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PubMed2002

Optical and electrochemical properties of optically transparent, boron-doped diamond thin films deposited on quartz.

The optical and electrochemical properties of transparent, boron-doped diamond thin film, deposited on quartz, are discussed. The films were deposited by microwave-assisted chemical vapor deposition, for 1-2 h, using a 0.5% CH4/H2 source gas mixture at 45 Torr and 600 W of power. A high rate of diamond nucleation was achieved by mechanically scratching the quartz. This pretreatment leads to the formation of a continuous film, in a short period of time, which consists of nanometer-sized grains of diamond. The thin-film electrode was characterized by cyclic voltammetry, atomic force microscopy, and UV-visible absorption spectrophotometry. The film's electrochemical response was evaluated using Ru(NH3)6(3+/2+) in 1 M KCl, Fe(CN)6(3-/4-) in 1 M KCl, and chlorpromazine (CPZ) in 10 mM HClO4. The film exhibited a low voltammetric background current and a stable and active voltammetric response for all three redox systems. The optical transparency of the polycrystalline film in the visible region was near 50% and fairly constant between 300 and 800 nm. The optical and electrical properties were extremely stable during 48-h exposure tests in various aqueous (HNO3, NaOH) solutions and nonaqueous (e.g., chlorinated) solvents. The properties were also extremely stable during anodic and cathodic potential cycling in harsh aqueous environments. This stability is in stark contrast to what was observed for an indium-doped tin oxide thin film coated on quartz. The spectroelectrochemical response (transmission mode) for CPZ was studied in detail, using a thin-layer spectroelectrochemical cell. Thin-layer voltammetry, potential step/ absorption measurements, and detection analytical figures of merit are presented. The results demonstrate that durable, stable, and optically transparent diamond thin films, with low electrical resistivity (approximately 0.026 omega x cm) laterally through the film, can be deposited on quartz.

Journal Article↗
PubMed2004

Roughness-induced acoustic second-harmonic generation during electrochemical metal deposition on the quartz-crystal microbalance.

This paper reports on the relation between the surface roughness and emission of compressional waves from the surface of an electrochemical quartz-crystal microbalance. The detection of the compressional waves took place with an ultrasonic microphone and the quartz crystal itself. As a model process, the electrochemical deposition of copper from an acidic copper sulfate solution has been chosen. For this system, the roughness of the layer can be tuned via the current density. Roughness may be a source of the longitudinal waves at twice the frequency of the exciting shear wave (acoustic second-harmonic generation, ASHG) if the flow profile above the quartz-crystal surface is not entirely laminar. Slight deviations from the laminar flow can be reached at high amplitudes of oscillation. Comparing the ASHG efficiency of a rough and smooth surface, we find that the rough surface is more efficient in generating second-harmonic waves. This suggests that ASHG can be used to obtain a roughness parameter independent from the resonance frequency or bandwidth (damping) of a quartz-crystal resonator. Such an independent determination of roughness should be very interesting in practical applications.

Journal Article↗
PubMed2002

Real-time monitoring of stain formation and removal on calcium hydroxyapatite surfaces using quartz crystal sensor technology.

Stain formation, stain inhibition and stain removal may be monitored in real-time using a novel method employing a quartz crystal resonance sensor (QCR), based upon quartz crystal microbalance (QCM) technologies. Crystalline hydroxyapatite (HA) surfaces were prepared on phosphate-terminated, polymer-modified gold surfaces of quartz crystal transducers. The resulting sensors were placed in a specially constructed flow cell, and the interaction of adsorbates from the tea stain solution monitored as a function of time. The ability of sodium tripolyphosphate (STP) to remove extrinsic stain and also to inhibit its formation was examined. The adsorption of material from the staining solution passed over the sensor was clearly observable, and once bound, the crystal based real-time data suggest that tea adsorbates were not removed in the absence of an active under conditions of continuous flow. STP was shown to rapidly remove existing stain, and exhibited a clear inhibitory action on stain formation irrespective of whether the HA had been previously exposed to tea chromogens. The continuous data generated by the QCR technique were in good agreement with the results obtained using a discontinuous spectrophotometric method. The presently described quartz crystal model for extrinsic dental stain should provide a valuable tool to aid understanding of the interactions of staining agents with a crystalline HA surface as a model tooth surface, and to evaluate the efficacy and mode of action of STP and putative stain removal agents.

