Pyrex Glass Surfaces Research Articles

Refractance‐window as an innovative approach for the drying of saffron petals and stigma

AbstractIn this research, the effects of different dryers including refractance‐window (RW) with 200 or 300 μm Mylar membrane, or Pyrex glass and oven drying, and various temperatures of 25, 60, 70, and 80 °C on saffron quality were surveyed. Levels of safranal, crocin, and picrocrocin for saffron stigma and anthocyanin content for saffron petal were considered as the major quality indices and modeling of their drying kinetics was carried out. While for saffron stigma, RW dryer through Pyrex glass surface and higher temperatures (70 and 80 °C) led to the highest contents of picrocrocin, safranal, crocin, for saffron petal, RW dryer through 200 μm Mylar membrane resulted in the maximum anthocyanin content (106.79 mg/L). Meanwhile, our comparison revealed that RW is a more reliable approach to dry saffron stigma while keeping its functional ingredients, that is, coloring, aromatic, and bitterness strength, than previously introduced novel approaches. The best Artificial Neural Networks (ANNs) topologies to predict RW (200 or 300 μm Mylar membrane, or Pyrex glass) or oven drying data for saffron stigma were those networks having feed‐forward backpropagation network type, hyperbolic tangent sigmoid transfer function and one hidden layer with 3, 7, 5, or 4 neurons in it, respectively.Practical applicationsSaffron is the dried stigmas of flowers called as “Crocus sativus L.” scientifically and “red gold” in the market because of its high value. Our aim of this research was to introduce a suitable alternative for common traditional drying of saffron as refractance‐Window (RW) and suggest appropriate modeling patterns for industrial application of this drying type in real situations. The second aim of this research was to determine the best drying conditions of saffron petal since the major weight of saffron flower is related to its petal, and anthocyanin of petal extracts could be used as a natural colorant in the food industry, but temperature has a substantial impact on anthocyanin stability.

Formation of gallium arsenide nanostructures in Pyrex glass

In this paper, we report on a simple, low-cost process to grow GaAs nanostructures of a few nm diameter and ∼50 nm height in Pyrex glass wafers. These nanostructures were grown by sequential plasma activation of GaAs and Pyrex glass surfaces using a low-temperature hybrid plasma bonding technology in air. Raman analyses of the activated surfaces show gallium oxide and arsenic oxide, as well as suppressed non-bridging oxygen with aluminate and boroxol chains in glass. The flow of alkaline ions toward the cathode and the replacement of alkaline ions by Ga and As ions in glass result in the growth of GaAs nanostructures in nanopores/nanoscratches in glass. These nanopores/nanoscratches are believed to be the origin of the growth of the nanostructures. It was found that the length of the GaAs nanostructures may be controlled by an electrostatic force. Cross-sectional observation of the bonded interface using high-resolution transmission electron microscopy confirms the existence of the nanostructures. A possible application of the nanostructures in glass is a filtration system for biomolecules.

Enhanced magnetic resonance signal of spin-polarized Rb atoms near surfaces of coated cells

We present a detailed experimental and theoretical study of edge enhancement in optically pumped Rb vapor in coated cylindrical pyrex glass cells. The Zeeman polarization of Rb atoms is produced and probed in the vicinity ($~$${10}^{\ensuremath{-}4}$ cm) of the cell surface by evanescent pump and probe beams. Spin-polarized Rb atoms diffuse throughout the cell in the presence of magnetic field gradients. In the present experiment the edge enhanced signal from the back surface of the cell is suppressed compared to that from the front surface, due to the fact that polarization is probed by the evanescent wave at the front surface only. The observed magnetic resonance line shape is reproduced quantitatively by a theoretical model and yields information about the dwell time and relaxation probability of Rb atoms on Pyrex glass surfaces coated with antirelaxation coatings.

