A wide range of inorganic nanostructures have been used as photocatalysts for generating H2. To increase activity, Z-scheme photocatalytic systems have been implemented that use multiple types of photoactive materials and electron mediators. Optimal catalysis has previously been obtained by interfacing different materials through aggregation or epitaxial nucleation, all of which lowers the accessible active surface area. DNA has now been used as a structure-directing agent to organize TiO2 and CdS nanocrystals. A significant increase in H2 production compared to CdS or TiO2 alone was thus observed directly in solution with no sacrificial donors or applied bias. The inclusion of benzoquinone (BQ) equidistant between the TiO2 and CdS through DNA assembly further increased H2 production. While the use of a second quinone in conjunction with BQ showed no more improvement, its location within the Z-scheme was found to strongly influence catalysis.
Combinations of rare earth doped upconverting nanoparticles (UCNPs) and gold nanostructures are sought as nanoscale theranostics due to their ability to convert near infrared (NIR) photons into visible light and heat, respectively. However, because the large NIR absorption cross-section of the gold coupled with their thermo-optical properties can significantly hamper the photoluminescence of UCNPs, methods to optimize the ratio of gold nanostructures to UCNPs must be developed and studied. We demonstrate here nucleic acid assembly methods to conjugate spherical gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated UCNPs and probe the effect on photoluminescence. These studies showed that while UCNP fluorescence enhancement was observed from the AuNPs conjugated UCNPs, AuNSs tended to quench fluorescence. However, conjugating lower ratios of AuNSs to UCNPs led to reduced quenching. Simulation studies both confirmed the experimental results and demonstrated that the orientation and distance of the UCNP with respect to the core and arms of the gold nanostructures played a significant role in PL. In addition, the AuNS-UCNP assemblies were able to cause rapid gains in temperature of the surrounding medium enabling their potential use as a photoimaging-photodynamic-photothermal agent.
Microbes produce
low-molecular-weight alcohols from sugar, but
these metabolites are difficult to separate from water and possess
relatively low heating values. A combination of photo-, organo-, and
enzyme catalysis is shown here to convert C4 butanol (BuOH)
to C8 2-ethylhexenal (2-EH) using only solar energy to
drive the process. First, alcohol dehydrogenase (ADH) catalyzed the
oxidation of BuOH to butyraldehyde (BA), using NAD+ as
a cofactor. To prevent back reaction, NAD+ was regenerated
using a platinum-seeded cadmium sulfide (Pt@CdS) photocatalyst. An
amine-based organocatalyst then upgraded BA to 2-EH under mild aqueous
conditions rather than harsh basic conditions in order to preserve
enzyme and photocatalyst stability. The process also simultaneously
increased total BuOH conversion. Thus, three disparate types of catalysts
synergistically generated C8 products from C4 alcohols under green chemistry conditions of neutral pH, low temperature,
and pressure.
The aim of this study was to develop ethosomes loaded with cryptotanshinone (CPT) and formulate them as a topical gel for the treatment of acne. Ethosomes were prepared and evaluated for vesicle size, CPT loading and encapsulation efficiency. Optimized ethosomes were formulated as Carbomer 974 gels and compared with conventional hydroethanolic gels for transdermal permeation and skin deposition in vitro. The anti-acne activity and skin irritation of the gel was investigated in rabbits. Optimized ethosomes had an average vesicle size of 69.1 ± 1.9 nm with CPT loading and encapsulation efficiency of 0.445 ± 0.007 mg/mL and 40.31 ± 0.67%, respectively. The transdermal flux and skin deposition of the optimized ethosomal gel were 2.5- and 2.1-times those of conventional gels. The ethosomal gel revealed better anti-acne effect with only slight skin irritation. This study demonstrates that ethosomal formulation is an effective dermal delivery system for CPT, and that CPT ethosomal gels are promising future acne treatments.
While success has been shown in utilizing
photocatalytic systems
to reduce CO2 in water, most of these studies have yielded
formic acid as the major product with trace amounts of formaldehyde
or methanol. One reason for this is the strong equilibrium of formaldehyde
toward the hydrate methanediol. To increase methanol yields from CO2, we show here the combined use of the biological catalyst
alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae with CO2 reduction products obtained from photoelectrochemical
cells (PEC). We first show that ADH can reduce very low micromolar
amounts of formaldehyde in solution. Upon adding ADH to the PEC products,
a rapid three- to four-fold gain in methanol production was observed,
which we also attribute to the lack of back reaction by the enzyme.
Lastly, because formaldehyde dehydrogenase (FalDH) showed very low
reactivity with formate, the addition of FalDH and ADH to the PEC
products demonstrated no difference in methanol yields as compared
to ADH alone.
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