Reversible Photoswitchable Wettability in Noncovalently Assembled Multilayered Films
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- 作者：Peter F. Driscoll ; Nipa Purohit ; Nantanit Wanichacheva ; Christopher R. Lambert ; W. Grant McGimpsey
- 刊名：Langmuir
- 出版年：2007
- 出版时间：December 18, 2007
- 年：2007
- 卷：23
- 期：26
- 页码：13181 - 13187
- 全文大小：140K
- 年卷期：v.23,no.26(December 18, 2007)
- ISSN：1520-5827
文摘
Reversible and irreversible photoinduced changes in surface wettability were observed in noncovalently assembledmultilayered films. The multilayered films studied were fabricated from a self-assembled monolayer (SAM) consistingof 4-(10-mercaptodecyloxy)pyridine-2,6-dicarboxylic acid on gold, Cu(II) ions complexed to the pyridine head groupof the SAM, and either cis- (film 1) or trans- (film 2) stilbene-4,4'-dicarboxylic acid complexed to the Cu(II) ions.Irradiation of film 1 at wavelengths corresponding to the absorption band of the cis-stilbene isomer resulted in anirreversible chemical change and an irreversible increase in wettability, as indicated by surface contact angle andgrazing incidence IR measurements. However, no evidence for cis-/trans-photoisomerization was observed. Films 3and 4, similar to films 1 and 2 in that they consist of an underlying SAM, an intermediate layer consisting of Cu(II)ions, and either cis- or trans-stilbene-4,4'-dicarboxylic acid as the capping ligand, were fabricated with a mixed SAMthat contained both 4-(10-mercaptodecyloxy)pyridine-2,6-dicarboxylic acid and 4-tert-butylbenzenethiol. Irradiationof these films at wavelengths corresponding to stilbene isomer absorption bands resulted in reversible cis- to trans-(film 3) and trans- to cis- (film 4) photoisomerization and reversible switching of the surface wettability between alow wetting state (cis-stilbene) and a high wetting state (trans-stilbene). The difference in observed behavior betweenfilms 1 and 2 and films 3 and 4 is attributed to the greater surface spacing afforded by the mixed monolayer, whichallows greater conformational flexibility and lowers the steric barriers to isomerization.