两种不同Pb源对PbSe纳米晶生长的影响

采用有机相合成法, 分别以PbO和醋酸铅[Pb(Ac)₂]作为铅源, 研究了在不同反应温度和反应时间下, 不同铅源对PbSe纳米晶生长的影响. 实验结果表明, 以PbO作为铅源, 油酸(OA)作为配体时, 在不同的反应温度下得到了球形PbSe纳米晶和截角八面体PbSe纳米晶; 选择Pb(Ac)₂作为铅源时, 在不同的温度下得到了PbSe纳米花和PbSe纳米星. 选择不同铅源得到的PbSe纳米晶形貌完全不同, 这主要是由于醋酸根的引入产生了不同的空间位阻, 引起纳米晶导向吸附并形成纳米花. 而随着反应温度的升高和反应时间的延长, 这些不同形貌的PbSe纳米晶最终会演变成纳米立方块, 这主要是由PbSe的晶体特性决定的.     

Electrochemical biosensing for dsDNA damage induced by PbSe quantum dots under UV irradiation

<正>An electrochemical sensor for the detection of the natural double-stranded DNA(dsDNA) damage induced by PbSe quantum dots(QDs) under UV irradiation was developed.The biosensing membranes were prepared by successively assembling 3- mercaptopropionic acid,polycationic poly(diallyldimethyl ammonium) and dsDNA on the surface of the gold electrode.Damage of dsDNA was fulfilled by immersing the sensing membrane electrode in PbSe QDs suspension and illuminating it with an UV lamp. Cyclic voltammetry was utilized to detect dsDNA damage with Co(phen)_3~(3+) as the electroactive probe.The UV irradiation,Pb~(2+) ions liberated from the PbSe QDs under the UV irradiation and the reactive oxygen species(ROS) generated in the presence of the PbSe QDs also under the UV irradiation were the three factors of inducing the dsDNA damage.The synergistic effect of the three factors might dramatically enhance the damage of dsDNA.This electrochemical sensor provided a simple method for detecting DNA damage,and may be used for investigating the DNA damage induced by other QDs.     

Surface only modification of bacterial cellulose nanofibres with organic acids

Bacterial cellulose (BC) nanofibres were modified only on their surface using an esterification reaction with acetic acid, hexanoic acid or dodecanoic acid. This reaction rendered the extremely hydrophilic surfaces of BC nanofibres hydrophobic. The hydrophobicity of BC increased with increasing carbon chain length of the organic acids used for the esterification reaction. Streaming (zeta-) potential measurements showed a slight shift in the isoelectric point and a decrease in ζ_plateau was also observed after the esterification reactions. This was attributed to the loss of acidic functional groups and increase in hydrophobicity due to esterification of BC with organic acids. A method based on hydrogen/deuterium exchange was developed to evaluate the availability of surface hydroxyl groups of neat and modified BC. The thermal degradation temperature of modified BC sheets decreased with increasing carbon chain length of the organic acids used. This is thought to be a direct result of the esterification reaction, which significantly reduces the packing efficiency of the nanofibres because of a reduction in the number of effective hydrogen bonds between them.     

Effects of atmospherically important solvated ions on organic acid adsorption at the surface of aqueous solutions

The effects of salts on the solubility of amphiphilic organic molecules are of importance to numerous atmospheric, environmental, and biological systems. A detailed picture of the influence of dissolved atmospheric salts, NaCl and Na(2)SO(4), on the adsorption of hexanoic acid at the vapor/water interface is developed using vibrational sum-frequency spectroscopy and surface tension measurements as a function of time, organic concentration, and solution pH. We have found that for hexanoic acid adsorption at the vapor/water interface, a fast initial adsorption is followed by two considerably slower processes: a reorientation of the polar headgroup and a restructuring of the headgroup solvation shell. The addition of salts affects this restructuring by reducing the range of water--headgroup interactions immediately upon surface adsorption for ion containing solutions. Reorientation of the organic headgroup with time occurs at the surface of both salt-containing and salt-free solutions, but the most stable orientation differs with the added ions. The dissolved salts also enhance the interfacial concentration of hexanoic acid, consistent with the known salting-out behavior of Cl(-) and SO(4)(2-) anions.     

