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Traditional fluorescent materials used in anti-counterfeiting field usually exhibit monochromatic luminescence at a single-wavelength excitation, which is easily be forged by sophisticated counterfeiters. In this work, Zn2GeO4:Mn, x%Li (x=0 and 20), Zn2GeO4­NaLiGe4O9:Mn, x%Li (x=50 and 70) and NaLiGe4O9:Mn micro-phosphors with the multi-chromatic and multi-mode luminescence have been successfully synthesized via a hydrothermal approach followed by an annealing treatment. As expected that these Li+ doped Zn2GeO4:Mn and NaLiGe4O9:Mn phosphors exhibit a double peak emission including a long green afterglow (~540 nm) and a red photoluminescence (∼668 nm). By tuning Li+ doping concentrations, a gradual colour output and a tuneable afterglow duration are achieved. Particularly, the Zn2GeO4:Mn,Li and NaLiGe4O9:Mn phosphors exhibit excellent performance as security inks for printing luminescent numbers and anti-counterfeiting patterns, which shows an afterglow time-dependent or excitation wavelength-dependent luminescence colour evolution. This work proves the feasibility of Li+ doping strategy in emission tuning, which can stimulate further studies on multi-mode luminescent materials in anti-counterfeiting applications.

Surface polarization characteristics provide crucial structural information of the Earth's surface. As two key elements of the natural geographical environment, rocks and soils play an important role in the study of surface processes. Inherent surface characteristics, such as surface roughness, composition, and density are critical parameters for the remote monitoring of land surfaces as they affect the polarization characteristics of scattered light waves. In this study, we investigated the relationship between surface roughness, composition, and density, and the polarization spectra of limestone-dolomite series rock. Results reveal a power function relationship between the surface roughness and the degree of polarization peaks among different detection zenith and azimuth angles. The depth and position of the absorbing waveband are significantly correlated with the characteristic component contents. The rock density was determined via the polarized reflection spectra, with the Earth's surface density calculations associated with a 2.6% divergence from the current recognized data. Our results demonstrate the ability of polarized spectra to retrieve surface roughness, composition, and density, with potential for further development in future work.

Solution-processable all-inorganic lead halide perovskites are under intensive attention due to their potential applications in low-cost high-performance optoelectronic devices such as photodetectors. However, solution processing usually generates structural and chemical defects which are detrimental to the photodetection performance of photodetectors. Here, a polymer additive of polyethylene glycol (PEG) was employed to passivate the localized defects in CsPbI2Br films through the Lewis acid-base interaction. The interfacial defects were passivated efficiently by introducing a trace amount of a PEG additive with a concentration of 0.4 mg mL-1 into the CsPbI2Br precursor solution, as suggested by the significantly reduced trap density of state, which was revealed using thermal admittance spectroscopy. Fourier transform infrared spectrum characterization showed that rather than Cs+ or I-, a Lewis acid-base interaction was established between Pb2+ and PEG to passivate the defects in the CsPbI2Br perovskite, which leads to large suppression of noise current. Both specific detectivity and linear dynamic range improved from 4.1 × 109 Jones and 73 dB to 2.2 × 1011 Jones and 116 dB, respectively. Our work demonstrates the feasibility of employing an environmentally stable polymeric additive PEG to passivate defects for high photodetection performance in all-inorganic perovskite photodetectors.

We propose and experimentally demonstrate the broadband power coupling and mode-order conversion based on the trapezoidal subwavelength grating (SWG) structures. The slowly varying trapezoidal SWGs alter the modal field distribution in two closely spaced waveguides and result in an enhanced and adiabatically changing coupling strength between them. As a result, high coupling efficiencies over broad bandwidths are obtained for the coupled-waveguide devices with small sizes. Simulations show that the complete power transfer and the mode-order conversion can be accomplished using the coupling structure. The power coupler has a 1-dB bandwidth of 708 nm spanning from 1353 nm to 2061 nm, while the mode-order converter has a conversion loss less than 1 dB and crosstalk below −12.5 dB over a 324-nm bandwidth from 1388 nm to 1712 nm. Both devices were fabricated and experimentally characterized. The power coupler shows a measured insertion loss of

Superionic states simultaneously exhibit properties of a fluid and a solid. Proton (H+) superionicity in ice, H3O, He-H2O, and He-NH3 compounds is well-studied. However, hydride (H-) superionicity in H-rich compounds is rare, being associated with instability and strongly reducing conditions. Silicon, sodium, and hydrogen are abundant elements in many astrophysical bodies. Here, we use first-principles calculations to show that, at high pressure, Na, Si, and H can form several hypervalent compounds. A previously unreported superionic state of Na2SiH6 results from unconstrained H- in the hypervalent [SiH6]2- unit. Na2SiH6 is dynamically stable at low pressure (3 GPa), becoming superionic at 5 GPa, and re-entering solid/fluid states at about 25 GPa. Our observation of H- transport opens up a new field of H- conductors. It also has implications for the formation of conducting layers at depth in exotic carbon exoplanets, potentially enhancing the habitability of such planets.

High-pressure investigation has been shown to be of paramount significance for changing the conventional lattice or bringing fascinating properties, especially inducing superconducting phases. Here we studied the application of pressure to the recently synthesized 2M-WS2 with the record Tc (8.8 K) among transition metal dichalcogenides (TMDs) at ambient pressure by electrical resistance investigations, synchrotron X-ray studies, and theoretical calculations. Tc in the initial 2M-WS2 dropped from the maximum to become undetected, accompanied by a phase transition into a semiconductor, 3R-WS2, at 15 GPa. The successive metallization and superconducting transitions in 3R-WS2 were observed at 48.8 GPa with Tc ≈ 2.5 K. This is the first experimental case in which superconductivity has been realized in the 3R phase among TMDs. We propose that the degradation of superconductivity in 2M-WS2 and the reemergence of superconductivity in 3R-WS2 are mainly attributable to changes in the density of states near the Fermi surface driven by the interlayer coupling.

