Investigation of the formation of CuInS2 nanoparticles by the oleylamine route: comparison of microwave-assisted and conventional syntheses

The formation of copper indium disulfide nanoparticles via the oleylamine route using copper iodide, indium chloride, and elemental sulfur has been investigated by applying conventional thermal heating as well as microwave irradiation. Oleylamine thereby acts as a capping ligand as well as a solvent. In an initial set of experiments, the onset of the reaction was determined to be around 115 °C by an in situ X-ray study using Synchrotron radiation. Using comparatively low synthesis temperatures of 120 °C, it is already possible to obtain nanoparticles of 2-4 nm with both heating methods but with irregular shape and size distribution. By applying higher temperatures of 220 °C, more crystalline and larger nanoparticles were obtained with slight differences in crystallite size and size distribution depending on the synthesis route. The size of the nanoparticles is in the range of 3-10 nm depending on the heating time. Using microwave irradiation, it is possible to obtain nanoparticles in only 90 s of total synthesis time. Control experiments to probe a nonthermal microwave effect were carried out ensuring an identical experimental setup, including the heating profile, the stirring rate, and the volume and concentration of the solutions. These experiments clearly demonstrate that for the preparation of CuInS(2) nanoparticles described herein no differences between conventional and microwave heating could be observed when performed at the same temperature. The nanoparticles obtained by microwave and thermal methods have the same crystal phase, primary crystallite size, shape, and size distribution. In addition, they show no significant differences concerning their optical properties.     

High resolution in heteronuclear 1H–13C NMR experiments by optimizing spectral aliasing with one‐dimensional carbon data

In the chemistry literature it is common to provide NMR data on both proton and carbon spectra based on one‐dimensional experiments, but often only proton spectra are assigned. The absence of a complete attribution of the carbons is in good part due to the difficulty in reaching the necessary resolution in the carbon dimension of two‐dimensional experiments. It has already been shown that high‐resolution heteronuclear spectra can be acquired within nearly the same acquisition time using a violation of the Nyquist condition. For a spectral width reduction by a given factor k, the resolution increases by the same factor as long as it is not limited by relaxation. The price to pay for such an improvement is a k‐fold ambiguity in the chemical shift of the signal along the folded or aliased dimension. The computer algorithm presented in this paper takes advantage of the peak list stemming from one‐dimensional spectra in order to calculate spectral widths for which the ambiguities in the aliased dimension of heteronuclear experiments are eliminated or at least minimized. The resolution improvement factor is only limited by the natural lineshape and reaches a typical value higher than 100. The program may be set to run automatically on spectrometers equipped with automatic sample changers. Applications to short‐range HSQC experiments and long‐range HMBC spectra of steroids, carbohydrates, a peptide and a mixture of isomers are shown as examples. Copyright © 2002 John Wiley & Sons, Ltd.     

Influence of the average content of sulfur in polysulfide polymers on the depolymerization of polysulfide polymers by dithionite ions

The results of our studies show that it is possible to depolymerize polysulfide polymers with a nominal sulfur content in excess of 2 per segment of polymer, without previous desulfurization, in order to obtain disulfide polymers. For this purpose it is necessary to take larger amounts of sodium dithionite per segment of polymer, than with a disulfide polymer, to obtain approximately the same of the average molecular weight of the depolymerized product. It is also possible to complete depolymerization with an amount below 2 moles of sodium hydroxide per mole of sodium dithionite, though the upper limit of the ratio of Na₂S₂O₄ to NaOH, at which depolymerization occurs, remains unchanged, i.e., 1:4. During the depolymerization reaction the occurrence of larger or smaller amounts of hydrosulfide, depending on the labile sulfur content, as well as the change of the color of the reaction dispersion, first white, then bright yellow or gray, thereafter white again and, finally, dingy pink, was observed. The reaction, representing in the best way the optimum conditions of depolymerization and the actual relations in the reaction system, is proposed.     

