Lead-free double perovskite nanocrystals (NCs) have emerged as a new category of materials that hold the potential for overcoming the instability and toxicity issues of lead-based counterparts. Doping chemistry represents a unique avenue toward tuning and optimizing the intrinsic optical and electronic properties of semiconductor materials. In this study, we report the first example of doping Yb 3+ ions into lead-free double perovskite Cs 2 AgBiX 6 (X = Cl − , Br − ) NCs via a hot injection method. The doping of Yb 3+ endows the double perovskite NCs with a newly emerged near-infrared emission band (sensitized from the NC hosts) in addition to their intrinsic trap-related visible photoluminescence. By controlling the Yb-doping concentration, the dual emission profiles and photon relaxation dynamics of the double perovskite NCs can be systematically tuned. Furthermore, we have successfully inserted divalent Mn 2+ ions in Cs 2 AgBiCl 6 NCs and observed emergence of dopant emission. Our work illustrates an effective and facile route toward modifying and optimizing optical properties of double perovskite Cs 2 AgBiX 6 (X = Cl − , Br − ) NCs with an indirect bandgap nature, which can broaden a range of their potential applications in optoelectronic devices.

Morphology control represents an important strategy for the development of functional nanomaterials and has yet to be achieved in the case of promising lead-free double perovskite materials so far. In this work, high-quality Cs 2 AgBiX 6 (X = Cl, Br, I) two-dimensional nanoplatelets were synthesized through a newly developed synthetic procedure. By analyzing the optical, morphological, and structural evolutions of the samples during synthesis, we elucidated that the growth mechanism of lead-free double perovskite nanoplatelets followed a lateral growth process from mono-octahedral-layer (half-unit-cell in thickness) cluster-based nanosheets to multilayer (three to four unit cells in thickness) nanoplatelets. Furthermore, we demonstrated that Cs 2 AgBiBr 6 nanoplatelets possess a better performance in photocatalytic CO 2 reduction compared with their nanocube counterpart. Our work demonstrates the first example with two-dimensional morphology of this important class of lead-free perovskite materials, shedding light on the synthetic manipulation and the application integration of such promising materials.

Freestanding nanowires have ultrahigh elastic strain limits (4 to 7%) and yield strengths, but exploiting their intrinsic mechanical properties in bulk composites has proven to be difficult. We exploited the intrinsic mechanical properties of nanowires in a phase-transforming matrix based on the concept of elastic and transformation strain matching. By engineering the microstructure and residual stress to couple the true elasticity of Nb nanowires with the pseudoelasticity of a NiTi shape-memory alloy, we developed an in situ composite that possesses a large quasi-linear elastic strain of over 6%, a low Young's modulus of ~28 gigapascals, and a high yield strength of ~1.65 gigapascals. Our elastic strain-matching approach allows the exceptional mechanical properties of nanowires to be exploited in bulk materials.

Colloidal ZnO nanoparticles (NPs) are widely used as an electron-transporting layer (ETL) in the solution-processed quantum-dot light-emitting diodes (QD-LEDs). However, the inherent drawbacks including surface defect sites and unbalanced charge injection prevent the device from realizing their further performance enhancement. In this work, a series of Mg doped ZnO (ZnO:Mg) and chloride-passivated ZnO (Cl@ZnO) NPs were synthesized by using a solution-precipitation strategy, and they exhibited tunable optical bandgaps and upward-shift of conduction-band maximum (CBM). Solution-processed QD-LEDs based on cadmium-free Cu-In-Zn-S/ZnS (CIZS/ZnS) nanocrystals (NCs) were fabricated by using ZnO:Mg and Cl@ZnO NPs as the ETLs, whose maximum peak external quantum efficiency (EQE) was nearly twice as high as that of QD-LEDs using ZnO NPs as the ETL (EQE = 1.54%). To take advantage of the benefits of ZnO:Mg and Cl@ZnO NPs, Cl@ZnO:Mg NPs were developed through the integration of Mg doping and Cl-passivation. Surprisingly, the cadmium-free QD-LEDs with the Cl@ZnO:Mg NPs as the ETL exhibited a maximum peak EQE of 3.72% and current efficiency of 11.08 cd A–1, which could be enhanced to be 4.05% and 12.17 cd A–1 by optimizing the Cl amount, respectively. The positive effects of the Mg doping and Cl-passivation on the cadmium-free QD-LEDs are primarily ascribed to the reduced electron injection barrier of ETL/the emitting layer interface and slower electron mobility, which can be verified by the ultraviolet photoelectron spectroscopy (UPS) measurements and current density–voltage characteristics of electron-only devices.

BackgroundNon-adherence to tuberculosis (TB) treatment threatens the success of treatment, increases the risk of TB spread, and leads to the development of drug resistance. The present study assessed non-adherence to anti-TB treatment among internal migrants with pulmonary TB living in Shenzhen, China, and examined risk factors for non-adherence in order to identify targets for intervention.MethodsA total of 794 internal migrants with TB treated at Bao’an Hospital for Chronic Disease Prevention and Cure, Shenzhen, were recruited. Structured questionnaires were used to collect data on these patients’ history and experiences with TB treatment. Ordinal logistic regression model were used to identify risk factors for non-adherence.ResultsThe proportion of patients who had missed one dose of medication within two weeks was 93/794 (11.71%), and those who missed at least two doses of medication within two weeks was 167/794 (21.03%), with a total of 33.74% of patients not adhering to TB treatment. Lack of knowledge about TB treatment and longer travel time to the nearest community health centers are significant predictors for non-adherence.ConclusionsThe present study shows that non-adherence is common among internal migrants with TB. Patients who lack knowledge about TB treatment or have to travel far to get treated are prone to miss one or more doses of medication. Interventions to improve health education and healthcare access are essential to reduce non-adherence to TB treatment among internal migrants.

Lead-free perovskites and their analogues have been extensively studied as a class of next-generation luminescent and optoelectronic materials. Herein, we report a new synthesis of colloidal Cs4M(II)Bi2Cl12 (M(II) = Cd,...

A series of Cu–In–Zn–S-based nanocrystals have been synthesized by using a heating-up approach and they exhibit bright luminescence with different colors.

The localized surface plasmonic resonance absorption wavelength can be tuned effectively by varying the crystal structure, morphology and surface ligands, which can be manipulated by varying the Cu : S precursor ratios and the post-treatment temperature by dodecanethiol.