Near infrared laser-mediated hydrophilicity-to-hydrophobicity switch of copper sulfide nanoflowers coating on cotton fabric

To our knowledge, surface hydrophobicity is normally fabricated by hydrophobic or fluorinated materials; however, it can be predicted. So, it is exciting and high value that using a single hydrophilic material directly obtains a hydrophobic surface, which may be a promising and significant aspect and a great challenge in surface and interface science. Herein, the copper sulfide (CuS) nanoflowers were in-situ deposited on the cotton fabric after cotton fabric was incubated with copper(II) chloride dihydrate and thioacetamide stirring for 3 h at 80 °C, labelled as Cot@PTA@CuS. Then, Cot@PTA@CuS was treated by near infrared (NIR) laser irradiation at 808 nm, recorded as Cot@PTA@CuS-NIR. Interestingly, Cot@PTA@CuS-NIR exhibits good hydrophobicity with WCAs of 136.5 ± 3.5° and hydrophobic stability within 30 min. Notably, the hydrophobicity of Cot@PTA@CuS-NIR is created without using the lower surface free energy materials, possessing significant progressiveness compared with conventional surface hydrophobicity fabricated by hydrophobic or fluorinated materials. The X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) demonstrate the formation of cuprous oxide (Cu2O) after NIR laser irradiation. Subsequently, the polydimethylsiloxane (PDMS) was selected to encapsulate CuS nanoflowers with improving the stability of CuS nanoflowers and obtaining superhydrophobicity, recorded as Cot@PTA@CuS-NIR@PDMS, achieving the results of killing two birds with one stone. Cot@PTA@CuS-NIR@PDMS also has an excellent photothermal effect and UV resistance. Finally, Cot@PTA@CuS-NIR@PDMS was used for efficient oil/water separation. Overall, this work renders a novel, feasible, and facile idea for gaining surface hydrophobicity by hydrophilic CuS nanoflowers with NIR laser irradiation, inspiring more scholars to create surface hydrophobicity by hydrophilic materials.