Preparation of aminofunctionalized TiO2 surfaces by binding of organophosphates

Titanium dioxide (TiO2) powder was chemically modified with 2-aminoethyl dihydrogen phosphate (AEPH2) and with 2-aminoethyl hydrogen ammonium phosphate (AEPHNH4) in order to achieve an aminofunctionalized high-surface-area TiO2 carrier suitable for more complex functionalizing. AEPH2 was found to form the monoammonium salt AEPHNH4 with ammonium ion rather than the diammonium salt AEP(NH4)2. The AEPHNH4 was thoroughly characterized by various techniques and compared with AEPH2. Bonding of AEPH2 and AEPHNH4 with TiO2 powder was studied. According to the 31P NMR and elemental analysis results, AEPH2 and AEPHNH4 form covalent chelate bidentate bonds between the phosphate group and the TiO2, while the amino groups remain accessible, creating uniform aminofunctionalized TiO2 surface fully occupied by AEP groups. Amount of AEP groups on TiO2 was limited to 1.5 wt-%.