InCl3 -Assisted Surface Defects Restoring to Enhance Lead-Free Cs2 ZrCl6 Nanocrystals for X-Ray Imaging and Blue LED Applications.

As one type of recent emerging lead-free perovskites, Cs2 ZrCl6 nanocrystals are widely concerned, benefiting from the eminent designability, high X-ray cutoff efficiency, and favorable stability. Improving the luminescence performance of Cs2 ZrCl6 nanocrystals has great importance to cater for practical applications. In view of the surface defects frequently formed by the liquid phase method, the particle morphology and surface quality of this material are expected to be regulated if certain intervention is made in the synthesis process. In the work, differing from normal cell lattice modulation based on the ion doping, the grain size and surface morphology of Cs2 ZrCl6 nanocrystals are optimized via adding a certain amount of InCl3 to the synthetic solution. The surface defects are restored to inhibit the defect-induced non-radiative transition, resulting in the improvement of the luminescence properties. Moreover, a flexible Cs2 ZrCl6 @polydimethylsiloxane film with excellent heat, water, and bending resistance and a light-emitting diode (LED) device are fabricated, exhibiting excellent application potential for X-ray imaging and blue LED.

Direct synthesis of CsPbX3 perovskite nanocrystal assemblies.

Inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) possess many advantageous optoelectronic properties, making them an attractive candidate for light emitting diodes, lasers, or photodetector applications. Such perovskite NCs can form extended assemblies that further modify their bandgap and emission wavelength. In this article, a facile direct synthesis of CsPbX3 NC assemblies that are 1 µm in size and are composed of 10 nm-sized NC building blocks is reported. The direct synthesis of these assemblies with a conventional hot-injection method of the NCs is achieved through the judicious selection of the solvent, ligands, and reaction stoichiometry. Only under selective reaction conditions where the surface ligand environment is tuned to enhance the hydrophobic interactions between ligand chains of neighbouring NCs is self-assembly achieved. These assemblies possess narrow and red-shifted photoluminescence compared to their isolated NC counterparts, which further expands the colour gamut that can be rendered from inorganic perovskites. This is demonstrated through simple down-converting light emitters.

Density-discriminating chromatic x-ray imaging based on metal halide nanocrystal scintillators.

X-ray imaging based on a single gray level shows visual blind parts and affects accurate judgment in some situations. Color-cognized x-ray imaging will boost the recognition capability, which has not yet been reported. Here, we propose a quartz-assisted chromatic x-ray imaging model based on metal halide nanocrystal (NC) stacked scintillators. Mutually inactive (BA)2PbBr4:Mn and Cs3Cu2I5:Tl enable x-ray energy- or density-dependent radioluminescence (RL) color variation. The upper scintillator light yield and the bottom scintillator transmittance are enhanced by elaborate in situ passivation of phenethylamine bromide and NC orientation regulation, respectively. Imaging targets with different densities are distinguished on RL spectra, and the color coordinates shift linearly on CIE 1931. An algorithm balances the image details of different gray areas and enhances the visual perception by color filling. This work provides color recognition between objects with different densities and takes a step toward chromatic x-ray imaging applied to practical scenarios.

A Versatile PDA(DOX) Nanoplatform for Chemo-Photothermal Synergistic Therapy against Breast Cancer and Attenuated Doxorubicin-Induced Cardiotoxicity.

Photothermal therapy (PTT) is a highly clinical application promising cancer treatment strategy with safe, convenient surgical procedures and excellent therapeutic efficacy on superficial tumors. However, a single PTT is difficult to eliminate tumor cells completely, and tumor recurrence and metastasis are prone to occur in the later stage. Chemo-photothermal synergistic therapy can conquer the shortcomings by further killing residual tumor cells after PTT through systemic chemotherapy. Nevertheless, chemotherapy drugs' extreme toxicity is also a problematic issue to be solved, such as anthracycline-induced cardiotoxicity. Herein, we selected polydopamine nanoparticles (PDA) as the carrier of the chemotherapeutic drug doxorubicin (DOX) to construct a versatile PDA(DOX) nanoplatform for chemo-photothermal synergistic therapy against breast cancer and simultaneously attenuated DOX-induced cardiotoxicity (DIC). The excellent photothermal properties of PDA were used to achieve the thermal ablation of tumors. DOX carried out chemotherapy to kill residual and occult distant tumors. Furthermore, the PDA(DOX) nanoparticles significantly alleviate DIC, which benefits from PDA's excellent antioxidant enzyme activity. The experimental data of the chemotherapy groups showed that the results of the PDA(DOX) group were much better than the DOX group. This study not only effectively inhibits cancer but tactfully attenuates DIC, bringing a new perspective into synergistic therapy against breast cancer.

