Electrochemical and spectroscopic characterization of screen-printed gold-based electrodes modified with self-assembled monolayers and Tc85 protein

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Visible and near-infrared luminescent Eu3+ or Er3+ doped laponite-derived xerogels and thick films: Structural and spectroscopic properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vibrational spectra of pilocarpine hydrochloride crystals

Pilocarpine is a natural substance with potential application in the treatment of several diseases. In this work Fourier Transform (FT)-Raman spectrum and the Fourier Transform infra red (FT-IR) spectrum of pilocarpine hydrochloride C11H17N2O2+.Cl- were investigated at 300 K. Vibrational wavenumber and wave vector have been predicted using density functional theory (B3LYP) calculations with the 6-31 G(d,p) basis set. A comparison with experiment allowed us to assign most of the normal modes of the crystal.

Comparative vibrational spectra of pilosine and epiisopilosine crystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

FAR INFRARED-LASER LINES AND ASSIGNMENTS OF CH3OH - A REVIEW

Methyl alcohol is the most important lasing molecule in the Far-Infrared (FIR) spectral region, and the most widely used for investigation and for applications. Since the last critical review of 1984, over seventy papers have been published dealing with the FIR laser lines and the infrared spectroscopy of CH3OH. In 1984 we could list about 330 FIR laser lines, 98 of which were measured in frequency and 105 assigned. Since then more than 70 papers were published increasing the number of the known laser lines to 575 (103 measured in frequency). Also the FIR and IR spectroscopy was largely improved thanks to the analysis of high resolution FT spectra, and the number of the correctly assigned laser lines has been increased to 224. The wavenumbers of the assigned lines can now be predicted with an accuracy of about 0.001 cm-1 or better, thus approaching the accuracy of the experimental frequency measurements.

Prediction of cassava starch edible film properties by chemometric analysis of infrared spectra

Cassava starch has been shown to make transparent and colorless flexible films without any previous chemical treatment. The functional properties of edible films are influenced by starch properties, including chain conformation, molecular bonding, crystallinity, and water content. Fourier-transform infrared (FTIR) spectroscopy in combination with attenuated total reflectance (ATR) has been applied for the elucidation of the structure and conformation of carbohydrates. This technique associated with chemometric data processing could indicate the relationship between the structural parameters and the functional properties of cassava starch-based edible films. Successful prediction of the functional properties values of the starch-based films was achieved by partial least squares regression data. The results showed that presence of the hydroxyl group on carbon 6 of the cyclic part of glucose is directly correlated with the functional properties of cassava starch films.

The investigation of alpha -> beta phase transition in poly(vinylidene fluoride) (PVDF)

The phase transition from the non-polar a-phase to the polar beta-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous for being a non-destructive technique. Films of alpha-PVDF were subjected to stretching under controlled rates and at 80 degrees C, the transition to beta-PVDF being monitored by the decrease in the Raman band at 794 cm(-1) characteristic of the a-phase, with the concomitant increase in the 839 cm(-1) band characteristic of the beta-phase. Poling with negative corona discharge was found to affect the alpha-PVDF morphology improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, viz. X-ray diffraction and infrared spectroscopy.

Assessment of maturity degree of composts from domestic solid wastes by fluorescence and fourier transform infrared spectroscopies

Methods of assessment of compost maturity are needed so the application of composted materials to lands will provide optimal benefits. The aim of the present paper is to assess the maturity reached by composts from domestic solid wastes (DSW) prepared under periodic and permanent aeration systems and sampled at different composting time, by means of excitation-emission matrix (EEM) fluorescence spectroscopy and Fourier transform infrared spectroscopy (FT-IR). EEM spectra indicated the presence of two different fluorophores centered, respectively, at Ex/Em wavelength pairs of 330/425 and 280/330 nm. The fluorescence intensities of these peaks were also analyzed, showing trends related to the maturity of composts. The contour density of EEM maps appeared to be strongly reduced with composting days. After 30 and 45 days of composting, FT-IR spectra exhibited a decrease of intensity of peaks assigned to polysaccharides and in the aliphatic region. EEM and FT-IR techniques seem to produce spectra that correlate with the degree of maturity of the compost. Further refinement of these techniques should provide a relatively rapid method of assessing the suitability of the compost to land application.

Unusual interactions binding iron tetrasulfonated phthalocyanine and poly(allylamine hydrochloride) in layer-by-layer films

Molecular-level interactions are found to bind iron tetrasulfonated phthalocyanine (FeTsPc) and the polyelectrolyte poly(allylamine hydrochloride) (PAH) in electroactive layer-by-layer (LBL) films. These interactions have been identified by comparing Fourier transform infrared (FTIR) and Raman spectroscopy data from bulk samples of FeTsPc and PAH with those from FeTsPc/PAH LBL films. of particular importance were the SO3- -NH3 interactions that we believe to bind PAH and FeTsPc and the interactions between unprotonated amine groups of PAH and the coordinating metal of the phthalocyanine. The multilayer formation was monitored via UV-vis spectroscopy by measuring the increase in the Q band of FeTsPc at 676 nm. Film thickness estimated with profilometry was ca. I I Angstrom per bilayer for films adsorbed on glass. Reflection absorption infrared spectroscopy (RAIRS) revealed an anisotropy in the LBL film adsorbed on gold with FeTsPc molecules oriented perpendicularly to the substrate plane. Cyclic voltammograms showed reproducible pairs of oxidation-reduction peaks at 1.07 and 0.81 V, respectively, for a 50-bilayer PAH/FeTsPc film at 50 mV/s (vs Ag/Ag+). The peak shape and current dependence on the scan rate suggest that the process is a diffusion controlled charge transport. In the presence of dopamine, the electroactivity of FeTsPc/PAH LBL films vanishes due to a passivation effect. Dopamine activity is not detected either because the interaction between Fe atoms and NH2 groups prevents dopamine molecules from coordinating with the Fe atoms.

