THESIS
2022
1 online resource (xvii, 106 pages) : illustrations (some color)
Abstract
The COVID-19 pandemic has transformed our social behaviors. Regular disinfection
actions using conventional disinfectants could be one most effective way to suppress
the virus transmission. While frequent spraying operations could be compulsory.
Photocatalytic coatings technology provides a reliable, safe, and continuously effective
surface disinfection solution which becomes more widely used both in Hong Kong and
globally. However, there has not been any testing protocols or standard developed to
evaluate the long-term performance of the photocatalyst coating in an actual
environment.
In this thesis, I present the process of evaluating the anti-microbial performance of photocatalytic wall paint. The evaluation was conducted through an onsite study for at
least 100 days in two primary s...[
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The COVID-19 pandemic has transformed our social behaviors. Regular disinfection
actions using conventional disinfectants could be one most effective way to suppress
the virus transmission. While frequent spraying operations could be compulsory.
Photocatalytic coatings technology provides a reliable, safe, and continuously effective
surface disinfection solution which becomes more widely used both in Hong Kong and
globally. However, there has not been any testing protocols or standard developed to
evaluate the long-term performance of the photocatalyst coating in an actual
environment.
In this thesis, I present the process of evaluating the anti-microbial performance of photocatalytic wall paint. The evaluation was conducted through an onsite study for at
least 100 days in two primary schools in Hong Kong, using adenosine triphosphate
(ATP) bioluminescence assay. About 500 sqm of wall areas are painted in both primary
schools and samples are collected on both painted and unpainted areas adopting
randomized controlled trials for the measurement. The selected locations include
different types of surfaces and locations that are in frequent contact with students and
staff. By comparing the measured values from the experimental group (locations with
the photocatalytic paint) and the control group (locations without the photocatalytic
paint) with long-term monitoring, the painted area shows consistently lower in
microbial activities, reflected in lower RLU values, with 0.5 log to 2.5 log difference
in various locations in both schools. The results confirm that the photocatalytic paint is
effective in reducing microbial activities on wall surfaces in both indoor and semi-outdoor
settings. Meanwhile, these results also demonstrate that the ATP
bioluminescence assay conducted in a systematic approach can serve as a reference to
the quick evaluation of the microbial activity following a general data processing
protocol as discussed in this thesis.
I also demonstrate the inhibitory activity of a novel visible light active photocatalyst,
boron-doped bismuth oxybromide (B-BiOBr), towards SARS-CoV-2 in 10% fetal
bovine serum without light or under irradiation at 426 nm by a light emitting diode
(LED). SARS-CoV-2 inactivation in the presence of B-BiOBr with LED irradiation
achieved > 99.999% (5.32-log) in less than 5 minutes, which is 400 to 10,000 times
higher than those achieved with conventional photocatalysts of tungsten or titanium
oxide nanomaterials, respectively. Even without LED irradiation, B-BiOBr in the dark
inactivated >99.9% (3.32-log) of SARS-CoV-2. LED irradiation at 426 nm alone,
without the photocatalyst, achieved about 71% (0.54-log) inactivation. The remaining
1.46-log inactivation came from the photocatalytic-induced reactive oxygen species.
This three-pronged approach that leverages different modes of action to engineer
disinfection strategies shows the potential to mitigate the environmental transmission of emerging pathogens.
Last but not least, a potential technology development routine for photocatalysis-based
long-lasting disinfection solution is proposed. Results from a few ongoing research are
supplemented.
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