Synthesis and Chromatographic Evaluation of Perfluorooctyl Stationary Phase for Separation of Basic Compounds

Fluorinated stationary phases provide unique separation effect on basic compounds, due to the fluorine atoms, and pentafluorophenyl stationary phases (PFPs) are the most widely used. Considering that some fluoroalkyls have higher fluorine contents than PFPs do, it is speculated that fluoroalkyl stationary phases should have potential new applications. Herein, we synthesized a silica-based stationary phase bonding perfluoroctyl (FC8) proved by characterization through elemental analysis and solid-state ¹³C cross-polarization/magic-anglespinning nuclear magnetic resonance. The chromatographic behavior of the stationary phase was evaluated with test compounds. In addition, to further study the applicability of FC8 materials, Corydalis decumbens (Thunb.) Pers. fraction, considered as a challenging medicine on reversed-phase chromatography columns, was chosen as a test sample. Results demonstrated that the FC8 stationary phase had better and more satisfactory separation performance than the PFP stationary phase on basic compounds.

     

Post-modification using aluminum isopropoxide after dye-sensitization for improved performance and stability of quasi-solid-state solar cells

In this study, dye-sensitized TiO₂ electrodes were immersed into a solution of aluminum isopropoxide and after hydrolysis quasi-solid-state solar cells were fabricated. The interaction between the dye and the resulting Al₂O₃ overlayer was investigated by ultraviolet–visible (UV–vis) spectrum, Fourier transform infrared (FTIR) spectrum and X-ray photoelectron spectrum (XPS). The current density–voltage (I–V) characteristics showed that the overlayer increased the photovoltage and decreased the photocurrent under low intensity irradiation, and increased both the photovoltage and photocurrent under AM 1.5 irradiation. The Al₂O₃ overlayer at the dye/electrolyte interface resulted in a 28% improvement in overall photo-to-electrical conversion efficiency from 2.60 to 3.32%. Dark current measurements showed that Al₂O₃ acted as an insulator barrier to retard recombination between the TiO₂ and dye/quasi-solid-state electrolyte interface. Without encapsulation, dye-sensitized solar cells with Al₂O₃ coating after sensitization also exhibited improved stability compared to cells without coating.     

A microfluidic device using a green organic light emitting diode as an integrated excitation source

A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively.     

Photocatalysis of PbS quantum dots in a quantum dot-sensitized solar cell: photovoltaic performance and characteristics

PbS QDs have been synthesized by an in situ photocatalysis method using the photocatalytic activity of nanocrystalline TiO(2) films. Both the photovoltaic response and size of the synthesized PbS QDs were analyzed. Compared with the conventional synthesis route, this method is simpler and produces less waste.     

树枝状吡啶亚胺铬催化剂的合成及其催化性能研究

以1. 0代聚酰胺-胺树枝状大分子为配体骨架、吡啶二甲醛为原料,合成了一种新型树枝状吡啶亚胺(DPI)配体,再以CrCl_3·6H_2O为络合试剂,制备DPI-Cr催化剂。采用IR、UV-Vis、MS、元素分析等确证了产物结构。考察溶剂种类、助催化剂种类、反应温度、乙烯压力以及Al/Cr摩尔比对DPI-Cr催化乙烯齐聚性能的影响。结果表明,DPI-Cr催化剂表现出良好的催化活性和烯烃选择性,优化反应条件下,催化效率可达4. 91×10~4g/mol Cr·h,C_6和C_8选择性为73. 90%。     

Preparation of chromium catalysts bearing bispyridylamine and its performance in ethylene oligomerization

Transition Metal Chemistry - A series of bispyridylamine ligands and chromium complexes designed for ethylene oligomerization have been synthesized, which was made up of both neutral organic ligand...     

A flexible blue light sensitive organic photodiode with high properties for the applications in low‐voltage‐control circuit and flexion sensors

Low‐voltage‐control circuit is one of the most important parts of the modern electrical control system due to the avoidance of operation risk and easy automation. Here, based on a C₆₀: m‐MTDATA bulk heterojunction, a blue‐light‐sensitive organic photodiode (OPD) is explored for the development of flexible low‐voltage‐control circuit. The control of circuit under 2000 V high voltage is achieved. The influences of the organic‐layer thickness, the donor/acceptor volume ratio and the matching of energy levels on the photocurrent are investigated. The maximum light/dark current ratio and current transfer ratio of 1.3 × 10⁴ and 1.3% are achieved, respectively. The highest photoresponse is up to 130 mA/W, markedly higher than some commercial inorganic photodiodes. This device could also be used as flexion and mechanical force sensors with the current density changing under different bending conditions. Therefore, this sort of OPD has a promising application in low‐voltage‐controlled, high‐voltage‐endurable hands for intelligent robots.     

Selective ethylene oligomerization bearing hyperbranched bispyridylamine chromium catalyst

Two new hyperbranched bispyridylamine ligands and multinuclear chromium complexes were synthesized with 1.0?G hyperbranched macromolecules, 2-chloropyridine, 2-chloro-4-methylpyridine and CrCl₃(THF)₃ as raw materials. The structures of hyperbranched ligands and chromium complexes were characterized by UV, FT-IR, ¹H NMR, ESI-MS, and elemental analysis. These hyperbranched chromium complexes were evaluated as catalyst precursors by using MAO as activator in the oligomerization of ethylene. Effects of reaction temperature, reaction pressure, Al/Cr molar ratio, concentration of catalyst, solvent, and the structure of catalysts on the catalytic activity and product selectivity were investigated. The oligomerization results showed that with increase of reaction temperature, reaction pressure, and Al/Cr molar ratio, the catalytic activity increased and then decreased; the catalytic activity continuously decreased as the amount of catalyst increased. The products were mainly based on C₆ and C₈. Under optimized conditions, the catalytic system of hyperbranched NNN/Cr(III)/MAO led to activity of 1.26?×?10⁵ g/(mol·Cr·h) and 63.34% selectivity for C₆ and C₈.     

Control of intramolecular π-π stacking interaction in cationic iridium complexes via fluorination of pendant phenyl rings

Intramolecular π-π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)(2)(F2phpzpy)]PF(6) (2) and [Ir(ppy)(2)(F5phpzpy)]PF(6) (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)(2)(phpzpy)]PF(6) (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 ? for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular π-π stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face π-π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π-π stacking interaction remains on the lowest triplet state.     

Generation and growth mechanism of metal (Fe, Co, Ni) nanotube arrays.

Nanotubes composed of layered or nonlayered materials have been synthesized through various methods, among which template-based electrodeposition technology provides a versatile technique for synthesizing one-dimensional nanostructured materials. However, the growth mechanism of nanotubes using the template method is seldom clarified. Herein, we present the systematic preparation of metal nanotube arrays and put forward the growth mechanism, termed current-directed tubular growth (CDTG), for template-based electrodeposition. There are competitive growth rates for metal atoms entering the crystal lattice, that is, v( parallel) (growth rate parallel to current direction) and v( perpendicular) (growth rate perpendicular to current direction). Metal nanotubes can be obtained at v( parallel)>v( perpendicular), while nanowires can be obtained at v( parallel) approximately v( perpendicular). The as-synthesized metal (Fe, Co, Ni) nanotubes are constructed from nonlayered materials, which are of body-centered cubic iron structure, hexagonal close packed cobalt structure, and face-centered cubic nickel structure, respectively. The CDTG mechanism is expected to have applications in designing and synthesizing other metal nanotubes and even compound nanotubes via template-based electrodeposition technology.