Ref HAL: hal-02512005_v1
DOI: 10.1063/10.0000705
WoS: 000524512300003
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The paper presents a brief review of the recent developments in the field of absorption of atomic and molecular species in carbon cellular structures. Such absorbing objects can be distinctly recognized among a large family of carbon porous materials owing to potential and already observed in experiments very high capacity to soak and to keep inside different substances, which at usual conditions outside the porous matrices may often stay only in a gaseous form. High capacity filling is attained owing to single graphene-like walls separating different cells in the whole structures providing their lightweight. This property of cellular structures makes them very promising for numerous technological applications such as hydrogen storage in fuel cells and molecular sieving in membranes made from such structures or for their usage in microelectronics, photovoltaics and production of Li-ion batteries. Independently of the targeted applications gases are good candidates for probing tests of carbon matrices themselves.

Ref HAL: hal-02507349_v1
DOI: 10.1016/j.mtcomm.2020.100987
WoS: 000571134300004
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Well-defined double hydrophilic block copolymers (DHBCs) of poly(ethylene glycol)-block-poly(N,N-diethyla-crylamide) (PEG-b-PDEAm) were synthesized via a reversible addition-fragmentation chain-transfer (RAFT) polymerization of N,N-diethylacrylamide (DEAm) using dithioester terminated PEG of different chain lengths as macro-chain transfer agents. Controlled molecular weight and narrow molecular weight distribution were achieved as proven by size exclusion chromatography (SEC). Cloud points (CP) were determined via turbidity measurements with ultraviolet-visible spectroscopy (UV-vis) and LCST by differential scanning micro-calori-metry (micro-DSC). They range from 32 to 40°C depending on the PDEAm length block and its concentration. Above the LCST, fluorescence spectroscopy and dynamic light scattering (DLS) demonstrated that the PEG-b-PDEAm copolymers self-organized into large aggregates. More interestingly, copolymers pre-aggregated at relatively high concentrations below the LCST.

Ref HAL: hal-02512091_v1
DOI: 10.1021/acs.jcim.0c00015
WoS: 000529208800023
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Due to their unique geometry complex, self-assembled nanoporous 2D molecular crystals offer a broad landscape ofpotential applications, ranging from adsorption and catalysis to optoelectronics, substrate processes, and future nanomachineapplications. Here we report and discuss the results of extensive all-atom Molecular Dynamics (MD) investigations of self-assembledorganic monolayers (SAOM) of interdigitated 1,3,5-tristyrilbenzene (TSB) molecules terminated by alkoxy peripheral chains Cncontaining n carbon atoms (TSB3,5-Cn) deposited onto highly ordered pyrolytic graphite (HOPG). In vacuo structural andelectronic properties of the TSB3,5-Cn molecules were initially determined using ab initio second order Møller−Plesset (MP2)calculations. The MD simulations were then used to analyze the behavior of the self-assembled superlattices, including relaxed latticegeometry (in good agreement with experimental results) and stability at ambient temperatures. We show that the intermoleculardisordering of the TSB3,5-Cn monolayers arises from competition between decreased rigidity of the alkoxy chains (loss ofintramolecular order) and increased stabilization with increasing chain length (afforded by interdigitation). We show that theinclusion of guest organic molecules (e.g., benzene, pyrene, coronene, hexabenzocoronene) into the nanopores (voids formed byinterdigitated alkoxy chains) of the TSB3,5-Cn superlattices stabilizes the superstructure, and we highlight the importance of alkoxychain mobility and available pore space in the dynamics of the systems and their potential application in selective adsorption.

Ref HAL: hal-02507269_v1
DOI: 10.1038/s42005-020-0313-7
WoS: 000520516200001
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Hybrid organolead perovskites (HOP) have started to establish themselves in the field of photovoltaics, mainly due to their great optoelectronic properties and steadily improving solar cell efficiency. Study of the lattice dynamics is key in understanding the electron-phonon interactions at play, responsible for such properties. Here, we investigate, via neutron and Raman spectroscopies, the optical phonon spectrum of four different HOP single crystals: MAPbBr3, FAPbBr3, MAPbI3, and α-FAPbI3. Low temperature spectra reveal weakly dispersive optical phonons, at energies as low as 2-5 meV, which seem to be the origin of the limit of the charge carriers mobilities in these materials. The temperature dependence of our neutron spectra shows as well a significant anharmonic behaviour, resulting in optical phonon overdamping at temperatures as low as 80 K, questionning the validity of the quasi-particle picture for the low energy optical modes at room temperature where the solar cells operate.

Ref HAL: hal-02504627_v1
Ref Arxiv: 2002.08279
Ref INSPIRE: 1781438
DOI: 10.1007/JHEP06(2020)131
WoS: 000543433700002
Ref. & Cit.: NASA ADS
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We use top-down holography to study the thermodynamics of a one-parameter family of three-dimensional, strongly coupled Yang-Mills-Chern-Simons theories with M-theory duals. For generic values of the parameter, the theories exhibit a mass gap but no confinement, meaning no linear quark-antiquark potential. For two specific values of the parameter they flow to an infrared fixed point or to a confining vacuum, respectively. As in the Klebanov-Strassler solution, on the gravity side the mass gap is generated by the smooth collapse to zero size of a cycle in the internal geometry. We uncover a rich phase diagram with thermal phase transitions of first and second order, a triple point and a critical point.

Ref HAL: hal-02434357_v1
DOI: 10.3389/fmats.2019.00340
WoS: 000509310000001
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Ref HAL: hal-02498343_v1
DOI: 10.1016/j.solidstatesciences.2020.106125
WoS: 000530687900001
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High temperature, high pressure conditions were used to insert liquid bismuth in 4-6 nm diameter amorphous silica nanotubes. A combination of transmission electron microscopy and neutron powder diffrac-tion indicate that the final composite consists in 5-6 nm semi-conducting Bi nanowires confined in insulating mesoporous -quartz. Such a nanostructured material could be of considerable interest for thermo-electric applications. HIGHLIGHTS:  Bismuth was inserted into 4-6 nm silica nanotubes under high-pressure, high-temperature conditions  The host amorphous nanotubes crystallize in the form of -quartz  The obtained nanocomposite consists of 5-6 nm Bi nanowires imbedded in mesoporous -quartz  The formation of Bi nanowires modifies their physical properties compared to bulk Bi