芯片毛细管电泳荧光检测器灵敏度的研究

本文采用倒置荧光显微镜,以汞灯为激发光源,自行设计组装了芯片毛细管电泳荧光检测系统。以荧光素异硫氰酸酯(FITC)为检测对象,对双通道门控光子计数器、CH151型光子计数探测器、电荷耦合器件(CCD)三种荧光检测器的灵敏度进行了比较研究。根据芯片毛细管电泳图谱分析,FITC在双通道门控光子计数器、CH151型光子计数探测器、CCD三种检测器中的检出限(S/N=3)分别为7.0×10-10mol/L,1.2×10-9mol/L,3.2×10-8mol/L。进一步采用CH151型光子计数探测器和CCD两种较常用检测器,对FITC和荧光素、曙红和荧光素两组荧光试剂的分离及检测进行了研究。结果表明,使用CH151型光子计数探测器作为检测器,灵敏度高,基线稳定,信噪比高。     

Electrochemical and Structural Characterisation of Dip-Coated Fe/Ti Oxide Films Prepared by the Sol-Gel Route

Thin solid films of mixed Fe/Ti oxide composition (Fe/Ti molar ratios: 0.5∶1, 1∶1, 1.5∶1) have been made from Fe(NO₃)₃ alcoholic solution to which Ti(OiPr)₄ was added. Films have been deposited by the dip-coating technique and heat-treated at 300°C and 500°C. Powders of Fe/Ti oxide heat-treated at 300°C are amorphous, while powders annealed at 500°C for 40 hours transformed to mixed rutile, pseudobrookite and hematite phases. The structure of the XRD amorphous films was identified with the help of near-normal reflection absorption (6°) (IRRA) and near-grazing incidence angle (NGIA) spectroscopy. NGIA FT-IR spectra of films are characterised with a single phonon mode appearing in the spectral range 600–950 cm⁻¹ which shifts with increasing Ti concentration from 675 cm⁻¹ (Fe₂O₃) to 904 cm⁻¹ (TiO₂) thus exhibiting one-mode behavior. Electrochemical investigations made with the help of cyclic voltammetry (CV) and chronocoulometry (CPC) performed in 0.01M LiOH and in 1M LiClO₄/propylene carbonate electrolytes revealed that films are able to uptake reversibly Li⁺ ions with a charge capacity (Q) per film thickness (d) in the range 0.1–0.26 mC/cm²nm and 0.06 mC/cm²nm, respectively. The temperature at which the films were prepared alters the rate of Li⁺ insertion which is faster for less compact films obtained at 300°C. In situ UV-VIS spectroelectrochemical measurements revealed that Fe/Ti oxide films bleached in the UV spectral region (300 nm<λ<450 nm) and colored in the VIS spectral region (450 nm<λ<800 nm), thus exhibiting mixed anodic and cathodic electrochromism.     

The sphere-rod transition of micelles of dodecyldimethylammonium bromide in aqueous NaBr solutions,and the effects of counterion binding on the micelle size,shape and structure

Micelle size and shape of dodecyldimethylammonium bromide have been determined by measurement of light scattering from its aqueous NaBr solutions. In water and in the presence of NaBr up to 0.07 M, the Debye plots give straight lines with positive slopes, and spherical micelles having molecular weight less than 30 000 are formed. At higher NaBr concentrations, the Debye plots decrease with increasing micelle concentration, indicating the aggregation of the primary spherical micelles into larger secondary micelles. The molecular weight and the radius of gyration of the secondary micelles increase with increasing NaBr concentration, and the relation between molecular weight and radius of gyration suggests that they are rodlike and flexible. Linear logarithmic relations between micelle molecular weight and ionic strength hold for spherical and rodlike micelles, respectively, and the threshold concentration of NaBr for the sphere-rod transition is located at 0.07 M. The spherical micelle of dodecyldimethylammonium ions has a size more than 20 surfactant ions larger in NaBr solutions than in NaCl solutions, and their rodlike micelle has a shorter length in NaBr solutions than in NaCl solutions, when compared at an identical aggregation number, indicating 2 more surfactant ions in its cross-section.     

