Phase transformation in the surface region of zirconia and doped zirconia detected by UV Raman spectroscopy

The phase evolution of yttrium oxide and lanthanum oxide doped zirconia (Y2O3-ZrO2 and La2O3-ZrO2, respectively) from their tetragonal to monoclinic phase has been studied using UV Raman spectroscopy, visible Raman spectroscopy and XRD. UV Raman spectroscopy is found to be more sensitive at the surface region while visible Raman spectroscopy and XRD mainly give the bulk information. For Y2O3-ZrO2 and La2O3-ZrO2, the transformation of the bulk phase from the tetragonal to the monoclinic is significantly retarded by the presence of yttrium oxide and lanthanum oxide. However, the tetragonal phase in the surface region is difficult to stabilize, particularly when the stabilizer's content is low. The phase in the surface region can be more effectively stabilized by lanthanum oxide than yttrium oxide even though zirconia seemed to provide more enrichment in the surface region of the La2O3-ZrO2 sample than the Y2O3-ZrO2 sample, based on XPS analysis. The surface structural tension and the enrichment of the ZrO2, component in the surface region of ZrO2-Y2O3 and ZrO2-La2O3 might be the reasons for the striking difference between the phase change in the surface region and the bulk. Accordingly, the stabilized tetragonal surface region can significantly prevent the phase transition from developing into the bulk when the stabilizer's content is high.

ZnO clusters encapsulated inside micropores of zeolites studied by UV Raman and laser-induced luminescence spectroscopies

Using microporous zeolites as host, sub-nanometric ZnO clusters were prepared in the micropores of the host by the incipient wetness impregnation method. A small amount of sub-nanometric ZnO clusters were introduced into the channels of HZSM-5 zeolite, whereas a large quantity of sub-nanometric ZnO clusters can be accommodated in the supercages of HY zeolite and no macrocrystalline ZnO exists on the extra surface of the HY material. The vibrations of the zeolite framework and ZnO were characterized by UV Raman spectroscopy. The optical properties of these ZnO clusters were studied by UV-visible absorption spectroscopy and laser-induced luminescence spectroscopy. It is found that there are strong host-guest interactions between the framework oxygen atoms of zeolite and ZnO clusters influencing the motions of the framework oxygen atoms. The interaction may be the reason why ZnO clusters are stabilized in the pores of zeolites. Different from bulk ZnO materials, these sub-nanometric ZnO clusters exhibit their absorption onset below 265 nm and show a purple luminescence band (centered at 410-445 nm) that possesses high quantum efficiency and quantum size effect. This purple luminescence band most likely originates from the coordinatively unsaturated Zn sites in sub-nanometric ZnO clusters. On the other hand, the differences in the pore structure between HZSM-5 and HY zeolites cause the absorption edge and the purple luminescence band of ZnO clusters in ZnO/HZSM-5 show a red shift in comparison with those of ZnO clusters in ZnO/HY.

Direct determination of sialic acids in serum by capillary electrophoresis with UV detection

A novel method for the determination of N-acetylneuraminic acid (NANA) and N-glycolylneuraminic acid (NGNA) has been developed using high-performance capillary electrophoresis with UV detection at 195 nm, without pre or post-column derivatisation. The acids were separated in a 50-cm, fused-silica capillary (50 mu m i.d, 45.5-cm effective length) with Na2B4O7-Na2HPO4 buffer. The detection limit for NANA is a concentration of 9.6 x 10(-6) M or, in terms of mass: 3.879 x 10(-14) mol (39 fmol). This method is applicable to determination of NANA in normal human serum. The results were also compared with those of the colorimetrie method.

