Yi Ni

Study and enhance the photovoltaic properties of narrow-bandgap Cu2SnS3 solar cell by p–n junction interface modification

Photovoltaic properties of narrow-bandgap Cu(2)SnS(3) (CTS) are studied for the first time by employing a superstrate solar cell structure of fluorine-doped tin oxide (FTO) glass/TiO(2)/In(2)S(3)/CTS/Mo. The structural, optical, and electronic characteristics of the CTS make it great potential as bottom cell absorber material for low-cost thin film tandem solar cell application. Furthermore, by inserting a thin low temperature deposited In(2)S(3) layer between the In(2)S(3) buffer layer and the CTS absorber layer, an enhancement in the performance of the solar cell can be achieved, leading to about 75% improvement (η=1.92%) over the unmodified device (η=1.10%).

Acetic acid denaturing pulsed field capillary electrophoresis for RNA separation

Based on our previous work of in‐capillary denaturing polymer electrophoresis, we present a study of RNA molecular separation up to 6.0 kilo nucleotide by pulsed field CE. This is the first systematic investigation of electrophoresis of a larger molecular mass RNA in linear hydroxyethylcellulose (HEC) under pulsed field conditions. The parameters that may influence the separation performance, e.g. gel polymer concentration, modulation depth and pulse frequency, are analyzed in terms of resolution and mobility. For denaturing and separating RNA in the capillary simultaneously, 2 M acetic acid was added into the HEC polymer to serve as separation buffer. Result shows that (i) in pulsed field conditions, RNA separation can be achieved in a wide range of concentration of HEC polymer, and RNA fragments between 0.3 and 0.6 kilo nucleotide are sensitive to the polymer concentration; (ii) under certain pulsed field conditions, RNA fragments move linearly as the modulation depth increases; (iii) 12.5 Hz is the resonance frequency for RNA reorientation time and applied frequency.

Electromigration behavior of nucleic acids in capillary electrophoresis under pulsed-field conditions.

We have presented a study focused on the migration pattern of double-stranded DNA (dsDNA) and RNA under pulsed field conditions. By calculating the dependence of nucleic acid mobility on its molecular size in a double logarithm plot, we found that (I) dsDNA molecules proceeded by a sigmoidal migration regime which was probably related to Ogston sieving, transition regime, and reptation model. Furthermore, the transition regime disappeared if DNA was resolved in a higher molecular mass HEC. (II) The migration pattern of RNA was relevant to the denaturant used for separation. When RNA was denatured by acetic acid, its mobility parabolically declined with its molecular size. The mobility was linearly decreased with the molecular size if urea was employed as denaturant. (III) RNA may migrate by Ogston, reptation without orientation mechanism when denatured by urea, whereas these two models were not suitable for RNA if denatured by acetic acid. Even though the electrophoretic conditions of PFCE were varied, the sigmoidal, linear, parabolic migration patterns could still be observed. (IV) Under certain modulation depth, the migration time (Tm) of acetic acid decreased with the increase of average separation voltage (Va), and when RNA denatured in 4.0M urea, Tm showed a linear correlation with Va. (V) The mobility of nucleic acids increased with the growth of artificial temperature in the capillary volume due to the decrease in the viscosity of the polymer. This is the first systematic and comparative research of high molecular mass nucleic acids in PFCE, which provides us deep insight into RNA and DNA migration behavior under pulsed electric field conditions.

The influence of polymer concentration, applied voltage, modulation depth and pulse frequency on DNA separation by pulsed field CE.

DNA fragments (0.1-10 kbp (kbp, kilo base pair)) separation by square-wave pulsed field CE in hydroxyethylcellulose (HEC, 1300 K) polymer was performed in this work. The effects of polymer concentration, pulse field strength, pulse frequency and modulation depth were investigated. We found that low HEC (about 0.1%) concentration is suitable for the separation of small DNA fragments (<1 kbp), whereas higher HEC concentration (>0.5%) is appropriated for high-mass DNA molecular (>1 kbp) separation. The mobility of DNA fragments is nearly linearly related to average separation voltage under pulsed field conditions. Higher modulation depth is suited to separate the longer DNA fragments and lower modulation depth favors the resolution of short DNA fragments. Thus, the intermediate modulation depth (100%) and pulse frequency (about 31.3 Hz) are prerequisite for high-resolution DNA separation.

Is pulsed electric field still effective for RNA separation in capillary electrophoresis

Pulsed field capillary electrophoresis (PFCE) is a predominant technique to cope with difficulties in resolving large DNA strands, yet it is still unclear whether pulsed electric field is effective for the separation of higher mass RNA. In this paper we focused on the role of pulsed electric field in large RNA fragments analysis by comparing RNA separation performance in PFCE with that in constant field CE. Separation performance in terms of migration mobility, plate numbers, resolution, and selectivity has been tested for the analysis of RNA from 0.1 to 10.0 kilo nucleotide (knt) under different electrophoretic conditions. Denaturation, important to obtain uniform and identifiable peaks, was accomplished by heating the sample in 4.0M urea prior to analysis and the presence of 4.0M urea in the electrophoresis buffer. Results demonstrate that unlike DNA in PFCE, the pulsed electric field mainly affects the separation performance of RNA between 0.4 and 2.0 knt. The migration mobility of long RNA fragments is not a strong function of modulation depth and pulsed frequency. Moreover, the logarithm of RNA mobility is almost inversely proportional to the logarithm of molecule size up to 6.0 knt with correlation coefficient higher than 0.99 in all the polymer concentrations measured here. Resonance frequency of RNA in PFCE was also observed. While these initial experiments show no distinct advantages of using PFCE for RNA separation, they do take further step toward characterizing the migration behavior of RNA under pulsed field conditions.

