The role of Pt on photocatalytic substrates such as TiO 2 (P25) for the decomposition of organic pollutants is still controversial in the scientific community. The well-observed behavior of an optimum catalytic activity as a function of the Pt loading is usually explained by the shift from charge separation to charge recombination behavior of Pt clusters. However, experiments supporting this explanation are still lacking to give a concise understanding of the effect of Pt on the photocatalytic activity.Here, we present an experimental study that tries to discriminate the different effects influencing the photocatalytic activity. Using atomic layer deposition in a fluidized bed reactor, we prepared TiO 2 (P25) samples with Pt loadings ranging from 0.04 wt % to around 3 wt %. In order to reveal the mechanism behind the photocatalytic behavior of Pt on P25, we investigated the different aspects (i.e., surface area, reactant adsorption, light absorption, charge transfer, and reaction pathway) of heterogeneous photocatalysis individually. In contrast to the often proposed prolonged lifetime of charge carriers in Ptloaded TiO 2 , we found that after collecting the excited electrons, Pt acts more as a recombination center independent of the amount of Pt deposited. Only when dissolved O 2 is present in the solution, charge recombination is suppressed by the subsequential consumption of electrons at the surface of the Pt clusters with the dissolved O 2 benefited by the improved O 2 adsorption on the Pt surface.Article pubs.acs.org/JPCC
Graphene oxide (GO)
has immense potential for widespread use in
diverse in vitro and in vivo biomedical
applications owing to its thermal and chemical resistance, excellent
electrical properties and solubility, and high surface-to-volume ratio.
However, development of GO-based biological nanocomposites and biosensors
has been hampered by its poor intrinsic biocompatibility and difficult
covalent biofunctionalization across its lattice. Many studies exploit
the strategy of chemically modifying GO by noncovalent and reversible
attachment of (bio)molecules or sole covalent biofunctionalization
of residual moieties at the lattice edges, resulting in a low coating
coverage and a largely bioincompatible composite. Here, we address
these problems and present a facile yet powerful method for the covalent
biofunctionalization of GO using colamine (CA) and the poly(ethylene
glycol) cross-linker that results in a vast improvement in the biomolecular
coating density and heterogeneity across the entire GO lattice. We
further demonstrate that our biofunctionalized GO with CA as the cross-linker
provides superior nonspecific biomolecule adhesion suppression with
increased biomarker detection sensitivity in a DNA-biosensing assay
compared to the (3-aminopropyl)triethoxysilane cross-linker. Our optimized
biofunctionalization method will aid the development of GO-based in
situ applications including biosensors, tissue nanocomposites, and
drug carriers.
Graphene's maximized surface‐to‐volume ratio, high conductance, mechanical strength, and flexibility make it a promising nanomaterial. However, large‐scale graphene production is typically cost‐intensive. This manuscript describes a microbial reduction approach for producing graphene that utilizes the bacterium
Shewanella oneidensis
in combination with modern nanotechnology to enable a low‐cost, large‐scale production method. The bacterial reduction approach presented in this paper increases the conductance of single graphene oxide flakes as well as bulk graphene oxide sheets by 2.1 to 2.7 orders of magnitude respectively while simultaneously retaining a high surface‐area‐to‐thickness ratio.
Shewanella
‐mediated reduction was employed in conjunction with electron‐beam lithography to reduce one surface of individual graphene oxide flakes. This methodology yielded conducting flakes with differing functionalization on the top and bottom faces. Therefore, microbial reduction of graphene oxide enables the development and up‐scaling of new types of graphene‐based materials and devices with a variety of applications including nano‐composites, conductive inks, and biosensors, while avoiding usage of hazardous, environmentally‐unfriendly chemicals.
Thermal atomic layer deposition of Au nanoparticles on titania in a fluidized bed reactor. Effects of precursor pulse time on Au nanoparticle size and loading.
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