The development of efficient, cost-effective and stable N-doped carbon material with catalytic activity as an excellent catalyst for the oxygen evolution reaction (OER) is critical for renewable energy systems. In this study, the unique tip-half-closed N-doped carbon nanohorns (THC-N-CNHs) were firstly produced by the positive pressure-assisted arc discharge method using N2 as the nitrogen source. Benefitting from the novel tip-half-closed structure and sufficient porosity, the specific surface area (SSA) of THC-N-CNHs is calculated to be 670 m2 g−1 without any further treatment, which is three times larger than that of traditional tip-closed CNHs. More importantly, the content of nitrogen can achieve ∼1.98 at% with noticeable pyridinic-N enrichment, increasing the number of active sites for the OER. Furthermore, the three-dimensional spherical feature and the unique pore structure for THC-N-CNHs lead to the fast transportation of electrons, and facile release of the evolved O2 bubbles during the OER process. Therefore, THC-N-CNHs exhibit excellent electrocatalytic activity toward the OER, with an overpotential of 328 mV at 10 mA cm−2, which is superior to that of most N-doped carbon material-based electrocatalysts. Meanwhile, the resulting catalyst also shows excellent durability after long-term cycling. Finally, we emphasize that THC-N-CNHs can be promising candidates as cheap, industrially scalable catalytic scaffolds for OER application.

The discovery of H3S and LaH10 is an important step towards the development of room temperature superconductors which fuels the enthusiasm for finding promising superconductors among hydrides at high pressure. In the present study, three new and stable stoichiometric MoH5, MoH6 and MoH11 compounds were found in the pressure range of 100–300 GPa. The highly hydrogen-rich phase of Cmmm-MoH11 has a layered structure that contains various forms of hydrogen: H, H2− and H3− units. It is a high-Tc material with an estimated Tc value in the range of 165–182 K at 250 GPa. The same structures are also found in NbH11, TaH11, and WH11, each material showing Tc ranging from 117 to 168 K. By combining the method of using two coupling constants λopt and λac, and two characteristic frequencies (optical and acoustic) with first-principle calculations, we found that the high values of Tc are mainly caused by the presence of high frequency optical modes, but the acoustic modes also play a noticeable role.

Hybrid organic inorganic lead halide perovskite semiconductors of the form CsyFA1−yPb(BrxI1−x)3 are promising candidate materials for high-efficiency photovoltaics. Notably, cation and anion substitution can be used to tune the band gaps to optimize performance and improve stability. However, multi-component materials can be prone to compositional and structural inhomogeneity and the extent, length scale and impact of this heterogeneity on lead halide perovskite properties are not well understood. Here we use synchrotron X-ray diffraction to probe the evolution of crystal structure across the tetragonal-to-cubic phase transition for a series of CsyFA1−yPb(BrxI1−x)3 thin films with x = 0.05 to 0.3 and y = 0.17 to 0.40. We find that the transition occurs across a broad temperature range of approximately 40 °C, much larger than for pure compounds such as MAPbI3 and MAPbBr3. We hypothesize that this smearing of the phase transition is due to compositional inhomogeneities that give rise to a distribution of local transition temperatures and we estimate the composition varies by about 10% to 15% with likely greater heterogeneity for the halide anion than the cation. This approach of mapping the transition is a simple and effective method of assessing heterogeneity, enabling evaluation of its impact.

The discovery of the high-temperature superconducting state in the compounds of hydrogen, carbon and sulfur with a critical temperature (Tc) of 288 K at high pressure is an important milestone towards room-temperature superconductors. Here, we have extensively investigated the high-pressure phases of CS2H10, and found four phases Cmc21, P3m1, Pm1 and Pm. Among them, P3m1 can be dynamically stable at a pressure as low as 50 GPa, and Cmc21 has a high Tc of 155 K at 150 GPa. Both Cmc21 and P3m1 are host–guest hydrides, in which CH4 molecules are inserted into Imm-H3S and R3m-H3S sublattices, respectively. Their Tc is dominated by the H3S lattice inside. The insertion of CH4 molecules greatly reduces the pressure required for the stability of the original H3S lattice, but it has a negative impact on superconductivity which cannot be ignored. By studying the effect of CH4 insertion in the H3S lattice, we can design hydrides with a Tc close to that of H3S and a greatly reduced pressure required for stability.

Silicon plays a crucial part in developing high-performance energy storage materials, owing to a high specific capacity compared to carbon. Moreover, nanoscale silicon is beneficial for reducing the inherent disadvantage of large volume change during repeated lithiation/de-lithiation, while artificial synthesis methods usually involve complex procedures and high costs. On account of the abundant natural reserve and low cost, the manipulation of silicate minerals is a simple and economical approach to prepare silicon nanosheets. In this regard, this mini review introduces different classes of silicate minerals and summarizes some typical molten salt-assisted reduction methods and other valuable methods applied to prepare silicon nanosheets for energy storage. Finally, the challenges and perspectives in this field are also proposed.

