Near-infrared spectroscopy of autunites

NIR spectroscopy has been applied to the study water in the interlayer of the autunite minerals. The spectra of autunites and metaautunites in the first HOH fundamental overtone are different and the spectra of autunites of different origins in the 6000-7500 cm(-1) region are considerably different. A number of conclusions are made based upon the NIR spectra: (a) The spectra of different autunites are different in the NIR spectral region; (b) the spectra of metaautunites show similarity; (c) the spectra of metaautunites are different from that of autunites. NIR spectroscopy provides a method of determination of the structure of water in the interlayer of natural autunites. The implication from the variation in the NIR spectra is that the structural arrangement of water for different autunites is different and is sample dependent. NIR spectroscopy has a wide potential for the study of the autunite minerals.     

Near-infrared spectroscopy of polymers

Although near–infrared (NIR) spectroscopy has been used over many decades for the – primarily quantitative – analysis of polymers containing OH–, NH– and CH–functionalities (e.g. determination of OH–number, water content and residual carbon–carbon double–bonds), it has never been established as a wide–spread analytical and physical tool comparable to other spectroscopic techniques. In the late seventies, however, two new developments have initiated a renaissance of NIR spectroscopy in analytical chemistry. On the one hand, chemo–metric data evaluation techniques have – in combination with diffuse reflection measurements – opened up the possibility of non–destructive, rational multicomponent analysis and identity control of solid polymers with varying morphologies. On the other hand, the introduction of optical light fibres has contributed to an enormous expansion of conventional NIR spectroscopy in terms of remote control. Thus, specific fibre–optic probes allow a separation of the spectrometer and the location of sample measurement over several hundred meters and tremendously alleviate the analysis of toxic and hazardous materials including process and reaction control. Recently, further progress is made by the development of new, rapid-scan NIR monochromator systems without mechanically moved parts, such as acousto–optic tunable filters. Last, but not least, it should be mentioned, that – although not treated here – the new approach of Fourier–Transform Raman spectroscopy with Nd–YAG laser excitation at 1064 nm is principally also a near–infrared technique.     

Thermoanalytical studies of natural potassium, sodium and ammonium alunites

Dynamic and controlled rate thermal analysis (CRTA) has been used to characterise alunites of formula [M(Al)₃(SO₄)₂(OH)₆] where M⁺ is the cations K⁺, Na⁺ or NH₄ ⁺. Thermal decomposition occurs in a series of steps: (a) dehydration, (b) well-defined dehydroxylation and (c) desulphation. CRTA offers a better resolution and a more detailed interpretation of water formation processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of water formation reveal the subtle nature of dehydration and dehydroxylation.     

Near-infrared laser spectroscopy of NiI

Laser-induced fluorescence spectrum of NiI in the near infrared region of 714-770 nm has been recorded. Seven bands belonging to three electronic transition systems were observed and analyzed: the (0,0), (1,0), and (2,0) bands of [13.3] (2)Sigma(+)-A (2)Pi(3/2) system; the (1,1) and (0,1) bands of [13.9] (2)Pi(3/2)-X (2)Delta(5/2) system; and the (0,0) and (1,0) bands of [13.9] (2)Pi(3/2)-A (2)Pi(3/2) system. Spectra of isotopic molecules confirmed the vibrational quantum number assignment of the observed bands. Least-squares fit of rotationally resolved transition lines yielded accurate molecular constants for the v=0-2 levels of the [13.3] (2)Sigma(+) state, the v=0 level of the A (2)Pi(3/2), and the v=1 level of the X (2)Delta(5/2) state. The vibrational separation, DeltaG(1/2), of the ground state was measured to be 276.674 cm(-1). With the observation of the [13.9] (2)Pi(3/2)-A (2)Pi(3/2) and [13.9] (2)Pi(3/2)-X (2)Delta(5/2) transitions, we accurately determined the energy separation between the A (2)Pi(3/2) and the X (2)Delta(5/2) to be 163.847 cm(-1). This confirms that the order of the A (2)Pi(3/2) and X (2)Delta(5/2) states in NiI is reversed when compared with other nickel monohalides.     

Near-infrared absorption spectroscopy of toluene-sulfonate-diacetylene crystals

The near-infrared (NIR) absorption of toluene-sulfonate-diacetylene crystals (PTS) has been investigated during thermal polymerization. It is shown by comparative NIR and IR spectroscopy of deuterated and of protonated PTS at various temperatures, that these absorptions are vibronic in nature. They can be assigned unambiguously to distinct parts of the molecule. No low-lying electronic state has been found.     

