Competition of Photo-Excitation and Photo-Desorption Induced Positive and Negative Photoconductivity Switch in Te Nanowires.

The photocurrent in tellurium nanowire (Te NW) exhibits a subtle influence by many extrinsic factors. Herein, we fabricate Te NW devices and explore their photoresponse properties in detail. It is observed that the current increases greatly at low environmental relative humidity (RH) under light illumination, demonstrating an evident positive photoconductivity (PPC). However, the photocurrent reduces at high RH, yielding a typical negative photoconductivity (NPC). In addition, when exposed to a proper relative humidity, Te NW devices show PPC immediately and then transfer to NPC gradually under illumination, exhibiting the RH sensitive PPC/NPC switch. It is proposed that the competition between photo-excitation and photo-desorption is responsible for this subtle switch of PPC/NPC. On the one hand, the adsorbed water molecules on the surface of Te nanowires, acting as electron acceptors, lead to an increase of conductance, exhibiting the PPC phenomenon. On the other hand, the photo-desorption of water molecules from the surface results in a decreased carrier concentration in the Te nanowires, yielding the NPC phenomenon. The in-depth understanding of such charge transfer processes between the absorbed water molecules and Te nanowires provides an effective route to modulate the carrier densities and control the PPC/NPC switch, which will accelerate the design and application of novel optoelectronic nanodevices.

Ferroelectric-gated MoSe2photodetectors with high photoresponsivity.

Ferroelectric transistors with semiconductors as the channel material and ferroelectrics as the gate insulator have potential applications in nanoelectronics. We report in-situ modulation of optoelectronic properties of MoSe2thin flakes on ferroelectric 0.7PbMg1/3Nb2/3O3-0.3PbTiO3(PMN-PT). Under the excitation of 638 nm laser, the photoresponsivity can be greatly boosted to 59.8 A W-1and the detectivity to 3.2 × 1010Jones, with the improvement rates of about 1500% and 450%, respectively. These results suggest hybrid structure photodetector of two-dimensional layered material and ferroelectric has great application prospects in photoelectric detector.

Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping.

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO6octahedra by the addition of edge-sharing NbO6octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb2O5·15WO3nanowires (Nb/W = 0.008) with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb2O5·15WO3nanowires do exhibit more advantages over h-WO3nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity (71 mAh g-1, at 10C, 1C = 100 mA g-1), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H+ions diffusion kinetics. It might be the crystallographic shear structure induced by Nb doping that does result in the marked improvement in the hydrogen-ion storage performance of WO3. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of electrochemical energy and information storage devices.

Photoluminescence and Boosting Electron-Phonon Coupling in CdS Nanowires with Variable Sn(IV) Dopant Concentration.

High-quality Sn(IV)-doped CdS nanowires were synthesized by a thermal evaporation route. Both XRD and Raman scattering spectrum confirmed the doping effect. The room temperature photoluminescence (PL) demonstrated that both near bandgap emission and discrete trapped-state emission appeared simultaneously and significantly, which were attributed to the strong exciton trapping by impurities and electron-phonon coupling during the light transportation. The PL intensity ratio of near bandgap emission to trapped-state emission could be tune via doped Sn(IV) concentration in the CdS nanowires. It is interesting that the trapped-state emission shows well separated peaks with the assistance of 1LO, 2LO, 4LO phonons, demonstrating the boosting electron-phonon coupling in these doped CdS nanowires. The influence of Sn(IV) dopant is further revealed by PL lifetime decay profile. The optical micro-cavity also plays an important role on this emission process. Our results will be helpful to the understanding of doping modulated carrier interaction, trapping and recombination in one-dimensional (1D) nanostructures.

Stable green and red dual-color emission in all-inorganic halide-mixed perovskite single microsheets.

Recently, all-inorganic perovskites have attracted tremendous attention due to their excellent optoelectronic properties and extensive potential applications. However, these perovskites usually show a single emission wavelength because of the high ionic migration. Herein, we synthesized all-inorganic halide-mixed perovskite CsPbBr x I3-x microsheets with high crystal quality using the anti-solvent solution method and observed extraordinary green and red dual-color emission in single CsPbBr x I3-x microsheets. Power dependent PL spectra reveal excitonic and defect related recombination features of CsPbBr3 and CsPbI3 for the green and red emission. Temperature dependent PL spectra indicated a distinctive exciton-phonon coupling strength in CsPbBr x I3-x microsheets compared with pure CsPbBr3 and CsPbI3. The PL dynamics showing longer emission lifetime further confirmed this conclusion. Our work not only provides a novel strategy to produce stable dual-color emission integration, but also promotes the fundamental insight into the emission dynamics and exciton/free carrier related photophysics in all-inorganic halide-mixed perovskites.