Invigorated by the high-temperature superconductivity in ternary hydrogen-dominated compounds under high pressures, we systematically explored high-pressure phase diagrams, electronic properties, lattice dynamics, and superconductivity of ternary Na-Al-H systems using ab initio methods. We found three stable compounds of ${\mathrm{NaAlH}}_{4}$, ${\mathrm{NaAlH}}_{6}$, and ${\mathrm{NaAlH}}_{8}$, as well as a metastable compound of ${\mathrm{NaAlH}}_{7}$ under high pressures. Except for ${\mathrm{NaAlH}}_{4}$, they all containing ${\mathrm{H}}^{\ensuremath{-}}$ and ${\mathrm{H}}_{2}$ units. Electronic structure calculations reveal that ${\mathrm{NaAlH}}_{7}$ and ${\mathrm{NaAlH}}_{8}$ are metallic, while ${\mathrm{NaAlH}}_{4}$ and ${\mathrm{NaAlH}}_{6}$ are semiconductors. In addition, ${\mathrm{NaAlH}}_{8}$ exhibits a phonon anomaly (dip) in multiple phonon branches along the A-M direction. The phonon anomaly induced by Fermi-surface nesting boosts the electron-phonon coupling strength, and as a result, a superconducting transition temperature ${T}_{c}$ of 55 K was produced at 300 GPa.

Halide perovskites have shown great potential for next-generation optoelectronics. Despite the high efficiency of devices achieved in the laboratory, instability in long-term device operation stall...

A ternary composites of MoO3/Ag/TiO2 nanotube arrays were synthesized by in-situ annealing of TiO2 nanotube arrays impregnated with AgNO3 over MoO3 powders. During the annealing process, the crystallization of the TiO2 nanotubes, the thermo-decomposition of AgNO3 to Ag nanoparticles, and the sublimation of MoO3 occur jointly. The photoelectrochemical measurements of the resultants indicate that MoO3/Ag/TiO2 nanotube arrays present better photoelectrochemical properties compared with Ag/TiO2 nanotube arrays and pristine TiO2 nanotube arrays. Especially, the highest photocurrent and open circuit voltage are up to 21.29 μA/cm2 and 0.058 V under visible light irradiation, whereas 1.77 and 3.87 times larger than those of TiO2 nanotube arrays, respectively. Superior photoelectrochemical stability and larger photo-conversion efficiency of the ternary composites are also demonstrated. The improved photoelectrochemical properties are related to the close interfacial contact among MoO3, Ag, and TiO2 as well as the surface plasma resonance of Ag in the ternary composites, which broaden the range of light response and enhance the efficiency of charge separation. This study provides a skillful solution to construct TiO2-based composite materials and demonstrates it is an unique architecture to promote the visible light driven photocatalytic application of TiO2.

Large-area high-quality graphene was synthesized on different types of copper foils preannealed under positive pressure H2 atmosphere between 1 and 2 standard atmospheres. The prepared graphene showed good electrical conductivity, transmittance, and uniformity. The sheet resistance values of the grown monolayer graphene film were all about 500 Ω/□, and the transmittance was as high as 97.24%. The carrier mobility of the monolayer graphene film was around 2000–3000 cm2/(V s). Furthermore, the monolayer coverage could be more than 95.00% controlled by adjusting the process parameters. The properties of the four layer-superposed graphene film nearly reached that of the commercialized indium tin oxide (ITO) glasses, which showed that the prepared graphene could be well applied to the transparent conductive electrode. The obtained graphene film has been used to construct Si/graphene solar cells without an antireflection film, which showed energy conversion efficiency among 4.99–5.62%.

Photothermal therapy is a very promising treatment method in the field of cancer therapy. The photothermal nanomaterials in near-infrared region (NIR-I, 750-900 nm) attracts extensive attention in recent years because of the good biological penetration of NIR light. However, the penetration depth is still not enough for solid tumors due to high tissue scattering. The light in the second near-infrared region (NIR-II, 1000-1700 nm) allows deeper tissue penetration, higher upper limit of radiation and greater tissue tolerance than that in the NIR-I, and it shows greater application potential in photothermal conversion. This review summarizes the photothermal properties of Au nanomaterials, two-dimensional materials, metal oxide sulfides and polymers in the NIR-II and their application prospects in photothermal therapy. It will arouse the interest of scientists in the field of cancer treatment as well as nanomedicine.

Effects of SDBD and DBD-VGs plasma actuations on film cooling performance of a plain wall were numerically investigated based on the RANS solutions and linearized body force model. With a user defined function (UDF), the plasma actuation forces were implemented into the momentum equations as the source terms in the commercial CFD solver ANSYS Fluent. With the experiment data and referenced numerical results, reliabilities of the linearized body force model and numerical methods were validated. At a range of dimensionless actuation strengths and frequencies, the film cooling effectiveness on the wall surface and flow structure development in the near-wall regions were analyzed and compared with the plasma-off case. The results show that both SDBD and DBD-VGs plasma actuations are beneficial for reducing the development of kidney vortex pair downstream of the cooling hole, thus significantly improving the film cooling effect on the wall surface. With SDBD plasma actuation, the streamwise velocity gradient in near-wall region is increased compared with the plasma-off case, resulting in delayed coolant flow lifting-off downstream of the cooling hole. However, with DBD-VGs plasma actuation, the development of anti-kidney vortex pair is intensified, which in turn weakens the development of kidney vortex pair and widens the coolant coverage on the wall surface along lateral direction. As the actuation strength and frequency increase, the film cooling effectiveness on the wall surface is enhanced along both streamwise and lateral directions. Compared with the plasma-off case, the area-averaged film cooling effectiveness for DBD-VGs plasma actuation case is increased by 331% at dimensionless actuation frequency of 2.5 and dimensionless actuation strength of 30, whereas for SDBD plasma actuation case the area-averaged film cooling effectiveness is only increased by 42.8% at dimensionless actuation frequency of 2.5 and dimensionless actuation strength of 60. With the same actuation parameters, compared against the SDBD case, a higher film cooling effectiveness is achieved on wall surface for the DBD-VGs plasma actuation case, and the coolant coverage along the lateral direction is significantly improved by DBD-VGs plasma actuation.

