Unveiling non-radiative center control in CsPbBr_(3) nanocrystals:A comprehensive comparative analysis of hot injection and ligandassisted reprecipitation approaches

Metal-halide perovskite nanocrystals(NCs)have gained significant attention in the field of optoelectronic and photonic devices due to their promising applications.Despite their exceptional optical properties,the impact of different synthetic strategies on the fundamental nature of NCs,such as nonradiative recombination centers,remains poorly understood.In this study,we investigated the photophysical properties of CsPbBr_(3) NCs synthesized using two distinct methods,hot injection and ligand-assisted reprecipitation,at the individual particle level.We observed different blinking behaviors under specific photoexcitation power densities and proposed,through intensity-lifetime analysis and Monte-Carlo simulations,that these different synthetic strategies can fabricate NCs with similar crystal structures but distinct surface quenchers with varying energy levels,which significantly affected the photo-induced blinking-down and blinking-up behaviors in individual NCs.Our findings indicate a practical and feasible approach for controlling defect engineering in perovskite NCs,with significant implications for their use in optoelectronic and other technological applications.

Effect of aging treatment on evolution of S'phase in rapid cold punched Al−Cu−Mg alloy

High-resolution transmission electron microscopy(TEM),X-ray diffractometer(XRD),and hardness test were used to study the evolution of long plate-shaped S'phase in the spray-formed fine-grained Al−Cu−Mg alloy during aging after rapid cold punching deformation.Results show that the long plate-shaped S'phase in the extruded Al−Cu−Mg alloy undergoes evident distortion,brittle failure,separation and redissolution,during rapid cold punching deformation,leading to the transformation of long plate-shaped S'phase into short rod or even redissolution and disappearance,causing the matrix to become a supersaturated solid solution.After the aging treatment,the reprecipitation of the phases occurs,and these aging phases are mainly long plate-shaped and granular.The incompletely dissolved S'phase acts as nucleation core,promoting uphill diffusion of the surrounding solute atoms.The S'phase gradually grows with increasing the aging time.The completely dissolved S'phase forms the incoherent equilibrium phase with the matrix to reduce its free energy.After rapid cold punching,the aging response of the deformed Al−Cu−Mg alloy is accelerated,and the hardness of the alloy is substantially increased.

Polymer-Controlled Synthesis of 1-(2-Pyridylazo)-2-Naphthol Hierarchical Architectures

The self-assembly of organic 1-(2-pyridylazo)-2-naphthol (PAN) into hierarchical architectures, such as microfibers, microrods, and sheaflike structures, in solution was successfully achieved by reprecipitation method with the assistance of thermoresponsive diblock copolymer poly(N,N-dimethylacrylamide)-b-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM). It was found that the morphology modification can be readily controlled by varying the polymer concentrations. The optical absorption and fluorescence emission properties of the as-prepared PAN architectures were investigated. Time-dependent spectra of the precipitating solution for sheaflike structures formation were measured to monitor the self-assembly process of PAN molecules. The results showed that the PAN microstructures exhibited intense fluorescence emission, indicating an unusual aggregation-induced emission enhancement (AIEE) phenomenon for PAN, which have great potential for future use in optoelectronic microdevices.

Morphology Control over the Organic Nanoparticles of 1,3-Diphenyl-5-(9-anthryl)-2-pyrazoline

The organic nanoparticles of a blue-light-emitting molecule,1,3-diphenyl-5-(9-anthryl)-2-pyrazoline,were prepared by reprecipitation method using acetonitrile as the solvent for the molecular precursor. Three morphologies,spherical,doughnut-shaped and cubic,could be observed on the silicon substrate for the nanoparticles by the volume-controlled addition of acetonitrile. The evolution of particle morphology as a function of acetonitrile addition was attributed to the variation of the growth habits of the particles in the different environment. The nanoparticles exhibit the novel photoluminescence spectra as compared to those of monomer and the bulk crystals.

Effect of Particle Size and Capping on Photoluminescence Quantum Efficiency of 1,3,5-Triphenyl-2-pyrazoline Nanocrystals

Organic nanocrystals of 1,3,5-triphenyl-2-pyrazoline (TPP) with a series of sizes were synthesized by reprecipitation method. The luminescence quantum efficiency of TPP nanocrystals increases from 24.2% for the nanocrystals with an average size of 300 nm to 34.6% for those with an average size of 20 nm. Surface capping by polyvinyl pyrrolidone (PVP) will improve the quantum efficiency of TPP nanocrystals. The size-dependence and capping-induced variation of the luminescence quantum efficiency was elucidated in viewpoint of aggregation quenching and the equilibrium between the TPP monomers and the aggregates in TPP nanocrystals.

Near UV luminescent Cs_(2)NaBi_(0.75)Sb_(0.25)Cl_(6)perovskite colloidal nanocrystals with high stability

Near UV highly luminescent colloidal Cs_(2)NaBiCl_(6)nanocrystals(NCs)were synthesized by a simple low-cost ligand-assisted reprecipitation method.In our strategy,metal chloride precursors were added to the mixture of anti-solvent and ligand at room-temperature.The obtained Cs_(2)NaBiCl_(6)NCs exhibited a bright blue emission with significantly improved photoluminescence quantum yield(PLQY)of 39.05%.The optical properties and stability were greatly enhanced by doping Sb where Cs_(2)NaBi_(0.75)Sb_(0.25)Cl_(6)showed a high PLQY of 46.57%,and both the powder and the colloidal solution exhibited superior stability.