A single septuple layer (SL) of MnBi2Te4 is a promising 2D ferromagnetic insulator for integrating magnetism with topology in van der Waals heterostructures, using topological insulators such as the nearly lattice matched Bi2Te3 with quintuple-layer (QL) units. Here, electrical transport measurements are performed on 1 SL MnBi2Te4/n QL Bi2Te3/1 SL MnBi2Te4 sandwich heterostructures (n = 0-4) to investigate the role of Bi2Te3 spacer thickness in tuning interlayer magnetic interactions. Magnetotransport reveals that even 1 QL Bi2Te3 is sufficient to switch the intrinsic antiferromagnetic coupling in 2 SL MnBi2Te4 to ferromagnetic, evidenced by Hall hysteresis and the absence of spin-flop transitions. Increasing n leads to a monotonic decrease in coercivity and Curie temperature, reflecting progressively weaker interlayer coupling, with a simultaneous enhancement in anomalous Hall response at n = 4. These results demonstrate reversible control of spin configuration by magnetic field and confirm the role of magnetic proximity-induced exchange coupling in determining the interlayer magnetic ground state, highlighting this atomic-scale spacer-engineered heterostructure as a compelling platform for spintronic applications and tunable symmetry-broken topological quantum phases.

Achieving long-wavelength, especially near-infrared (NIR), room-temperature phosphorescence (RTP) from carbon dots (CDs) remains a significant challenge. Herein, a molten-salt-assisted in-situ confinement strategy combined with conjugation engineering is developed to rapidly synthesize long-wavelength phosphorescent CDs within minutes. During cooling, the molten salt solidifies into a dense and rigid matrix that confines the emissive centers and suppresses nonradiative relaxation, while metal coordination further increases the local rigidity and regulates the electronic structures. Urea-derived N species facilitate n–π* transitions, and Cd-associated spin-orbit coupling provides an additional enhancement of intersystem crossing. The tunable emission of these CDs stems from the continuous variation in the contents of C=C bonds and graphitic N. Notably, the CDs exhibit efficient solid-state red fluorescence at 634 nm with a fluorescence quantum yield of 30.69%, and long-lived delayed emission at 645 nm with a delayed-emission quantum yield of 6.16%. Temperature-dependent spectra and wavelength-resolved lifetime measurements reveal the coexistence of low-temperature NIR phosphorescence at 730 nm and TADF-dominated delayed fluorescence around 660 nm upon warming. These unique long-lived emission properties enable promising applications in white LEDs, dynamic anti-counterfeiting, and advanced information encryption.

Quantum materials that combine magnetism with topological order are emerging as key platforms for next-generation spintronics and low-energy electronics. They enable the realization of emergent quantum phenomena, such as the quantum anomalous Hall effect and axion insulator states. The ferromagnetic insulator (FMI)/topological insulator (TI)/FMI sandwich structure of a single-septuple layer (1SL) MnBi2Te4/four-quintuple layer (4QL) Bi2Te3/1SL MnBi2Te4 holds great potential to achieve such desirable quantum phenomena at an elevated temperature, owing to its large Dirac point band gap and high Curie temperature. Here, spin- and angle-resolved photoemission spectroscopy (spin-ARPES) is employed to directly verify that the band gap arises from broken time-reversal symmetry via proximity-driven magnetization. This study demonstrates direct control of the spin state via external magnetic fields and unambiguously confirms the exchange interaction as the gap-opening mechanism. The robust magnetic gap and controllable spin texture make this heterostructure a suitable candidate for spintronic applications and magnetic topological quantum phases.

Aggregation-caused quenching (ACQ) of carbon dots (CDs) is the main obstacle to their solid-state application. Herein, self-quenching-resistant CDs with tunable solid-state fluorescence (SSF) were obtained via the electrochemical method in separate electrodes simultaneously, where redox reactions from the cathode and anode are employed to develop a differentiated strategy for surface-state modulation through molecular modification. The key feature of this approach is the tunable emission from morphological changes of o-phenylenediamine within the anode and cathode, and considerable steric hindrance from long chains and guanidino groups on CDs introduced by d-arginine. The guanidino groups, in particular, enhanced spatial steric hindrance in situ and suppressed ACQ through a hydrogen-bonding network. Furthermore, such SSF CDs with emission at 550 nm (Y-CDs) and a main emission at 646 nm (R-CDs) exhibit great potential for applications in light emitting diodes (LEDs) and multi-mode anti-counterfeiting.