We adopt a thermodynamically consistent multi-phase, multi-component phase-field model to investigate the morphological evolution of peritectic transition in carbon steel though 2-D and 3-D simulations. By using phase-field method, we rationalize the peritectic solidification in both 2-D and 3-D simulations under different liquid supersaturations as well as on the δ particle with distinct microstructures. Through the comparison between 2-D and 3-D simulation results, we clarify the reason for the different growth rate of γ phase in two and three dimensions. In 3-D simulation, we observe the unequal growth rate of γ phase in radial and axis directions. In addition, a novel measurement method is proposed to determine the dynamic contact angle. We anticipate that the simulation results can be applied to interpret the isothermal peritectic transition with a liquid supersaturation in alloys.

In order to study the effect of negative valve overlap on combustion and emission characteristics of a homogeneous charge compression ignition engine fueled with natural gas and hydrogen, the test and the simulation were conducted using an engine cycle model coupling the chemical kinetic reaction mechanism under different valve timing conditions. Results show that the internal EGR formed by using negative valve overlap could heat the inlet mixtures and improve the spontaneous ignition characteristic of the engine. The residual exhaust gas could slow down the heat release rate, decrease the pressure rise rate and the maximum combustion temperature, and reduce the NOx emission simultaneously. Among the three NVO schemes, the strategy of changing the intake valve opening timing individually can create the least power loss, and the symmetric NVO strategy which changes both the exhaust valve closing timing and the intake valve opening timing simultaneously can achieve the best heating effect of inlet mixtures and the satisfactory decrease of combustion temperature, as well as the largest reduction of NOx emission.

An improved wedge-shape method is employed to calculate the absolute surface energies of wurtzite ZnO high index polar surfaces. From the viewpoints of atomic structure and surface energy, the stabilization mechanism of high index polar surfaces is systematically investigated. Under different conditions (O and Zn rich), the stable surface structures are discussed, and it is found that some high index polar surfaces may have lower surface energy than conventional ( 10 1 ¯ 0 ) or ( 0001 ) surfaces. This may be of vital importance to the surface morphology of nanostructures. In addition, the calculation results are well in agreement with experimental observations. The present theoretical and experimental work can provide important insights to the growth and surface treatment of complex nanostructures.

Using the hybrid exchange-correlation functional within the density-functional theory, we have systematically investigated the structural and electronic properties of MO (M = Be, Mg, Ca, Sr, Ba, Zn, Cd) in binary rocksalt (B1), zincblende (B3) and wurtzite (B4) phases, including the structural parameters, bulk moduli, band gaps and deformation potentials. Our results agree well with the experimental data and other theoretical results, and give a better understanding of the relationship between the geometric and electronic structure. After calculating the band alignment, we find that in both the B1 and B3 structures, the valence band maximum (VBM) has an obvious decrease from BeO to MgO to CaO, then it goes up from SrO to BaO to ZnO to CdO. Moreover, the properties of the ternary alloys M$_x$Zn$_{1-x}$O were studied through the application of the special quasirandom structure method. The critical value of the ZnO composition for the transition from the B3 structure to the B1 structure gradually increases from (Ca, Zn)O to (Mg, Zn)O to (Sr, Zn)O to (Ba, Zn)O to (Cd, Zn)O, indicating that (Ca, Zn)O can exist in the B3 structure with the lowest ZnO composition. These results provide a good guideline for the accessible phase space in these alloy systems.

Using density functional theory, the electronic properties of six different AlN(0001)/β-Ga2O3(100) are analyzed. Atomic relaxation, formation energy, binding energy, electron distribution, and band offsets are investigated. The analysis shows that, for the B-Al, B-N, and C N models, not only the thermodynamic stability is high but also interface bonding is relatively strong. Furthermore, after undergoing structural optimization, interface spacing is reduced significantly. The charge analysis shows that significant charge transfer occurs between the three models, and Al-O, N O as well as Ga-N bonds are formed between the interface atoms. The obtained conduction-band offsets (CBOs) of the three models are 1.7 eV, 1.86 eV, and 1.85 eV, which are very similar to the experimentally obtained values. The study of band structure shows that the heterostructure has the theoretical basis of producing 2DEG with high surface charge density. However, for the A-Al, A-N, and C-Al models, the three models are either thermodynamic unstable or associated with weak interface bonding. Furthermore, relaxation mainly occurs in the horizontal direction, and the atoms at the interface are arranged in the form of diluted- and dense-patches. There is no clear charge transfer and chemical bond between the interface atoms, which are bound together via physical adsorption.

A dual heterogeneous structure with both heterogeneous grain structure and coherent L12 nanoprecipitates was obtained in a CoCrNi-based medium entropy alloy (MEA) with chemical composition of Co34.5Cr32Ni27.5Al3Ti3 (in at%). The volume fraction of L12 phase is observed to become higher and the corresponding interspacing becomes smaller after aging, resulting in a more severe heterogeneity. The unaged samples are found to have better tensile properties as compared to those for the CoCrNi MEA with homogeneous and heterogeneous grain structures. The aged samples display an even better synergy of strength and ductility than the corresponding unaged samples. The hetero-deformation-induced hardening plays a more important role in the aged samples than in the unaged samples, especially at the elasto-plastic transition stage, producing higher density of geometrically necessary dislocations for better tensile properties. Multiple deformation twins, stacking faults and Lomer-Cottrell locks are the dominant deformation mechanisms for the unaged samples, while interactions between these defects and L12 nanoprecipitates play important roles in the aged sample, the shearing hardening mechanism is observed for L12 nano-particles.

