Surface modification of TiO2 nanoparticles with terephthalic acid in supercritical carbon dioxide

Abstract

This paper presents a supercritical CO2 strategy for surface modification of TiO2 nanoparticles with carboxylic acids. The reaction between TiO2 nanoparticles and terephthalic acid molecules in sc-CO2 provides carboxylic acid-modified TiO2 nanoparticles with a modification efficiency much higher than the conventional solvent immersion method. From the statistical method of response surface methodology, modifier ratio 4.04 (mol/mol), temperature 401.5 K, and pressure 14.8 MPa resulted in an optimum modification rate of 25.34%. The modified TiO2 was characterized by FTIR, TG-DTA, FE-SEM, TEM-EDS, and zeta potential analysis. The results showed the surface modification of TiO2 in sc-CO2 is made of modifier molecules bonding chemically. Surface modification by terephthalic acid affects the surface electrical property of TiO2 nanoparticles in water, leading to a positive charge surface. Since this method is ecologically and environmentally friendly, it can be applied in precursor composites for the synthesis materials of biomedical application.