Plasma-Induced 2D Electron Transport at Hetero-Phase Titanium Oxide Interface.

Interfaces of metal oxide heterojunctions display a variety of intriguing physical properties that enable novel applications in spintronics, quantum information, neuromorphic computing, and high-temperature superconductivity. One such LaAlO3 /SrTiO3 (LAO/STO) heterojunction hosts a 2D electron liquid (2DEL) presenting remarkable 2D superconductivity and magnetism. However, these remarkable properties emerge only at very low temperatures, while the heterostructure fabrication is challenging even at the laboratory scale, thus impeding practical applications. Here, a novel plasma-enabled fabrication concept is presented to develop the TiO2 /Ti3 O4 hetero-phase bilayer with a 2DEL that exhibits features of a weakly localized Fermi liquid even at room temperature. The hetero-phase bilayer is fabricated by applying a rapid plasma-induced phase transition that transforms a specific portion of anatase TiO2 thin film into vacancy-prone Ti3 O4 in seconds. The underlying mechanism relies on the screening effect of the achieved high-density electron liquid that suppresses the electron-phonon interactions. The achieved "adiabatic" electron transport in the hetero-phase bilayer offers strong potential for low-loss electric or plasmonic circuits and hot electron harvesting and utilization. These findings open new horizons for fabricating diverse multifunctional metal oxide heterostructures as an innovative platform for emerging clean energy, integrated photonics, spintronics, and quantum information technologies.

Overcoming Ion Transport Barrier by Plasma Heterointerface Engineering: Epitaxial Titanium Carbonitride on Nitrogen-Doped TiO2 for High-Performance Sodium-Ion Batteries.

Anatase TiO2 is a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its high specific capacity, low cost, and excellent cycle stability. However, low electrical conductivity and poor Na+ ion transport in TiO2 limit its practical applications. Here, substantially boosted Na+ ion transport and charge transfer kinetics are demonstrated by constructing a near-ideal non-rectifying titanium carbonitride/nitrogen-doped TiO2 (TiCx N1- x /N-TiO2 ) heterostructure. Owing to the fast plasma effects and metastable hybrid phases, the TiCx N1- x is epitaxially grown on TiO2 . Energy band engineering at the interface induces high electron densities and a strong built-in electric field, which lowers the Na+ diffusion barrier by a factor of 1.7. As a result, the TiCx N1- x /N-TiO2 electrode exhibits excellent electrochemical performance. The reversible specific capacities at rates of 0.1 and 10 C reach 312.3 and 173.7 mAh g-1 , respectively. After 600 cycles of charge and discharge at 10 C, the capacity retention rate is 98.7%. This work discovers an effective non-equilibrium plasma-enabled process to construct heterointerfaces that can enhance Na+ ion transport and provides generic guidelines for the design of heterostructures for a broader range of energy storage, separation, and other devices that rely on controlled ionic transport.

Ultra-sensitive nanometric flat laser prints for binocular stereoscopic image.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) with tantalizing layer-dependent electronic and optical properties have emerged as a paradigm for integrated flat opto-electronic devices, but their widespread applications are hampered by challenges in deterministic fabrication with demanded shapes and thicknesses, as well as light field manipulation in such atomic-thick layers with negligible thicknesses compared to the wavelength. Here we demonstrate ultra-sensitive light field manipulation in full visible ranges based on MoS2 laser prints exfoliated with nanometric precisions. The nontrivial interfacial phase shifts stemming from the unique dispersion of MoS2 layers integrated on the metallic substrate empower an ultra-sensitive resonance manipulation up to 13.95 nm per MoS2 layer across the entire visible bands, which is up to one-order-of-magnitude larger than their counterparts. The interlayer van der Waals interactions and the anisotropic thermal conductivity of layered MoS2 films endow a laser exfoliation method for on-demand patterning MoS2 with atomic thickness precision and subwavelength feature sizes. With this, nanometric flat color prints and further amplitude-modulated diffractive components for binocular stereoscopic images can be realized in a facile and lithography-free fashion. Our results with demonstrated practicality unlock the potentials of, and pave the way for, widespread applications of emerging 2D flat optics.

Plasma Enabled Fe2O3/Fe3O4 Nano-aggregates Anchored on Nitrogen-doped Graphene as Anode for Sodium-Ion Batteries.

Low electrical conductivity severely limits the application of Fe2O3 in lithium- and sodium-ion batteries. In respect of this, we design and fabricate Fe2O3/Fe3O4 nano-aggregates anchored on nitrogen-doped graphene as an anode for sodium-ion batteries with the assistance of microwave plasma. The highly conductive Fe3O4 in the composite can function as a highway of electron transport, and the voids and phase boundaries in the Fe2O3/Fe3O4 heterostructure facilitate Na+ ion diffusion into the nano-aggregates. Furthermore, the Fe-O-C bonds between the nano-aggregates and graphene not only stabilize the structural integrity, but also enhance the charge transfer. Consequently, the Fe2O3/Fe3O4/NG anode exhibits specific capacity up to 362 mAh g-1 at 100 mA g-1, excellent rate capability, and stable long-term cycling performance. This multi-component-based heterostructure design can be used in anode materials for lithium- and sodium-ion batteries, and potential opens a new path for energy storage electrodes.

