According to their restricted conformational freedom, heterocyclic -amino acids are usually considered to be related to Z-vinylogous -amino acids. In this context, oligomers alternating -amino acids and thiazole-based -amino acids (ATCs) were expected to fold into a canonical 12-helical shape as described for /-hybrid peptides composed of cis-/-unsaturated -amino acids. However, through a combination of X-ray crystallography, NMR spectroscopy, FTIR experiments, and DFT calculations, it was determined that the folding behavior of ATC-containing hybrid peptides is much more complex. The homochiral /(S)-ATC sequences were unable to adopt a stable conformation, whereas the heterochiral /(R)-ATC peptides displayed novel ribbon structures stabilized by unusual C-9/12-bifurcated hydrogen bonds. These ribbon structures could be considered as a succession of pre-organized / dipeptides and may provide the basis for designing original -helix mimics.

A general method is proposed to produce oriented and highly crystalline conducting polymer layers. It combines the controlled orientation/crystallization of polymer films by high-temperature rubbing with a soft-doping method based on spin-coating a solution of dopants in an orthogonal solvent. Doping rubbed films of regioregular poly(3-alkylthiophene) s and poly(2,5-bis(3-dodecylthiophen- 2-yl) thieno[3,2-b] thiophene) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) yields highly oriented conducting polymer films that display polarized UV-visible-near-infrared (NIR) absorption, anisotropy in charge transport, and thermoelectric properties. Transmission electron microscopy and polarized UV-vis-NIR spectroscopy help understand and clarify the structure of the films and the doping mechanism. F(4)TCNQ(-) anions are incorporated into the layers of side chains and orient with their long molecular axis perpendicular to the polymer chains. The ordering of dopant molecules depends closely on the length and packing of the alkyl side chains. Increasing the dopant concentration results in a continuous variation of unit cell parameters of the doped phase. The high orientation results in anisotropic charge conductivity (sigma) and thermoelectric properties that are both enhanced in the direction of the polymer chains (sigma = 22 +/- 5 S cm(-1) and S = 60 +/- 2 mu V K-1 ). The method of fabrication of such highly oriented conducting polymer films is versatile and is applicable to a large palette of semiconducting polymers.

We report the direct and unambiguous evidence of the existenceof inner semiconducting tube (iSCT) photoluminescence (PL)from measurements performed on four individual free-standingindex-identified double-walled carbon nanotubes (DWNTs).Based on thorough Rayleigh scattering, Raman scattering andPL experiments, we are able to demonstrate that the iSCT PLis observed with a quantum yield estimated as a few 10−6 independentlyof the semiconducting or metallic nature of theouter tube. This result is mainly attributed to ultrafast excitontransfer from inner to outer tube. Furthermore, by carryingout PL excitation experiments on the (14,1)@(15,12) DWNT,we show that the iSCT PL can be detected through the opticalexcitation of the outer tube (Fig. 1) indicating that the excitontransfer can also occur in the opposite way.

We report the direct and unambiguous evidence of the existence of inner semiconducting tube (iSCT) photoluminescence (PL) from measurements performed on four individual free-standing index-identified double-walled carbon nanotubes (DWNTs). Based on thorough Rayleigh scattering, Raman scattering and PL experiments, we are able to demonstrate that the iSCT PL is observed with a quantum yield esti-mated as a few 10-6 independently of the semiconducting or metallic nature of the outer tube. This result is mainly attributed to ultrafast exciton transfer from inner to outer tube. Furthermore, by carrying out PL excitation experiments on the (14,1)@(15,12) DWNT, we show that the iSCT PL can be detected through the optical excitation of the outer tube (Figure 1) indicating that the exciton transfer can also occur in the opposite way.