Preparation, characterization, and analytical applications of a novel polymer stationary phase with embedded or grafted carbon fibers

A polymer-based chromatographic stationary phase with embedded or grafted multi-walled carbon nanotubes (MWCNTs) has been developed. Three different synthetic methods were utilized to combine the nano-fibers with the substrate of polystyrene-divinylbenzene (PS-DVB). After optimizing the synthetic conditions, this novel polystyrene-divinylbenzene-carbon nanotube (PS-DVB-CNT) stationary phase was characterized by scanning electron microscopy, Raman spectroscopy, thermogravimetric analysis, chemical adsorption and desorption measurement, and mechanical stability test. Compared to PS-DVB particles, PS-DVB-CNT particles have certain improvement in physical and chromatographic performances because the addition of MWCNTs has altered the structures of the particles. The novel stationary phase owns satisfactory resolution, wide pH endurance, and long lifetime, which can be used as an extent to normal HPLC.     

配位聚合物M(H2O)2[Ni(CN)4]·xH2O的合成、晶体结构及性能研究

以[Ni(CN)4]2-为构筑基元,与过渡金属离子Mn2+通过溶液缓慢扩散法合成出二维Hofmann类氰基桥联配位聚合物Mn(H2O)2[Ni(CN)4]·4H2O(1),并解析了其晶体结构.配位聚合物1属正交晶系,空间群Cmcm,晶胞参数a=0.73080(5)nm,b=1.21372(8)nm,c=1.40875(9)nm,α=β=γ=90°,Ni和Mn中心通过氰桥交互连接构成二维波浪形层状结构.通过混合法得到系列Hofmann类配位聚合物M(H2O)2[Ni(CN)4]·xH2O(M=Mn,Fe,Co,Ni,Cd)的粉末样品,粉末XRD结果表明,系列配位聚合物具有与1相同的晶体结构;变温粉末XRD和热重分析结果表明,系列配位聚合物具有较高的热稳定性.以Mn(H2O)2[Ni(CN)4]·xH2O的脱水样品为构筑模块与柱状配体pyrazine组装构筑的三维多孔配位聚合物具有一定的储气性能.     

基于同一天然手性源(4R)-羟基脯氨酸的(2S,4S)/(2S,4R)-4-氟谷氨酸的立体专一性合成

基于同一天然手性源(4R)-羟基脯氨酸,通过Mitsunobo反应、全氟丁基磺酰氟作用下的氟化反应以及NaIO4/RuO2作用下的氧化反应,立体专一性地合成了(2S,4S)/(2S,4R)-4-氟谷氨酸.     

Theoretical studies on the electronic structures and spectra of single silicon-doped SWCNTs

The equilibrium geometries and electronic structures of a series of SWCNTs doped with a silicon atom were studied by using density function theory (DFT). The most stable doping site of silicon predicted at B3LYP/6-31G(d,p) level was located near the boundary of the SWCNTs. The energy gaps of (3,3) C₄₈, (3,3) C₆₀ and (3,3) C₇₂ were respectively decreased by 0.43, 0.25 and 0.14 eV after doping. Based on the B3LYP/6-31G(d) optimized geometries, the electronic spectra of the doped SWCNTs were computed using the INDO/CIS method. The first UV absorption at 973.9 nm of (5,5)-Si(L) (C₅₉Si) compared with that at 937.5 nm of (5,5) (C₆₀) was red-shifted. The ¹³C NMR spectra and nuclear independent chemical shifts (NICS) of the doped SWCNTs were investigated at B3LYP/6-31G(d) level. The chemical shift at 119.4 of the carbon atom bonded with the silicon atom in (3,3)-Si(L) (C₅₉Si) in comparison with that at 144.1 of the same carbon atom in (3,3) (C₆₀) moved upfield. The tendency of the aromaticity (NICS = −0.1) for (3,3)-Si(H) (C₄₇Si) with respect to that of the anti-aromaticity (NICS = 6.0) for (3,3) (C₄₈) was predicted.      

