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Spectroscopic ellipsometry on a novel cyanine dyes in Langmuir–Blodgett multilayers

Year: 2006

Journal: Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volumes 284-285, 15 August 2006, Pages 414-418, 20111221

Authors: Chuang Wang, Shihong Ma, Hao Zeng, Jing Lia, Liangyao Chen, Wencheng Wang and He Tian

Organizations: Department of Optical Science and Engineering, State Key Lab of Advanced Photonic Materials and Devices, Fudan University, Shanghai 200433, China, Department of Physics, Fudan University, Shanghai 200433, China, Chemistry and Pharmaceutics Institute, East China University of Science and Technology, Shanghai 200237, China

We have investigated on cyanine dye (HQ) in Langmuir–Blodgett (LB) films by spectroscopic ellipsometer (SE) and compared the results with that obtained by using small angle X-ray diffraction (SAXD). It is found from the isotherms that there is a critical point on Langmuir films near the area 0.8 nm2/molecule for HQ LB films with and without Cd2+ ions, respectively and suggested that the facts should result from the phase transition due to the change of molecular tilt angle on surface of sub-phase. The refractive indexes as a function of the wavelength λ are reported by the SE method using the three layers-model (air-LB film-silicon wafer) and Cauchy dispersion equation, for the first time presented in literature. The thickness of a single deposited layer is 2.45 nm on average. The thickness of per monolayer is agreement with those obtained by SAXD measurements.