Laser Induced Modification in Glasses by CW Laser Backside Irradiation (CW-LBI)

We studied on the modification inside glass formed in the trajectory of a platinum particle implanted by laser illumination. A 1-μm-thick platinum film was deposited on the surface of Pyrex glass. The platinum film was irradiated by a focused Ar ion laser beam with a laser power of 4.2 W from the other side through the glass. As a result, platinum film was melted and a platinum particle with the diameter of 5 μm was implanted into the glass. The glass around the platinum particle heated by the laser illumination was softened, which enables the platinum particle migration in the glass. The threshold fluence for the platinum particle implantation was 0.1 MW/cm2. The speed of the platinum particle migration increased in the range from 0.1 mm/s to 10 mm/s with increasing laser fluence. Platinum was not detected and no clear composition change was detected in the trajectory of the platinum particle migration by energy dispersive X-ray spectroscopy. Etching of the modified zone formed cone shaped structures. The modified zone was bended and curved by changing the direction of the laser beam.

Laser Induced Modification in Glasses by CW Laser Backside Irradiation (CW-LBI)

We demonstrate metal particle implantation technique into glass plate by continuous-wave (CW) laser beam illumination. Platinum film with the thickness of 1 μm was deposited on one side of Pyrex glass surface. The platinum film was radiated with a focused Ar ion laser beam from the other side of the glass. The laser power was set at 4.2 W. As a result, the platinum film was melted and a platinum particle with the diameter of 5 μm was implanted into the glass within 0.1 s after the laser illumination. The glass around the platinum particle heated by the laser illumination was softened, which enables the platinum particle migration in the glass. Interestingly, the particle moved more than 3 mm toward the light source with the speed of ∼ 0.2 mm/s. Energy dispersive X-ray spectroscopy (EDS) clarify that the particle was platinum, and silicon and oxygen, which were components of glass, were not detected. Trajectory of the platinum particle migration was modified and was able to be observed by an optical microscope. No platinum was detected in the trajectory of the platinum particle. The diameter of the modified zone was ∼ 10 μm.

Method for Measuring the Dwell Time of Spin-Polarized Rb Atoms on Coated Pyrex Glass Surfaces Using Light Shift

We present a simple method for directly measuring the average dwell time of spin-polarized Rb atoms on coated Pyrex glass surfaces. The method relies on the light shift of the Zeeman resonances of spin-polarized Rb atoms pumped and probed by evanescent waves, and does not depend on the microscopic details of surface interactions. We use a cell whose length is adjustable between 70 and 500 microm. The inverse of the difference between the frequency shifts caused by sigma+ and sigma- pump beams depends linearly on the cell length, from which we obtain the average dwell time tau(s). For a Pyrex glass cell coated with octadecyltrichlorosilane we find that tau(s)=0.53+/-0.03 mus at a cell wall temperature of 103 degrees C. The temperature dependence of tau(s) is fitted to tau(s)=tau[mean](0) exp(E(a)/kT), yielding a preexponential factor tau[mean](0)=2.2(-1.4)(+5.1) ns and an activation energy E(a)=0.19+/-0.03 eV.

Method for measuring surface-interaction parameters of spin-polarized Rb atoms on coated Pyrex glass surfaces using edge enhancement

We present a method for measuring surface interaction parameters of spin-polarized Rb atoms on coated Pyrex glass surfaces based on edge enhancement in optically pumped Rb vapor. The best fit to the measured magnetic resonance lines using a theoretical model yields a dwell time ${\ensuremath{\tau}}_{s}=1.8\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ and a spin relaxation probability ${\ensuremath{\xi}}_{s}=0.015$ for a spin-polarized Rb atom on a Pyrex glass surface coated with dichlorooctamethyl-tetrasiloxane (Surfasil), and ${\ensuremath{\tau}}_{s}=0.5\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ and ${\ensuremath{\xi}}_{s}=0.001$ on a surface coated with octadecyltrichlorosilane (OTS).