Global optimization of the infrared matrix-assisted laser desorption electrospray ionization (IR MALDESI) source for mass spectrometry using statistical design of experiments

Design of experiments (DOE) is a systematic and cost-effective approach to system optimization by which the effects of multiple parameters and parameter interactions on a given response can be measured in few experiments. Herein, we describe the use of statistical DOE to improve a few of the analytical figures of merit of the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source for mass spectrometry. In a typical experiment, bovine cytochrome c was ionized via electrospray, and equine cytochrome c was desorbed and ionized by IR-MALDESI such that the ratio of equine:bovine was used as a measure of the ionization efficiency of IR-MALDESI. This response was used to rank the importance of seven source parameters including flow rate, laser fluence, laser repetition rate, ESI emitter to mass spectrometer inlet distance, sample stage height, sample plate voltage, and the sample to mass spectrometer inlet distance. A screening fractional factorial DOE was conducted to designate which of the seven parameters induced the greatest amount of change in the response. These important parameters (flow rate, stage height, sample to mass spectrometer inlet distance, and laser fluence) were then studied at higher resolution using a full factorial DOE to obtain the globally optimized combination of parameter settings. The optimum combination of settings was then compared with our previously determined settings to quantify the degree of improvement in detection limit. The limit of detection for the optimized conditions was approximately 10 attomoles compared with 100 femtomoles for the previous settings, which corresponds to a four orders of magnitude improvement in the detection limit of equine cytochrome c.     

The Correlation between segment interaction parameter and interface width of polymer blends

The correlation between the segment interaction parameter and the interface width of incompatible polymer blends can be used to obtain information on the segment interaction of incompatible polymers via an accurate measurement of the narrow interface width by neutron reflectometry. Several model systems are discussed including polystyrene/poly(cyclohexyl acrylate-stat-n-butyl methacrylate), polystyrene/ poly (styrene- stat-p-bromo styrene) and poly styrene/poly(methyl methacrylate).     

Numerical Simulation on the Dissociation,Formation, and Recovery of Gas Hydrates on Microscale Approach

Investigations into the structures of gas hydrates, the mechanisms of formation, and dissociation with modern instruments on the experimental aspects, including Raman, X-ray, XRD, X-CT, MRI, and pore networks, and numerical analyses, including CFD, LBM, and MD, were carried out. The gas hydrate characteristics for dissociation and formation are multi-phase and multi-component complexes. Therefore, it was important to carry out a comprehensive investigation to improve the concept of mechanisms involved in microscale porous media, emphasizing micro-modeling experiments, 3D imaging, and pore network modeling. This article reviewed the studies, carried out to date, regarding conditions surrounding hydrate dissociation, hydrate formation, and hydrate recovery, especially at the pore-scale phase in numerical simulations. The purpose of visualizing pores in microscale sediments is to obtain a robust analysis to apply the gas hydrate exploitation technique. The observed parameters, including temperature, pressure, concentration, porosity, saturation rate, and permeability, etc., present an interrelationship, to achieve an accurate production process method and recovery of gas hydrates.     

Improved PSD and CID on a MALDI TOFMS

The influence of several instrument-operating parameters on the product-ion resolution and mass accuracy in matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) post-source decay (PSD) and collision-induced dissociation (CID) experiments is reported. Voltages commonly applied to the reflectron for PSD and CID experiments were found to be non-ideal; optimization of these voltages resulted in better resolution across each segment of the measured PSD spectrum. Mass resolution, calculated as M/DeltaM (FWHM) for the product-ion peaks, was as high as 2500. Additionally, precursor-ion selection and segment mass range setup were each found to have dramatic influences on product-ion mass accuracy. An understanding of the influence of these variables aided in the interpretation of (a-NH3) and (b - NH3) ions observed in the PSD/CID spectra of a number of peptides. In addition, product ions resulting from coincidence peaks in the precursor-ion selection window were found to be a general problem. With the improvements to resolution and optimization of these mass accuracy variables, the mass accuracy of product ions from MALDI TOF PSD and CID experiments was tested with several reference materials, including the peptides Substance P, bradykinin, angiotensin I, and angiotensin II and the synthetic polymers poly(methyl methacrylate) and polystyrene. The absolute error (Da) for each test material was, on average, below 0.1 Da, demonstrating a significant improvement in mass accuracy using the improved operational parameters and an extension of the use of poly(ethylene glycol) (PEG) as a mass calibrant for the PSD/CID spectra.     

Transmission spectra of light to the mammalian retina

A simple method has been developed to determine the optical properties of the anterior segment of the intact eye. This consists of a probe that is inserted into the posterior sclera and detects light passing through the anterior segment. The probe is connected to a charge-coupled device spectrophotometer via a fiber optic bundle. It was determined that the young rat anterior segment transmits light down to 300 nm, whereas calf and rabbit eyes transmit no UVB and only part of the UVA to the posterior segment. The absorbing species in these animals is most likely NAD(P)H, which has an absorption maximum at approximately 345 nm and is associated with zeta-crystallin. A young primate anterior segment transmits almost no UV with a steep increase in transmission at CA 400 nm. Because some experiments employed a light tube that is used to illuminate the retina during vitrectomies, this method can be used to determine the transmission spectra of the anterior segment of humans in vivo.     

