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ABSTRACT: A semiconductor/environment interface has been formed in which suspended silicon nanowires (SiNWs) are in direct contact with photoactive TiO(2) quantum dots. The photoactivity of TiO(2) competes with the intrinsic photoresponses of p-type silicon nanowires. Rational control of the competitive mechanism realizes remarkable mirror-imaging photo-switching and superior rectifying effects in a single SiNW-based device.
Angewandte Chemie International Edition 02/2013; · 13.45 Impact Factor
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ABSTRACT: A molecular-scale gap array is introduced into a single-layer graphene sheet by a lithographic dash-line cutting process. Electrically active molecules are then covalently wired into these point contacts in high yield, thus forming stable molecular devices that for example are able to reversibly switch their conductance by chemical treatment.
Angewandte Chemie International Edition 11/2012; · 13.45 Impact Factor
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Shaohua Dong,
Hongtao Zhang,
Liu Yang,
Meilin Bai,
Yuan Yao,
Hongliang Chen, Lin Gan,
Tieying Yang,
Hong Jiang,
Shimi Hou,
Lijun Wan,
Xuefeng Guo
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ABSTRACT: Molecular engineering and chemical self-assembly are combined with materials fabrication to achieve air-stable solution-processable oligothiophene-based field-effect transistors with mobilities up to 6.2 cm(2) V(-1) s(-1) , which ranks as the highest among oliogthiophene-based semiconducting materials.
Advanced Materials 09/2012; · 13.88 Impact Factor
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ABSTRACT: An intrinsic mechanism of photoinduced hole transfer reactions occurring at the grapheme-PbS interface is described with the purpose of building a tunable photosensor with a responsivity of more than 10(3) A W(-1) . It is remarkable that rational utilization of this finding also realizes symmetric, opposing photoswitching effects, which are effectively mirror images, in a single pristine graphene device. These results highlight the vital importance of interface modification as a powerful tool for creating future ultrasensitive optoelectronic devices.
Advanced Materials 04/2012; 24(20):2715-20. · 13.88 Impact Factor
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ABSTRACT: Semiconductor nanowires (NWs) or nanobelts (NBs) have attracted more and more attention due to their potential application in novel optoelectronic devices. In this review, we present our recent work on novel NB photodetectors, where a three-terminal metal-semiconductor field-effect transistor (MESFET) device structure was exploited. In contrast to the common two-terminal NB (NW) photodetectors, the MESFET-based photodetector can make a balance among overall performance parameters, which is desired for practical device applications. We also present our recent work on graphene nanoribbon/semiconductor NW (SNW) heterojunction light-emitting diodes (LEDs). Herein, by taking advantage of both graphene and SNWs, we have fabricated, for the first time, the graphene-based nano-LEDs. This achievement opens a new avenue for developing graphene-based nano-electroluminescence devices. Moreover, the novel graphene/SNW hybrid devices can also find use in other applications, such as high-sensitivity sensor and transparent flexible devices in the future.
Nanoscale Research Letters 04/2012; 7(1):218. · 2.73 Impact Factor
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ABSTRACT: Fast and efficient surface functionalization of graphene is achieved by the electrochemical formation of aryl radicals from diazonium salts under mild conditions. Precise control of the ratio of electron-deficient nitro groups to electron-rich amino groups is also demostrated, potentially resulting in the controllable tuning of the electrical properties of graphenes.
Small 02/2012; 8(9):1326-30. · 8.35 Impact Factor
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ABSTRACT: We detailed a facile detection technique to optically characterize graphene growth and domains directly on growth substrates through a simple thermal annealing process. It was found that thermal annealing transformed the naked Cu to Cu oxides while keeping graphene and graphene-covered Cu intact. This increases the interference color contrast between Cu oxides and Cu, thus making graphene easily visible under an optical microscope. By using this simple method, we studied the factors that affect graphene nucleation and growth and achieved graphene domains with the domain size as large as ~100 μm. The concept of chemically making graphene visible is universal, as demonstrated by the fact that a solution process based on selective H(2)O(2) oxidation has been developed to achieve the similar results in a shorter time. These techniques should be valuable for studies towards elucidating the parameters that control the grains, boundaries, structures and properties of graphene.