The altermagnet candidate MnTe has recently gained significant interest due to its unconventional magnetic ordering. One of the key features of altermagnetism is the momentum-dependent spin-split band and its temperature-dependent evolution. Yet a fully momentum-resolved experimental investigation, including out-of-plane direction, is still lacking. Here, we systematically investigate the electronic structure of epitaxially grown MnTe by using angle-resolved photoemission spectroscopy (ARPES). Our photon-energy-dependent ARPES data reveal significant out-of-plane dispersions consistent with previous theoretical calculations. More interestingly, we identify two distinct temperature-dependent electronic band structure evolutions at different out-of-plane momentum positions: momentum-dependent energy shifts at the nodal plane and substantial spectral weight suppression at the off-nodal plane. These findings may suggest the importance of considering both the itinerant and localized nature of the magnetic ordering and momentum-dependent interactions. Our work provides crucial insights into the complex correlation between momentum, temperature, and electronic structure in MnTe, contributing to a deeper understanding of altermagnetism.

All-inorganic halide perovskite CsPbX3 (X=Cl, Br, I) nanocrystals (NCs) have become attractive optoelectronic materials due to their excellent optical and electronic properties. However, the ionic properties and surface defects of halide perovskite make them highly susceptible to decomposition and degradation in water, which significantly hinders the stability and luminescence performance of CsPbX3 NCs. Therefore, synthesizing high-stability perovskite nanocrystals in the aqueous phase is a crucial challenge. Here, we have developed a method for the synthesis of CsPbClxBr3-x NCs with high stability via in-situ crystallization in aqueous phase using cesium trifluoroacetate (CsTFA) as cesium source and surface ligand. CsTFA not only provides Cs+ for the perovskite lattice but also possesses its own TFA- as a strong surface ligand, which, in cooperation with 4-bromobutyric acid (BBA) and oleylamine (OLA) surface ligands, will facilitate the formation of more regular nanocrystals and substantially reduce the defects on the crystal surface. The CsPbClxBr3-x NCs obtained in an aqueous solution exhibit a cubic crystal structure with photoluminescence quantum yields > 90 %. After being dispersed in an aqueous solution for 90 h, the wavelength and full width at half-maximum of the PL of CsPbClxBr3-x NCs have no significant change, and the PL intensity can maintain 90.3 % of their initial one, indicating that the structure of CsPbClxBr3-x NCs is unchanged. Moreover, the CsPbClxBr3-x NCs sample maintained high stability and good luminescence properties even after dilution with water tens of times. The results provide a viable design strategy for synthesizing cesium-based perovskite nanocrystals with high stability using CsTFA in an aqueous phase or other medium.

All-inorganic perovskite CsPbBr3 (CPB) nanocrystals (NCs) exhibit excellent photoelectric properties, yet their susceptibility to decomposition in high humidity conditions hampers their large-scale application. Exploring an effective strategy to improve the water stability and optical properties while enhancing the electrical properties is undoubtedly a tremendous challenge. In this work, we present a convenient and feasible aqueous-phase synthesis strategy for the fabrication of three-dimensional/two-dimensional (3D/2D) TFA-CPB/WS2 heterostructures through the incorporation of multifunctional additive cesium trifluoroacetate (Cs-TFA) and 2D WS2 nanosheets (NSs). WS2 NSs not only passivate the surface defects via the intrinsic properties but also promote the Van der Waals epitaxial growth of TFA-CPB NCs along the (002) crystal planes due to their well-matched lattice. Simultaneously, WS2 NSs can effectively facilitate interfacial charge transfer and extraction through a Type-II energy band alignment with the NCs. The results demonstrate that the photoluminescence intensity of TFACPB/WS2 heterostructures retains 50.32 % of the initial intensity after 108 h. The TFA-CPB/WS2 heterostructures-based photodetector exhibit a light on/off ratio of 1934.6 and a responsivity of 141.93 mA & sdot;W-1 under UV irradiation at 4 V bias and 5 mW & sdot;cm-2 light intensity, with the rise and fall times of 10 ms and 34 ms, respectively. The efficient preparation of aqueous-phase 3D/2D TFA-CPB/WS2 heterostructures and the application of photodetectors will promote the further development of perovskite-based photodetectors with a degree of scientific value and application potential.

