Attenuated Total Reflection IR Spectroscopy Research Articles

Strong Activity Enhancement of the Photocatalytic Degradation of an Azo Dye on Au/TiO2 Doped with FeOx

The doping of Au/TiO2 with FeOx is shown to result in a strong enhancement of its photocatalytic activity in the degradation of the azo dye Orange II. In order to examine the source of this enhancement, Au-FeOx/TiO2 nanocomposites containing different molar ratios of Au:Fe were synthesized, and X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and high-resolution transmission electron microscope (HRTEM) analyses indicated that the TiO2-supported Au nanoparticles were partially covered with an amorphous layer of FeOx species, in which the iron was present as Fe2+ and Fe3+. The metal-semiconductor system, i.e., Au/TiO2, showed only a moderate degradation rate, whereas doping with FeOx strongly enhanced the degradation activity. The bandgap energy decreased gradually from Au/TiO2 (3.13 eV) to the catalyst with the highest FeOx loading Au-FeOx (1:2)/TiO2 (2.23 eV), and this decrease was accompanied by a steady increase in the degradation activity of the catalysts. XPS analyses revealed that compared to Au/TiO2, on Au-FeOx/TiO2 a much higher population density of chemisorbed and/or dissociated oxygen species was generated, which together with the decreased bandgap resulted in the highest photocatalytic activity observed with Au-FeOx (1:2)/TiO2. The processes occurring during reaction on the catalyst surface and in the bulk liquid phase were investigated using operando attenuated total reflection IR spectroscopy (ATR-IR) combined with modulation excitation spectroscopy (MES), which showed that the doping of Au/TiO2 with FeOx weakens the interaction of the dye with the catalyst surface and strongly enhances the cleavage of the azo bond.

Fiber attenuated total reflection infrared spectroscopy of kidney tissue during live surgery.

More than 90% of solid kidney tumors are cancerous and have to be treated by surgical resection where surgical outcomes and patient prognosis are dependent on the tumor discrimination. The development of alternative approaches based on a new generation of fiber attenuated total reflection (ATR) probes could aid tumor identification even under intrasurgical conditions. Herein, fiber ATR IR spectroscopy is employed to distinguish normal and cancerous kidney tissues. Freshly resected tissue samples from 34 patients are investigated under nearly native conditions. Spectral marker bands that allow a reliable discrimination between tumor and normal tissue are identified by a supervised classification algorithm. The absorbance values of the bands at 1025, 1155 and 1240 cm-1 assigned to glycogen and fructose 1,6-bisphosphatase are used as the clearest markers for the tissue discrimination. Absorbance threshold values for tumor and normal tissue are determined by discriminant analysis. This new approach allows the surgeon to make a clinical diagnosis.

Data fusion of GC-IMS data and FT-MIR spectra for the authentication of olive oils and honeys-is it worth to go the extra mile?

The potential benefit of data fusion based on different complementary analytical techniques was investigated for two different classification tasks in the field of foodstuff authentication. Sixty-four honey samples from three different botanical origins and 53 extra virgin olive oil samples from three different geographical areas were analyzed by attenuated total reflection IR spectroscopy (ATR/FT-IR) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The obtained datasets were combined in a low-level data fusion approach with a subsequent multivariate classification by principal component analysis-linear discriminant analysis (PCA-LDA) or partial least squares-discriminant analysis (PLS-DA). Performing a back projection of PCA loadings, the influence of variables in the FT-IR spectra (one-dimensional) and the GC-IMS profiles (two-dimensional) on the discrimination was visualized within the original axis of the two data sources. Validation results of the classification models were compared to the results that could be obtained by using the individual data blocks separately. For both the honey and olive oil samples, a decreased cross-validation error rate and more robust model was obtained due to the low-level data fusion. The results show that data fusion is an effective strategy for improving the classification performance, particularly for challenging classification tasks such as the discrimination of olive oils with different geographical origin. Graphical abstract.

Pretreatment of polypropylene films for the creation of thin polymer layers, part 1: The use of chemical, electrochemical, and UV methods

AbstractThe surface of a polypropylene (PP) film was activated with chemical, electrochemical, and physical methods, and the effectiveness of these methods was compared. The effects of PP activation were assessed with attenuated total reflection IR spectroscopy (ATR‐IR), SEM microscopy, and an analysis, based on the liquid contact angle, of the free energy components of the surface. The activation of the PP surface, which was dependent on the oxidizing medium, increased the energy of the PP surface layer and formed new chemical (carbonyl) groups, which were identified by IR (ATR) absorption spectroscopy and confirmed by selective surface dyeing. The treatments were ranked in the following order of increasing effectiveness: UV irradiation < 3M nitric acid < 30% hydrogen peroxide < silver nitrate (electrochemical method) < chromic mixture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

