Two-dimensional correlation analysis of continuous online in situ ATR-FTIR on the adsorption of butyl xanthate at the surface of a-PbO

The adsorption behavior of butyl xanthate on the surface of lead oxide was investigated using continuous online in situ attenuated total reflectance Fourier transform infrared（ATR-FTIR） spectroscopy technique and two dimensional（2D） correlation analysis.The adsorbed layer studied was prepared by coating α-PbO particles onto the surfaces of the ZnSe crystal.The appearance of spectral peaks at 1203 cm^-1,1033 cm^-1 and their red shift indicated the formation and aggregation of xanthate at the surface of α-PbO.According to 1R intensity changes after rinsing with deionized water and a NaOH solution,the adsorption was proved to be a chemisorption type.The competition between xanthate and OH for the surfaces leads to desorption of xanthate at higher pH.The technique of 2D correlation ATR-FTIR spectroscopy was used to evaluate the changing order of spectral intensities in the adsorption process,and the results indicated that xanthate micelles were formed at the surfaces.The adsorption kinetics of butyl xanthate was found to be a pseudo-second-order reaction model and the adsorption capacity of butyl xanthate at α-PbO was as high as 281 mg g^-1 after 150 min.     

Investigation of the manganese stress on wheat plant by attenuated total reflectance Fourier transform infrared spectroscopy

ABSTRACT

The present paper deals with the investigation of the changes in chemical contents of the leaf of wheat seedling stressed by excess manganese using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) technique. The infrared spectra of the leaves of control and manganese-treated wheat plants have been recorded in the spectral region 485–4000?cm^?1 at a resolution of 4?cm^?1. The recorded spectrum has been analyzed with the help of curve-fitting method for the quantitative estimation of chemical contents and conformational changes. The study indicated changes arising in the polysaccharide, lignin, amino acid, secondary structure of protein, and lipid in the leaves of control and manganese-treated wheat plants. Manganese treatment increased the amount of cellulose, lignin, and amide II till 200?μM concentration, while a decrease was observed at 1000?µM concentration. Manganese induced conformational changes in the secondary structure of protein which was indicated by shifting of the bands to the higher wavenumber and change in the β sheet/α helix ratio. In addition, manganese stress decreased lipid content in the leaves of the wheat seedlings. The study demonstrates the potential of attenuated total reflectance FTIR for the non-invasive and rapid monitoring of the plants stressed with heavy metals.     

Polysulfobetaine films prepared by electrografting technique for reduction of biofouling on electroconductive surfaces

The sulfobetaine films were prepared on stainless steel and golden surfaces. In the first step, the poly(2-(dimethylamino)ethyl methacrylate) film was created by employing the electrografting polymerization technique. In the second step, this film was modified to polysulfobetaine, i.e. the polymer film bearing the zwitterionic groups. The presence of the electrografted film and its modification were determined by contact angle measurements, infrared spectroscopy in reflectance mode and X-ray photoelectron spectroscopy. The prepared films were homogeneous with the thickness from about 5 to 26 nm as determined by X-ray photoelectron spectroscopy. The atomic force microscopy measurements showed the increase of surface roughness upon the surface coating. In vitro tests using adherent RAT-2 fibroblast cells and fluorescently labelled bovine serum albumin proteins showed that prepared polysulfobetaine films can be used in applications requiring the resistance against cell attachment and biofouling.     

Synthesis and enrichment of a macromolecular surface modifier PP-b-PVP for polypropylene

Polypropylene-block-poly(vinylpyrrolidone) copolymer was synthesized through the esterification of dicarboxyl-terminated polypropylene with monohydroxyl-terminated poly(vinylpyrrolidone) and used as a macromolecular surface modifier to improve the surface hydrophilicity of PP. The results of ATR-FTIR and contact angles measurements indicated that PP-b-PVP could diffuse preferably onto the surface by the inducement of high energy interface and lower the water contact angle of polypropylene. Lower loading and lower molecular weight of PP and PVP segment would result in higher surface selective enrichment.     