The persistent luminescent (PSL) phosphors Sr2-x-yMgSi2O7: xEu2+, yDy3+ (x=0∼0.08, y=0∼0.08) were synthesized by a solid-state reaction method in a weak reductive atmosphere of 5%-H2/N2. Comprehensive measurements were carried out to study the effects of Eu2+ and Dy3+ doping amount on the crystal phase, photoluminescence (PL), afterglow decay properties, and trap energy levels. The results indicated that the impurity phases decreased and disappeared, and crystalline grains tended to be larger and denser with the doping amount of Eu2+ and Dy3+ increasing. We shed light on the origination of asymmetric PL peak, concentration quenching of Eu2+ ions, time evolution of PSL specture and chromaticity of Eu2+, Dy3+ co-doped phosphors. Based on the deconvolutions of X-ray photoelectron spectroscopy (XPS) spectra and thermoluminescence (TL) spectra, the types and energy depth of traps in these phosphors were systematically studied. According to the data of PL, PLE, and TL, we deduced a schematic diagram of the energy level and discussed the mechanism of PSL of the phosphors. As Dy3+ dopant increases, the Eu2+, Dy3+ co-doped phosphors not only generate more defects of VO•• and VSrʺ, but also introduce DySr• defect with proper trap depth, meanwhile, a thermally assisted tunneling mechanism will gradually dominate during the persistent luminescence, which is responsible for that the phosphor with x=0.02, y=0.01 presents the best long afterglow property.

All‐inorganic perovskite CsPbBr3 (CPB) nanocrystals (NCs) are not widely applied in aqueous environments due to their readily decomposable nature. Therefore, the aqueous‐phase preparation of CPB NCs has been a considerable challenge. In this work, a feasible method is proposed for preparing aqueous‐phase core–shell CPB nanorods (NRs) encapsulated with polydopamine (PDA) by employing a multifunctional additive cesium trifluoroacetate (Cs‐TFA). Highly luminescent TFA‐CPB NRs are obtained via a chemical transformation of Cs4PbBr6 NCs in water. Subsequently, PDA constitutes a robust shell on the surface of TFA‐CPB NRs through the covalent oxidative polymerization, which effectively reduces the original dynamic properties of surface ligands, retards the decomposition of ligands and inhibits the leakage of Pb2+ ions. The results demonstrate that the fluorescence intensity of TFA‐CPB@PDA NRs maintains 49.3% of the initial intensity after 136 days. Meanwhile, the NRs exhibit low cytotoxicity, and the cell viability remains at 80% when the concentration of the NRs is 200 μg mL−1. The reliable preparation of aqueous‐phase core–shell perovskite NRs (PNRs) will facilitate their development in many fields, such as materials science, biology, medicine, and their applications in aqueous environments.

The fabrication of high -quality perovskite films with low defect density in ambient air is an important approach to enhance the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). In this paper, efficient and stable PSCs were fabricated in ambient air, and p-xylilenediamine bromide (PhDMADBr) assisted additive or interface engineering were carried out to modify perovskite films, which was dispersed into the electron transport layer (ETL) or deposited in the ETL/ perovskite interface. Notably, interaction between PhDMADBr and perovskite layer could reduce defect density and release residual stress of the active layer, which would induce a high -quality perovskite film, and accelerate the transport rate and prolong lifetimes of charge carriers, contributing to the PCE and stability of devices. As a result, compared with the PCE of the control device (22.54 %), the PhDMADBr modified target PSCs exhibited the enhanced PCE of 24.15 % and 23.74 % after additive or interface treatments in ambient air, respectively. Except the improvement of the PCE, PhDMADBrbased devices also presented the enhanced moisture stability. The average efficiency retained the 88 % or 84 % of initial efficiency after 120 h with RH of 40 +/- 5 % for additive or interface modification, respectively. In contrast, the PCE of the control devices would decline to 51 % of initial efficiency after storage for 120 h.

Topological insulators (TIs) are emergent materials with unique band structure, which allow the study of quantum effect in solids, as well as contribute to high performance quantum devices. To achieve the better performance of TI, here we present a co-doping strategy using synergistic rare-earth Sm and transition-metal Fe dopants in Bi2Se3 single crystals, which combine the advantages of both transition metal doped TI (high ferromagnetic ordering temperature and observed QAHE), and rare-earth doped TI (large magnetic moments and significant spin orbit coupling). In the as-grown single crystals, clear evidences of ferromagnetic ordering were observed. The angle resolve photoemission spectroscopy indicate the ferromagnetism opens a 44 meV band gap at surface Dirac point. Moreover, the carrier mobility at 3 K is   7400 cm2/Vs, and we thus observed an ultra-strong Shubnikov-de Haas oscillation in the longitudinal resistivity, as well as the Hall steps in transverse resistivity below 14 T. Our transport and angular resolved photoemission spectroscopy results suggest that the rare-earth and transition metal co-doping in Bi2Se3 system is a promising avenue implement the quantum anomalous Hall effect, as well as harnessing the massive Dirac fermion in electrical devices.

