Promoted Exchange Reaction between Alkanethiolate Self-Assembled Monolayers and an Azide-Bearing Substituent

The possibility of ultraviolet (UV) light promoted exchange reaction (UVPER) between the primary alkanethiolate (AT) self-assembled monolayers (SAMs) and an azide-functionalized substituent (12-azido-1-dodecanethiol, C12N3), capable of click reaction with ethynyl-bearing species, is demonstrated. This reaction resulted in the mixed AT/C12N3 films, with the portion of C12N3 precisely controlled by selection of a suitable UV dose. As the primary matrix, either nonsubstituted or oligo(ethylene glycol) (OEG)-substituted AT SAMs were used, targeting mixed SAMs of chemical and biological significance. To demonstrate the flexibility of the approach, UV light with two different wavelengths (254 and 375 nm) was used, applied to the nonsubstituted and OEG-substituted AT SAMs, respectively. The surface density of the chemically active azide groups embedded in the nonreactive primary matrix could be varied according to the composition of the mixed SAMs, as demonstrated by the subsequent click reaction between these SAMs and several representative functional moieties bearing a suitable group for the click reaction with azide. For the OEG-AT/C12N3 films, this resulted in the preparation of templates for specific protein adsorption, comprising biotin-bearing moieties embedded in the protein-repelling OEG-AT matrix. The density of the biotin receptors was varied according to the density of the C12N3 moieties. The templates exhibited much higher affinity to the specific protein (avidin) as compared to a nonspecific one. The surface density of avidin could be varied in accordance with the density of the biotin receptors, i.e., directly controlled by the UV dose within the UVPER procedure. The entire approach was extended to lithography, relying on a commercial maskless UV lithography setup. Representative gradient patterns of specifically attached avidin in the protein-repelling OEG-AT matrix were fabricated

New 4,4'-Bis(9-carbazolyl)-Biphenyl Derivatives with Locked Carbazole-Biphenyl Junctions: High-Triplet State Energy Materials

We synthesized a series of 4,4'-bis(9-carbazolyl)-biphenyl (CBP) derivatives, using methyl groups as spatially demanding groups, locking the angle between the carbazole subunit and the biphenyl backbone as potential matrix material for blue organic light-emitting diodes (OLEDs). The locked rotation was achieved by four methyl groups either in positions 1 and 8 of the carbazole subunit (1) or in positions 3, 5, 3', and 5' of the biphenyl subunit (2), and the fixed spatial arrangement was confirmed by X-ray analysis. The physical properties of CBP derivatives based on parent structure 2 were further tailored by electron-withdrawing CF3 groups in positions 3 and 6 (3) or positions 2 and 7 of the carbazole subunits (4) or alternatively by electron-donating CH3O groups in positions 2 and 7 (5) of the same building blocks. Increased triplet energies (ET) compared to that of the parent compound CBP were found for all synthesized CBP derivatives 1-5. Enhanced glass transition temperatures ranging between 129 and 202 °C further corroborate the application potential of these derivatives for matrix material in blue OLEDs

Improved Photostability of a Cu-I Complex by Macrocyclization of the Phenanthroline Ligands

The development of molecular materials for conversion of solar energy into electricity and fuels is one of the most active research areas, in which the light absorber plays a key role. While copper(I)-bis(diimine) complexes [Cu$^{l}$ (L) $_{2}$] $^{+}$ are considered as potent substitutes for [Ru$^{ll}$ (bpy) $_{3}$] $^{2+}$, they exhibit limited structural integrity as ligand loss by substitution can occur. In this article, we present a new concept to stabilize copper bis(phenanthroline) complexes by macrocyclization of the ligands which are preorganized around the Cu$^{l}$ ion. Using oxidative Hay acetylene homocoupling conditions, several Cu$^{l}$ complexes with varying bridge length were prepared and analyzed. Absorption and emission properties are assessed; rewardingly, the envisioned approach was successful since the flexible 1,4-butadiyl-bridged complex does show enhanced MLCT absorption and emission, as well as improved photostability upon irradiation with a blue LED compared to a reference complex

Conception de cellules photovoltaïques à base de semi-conducteurs de type p sensibilisés par un colorant

Ce travail a porté sur la sensibilisation d oxydes semi-conducteurs de type p (SCp) pour la conversion photovoltaïque. Un important travail de synthèse et de caractérisation physicochimique a ainsi été mené à bien : de nouveaux colorants organiques ont été obtenus et ont permis de considérablement améliorer les propriétés photovoltaïques des cellules à base de NiO. De plus, les tout premiers colorants inorganiques pour la sensibilisation de SCp ont été isolés et ont permis de déterminer une fonction d ancrage efficace, alternative aux acides carboxyliques. De nouveaux médiateurs redox ont été également synthétisés et étudiés, permettant notamment de monter une cellule tandem délivrant une tension de circuit ouvert de 950 mV. Enfin, les propriétés intrinsèques de l oxyde de nickel limitent les performances des systèmes photovoltaïques, et plusieurs approches ont été explorées afin de corriger les défauts de ce matériau. Cependant, la mise au point d un nouveau semiconducteur de type p, fonctionnalisable par un colorant, et donnant accès à des performances photovoltaïques améliorées, est la solution la plus séduisante. Dans cette optique, les résultats obtenus avec la delafossite CuGaO2 sont très encourageants, et augurent un bel avenir à cette technologie nouvelle et fascinante.This work deals with the sensitization of p-type semi-conductors for photovoltaic conversion. New organic dyes were synthetised and characterised, which allow us to enhance NiO sensitized solar cells photoconversion yield. Moreover, the first organometallic dyes for ptype semi-conductors sensitization were prepared, which gave us a way to identify an optimal anchoring group instead of a carboxylic acid group which is usually used. New redox mediators were alos studied, and a tandem dye solar cell with a Voc of 950 mV was built. Nickel oxide is by far the major semiconductor used for the fabrication of p-DSSCs. It enables the development of this new type of research field, but it possesses a too accessible valence band potential to permit the fabrication of solar cells delivering a high voltage. Therefore, the use of new p-SCs with deeper valence band potentials would be most certainly beneficial to develop p-DSSCs with much higher solar energy conversion efficiencies. Results which were obtained with CuGaO2 delafossite are very encouraging. Taking into account that we have barely started to explore this new research field and the number of adjustable parameters, there are certainly plenty of exciting discoveries to be made and we can anticipate that important progresses will be achieved in the near future.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Mutual influence of gold and silver nanoparticles on Tris-(2,2′bipyridine)-Ru(II) core complexes: Post-functionalization processes, optical and electrochemical investigations

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