Efficient and inexpensive MPCVD method to synthesize Co3O4/MoS2 heterogeneous composite materials with high stability for supercapacitors

Large-sized metal oxide particles have the potential to constitute cheap, high-performance, and high-stability supercapacitor electrode materials. Herein, the marketable large-sized Co3O4 particles (~6 [my]m) as the starting raw material, inexpensive Co3O4/MoS2 core-shell heterogeneous composites have been one-step fabricated via an improvised MPCVD system modified by a domestic microwave oven. After that, the surface morphology, composition structure, and valence state of elements were analyzed to the confirmed successful synthesis of MoS2 on the surface of Co3O4. Besides, the performance was tested by cyclic voltammetry and galvanostatic charge-discharge method. The results show that the synergistic effect of Co3O4 core and MoS2 shell can effectively improve the material's electrochemical performance. The specific capacitance of Co3O4/MoS2 composite can reach 337 F g-1 with a current density of 0.5 A g-1, which is six times more than the raw Co3O4 powder. Furthermore, it could maintain 93.6% of the initial specific capacitance after 2000 charges and discharges. Finally, the mechanism of material performance improvement is proposed

TiO2−x films for bolometer applications: recent progress and perspectives

The bolometer is widely used in military and civilian infrared imaging due to its advantages of non-cooling, small size and portability. Thermosensitive materials seriously affect the performance of bolometers. As a kind of heat-sensitive material, the TiO _2−x material has the advantages of good thermal stability, large-area preparation, and compatibility with the complementary metal-oxide semiconductor (CMOS) process. However, there is almost no review on the application of titanium oxide for bolometers. In this paper, we introduce the bolometer’s main thermal and photoelectric performance parameters and the critical technologies to manufacture the bolometer. Finally, we will particularly emphasize the effects of preparation process parameters of TiO _2 on the performance parameters temperature coefficient of resistance (TCR), 1/ f noise, etc

Epitaxial growth of successive CdSe ultrathin films and quantum dot layers on TiO2 nanorod arrays for photo-electrochemical cells

In this work, successive cadmium selenide (CdSe) ultrathin films and quantum dot layers were successfully deposited on TiO2 nanorod arrays by the electrochemical atomic layer epitaxy method (ECALE). The underpotential deposition (UPD) processes of the successive CdSe films and quantum dot layers were recorded in detail. The photo-electrochemical properties of the CdSe coated TiO2 nanorod array electrodes were also investigated, and the maximum current density reached 14.6 mA cm−2 under one sun (AM 1.5G, 100 mW cm−2). Using the ECALE method to grow a buffer layer between quantum dots and their supporting material will be useful for other energy-providing materials

Facile and Controllable Synthesis of Large-Area Monolayer WS₂ Flakes Based on WO₃ Precursor Drop-Casted Substrates by Chemical Vapor Deposition

Monolayer WS2 (Tungsten Disulfide) with a direct-energy gap and excellent photoluminescence quantum yield at room temperature shows potential applications in optoelectronics. However, controllable synthesis of large-area monolayer WS2 is still challenging because of the difficulty in controlling the interrelated growth parameters. Herein, we report a facile and controllable method for synthesis of large-area monolayer WS2 flakes by direct sulfurization of powdered WO3 (Tungsten Trioxide) drop-casted on SiO2/Si substrates in a one-end sealed quartz tube. The samples were thoroughly characterized by an optical microscope, atomic force microscope, transmission electron microscope, fluorescence microscope, photoluminescence spectrometer, and Raman spectrometer. The obtained results indicate that large triangular monolayer WS2 flakes with an edge length up to 250 to 370 μm and homogeneous crystallinity were readily synthesized within 5 min of growth. We demonstrate that the as-grown monolayer WS2 flakes show distinctly size-dependent fluorescence emission, which is mainly attributed to the heterogeneous release of intrinsic tensile strain after growth

PbTe Nanowires Electrochemically Deposited on Si Substrates as PbTe/Si Heterojunction Infrared Photodetectors

The epitaxy of PbTe semiconductor materials on Si substrates can be combined with existing microelectronic technology to produce infrared focal plane arrays. In this work, we used the reactive ion etching(RIE) method to fabricate Si holes. Then, we used the electrochemical epitaxial deposition method to deposit PbTe material on the Si holes to prepare the PbTe/Si heterojunction photodetectors. The detectors have low dark current, and the fastest response speed can reach 0.16 s. We can deposit lead telluride through a simple, template-free electrochemical method. By precisely controlling conditions such as precursor concentration, reaction time, and deposition potential, the morphology of lead telluride can be transformed from pyramid-shaped to a nanowire. This facile etching route could also be extended to the preparation of varying morphologies of functional inorganic materials

Growth and spectroscopic properties of Ti-doped sapphire single-crystal fibers

Titanium doped sapphire (Ti:Al2O3) crystal fibers have been grown by the micro-pulling-down (mu-PD) method using different pulling rate in the range (0.1-0.5 mm/min). The present work has investigated the crystal growth, including diameter, bubbles defects and segregation properties. The fiber's absorption and IR emission experiments are analyzed. The lifetime of Ti3+ in the IR range obtained at room temperature is 3.1 mu s. Moreover, the two blue emissions at 420 nm and 470 nm bands have been discussed. (C) 2015 Elsevier B.V. All rights reserved

Anomalous temperature coefficient of resistance in graphene nanowalls/polymer films and applications in infrared photodetectors

Graphene nanowalls (GNWs) exhibit outstanding optoelectronic properties due to their peculiar structure, which makes them a great potential in infrared (IR) detection. Herein, a novel IR detector that is composed of polydimethylsiloxane (PDMS) and designed based on GNWs is demonstrated. Such detector possesses an anomalous temperature coefficient of resistance of 180% K−1 and a relatively high change rate of current (up to 16%) under IR radiation from the human body. It primarily attributes to the ultra-high IR absorption of the GNWs and large coefficient of thermal expansion of PDMS. In addition, the GNW/PDMS device possesses excellent detection performance in the IR region with a responsivity of ~1.15 mA W−1. The calculated detectivity can reach 1.07×108 cm Hz1/2 W−1, which is one or two orders of magnitude larger than that of the traditional carbon-based IR detectors. The significant performance indicates that the GNW/PDMS-based devices reveal a novel design concept and promising applications for the future new-generation IR photodetectors