Negative Differential Resistance, Memory and Reconfigurable Logic Functions based on Monolayer Devices derived from Gold Nanoparticles Functionalized with Electro-polymerizable Thiophene-EDOT Units

We report on hybrid memristive devices made of a network of gold nanoparticles (10 nm diameter) functionalized by tailored 3,4(ethylenedioxy)thiophene (TEDOT) molecules, deposited between two planar electrodes with nanometer and micrometer gaps (100 nm to 10 um apart), and electropolymerized in situ to form a monolayer film of conjugated polymer with embedded gold nanoparticles (AuNPs). Electrical properties of these films exhibit two interesting behaviors: (i) a NDR (negative differential resistance) behavior with a peak/valley ratio up to 17, and (ii) a memory behavior with an ON/OFF current ratio of about 1E3 to 1E4. A careful study of the switching dynamics and programming voltage window is conducted demonstrating a non-volatile memory. The data retention of the ON and OFF states is stable (tested up to 24h), well controlled by the voltage and preserved when repeating the switching cycles (800 in this study). We demonstrate reconfigurable Boolean functions in multiterminal connected NP molecule devices.Comment: Full manuscript, figures and supporting information, J. Phys. Chem. C, on line, asap (2017

Synthesis of Hybrid Electroactive Materials by Low-Potential Electropolymerization of Gold Nanoparticles Capped with Tailored EDOT-Thiophene Precursor Units

The synthesis of gold nanoparticles (GNPs) capped with alkanethiols with terminal bithiophenic polymerizable groups, consisting of 3,4-ethylenedioxythiophene (EDOT) and 3-alkylsulfanylthiophene, is described. Transmission electron microscopy (TEM) and light diffusion show that these stabilized GNPs have an average size of 2–3 nm with low polydispersity. The electrochemical behavior of C10S-Au is investigated in dichloromethane in the presence of Bu4NPF6. The results show that these capped GNPs undergo straightforward and efficient electropolymerization under potentiodynamic or potentiostatic conditions. TEM images show that the electrodeposited films of the composite material present a very homogeneous structure, in which the size of the GNPs incorporated into the polythiophene matrix is unchanged. Results of cyclic voltammetry and spectroelectrochemistry obtained on polymer films deposited on platinum electrodes and transparent indium tin oxide electrodes, respectively, show that the reversible charging–discharging process and electrochromic behavior typical of poly(thiophenes) are preserved in the hybrid electroactive material

The contribution of CXCL12-expressing radial glia cells to neuro-vascular patterning during human cerebral cortex development

This study was conducted on human developing brain by laser confocal and transmission electron microscopy (TEM) to make a detailed analysis of important features of blood-brain barrier (BBB) microvessels and possible control mechanisms of vessel growth and differentiation during cerebral cortex vascularization. The BBB status of cortex microvessels was examined at a defined stage of cortex development, at the end of neuroblast waves of migration, and before cortex lamination, with BBB-endothelial cell markers, namely tight junction (TJ) proteins (occludin and claudin-5) and influx and efflux transporters (Glut-1 and P-glycoprotein), the latter supporting evidence for functional effectiveness of the fetal BBB. According to the well-known roles of astroglia cells on microvessel growth and differentiation, the early composition of astroglia/endothelial cell relationships was analyzed by detecting the appropriate astroglia, endothelial, and pericyte markers. GFAP, chemokine CXCL12, and connexin 43 (Cx43) were utilized as markers of radial glia cells, CD105 (endoglin) as a marker of angiogenically activated endothelial cells (ECs), and proteoglycan NG2 as a marker of immature pericytes. Immunolabeling for CXCL12 showed the highest level of the ligand in radial glial (RG) fibers in contact with the growing cortex microvessels. These specialized contacts, recognizable on both perforating radial vessels and growing collaterals, appeared as CXCL12-reactive en passant, symmetrical and asymmetrical, vessel-specific RG fiber swellings. At the highest confocal resolution, these RG varicosities showed a CXCL12-reactive dot-like content whose microvesicular nature was confirmed by ultrastructural observations. A further analysis of RG varicosities reveals colocalization of CXCL12 with Cx43, which is possibly implicated in vessel-specific chemokine signaling

