Deciphering Charging Status, Absolute Quantum Efficiency, and Absorption Cross Section of MultiCarrier States in Single Colloidal Quantum Dot

Upon photo- or electrical-excitation, colloidal quantum dots (QDs) are often found in multi-carrier states due to multi-photon absorption and photo-charging of the QDs. While many of these multi-carrier states are observed in single-dot spectroscopy, their properties are not well studied due to random charging/discharging, emission intensity intermittency, and uncontrolled surface defects of single QD. Here we report in-situ deciphering the charging status, and precisely assessing the absorption cross section, and determining the absolute emission quantum yield of mono-exciton and biexciton states for neutral, positively-charged, and negatively-charged single core/shell CdSe/CdS QD. We uncover very different photon statistics of the three charge states in single QD and unambiguously identify their charge sign together with the information of their photoluminescence decay dynamics. We then show their distinct photoluminescence saturation behaviors and evaluated the absolute values of absorption cross sections and quantum efficiencies of monoexcitons and biexcitons. We demonstrate that addition of an extra hole or electron in a QD changes not only its emission properties but also varies its absorption cross section

Inhibitory effect of microRNA34a on retinal pigment epithelial cell proliferation and migration,”

Citation: Hou Q, Tang J, Wang Z, et al. Inhibitory effect of microRNA-34a on retinal pigment epithelial cell proliferation and migration. Invest Ophthalmol Vis Sci. 2013;54:6481-6488. DOI:10.1167/iovs.13-11873 PURPOSE. Retinal pigment epithelial (RPE) cells play important roles in ophthalmologic diseases such as proliferative vitreoretinopathy, AMD, and diabetic retinopathy. MicroRNA34a (miR-34a) has been reported to be important in the regulation of cell proliferation, migration, differentiation, and apoptosis. In this study, we explored the effects of miR-34a on RPE cells. METHODS. The expression level of miR-34a in subconfluent and postconfluent ARPE-19 cells was investigated with quantitative real-time PCR. MicroRNA mimic and small interfering RNA (siRNA) were transiently transfected into RPE cells. Transfected RPE cells were analyzed with WST-1 proliferation assay, and their migration was analyzed with transwell assay and in vitro scratch study. The expression or activation of target proteins was detected by Western blotting. RESULTS. MicroRNA-34a was significantly downregulated in subconfluent ARPE-19 cells compared with postconfluent cells. Introduction of miR-34a inhibited the proliferation and migratory ability of RPE cells without obvious cell apoptosis. In miR-34a transfected cells, many important proliferation and/or migration related molecules such as c-Met, CDK2, CDK4, CDK6, E2F1, and phosphorylated-Cdc2 (p-Cdc2) were downregulated. Small interfering RNA designed to target c-Met also inhibited the proliferation and migration of RPE cells and downregulated CDK2, CDK6, E2F1, and p-Cdc2. CONCLUSIONS. MicroRNA-34a is downregulated in subconfluent RPE cells. MicroRNA-34a can inhibit the proliferation and migration of RPE cells through downregulation of its targets c-Met and other cell cycle-related molecules. Our results indicated that miR-34a is involved in the regulation of RPE cells

Polymer-assisted synthesis of a 3D hierarchical porous network-like spinel NiCo2O4 framework towards high-performance electrochemical capacitors

National Natural Science Foundation of China [51202004, 21173120]; Nature Science Foundation of Anhui Province [KJ2013A051]; Specialized Research Fund for the Doctoral Program of Higher Education of China [20060287026]; Nature Science Foundation of Jiangsu Province [BK2011030]; Foundation of Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education [201201]We have developed a facile yet scalable polymer-assisted chemical solution route to prepare a three-dimensional (3D) hierarchical porous network-like NiCo2O4 framework for advanced electrochemical capacitors (ECs). The unique interconnected hierarchical porous framework is constructed by nanosized spinel NiCo2O4 building blocks of 20-30 nm size, thus, a 3D continuous electron transport expressway, convenient electrolyte penetration-diffusion and large electrode-electrolyte interface are obtained simultaneously. The combination of these appealing structural features in the striking network-like NiCo2O4 framework results in a drastically enhanced kinetic behavior, large specific capacitance (SC) and a remarkable cycling stability at high rates. The unique network-like NiCo2O4 electrode features a SC of 587 F g(-1) at 2 A g(-1), and can deliver up to 518 F g(-1) at a large current density of 16 A g(-1). Also, a SC deterioration of similar to 6% of the maximum SC is evident after continuous 3500 charge-discharge cycles at varying current densities, ranging from 2 to 16 A g(-1). Furthermore, the synthetic strategy presented here can be easily extended to fabricate other binary complex metal oxides and/or ternary metal oxides with a controlled composition and porous structure, which may be promising candidates for high-performance ECs, and even advanced Li-ion batteries

