Ambipolar transport in Ni-catalyzed InGaAs nanowire field-effect transistors for near-infrared photodetection.

Weak n-type characteristics or poor p-type characteristics are limiting the applications of binary semiconductors based on ambipolar field-effect transistors (FETs). In this work, a ternary alloy of In0.2Ga0.8As nanowires (NWs) is successfully prepared using a Ni catalyst during a typical solid-source chemical-vapor-deposition process to balance the weak n-type conduction behavior in ambipolar GaAs NWFETs and the poor p-type conduction behavior in ambipolar InAs NWFETs. The presence of ambipolar transport, contributed by a native oxide shell and the body defects of the prepared In0.2Ga0.8As NWs, is confirmed by the constructed back-gated NWFETs. As demonstrated by photoluminescence, the bandgap of the prepared In0.2Ga0.8As NWs is 1.28 eV, offering the promise of application in near-infrared (NIR) photodetection. Under 850 nm laser illumination, the fabricated ambipolar NWFETs show extremely low dark currents of 50 pA and 0.5 pA when positive and negative gate voltages are applied, respectively. All the results demonstrate that with careful design of the surface oxide layer and the body defects, NWs are suitable for use in next-generation optoelectronic devices.

Defect-engineered three-dimensional vanadium diselenide microflowers/nanosheets on carbon cloth by chemical vapor deposition for high-performance hydrogen evolution reaction.

In the past decades, defect engineering has become an effective strategy to significantly improve the hydrogen evolution reaction (HER) efficiency of electrocatalysts. In this work, a facile chemical vapor deposition (CVD) method is firstly adopted to demonstrate defect engineering in high-efficiency HER electrocatalysts of vanadium diselenide nanostructures. For practical applications, the conductive substrate of carbon cloth (CC) is selected as the growth substrate. By using a four-time CVD method, uniform three-dimensional microflowers with defect-rich small nanosheets on the surface are prepared directly on the CC substrate, displaying a stable HER performance with a low Tafel slope value of 125 mV dec-1and low overpotential voltage of 295 mV at a current density of 10 mA cm-2in alkaline electrolyte. Based on the results of x-ray photoelectron spectra and density functional theory calculations, the impressive HER performance originates from the Se vacancy-related active sites of small nanosheets, while the microflower/nanosheet homoepitaxy structure facilitates the carrier flow between the active sites and conductive substrate. All the results present a new route to achieve defect engineering using the facile CVD technique, and pave a novel way to prepare high-activity layered electrocatalysts directly on a conductive substrate.

Ultrahigh Hole Mobility of Sn-Catalyzed GaSb Nanowires for High Speed Infrared Photodetectors.

Owing to the relatively low hole mobility, the development of GaSb nanowire (NW) electronic and photoelectronic devices has stagnated in the past decade. During a typical catalyst-assisted chemical vapor deposition (CVD) process, the adopted metallic catalyst can be incorporated into the NW body to act as a slight dopant, thus regulating the electrical properties of the NW. In this work, we demonstrate the use of Sn as a catalyst and dopant for GaSb NWs in the surfactant-assisted CVD growth process. The Sn-catalyzed zinc-blende GaSb NWs are thin, long, and straight with good crystallinity, resulting in a record peak hole mobility of 1028 cm2 V-1 s-1. This high mobility is attributed to the slight doping of Sn atoms from the catalyst tip into the NW body, which is verified by the red-shifted photoluminescence peak of Sn-catalyzed GaSb NWs (0.69 eV) compared with that of Au-catalyzed NWs (0.74 eV). Furthermore, the parallel array NWs also show a high peak hole mobility of 170 cm2 V-1 s-1, a high responsivity of 61 A W-1, and fast rise and decay times of 195.1 and 380.4 µs, respectively, under the illumination of 1550 nm infrared light. All of the results demonstrate that the as-prepared Sn-catalyzed GaSb NWs are promising for application in next-generation electronics and optoelectronics.

Influence of CYP2D6 and ß2-adrenergic receptor gene polymorphisms on the hemodynamic response to propranolol in Chinese Han patients with cirrhosis.

BACKGROUND AND AIM: Propranolol is widely used to prevent gastroesophageal variceal bleeding; however, some patients could not benefit from propranolol. This study is to evaluate the relationship between CYP2D6 and ß2-adrenergic receptor (ß2-AR) gene polymorphisms and the hemodynamic response to propranolol in Chinese Han patients. METHODS: The clinical data of patients with gastroesophageal varices undergoing hepatic venous pressure gradient (HVPG) measurement before and 7 days after oral propranolol administration in our department were collected. Four single nucleotide polymorphisms of CYP2D6 and ß2-AR genes were detected. The relationship was identified by logistic regression model. RESULTS: Thirty patients were involved in the analysis. Sixty milligram propranolol twice each day was well tolerated by all the patients. The initial and secondary average of HVPG was 17.4 ± 5.8 mmHg vs. 13.2 ± 4.8 mmHg, respectively (t = 5.726, P < 0.001). Twenty patients responded to propranolol. The mean reduction value of HVPG was 6.6 ± 3.6 mmHg (range from 3 to 19). Genotype analysis showed: 20 homozygotes for C/C188 and 10 for heterozygous C/T188, 8 homozygotes for G/G4268 and 22 heterozygotes for G/C4268, 14 homozygotes for Gly16 and 10 heterozygotes, and 6 homozygotes for Arg16, 27 homozygotes for Gln27 and 3 heterozygotes. The multivariate logistic regression analysis indicated that CYP2D6 (188C>T) genotype was an independent predicting factor for HVPG response to propranolol (P = 0.033). CONCLUSIONS: CYP2D6 (188C>T) gene polymorphisms influence the hemodynamic response to propranolol in this population of Chinese Han patients with gastroesophageal varices. However, HVPG response cannot be completely predicted from CYP2D6 and ß2-AR gene polymorphisms.

In Situ Growth of GeS Nanowires with Sulfur-Rich Shell for Featured Negative Photoconductivity.

The negative photoconductivity (NPC) effect originating from the surface shell layer has been considered as an efficient approach to improve the performance of optoelectronic nanodevices. However, a scientific design and precise growth of NPC-effect-caused shell during nanowire (NW) growth process for achieving high-performance photodetectors are still lacking. In this work, GeS NWs with a controlled sulfur-rich shell, diameter, and length are successfully prepared by a simple chemical vapor deposition method. As checked by transmission electron microscopy, the thickness of the sulfur-rich shell ranges from 10.5 ± 1.5 to 13.4 ± 2.5 nm by controlling the NW growth time. The composition of the sulfur-rich shell is studied by X-ray photoelectron spectroscopy, showing the decrease of S in the GeSx shell from the surface to core. When configured into the well-known phototransistor, a featured NPC effect is observed, benefiting the high-performance photodetector with high responsivity of 105 A·W-1 and detectivity of 1012 Jones for λ = 405 nm with ultralow intensity of 0.04 mW·cm-2. However, the thicker-shell NW phototransistor shows an unstable photodetector behavior with smaller negative photocurrent because of more hole-trapping states in the thicker shell. All results suggest a careful design and controlled growth of an NPC-effect-caused shell for future optoelectronic applications.