Effects of diffusion and surface interactions on the line shape of electron paramagnetic resonances in the presence of a magnetic field gradient

In an evanescent wave magnetometer the Zeeman polarization is probed at micrometer to submicrometer distances from the cell surface. The electron paramagnetic resonance lines of an evanescent wave magnetometer in the presence of a magnetic field gradient exhibit edge enhancement seen previously in nuclear magnetic resonance lines. We present a theoretical model that describes quantitatively the shape of the magnetic resonance lines of an evanescent wave magnetometer under a wide range of experimental conditions. It accounts for diffusion broadening in the presence of a magnetic field gradient as well as interactions of spin polarized Rb atoms with the coated Pyrex glass surfaces. Depending on the field gradient, cell thickness, and buffer gas pressure, the resonance line may have the form of a single asymmetric peak or two peaks localized near the front and back surfaces in frequency space. The double-peaked response depends on average characteristics of the surface interactions. Its shape is sensitive to the dwell time, relaxation probability, and average phase shift of adsorbed spin polarized Rb atoms.

Multifractal properties of Pyrex and silicon surfaces blasted with sharp particles

The blasting of brittle materials with sharp particles is an important fabrication technology in many industrial processes. In particular, for microsystems, it allows the production of devices with feature sizes down to few tens of microns. An important parameter of this process is the surface roughness of post-blasted surfaces. In this work the scaling properties of Pyrex glass and silicon surfaces after bombardment with alumina particles are investigated. The targets were bombarded at normal incidence using alumina particles with two different average sizes, 29 μm and 9 μm. This investigation indicates that the resulting surfaces are multifractal. Applying multifractal detrended fluctuation analysis (MFDFA) allowed us to determine the singularity spectrum of the surfaces. This spectrum did not depend on the target material or on the size of the particles. Several parameters quantifying relevant quantities were determined. It was found that long range correlations are responsible for the observed multifractal behaviour.

Protolytic behavior of hydroxylated Pyrex glass surfaces in NaCl media

Adsorption of hydrogen ions from aqueous NaCl solutions at the Pyrex glass–water interface was investigated by acid–base titration (glass electrode) at 25 °C and at the ionic strengths 0.010, 0.030, 0.10, 1.0, and 3.0 mol dm −3. The pH values ranged from 2 to 7. The Pyrex samples had a specific surface area of 19.2 × 10 3 m 2 kg −1 and a porous structure (pores 2.4 nm thick, 280 nm long). The reactions were found to be extremely slow but showed good reversibility. The potentiometric data, due to the small effect of ionic strength on the equilibria, were fitted with a simple nonelectrostatic model based on strong specific interactions of medium ions with deprotonated silanol, >SiO −, and boranol, >BO −, as well as with protonated sites. The acid–base properties are described by the reactions and equilibrium constants at the infinite dilution reference state: >SiONa + H + ⇄ >SiOHNa +, log β 110 Si = 3.1 ± 0.2 ; >SiONa + 2H + + Cl − ⇄ >SiOH 2Cl + Na +, log β 201 Si = 6.75 ± 0.15 ; >SiONa + H + ⇄ >SiOH + Na +, log β 100 Si = 1.8 ± 0.2 , >BONa + H + ⇄ >BOH + Na +, log β 100 B = 6.4 ± 0.2 ; >BONa + H + ⇄ >BOHNa +, log β 110 B = 6.6 ± 0.2 ; >BONa + 2H + ⇄ >BOH + 2 + Na +, log β 200 B = 11.56 ± 0.15 .

Multiprobe SPM System Using Optical Interference Patterns

This paper proposes a new composition of the multiprobe scanning probe microscopy (SPM) system using optical interference patterns for a parallel nanoimaging in a large-area measurement. We achieved large-scale integration with 50 000 probes fabricated with microelectromechanical systems (MEMS) technology and measured the optical interference patterns with charge-coupled device (CCD), which was difficult in a conventional single scanning probe. In this research, the multiprobes are made of SiN by MEMS process, and the multiprobes are joined with the Pyrex glass by anodic bonding. We designed, fabricated, and evaluated the characteristics of the multiprobe. In addition, we changed the probe shape to decrease the warpage of the SiN probe. We used the supercritical drying to avoid stiction of the SiN probe with the Pyrex glass surface and fabricated the SiN probe without stiction. We took some interference patterns by CCD and measured the position of them. We calculated the probe height using the interference displacement and compared the result with the theoretical deflection curve. As a result, these interference patterns matched the theoretical deflection curve. We found that this multiprobe chip using interference patterns is effective in measurement for a parallel nanoimaging. We also composed the multiprobe SPM system and evaluated the fundamental characteristics

