Hollow heterostructured g-C3N4@CeO2 photocatalysts with rich oxygen vacancies are controllable designed by a facile strategy. The synergetic effect and oxygen vacancies of g-C3N4@CeO2 play the major role in the process of CO2 reduction, leading to CH4 generating much earlier and higher concentration than that of the pristine g-C3N4 and CeO2 alone. Meanwhile, the unique hollow structures can make multiple reflections of light in the cavity, and thus enhance the utilization efficiency of light. Moreover, the L-cysteine offers amine groups and meanwhile is anchored on the surface of g-C3N4 during the synthesis process, and thus contributes greatly to the enhanced CO2 adsorption capability. Additionally, the large CO2 adsorption capability is also beneficial for the enhanced photocatalytic activity. Therefore, the novel photocatalysts exhibit a remarkable reduction performance for CO2 reduction under visible light irradiation. The g-C3N4@CeO2 (CeO2 49.7 wt %) shows the highest yields of CH4 (3.5 μmol g−1), CH3OH (5.2 μmol g−1) and CO (16.8 μmol g−1), which are higher than most of other latest reported g-C3N4 based photocatalysts for CO2 photoreduction, including coupled with semiconductors and noble metal cocatalysts. This strategy might represent a novel way for the effective conversion of CO2 to clean fuels and can also be great potential used in the energy and environmental science.

Controlled assemble of hollow heterostructured g-C3N4@CeO2 with rich oxygen vacancies for enhanced photocatalytic CO2 reduction

The impact of cerium oxide nanoparticles on the salt stress responses of Brassica napus L.

Background: Hepatic ischemia reperfusion is one the main causes for graft failure following transplantation. Although, the molecular events that lead to hepatic f

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Prophylactic Treatment with Cerium Oxide Nanoparticles Attenuate Hepatic Ischemia Reperfusion Injury in Sprague Dawley Rats

Cerium oxide nanoparticles alter the salt stress tolerance of Brassica napus L. by modifying the formation of root apoplastic barriers

Cerium oxide nanoparticles (or nanoceria) have demonstrated great potential as antioxidants in various cell culture models. Despite such promise for reducing reactive oxygen species and an ability for surface functionalization, nanoceria has not been extensively studied for cancer applications to date. Herein, we engineered the surface of nanoceria with dextran and observed its activity in the presence bone cancer cells (osteosarcoma cells) at different pH values resembling the cancerous and noncancerous environment. We found that dextran coated nanoceria was much more effective at killing bone cancer cells at slightly acidic (pH 6) compared to physiological and basic pH values (pH 7 and pH 9). In contrast, minimal toxicity was observed for healthy (noncancerous) bone cells when cultured with nanoceria at pH = 6 after 1 day of treatment in the concentration range of 10–1000 μg/mL. Although healthy bone cancer cell viability decreased after treatment with high ceria nanoparticle concentrations (250–1000 μg...

pH-Dependent Activity of Dextran-Coated Cerium Oxide Nanoparticles on Prohibiting Osteosarcoma Cell Proliferation

Cerium oxide (CeO2) nanoparticles, which are used in a variety of products including solar cells, gas sensors, and catalysts, are expected to increase in industrial use. This will subsequently lead to additional occupational exposures, making toxicology screenings crucial. Previous toxicology studies have presented conflicting results as to the extent of CeO2 toxicity, which is hypothesized to be due to the ability of Ce to exist in both a +3 and +4 valence state. Thus, to study whether valence state and oxygen vacancy concentration are important in CeO2 toxicity, CeO2 nanoparticles were doped with gadolinium to adjust the cation (Ce, Gd) and anion (O) defect states. The hypothesis that doping would increase toxicity and decrease antioxidant abilities as a result of increased oxygen vacancies and inhibition of +3 to +4 transition was tested. Differences in toxicity and reactivity based on valence state were determined in RLE-6TN rat alveolar epithelial and NR8383 rat alveolar macrophage cells using enhanced dark field microscopy, electron paramagnetic resonance (EPR), and annexin V/propidium iodide cell viability stain. Results from EPR indicated that as doping increased, antioxidant potential decreased. Alternatively, doping had no effect on toxicity at 24 h. The present results imply that as doping increases, thus subsequently increasing the Ce3+/Ce4+ ratio, antioxidant potential decreases, suggesting that differences in reactivity of CeO2 are due to the ability of Ce to transition between the two valence states and the presence of increased oxygen vacancies, rather than dependent on a specific valence state.

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The Effect of Cerium Oxide Nanoparticle Valence State on Reactive Oxygen Species and Toxicity.