MnWO4/生物质衍生碳纳米复合催化剂的制备及催化性能

通过共沉淀法合成了双金属氧化物MnWO₄镶嵌生物质衍生碳（MnWO₄/BC）纳米复合催化剂,并将其作为对电极（counter electrode,CE）催化剂组装了染料敏化太阳能电池（dye-sensitized solar cell,DSSC）,探究了MnWO₄/BC在非碘体系中的催化性能和光伏性能。结果表明：在铜氧化还原（Cu²⁺/Cu⁺）电对DSSC中获得的光电能量转换效率（power conversion efficiency,PCE）为3.57%（D35）和1.59%（Y123）,高于Pt电极的PCE（3.12%,1.16%）;50次连续循环伏安测试表明,MnWO₄/BC催化剂具有较好的电化学稳定性。     

Application of an efficient strategy based on liquid–liquid extraction,high‐speed counter‐current chromatography,and preparative HPLC for the rapid enrichment,separation, and purification of four anthraquinones from Rheum tanguticum

This study presents an efficient strategy based on liquid–liquid extraction, high‐speed counter‐current chromatography, and preparative HPLC for the rapid enrichment, separation, and purification of four anthraquinones from Rheum tanguticum. A new solvent system composed of petroleum ether/ethyl acetate/water (4:2:1, v/v/v) was developed for the liquid–liquid extraction of the crude extract from R. tanguticum. As a result, emodin, aloe‐emodin, physcion, and chrysophanol were greatly enriched in the organic layer. In addition, an efficient method was successfully established to separate and purify the above anthraquinones by high‐speed counter‐current chromatography and preparative HPLC. This study supplies a new alternative method for the rapid enrichment, separation, and purification of emodin, aloe‐emodin, physcione, and chrysophanol.     

对电极材料对非贵金属电催化剂耐久性评价的影响

质子交换膜燃料电池(PEMFCs)环境友好,具有高的能量转换效率,已受到了广泛的关注.目前,铂基电催化剂广泛使用在 PEMFCs中,但铂的储量有限,活性低,耐久性差,成本高,急需开发高性能的非贵金属电催化剂替代铂基电催化剂.非贵金属电催化剂的电化学表征基本上都沿用了铂基电催化剂的评价体系和方法,不一定适用于非贵金属电催化剂的表征.
　　本文选用铂和石墨为对电极考察其对非贵金属电催化剂在酸性电解质中耐久性测试的影响.当使用铂对电极时,商业 Pt/C电催化剂的氧还原(ORR)活性随着耐久性测试圈数的增加而降低,而非贵金属电催化剂的氧还原活性在耐久性测试过程中的变化规律与商业 Pt/C不同,呈现先降低,后升高的规律.耐久性测试前后的透射电镜(TEM)分析表明非贵金属电催化剂经过耐久性测试后,在电催化剂表面生长了铂纳米颗粒.高分辨透射电镜(HRTEM)和能量色散 X射线光谱(EDX)进一步证明以铂为对电极的三电极体系,在进行非贵金属电催化剂耐久性测试的过程中,非贵金属电催化剂表面生长了铂纳米颗粒,使得非贵金属电催化剂的 ORR活性在耐久性测试后得到显著提高.耐久性测试前后,非贵金属电催化剂氧还原过程的电子转移数由3.7变为4.0,再次证明了耐久性测试过程中铂颗粒的生成.在三电极电化学体系中,当工作电极发生阴极反应时,对电极为阳极反应,反之亦然,即在工作电极上发生的任何电化学过程,都会在对电极上完成相反的电化学过程.在循环电位扫描过程中,当铂对电极的电压高于1.0 V (vs RHE)时,开始发生铂的溶解现象,并且当电压高于1.2 V (vs RHE)时,铂的溶解量会急剧增加,部分溶解的铂会扩散到工作电极附近,并在工作电极的非贵金属电催化剂表面发生沉积作用.随着扫描圈数的增加,沉积的铂纳米颗粒的数量增加,颗粒变大,从而使非贵金属电催化剂的表观 ORR活性显著提高.该现象使得非贵金属电催化剂在酸性电解质中无法表现出其真实的耐久性.当选用石墨棒为对电极材料时,非贵金属电催化剂在酸性电解质中的 ORR活性不会受到对电极材料的影响.
　　通过考察对电极材料对非贵金属电催化剂在酸性电解质中耐久性能的影响,可以得出结论,即对非贵金属电催化剂在酸性电解质中的耐久性测试中,不宜使用铂对电极,应该使用石墨为对电极材料,以防止对电极材料干扰耐久性测试.     