Thermal oxidation of clay-nanoreinforced polypropylene

The thermo-oxidation process at low temperatures for a montmorillonite-nanoreinforced polypropylene (PP) was studied. Experimental aging kinetic data at 100, 80 and 60 °C have been obtained and compared with a computational simulation in which a kinetic model based on the closed loop approach was used. As a result, it has been found that the montmorillonite role is not limited to a role of inert filler in the polymer matrix but induces a slight catalytic effect leading to induction period reduction. This effect has been well simulated by increasing initial hydroperoxyde concentration. The consequences of kinetic control by oxygen diffusion have also been investigated by using micro ATR-FTIR mapping to assess concentration profiles of the oxidation products across the sample thickness. It has been found that the oxidized layer thickness is close to 17 μm for the pure polypropylene whereas it is around 10 μm for the nanocomposite at 100 °C. These profile variations have been attributed to differences in oxygen diffusion coefficient values. Simulations based on the kinetic model including diffusion-reaction coupling describe these profiles well.     

基于红外光谱聚类分析的纳滤膜污染动态发展行为研究

污水再生利用是解决水资源短缺问题的有效对策。纳滤技术由于能够生产高质量的再生水,成为污水深度处理、再生利用的有效方法之一。然而,在纳滤过程中存在复杂的、动态的膜污染现象,会导致产水通量、产水质量下降等问题。研究膜污染动态发展的行为,对于膜污染的分阶段针对性控制具有重要意义。有机物是污染层动态发展过程的重要指示性成分,红外光谱是表征污染层发展过程中表面有机物官能团变化情况的重要手段。但由于红外光谱中峰的数量多,系列样品之间峰强度的差别较小（尤其是当膜污染过程中的采样间隔较小时）,利用直观观察不易甄别不同样品间的谱图差异及其变化趋势,在此水平上难以对膜污染阶段进行准确识别、对各阶段特征进行有说服力的分类概括。为探索膜污染的动态发展过程,本研究将傅里叶变换红外光谱与统计学聚类分析相结合,对膜污染过程中不同时间点的膜样本进行红外光谱分析,再对红外光谱数据进行一系列预处理和系统聚类分析,从而客观解读膜污染动态发展过程中系列样品红外光谱分阶段变化规律。考虑到类别间距离度量方法、红外吸收峰强度标准化、峰之间自相关性、峰与样本之间交互作用等因素的影响,研究采用对应分析对红外数据进行预处理,提取各样本在主要维度上的得分,随后基于标准化欧式距离对各样本进行聚类。在为期一个月的城市污水深度处理纳滤试验过程中,由于污染物在膜表面累积,纳滤膜发生了较为严重的污染。通过对13个不同时间点的膜样本进行红外光谱聚类发现,膜污染可清晰划分为如下阶段：空白膜、阶段Ⅰ（3 h～8 d）、阶段Ⅱ（10～15 d）和阶段Ⅲ（20～30 d）。采用红外聚类,得到膜表面X射线光电子能谱（XPS）和三磷酸腺苷（ATP）含量分析等方法的交互验证。结果表明,随着膜污染的发展,膜表面有机物成分与共存微生物量发生协同变化,各阶段大致特征为：阶段Ⅰ各类有机污染物初步覆盖,微生物开始富集;阶段Ⅱ多糖类污染物比例上升,微生物的富集趋于稳定;阶段Ⅲ整体污染趋于成熟,有机污染物氢键特征更加明显。该研究通过对红外数据进行聚类分析,能够灵敏地探测各红外图谱之间的差别,有助于对红外光谱规律的深度挖掘,为膜污染阶段的识别和划分提供了一种客观、自动、可量化的辅助性方法,并且有助于归纳出不同阶段的污染层特征,可作为膜污染时序特征的侦查手段。此外,除了膜污染的研究,在材料、吸附等领域,只要有一系列变化的红外光谱,均可尝试采用红外光谱聚类分析方法,获取基于红外特征的定类信息或分阶段规律。     