Regionally specific hyperfine polarization of Rb atoms in the vicinity(∼10−5cm)of surfaces

We made regionally specific measurement of the hyperfine polarization $⟨\mathbit{S}∙\mathbit{I}⟩$ of Rb atoms in the vicinity $(\ensuremath{\sim}{10}^{\ensuremath{-}5}\phantom{\rule{0.3em}{0ex}}\mathrm{cm})$ of coated and uncoated Pyrex glass surfaces in optical pumping cells. This is in contrast to the previous hyperfine polarization studies, where the quantity measured is the bulk hyperfine polarization, which depends on surface interactions averaged over the entire cell surfaces. We probe the hyperfine polarization of the Rb atoms in the vicinity of cell surfaces using the evanescent wave of a weak laser beam. We find that the polarization in the vicinity of uncoated surfaces is significantly lower than that in the bulk. The polarization decreases rapidly with decreasing distance from the surface. By contrast, the polarization in the vicinity of a silicone-coated Pyrex glass surface is independent of the distance from the cell surface and is equal to the bulk polarization. Regionally specific measurement of the hyperfine polarization as a function of the penetration depth of the evanescent wave allows us to deduce the hyperfine polarization, its normal gradient, as well as the normal gradient coefficient ${\ensuremath{\mu}}_{\mathbit{S}∙\mathbit{I}}$ at the cell surface. We present the values of these quantities for three representative uncoated cells.

Passive valves based on hydrophobic microfluidics

Abstract Fluid–surface interactions can become dominant in microfluidics, which is a central technology in a number of miniaturized systems for chemical, biological and medical applications. In this paper, two kinds of hydrophobic valves in microfluidic applications were presented. One is based on special geometrical designs and chemical modification for silicon dioxide and glass microchannels. Silicon dioxide and Pyrex glass surfaces, which are hydrophilic originally, are modified with octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) to be hydrophobic, with the contact angles up to ∼102 and 103°, respectively, for water. The formation of OTS SAMs takes

Hyperfine polarization and its normal gradient coefficient of (87)Rb atoms in the vicinity (approximately 10(-5) cm) of coated and uncoated Pyrex glass surfaces.

We have made regionally specific measurement of the hyperfine polarization <S.I> of 87Rb atoms in the vicinity ( approximately 10(-5) cm) of coated and uncoated Pyrex glass surfaces. We find that the polarization near an uncoated surface decreases rapidly with decreasing distance from the surface whereas for a silicone-coated surface the polarization is independent of the distance from the surface. We have also determined the normal gradient coefficient micro (S.I) of the hyperfine polarization in uncoated cells. In a representative uncoated cell, at a Rb density 7.35 x 10(13) cm(-3) and a pump beam intensity 1.3 W/cm(2), we find micro(S.I)=24+/-7 microm(-1).

Determination of the surface area of annealed continuous gold film and pyrex glass in situ by the BET adsorption isotherm and ex situ by Atomic Force Microscopy in air

The relative surface area, Rsa, of annealed continuous thin gold film, thermally evaporated onto a Pyrex glass substrate at 78 K in an ultrahigh-vacuum (UHV) environment, and Pyrex glass has been determined in situ by the BET (Brunauer–Emmett–Teller) isotherm method, as well as ex situ by Atomic Force Microscopy (AFM) in air. It has been measured by the BET isotherm method that Rsa for clean, continuous and annealed gold film, investigated under UHV conditions, is equal to 6.3, whereas after its exposure to air, at about 100 Pa, Rsa decreased from 6.3 to 5.7. Further exposure to air, at atmospheric pressure, reduced Rsa from 5.7 to 2.2, whereas the exposure of contaminated Au film to the atomic hydrogen flux caused the increase of Rsa from 2.2 to 4.2. On the other hand, Rsa calculated directly from the AFM image of gold film in air is equal to 1.0. In contrast to thin gold film, the Pyrex glass surface area, measured under UHV conditions by the BET adsorption isotherm and in air by the AFM technique, is equal to its geometric area, i.e., Rsa=1.0.