KOPOLIMERISASI CANGKOK (GRAFT COPOLYMERIZATION) N-ISOPROPILAKRILAMIDA PADA FILM SELULOSA YANG DIINDUKSI OLEH SINAR ULTRAVIOLET DAN KARAKTERISASINYA

Graft Copolymerization of N-Isopropylacrylamide on Cellulose Film Induced by UV-Irradiation and its Characterization. The effect of monomer and initiator concentrations, graft polymerization temperature, polymerization system and organic solvents on photografting of N-isopropylacrylamide on regenerated cellulose films (thickness = 20 µm) in UV irradiation were investigated. The higher percentage of grafting was afforded for the system with the higher monomer and initiator concentration. The photografting initiated even in the system at 30 °C by using a longer irradiation time. It was found that the maximum percentage of grafting was attained at 2.5 (%Vol) of methanol/acetone in the mixed solvent. The resulting NIPAAm-grafted cellulose films were characterized by attenuated total-reflection IR spectroscopy, showed a peak at 1640 and 1550 cm -1 due to the amide groups of the NIPAAm-grafted chains. According to scanning electron microscopy characterization, the grafted chains was found to distribute inside the film sample even in the grafted films with lower percentage of grafting. The grafted samples showing a temperatureresponsive character swelling and shrinking in water at 5 °C and 50 °C, respectively.

CO Adsorption on Hydrated Ru/Al2O3: Influence of Pretreatment

The adsorption of CO on hydrated H2-, O2-, H2S-, and He-pretreated 5 wt % Ru/Al2O3 was investigated using attenuated total reflection IR spectroscopy (ATR-FTIR) to determine how the oxidation state of Ru influences CO-H2O interactions. The frequencies of the three IR bands (high frequency (HF), midfrequency (MF), and low frequency (LF)) that are observed when CO adsorbs on Ru/Al2O3 are influenced by (1) CO coverage (CO−CO interactions), (2) Ru oxidation state, (3) pretreatment gas, and (4) pretreatment time. Water red-shifts the CO features by as much as 116 cm−1and influences the MF/LF ratio in a complex mechanism involving both (1) blockage of CO adsorption on the LF site and (2) the formation of OH---CO interactions. While the LF band position is correlated to the adsorbate electronegativity and the MF band slightly correlates to CO coverage, the HF position is independent of either CO coverage or adsorbate electronegativity. These varying degrees of correlations can be rationalized using the extent of...

Para-Sulfonatocalix[6]arene-modified silver nanoparticles electrodeposited on glassy carbon electrode: Preparation and electrochemical sensing of methyl parathion

In this paper, a new electrochemical sensor, based on modified silver nanoparticles, was fabricated using one-step electrodeposition approach. The para-sulfonatocalix[6]arene-modified silver nanoparticles coated on glassy carbon electrode (pSC(6)-Ag NPs/GCE) was characterized by attenuated total reflection IR spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), etc. The pSC(6) as the host are highly efficient to capture organophosphates (OPs), which dramatically facilitates the enrichment of nitroaromatic OPs onto the electrochemical sensor surface. The combination of the host-guest supramolecular structure and the excellent electrochemical catalytic activities of the pSC(6)-Ag NPs/GCE provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs. In this work, methyl parathion (MP) was used as a nitroaromatic OP model for testing the proposed sensor. In comparison with Ag NPs-modified electrode, the cathodic peak current of MP was amplified significantly. Differential pulse voltammetry was used for the simultaneous determination of MP. Under optimum conditions, the current increased linearly with the increasing concentration of MP in the range of 0.01-80microM, with a detection limit of 4.0nM (S/N=3). The fabrication reproducibility and stability of the sensor is better than that of enzyme-based electrodes. The possible underlying mechanism is discussed.

Insights into pore surface modification of mesoporous polymer–silica composites: introduction of reactive amines

Pore surface engineering of mesoporous materials is fundamental for the development of highly selective sorbents, solid catalysts or drug delivery systems. In the present study, tailored mesoporous amine-functionalized polymer–silica composites are synthesized using a two-step mesopore surface-confined polymerization technique. For this, a functional polymer, polychloromethylstyrene (PCMS), is first introduced as a uniform coating on the mesopore surface of mesoscopically ordered silica, e.g. SBA-15 or KIT-6 materials. In the second step, selected amines, as model functions, are attached to the polymer surface by nucleophilic substitution, generating a variety of nanoporous amino-polymer–silica composites. In particular, it is shown that this approach allows for a tuning of surface concentration of the organic groups either by varying polymer loading or by copolymerization of the CMS monomers with non-reactive monomers (styrene). Moreover, this method is suitable for facile introduction of diverse types of amine groups, e.g. secondary amines, diamines, linear or branched polyamines. The pristine mesoporous silica hosts and the different functional mesoporous polymer–silica composites are characterized in detail by nitrogen physisorption, powder X-ray diffraction, elemental analysis, thermogravimetry–differential thermal analysis coupled with mass spectrometry (TG-DTA/MS), attenuated total reflection-IR spectroscopy (ATR-IR) and scanning electron microscopy. In addition, the obtained functionalized mesoporous composites are proven active as base catalysts in the Knoevenagel condensation. From these investigations, it appeared that the preparation method should be highly flexible and appropriate to enable modulation of location and distribution of various functional groups within mesopores.

