Surface-modified ZnSe waveguides for label-free infrared attenuated total reflection detection of DNA hybridization

This communication presents a novel label-free biosensing method to monitor DNA hybridization via infrared attenuated total reflection (IR-ATR) spectroscopy using surface-modified ZnSe waveguides. Well-defined carboxyl-terminated monolayers were formed at H-terminated ZnSe by direct photochemical activation. Chemical activation of the acidic function was obtained by using succinimide/carbodiimide linkers. The sequential surface modification reactions were characterized by XPS and IR-ATR spectroscopy. Finally, a single stranded DNA probe with a C6-NH(2) 5' modifier was coupled to the ester-terminated surface via peptide bonding, and the hybridization of the immobilized DNA sequence with its complementary strand was directly evaluated by IR-ATR spectroscopy in the mid-infrared (MIR) spectral regime (3-20 μm) without requiring an additional label. A shift of the vibrational modes corresponding to the phosphodiester and deoxyribose structures of the DNA backbone was observed. Hence, this approach substantiates a novel strategy for label-free DNA detection utilizing mid-infrared spectroscopy as the optical sensing platform.     

中红外光谱透射比标准物质研制

采用物化性质稳定的单晶硅作为基质,以直流磁控溅射方式轻蒸镀不同厚度的镍、铬混合膜层,实现了中红外波段(500~4000 cm^–1)不同透射比标准物质的研制。研制的中红外光谱透射比标准物质其透射比标称值分别为10%和50%,扩展不确定度优于0.008(k=2)。该标准物质具有量值稳定、光谱平坦等特点,可用于各类傅里叶变换红外光谱设备的透射比校准。     

Comparison of various chemometric evaluation approaches for on-line FT-NIR transmission and FT-MIR/ATR spectroscopic data of methyl methacrylate solution polymerization

For the evaluation of vibrational spectroscopic data acquired on-line to a chemical reaction a broad range of different chemometric algorithms is available. The present study reports the comparative results obtained by different chemometric techniques from the data acquired by light-fiber coupled Fourier-transform near infrared (FT-NIR) transmission spectroscopy and Fourier-transform mid-infrared (FT-MIR) spectroscopy in the attenuated total reflection (ATR) mode to monitor the solution polymerization of methyl methacrylate (MMA). We have found that the results obtained by the application of multivariate curve resolution (MCR) methods to the MIR spectral data acquired during the polymerization of MMA are quite comparable to the results derived by partial least-squares calibration. In the case of the NIR data univariate calibration yields somewhat poorer results than multivariate calibration and MCR, but still inside an acceptable range.     

Technical solutions for analysis of grape juice,must, and wine: the role of infrared spectroscopy and chemometrics

Information about constituents of grape juice, must, and wine can be used for management and decision support systems in order to improve, monitor, and adapt grape and wine production to new challenges. Numerous sensors that gather this information are either currently available or in development. Nevertheless there is still a need to adapt these sensors to special requirements, for example robustness, calibration and maintenance, operating costs, duration, sensitivity, and specificity to a particular application. The sensors commonly used by the wine industry are those that are based on mid-infrared (MIR), near-infrared (NIR), visible (VIS) and ultraviolet (UV) spectroscopy. This article reviews some recent technical solutions for analysis of juice, must and wine based on the combination of infrared spectroscopy and chemometrics.     

Mid-IR fiber-optic reflectance spectroscopy for identifying the finish on wooden furniture

Mid-IR fiber-optic reflectance spectroscopy (FORS) is a totally noninvasive infrared analytical technique allowing the investigation of artworks without the need for any sampling. The development and optimization of this analytical methodology can provide a tool that is capable of supporting conservators during the first steps of their interventions, yielding fast results and dramatically reducing the number of samples needed to identify the materials involved. Furthermore, since reflection IR spectra suffer from important spectral anomalies that complicate accurate spectral interpretation, it is important to characterize known reference materials and substrates in advance. This work aims to verify the possibility of investigating and identifying the most widely used wood finishes by means of fiber-optic (chalcogenide and metal halides) mid-infrared spectroscopy. Two historically widely employed wood finishes (beeswax, shellac) and two modern ones (a hydrogenated hydrocarbon resin and a microcrystalline wax) were investigated in an extended IR range (from 1000 to 6000 cm⁻¹) with reflectance spectroscopy and with FORS. The broad spectral response of the MCT detector was exploited in order to include overtones and combination bands from the NIR spectral range in the investigation. The reflectance spectra were compared with those collected in transmission mode in order to highlight modifications to shapes and intensities, to assign absorptions, and finally to select “marker” bands indicating the presence of certain finishing materials, even when applied onto a substrate such as wood, which shows many absorptions in the mid-infrared region. After the characterization, the different products were applied to samples of aged pear wood and investigated with the same techniques in order to check the ability of mid-IR FORS to reveal the presence and composition of the product on the wooden substrate.     

