Efficient Luminescence from CsPbBr₃ Nanoparticles Embedded in Cs₄PbBr₆

This work was financially supported by the “Advanced Research Center of Green Materials Science and Technology” from The Featured Area Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (107L9006) and the Ministry of Science and Technology in Taiwan (MOST 107-2113-M-002-008-MY3, MOST 107-2923-M-002-004-MY3, and MOST 107-3017-F-002-001), the National Centre for Research and Development Poland Grant (No. PL-TW/V/1/2018), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB20000000), the CAS/SAFEA International Partnership Program for Creative Research Teams, and the NSFC (Nos. U1805252 and 11774345). J.P.A. acknowledges financial support from EPSRC, U.K.Cs4PbBr6 is regarded as an outstanding luminescent material with good thermal stability and optical performance. However, the mechanism of green emission from Cs4PbBr6 has been controversial. Here we show that isolated CsPbBr3 nanoparticles embedded within a Cs4PbBr6 matrix give rise to a “normal” green luminescence while superfluorescence at longer wavelengths is suppressed. High-resolution transmission electron microscopy shows that the embedded CsPbBr3 nanoparticles are around 3.8 nm in diameter and are well-separated from each other, perhaps by a strain-driven mechanism. This mechanism may enable other efficient luminescent composites to be developed by embedding optically active nanoparticles epitaxially within inert host lattices.PostprintPeer reviewe

Mechanical-force-induced non-local collective ferroelastic switching in epitaxial lead-titanate thin films.

Ferroelastic switching in ferroelectric/multiferroic oxides plays a crucial role in determining their dielectric, piezoelectric, and magnetoelectric properties. In thin films of these materials, however, substrate clamping is generally thought to limit the electric-field- or mechanical-force-driven responses to the local scale. Here, we report mechanical-force-induced large-area, non-local, collective ferroelastic domain switching in PbTiO3 epitaxial thin films by tuning the misfit-strain to be near a phase boundary wherein c/a and a1/a2 nanodomains coexist. Phenomenological models suggest that the collective, c-a-c-a ferroelastic switching arises from the small potential barrier between the degenerate domain structures, and the large anisotropy of a and c domains, which collectively generates much larger response and large-area domain propagation. Large-area, non-local response under small stimuli, unlike traditional local response to external field, provides an opportunity of unique response to local stimuli, which has potential for use in high-sensitivity pressure sensors and switches

Irreproducibility in searches of scientific literature: A comparative analysis.

Repeatability is the cornerstone of science, and it is particularly important for systematic reviews. However, little is known on how researchers' choice of database, and search platform influence the repeatability of systematic reviews. Here, we aim to unveil how the computer environment and the location where the search was initiated from influence hit results.We present a comparative analysis of time-synchronized searches at different institutional locations in the world and evaluate the consistency of hits obtained within each of the search terms using different search platforms.We revealed a large variation among search platforms and showed that PubMed and Scopus returned consistent results to identical search strings from different locations. Google Scholar and Web of Science's Core Collection varied substantially both in the number of returned hits and in the list of individual articles depending on the search location and computing environment. Inconsistency in Web of Science results has most likely emerged from the different licensing packages at different institutions.To maintain scientific integrity and consistency, especially in systematic reviews, action is needed from both the scientific community and scientific search platforms to increase search consistency. Researchers are encouraged to report the search location and the databases used for systematic reviews, and database providers should make search algorithms transparent and revise access rules to titles behind paywalls. Additional options for increasing the repeatability and transparency of systematic reviews are storing both search metadata and hit results in open repositories and using Application Programming Interfaces (APIs) to retrieve standardized, machine-readable search metadata

Atomically thin van der Waals tunnel field-effect transistors and its potential for applications

Power dissipation is a crucial problem as the packing density of transistors increases in modern integrated circuits. Tunnel field-effect transistors (TFETs), which have high energy filtering provided by band-to-band tunneling (BTBT), have been proposed as an alternative electronics architecture to decrease the energy loss in bias operation and to achieve steep switching at room temperature. Very recently, the BTBT behavior has been demonstrated in van der Waals heterostructures by using unintentionally doped semiconductors. The reason of the BTBT formation is attributed to a significant band bending near the heterointerface, resulting in carrier accumulations. In this work, to investigate charge transport in type-III transistors, we adopted the same band-bending concept to fabricate van der Waals BP/MoS2 heterostructures. Through analyzing the temperature dependence of their electrical properties, we carefully ruled out the contribution of metal-semiconductor contact resistances and improved our understanding of carrier injection in 2D type-III transistors. The BP/MoS2 heterostructures showed both negative differential resistance and 1/f2 current fluctuations, strongly demonstrating the BTBT operation. Finally, we also designed a TFET based on this heterostructure with an ionic liquid gate, and this TFET demonstrated an subthreshold slope can successfully surmount the thermal limit of 60 mV/decade. This work improves our understanding of charge transport in such layered heterostructures and helps to improve the energy efficiency of next-generation nanoscale electronics

4,6-Dimethyldibenzothiophene Hydrodesulfurization on Nickel-Modified USY-Supported NiMoS Catalysts: Effects of Modification Method

The effects of the method of modifying USY zeolite with nickel on the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) have been investigated. USY zeolites were modified with a small amount of Ni by three different methods, namely, the in situ synthesis method, the ion-exchange method, and the impregnation method, and the resulting Ni-modified USY zeolites were used as supports for NiMo sulfide catalysts. We found that the Ni modification method affects the textural properties, the acidity of the Ni-modified USY zeolites, the Ni–Mo–S active-phase morphology, the dispersion of the active metals, the structure of the Ni–Mo–S active phase, the sulfidation degree of the active metals, the 4,6-DMDBT HDS reaction rate constant, the turnover frequency, and the selectivity of the 4,6-DMDBT HDS pathways. Although the impregnation modification method was found to promote the dispersion of active metals most strongly and the ion-exchange modification method was found to enhance the sulfidation degrees of both Ni and Mo the most strongly, these changes did not enhance the catalyst activity the most significantly. Rather, the best catalytic activity was observed over the NiMo/USNiY catalyst (prepared by the in situ synthesis method), which was closely related to the proportion of NiMoS structures in the Ni–Mo–S active phase. Among the three investigated modification methods, the in situ synthesis method was found to be the most suitable for the purpose of preparing highly active HDS catalysts for 4,6-DMDBT