The preparation of coatings based on silver nanoparticles and TEOS

Zahvaljujući dobrim fizikalnim i kemijskim svojstvima te brojnim područjima potencijalne uporabe nanočestice srebra izazvale su znatan interes u znanstvenoj zajednici i gospodarstvu. Srebro je od davnina poznato po svome antibakterijskom djelovanju, netoksičnosti i neškodljivosti za okoliš. Stoga broj različitih primjena nanočestica srebra kontinuirano raste, posebice u području zaštite površina od rasta mikroorganizama. U ovom su radu pripravljene nanočestice srebra u svrhu nanošenja na kamenu površinu kao zaštitnog baktericidnog sloja. Srebrne nanočestice su pripravljene redukcijom srebrovog nitrata, AgNO3, s natrijevim borhidridom, NaBH4, te su nanešene na umjetni mramor koji je ranije pripravljen prešanjem i sinteriranjem praha CaCO3 u tablete. Nadalje, kako bi se smanjila brzina otpuštanje nanočestica srebra te hidrofobirala površina, na površinu je nanesen TEOS te potom pušten da hidrolizira i gelira. Pripravljeni uzorci potom su karakterizirani rendgenskom difrakcijskom analizom (XRD), infracrvenom spektroskopijom s Fourierovim transformacijama (FTIR) i difuznom refleksijskom spektroskopijom (DRS). Hidrofobnost pripremljenih uzoraka s TEOS-om ispitana je mjerenjem kontaktnog kuta. Provedeni mikrobiološki testovi s bakterijom Escherichia coli dali su negativne rezultate što ukazuje da u korištenim koncentracijama nanočestice srebra nisu učinkovite kao baktericidno sredstvo za zaštitu kamenih površina.Silver nanoparticles have received considerable attention due to their attractive physical and chemical properties and potential applications with high academic and industrial impacts. Colloidal silver have been known for a long time to possess antimicrobial properties and also to be nontoxic and environmental friendly. That is why the aplications of silver nanoparticles increase continuously, especially for antmicrobial protection of surfaces. In this study nanoparticles of silver were prepared with the purpose of using them as coatings for protection of stone surfaces from bacteria growth. Silver nanoparticles were prepared through chemical reduction of silver nitrate, AgNO3, by sodium borohydride, NaBH4, and were applied as a coating on artificial marble stone surface, which was previously made by pressing and sintering CaCO3 powder into tablets. In addition to improve efficiency of silver nanoparticles by attaining time release of silver as well as hydrophobicity of the stone surface, TEOS was applied on the surface and allowed to hydrolize and form gel. Tablets were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and diffuse reflectance spectroscopy (DRS. Hydrophobicity of the tablets with gel coating was determined through contact angle measurement. Conducted microbiological tests of the samples using bacteria Escherichia coli have shown negative results which points out that in applied concentration silver nanoparticles are not effective as antimicrobial agent for stone surface protection