TiO2–Ag–NP adhesive photocatalytic films able to disinfect living indoor spaces with a straightforward approach

Abstract

TiO2–Ag doped nanoparticulate (TiO2–Ag–NP) adhesive photocatalytic films were used to assess the ability in dropping down the burden of indoor microbial particles. The application of an easy-to use photocatalytic adhesive film to cleanse indoor living spaces from microbial pollution, represents a novelty in the field of photocatalytic devices. Reduction was attained by photocatalysis in selected spaces, usually with overcrowding (≥ 3 individuals) in the common working daily hours, and upon indoor microclimate monitoring. TiO2–Ag doped nanoparticulate (TiO2–Ag–NP) adhesive photocatalytic films were applied within five types of living spaces, including schools and job places. The microbial pollution was assessed at time 0 (far from routine clean, ≥ 9 h) and throughout 2–4 weeks following the photocatalyst application by relative light unit (RLU) luminometry and microbial indirect assessment (colony forming units per cubic meter, CFU/m3). TiO2–Ag–NP photocatalyst reduced RLU and CFU/m3 by rates higher than 70% leading to RLU ≤ 20 and microbial presence ≤ 35 CFU/m3. The described TiO2–Ag–NP is able to reduce microbial pollution to the lowest RLU threshold (≤ 20) within 60 min in open daylight in a standardized test room of 100 m2. The correlation between RLU and CFU/m3 was positive (r = 0.5545, p < 0.05), assessing that the microbial reduction of indoor areas by the TiO2–Ag–NP adhesive film was real. Titania photocatalysts represent promising tools to ensure air cleaning and sanitization in living indoor microclimates with a low cost, feasible and straightforward approach. This approach represents an easy to handle, cost effective, feasible and efficacious approach to reduce microbial pollution in indoor spaces, by simply attaching a TiO2–Ag–NP adhesive film on the wall.

On coming back, the scaring COVID‐19 concern. Addressing indoor microclimates with innovative and straightforward solutions to prevent SARS‐CoV2 spreading

“…14 Considering a seasonal period of 1 year (12 months), and adopting a single type of exponential smoothing and an additive type of seasonality, the value of alpha was 0.6182 for the forecast with the application of an indoor safety device (ISD) (Figure 1B), in respect to α = 0.9999 (p = 0.00148), considering the distribution of SARS-CoV2infected people during the investigated year (Figure 1A). The application of TiO 2 photocatalysis in indoor microclimates, particularly if this ISD is easy-to-use, and behaves as a straightforward technology, and has an eco-friendly availability, 9 should reduce airborne nanoparticles from the indoor space, particularly if also the bacterial growth rate is drastically reduced. 9,15 The approach ensures a healthy microclimate and living environment for people staying in an indoor…”

“…Although we evaluated bacterial rate growth in our research, 9 the photocatalytic technology is based on a titania approach, as well. 9,11 The results are summarized in Figure 1.…”

“…Titania (TiO 2 ) photocatalysts are nontoxic, 9 they are able to destroy bacterial and other microbes via the photo-oxidation of water (usually as a layer on the photocatalyst device) to generate ROS, such as hydroxyl radicals (OH•). Therefore, devices equipped with TiO 2 -photoicatalysts are enabled to greatly damage microbial lipid membranes and protein thiols, 9 as well as lipid envelopes in coated viruses.…”

“…Titania (TiO 2 ) photocatalysts are nontoxic, 9 they are able to destroy bacterial and other microbes via the photo-oxidation of water (usually as a layer on the photocatalyst device) to generate ROS, such as hydroxyl radicals (OH•). Therefore, devices equipped with TiO 2 -photoicatalysts are enabled to greatly damage microbial lipid membranes and protein thiols, 9 as well as lipid envelopes in coated viruses. 11 TiO 2 -mediated photocatalysis can reduce the rate of virus growth by 99.9% within 6 h. 11 We recently described a device equipped with a TiO 2 photocatalyst as a straightforward, easy-to-use, and eco-friendly tool to cleanse indoor spaces.…”

“…Based on recently published data from our research group, where the microbial growth rate decreased by the same extent, 9 that is, 99.9%, we evaluated a forecast analysis of the increase in SARS-CoV2 infected people, considering the period from January 2021 to January 2022 and data publicly available from the Italian Ministry of Health, 13 considering that the TiO 2 technology reduces gradually the incidence of infected people, and that reduction depends on seasonality and increases, for cumulative effect, along with prolonged use. Although we evaluated bacterial rate growth in our research, 9 the photocatalytic technology is based on a titania approach, as well. 9,11 The results are summarized in Figure 1.…”