Benoit Mahler

French National Centre for Scientific Research | CNRS · Institut Lumière Matière - UMR 5306 (ILM)

Upcycling of polyethersulfone (PES), a high-performance polymer based on an aromatic-rich aryl-ether-based backbone, can advantageously yield both starting Bisphenol S (BPS) comonomer and valuable OLED derivatives, providing complete atom valorization...

Liquid scintillation processes are commonly used for various applications involving radioactivity levels analysis, as well as experiments in the field of high energy physics, most commonly in the form of...

Upcycling of polyethersulfone (PES), a high-performance polymer based on an aromatic-rich aryl-ether-based backbone, can advantageously yield both starting Bisphenol S (BPS) comonomer and valuable OLED derivatives, providing complete atom valorisation strategy for PES waste. Deprotonated selected amines proved particularly efficient at depolymerizi...

We report the conformational control of 2D ultra-thin indium sulfide nanoribbons by tuning their amine ligands' alkyl chain. The initial orthorhombic InS nanoribbons bare octylamine ligands and display a highly curved geometry with a characteristic figure of eight shapes. Exchanging the native ligand by oleylamine induces their complete unfolding t...

We report the conformational control of 2D ultra-thin indium sulfide nanoribbons by tuning their amine ligands' alkyl chain. The initial orthorhombic InS nanoribbons bare octylamine ligands and display a highly curved geometry with a characteristic figure of eight shapes. Exchanging the native ligand by oleylamine induces their complete unfolding t...

The ability of thin materials to shape-shift is a common occurrence that leads to dynamic pattern formation and function in natural and man-made structures. However, harnessing this concept to rationally design inorganic structures at the nanoscale has remained far from reach due to a lack of fundamental understanding of the essential physical comp...

We have fabricated planar interdigitated photodetectors exhibiting high responsivity. These detectors are based on thin layers of methylammonium lead bromide (MAPbBr3) at 90 nm thickness. MAPbBr3 thin films were first characterized on glass (borosilicate) substrates using absorption and photoluminescence measurements showing a high absorption edge...

The ability of thin materials to shape-shift is a common occurrence that leads to dynamic pattern formation and function in natural and man-made structures. However, harnessing this concept to design inorganic structures at the nanoscale rationally has remained far from reach due to a lack of fundamental understanding of the essential physical comp...

We study the low-temperature (T = 4.7 K) emission dynamics of a thin film of methylam-monium lead bromide (MAPbBr 3), prepared via the anti-solvent method. Using intensity-dependent (over 5 decades) hyperspectral microscopy under quasi-resonant (532 nm) continuous wave excita-tion, we revealed spatial inhomogeneities in the thin film emission. This...

The difference between in-plane and out-of-plane bonding energy of transition metal dichalcogenides has provided the possibility of isolating single layers. A one step synthesis protocol to produce size-controlled single layers has always been challenging. Here we developed a new colloidal synthesis to produce monodisperse size-controlled 1T'-WS2 n...

We explore the effect of shell thickness on the time and spectral response of CdSe/CdS core–crown and CdSe/CdZnS core–shell nanoplatelets (NPLs) under X-ray and intense optical excitation. From their intensity-dependent spectral and timing response, we demonstrate that the exciton–exciton interaction in the bi-exciton (XX) changes from attractive t...

Chiral halide perovskite nanocrystals have many applications in next‐generation optoelectronic devices due to their interaction with polarized light. Through careful selection of chiral organic surface ligands, control over the circular dichroism (CD) and circularly polarized luminescence (CPL) of these materials can be achieved. However, while rec...

We report the synthesis of ultrathin indium sulfide In₂S₃ nanoribbons which display a giant aspect ratio using a simple and fast solvothermal method. They have a sub-nanometer thickness controlled at the atomic level, a width of (8.7 ± 0.1) nm and a length which can reach several micrometers. We determine the atomic compositio...

Chiral halide perovskite nanocrystals have many applications in next-generation optoelectronic devices due to their interaction with circularly polarized light. Through the careful selection of chiral organic surface ligands, control over the circular dichroism (CD) and circularly polarized luminescence (CPL) of these materials can be achieved. How...

