Significantly enhanced superconductivity in monolayer FeSe films on SrTiO3(001) via metallic δ-doping.

Superconductivity transition temperature (Tc) marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For 2D superconductivity, the paired electrons condense into a coherent superfluid state at Tc, which is usually lower than the pairing temperature, between which intrinsic physics including Berezinskii-Kosterlitz-Thouless transition and pseudogap state are hotly debated. In the case of monolayer FeSe superconducting films on SrTiO3(001), although the pairing temperature (Tp) is revealed to be 65-83 K by using spectroscopy characterization, the measured zero-resistance temperature ([Formula: see text]) is limited to 20 K. Here, we report significantly enhanced superconductivity in monolayer FeSe films by δ-doping of Eu or Al on SrTiO3(001) surface, in which [Formula: see text] is enhanced by 12 K with a narrowed transition width ΔTc ∼ 8 K, compared with non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, we demonstrate lowered work function of the δ-doped SrTiO3(001) surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity. Our work provides a practical route to enhance 2D superconductivity by using interface engineering.

Quantized anomalous Hall resistivity achieved in molecular beam epitaxy-grown MnBi2Te4 thin films.

The intrinsic magnetic topological insulator MnBi2Te4 provides a feasible pathway to the high-temperature quantum anomalous Hall (QAH) effect as well as various novel topological quantum phases. Although quantized transport properties have been observed in exfoliated MnBi2Te4 thin flakes, it remains a big challenge to achieve molecular beam epitaxy (MBE)-grown MnBi2Te4 thin films even close to the quantized regime. In this work, we report the realization of quantized anomalous Hall resistivity in MBE-grown MnBi2Te4 thin films with the chemical potential tuned by both controlled in situ oxygen exposure and top gating. We find that elongated post-annealing obviously elevates the temperature to achieve quantization of the Hall resistivity, but also increases the residual longitudinal resistivity, indicating a picture of high-quality QAH puddles weakly coupled by tunnel barriers. These results help to clarify the puzzles in previous experimental studies on MnBi2Te4 and to find a way out of the big difficulty in obtaining MnBi2Te4 samples showing quantized transport properties.

Controlling the Zero Hall Plateau in a Quantum Anomalous Hall Insulator by In-Plane Magnetic Field.

We investigate the quantum anomalous Hall plateau transition in the presence of independent out-of-plane and in-plane magnetic fields. The perpendicular coercive field, zero Hall plateau width, and peak resistance value can all be systematically controlled by the in-plane magnetic field. The traces taken at various fields almost collapse into a single curve when the field vector is renormalized to an angle as a geometric parameter. These results can be explained consistently by the competition between magnetic anisotropy and in-plane Zeeman field, and the close relationship between quantum transport and magnetic domain structure. The accurate control of zero Hall plateau facilitates the search for chiral Majorana modes based on the quantum anomalous Hall system in proximity to a superconductor.

Suppressing singlet-triplet annihilation processes to achieve highly efficient deep-blue AIE-based OLEDs.

Aggregation-induced emission (AIE) materials are attractive for the fabrication of high efficiency organic light-emitting diodes (OLEDs) by harnessing "hot excitons" from the high-lying triplet exciton states (Tn, n ≥ 2) and high photoluminescence (PL) quantum efficiency in solid films. However, the electroluminescence (EL) efficiency of most AIE-based OLEDs does not meet our expectation due to some unrevealed exciton loss processes. Herein, we further enhance the efficiency of blue AIE-based OLEDs, and find experimentally and theoretically that the serious exciton loss is caused by the quenching of radiative singlet excitons and long-lived triplet excitons [singlet-triplet annihilation (STA)]. In order to suppress the STA process, 1-(2,5-dimethyl-4-(1-pyrenyl)phenyl)pyrene (DMPPP) with triplet-triplet annihilation up-conversion was doped in two AIE emitters to reduce the triplet excitons on the lowest triplet excited state (T1) of AIE molecules. It can be seen that the external quantum efficiency (EQE) of the resulting blue OLEDs was enhanced to 11.8% with CIE coordinates of (0.15, 0.07) and a negligible efficiency roll-off, realizing the efficiency breakthrough of deep-blue AIE-based OLEDs. This work establishes a physical insight in revealing the exciton loss processes and the fabrication of high-performance AIE-based OLEDs.

Low-dimensional phase suppression and defect passivation of quasi-2D perovskites for efficient electroluminescence and low-threshold amplified spontaneous emission.

