Intrinsic magnetic topological insulators offer low disorder and large magnetic bandgaps for robust magnetic topological phases operating at higher temperatures. By controlling the layer thickness, emergent phenomena such as the quantum anomalous Hall (QAH) effect and axion insulator phases have been realized. These observations occur at temperatures significantly lower than the Néel temperature of bulk MnBi 2 Te 4 , and measurement of the magnetic energy gap at the Dirac point in ultra-thin MnBi 2 Te 4 has yet to be achieved. Critical to achieving the promise of this system is a direct measurement of the layer-dependent energy gap and verification of a temperature-dependent topological phase transition from large bandgap QAH insulator to a gapless TI paramagnetic phase. Here we utilize temperature-dependent angle-resolved photoemission spectroscopy to study epitaxial ultra-thin MnBi 2 Te 4 . We directly observe a layer-dependent crossover from a 2D ferromagnetic insulator with a bandgap greater than 780 meV in one septuple layer (1 SL) to a QAH insulator with a large energy gap (>70 meV) at 8 K in 3 and 5 SL MnBi 2 Te 4 . The QAH gap is confirmed to be magnetic in origin, as it becomes gapless with increasing temperature above 8 K.

This work presents the enhanced electrochemiluminescence (ECL) of a newly prepared nanosilver-carbon nanodot (Ag-C-dot) composite and its application for the sensitive detection of sulfide (S(2-)) ions. The Ag-C-dot composite was easily prepared by adding silver nitrate into C-dot colloids through an alkaline reduction. The obtained Ag-C-dots were characterized by UV-vis spectra, fluorescence spectra and transmission electron microscopy. The electrochemical and ECL behaviors of the Ag-C-dot composite were investigated by cyclic voltammetry. Moreover, a simple label-free method to detect S(2-) ions with a high selectivity and sensitivity has been developed based on the ECL of the Ag-C-dot composite in aqueous media. The sensing mechanism could be due to the strong and specific interaction between the S(2-) ions and the Ag atoms/ions on the surface of the Ag-C-dot composite, which dramatically affects the resulting ECL of the Ag-C-dot composite. The linear response to detect S(2-) ions ranges from 0.05 to 100 μM with a detection limit of 0.027 μM (~1 ppb). This work indicates that the Ag-C-dot nanocomposite possesses potential applications for environment sensing.

In this study, we report a metal-ion-assisted precipitation etching strategy that can be used to manipulate the optical properties associated with the assembling of sulfur quantum dots (S dots) using copper ions. Transmission electron microscopy confirmed that the S dots were mainly distributed within 50−80 nm and that they exhibited an ambiguous boundary. After the post-synthetic Cu 2+ -assisted modification was completed, the assisted precipitation-etching S dots (APE-S dots) were observed to exhibit a relatively clear boundary with a high fluorescence (FL) quantum yield (QY) of 32.8%. Simultaneously, the Fourier transform infrared radiation, X-ray photoelectron spectra, and timeresolved FL decay spectra were used to illustrate the improvement in the FL QY of the APE-S dots.

Cesium-based all-inorganic perovskite solar cells (PSCs), such as CsPbIBr 2 PSCs, have attracted wide attention for good thermal and wet stability, but the low open-circuit voltage (V oc ) mainly caused by the inadequate coverage of CsPbIBr 2 films is the main reason for limiting their development. The CsPbIBr 2 films grown on TiO 2 substrate directly have a large number of pinholes, which bring a lot of defects and lead to an increase of nonradiative recombination. In this work, a strategy extended for CsPbIBr 2 films by precoating methylammonium acetate (MAAc) ionic liquid onto a TiO 2 layer before depositing the CsPbIBr 2 film is demonstrated. The uniformly distributed MA + will be the nucleation center at the bottom of the CsPbIBr 2 film, which exhibited a notable impact on the crystallization kinetics of CsPbIBr 2 films. This effect simultaneously enhanced the crystal quality of the CsPbIBr 2 film and interfacial contact between the electron transporting layer (ETL) and CsPbIBr 2 layer. It is instrumental in decreasing the trap state density, suppressing nonradiative recombination, and extracting the charge carriers. Therefore, the stability of the optimized device has been improved considerably, and the champion power conversion efficiency (PCE) is up to 8.85% with a high V oc of 1.26 V. Benefiting from passivation, the PSC with 2 M MAAc IL interfacial modification remains 82% of its initial PCE after 30 days of exposing the device to ambient air at room temperature.

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This study reports a host-guest interaction strategy for systematically manipulating the optical properties of cesium lead halide perovskite nanocrystals (CsPbBr NCs) by protectant-mediated mercapto-β-cyclodextrin (SH-β-CD). The fluorescence of CsPbBr NCs can be adjusted over 405-510 nm with the quantum yields (QY) maintained at 50-90%.

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Combining magnetism and nontrivial band topology gives rise to quantum anomalous Hall (QAH) insulators and exotic quantum phases such as the QAH effect where current flows without dissipation along quantized edge states. Inducing magnetic order in topological insulators via proximity to a magnetic material offers a promising pathway towards achieving QAH effect at high temperature for lossless transport applications. One promising architecture involves a sandwich structure comprising two single layers of MnBi2Te4 (a 2D ferromagnetic insulator) with ultra-thin Bi2Te3 in the middle, and is predicted to yield a robust QAH insulator phase with a bandgap well above thermal energy at room temperature (25 meV). Here we demonstrate the growth of a 1SL MnBi2Te4 / 4QL Bi2Te3 /1SL MnBi2Te4 heterostructure via molecular beam epitaxy, and probe the electronic structure using angle resolved photoelectron spectroscopy. We observe strong hexagonally warped massive Dirac Fermions and a bandgap of 75  15meV. The magnetic origin of the gap is confirmed by the observation of broken time reversal symmetry and the exchange-Rashba effect, in excellent agreement with density functional theory calculations. These findings provide insights into magnetic proximity effects in topological insulators, that will move lossless transport in topological insulators towards higher temperature.