Physical and Surface Chemical Analysis of High-Quality Antimicrobial Cotton Fabrics Functionalized with CuO_x Grown In Situ from Different Copper Salts: Experimental and Theoretical Approach

The emergence of harmful microorganisms poses a public health challenge. Antimicrobial cotton textiles with semiconductor oxides offer a promising solution to mitigate pathogen spread. Here, we study the physicochemical interactions between copper oxides (CuO_x) and cellulose in cotton fiber functionalized with these same oxides for antimicrobial properties. Fabrics were treated by an exhaust dyeing method using a 2% on-weight-of-fiber (owf) copper precursor with acetate, nitrate, and sulfate anions. Nonfunctionalized (NF) fabrics with a yellow hue turned reddish brown after the functionalization with CuO_x. Copper (Cu) content in the functionalized fabrics increased by 27-40% compared to 0.009% in the NF fabric. The percentage of Cu exhaustion was higher with the acetate salt than nitrate and sulfate, resulting in darker fabrics according to colorimetry. XPS analysis of cotton suggests a chemical interaction between the hydroxyl groups of cellulose and CuO_x. The nature and strength of potential interactions between Cu cations and the cellulose surface were investigated using the quantum theory of atoms in molecules and crystals. Based on topological parameters, the interaction between Cu and the hydroxyl groups of cellulose exhibits a covalent character. Furthermore, the XPS spectrum of functionalized fabrics exhibited peaks corresponding to Cu¹⁺ and Cu²⁺ ions, assigned to the Cu₂O and CuO phases, respectively. Electron diffraction patterns confirmed copper oxide crystalline phases, where Cu₂O was indexed in the cuprite system and CuO in the tenorite system. Regarding morphology, no defined forms of CuO_x were observed on the cotton surface, regardless of the salt used for treatment. Likewise, all fabrics functionalized with CuO_x inhibited the growth of Escherichia coli and Pseudomonas aeruginosa strains by more than 99%. Therefore, cotton fabrics functionalized with a mixture of Cu₂O and CuO have excellent antimicrobial properties that can be used in environments with a high bacterial load.