Quasi-2D metal halide perovskites are promising candidates for light-emitting applications owing to their large exciton binding energy and strong quantum confinement effect. Usually, quasi-2D perovskites are composed of multiple phases with various numbers of layers (n) of metal halide octahedron sheets, enabling light emission from the lowest-bandgap phase by cascade energy transfer. However, the energy transfer processes are extremely sensitive to the phase distribution and trap density in the quasi-2D perovskite films, and the insufficient energy transfer between different-n phases and the defect-induced traps would result in nonradiative losses. Here, significantly reduced nonradiative losses in the quasi-2D perovskite films are achieved by tailoring the low-dimensional phase components and lowering the density of trap states. Butylammonium bromide (BABr) and potassium thiocyanate (KSCN) are employed to synergistically decrease the nonradiative recombination in the quasi-2D perovskite films of PEABr : CsPbBr3. The incorporation of BABr is found to suppress the formation of the n = 1 phase, while adding KSCN can further reduce the low-n phases, passivate the notorious defects and improve the alignment of the high-n phases. By incorporating appropriate contents of BABr and KSCN, the resultant quasi-2D perovskite films show high photoluminescence quantum yield (PLQY) and highly ordered crystal orientation, which enable not only the green light-emitting diodes (LEDs) with a high external quantum efficiency (EQE) of 16.3%, but also the amplified spontaneous emission (ASE) with a low threshold of 2.6 µJ cm-2. These findings provide a simple and effective strategy to develop high-quality quasi-2D perovskites for LED and laser applications.

Abiotic degradation of field wheat straw as a notable source of atmospheric carbonyls in the North China Plain.

Carbonyl compounds (carbonyls) play a crucial role in atmospheric chemistry, but their atmospheric sources are not fully identified. Here we show unexpectedly high carbonyl emissions from extensive field returning wheat straw over the North China Plain (NCP). The emission rates of carbonyls exhibit distinct diurnal variations with the noontime peak value of total carbonyls greater than 135 µg∙kg-1 (dry straw weight) ∙h-1. The carbonyl emission is mainly attributed to biomass abiotic degradation processes that are affected by air temperature and sunlight intensity. Given that the photolysis of carbonyls is the major primary source of ROx radicals in the troposphere, carbonyl emissions would lead to increasing atmospheric oxidants. The mean daytime O3 concentration over the NCP increases by 12.3% when coupling carbonyl emissions from wheat straw with the current emission inventory through the model simulation. It might be one of the important reasons for the occurrence of the most serious O3 pollution in June when winter wheat is intensively harvested in the region. Further studies are warranted to explore the influence of field returning wheat straw on regional air quality.

Construction of carboxymethyl konjac glucomannan/chitosan complex nanogels as potential delivery vehicles for curcumin.

Construction of nanoscale delivery systems from natural food biopolymer complexes have attracted increasing interests in the fields of food industries. In this study, novel carboxymethyl konjac glucomannan/ chitosan (CMKGM/CS) nanogels with and without 1-ethyl-3-(3-dimethylaminopropyl) /N-hydroxysuccinimide) (EDC/NHS)-initiated crosslinking were prepared. The physicochemical and structural properties of the CMKGM/CS nanogels and their potential to be a delivery vehicle for curcumin were investigated. Compared to original uncrosslinked nanogels, crosslinking did not alter particle size and morphology but decreased zeta potential of nanogels. Fourier transform infrared spectrum confirmed that the amide linkage was formed between CMKGM and CS, which obviously enhanced the stability of crosslinked nanogels under gastrointestinal conditions. Furthermore, the crosslinked nanogels not only had higher encapsulation efficiency of curcumin but also better sustained release behavior under simulated gastrointestinal conditions. These findings suggested that the crosslinked CMKGM/CS nanogels might be a promising delivery system for nutrients.

Preparation and characterization of citric acid crosslinked konjac glucomannan/surface deacetylated chitin nanofibers bionanocomposite film.

