Optical Properties of GaSb Nanofibers

Amorphous GaSb nanofibers were obtained by ion beam irradiation of bulk GaSb single-crystal wafers, resulting in fibers with diameters of ~20 nm. The Raman spectra and photoluminescence (PL) of the ion irradiation-induced nanofibers before and after annealing were studied. Results show that the Raman intensity of the GaSb LO phonon mode decreased after ion beam irradiation as a result of the formation of the amorphous nanofibers. A new mode is observed at ~155 cm-1 both from the unannealed and annealed GaSb nanofiber samples related to the A1g mode of Sb–Sb bond vibration. Room temperature PL measurements of the annealed nanofibers present a wide feature band at ~1.4–1.6 eV. The room temperature PL properties of the irradiated samples presents a large blue shift compared to bulk GaSb. Annealed nanofibers and annealed nanofibers with Au nanodots present two different PL peaks (400 and 540 nm), both of which may originate from Ga or O vacancies in GaO. The enhanced PL and new band characteristics in nanostructured GaSb suggest that the nanostructured fibers may have unique applications in optoelectronic devices

Actions of amantadine at synaptic and extrasynaptic cholinergic receptors in the central nervous system of the cockroach Periplaneta americana

The effects of amantadine were investigated on cercal afferent, giant interneurone synapses and on the cell body membrane of the fast coxal depressor motoneurone (Df), in the cockroach Periplaneta americana. Bath-applied amantadine at concentrations above 2.0 × 10-5 M significantly reduced the amplitude of unitary and compound epsps recorded by sucrose-gap methods from cercal afferent, giant interneurone synapses in the desheathed sixth abdominal ganglion. Complete block of synaptic transmission was achieved at 1.0 × 10-3 M amantadine. Synaptic blockade, which was not accompanied by changes in resting potential, was almost fully reversed by washing the ganglion in normal saline. From the dose-dependence of the synaptic blocking action, a Hill coefficient of 0.94 was estimated, indicating that there is no co-operativity in the binding of amantadine to its site of action. Bath-application of amantadine (5.0 × 10-5 M) resulted in a parallel shift to the right of the dose-response curve for the depolarizing postsynaptic actions of acetylcholine. Nevertheless, even at a concentration of 2.0 × 10-3 M, amantadine failed to protect the synaptic acetylcholine receptor/ion channel complex from the blocking action of α-bungarotoxin (5.0 × 10-7 M). In addition, the block by amantadine of the acetylcholine-induced current recorded from the cell body membrane of the fast coxal depressor motoneurone (Df), was strongly dependent on membrane potential in the range - 120mV to - 70mV. An action of amantadine at the open acetylcholine receptor/ion channel complex is proposed.</p

P-to n-type Conversion in GaSb by ion-beam milling

Inversion in conductivity type of GaSb from p- to n- has been observed as a result of argon ion beam milling. Electron beam induced current (EBIC) measurements have been employed for detecting the type conversion. Enhancement in the luminescence intensity is seen after ion beam treatment. The type conversion is proposed to occur due to a combined effect of generation of native donors and gettering of native accepters originally present in the as-grown samples