A GIS-based spatial multi-index model for flood risk assessment in the Yangtze River Basin, China

This paper developed a GIS-based spatial multi-index model for large basin-scale flood risk assessment. In terms of the risk definition proposed by the IPCC, the flood risk in the Yangtze River Basin (YRB) was classified into indexes of hazard, vulnerability, and exposure. The model systematically accounts for various flood risk indicators related to the economic, social and ecological environment of the YRB. Using the robust data space analysis and processing capabilities of ArcGIS, these flood risk indicators were superimposed and analyzed to generate an integrated flood risk spatial distribution map for the YRB. The modeling results were verified reasonably well using observation data from the YRB floods in 1998, 2008, and 2016. We found that 24.90% of the study area was at very high and high risk in 1998, and the risk in these areas decreased to 15.95% and 17.61% in 2008 and 2016, respectively. We believe that the GIS-based spatial multi-index model can be applied to other areas where basin-scale flood risk assessment is desired and contribute to further scientific research on flood forecasting and mitigation

Template-engaged synthesis of uniform mesoporous hollow NiCo2O4 sub-microspheres towards high-performance electrochemical capacitors

National Natural Science Foundation of China [51202004]; Nature Science Foundation of Anhui Province [KJ2013A051]An efficient template-engaged synthetic strategy, where silica spheres were applied as hard templates, was developed to synthesize hierarchical mesoporous hollow NiCo2O4 sub-microspheres assembled entirely from ultrathin nanosheets with a thickness of a few nanometers. The as-prepared mesoporous hollow NiCo2O4 sub-microspheres are very uniform in size, mesoporous in textual property, and structurally robust benefiting from the in situ template removal. The morphologies of the hollow submicrospherical architecture can be tuned easily by varying the concentrations of Ni2+, Co2+, and the precipitant. When evaluated as an appealing electroactive material for electrochemical capacitors (ECs), the as-fabricated hierarchical hollow NiCo2O4 sub-microspheres delivered a specific capacitance (SC) of 678 F g(-1) at a current density of 1 A g(-1), and even kept it as high as 540 F g(-1) at 10 A g(-1). Additionally, a desirable cycling stability of 13% SC degradation over 3500 continuous cycles at a current density of 10 A g(-1) is observed, suggesting their promising application in advanced ECs

Facile synthesis of Co2P2O7 nanorods as a promising pseudocapacitive material towards high-performance electrochemical capacitors

National Natural Science Foundation of China [51202004]; Natural Science Foundation of Anhui Province [KJ2013A051]In the present work, we developed an efficient one-step template-free strategy to fabricate intriguing one-dimensional (1D) Co2P2O7 nanorods (NRs) at room temperature, and utilized the unique monoclinic Co2P2O7 NRs as an excellent electrode material for high-performance pseudocapacitors using 3 M KOH as an electrolyte. Strikingly, the as-synthesized 1D Co2P2O7 NR electrode delivered a specific capacitance (SC) of 483 F g(-1) at 1 A g(-1), and even at 402 F g(-1) a high current loading of 10 A g(-1). And the SC retention of similar to 90% over continuous 3000 charge-discharge cycles at a current density of 6 A g(-1) confirmed its stable long-term cycling ability at high current density. More significantly, the underlying electrochemical energy-storage mechanism of the Co2P2O7 NR electrode in alkaline KOH aqueous solution was tentatively proposed. And the appealing strategy was proposed for future exploration and development of other low-cost pseudocapacitive materials for next-generation ECs

The mechanism of stress corrosion cracking of Alloy 690TT in a caustic solution containing lead

This study investigated the PbSCC of Alloy 690TT exposed to a caustic solution at 320 degrees C. Characterization of the resulting films indicates that lead is involved in the formation of oxides and evenly distributed in the films. TEM analysis was carried out to elucidate the role of lead in IGSCC by investigating the oxides at the crack tip. Lead penetrates into the crack tip and disperses in the intergranular oxides, enhancing the oxidation of grain boundaries. Thus, microcracks initiate within oxides under stress and connect with the main SCC crack stemming from the pit, resulting in propagation of the IGSCC