Search

Lead‐based halide perovskite nanomaterials with excellent optical properties have aroused great attention in the fields of solar cells, light‐emitting diodes, lasing, X‐ray imaging, etc. However, the toxicity of lead prompts researchers to develop alternatives to cut down the usage of lead. Herein, all‐inorganic manganese‐based perovskite derivatives, CsMnCl3 nanocrystals (NCs), with uniform size and morphology have been synthesized successfully via a modified hot‐injection method. These NCs have a direct bandgap of 4.08 eV and a broadband emission centered at 660 nm. Through introducing modicum lead (1%) into the CsMnCl3 NCs, the photoluminescence intensity greatly improves, and the quantum yield (PLQY) increases from 0.7% to 21%. Furthermore, the CsMnCl3:1%Pb NCs feature high‐efficiency of X‐ray absorption and radioluminescence, which make these NCs promising candidates for X‐ray imaging. [ABSTRACT FROM AUTHOR]

ABX3‐type halide perovskite nanocrystals (NCs) have been a hot topic recently due to their fascinating optoelectronic properties. It has been demonstrated that A‐site ions have an impact on their photophysical and chemical properties, such as the optical band gap and chemical stability. The pursuit of halide perovskite materials with diverse A‐site species would deepen the understanding of the structure–property relationship of the perovskite family. In this work we have attempted to synthesize rubidium‐based perovskite NCs. We have discovered that the partial substitution of Rb+ by Cs+ help to stabilize the orthorhombic RbPbBr3 NCs at low temperature, which otherwise can only be obtained at high temperature. The inclusion of Cs+ into the RbPbBr3 lattice results in highly photoluminescent Rb1−xCsxPbBr3 NCs. With increasing amounts of Cs+, the band gaps of the Rb1−xCsxPbBr3 NCs decrease, leading to a redshift of the photoluminescence peak. Also, the Rb1−xCsxPbBr3 NCs (x=0.4) show good stability under ambient conditions. This work demonstrates the high structural flexibility and tunability of halide perovskite materials through an A‐site cation substitution strategy and sheds light on the optimization of perovskite materials for application in high‐performance optoelectronic devices. Adding stability: Lead halide perovskite nanocrystals (NCs) attract tremendous attention due to their extraordinary optical properties. Herein, we show that the partial substitution of Rb+ by Cs+ helps to stabilize the orthorhombic RbPbBr3 NCs at low temperature, which otherwise could only be obtained at high temperature (above 300 °C, see figure). [ABSTRACT FROM AUTHOR]

Exploring novel lanthanide-activated upconversion nanoparticles with distinctive spectral fingerprints and emission lifetimes has long been a great concern for extended optical applications. Herein, we report the study of photon upconversion emissions in Yb3+–Tb3+ and Yb3+–Eu3+ activated nanoparticles with near-infrared excitation. In these nanoparticles, a high content of Yb3+ is required for the simultaneous excitation of two Yb3+ ions, yielding a Yb3+ dimer with a higher excited energy to upconvert photons onto Tb3+ and Eu3+. The optimum doping concentration of Yb3+ ions for Yb3+–Tb3+ and Yb3+–Eu3+ pairs was determined to be 80% and 60%, respectively, which are much higher than that of Yb3+–Er3+/Tm3+ pairs. Notably, the upconversion emission lifetime of the as-prepared nanoparticles was prolonged to 2.3 ms (Tb3+) and 4.0 ms (Eu3+), respectively. Through the epitaxial growth of a Nd3+ doped shell layer, the upconversion emissions of Tb3+ and Eu3+ were intensified 25-fold. At the same time, an extra excitation band in the shorter near-infrared region from Nd3+ at 808 nm was achieved. Moreover, the emissions of Tm3+ were employed to compensate for those of Tb3+ and Eu3+ for multicolor emissions. These results highlight the upconversion emissions of Tb3+ and Eu3+ for potential multicolor imaging and multiplexed detection applications. [ABSTRACT FROM AUTHOR]

Upconversion emissions from rare-earth nanoparticles have attracted much interest as potential biolabels, for which small particle size and high emission intensity are both desired. Herein we report a facile way to achieve NaYF(4):Yb,Er@CaF(2) nanoparticles (NPs) with a small size (10-13 nm) and highly enhanced (ca. 300 times) upconversion emission compared with the pristine NPs. The CaF(2) shell protects the rare-earth ions from leaking, when the nanoparticles are exposed to buffer solution, and ensures biological safety for the potential bioprobe applications. With the upconversion emission from NaYF(4):Yb,Er@CaF(2) NPs, HeLa cells were imaged with low background interference., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)