Fabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsFabrication and Characterization of Dicyanopyrazine-Linked PorphyrinLangmuir-Blodgett FilmsLangmuir-Blodgett Films of Dicyanopyrazine-Linked Porphyrin Langmuir-Blodgett Films

Abstract

Porphyrin is a heterocyclic macrocycle comprised of four pyrrole subunits linked through methane bridges. Unique properties of a porphyrin can be realized by the introduction of functional groups such as electrochemically or photochemically active molecules. Porphyrin and its derivatives have recently received much attention because of their potential applications in data storage, photonic and optoelectronic materials, photodynamic therapy, photovoltaic cells, and chemical sensors.[1] One important consideration in such applications is the possibility of forming the organic compounds into thin films. The Langmuir-Blodgett (LB) technique is one of the most popular methods for fabricating molecularly assembled thin films utilizing air-water interfaces.[2] The typical procedure to obtain the LB film is as follows. Amphiphilic molecules dissolved in an organic solvent are spread at the air-water interface. The solid-like monolayer can be formed by adjusting the surface pressure. Stable monolayers at the air-water interface can be transferred onto hydrophilic or hydrophobic solid substrates via dipping the substrates. This technique is useful for not only fabricating monomer films but also polymer films on various solid substrates such as glass, chromium, quartz, mica, and silicon.[3,4] In this work, we have fabricated 2-DCPP multilayer Langmuir-Blodgett (LB) films on silanized Si(111) and quartz substrates. X-ray photoelectron spectroscopy (XPS) is used to analyze the structural compositions of 2-DCPP LB films. Atomic force microscopy (AFM) is performed to analyze the surface morphology of the LB films, and ellipsometry is used to measure the film thickness. UV-vis spectroscopy is performed to measure electronic transitions of the 2-DCPP films. Figure 2 shows UV-vis spectra of 2-DCPP LB films on quartz. In the case of 2-DCPP LB multilayer films, the Soret band for each porphyrin appears at 436.9 nm, with two additional Q bands at 576.0 and 662.7 nm. XPS has been used to verify the formation of 2-DCPP LB films on silanized Si(111) substrates. XPS survey spectra of the LB films (not shown here) detected C 1s, N 1s, O 1s, Cd 3d, K 2p and Cl 2p peaks for a 2-DCPP LB films. Exclude K 2p and Cl 2p from XPS peaks reveal the changes in the electronic structures of the film caused by increase of the transfer LB films. AFM has been used to reveal the surface roughness of LB Films on silanized Si(111). The measured surface roughness of 2, 6, 10, 14, 18 layers LB films on silanized Si(111) are 1.198, 2.752, 3.731, 4.028 and 4.665 nm, respectively. The ellipsometric thicknesses of the LB multilayers are 64.8, 188.0, 311.2, 453.6 and 574.6 ?. These results are generally consistent with the result of the UV-vis spectroscopy measurement