Novel
photoactive and enzymatically active nanomotors were developed
for efficient organic pollutant degradation. The developed preparation
route is simple and scalable. Light-absorbing polypyrrole nanoparticles
were equipped with a bi-enzyme [glucose oxidase/catalase (GOx/Cat)]
system enabling the simultaneous utilization of light and glucose
as energy sources for jet-induced nanoparticle movement and active
radical production. The GOx utilizes glucose to produce hydrogen peroxide,
which is subsequently degraded by Cat, resulting in the generation
of active radicals and/or oxygen bubbles that propel the particles.
Uneven grafting of GOx/Cat molecules on the nanoparticle surface ensures
inhomogeneity of peroxide creation/degradation, providing the nanomotor
random propelling. The nanomotors were tested for their ability to
degrade chlorophenol, under various experimental conditions, that
is, with and without simulated sunlight illumination or glucose addition.
In all cases, degradation was accelerated by the presence of the self-propelled
nanoparticles or light illumination. Light-induced heating also positively
affects enzymatic activity, further accelerating nanomotor diffusion
and pollutant degradation. In fact, the chemical and photoactivities
of the nanoparticles led to more than 95% removal of chlorophenol
in 1 h, without any external stirring. Finally, the quality of the
purified water and the extent of pollutant removal were checked using
an eco-toxicological assay, with demonstrated significant synergy
between glucose pumping and sunlight illumination.
In this contribution, four different commercial TiO2 catalysts (P25, P90, PC105, and PC500) were screened for the photocatalytic production of hydrogen using ethanol as the sacrificial agent. The physico-chemical properties of the TiO2 powders were characterized by using different methods. The photocatalysts mainly vary in the ratio of anatase and rutile phases, and in the surface area. It was found that the photocatalytic activity is governed by the surface area of the photocatalyst. Pure TiO2,PC500 showed the best performance, and in comparison to P25, the activity was more than ten times higher due to its high surface area of about 270 m2 g−1. For further improvement of the photocatalytic activity, platinum nanoparticles (PtNPs) were immobilized onto TiO2,PC500 using two methods: a colloidal approach and a photodeposition method. For the reduction of the platinum salt precursor in the colloidal approach, different green reducing agents were used in comparison to ascorbic acid. The obtained platinum nanoparticles using natural reductants showed a higher photocatalytic activity due to the formation of smaller nanoparticles, as proven by transmission electron microscopy (TEM). The highest activity was obtained when mangosteen was used as the green reducing agent. Compared to ascorbic acid as a classical reducing agent, the photocatalytic activity of the Pt@TiO2,PC500 prepared with mangosteen was about 2–3 times higher in comparison to other as-prepared photocatalysts. The Pt@TiO2,PC500 catalyst was further studied under different operating conditions, such as catalyst and sacrificial agent concentration.
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