Degradation products formed during UV-irradiation of humic waters

Natural humic lake water and aqueous solutions of humic substances were treated with ultraviolet (UV) radiation (λ = 254 nm). The effects on the dissolved organic carbon content (DOC) and the absorbance at 254 nm (Abs254) and 460 nm (Abs460) were monitored and the identity and concentrations of gas chromatographable organic degradation products were determined. The DOC content and the (Abs254) of the humic solutions decreased continuously with increasing UV-dose. Several aromatic and aliphatic degradation products were identified and roughly quantified The concentrations of aromatic hydroxy carboxylic acids and hydroxy aldehydes increased when relatively low UV-doses were used, but declined following further irradiation. The concentrations of aliphatic dibasic acids increased over the full range of UV-doses

UV-photooxidation as pretreatment step in inorganic analysis of environmental samples

Many laboratories deal with the determination of heavy metals, carbon, nitrogen and phosphorus. The first step in chemical analysis is a proper preparation of the investigated samples. The presence of organic substances can cause problems in many analytical methods. This paper describes the application of UV irradiation as a method of destruction of organic matter in the investigated samples.

水质对UV/H_2O_2降解邻苯二甲酸二甲酯反应动力学的影响

研究了不同初始pH值、浊度与常见阴离子浓度等水质条件对UV/H2O2工艺降解邻苯二甲酸二甲酯(DMP)反应速率的影响,并进一步比较了去离子水和自来水中DMP的降解速率。结果表明,UV/H2O2对DMP的光降解过程符合一级反应动力学模型,不同水质条件对降解速率有不同程度的影响。酸性条件较碱性条件更有利于DMP降解;水的浊度大于7NTU时,光降解速率常数迅速下降;NO3-、Cl-、HCO3-等阴离子对DMP降解有抑制作用,且随离子浓度增大,抑制作用增强,3种离子对DMP光降解的抑制程度顺序为HCO3->NO3->Cl-。在5个30W低压汞灯照射下,当H2O2的浓度为20mg.L-1时,DMP在去离子水和自来水中光降解速率常数分别为0.0428min-1和0.0315min-1,自来水中的光降解速率常数较去离子水中的低,这可能是水中多种离子影响的结果。

水中无机阴离子对UV/H_2O_2降解LAS的影响及机理

研究了UV/H2O2工艺对直链烷基苯磺酸钠(LAS)的去除效果以及水中常见无机阴离子对LAS降解的影响和机理.结果表明,UV/H2O2工艺可以有效的去除水中LAS,光降解过程符合一级反应动力学模型.在H2O2投加量为8 mg.L-1,14 W低压汞灯照射下,LAS在蒸馏水和自来水中光降解速率常数分别为0.0180 min-1和0.0122 min-1;NO3-、Cl-、SO42-和HCO3-对LAS光降解有抑制作用,4种离子在浓度分别为5、10、15 mmol.L-1时,对LAS光降解的抑制程度均为HCO3->NO3->Cl->SO42-;随着离子浓度增大,抑制作用增强;自来水中的光降解速率常数低于蒸馏水中的光降解速率常数是由于水中多种离子影响的结果.

脱落酸对UV-C胁迫下小麦幼苗光合特性及抗氧化酶活性的影响

研究了UV-C辐射下短期和长期脱落酸(ABA)处理对小麦幼苗CO2同化作用、羧化效率、光合CO2响应以及抗氧化酶活性等的影响.结果表明,在无UV-C辐射情况下,短期和长期ABA处理能提高光合速率,比对照增加14·69%和20·46%,降低气孔导度,比对照降低14·74%和17·31%,但对胞间CO2浓度和羧化效率影响不大.当受到UV-C辐射时,光合速率、羧化效率、气孔导度和胞间CO2浓度逐渐降低.长期ABA处理变化最小,其次为ABA短期处理,对照降低最大.ABA处理能够提高小麦光合对CO2的响应,UV-C辐射抑制光合对CO2的响应.ABA处理能够提高小麦抗氧化酶(CAT、SOD、POD)活性而降低MDA含量.在UV-C辐射下,CAT活性先升高随后降低,在辐射处理1h时活性达最大值,ABA处理的SOD和POD活性先升高后降低,且ABA长期处理比短期处理增加明显,对照则逐渐降低.ABA处理可能通过提高小麦CO2同化作用和抗氧化酶活性增强对UV-C胁迫的抗性,且ABA长期处理比短期处理效果更明显.

