Optical studies of shear stress effect on organic thin films

Abstract: We have studied the effect of shear stress by using the sapphire-anvil cell, which was developed to generate shear stress on a thin film under high pressure. We have tried to synthesize the charge-transfer (CT) salt of TMPD (N,N,N′,N′-tetramethyl-p-phenylenediamine) and TCNQ (7,7,8,8,-tetracyanoquinodimethane) by the shear stress effect. The shear deformation caused a change of the color of the thin film to blue-black at the outer part on the sapphire culet, while the color at the center part remained as orange of neutral TCNQ. The thin film on the anvils was examined by Raman spectroscopy under a microscope. The Raman bands attributed to C were observed at 1386cm−1 and 1452cm−1 for the CT salt and neutral TCNQ, respectively. For the blue-black thin film at the outer part, the Raman band appeared at 1386cm−1, while at the center part, it was observed at 1452cm−1. From the Raman spectra, the formation of the CT salt from TMPD and TCNQ by the shear stress effect was confirmed. In addition, the estimation of the shear stress effect on Pt(dpg)2, bis(diphenylglyoximato)-platinum(II), was performed by comparing the Raman band under the shear stress with one under hydrostatic pressure. It was noted that the shear stress with the sapphire anvil cell was applied more strongly at the outer part on the culet than at the center part. [Copyright &y& Elsevier]