烟气中有机酸的分析

 应用甲酯衍生化试剂对卷烟烟气粒相物中有机酸进行甲酯衍生化 ,经固相微萃取 (SPME)后通过气 质联用仪分离鉴定。分析了 4个品牌的卷烟烟气 ,共鉴定了 60多种挥发及半挥发性有机酸。对丁酸、己酸、糠酸、辛酸、壬酸、苯甲酸、苯乙酸、十四酸、十六酸进行了定量分析。该方法用于烟气中有机酸的定性、定量分析 ,灵敏度较高 ,快速简便。     

Development of a headspace solid-phase microextraction-gas chromatography-mass spectrometry method for the identification of odour-causing volatile compounds in packaging materials

A method for the identification of volatile organic compounds in packaging materials is presented in this study. These compounds are formed by thermooxidative degradation during the extrusion coating process in the manufacture of packaging. Headspace solid-phase microextraction (HS-SPME) was used as sample preparation technique prior to the determination of the volatile organic compounds by gas chromatography-mass spectrometry (GC-MS). The effects of extraction variables, such as the type of fibre, the incubation temperature, the pre-incubation time, the size of the vial and the extraction time on the amounts of the extracted volatile compounds were studied. The optimal conditions were found to be: carboxen-polydimethylsiloxane 75 microm fibre, 5 min of pre-incubation time, 100 degrees C of incubation temperature, 20-ml vial, and 15 min of extraction time. The chromatograms obtained by HS-SPME and static headspace extraction were compared in order to show that the HS-SPME method surpasses the static headspace method in terms of sensitivity. Twenty-five compounds were identified including carbonyl compounds (such as 3-methyl-butanal, 3-heptanone or octanal), carboxylic acids (such as pentanoic acid or hexanoic acid) known as odour causing compounds and hydrocarbons (such as decane, undecane or dodecane). Finally, the method was applied to different packaging samples (one odour-unacceptable, two odour-acceptable, and three odourless samples) and to the raw materials in order to find out the odour-responsible volatile organic compounds and their source.     

Facile synthesis of PbSe hollow nanostructure assemblies via a solid/liquid-phase chemical route and their electrogenerated chemiluminescence properties

Spherical PbSe hollow nanostructure assemblies (HNSAs) were synthesized by a simple one‐pot solid/liquid‐phase reaction in which solid KPbI₃ ? 2 H₂O and SeO₂ are heated in oleic acid/dodecylamine/1‐octadecene at 250 °C for 30 min. XRD analysis shows that the obtained product is cubic‐phase PbSe and well crystallized. FESEM and TEM images reveal that the obtained spherical PbSe assemblies are made up of small, irregular, and fused hollow nanostructure building blocks. On the basis of temperature‐ and time‐dependent investigations as well as control experiments, molten‐salt corrosion of solid PbSe nanocrystal aggregates formed in situ during the high‐temperature ripening stage is suggested to explain the formation of such novel assemblies. Moreover, when the reaction temperature is further increased to 280 or 320 °C with other conditions unchanged, cubic and orthorhombic mixed‐phase PbSe HNSAs is generated. The obtained PbSe HNSAs exhibit excellent electrogenerated chemiluminescence (ECL) performance. Two strong and stable emission peaks at about ?1.4 and +1.5 V (vs. Ag/AgCl) are observed. In particular, the ECL intensity is influenced by the crystal phase of PbSe.     

CdS/TiO_2纳米管可见光催化剂的制备、表征及光催化活性

以纳米颗粒TiO2(P25)为原料,采用水热合成法制备了具有锐钛矿晶型的TiO2纳米管(TNTs),考察了水热反应温度和焙烧温度对TNTs形貌和结构的影响.以具有双官能团结构的有机分子2-巯基丙酸为偶联剂,采用原位合成和在线组装的方法将CdS量子点(QDs)负载于TNTs上,制得了CdS/TNTs可见光催化剂,研究了2-巯基丙酸浓度对CdS负载量和CdS/TNTs光催化活性的影响.结果表明,在水热温度为150oC,焙烧温度为400oC的条件下,可制得管径为8～10nm,管壁为2～3nm,管长为数百纳米的锐钛矿型TNTs.经CdSQDs修饰后,TNTs的吸收阈值拓展至580nm,在模拟可见光照射下,CdS/TNTs表现出优异的光催化降解罗丹明B性能.     

液体石蜡体系中CdSeS三元量子点的制备及性能

采用液体石蜡为反应溶剂, 油酸为Cd源的溶剂和配体, 在无磷条件下通过用高温热解法合成了高质量的CdSeS三元合金量子点. 用透射电子显微镜(TEM), X射线粉末衍射仪(XRD)和能量色散X射线分析仪(EDX)等对产物的性能进行了表征. 结果表明, 反应温度、 反应时间和Se与S的比例等因素均对量子点的生长过程及光学性能产生影响. 采用该方法制得的CdSeS三元合金量子点均为立方闪锌矿结构, 且形成了一种内富S外富Se的成分梯度结构, 其最大发射波长可在370~595 nm(近紫外~橙红色)范围内连续可调, 量子效率最高可达65%. 该体系下制备的CdSeS三元量子点具有良好的热稳定性和光稳定性.     