High photon-to-heat conversion efficiency in the wavelength region of 250-1200 nm based on a thermoelectric Bi2Te3 film structure.

In this work, 4-layered SiO2/Bi2Te3/SiO2/Cu film structures were designed and fabricated and the optical properties investigated in the wavelength region of 250-1200 nm for their promising applications for direct solar-thermal-electric conversion. A typical 4-layered film sample with the structure SiO2 (66.6 nm)/Bi2Te3 (7.0 nm)/SiO2 (67.0 nm)/Cu (>100.0 nm) was deposited on a Si or K9-glass substrate by magnetron sputtering. The experimental results agree well with the simulated ones showing an average optical absorption of 96.5%, except in the shorter wavelength region, 250-500 nm, which demonstrates the superior absorption property of the 4-layered film due to the randomly rough surface of the Cu layer resulting from the higher deposition power. The high reflectance of the film structure in the long wavelength region of 2-20 µm will result in a low thermal emittance, 0.064 at 600 K. The simpler 4-layered structure with the thermoelectric Bi2Te3 used as the absorption layer may provide a straightforward way to obtain solar-thermal-electric conversion more efficiently through future study.

Excellent color rendering index and high quantum efficiency of rare-earth-free fluosilicate glass for single-phase white light phosphor.

A rare-earth-free Sn-doped fluosilicate (SF) glass for single-phase white light phosphor has been investigated, which has a high color rendering index (98.3) and a quantum efficiency (85%). Moreover, by combining with a 280 nm LED chip directly, the Commission Internationale de l'Éclairage (CIE) coordinate (x=0.32, y=0.33) and correlated color temperature (5620 K) are close to the standard white light illumination. SF glass is a promising candidate as an alternative single-phase white light phosphor for use in general lighting devices.

[The spectra properties of 2-(2'-hydroxyphenyl)benzothiazole in different solvents].

2-(2 -hydroxyphenyl)benzothiazole (HBT) is a typical compound with excited--state intramolecular proton transfer (ESIPT) effect. The mechanism of the influence of the solvent polarity on the ESIPT effect of HBT was investigated by means of absorption and fluorescence spectra in different polar solvents. The absorption spectra of HBT molecule in all solvents have the similar configuration and are mainly situated in the UV region from 260 to 370 nm. The absorption peaks are located at 287 and 335 nm and have the decline trend with the increase in the solvent polarity. In addition, there is a very weak absorption band at 400 nm and it is attributable to the absorption from the keto form of HBT. Under UV excitation at 335 nm, the fluorescence spectra in all the solvents were obtained. All the fluorescence spectra exhibit dual fluorescence peaks, which are located at 385 and 512 nm respectively. The former is attributed to the emission from the HBT enol forms, named the normal fluorescence, and the latter the emission from the keto tautomer emission, named ESIPT fluorescence. The fluorescence spectra of HBT show that the intensity of the normal fluorescence is obviously increased and the intensity of the ESIPT fluorescence is decreased with enhancing the polarity of the solvents. This indicates that the strong polar solvents are not favorable to the ESIPT of HBT. Because the solvated enols in the polar solvent prevent the ESIPT from happening, the ESIPT efficiency of HBT in cyclohexane is the largest and that of HBT in ethanol is the smallest. The three fluorescence bands of HBT in different polarity solvents were observed with 400 nm excitation. One fluorescence band at ca. 510 nm is referred to as the ESIPT fluorescence. This confirms that the weak absorption at 400 nm results from the keto tautomer and the enol and keto forms can coexist under the normal condition, but the enol form is the absolutely predominant. In addition, the other two unknown fluorescent emission bands appear at 436 and 456 nm respectively. Their possible origin is the emission from the deprotonated anion of HBT keto tautomer.

[Study on the fluorescence spectra of 7-hydroxyquinoline in dimethyl sulfoxide solution].

7-hydroxyquinoline (7-HQ) is a kind of organic molecule with excited-state proton transfer (ESPT) effect. 7-HQ in ethanol solution causes ESPT reaction under the excitation of ultraviolet light. The fluorescence spectrum of the sample exhibits two bands. In contrast, 7-HQ in dimethyl sulfoxide (DMS) solution does not cause ESPT reaction. The fluorescence spectrum of the sample exhibits a single band. But after the sample was irradiated with a strong UV light, its fluorescence spectrum also exhibits two bands. This phenomenon is reported for the first time in the present paper, and its cause is investigated through the study on the absorption spectra and fluorescence spectra of 7-HQ in ethanol, dimethyl sulfoxide and N, N-dimethyl formamide solution. The conclusion is that the change in the fluorescence spectrum of 7-HQ in DMS solution is due to the fact that 7-HQ causes ESPT reaction which results from the photodecomposition of DMS and the product of water after the solution was irradiated with strong UV light.