Novel bionanocomposite films were prepared by combining konjac glucomannan/surface deacetylated chitin nanofibers (KGM/S-ChNFs) with different concentrations of citric acid (CA) (10%-25%) via a solution casting method. The effect of CA-induced crosslinking on the rheological behavior of film-forming solutions (FFS) as well as the structural and physicochemical properties of the resulting bionanocomposite films were evaluated. The results revealed that the increased CA loadings increased the shear viscosity of FFS. Fourier transform infrared spectra and scanning electron microscopy results confirmed the successful crosslinking between CA and S-ChNFs. The addition of 20 wt% CA was defined as the optimal condition, resulting in minimum water sensitivity and permeability, while maintaining a good combination of tensile strength and antimicrobial properties. This work supported the conclusion that CA crosslinking was an effective pathway for the preparation of polysaccharide-based bionanocomposite films with improved properties, which may be a promising material for active food packaging applications.

Investigating and manipulating the molecular beam epitaxy growth kinetics of intrinsic magnetic topological insulator MnBi2Te4within-situangle-resolved photoemission spectroscopy.

Intrinsic magnetic topological insulator MnBi2Te4is the key to realizing the quantum anomalous Hall effect and other related quantum phenomena at a sufficiently high temperature for their practical electronic applications. The research progress on the novel material, however, is severely hindered by the extreme difficulty in preparing its high-quality thin films with well-controlled composition and thickness. Combining molecular beam epitaxy (MBE) andin-situangle-resolved photoemission spectroscopy (ARPES), we have systematically studied the growth conditions and kinetics of MnBi2Te4thin films prepared by simple co-evaporation of Mn, Bi and Te. The transition and competition between the Mn-doped Bi2Te3and MnBi2Te4phases under different growth conditions have been mapped, which gives the recipe and the key principles of growing high-quality MnBi2Te4thin films. Particularly, to obtain high quality MnBi2Te4films, it is crucial to raise the growth temperature as high as allowed by the nucleation of the films to minimize density of Mn substitutional atoms on Bi sites. The ARPES data also reveal the kinetic process in the nucleation and ripening of MnBi2Te4islands. These results offer the essential information for designing and optimizing the MBE growth procedure of MnBi2Te4-like compounds to achieve the exotic topological quantum effects.

Novel synthesis of mussel inspired and Fe3+ induced pH-sensitive hydrogels: Adhesion, injectable, shapeable, temperature properties, release behavior and rheological characterization.

A novel EGCG-loaded DCKGM-CCKGM-Fe3+hydrogel was prepared by Dopamine-carboxymethyl konjac glucomannan (DCKGM) and an l-Cysteine-carboxymethyl konjac glucomannan (CCKGM) with Fe3+ as a cross-linking agent. Due to the dynamic property of Fe3+-phenolic hydroxyl coordination bond and intermolecular hydrogen bonding, the resultant hydrogel featured injectable, adhesive, temperature and pH-sensitive properties. The mechanisms were characterized using Rheological analysis, Fourier transform infrared spectroscopy, X-ray diffraction patterns, and scanning electron microscopy. Furthermore, the weak alkaline condition (pH 7.4) can trigger the release of EGCG, there was a cumulative release of 54.71 % of the loaded EGCG within 12 h in PBS at pH 1.2. When the pH of PBS was increased to 7.4, the cumulative release of EGCG increased to 68.54 %. Consequently, the EGCG-loaded DCKGM-CCKGM-Fe3+hydrogel (Fe3+Hydrogel) is a good candidate for the carrier for drug delivery. This paper provided a novel way for the preparation of hydrogel.

Preparation of an intelligent film based on chitosan/oxidized chitin nanocrystals incorporating black rice bran anthocyanins for seafood spoilage monitoring.

A novel intelligent film was developed by immobilizing 1%, 3% and 5% black rice bran anthocyanins (BACNs) into oxidized-chitin nanocrystals (O-ChNCs)/ chitosan (CS) matrix. The ultraviolet-visible spectrum of BACNs solutions showed color variations from red to greyish green in a range of pH 2.0-12.0. Fourier transform infrared spectrum and atomic force microscope of the films showed that O-ChNC and BACNs were well dispersed into the CS matrix. Although the incorporation of BACNs decreased the mechanical and barrier properties of the CS/O-ChNCs/BACNs (COB) films, it endowed the COB films with excellent UV-barrier, antioxidant and pH sensitivity character. The results of the application trial showed that the COB films containing 3% of BACNs (COB-3) were able to monitor the spoiling of fish and shrimp by visible color changes. Therefore, the developed COB-3 films could be used as an intelligent food packaging for monitoring animal-based protein food spoilage.

Transparent bionanocomposite films based on konjac glucomannan, chitosan, and TEMPO-oxidized chitin nanocrystals with enhanced mechanical and barrier properties.

