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ABSTRACT: We present a single-step template-free self-assembly method for constructing 1D-chains and 1D-networks of Au-nanoparticles.
The chains are formed by simply increasing the ion concentration of nanoparticle solution so that the attractive van der waals force prevails over the repulsive Coulomb interaction. A combination of this method and the previously developed charge trapping
technique allows us to place the 1D-chains/networks at designed locations. Further, the nanoparticle structures are stable
enough to withstand the subsequent e-beam lithographic processes for formation of nanoparticle-based electronics such as a
single electron transistor. Prominent Coulomb oscillation was observed at temperatures as high as 120K.
KeywordsSelf-assembly-Single electron transistor-Nanoparticle-Nanoelectronics
Journal of Nanoparticle Research 04/2012; 12(8):2859-2864. · 3.29 Impact Factor
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ABSTRACT: The photo-response of a ZnO nanoparticle embedded in a nanopore made on a silicon nitride membrane is investigated. The ZnO nanoparticle is manipulated onto the nanopore and sandwiched between aluminum contact electrodes from both the top and bottom. The asymmetric device structure facilitates current-voltage rectification that enables photovoltaic capacity. Under illumination, the device shows open-circuit voltage as well as short-circuit current. The fill factor is found to increase at low temperatures and reaches 48.6% at 100 K. The nanopore structure and the manipulation technique provide a solid platform for exploring the electrical properties of single nanoparticles.
Nanotechnology 04/2012; 23(16):165201. · 3.98 Impact Factor
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Ko-Shing Chang,
Chih-Jung Sun,
Pei-Ling Chiang,
Ai-Chuan Chou,
Ming-Chou Lin,
Chieh Liang,
Hui-Hsing Hung,
Yu-Hsiu Yeh, Chii-Dong Chen,
Chien-Yuan Pan,
Yit-Tsong Chen
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ABSTRACT: A silicon nanowire field-effect transistor (SiNW-FET) coated with a polyvinyl chloride (PVC) membrane containing valinomycin (VAL) was employed as a biosensor (referred to as VAL-PVC/SiNW-FET) to detect the K(+)-efflux from live chromaffin cells. The detection sensitivity of K(+) with the VAL-PVC/SiNW-FET covers a broad range of concentrations from 10(-6) to 10(-2) M. The apparent association constants between VAL and Li(+), Na(+), K(+), and Cs(+) in Tris buffer solution were determined to be 67±42, 120±23, 5974±115, and 4121±140 M(-1), respectively. By culturing chromaffin cells on the VAL-PVC/SiNW-FET, the conductance was significantly increased by nicotine stimulation in a bath buffer without Na(+). The K(+) concentration at the cell surface was determined to be ~20 μM under the stimulation of 5 mM nicotine. These results demonstrate that the VAL-PVC/SiNW-FET is sensitive and selective to detect the released K(+) from cells and is suitable for applications in cellular recording investigations.
Biosensors & bioelectronics 01/2012; 31(1):137-43. · 5.43 Impact Factor
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ABSTRACT: A movable carbon nanotube (CNT) cantilever gate is developed for the detection of embedded charge defects in suspended nanowires. The CNT gate is composed of a gold probe welded to a thick CNT, which is in turn attached to a thinner CNT. The rigid welding of the thicker CNT to the gold probe allows for precise placement along the measured nanowire while the joint between the thinner and thicker CNT absorbs the push and pull forces of repeated relocation. For demonstration purpose, the CNT gate determines the site of the embedded charges and measures the amount of trapped electrons.
Applied Physics Letters 07/2011; 99(5):053104-053104-3. · 3.84 Impact Factor
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ABSTRACT: Voltage controlled photoluminescence (PL) blinking behavior in CdSe nano-particles (NPs) is studied. The NPs are sandwiched between a p-type silicon substrate and a thin Au electrode, which serve respectively as source and drain electrodes. The blinking PL from the NPs can be controlled by the bias voltage across the two electrodes. However, luminescence diminishes when photo excitation power is weak or bias is lower than a threshold voltage. The observed PL blinking is explained by a circuit model, which involves charge tunneling, Fowler-Nordheim (F-N) emission, and charging effect. The blinking intensity is controlled by the number of F-N emitted electrons whereas the pulse interval is associated with the time required for hole accumulation in the NPs. The intensity of luminescence blinking for NP clusters is found to be much higher compared to that of blinking from isolated NPs. This is explained by a collective recombination of F-N emitted electrons and accumulated holes in the NP clusters. This study provides a simple way of controlling PL blinking.
