[en] Based on daily precipitation records in the Sichuan province, spatiotemporal changes in extreme precipitation from 1961 to 2017 and the relation to ocean-atmospheric climate were investigated. The trends and their statistical significance were computed with the nonparametric Sen’s and Mann–Kendall tests. The characteristics of mutation and period were investigated with heuristic segmentation and continuous wavelet transform. The relations between extreme precipitation and ocean-atmospheric climate were diagnosed by cross-wavelet analysis. The results comprised three aspects. (1) The intensity, frequency, and duration of extreme precipitation increased in the Sichuan plateau, while the intensity and frequency of extreme precipitation decreased, but the duration of extreme precipitation did not change in the Sichuan basin. The contrary trends of extreme precipitation indices may have been influenced by the complex local geography, dramatically increased human activity, and source transportation of water vapor. (2) Temporally, the trends in extreme precipitation indices constituted slight changes in the Sichuan province. The Sichuan province experienced notable climate change because abrupt change points were observed for most of the extreme precipitation indices. Extreme precipitation was a fluctuation process from 1961 to 2017. (3) Because there was a decrease in precipitation during the warm phase periods of El Niño events and an increase during the cool phase periods of La Niña events in the Sichuan province, we show that the El Niño-Southern Oscillation (ENSO) has longer and stronger relations with extreme precipitation than the South Asian Summer Monsoon (SASM) or East Asian Summer Monsoon (EASM). The results of the present study will facilitate better decisions concerning preparedness for extreme precipitation events and management of water hazards in the Sichuan province.

[en] Quantum dots (QDs) fluorescent probes based on oligonucleotide aptamers and peptides with specific molecular recognition have attracted much attention. In this paper, CdSe/ZnS QDs probes for targeted delivery to mouse and human cells using aptamer GS24 and peptide T7 specific to mouse/human transferrin receptors were developed. Capillary electrophoresis analyses indicated that the optimal molar ratios of QDs to aptamer or peptide were 1:5. Fluorescence and confocal microscope imaging revealed QD-GS24 and QD-T7 probes were able to specifically recognize B16 cells and HeLa cells respectively. Quantitative flow cytometry analysis indicated the transportation of QD-GS24 or QD-T7 into cells could be promoted by corresponding free transferrin. Transmission electron microscopy confirmed the uptake of probes in cells and the effective intracellular delivery. MTT assay suggested the cytotoxicity of probes was related to the surface ligand, and aptamer GS24 (or peptide T7) could reduce the cytotoxicity of probes to a certain degree. The study has great significance for preparing QDs fluorescent probes using non-antibody target molecules. (paper)

[en] In this article, water-soluble CdTe/CdS quantum dots (QDs) were synthesized in aqueous solution with captosuccinic acid as stabilizer. The absorption and fluorescence spectra showed that the as-prepared QDs had good optical properties. It was observed that the quantum yield (QY) of QDs was greatly increased after a heating-cooling cycle (from 22 to 41%). Then, the QDs were used to prepare fluorescent probes. The experiment results showed that the transferrin (Tf) could conjugate to QDs effectively and the HepG2 cells could be recognized successfully. This study is of great significance for the preparation of high-quality QDs and their applications in life science.

[en] Highlights: ► The mesoscopic N-doped TiO₂ spheres show higher energy conversion efficiency. ► EIS shows retards charge recombination occurred on N-doped TiO₂ spheres photoanode. ► The acceleration of electron transfer rate was verified by IMPS. - Abstract: The photovoltaic performance of quantum dot-sensitized solar cell (QDSSC) based on mesoscopic nitrogen-doped TiO₂ spheres prepared by solvothermal method was investigated. The results indicate that CdSe_xS_(1−x)/CdSe QDSSC based on this mesoscopic nitrogen-doped TiO₂ spheres shows an energy conversion efficiency of 3.67%, which is higher than that of the undoped TiO₂ spheres (2.14%). The electrochemical impedance spectroscopy shows retards charge recombination is occurred on nitrogen-doped TiO₂ spheres photoanode. The improvement of the photovoltaic performance of QDSSC could be attributed to the retarding charge recombination, the acceleration of the transfer rate of electrons, higher quantum dots loading and enhanced light scattering in the N-doped TiO₂ spheres film. A higher photovoltaic performance could be expected for other QDSSC with this N-doped TiO₂ sphere material.

[en] A novel method concerning the coding technology of polystyrene beads with Si encapsulated quantum dot (QD) particles (Si - QDs particles) is studied in this paper. In the reverse microemulsion system containing tetraethoxysilane (TEOS), water-soluble QDs (emission peak at 600 nm) were enveloped within the silica shell, forming Si - QDs particles. The Si - QDs particles were characterized by TEM, showing good uniform size, with an average diameter of about 167.0 nm. In comparison with the pure water-soluble QDs, the encapsulation of water-soluble QDs in the silica shell led to an enhancement in anti-photobleaching by providing inert barriers for the QDs. Images presented by SEM and confocal laser scanning microscopy demonstrated that the Si - QDs particles were equably coated on the surface of carboxyl functionalized polystyrene (PS) beads. Then, with the assistance of ethyl-3-(dimethyl aminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS), human IgG could be successfully crosslinked to Si - QDs particle coated PS-COOH beads. Furthermore, the Si - QDs coated PS-COOH beads with human IgG were examined in immunoassay experiments, and the results indicated that these beads could be applied in the specific recognition of goat-anti-human IgG in solution. This investigation is expected to provide a new route to bead coding in the field of suspension microarrays, based on the use of QDs