反离子对离子液体氯化1-(2-羟乙基)-3-十二烷基咪唑在水溶液中自组装的影响

用表面张力法和荧光探针技术分别测定了阳离子型离子液体表面活性剂氯化1-(2-羟乙基)-3-十二烷基咪唑([C2OHC12im]Cl)在无机盐(NaX,X=Cl-,Br-,I-和Na2SO4)水溶液中的自组装参数。 结果表明,反离子通过结合[C2OHC12im]+并中和其表面电荷,使[C2OHC12im]+的临界胶束浓度(CMC)和胶束平均聚集数(Nm)等自组装参数明显改变;改变幅度按照Cl-＜Br-＜I-＜SO2-4次序递增;但是反离子(Cl-、Br-和SO2-4)种类对临界胶束平均聚集数(Nm,c)和胶束微极性([I1/I3]m)的影响不甚明显;随着Br-浓度增加,lg CMC线性减小,而Nm则以幂函数形式递增。     

碳纳米纤维负载Co3S4复合材料的合成及其在染料敏化太阳电池对电极的应用

采用水热法合成四硫化三钴（Co₃S₄）催化材料,并利用球磨和喷涂技术将其制备成对电极,结合新型无碘电解液Co²⁺/Co³⁺用于染料敏化太阳电池（dye-sensitized solar cells,简称DSCs）来研究其光电性能。测试结果显示,基于Co₃S₄对电极,DSCs的能量转化效率（power conversion efficiency,简称PCE）只有6.06%,远远低于Pt对电极（8.05%）。为了提高Co₃S₄的催化能力,采用静电纺丝技术制备碳纳米纤维（electrospun carbon nanofibers,简称ECs）,结合水热法制备出不同负载量的碳纳米纤维负载四硫化三钴（Co₃S₄/ECs）复合催化材料用于对电极,结果表明,Co₃S₄/ECs的PCE最高可达（8.22±0.08）%,优于Pt对电极。     

染料敏化太阳能电池对电极La2Mo2O7复合MWCNTs非Pt催化剂的制备与性能

通过高温固相法对醋酸镧（C₆H₉O₆La·xH₂O）与高钼酸铵（（NH₄）₆Mo₇O₂₄·4H₂O）在一定条件下热解制备非Pt催化剂La₂Mo₂O₇（La₂O₃-2MoO₂）。进一步采用2种方法将La₂Mo₂O₇与多壁碳纳米管（MWCNTs）进行复合,一种是将La₂Mo₂O₇喷涂到MWCNTs表层之上得到La₂Mo₂O₇/MWCNTs,另一种是将两者均匀混合掺杂得到La₂Mo₂O₇@MWCNTs,再将上述2种复合材料应用于染料敏化太阳能电池对电极进行相应研究。通过扫描电子显微镜（SEM）表征了复合催化材料的微观形貌,X射线衍射（XRD）确定了微观结构。采用电流密度-光电压曲线、循环伏安,交流阻抗以及塔菲尔极化分析了材料的光电性能。实验结果表明在电解液I₃^-/I^-中,基于La₂Mo₂O₇/MWCNTs与La₂Mo₂O₇@MWCNTs的对电极,相同的条件下在光电池中获得的光电转换效率分别为6.09%和4.84%,明显高于MWCNTs的3.94%和La₂Mo₂O₇的0.87%。电极性能的提高可归因于La₂Mo₂O₇复合催化剂相对大的比表面积和高导电性。     

MICELLIZATION STUDIES OF DODECYL BENZENESULFONIC ACID AND ITS INTERACTION WITH POLYVINYLPYRROLIDONE

Dodecyl benzenesulfonic acid (DBSA) surfactant was used in the present study to find the effect of concentration on its electrical conductance in solution from 293-323K above and below the critical micelle concentration (CMC). The micellization parameters i.e. degree of counter ion binding (β), aggregation number (n) and number of counter ion micelle(m) were measured. The interaction of DBSA with polyvinylpyrrolidone (PVP) was also studied at 293K throughconductance and surface tension measure ments. A number of important parameters i.e. critical aggregation concentration (CAC), Gibb‘s free energy (△G) and binding ratio (R) were determined and the effect of NaCl on the CAC and polymer saturation point (PSP) was also investigated.