Influence of Water Molecules on CO2 Reduction at the Pt Electrocatalyst in the Membrane Electrode Assembly System.

CO2 electroreduction using a Pt catalyst in an aqueous solution system is known to produce only H2. Recently, a remarkable result has been reported that CH4 can be obtained by reducing CO2 using a membrane electrode assembly (MEA) containing a Pt catalyst. A big difference that exists between the two systems is the number of water molecules. Therefore, this study investigated the influence of water molecules on the CO2-reduction process at the Pt electrocatalyst in the MEA system. As a result, cyclic voltammetry indicated that adsorbed CO (COads) was formed by CO2 reduction in the MEA system more preferably than the aqueous solution system. In detail, the ratio of COads at the atop sites (linear CO, COL) on Pt, which participates in the CH4 generation reaction, to the total COads formed by the CO2 reduction became higher as the lower relative humidity (RH) at 50 °C in the MEA system. Cyclic voltammetry combined with in-line mass spectrometry revealed that the amount of COL and CH4 generated by the CO2 reduction reached their maximums at 63.1% RH. CH4 production by the extremely low-overpotential CO2 reduction was significantly achieved under all the RH conditions. Consequently, the Faradaic efficiency of the CH4 production at 63.1% RH was improved by 1.35 times compared to that at 100% RH. These results would be mainly obtained based on the H2O-involved chemical equilibrium of the reactions for the COads and CH4 formation. Overall, the present study experimentally clarified that the formation of COads (particularly COL) and the following CH4 from the CO2 reduction at the Pt electrocatalyst in the MEA system was facilitated by appropriately controlling the water-molecule content.

Energy conversion efficiency comparison of different aqueous and semi-aqueous CO2 electroreduction systems.

An energy conversion efficiency index, that is independent of the anode reaction performance, is proposed for CO2 reduction in aqueous and semi-aqueous systems. The energy conversion efficiency of CO2 reduction under 107 typical conditions was calculated based on the derived formula. Notably, the resulting efficiency trends of the reduction products differed from their faradaic efficiency trends. When the products were CO, HCOOH, C2H4, and CH4, the electrocatalysts with the higher energy conversion efficiencies were Au, Pd, Cu, and Pt, respectively. Based on the discussion on the overall energy conversion efficiency of all products, Pt should be a specific energetically advantageous catalyst for CO2 reduction because the activation energy is negligibly small. Moreover, the energy conversion and faradaic efficiencies were discovered to not only depend on the electrocatalyst species, but also on the complexity of the reaction, including the number of reaction electrons. Our proposed method for evaluating the energy conversion efficiency of cathode reactions can potentially serve as a novel platform for comparing the CO2 reduction efficiencies of different electroreduction systems.

Highly efficient hole injection from Au electrode to fullerene-doped triphenylamine derivative layer.

Triphenylamine derivatives are superior hole-transport materials. For their application to high-functional organic semiconductor devices, efficient hole injection at the electrode/triphenylamine derivative interface is required. Herein, we report the design and evaluation of a Au/fullerene-doped α-phenyl-4'-[(4-methoxyphenyl)phenylamino]stilbene (TPA) buffer layer/TPA/Au layered device. It exhibits rectification conductivity, indicating that hole injection occurs more easily at the Au/fullerene-doped TPA interface than at the Au/TPA interface. The Richardson-Schottky analysis of the device reveals that the hole injection barrier (ΦB) at the Au/fullerene-doped TPA interface decreases to 0.021 eV upon using C70 as a dopant, and ΦB of Au/TPA is as large as 0.37 eV. The reduced ΦB of 0.021 eV satisfies the condition for ohmic contact at room temperature (ΦB [Formula: see text] 0.025 eV). Notably, C70 doping has a higher barrier-reduction effect than C60 doping. Furthermore, a noteworthy hole-injection mechanism, in which the ion-dipole interaction between TPA and fullerenes plays an important role in reducing the barrier height, is considered based on cyclic voltammetry. These results should facilitate the design of an electrode/organic semiconductor interface for realizing low-voltage driven organic devices.

H2-CO2 polymer electrolyte fuel cell that generates power while evolving CH4 at the Pt0.8Ru0.2/C cathode.

Generating electric power using CO2 as a reactant is challenging because the electroreduction of CO2 usually requires a large overpotential. Herein, we report the design and development of a polymer electrolyte fuel cell driven by feeding H2 and CO2 to the anode (Pt/C) and cathode (Pt0.8Ru0.2/C), respectively, based on their theoretical electrode potentials. Pt-Ru/C is a promising electrocatalysts for CO2 reduction at a low overpotential; consequently, CH4 is continuously produced through CO2 reduction with an enhanced faradaic efficiency (18.2%) and without an overpotential (at 0.20 V vs. RHE) was achieved when dilute CO2 is fed at a cell temperature of 40 °C. Significantly, the cell generated electric power (0.14 mW cm-2) while simultaneously yielding CH4 at 86.3 µmol g-1 h-1. These results show that a H2-CO2 fuel cell is a promising technology for promoting the carbon capture and utilization (CCU) strategy.

Effective induction of death in mesothelioma cells with magnetite nanoparticles under an alternating magnetic field.