TiO2 Nanosheet Arrays with Layered SnS2 and CoOx Nanoparticles for Efficient Photoelectrochemical Water Splitting.

Converting solar energy into sustainable hydrogen fuel by photoelectrochemical (PEC) water splitting is a promising technology to solve increasingly serious global energy supply and environmental issues. However, the PEC performance based on TiO2 nanomaterials is hindered by the limited sunlight-harvesting ability and its high recombination rate of photogenerated charge carriers. In this work, layered SnS2 absorbers and CoOx nanoparticles decorated two-dimensional (2D) TiO2 nanosheet array photoelectrode have been rationally designed and successfully synthesized, which remarkably enhanced the PEC performance for water splitting. As the result, photoconversion efficiency of TiO2/SnS2/CoOx and TiO2/SnS2 hybrid photoanodes increases by 3.6 and 2.0 times under simulated sunlight illumination, compared with the bare TiO2 nanosheet arrays photoanode. Furthermore, the TiO2/SnS2/CoOx photoanode also presented higher PEC stability owing to CoOx catalyst served as efficient water oxidation catalyst as well as an effective protectant for preventing absorber photocorrosion.

Positive and Negative Photoconductivity Conversion Induced by H2O Molecule Adsorption in WO3 Nanowire.

Negative photoconductivity effect has been observed in the Au/WO3 nanowire/Au devices in a high humidity environment, which might be attributed to the accumulation of H+ ions on the surface of WO3 nanowire. Under illumination with violet light (445 nm), the photo-excited holes can oxidize the adsorbed H2O molecules to produce H+ ions and O2, while the photo-excited electrons at the conduction band bottom do not have enough energy to reduce H+ ions. These H+ ions will accumulate on the surface of the hexagonalWO3 nanowire. They will capture mobile electrons and then reduce the concentration of carriers, which will result in a significant increase in the height of interface barrier and then a significant decrease in the conductance of the Au/h-WO3 nanowire/Au device. By adjusting the relative humidity, light intensity, or bias voltage, the concentration and distribution of H+ ions and then the conversion between positive and negative photoconductivity, as well as resistive switching properties, can be well regulated in this kind of devices.

In-Plane Anisotropic Raman Response and Electrical Conductivity with Robust Electron-Photon and Electron-Phonon Interactions of Air Stable MoO2 Nanosheets.

The monoclinic m-MoO2 shows strong in-plane anisotropy that is essential to design anisotropic nanodevices. However, there is not yet detailed study on the anisotropy of m-MoO2 nanostructures. Here, the in-plane anisotropic Raman spectra and electrical conductivity of single-crystal m-MoO2 nanosheets were investigated systematically for the first time. Angle-resolved polarized Raman spectroscopy (ARPRS) shows distinct dependence on the excitation laser wavelength and sample thickness, demonstrating the robust wavelength-dependent optical absorption, electron-photon/electron-phonon interactions, and anisotropic phonon polarization in m-MoO2 nanosheets. Such results agree well with the semiclassical Placzek model. Moreover, the angle-dependent electrical conductivity of starburst-like m-MoO2 nanosheet devices shows a strong anisotropy with a conductivity ratio (σmax/σmin) of up to 10.1, which is the largest value in the previously reported 2D materials. This work underscores the importance of understanding the in-plane anisotropic light-matter interactions for the application of m-MoO2 nanosheets in anisotropic plasmonics and artificial synapse.

Surface polarons and optical micro-cavity modulated broad range multi-mode emission of Te-doped CdS nanowires.