中红外、近红外和拉曼光谱法测定商品农药制剂中氰戊菊酯和马拉硫磷的含量

利用近红外、中红外和拉曼光谱法定量分析了商品农药制剂中有效成分氰戊菊酯和马拉硫磷的含量.采用偏最小二乘法(Partial least squares,PLS)建立氰戊菊酯和马拉硫磷的定量模型并进行了优化,用独立检验集对模型适应性进行评价.近红外和中红外法测定氰戊菊酯、马拉硫磷定量模型的相关系数分别是0.9981,0.9994和0.9946,0.9998,外部验证集标准差分别是0.082,0081和0.092,0.075,两种方法的定量效果接近;拉曼法氰戊菊酯和马拉硫磷定量模型的相关系数分别为0.9872和0.9993,外部验证集标准差分别为0.254和0.317,预测精度不及近红外和中红外法高.MIR-ATR,NIR和Raman 3种方法均能满足现场检测农药质量的需要.     

Characterization of InAlAs/InGaAs/InP mid-infrared quantum cascade lasers

A mid-infrared laser characterization system, including a GPIB programmable I-P and I-V set-up based on direct waveform measurement with extraordinary wide pulse duration and duty cycle tuning range, in conjunction with a Fourier transform infrared spectroscopy system adapted with double modulation technique, has been developed. Based on this characterization system, the characteristics of gas source MBE grown InAlAs/InGaAs/InP quantum cascade lasers (QCL), especially their thermal property, have been evaluated. The results show that in the combination of I-P, I-V and spectral measurements at various driving pulse parameters, the thermal resistance, lasing conditions as well as spectral characteristics of the mid-infrared QCL could be deduced. This characterization system is also a useful tool for the evaluation of other types of diode lasers in the mid-infrared band.     

红外光谱法研究温度变化对卵粘蛋白构象的影响

采用傅里叶变换红外(FTIR)光谱法和二维相关分析(2D Correlation analysis)技术研究了卵粘蛋白(Ovomucin)的构象转变与温度之间的关系. 结果表明, 当温度为55~65℃时, 卵粘蛋白的红外谱峰的位置和强度发生较大改变. 二维相关分析表明, 在升温过程中, 与肽链相比卵粘蛋白分子中的糖链对温度变化更为敏感, 且优先发生构象改变, 糖链分子的存在利于维持卵粘蛋白构象的热稳定性. 在25~95℃升温过程中, 卵粘蛋白分子二级结构的变化次序依次为α-螺旋、 β-折叠、 β-转角和无规卷曲. 由温度变化引起的卵粘蛋白分子结构动态变化的微观信息, 为揭示变温微扰引起的蛋白构象变化机理提供了初步的理论依据.     

二阶导数预处理法在中红外光谱定量分析中的应用研究

介绍了运用最小二乘法建立傅立叶变换中红外光谱定量分析模型的原理和方法。以苯甲酸和邻苯二甲酸氢钾为实验材料获取红外吸收光谱,采用MAT-LAB工程语言编程,分别以吸收光谱和二阶导数光谱,进行中红外光谱定量分析建模波数信息选择,优选出2~4个波数点的光谱信息,建立了中红外光谱定量分析模型。用此模型预测混合物的量,预测值与实际值的相对误差小于5.0%。     

Mid-infrared second-order susceptibility of alpha-quartz and its application to visible-infrared surface sum-frequency spectroscopy

We provide the first account of the second-order susceptibility of quartz down to 10 mum (1000 cm(-1)) and show how this data may be used along with the sum-frequency response of an amorphous gold surface to elucidate the nonlinear susceptibility of any material in the mid-infrared region. Crystalline quartz is an established material for use in second-harmonic and sum-frequency generation studies of new systems, on account of its well-characterized linear and nonlinear optical properties. Previous knowledge of its nonlinear susceptibility has been limited to its transparent region, wavelengths shorter than about 3 mum. Longer wavelength chi((2)) values for quartz are particularly important for techniques such as vibrational sum-frequency spectroscopy which are expanding into the mid-IR with the increasing availability of widely tunable infrared laser sources.     