Quantum anomalous Hall (QAH) insulators transport charge without resistance along topologically protected chiral 1D edge states. Yet, in magnetic topological insulators to date, topological protection is far from robust, with zero-magnetic field QAH effect only realized at temperatures an order of magnitude below the Néel temperature TN, though small magnetic fields can stabilize QAH effect. Understanding why topological protection breaks down is therefore essential to realizing QAH effect at higher temperatures. Here a scanning tunneling microscope is used to directly map the size of exchange gap (Eg,ex) and its spatial fluctuation in the QAH insulator 5-layer MnBi2Te4. Long-range fluctuations of Eg,ex are observed, with values ranging between 0 (gapless) and 70 meV, appearing to be uncorrelated to individual surface point defects. The breakdown of topological protection is directly imaged, showing that the gapless edge state, the hallmark signature of a QAH insulator, hybridizes with extended gapless regions in the bulk. Finally, it is unambiguously demonstrated that the gapless regions originate from magnetic disorder, by demonstrating that a small magnetic field restores Eg,ex in these regions, explaining the recovery of topological protection in magnetic fields. The results indicate that overcoming magnetic disorder is the key to exploiting the unique properties of QAH insulators.

Since the first realisation of the quantum anomalous Hall effect (QAHE) in a dilute magnetic-doped topological insulator thin film in 2013, the quantisation temperature has been limited to less than 1 K due to magnetic disorder in dilute magnetic systems. With magnetic moments ordered into the crystal lattice, the intrinsic magnetic topological insulator MnBi2Te4 has the potential to eliminate or significantly reduce magnetic disorder and improve the quantisation temperature. Surprisingly, to date, the QAHE has yet to be observed in molecular beam epitaxy (MBE)-grown MnBi2Te4 thin films at zero magnetic field, and what leads to the difficulty in quantisation is still an active research area. Although bulk MnBi2Te4 and exfoliated flakes have been well studied, revealing both the QAHE and axion insulator phases, experimental progress on MBE thin films has been slower. Understanding how the breakdown of the QAHE occurs in MnBi2Te4 thin films and finding solutions that will enable mass-produced millimetre-size QAHE devices operating at elevated temperatures are required. In this mini-review, we will summarise recent studies on the electronic and magnetic properties of MBE MnBi2Te4 thin films and discuss mechanisms that could explain the failure of the QAHE from the aspects of defects, electronic structure, magnetic order, and consequences of their delicate interplay. Finally, we propose several strategies for realising the QAHE at elevated temperatures in MnBi2Te4 thin films.

The kagome metal FeSn consists of alternating layers of kagome-lattice Fe3Sn and honeycomb Sn2 and exhibits great potential for applications in future low-energy electronics and spintronics because of an ideal combination of topological phases and high-temperature magnetic ordering. Robust synthesis methods for ultrathin FeSn films, as well as an understanding of their air stability, are crucial for its development and long-term operation in future devices. In this work, we realize large-area, <10 nm thick, epitaxial FeSn thin films and explore the oxidation process via synchrotron-based photoelectron spectroscopy using in situ oxygen and water dosing, as well as ex situ air exposure. Upon exposure to the atmosphere, the FeSn films are shown to be highly reactive, with a stable ∼3 nm thick oxide layer forming at the surface within 10 min. Notably, the surface Fe remains largely unoxidized when compared with Sn, which undergoes near-complete oxidation. Additionally, the band structure remains metallic under oxygen exposure. These are further confirmed with controlled in situ dosing of O2 and H2O, where only the Sn2 (stanene) interlayers within the FeSn lattice oxidize, suggesting the Fe3Sn kagome layers remain almost pristine. These results are in excellent agreement with first-principles calculations, which show that Fe-O bonds to the Fe3Sn layer are energetically unfavorable and a large formation energy preference of 1.37 eV for Sn-O bonds in the stanene Sn2 layer over Sn-O bonds in the kagome Fe3Sn layer. The demonstration that oxidation only occurs within the stanene layers and the preservation of the Dirac bands may provide additional avenues in how to engineer, handle, and prepare future kagome metal devices.