The optical confinement and strong carrier coupling within a semiconductor nanostructure cavity are crucial for the modulation of emission properties. Fundamental understanding of the light-matter interaction in a low dimensional system is important. In this paper, we synthesized high-quality hexagonal Te-doped CdS nanowires by two-step chemical vapor deposition and investigated systematically the doping concentration, temperature, excitation power, excitation wavelength dependent Raman, photoluminescence and carrier lifetime decay. Scanning electron microscopy, energy dispersive x-ray spectrometry and x-ray diffraction confirmed Te-doping in the as-prepared samples. The strong surface optical (SO) phonon mode is observed in the micro-Raman spectra of an individual Te-CdS nanowire, which is unsuitable in large-sized structures. In situ micro-photoluminescence (µ-PL) characterization shows dominant confined defect state emission with whispering gallery mode (WGM) characteristics. The emission peak position shifts under increased excitation power, demonstrating the inelastic scattering by bound carriers. In addition, the short wavelength emission modes are dominant at a low temperature (80 K) while the long wavelength emission modes are dominant at a high temperature (300 K) due to different recombination processes contributing to the WGM resonant bands, which was also confirmed by the time-resolved PL measurement. All these results reflect strong coupling between the surface evanescent-wave in the WGM cavity and the SO phonon/polaron, which will facilitate the rational tailoring of surface/interface relevant properties for nanophotonic device applications.

Modulating memristive performance of hexagonal WO3 nanowire by water-oxidized hydrogen ion implantation.

In a two-terminal Au/hexagonal WO3 nanowire/Au device, ions drifting or carriers self-trapping under external electrical field will modulate the Schottky barriers between the nanowire and electrodes, and then result in memristive effect. When there are water molecules adsorbed on the surface of WO3 nanowire, hydrogen ions will generate near the positively-charged electrode and transport in the condensed water film, which will enhance the memristive performance characterized by analogic resistive switching remarkably. When the bias voltage is swept repeatedly under high relative humidity level, hydrogen ions will accumulate on the surface and then implant into the lattice of the WO3 nanowire, which leads to a transition from semiconducting WO3 nanowire to metallic HxWO3 nanowire. This insulator-metal transition can be realized more easily after enough electron-hole pairs being excited by laser illumination. The concentration of hydrogen ions in HxWO3 nanowire will decrease when the device is exposed to oxygen atmosphere or the bias voltage is swept in atmosphere with low relative humidity. By modulating the concentration of hydrogen ions, conductive hydrogen tungsten bronze filament might form or rupture near electrodes when the polarity of applied voltage changes, which will endow the device with memristive performance characterized by digital resistive switching.

The Effect of a Brief Intervention for Patients with Ischemic Stroke: A Randomized Controlled Trial.

BACKGROUND: Depression and anxiety are common after stroke. There is inconclusive evidence of the benefit of psychotherapy for poststroke depression and anxiety. Here, we used a brief intervention, Neuro-Linguistic Programming (NLP) brief therapy plus health education, to evaluate the changes in patients with ischemic stroke. METHODS: One hundred eighty patients were randomly allocated to receive 4 sessions of NLP plus health education (n = 90) or usual care (n = 90). A set of questionnaires was used preintervention and postintervention as well as at the 6-month follow-up. The primary outcomes were the prevalence of depression and anxiety, and the awareness of stroke knowledge. RESULTS: More patients in the intervention group achieved remission of depressive (odds ratio [OR], 2.81; 95% confidence interval [CI], 1.41-5.59) and anxious symptoms (OR, 2.19; 95% CI, 1.15-4.18) after intervention. At the 6-month follow-up, we found no differences between groups in both the prevalence of depression and anxiety. After intervention, the intervention group had better awareness rates on most of the stroke knowledge items (P < .05). It also had better quality of life and physical function both after intervention and at the follow-up (P < .05). CONCLUSIONS: NLP plus health education could reduce depression and anxiety immediately after intervention, but not at the 6-month follow-up. The intervention could also improve the awareness of stroke knowledge and benefit patients on quality of life and physical function.

Ultrahigh sensitivity and gain white light photodetector based on GaTe/Sn:CdS nanoflake/nanowire heterostructures.

