A binary ligand system composed of aliphatic carboxylic acids and primary amines of various chain lengths is commonly employed in diverse synthesis methods for CsPbBr3 nanocrystals (NCs). In this work, we have carried out a systematic study examining how the concentration of ligands (oleylamine and oleic acid) and the resulting acidity (or basicity) affects the hot-injection synthesis of CsPbBr3 NCs. We devise a general synthesis scheme for cesium lead bromide NCs which allows control over size, size distribution, shape, and phase (CsPbBr3 or Cs4PbBr6) by combining key insights on the acid–base interactions that rule this ligand system. Furthermore, our findings shed light upon the solubility of PbBr2 in this binary ligand system, and plausible mechanisms are suggested in order to understand the ligand-mediated phase control and structural stability of CsPbBr3 NCs.
We report the colloidal synthesis of strongly fluorescent CsPbBr 3 perovskite nanowires (NWs) with rectangular section and with tuneable width, from 20 nm (exhibiting no quantum confinement, hence emitting in the green) down to around 3 nm (in the strong quantumconfinement regime, emitting in the blue), by introducing in the synthesis a short acid (octanoic acid or hexanoic acid) together with alkyl amines (octylamine and oleylamine). Temperatures below 70 °C promoted the formation of monodisperse, few unit cell thick NWs that were free from byproducts. The photoluminescence quantum yield of the NW samples went from 12% for non-confined NWs emitting at 524 nm to a maximum of 77% for the 5 nm diameter NWs emitting at 497 nm, down to 30% for the thinnest NWs (diameter ~ 3nm), in the latter sample most likely due to aggregation occurring in solution.
Current colloidal synthesis methods for CdSe nanoplatelets (NPLs) routinely yield samples that emit, in discrete steps, from 460 to 550 nm. A significant challenge lies with obtaining thicker NPLs, to further widen the emission range. This is at present typically achieved via colloidal atomic layer deposition onto CdSe cores, or by synthesizing NPL core/shell structures. Here, we demonstrate a novel reaction scheme, where we start from 4.5 monolayer (ML) NPLs and increase the thickness in a two-step reaction that switches from 2D to 3D growth. The key feature is the enhancement of the growth rate of basal facets by the addition of CdCl, resulting in a series of nearly monodisperse CdSe NPLs with thicknesses between 5.5 and 8.5 ML. Optical characterization yielded emission peaks from 554 nm up to 625 nm with a line width (fwhm) of 9-13 nm, making them one of the narrowest colloidal nanocrystal emitters currently available in this spectral range. The NPLs maintained a short emission lifetime of 5-11 ns. Finally, due to the increased red shift of the NPL band edge photoluminescence excitation spectra revealed several high-energy peaks. Calculation of the NPL band structure allowed us to identify these excited-state transitions, and spectral shifts are consistent with a significant mixing of light and split-off hole states. Clearly, chloride ions can add a new degree of freedom to the growth of 2D colloidal nanocrystals, yielding new insights into both the NPL synthesis as well as their optoelectronic properties.
includes self-assembled fullerene crystals design from zero-to-higher dimensions, mesoporous fullerene crystals and their conversion into graphitic mesoporous carbons, high surface area nanoporous carbon material design from agro-waste for electrochemical supercapacitors and VOC adsorption. Somobrata AcharyaSomobrata Acharya received his Ph.D. degree from Jadavpur University, India. He is currently Associate Professor in the Centre for Advanced Materials (CAM), Indian Association for the Cultivation of Science (IACS), India. He is carrying out research in interdisciplinary areas probing structure-property relationship and possible applications of semiconductor nanomaterials in the areas of energy generation and consumption. His research area includes heterostructures, 2D nanostructures, superlattices, supramolecular assemblies and their suitable applications. Katsuhiko ArigaKatsuhiko Ariga received his Ph.D. degree from Tokyo Institute of Technology. He is currently the Director of Supermolecules Group and Principal Investigator of World Premier International (WPI) Research Centre for Materials Nanoarchitectonics (MANA), the National Institute for Materials Science (NIMS). His research is oriented to supramolecular chemistry, surface science, and functional nanomaterials (Langmuir-Blodgett film, layer-by-layer assembly, self-organized materials, sensing and drug delivery, molecular recognition, mesoporous material, etc. and he is now trying to combine them into a unified field. AbstractDesigning nanoscale components and units into functional defined systems and materials has recently received attention as a nanoarchitectonics approach. In particular, exploration of nanoarchitectonics in two-dimensions (2D) has made great progress these days. Basically, 2D nanomaterials are a center of interest owing to the large surface areas suitable for a variety of surface active applications. The increasing demands for alternative energy generation have significantly promoted the rational design and fabrication of a variety of 2D nanomaterials since the discovery of graphene. In 2D nanomaterials, the charge carriers are confined along the thickness while being allowed to move along the plane. Owing to the large planar area, 2D nanomaterials are highly sensitive to external stimuli, a characteristic suitable for a variety of surface active applications including electrochemistry. Because of the unique
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