We combined a 3D graphene foam network with a ZnO NRs array and further introduced this mixed-dimensional heterostructure into a PEC biosensing system. The 3D graphene served as a conductive matrix and provided an extra-large spatial surface area for more effective synthesis of ZnO NRs, while the ZnO NRs array functioned as a photoactive material to generate charge carriers and provided reaction sites at the surface for glutathione (GSH) oxidation. Therefore, an elevated photoresponse as well as an improved PEC biosensing performance in the linear range from 5 to 300 μM and an estimated detection limit of 1.53 μM through 3σ were obtained due to the vast reactive surface area and efficient electron transfer of the designed photoanode. The proposed strategy verified that such a spatial bioactive platform is promising in biosensing related fields or other photoelectric energy conversion fields.

Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures. It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature superconductivity. However, this phenomenon has been observed only at very high pressure. Here, we theoretically search for superconductors with very high critical temperatures, but at much lower pressures. We describe two of such sodalite-type clathrate hydrides, YbH6 and LuH6. These hydrides are metastable and are predicted to superconduct with T c ∼ 145 K at 70 GPa and T c ∼ 273 K at 100 GPa, respectively. This striking result is a consequence of the strong interrelationship between the f states present at the Fermi level, structural stability, and the final T c value. For example, TmH6, with unfilled 4f orbitals, is stable at 50 GPa, but has a relatively low value of T c of 25 K. The YbH6 and LuH6 compounds, with their filled f-shells, exhibit prominent phonon “softening”, which leads to a strong electron-phonon coupling, and as a result, an increase in T c.

Pressure has an important effect on chemical bonds and their chemical properties. The atypical compounds NaCl3 and CsF3 are predicted to be stable at high pressure and show unique physical and chemical properties. By using ab initio random structure searching and density functional theory calculations, we predicted multiple thermodynamically stable atypical compounds, which are RbF2, RbF3, RbF4, and RbF5 in the pressure range of 0–300 GPa. In these stable compounds, homonuclear bondings of F3, F4, and F5 species are easily formed. The electron structure calculation showed that except for Fd-3m phase of RbF2, these stable compounds are insulators and F 5p orbitals play an important role in the Fermi level. It is interesting that the compounds RbF5 could be stable at nearly ambient pressure and 0 K which will stimulate experimental studies in the future.

The recent discovery of H_{3}S and LaH_{10} superconductors with record high superconducting transition temperatures T_{c} at high pressure has fueled the search for room-temperature superconductivity in the compressed superhydrides. Here we introduce a new class of high T_{c} hydrides with a novel structure and unusual properties. We predict the existence of an unprecedented hexagonal HfH_{10}, with remarkably high value of T_{c} (around 213-234 K) at 250 GPa. As concerns the novel structure, the H ions in HfH_{10} are arranged in clusters to form a planar "pentagraphenelike" sublattice. The layered arrangement of these planar units is entirely different from the covalent sixfold cubic structure in H_{3}S and clathratelike structure in LaH_{10}. The Hf atom acts as a precompressor and electron donor to the hydrogen sublattice. This pentagraphenelike H_{10} structure is also found in ZrH_{10}, ScH_{10}, and LuH_{10} at high pressure, each material showing a high T_{c} ranging from 134 to 220 K. Our study of dense superhydrides with pentagraphenelike layered structures opens the door to the exploration of a new class of high T_{c} superconductors. Published version

Hydrogen is rarely observed as ligand in hypervalent species, however, we find that high-pressure hydrogenation may stabilise hypervalent hydrogen-rich materials. Focussing on ternary silicon hydrides via lithium doping, we find anions composed of hypervalent silicon with H ligands formed under high pressure. Our results reveal two new hypervalent anions: layered-SiH$_{5}^{-}$ and tricapped trigonal prismatic SiH$_{6}^{2-}$. These differ from octahedral SiH$_{6}^{2-}$ described in earlier studies. In addition, there are further hydrogen-rich structures Li$_{3}$SiH$_{10}$ and Li$_{2}$SiH$_{6+\delta}$ which may be stabilised at high pressure. Our work provides pointers to future investigations on hydrogen-rich materials., Comment: 6 pages, 4 figures

The excellent grain refinement effectiveness and good electrical conductivity is difficult to be simultaneously obtained due to the influence of both the grain boundary and excessive Ti in the usually used refiners, such as Al-5Ti-1B master alloy. In order to solve this problem, in this work, Al-Ti-B mater alloys with less or without excessive Ti but with high refinement potency TiB2 have been tried to prepare, and the grain refinement effectiveness of them and its influence on the electrical conductivity of the refined Al have been investigated. It is found that the grain refinement effectiveness of the Al-Ti-B master alloys prepared using the Al-5Ti-1B and Al-B master alloys as the starting materials at 720 °C is much better than those prepared using the Al-10Ti and Al-B master alloys, which is because that the high refinement potency TiB2 with TiAl3 2DC in the Al-5Ti-B can be kept in the prepared master alloys. As a result, using the prepared Al-Ti-B master alloys as the refiners, both the good grain refinement effectiveness and improved electrical conductivity of Al can be realized. Keywords: Grain refinement, Electrical conductivity, Al, Master alloys

