Surface Chemistry Of Glass Research Articles

Tailoring the Hydroxyl Density of Glass Surface for Anionic Ring-Opening Polymerization of Polyamide 6 to Manufacture Thermoplastic Composites.

Reactive thermoplastics matrices offer ease of processing using well-known molding techniques (such as Resin Transfer Molding) due to their initially low viscosity. For Polyamide 6 (PA6)/glass composites, the hydroxyl groups on the glass surface slow down the anionic ring-opening polymerization (AROP) reaction, and can ultimately inhibit it. This work aims to thoroughly control the hydroxyl groups and the surface chemistry of glass particulates to facilitate in situ AROP-an aspect that has been barely explored until now. A model system composed of a PA6 matrix synthesized by AROP is reinforced with calcinated and silanized glass microparticles. We systematically quantify, by TGA and FTIR, the complete particle surface modification sequence, from the dehydration, dehydroxylation and rehydroxylation processes, to the silanization step. Finally, the impact of the particle surface chemistry on the polymerization and crystallization of the PA6/glass composites was quantified by DSC. The results confirm that a careful balance is required between the dehydroxylation process, the simultaneous rehydroxylation and silane grafting, and the residual hydroxyl groups, in order to maintain fast polymerization and crystallization kinetics and to prevent reaction inhibition. Specifically, a hydroxyl concentration above 0.2 mmol OH·g−1 leads to a slowdown of the PA6 polymerization reaction. This reaction can be completely inhibited when the hydroxyl concentration reaches 0.77 mmol OH·g−1 as in the case of fully rehydroxylated particles or pristine raw particles. Furthermore, both the rehydroxylation and silanization processes can be realized simultaneously without any negative impact on the polymerization. This can be achieved with a silanization time of 2 h under the treatment conditions of the study. In this case, the silane agent gradually replaces the regenerated hydroxyls. This work provides a roadmap for the preparation of reinforced reactive thermoplastic materials.

Surface Modification of Bioresorbable Phosphate Glasses for Controlled Protein Adsorption.

The traditional silicate bioactive glasses exhibit poor thermal processability, which inhibits fiber drawing or sintering into scaffolds. The composition of the silicate glasses has been modified to enable hot processing. However, the hot forming ability is generally at the expense of bioactivity. Metaphosphate glasses, on the other hand, possess excellent thermal processability, congruent dissolution, and a tailorable degradation rate. However, due to the layer-by-layer dissolution mechanism, cells do not attach to the material surface. Furthermore, the congruent dissolution leads to a low density of OH groups forming on the glass surface, limiting the adsorption of proteins. It is well regarded that the initial step of protein adsorption is critical as the cells interact with this protein layer, rather than the biomaterial itself. In this paper, we explore the possibility of improving protein adsorption on the surface of phosphate glasses through a variety of surface treatments, such as washing the glass surface in acidic (pH 5), neutral, and basic (pH 9) buffer solutions followed or not by a treatment with (3-aminopropyl)triethoxysilane (APTS). The impact of these surface treatments on the surface chemistry (contact angle, ζ-potential) and glass structure (FTIR) was assessed. In this manuscript, we demonstrate that understanding of the material surface chemistry enables to selectively improve the adsorption of albumin and fibronectin (used as model proteins). Furthermore, in this study, well-known silicate bioactive glasses (i.e., S53P4 and 13-93) were used as controls. While surface treatments clearly improved proteins adsorption on the surface of both silicate and phosphate glasses, it is of interest to note that protein adsorption on phosphate glasses was drastically improved to reach similar protein grafting ability to the silicate bioactive glasses. Overall, this study demonstrates that the limited cell/phosphate glass biological response can easily be overcome through deep understanding and control of the glass surface chemistry.

