Browsing by Author "Zhang, Jing"

Now showing 1 - 5 of 5
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    Efficient hydrogen evolution in transition metal dichalcogenides via a simple one-step hydrazine reaction
    (Springer Nature, 2016) Cummins, Dustin R.; Martinez, Ulises; Sherehiy, Andriy; Kappera, Rajesh; Martinez-Garcia, Alejandro; Schulze, Roland K.; Jasinski, Jacek; Zhang, Jing; Gupta, Ram K.; Lou, Jun; Chhowalla, Manish; Sumanasekera, Gamini; Mohite, Aditya D.; Sunkara, Mahendra K.; Gupta, Gautam
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    Electrochemical Behavior of Two-Dimensional Atomic Layers
    (2016-11-22) Zhang, Jing; Lou, Jun
    In this thesis several aspects of the electrochemical behaviors of two-dimensional layered materials are discussed. First, large-area continuous few-layer molybdenum disulfide film is prepared by simple solid-gas elemental reaction and transferred onto fluorine doped tin oxide glass substrate as the counter electrode for dye-sensitized solar cells. The catalytic activity of the MoS2 atomic layers are dramatically improved by craving the MoS2 film and creating artificial edges on it. Electrochemical analysis shows that the edges contribute to the improve catalytic activity of MoS2. Second, large-area continuous hexagonal boron nitride film is grown by chemical vapor deposition method. The film is transferred onto copper substrate and tested as the corrosion-inhibiting coating in sodium sulphate aqueous solution. The sample with 30nm h-BN coating shows significantly suppressed copper dissolution peak and only one fourth of the corrosion rate of the uncoated sample. Electrochemical impedance spectroscopy analysis reveals that the charge transfer resistance is much higher when h-BN film is present. Third, we invent a local probe electrochemical measurement method and successfully applied it to the electrolysis catalytic activity measurement of various kinds of transition metal dichalcogenides. The catalytic activity and turnover frequencies of the 2H-MoS2 basal plane versus edge as well as the 1T’-MoS2 basal plane are identified by this measurement. At the same time, the basal plane activity and turnover frequencies of transition metal dichalcogenides from different element groups has been obtained. We have shown that the general trend of the transition metal dichalcogenides in the form of volcano plot follows the trend of metals. VB-VIA dichalcogenides have been identified as the preferential selection for hydrogen evolution reaction catalysts. Last, we discussed the measurement of layered materials in photoelectrolysis using the local probe electrochemical method. Gallium selenide as a good photoconductor, is examined as the photoelectrolysis catalyst and shows promising photoelectrochemical hydrogen evolution performance. The turnover frequency and photon-to-electron conversion efficiency are obtained from our measurements.
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    Excitonic Resonant Emission–Absorption of Surface Plasmons in Transition Metal Dichalcogenides for Chip-Level Electronic–Photonic Integrated Circuits
    (American Chemical Society, 2016) Zhu, Zhuan; Yuan, Jiangtan; Zhou, Haiqing; Hu, Jonathan; Zhang, Jing; Wei, Chengli; Yu, Fang; Chen, Shuo; Lan, Yucheng; Yang, Yao; Wang, Yanan; Niu, Chao; Ren, Zhifeng; Lou, Jun; Wang, Zhiming; Bao, Jiming
    The monolithic integration of electronics and photonics has attracted enormous attention due to its potential applications. A major challenge to this integration is the identification of suitable materials that can emit and absorb light at the same wavelength. In this paper we utilize unique excitonic transitions in WS2 monolayers and show that WS2 exhibits a perfect overlap between its absorption and photoluminescence spectra. By coupling WS2 to Ag nanowires, we then show that WS2 monolayers are able to excite and absorb surface plasmons of Ag nanowires at the same wavelength of exciton photoluminescence. This resonant absorption by WS2 is distinguished from that of the ohmic propagation loss of silver nanowires, resulting in a short propagation length of surface plasmons. Our demonstration of resonant optical generation and detection of surface plasmons enables nanoscale optical communication and paves the way for on-chip electronic–photonic integrated circuits.
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    Nanoantenna-Enhanced Light-Matter Interaction in Atomically Thin WS2
    (American Chemical Society, 2015) Kern, Johannes; Trügler, Andreas; Niehues, Iris; Ewering, Johannes; Schmidt, Robert; Schneider, Robert; Najmaei, Sina; George, Antony; Zhang, Jing; Lou, Jun; Hohenester, Ulrich; de Vasconcellos, Steffen Michaelis; Bratschitsch, Rudolf
    Atomically thin transition metal dichalcogenides (TMDCs) are an emerging class of two-dimensional semiconductors. Recently, the first optoelectronic devices featuring photodetection as well as electroluminescence have been demonstrated using monolayer TMDCs as active material. However, the lightﾖmatter coupling for atomically thin TMDCs is limited by their small absorption length and low photoluminescence quantum yield. Here, we significantly increase the lightﾖmatter interaction in monolayer tungsten disulfide (WS2) by coupling the atomically thin semiconductor to a plasmonic nanoantenna. Due to the plasmon resonance of the nanoantenna, strongly enhanced optical near-fields are generated within the WS2ﾠmonolayer. We observe an increase in photoluminescence intensity by more than 1 order of magnitude, resulting from a combined absorption and emission enhancement of the exciton in the WS2monolayer. The polarization characteristics of the coupled system are governed by the nanoantenna. The robust nanoantennaﾖmonolayer hybrid paves the way for efficient photodetectors, solar cells, and light-emitting devices based on two-dimensional materials.
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    Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2ﾠheterostructures
    (Springer Nature, 2016) Chen, Hailong; Wen, Xiewen; Zhang, Jing; Wu, Tianmin; Gong, Yongji; Zhang, Xiang; Yuan, Jiangtan; Yi, Chongyue; Lou, Jun; Ajayan, Pulickel M.; Zhuang, Wei; Zhang, Guangyu; Zheng, Junrong
    Van der Waals heterostructures composed of two-dimensional transition-metal dichalcogenides layers have recently emerged as a new family of materials, with great potential for atomically thin opto-electronic and photovoltaic applications. It is puzzling, however, that the photocurrent is yielded so efficiently in these structures, despite the apparent momentum mismatch between the intralayer/interlayer excitons during the charge transfer, as well as the tightly bound nature of the excitons in 2D geometry. Using the energy-state-resolved ultrafast visible/infrared microspectroscopy, we herein obtain unambiguous experimental evidence of the charge transfer intermediate state with excess energy, during the transition from an intralayer exciton to an interlayer exciton at the interface of a WS2/MoS2ﾠheterostructure, and free carriers moving across the interface much faster than recombining into the intralayer excitons. The observations therefore explain how the remarkable charge transfer rate and photocurrent generation are achieved even with the aforementioned momentum mismatch and excitonic localization in 2D heterostructures and devices.