Surface Functional Groups on Carbon and Silica

Snoeyink, Vernon L.; Weber, Walter J.

doi:10.1016/b978-0-12-571805-9.50007-5

Cited by 52 publications

(13 citation statements)

References 164 publications

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“…Ideal Nernstian behaviour would produce a potential difference of 59 mV for each pH unit, and values approaching this limit are found in our experiments. Confirming evidence that 'amorphous carbons' possess such proton-binding groups can be found in the literature (Snoeyink & Weber, 1972;Soffer & Folman, 1972;Oren et al, 1984), and our own measurements with a commercially available, glassy carbon electrode also showed a Nernstian response, as expected.…”

Section: S U R F a C E -P O T E N T I A L M E A S U R E M E N T S O Nsupporting

confidence: 90%

Interfacial energies and surface‐tension forces involved in the preparation of thin, flat crystals of biological macromolecules for high‐resolution electron microscopy

Glaeser

Zilker

Radermacher

et al. 1991

Journal of Microscopy

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SUMMARY It is generally agreed that surface‐tension forces and the direct interaction between the specimen and either the air‐water interface or the water‐substrate interface can influence significantly the preparation of biological materials for electron microscopy. Even so, there is relatively little systematic information available that would make it possible to control surface‐tension forces and interfacial energies in a quantitative fashion. The main objective in undertaking the present work has been to understand somewhat better the factors that influence the degree of specimen flatness of large, monolayer crystals of biological macromolecules. However, the data obtained in our work should be useful in understanding the preparation of specimens of biological macromolecules in general. Data collection by electron diffraction and electron microscopy at high resolution and high tilt angles requires thin crystals of biological macromolecules that are flat to at least 1°, and perhaps less than 0·2°, over areas as large as 1 μm2 or more. In addition to determining empirically by electron diffraction experiments whether sufficiently flat specimens can be prepared on various types of modified or unmodified carbon support films, we have begun to use other techniques to characterize both the surfaces involved and the interaction of our specimen with these surfaces. In the specific case of large, monolayer crystals of bacteriorhodopsin prepared as glucose‐embedded specimens on hydrophobic carbon films, it was concluded that the initial interfacial interaction involves adsorption of the specimen to the air‐water interface rather than adsorption of the specimen to the substrate. Surface‐tension forces at the air‐water interface and an apparently repulsive interaction between the specimen and the hydrophobic carbon seem to be major factors influencing the specimen flatness in this case. In the more general case it seems likely that interfacial interactions with either the substrate or the air‐water interface can be variously manipulated in the search to find desirable conditions of specimen preparation.

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Section: S U R F a C E -P O T E N T I A L M E A S U R E M E N T S O Nsupporting

confidence: 90%

Interfacial energies and surface‐tension forces involved in the preparation of thin, flat crystals of biological macromolecules for high‐resolution electron microscopy

Glaeser

Zilker

Radermacher

et al. 1991

Journal of Microscopy

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“…41 ( 8 = 3 8 solubility level of quartz in natural waters ranges from 0.03-30 mg 1-S O 2 , and some geochemical investigations seem to preclude either dissolution or precipiof kinetic constraints (Berner, 1971). But, as summa-tation of quartz in fresh surface water (pH < 9) because rized by Yariv & Cross (1979), in natural suspension as well as in experiments, different results can be obtained. Henderson, Syers & Jackson (1970) show that mechanical grinding increases quartz surface's reactivity (solubility?…”

Section: Combined Actionmentioning

confidence: 98%

Variations in the surface texture of suspended quartz grains in the Loire River: an SEM study

Manickam

Barbaroux

1987

Sedimentology

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Statistical size distribution and scanning electron microscopic studies of suspended sand grains in the Loire River at Montjean, France were carried out over a period of a year (hydrological cycle) to discern seasonal variations. The sand fraction in suspension is better sorted during winter (average mean = 0.69 mm, median = 0.65–0.95 mm, sorting value, σ= 1.1–1.35) and is dominated by quartzo‐feldspathic minerals. During summer, on the contrary, this fraction is rich in mica minerals and is poorly sorted (average mean = 1.21 mm, median = 0.33–0.95 mm, sorting value, σ= 1.4–2.0). The grain size of the coarser fraction shows a tendency to increase with river discharge up to an optimum discharge of about 1000 m3 s‐1 and thereafter decreases. Scanning electron photomicroscopy of quartz grains from the suspended sand population indicates that both mechanical and chemical features occur. The former (conchoidal fractures, mechanical fractures and breakage) dominate in the samples collected near the water surface during winter floods and the latter (solution pits, vermicular features, silica flowers, neogene silica and diatoms) in the samples from the bottom during low summer flows. During summer, chemical action takes place on sediments prior to or upon their deposition. Sediments that are resuspended during winter floods undergo mainly physical processes (attrition/abrasion). Mixed surface features are, therefore, observed during average and low river discharge. Inheritance of these surface features from the source area is, however, not completely excluded. Thus, the history of quartz grains in suspension can be reconstructed from SEM exoscopic studies: therefore, it can be proposed that the fluvial quartz grain surface textures result from a combination of alternating chemical and physical processes.

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“…The homogeneous planar sections consist of graphene structures with π -electron clouds perpendicular to the surface, which may be responsible for physisorption and catalysis. The surface may contain active groups (e.g., pyrone or chromene groups), which act as chemisorption sites and may be responsible for reaction with the adsorbate [22,23].…”

Section: Conceptual Modelmentioning

confidence: 99%