3-巯基异丁酸衍生物对碲化镉量子点水相合成的影响

为探索适宜制备粒径分布窄、荧光量子产率高、发光区域在红光至近红外光区段的量子点的巯基酸的条件, 我们研究了三类3-巯基异丁酸(MIBA)衍生物在以亚碲酸钠为碲源的水相法水热制备CdTe量子点中的影响. 这三类衍生物包括设计合成的主链亲水性衍生物3-巯基异丁酰甘氨酸(MIBGly)、3-巯基异丁酰-3-氨基丙酸(MIBAPA)和3-巯基异丁酰天冬氨酸(MIBAsp), 支链亲水性衍生物N-乙酰基半胱氨酸(ACys)和支链疏水性衍生物3-巯基-2-甲基丁酸(MMBA)和3-巯基-2,2-二甲基丙酸(MDMPA). 以这三类MIBA 衍生物为修饰剂时,CdTe量子点均能够保持MIBA体系较窄的荧光半峰宽. 采用亲水性的MIBA衍生物(MIBGly、MIBAPA、MIBAsp和ACys)比采用疏水性的MIBA衍生物(MMBA和MDMPA)更有利于制备发射波长较长的量子点. 采用支链亲水性的MIBA衍生物((ACys)比采用主链亲水性的MIBA衍生物(MIBGly、MIBAPA和MIBAsp)更容易获得高荧光量子产率的量子点.     

Ultrasound-assisted synthesis of ethyl hexanoate using heterogeneous catalyst: Optimization using Box-Behnken design

Ultrasound-assisted synthesis of ethyl hexanoate was studied in a solvent-free system using Amberlyst-15 as a heterogeneous catalyst. The effect of reaction parameters was evaluated by employing Box Behnken Design. Maximum conversion was obtained as 83.9% experimentally with operating temperature 60 °C, ethanol to hexanoic acid molar ratio as 3, 60% duty cycle, 11% catalyst loading, 10% molecular sieves, and 80 W input power which were optimized through one parameter at a time. The optimal conditions for maximum 86.66% conversion obtained by Box Behnken Design operated in Response Surface Methodology were 62.8 °C temperature, 3.31 ethanol to hexanoic acid molar ratio, and 51.58% duty cycle. The absence of external mass transfer resistances was proved by evaluating Mear's criterion. Thiele modulus and effectiveness factor were determined to study the influence of internal mass transfer resistance qualitatively. The kinetics of the heterogeneous reaction was modeled using Langmuir-Hinshelwood model. The activation energy was calculated as 24.61 kJ/mol.     

油胺/油酸稳定的CdSe量子点的绿色合成

以液体石蜡为高温反应溶剂,油酸和油胺为混合稳定剂,利用高温热解法一步合成了高质量的CdSe量子点。通过紫外-可见吸收光谱、荧光发射光谱、红外光谱和X射线衍射等手段对量子点的光学性质和结构进行了表征。结果表明,油胺/油酸混合表面活性剂稳定的量子点吸收光谱峰形更尖锐,荧光发射光谱半峰宽更窄。反应温度和反应时间均对量子点的生长过程和光学性质有明显影响,220℃下反应15 min,荧光量子产率可达26%。得到的CdSe量子点为立方晶型,表面同时包覆了油酸和油胺,具有良好的光稳定性。该方法无需使用三烷基膦,价廉环保,且合成的CdSe量子点性质稳定、性能优越,有利于其在分析检测领域中的应用。     

Preparation of a Water-Soluble ZnXCd1-XS Quantum Dot Photocatalyst at Room Temperature Assisted by 3-Mercaptopropionic Acid

An effective path to synthesize Zn_xCd_1-xS quantum dots (ZCS QDs) in aqueous phase at room temperature has remained relatively unexplored. Here, we developed a room-temperature, aqueous-phase approach to ZCS QDs, using 3-mercaptopropionic acid (MPA) to adjust the pH of the reaction precursor solution to regulate the competition between sulfur source and hydroxyl group, and realize the large-scale preparation of water-soluble ZCS QDs photocatalyst at room temperature. Without recombination with other materials, and only by regulating the ratio of pH, excess sulfur sources and Zn/Cd, the photocatalytic degradation of rhodamine B (RhB) can reach 98% within 1 min, showing high photocatalytic activity. ZCS QDs show high stability and recoverability, and are expected to be able to deal with organic pollutants on a large scale. This study provides a new idea for the preparation of other QDs at room temperature.     