Coloring Agents↗
PubMed2002

Impedance analysis of an electrode-separated piezoelectric sensor as a surface monitoring technique for surfactant adsorption on quartz surface.

This paper describes the measurement of the kinetics of adsorption of sodium dodecyl sulfate (SDS), an anionic surfactant, onto a quartz surface with a pre-adsorbed layer of Ca2+ as an ion bridge, using an electrode-separated piezoelectric sensor (ESPS). An impedance analysis method was employed to characterize the responses of the ESPS. The impedance and frequency parameters of the ESPS were examined as functions of the conductivity, permittivity, viscosity and density of the liquid. The adsorption process of SDS onto the quartz surface resulted in an increase in both the mass and energy dissipation of the oscillating quartz crystal. The adsorption densities could be estimated by the ESPS method after taking into consideration the effects of surface viscosity and roughness. The adsorption and desorption rate constants of SDS onto the quartz surface were calculated as ka = (88.1 +/- 0.26) mol(-1) L s(-1) and kd = (4.92 +/- 0.53) x 10(-3) s(-1), respectively, based on the Langmuir model. ESPS was shown to be a powerful means of examining anionic surfactant adsorption to the solid/liquid interface.

Journal Article↗
PubMed2002

Selective sensing of triazine herbicides in imprinted membranes using ion-sensitive field-effect transistors and microgravimetric quartz crystal microbalance measurements.

A series of triazine herbicides consisting of the chlorotriazine atranex (atrazine), (1), prozinex, (2), tyllanex, (3), simanex, (4) and the methylthiolated triazines ametrex, (5), prometrex, (6) and terbutex, (7), were imprinted in an acrylamide-methacrylate copolymer. The polymer was deposited on the gate surface of ion-sensitive field-effect transistors (ISFETs) and piezoelectric Au-quartz crystals. Selective sensing of the imprinted substrates was accomplished by the imprinted polymer membrane associated with the ISFETs and Au-quartz crystals. Binding of the substrates onto the imprinted polymer associated with the gate of the ISFET alters the electrical charge and potential of the gate interface, thus allowing the potentiometric transduction of the binding events. The association of the substrates with the imprinted membrane linked to the Au-quartz crystal results in the membrane swelling, thus enabling the microgravimetric quartz crystal microbalance assay of the substrate binding events. The specificity of the imprinted recognition sites is attributed to complementary H-bond and electrostatic interactions between the substrates and the acrylamide-methacrylic acid copolymer.

Electrochemistry↗
PubMed1999

Comments on the characteristics of incommensurate modulation in quartz: discussion about a neutron scattering experiment.

From analysis of the elastic neutron scattering data of Dolino et al. [J. Phys. (Paris) (1984), 45, 361-371], it is shown that, besides the well identified components u(x) and u(y) of the acoustic displacements in the incommensurate (IC) phase of quartz, there also exists a strong component of the u(z) vector of the modulation. The existence of the large u(z) is not consistent with the currently accepted model for the IC transition in quartz, since the long-period IC modulation observed in quartz cannot induce any noticeable acoustic component u(z). The need for a new model is keenly felt in order to understand the origin of the IC modulation in quartz.

Journal Article↗
PubMed2004

Pressure and temperature effects on the degree of symmetry and chirality of the molecular building blocks of low quartz.

