12 research outputs found
Unbiased Sunlight-Driven Artificial Photosynthesis of Carbon Monoxide from CO<sub>2</sub> Using a ZnTe-Based Photocathode and a Perovskite Solar Cell in Tandem
Solar
fuel production, mimicking natural photosynthesis of converting
CO<sub>2</sub> into useful fuels and storing solar energy as chemical
energy, has received great attention in recent years. Practical large-scale
fuel production needs a unique device capable of CO<sub>2</sub> reduction
using only solar energy and water as an electron source. Here we report
such a system composed of a gold-decorated triple-layered ZnO@ZnTe@CdTe
core–shell nanorod array photocathode and a CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell in tandem. The assembly
allows effective light harvesting of higher energy photons (>2.14
eV) from the front-side photocathode and lower energy photons (>1.5
eV) from the back-side-positioned perovskite solar cell in a single-photon
excitation. This system represents an example of a photocathode–photovoltaic
tandem device operating under sunlight without external bias for selective
CO<sub>2</sub> conversion. It exhibited a steady solar-to-CO conversion
efficiency over 0.35% and a solar-to-fuel conversion efficiency exceeding
0.43% including H<sub>2</sub> as a minor product
The mean, standard deviation and coefficient of variation for all repetitions (N = 7) of the dynamic phantom.
<p>Lac and Pyr refer to the total volume under the spectral and temporal curves for each tracer; <i>k<sub>PL</sub></i> is the forward reaction rate (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071274#pone.0071274.e006" target="_blank">Equations 6</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071274#pone.0071274.e010" target="_blank">8</a>).</p
A schematic view of the dynamic chemical phantom structure.
<p>The injection and exhaust ports were fitted with catheters to facilitate rapid mixture of reagents at isocenter. A thin acrylic sheet was attached to the top to seal the fill cavity. This top could be removed to allow cleaning after injection. The phantom rested on a sled that allowed convenient removal and insertion of the phantom and included warm circulating water to maintain constant temperature.</p
Dynamic signal evolution across (N = 7) injections.
<p>The mean signal for lactate and pyruvate, normalized to peak carbon signal for each injection, are displayed with error bars that indicate the minimum and maximum values at each time over all injections. Total HP <sup>13</sup>C was estimated by summing signal from HP <sup>13</sup>C Lactate and HP <sup>13</sup>C Pyruvate. The average linewidth for pyruvate and lactate peaks were 19±5 Hz and 17±5 Hz, respectively.</p
Spectroscopic images of the reaction carried out in a standard imaging phantom.
<p>Proton imaging (top left) shows the phantom structure in high resolution. Spectroscopic imaging data acquired using a radial EPSI sequence allows metabolite-specific visualization of tracer distribution (bottom row). Spectroscopic data can be intrinsically registered to high-resolution proton images (top center and right).</p
One-Pot Synthesis of Intermetallic Electrocatalysts in Ordered, Large-Pore Mesoporous Carbon/Silica toward Formic Acid Oxidation
This study describes the one-pot synthesis and single-cell characterization of ordered, large-pore (>30 nm) mesoporous carbon/silica (OMCS) composites with well-dispersed intermetallic PtPb nanoparticles on pore wall surfaces as anode catalysts for direct formic acid fuel cells (DFAFCs). Lab-synthesized amphiphilic diblock copolymers coassemble hydrophobic metal precursors as well as hydrophilic carbon and silica precursors. The final materials have a two-dimensional hexagonal-type structure. Uniform and large pores, in which intermetallic PtPb nanocrystals are significantly smaller than the pore size and highly dispersed, enable pore backfilling with ionomers and formation of the desired triple-phase boundary in single cells. The materials show more than 10 times higher mass activity and significantly lower onset potential for formic acid oxidation as compared with commercial Pt/C, as well as high stability due to better resistivity toward CO poisoning. In single cells, the maximum power density was higher than that of commercial Pt/C, and the stability highly improved, compared with commercial Pd/C. The results suggest that PtPb-based catalysts on large-pore OMCSs may be practically applied as real fuel cell catalysts for DFAFC
Chalcogen Bridged Thieno- and Selenopheno[2,3‑<i>d</i>:5,4‑<i>d</i>′]bisthiazole and Their Diketopyrrolopyrrole Based Low-Bandgap Copolymers
We
report the synthesis and characterization of four novel small
bandgap copolymers incorporating the electron-deficient thienoÂ[2,3-<i>d</i>:5,4-<i>d</i>′]Âbisthiazole and selenophenoÂ[2,3-<i>d</i>:5,4-<i>d</i>′]Âbisthiazole building blocks
with a series of electron-deficient diketopyrrolopyrole units. The
four resultant copolymers were synthesized via palladium Stille cross-coupling
reaction, and their optical, thermal stability, electrochemical, and
field-effect charge transport properties were investigated. All copolymers
showed low optical bandgaps (1.53–1.56 eV); in addition, X-ray
diffraction on solution-cast films revealed that the selenium-containing
copolymers exhibit higher crystallinity compared to their thiophene
counterparts
ATC tumors display significant metabolic heterogeneity.
<p>A) Control and irradiated tumors (IR) were serially sectioned and H&E staining was used to evaluate overall tumor architecture. Control tumors were substantially larger, but the majority of the tumor core consisted of non viable tissue (NVT). In contrast the majority of the irradiated tumor volume consisted of apparently viable tissue (VT). Irradiated tumors exhibited a high degree of aberrant cellular morphology as illustrated in the right lower panel inset. B) ATC tumor imaged at 2 weeks following tumor cell injection. Single snapshot imaging was performed 20 seconds after injection of labeled pyruvate. Spatial heat maps were generated from raw data and superimposed onto T2 weighted anatomic images for both pyruvate and lactate. Chemical spectra obtained in two separate voxels demonstrating differential conversion of pyruvate into lactate are shown.</p
HP-MRS can detect both acute and chronic IR induced changes in ATC reducing potential.
<p>A) Control (n = 4) and irradiated (5 Gy) (n = 3) tumors were imaged pre- and post- IR (or sham). Generation of labeled lactate (nLac) and conversion rate constants (Kpl) were calculated and changes from first to second measurement were recorded. B) Control and irradiated ATC tumors demonstrating difference in size using anatomic imaging (T2 weighted sequential slices). C) Reducing potential levels in control (n = 3) and irradiated (n = 3) tumors at 2 weeks post irradiation (5 Gy).</p
IR cytotoxicity in ATC is driven by changes in ROS levels.
<p>A) ATC (U-HTH83) intra-cellular ROS levels can be manipulated through the addition of exogenous ROS sources (H<sub>2</sub>O<sub>2</sub>) or ROS scavenging NAC. B) IR induces a dose dependent increase in intra-cellular ROS levels, which is neutralized by the addition of NAC. C) IR cytoxicity as measured using surviving fraction can be potentiated by the addition of H<sub>2</sub>O<sub>2</sub> or reversed by NAC. Data are presented as averages with error bars representing standard deviation. Each experiment was performed at least in duplicate. *indicates p-value <0.05 compared to corresponding control condition unless otherwise indicated as in panel C. All experiments were conducted using the U-HTH83 cell line. (CNT = control, DCFDA = 2′,7′-dichlorodihydrofluorescein diacetate).</p