Near-infrared spectroscopy of torbernites and metatorbernites

A suite of torbernites and metatorbernites have been analysed by near-infrared spectroscopy. The spectra of torbernites and metatorbernites in the first HOH fundamental overtone are different and the spectra of torbernites of different origins in the 6000-7500 cm(-1) region vary. NIR spectroscopy provides a method of studying the hydration of cations in the interlayer of torbernite. NIR spectroscopy shows that the spectra of torbernites from different origins in the water HOH first fundamental overtone and combination regions are different. This difference implies the hydration of cations is different for torbernite minerals. The structural arrangement of the water molecules in the interlayer is sample dependent. The NIR spectra of metatorbernites are different from that of torbernites and a similarity of the spectra of metatorbernites suggests that the water structure in metatorbernites is similar.     

Near-infrared spectroscopy applications in pharmaceutical analysis

Near-infrared (NIR) spectroscopy is a fast and non-destructive analytical technique that offers many advantages for a broad range of industrial applications. In this work, we reviewed recent developments in the pharmaceutical domain where it can be applied from raw material identification to final product release. The characteristics of NIR allow the technique to be implemented as a process analytical technology (PAT). Moreover, recent instrumental developments open the perspectives of numerous applications in the NIR imaging area. After “Introduction”, according to their subject, the applications are discussed in the parts “Identification”, “Water content”, “Assay” and “Other applications”.     

Near-infrared spectroscopy of newly developed PEGylated lipids

Near-infrared (NIR) spectroscopy has been used to analyze a suite of synthesized PEGylated lipids (1-3) trademarked as QuSomes. The three amphiphiles used in this study, differ in their hydrophobic chain length and contain various units of polyethylene glycol (PEG) head groups. Whilst the spectra of QuSomes show a common pattern, differences in the spectra are observed which enable the lipids to be distinguished. NIR absorption spectra of these new artificial lipids have been recorded in the spectral range of 4800-9000 cm(-1) (approximately 2100-1100 nm) by using a new miniaturized spectrometer based on micro-optical-electro-mechanical systems (MOEMS) technology. Three NIR spectral regions are identified, (a) the high wavenumber region between 6500 and 9000 cm(-1) attributed to the first overtone of the hydroxyl stretching and second overtone of the C-H stretching mode; (b) the 5350-5900 cm(-1) region attributed to first overtone of the C-H stretching mode; and (c) the 4800-5300 cm(-1) region attributed to the combination O-H stretching and second overtone of the C=O stretching mode. For each of these regions, the lipids show distinctive spectra which allow their identification and characterization. NIR spectroscopy is a less used technique which does have great potential for the study of lipids, particularly to examine the behaviour of nanovesicles (liposomes) formed from lipids in aqueous suspensions. The study of such lipids is important since they are used as membrane models and prominent candidate for substance and drug delivery systems.     

Near-infrared diode laser spectroscopy of free radicals

Spectroscopic results on the radicals HCSi, CCO, and FeC obtained by studying in detail energy level structures using 0.8 microm diode laser system are reported. Of these radicals, the CCO radical was investigated mainly using Fabry-Perot type diode lasers with inconvenient mode gaps in the early stage of our near-infrared diode laser spectroscopic study of free radicals, and on the other hand, the FeC and HCSi radicals were studied using an external cavity diode laser. For the FeC radical, which is an interesting radical composed of an iron atom having 3d electrons, information on spin-orbit interaction between the triplet electronic ground state and a low-lying singlet electronic excited state is reported somewhat in detail. For the HCSi and CCO radicals, spectral particularities produced by a Renner-Teller interaction and a spin-orbit interaction are described for their high-resolution spectroscopic interest.     

