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Home List of Titles Multilayer nanostructured porphyrin arrays constructed by layer-by-layer self-assembly
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/150163
- Multilayer nanostructured porphyrin arrays constructed by layer-by-layer self-assembly
- Smith, Arthur R. G.; Ruggles, Jeremy L.; Yu, Aimin; Gentle, Ian R.
- UV-vis absorption, atomic force microscopy (AFM), contact angle, and X-ray reflectivity experiments were performed on thin films deposited on crystalline silicon substrates as alternating layers of a porphyrin with anionic functionality, tetra-5,10,15,20-(4-sulfonatophenyl)porphine (TSPP) or the metalated version, Cu(II)TSPP, and the cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA). The films were made by dipping in alternating aqueous solutions containing film components (layer-by-layer deposition). Modeling of the X-ray reflectivity data revealed differences in the films' thickness depending on the method of film deposition. An unusual decrease in film thickness after each polyelectrolyte dip was also observed for films using TSSP. UV-vis measurements revealed that a similar amount of TSSP was included within films despite the method of formation. UV-vis measurements also revealed the presence of free-base, H-aggregate, and J-aggregate forms of the porphyrin after TSPP dipping, and the subsequent disappearance of the J-aggregate after dipping in the PDDA solution. A model of film formation was proposed on the basis of the concept of two different types of porphyrin aggregates being present after dipping in porphyrin solution. A layer of porphyrin molecules initially attach to the Si surface such that the planar molecules are arranged side by side as H-aggregates with an excess of J-aggregated material on top. The J-aggregate is then removed and replaced by a layer of PDDA. A change in contact angle of 14° was observed between porphyrin and polyelectrolyte layers due to the more hydrophobic nature of the polymer. The presence of the J-aggregate was confirmed in AFM images obtained from the porphyrin layer. Exposure of the films to solutions of alternating pHs of 10 and 1.8 resulted in reproducible switching of the UV-vis spectra, indicating a possible sensing application.
- Publication type
- Journal article
- Langmuir, Vol. 25, no. 17 (Jul 2009), pp. 9873-9878
- Publication year
- FOR Code(s)
- 0306 Physical Chemistry (Incl. Structural); 0903 Biomedical Engineering; 0904 Chemical Engineering
- AFM image; Agglomeration; Alternating layers; Aqueous solutions; Atomic force microscopy; Cationic polyelectrolyte; Chlorine compounds; Contact angle; Copper; Crystalline silicon substrates; Dyes; Film deposition; Film formations; Film preparation; H-aggregates; Hydrophobic nature; J aggregates; Layer by layer deposition; Layer by layer self assembly; Planar molecules; Poly(diallyldimethylammonium chloride); Polyelectrolytes; Porphine; Porphyrin arrays; Porphyrin molecules; Porphyrins; Reflection; Self assembly; Semiconducting silicon compounds; Sensing applications; Si surfaces; UV; X ray diffraction; X ray reflectivity
- American Chemical Society
- Publisher URL
- Copyright © 2009 American Chemical Society. The American Chemical Society does not allow Swinburne researchers to archive either the accepted manuscript or the published version of the article.
- Peer reviewed