Functional thin film coatings of porphyrins and phthalocyanines by layer-by-layer assembly

Official URL: https://risc01.sabanciuniv.edu/record=b2352860 _(Table of contents)

Layer-by-layer self-assembly is a versatile and environmental-friendly deposition mechanism for functional thin film coatings. Aqueous dispersions of nanoparticles, polyelectrolytes and macrocyclic compounds are well-known molecular candidates for LbL deposition. Nevertheless, in order to have controlled film properties in nanometer scale pH, concentration, deposition architecture and material distribution need to be precisely adjusted. Prepared multilayer coatings by LbL mechanism can demonstrate exceptional improvements in various application fields such as corrosion-protection and photodynamic therapy. Phthalocyanines and porphyrins are highly favored macrocyclic molecules in numerous areas due to their π-conjugated, delocalized electronic structures. Solar cells, photodynamic therapy, liquid crystals are only some of the functional utilization areas of phthalocyanines. Although their hydrophobic feature is desired for practical purposes, attachment of hydrophilic functional groups make them great candidates for LbL deposition. In this doctoral study, various metallated phthalocyanine types and their derivatives have been used for homogeneous and uniform thin film formation via layer-by-layer (LbL) coating method for potential anti-corrosive and photodynamic therapy purposes. Influence of pH and concentration for nickel(II)phthalocyanine tetrasulfonic acid tetrasodium salt on multilayer film properties; protection of alternating bilayer and tetralayer coatings of oppositely charged polyelectrolytes with nickel(II)phthalocyanine tetrasulfonic acid tetrasodium salt and copper phthalocyanine- 3,4‵,4‶,4‷-tetrasulfonic acid tetrasodium salt against corrosion; surface distribution of encapsulated zinc(II) phthalocyanine nanospheres and finally sequential adsorption of 5,10,15,20-(tetra-4- carboxyphenyl)porphyrin and zinc(II) phthalocyanine tetrasulfonic acid are examined on glass, silicon wafer and stainless-steel substrates by LbL mechanism. Dynamic light scattering (DLS) is applied for zeta potential determination. Electrochemical measurements are performed by potentiostat for anti-corrosion properties of multilayer films. Surface distribution of encapsulated nanospheres and topography are analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. Thickness of deposited coatings are evaluated by surface profiler and spectroscopic ellipsometry. In addition, quartz-crystal microbalance detector (QCM-D) is utilized for adsorption amount detection. Due to the colorful appearances of prepared coatings, multilayer film growth is monitored by ultra-violet visible spectroscopy (UV-Vis). Overall, sequential adsorption of polyelectrolytes and different phthalocyaninederivatives are successfully controlled. Obtained multilayer thin films are promising candidates for corrosion protection and photodynamic therapy