Self-assembled arrays of zinc oxide nanoparticles from monolayer films of diblock copolymer micelles

A hexagonal array of optically active ZnO nanoparticles was synthesized in situ on the solid substrate by utilizing a single-layered film of diblock copolymer micelles as a nanostructured template.X1135sciescopu

Near ultraviolet light emitting diode composed of n-GaN/ZnO coaxial nanorod heterostructures on a p-GaN layer

The authors report on the fabrication and characteristics of near ultraviolet nanorod light emitting diodes (LEDs) composed of n-GaN/ZnO nanorod heterostructures on p-GaN substrates. The nanorod LEDs consist of the vertically aligned n-GaN/ZnO coaxial nanorod arrays grown on a p-GaN substrate. The LEDs demonstrated strong near ultraviolet emission at room temperature. The nanorod LEDs were turned on a forward-bias voltage of 5 V, and exhibited a large light emitting area. From electroluminescent spectra, dominant emission peaks were observed at 2.96 and 3.24 eV for an applied current of 2 mA. The origins of the strong and large area light emission are also discussed in terms of enhanced carrier injection from n-GaN nanostructures to p-GaN substrates.open114148sciescopu

Photoluminescent characteristics of Ni-catalyzed GaN nanowires

The authors report on time-integrated and time-resolved photoluminescence (PL) of GaN nanowires grown by the Ni-catalyst-assisted vapor-liquid-solid method. From PL spectra of Ni-catalyzed GaN nanowires at 10 K, several PL peaks were observed at 3.472, 3.437, and 3.266 eV, respectively. PL peaks at 3.472 and 3.266 eV are attributed to neutral-donor-bound excitons and donor-acceptor pair, respectively. Furthermore, according to the results from temperature-dependent and time-resolved PL measurements, the origin of the PL peak at 3.437 eV is also discussed. (c) 2006 American Institute of Physics.X1147sciescopu

Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays

We report enhanced light output of GaN-based light-emitting diodes (LEDs) with vertically aligned ZnO nanorod arrays. The ZnO nanorod arrays were prepared on the top layer of GaN LEDs using catalyst-free metalorganic vapor phase epitaxy. Compared to conventional GaN LEDs, light output of GaN LEDs with the ZnO nanorod arrays increased up to 50% and 100% at applied currents of 20 and 50 mA, respectively. The source of the enhanced light output is also discussed. (C) 2008 American Institute of Physics.open11132146sciescopu

Biomimetic engineered muscle with capacity for vascular integration and functional maturation in vivo.

Tissue-engineered skeletal muscle can serve as a physiological model of natural muscle and a potential therapeutic vehicle for rapid repair of severe muscle loss and injury. Here, we describe a platform for engineering and testing highly functional biomimetic muscle tissues with a resident satellite cell niche and capacity for robust myogenesis and self-regeneration in vitro. Using a mouse dorsal window implantation model and transduction with fluorescent intracellular calcium indicator, GCaMP3, we nondestructively monitored, in real time, vascular integration and the functional state of engineered muscle in vivo. During a 2-wk period, implanted engineered muscle exhibited a steady ingrowth of blood-perfused microvasculature along with an increase in amplitude of calcium transients and force of contraction. We also demonstrated superior structural organization, vascularization, and contractile function of fully differentiated vs. undifferentiated engineered muscle implants. The described in vitro and in vivo models of biomimetic engineered muscle represent enabling technology for novel studies of skeletal muscle function and regeneration

Local structure around Ga in ultrafine GaN/ZnO coaxial nanorod heterostructures

The structure of tubular GaN coaxially grown on ZnO nanorods with thickness of 6-12 nm was investigated using x-ray absorption fine structure (XAFS) at the Ga K edge. The XAFS measurements revealed that the GaN had a distorted-wurtzite structure, and that there were more distortions in the bond length of Ga-Ga pairs than in Ga-N pairs. However, no extra disorders were observed in any of the pairs. These results strongly suggest that Ga atoms first bonded to the ZnO template. Unlike other techniques, the XAFS determines structure around a selected species atom in nano-heterostructures. (c) 2006 American Institute of Physics.open1188sciescopu

Orientation-dependent x-ray absorption fine structure of ZnO nanorods

The local structure of two samples of vertically well-aligned ZnO nanorods with average diameters of 13 and 37 nm were studied using orientation-dependent x-ray absorption fine structure (XAFS) at the Zn K edge. The aligned ZnO nanorod samples were fabricated on sapphire (0001) substrates with a catalyst-free metalorganic vapor-phase epitaxy method. The XAFS measurements showed that both nanorod samples have a well-ordered wurtzite structure and that no vacancy was observed at either site of zinc or oxygen atoms. However, we found that in both samples the lattice constants of a and b were shrunken by similar to0.04 Angstrom while c was elongated by similar to0.1 Angstrom, compared with those of their bulk counterparts. Furthermore, there was a substantial amount of disorder in the bond length of the only Zn-O pairs located near the ab plane. This may suggest that the terminating atoms at the boundaries of the nanorods are oxygen atoms. (C) 2005 American Institute of Physics.open114545sciescopu

Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures

We report low-temperature near-field spectroscopy of isolated ZnO/ZnMgO single-quantum-well structures (SQWs) on the end of ZnO nanorod to define their potential for nanophotonics. First, absorption spectra of isolated ZnO/ZnMgO nanorod SQWs with the Stokes shift as small as 3 meV and very sharp photoluminescent peaks indicate that the nanorod SQWs are of very high optical quality. Furthermore, we performed polarization spectroscopy of isolated ZnO SQWs, and observed valence-band anisotropy of ZnO SQWs in photoluminescence spectra directly. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices. (c) 2005 American Institute of Physics.open111828sciescopu

Evaluation of the discrete energy levels of individual ZnO nanorod single-quantum-well structures using near-field ultraviolet photoluminescence spectroscopy

Spatially and spectrally resolved photoluminescence imaging of individual ZnO/ZnMgO nanorod single-quantum-well structures (SQWs) with a spatial resolution of 55 nm was performed using the optical near-field technique with a metallized UV fiber probe. Using excitation power density-dependent photoluminescence spectra of a ZnO/ZnMgO SQW nanorod, we observed the discrete energy levels in a ZnO quantum-well layer. (C) 2004 American Institute of Physics.open112930sciescopu