Search

Boron nitride nanosheets (BNNSs) have garnered significant attention across diverse fields; however, accomplishing on‐demand, large‐scale, and highly efficient preparation of BNNSs remains a challenge. Here, an on‐demand preparation (OdP) method combining high‐pressure homogenization and short‐time ultrasonication is presented; it enables a highly efficient and controllable preparation of BNNSs from bulk hexagonal boron nitride (h‐BN). The homogenization pressure and number of cycles are adjusted, and the production efficiency and yield of BNNSs reach 0.95 g g−1h−1 and 82.8%, respectively, which significantly exceed those attained by using existing methods. The universality of the OdP method is demonstrated on h‐BN raw materials of various bulk sizes from various producers. Furthermore, this method allows the preparation of BNNSs having specific sizes based on the final requirements. Both simulation and experimental results indicate that large BNNSs are particularly suitable for enhancing the thermal conductivity and electrical insulation properties of dielectric polymer nanocomposites. Interestingly, the small BNNS‐filled photonic nanocomposite films fabricated via the OdP method exhibit superior daytime radiative cooling properties. Additionally, the OdP method offers the benefits of low energy consumption and reduced greenhouse gas emissions and fossil energy use. These findings underscore the unique advantages of the OdP method over other techniques for a high‐efficiency and controllable preparation of large BNNSs. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) hosts a variety of vegetation types, ranging from broadleaved and needle-leaved forests at the lower altitudes and in mesic areas to alpine grassland at the higher altitudes and in xeric areas. Accurate and detailed mapping of the vegetation distribution on the TP is essential for an improved understanding of climate change effects on terrestrial ecosystems. Yet, existing land cover datasets for the TP are either provided at a low spatial resolution or have insufficient vegetation types to characterize certain unique TP ecosystems, such as the alpine scree. Here, we produced a 10 m resolution TP land cover map with 12 vegetation classes and 3 non-vegetation classes for the year 2022 (referred to as TP_LC10-2022) by leveraging state-of-the-art remote-sensing approaches including Sentinel-1 and Sentinel-2 imagery, environmental and topographic datasets, and four machine learning models using the Google Earth Engine platform. Our TP_LC10-2022 dataset achieved an overall classification accuracy of 86.5 % with a kappa coefficient of 0.854. Upon comparing it with four existing global land cover products, TP_LC10-2022 showed significant improvements in terms of reflecting local-scale vertical variations in the southeast TP region. Moreover, we found that alpine scree, which is ignored in existing land cover datasets, occupied 13.99 % of the TP region, and shrublands, which are characterized by distinct forms (deciduous shrublands and evergreen shrublands) that are largely determined by the topography and are missed in existing land cover datasets, occupied 4.63 % of the TP region. Our dataset provides a solid foundation for further analyses which need accurate delineation of these unique vegetation types in the TP. TP_LC10-2022 and the sample dataset are freely available at 10.5281/zenodo.8214981 and 10.5281/zenodo.8227942 , respectively. Additionally, the classification map can be viewed at https://cold-classifier.users.earthengine.app/view/tplc10-2022 (last access: 6 June 2024). [ABSTRACT FROM AUTHOR]

Passive daytime radiative cooling dissipates heat from surfaces by reflecting sunlight and emitting infrared radiation to the cold outer space, featuring a zero‐energy consumption. Polymer‐dielectric radiative cooling coatings have received significant attention because of their scalable preparation, low cost, and ease of use. However, current dielectric scatterers reveal limited solar reflectance in the polymer‐dielectric coatings due to the optical crowding, which reduces cooling effect and hinders practical application. Employing a scalable emulsion templated method, reversed yolk–shell dielectric scatterers (RYSS) are developed to alleviate optical crowding effects in polymer‐dielectric coatings. This results in coatings with a solar reflectance of ≈97.4% and an infrared emittance of ≈96.9%, while achieving a substantial reduction in scatterers content. Besides, simulation results show that RYSS outperforms core–shell, hollow, and solid scatterers in enhancing solar reflectance. Using phase change materials as emulsion templates, RYSS with high heat storage effectively enhance daytime cooling and reduce nighttime over‐cooling. Moreover, cooling experiments on concentrating photovoltaics demonstrate a temperature drop of 42 °C (≈26.2 times extension of lifetime) and a notable 22% increase in open‐circuit voltage. This work suggests that RYSS presents a promising solution to overcome the challenges of radiative cooling materials and pave the way for their practical applications. [ABSTRACT FROM AUTHOR]

In this work, a paper‐based electrochemical aptamer sensor was developed for the detection of aflatoxin B1 (AFB1) using a combination of MXene–Ti3C2Tx and nucleic acid aptamers. The prepared single‐layer or few‐layer MXene suspension is suction‐filtered onto MXene paper, which is cut to prepare MXene electrodes. To accomplish AFB1 specific detection, an amino‐labeled AFB1 aptamer is mounted on the surface of the carboxy‐functionalized MXene electrode. When AFB1 is present, it particularly binds to the aptamer to form a 3D structure, reducing the efficiency of electron transmission on the sensor surface. The difference in impedance signal change at the electrode/electrolyte interface is used to quantify AFB1. The results indicated that the detection range is 0.05–100 ng/mL, the detection limit is 0.04 ng/mL, and the recovery rate of AFB1 in corn samples is 97.8%–111.52% with the optimal detection conditions. The MXene paper‐based label‐free aptasensor is versatile and can detect different targets by simply swapping out the aptamers of different targets. The sensor also has a wide range of applications in food analysis and environmental testing. Practical applications: A paper‐based electrochemical aptamer sensor was developed to detect aflatoxin B1 using a combination of MXene–Ti3C2Tx and nucleic acid aptamers.The design is based on the preparation of MXene electrodes by pumping and filtering monolayer or multilayer MXene suspensions onto MXene paper and cutting.The MXene paper‐based label‐free aptamer sensor was designed to be versatile, allowing the detection of different targets by simply replacing the aptamer with one from a different targets. [ABSTRACT FROM AUTHOR]