With the objective of finding an avenue for development of magnetic hyperthermia as an effective mesothelioma treatment, the influence of heating by magnetite nanoparticles (MNPs) with a diameter of ~40nm, which were incorporated into cells and then subjected to AC magnetic field, on induction of cell death was investigated in all three histological subtypes of human mesothelioma cells (i.e., epithelioid NCI-H28, sarcomatoid NCI-H2052, and biphasic MSTO-211H cells). Cellular uptake of MNPs was observed in all cell types, but the amount of MNPs incorporated per cell into MSTO-211H cells was smaller than in NCI-H28 and NCI-H2052 cells. On the other hand, cell death induced by cellular uptake of MNPs was observed specifically in MSTO-211H cells. Hence, when cells are heated by intracellular MNPs under AC magnetic field, a high degree of cell mortality in NCI-H28 and NCI-H2052 cells is induced by the temperature increase derived from the high amount of intracellular MNPs, but the combination of intracellular heating and cell-type-specific toxicity of MNPs induced high rates of cell death in MSTO-211H cells even at a lower temperature. Almost all of the heated cells were dead after 24-h incubation at 37°C in all histological subtypes. Additionally, higher mortalities were observed in all three types of mesothelioma cells after MNPs-heating, as compared to the heating with a thermostatic bath. Herein, the significance of cellular uptake of MNPs for effectively inducing cell death in mesothelioma has been demonstrated in vitro.

Correction: Stimuli-responsive magnetic nanoparticles for tumor-targeted bimodal imaging and photodynamic/hyperthermia combination therapy.

Correction for 'Stimuli-responsive magnetic nanoparticles for tumor-targeted bimodal imaging and photodynamic/hyperthermia combination therapy' by Kyoung Sub Kim, et al., Nanoscale, 2016, DOI: 10.1039/c6nr02273a.

Stimuli-responsive magnetic nanoparticles for tumor-targeted bimodal imaging and photodynamic/hyperthermia combination therapy.

Despite magnetic nanoparticles having shown great potential in cancer treatment, tremendous challenges related to diagnostic sensitivity and treatment efficacy for clinical application remain. Herein, we designed optimized multifunctional magnetite nanoparticles (AHP@MNPs), composed of Fe3O4 nanoparticles and photosensitizer conjugated hyaluronic acid (AHP), to achieve enhanced tumor diagnosis and therapy. Fe3O4 nanoparticles (MNPs) were synthesized by a facile hydrolysis method. MNPs have higher biocompatibility, controllable particle sizes, and desirable magnetic properties. The fabricated AHP@MNPs have enhanced water solubility (average size: 108.13 ± 1.08 nm), heat generation properties, and singlet oxygen generation properties upon magnetic and laser irradiation. The AHP@MNPs can target tumors via CD44 receptor-mediated endocytosis, which have enhanced tumor therapeutic effects through photodynamic/hyperthermia-combined treatment without any drugs. We successfully detected tumors implanted in mice via magnetic resonance imaging and optical imaging. Furthermore, we demonstrated the photodynamic/hyperthermia-combined therapeutic efficacy of AHP@MNPs with synergistically enhanced efficacy against cancer.

Sedimentation-induced detachment of magnetite nanoparticles from microalgal flocs.

The objective of this study is to develop a simple, one-step approach to separate adsorbed Fe3O4 nanoparticles from microalgal flocs for further downstream processing. Using the wild-type strain of fresh-water algae Chlamydomonas reinhardtii, effective removal of nanoparticles from microalgal flocs by both centrifugal sedimentation (at 1500 or 2000g) and magnetic sedimentation (at 1500 Oe) is demonstrated. At the physiological pH of the solution (i.e., pH 7.0), where the electrostatic force between the nanoparticles and the microalgal cells is strongly attractive, larger separation force was achieved by simply increasing the density and viscosity of the solution to 1.065g/mL and 1.244cP, respectively. The method described here offers significant opportunity for purifying microalgal biomass after nanoparticle-flocculation-based harvesting and decreasing the cost of microalgal biotechnology. This may also find avenues in other applications that apply flocculation, such as algal biofilm formation in photobioreactors and wastewater treatment.

Induction of Cell Death in Mesothelioma Cells by Magnetite Nanoparticles.

Nanoparticle uptake and cell death following addition of magnetite nanoparticles (MNPs) with a diameter of ∼10 nm were evaluated in three histological types of human mesothelioma cells, NCI-H28 (epithelioid), NCI-H2052 (sarcomatoid), and MSTO-211H (biphasic) cells, and human breast cancer MCF-7 cells. Dose-dependent cell death was observed in MSTO-211H cells but not in MCF-7 cells, although cellular uptake of MNPs was observed in both cell types. Mesothelioma NCI-H28 and NCI-H2052 cells showed behavior more similar to that of breast cancer MCF-7 cells than that of mesothelioma MSTO-211H cells. DNA fragmentation and microarray analyses suggested that MNPs induced transforming growth factor ß2 related apoptosis in MSTO-211H cells. On the other hand, the viability of human mesothelioma cells containing MNPs with a diameter of ∼40 nm was investigated after exposure to an alternating magnetic field. Temperature increase under the alternating magnetic field and high rates of cell death were observed in all three histological types of human mesothelioma.