[en] Highlights: ► A convenient method was designed to assess cell efficiency of QDs probes for cellular labeling. ► The relationship between conjugation methods and effectiveness was evaluated clearly. ► QDs-Tf probe synthesized by EDC coupling had the highest labeling efficiency, followed by electrostatic interaction, and dTf coating. - Abstract: In this paper, we prepared three types of transferrin-quantum dots conjugates (QDs-Tf) using three different methods (electrostatic interaction, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling, denatured transferrin (dTf) coating). Fluorescence emission spectra, surface characteristics, zeta potentials of quantum dots (QDs) and QDs-Tf fluorescent probes were characterized by spectrophotometer, capillary electrophoresis, and dynamic light scattering. Fluorescent imaging of HeLa cells was also performed by QDs and QDs-Tf fluorescent probes. It was found that the fluorescence imaging performances of QDs-Tf probes prepared by electrostatic interaction and EDC coupling were better compared with the one prepared by dTf coating. Then a real-time single cell detection system was established to quantitatively evaluate cell labeling effects of QDs-Tf fluorescent probes. It was found that for cell labeling efficiency, the proportion of cells labeled by quantum dot probes to a group of cells, QDs-Tf probe prepared by EDC coupling showed the highest labeling efficiency (85.55 ± 3.88%), followed by electrostatic interaction (78.86 ± 9.57%), and dTf coating showed the lowest (40.09 ± 10.2%). This efficiency order was confirmed by flow cytometry results. This study demonstrated the relationship between conjugation methods and the resultant QDs-Tf probes and provided a foundation for choosing appropriate QDs-Tf probes in cell labeling.

[en] This paper describes a highly efficient method for size determination of water-soluble CdSe/ZnS core-shell quantum dots (QDs) by capillary electrophoresis (CE) using polymer additive as sieving medium. The influence of some factors, such as kinds and concentrations of the sieving medium, pH, concentrations of the background electrolyte (BGE) and applied voltage, on the separation of QDs was investigated. Under the optimal separation conditions, four different sized QDs were successfully separated, and the relative standard deviation (RSD) of the migration times for these QDs was below 1.013%. In addition, an equation was fit by taking into account the correlation existing between the electrophoretic mobilities and the sizes of a set of QDs. The feasibility of this equation to measure the sizes of other QDs was confirmed by comparison with the sizes obtained by transmission electron microscopy (TEM) experiment. This work offers a novel method for size determination of QDs, and provides an important reference on the study of QDs based on CE.

[en] The resonance energy transfer between chemiluminescence donor (luminol-H₂O₂ system) and quantum dots (QDs, emission at 593 nm) acceptors (CRET) was investigated. The resonance energy transfer efficiencies were compared while the oil soluble QDs, water soluble QDs (modified with thioglycolate) and QD-HRP conjugates were used as acceptor. The fluorescence of QD can be observed in the three cases, indicating that the CRET occurs while QD acceptor in different status was used. The highest CRET efficiency (10.7%) was obtained in the case of oil soluble QDs, and the lowest CRET efficiency (2.7%) was observed in the QD-HRP conjugates case. This result is coincident with the quantum yields of the acceptors (18.3% and 0.4%). The same result was observed in another similar set of experiment, in which the amphiphilic polymer modified QDs (emission at 675 nm) were used. It suggests that the quantum yield of the QD in different status is the crucial factor to the CRET efficiency. Furthermore, the multiplexed CRET between luminol donor and three different sizes QD acceptors was observed simultaneously. This work will offer useful support for improving the CRET studies based on quantum dots

[en] The photoluminescence of water-soluble CdSe/ZnS core/shell quantum dots is found to be temperature-dependent: as temperature arising from 280 K to 351 K, the photoluminescence declines with emission peak shifting towards the red at a rate of ∼0.11 nm K^-1. And the studies show that the photoluminescence of water-soluble CdSe/ZnS quantum dots with core capped by a thinner ZnS shell is more sensitive to temperature than that of ones with core capped by a thicker one. That is, with 50% decrement of the quantum yield the temperature of the former need to arise from 280 K to 295 K, while the latter requires much higher temperature (315.6 K), which means that the integrality of shell coverage is a very important factor on temperature-sensitivity to for the photoluminescence of water-soluble CdSe/ZnS quantum dots. Moreover, it is found that the water-soluble CdSe quantum dots with different core sizes, whose cores are capped by thicker ZnS shells, possess almost the same sensitivity to the temperature. All of the studies about photoluminescence temperature-dependence of water-soluble CdSe/ZnS core/shell quantum dots show an indispensable proof for their applications in life science

[en] A flow cytometric detecting technology based on quantum dots (QDs)-encoded beads has been described. Using this technology, several QDs-encoded beads with different code were identified effectively, and the target molecule (DNA sequence) in solution was also detected accurately by coupling to its complementary sequence probed on QDs-encoded beads through DNA hybridization assay. The resolution of this technology for encoded beads is resulted from two longer wavelength fluorescence identification signals (yellow and red fluorescent signals of QDs), and the third shorter wavelength fluorescence signal (green reporting signal of fluorescein isothiocyanate (FITC)) for the determination of reaction between probe and target. In experiment, because of QDs' unique optical character, only one excitation light source was needed to excite the QDs and probe dye FITC synchronously comparing with other flow cytometric assay technology. The results show that this technology has present excellent repeatability and good accuracy. It will become a promising multiple assay platform in various application fields after further improvement