Tea Polyphenols Reducing Lipopolysaccharide-induced Inflammatory Responses in RAW264.7 Macrophages via NF-κB Pathway

The anti-inflammatory activity of tea polyphenols(TPs) in RAW264.7 macrophages stimulated by lipopolysaccharide(LPS) was investigated in this paper. RAW264.7 macrophages were treated with different concentrations of TP(0, 12.5, 25, 50, 100, and 200 μg/mL) and then stimulated by LPS. Another blank control group was set up. The expression of pro-inflammatory cytokines associated with the nuclear factor-kappa B(NF-κB) signaling pathway was investigated before and after TP treatment. Pretreatment of RAW264.7 cells with TP decreased the expression of tumor necrosis factor-α(TNF-α), interleukin-6(IL-6) and interleukin 1 beta(IL-1β) pro-inflammatory cytokines. In addition, TP inhibited the phosphorylation of p65 and IκB by blocking the phosphorylation and the degradation of NF-κB inhibitor protein. In conclusion, TP exerts anti-inflammatory effects by regulating the release of inflammatory mediators via the NF-κB signaling pathway.     

A single pump column-switching technique coupled with polystyrene-divinylbenzene-carbon nanotubes column for the determination of trace anions in different concentrated organic matrices by ion chromatography

An ion chromatographic method with on-line sample pretreatment was developed for the trace analysis of seven common anions in concentrated matrices. The pretreatment column used in this study consisted of polystyrene-divinylbenzene (PS-DVB) and multi-walled carbon nanotubes (MWCNTs). It was too hydrophobic to retain different inorganic anions, but it showed a strong affinity for organic compounds. Thus, this chromatographic system could be used to detect trace anions in organic solvents, organic acids and relevant salts. The addition of MWCNTs decreased the surface areas of stationary phases and the retention times of organic matrices were shortened. Compared with conventional column-switching technique, only a single instrument (ICS2100) was needed in this system, including a pump, a conductivity detector, an eluent generator, a six-port valve and a ten-port valve. An electrochemical self-generating suppressor (ESGS) was adopted to convert the eluent of KOH into water for the matrix elimination. Two different eluent were employed in the chromatographic system, one for separation and the other for matrix elimination. The sample pretreatment and analysis were realized simultaneously. After optimization of this system, a calibration study was conducted by preparing and analyzing eight concentrations (between 5 and 5000 μg L(-1)) of mixture standards of seven anions in deionized water. The linearity was between 0.9990 and 0.9998, and the detection limits ranged from 0.41 to 3.17 μg L(-1). A spiking study was performed on three representative organic chemicals with satisfactory recoveries between 88.1% and 118.5% when the concentrations of the matrices did not exceed 10 g L(-1).     

Highly selective fluorescent OFF-ON thiol probes based on dyads of BODIPY and potent intramolecular electron sink 2,4-dinitrobenzenesulfonyl subunits

Two highly selective OFF-ON green emitting fluorescent thiol probes (1 and 2) with intense absorption in the visible spectrum (molar extinction coefficient ε is up to 73?800 M(-1) cm(-1) at 509 nm) based on dyads of BODIPY (as electron donor of the photo-induced electron transfer, i.e.PET) and 2,4-dinitrobenzenesulfonyl (DNBS) (as electron acceptor of the PET process) were devised. The single crystal structures of the two probes were determined. The distance between the electron donor (BODIPY fluorophore) and the electron acceptor (DNBS) of probe 2 is larger than that of probe 1, as a result the contrast ratio (or the PET efficiency) of probe 2 is smaller than that of probe 1. However, fluorescence OFF-ON switching effects were observed for both probe 1 and probe 2 in the presence of cysteine (the emission enhancement is 300-fold for probe 1 and 54-fold for probe 2). The fluorescence OFF-ON sensing mechanism is rationalized by DFT/TDDFT calculations. We demonstrated with DFT calculations that DNBS is ca. 0.76 eV more potent to accept electrons than the maleimide moiety. The probes were used for fluorescent imaging of cellular thiols.     

