Perovskite nanocrystals (NCs) have become leading candidates for solution-processed optoelectronics applications. While substantial work has been published on 3-D perovskite phases, the NC form of the zero-dimensional (0-D) phase of this promising class of materials remains elusive. Here we report the synthesis of a new class of colloidal semiconductor NCs based on CsPbBr, the 0-D perovskite, enabled through the design of a novel low-temperature reverse microemulsion method with 85% reaction yield. These 0-D perovskite NCs exhibit high photoluminescence quantum yield (PLQY) in the colloidal form (PLQY: 65%), and, more importantly, in the form of thin film (PLQY: 54%). Notably, the latter is among the highest values reported so far for perovskite NCs in the solid form. Our work brings the 0-D phase of perovskite into the realm of colloidal NCs with appealingly high PLQY in the film form, which paves the way for their practical application in real devices.
Zero-dimensional perovskite-related structures (0D-PRS) are a new frontier of perovskite-based materials. 0D-PRS, commonly synthesized in powder form, manifest distinctive optical properties such as strong photoluminescence (PL), narrow emission linewidth, and high exciton binding energy. These properties make 0D-PRS compelling for several types of optoelectronic applications, including phosphor screens and electroluminescent devices. However, it would not be possible to rationally design the chemistry and structure of these materials, without revealing the origins of their optical behaviour, which is contradictory to the well-studied APbX3 perovskites. In this work, we synthesize single crystals of Cs4PbBr6 0D-PRS, and investigated the origins of their unique optical and electronic properties. The crystals exhibit a PL quantum yield higher than 40%, the highest reported for perovskite-based single crystals. Time-resolved and temperature dependent PL studies, supported by DFT calculations, and structural analysis, elucidate an emissive behaviour reminiscent of a quantum confined structure rather than a typical bulk perovskite material.
We present a novel approach to produce gold nanoclusters (Au NCs) in the pores of mesoporous silica nanoparticles (MSNs) by sequential and controlled addition of metal ions and reducing agents.
Tin(II) ketoacidoximates of the type [HON=CRCOO]2Sn (R = Me 1, CH2Ph 2) and (MeON=CMeCOO)3Sn](-) NH4(+)·2H2O 3 were synthesized by reacting pyruvate- and hydroxyl- or methoxylamine RONH2 (R = H, Me) with tin(II) chloride dihydrate SnCl2·2H2O. The single crystal X-ray structure reveals that the geometry at the Sn atom is trigonal bipyramidal in 1, 2 and trigonal pyramidal in 3. Inter- or intramolecular hydrogen bonding is observed in 1-3. Thermogravimetric (TG) analysis shows that the decomposition of 1-3 to SnO occurs at ca. 160 °C. The evolved gas analysis during TG indicates complete loss of the oximato ligand in one step for 1 whereas a small organic residue is additionally removed at temperatures >400 °C for 2. Above 140 °C, [HON=C(Me)COO]2Sn (1) decomposes in air to spherical SnO particles of size 10-500 nm. Spin coating of 1 on Si or a glass substrate followed by heating at 200 °C results in a uniform film of SnO. The band gap of the produced SnO film and nanomaterial was determined by diffuse reflectance spectroscopy to be in the range of 3.0-3.3 eV. X-ray photoelectron spectroscopy indicates surface oxidation of the SnO film to SnO2 in ambient atmosphere.
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