nanowires have a strong visible emission centered at 600 nm and the ZnS-rich solid-solution nanowires exhibited a weak emission peak in the UV range and a broad band in the range 400–600 nm. The formation mechanism, processes, and optical emissions of GaP–ZnS solid-solution nanowires were discussed in detail.Keywords: crystallography; nanowires; optical property; solid solution; synthesis;

Crystallography and cathodoluminescence of pyramid-like GaN nanorods epitaxially grown on a sapphire substrate

Co-reporter:Baodan Liu, Zaien Wang, Fang Yuan, Dierre Benjamin, Takashi Sekiguchi and Xin Jiang

RSC Advances 2013 vol. 3(Issue 45) pp:22914-22917

Publication Date(Web):03 Oct 2013

DOI:10.1039/C3RA44371J

Pyramid-like GaN nanorods have been epitaxially grown on a [001]-oriented sapphire substrate. The as-synthesized GaN nanorods exhibited decent crystal quality and a strong luminescence in UV range.

Microstructure and cathodoluminescence study of GaN nanowires without/with P-doping

Co-reporter:Baodan Liu;Tao Hu;Zaien Wang;Lizhao Liu;Fuwen Qin;Nan Huang;Xin Jiang

Crystal Research and Technology 2012 Volume 47( Issue 2) pp:207-212

Publication Date(Web):

DOI:10.1002/crat.201100574

Abstract

In this work, P-doped GaN nanowires were synthesized in a co-deposition CVD process and the effects of P-doping on the microstructure and cathodoluminescence (CL) of GaN nanowires were studied in details. SEM observation and CL measurments demonstrated that P-doping has led to a rough morphology evolution and a depression of the band-gap emission of GaN nanowires, whereas the visible emission of GaN nanowires was obviously enhanced. Finally, the corresponding morphology transition and optical properties of GaN nanowires with P-doping were discussed. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Morphology-controlled syntheses of α-MnO2 for electrochemical energy storage

Co-reporter:Weidong He, Wenjin Yang, Chenggang Wang, Xiaolong Deng, Baodan Liu and Xijin Xu

Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 22) pp:NaN15243-15243

Publication Date(Web):2016/05/10

DOI:10.1039/C6CP02548J

Manganese dioxide (MnO2) nanoarchitectures including microspheres assembled by nanosheets and hollow urchins assembled by nanorods have been successfully synthesized using a facile and efficient hydrothermal method at 150 °C. The effects of concentrations of the reactants and reaction time on the structures and morphologies of MnO2 were systematically investigated. The experimental results showed that the morphologies of MnO2 transformed into nanosheet-assembled microspheres (10 min) from nanorod-assembled hollow urchins (5 min) by tuning the suitable reaction time. The nanorod-assembled hollow urchins experienced the morphology transformation cycle from urchin to a disordered structure to urchin with the extension of the reaction time. Furthermore, the nanorods with different diameters and lengths were formed with different concentrations of reactants at the same reaction time (8 h). The MnO2 nanorods fabricated with 0.59 g KMnO4 showed a maximum specific capacitance (198 F g−1) with a good rate capability and excellent cycling stability (maintained 94% after 2000 cycles). Furthermore, the nanosheet-assembled microspheres exhibited the higher specific capacitance of 131 F g−1 at 1 A g−1 with a long-term cycling stability for the samples at different reaction times. These results indicated their promising applications as high-performance supercapacitor electrodes and provided a generic guideline in developing different nanostructured electrode materials for electrochemical energy storage.

3D Co3O4@MnO2 heterostructures grown on a flexible substrate and their applications in supercapacitor electrodes and photocatalysts

Co-reporter:Xin Zheng, Zhicheng Han, Wenjin Yang, Fengyu Qu, Baodan Liu and Xiang Wu

Dalton Transactions 2016 - vol. 45(Issue 42) pp:NaN16858-16858

Publication Date(Web):2016/09/21

DOI:10.1039/C6DT03076A

In this work, flexible 3D Co3O4@MnO2 heterostructures have been successfully obtained without using any surfactants. The as-prepared flexible electrodes exhibit high efficiency, high discharge areal capacitance (1397.2 mF cm−2 at 1 mA cm−2), long cycle life (13.9% loss after 6000 repetitive cycles at 1 mA cm−2) and excellent electrical stability. In addition, hybrid 3D Co3O4@MnO2 structures are also used as photocatalysts for the photocatalytic degradation of several harmful organic dyes under visible light illumination. The results show that the as-grown products possess excellent photocatalytic performance, demonstrating their potential applications in wastewater treatment.