Abstract
One of the current research objectives is the development of new films for the conservation of glass heritage objects. The value of historical glass objects is given by the technology and raw materials used in production as well as their transparency and color. Their colors are correlated with oxide composition rich in transitional metals, which decrease resistance of corrosive agents from the atmosphere. In this paper, SiO2-ZnO gels have been designed to protect historical glass objects. The sol–gel method used to obtain gels is a powerful tool for functionalizing different materials. An important functionalization is the antibacterial activity. By applying a gel, the coated material is able to decrease the growth of bacteria. After deposition, some gels must be strengthened by heat treatment. The effect of ZnO content (10 mol% and 20 mol%) on the properties of the studied gels was investigated by Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and antibacterial tests. Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and the halotolerant bacterium, Virgibacillus halodenitrificans, isolated from a salt crystal from Unirea mine, Slănic Prahova, Romania, were used. The gel Gel 2 (SiO2-ZnO (20 mol%)) showed the best properties.
Highlights
Heritage objects from glass such as windows [1], stained glass windows [2,3], pottery [4], and mosaics [5,6] can be protected from the destructive activity of bacteria and environmental acid agents by utilizing organic or inorganic coatings
The results reveal that 1% doping of the transparent hybrid thin film with silver ions resulted in high antibacterial properties [20]
The absorption bands at 460 cm−1 in the silica gel spectrum are shifted to smaller wavenumbers in ZnO-containing gels, which could be attributed to the formation of the Zn–O–Si bond
Summary
Heritage objects from glass such as windows [1], stained glass windows [2,3], pottery [4], and mosaics [5,6] can be protected from the destructive activity of bacteria and environmental acid agents by utilizing organic or inorganic coatings. Historic glass objects can be preserved by coating with silica gels [7,8,9] Sometimes they are heat-treated at temperatures below. Due to the different softening and melting temperatures of the glasses, the working method and the composition of the protective gels must be adapted. The effect of ZnO on the antibacterial properties and transparency of SiO2 -ZnO gels obtained by sol–gel method and heat-treated at 400 ◦ C were investigated. It was evaluated the possible growth-inhibitory effect over a wide concentration range (0.05–2 mg/mL) on reference Gram-negative and Gram-positive bacterial strains, Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923. Along with these relevant model microorganisms, Virgibacillus halodenitrificans, isolated from the natural environment from Romania [22,23], was used for the studies
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