We establish quantitative correlations between pressure and temperature (PT) changes, and the degree of symmetry and of chirality of the main molecular building blocks of low quartz that these PT changes induce. The distortion from ideal tetrahedral symmetry, from helicity (deviation from C2 symmetry), and the level of chirality are evaluated quantitatively using the continuous-symmetry and chirality-measures approach. These measures are global and reflect all changes in bond angles and bond lengths. The specific molecular building blocks analyzed are the SiO4 elementary building block (which is found to be chiral!), the Si(OSi)4 unit, the second-shell SiSi4 tetrahedron [composed of the five Si atoms of Si(OSi)4] and the four-tetrahedra helix fragment, -O(SiO3)4-. The temperature and pressure effects on symmetry and chirality were found to mirror each other in all building blocks. By employing this quantitative approach to symmetry and chirality we were able to combine the pressure effects and temperature effects into a unified picture. Furthermore, the global nature of the symmetry measure allows the comparison of the behavior of isostructural materials such as germania and quartz. For these crystals it has been shown that the symmetry/chirality behavior of germania at low pressures is a predictor for the behavior of these structural properties in quartz at higher pressures. Finally, given that the rigid SiO4 unit undergoes only minor structural changes, it has been a useful observation that the symmetry/chirality of the small SiSi4 tetrahedron is a very sensitive probe for the symmetry and chirality changes in quartz as a whole.

Journal Article↗
PubMed2003

A precise measurement of some nonlinear effects and its application to the evaluation of nonlinear elastic constants of quartz and GaPO4.

This paper deals with a precise measurement of amplitude frequency and intermodulation effects, and its application to the evaluation of nonlinear elastic constants of quartz and gallium orthophosphate (GaPO4). An evaluation is based on the methods used previously concerning determination of the higher-order material constants in the quartz. Using a measurement of the intermodulation products and measurement of drive level dependence of resonant frequency of quartz resonators, we have determined some effective elastic constants of fourth order. The computer-based method of solution of the set of equations gives an access to obtain a number of effective nonlinear stiffnesses of fourth order. The measurements and computer solutions are performed on different Y-cuts resonators, both for quartz and gallium orthophosphate resonators, vibrating in fundamental thickness shear mode. The experimental results are discussed.

Journal Article↗
PubMed2004

A new triply rotated quartz cut for the fabrication of low loss IF SAW filters.

Analysis of the quartz properties shows the existence of unexplored angular domains for which Rayleigh waves can be efficiently excited, exhibiting physical characteristics better than the ones of the (ST,X) cut. This paper presents a family of quartz cuts allowing significant improvements of surface acoustic wave (SAW) devices on quartz. A first set of experiments has been performed, confirming the theoretical predictions of the basic properties of SAW on these cuts. A second set of measurements then was achieved to refine the identification of coefficients needed to perform industrial SAW design. A demonstration of the improvements accessible using this new cut is presented. A low loss SAW filter working at 71 MHz has been fabricated using smaller aluminum thickness than that for standard quartz cuts, and exhibiting all the properties required for its industrial implementation.

Journal Article↗
PubMed2003

Optical feedback laser with a quartz crystal plate in the external cavity.

We studied the optical feedback characteristics of a single-mode He-Ne laser with a quartz crystal plate in the external cavity. The fringe frequency of the laser system can be doubled when the quartz crystal plate is positioned at a certain angle between the crystalline axis and the beam in the crystal plate. Theoretical analysis shows that the birefringent effect of the quartz crystal plate and the laser beam's second pass through the external cavity result in this phenomenon. The experimental results are in good agreement with the theoretical analysis. A quartz crystal plate can double the resolution of a self-mixing sensing system.

Journal Article↗
PubMed2006

The Glória quartz-monzodiorite: isotopic and chemical evidence of arc-related magmatism in the central part of the Paleoproterozoic Mineiro belt, Minas Gerais State, Brazil.