Critical angle reflection imaging for quantification of molecular interactions on glass surface

Quantification of molecular interactions on a surface is typically achieved via label-free techniques such as surface plasmon resonance (SPR). The sensitivity of SPR originates from the characteristic that the SPR angle is sensitive to the surface refractive index change. Analogously, in another interfacial optical phenomenon, total internal reflection, the critical angle is also refractive index dependent. Therefore, surface refractive index change can also be quantified by measuring the reflectivity near the critical angle. Based on this concept, we develop a method called critical angle reflection (CAR) imaging to quantify molecular interactions on glass surface. CAR imaging can be performed on SPR imaging setups. Through a side-by-side comparison, we show that CAR is capable of most molecular interaction measurements that SPR performs, including proteins, nucleic acids and cell-based detections. In addition, we show that CAR can detect small molecule bindings and intracellular signals beyond SPR sensing range. CAR exhibits several distinct characteristics, including tunable sensitivity and dynamic range, deeper vertical sensing range, fluorescence compatibility, broader wavelength and polarization of light selection, and glass surface chemistry. We anticipate CAR can expand SPR′s capability in small molecule detection, whole cell-based detection, simultaneous fluorescence imaging, and broader conjugation chemistry.

On the stability and necessary electrophoretic mobility of bare oil nanodroplets in water.

Hydrophobic oil droplets, particles, and air bubbles can be dispersed in water as kinetically stabilized dispersions. It has been established since the 19th century that such objects harbor a negative electrostatic potential roughly twice larger than the thermal energy. The source of this charge continues to be one of the core observations in relation to hydrophobicity, and its molecular explanation is still debated. What is clear though is that the stabilizing interaction in these systems is understood in terms of electrostatic repulsion via Derjaguin, Landau, Verwey, and Overbeek theory. Recent work [A. P. Carpenter et al., Proc. Natl. Acad. Sci. U. S. A. 116, 9214 (2019)] has added another element into the discussion, reporting the creation of bare near-zero charged droplets of oil in neat water that are stable for several days. Key to the creation of the droplets is a rigorous glassware cleaning procedure. Here, we investigate these conclusions and show that the cleaning procedure of glassware has no influence on the electrophoretic mobility of the droplets and that oil droplets with near-zero charge are unstable. We provide an alternative possible explanation for the observations involving glass surface chemistry.

Low-temperature metalorganic chemical vapor deposition of molybdenum disulfide on multicomponent glass substrates

Industrially relevant substrates, such as amorphous oxides and metallic substrates, typically cannot withstand the elevated temperatures (>800 °C) required for metalorganic chemical vapor deposition (MOCVD), thus limiting the applicability of these substrates for the realization of electronic-grade 2D materials. This work demonstrates MOCVD of crystalline MoS2 on multicomponent glass at temperatures ranging from 400 to 600 °C. Incorporated to understand the effects of ions in the glass on 2D layer growth, nitrogen plasma treatment of the glass surface enables increased domain size and minimized the effects of low temperature on electronic characteristics. Trends of growth morphology, crystalline quality, and film stoichiometry are examined as a function of glass chemistry, growth temperature, and degree of surface treatment. It is found that glass surface chemistry and growth temperature are the dominant factors in controlling domain size, which is improved with increasing plasma treatment, introducing alkali-containing glass, and growth temperature. While crystalline quality is improved with higher temperature, the films no longer remain stoichiometric. Finally, we demonstrate that glass surface chemistry has important impacts on electronic transport properties.

Environmental mud adhesion on optical glass surface: Effect of mud drying temperature on surface properties

Mud formation in humid air ambient from dust particles on the glass surfaces is investigated. Mud drying temperature and the characteristics of mud liquid created at the interface between wet mud and the glass surface are examined. Effects of dried mud liquid layer on the glass surface are assessed using analytical tools including scanning electron and atomic force microscopes, energy dispersive spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. Dry mud adhesion on the glass surface is evaluated incorporating the micro-tribometer and UV visible transmittance tests are carried out to determine optical properties of the glass substrate after dry mud removal. It is found that mud drying temperature has significant effect on the glass surface chemistry and topology; in which case, increasing mud drying temperature increases OH− and KOH attack on the glass surface while forming cavities-like structures and randomly distributed few micro-cracks. The tangential force required for dry mud removal from the glass surface increases with increasing mud drying temperature. Transmittance of UV visible spectrum is suppressed by the mud residues on the glass surface, which is more pronounced at high temperatures.

High-Precision Dispensing of Nanoliter Biofluids on Glass Pedestal Arrays for Ultrasensitive Biomolecule Detection.