We have synthesized CdS(1.3 nm)/CdSe(1.7 nm)/CdS(3.4 nm) spherical quantum wells (SQWs) with a diameter of 13nm and demonstrated the first photon-antibunching from their emission, labelling them as single-photon sources. Antibunching survives even at high excitation intensities, ruling-out strong emission from the bi-exciton. For the largest intens...

We report the first doping of crystalline methylammonium lead bromide perovskite (MAPbBr3) films with CdSe/CdZnS core/shell quantum dots (QDs), using a soft-chemistry approach that preserves their high quantum yield and...

Modern syntheses of colloidal nanocrystals yield extraordinarily narrow size distributions that are believed to result from a rapid "burst of nucleation" (La Mer, JACS, 1950, 72(11), 4847-4854) followed by diffusion limited growth and size distribution focusing (Reiss, J. Chem. Phys., 1951, 19, 482). Using a combination of in situ X-ray scattering,...

We report the synthesis of ultrathin indium sulfide In2S3 nanoribbons (NR) which display a giant aspect ratio using a simple and fast solvothermal method. We show that these NR have a thickness controlled at the atomic level below the nanometer, a width of 8.7 +/- 0.1 nm and a length which can reach several micrometers. We determined the atomic com...

We report the synthesis of ultrathin indium sulfide In2S3 nanoribbons (NR) which display a giant aspect ratio using a simple and fast solvothermal method. We show that these NR have a thickness controlled at the atomic level below the nanometer, a width of 8.7 +/- 0.1 nm and a length which can reach several micrometers. We determined the atomic com...

Chiral halide perovskite nanocrystals have many applications in next-generation optoelectronic devices due to their interaction with circularly polarized light. Through the careful selection of chiral organic surface ligands, control over the circular dichroism (CD) and circularly polarized luminescence (CPL) of these materials can be achieved. How...

We have synthesized CdS(1.3 nm)/CdSe(1.7 nm)/CdS(3.4 nm) spherical quantum wells with 13 nm diameter and demonstrated the first antibunching of their emission, labelling them as single-photon sources. Antibunching survives even at high excitation intensities, ruling-out bi-exciton emission. For the largest intensities, antibunching coupled to spect...

We explore the effect of the shell thickness on the time response of CdS/CdSe/CdS spherical quantum wells (SQWs) nanoscintillators under X-ray excitation. We first compare the spectral and timing properties under low and intense optical excitation, which allows us to identify the complex temporal and spectral response of the highly excited species....

We report the first doping of crystalline methylammonium lead bromide (MAPbBr$_3$) perovskite thin-films with CdSe/CdZnS core/shell quantum dots (QDs), using a soft-chemistry method that preserves their high quantum yield and other remarkable fluorescence properties. Our approach produces MAPbBr$_3$ films of 100 nm thickness doped at volume ratios...

We report the synthesis and optical characterization of fully inorganic gradient-shell CdSe/CdZnS nanocrystals (NCs) with high luminescence quantum yield (QY, 50%), which were obtained by replacing native oleic-acid (OA) ligands with halide ions (Cl-and Br-). Absorption, photoluminescence excitation (PLE) and photoluminescence (PL) spectra in solut...

Here we report the emission properties of low-dimensional perovskite materials: quantum dots and two-dimensional perovskites under high energy excitation from X-, gamma-ray, alpha particle, and thermal neutron, aimed towards fast-timed imaging and particle detection applications. 1. Introduction Scintillators are materials that down-convert high en...

We report the synthesis and optical characterization of fully inorganic gradientshell CdSe/CdZnS nanocrystals (NCs) with high luminescence quantum yield (QY, 50 percent), which were obtained by replacing native oleic-acid (OA) ligands with halide ions (Br and Cl). Absorption, photoluminescence excitation (PLE) and photoluminescence (PL) spectra in...

The influence of ligands on the low frequency vibration of cadmium selenide colloidal nanoplatelets of different thicknesses is investigated using resonant low frequency Raman scattering. The strong vibration frequency shifts induced by ligand modifications as well as sharp spectral linewidths make low frequency Raman scattering a tool of choice to...

The influence of ligands on the low frequency vibration of different thicknesses cadmium selenide colloidal nanoplatelets is investigated using resonant low frequency Raman scattering. The strong vibration frequency shifts induced by ligand modifications as well as the sharp spectral linewidths make low frequency Raman scattering a tool of choice t...

