Electrostatic Charging of Hydrophilic Particles Due to Water Adsorption

Gouveia, Rubia F.; Galembeck, Fernando

doi:10.1021/ja900704f

Cited by 120 publications

(128 citation statements)

References 31 publications

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“…Topography and capacitance gradient (dC/dz) images of unmodified, cationic and anionic cellulose films were obtained using a Park NX-10 Atomic Force Microscope (Gouveia and Galembeck 2009;Ferreira et al 2015). PPP-EFM probes (NanoWorld) with spring constant of 2.8 N/m and resonance frequency within 75 kHz were used for measurements.…”

Section: Scanning Probe Microscopymentioning

confidence: 99%

Surface modified cellulose scaffolds for tissue engineering

et al. 2016

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We report the ability of cellulose to support cells without the use of matrix ligands on the surface of the material, thus creating a two-component system for tissue engineering of cells and materials. Sheets of bacterial cellulose, grown from a culture medium containing Acetobacter organism were chemically modified with glycidyltrimethylammonium chloride or by oxidation with sodium hypochlorite in the presence of sodium bromide and 2,2,6,6-tetramethylpipiridine 1-oxyl radical to introduce a positive, or negative, charge, respectively. This modification process did not degrade the mechanical properties of the bulk material, but grafting of a positively charged moiety to the cellulose surface (cationic cellulose) increased cell attachment by 70% compared to unmodified cellulose, while negatively charged, oxidised cellulose films (anionic cellulose), showed low levels of cell attachment comparable to those seen for unmodified cellulose. Only a minimal level of cationic surface derivitisation (ca 3% degree of substitution) was required for increased cell attachment and no mediating proteins were required. Cell adhesion studies exhibited the same trends as the attachment studies, while the mean cell area and aspect ratio was highest on the cationic surfaces. Overall, we demonstrated the utility of positively charged bacterial cellulose in tissue engineering in the absence of proteins for cell attachment.

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Section: Scanning Probe Microscopymentioning

confidence: 99%

Surface modified cellulose scaffolds for tissue engineering

et al. 2016

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“…Some more important ones are via ion exchange with the atmosphere, as induced by neutralization by ions from the ambient atmosphere, 77,78 by air circulation, 66 and by reduced pressure. 31,79 These processes may be linked to the adsorption and desorption of water from the atmosphere, 80 and they are probably most relevant to ionic charge at the surface produced by low frictional energies. An exchange of the triboelectric surface charge with the ambient atmosphere has also been proposed in the older triboelectric literature, 18,19,81 and its mechanism is likely related to the charge-transfer mechanism between dispersing water droplets and air, first studied by Lenard, who was inspired by the observation of negatively charged air at waterfalls ("Wasserfallelektrizität").…”

Section: Water As a Sink Of Chargementioning

confidence: 99%

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Knorr¹

2011

AIP Advances

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Though triboelectric charging of insulators is common, neither its mechanism nor the nature of the charge is well known. Most research has focused on the integral amount of charge transferred between two materials upon contact, establishing, e.g., a triboelectric series. Here, the charge distribution of tracks on insulating polymer films rubbed by polymer-covered pointed swabs is investigated in high resolution by Kelvin probe force microscopy. Pronounced bipolar charging was observed for all nine rubbing combinations of three different polymers, with absolute surface potentials of up to several volts distributed in streaks along the rubbing direction and varying in polarity on μm-length scales perpendicular to the rubbing direction. Charge densities increased considerably for rubbing in higher relative humidity, for higher rubbing loads, and for more hydrophilic polymers. The ends of rubbed tracks had positively charged rims. Surface potential decay with time was strongly accelerated in increased humidity, particularly for polymers with high water permeability. Based on these observations, a mechanism is proposed of triboelectrification by extrusions of prevalently hydrated protons, stemming from adsorbed and dissociated water, along pressure gradients on the surface by the mechanical action of the swab. The validity of this mechanism is supported by explanations given recently in the literature for positive streaming currents of water at polymer surfaces and by reports of negative charging of insulators tapped by accelerated water droplets and of potential built up between the front and the back of a rubbing piece, observations already made in the 19th century. For more brittle polymers, strongly negatively charged microscopic abrasive particles were frequently observed on the rubbed tracks. The negative charge of those particles is presumably due in part to triboemission of electrons by polymer chain scission, forming radicals and negatively charged ions

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“…For example, effects such as counterions deposited on the sample or the ambient air humidity during the KFM measurement could influence the signal. 21 Nevertheless, it is conceivable that, in carefully controlled, simple cases, there is indeed a correlation between the charge of a surface in water at given pH and the KFM signal in air.…”

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Kelvin-probe force microscopy of the pH-dependent charge of functional groups

Stone

Mesquida

2016

Applied Physics Letters

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Kelvin-probe Force Microscopy (KFM) is an established method to map surface potentials or surface charges at high, spatial resolution. However, KFM does not work in water, which restricts its applicability considerably, especially when considering common, functional chemical groups in biophysics such as amine or carboxy groups, whose charge depends on pH. Here, we demonstrate that the KFM signal of such groups taken in air after exposure to water correlates qualitatively with their expected charge in water for a wide range of pH values. The correlation was tested with microcontact-printed thiols exposing amine and carboxy groups. Furthermore, it was shown that collagen fibrils, as an example of a biological material, exhibit a particular, pH-sensitive surface charge pattern, which could be caused by the particular arrangement of ionizable residues on the collagen fibril surface.

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Electrostatic Charging of Hydrophilic Particles Due to Water Adsorption

Cited by 120 publications

References 31 publications

Surface modified cellulose scaffolds for tissue engineering

Surface modified cellulose scaffolds for tissue engineering

Squeezing out hydrated protons: low-frictional-energy triboelectric insulator charging on a microscopic scale

Kelvin-probe force microscopy of the pH-dependent charge of functional groups

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