Electrophoretic Mobility and Electric Conductivity of Suspensions of Charge-Regulating Colloidal Spheres

Keh, Huan J.; Ding, Jau M.

doi:10.1021/la0115435

Cited by 17 publications

(18 citation statements)

References 31 publications

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“…Moreover, Cdot are porous, that is, permeable to the fluid and ions. Therefore, the electrophoretic mobility of porous spherical Cdot under internal flow field contributes to the effective electrical conductivity of the water based Cdot nanofluid 48 . Thus, with increasing volume fraction, the overall electrical conductivity of the nanofluids increases.…”

Section: Resultsmentioning

confidence: 99%

Turning date palm fronds into biocompatible mesoporous fluorescent carbon dots

Kavitha

Kumar

2018

Sci Rep

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Here, we demonstrate the synthesis of mesoporous carbon dots (Cdot) from date palm fronds and their excellent excitation wavelength-independent photoluminescence (PL), with high photo- and storage-stability, superior biocompatibility and thermal and electrical conductivity for the first-time by a simple, green, one-step carbonization method. Interestingly, the as-obtained Cdot manifest the spherical shape of about 50 nm average diameter having surface mesopores of size less than 10 nm with sp2 hybridized carbon. The as-synthesised mesoporous Cdot, first of its kind, evince yellow-green PL (preferred over blue PL for biological applications) around 450 nm under excitation wavelength range of 320–420 nm with absolute quantum yield of 33.7% exhibiting high photo- and storage-stability. The thermal and electrical conductivity of Cdot/water nanofluids without any surfactants is illustrated. Application of Cdot as interfacial material in organic photovoltaic cell is manifested. The Cdot exhib visible sunlight driven photocatalytic and antibacterial activity. Mesoporous Cdot further reveal excellent biocompatibility with fibroblast cell (greater than 95% viability). The novelty of this study in the formation of multifunctional mesoporous Cdot from date palm fronds could inspire both research and industrial interests in the synthesis of biomass-derived Cdot and their application in a wide array of fields.

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Section: Resultsmentioning

confidence: 99%

Turning date palm fronds into biocompatible mesoporous fluorescent carbon dots

Kavitha

Kumar

2018

Sci Rep

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“…However, the particles may influence the conductivity because they may produce significant electric fields in the suspension if their volume fraction is high enough. A recent analytical study [13] of conductivity and mobility of colloids led to closed-form equations for interacting particle suspensions but valid for low zeta potential (smaller than 25 mV). As we will see, the zeta potential is not low in our systems, so that here only a simple model will be used for conductivity.…”

Section: Resultsmentioning

confidence: 99%

Heteroaggregation, repeptization and stability in mixtures of oppositely charged colloids

Raşa

Philipse

Meeldijk

2004

Journal of Colloid and Interface Science

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We report a study of mixtures of initially oppositely charged particles with similar size. Dispersions of silica spheres (negatively charged) and alumina-coated silica spheres (positively charged) at low ionic strength, mixed at various volume ratios, exhibited a surprising stability up to compositions of 50% negative colloids as well as spontaneous repeptization of particles from the early-stage formed aggregates. The other mixtures were found to contain large heteroaggregates, which were imaged using cryogenic electron microscopy. Electrophoretic mobility, electrical conductivity, static and dynamic light scattering and sedimentation were studied as a function of volume fraction of the mixed dispersions to investigate particle interactions and elucidate the repeptization phenomenon.

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“…8 This conceptscharge compensations is well-developed and extensively modeled in colloid chemistry. 9, 10 Menon and Zydney suggested that it also applies to proteins and proposed a model to analyze the adjustment of charge of the macromolecule and the surrounding buffer upon annihilation of a positive charge from the surface of the protein.…”

Section: Introductionmentioning

confidence: 99%

Significance of Charge Regulation in the Analysis of Protein Charge Ladders

2003

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Analysis of protein charge ladders using capillary electrophoresis (CE) provides a method of determining charges of proteins. This method has disregarded the effect of charge compensationsa response of the protein and its environment to a change in electrostatic potential on the surface of the protein. This work examines the difference in charge, ∆Z, between the first two rungs of the ladder of bovine carbonic anhydrase II (BCAII) as a function of pH and ionic strength using CE. These data were analyzed in three ways: using models based on Hückel theory and on charge regulation, and using linear regression. These analyses were in only qualitative agreement, and the differences between them suggest that simple theoretical models for the behavior of colloidal particles cannot establish the value of ∆Z accurately in proteins. Linear regression of mobilities of the rungs of charge ladderssa method proposed in earlier workscontinues to be a computationally convenient method of estimating the charge Z 0 of native proteins, but the accuracy of this method depends on the value of ∆Z. The absolute value of ∆Z cannot presently be established accurately. In the case of BCAII, we suggest ∆Z ) -0.93 for the difference in charge between the first two rungs of the charge ladder at pH ) 8.4 and 10 mM ionic strength. An estimate of the uncertainty in this value for BCAII due to uncertainties in the values of pK a of amino acids and of the hydrodynamic radius is (0.02. Other uncertainties not considered in this analysis will make this value larger. IntroductionA protein charge ladder is a collection of derivatives of a protein generated by converting its charged groups (most commonly lysine -NH 3 + but also aspartate or glutamate -CO 2 -) into electrically neutral ones ( -NHCOCH 3 or -CO 2 CH 3 ). 1 In free solution capillary electrophoresis (CE), these modified proteins separate into distinct peaks or "rungs"; each rung contains regioisomers with approximately the same charge: that is, at least nominally, the same number of modified groups. Charge ladders provide a self-calibrating tool for estimating certain basic physical parameters of proteins such as charge, 2,3 hydrodynamic radius, 4 and electrostatic contributions to the free energy of binding of ligands 5,6 and of protein folding. 7 The simplest analysis of charge ladders assumes that the charge difference (∆Z) between the consecutive rungs of a charge ladder generated by acetylation of lysine -NH 3 + groups is a full unit of charge (∆Z ) -1). Menon and Zydney have made the point that ∆Z may have a value different from -1 if the change in charge of the -amino group on acetylation (which is, in fact, -1, provided that this group is completely protonated before acetylation) is offset by a compensating change in charge elsewhere in the protein. 8 This conceptscharge compensations is well-developed and extensively modeled in colloid chemistry. 9,10 Menon and Zydney suggested that it also applies to proteins and proposed a model to analyze the adjustment of charge of the macro...

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Electrophoretic Mobility and Electric Conductivity of Suspensions of Charge-Regulating Colloidal Spheres

Cited by 17 publications

References 31 publications

Turning date palm fronds into biocompatible mesoporous fluorescent carbon dots

Turning date palm fronds into biocompatible mesoporous fluorescent carbon dots

Heteroaggregation, repeptization and stability in mixtures of oppositely charged colloids

Significance of Charge Regulation in the Analysis of Protein Charge Ladders

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