The Glória quartz-monzodiorite, one of the mafic plutons of the Paleoproterozoic Mineiro belt, is intrusive into banded gneisses, amphibolites, schists and phyllites of the Rio das Mortes greenstone belt, in the southern portion of the São Francisco Craton, State of Minas Gerais, Brazil. The Glória quartz-monzodiorite yields a SHRIMP U-Pb zircon age of 2188 +/- 29 Ma, suggesting a tectonic relationship with the pre-collisional phase of the Mineiro belt. According to the Nd isotopic evidence (epsilonNd(T) = -3.4; T DM = 2.68 Ga) the original magmas was formed by a mixture among Archean crustal material and Paleoproterozoic juvenile magma. The Glória quartz-monzodiorite shows metaluminous and calc-alkaline tendency with intermediate K content, comparable to that of volcanic-arc rocks. The primary mineralogical assemblage was partly modified by metamorphism, dated between 2131-2121 Ma in nearby coeval plutons. Such metamorphism is significantly older than the reported metamorphic episodes of the Mineiro belt in the Quadrilátero Ferrífero region (2059-2041 Ma) in the eastern portion of the study area. This evidence, together with chemical and isotopic data from other mafic and felsic plutons coeval with the Glória quartz-monzodiorite, indicate a tectonic and magmatic migration within the Mineiro belt from west to east.

Journal Article↗
PubMed1995

The enzymatic removal of a surfactant coating from quartz and kaolin by P388D1 cells.

The macrophage-like cell line, P388D1, was exposed to dipalmitoyl lecithin (DPL)-coated respirable quartz and kaolin, and the disappearance of the DPL was monitored for up to 9 days. The coating was removed rapidly at first (about 50% in the first 3 days) and then more slowly over the remaining 6 days, until about 30% remained on day 9. The rate of DPL digestion was independent of the type of dust and the amount of coated dust within the cell, indicating the existence of an extracellular phospholipase activity. This extracellular phospholipase activity was partially characterized. It was sensitive to temperatures above 56 degrees C, the presence of EDTA, the action of the proteases trypsin and proteinase K, and pH, being active at pH 7 but not at pH 5. This is consistent with reports in the literature of the existence of an extralysosomal phospholipase which is active at pH 7 and dependent on the presence of divalent metal ions. There was a dust-dependent difference in the extracellular rate of DPL digestion from quartz and kaolin. The coating was removed more slowly from the kaolin than it was from quartz. The removal of the DPL coating seen in the presence of cells was presumably due to both an intracellular and an extracellular phospholipase.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Localization of transglutaminase activity in type II epithelial cell cultures and elevation of enzyme activity in lungs of rats instilled with quartz.

Transglutaminase activity, assessed by the incorporation of [14C]-putrescine into N-acetylated dephosphorylated beta-casein, was not detectable in sonicates of alveolar macrophages and fibroblasts but was located in all preparations of rat alveolar type II cells. Enzyme activity was induced in these cells up to 7 days in vitro but not stimulated further by the direct addition of quartz to the cultures. Transglutaminase activity in whole lung sonicates increased significantly after short-term exposure to DQ-12 quartz. An increase in the numbers of type II cells and subsequent release of activated transglutaminase, concomitant with a quartz-induced elevation in lung calcium levels and potential protein substrates, is likely to lead to an increase in protein crosslinking both in the alveolar space and interstitium.

Animals↗
PubMed2002

Quartz-crystal sensors for biosensing and chemical analysis.

The principle and applications of quartz-crystal sensors based on the three basic concepts for mass, viscosity, and viscoelastic changes are reported. In the general discussion the realization of a resonant frequency-resonant resistance diagram is described in detail. As an example of application to mass sensing, gas sensing with a carbon-coated quartz crystal is reported. Determination of the blood coagulation factor is used as an example of the application to viscosity sensing. As an example of viscoelastic measurement, an ion-exchange polymer-coated quartz crystal is investigated to show that viscoelasticity changes more than mass in the transport process. The possibility of developing new biosensors and chemical sensors is discussed on the basis of these results.