Structural modulation of internal charge transfer in small molecular donors for organic solar cells

Donor-acceptor molecules with small chain extension have been synthesized and used as active material in organic solar cells. The effect of fusion of a phenyl group on the end dicyanovinylene acceptor is discussed

Facile Synthesis of 3-Alkoxy-4-cyanothiophenes As New Building Blocks for Donor−Acceptor Conjugated Systems

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Small D-pi-A Systems with o-Phenylene-Bridged Accepting Units as Active Materials for Organic Photovoltaics

Donor-acceptor (D--A) systems that combine triarylamine donor blocks and dicyanovinyl (DCV) acceptor groups have been synthesized. Starting from the triphenylamine (TPA)thiopheneDCV compound (1) as a reference system, various synthetic approaches have been developed for controlling the light-harvesting properties and energy levels of the frontier orbitals in this molecule. Thus, the introduction of methoxy groups onto TPA, the replacement of one phenyl ring of TPA by a thiophene ring, or the extension of the -conjugating spacer group lead to the modulation of the HOMO level. On the other hand, the fusion of the DCV group onto the vicinal thiophene ring by an ortho-phenylene bridge allows for a specific fine-tuning of the LUMO level. The electronic properties of the molecules were analyzed by using UV/Vis spectroscopy and cyclic voltammetry and the compounds were evaluated as donor materials in basic bilayer planar heterojunction solar cells by using C-60 as acceptor material. The relationships between the electronic properties of the donors and the performance of the corresponding photovoltaic devices are discussed. Bilayer planar heterojunction solar cells that used reference compound 1 and C-70 afforded power-conversion efficiencies of up to 3.7%

Evidence for the contribution of sulfur–bromine intramolecular interactions to the self-rigidification of thiophene-based π-conjugated systems

Bithiophene associating 3,4-ethylenedioxythiophene and 3-bromothiophene, and the corresponding polymer exhibit self-rigidified structures of the conjugated backbones resulting from the association of S–Br and S–O non-bonded intramolecular interactions

Oligothiophene-derivatized azobenzene as immobilized photoswitchable conjugated systems

Immobilization of an azobenzene-bithiophene compound on a gold surface leads to self-assembled monolayers with photoswitchable electrical properties

Effects of structural factors on the pi-dimerization and/or disproportionation of the cation radical of extended TTF containing thiophene-based pi-conjugated spacers.

The electrochemical and chemical oxidation of extended TTF 4 and 5 are analysed by cyclic voltammetry, Visible/NIR and ESR spectroscopies, and the X-ray structures of the new salts 5·BF4(CH2Cl2) and 4·ClO4(THF)1/2 are presented. The effects of structural factors on the π-dimerization or the disproportionation reaction of the cation radical are shown. The oxidation of compound 4 presents the successive formation of stable cation radical and dication species both in dichloromethane (DCM) and in a CH3CN/THF mixture. In contrast, for compound 5, the stability of the oxidation states strongly depends on the nature of the solvent. In DCM, the oxidation of 5 proceeds by two close one-electron transfers while in CH3CN/THF the dication is directly formed via a two-electron process. The X-ray structures of the two salts reveal the formation of pi-dimers of cation radical. While the dimer (5(2))2+ is due mainly to π–π interactions between the conjugating spacer, the multiplication of the sulfur atoms in compound 4 contributes to stabilize the dimer by the combined effects of S–S and π–π interactions. Visible/NIR and ESR experiments confirm the higher tendency of 4+· to dimerize with the occurrence of dimer and monomer in solution, while for 5+· only the monomer is detected in DCM. On the other hand, by dissolution of 5·BF4(CH2Cl2) in CH3CN, only the neutral and the dicationic states of compounds 5 are observed owing to the disproportionation reaction