Analyses of trace amounts of dyes with a new enhanced sensitivity FTIR spectroscopic technique: MU-ATR (metal underlayer ATR spectroscopy)

The identification of organic dyes is a challenging task in all the fields such as the forensic and conservation sciences, especially in cases where the amount of sample is extremely small. In this paper we propose a new enhanced FTIR method (MU-ATR metal underlayer ATR spectroscopy), which we believe is the first of its kind, for the analysis of a few ng of dyes. With this method, dyed fiber micro-extracts can be analyzed using a commercial FTIR microscope with a fixed incident angle, obtaining the same separation between the different classes of dyes investigated as we obtained analyzing pure dyes in transmission mode.     

Diffusion measurements using ATR‐FTIR spectroscopy: Acetone diffusion in polypropylene—use of penetrant fluid pressure to improve sample/IRE contact

In this article, we present a simple method for improving the contact between a film sample and the internal reflection element (or crystal) when diffusion into thin polymer films is measured with attenuated total reflectance (ATR)‐Fourier transform infrared spectroscopy. Intimate film/crystal contact is particularly important for making measurements on premade films and materials that cannot be solution‐coated onto the crystal. This method is based on controlling the penetrant fluid pressure above a threshold value (>230 kPa) in the ATR flow cell. Measurements of acetone diffusion into a commercial polypropylene film at 300 K and varied pressures indicated that the diffusion time constant was constant at pressures above this threshold. We also monitored the absorbance of a polymer band that had no overlap with the acetone spectrum to examine whether adequate sample‐film/crystal contact was reached and maintained. From these observations, we concluded that an apparently good match between the experimental data and a model calculation does not alone justify confidence in the accuracy of the calculated diffusion time constant. Additionally, the practice of using a reference band to correct the uncertainty in absorbance for bands of interest (due to imperfect sample/crystal contact) yielded inconsistent results. We also report further measurements of acetone diffusivity in a polypropylene film at temperatures ranging from 278 to 308 K that yielded an estimated activation energy for diffusion of 98 kJ/mol. © 2000 John Wiley & Sons, Inc.* J Polym Sci B: Polym Phys 38: 1773–1787, 2000     

Spectroscopic characterization of ambers and amber-like materials

Longitudinal acoustic (LA) phonon of Baltic, Dominican and Kuji ambers, amber-like rosin and synthetic acrylic resin has been investigated by means of Brillouin light scattering (BLS) at room temperature. We observed a pair of LA phonon peaks and a broad quasi-elastic scattering peak in backscattering spectra from ambers. The LA phonon frequencies were found to be 16.97–17.11 GHz for Baltic ambers, 17.23–17.68 GHz for Dominican ambers and 17.70–17.97 GHz for Kuji ambers, respectively. We would like to point out that the LA phonon frequency can be a good physical quantity to specify the amber-producing district. We also present a correlation between the BLS spectrum and infrared absorption spectrum of ambers and amber-like materials.     

FTIR spectroscopy and X-ray diffraction characterization of Nb doped sol-gel silica

Nb doped silica was prepared by the sol-gel method. The experimental variables were the pH (acidic and basic) and the Nb concentration (1.0–10.0 wt.%). The samples were calcined at 300°C and 600°C and analyzed by XRD, and FTIR. The TGA and DTA of the gels were also performed. From the XRD results the radial distribution function allowed us to establish the existence of the Si–O–Nb bond in the powders.     

基于小波和小波包变换的苯丙酮尿症傅里叶变换衰减全反射红外光谱筛查模型的研究

应用小波和小波包变换对傅里叶变换衰减全反射红外光谱(FTIR/ATR)进行去噪处理,以提高苯丙酮尿症(PKU)筛查模型的性能。首先优化小波和小波包变换的参数,然后分别对原始光谱(OS)、9点平滑光谱(9S)和一阶微分9点平滑光谱(1D9S)进行去噪处理,以均方根误差(RMSE)、平均相对误差(MRE)、预测准确率(Acc)等为指标,考察小波和小波包变换对模型性能的影响。结果与变换前相比,模型性能均有所提高,其中小波变换以1D9S+sym12处理结果为最优,而小波包变换以1D9S+sym1为最优;Acc全部提高为100%。     

Quantitative analysis of near surfaces three‐dimensional orientation of polymer chains in PET and PEN films using polarized ATR FTIR spectroscopy