Scientific Reports 01/2012; 2:707.
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ABSTRACT: We report novel graphene nanoribbon (GNR)/semiconductor nanowire (SNW)
heterojunction light-emitting diodes (LEDs) for the first time. The GNR and SNW
have a face-to-face contact structure, which has the merit of bigger active
region. ZnO, CdS, and CdSe NWs were employed in our case. At forward biases,
the GNR/SNW heterjunction LEDs could emit light with wavelengths varying from
ultraviolet (380 nm) to green (513 nm) to red (705 nm), which were determined
by the band-gaps of the involved SNWs. The mechanism of light emitting for the
GNR/SNW heterojunction LED was discussed. Our approach can easily be extended
to other semiconductor nano-materials. Moreover, our achievement opens the door
to next-generation display technologies, including portable, "see-through", and
conformable products.
03/2011;
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ABSTRACT: We have developed a simple and scalable graphene patterning method using electron-beam or ultraviolet lithography followed by a lift-off process. This method, with the merits of: high pattern resolution and high alignment accuracy, being free from additional etching or harsh processes, being universal to arbitrary substrates, and being compatible to Si microelectronic technology, can easily be applied to diverse graphene-based devices, especially in array-based applications, where large-scale graphene patterns are desired. We have applied this method to fabricate CdSe nanobelt (NB)/graphene Schottky junction solar cells, which have potential applications in integrated nano-optoelectronic systems. A typical as-fabricated solar cell shows excellent photovoltaic behavior, with an open-circuit voltage of ∼0.51 V, a short-circuit current density of ∼5.75 mA cm(-2), and an energy conversion efficiency of ∼1.25%. We attribute the high performance of the cell to the as-patterned high-performance graphene, which can form an ideal Schottky contact with CdSe NB. Our results suggest that both the developed graphene patterning method and the as-fabricated CdSe NB/graphene Schottky junction solar cells have reachable application prospects.
Nanoscale 03/2011; 3(4):1477-81. · 5.91 Impact Factor
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Angewandte Chemie International Edition 08/2010; 49(36):6319-23. · 13.45 Impact Factor
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Angewandte Chemie 08/2010; 122(36):6463 - 6467.
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Advanced Materials 08/2010; 22(30):3282-7. · 13.88 Impact Factor
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ABSTRACT: In this study, we detailed our design for making a photoactive semiconductor/dielectric interface in order to study charge dynamics at the interface in combination with photoexcitation, using organic thin-film transistors (OTFTs) as local probes. The photoactive semiconductor/dielectric interface is formed from a hybrid gate dielectric (polymethyl methacrylate (PMMA) and titanium oxide (TiO2)). Because the photogenerated electrons from TiO2 nanoparticles under UV illumination can serve as the trapping centers for quenching hole carriers, p-type semiconductors showed the decrease of the hole mobility. Interestingly, n-type semiconductors displayed symmetric, opposing photoswitching effects at the same condition, showing that the photogenerated holes can function as a local positive gate voltage for improving the electron mobility. On the basis of this understanding, a remarkable example of mirror-image photoswitching effects in a single ambipolar OTFT was realized. These results may offer grounds for the creation of the future practical/multifunctional organic optoelectronic devices.Keywords (keywords): photoswitching; organic thin-film transistors; titanium oxide; mobility; charge trapping/detrapping
03/2010;
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ABSTRACT: Because of the one-dimensional (1D) nanostructural nature of single-walled carbon nanotubes (SWNTs) and their advantages of chemical flexibility and sensitivity arising from the susceptibility of their active surfaces to interacting species, great effort has been made to integrate carbon nanotube field-effect transistors (NTFETs) into functional optoelectronic devices capable of converting external stimuli to easily detectable electrical signals. In this Review article, we aim to capture recent advances of rational design and chemical functionalization of NTFETs for the purpose of switching or biosensing applications. To provide a deeper understanding of the device responses to analytes, this review will also survey the proposed sensing mechanisms. As demonstrated by these remarkable examples, the concept of combining the proper selection of functional molecular materials and molecular self-assembly with device micro/nanofabrication offers attractive new prospects for constructing NTFET-based molecular optoelectronic devices with desired functionalities.
Coordination Chemistry Reviews.
