Multifunctional properties of cotton fabric tailored via green synthesis of TiO<sub>2</sub>/curcumin composite

In this study, a novel green process was developed to produce a multifunctional cotton (CO) fabric incorporating TiO2/curcumin composites that simultaneously provides UV protection and photocatalytic performance. For this purpose, TiO2 was synthesised using the sol–gel process; loaded with the natural colourant curcumin as a visible light absorber at two temperatures, i.e., 70 and 350 °C; and applied to the CO fabric via the pad–dry–cure process. For comparison, TiO2 was synthesised without curcumin under the same conditions. The synthesis conditions at 70 °C ensured the formation of predominantly amorphous TiO2, while curcumin promoted TiO2 crystallisation despite the low synthesis temperature. A 350 °C synthesis temperature was high enough to form the polymorphic TiO2 anatase phase. Although the increase in synthesis temperature and the presence of curcumin in the composites caused a bathochromic shift in light absorption, the photocatalytic activity of all samples was mainly driven by UV light. Chemically modifying the CO fabric significantly reduced the light transmittance of the samples, with the highest absorption of UV light obtained for the sample containing the TiO2/curcumin composite synthesised at 70 °C. This sample provided excellent UV protection with a UPF value of 51.6. All chemically modified CO samples showed photocatalytic activity, degrading coffee stains and decolourising methylene blue and Rhodamine B dye solutions. The highest photocatalytic efficiency and recyclability were obtained again for the CO sample with the TiO2/curcumin composite synthesised at 70 °C, demonstrating the synergistic effect between TiO2 and curcumin in the composite prepared under these synthesis conditions.