Polarized attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy was utilized to characterize the three‐dimensional orientation of polymer chains near highly anisotropic surfaces generated by uniaxial drawing. A versatile method was proposed to analyze the molecular orientation of the polymers by combining the experimental refractive indices and optimized contact pressure by an anvil for solving the optical contact problem. This method is effective even when changes in the molecular orientation along the thickness direction caused by drawing are remarkable. In addition, this method enables quantitative comparison of the molecular orientation among different polymers in the same coordinate system. From the molecular orientation analysis of poly (ethylene terephthalate) (PET) and poly (ethylene naphthalate) (PEN), it was revealed that this method has a broader range of applications with high accuracy in estimating the molecular orientation of polymers compared with the conventional methods. The significant changes in the molecular orientation caused by uniaxial and biaxial drawing of PET and PEN films were quantitatively analyzed, and the reasons for the significant in‐plane orientation of PEN chains on the film plane are discussed. In addition, the difference in the molecular orientation between both sides of the films was also demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 870–879, 2010     

Some observations on FTIR emission spectroscopy of black solid samples

Application of FTIR emission spectroscopy to the study of optically opaque polymer samples containing high levels of carbon black/carbon fibre filler is considered. The effects of reduced emission and self-absorption are discussed.ICI Films     

FTIR spectroscopic studies of layer systems transferred onto germanium supports

An ATR attachment was adapted to a FTIR spectrometer. The increased sensitivity makes it possible to measure spectra of transferred monolayers. The characteristic vibrational frequencies of the transferred multilayer systems of two different substance types (octadecanoic acid, octadecylamine) were investigated in dependence on the layer number. A direct correlation between the absorbance and the transferred substance quantity was found. The absence of interaction between the first layer and the germanium surface was evidenced by the lack of a difference between multilayer spectra divided by the layer number, and the measured spectrum of one layer.     

Use of FTIR spectroscopy in the investigation of catalytic reactions in zeolites—Possibilities and limitations

FTIR-spectroscopic investigations of catalytic reactions yield detailed information about the interaction of adsorbed molecules with the catalyst and kinetic data of the surface reaction, if the participating molecules show vibrations whose position and intensity in the IR-spectrum depend on the sorption state and the quantity adsorbed. In this paper, the possibilities and limitations of the method are represented by two examples.     

A critical comparison of solid sample preparation techniques in infrared spectroscopy

The growing capabilities of FTIR spectrometers and computers have opened the use of new sample preparation techniques in infrared spectroscopy. In addition to the established KBr pellet technique and ATR spectroscopy, diffuse reflectance and photoacoustic spectroscopy are increasing in importance. A systematic experimental comparison of these techniques has been made in order to make proper use of their mutual advantages.     

Real time observation of microwave-enhanced reactions via fast FTIR spectroscopy

Microwave-enhanced reactions are very fast in comparison to thermal reactions. The determination of optimal end point often fails because conventional analytical methods are too slow. Therefore, we established a fast method using FTIR spectroscopy. The result of the reaction control analysis is obtained within less than 1 min.     

Raman and FTIR spectroscopic characterization of electrochemically synthesized poly(triphenylamine), PTPA

Triphenylamine was electrochemically polymerized in a mixture of toluene and acetonitrile with different electrolyte salts. The poly(triphenylamine) (PTPA) films are insoluble in polar solvents and show high stability and no degradation or loss in electrochemical properties when stored in a laboratory atmosphere. The PTPA films were characterized in situ by FTIR external reflection spectroscopy and by Raman spectroscopy. Electronic Publication     

Band distortions in emission and specular reflection FTIR spectroscopy

General equations for emittance and reflectance of multilayer systems are given. It is demonstrated that band distortions can be avoided by application of the appropriate working equations. An opaque (thick) sample is employed as a reference.     

红外光谱法热分析液晶相变过程

液晶物质在升温过程中会发生多个相转变过程 ,DSC热分析可测量这些相转变的能量变化 ,但却不能提供变化的微观原因和细节 .而温度升高对液晶样品的红外光谱图强度、峰形和吸收频率都有显著影响 .引起这样变化的原因一是热膨胀改变了分子内部化学键的力常数和相互作用 ,从而改变了分子振动偶极矩的性质 ;二是分子中有红外吸收的基团浓度随温度升高而改变 .红外光谱可以给出样品能量变化过程中分子结构变化的细节 ,通过计算还可获得分子结构变化的表观焓变 .前人做过的探索性工作 [1～ 3]都集中在一个或几个功能团的变化上 .在能量变化上仅…     

ATR and transmission analysis of pigments by means of far infrared spectroscopy

In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared (MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation. The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated on a real case study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Adsorption behavior of human serum albumin on ATR crystal studied by in situ ATR/FTIR spectroscopy and two-dimensional correlation analysis