As a novel type of carbon materials, graphynes possesses the merits of high carrier mobility and large surface areas, etc. However, to date, the main research of graphynes is focused on theoretical calculation whereas few strategies have been reported for the fabrication of graphynes. In this work, a facile method named ultrasound-promoted synthesis was developed to fabricate γ-graphyne using PhBr6 and CaC2 as the raw materials. The reaction system in argon atmosphere ultrasonically vibrated for 24 h in the ultrasonic bath at a power of 180 W and frequency of 53 kHz. The structure, morphology, and component of the obtained samples were detected by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, FT-IR spectra, scanning electron microscopy, transmission electron microscopy, and the selected area electron diffraction. The electrochemical and photoelectrochemical measurements indicate that γ-graphyne can be used as superior electrode mateirals in supercapacitor and photoelectrochemical catalysis. From the results of galvanostatic charge/discharge measurements, the γ-graphyne supercapacitor delivers a maximum specific capacitance of 81 F/g at 0.2 A/g and a capacitance retention rate of 87.5% after 5000 cycles at 3 A/g. Moreover, UV-vis light photoelectrochemical response and high carrier density are observed for γ-graphyne. It is also demonstrated that the charge-transfer resistance is low by Tafel slopes and Nyquist plots. This work puts forward a new and facile strategy for the fabrication of γ-graphyne and explores its application in the field of solar energy conversion and storage.

In order to improve the low utilization of stator core space and permanent magnets in conventional transverse flux permanent magnet machine (TFM), a kind of novel bipolar magnetic field crosslinking transverse flux permanent magnet machine (BFCTFM) is proposed. The novel special "9" shaped stator core structure of the novel motor can simultaneously crosslink the bipolar magnetic fields between stator and rotor. The novel machine with "9" shaped stator structure effectively improves the stator space utilization, thus enhancing the motor power density and torque density. The no-load back EMF waveform and harmonic analysis is performed and finite element software is used to analyze the torque characteristics with different structural parameters. The torque quality comparison between the BFCTFM and the normal TFM verifies that the novel machine can achieve higher power density and lower torque ripple.

Controllable synthesis of tin-doped all-inorganic perovskite (e.g. CsPb1-XSnXBr3) nanocrystals while maintaining tin at the divalent state is of great importance for tuning their optoelectronic properties by changing the chemical composition and geometrical size; however, this remains a non-negligible challenge. In contrast to the conventional high-temperature (>150 °C) synthesis reaction that would more likely facilitate oxidation of divalent Sn2+ to quadrivalent Sn4+, this work demonstrates a facile low-temperature (105-150 °C) hot-injection method to synthesize quantum-confined Sn2+-doped CsPb1-XSnXBr3 nanocrystals with sizes ranging from ∼6.2 nm to ∼8.3 nm depending on the reaction temperature. The optimized reaction temperature of 135 °C led to a Sn2+-doping ratio of 3.4% in CsPb1-XSnXBr3 nanocrystals which exhibited uniform nanoplatelets with an average lateral size of ∼7.4 nm. Furthermore, for the first time, we show that the perovskite nanocrystals are promising for the development of low-cost and trap-assisted photomultiplication UV-photodetectors, and the photodetectors based on CsPb0.966Sn0.034Br3 nanocrystals exhibited wavelength-dependent detectivities in the magnitude of 1011 Jones for UV light extending from 310 nm to 400 nm at a reverse bias of -7 V. The high EQE of ∼1940% at around 340 nm indicates that the devices had a gain at the large reverse bias condition, which is attributed to the formation of interfacial traps by CsPb0.966Sn0.034Br3 nanocrystals that can make the electron injection barrier thin enough to allow electron tunneling in the photodetectors for photomultiplication.

Visible light excitation is especially important for the NIR emitting materials that are employed in biochemistry and cell biology, since living tissues are generally damaged under UV light irradiation. Here, two new bis-β-diketones, L1 and L2 (L1 = 4,4'-di(4,4',4''-trifluoro-1,3-dioxobutyl)-triphenylamine; L2 = 4-(N,N-dimethylamino)-4',4''-di(4,4',4''-trifluoro-1,3-dioxobutyl)-triphenylamine), featuring intra-ligand charge transfer (ILCT) excited states, have been designed and prepared for the synthesis of a series of anionic quadruple-stranded dinuclear helicates (HNEt3)2[M2L14] and (HNEt3)2[M2L24], where M = Yb, Gd and Y. 1H NMR and electrospray mass spectrometry confirm the formation of single complex species in solution. According to the comprehensive spectral characterization and in combination with quantum chemical modelling, the ILCT feature of L1 and L2 is confirmed. The presence of ILCT allows the use of lower energy excitation wavelengths in the visible spectral region to sensitize ytterbium NIR luminescence. In (HNEt3)2[Yb2L24], the introduction of strong electron donating N,N-dimethyl leads to a remarkable red shift of the absorbance edge to 560 nm compared with that in (HNEt3)2[Yb2L14] at 450 nm. Upon excitation with blue light, the two ytterbium helicates show excellent NIR luminescence in the range of 900-1100 nm, with the luminescence quantum yields reaching 1.1% for (HNEt3)2[Yb2L14] and 1.5% for (HNEt3)2[Yb2L24] in CH3CN. Luminescence mechanism experiments show that the ILCT singlet path and classic triplet state path together participate in sensitizing Yb(iii) ion NIR luminescence.

