Cesium lead halide perovskite nanocrystals for ultraviolet and blue light blocking

Colorimetric Sensing of the Peroxide Number of Milk Powder Using CsPbBr3 Perovskite Nanocrystals

In this study, a wavelength-shift-based colorimetric sensing approach for the peroxide number of milk powder using CsPbBr₃ perovskite nanocrystals (CsPbBr₃ NCs) has been developed. Through the fat extraction, REDOX reactions and halogen exchange, as well as the optimized experimental conditions, a colorimetric sensing method was established to determine the peroxide number of milk powder samples. The integrated process of milk powder fat extraction and the REDOX process greatly shortened the determination time. This colorimetric method has a good linear correlation in the range of the peroxide number from 0.02 to 1.96 mmol/kg, and the detection limit was found to be 3 μmol/kg. This study further deepens the application prospect of wavelength-shift-based colorimetric sensing using CsPbBr₃ NCs.

Defect Regulation of Terbium-Doped Y2Zr2O7 Transparent Ceramic for Wide-Range Multimode Tunable Light-Shielding Windows

In the most promising new window materials, the light-blocking property of the state-of-the-art transparent polycrystalline ceramics is still located in the UV range, which undoubtedly limits their applications. Herein, a transparent Y₂Zr₂O₇:Tb (YZO:Tb) ceramic for light-shielding windows was prepared by a solid-state reaction and vacuum sintering method. Two simple and efficient routes, with doping concentrations varying and air-annealing temperatures regulating, were developed for the first time to control the content of defect clusters [Tb_Y⁴⁺-O^2--Tb_Y⁴⁺] and [Tb_Y⁴⁺-e^•], enabling the optical cutoff waveband of these ceramics spanning from UV and BV to green light. These defect clusters generated from an air-annealing process were proposed for the relevant reaction mechanisms concerning light erasure behavior. The controllably tailoring of optical cutoff wavelength from Tb single-doped YZO ceramics, adjusted by defect clusters, may open a novel door to develop lanthanide-doped transparent ceramics for wide-range tunable light-shielding windows.

Recent Advances in Colloidal Quantum Dots or Perovskite Quantum Dots as a Luminescent Downshifting Layer Embedded on Solar Cells

The solar cell has a poor spectral response in the UV region, which affects its power conversion efficiency (PCE). The utilization of a luminescent downshifting (LDS) layer has been suggested to improve the spectral response of the photovoltaics in the short wavelength region through photoluminescence (PL) conversion and antireflection effects, which then enhance the PCE of the solar cell. Recently, colloidal quantum dots (CQDs) or perovskite quantum dots (PQDs) have been gaining prime importance as an LDS material due to their eminent optical characteristics, such as their wide absorption band, adjustable visible emission, short PL lifetime, and near-unity quantum yields. However, the instability of QDs that occurs under certain air, heat, and moisture conditions limits its commercialization. Thus, in this review, we will focus on the physical and optical characteristics of QDs. Further, we will discuss different synthesis approaches and the stability issues of QDs. Different approaches to improve the stability of QDs will be discussed in detail alongside the recent breakthroughs in QD-based solar cells for various applications and their current challenges. We expect that this review will provide an effective gateway for researchers to fabricate LDS-layer-based solar cells.

Effect of Relative Humidity on the Thickness of Assembled Silica Colloidal Crystal Films

In order for the colloidal crystal films to be better applied, the influence of relative humidity on the preparation of silica colloidal crystal (SCC) films was systematically studied to solve the problem of different thicknesses of SCC films prepared by different batches under the conditions with the same temperature, concentration of suspension and diameter of the particles. SCC films with 190 nm particles were prepared by static vertical deposition method under different humidity regulated by saturated salt solutions, and the thickness of the films was obtained by an interferometric method. The results showed that the increase in humidity would reduce the thickness of the prepared films, which was believed to be caused by the decrease in evaporation rate after the wetting film absorbs water vapor. A new formula for calculating film thickness was proposed and verified from a series of experiments. With the control of humidity, high-quality SCC films with controlled thickness can be repeatedly prepared.