Animals↗
PubMed2001

Development of a sensor for calcium based on quartz crystal microbalance.

A new sensor for calcium based on a piezoelectric quartz crystal is presented. The selectivity depends on the ratio lipophilic salt/ionophore of the composition of the coating of the quartz crystal. A crystal coated with a THF solution of PVC (34.5% w/w), DOS (62.1% w/w) and 10,19-bis[(octadecylcarbamoyl) methoxyacetyl]-1,4,7,13,16-pentaoxa-10,19-diaza cycloheneicosane (3.4% w/w) and a salt/ionophore molar proportion of 60%, corresponding to a frequency decrease of the dry crystal of 6.0 kHz, showed a detection limit to calcium of 2.2 mg/L. Both a standard calcium chloride solution and a commercially balanced salt solution for tissue culture were analyzed subsequent to ion chromatographic separation. The results obtained with the sensor developed were compared with those obtained with a conductivity detector. Although the results from both detectors agreed for the standard solution, only the quartz crystal sensor was able to give reliable results for the tissue culture solution.

Calcium↗
PubMed1997

Quartz crystal microbalance investigation of the interaction of bacterial toxins with ganglioside containing solid supported membranes.

The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability of the gangliosides GM1, GM3, GD1a, GD1b, GT1b and asialo-GM1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies. To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental adsorption isotherms. Cholera toxin shows a high affinity for GM1 (Ka = 1.8.10(8)M-1), a lower one for asialo-GM1 (Ka = 1.0.10(7)M-1) and no affinity for GM3. The C-fragment of tetanus toxin binds to ganglioside GD1a, GD1b and GT1b containing membranes with similar affinity (Ka approximately 10(6)M-1), while no binding was observed with GM3. Pertussis toxin binds to membranes containing the ganglioside GD1a with a binding constant of Ka = 1.6.10(6)M-1, but only if large amounts (40 mol%) of GD1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment of tetanus toxin to GD1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to GD1a.

Cholera Toxin↗
PubMed2000

8-Hydroxydeoxyguanosine in leukocyte DNA and urine of quartz-exposed workers and patients with silicosis.

OBJECTIVE: To examine radical-induced DNA damage and its elimination in workers exposed to quartz and in patients with silicosis, and to assess the relationship of these effects to lung function. METHODS: Blood and spontaneous urine samples were obtained from active, quartz-exposed workers without silicosis (n = 63), and from retired workers with silicosis (n = 42). Levels of 8-hydroxydeoxyguanosine (8-OHdG) were determined in peripheral blood leukocyte DNA and urine, by the use of high-performance liquid chromatography coupled with ultra violet- (UV) and electrochemical detection. RESULTS: No significant differences in the mean levels of 8-OHdG in leukocyte DNA and of urinary excretion of 8-OHdG were found between silicosis patients and quartz-exposed healthy workers. However, in the group of silicosis patients with increased oxidative DNA damage the urinary excretion of 8-OHdG was lower than in the corresponding group of active workers without silicosis. In the case of silicosis, urinary 8-OHdG correlated positively, and 8-OHdG in DNA correlated negatively, with forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Healthy workers with a personally estimated high dust exposure in the workplace showed higher levels of 8-OHdG in DNA than did workers with moderate dust exposure. No association of 8-OHdG formation and/or elimination with duration of employment, field of activity, smoking or age was found. CONCLUSION: Our findings suggest that a less effective repair of 8-OHdG is associated with a higher degree of pulmonary airway obstruction in patients with silicosis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1982

A quartz cell for studying planar lipid bilayer membranes.

A quartz chamber is proposed for use in experiments with planar lipid bilayer membranes. Membranes are formed in a hole made on the lateral wall of a fused quartz test tube, immersed in an electrolyte solution. The quartz cell is easy to clean, chemically inert and easily made. Membranes formed in this chamber had specific resistances higher than 10(8) omega.cm2 and excellent mechanical stability.

Lipid Bilayers↗