Alginate-assisted Water-bath ZnO Growth on Cotton Fabrics for Multifunctional Thermal-management Textiles

A multifunctional cotton-based fabric was prepared by alginate-assisted in situ growth of zinc oxide (ZnO) nanoparticles on commercial cotton using a water-bath process (90 °C, 3 h). The ZnO/cotton composite fabric (ZNCF) showed increased surface hydrophobicity, with a water contact angle (WCA) of up to 117°, compared with rapid water absorption by untreated cotton. In a skin-contact heat-dissipation test, the surface temperature of the arm covered with ZNCF was 2.8 °C higher than that covered with conventional cotton, indicating improved heat transfer from skin to fabric. Under simulated sunlight, ZNCF reduced surface heating by 10.7 °C relative to conventional cotton. UV-vis spectra showed enhanced absorption in the 200–400 nm region, supporting UV-shielding behavior under the tested spectral condition. ZNCF also promoted methylene blue degradation under light irradiation and inhibited the growth of Escherichia coli and Staphylococcus aureus in OD-based and agar-plate antibacterial assays. Combustion-residue observation further showed a larger and denser residue for ZNCF than for untreated cotton. This study provides a simple alginate-assisted route for preparing protective and functional thermal-management cotton textiles.