Copper sulfate-embedded and copper oxide-embedded filter paper and their antimicrobial properties

In this study, copper sulfate was successfully embedded in filter paper through soaking and copper oxide was successfully embedded in filter paper via in situ technique using the copper sulfate-embedded paper as the starting material. Using color analysis, the filter paper soaked with copper sulfate solution was observed to change color from white to blue, indicating the presence of embedded copper sulfate salts. Furthermore, upon soaking this filter paper with sodium hydroxide solution, the color changed from blue to brown, indicating the presence of copper oxide. X-ray diffraction (XRD) spectroscopy confirms the observed results of the color analysis. Scanning electron microscopy (SEM) and electron dispersive x-ray (EDX) spectroscopy were used to determine the surface morphology and elemental composition of the samples, respectively. The antimicrobial property of the filter paper with copper-based particles was tested against Gram-negative bacterium (Escherichia coli) and Gram-positive bacterium (Staphylococcus aureus), and two species of fungi (Candida albicans and Aspergillus niger) using disc diffusion method. The reactivity of the copper sulfate-embedded filter paper against E. coli was found to be severe, whereas that against S. aureus was moderate. The reactivity of the samples against the two fungi was mild, having a relatively small zone of inhibition. For the copper oxide-embedded paper, the reactivity of the paper to both bacteria was moderate, whereas it shows no reactivity to C. albicans and only a mild reactivity to A. niger. After 60 min of contact with Escherichia coli, both the copper sulfate-embedded and copper oxide-embedded filter papers reduced the amount of colony forming unit to more than 99.9%.