Precise dispensing of nanoliter droplets is necessary for the development of sensitive and accurate assays, especially when the availability of the source solution is limited. Conventional approaches are limited by imprecise positioning, large shear forces, surface tension effects, and high costs. To address the need for precise and economical dispensing of nanoliter volumes, we developed a new approach where the dispensed volume is dependent on the size and shape of defined surface features, thus freeing the dispensing process from pumps and fine-gauge needles requiring accurate positioning. The surface we fabricated, called a nanoliter droplet virtual well microplate (nVWP), achieves high-precision dispensing (better than ±0.5 nL or ±1.6% at 32 nL) of 20-40 nL droplets using a small source drop (3-10 μL) on isolated hydrophilic glass pedestals (500 μm on a side) bonded to arrays of polydimethylsiloxane conical posts. The sharp 90° edge of the glass pedestal pins the solid-liquid-vapor triple contact line (TCL), averting the wetting of the glass sidewalls while the fluid is prevented from receding from the edge. This edge creates a sufficiently large energy barrier such that microliter water droplets can be poised on the glass pedestals, exhibiting contact angles greater >150°. This approach relieves the stringent mechanical alignment tolerances required for conventional dispensing techniques, shifting the control of dispensed volume to the area circumscribed by the glass edge. The effects of glass surface chemistry and dispense velocity on droplet volume were studied using optical microscopy and high-speed video. Functionalization of the glass pedestal surface enabled the selective adsorption of specific peptides and proteins from synthetic and natural biomolecule mixtures, such as venom. We further demonstrate how the nVWP dispensing platform can be used for a variety of assays, including sensitive detection of proteins and peptides by fluorescence microscopy or MALDI-TOF.

Polymer nanocomposite – fiber model interphases: Influence of processing and interface chemistry on mechanical performance

Electrophoretic deposition (EPD) has been established as a scalable and environmentally friendly approach for depositing carbon nanotubes (CNTs) from aqueous colloidal dispersions onto a variety of fibrous surfaces. EPD facilitates the micro/nano hybridization of CNTs and reinforcing fibers, enabling the controlled engineering of hierarchically-structured composites. Model studies have shown that the chemistry of the CNTs in the fiber/matrix interphase plays a critical role in the mechanical performance of the composite. Composite interphases were replicated on planar glass substrates to systematically study the influence of CNT functionalization, glass surface chemistry, and aqueous dispersion quality on the mechanical performance under shear loading. CNTs were functionalized using a novel ultrasonicated-ozonolysis (USO) and polyethyleneimine (PEI) process to prepare films on silane-treated glass surfaces. The epoxy-infused films exhibited a 50% improvement as compared to untreated glass/epoxy interfaces. Detailed surface analysis using X-ray photoelectron spectroscopy shows chemical bonds in the interphase, and computational modeling of the valence band spectra provides additional insight into the chemical nature of the bond. The formation of a PEI–CNT rich interphase facilitates a more homogeneous, ductile fracture zone relative to the brittle glass epoxy interface, and increases composite strength by shifting the fracture surface away from the glass surface. Intentional destabilization of the CNT dispersion resulted in re-agglomeration, diminishing any benefit of the PEI, thereby demonstrating the importance of a stable dispersion provided by the USO processing. The results replicate the trends observed previously in more complex composite systems and provide new insight into interfacial engineering of nanostructured composites.

Tunable photoluminescence induced by thermal reduction in rare earth doped glasses

In this paper, we show that the photoluminescence of Eu and Eu–Yb doped silicate glasses can be tuned by heat-treating the glasses in reducing atmosphere and by adjusting their host compositions. The control over the rare earth redox state in glasses is crucial for their potential applications as phosphor materials. By subjecting the glasses to a H2-bearing atmosphere around the glass transition temperature, Eu3+ ions are reduced to Eu2+, and this leads to modification of the glass surface chemistry and structure. Both the underlying reduction mechanisms and the composition dependence of luminescence are clarified based on static and dynamic emission spectroscopy, surface analysis, and structural considerations. The tunability of the energy transfer (i.e., quantum cutting) from Eu2+ to Yb3+ in the co-doped Eu–Yb glasses is also explored.

