In this survey, N, La co-doped TiO 2 nanocrystals are synthesized through simple sol-gel method. Results reveal that both elements of N and La are introduced successfully into the structure of TiO 2 and exist as the form of La (Ti-O-La) bonds, N (N-Ti-O) bonds and N (Ti-O-N) bonds by several characterization analysis, thereby resulting in the formation of new impurity energy level between the forbidden bands, and great enhancement of light absorption ability in visible light region. These resulting samples are fabricated for low-temperature-based dye-sensitized solar cells (DSSCs), and the highest temperature of the whole process is 120 • C. EIS, Bode plot and I-V analysis are employed to measure photovoltaic performance of DSSCs. The photoelectric conversion efficiency (η) of DSSCs with co-doped TiO 2 materials as the photoanode is 5.33%, and when compared to pure TiO 2 -based cell (4.02%), the η is increased by 32.6%. Dye-sensitized solar cells (DSSCs) have attracted a lot of research interest due to the low-cost, easy fabrication, good stability, and high photoelectric conversion efficiency.1 However, the traditional fabrication procedure of DSSCs requires not only the heavy FTO substrate, but also a high temperature calcination process at about 500 • C. These will limit the large area production and commercial application of DSSCs. In order to overcome these problems, flexible DSSCs with their incomparable advantages have attracted more interest of scientists, 2 compared with the traditional high temperaturebased DSSCs. By using the flexible substrate, the high temperature calcination process is not needed, which can save energy and reduce the production cost. More importantly, a wide range of flexible substrates can be applied in the fabrication of flexible DSSCs. Generally, the transparency of the solar cell substrate need to be more than 80%, and thus only FTO can be employed in the high temperature-based DSSCs. For the low temperature-based DSSCs, the substrate can involve FTO, ITO-PET (ITO-coated pol(ethylene terephthalate), ITO-PEN (ITO-coated polyethylene naphthalate), Ti foil and Ti meshes, [3][4][5] ZnO/Al thin film with high transmittance, 6 etc. It is believed that the cell based on the flexible substrate should possess the merits of being light weight, foldable and easy to carry, and thus can be used in portable electronic products. Furthermore, the cell preparation process is simple and suitable for industrial roll-to-roll mass production. It is known that the fabrication of photoanode at low temperature is essential for these flexible DSSCs. The paste employed for the generation of photoanode does not have to undergo a high temperature (about 500• C) annealing process, since no organic materials are introduced. After a slight agitation, the paste could be dried at low temperature(<150• C). Unfortunately, it is reported that the short-circuit current (J sc ) is low without the high temperature calcination process, which is the main reason for the poorer efficiency realized for the low temperatur...

To study the spatial and temporal trends of water quality in the Yuqiao Reservoir (Ji County, Tianjin) in China, water quality data for ten physical and chemical parameters from three monitoring stations (S1, S2 and S3) was collected from 1989 to 2007 and from an other three stations (S4, S5 and S6) during the period of 1999-2007. A one-way ANOVA was employed to evaluate the spatial variation of water quality for each station. The results showed that there were statistically significant spatial differences for most water quality parameters except temperature and dissolved oxygen in the entire reservoir, and the concentrations of most parameters were higher in the uppermost part of the reservoir. The temporal trend study was conducted using the Seasonal-Kendall's test. The results revealed improving trends of water quality from 1989 to 2007, including a reduction of total phosphorous, temperature and biochemical oxygen demand and an increase of dissolved oxygen. High N:P ratios, ranging from 52.61 to 78.75, indicated that the reservoir was a phosphorous-limited environment. This study suggests long-term spatial and temporal variations of water quality in the Yuqiao Reservoir, which could be informative for water quality managers and scientists.

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