The red persistent luminescence phosphors SrS: , (x = 0∼0.001, y = 0∼0.003) were synthesized by the solid-state reaction method in a weak reducing atmosphere of active carbon. The synthetic parameters, photoluminescence characteristics, and dynamic properties of thermoluminescence of the phosphors were studied systematically. According to the results of photoluminescence spectra of SrS: , , the energy level scheme of the phosphors was confirmed quantitatively. Based on the studies of the scanning electron microscope (SEM), UV-Visible absorbance spectra, afterglow decay curves, thermoluminescence(TL) spectra, and X-ray photoelectron spectroscopy (XPS) spectra, we found that the SrS: , (SSEP) phosphor presented the best persistent luminescence property, which mainly resulted from its outstanding absorbance characteristic, deeper depth of ( ) defects, and fewer defect concentration belonging to the higher-order kinetics. Those comprehensive results deduced that a complex defect ( )- should present in the Eu2+ doping phosphors, and the Pr3+ doping will produce defects, which can suppress the formation of ( ) defects and increase their energy depth.

Topological insulators are emerging materials with insulating bulk and symmetry protected nontrivial surface states. One of the most fascinating transport behaviors in a topological insulator is the quantized anomalous Hall insulator, which has been observed inmagnetic-topological-insulator-based devices. In this work, we report a successful doping of rare earth element Tb into Bi$_{1.08}$Sb$_{0.9}$Te$_2$S topological insulator single crystals, in which the Tb moments are antiferromagnetically ordered below ~10 K. Benefiting from the in-bulk-gap Fermi level, transport behavior dominant by the topological surface states is observed below ~ 150 K. At low temperatures, strong Shubnikov-de Haas oscillations are observed, which exhibit 2D-like behavior. The topological insulator with long range magnetic ordering in rare earth doped Bi$_{1.08}$Sb$_{0.9}$Te$_2$S single crystal provides an ideal platform for quantum transport studies and potential applications.

We propose a novel ligand-assisted reprecipitation method to synthesize aqueous-phase CsPbBr3 nanocrystals, the fluorescence intensity of which remained at 51% after 120 h. As a multifunctional additive, cesium trifluoroacetate (Cs-TFA) can improve the surface adsorption energy and induce nanocrystals to show significant anodic electrochemiluminescence (ECL) and stable cathodic ECL performances.

In this study, we proposed a novel Ru(bpy)32+-Au-WS2 nanocomposite (Ru-Au-WS2 NCs) nano-hybrid electrochemiluminescence (ECL) probe for the highly sensitive detection of carcinoembryonic antigen (CEA). This system utilizes Au nanoparticles (Au NPs) as a bridge to graft the high-performance of a Ru(bpy)32+ ECL emitter and WS2 nanosheet with excellent electrochemical performance into an ECL platform, which shows outstanding anodic ECL performance and biosensing platform due to the synergetic effect and biocompatibility of Au NPs and WS2 nanosheet. Because the ECL intensity of Ru(bpy)32+ is sensitively affected by the antibody-antigen insulator, a preferable linear dependence was obtained in the concentration range of CEA from 1 pg·mL−1 to 350 ng·mL−1 with high selectivity (LOD of 0.3 pg·mL−1, S/N = 3). Moreover, the ECL platform had good reproducibility and stability and exhibited excellent anti-interference performance in the detection process of CEA. We believe that the platform we have developed can expand the opportunities for the detection of additional high specificity-related antibodies/antigens and demonstrate broad prospects for disease diagnosis and biochemical research.

Layered magnetic materials,such as MnBi2Te4,have drawn much attention owing to their potential for realizing two-dimensional(2D)magnetism and possible topological states.Recently,FeBi2Te4,which is isostructural to MnBi2Te4,has been synthesized in experiments,but its detailed magnetic ordering and band topology have not been clearly understood yet.Here,based on first-principles calculations,we investigate the magnetic and electronic properties of FeBi2Te4 in bulk and 2D forms.We show that different from MnBi2Te4,the magnetic ground states of bulk,single-layer,and bilayer FeBi2Te4 all favor a 120° noncollinear antiferromagnetic ordering,and they are topologically trivial narrow-gap semiconductors.For the bilayer case,we find that a quantum anomalous Hall effect with a unit Chern number is realized in the ferromagnetic state,which may be achieved in experiment by an external magnetic field or by magnetic proximity coupling.Our work clarifies the physical properties of the new material system of FeBi2Te4 and reveals it as a potential platform for studying magnetic frustration down to 2D limit as well as quantum anomalous Hall effect.