Local surface warming assessment in response to vegetation shifts over arid lands of Central Asia (2001-2020).

The Northern Eurasia Earth Science Partnership Initiative (NEESPI) was established to address the large-scale environmental change across this region. Regardless of the increasingly insightful literature addressing vegetation change across Central Asia, the biogeophysical warming effects of vegetation shifts still need to be clarified. To contribute, the utility of robust satellite observation is explored to evaluate the surface warming effects of vegetation shifts across Central Asia, which is among NEEPSI's hotspots. We estimated an average increase of +1.9 °C in daytime local surface temperature and + 1.5 °C in the nighttime due to vegetation shift (2001-2020). Meanwhile, the mean local latent heat increased by 4.65Wm-2, following the mild reduction of emitted longwave radiation (-0.8Wm-2). We found that vegetation shifts led to local surface warming with a bright surface, noting that the average air surface temperature was revealed to have increased significantly (2001-2020). This signal was driven mainly by agricultural expansion in western Kazakhstan stretching to Tajikistan and Xinjiang, then deforestation confined in Tajikistan, southeast Kazakhstan, and the northwestern edge of Xinjiang, and finally, grassland encroachment occurred massively in the west to central Kazakhstan. These findings address the latest information on Central Asia's vegetation shifts that may be substantial in landscape change mitigation plans.

Nonlinear optical response and ultrafast all-optical modulation of Nb4C3.

MXenes exhibit a variety of unique electronic, optical, chemical, and mechanical properties. In this work, the nonlinear optical (NLO) properties of Nb4C3Tx are systematically investigated. The Nb4C3Tx nanosheets exhibit saturable absorption (SA) response from visible region to near-infrared region and better saturability under 6 ns pulse excitation than that under 380 fs excitation. The ultrafast carrier dynamics show a relaxation time of ∼6 ps, which suggests a high optical modulation speed of ∼160 GHz. Consequently, an all-optical modulator is demonstrated by transferring the Nb4C3Tx nanosheets to the microfiber. The signal light can be modulated well by pump pulses with a modulation rate of 5 MHz and an energy consumption of 12.564 nJ. Our study indicates that Nb4C3Tx is a potential material for nonlinear devices.

The effects of landscape change on habitat quality in arid desert areas based on future scenarios: Tarim River Basin as a case study.

Human activities have caused spatiotemporal patterns of land use and land cover (LULC) change. The LULC change has directly affected habitat quality (HQ) and ecosystem functions. Assessing, simulating, and predicting spatiotemporal changes and future trends under different scenarios of LULC-influenced HQ is beneficial to land use planners and decision-makers, helping them to formulate plans in a sustainable and responsible way. This study assesses and simulates the HQ of the Tarim River Basin (TRB) using the future land use simulation model (FLUS), the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, and partial least squares regression (PLSR). Since 2000, the TRB has experienced a declining trend in HQ from 0.449 to 0.444, especially in the lower elevations (740-2000m) and on sloped land (<10°). The decline will continue unless effective and sustainable plans are implemented to halt it. Agricultural and settlement areas have a lower HQ and a higher degree of habitat degradation than native habitats. This shows that the expansion of oasis agriculture (with an annual growth rate of 372.17 km2) and settlements (with an annual growth rate of 23.50 km2) has caused a decline in native habitat and subsequent habitat fragmentation. In other words, changes in LULC have caused a decline in the HQ. Moreover, there is a significant negative correlation between HQ and urbanization rate (p<0.01), and the PLSR also indicate that number of patches (NP), area-weighted mean fractal dimension index (FRAC_AM), percentage of landscape (PLAND), and largest patch index (LPI) were also important contributors to worsening the HQ. Therefore, the TRB urgently needs appropriate strategies to preserve its natural habitats into the future, based on the ecological priority scenario (EPS) and harmonious development scenario (HDS), which can help to maintain a high-quality habitat.

Unveiling Charge Carrier Recombination, Extraction, and Hot-Carrier Dynamics in Indium Incorporated Highly Efficient and Stable Perovskite Solar Cells.