Controlling the phenotype and function of mesenchymal stem cells in vitro by adhesion to silane-modified clean glass surfaces

The behaviour of human mesenchymal stem cells (hMSC) when cultured in contact with a range of silane-modified surfaces was examined to determine if changing the surface chemistry affected the early differentiation potential of mesenchymal stem cells in vitro over a 7-day period. Cells were cultured for 1 and 7 days in direct contact with glass which had been functionalized by surface treatment to provide a range of different surfaces: -CH 3, -NH 2, -SH, -OH, and -COOH modified surfaces and a clean glass reference (TAAB). Viable cell adhesion was quantified by Lactate Dehydrogenase assay, and morphology and viability was qualitatively evaluated using calcein AM, ethidium homodimer, cytoskeletal (F Actin), extra-cellular matrix (fibronectin and vitronectin) and Hoechst staining (nucleus). The expression of selected differentiation markers, Collagen II (chondrocytes), CBFA1 (bone transcription factor), Collagen I (MSC marker) and TGF- β3 (extra-cellular matrix production) was determined using real time polymerase chain reaction. The expression of ornithine decarboxylase was evaluated as a marker of proliferation. Surfaces of the -NH 2 group demonstrated the greatest level of cell adhesion by the 7-day period, and mRNA expression profiles indicated osteogenic differentiation, increased CBFA1 and decreased Collagen II expression. Cells cultured in contact with the -COOH surfaces displayed different cell morphologies, fibronectin and vitronectin spatial distributions compared with the cells in contact with the -NH 2 surfaces, in addition to an increase in Collagen II expression, indicative of chondrogenic differentiation. The modifications to the surface chemistry of glass did affect cell behaviour, both in terms of viable cell adhesion, morphology and profiles of mRNA expression, providing the means to alter the differentiation potential of the MSCs.

Attachment Efficiencies of Salt Aerosols onto Infrastructure and Implications for Atmospheric Corrosion

To support a holistic approach to the modeling of atmospheric corrosion, an experimental program was undertaken to delineate the effects of relative humidity, wind speed, and infrastructure surface chemistry on the efficiency of salt aerosol retention. The fundamental adhesion between a salt crystal and a metal oxide surface was studied using colloid probe atomic force microscopy. The magnitude of adhesion was dependant upon the probe dimensions, surface chemistry, and relative humidity. Parallel experiments investigated the removal of salt particles/aerosols from both clean hydrophilic and hydrophobized glass slide surfaces in a wind tunnel. The efficiency of the removal of particulates from glass surfaces was found to be a function of relative humidity, and the influence of humidity and wind velocity appeared to be magnified by increasing the glass hydrophobicity. Furthermore, alterations in the glass surface chemistry led to notable differences in the size and distribution of adsorbed salts. The experimentally determined salt retention efficiencies enable current holistic lifetime prediction models to be updated and expanded, and provides insight into the ability of surface chemistry to control aerosol retention processes and thus atmospheric corrosion. © 2005 The Electrochemical Society. All rights reserved.

Properties of Glass Fiber for Filtration: Influence of Forming Process

Glass fiber used in filtration applications is typically produced by either of three types of processes: (1) continuous draw, (2) centrifugal (rotary) spinning, or (3) flame attenuation. Each process imparts to the fiber a unique set of characteristics such as diameter, length, and surface chemistry and structure. These in turn dictate the key performance properties of the fiber in nonwoven products. Diameter distribution is perhaps the most fundamental to filtration efficiency; this can vary appreciably with fiberization process even for fibers of the same bulk chemistry and “mean” diameter. Likewise length distributions are unique to each process and, for discontinuous fiber, have a distinct correlation to the diameter distributions. Complete characterization, therefore, often requires bivariate analyses. Finally, glass surface chemistry and structure, which are critically important for key properties such as fiber tensile strength, chemical durability / reactivity, and dispersability, are also highly dependent upon the fiber forming process. By controlling initial glass chemistry and fiberization process parameters, a wide range of fiber dimension, morphologies and surface properties can be achieved. As such glass fiber has some unique opportunities in meeting existing and new demands in filtration markets.

Immobilized probe and glass surface chemistry as variables in microarray fabrication.

