Ytterbium-Doped Cesium Lead Chloride Perovskite as an X-ray Scintillator with High Light Yield.

Ytterbium-doped cesium lead halides are quantum cutting materials with exceptionally high photoluminescence quantum yields, making them promising materials as scintillators. In this work, we report ytterbium-doped cesium lead chloride (Yb3+:CsPbCl3) with an X-ray scintillation light yield of 102,000 photons/MeV at room temperature, which is brighter than the current state-of-the-art commercial scintillators. The high light yield was achieved based on a novel method of synthesizing Yb3+:CsPbCl3 powders using water and low-temperature processing. The combination of high light yield and the simple and inexpensive manufacturing method reported in this work demonstrates the great potential of Yb3+:CsPbCl3 for scintillation applications.

Crystallization of high aspect ratio HKUST-1 thin films in nanoconfined channels for selective small molecule uptake.

We present the ability to create unique morphologies of a prototypical metal organic framework (MOF), HKUST-1, by carrying out its crystallization within a set of nano-confined fluidic channels. These channels are fabricated on cyclic olefin copolymer by the high-fidelity hot embossing imprinting method. The picoliter volume synthesis in the nanochannels is hypothesized to bias the balance between nucleation and growth rates to obtain high aspect ratio large-crystalline domains of HKUST-1, which are grown in defined morphologies due to the patterned nanochannels. Confined crystal growth is achieved in nanofluidic channels as shallow as 50 nm. HKUST-1 crystalline domains with aspect ratios greater than 2500, and lengths up to 144 µm are obtained using the nanochannels, exceeding values obtained using chemical modulation and other confinement methods. HKUST-1 crystals are characterized using optical microscopy and scanning electron microscopy with energy dispersive spectroscopy. Porosity of the MOF and selective molecular uptake is demonstrated through inclusion of anthracene and methylene blue within the HKUST-1 framework, and with exclusion of rhodamine B and riboflavin, characterized using a confocal fluorescence microscope. We attribute this selectivity to the analyte size and electrostatic characteristics. Nanoconfined crystallization of MOFs can thus yield control over crystalline morphology to create ideal MOF crystals for enabling selective molecular enrinchment and sensing.