The development of biopolymer-based films for food packaging is increasing owing to their environmental appeal, renewability, and biodegradability. In this study, transparent and biodegradable konjac glucomannan (KGM)/chitosan (CS)/TEMPO-oxidized chitin nanocrystal (TEMPO-ChNCs) bionanocomposite films were prepared. The TEMPO-ChNCs were prepared from chitin using the 2,2,6,6-tetramethylpiperidine-1-oxylradical (TEMPO) oxidation method and were used as a reinforcement nanofiller for the bionanocomposite films. The effect of TEMPO-ChNCs content on both rheological properties of film-forming solutions (FFS) and structural and physical properties of the resultant films was investigated. The rheological results of the FFS revealed that the TEMPO-ChNCs interacted with KGM and CS through electrostatic interaction and the hydrogen bonds in the bionanocomposite matrix, which was in agreement with the Fourier transform infrared spectroscopy and X-ray diffraction results. The microstructure of the films showed that 3% (w/w) TEMPO-ChNCs were homogeneously dispersed within the KGM/CS matrix, reducing the free volume of the biocomposite matrix and improving the final film mechanical and barrier properties (P < 0.05). Furthermore, these bionanocomposite films exhibited good thermal stability. The incorporation of TEMPO-ChNCs in the KGM/CS matrix produced flexible and transparent bionanocomposite films. Thus, this bionanocomposite films has potential use in food packaging applications.

Fabrication of chitosan-coated konjac glucomannan/sodium alginate/graphene oxide microspheres with enhanced colon-targeted delivery.

Microspheres play an increasingly important role in the food and medicine industries. In this study, konjac glucomannan (KGM)/sodium alginate (SA)/graphene oxide (GO) solution was injected into CaCl2 solution under high-voltage static electricity assistance to fabricate microspheres. Then, chitosan (CS) was coated on the surface of the microspheres to enhance their stability. SEM images confirmed that increasing voltage decreased the particle size of microspheres obviously. Furthermore, GO was beneficial in maintaining the full structure of freeze-dried microspheres, and the CS membrane improved the surface of the microspheres with no relatively obvious gully. Results indicated that KGM interacted with SA by hydrogen bond, and GO improved this interaction in microspheres. Furthermore, swelling tests showed that the microspheres exhibited different swelling properties in different media, and the CS membrane could improve the stability of microspheres in simulated intestinal fluid and simulated colon fluids. Moreover, GO could greatly improve the ciprofloxacin (CPFX) loading efficiency of microspheres, and achieving a sustained release effect of CPFX. Thus, CS-coated KGM/SA/GO microspheres showed great potential application in drug and/or nutrition factor colon-targeted delivery.

Fabrication of novel Konjac glucomannan/shellac film with advanced functions for food packaging.

In this study, a novel composite film was fabricated from Konjac glucomannan (KGM) combined with shellac (SHL) via a casting and solvent evaporation method. Rotary rheometry, field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) were applied to characterize the structure of the film. Physical properties were also investigated to evaluate the effect of SHL on KGM-based films. The results indicated that KGM-SHL gels exhibit a shear-thinning behaviour when the shear rate is increased. Meanwhile, FE-SEM images confirmed that all blended films had a continuous and homogeneous appearance without phase separation. The newly formed chemical bonds after blending were observed by FTIR. Moreover, thermal tolerance and mechanical properties of the films, such as tensile strength and elongation at break, were improved by adding SHL. In addition, the presence of SHL in the films led to an increase in water resistance. Therefore, the improved KGM-SHL films can be considered as a potential material for food packaging.

Effects of konjac glucomannan on the structure, properties, and drug release characteristics of agarose hydrogels.

Pure agarose (AG) hydrogels have strong rigidity and brittleness, which greatly limit their applications. Therefore, in this study, konjac glucomannan (KGM) was used to improve the properties of AG hydrogels. The effect of KGM on the structure and properties of AG hydrogels was investigated by rotational rheometry, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy. The results showed that the flexibility of the composite hydrogels increases with KGM concentration, which may be attributed to a synergistic interaction between KGM and AG resulting in a compact network structure. In vitro drug release behavior of composite hydrogels was investigated under different environments using model drug ciprofloxacin. The results showed that the encapsulation, drug loading efficiencies, and sustained release capacity of AG hydrogels were enhanced by the incorporation of KGM. These results suggested that KGM has the potential to enhance the properties and drug release characteristics of AG hydrogels.