固态氢分子基质隔离高分辨光谱实验装置及其应用

建立了用傅立叶变换红外光谱和中红外差频激光光谱方法研究氢基质隔离光谱的测量装置. 作为装置的测试, 观测了3 cm长的固态氢分子晶体在1-5 μm波段的吸收光谱. 并用中红外差频激光测量其在2410 cm-1附近的W0(0)(v=0→0, J=6→0)谱线的高分辨精细结构. 通过在低温基片上喷溅沉积氢分子晶体薄膜的方法, 对氢基质隔离的CO2分子的高分辨红外吸收光谱进行了研究.     

Raman spectroscopic quantification of milk powder constituents

Raman spectroscopy has significant potential for the quantification of food products. Milk powder is an important foodstuff and ingredient that is produced on large scale (over 20 million tonnes per annum). Raman spectroscopy, unlike near- and mid-infrared spectroscopies, has not been used extensively to quantify milk powder constituents. The effect of sample presentation on spectroscopic calibrations of protein and fat for 136 New Zealand milk powders was assessed using Raman spectroscopy. Prediction models were produced to quantify a protein concentration range of 32.19-37.65% w/w for skim milk powder, and a protein concentration range of 23.34-25.02% w/w and a fat concentration range of 26.26-29.68% w/w for whole milk powder (where ratios of prediction to deviation exceeded 2.6 with one exception). The resultant calibrations were not influenced by sample orientation; the sample temperature during data collection did affect the calibrations. Calcium fortification in the form of calcium carbonate was identified within a sub-set of samples, reinforcing the efficacy of Raman spectroscopy for identifying both crystalline and non-crystalline constituents within milk powder.     

Determination of Fipronil in Acetamiprid Formulation by Attenuated Total Reflectance-Mid-Infrared Spectroscopy Combined with Partial Least Squares Regression

There is a high demand for rapid determination of fipronil in pesticide preparations because it has been restricted and even prohibited in many countries. An infrared-based methodology was developed for this analyte in acetamiprid formulations by attenuated total reflectance mid-infrared spectroscopy. The quantitative calibration models of fipronil were established by partial least squares regression. The determination coefficients (R²) of the model were above 0.99 while both the root mean square error of prediction and root mean square error of calibration were below 0.0011, which showed the partial least squares model accurately predicted fipronil concentrations in acetamiprid. The accuracy was further demonstrated by comparison with another two models' results of low (<1.0%, w/w) and high concentration sample sets (1.0%–4.5%, w/w). These results demonstrate the potential of infrared spectroscopy to quickly detect fipronil in acetamiprid.     

Combinatorial investigation of structure–properties relationships and microcosmic curing mechanism of dental adhesives functional monomers

Pyromellitic dimethacrylate (PMDM), a dental adhesive functional monomer has been investigated by FTIR and two-dimensional infrared spectroscopy (2D-IR) methods. With the comparison of the curing processes among three samples (Base-Resin, PMDM and monomethacrylate monomer 4-methacryloxyethyl trimellitic anhydride (4-META)), better properties and faster curing of newly used PMDM has been found. Assignments of Base-Resin, PMDM and 4-META in the mid-infrared (MIR) and near-infrared (NIR) regions are ascertained detailedly. According to the high resolution of 2D-NIR maps, assignments of the dental adhesive functional monomers are further validated and the mechanism of the curing process has been accurately concluded as well; similar 2D-NIR spectra of all three samples show the same transformation process from the double-bonds to the single-bonds during visible-light curing.     

Covalent attaching protein to graphene oxide via diimide-activated amidation

In this paper, graphene oxide nanosheets (GOS) are functionalized by bovine serum albumin (BSA) via diimide-activated amidation under ambient conditions. The obtained GOS–BSA conjugate is highly water-soluble. Results of atomic force microscopy (AFM), Raman spectra and Fourier transform infrared spectroscopy analysis confirm that GOS–BSA conjugate contains both GOS and BSA protein. AFM image shows that GOS are fully exfoliated. Results of cyclic volatammograms show that the protein in the GOS–BSA conjugate retains its bioactivity. The present method may also provide a way to synthesize graphene-based composites with other biomolecules.     