BackgroundGlobal gene expression studies with microarrays can offer biological insights never before possible. However, the technology possesses many sources of technical variability that are an obstacle to obtaining high quality data sets. Since spotted microarrays offer design/content flexibility and potential cost savings over commercial systems, we have developed prehybridization quality control strategies for spotted cDNA and oligonucleotide arrays. These approaches utilize a third fluorescent dye (fluorescein) to monitor key fabrication variables, such as print/spot morphology, DNA retention, and background arising from probe redistributed during blocking. Here, our labeled cDNA array platform is used to study, 1) compression of array data using known input ratios of Arabidopsis in vitro transcripts and arrayed serial dilutions of homologous probes; 2) how curing time of in-house poly-L-lysine coated slides impacts probe retention capacity; and 3) the retention characteristics of 13 commercially available surfaces.ResultsWhen array element fluorescein intensity drops below 5,000 RFU/pixel, gene expression measurements become increasingly compressed, thereby validating this value as a prehybridization quality control threshold. We observe that the DNA retention capacity of in-house poly-L-lysine slides decreases rapidly over time (~50% reduction between 3 and 12 weeks post-coating; p < 0.0002) and that there are considerable differences in retention characteristics among commercially available poly-L-lysine and amino silane-coated slides.ConclusionsHigh DNA retention rates are necessary for accurate gene expression measurements. Therefore, an understanding of the characteristics and optimization of protocols to an array surface are prerequisites to fabrication of high quality arrays.

COATED GLASS MICROSPHERES IN ERF APPLICATIONS

ER fluids (ERFs) typically consist of a concentrated dispersion of solid particles in a non-conducting base fluid. As a result, particle sedimentation represents a significant problem for many formulations since, in most cases, the particulate phase is of higher density than the base fluid. To remedy this situation, higher density fluids have been widely used in ERFs (ρ &gt; 1.1 g/cc) rather than less expensive mineral oils that display lower densities (0.8-0.9 g/cc). An alternative approach to density "matching" has been explored by Qi and Shaw who have successfully developed ERF particles based on low density, micron-sized hollow glass "balloons" that are polymer coated. These microballons are commercially available from the PQ Corporation and they exhibit an effective density of 0.7 g/cc. Using these materials, it becomes possible to engineer ERF particles that are "neutrally buoyant" in mineral oils by adjusting the coating weight of an ER active polymer on the glass spheres. In this study, a simple solution coating process was developed exploiting the unique surface chemistry of glass which contains -Si-O-Si- and -Si-OH sites capable of hydrogen bonding with hydrophillic polymers. A number of water-soluble ionic polysaccharides were evaluated as coatings because of their ability to form hydrogen bonds with glass surfaces. A synthetic alcohol-soluble polymer, sulfonated polyphenylene oxide, was also evaluated because of its thermal stability and mechanical durability.

Structure and ionic transport in disordered silicates

AbstractA brief review is given of the ways in which the local structure in glass can influence the microstructure that supports ionic transport. This in turn contributes to the co-operative nature of ion dynamics and ways in which this underpins the ‘mixed alkali effect’ are discussed. Glass microstructure too is expected to affect glass fracture as well as the chemistry of glass surfaces. In melts, though, these restrictions appear to vanish as the rigidity of intermediate range order is lost.

Effect of RCA cleaning on the surface chemistry of glass and polysilicon films as studied by ToF-SIMS and XPS

The surface chemistry of an alkaline-earth boroaluminosilicate glass is changed by contact with chemical solutions. The present study shows that RCA cleaning creates a silica-rich surface on the glass. This altered surface can be removed by hydrofluoric acid etching. During the RCA cleaning process, glass components can be transferred to a polysilicon film placed in the same alkaline solution. The acidic solution in turn removes most of the contamination from the polysilicon. © 1998 John Wiley & Sons, Ltd.