沉淀聚合制备磺酸掺杂的聚苯胺

以二丁基萘磺酸(DBNSA)或十二烷基苯磺酸(DBSA)为有机酸,水为主要反应介质的条件下进行沉淀聚合直接制备有机酸掺杂的聚苯胺(PAn).讨论了酸度、温度和氧化剂用量等反应条件对产物的影响。2L规模扩大实验的产率约为75%～80%,所得PAn具有高电导率(3.0S·cm^-1),并易溶于普通有机溶剂。其中PAn-DBNSA在各方面较具优势。     

Determination of ζ‐potential,charge, and number of organic ligands on the surface of water soluble quantum dots by capillary electrophoresis

The number of charges and/or organic ligands covalently attached to the surface of CdTe quantum dot nanoparticles has been determined from their electrophoretic mobilities measured in capillaries filled with free electrolyte buffers. Three sizes of water soluble CdTe quantum dots with 3‐mercaptopropionic and thioglycolic acids as surface ligands were prepared. Their electrophoretic mobilities in different pH and ionic strength values of separation buffers were measured by capillary electrophoresis with laser induced fluorescence detection. The ζ‐potentials determined from electrophoretic mobilities using analytical solution of Henry function proposed by Ohshima were in the range from ?30 to ?100 mV. Charges of QDs were calculated from ζ‐potentials. As a result, numbers of organic ligands bonded to QDs surface were determined to be 13, 14, and 15 for the sizes of 3.1, 3.5, and 3.9 nm, respectively. The dissociation constants of organic ligands bonded on QDs surfaces estimated from the dependence of QDs charge on pH of the separation buffer were 7.8 and 7.9 for 3‐mercaptopropionic acid and 6.9 for thioglycolic acid.     

负载型过氧磷钨杂多化合物上正己醇催化氧化成正己酸

由正己醇合成正己酸不仅可以提高附加值,还能生产己酸类香料以及多种医药产品．利用杂多过氧磷钨季铵盐催化剂,以对环境友好的H2O2 为氧化剂催化十八醇氧化成十八酸的研究已有报道［1,2],但合成负载型相转移催化剂并用于本课题的研究还未见报道．由于过氧磷钨十八烷基季铰盐催化剂（POWP）通常只有很小的比表面积,而SiO2不仅有大的比表面积,同时它所具有的表面羟基是杂多化合物的良好载体［2],POWP负载后的催化剂（POWPS）与未负载的POWP相比,将正己醇氧化为正已酸的收率提高了10多个百分点．     

Structure and optoelectronic properties of PbSe quantum dots /PVA. Does the polymer molecular weight matter?

Polyvinyl alcohol (PVA) with different molecular weights (8000, 14,000, and 132,000 g/mol) capped lead selenide (PbSe) quantum dots (QDs) are prepared. The nanocomposites are characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM studies show that the particle size of PbSe QDs decrease with the increase in PVA molecular weight and/or PVA amount. This may be due to the increase in molecular weight inhibiting further growth of PbSe into the polymer matrix. Thermogravimetric analysis showed that the introduction of PbSe QDs into PVA decreases the crystallinity of the polymer. The optical absorption spectroscopy of prepared nanocomposites showed that the absorption peaks are strongly shifted to the lower wavelength (blue shift) from near infrared region to visible region by increasing the PVA molecular weight. The (I–V) characteristic curves of the PVA/PbSe nanocomposite films under illumination showed a photovoltaic cell‐like behavior. The results indicated that as the molecular weight of polymer increases, the conversion efficiency increases. Copyright © 2010 John Wiley & Sons, Ltd.     

CdS量子点的一步法合成及量子产率

以油酸为配体,十八烯为溶剂,采用一步法合成了CdS量子点,研究了反应温度、反应时间和Cd/S的摩尔比对量子点光谱性能的影响.X射线衍射(XRD)和高分辨透射电镜(HRTEM)测试结果表明,所获得的CdS量子点为立方闪锌矿结构,且尺寸分布均一,结晶度高,其较强的带边发光、尖锐的紫外吸收峰以及狭窄的荧光发射峰进一步表明量子...     

碲化镉量子点光催化降解溴化乙锭的研究

以巯基乙酸为稳定剂, 水相合成出不同粒径的碲化镉量子点, 对其进行适当的光照处理, 以提升其光学性质和稳定性. 将其用作光催化剂, 以紫外灯为光源, 降解具有强诱变作用的常用核酸荧光染料——溴化乙锭. 考察了光照时间和溶液 pH 对降解率的影响. 以溴化乙锭在620 nm处的特征荧光发射峰为参数表征降解率, 在反应4 h后, 对15 mg/L溴化乙锭水溶液的降解率近90%, 同时, 对琼脂糖凝胶中的溴化乙锭也有降解作用.     

Formation of PbSe nanocrystals: A growth toward nanocubes

In this paper we report an electron microscopic observation of crystal shape development when PbSe nanocrystals were synthesized using a dynamic injection technique at different temperatures in the presence of oleic acid. A two-step evolution mechanism was proposed, indicating that the shape evolution of PbSe nanocrystals is dependent on the growth time, whereas the crystalline size can be tuned by varying the growth temperature under the studied conditions. It also implies that a higher growth rate in the 111 direction compared to that in the 100 direction results in the formation of nanocubes.