Optoelectronic diode based on PN heterostructure is one of the most fundamental device building blocks with extensive applications. Here we reported the fabrication and optoelectronic properties of GaTe/Sn : CdS nanoflake/nanowire PN heterojunction photodetectors. With high quality contacts between metal electrodes and Sn : CdS or GaTe, the electrical measurement of GaTe/Sn : CdS hybrid heterojunction under dark condition demonstrates an excellent diode characteristic with well-defined current rectification behavior. The photocurrent increases drastically under LED white light as well as red, green, UV illumination. The on-off ratio of current is about 100 for forward bias and 3000 for reverse bias, which clearly indicates the ultrahigh sensitivity of the heterostructure photodetector to white light. The responsivity and optical gain are determined to be 607 A W(-1) and (1.06-2.16) × 10(5)%, which is higher than previous reports of single GaTe or CdS nanostructures. Combination the Ids-Vds curves under different illumination power with energy band diagrams, we assign that both the light modulation effect under forward and reverse bias and the surface molecular oxygen adsorption/desorption mechanism are dominant to the electrical transport behavior of GaTe/Sn : CdS heterojunction. This heterostructure photodetector also shows good stability and fast response speed. Both the high photosensibility and fast response time described in the present study suggest strongly that the GaTe/Sn : CdS hybrid heterostructure is a promising candidate for photodetection, optical sensing and switching devices.

Memristive properties of hexagonal WO3 nanowires induced by oxygen vacancy migration.

Tungsten trioxide (WO3) is always oxygen-deficient or non-stoichiometric under atmospheric conditions. Positively charged oxygen vacancies prefer to drift as well as electrons when the electric field is strong enough, which will alter the distribution of oxygen vacancies and then endow WO3 with memristive properties. In Au/WO3 nanowire/Au sandwich structures with two ohmic contacts, the axial distribution of oxygen vacancies and then the electrical transport properties can be more easily modulated by bias voltage. The threshold electric field for oxygen vacancy drifting in single-crystal hexagonal WO3 nanowire is about 106 V/m, one order of magnitude less than that in its granular film. At elevated temperatures, the oxygen vacancy drifts and then the memristive effect can be enhanced remarkably. When the two metallic contacts are asymmetric, the WO3 nanowire devices even demonstrate good rectifying characteristic at elevated temperatures. Based on the drift of oxygen vacancies, nanoelectronic devices such as memristor, rectifier, and two-terminal resistive random access memory can be fabricated on individual WO3 nanowires.

Ethnic-specific meta-analyses of association between the OPRM1 A118G polymorphism and alcohol dependence among Asians and Caucasians.

BACKGROUND: Many studies have investigated the association between the OPRM1 A118G polymorphism (rs1799971) and alcohol dependence, but the results were inconsistent. To better understand this relationship, ethnicity-specific meta-analyses were conducted. METHODS: We retrieved all eligible studies published up to April 12, 2011 from the PubMed/MEDLINE, EMBASE, and ISI Web of Science databases. Ethnicity-specific meta-analyses were performed using either fixed- or random-effect models as appropriate. RESULTS: Twelve independent studies with 1900 cases and 2382 controls were included. Five studies were conducted in Asians and seven in Caucasians. Ethnicity-specific meta-analyses revealed that the A118G polymorphism was significantly associated with alcohol dependence risk in Asians (GA vs. AA: odds ratio [OR], 1.73; 95% confidence interval [CI], 1.33-2.25; GA+GG vs. AA: OR, 1.57; 95% CI, 1.22-2.02), but not in Caucasians (GA vs. AA: OR, 1.05; 95% CI, 0.75-1.49; GA+GG vs. AA: OR, 1.11; 95% CI, 0.79-1.55). CONCLUSIONS: The OPRM1 A118G polymorphism may contribute to the susceptibility of alcohol dependence in Asians but not in Caucasians.

Successful resuscitation by emergency room thoracotomy in a patient in agonal state with hemorrhagic shock resulting from penetrating cardiac injury.

A 23-year-old male patient, who was stabbed in the left chest at the fourth intercostal space leaving a 4-cm wound, was in agonal state with blood pressure of 0/0 kPa when admitted. The patient underwent emergency room thoractomy on stretcher through the left fourth intercostal anterior lateral incision 16 min after injury. The exploration revealed 2 500 ml blood in the plural cavity, 4-cm wound in the pericardium, 2-cm wound in the right ventricle of the heart without asystole, and 5-cm wound in the left upper lobe of the lung. Within 4 min the wound in the heart was sutured with the pericardium as the backing. The patient was discharged with full recovery 8 d after injury.