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Lead halide perovskite nanocrystals are promising materials for classical and quantum light emission. To understand these outstanding properties, a thorough analysis of the band-edge exciton emission is needed which is not reachable in ensemble and room temperature studies because of broadening effects. Here, we report on a cryogenic-temperature study of the photoluminescence of single CsPbBr$_3$ NCs in the intermediate quantum confinement regime. We reveal the size-dependence of the spectral features observed: the bright-triplet exciton energy splittings, the trion and biexciton binding energies as well as the optical phonon replica spectrum. In addition, we show that bright triplet energy splittings are consistent with a pure exchange model and that the variety of polarisation properties and spectra recorded can be rationalised simply by considering the orientation of the emitting dipoles and the populations of the emitting states.

Two-dimensional (2D) van der Waals heterostructures have attracted enormous research interests due to their emergent electrical and optical properties. The comprehensive understanding and efficient control of interlayer couplings in such devices are crucial for realizing their functionalities, as well as for improving their performance. Here, we report a successful manipulation of interlayer charge transfer between 2D materials by varying different stacking layers consisting of graphene, hexagonal boron nitride, and tungsten disulfide. Under visible-light excitation, despite being separated by few-layer boron nitride, the graphene and tungsten disulfide exhibit clear modulation of their doping level, i.e., a change of the Fermi level in graphene as large as 120 meV and a net electron accumulation in WS2. By using a combination of micro-Raman and photoluminescence spectroscopy, we demonstrate that the modulation is originated from simultaneous manipulation of charge and/or energy transfer between each of the two adjacent layers. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version

van der Waals two-dimensional layered heterostructures have recently emerged as a platform, where the interlayer couplings give rise to interesting physics and multifunctionalities in optoelectronics. Such couplings can be rationally controlled by dielectric, separation, and stacking angles, which affect the overall charge or energy-transfer processes, and emergent potential landscape for twistronics. Herein, we report the efficient Förster resonance energy transfer (FRET) in WS

On the basis of the calculation of the stress field around the corrosion-damaged areas on the external part of a pipeline used for the transport of hydrocarbons, an analysis of the effect of the level of post-repair burst pressure by composite patches is proposed. This work examines some points of views on the burst pressure standards calculation on real test on pipeline with external corrosion defects. This study divided to three parts. In the first, an inspection is given for a real pipe exhibiting a surface corrosion defect. The corrosion defects were collected and divided into six important defects. The internal pressure has increased to the burst of pipeline. The second part illustrated a numerical study of the defects interaction effect on the safety of pipeline. The third part of this study is showing a finite element analysis of repaired pipe using the composite repair; we will study the effect of the composite sleeve number on the structural integrity of the pipe. The principle of failure assessment (FAD) diagram is described, and particularly, the definition of the non- dimensional applied crack tip loading $${k}_{\mathrm{r}}$$ , the non- dimensional net applied stress (or load) $${S}_{\mathrm{r}}$$ or $${L}_{\mathrm{r}}$$ is given. The interest lays in the fact that many pipes defects are scratch or gouge types. In the FAD, results demonstrated that the composite repair method does not affect the interpolation curve and, at the same time, had a slightly effect on the function point.

Optically bright lead halide perovskite nanocrystals of different morphologies ranging from nanocubes to flat nanoplatelets to elongated nanowires have been reported. The morphology of the nanocrystals is expected to affect various properties such as the band edge energy and the electron-hole exchange interaction. However, aside from nanocubes, the investigation of optical properties in the lead halide perovskite nanocrystals of different morphologies at the single emitter level has been lacking. We have performed optical spectroscopy in single CsPbBr

van der Waals two-dimensional layered heterostructures have recently emerged as a platform, where the interlayer couplings give rise to interesting physics and multifunctionalities in optoelectronics. Such couplings can be rationally controlled by dielectric, separation, and stacking angles, which affect the overall charge or energy-transfer processes, and emergent potential landscape for twistronics. Herein, we report the efficient Förster resonance energy transfer (FRET) in WS2/hBN/MoSe2 heterostructure, probed by both steady-state and time-resolved optical spectroscopy. We clarified the evolution behavior of the electron-hole pairs and free electrons from the trions, that is, ∼59.9% of the electron-hole pairs could transfer into MoSe2 by FRET channels (∼38 ps) while the free electrons accumulate at the WS2/hBN interface to photogate MoSe2. This study presents a clear picture of the FRET process in two-dimensional transition-metal dichalcogenides' heterojunctions, which establishes the scientific foundation for developing the related heterojunction optoelectronic devices. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version Q.X. gratefully acknowledges the Singapore Ministry of Education Tier3 Programme “Geometrical Quantum Materials” (MOE2018-T3-1-002), AcRF Tier2 grant (MOE2017-T2-1-040), and Tier1 grant (RG 194/17). Q.X. also acknowledges strong support from Singapore National Research Foundation Competitive Research Programme “Integrated On-chip Planar Coherent Light Sources” (NRF-CRP-21-2018-0007), and National Research Foundation-Agence Nationale de la Recherche (NRF-ANR) Grant (NRF2017-NRF-ANR005 2DCHIRAL). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant Number JPMXP0112101001, JSPS KAKENHI Grant Numbers JP20H00354 and the CREST(JPMJCR15F3), JST. Author Contributions: Q.X. supervised the research. Z. H. conceived the idea. Z.H. and X.L. prepared the heterostructures. P.H.M. and H.V.D. performed the numerical simulation. Z.H., X.L., and M.R.A. performed the micro-spectroscopy experiments. K.W. and T.T. provided the h-BN bulk crystals. Z.H., X.L., and Q.X. analyzed the data. Z.H. wrote the manuscript with input from all authors.

International audience; At cryogenic temperature and at the single emitter level, the optical properties of single-wall carbon nanotubes depart drastically from that of a one-dimensional (1D) object. In fact, the (usually unintentional) localization of excitons in local potential wells leads to nearly 0D behaviors such as photon antibunching, spectral diffusion, inhomogeneous broadening, etc. Here, we present an hyperspectral imaging of this exciton self-localization effect at the single nanotube level using a super-resolved optical microscopy approach. We report on the statistical distribution of the traps localization, depth and width. We use a quasi-resonant photoluminescence excitation approach to probe the confined quantum states. Numerical simulations of the quantum states and exciton diffusion show that the excitonic states are deeply modified by the interface disorder inducing a remarkable discretization of the excitonic absorption spectrum and a quenching of the free 1D exciton absorption.

International audience; Hydrogen plays a decisive role in many future energy systems. For this reason, much research has been performed to see the effect of hydrogen on network canalizations. This paper studied the possibility of hydrogen transportation using the natural gas pipeline. In this paper, the effect of hydrogen embrittlement (HE) on the mechanical properties of pipe steels was examined. It appeared that the yield stress and ultimate strength were few sensitive to HE. However, fracture toughness and elongation at failure exhibited a severe decrease. Failure pressure established by different codes involved a flow stress which is a combination of yield stress and flow stress. Pipe defect assessment involved fracture toughness and flow stress upon using Failure Assessment Diagram (FAD) or Crack Driving Force (CDF) methods. In this paper, the consequence of hydrogen embrittlement on the failure and critical pressures of a pipe with a semi-elliptical defect was examined. The influence of assessment method, relative defect depth and working pressure were examined through the comparison of respective safety factors.