Facile purification of CsPbX3 (X = Cl-, Br-, I-) perovskite nanocrystals.

CsPbI3 perovskite nanocrystals are a promising optoelectronic material when stabilized in their cubic phase. While ongoing efforts have addressed this structural challenge through a variety of meta-stabilization approaches, the postsynthesis purification of these nanocrystal dispersions has remained a challenge. In this article, we undertake a detailed investigation into the chemical, optical, and structural changes that arise during purification of CsPbI3 nanocrystals. It is found that nanocrystal degradation can only be avoided through the judicious control of additives within each purification cycle. Under optimized additive-to-nanocrystal ratios, multiple purification cycles can be readily achieved, while retaining the quality and phase stability of the CsPbI3. This facile purification protocol ensures the preparation of high purity and high quality CsPbI3 nanocrystal inks that are suitable for better characterization or integration in optoelectronic devices. The approach has been generalized for CsPbX3 (X = Cl-, Br-, and I-).

Synthetic Evolution of Colloidal Metal Halide Perovskite Nanocrystals.

Metal halide perovskite semiconductor nanocrystals have emerged as a lucrative class of materials for many optoelectronic applications. By leveraging the synthetic toolboxes developed from decades of research into more traditional semiconductor nanocrystals, remarkable progress has been made across these materials in terms of their structural, compositional, and optoelectronic control. Here, we review this progress in terms of their underlying formation stages, synthetic approaches, and postsynthetic treatment steps. This assessment highlights the rapidly maturing nature of the perovskite nanocrystal field, particularly with regard to their lead-based derivatives. It further demonstrates that significant challenges remain around precisely controlling their nucleation and growth processes. In going forward, a deeper understanding of the role of precursors and ligands will significantly bolster the versatility in the size, shape, composition, and functional properties of these exciting materials.

Flexible, Printable Soft-X-Ray Detectors Based on All-Inorganic Perovskite Quantum Dots.

Metal halide perovskites represent a family of the most promising materials for fascinating photovoltaic and photodetector applications due to their unique optoelectronic properties and much needed simple and low-cost fabrication process. The high atomic number (Z) of their constituents and significantly higher carrier mobility also make perovskite semiconductors suitable for the detection of ionizing radiation. By taking advantage of that, the direct detection of soft-X-ray-induced photocurrent is demonstrated in both rigid and flexible detectors based on all-inorganic halide perovskite quantum dots (QDs) synthesized via a solution process. Utilizing a synchrotron soft-X-ray beamline, high sensitivities of up to 1450 µC Gyair -1 cm-2 are achieved under an X-ray dose rate of 0.0172 mGyair s-1 with only 0.1 V bias voltage, which is about 70-fold more sensitive than conventional α-Se devices. Furthermore, the perovskite film is printed homogeneously on various substrates by the inexpensive inkjet printing method to demonstrate large-scale fabrication of arrays of multichannel detectors. These results suggest that the perovskite QDs are ideal candidates for the detection of soft X-rays and for large-area flat or flexible panels with tremendous application potential in multidimensional and different architectures imaging technologies.

Flexible photodetectors based on reticulated SWNT/perovskite quantum dot heterostructures with ultrahigh durability.

Recently, single-walled carbon nanotube (SWNT) films have been regarded as a promising channel material for flexible photodetectors due to their high intrinsic carrier mobility, conductivity, and mechanical flexibility. However, the application of SWNTs in photonic devices is limited due to their weak light absorption and the absence of a gain mechanism. Here, we demonstrate a high-performance flexible photodetector that consists of a reticulated SWNT film covered with a thin film of CsPbI3 perovskite colloidal quantum dots. The unique hierarchical reticulated structure of the SWNTs provides such films with extremely high tensile strength and great extensibility, which can ensure the appropriate toughness for achieving flexible photodetectors. Meanwhile, the perovskite quantum dots enhance light absorption, thereby sensitizing the creation of free electrical carriers within the SWNTs. This hybrid photodetector exhibits an extended photonic response and gain compared with the original pure SWNT devices. In addition, the device exhibits good robustness against repetitive bending and stretching, suggesting its applicability as a large-area wearable flexible photodetector.

Stabilizing the cubic perovskite phase of CsPbI3 nanocrystals by using an alkyl phosphinic acid.

CsPbI3 nanocrystals suffer from a facile cubic perovskite to orthorhombic phase transformation, which deteriorates their appealing optoelectronic properties. Here, we report a new colloidal synthesis that replaces the conventionally used oleic acid with an alkyl phosphinic acid to grow high-quality, phase-stable cubic perovskite CsPbI3 nanocrystals.