Titanium dioxide (TiO2) is well established as one of the most common photocatalysts used for many environmental, anti-pollution and antibacterial applications. However, in this work, novel photocatalytic TiO2 nanopowders were modified with additions of 1 mol% copper, zinc or copper + zinc (with various Cu:Zn ratios). These were prepared via a green sol%gel route and thermally treated at 450 °C. For the first time, a direct comparison of the effects of these two modifying agents was performed, both as single and co-substitution. The compounds were thoroughly characterised by means of advanced X-ray diffraction (Whole Powder Pattern Modelling, WPPM) and spectroscopic methods (Raman and UV%vis). For functional properties, the photocatalytic activity in the gas-solid phase (nitrous oxides (NOx) and isopropanol degradation (VOCs)) was tested under UV and visible light, and antibacterial activity against Gram positive and Gram negative bacterial strains was also investigated. Neither copper nor zinc entered into the TiO2 structure, but nucleated as oxides at the surface of titania nanoparticles, thus creating a nano-heterojunction between the semiconductor materials; this also retarded the anatase-to-rutile phase transition. When comparing and contrasting their functional properties, it was found that Zn modification gave greater photocatalytic activity than that with Cu. On the contrary, for antibacterial activity, copper was shown to be a better additive. Co-modification with both metals did not improve the antibacterial behaviour, but did lead to an increase in photocatalytic activity in some cases.
COBISS.SI-ID: 2229607
In order to avoid the potential health problems associated with nanosized particles, solvothermal synthesis was employed for the preparation of doped and undoped, hierarchically structured, spherical anatase, ranging in size from 2 to 6.4 μm. The resulting particles showed a mesoporous microstructure and, consequently, a high specific surface area of up to 208 m2 g−1. A detailed SEM analysis confirmed the hierarchical structure of the spheres, consisting of subunits with a size from 10 to 21 nm, depending on the starting composition. For the thermal stabilization of the anatase phase and to slow down the growth of the nanosize particles during heating, various dopants were added to the anatase. As a result, anatase codoped with Ce, Si and Zr exhibited a high thermal stability up to 1000 °C, compared to 700 °C for the undoped anatase. The photocatalytic activities of the synthesized solids were quantitatively evaluated by monitoring the rate of degradation for isopropanol in a gas phase reactor system. Among the samples that were heat treated at 500 °C, the highest photocatalytic activity was exhibited by the Ce-doped sample. In the case of the samples which were heat treated at 1050 °C, the undoped and Ce-doped samples were inactive under UV light, while the samples doped with Ce, Zr and Si exhibited considerable photocatalytic activity.
COBISS.SI-ID: 2102375
Extremely well-preserved limestone monuments were discovered in healing mud – fango at the archaeological site of Varaždinske Toplice that were more than 1500 years exposed to sulphur substances, anaerobiosis and elevated temperature from a nearby thermal spring. Characteristics of this peculiar environment including a neutral pH and heavy metals were crucial for long-term preservation of limestone monuments despite high concentration of microorganisms and their metabolic activities.
COBISS.SI-ID: 37578285
Microbial biofilms colonize and contribute to deterioration of stone surfaces. Some biofilms are particularly well observed because they synthetise diverse pigments. In this study, yellow biofilms from selected caves were spectroscopically characterized, and frequently occuring bacterial taxa in these structures were identified.
COBISS.SI-ID: 38362157
The book chapter comprehensively summarizes problems of biofilms around lamps in show caves which deteriorate the substrate on which they are attached: species composition, transport of inoculum, survival strategies of organisms at stressful conditions, mechanisms of biodeteriration, remediation actions for colonized surfaces and methods of biofilm growth control.
COBISS.SI-ID: 39000365