No abstract

By cutting MoS2 microcrystals to quantum dots (QDs) of sizes below 10 nm, the photoluminescence (PL) at ca. 450 nm can be detected easily due to the quantum confinement effects across the 2D planes. The PL is stable under continuous irradiation of UV light but gradually quenches when treated with an increasing concentration of hydrogen peroxide. Time-resolved PL and Raman spectra imply that H2O2 causes the partial oxidation of MoS2 QDs. First-principles calculations reveal that the MoS2 QDs with oxygen impurity are of indirect bandgap structures showing no notable PL. And absorption spectra verify that the PL of MoS2 QDs quenched by H2O2 is attributed to the oxidation. The integrated PL intensity and H2O2 concentration show an exponential relationship in the range of 2–20 μM, suggesting that MoS2 QDs are potential fluorescent probes for hydrogen peroxide sensing in a physiological environment.

Black phosphorus (BP) has recently attracted considerable attention due to its unique structure and fascinating optical and electronic properties as well as possible applications in photothermal agents. However, its main drawback is rapid degradation in ambient environments of HO and O, which has led to much research on the improvement of its stability. Unfortunately, this research has not shown great improvement in carrier mobilities. Here, we perform scanning tunneling microscopy observations of few-layer BP (FLBP) sheets exfoliated in ultrahigh vacuum and reveal, for the first time, the existence of lattice oxygen introduced during crystal growth. As a proof-of-concept application, hydrogenation is conducted to remove the lattice oxygen atoms followed by phosphorization, which repairs the phosphorous vacancies caused by mechanical exfoliation and hydrogenation. The resulting FLBP sheets show high ambipolar field-effect mobilities of 1374 cm V s for holes and 607 cm V s for electrons at 2 K. After storage in air for 3 days, the hole and electron mobilities only decrease to 1181 and 518 cm V s, respectively, and no structural degradation is observed. This work suggests an effective means to improve both the mobility and stability of BP sheets rendering practical application of FLBP sheets possible.

Photocatalytic hydrogen evolution from water is a promising approach for renewable energy generation and storage. However, traditional photocatalysts suffer from limited hydrogen evolution rate due to the lack of active...

Despite intensive explorations, lead-free, low toxicity, efficient, and stable blue fluorescent materials are still highly desirable. Cs2NaInCl6 double perovskite (DP) is considered as a promising candidate for solid-state lighting due to its low toxicity and good stability. In this work, Mg-doped Cs2NaInCl6 DPs are prepared by a solvothermal method. The Mg2+-doped Cs2NaInCl6 DPs exhibit blue photoluminescence (PL) at about 445 nm with a full-width at half maximum of 58.0 nm, which is independent of the excitation wavelength. The large Stokes shift (129.5 nm), long PL lifetime (10.44 μs), and huge Huang–Rhys factor (40.2) suggest that the blue PL originates from self-trapped excitons. After optimizing the reaction conditions and doping concentration, a high photoluminescence quantum yield of 86.98% is obtained. Moreover, the Mg-doped Cs2NaInCl6 DPs exhibit good resistance to irradiation and moisture, which are expected to remedy the shortage of current blue emitting materials.

The room-temperature d0 ferromagnetism in black phosphorous (BP) oxide is investigated experimentally and theoretically. Electrochemical oxidation does not alter the single-crystal structure of BP and the degree of oxidation depends on the oxidation time, thereby resulting in changeable d0 ferromagnetism caused by surface P-O bonds. First-principles calculation reveals that different surface P-O bonds have different binding energies and contributions to the ferromagnetism and the bridge and dangling oxygen atoms are responsible for the observed ferromagnetism which stems from p orbital spin polarization of the oxygen and phosphorus atoms.

Multicolor fluorescence of mixed halide perovskites enormously enables their applications in photonics and optoelectronics. However, it remains an arduous task to obtain multicolor emissions from perovskites containing single halogen to avoid phase segregation. Herein, a fluorescent composite containing Eu-based metal-organic frameworks (MOFs), 0D Cs 4 PbBr 6 , and 3D CsPbBr 3 is synthesized. Under excitations at 365 nm and 254 nm, the pristine composite emits blue (B) and red (R) fluorescence, which are ascribed to radiative defects within Cs 4 PbBr 6 and 5 D 0 → 7 F J transitions of Eu 3+ , respectively. Interestingly, after light soaking in the ambient environment, the blue fluorescence gradually converts into green (G) emission due to the defect repairing and 0D-3D phase conversion. This permanent and unique photochromic effect enables anticounterfeiting and microsteganography with increased security through a micropatterning technique. Moreover, the RGB luminescence is highly stable after encapsulation by a transparent polymer layer. Thus, trichromatic light-emitting modules are fabricated by using the fluorescent composites as color-converting layers, which almost fully cover the standard color gamut. Therefore, this work innovates a strategy for construction of tunable multicolor luminescence by manipulating the radiative defects and structural dimensionality.

No abstract