Innovative Ag@Cu/white sand and polysaccharide based nanocomposites: A simple route to conductive and antibacterial paper coatings

In this work, we presented a simple method for preparing nanocomposite pigments via doping the naturally occurring white sand pigment using silver (Ag) and copper (Cu). The nanocomposites (Ag@WS, Cu@WS, and Ag&Cu@WS) were produced in two suspensions at 25 % and 50 % w/v concentrations, utilizing casein (Cas) and nanostarch (NanoSt) as bio-friendly binders. The prepared nanocomposite pigments were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction crystallography (XRD), and dynamic light scattering (DLS), as well as topographical analysis including scanning electron microscopy (SEM), EDX, and transmission electron microscopy (TEM). The coated paper sheets were characterized using topographical analysis and mechanical, optical, physical, and electrical properties. The antimicrobial activity assay was carried out on the coated paper sheets using the most infectious microbial pathogens. FTIR and XRD analyses confirmed the presence of Cas and NanoSt in the samples. The addition of white sand (WS) and doped nano-metals influenced the crystallographic structure of the polysaccharides. A small amount of Ag, Cu, and Ag&Cu nanoparticles was investigated through EDX. The white sand was a plate structure decorated with spherical Ag, Cu, and Ag&Cu nanoparticles, with an average size of about 147, 105, and 78 nm, as observed from TEM images and DLS. The antimicrobial activity assays revealed that nanocomposite pigment embedded with bimetallic Ag&Cu nanoparticles exhibited a synergistic effect, resulting in enhanced broad-spectrum antibacterial and antifungal activities. The electrical performance of the coated paper was enhanced by using Ag&Cu@WS nanocomposite pigment. Incorporating 50 % Cu@WS into the coating resulted in significant improvements in the mechanical properties of the paper. Specifically, tensile strength increased by 6.3 N/mm, tensile index by 69.06 N m/g, stretching by 1.68 %, tensile energy absorption by 71.4 J/m2, burst strength by 257.75 kPa, and burst index by 2.83 kPa m2/g. Furthermore, incorporating 50 % Ag&Cu@WS increased the opacity to 93.2 % and reduced the roughness of the coated paper by 36 % compared to using 50 % Ag@WS or 50 % Cu@WS alone. [Display omitted] •Multifunction paper coating nanocomposites based Cas, NanoSt, WS dopped Ag and Cu individual and together.•Coated paper with Ag&Cu@WS enhances the electrical performance and antimicrobial activity.•Paper sheets coated with Ag&Cu@WS present an improvemen