Fabrication and characterization of GaAs quantum well buried in AlGaAs/GaAs heterostructure nanowires

We developed a growth method for forming a GaAs quantum well contained in an AlGaAs/GaAs heterostructure nanowire by using selective-area metal organic vapor phase epitaxy. To find the optimum growth condition of AlGaAs nanowires, we changed the growth temperature between 800 and 850℃ and found that best uniformity of the shape and the size was obtained near 800℃ but lateral growth of AlGaAs became larger, which resulted in a wide GaAs quantum well grown on the top (111)B facet of the AlGaAs nanowire. To form the GaAs quantum well with a reduced lateral size atop the AlGaAs nanowire, a GaAs core nanowire about 100 nm in diameter was grown before the AlGaAs growth, which reduced the lateral size of AlGaAs to roughly half compared with that without the GaAs core. Photoluminescence measurement at 4.2 K indicated spectral peaks of the GaAs quantum wells about 60 meV higher than the acceptor-related recombination emission peak of GaAs near 1.5 eV. The photoluminescence peak energy showed a blue shift of about 15 meV, from 1.546 to 1.560 eV, as the growth time of the GaAs quantum well was decreased from 8 to 3 sec. Transmission electron microscopy and energy dispersive X-ray analysis of an AlGaAs/GaAs heterostructure nanowire indicated a GaAs quantum well with a thickness of 5-20 nm buried along the direction between the AlGaAs shells, showing a successful fabncation of the GaAs quantum well

Semiconductor nanowires and nanotubes: from fundamentals to diverse applications

Research in the field of semiconductor nanowires (SNWs) and nanotubes has been progressing into a mature subject with several highly interdisciplinary subareas such as nanoelectronics, nanophotonics, nanocomposites, biosensing, optoelectronics, and solar cells. SNWs represent a unique system with novel properties associated to their one-dimensional (1D) structures. The fundamental physics concerning the formation of discrete 1D subbands, coulomb blockade effects, ballistic transport, and many-body phenomena in 1D nanowires and nanotubes provide a strong platform to explore the various scientific aspects in these nanostructures. A rich variety of preparation methods have already been developed for generating well-controlled 1D nanostructures and from a broad range of materials. The present special issue focuses on the recent development in the mechanistic understanding of the synthesis, the studies on electrical/optical properties of nanowires and their applications in nanoelectronics, nanophotonics, and solar-energy harvesting.Published versio

Polaprezinc attenuates cyclophosphamide-induced cystitis and related bladder pain in mice

AbstractCav3.2 T-type Ca2+ channels targeted by H2S, a gasotransmitter, participate in cyclophosphamide-induced cystitis and bladder pain. Given that zinc selectively inhibits Cav3.2 among T-channel isoforms and also exhibits antioxidant activity, we examined whether polaprezinc (zinc-l-carnosine), a medicine for peptic ulcer treatment and zinc supplementation, reveals preventive or therapeutic effects on bladder inflammation and/or pain in the mouse with cyclophosphamide-induced cystitis, a model for interstitial cystitis. Systemic administration of cyclophosphamide caused cystitis-related symptoms including increased bladder weight and vascular permeability, and histological signs of bladder edema, accompanied by bladder pain-like nociceptive behavior/referred hyperalgesia. All these symptoms were significantly attenuated by oral preadministration of polaprezinc at 400 mg/kg. The same dose of polaprezinc also prevented the increased malondialdehyde level, an indicator of lipid peroxidation, and protein upregulation of cystathionine-γ-lyase, an H2S-generating enzyme, but not occludin, a tight junction-related membrane protein, in the bladder tissue of cyclophosphamide-treated mice. Oral posttreatment with polaprezinc at 30–100 mg/kg reversed the nociceptive behavior/referred hyperalgesia in a dose-dependent manner without affecting the increased bladder weight. Together, our data show that zinc supplementation with polaprezinc prevents the cyclophosphamide-induced cystitis probably through the antioxidant activity, and, like T-channel blockers, reverses the established cystitis-related bladder pain in mice, suggesting novel therapeutic usefulness of polaprezinc