David M. Wieliczka

Wedge shaped cell for highly absorbent liquids: infrared optical constants of water

We designed an improved wedge shaped cell for measuring Lambert absorption coefficient spectra alpha(nu) of highly absorbent liquids. The design allows for accurate determination of the apex angle of the wedge, sealing the cell, and injection of the liquid without disassembling the cell. We measured alpha(nu) for water through the 500-12,500-cm(-1) wavenumber region to determine the range of alpha(nu) for which the cell provided accurate measurements. We then determined the imaginary part of the complex refractive index N(nu) = n(nu) + ik(nu) from alpha(nu) and used Kramers-Kronig methods to compute n(nu) from k(nu).

An XPS study of the elemental enrichment on aluminum alloy surfaces from chemical cleaning

The native oxide structure on aluminum alloys is usually modified by chemical treatments prior to the application of corrosion resistant coatings to increase adhesion and performance. Certain commercial modifications were studied to determine their effects on the alloy surfaces, which might have substantial implications on the interface between the alloys and plasma polymers deposited on them. An X-ray photoelectron spectroscopy (XPS) depth profiling investigation of the effects of these chemical cleaners revealed enrichments of alloying elements on the metal surface beneath the modified oxide. Aspects of the enrichment phenomena showed a correlation with data from corrosion-performance testing of interface engineered corrosion protection systems. The authors would like to acknowledge the support of DARPA through the US Air Force contract # AF F33615-96-C-5055.

Raman Imaging of Dental Adhesive Diffusion

The clinical success of dental composites depends critically upon the adhesive bond that secures it to the tooth. Previous efforts to characterize the adhesive/dentin interface have generally required sample preparation that alters or damages the interface. Using micro-Raman spectroscopy, we have collected chemical and morphologic information on the dentin/adhesive interface with minimal sample preparation. Results from this technique have provided direct evidence of adhesive penetration and demineralization depth for two adhesive systems.

Water (H 2 O)

This chapter discusses the spectral measurements of the optical properties of water and compilations of waters refractive index and absorption coefficient. Rubens presented refractometer measurements of the refractive index n (λ) of water to a long-wavelength limit of 1.256 μm. These measurements of n (λ) were extended to a new long-wavelength limit of 2.327 μm, by Seegerts doctoral work. Rubens and Ladenberg also published their measurements of the reflectance and absorption spectra. Dorseys presented a technical perspective thorough compilation of waters optical properties. He presented data about 320 references that spanned the spectral range from the low frequency to the X-ray region. Pontier and Dechambenoy measured reflectance spectra of water for angles of incidence of 0 degrees, 50, and 60 degrees in the 1-38 μm and 1-28 μm regions, respectively. The reflectance and absorption spectra and the appropriate Fresnel equations are used to determine n and k throughout the 1-40 μm wavelength regions.

Raman Mapping of the Dentin/Adhesive Interface

The degree of adhesive penetration into dentin has been studied through micro-Raman spectroscopic examination of the dentin/adhesive interface. In contrast to previous studies, for the specimen examined in this work the adhesive penetrates less than 2 μm into the acid-etched and, thus, decalcified dentin. There is strong spectroscopic evidence that, upon acid etching of the dentin surface, which is typically performed immediately before the adhesive is applied, the collagen matrix collapses upon itself.

The interferometric system using optical vortices as phase markers

In this paper the idea of the interferometer which use the optical vortices generated in the reference field is presented. The two simple measurements and analysis schemes are briefly described. The characteristic problem for such kind of interferometry, i.e. optical vortices localization is treated in more details. The advantages, disadvantages, and future development are shortly discussed.

Nanoparticle fabrication of hydroxyapatite by laser ablation in water

Synthetic polycrystalline hydroxyapatite was ablated in water with 337 nm radiation from a UV nitrogen pulsed laser. According to transmission electron microscopy micrographs, the ablated particles were approximately spherical and had a size of ∼80 nm. Raman spectroscopic analysis demonstrated that particles had the same structure as the original crystal. X-ray photoelectron spectroscopy showed that the surface chemical composition was close to that of the original material. The characteristics of the ablated particles and estimations of the temperature rise of the hydroxyapatite surface under laser irradiation are consistent with the mechanism of explosive boiling being responsible for ablation. The experimental observations offer the basis for preparation of hydroxyapatite nanoparticles by laser ablation in water.