Wide area illumination Raman scheme for simple and nondestructive discrimination of seawater cultured pearls

AbstractRaman spectroscopy, along with discriminant partial least squares (PLS), was successfully used to discriminate among three different groups of cultured pearls (fresh water, Akoya and South seawater). The discrimination between Akoya and South seawater pearls using XRF (X‐ray fluorescence), one of the most frequently adopted analytical methods in pearl analysis, has been especially difficult owing to their similar mineral compositions. The selective Raman features helped in effectively discriminating between these two pearl groups. The difference in the intensities of the CaCO3 bands of Akoya and South seawater pearls provided a valuable clue. Along with the selective Raman feature, a reproducible Raman spectral collection achieved using a wide area illumination (WAI) scheme played an important role in the determination of the pearl groups, although the pearls were hard‐surfaced, round, solid samples of different sizes and surface shapes. Unwanted spectral variation originating from sensitivity to sample placement relative to the focal plane and from unsuccessful sample representation due to the probing of a localized area, factors that could possibly deteriorate Raman reproducibility, were substantially lessened using the WAI scheme. ATR (attenuated total reflection) IR spectroscopy requiring direct contact with the pearl could be inadequate for discrimination or classification where large numbers of repeating and reproducible measurements are required. Copyright © 2009 John Wiley & Sons, Ltd.

Maleimido‐Terminated Self‐Assembled Monolayers

Four approaches have been explored for the preparation of maleimido-functionalized self-assembled monolayers (SAMs) on silicon. SAMs prepared by self-assembly of maleimido-functionalized alkyltrichlorosilanes (11-maleimido-undecyl-trichlorosilane) on oxide-covered silicon yield higher signals from maleimido functionalities in ATR-IR (attenuated total reflection IR) spectroscopy and XPS (X-ray photoelectron spectroscopy) than the other three methods. The surface composition of maleimido groups was tailored further by the formation of mixed monolayers with nonfunctionalized alkyltrichlorosilanes (decyltrichlorosilane). The order of the alkyl chains within the monolayers only slightly depends on the composition of the mixed monolayers. We utilized the maleimido-terminated SAMs to bind various nucleophilic compounds, alkylamines, alkylthiols, and thiol-tagged DNA oligonucleotides by means of conjugate addition.

ATR-IR spectroscopy at the metal–liquid interface: influence of film properties on anomalous band-shape

Attenuated total reflection (ATR) spectra of adsorbates and solvent on thin metal films were investigated with emphasis on the band-shape of absorption bands. Distorted band-shapes are found even far from the critical angle. Strong absorption bands are more distorted. The band-shape strongly depends on the optical constants of the metal film and its thickness. The distortion increases with increasing thickness and increasing refractive index of the thin metal film. For a 10 nm thick Pt film the measured band-shapes for liquid water and ethanol are in good agreement with theoretical predictions using the bulk optical constants for Pt. For CO adsorbed on a 1 nm Pt film a distorted band-shape is observed whereas calculations assuming bulk optical constants predict band-shape distortion only for considerably thicker Pt films. The effective optical constants for very thin metal films deviate considerably from the bulk values, due to the island structure of the film and non-adiabatic effects can lead to distorted band-shapes. Structural changes within a Pt film, induced by hydrogen treatment, leads to a change in the band-shape for adsorbed CO. The results show that band-shape analysis is a valuable tool for in situ ATR IR spectroscopy of metal films.

Properties of insoluble monolayers and Langmuir-Blodgett multilayers of a series of isomeric alkylphenyl carboxylic acids

The properties of insoluble monolayers and Langmuir-Blodgett multilayers of a series of isomerically pure alkylphenyl carboxylic acids have been investigated. The compounds, of general formula CH 3(CH 2) n − 1 Ph(CH 2) m COOH, where Ph is a phenyl ring, all have m + n = 18 where the number of methylene “spacer” groups between the Ph group and the acid head-group is varied between 0 and 8. The stability of floating monolayers of the isomers depends markedly on the pH of the subphase and is sensitive to the hydrophobic chain structure. The dissociation of the acid groups (measured via attenuated total reflection (ATR) IR in multilayers) with pH is, however, the same for the n = 10 and n = 17 compounds. Quantitative analysis of IR spectra (from both ATR and reflection-absorption IR spectroscopy measurements) of multilayers deposited from calcium-containing subphases has been performed. It is demonstrated that the n = 15 acid is less well ordered and has a larger tilt angle (from the vertical) than the other acids, in line with the conclusions drawn from the π- A isotherms of the floating monolayers.