Adsorption isotherms of He and H2 at liquid He temperatures

The adsorption isotherms of He and H2 at 4.2 K on stainless steel and Pyrex glass and of He on stainless steel at eight different temperatures between 1.9 and 4.2 K for pressures between 10−12 and 10−5 Torr have been measured. The measured data have been compared to different theoretical models describing adsorption isotherms. The Dubinin–Radushkevich–Kaganer (DRK) equation describes the measured He isotherms well for pressures down to about 10−9 Torr. The adsorption isotherms of He on stainless steel appear to follow the DRK equation as long as the energy to compress the gas from the measured equilibrium pressure to the saturated vapor pressure at the temperature of the measurement is smaller than the isosteric heat of adsorption. At pressures lower than about 10−9 Torr, the isotherms deviate from the DRK equation. The measurements show that the empirical constants in the DRK equation for He on stainless steel have similar values to He on Cu plated stainless steel while for He on the Pyrex glass surface the values are different. The isosteric heat of adsorption for He on stainless steel has been calculated from the measured isotherms and it decreases almost linearly from 8.5 meV/atom at a surface coverage of 1.8×1014 He atoms/cm2 down to 2.5 meV/atom at a surface coverage of 1.1×1015 He atoms/cm2. In the region where the DRK equation is not valid, the He isotherms can be described by a simple power law P=βSα, where P is the equilibrium pressure, S the surface coverage, α=1.63, and β varies with temperature.

Photochemically-activated electrodes: application in design of reversible immunosensors and antibody patterned interfaces

Antigen monolayers assembled onto Au electrodes associated with a quartz crystal act as electrochemical or microgravimetric quartz-crystal-microbalance (QCM) sensing interfaces for the complementary antibody. Electrochemical analysis of the antibody (Ab) is based on the insulation of the antigen monolayer electrode by the associated Ab towards a redox probe in the electrolyte solution. Ferrocene-modified glucose oxidase (Fc-GOx) and glucose are employed as redox probes for the amperometric transduction of the Ab association to the electrode. Bioelectrocatalyzed oxidation of glucose provides an electrochemical route to amplify the antigen-Ab complex formation. Electrochemical analysis of the dinitrophenyl antibody, DNP-Ab, by a dinitrophenyl-lysine monolayer electrode is presented. QCM analysis of the Ab is based on the frequency changes of the quartz crystal resulting from the association of the Ab to the crystal assembly. This method is discussed with the analysis of the fluorescein antibody, Flc-Ab, using a fluorescein monolayer-modified quartz crystal. A novel method to tailor reversible immunosensor devices by the application of photoisomerizable antigen monolayers on electrodes is presented. The antigen is modified by photoactive units exhibiting reversible photoisomerizable properties. In one photoisomer state, the antigen exhibits affinity for the Ab and enables its electrochemical or QCM analysis. Photoisomerization to the complementary state perturbs the antigen structure and the monolayer lacks affinity for the Ab. This enables the washing-off of the Ab and the regeneration of the actively sensing interface by a second illumination process that restores the antigen monolayer-modified surface. This method is exemplified by the development of a reversible DNP-Ab sensing electrode. N-Mercaptobutyl dinitrospopyran was assembled as a photoisomerizable monolayer on a Au electrode. The dinitrospiropyran monolayer, SP-state, exhibits affinity for the DNP-Ab and enables the amperometric detection of the Ab using Fc-GOx and glucose as redox probe. The complementary photoisomerized protonated dinitromerocyanine monolayer, MRH +-state, lacks affinity for the DNP-Ab. By photoisomerization of the DNP-Ab associated with the SP-monolayer electrode to the MRH +-monolayer state, the DNP-Ab is washed-off, and by a second illumination process, the MRH +-monolayer is re-isomerized to the SP-monolayer assembly, which is the active interface for further analysis of the DNP-Ab. Cyclic amperometric detection of the DNP-Ab by the photoisomerizable dinitrospiropyran monolayer is demonstrated. The association of the DNP-Ab to the SP-monolayer electrode and the dissociation of the Ab from the MRH +-monolayer electrode are confirmed by QCM experiments using a dinitrospiropyran monolayer-modified quartz crystal. The insulating features of an antigen-Ab complex on a conductive surface and the photochemically controlled association of an antibody to a photoisomerizable monolayer assembled onto the surface were used to develop means for micropatterning of surfaces by the antibody. A dinitrospiropyran antigen monolayer was assembled onto conductive ITO glass. A DNP-Ab solution was used as ‘ink solution’ to pattern the surface. The Ab-pattern was imaged by electrochemical copper deposition onto the Ab-lacking surface domains. The dinitrospiropyran monolayer assembled onto ITO or Pyrex glass surfaces was employed as an active interface for the photolithographic patterning of the surface with the DNP-Ab. Irradiation of the dinitrospiropyran monolayer, SP-state, through a grid-mask generated surface domains of protonated dinitromerocyanine, MRH +-state, which lacks affinity for the DNP-Ab. The DNP-Ab covalently-linked to agarose beads (50 μm) was selectively associated to the SP-monolayer sites and the micro-pattern of the resulting antibody was imaged. Methods for employing this photolithographic patterning of DNP-Ab to generate microstructures of any biomaterial, and, specifically, neural networks, are discussed.