New tool for epidermal and cosmetic formulation studies by attenuated total-reflection spectroscopy using a flexible mid-infrared fiber probe

The potential of mid-infrared attenuated total-reflection spectroscopy for dermatology studies has been increased by the development of a flexible fiber-optic probe from silver halide material. Such a tool significantly eases epidermal surface characterization. Spectra of human forearm skin and of bovine udder skin (BUS-model), which is used as a substitute for in-vivo tests on man, were compared, and as an example low concentrations of vitamin E acetate (alpha-tocopherol acetate) in the stratum corneum were measured after topical skin application. Depth profiling was enabled by repeated steps of tape stripping and subsequent skin measurement. The infrared methodology is rapid and can be applied to small areas of skin. It is also sufficiently sensitive for analysis of a large variety of cosmetic formulations and dermatopharmaca. Discrimination of vehicle formulations is possible because of the large information content of mid-infrared spectra.     

The mid-infrared (attenuated total reflection) spectroscopy of ethylene carbonate in water.

Ethylene carbonate (EC) and water solution compositions ranging from pure water to 60 mass% EC have been examined using infrared (attenuated total reflection) spectroscopy. The fundamental vibrational modes of EC in the mid-infrared between 2050 and 1000 cm(-1) were fitted to mixed Lorentzian-Gaussian bandshapes. The spectral data for EC bands between 1000 and 650 cm(-1) are also shown but were not curve-fitted due to baseline distortions from water librational modes. The results of the band analysis have provided information regarding the molecular structure of these solutions, and the fact that the structure is also concentration dependent. The Fermi resonance coupling between the v2 and 2v7 vibrations of EC have been analysed using a standard perturbation model.     

红外光谱技术在茶叶分析中的应用综述

在总结大量文献的基础上,对中、近红外光谱技术在茶叶分析中的应用进行了较为全面的综述;指出红外光谱技术因具有速度快、成本低及重现性好等优点,近年来在生物和食品等领域得到了越来越广泛的应用.     

Noninvasive Surface Detection of Papillary Thyroid Carcinoma by Fourier Transform Infrared Spectroscopy

Previously Fourier transform infrared(FTIR) spectroscopy has been applied to detecting thyroid cancer during operations and to discriminating cervical metastatic ones from non-metastatic lymph nodes. This study explored the possibility of establishing a sensitive, accurate and noninvasive screen or diagnosis by preoperative FTIR spectroscopy. 111 patients undergone a thyroid operation and 50 healthy volunteers were enrolled in the study. The FTIR spectra were obtained by two mid-infrared optical fibers with an attenuated total reflectance(ATR) probe closely contacting the subjects' skin on the thyroid nodules. The FTIR spectra obtained from normal thyroid, nodular goiter(NG) and papillary thyroid carcinoma(PTC) patients were compared. A Fisher's discriminant analysis was created based on these data. There were 41 PTC patients and 70 NG patients according to their histopathological examinations. A total of 23(of 39) parameters were statistically different among the three groups(P<0.05). The F₁₃₀₀ and F₁₀₈₀ parameters were significantly different between the three groups. In total, 9 out of 39 FTIR parameters were selected as independent factors by the Wilks' lambda stepwise discriminant analysis. The discrimination accuracy of papillary thyroid carcinoma in the three groups was 88.8%. Surface detection of PTC by FTIR spectroscopy is feasible. FTIR spectroscopy can be used for rapid and noninvasive PTC screen and auxiliary diagnosis.     

Utilization of spectral vector properties in multivariate chemometrics analysis of hyperspectral infrared imaging data for cellular studies

A suite of numerical techniques was utilized in a concerted fashion for the efficacious multivariate chemometrics analysis of hyperspectral infrared imaging data of exfoliated oral mucosa cells. Based on the vector representation of infrared spectrum a1xnu), spectral vector properties (SVP) are demonstrated to possess underpinning spectral information that was exploited in crucial chemometrics analyses; which include outlier spectra identification, selection for a subset of imaged mid-infrared spectra that contain good oral mucosa cell signals, and, for the first time, obtain major biochemical constituent spectra via the band-target entropy minimization (BTEM) curve resolution algorithm. The relative concentration spatial distribution of the major biochemical constituents observed, namely membrane lipids and various cellular protein structures (alpha-helix, beta-sheet, turns and bends), were subsequently acquired through multi-linear regression and were displayed as chemical contour maps. Amongst the set of numerical algorithms employed, two novel unsupervised clustering algorithms were developed and tested. One is useful for outlier spectra detection, and the other aids the selection of pertinent spatially distributed spectra that possess oral mucosa cell mid-infrared spectra with good signal-to-noise ratio. It is anticipated that this developed numerical suite will serve as an effective multivariate chemometrics protocol for cellular studies and biomedical diagnostics via infrared imaging.