Polyphenol-metal complexes for surface functionalization

Abstract

Recently, polyphenol-metal complexes based surface functionalization has been drawing attention in various research areas. Tannic acid (TA), a representative polyphenol, has adhesive property with catechol groups and forms complex with Fe(III) ion ( $Fe^{III}$ ) in a few seconds. $TA-Fe^{III}$ generates structurally rigid nanofilms on surfaces in a fast and eco-friendly way. In this regard, the surface could be functionalized by $TA-Fe^{III}$ with various methods which are micro contact printing $(\mu cp)$ and spray-assisted coating in this paper. First research was focused on generating spatio-selective crystallization of $CaCO_3$ using $TA-Fe^{III}$ $\mu cp$ . Poly((3-(methacryloylamino)propyl)-dimethyl(3-sulfopropyl)ammonium hydrox-ide) (poly(MPDSAH)) surface which is known as anti-fouling and zwitterionic polymer was used as a patterning platform. Because of its zwitterionic property, that nucleation of $CaCO_3$ was inhibited on poly(MPDSAH) surface. Meanwhile, $TA-Fe^{III}$ patterned on poly(MPDSAH) induced $CaCO_3$ nucleation and generated amorphous calcium carbonate (ACC). Consequently, the $CaCO_3$ patterning on zwitterionic polymer surface was succeeded. For the phase fine control of $CaCO_3$, we introduced casein, phosphorylated protein, as a crystallization promoting agent. Another method for surface functionalization with $TA-Fe^{III}$ is spray-assisted nanocoating. We investigated $TA-Fe^{III}$ film thickness increase and morphology in various concentrations of TA and $Fe^{III}$ solutions. Also, spray-assisted $TA-Fe^{III}$ nanofilm was characterized by Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). Addi-tionally, spray-assisted $TA-Fe^{III}$ coating method was applied to various substrates and exhibited successful surface modification with surface-independence. For practical applications, we employed this coating method to glass, fruits, and fabrics for UV-protection, anti-fogging, and anti-bacterial properties. Spray-assisted polyphenol-metal complex coating with substrate-independence could be potentially applied to coating industries used in practical life such as ships, automobiles, plastic, glass, food, and fabric.