Optically enhanced magnetic resonance for the study of atom-surface interaction

We study surface-induced spin relaxation with a laser-assisted magnetic resonance experiment. Optical pumping with polarization-modulated light in a transverse magnetic field creates the spin polarization. For detection a probe laser beam is reflected at the surface and the change of its polarization is monitored. We present a comprehensive theoretical description, taking into account the spin relaxation at the surface, which leads to a spatially inhomogeneous magnetization near the surface as a result of the transient behavior of the atoms in this region. Analytical expressions are derived for the magnetic resonance signal, which show that the wall relaxation causes a clear modification of the line shape, characterized by pronounced wings. The experimental results obtained with bare and silicone-coated Pyrex-glass surfaces are well described by the theory. The bare glass surface causes strong relaxation, whereas the siliconecoated surface is only weakly depolarizing. The analysis of the magnetic-resonance line shape indicates that the depolarization probability per wall collision is ∼ 0.01 in the latter case. The results are compared with corresponding results from the analysis of the optical resonance line measured with the same setup. Both types of measurements can be interpreted within the same theoretical framework and are fully consistent with one another.

Interaction of spin-polarized atoms with a surface studied by optical-reflection spectroscopy.

We present an experiment for the investigation of the interaction of spin-polarized Na atoms with a dielectric surface. A laser beam, which is resonant with an atomic transition, probes the spin polarization near the surface. It is reflected at the surface and the change of its polarization is measured. Our analysis takes into account that the spin polarization is reduced near the surface because of surface-induced spin relaxation. The theory shows that strong wall relaxation leads to a clear modification of the shape and strength of the optical line. The dependence of the line shape on the angle of incidence immediately below the critical angle of total internal reflection provides a sensitive tool for the quantitative determination of the depolarization probability \ensuremath{\varepsilon} per wall collision. Measurements performed at a Pyrex glass surface provide a clear experimental confirmation of the theory and yield a value of \ensuremath{\varepsilon}\ensuremath{\approxeq}0.5. The case of weak wall relaxation is exemplified by experimental results from a silicone-coated glass surface, which are equally well reproduced by the theory. The method offers the prospect of using surface-induced spin relaxation for the study of surface properties and atom-surface interactions for various surfaces. \textcopyright{} 1996 The American Physical Society.

The effect of non-equilibrium adsorption at the solid—vapor interface on the recedence of aqueous films and dewetting of solid surfaces

Abstract Phenomena involving the recedence of relatively thick films were investigated in the paraffin—water and Pyrex—dodecylammoniumacetate—water systems. Non-equilibrium adsorption was found to enhance the dewetting or recedence velocity of aqueous films from the surface of Pyrex glass. An explanation, based on the enhanced zipper-like adsorption at the solid—vapor interface as the liquid—vapor interface is destroyed, is presented to explain the existence of a maximum recedence velocity. These effects are absent in the paraffin—water system. This work reflects recedence behavior in practical non-quiescent systems.