Two-dimensional 4H-SnS2 single crystals of several square millimeters were grown using chemical vapor transport method. A bulk 4H-SnS2 can be easily exfoliated into few-layer 4H-SnS2 using mechanical exfoliation technique. Few-layer and multilayer 4H-SnS2 of 3, 8, 13, 27, 43, and 71 monolayers were stably obtained in ambient. The Raman spectra of few-layer and multilayer 4H-SnS2 reveal a single dominant A1g Raman mode. The A1g Raman mode of few-layer 4H-SnS2 is redshifted and broadened with reduced layer number, indicating that the phonon confinement effect is layer-dependent. The Raman tensor of the few-layer 4H-SnS2 can be fixed with the phonon confinement effect. This effect also significantly influences the thermodynamic properties of few-layer 4H-SnS2. The results provide valuable insights for the design of next-generation photonic and thermoelectric devices based on 4H-SnS2.

Among Group III-A metal monochalcogenides, gallium telluride (GaTe) is one of the less studied materials in terms of applications and optical characterization. For the temperature dependence of the energy transitions in GaTe, photoluminescence (PL) spectroscopy is commonly used, and photomodulated reflectance (PR) is yet to be reported. In this work, layered monoclinic GaTe single crystals were synthesized by the Bridgman technique and used for the investigation of the conduction band (CB) edge and free-exciton (FX) state transitions using PR spectroscopy. Both energy transitions (i.e., absorption and emission) were present at room temperature at 1.656 and 1.647 eV for the CB edge transition (≡Eg) and for the FX state transition, respectively, and show a blueshift at cryogenic temperatures that can be fitted with Varshni's equation. The estimated E(0) is 1.794 eV for Eg and 1.776 eV for the FX transitions at 0 K. The energy of the FX state transition is ∼18 meV lower than that of the band gap (Eg) at 0 K. PL spectroscopy confirms that the PL emission is only the FX state transition that is lower than Eg. The temperature-induced band-gap shifting is related to performing temperature-dependent photodetector experiments using various incident light wavelengths. At 80 K, the responsivity of the single-crystal GaTe photodetector to the energies of wavelengths (735 and 845 nm) smaller than Eg is relatively smaller than that to 630 nm incident light. This indicates that the low-temperature band-gap shift plays a role in applications of GaTe in optoelectronics.

We fabricated two emerging nanorod-based smart windows with WO3 and NiO nanorods grown on the ITO/glass and ITO/muscovite mica (MM) substrates, respectively. The WO3/ITO/glass and WO3/ITO/MM substrates are excellent working electrodes, while the NiO/ITO/glass and NiO/ITO/MM substrates are exceptional counter electrodes. The nanorod-based WO3/Li+(s)/NiO@glass smart window consists of a WO3/ITO/glass working electrode, a NiO/ITO/glass counter electrode, and a solid-gel LiClO4 electrolyte (labeled as Li+(s)), respectively. The other nanorod-based WO3/Li+(s)/NiO@MM is comprised of a WO3/ITO/MM working electrode, a NiO/ITO/MM counter electrode, and a solid-gel LiClO4 electrolyte, respectively. Both the nanorod-based WO3/Li+(s)/NiO@glass and WO3/Li+(s)/NiO@MM smart windows have brilliant dual-band (red and near-infrared lights) electrochromic behaviors, such as large transmittance differences (ΔT), fast response times (bleaching time, tb, and coloration time, tc) at red (680 nm) and near infrared (1000 nm) lights and great electrochromic retention (4000 cycles), and outstanding pseudocapacitive performances like good specific capacitances of ∼18.4 F/g and ∼7.6 F/g, intensive power densities of ∼1779 W/kg and ∼2100 W/kg with corresponding energy densities of ∼5.4 Wh/kg and ∼2.2 Wh/kg, enormous pseudocapacitive retention (10,000 cycles), and so on. Therefore, the brilliant dual-band electrochromic behaviors and outstanding pseudocapacitive performances make the nanorod-based WO3/Li+(s)/NiO@glass and WO3/Li+(s)/NiO@MM smart windows tremendous for use in multifunctional energy-saving-conversion devices.

Recently, significant attention has been focused on developing electrode materials with exceptional performance for electrochemical energy storage and conversion devices. Transition metal nitrides (TMNs) are emerging as a promising option for a wide range of these devices due to their superior electrical conductivity compared to transition metal oxides, transition metal dichalcogenides, and transition metal phosphates. Despite limited coverage on the rapid adoption of TMNs as electrode materials, our mini-review provides an up-to-date overview of their utilization as high-performance electrodes in supercapacitors, water splitting, lithium-sulfur batteries, and lithium-ion batteries, along with the corresponding mechanisms. We investigate how the intentional design of nanostructures can enhance the performance of supercapacitors, catalysis based water splitting processes, and batteries. The objective of this review article is to provide a comprehensive overview of recent advancements in fabrication methods, working mechanisms, potential applications, engineering strategies for performance enhancement, as well as the advantages and disadvantages associated with TMNs. Finally, we discuss current challenges and future prospects in the field.

