Interfacial Synthesis of Highly Stable CsPbX₃/Oxide Janus Nanoparticles

The poor stability of CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) has severely impeded their practical applications. Although there are some successful examples on encapsulating multiple CsPbX₃ NCs into an oxide or polymer matrix, it has remained a serious challenge for the surface modification/encapsulation using oxides or polymers at a single particle level. In this work, monodisperse CsPbX₃/SiO₂ and CsPbBr₃/Ta₂O₅ Janus nanoparticles were successfully prepared by combining a water-triggered transformation process and a sol–gel method. The CsPbBr₃/SiO₂ NCs exhibited a photoluminescence quantum yield of 80% and a lifetime of 19.8 ns. The product showed dramatically improved stability against destruction by air, water, and light irradiation. Upon continuous irradiation by intense UV light for 10 h, a film of the CsPbBr₃/SiO₂ Janus NCs showed only a slight drop (2%) in the PL intensity, while a control sample of unmodified CsPbBr₃ NCs displayed a 35% drop. We further highlighted the advantageous features of the CsPbBr₃/SiO₂ NCs in practical applications by using them as the green light source for the fabrication of a prototype white light emitting diode, and demonstrated a wide color gamut covering up to 138% of the National Television System Committee standard. This work not only provides a novel approach for the surface modification of individual CsPbX₃ NCs but also helps to address the challenging stability issue; therefore, it has an important implication toward their practical applications

Improving the Stability and Size Tunability of Cesium Lead Halide Perovskite Nanocrystals Using Trioctylphosphine Oxide as the Capping Ligand

Recently, all-inorganic cesium lead halide (CsPbX₃, X = Cl, Br, and I) nanocrystals (NCs) have drawn wide attention because of their excellent optoelectronic properties and potential applications. However, one of the most significant challenges of such NCs is their low stability against protonic solvents. In this work, we demonstrate that by incorporating a highly branched capping ligand, trioctylphosphine oxide (TOPO), into the traditional oleic acid/oleylamine system, monodisperse CsPbX₃ NCs with excellent optoelectronic properties can be achieved at elevated temperatures (up to 260 °C). The size of such NCs can be varied in a relatively wide range. The capping of TOPO on NCs has been verified through Fourier transform infrared spectroscopy measurement. More importantly, the presence of TOPO can dramatically improve the stability of CsPbX₃ NCs against ethanol treatment. After ethanol treatment for 100 min, the emission intensity of the TOPO-capped sample dropped only 5%, whereas that of non-TOPO-capped NCs dropped up to 86%. This work may shed some light on the preparation and application of CsPbX₃ NCs with higher stability

From Nonluminescent Cs₄PbX₆ (X = Cl, Br, I) Nanocrystals to Highly Luminescent CsPbX₃ Nanocrystals: Water-Triggered Transformation through a CsX-Stripping Mechanism

We report a novel CsX-stripping mechanism that enables the efficient chemical transformation of nonluminescent Cs₄PbX₆ (X = Cl, Br, I) nanocrystals (NCs) to highly luminescent CsPbX₃ NCs. During the transformation, Cs₄PbX₆ NCs dispersed in a nonpolar solvent are converted into CsPbX₃ NCs by stripping CsX through an interfacial reaction with water in a different phase. This process takes advantage of the high solubility of CsX in water as well as the ionic nature and high ion diffusion property of Cs₄PbX₆ NCs, and produces monodisperse and air-stable CsPbX₃ NCs with controllable halide composition, tunable emission wavelength covering the full visible range, narrow emission width, and high photoluminescent quantum yield (up to 75%). An additional advantage is that this is a clean synthesis as Cs₄PbX₆ NCs are converted into CsPbX₃ NCs in the nonpolar phase while the byproduct of CsX is formed in water that could be easily separated from the organic phase. The as-prepared CsPbX₃ NCs show enhanced stability against moisture because of the passivated surface. Our finding not only provides a new pathway for the preparation of highly luminescent CsPbX₃ NCs but also adds insights into the chemical transformation behavior and stabilization mechanism of these emerging perovskite nanocrystals

The Role of Bismuth in Suppressing the CO Poisoning in Alkaline Methanol Electrooxidation: Switching the Reaction from the CO to Formate Pathway

While tuning the electronic structure of Pt can thermodynamically alleviate CO poisoning in direct methanol fuel cells, the impact of interactions between intermediates on the reaction pathway is seldom studied. Herein, we contrive a PtBi model catalyst and realize a complete inhibition of the CO pathway and concurrent enhancement of the formate pathway in the alkaline methanol electrooxidation. The key role of Bi is enriching OH adsorbates (OHad) on the catalyst surface. The competitive adsorption of CO adsorbates (COad) and OHad at Pt sites, complementing the thermodynamic contribution from alloying Bi with Pt, switches the intermediate from COad to formate that circumvents CO poisoning. Hence, 8% Bi brings an approximately 6-fold increase in activity compared to pure Pt nanoparticles. This notion can be generalized to modify commercially available Pt/C catalysts by a microwave-assisted method, offering opportunities for the design and practical production of CO-tolerance electrocatalysts in an industrial setting