New transparent metal-like bilayer composite films with highly conducting layers of theta-(BET-TTF)(2)Br center dot 3H(2)O nanocrystals

A flexible low-density metallic material, which is extremely transparent, w as obtained using as active component the highly conducting molecular metal theta-(BET-TTF)Br-2 . 3H(2)O, BET-TTF = bis(ethylenethio)tetrathiafulvalen e. This material is a bilayer (BL) film that was prepared by treating a pol ycarbonate film containing 2 wt.-% of molecularly dispersed BET-TTF with va por of a Br-2/CH2Cl2 solution. Optimum conditions for the preparation of ve ry transparent metallic materials were established. The X-ray diffraction p atterns indicate that the conducting layer of the BL films is formed by wel l a* oriented theta-(BET-TTF)(2)Br . 3H(2)O nanocrystals, which are clearly observed in the SEM images. Conductivity measurements confirm that the nan ocrystalline layers have the same transport properties as those of the sing le crystals, displaying metal-like behavior down to He temperature and the highest room temperature conductivity (120 Omega (-1) cm(-1)) reported so f ar for this kind of film.