Spectroscopic and Morphologic Characterization of the Dentin/ Adhesive Interface

The potential environmental risks associated with mercury release have forced many European countries to ban the use of dental amalgam. Alternative materials such as composite resins do not provide the clinical function for the length of time characteristically associated with dental amalgam. The weak link in the composite restoration is the dentin/adhesive bond. The purpose of this study was to correlate morphologic characterization of the dentin/adhesive bond with chemical analyses using micro-Fourier transform infrared and micro-Raman spectroscopy. A commercial dental adhesive was placed on dentin substrates cut from extracted, unerupted human third molars. Sections of the dentin/adhesive interface were investigated using infrared radiation produced at the Aladdin synchrotron source; visible radiation from a Kr+ laser was used for the micro-Raman spectroscopy. Sections of the dentin/adhesive interface, differentially stained to identify protein, mineral, and adhesive, were examined using light microscopy. Due to its limited spatial resolution and the unknown sample thickness the infrared results cannot be used quantitatively in determining the extent of diffusion. The results from the micro-Raman spectroscopy and light microscopy indicate exposed protein at the dentin/adhesive interface. Using a laser that reduces background fluorescence, the micro-Raman spectroscopy provides quantitative chemical and morphologic information on the dentin/adhesive interface. The staining procedure is sensitive to sites of pure protein and thus, complements the Raman results.

Dentin etch chemistry investigated by Raman and infrared spectroscopy

Micro-Raman and infrared spectroscopy were used to investigate the influence of surface treatment on the diffusion of a dental adhesive into dentin. The commercial dentin adhesive Scotchbond MultiPurpose Plus (3M) was placed on coronal dentin substrates that were cut from extracted, unerupted third molars. Prior to placement of the adhesive, one surface was treated with a phosphoric acid etch and the other with a citric acid–iron(III) chloride etch. Thin sections, ∼3 μm in thickness, were prepared and mounted on silver chloride disks for infrared spectroscopic studies with the remaining bulk sample being used for the Raman studies. The infrared studies were performed at the Aladdin Synchrotron radiation source at the Synchrotron Radiation Center, Stoughton, WI, USA. The Raman studies employed a krypton ion laser in conjunction with a microscope equipped with a 100× objective and confocal aperture. In both studies the sample was translated in 1 μm steps at the focus of the respective radiation, providing a line scan across the interface. The infrared results clearly show the interface but owing to the diffraction limit of ∼15 μm, accurate dimensional information could not be obtained. The Raman results clearly indicate a broad interface associated with the sample etched with phosphoric acid and the presence of a much more abrupt interface with the citric acid etch. Additionally, a thin layer of exposed collagen exists at the dentin–adhesive interface. Copyright  2000 John Wiley & Sons, Ltd.

X-ray photoelectron spectroscopy study of self-assembled monolayers of alkanethiols on (001) GaAs

Self-assembled monolayers of several alkanethiol molecules, with varying chain length and terminal groups, were investigated using x-ray photoelectron spectroscopy (XPS). The chain lengths varied from 10 to 15 methylene units, and the terminal group was either hydrophilic carboxylic acid and hydroxyl or hydrophobic methyl. The alkanethiol molecules were deposited on GaAs surfaces from liquid solutions. The impact of atmospheric exposure was examined by investigating one set of samples stored under atmospheric conditions and a second set that was stored in a nitrogen atmosphere prior to analysis. Carbon, oxygen, gallium, and arsenic core level XPS spectra were obtained on all surfaces. The intensity of the gallium and arsenic core levels indicates a considerable difference in the Ga∕As ratio dependent on the terminal group of the alkanethiol. Additionally, the carbon and oxygen spectra indicate varying chemical bonding on the surface with the alkanethiol’s having a carboxylic acid terminal group showing a ...