Colorimetric sensing of chloride in sweat based on fluorescence wavelength shift via halide exchange of CsPbBr3 perovskite nanocrystals

Considering the high importance of the rapid detection of chloride ion (Cl^-) in sweat for the diagnosis of fibrotic cysts, we have investigated the heterogeneous halide exchange between CsPbBr₃ perovskite nanocrystals (PNCs) in n-hexane and Cl^- in aqueous solution. The results show that CsPbBr₃ PNCs could achieve fast halide exchange with Cl^- in the aqueous phase under magnetic stirring at pH = 1, accompanied by a significant wavelength blue shift and vivid fluorescence color changes from green to blue. Therefore, a fluorescence wavelength shift-based colorimetric sensing of Cl^- based on the halide exchange of CsPbBr₃ PNCs has been developed to realize the rapid detection of Cl^- in sweat. Compared with the conventional fluorescence intensity-based method, this method is of high convenience since the whole procedure could be achieved within 5 min without any sample pretreatment (even no dilution), demonstrating promising application prospects. Graphical Abstract Fluorescence wavelength-shift based colorimetric sensing of chloride in sweat via halide exchange of CsPbBr₃ perovskite nanocrystals.

Transparent Nanostructured BiVO4 Double Films with Blue Light Shielding Capabilities to Prevent Damage to ARPE-19 Cells

The hazards posed by blue light to human eyes are attracting significant attention owing to increasing exposure to electronic devices as well as artificial illumination. Therefore, in this study, nanostructured BiVO₄ (BVO) double films were developed using an economical and environmentally friendly sol-gel spin-coating method; the films exhibited excellent blue light shielding capabilities. They could block 65.25% of the blue light in the 415-455 nm wavelength range while simultaneously maintaining an average transmittance greater than 85% in the 500-800 nm wavelength range. Moreover, the damp heat test (85 °C, 85% relative humidity) showed the excellent stability of the BVO filters as their transmittances remained unchanged for 15 days. Importantly, cell experiments were performed to further confirm the protective effects of the BVO filters against the hazards posed by blue light to ARPE-19 cells (human retinal pigment epithelium cell line). Furthermore, the blue light weighted radiance L_B decreased by 34.32%, and the color rendering index showed negligible differences after applying an upscaled BVO filter to a phone screen. These cost-efficient, ecofriendly, highly reliable, and large-area nanostructured BVO films with high blue light shielding efficiency have potential applications in various areas.

Size-selected and surface-passivated CsPbBr3 perovskite nanocrystals for self-enhanced electrochemiluminescence in aqueous media

In this work, CsPbBr3 perovskite nanocrystals (NCs) synthesized via a ligand-assisted reprecipitation method (LCPB) were discovered to emit self-enhanced electrochemiluminescence (ECL) with the surface oleylamine as both a coreactant and a stabilizer. Solvent regulation and tri-n-octylphosphine post-treatment were manipulated for size-selected and surface-passivated LCPBs, which showed remarkable aqueous ECL performance with respect to efficiency and stability. Furthermore, thanks to the self-enhancement mode with a shorter charge transfer pathway and less energy loss, the ECL efficiency obtained for these as-synthesized LCPBs in aqueous solution without any additional coreactant was up to 57.08% using the Ru(bpy)32+-tripropylamine system as the standard. As a proof-of-concept, the products were successfully employed for the bioanalyses of hydrogen peroxide, ascorbic acid, and cancer cells based on inhibition, coreaction, and impedance detection principles, respectively. More importantly, the basic properties of LCPBs in aqueous media including surface chemistry, charge transfer process, and ECL mechanism were studied systematically. Such efforts are aimed at perfecting the fundamental research of all-inorganic perovskite NCs and opening an avenue for the design of highly crystalline and luminescent perovskites as advanced ECL emitters for applications in the ECL domain.

Advances in the Stability of Halide Perovskite Nanocrystals

Colloidal halide perovskite nanocrystals are promising candidates for next-generation optoelectronics because of their facile synthesis and their outstanding and size-tunable properties. However, these materials suffer from rapid degradation, similarly to their bulk perovskite counterparts. Here, we survey the most recent strategies to boost perovskite nanocrystals stability, with a special focus on the intrinsic chemical- and compositional-factors at synthetic and post-synthetic stage. Finally, we review the most promising approaches to address the environmental extrinsic stability of perovskite nanocrystals (PNCs). Our final goal is to outline the most promising research directions to enhance PNCs' lifetime, bringing them a step closer to their commercialization.