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An exfoliated monolayer CrI3 possessing the ferromagnetic (FM) nature of out-of-plane Ising spin-up (or spin-do Psi n) electrons can be considered as a qubit Psi ith a quantum state of |Psi>=|up arrow>=|0> (or |Psi>=|down arrow>=|1>) due to the theory of the Bloch sphere. Therefore, here a bipartite quantum system of the antiferromagnetic (AFM) and FM bilayer CrI3 is proposed for four fundamental t Psi o-qubit (2Q) quantum states (-|Psi Psi>) of |up arrow down arrow>=|01>, |down arrow up arrow>=|10>, |up arrow up arrow>=|00> and |down arrow down arrow>=|11>, respectively. Energy-resolved magnetic circular dichroism (MCD) spectropolarimetry was used to detect d-d transitions of the FM and AFM bilayer CrI3 for the four fundamental quantum states. The obtained MCD spectra of the d-d transitions with spin-frustration and spin-parallelism possess quantum signals of the four fundamental 2Q quantum states at BB = 0, Psi here BB is the angle between the magnetic field and the surface normal. Hence, the bilayer CrI3 is a potential candidate for use in quatum computer.

This work demonstrates the capability of a van der Waals layered GaTe single crystal to detect a wide range of wavelengths at small power density (0.05 W m −2 ) while being operated at a low bias voltage of 0.2 V.

The photo-Fenton process serves as a highly efficient approach for removing contaminants from wastewater. In this study, we developed a Fe-doped TiO2/SnO2 heterojunction catalyst to enhance the efficiency of photo -Fenton catalytic activity under visible light. To investigate the physical properties of the catalysts, various characterization techniques were utilized, including XRD, SEM, TEM, HR-TEM, UV-VIS, PL, and XPS. The 7% mol Fe-doped TiO2/SnO2-OVs (TFS-7) heterostructure exhibited the highest rate constant of 17.03 x 10-3 min-1; 8.4 and 2.1 times higher than the individual components. This enhanced performance is mainly attributed to the rapid migration of photoinduced electrons to Fe3+ and the subsequent generation of Fe2+, which improved electron transfer capacity and facilitated the rapid production of hydroxyl radicals (center dot OH) through the reaction between Fe2+ and H2O2. We proposed a S-scheme mechanism for the Fe-doped TiO2/SnO2-OVs catalyst based on the analysis of reactive species trapping experiments, photoluminescence (PL) spectra, ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT). These findings offer not only a straightforward approach for synthesizing highly active photocatalysts for the degradation of RhB dye, but also a framework for the construction of heterostructure photocatalysts.

A tunable bandgap without doping is highly desirable for applications in optoelectronic devices. Herein, we develop a new method which can tune the bandgap without any doping. In the present research, the bandgap of Fe2O3 nanostructured films is simply tuned by changing the synthesis temperature. The Fe2O3 nanostructured films are synthesized on ITO/glass substrates at temperatures of 1100, 1150, 1200, and 1250 °C using the hot filament metal oxide vapor deposition (HFMOVD) and thermal oxidation techniques. The Fe2O3 nanostructured films contain two mixtures of Fe2+ and Fe3+ cations and two trigonal (α) and cubic (γ) phases. The increase of the Fe2+ cations and cubic (γ) phase with the elevated synthesis temperatures lifted the valence band edge, indicating a reduction in the bandgap. The linear bandgap reduction of 0.55 eV without any doping makes the Fe2O3 nanostructured films promising materials for applications in bandgap engineering, optoelectronic devices, and energy storage devices.

Not only do the outstanding electrochromic devices provide a fast switching response, but they can also block light and heat to reduce energy consumption in buildings. Herein, we fabricated an outstanding WO3/NiO nanorods-based electrochromic device consisting of a working electrode of 1D WO3 nanorods/ITO/glass substrate and a counter electrode of 1D NiO nanorods/ITO/glass substrate. The 1D NiO nanorods with a large surface area act as an ion storage layer, which can offer a huge number of electrons to form small polarons and the localized surface plasmon resonance on the 1D WO3 nanorods. The high small polaron content causes strong lattice distortion, which helps the Li+ ions easily diffuse into the 1D WO3 nanorods and gives the 1D WO3/NiO nanorods-based electrochromic device excellent electrochromic characteristics. The electrochromic characteristics include high optical transmittance difference (~61, ~89 %), high coloration efficiency (174, 386 cm2/C) and fast coloration/bleaching switching times (~2.05/~0.74 s, ~0.85/~1.0 s) at the wavelengths of 680 and 1000 nm, respectively. These characteristics make the WO3/NiO nanorods-based electrochromic device a very promising smart window candidate for lighting control and energy-saving applications.