Two-dimensional (2D) hybrid lead bromide perovskites are candidates for high light yield, fast scintillators. In this paper, we discuss the effect of commensurate Lithium doping (1:1 Li:Pb precursor ratio) on the scintillation properties of two previously reported high light yield 2D-perovskite crystals, PEA2PbBr4 and BA2PbBr4. The effect of Lithiu...

Two-dimensional (2D) hybrid lead bromide perovskites are candidates for high light yield, fast scintillators. In this paper, we discuss the effect of commensurate Lithium(Li)-doping (1:1 Li:Pb precursor ratio) on the scintillation properties of two previously reported high light yield 2D-perovskite crystals, PEA2PbBr4 and BA2PbBr4. The effect of Li...

Here we report the emission properties of perovskite quantum dots and two- dimensional perovskites under high energy excitation from X-, gamma-ray, alpha particle and thermal neutron, aimed towards fast-timed imaging and particle detection applications.

Two-dimensional (2D) hybrid lead halide perovskites are potential candidates for high light yield scintillators as they have small bandgaps between 3 and 4 eV and large exciton-binding energy. Here we discuss the scintillation properties from a total of eleven organic/inorganic hybrid perovskite crystals with two already reported crystals, (PEA)2Pb...

A major challenge in the field of up-converting (UC) nanomaterials is to enhance their efficiencies. The –OH defects on the surface of the nanoparticles are thought to be the main cause of luminescence quenching, but there are no comparative studies in the literature showing the impact of anhydrous vs. hydrous synthesis on up-conversion efficiency....

- Synthesis and structural characterization of LiYF4: 20%Yb3+,0.5% Tm3+ nanocrystals - UC of the nanocrystals compared to a single crystal - Upconversion quantum yield measurements and results - lifetime in the excited state 3H4!3H6 - excitation in the excited state of 1G4!3H6 - emission of the 1D2!3H6 under di�erent excitation conditions - lifetim...

Motivated by the technologically important spectral conversion of sunlight for efficient photocatalysis, we present a detailed analysis of the multi-color excitation of LiYF4:Yb3+,Tm3+ nanocrystals leading to UV emission through upconversion. We demonstrate in particular that the combination of blue and IR light for generating upconversion UV emiss...

While 1T′ phase-pure MX2 (M = Mo, W; X = Se, Te) have recently been reported to be superconductors, Weyl semimetals, or quantum spin Hall insulators, the electronic properties of phase-pure 1T′-WS2 samples are still lacking thorough investigation. Here, we report the study of single-layer 1T′-WS2 nanosheets prepared from lithium exfoliation of WS2....

We present a novel route for the synthesis of zinc blende CdSe nanoplatelets (NPLs) that exclude the use of short-chain alkyl carboxylates. CdSe NPLs obtained without acetates are shown to be extremely asymmetric and rectangular. The effects of several experimental parameters such as the nature of cadmium carboxylates, selenium precursors, and prec...

One of the key issues in upconversion materials is the design of an appropriate complex nano-architecture in order to control energy migration. We propose here a numerical tool based on a Monte-Carlo approach capable of modeling the energy migration in particles with diameters of up to a few tens of nanometers. In order to validate the approach, th...

Resonant acoustic modes from ultrathin CdS colloidal nanoplatelets (NPLs) are probed under high pressure using low frequency Raman spectroscopy. In particular we focus on the characterization of the recently evidenced mass load effect that is responsible for a significant downshift of the NPL breathing frequency due to the inert mass of organic lig...

Resonant acoustic modes from ultrathin CdS colloidal nanoplatelets (NPLs) are probed under high pressure using low frequency Raman spectroscopy. In particular we focus on the characterization of the recently evidenced mass load effect that is responsible for a significant downshift of the NPLs breathing frequency due to the inert mass of the organi...

In this article we study the ultrafast dynamics of excitons and charge carriers photogenerated in two-dimensional in-plane heterostructures, namely, CdSe-CdTe nanoplatelets. We combine transient absorption and two-dimensional electronic spectroscopy to study charge transfer and delocalization from a few tens of femtoseconds to several nanoseconds....

The present invention relates to a population of semiconductor nanoplatelets, each member of the population comprising a nanoplatelet core including a first semiconductor material and a shell including a second semiconductor material on the surface of the nanoplatelet core, wherein the population exhibits fluorescence quantum efficiency at 100 °C o...