Capillary electrophoresis of a wide range of DNA fragments in a mixed solution of hydroxyethyl cellulose

We carried out capillary electrophoresis of 0.1–10.0 kilo base pair DNA fragments in a mixed hydroxyethyl cellulose (HEC) polymer. The mixed HEC polymer was prepared with different molecular weights (Mw) (90k, 250k, 720k and 1300k). The effects of important parameters, including the ratio of the mixture composition and the concentration of the mixing polymer, on the separation performance were investigated. Results show that these parameters can not only shorten the migration time of DNA without great deterioration in resolution, but they can also decrease the viscosity of the polymer, and thus make it easy to fill the capillary. Finally, we separated φ×174-Hirc II digest and λ-EcoT14 I DNA digest with high resolution in the mixed HEC solution within 18 min.

Rapid identification and quantitation for oral bacteria based on short-end capillary electrophoresis

High-speed capillary electrophoresis (HSCE) is a promising technology applied in ultra-rapid and high-performance analysis of biomolecules (such as nucleic acids, protein). In present study, the short-end capillary electrophoresis coupled with one novel space domain internal standard method (SDIS) was employed for the rapid and simultaneous analysis of specific genes from three oral bacteria (Porphyromonas gingivalis (P.g), Treponema denticola (T.d) and Tannerela forsythia (T.f)). The reliability, reproducibility and accuracy properties of above mentioned SDIS method were investigated in detail. The results showed the target gene fragments of P.g, T.d and T.f could be precisely, fast identified and quantitated within 95s via present short-end CE system. The analyte concentration and the ratio of space domain signals (between target sample and internal standard sample) featured a well linear relationship calculated via SDIS method. And the correlation coefficients R(2) and detection limits for P.g, T.d, T.f genes were 0.9855, 0.9896, 0.9969 and 0.077, 0.114 and 0.098ng/μl, respectively.

Analysis of small interfering RNA by capillary electrophoresis in hydroxyethylcellulose solutions.

The analysis of small interfering RNA (siRNA) is important for gene function studies and drug developments. We employed CE to study the separation of siRNA ladder marker, which were ten double‐stranded RNA (dsRNA) fragments ranged from 20 to 1000 bp, in solutions of hydroxyethylcellulose (HEC) polymer with different concentrations and molecular weights (Mws). Migration mechanism of dsRNA during CE was studied by the mobility and resolution length (RL) plots. We found that the RL depended on not only the concentration of HEC, but also the Mw of HEC. For instance, RL of small dsRNA fragment was more influenced by concentration of high Mw HEC than large dsRNA fragment and RL of large dsRNA fragment was more influenced by concentration of low Mw HEC than small dsRNA fragment. In addition, we found electrophoretic evidence that the structure of dsRNA was more compact than dsDNA with the same length. In practice, we succeeded to separate the glyceraldehyde 3‐phosphate dehydrogenase siRNA in the mixture of the siRNA ladder marker within 4 min.

Gene analysis of multiple oral bacteria by the polymerase chain reaction coupled with capillary polymer electrophoresis.

Capillary polymer electrophoresis is identified as a promising technology for the analysis of DNA from bacteria, virus and cell samples. In this paper, we propose an innovative capillary polymer electrophoresis protocol for the quantification of polymerase chain reaction products. The internal standard method was modified and applied to capillary polymer electrophoresis. The precision of our modified internal standard protocol was evaluated by measuring the relative standard deviation of intermediate capillary polymer electrophoresis experiments. Results showed that the relative standard deviation was reduced from 12.4-15.1 to 0.6-2.3%. Linear regression tests were also implemented to validate our protocol. The modified internal standard method showed good linearity and robust properties. Finally, the ease of our method was illustrated by analyzing a real clinical oral sample using a one-run capillary polymer electrophoresis experiment.

Design of separation length and electric field strength for high-speed DNA electrophoresis

Gel‐based DNA separation on microchip will play an important role in future genomic analysis due to its potential for high‐efficiency and high‐speed. Optimal design of microchip and separation condition is essential to take full advantage of high‐speed separation on microchip. Separation length L and electric field strength E, which are crucial for design of microchip system, are focused on in this paper. Simultaneous optimization of L and E was carried out to achieve the most rapid separation. It was shown that the condition of L and E and the shortest separation time is closely related to the shape of resolution Rs surface in a three‐dimensional space with axes E, L, and Rs. This surface was investigated, taking sample injection, detector, diffusion, and Joule heating into account. Thermal gradient broadening due to Joule heating helps to produce camber or ridge shape of Rs surface, which is essential for the shortest separation length and separation time. Sample plug length and detection volume should be more carefully controlled in microchip. The property of diffusion coefficient was shown to play a key role in determining Rs surface.