增强UV-C辐射作用下小麦和豌豆幼苗光合响应及其相对抗性

以小麦和豌豆为材料,研究了UV-C辐射(波长<280nm)对叶片光合特性及抗氧化酶活性的影响.结果表明:UV-C辐射增强,可使豌豆叶片光合速率减弱,气孔导度、胞间CO2浓度、蒸腾速率和羧化效率明显降低,而对小麦叶片上述各项指标的影响则是先增加、后降低;在UV-C辐射下,豌豆的CO2补偿点逐渐升高,而小麦的CO2补偿点先降低、后升高.UV-C辐射除了使豌豆的POD活性和小麦的SOD活性逐渐降低外,其他抗氧化酶活性则呈先升高、后降低的变化趋势.小麦对短时间UV-C辐射的抗性比豌豆强,但随着UV-C辐射时间的延长,小麦和豌豆的抗氧化酶活性均降低,光合作用减弱.

Click-together azobenzene dendrons: Synthesis and characterization

We synthesized 1,2,3-triazole-linked azobenzene dendrons of four generations. No protection-deprotection approach was needed during the generation development via click reaction. The photoisomerization of azobenzene dendrons was Studied using UV-vis spectra. The cis isomers of these dendrons were more stable than trans isomers in the dark; however, the cis isomers could be quickly converted to trans forms under visible light exposure in seconds. The trans form could change to cis form reversibly by UV irradiation as well.

刺五加叶的HPLC-UV和ESI-MS指纹图谱研究

对12批不同来源的刺五加叶提取物进行指纹图谱研究,并利用ESI-MS指纹图谱鉴别刺五加叶与山楂叶。分别采用高效液相色谱(HPLC-UV)和电喷雾电离质谱(ESI-MS)测定12批不同来源的刺五加叶提取物,利用ESI-MS技术测定刺五加叶与山楂叶提取物,得到了分离度、精密度和重现性均较好的刺五加叶HPLC-UV及ESI-MS指纹图谱;同时,利用刺五加叶与山楂叶ESI-MS指纹图谱的差异,成功鉴别了二者,可为刺五加叶药材的质量控制提供参考。

Cinnamate-Functionalized Poly(ester-carbonate): Synthesis and Its UV Irradiation-Induced Photo-Crosslinking

A functionalized. cyclic carbonate monomer containing a cinnamate moiety, 5-methyl-5-cinnamoyloxymethyl-1,3-dioxan-2-one (MC), was prepared for the first time with 1,1,1-tri(hydroxymethyl) ethane as a starting material. Subsequent polymerization of the new cyclic carbonate and its copolymerization with L-lactide (LA) were successfully performed with diethyl zinc (ZnEt2) as initiator/catalyst. NMR was used for microstructure identification of the obtained monomer and copolymers. Differential scanning calorimetry (DSC) was used to characterize the functionalized poly(ester-carbonate). The results indicated that the copolymers displayed a single glass transition temperature (T-g) and the T, decreased with increasing carbonate content and followed the Fox equation, indicative of a random microstructure of the copolymer. The photo-crosslinking of the cinnamate-carrying copolymer was also demonstrated.

ESI-MS和HPLC-UV法研究大黄、黄柏、赤芍炮制前后化学成分变化

目的:考察大黄、黄柏、赤芍炮制前后化学成分在质和量方面的变化,以探讨中药的炮制机理。方法:利用电喷雾质谱法(ESI-MS)和高效液相色谱法(HPLC-UV),对大黄、黄柏、赤芍炮制前后的化学成分进行详细研究。质谱:电喷雾电离源(ESI),加热毛细管温度为200℃,喷雾电压为4.5kV;液相色谱:色谱柱为Agilent Zorbax C18柱(4.6mm×150mm,5μm),柱温均为28℃。结果:大黄经酒制和醋制后,其化学成分的含量变化较大;黄柏经酒制后巴马汀的含量略有增加,而小檗碱的含量呈下降趋势;盐制对于黄柏的化学成分几乎无影响;赤芍经酒制和炒制后,芍药苷的含量都呈下降趋势。结论:不同炮制方法对化学成分的影响不同,为进一步阐明中药材炮制入药的科学内涵提供了实验依据。