含X-型二维液晶基元和顺式-4,4′-双(4-羟基苯基偶氮)二苯并-18-冠-6冠醚环液晶共聚酯的合成与表征

以4,4'-(α,ω-辛二酰氧)二苯甲酰氯(M1)、2,5-双[4-'(对癸氧基苯基)苯甲酰氧基]对苯二酚(M2)和顺式-4,4'-双(4-羟基苯基偶氮)二苯并-18-冠-6(M3)为单体,通过溶液共缩聚反应,合成了一系列新的含X-型二维液晶基元和顺式-4,4'-双(4-羟基苯基偶氮)二苯并-18-冠-6冠醚环的主链犁液晶共聚酯.单体1(M1)由对羟基苯甲酸和辛二酰氯,通过酯化和取代反应制备,单体2(M2)由2,5-二羟基苯醌和对癸氧基苯基苯甲酰氯通过酯化和还原反应制备,单体3(M3)由顺式-二氨基二苯并-18-冠-6和苯酚通过重氮化和偶联反应制备.共聚酯的分子量小高,[η]在0.30～0.39之间.单体的化学结构通过 IR、UV、1H-NMR、MS 和元素分析等方法确证.共聚酯的外观为黄色粉状固体,除共聚酯 CP9 外,室温下不溶于 CHCl3 和 THF 溶剂.共聚酯的性质采用 GPC、[η]、DSC、TG、WAXD 和 POM 等方法进行了研究.发现所有的共聚酯加热到各自的熔融温度以上都能形成液晶态,在液晶态可以观察到近晶相和向列相的典型织构.共聚酯的熔融温度(Tm)和各向同性温度(T1)随共聚酯分子中顺式-4,4'-双(4-羟基苯基偶氮)二苯并-18-冠-6用量的改变呈规律性变化.WAXD 研究进一步证实了共聚酯的液晶性.     

Closely adjacent gold nanoparticles linked by chemisorption of neutral rhodamine 123 molecules providing enormous SERS intensity

Addition of neutral R123 molecules (10(-7) M) to an as-prepared gold nanoparticles (AuNPs) suspension generated flocculates that are a small number of closely adjacent particles. Formation of AuNP flocculates was evidenced by the coupled localized plasmon peak at 720-750 nm. The AuNP flocculates provided pronounced SERS spectra of adsorbed neutral R123 molecules (SERS-A) as anticipated by FDTD (Finite Difference Time Domain) simulations. The observed SERS spectra are significantly different from those of cationic R123(+) molecules (SERS-B), which electrostatically adsorbed on Cl(-)-treated AuNPs. The difference is not simply due to deprotonation but reflects a distinct difference in adsorption nature between neutral R123 and cationic R123(+) molecules. Indeed neutral R123 molecules exclusively gave an Au-N stretching band at 202 cm(-1), showing the chemisorption on Au surfaces through lone pair electrons at the amino groups. The different adsorption nature is further evidenced by the observation that cationic R123(+) molecules adsorbed on as-prepared (without NaCl addition) AuNP flocculates gave both SERS-A and SERS-B spectra. Thus, the cationic R123(+) molecules form the flocculates both by chemisorption and electrostatic adsorption owing to modest surface charge on as-prepared AuNPs.     

Crown ether complex cation ionic liquids: preparation and applications in organic reactions

A series of crown ether complex cation ionic liquids (CECILs) were designed, synthesised and characterised by NMR spectroscopy, HRMS, thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. Their applications in various organic reactions were investigated: [15-C-5Na][OH], [15-C-5Na][OAc], [18-C-6K][OH] and [18-C-6K][OAc] (15-C-5=[15]crown-5; 18-C-6=[18]crown-6) efficiently catalysed the Michael addition of alkenes and relevant nucleophiles; [18-C-6K][OH] and [15-C-5Na][OH] effectively catalysed the Henry reaction of nitromethane and aromatic aldehydes; [18-C-6K][OH] has excellent catalytic efficiency for Knoevenagel condensation of aromatic aldehydes and malononitrile; PdCl(2) /[18-C-6K](3)[PO(4)]/K(2)CO(3) efficaciously catalysed the Heck reaction of olefins and aromatic halides; [18-C-6K][BrO(3)] can be used as both oxidant and solvent in the oxidation reaction of aromatic alcohols. The CECIL catalysts [15-C-5Na][OH] (Michael addition) and [18-C-6K][OH] (Henry reaction) can be recycled and reused several times without obvious loss of activity and their recovery is very simple.