This study describes the elimination of threading dislocations (TDs) in GaN nanostructures. Cross-sectional transmission electron microscopy (XTEM) analysis reveals that the nominal [0001] line direction of a TD changes when it enters a GaN nanostructure and the dislocation then terminates at a sidewall facet. It is suggested that the driving force for this process is the reduction of dislocation line energy, and for a pure-edge dislocation, this TD elimination process can be accomplished simply by dislocation climb. This mechanism is active whenever a threading defect is in close proximity to a surface. Preliminary XTEM analysis of defects in AlGaN and InGaN core–shell growth onto GaN nanostructures is also shown. Although more work is required to improve the quality of core–shell InGaN epitaxial growth, nanostructures appear to offer a route to defect-free, nonpolar GaN-based devices.

Syntaxial growth of Mn11Ge8/Ge nanowire heterostructures was carried out using a vapor–solid–solid (VSS) growth process, and transmission electron microscopy imaging and selected-area electron diffraction were used to study the structure, orientation, and interface of each phase. Preferred crystallographic relationships were found to exist between the Mn11Ge8 seeds, which exhibit a single uniaxial growth direction, and the seeded Ge nanowires, which exhibit multiple growth directions. The crystallographic relationships for individual nanowire heterostructures were characterized in the context of microtexture analysis, which has not previously been applied to nanowire heterostructures. Fiber and off-normal fiber textures were predominant, although examples of epitaxial and uniaxial in-plane textures were also identified. Microtexture analysis of VSS-grown nanowire systems is shown to provide a useful perspective on the products of synthesis that can lead to new insights into growth mechanisms.

It was observed that silicon and germanium nanowires can exhibit significant electrostatic charging and respond strongly to externally applied electric fields. This includes nanowires in air and dispersed in low-conductivity, low-dielectric-constant solvents such as hexane, toluene, and benzene. The electrostatic charging of semiconductor nanowires was investigated as a tool for nanowire manipulation. By charging a substrate, nanowires could be deposited on surfaces with very high coverage and onto selected locations of the surface. The density of deposited nanowires could be adjusted systematically by varying the strength of the electric field. Alternating electric fields, applied between two electrodes, resulted in nanowires oriented with respect to the field orientation.

SrAl2O4:Eu2+,Dy3+ polynary complex nanobelts with long-persisting phosphorescence were synthesized via a facile but efficient combustion method followed by a postannealing reaction at temperature above 900 °C. All the samples emit greenish-yellow light from the d-f transition of Eu2+, and moreover, their wavelength redshifts with increasing calcination temperature since the increase in crystal size and crystalline quality causes a large average optical path and high crystal symmetry, respectively. The decay constant of the sample calcined at low temperature is smaller than that of the one annealed at high temperature owing to the presence of higher densities and depths of electron traps donated by host defects, and the initial brightness of the sample calcined at low temperature is relatively low owing to the small volume fraction from relatively low crystallinity.

A simple and controllable fabrication of TiO2 nanowires by electrospinning and their applications to the electron transporting layer for hybrid organic–inorganic photovoltaic cells are reported. TiO2 nanowires were directly electrospun onto an indium tin oxide on glass substrate from a solution in methanol of polyvinylpyrrolidone, titanium(IV) butoxide, and acetylacetone. The nanowire electrode obtained was consequently subjected to calcination at 450 °C. Solution of blended [6,6]-phenyl-C61-butyric acid methyl ester and poly(3-hexylthiophene) was spin coated on the TiO2 nanowire electrode, followed by thermal annealing and deposition of Au electrode. Hybrid organic–inorganic photovoltaic cells made of TiO2 nanowires exhibited remarkable improvement of the cell efficiencies in terms of photocurrent density and open-circuit voltage as compared with those of references, TiO2 flat films. Maximum energy conversion efficiency of hybrid organic–inorganic photovoltaic cells made of TiO2 nanowires of 1.27% was achieved.

Ga2O3/SnO2 core–shell nanowires were synthesized by combining thermal evaporation and atomic layer deposition (ALD), and nanowire network sensors were fabricated by directly depositing them on the substrate with interdigitated Pt electrodes. Crystalline Ga2O3 nanowires of ∼20 nm diameter were grown on Au-catalyzed substrate at 800 °C. ALD-grown SnO2 shell layer was composed of interconnected nanoparticles of <10 nm, and its thickness was varied depending on the number of ALD cycles. The core–shell nanowire sensors exhibited the highest ethanol gas response at 400 °C, which was ∼200 °C lower than that for Ga2O3 nanowire sensor. The 100 cycle SnO2-coated nanowire sensor whose shell thickness was close to the Debye length of SnO2 had higher ethanol gas response in all the temperatures investigated. In addition, the core–shell nanowire sensors showed an order of magnitude higher gas response toward ethanol against other gases, such as H2, CO, and NH3.

Gold nanoparticle–coated ZnO tetrapods have been utilized as a substrate for the detection of fluorescently labeled protein tetramethylrhodamine isothiocyanate bovine serum albumin and phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(Lissamine rhodamine B sulfonyl) down to the concentrations of 15 pM and 79 nM, respectively. Our detection scheme is based on enhanced fluorescence excitation of the biomolecular analytes by the surface plasmon polaritons of gold nanoparticles coated on the ZnO tetrapod whiskers. This enhanced excitation is confirmed using COMSOL Multiphysics, where the optical near field is shown to be dependent on the coating density of the gold nanoparticles and branching of the ZnO nanostructures.