We report the synthesis of luminescent crystals based on hexagonal-phase NaYF4 upconversion microrods. The synthetic procedure involves an epitaxial end-on growth of upconversion nanocrystals comprising different lanthanide activators onto the NaYF4 microrods. This bottom-up method readily affords multicolor-banded crystals in gram quantity by varying the composition of the activators. Importantly, the end-on growth method using one-dimensional microrods as the template enables facile multicolor tuning in a single crystal, which is inaccessible in conventional upconversion nanoparticles. We demonstrate that these novel materials offer opportunities as optical barcodes for anticounterfeiting and multiplexed labeling applications.
The ultimate frontier in nanomaterials engineering is to realize their composition control with atomic scale precision to enable fabrication of nanoparticles with desirable size, shape and surface properties. Such control becomes even more useful when growing hybrid nanocrystals designed to integrate multiple functionalities. Here we report achieving such degree of control in a family of rare-earth-doped nanomaterials. We experimentally verify the co-existence and different roles of oleate anions (OA−) and molecules (OAH) in the crystal formation. We identify that the control over the ratio of OA− to OAH can be used to directionally inhibit, promote or etch the crystallographic facets of the nanoparticles. This control enables selective grafting of shells with complex morphologies grown over nanocrystal cores, thus allowing the fabrication of a diverse library of monodisperse sub-50 nm nanoparticles. With such programmable additive and subtractive engineering a variety of three-dimensional shapes can be implemented using a bottom–up scalable approach.
Luminescent solar concentrators (LSCs) are able to efficiently harvest solar energy through large-area photovoltaic windows, where fluorophores are delicately embedded. Among various types of fluorophores, all-inorganic perovskite nanocrystals (NCs) are emerging candidates as absorbers/emitters in LSCs due to their size/composition/dimensionality tunable optical properties and high photoluminescence quantum yield (PL QY). However, due to the large overlap between absorption and emission spectra, it is still challenging to fabricate high-efficiency LSCs. Intriguingly, zero-dimensional (0D) perovskites provide a number of features that meet the requirements for a potential LSC absorber, including i) small absorption/emission spectral overlap (Stokes shift up to 1.5 eV); ii) high PL QY (>95% for bulk crystal); iii) robust stability as a result of its large exciton binding energy; and iv) ease of synthesis. In this work, as a proof-of-concept experiment, Cs 4 PbBr 6 perovskite NCs are used to fabricate semi-transparent large-area LSCs. Cs 4 PbBr 6 perovskite film exhibits green emission with a high PL QY of ≈58% and a small absorption/emission spectral overlap. The optimized LSCs exhibit an external optical efficiency of as high as 2.4% and a power conversion efficiency of 1.8% (100 cm 2 ). These results indicate that 0D perovskite NCs are excellent candidates for high-efficiency LSCs compared to 3D perovskite NCs.
Probing the nature of nanocrystalline materials such as the surface state, crystal structure, morphology, composition, optical and magnetic characteristics is a crucial step in understanding their chemical and physical performance and in exploring their potential applications. Upconversion nanocrystals have recently attracted remarkable interest due to their unique nonlinear optical properties capable of converting incident near-infrared photons to visible and even ultraviolet emissions. These optical nanomaterials also hold great promise for a broad range of applications spanning from biolabeling to optoelectronic devices. In this review, we overview the instrumentation techniques commonly utilized for the characterization of upconversion nanocrystals. A considerable emphasis is placed on the analytical tools for probing the optical properties of the luminescent nanocrystals. The advantages and limitations of each analytical technique are compared in an effort to provide a general guideline, allowing optimal conditions to be employed for the characterization of such nanocrystals. Parallel efforts are devoted to new strategies that utilize a combination of advanced emerging tools to characterize such nanosized phosphors.
The architectural design and fabrication of low-cost and reliable organic X-ray imaging scintillators with high light yield, ultralow detection limits, and excellent imaging resolution is becoming one of the most attractive research directions for chemists, materials scientists, physicists, and engineers due to the devices' promising scientific and applied technological implications. However, the optimal balance between the X-ray absorption capability, exciton utilization efficiency, and photoluminescence quantum yield (PLQY) of organic scintillation materials is extremely difficult to achieve because of several competitive nonradiative processes, including intersystem crossing and internal conversion. Here, we introduced heavy atoms (Cl, Br, I) into thermally activated delayed fluorescence (TADF) chromophores to significantly increase their X-ray absorption cross-section while maintaining their unique TADF properties and high PLQY. Most importantly, the X-ray imaging screens fabricated using TADF-Br chromophores exhibited a relative light yield of approximately 20,000 photons/MeV, which is comparable with some inorganic scintillators. In addition, the detection limit of 64.5 nGy s -1 is several times lower than the standard dosage for X-ray diagnostics, demonstrating its high potential in medical radiography. Moreover, a high X-ray imaging resolution of 18.3 line pairs (lp) mm -1 was successfully achieved, exceeding the resolution of all the reported organic scintillators and most conventional inorganic scintillators. This study could help revive research on organic X-ray imaging scintillators and pave the way toward exciting applications for radiology and security screening.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.