The time-dependent adsorption behavior of human serum albumin (HSA) onto an ATR (ZnSe) crystal was investigated by two-dimensional (2D) correlation analysis and in situ ATR-FTIR spectroscopy following the secondary structural changes in the amide I region. The two major advantages of the generalized 2D correlation spectroscopy were first tested. New extra bands have been resolved by 2D correlation analysis, but they are either artifacts or a result of uncertainty on band position in generalized 2D correlation spectroscopy. The sequence of the intensity variations of the three sub-bands under the amide I band profile deduced from the 'sequential order' rules is contradictory to the experimental observation, which supports our argument on the 'sequential order' rules in generalized 2D correlation spectroscopy (H. Huang, Anal. Chem., 2007, 79, 8281-8292). Subsequent detailed analysis on the in situ ATR-IR spectra shows that the adsorption process of HSA on the ATR (ZnSe) crystal in aqueous solutions can be divided into three stages: no obvious conformational transitions in the first 25 min of adsorption of HSA molecules; large structural rearrangement from α-helix to random coil and short extended chain structures in a fully cooperative way from 25 to 50 min of adsorption; and further slight conformational transformation of short extended chain and turn structures into random coil with no sequential order after 50 min of adsorption.     

ATR‐FTIR Kretschmann spectroscopy for interfacial studies of a hidden aluminum surface coated with a silane film and epoxy II. Analysis by integrated ATR‐FTIR and EIS during exposure to electrolyte with complementary studies by in situ ATR‐FTIR and in situ IRRAS

The destabilization of the interface between a polymer and a metal surface is of considerable interest in several application areas, including the ongoing research on environmentally friendly pretreatments as a replacement for the Cr(VI)‐containing systems where the understanding of mechanisms and performance of a confined metal/polymer interface is of utmost importance. Processes at hidden interfaces are, however, difficult to analyze in detail and at relevant climatic conditions. This study has been divided in two parts, where the subject of Part I is the surface characterization by ATR‐FTIR Kretschmann and IRRAS spectroscopy of aluminum coated with an amino‐functional silane, and the interfacial analysis by ATR‐FTIR Kretschmann after further application of an epoxy film. This second part describes the interaction between the coated sample and an electrolyte. The analysis is performed by integrated in situ ATR‐FTIR Kretschmann and EIS, which requires model systems with evaporated metal films on an internal reflection element. Complementary analyses were also conducted on substrates in the absence of the metal film, and or in the absence of an epoxy top‐coat, respectively. Changes in the interfacial region were observed and assigned to the water uptake including swelling of the epoxy, and the formation of aluminium oxidation and hydration products. Complementary studies allowed the distinction between water uptake in the silane film and the epoxy, respectively, as well as reformations of the siloxane network. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigation of biodeteriorated historical textiles by conventional and synchrotron radiation FTIR spectroscopy

We have examined specimens of historical biodeteriorated cellulose textiles using synchrotron radiation and conventional source FTIR spectroscopy. The main aim of our research was to investigate structural changes caused by ageing and biodeterioration in different types of cellulose fibres. We compared the results, obtained with both methods regarding spectral quality and information obtained with each method. Additionally, we obtained mapping images of the cross sections of the investigated specimens using synchrotron FTIR in order to analyze structural changes in cross sections, caused due to biodeterioration.     

ATR‐FTIR Kretschmann spectroscopy for interfacial studies of a hidden aluminum surface coated with a silane film and epoxy I. Characterization by IRRAS and ATR‐FTIR

Interfacial analysis is essential in many areas of interest, for instance within the ongoing research on environmentally friendly pretreatments of metal surfaces. While studies of the hidden interface between a metal and polymer top‐coat are of great importance, properties of a surface confined between two media are difficult to analyze in detail. Within the two parts of this study, ATR‐FTIR spectroscopy in the Kretschmann geometry is employed as the main analytical tool to study the interface between a thermo‐cured epoxy and aluminum pretreated with a silane film. The technique requires model systems based on thin metal films, but in contrast to most analytical techniques it permits the analysis of a hidden interface. Initial characterization of the silane film formed from a pH‐regulated γ‐APS and BTSE solution was conducted by both ATR‐FTIR Kretschmann and IRRAS spectroscopy. Absorption bands were obtained at 1250–900 cm^?1, assigned to Si? O functionalities, and at ～1570 and ～1410 cm^?1 assigned to acetate existing as a counter‐ion to γ‐APS. After application of the epoxy film, interfacial alterations were detected upon thermal curing including the densification of the epoxy film, the dehydration of aluminum and the formation of molecular epoxy reaction products. Few alterations could be assigned to the silane film. Calculated spectra derived from optical data can verify experimental results and aid data interpretation, and effects of metal oxidation of aluminum were confirmed by introducing gold as an additional substrate. The results showed that ATR‐FTIR Kretschmann spectroscopy is clearly a valuable tool for the study of hidden interfaces of stratified media. Copyright © 2011 John Wiley & Sons, Ltd.