Perovskite solar cells (PSCs) have been propelled into the limelight over the past decade due to the rapid-growing power conversion efficiency (PCE). However, the internal defects and the interfacial energy level mismatch are detrimental to the device performance and stability. In this study, it is demonstrated that a small amount of indium (In3+ ) ions in mixed cation and halide perovskites can effectively passivate the defects, improve the energy-level alignment, and reduce the exciton binding energy. Additionally, it is confirmed that In3+ ions can significantly elevate the initial carrier temperature, slow down the hot-carrier cooling rate, and reduce the heat loss before carrier extraction. The device with 1.5% of incorporated In3+ achieves a PCE of 22.4% with a negligible hysteresis, which is significantly higher than that of undoped PSCs (20.3%). In addition, the unencapsulated PSCs achieve long-term stability, which retain 85% of the original PCE after 3,000 h of aging in dry air. The obtained results demonstrate and promote the development of practical, highly efficient, and stable hot-carrier-enhanced PSCs.

Regulation of the luminescence mechanism of two-dimensional tin halide perovskites.

Two-dimensional (2D) Sn-based perovskites are a kind of non-toxic environment-friendly luminescent material. However, the research on the luminescence mechanism of this type of perovskite is still very controversial, which greatly limits the further improvement and application of the luminescence performance. At present, the focus of controversy is defects and phonon scattering rates. In this work, we combine the organic cation control engineering with temperature-dependent transient absorption spectroscopy to systematically study the interband exciton relaxation pathways in layered A2SnI4 (A = PEA+, BA+, HA+, and OA+) structures. It is revealed that exciton-phonon scattering and exciton-defect scattering have different effects on exciton relaxation. Our study further confirms that the deformation potential scattering by charged defects, not by the non-polar optical phonons, dominates the excitons interband relaxation, which is largely different from the Pb-based perovskites. These results enhance the understanding of the origin of the non-radiative pathway in Sn-based perovskite materials.

Electrochemical synthesis of annealing-free and highly stable black-phase CsPbI3 perovskite.

All-inorganic CsPbI3 halide perovskite has become a hot research topic for applications in next-generation optoelectronic devices. However, the main limitations are the high-temperature synthesis and poor phase stability. In this study, we demonstrate a unique solution-phase strategy for the low-temperature preparation of black-phase CsPbI3 by in situ electrochemistry. By controllable adjustment of the electrochemical growth process, annealing-free black-phase CsPbI3 can be synthesized. The black-phase CsPbI3 showed high-purity red photoluminescence at approximately 690 nm with ultra-high environmental stability for up to 11 days at a high relative humidity of 70%. The underlying mechanisms of the formation of the highly stable black-phase CsPbI3 at room temperature have been discussed in this study. The results provide a new platform for the large scale, low-temperature, and convenient synthesis of black-phase CsPbI3 perovskite.

Quantum Dot Self-Assembly Enables Low-Threshold Lasing.

Perovskite quantum dots (QDs) are of interest for solution-processed lasers; however, their short Auger lifetime has limited lasing operation principally to the femtosecond temporal regime the photoexcitation levels to achieve optical gain threshold are up to two orders of magnitude higher in the nanosecond regime than in the femtosecond. Here the authors report QD superlattices in which the gain medium facilitates excitonic delocalization to decrease Auger recombination and in which the macroscopic dimensions of the structures provide the optical feedback required for lasing. The authors develope a self-assembly strategy that relies on sodiumd-an assembly director that passivates the surface of the QDs and induces self-assembly to form ordered three-dimensional cubic structures. A density functional theory model that accounts for the attraction forces between QDs allows to explain self-assembly and superlattice formation. Compared to conventional organic-ligand-passivated QDs, sodium enables higher attractive forces, ultimately leading to the formation of micron-length scale structures and the optical faceting required for feedback. Simultaneously, the decreased inter-dot distance enabled by the new ligand enhances exciton delocalization among QDs, as demonstrated by the dynamically red-shifted photoluminescence. These structures function as the lasing cavity and the gain medium, enabling nanosecond-sustained lasing with a threshold of 25 µJ cm-2 .