Study of physical, optical and biological properties of antibacterial bank-note paper including Nano-silver

The purpose of this research is production of antibacterial banknote paper using silver nanoparticles. Bank-notes have been a part of commercial exchanges from the past. There are about 8 billion Bank-note leaves in Iran that have been in circulation in a 5-year period. This amount of Bank-notes and the frequency with which they are touched can promote transmission of many pathogenic factors, especially bacteria. Based on scientific research results, Bank-notes are seriously contaminated and must be considered a potential danger to society. In the field of antibacterial paper, an investigation was performed on two materials, chitosan and Nanosilver particles to produce filter paper and Nanosilver and chitosan particles were applied as negatively and positively charged layers over the fibers (LBL), respectively. It was found that with increasing numbers of the layers, there were increases antibacterial properties.
In this study, Laboratory pulp made from Iranian cotton fiber, were used to produce antibacterial bank-note paper. To prepare above mentioned pulp, its freeness was received to 12 oSR by laboratory Defibrator. Then, obtained pulp was bleached by H2O2 in 120 oC, pH=11, 120min. and after refining to 34 oSR, were adjusted 3.1% consistency and neutral pH to adding additives. Antibacterial Nano-silver with amounts of 25, 50, 75 and 100 ppm as antibacterial material and 0.3% Cationic-Polyacrylamid (C-PAM) as retention aids were used as additives. Then, standard handsheets 90 g/m2 were made from above pulps and compared to reference handsheets in pHysical and optical properties. For biological test of papers, bacterial inhibition measurment of S.Aureus and E.Coli as to indicator bacteria in biological tests was used.
Results showed that increasing in nano-silver consumption was led to increasing in ash content, smoothness and opacity of paper; lacking in brightness and had no effect in wax test and bulk of paper. Biological test results showed that by increasing in nano-silver consumption, antibacterial properties of paper and consequently bacterial inhibition area were increased .
According to all results, 25 ppm of nano-silver consumption was determined as optimized treatment. In this consumption level of nanosilver, pHysical and optical properties of paper are very similar to control samples with accepted antibacterial properties. By adding of low levels of Nanosilver in pulp suspension and then applying supplemental refining of the fiber furnish, both antibacterial and mechanical properties of Bank-note paper likely will be increased.