Acetylene Used as a New Linker for Molecular Junctions in Phenylene鈥揈thynylene Oligomer Langmuir鈥揃lodgett Films

详细信息    查看全文

• 作者：Luz Marina Ballesteros ; Santiago Mart铆n ; Cristina Momblona ; Santiago Marqu茅s-Gonz谩lez ; Mar铆a Carmen L贸pez ; Richard J. Nichols ; Paul J. Low ; Pilar Cea
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：April 26, 2012
• 年：2012
• 卷：116
• 期：16
• 页码：9142-9150
• 全文大小：429K
• 年卷期：v.116,no.16(April 26, 2012)
• ISSN：1932-7455

文摘

Langmuir and Langmuir鈥揃lodgett films have been fabricated from an acetylene-terminated phenylene鈥揺thynylene oligomer, namely 4-((4-((4-ethynylphenyl)ethynyl)phenyl)ethynyl)benzoic acid (HOPEA). Characterization of the Langmuir film by surface pressure vs area per molecule isotherms and Brewster angle microscopy reveals the formation of a high quality monolayer at the air鈥搘ater interface. One layer Langmuir鈥揃lodgett (LB) films were readily fabricated by the transfer of HOPEA Langmuir films onto solid substrates by the withdrawal of the substrate. The deposition mode was Z-type. Quartz crystal microbalance (QCM) experiments confirm the formation of directionally oriented, monolayer LB films, in which the HOPEA molecules are linked to the gold substrate by attachment through the acid group. The morphology of these films was analyzed by atomic force microscopy (AFM), which revealed an optimum transference surface pressure of 18 mN m^鈥? for the formation of homogeneous films. Cyclic voltammetry also showed a significant blockage of gold electrodes covered by HOPEA monolayers. Electrical properties of HOPEA monolayers sandwiched between a bottom gold electrode and a gold STM (scanning tunneling microscope) tip have been recorded, revealing that the acetylene group is an efficient linker for electron transport. In addition, the STM experiments indicate a nonresonant tunneling mechanism of charge transport through these metal鈥搈olecule鈥搈etal junctions.