基于溶液温度差谱分析的ATR-FTIR原位测量方法

作为一种原位、快速、无损坏的中红外光谱分析技术,ATR-FTIR已在很多工程领域得到越来越多的应用,尤其是针对结晶过程溶液浓度的原位实时测量。水是一种常用的结晶溶剂,在中红外波段具有强吸收峰,并且在不同温度下具有光谱吸收差异性,因而不能忽略溶剂水和温度对溶液浓度的中红外光谱测量带来的影响。以朗伯-比尔定律为基础,提出采用溶液光谱减去相应温度下的溶剂光谱的方法,从而能准确地测量溶液浓度。以L-谷氨酸溶液结晶过程为例,对L-谷氨酸水溶液的原始光谱数据、溶液光谱扣除常温(25℃)溶剂水的光谱数据以及溶液光谱对应温度扣除溶剂水的光谱数据分别进行建模。结果表明,提出的对应温度差谱法能有效消除溶剂水峰对溶质光谱测量的干扰,明显地降低了溶液浓度光谱标定模型的预测误差。该方法对提高原位ATR-FTIR光谱检测精度的实际应用具有一定的参考价值。     

Chemical and mechanical stability of EPDM in a PEM fuel cell environment

Proton exchange membrane (PEM) fuel cell stack requires elastomeric gaskets in each cell to keep the reactant gases within their respective regions. Long-term durability of the fuel cell stacks depends heavily on the functionality of the elastomeric gasket material. Chemical and mechanical stability of the elastomeric material is of great concern to the overall performance of the fuel cell stacks. The degradation of a commercially available gasket material, ethylene-propylene-diene monomer (EPDM), was investigated in a simulated PEM fuel cell environment in this work. One solution and two temperatures, based on actual fuel cell operation, were used in this study. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environment over time. Atomic absorption spectrometry was used to identify the leachants in the soaking solution from the elastomeric material. Microindentation test and dynamic mechanical analysis (DMA) were conducted to assess the change of mechanical properties of the samples exposed to the environment. The atomic absorption spectrometer analysis shows that silicon and calcium were leached from the material into the soaking solution. The ATR-FTIR results indicate that the chemical changes were not apparent. The microindentation test and DMA results reveal that mechanical properties were not changed significantly.     

Artificial neural network for quantitative determination of total protein in yogurt by infrared spectrometry

A method has been introduced for quantitative determination of protein content in yogurt samples based on the characteristic absorbance of protein in 1800-1500 cm^− 1 spectral region by mid-FTIR spectroscopy and chemometrics. Successive Projection Algorithm (SPA) wavelength selection procedure, coupled with feed forward Back-Propagation Artificial Neural Network (BP-ANN) model was the benefited chemometric technique. Relative Error of Prediction (REP) in BP-ANN and SPA-BP-ANN methods for training set was 7.25 and 3.70 respectively. Considering the complexity of the sample, the ANN model was found to be reliable, while the proposed method is rapid and simple, without any sample preparation step.     

Design and characterization of bi-soft segmented polyurethane microparticles for biomedical application

Bi-soft segmented poly(ester urethane urea) microparticles were prepared and characterized aiming a biomedical application. Two different formulations were developed, using poly(propylene glycol), tolylene 2,4-diisocyanate terminated pre-polymer (TDI) and poly(propylene oxide)-based tri-isocyanated terminated pre-polymer (TI). A second soft segment was included due to poly(?-caprolactone) diol (PCL). Infrared spectroscopy, used to study the polymeric structure, namely its H-bonding properties, revealed a slightly higher degree of phase separation in TDI-microparticles. TI-microparticles presented slower rate of hydrolytic degradation, and, accordingly, fairly low toxic effect against macrophages. These new formulations are good candidates as non-biodegradable biomedical systems.