In this paper, we review recent progress on colloidal growth of 2D nanocrystals. We identify the four main sources of anisotropy which lead to the formation of plate- and sheet-like colloidal nanomaterials. Defect-induced anisotropy is a growth method which relies on the presence of topological defects at the nanoscale to induce 2D shapes objects....

Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to the values e...

We explore the gold functionalization of 2D CdSe nanoplatelets (NPL) as a possible way to tune their electronic and transport properties. We demonstrate that the size and location of the gold tip can be controlled using light and temperature. The Au tip-CdSe NPL hybrid present a large rise of the conductance compared to the pristine semiconductor (...

Luminescent colloidal CdSe nanoplatelets with atomically defined thicknesses have recently been developed, and their potential for various applications has been shown. To understand their special properties, experiments have until now focussed on the relatively short timescales of at most a few ns. Here, we measure the photoluminescence decay dynam...

Nanotower- and nanowall-like indium oxide structures were grown directly on fluorine-doped tin oxide (FTO)/In2O3 seeded substrates and pristine FTO substrates, respectively, by a straightforward solvothermal method. The tower-like nanostructures are proposed to form via a self-assembly process on the In2O3 seeds. The wall-like nanostructures are pr...

Nanotower- and nanowall-like indium oxide structures were grown directly on fluorine-doped tin oxide (FTO)/In2O3 seeded substrates and pristine FTO substrates, respectively, by a straightforward solvothermal method. The tower-like nanostructures are proposed to form via a self-assembly process on the In2O3 seeds. The wall-like nanostructures are pr...

Electronic coherence has attracted considerable attention for its possible role in dynamical processes in molecular systems. However, its detection is challenged by inhomogeneous line broadening and interference with vibrational coherences. In particular, reports of "persistent" coherent exciton superpositions at room temperature remain controversi...

In recent years, a lot of attention has been devoted to monolayer materials, in particular to transition metal dichalcogenides (TMDCs). While their growth on a substrate and their exfoliation are well developed, the colloidal synthesis of monolayers in solution remains challenging. This paper describes the development of synthetic protocols for pro...

We present the synthesis of a novel type of chalcogenide nanoplatelets. Starting from CdS core or CdSe/CdS core/shell nanoplatelets, we use sequential cation exchange to copper and then to either zinc or lead to obtain ZnS and PbS core or ZnSe/ZnS and PbSe/PbS core/shell structures. The procedure preserves well the 2D geometry of the nanoplatelets,...

The first functional light‐emitting diodes (LEDs) based on quasi 2D colloidal core/shell CdSe/CdZnS nanoplatelets (NPLs). The solution‐processed hybrid devices are optimized with respect to their electroluminescent characteristics, first, by improving charge injection through exchanging the as‐synthesized NPL long‐chain ligands to shorter ones such...

In the search for better‐performing colloidal lightemitting diodes (LEDs), nanocrystals of anisotropic morphologies remain to be explored. On page 295, Z. Chen et al. present the first functional LEDs based on quasi‐2D core/shell CdSe/CdZnS nanoplatelets, where quantum confinement takes place in the direction of thickness. These solution‐processed...

We use two-dimensional electronic spectroscopy to study the lineshapes and linewidths of excitons in colloidal nanoplatelets at room temperature and the coherences induced by the superposition of the two first excitonic states.

Metallic structures open the possibility to optimize the emission of a single emitter for the generation of single photons. High collection efficiency can be achieved and the radiative decay rate can be increased through the well-known Purcell effect. For emitters operating at room temperature and thus showing a large linewidth, plasmonic structure...

Free standing two dimensional materials appear as a novel class of structures. Recently, the first colloidal two dimensional heterostructures have been synthesized. These core/shell nanoplatelets are the first step toward colloidal quantum wells. Here, we study in details the spectroscopic properties of this novel generation of colloidal nanopartic...

form only given. Metallic structures open the possibility to optimize the emission of a single emitter for the generation of single photons. High collection efficiency can be achieved and the radiative decay rate can be increased through the well-known Purcell effect. For emitters operating at room temperature and thus showing a large linewidth, pl...

Free-standing two-dimensional nanostructures, which are referenced as nanoplates, nanomembranes, or nanosheets, are at the center of intense research and development. These structures can be metallic, dielectric, or semiconductor and have a controlled and a uniform thickness th