Last two decades has witnessed various technical programs towards the development of new dielectric films for high temperature and high energy density capacitor technology. Yet, the organic polypropylene film still holds its top position for film capacitors required for electric and electronic power applications such as power grid, hybrid electric vehicles, oil and gas exploration, and aviation. However, its low temperature stability determined by its structural nature limits its further adoption for more rising markets. This work thus developed a creative method (ultrathin coating of inorganic compound using atomic layer deposition) to increase the high temperature stability and the dielectric strength of such a strategically important polymer film from below 105 °C to above 140 °C. Several techniques also confirmed the effective minimization of the dimensional change and crystallinity loss at higher temperatures, i.e., Thermomechanical analysis, Dynamic mechanical analysis, Dynamic Scanning calorimetry, x-ray diffraction and electron microscopy techniques. This breakthrough discovery adds a huge value to the commercial PP films and relevant capacitor industry and will extend the operation of high-performance PP film capacitors to various high standard applications.

A series of YGa1.5Al1.5(BO3)4:Tb3+,Eu3+ inorganic luminescence materials were successfully synthesized through a high-temperature solid-state reaction. Powder X-ray diffraction was used to confirm the crystal structure and phase purity of the obtained samples. Then, scanning electron microscopy elemental mapping was taken to characterize the distribution of the doped ions. Detailed investigations on the photoluminescence emission and excitation spectra and fluorescence lifetime revealed that trivalent europium ions can be well sensitized by trivalent terbium ions under near-ultraviolet excitation. Additionally, the energy transfer from Tb3+ to Eu3+ can be controlled to realize multi-colour emissions covering the green to red visible region. Concentration quenching does not take place in Tb3+ or Eu3+ singularly-doped YGAB due to its structure isolation. Therefore, satisfactory luminescence properties related to the structure specificity make these phosphors suitable for WLEDs.

A series of mixed-phases TiO2 is fabricated via a mild hydrothermal process using titanium trichloride as the Ti source and ammonia water for regulating the ratio of anatase, rutile, and brookite. As a result, TiO2 nanocrystals comprised of anatase/brookite, anatase/rutile/brookite and anatase/rutile phases can be obtained. The longest optical edge is observed for triphase TiO2 system among all of the as-prepared samples in UV–vis absorption spectroscopy. However, the results for the photodegradation of levofloxacin indicate that the diphase TiO2 (A61B39) shows higher degradation ratio of levofloxacin instead of triphase TiO2. The reasons for these are attributed to the lowest recombination rate of photoinduced charges, the most negative of flat potential, and the larger specific surface area (SBET = 101 m2/g) for A61B39 sample, which are demonstrated by photoluminescence spectra, Mott-Schottky plots, and N2 adsorption-desorption isotherms. Besides, the intimate interfacial structure of different phase can be observed from high resolution transmission electron microscopy, which contributes to charge transfer. Meanwhile, the photodegradation mechanism of levofloxacin over A61B39 is expounded. This work demonstrates a facile method to regulate the phase ratio of TiO2 and facilitate its application in environmental remediation.

A composite of methylammonium lead iodide perovskite (MAPbI[Formula: see text] and carbon dots is prepared under ultrasound irradiation. Characterizations of X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, emission field scanning electron microscopy, Raman spectra and UV-Vis diffuse reflectance spectroscopy are performed. Excellent photoelectrochemical properties of prepared composites are examined by a collection of measurements including photocurrent density, open-circuit potential, current–voltage curves, cyclic voltammetry curves and Nyquist plots. The results imply that the as-prepared composites exhibit better electrochemical and photoelectrochemical properties as well as stability than those of blank MAPbI3. The improved properties are due to the formed Pb–O–C bridge bonds in the composites, which can promote the generation and transport of charge carriers. This work provides a novel sonochemical synthesis strategy and investigation on the photoelectrochemical performance of MAPbI3/carbon dots composites.

The nanosheet-assembled Bi2WO6 microspheres could be successfully synthesized in large quantities by a facile hydrothermal strategy in the presence of surfactant hexadecyl trimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) under mild conditions. The morphology and size of as-prepared Bi2WO6 could be readily controlled by adjusting the synthetic parameters such as hydrothermal time. The probable formation mechanism of nanosheet-assembled Bi2WO6 microspheres was discussed in detail. The hierarchical nanosheet-assembled microspheres could be constructed by orderly arranged nanosheets. The photocatalytic activity of the nanosheet-assembled Bi2WO6 microspheres was evaluated by degrading rhodamine B (RhB) under irradiation of visible light. The brilliant photodegradation efficiency is about 98% under visible light irradiation for 50 min. The results suggest that the as-prepared Bi2WO6 microspheres have good prospects as the photocatalyst for the removal of organic pollutants.

A vector-space formalism is developed for optimizing single-atom manipulation outcomes under focused electron irradiation., Atomic engineering is envisioned to involve selectively inducing the desired dynamics of single atoms and combining these steps for larger-scale assemblies. Here, we focus on the first part by surveying the single-step dynamics of graphene dopants, primarily phosphorus, caused by electron irradiation both in experiment and simulation, and develop a theory for describing the probabilities of competing configurational outcomes depending on the postcollision momentum vector of the primary knock-on atom. The predicted branching ratio of configurational transformations agrees well with our atomically resolved experiments. This suggests a way for biasing the dynamics toward desired outcomes, paving the road for designing and further upscaling atomic engineering using electron irradiation.