Near-infrared transmittance spectroscopy for radiochemical ageing of EPDM

The feasibility of using near-infrared spectroscopy as a sensitive technique to follow the influence of gamma-irradiation upon ageing of different EPDM (ethylene propylene diene monomer) elastomers has been evaluated. Although identification is difficult, differences can be observed between the non-irradiated and irradiated materials for total integrated doses from 50 to 450 kGy using a dose rate of 1 kGy h(-1) under an oxygen flow. The decrease in intensity of bands at 7040, 4610 and 4910 cm(-1) are linked to the disappearance of additives present in the elastomer such as excess of vulcanising or antioxidant agents and occur for the lowest irradiation dose. This disappearance is confirmed by TGA (thermogravimetric analysis). The increase in band intensities assigned to the formation of hydroxyl and carbonyl groups (5100, 4860 and 4670 cm(-1)) irradiation indicates an increase in oxidation with irradiation in the presence of oxygen. No bands linked to the presence of C=C from the diene have been detected, probably owing to the low concentration in the material and the weak intensity in near-infrared region. For strong irradiation doses (450 kGy), the three formulations studied show no difference in their NIR spectra, which is confirmed by the TGA of these irradiated materials. PCA performed at 5000-4600 cm(-1) or 7090-6980 cm(-1) shows efficient discrimination.     

Near-infrared fluorescence spectroscopy of single-walled carbon nanotubes and its applications

Semiconducting single-walled carbon nanotubes (SWCNTs) emit fluorescence at near-infrared (NIR) wavelengths that are characteristic of the specific diameter and the chiral angle. While providing a convenient method for structural identification of semiconducting SWCNTs, NIR fluorescence of SWCNTs also offers a powerful approach for sensor development and in vivo or real-time imaging of biological systems.This article provides an introductory overview of the approaches to obtaining individually dispersed semiconducting SWCNTs with reasonably good purity, which is a critical step in acquiring NIR fluorescence spectra. It also summarizes the progress since 2002 in sensor design and applications in bioimaging in vitro and in vivo using NIR fluorescence of semiconducting SWCNTs.     

Near-infrared Fourier transform Raman spectroscopy: Facing absorption and background

Visible wavelength excitation enables Raman spectra to be recorded successfully from approximately 10% of the “real, live” samples encountered in routine analytics without recourse to purification procedures. Fluorescence from impurities present in the sample often masks the Raman spectrum. This is especially true of the industrial environment. The great advantage of the newly-developed technique of near-infrared Fourier transform Raman spectroscopy (NIR FTR) is that fluorescence arising from sample impurity is not excited. Now about 90% of all samples show Raman spectra. However, it is possible to increase both the number of samples open to study using NIR FTR and to improve the quality of the spectra by optimizing the sampling arrangement. This involves taking into consideration the optical properties of the sample, especially the absorption spectrum and thermal emission characteristics, according to Planck's and Kirchhoff's laws. Only a few samples continue to show continuous backgrounds; this is sometimes true even if no background is apparent with visible excitation. The sources of such backgrounds are described, as are means to reduce or eliminate most of them.     

Near-infrared spectroscopy of ethylene and ethylene dimer in superfluid helium droplets

The nu(5)+nu(9) spectra of ethylene, C(2)H(4), and its dimer, solvated in helium nanodroplets, have been recorded in the wavelength region near 1.6 microm. The monomer transitions show homogeneous broadening of approximately 0.5 cm(-1), which is interpreted as due to an upper state vibrational relaxation lifetime of approximately 10 ps. Nearly resonant vibrational energy transfer (nu(5)+nu(9)-->2nu(5)) is proposed as the relaxation pathway. The dimer gives a single unresolved absorption feature located 4 cm(-1) to the red of the monomer band origin. The scaling of moments of inertia upon solvation in helium is 1.18 for the monomer and >2.5 for the dimer. In terms of the adiabatic following approximation, this classifies the monomer as a fast rotor and the dimer as a slow rotor.     

Near-infrared spectroscopy and chemometric modelling for rapid diagnosis of kidney disease

Rapid diagnosis is important for efficient treatment in clinical medicine. This study aimed at development of a method for rapid and reliable diagnosis using near-infrared (NIR) spectra of human serum samples with the help of chemometric modelling. The NIR spectra of sera from 48 healthy individuals and 16 patients with suspected kidney disease were analyzed. Discrete wavelet transform (DWT) and variable selection were adopted to extract the useful information from the spectra. Principal component analysis (PCA), linear discriminant analysis (LDA) and partial least squares discriminant analysis (PLSDA) were used for discrimination of the samples. Classification of the two-class sera was obtained using LDA and PLSDA with the help of DWT and variable selection. DWT-LDA produced 93.8% and 83.3% of the recognition rates for the validation samples of the two classes, and 100% recognition rates were obtained using DWT-PLSDA. The results demonstrated that the tiny differences between the spectra of the sera were effectively explored using DWT and variable selection, and the differences can be used for discrimination of the sera from healthy and possible patients. NIR spectroscopy and chemometrics may be a potential technique for fast diagnosis of kidney disease.     

