7 research outputs found
Single atom Cu(I) promoted mesoporous titanias for photocatalytic Methyl Orange depollution and H 2 production
Tailoring the physicochemical properties and hence reactivity of semiconductor photocatalysts in a predictable fashion, remains a challenge to their industrial application. Here we demonstrate the striking promotional effect of incorporating single Cu(I) atoms, on aqueous phase photocatalytic dye degradation and H2 production over surfactant-templated mesoporous TiO2. X-ray absorption spectroscopy reveals that ultra-low concentrations of copper (0.02-0.1 wt%) introduced into the mesoporous TiO2 surface create isolated Cu (I) species which suppress charge recombination, and confer a six-fold photocatalytic promotion of Methyl Orange degradation and four-fold enhancement of H2 evolution. The impact of mesopore structure and photophysical properties on photocatalytic activity is also quantified for the first time: calcination increases mesopore size and nanocrystalline order, and induces an anatase to rutile phase transition that is accompanied by a decrease in the optical band gap, increased charge carrier lifetime, and a concomitant significant activity enhancement
Predictive Removal of Interfacial Defect-Induced Trap States between Titanium Dioxide Nanoparticles via Sub-Monolayer Zirconium Coating
First principles modeling of anatase TiO2 surfaces and their interfacial contacts shows that defect-induced trap states within the band gap arise from intrinsic structural distortions, and these can be corrected by modification with Zr(IV) ions. Experimental testing of these predictions has been undertaken using anatase nanocrystals modified with a range of Zr precursors and characterized using structural and spectroscopic methods. Continuous-wave electron paramagnetic resonance (EPR) spectroscopy revealed that under illumination, nanoparticle-nanoparticle interfacial hole trap states dominate, which are significantly reduced after optimizing the Zr doping. Fabrication of nanoporous films of these materials and charge injection using electrochemical methods shows that Zr doping also leads to improved electron conductivity and mobility in these nanocrystalline systems. The simple methodology described here to reduce the concentration of interfacial defects may have wider application to improving the efficiency of systems incorporating metal oxide powders and films including photocatalysts, photovoltaics, fuel cells, and related energy applications
Carbon nanotube-modified sodium dodecyl sulfate-polyacrylamide gel electrophoresis for molecular weight determination of proteins
The effect of incorporating carbon nanotubes (CNTs) in the gel matrix on the electrophoretic mobility of proteins based on their molecular weight differences was investigated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). More specifically, a reduction in standard deviation in the molecular weight calibration plots by 55% in the case of multiwalled carbon nanotubes (MWCNTs) and by 34% in the case of single-walled carbon nanotubes (SWCNTs) compared with that of pristine polyacrylamide gels was achieved after incorporating an insignificant amount of functionalized CNTs into the gel matrix. A mechanism based on a more uniform pore size distribution in CNT modified polyacrylamide gel matrix is proposed. Furthermore, the impact of SWCNTs and MWCNTs on the mobility of proteins in different molecular weight regimes at a given acrylamide concentration offers a tunable gel matrix in terms of the selection of molecular weight ranges of proteins. The robustness and excellent reproducibility of the CNT-PAGE protocol are expected to have a significant impact on the molecular weight determination of newly isolated proteins
Homogeneous Photochemical Water Oxidation by Biuret-Modified Fe-TAML: Evidence of Fe<sup>V</sup>(O) Intermediate
Water splitting, leading to hydrogen
and oxygen in a process that
mimics natural photosynthesis, is extremely important for devising
a sustainable solar energy conversion system. Development of earth-abundant,
transition metal-based catalysts that mimic the oxygen-evolving complex
of photosystem II, which is involved in oxidation of water to O<sub>2</sub> during natural photosynthesis, represents a major challenge.
Further, understanding the exact mechanism, including elucidation
of the role of active metal-oxo intermediates during water oxidation
(WO), is critical to the development of more efficient catalysts.
Herein, we report Fe<sup>III</sup> complexes of biuret-modified tetra-amidomacrocyclic
ligands (Fe-TAML; <b>1a</b> and <b>1b</b>) that catalyze
fast, homogeneous, photochemical WO to give O<sub>2</sub>, with moderate
efficiency (maximum TON = 220, TOF = 0.76 s<sup>–1</sup>).
Previous studies on photochemical WO using iron complexes resulted
in demetalation of the iron complexes with concomitant formation of
iron oxide nanoparticles (NPs) that were responsible for WO. Herein,
we show for the first time that a high valent Fe<sup>V</sup>(O) intermediate
species is photochemically generated as the active intermediate for
the oxidation of water to O<sub>2</sub>. To the best of our knowledge,
this represents the first example of a molecular iron complex catalyzing
photochemical WO through a Fe<sup>V</sup>(O) intermediate