Antifungal properties of anatase and rutile crystallites isolated from commercial titania P25 photocatalyst were investigated by mycelium growth in the dark and under indoor light. Investigated fungi, i.e., Pseudallescheria boydii, Scedosporium apiospermum, Pseudallescheria ellipsoidea, Scedosporium aurantiacum, Aspergillus versicolor, Aspergillus flavus, Stachybotrys chartarum, Penicillium chrysogenum, Aspergillus melleus, were isolated from air and from moisture condensed on walls. Anatase and rutile were isolated from homogenized P25 (homo-P25) by chemical dissolution, and then purified by washing and thermal treatment. For comparison, homo-P25 was also thermally treated at 200 °C and 500 °C. Titania samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and scanning transmission electron microscopy (STEM). It was found that properties of titania, i.e., band-gap energy, impurities adsorbed on the surface, nanoparticle aggregation, and kind of fungal structure, highly influenced resultant antifungal activities. It is proposed that some fungi could uptake necessary water and nutrient from titania surface. It was also found that even when differences in mycelium growth were not significant, the sporulation and mycotoxin generation were highly inhibited by light and presence of titania.

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Commercial titania photocatalysts were modified with silver and gold by photodeposition, and characterized by diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). It was found that silver co-existed in zero valent (core) and oxidized (shell) forms, whereas gold was mainly zero valent. The obtained noble metal-modified samples were examined with regard to antibacterial (Escherichia coli (E. coli)) and antifungal (Aspergillus niger (A. niger), Aspergillus melleus (A. melleus), Penicillium chrysogenum (P. chrysogenum), Candida albicans (C. albicans)) activity under visible-light irradiation and in the dark using disk diffusion, suspension, colony growth (“poisoned food”) and sporulation methods. It was found that silver-modified titania, besides remarkably high antibacterial activity (inhibition of bacterial proliferation), could also decompose bacterial cells under visible-light irradiation, possibly due to an enhanced generation of reactive oxygen species and the intrinsic properties of silver. Gold-modified samples were almost inactive against bacteria in the dark, whereas significant bactericidal effect under visible-light irradiation suggested that the mechanism of bacteria inactivation was initiated by plasmonic excitation of titania by localized surface plasmon resonance of gold. The antifungal activity tests showed efficient suppression of mycelium growth by bare titania, and suppression of mycotoxin generation and sporulation by gold-modified titania. Although, the growth of fungi was hardly inhibited through disc diffusion (inhibition zones around discs), it indicates that gold does not penetrate into the media, and thus, a good stability of plasmonic photocatalysts has been confirmed. In summary, it was found that silver-modified titania showed superior antibacterial activity, whereas gold-modified samples were very active against fungi, suggesting that bimetallic photocatalysts containing both gold and silver should exhibit excellent antimicrobial properties.

Modified titania photocatalysts were synthesized by the pressure method using titanium(IV) oxide from Grupa Azoty Zakłady Chemiczne “Police” S.A., Police, Poland, and d-glucose solution. Characterization of obtained composites was performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis, and measurements of zeta potential and specific surface area (SSA). The possibility of using glucose-titania composites as photocatalysts for simulated solar-assisted disinfection against gram-negative Escherichia coli and gram-positive Stapchyloccocus epidermidis bacteria were examined in two reaction systems, i.e., for suspended and immobilized photocatalysts (on the concrete). It was found that an increase in the d-glucose concentration, i.e., higher carbon content, led to a decrease in antibacterial properties. The sample obtained from 1% of d-glucose solution at 100 °C (TiO2-1%-G-100) showed superior photocatalytic activity under UV-Vis irradiation toward both bacteria species. Water disinfection was more efficient for suspended photocatalyst than that for supported one, where complete disinfection was reached during 55–70 min and 120 min of irradiation, respectively. For the first time, it has been shown that titania modified with monosaccharides can be efficiently used for water disinfection, and the immobilization of photocatalyst on the concrete might be a prospective method for public water supplies.

Regarding catalytic and plasmonic properties of gold nanoparticles (NPs), the novel area of research on photocatalytic gold properties has been recently started. In contrast with catalytically active gold NPs, where nanosized gold is recommended, our results showed that polydispersity of deposited gold NPs on semiconducting support was beneficial for photocatalytic activity under visible light irradiation. It is thought that wide size/shape distribution of gold NPs, and thus the ability of absorption of light in a wide wavelengths range is responsible for the high level of photoactivity. Though desirable absorption properties of plasmonic photocatalysts can be easily obtained by preparation of nanoparticles of different sizes and shapes, their photocatalytic activities under visible light irradiation are still low and should be enanced. The improvement of photocatalytic activities under visible light irradiation was achieved by enlargement of interfacial contact between titania and NPs of noble metals, extension of photoabsorption ranges (by preparation of NPs of various sizes and shapes or composed of two kinds of noble metals), and by deposition of noble metals NPs on faceted titania, i.e., octahedral (OAPs) and decahedral (DAPs). Plasmonic photocatalysts composed of titania and NPs of silver, gold or copper showed also high antiseptic properties under visible light irradiation, due to possible synergism of antiseptic properties of noble metals and photodisinfection properties of photocatalyst, since reactive oxygen species or photogenerated holes are formed on the surface of irradiated semiconductor.