There are many candidate materials that can be used as channel materials for the next-generation field effect transistors (FETs). CrI3 is one of the particular candidates for application in FET, because it is a two-dimensional (2D) ferromagnet and has giant tunneling magnetoresistance. The ferromagnetic nature extends to not only electronics but also spintronics. In this study, the large-area, layered, and crystalline 2D CrI3 were synthesized by horizontal Bridgman method. The suspended CrI3 FETs were fabricated for explorations of intrinsic electron transport in the CrI3 channel and of electrical contact problems. The suspended FET structure lets the CrI3 channel free from trapping charges in the SiO2-capped Si substrate. The on–off ratio of the suspended CrI3 FET is up to 104, making the 2D layered CrI3 potential for future FETs. The investigations of the mobility and the interface-trap density at various temperatures reveal that the trapping charges as well as the interface-trap densities are increased with further gas adsorption on the surface of the CrI3 flake. The performance of the suspended CrI3 FET can be improved, if the gas adsorption problem can be carefully treated.

One-dimensional (1D) Magneli-phase W18O49 nanorods were synthesized on indium-tin-oxide thin-film coated glass substrates at 1350, 1400, 1450, 1500 and 1550 degrees C using the hot filament metal oxide vapor deposition technique. The 1D Magneli-phase W18O49 nanorods containing various mixtures of W5+ and W6+ cations all had a monoclinic crystal structure. Both the W5+ cations and the valence-band (VB) edges increased with elevated synthesis temperatures. The gain of the W5+ cations lifted the VB edges, implying a reduction in the bandgap (E-g). At a synthesis temperature of 1550 degrees C the VB edge was evidently 0.30 eV higher than that at 1350 degrees C, but at a synthesis temperature of 1550 degrees C the corresponding E-g was 0.3 eV smaller than that at 1350 degrees C. This shows that the E-g of the 1D Mageli-phase W18O49 nanorods can be tuned by simply controlling the synthesis temperature without any doping, giving the 1D Magneli-phase W18O49 nanorods good potential for application in bandgap engineering and optoelectronic nanodevices. (C) 2019 The Authors. Published by Elsevier Ltd.

Correction for ‘Doping-free bandgap tuning in one-dimensional Magnéli-phase nanorods of Mo4O11’ by Duy Van Pham et al., Nanoscale, 2016, 8, 5559–5566.

One-dimensional nanorods of MoO2, MoO3 and Magneli-phase Mo4O11 were effortlessly prepared using the hot-filament metal oxide vapor deposition technique. Long straight and uniform nanorods were grown on indiumtin-oxide (ITO) thin film coated glass substrates. Thermal reduction and oxidation were then used to process 1D Magneli-phase Mo4O11 nanorods synthesized at 1000, 1050, 1100, 1150, and 1200 degrees C into 1D MoO2 and MoO3 nanorods, respectively. The nanorods prepared at higher synthesis temperatures were thinner and longer. The 1D Magneli-phase Mo4O11 nanorods consisted of various combinations of two orthorhombic (alpha ) and monoclinic (eta) crystals and varying mixtures of Mo4+, Mo5+ and Mo6+ (3d(5/2) and 3d(3/2)) cations. The 1D MoO2 nanorods were comprised of only monoclinic (eta) crystals and various complex mixtures of Mo4+, Mo5+ and Mo6+ (3d(5/2) and 3d(3/2)) cations. The 1D MoO3 nanorods contained only orthorhombic (alpha) crystals and varying mixtures of Mo5+ and Mo6+ (3d(5/2) and 3d(3/2)) cations. Comparison of the crystal phases and 3d valences showed that the MoO2 nanorods supplied more oxidation states than the Mo4O11 or MoO3 nanorods. According to the results of cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance (EI) spectroscopy, the capacitive performance of the MoO2 nanorod-based pseudocapacitor was much better than that of the MoO3 and Magneli-phase Mo4O11 nanorod-based pseudocapacitors. The crystal phases and 3d-valence conversions clearly had a tremendous impact on the capacitive behaviors of the MoO2, MoO3, and Magneli-phase Mo4O11 nanorod-based pseudocapacitors.

We synthesized one-dimensional (1D) Magnéli-phase nanorods of Mo4O11 using the hot filament metal-oxide vapor deposition technique. The 1D Magnéli-phase Mo4O11 nanorods synthesized at 1000, 1050, 1100, 1150, and 1200 °C contain varying combinations of two orthorhombic (α) and monoclinic (η) phases, and various mixtures of Mo(4+), Mo(5+) and Mo(6+) cations, while those synthesized at a higher temperature look bluer. The shifts of the transmittance maximum and absorbance minimum of the 1D Magnéli-phase Mo4O11 nanorods are inversely and linearly proportional to the elevated temperature, verifying that the bandgaps (Eg) are inversely proportional to the elevated temperature. The bandgap (Eg) of the 1D Magnéli-phase Mo4O11 nanorods can be tuned by simply controlling the synthesis temperature without doping with other materials, giving the 1D Magnéli-phase Mo4O11 nanorods good potential for use in optoelectronic nanodevices and bandgap engineering.