3-氨基丙基三甲氧基硅烷自组装提高染料敏化太阳能电池的效率

以3-氨基丙基三甲氧基硅烷(APTS)修饰的二氧化钛为负极制备的染料敏化太阳能电池在100 mW·cm^-2的模拟太阳光照下的短路电流、开路电压、光电转换效率分别为18.32 mA·cm^-2、775.9 mV、9.15%. 而没有经过ATPS修饰的电池三项性能参数分别为18.08 mA·cm^-2、749.9 mV、7.70%, 修饰后电池的光电转换效率提高了18.8%, 同时填充因子由0.57提高为0.64. 暗电流-电压曲线显示起始电压从-0.30 V变化到-0.40 V, 表明二氧化钛电极和电解液之间的暗反应得到了有效抑制, APTS作为阻挡层减少了二氧化钛电极表面的缺陷与表面态. 另外, 通过实验设计, 将APTS与染料层-层自组装于二氧化钛电极上, 通过X射线光电子能谱(XPS)研究了二氧化钛层、APTS、染料的作用形式. 定性与定量结果表明: APTS中的乙氧基部分脱除后形成了Si―O―Ti单桥或者双桥键, 钌染料cis-Ru(dcpyH₂)₂(SCN)₂通过分子中的部分―COOH与APTS中的―NH₂形成的静电作用力吸附在TiO₂电极上. 傅里叶变换红外(FT-IR)光谱的结果进一步证明了这种分子间作用.     

Mechanical and dielectric properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment

Mechanical and dielectric properties of two series of segmented polyurethanes having soft segment concentration of 50 and 70% and a varying degree of crosslinking through the hard segment were studied. The degree of crosslinking in each series was varied by varying the butane diol/trimethylol propane ratio in the chain extender mixture. Tensile strength, elongation at break decrease, but elastic recovery increases monotonically with increasing crosslinking. The plateau modulus in the dynamic mechanical test decreases and then increases with increasing TMP content. Crosslinking causes broadening of the soft segment glass transition as seen by permittivity and loss factor measurements. It also affects high temperature behavior (above the glass transition of the hard segment); it lowers permittivity, loss factor, and ionic conductivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 237–251, 1998     

Optimisation of sensitivity in the multi-elemental determination of 83 isotopes by ICP-MS as a function of 21 instrumental operative conditions by modified simplex, principal component analysis and partial least squares

The optimisation of the sensitivity in the ICP-MS determination of 83 isotopes, as a function of 21 operative parameters was performed by generating an initial experimental design that was used to define, by principal component analysis, the multi-criteria target function. The first PC, which contained an overall evaluation of the signal intensity of all isotopes, was used to rank the experiments. The modified simplex optimisation technique was then applied on the ranked experiments. The increase in signal intensity was, on the average, 3.9 times for the isotopes considered for the simplex procedure. When finally convergence was achieved, a PLS regression model calculated on the available experiments allowed to investigate the effect played by each factor on the experimental response. Simplex and PCA proved to be extremely effective to obtain the optimisation and to generate the multi-criteria target function: they can be suggested as an automatic method to perform the optimisation of the instrumental operative conditions.     

High-throughput nitric oxide assay in biological fluids using microchip capillary electrophoresis

In order to develop a high-throughput screening method for the nitrogen monoxide metabolites, nitrite and nitrate, in biological fluids, we have investigated the simultaneous determination of these metabolites using microchip capillary electrophoresis (MCE). In this study, the control of applied voltage to obtain higher sensitivity by increasing the sample injection volume was investigated. Also, the improvement of reproducibility by correcting the injection volume using the internal standard was investigated. By increasing the sample volume, the limits of detection achieved for nitrite and nitrate were 24 and 12 microM, respectively. Because we used a 10-fold diluted sample when detecting nitrite and nitrate in human serum, it was necessary to increase the sensitivity by a factor of 10-50. The run-to-run and day-to-day relative standard deviations achieved were improved to less than 10% by using an internal standard to correct the injection volume. Moreover, we obtained successful separation of nitrite and nitrate in spiked human serum within 6.5 s under optimum analytical conditions. As a result, although it is necessary to obtain greater sensitivity, it was concluded that determination of the amount of NO metabolites in biological fluids using MCE is possible.     