The uniform, rapid, and steady multi-jetting of nanofibers is the key to applying electrospinning technology in mass production. This paper aims to study an air-assisted multi-jet electrospinning method with a curvedly arranged multi-spinneret that can steadily and continuously produce nanofibers. An electrospinning device with a multi-spinneret which utilizes air flow to stretch and constrain jets is developed. The spinnerets are curvedly arranged in a 5 × 5 array, which can reduce the electric field interference between them. The air flow is guided through the gas hood and evenly distributed around each spinneret to form sheath layers, which mitigates the electric field interference between the spinnerets by reducing surface charge density of the jets and which stretches and constrains the jet, improving jetting stability and continuity. The influences of the electric field strength and the collection distance on jet ejection and deposition behavior are studied, and the influence of auxiliary air pressure on jet ejection initiation is also analyzed. The results show that the critical voltage of jet ejection of the central spinnerets is reduced from 8.2 kV to 3.4 kV when the auxiliary air pressure is increased from 0 kPa to 50 kPa, that of the inner spinnerets is reduced from 9.1 kV to 4.0 kV, and that of the outer spinnerets is reduced from 13.1 kV to 5.2 kV. The critical voltage of the outer spinnerets is higher than that of the inner spinnerets, and the critical voltage of the spinnerets in the center is the lowest. The design and development of the multi-spinneret curvedly arranged in a 5 × 5 array and the introduction of sheath air flow provide an effective means for uniform, rapid, and steady multi-jetting of nanofibers, which is beneficial in promoting the use of electrospinning technology in mass production applications.

2D transition metal dichalcogenide (2D‐TMD) materials and their van der Waals heterostructures (vdWHs) have inspired worldwide efforts in the fields of electronics and optoelectronics. However, photodetectors based on 2D/2D vdWHs suffer from performance limitations due to the weak optical absorption of their atomically thin nature. In this work, taking advantage of an excellent light absorption coefficient, low‐temperature solution‐processability, and long charge carrier diffusion length, all‐inorganic halides perovskite CsPbI3− xBrx quantum dots are integrated with monolayer MoS2 for high‐performance and low‐cost photodetectors. A favorable energy band alignment facilitating interfacial photocarrier separation and efficient carrier injection into the MoS2 layer inside the 0D–2D mixed‐dimensional vdWHs are confirmed by a series of optical characterizations. Owing to the synergistic effect of the photogating mechanism and the modulation of Schottky barriers, the corresponding phototransistor exhibits a high photoresponsivity of 7.7 × 104 A W−1, a specific detectivity of ≈5.6 × 1011 Jones, and an external quantum efficiency exceeding 107%. The demonstration of such 0D–2D mixed‐dimensional heterostructures proposed here would open up a wide realm of opportunities for designing low‐cost, flexible transparent, and high‐performance optoelectronics.

For graphene films, the change of crystal structure induced by ion bombardment as well as the doping and strain generated in thermal annealing process is addressed in this work. Experimental results show that both the structure and number of defects for graphene depends strongly on the ion dose. Furthermore, it is found that the structure defects caused by ion bombardment in graphene can be healed and the graphene samples are all doped in subsequent thermal annealing. The frequency shift of G and 2D peaks in Raman spectra reveals that compressive strain in graphene results from the thermal annealing treatment and the occurrence of strain is influenced by the thermal annealing and defects in graphene. For graphene, since defects and thermal annealing are unavoidable for the fabrication of graphene-based devices, the systematical investigation on these two aspects in this work is, therefore, of great importance and significance.

We present a facile, environment-friendly and mild method to fabricate graphene hydrogel by heating graphene oxide (GO) suspension containing sodium bicarbonate (NaHCO3). This method demonstrates a new type of in situ reduction-assembly approach to construct graphene hydrogel through simultaneous water evaporation and GO reduction. The freeze-dried graphene aerogel (G-Gel) shows excellent adsorptivity to heavy metal ions and dyes. The thermally treated G-Gel (TG-Gel) exhibits promising performance in recyclable selective absorption of oils and organic solvents.

We report a facile, low-cost and green route to fabricate platinum nanoparticle (Pt NP) decorated three-dimensional (3D) graphene assembled on fluorine-doped tin oxide (FTO) electrodes (Pt/3D-G/FTO) with enhanced electrocatalytic activity. The fabrication process was accomplished by preparation of 3D graphene (3D-G/FTO) electrodes through electrochemical reduction of a graphene oxide suspension followed by electrodeposition of Pt NPs onto them. The Pt/3D-G/FTO electrode exhibits much higher catalytic activity and better stability for methanol oxidation compared with the electrodes prepared by electrodeposition of Pt NPs onto two-dimensional graphene sheets substrate (Pt/G/FTO) or bare FTO (Pt/FTO) under the same condition. These enhancements can be attributed to the high surface area, large void volume and high electrical conductivity as well as smaller size of Pt NPs in the hollows of the 3D architecture and a large amount of ridges on it.

A series of high solid content carboxylic acid/sulfonic acid waterborne polyurethanes was prepared by the emulsion dispersion method. The particle size and solid content were measured. By changing the particle size of the large particles to achieve different particle size ratios, high solid content waterborne polyurethanes were obtained at specific particle size ratios. When the particle size ratio was &gt, 7, 4&ndash, 5 or 2&ndash, 3, the aqueous polyurethane could reach a higher solid content (more than 56%). This indicated that solid content is related to particle size distribution in high solid content waterborne polyurethane. Moreover, the corresponding three-dimensional stacked models (simple cubic accumulation, face-centered cubic accumulation, cubic close packing and hexagonal closest packing) were established.

In article number 1801219, Zhuo Kang, Yue Zhang, and co‐workers fabricate an ultrasensitive photodetector based on an all‐inorganic perovskite quantum dot‐monolayer MoS2 mixed dimensional van der Waals heterostructure. Owing to the synergistic effect of photogating and Schottky barriers modulation, the corresponding phototransistor exhibits an ultrahigh photoresponsivity of 7.7 × 104 A W−1, a specific detectivity of ≈5.6 × 1011 Jones, and an external quantum efficiency exceeding 107%.