Surface chemistry of multicomponent silicate gels

The surface chemistry of a calcium boroaluminosilicate gel was studied and compared with the corresponding behavior of a pure silica gel. The experiments were performed, in situ, by transmission FTIR utilizing high surface area, free-standing, monolithic xerogel foils. The foils could be vacuum-evacuated, heated, and/or exposed to water and organic vapors within the FTIR cell. The spectra of the dehydrated calcium boroaluminosilicate showed only isolated surface silanols (Si-OH) and boranols (B-OH). They were found to be inactive upon subsequent exposure to water vapor, but readily participated in H-bonding with basic organic adsorbates. The frequency shifts associated with the adsorption of organic vapors were lower on the multicomponent surface than on the silica surface. This reveals that the silanols are less interactive, or acidic, on the multicomponent surface. The adsorption of molecular water occurred faster and with greater tenacity on the calcium boroaluminosilicate. This is attributed to the prevalence of surface sites associated with Ca, B, and Al where the chemisorption of water may occur. Some of these sites were revealed by pyridine adsorption studies; i.e., pyridine was found to form coordinate bonds with unsaturated B III and Al III Lewis acid sites. Otherwise, the chemical behavior of Ca and Al on the surface was not directly evident in the FTIR spectra. Finally, the chemisorption of methoxytrimethylsilane was examined and found to occur preferentially at the boranol sites. However, the chemisorbed silanes on the boranols were found to be more easily hydrolyzed than those on the silanols. In general, this study illustrates several principles about the surface chemistry of calcium boroaluminosilicates, and offers an experimental approach for direct examination of multicomponent gel or glass surface chemistry in any multicomponent system that can be synthesized using the alkoxide method.

Glass surface chemistry via gas chromatography

We have developed special methods of inverse gas chromatography for surface characterization that are based on the use of capillary chromatography columns. The methods have adequate sensitivity so that low-surface-area materials such as glasses can be studied directly, rather than indirectly from analogous powdered samples (e.g. fused silica versus silica gels). Any material can be studied that can be drawn into capillary tubing of about 50–500 μm i.d.. When desired, powdered samples can also be examined. This paper describes the methods we have developed and presents examples that illustrate how the inverse chromatograms are interpreted and what types of information can be obtained.

Book Review - Reviewer: David C. Joy is an electron microscopist and a Member of the Materials Physics Research Departmental AT…T Bell Laboratories in Murray Hill, NJ. His research interests include analytical SEM and STEM development and application. - Reviewer: Prof. Carlo G. Pantano teaches undergraduate and graduate courses in glass science at Pennsylvania State University. His research efforts focus

Book Review - <i>Reviewer</i>: David C. Joy <i>is an electron microscopist and a Member of the Materials Physics Research Departmental AT…T Bell Laboratories in Murray Hill, NJ. His research interests include analytical SEM and STEM development and application</i>. - <i>Reviewer: Prof</i>. Carlo G. Pantano <i>teaches undergraduate and graduate courses in glass science at Pennsylvania State University. His research efforts focus

Aqueous h 2o 2 production from o 3 in glass impingers

The aqueous generation of H 2O 2 from bubbling ozonized air through water in glass impingers is investigated. O 3 loss is monitored throughout each experiment. Aqueous H 2O 2 is measured at the end of each experiment. The mole quantities of O 3 lost (ΔO 3) and H 2O 2 formed (ΔH 2O 2) are calculated. There is a stoichiometric relationship between ΔO 3 and ΔH 2O 2 which is independent of bubbling time, solution acidity and initial O 3 concentration but is dependent upon the liquid water content of each impinger. For 10 ml of water in each impinger, the AO 3 to ΔH 2O 2 mole ratio is between 2:1 and 3:1 and for 20 ml is between 1:1 and 1:2. Increasing the solution acidity increases the rates of O 3 loss and H 2O 2 generation. This result contradicts mechanisms in which a O 3 + HO − reaction is used to initiate radical formation and H 2O 2 production. These results are interpreted through a combination of glass surface chemistry and bulk aqueous chemistry. The O 3-H 2O 2 impinger mechanisms involve O 3 adsorption and/or reaction on the impinger surface and its surface products subsequent reaction with water or trace impurities in the water. Experiments using tetrafluorethylene (TFE) impingers in place of glass impingers are conducted to examine the role of surface chemistry. The TFE impingers are found to substantially increase ΔO 3 and ΔH 2O 2 without changing their mole ratio. This is attributed to an enhanced O 3-H 2O surface chemistry or O 3 reaction with unsaturated Teflon linkages or impurities in the Teflon from machining.