Variations in the mechanical properties of end products from mixed plastics

From well selected polymers, using an experimental plan methodology, we show the different influences (nature, processing conditions, composition) on the properties of end products from mixed plastics such as strain and stress at rupture, flexural modulus, impact strength and extrusion flow rate. From models, it is possible to adjust necessary formulations to obtain a good quality level and, eventually, an improvement of poor properties. Mixed plastics can be considered as a polyethylene matrix containing other polymers such as polypropylene (PP), polystyrene (PS) or poly(vinyl chloride) (PVC). Poly(ethylene terephthalate) (PET) is neglected in this study. Properties such as strain at rupture or impact strength are drasticly affected by the level of polypropylene, polystyrene or poly(vinyl chloride): 5 or 10% nullify these properties. Other properties such as stress at rupture, flexural modulus or extrusion flow rate highly depend on the relative ratio of polymers. To improve the poor properties or to obtain a good level in a property, it is necessary to add well adapted compatibilizers or to dope the mixed plastics material by one of the polymers.     

Figures of merit of pneumatic and ultrasonic sample introduction systems in inductively coupled plasma–multichannel-based emission spectrometry in an ultra-clean environment

Conventional figures of merit such as limits of detection, signal to background ratio or repeatability, are used to determine the performance of pneumatic and ultrasonic sample introduction systems in an ultra-clean environment with an axially viewed inductively coupled plasma-atomic emission spectrometry and multichannel detection. We observed that the ultrasonic nebuliser offered a large improvement of signal intensity (10-133 greater) compared to a cyclone chamber coupled with a pneumatic Meinhard nebuliser. This improvement is associated with an average increase of signal to background ratio by a factor 86 and an average decrease of detection limits by a factor 6. The improvement factors generally depend on the element and for the same element on spectral lines. Typically, the observed values of detection limits in this work are lower than those published and obtained in non-ultra-clean conditions. The results emphasize that the environmental conditions of cleaning and analysis are essential to avoid and control cross contamination of the samples and hence to obtain low detection limits.     

Sensitivity improvement of 1H-15N cross-polarization at high MAS frequency applied to NMR structural characterization of organic solids

(15)N CP/MAS solid state NMR should be a method of choice to obtain essential structural information on organic materials containing nitrogen atoms. However, the technique is generally not selected for the characterization of non-labelled chemical compounds, which represents the most common situation encountered by chemists. Actually, due to the poor sensitivity of (15)N the method is time-consuming and a very fine calibration is often a prerequisite to reach a sufficient signal/noise. The main drawback comes from the weakness of (15)N-(1)H dipolar couplings which leads to a splitting of the static Hartman Hahn condition into very narrow sideband conditions under MAS. Practically, it is more difficult to obtain a high enough CP transfer level on (15)N for the entire spectrum than on other more conventional nuclei like (13)C. An experimental investigation of the CP efficiency using the ramp and adiabatic CP transfer experiments is here proposed. Preliminary adjustments of experimental settings were first made on an (15)N-labeled substituted heterocyclic model system, and then applied to several other organic compounds. Particular attention was paid to the detection of non-protonated nitrogen atoms with a significant chemical shift anisotropy, which represented the least favourable case. It was experimentally demonstrated that, for these atoms, the adiabatic passage provided a much higher transfer level than the more conventional ramp sequence leading to an enhancement factor of up to 3.5 at a MAS frequency of 30 kHz. The resulting sensitivity rendered possible the detection of non-protonated nitrogen atoms at natural abundance with 2.5-mm rotors at 9.4 T.     

Uncovering toxicological complexity by multi-dimensional screenings in microsegmented flow: modulation of antibiotic interference by nanoparticles

The technique of microsegmented flow was applied for the generation of two- and higher dimensional concentration spaces for the screening of toxic effects of selected substances on the bacterium Escherichia coli at the nanolitre scale. Up to about 5000 distinct experiments with different combinations of effector-concentrations could be realized in a single experimental run. This was done with the help of a computer program controlling the flow rates of effector-containing syringe pumps and resulted in the formation of multi-dimensional concentration spaces in segment sequences. Prior to the application of this technique for toxicological studies on E. coli the accuracy of this method was tested by simulation experiments with up to five dissolved dyes with different spectral properties. Photometric microflow-through measurement of dye distribution inside the concentration spaces allowed the monitoring of microfluid segment compositions. Finally, we used this technique for the investigation of interferences of the antibiotics ampicillin and chloramphenicol towards E. coli cultures and their modulation by silver nanoparticles by measuring bacterial autofluorescence. Each concentration point in this three-dimensional concentration space was represented by 4 or 5 single segments. Thus, a high reliability of the measured dose/response relations was achieved. As a result, a complex response pattern was discovered including synergistic and compensatory effects as well as the modulation of the range of stimulation of bacterial growth by a sublethal dose of chloramphenicol by silver nanoparticles.     