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Antibacterial properties of 15 titania photocatalysts, mono-and dual-modifi ed with nitrogen and carbon were examined. Amorphous TiO 2 , supplied by Azoty Group Chemical Factory Police S.A., was used as titania source (Ar-TiO 2 , C-TiO 2 , N-TiO 2 and N,C-TiO 2 calcined at 300 o C, 400 o C, 500 o C, 600 o C, 700 o C). The disinfection ability was examined against Escherichia coli K12 under irradiation with UV and artifi cial sunlight and in dark conditions. It has been found the development of new photocatalysts with enhanced interaction ability with microorganisms might be a useful strategy to improve disinfection method conducted under artifi cial sunlight irradiation. The effi ciency of disinfection process conducted under artifi cial sunlight irradiation with carbon (C-TiO 2 ) and carbon/nitrogen (N,C-TiO 2 ) photocatalysts was similar as obtained under UV irradiation. Furthermore, during dark incubation, any toxicity of the photocatalyst was noted.

StreszczenieWstęp: Grzyby pleśniowe obecne w kurzu lub rozwijające się na pożywce z materiałów budowlanych są jedną z głównych przyczyn pogarszania się jakości powietrza w pomieszczeniach użytkowych i mieszkaniach. Dotychczas opracowane systemy oczyszczania powietrza nie gwarantują całkowitego usunięcia czynników szkodliwych dla zdrowia człowieka i zwierząt, dlatego szuka się rozwiązań alternatywnych. Jedno z nich polega na fotokatalizie z wykorzystaniem ditlenku tytanu (TiO 2 ), którego przeciwgrzybowe właściwości nie zostały w pełni poznane. Celem badania była ocena wpływu TiO 2 aktywowanego światłem widzialnym na przeżywalność grzybów pleśniowych. Materiał i metody: W badaniach wykorzystano komercyjny ditlenek tytanu P 25 (Aeroxide P 25, prod. Evonik, Niemcy) i ditlenek tytanu modyfikowany azotem (N-TiO 2 ). Zastosowano sztuczne światło słoneczne (UV-VIS -ultraviolet -visible spectroscopy, ultrafiolet -promieniowanie widzialne). Aktywność przeciwgrzybową fotokatalizatorów określono dla Penicillium chrysogenum i Aspergillus niger. Przeżywalność grzybów wyznaczono na podstawie zmian ich stężenia w zawiesinie. Wyniki: Stwierdzono, że N-TiO 2 ma lepsze właściwości biobójcze względem P. chrysogenum i A. niger niż komercyjny fotokatalizator P 25. Do pełnej eliminacji grzybów konieczne jest aktywowanie N-TiO 2 sztucznym światłem słonecznym przez co najmniej 3 godz., natomiast stężenie fotokatalizatora nie może być mniejsze niż 0,01 g×dm -3 dla P. chrysogenum i 0,1 g×dm -3 dla A. niger. Wnioski: Ditlenek tytanu modyfikowany azotem wykazuje dobre właściwości fotokatalityczne w świetle UV-VIS i w przyszłości może być wykorzystywany w filtrach wodnych lub oczyszczaczach powietrza do eliminacji czynników szkodliwych, w tym grzybów pleśniowych. Med. Pr. 2018;69(1):59-65 Słowa kluczowe: fotokataliza, ditlenek tytanu, UV-VIS, Penicillium chrysogenum, Aspergillus niger, oczyszczanie powietrza wewnętrznego Abstract Background: In public and residential buildings, fungi are usually found in the dust or growing on building materials medium such. It has been known that a number of their spores may contaminate the indoor environment and deteriorate air quality in accommodation spaces. Previously designed air cleaning systems do not guarantee a complete removal of agents harmful to humans and animals. Therefore, there is a great need to develop a new solution to remove molds from indoor air. In recent years, photocatalysis based on titanium dioxide (TiO 2 ) has been proposed as an effective method for air pollutants removal. The aim of the study was to determine the effect of TiO 2 activated under artificial sun light (UV-VIS -ultraviolet -visible spectroscopy) on survival of fungi Penicillium chrysogenum and Aspergillus niger. Material and Methods: The commercial P 25 (Aeroxide P 25, Evonik, Germany) and nitrogen modified titanium dioxide (N-TiO 2 ) were used. The microbiological study was performed using Penicillium chrysogenum and Aspergillus niger fungi. The survival of fungi was determined on the basis of changes in their con...