Study of fluorine losses in oxyfluoride glasses

Glasses in PbGeO3-PbF-CdF2 and GeO2-PbO-PbF2-CdF2 systems were studied and the fluorine losses during synthesis were investigated. Samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and Raman scattering spectroscopy. The use of stoichiometric germanate glass, PbGeO3, instead of introducing individual oxides (GeO2 + PbO) lead to decreasing fluorine losses, as detected by a fluorine ion selective electrode. The main structural features obtained from vibrational spectroscopy could be described by a metagermanate basic structure permeating fluorine rich regions. (c) 2005 Elsevier B.V. All rights reserved.

Photoinduced phenomena in layer-by-layer films of poly(allylamine hydrochloride) and Brilliant Yellow azodye

The nanoscale interactions between adjacent layers of layer-by-layer (LBL) films from poly(allylamine hydrochloride) (PAH) and azodye Brilliant Yellow (BY) have been investigated, with the films employed for optical storage and the formation of surface-relief gratings. Using Fourier transform infrared spectroscopy, we identified interactions involving SO3- groups from BY and NH3+ groups from PAH. These electrostatic interactions were responsible for the slow kinetics of writing in the optical storage experiments, due to a tendency to hinder photoisomerization and the subsequent reorientation of the azochromophores. The photoinduced birefringence did not saturate after one hour of exposure to the writing laser, whereas in azopolymer films, saturation is normally reached within a few minutes. on the other hand, the presence of such interactions prevented thermal relaxation of the chromophores after the writing laser was switched off, leading to a very stable written pattern. Moreover, the nanoscale interactions promoted mass transport for photoinscription of surface-relief gratings on PAH/BY LBL films, with the azochromophores being able to drag the inert PAH chains when undergoing the trans-cis-trans photoisomerization cycles. A low level of chromophore degradation was involved in the SRG photoinscription, which was confirmed with micro-Raman and fluorescence spectroscopies.

Preparation of Pb(Zr,Ti)O-3 thin films by soft chemical route

Lead zirconate titanate, Pb(Zr0.3Ti0.7)O-3 (PZT) thin films were prepared with success by the polymeric precursor method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Micro-Raman spectroscopy and X-ray diffraction (XRD) were used to investigate the formation of the PZT perovskite phase. X-ray diffraction revealed that the film showed good crystallinity and no presence of secondary phases was identified. This indicates that the PZT thin films were crystallized in a single phase. PZT thin films showed a well-developed dense grain structure with uniform distribution, without the presence of rosette structure. The Raman spectra undoubtedly revealed these thin films in the tetragonal phase. For the thin films annealed at the 500-700 degreesC range, the vibration modes of the oxygen sublattice of the PZT perovskite phase were confirmed by FT-IR. The room temperature dielectric constant and dielectric loss of the PZT films, measured at 1 kHz were 646 and 0.090, respectively, for thin film with 365 nm thickness annealed at 700 degreesC for 2 h. A typical P-E hysteresis loop was observed and the measured values of P-s, P-r and E-c were 68 muC/cm(2), 44 muC/cm(2) and 123 kV/cm, respectively. The leakage current density was about 4.8 x 10(-7) A/cm(2) at 1.5 V. (C) 2003 Elsevier Ltd. All rights reserved.

Effects of post-annealing on the dielectric properties of Au/BaTiO3/Pt thin film capacitors

Barium titanate thin films were prepared by the polymeric precursor method and deposited onto Pt/Ti/SiO2/Si substrates. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR) and micro-Raman spectroscopy were used to investigate the formation of the BaTiO3 perovskite phase. Afterwards, the films were submitted to post-annealing treatments in oxygen and nitrogen atmospheres at 300 degreesC for 2 h, and had their dielectric properties measured. It was observed that the electric properties of the thin films are very sensitive to the nature of the post-annealing atmosphere. This study demonstrates that post-annealing in an oxygen atmosphere increases the dielectric relaxation phenomenon and that post-annealing in a nitrogen atmosphere produces a slight dielectric relaxation. (C) 2004 Elsevier B.V All rights reserved.

Study of structural and photoluminescent properties of Ca8Eu2(PO4)(6)O-2

In this work it is presented for the first time the nanostructured hydroxyapatites doped with 0.5, 1.0 and 2.0 wt% of Eu3+ prepared at room temperature by the mechanical alloying technique. X-ray diffraction powder (XRD), infrared (IR) and Raman scattering spectroscopy, scanning electron microscopy (SEM), microhardness measurements as well as luminescent data of Eu3+ were used to investigate the structural and optical properties of these nanomaterials. The electrical and dielectrical analyses were used with the intention of having a better comprehension about the electromagnetic fields in pure and doped hydroxyapatites.