Optics Express 12/2010; 18(26):26872-8. · 3.59 Impact Factor
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Advanced Functional Materials 11/2010; 21(3):474 - 479. · 10.18 Impact Factor
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Nano Today 05/2009; 4:235-243. · 15.35 Impact Factor
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ABSTRACT: Coaxial metal-oxide-semiconductor (MOS) Au-Ga2O3-GaN heterostructure nanowires were successfully fabricated by an in situ two-step process. The Au-Ga2O3 core-shell nanowires were first synthesized by the reaction of Ga powder, a mediated Au thin layer, and a SiO2 substrate at 800 degrees C. Subsequently, these core-shell nanowires were nitridized in ambient ammonia to form a GaN coating layer at 600 degrees C. The GaN shell is a single crystal, an atomic flat interface between the oxide and semiconductor that ensures that the high quality of the MOS device is achieved. These novel 1D nitride-based MOS nanowires may have promise as building blocks to the future nitride-based vertical nanodevices.
Nano Letters 10/2008; 8(10):3288-92. · 13.20 Impact Factor
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ABSTRACT: Exocytosis of a single bovine adrenal chromaffin cell, triggered by histamine stimulation, was investigated via the electric responses detected with single-walled carbon-nanotube field-effect transistors (SWCNT-FET) and the morphological changes acquired by atomic force microscopy (AFM). Secretion of chromogranin A (CgA), stored in the vesicles of a single chromaffin cell, can be monitored in situ by the antibody against CgA (CgA-antibody) functionalized on the SWCNT-FET devices. The SWCNT-FET can further discriminate the amount of released CgA with different levels of histamine stimulations. The AFM morphological studies on a chromaffin cell indicate that the depression structures on the cell surface, caused by the histamine-evoked exocytotic fusion pores, appeared much more frequently than those without histamine stimulation or with the pretreatment of mepyramine before histamine stimulation. The vesicle diameters are about 50 nm calculated from the obtained three-dimensional AFM images. In comparison, the fusion pores of chromaffin cells stimulated by high-K (+) buffer solution were also investigated to have a wider-ranging distribution of vesicle diameters of 60-260 nm. This work demonstrates that the combination of novel techniques, SWCNT-FET and AFM, can provide further insights into the fundamental properties of exocytosis in neuroendocrine cells.
The Journal of Physical Chemistry B 08/2008; 112(30):9165-73. · 3.70 Impact Factor
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Small 09/2007; 3(8):1356-61. · 8.35 Impact Factor
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Small 09/2007; 3(8):1350-5. · 8.35 Impact Factor
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ABSTRACT: Very dense and uniformly distributed nitrogen-doped tungsten oxide (WO(3)) nanowires were synthesized successfully on a 4-inch Si(100) wafer at low temperature. The nanowires were of lengths extending up to 5 mum and diameters ranging from 25 to 35 nm. The highest aspect ratio was estimated to be about 200. An emission peak at 470 nm was found by photoluminescence measurement at room temperature. The suggested growth mechanism of the nanowires is vapor-solid growth, in which gaseous ammonia plays a significant role to reduce the formation temperature. The approach has proved to be a reliable way to produce nitrogen-doped WO(3) nanowires on Si in large quantities. The direct fabrication of WO(3)-based nanodevices on Si has been demonstrated.
Small 05/2007; 3(4):658-64. · 8.35 Impact Factor
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ABSTRACT: In this study, distinct regions of trapped charges on glass substrates created by electron beam bombardment were utilized to attract and to immobilize DNA molecules. The negatively charged DNA molecules were attracted by the positive charge layer beneath the substrate surface resulting from escape of secondary electrons. With this mechanism, we demonstrated high-precision patterning of unmodified DNA molecules, independent of the length, sequence, and number of DNA strands, and with an attachment to the glass surface strong enough to withstand vigorous washing with water. DNA patterns with the line width of 50 nm were achieved.
Nanotechnology 09/2006; 17(19):4854. · 3.98 Impact Factor
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ABSTRACT: TaSi2 nanowires have been synthesized on a Si substrate by annealing NiSi2 films at 950 degrees C in an ambient containing Ta vapor. The nanowires could be grown up to 13 microm in length. Field-emission measurements show that the turn-on field is low at 4-4.5 V/microm and the threshold field is down to 6 V/microm with the field enhancement factor as high as 1800. The metallic TaSi2 nanowires exhibit excellent electrical properties with a remarkable high failure current density of 3 x 10(8) A cm(-2). In addition, effects of annealing temperatures and capability of metal silicide mediation layer on the growth of nanowires are addressed. This simple approach promises future applications in nanoelectronics and nano-optoelectronics.