The iodide/iodate actinometer in UV disinfection: determination of the fluence rate distribution in UV reactors

Thirty-seven Suprasil quartz spheres, each approximately 1 cm in diameter and containing an iodide-iodate actinometric solution, were attached to a metal rack and inserted into a bench-scale UV reactor filled with water. The spheres were located at various distances and heights around a 12.4 W low-pressure Hg lamp housed inside a 3.2 cm-radius quartz sleeve in the middle of an annular batch reactor. UV light exposure at 254 nm was performed with the percent transmittance of the water present in the reactor at either 73% or 100% defined over a 1 cm path length. The spheres were simultaneously exposed to the UV light for a given period of time, after which the solutions were removed from the spheres and the yield of triiodide determined from the increase in absorbance at 352 nm. The resulting fluence rate at each site was then calculated on basis of the yield of triiodide. These results were compared with the predictions of a mathematical model based on the multiple point source summation approximation, including reflection and refraction at the air-quartz-water interface. Initially, the agreement was not satisfactory, especially in regions at an oblique angle to the lamp. The model was modified from a multiple point source model to a multiple cylindrical segment model by incorporating a cosine factor. The agreement between the new model and the experimental data was excellent and these experiments provide a strong validation of the model, even under conditions in which the fluence rate varied by >1000-fold between extreme sites in the reactor.     

利用β-N-乙酰氨基葡萄糖苷酶快速酶切分析中国仓鼠卵巢细胞表达的西妥昔单抗抗原结合区的聚糖比例

西妥昔单抗具有较复杂的糖基化修饰,在抗原结合片段(Fab)和可结晶片段(Fc)的重链上都含有2个N-糖基化位点,其中Fab段的糖基化最为复杂,要研究清楚该位点的糖基化修饰,开发专一性切糖技术和稳定的聚糖比例分析方法是当前迫切需要解决的难题。以中国仓鼠卵巢(CHO)细胞表达的西妥昔单抗为研究对象,使用β-N-乙酰氨基葡萄糖苷酶(Endo F2)开发了一种快速Fab段聚糖释放的方法,利用超高效液相色谱-高分辨质谱(UPLC-HRMS)进行了定性和聚糖比例分析。第一步对抗体原液进行非变性酶切,抗体原液经超纯水稀释后,加入糖苷酶Endo F2进行酶切,通过质谱对质量数的解析,结果表明Endo F2酶切时间5 min, Fab段的聚糖就能完全切除,而Fc段的聚糖不受影响,实现了快速酶切,而且切糖具有很好的专一性。第二步对Fab段聚糖进行比例分析,将释放的聚糖经对氨基苯甲酰胺(2-AB)荧光标记后使用超高效液相色谱联用荧光检测器(FLR)进行检测,在亲水作用色谱(HILIC)柱上得到良好的分离并可以进行稳定地聚糖比例分析。3次独立试验结果表明,酶切后的质谱图基本一致,且聚糖的比例结果也基本一致,表明Endo F2酶切方法和聚糖比例分析方法都具有较好的稳定性和可靠性。此外,通过测定来自两个不同工艺生产的样品,数据显示两者的糖谱上具有非常明显的差异,表明利用开发的方法可以实现对抗体生产工艺进行监测研究,对抗体生产工艺的评估具有非常重要的意义。     

Synthesis of the C8-C20 and C21-C30 segments of pectenotoxin 2

In this study, we synthesized the C8-C20 and C21-C30 segments of the diarrhetic shellfish toxin pectenotoxin 2. The C8-C20 segment was assembled from a phosphonate corresponding to the C8-C15 segment (prepared from l-malic acid in 19 steps) and an aldehyde corresponding to the C16-C20 segment (synthesized from 3-methyl-3-butenol in nine steps) by a twelve-step process including the Horner-Wadsworth-Emmons reaction, regio- and stereoselective reduction of the resulting enone, diastereoselective epoxidation, and 5-exo epoxide cleavage forming the C-ring. The C21-C30 segment was constructed in 13 steps from (S)-glycidol via a route involving E-ring formation by 5-exo epoxide cleavage and stereoselective methylation at C27 by the Evans method.