Biomimetically modified chitosan for electrophoretic deposition of composites

A one-step cathodic electrophoretic deposition (EPD) method has been developed for the deposition of chitosan (CHIT) films modified with catechol. Our approach was based on the use of 3,4-dihydroxybenzaldehyde (DHBA) molecules, which contain a catechol moiety for CHIT modification using a Schiff base reaction. We discussed the deposition mechanism as well as advantages of our one-step EPD method, compared to other techniques. It was found that the EPD method allowed the fabrication of redox-active films. A conceptually new strategy has been developed based on the use of CHIT-DHBA as a reducing, capping, dispersing, charging and film forming agent for the in-situ reduction of Ag+ ions, followed by catecholate type bonding of CHIT-DHBA to Ag particles, their electrosteric dispersion and EPD of composite CHIT-DHBA-Ag films. Building on the processing advantages offered by one-step cathodic deposition and remarkable bonding properties of catechol we performed EPD of CHIT-DHBA-hydroxyapatite (HA) and CHIT-DHBA-TiO2 films. Another major finding was the use of CHIT-DHBA for electrosteric co-dispersion and charging of HA and TiO2, followed by EPD of composite CHIT-DHBA-TiO2-HA films. Comprehensive electrochemical and electron microscopy testing was used to characterize the microstructure of the films, as well as the electrochemical properties. The results of this investigation pave the way for the synthesis and agglomerate-free processing of various functional inorganic materials and fabrication of organic-inorganic composites for biomedical, sensor and water purification applications.