Nano Letters 09/2006; 6(8):1637-44. · 13.20 Impact Factor
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ABSTRACT: Nanoposts of 10–40 nm top diameter on an InGaN/GaN quantum well structure were fabricated using electron-beam lithography and inductively coupled plasma reactive ion etching. Significant blue shifts up to 130 meV in the photoluminescence (PL) spectrum were observed. The blue-shift range increases with decreasing post diameter. For nanoposts with significant strain relaxation, the PL spectral peak position becomes less sensitive to carrier screening. On the basis of the temperature-dependent PL and time-resolved PL measurements and a numerical calculation of the effect of quantum confinement, we conclude that the optical behaviours of the nanoposts are mainly controlled by the combined effect of 3D quantum confinement and strain relaxation.
Nanotechnology 02/2006; 17(5):1454. · 3.98 Impact Factor
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ABSTRACT: Programmable patterning is one of the critical issues in pursuit of the long term goal of constructing the nanodevices, which we focus on in this research is biomolecule patterning. In this paper, we demonstrate a physical method of arranging DNA into specific desired nanoscale patterns on a glass substrate by using focused electron beam. Electron beam bombardment produces the distinct regions with trapped charges on a glass substrate, which exert the electrostatic attractive force for the DNA molecules. Various DNA patterns with the dimension ranging from micrometers to nanometers could be obtained without any chemical modification. DNA patterning by electron beam induced charge accumulation has been demonstrated by using both long (linear λ,-phage DNA) and short (20-mer) DNA strands. The relationship between the amount of immobilized DNA and the electron beam doses is examined in this paper.
Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on; 07/2005
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ABSTRACT: Two-dimensional (2D) arrays of gold nanoparticles with sulfur-containing fullerene nanoparticles were self-assembled through the formation of Au−S covalent bonds. Disulfide functional groups were introduced into the C60 molecule by reacting propyl 2-aminoethyl disulfide with C60. The 2D arrays were formed at the interface of the aqueous phase of gold particles and organic phase of fullerene particles as a blue transparent film. Transmission electronic microscope images showed that the fullerene spacing between adjacent Au (10 nm) particles was about 2.1 ± 0.4 nm, which was consistent with the result of 2.18 nm by molecular molding calculations (MM+). The UV−visible spectrum of this film showed a red shift and increased bandwidth due to the small spacing between gold nanoparticles. The arrays were deposited on the top of pairs of gold electrodes to form 2D colloidal single electron devices. The electrode pairs were made by electron beam lithographic techniques, and the separation between tips of the two electrodes in a pair was about 100 nm. Electron transport measurements at low temperatures exhibited Coulomb blockade type current−voltage characteristics due to the charge effects. The assembled arrays have potential applications as nanoelectronics.
03/2002;
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ABSTRACT: Novel arrays of gold nanoparticles with sulfur containing fullerene nanoparticles were self-assembled through the formation of Au-S covalent bonds. Disulfide functional groups were introduced into C60 molecule by reacting propyl 2-aminoethyl disulfide with C60. The two dimensional(2D) arrays were formed at the interface of aqueous phase of gold particles and organic phase of fullerene particles as a blue transparent film. TEM images showed that the fullerene spacing between adjacent Au(∼10 nm) particles was about 2.1±0.4 nm, which was consistent with the result of 2.18 nm by molecular molding calculations(MM+). The arrays were deposited on the top of pairs of gold electrodes to form 2D colloidal single electron devices. The electrode pairs were made by electron beam lithography techniques, and the separation between tips of the two electrodes in a pair was less then 100 nm. Transport measurements at low temperatures exhibited Coulomb-Blockade type current-voltage characteristics, the lower the temperature the more pronounced the Coulomb gap. Also, step-by-step method was used to assemble one-dimensional(1D) array of gold nanoparticles with fullerene derivative between two electrodes spaced with 15 nm. The Coulomb blockade behavior of 1D arrays was clearer than that of 2D arrays.
MRS Proceedings. 12/2000; 707.
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ABSTRACT: Carbon coils of micrometer to nanometer wire diameter were grown bi-directionally by catalyst-assisted chemical vapor deposition. Electron microscope images showed the highly disordered structure of the carbon coils. Chemical compositions of the coils were identified with elemental analysis, atmospheric pressure-laser desorption ionization-Fourier-transform ion cyclotron resonance-mass spectroscopy and secondary ion mass spectrometric characterizations, and attenuated total reflection-infrared spectroscopic examination. Micro-Raman scattering spectroscopy and electron energy loss spectroscopy were also used to study the vibrational and electronic properties of the helical structure. The electric transport in a single carbon coil was measured from ambient temperature to 64 mK. The temperature-dependent resistance was analyzed with the Efros-Shklovskii variable range hopping model, indicating three-dimensional electron hopping conduction in the disordered helical wires. The analysis also provides a basic understanding of the electron transport with an electron hopping length of ∼5 nm inside the disordered carbon coils.
Carbon.