Near-infrared spectroscopy investigation of the water confined in tricalcium silicate pastes

Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrational spectrum of water entrapped in a tricalcium silicate paste. The overall free water, which decreases as a function of time due to the formation of the hydrated phases (portlandite, Ca(OH)(2), and hydrated calcium silicate, C-S-H) during the hydration reaction, is quantified by the decrease in the area of the NIR band at about 5000 cm(-1). The coexistence of two types of water in the hydrated phases (a "surface-interacting water" (type I) and a "bulklike water" (type II)) during the hydration is obtained by the analysis of the band at about 7000 cm(-1). The deconvolution of this band allows the quantification of the two water types. As the reaction advances, part of the "bulklike water" is converted to "surface-interacting water" in direct agreement with the C-S-H surface development. Finally, the Ca(OH)(2) formation can be concurrently monitored by NIR through the increase of a very sharp peak at 7083 cm(-1). Near-infrared spectroscopy allows determination in a very simple way of the most important features of the tricalcium silicate setting process.     

Near-infrared spectroscopy to uranyl arsenates of the autunite and metaautunite group

A suite of uranyl arsenates have been analysed by near-infrared spectroscopy (NIR). The NIR spectra of zeunerite and metazeunerite in the first HOH fundamental overtone are different and the spectra of uranyl arsenates of different origins in the 6000-7500 cm(-1) region are different. NIR spectroscopy provides a method of determination of the hydration of uranyl arsenates and has implications for the structure of water in the interlayer. Such a conclusion is also supported by the water OH stretching region where considerable differences are observed. NIR is an excellent technique for the study of the autunite minerals and may be used to distinguish between different autunite phases such as the partially dehydrated autunites for example zeunerite and metazeunerite.     

Near-infrared spectroscopy of LiNH3: first observation of the electronic spectrum

Electronic spectra of LiNH(3) and its partially and fully deuterated analogues are reported for the first time. The spectra have been recorded in the near-infrared and are consistent with two electronic transitions in close proximity, the ?(2)E-X(2)A(1) and B(2)A(1)-X(2)A(1) systems. Vibrational structure is seen in both systems, with the Li-N-H bending vibration (ν(6)) dominant in the ?(2)E-X(2)A(1) system and the Li-N stretch (ν(3)) in the B(2)A(1)-X(2)A(1) system. The prominence of the 6(0)(1) band in the ?(2)E-X(2)A(1) spectrum is attributed to Herzberg-Teller coupling. The proximity of the B(2)A(1) state, which lies a little more than 200 cm(-1) above the ?(2)E state, is likely to be the primary contributor to this strong vibronic coupling.     

Near-infrared diode laser spectroscopy in chemical process and environmental air monitoring

This review covers the rapidly expanding field of near-infrared tunable diode laser spectroscopy where the availability of new lasers has led to the development of simple and inexpensive spectroscopic systems for the detection and monitoring of gas species. The latest diode lasers and the specific techniques associated with diode laser spectroscopy are described. Specific examples covering chemical vapour deposition reaction diagnostics, remote vehicle emission sensing, balloon-borne atmospheric monitoring and combustion diagnostics then illustrate the technique advantages of rapid, highly selective, in situ monitoring.     

Near-infrared spectroscopy for liquids of microliter volume using capillaries with wall transmission

In the present study we propose a capillary tube method for measuring near-infrared (NIR) spectra of microliter liquid and solution samples. This method enables one to measure NIR spectra of liquids and solutions of only 2.5 microl. As an example of the capillary tube method, Fourier-transform NIR spectra of benzene were measured using a capillary tube with a diameter of 1 mm. Positions and intensities of the NIR bands in the spectra obtained by the capillary tube were almost identical to those measured using a quartz cuvette cell. Moreover, capillary NIR spectra of human blood serum obtained from a patient with backbone neoplasm were also measured. Subtraction of the NIR spectrum of water from those of human blood serum develops unambiguously some NIR bands due to blood components such as proteins and glucose. Our results suggest that capillary NIR spectroscopy will open new areas of NIR applications for small amounts of liquid and solution samples.