Novel thermally conductive coating for cotton fabrics based on reduced graphene oxide decorated with in situ synthesized silver nanoparticles

The application of thermally conductive materials as coating on fiber surfaces represents an innovative technology solution for conveying heat dissipation capability to IR-opaque textiles. In this work, a sustainable and scalable approach to manufacture a hybrid nanocomposite coating for cotton, formed by Reduced Graphene Oxide (RGO) sheets functionalized by histidine (His) and decorated by Ag nanoparticles (NPs), is reported for increasing thermal conductivity of cotton fabrics. Tens nm in size Ag NPs were synthesized, in situ, at the coordinating sites of the His-RGO modified cotton impregnated by H2O/CH3OH solutions of the AgNO3 precursor, under UV-light exposure, without using chemical reductants. The physical chemical properties of the nanocomposite modified fabrics were comprehensively investigated, integrating chemical, structural and morphological analysis, with characterizations of their thermal, electrical, oxygen permeability, surface wettability and mechanical properties. Thermal conductivity of cotton was measured by Differential Scanning calorimetry (DSC) technique, which was here validated by Transient Plane Source (TPS) method, assessing the effectiveness of DSC in measuring thermal conductivity of textiles. The resulting coating exhibits a thermal conductivity, which was twice as high as untreated cotton, maintaining its breathability, increasing its flexibility, while simultaneously reducing its wettability. This notable enhancement can be attributed to the synergistic effect of the conductive Ag nanostructures formed among the His-RGO sheets within the nanocomposite, and it matches the thermal conductivity achieved by current state-of-the-art methods, while offering additional advantages of being more eco-friendly, scalable, and sustainable. The reported characterization of the structural properties of the achieved coating opens the venue to interesting perspectives towards its application in passive conducting cooling textiles for personal thermal comfort management.