A simple solid-state method has been described for the synthesis of CaC2 from CaO and graphite powders by using a 2.45 GHz microwave reactor. The reaction mechanism of CaC2 formation in the microwave environment is explained and compared with that of the conventional method. The whole microwave process completed within 180 min because of efficient coupling of microwaves with graphite powder. X-ray diffraction quantitative analysis results revealed 71.8% CaC2 formation at 1700 °C for 30 min of microwave exposure, whereas conventional heat treatment at 1700 °C for 30 min showed 14.1% CaC2 and 1750 °C for 60 min showed 62.8% CaC2. The X-ray photoelectron spectroscopy quantitative chemical state analysis based on C 1s spectra indicated 54.02% CaC2 in microwave heat-treated samples and 30.75% CaC2 in conventional heat-treated samples. The preliminary experimental results suggest that synthesis of CaC2 by microwave reactor is fast because of rapid volumetric heating.

Solid-State Synthesis of Calcium Carbide by Using 2.45 GHz Microwave Reactor

MoSi2- and WSi2-based ceramic composite thick-film thermocouples were deposited on alumina substrates by a screen printing technique, and subsequently thermally processed and embedded within an alumina preform. The one leg of the thermocouple was formed with a MoSi2-Al2O3 composite, while the other leg was composed of a WSi2-Al2O3 composite. Four compositions were prepared by adjusting the volume percentages of MoSi2 and WSi2 from 50 to 90 vol%. The phase formation and microstructure of the sintered thermocouples were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermoelectric response of the thermocouples was measured by a typical hot-cold junction temperature measurements using secondary thermocouples. The thermoelectric voltage and Seebeck coefficients of thermocouples generally increased with increasing metal silicide content, as well as, temperature difference. The highest thermoelectric performance was achieved with [90–10] vol% MoSi2-Al2O3//[90–10] vol% WSi2-Al2O3 composite thermocouples, which may be related to the increased amount of the 5–3 metal silicide phases (Mo5Si3, W5Si3) that were present in the composite systems after sintering. The 5–3 metal silicide content was shown to increase with metal silicide content after sintering. The measured effective Seebeck coefficients of the MoSi2-Al2O3//WSi2-Al2O3 composite thermocouples were higher than their estimated Seebeck coefficients. A long thermocouple (22.9 cm length, 0.6 cm width) with the legs composed of [90–10] vol% MoSi2-Al2O3 and [90–10] vol% WSi2-Al2O3 displayed stable thermoelectric performance at 1350 °C with a peak thermoelectric voltage of 19.3 mV.

MoSi2- and WSi2-based embedded ceramic composite thermocouples for high-temperature and harsh-environment sensing

The short service life of refractory lining in a slagging gasifier in the integrated gasification combined cycle results in low availability and high operating cost. For longer life of the refractory lining, estimation of slag penetration length and monitoring of wall temperature are important. In this paper, we have investigated two types of embedded sensors in the refractory lining of gasifier, namely, thermistor and interdigital capacitor, to estimate the wall temperature profile and extent of slag penetration. Conventional correlation-based approaches are not satisfactory for estimating outputs of interest from the raw sensor data for these systems because of high temperature gradient along the sensor as well as temporal change in the refractory properties due to slag penetration. Therefore, a thermal model of refractory brick, slag penetration model, and models of the embedded sensors are developed and used to estimate temperature and slag penetration profile by using linear and nonlinear estimators.

Estimations of Gasifier Wall Temperature and Extent of Slag Penetration Using a Refractory Brick with Embedded Sensors

MoSi2- and WSi2-based electroconductive ceramic composites were fabricated using 40-80 vol% fine- and coarse-Al2O3, and ZrO2 particles (refractory oxides) after sintering in argon Their chemical and thermal stability was tested between 1400°-1600°C for up to 48 h X-ray diffraction analysis showed the formation of secondary 5-3 metal silicide (Mo5Si3, W5Si3) and silica phases on the grain boundaries and surface The fraction of the W5Si3 (114-388 vol%) was significantly higher than that of the Mo5Si3 (33-73 vol%) in the composites after annealing at 1400°C for 48 h The rates of grain growth in the composites (0013-0023 μm/h) were highly decreased by a grain boundary pinning effect This effect was relatively better with addition of the coarse-grained oxides due to their more homogeneous distribution throughout the microstructure The percolation threshold for the composites was generally above 20 vol% silicide addition except for the MoSi2-Al2O3 (fine-grained), which exhibited 88 and 81 S/cm electrical conductivity at 900° and 1000°C, respectively At 60 vol% silicide content, MoSi2-Al2O3 (coarse-grained) and WSi2-Al2O3 (fine-grained) showed higher electrical conductivity (126-128 S/cm) at 900°C The density, porosity level, particle distribution, intrinsic conductivity of silicide phase, particle size, and fraction of the secondary 5-3 silicide phase highly influenced their electrical properties

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Rajalekshmi C. Pillai

Papers

The Effect of Cerium Oxide Nanoparticle Valence State on Reactive Oxygen Species and Toxicity.

Solid-State Synthesis of Calcium Carbide by Using 2.45 GHz Microwave Reactor

MoSi2- and WSi2-based embedded ceramic composite thermocouples for high-temperature and harsh-environment sensing

Estimations of Gasifier Wall Temperature and Extent of Slag Penetration Using a Refractory Brick with Embedded Sensors

Stability and electrical properties of MoSi2- and WSi2-oxide electroconductive composites