Charging and Aggregation of Latex Particles by Oppositely Charged Dendrimers

Lin, Wen-Shin; Galletto, Paolo; Borkovec, Michal

doi:10.1021/la049006i

Cited by 110 publications

(232 citation statements)

References 37 publications

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“…By using 40-nm beads with identical carboxyl surface modifications at DH ϭ 9.6 nm, we fluorescently observed free-flow electrophoresis and corrected for electroosmosis, finding an effective surface charge density of eff ϭ 4,500 Ϯ 2,000 e/m 2 . This value is virtually independent from the used salt concentrations (28). With this inferred effective charge, Eq.…”

Section: Theoretical Approachmentioning

confidence: 72%

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Why molecules move along a temperature gradient

Duhr

Braun

2006

Proc. Natl. Acad. Sci. U.S.A.

892

987

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Molecules drift along temperature gradients, an effect called thermophoresis, the Soret effect, or thermodiffusion. In liquids, its theoretical foundation is the subject of a long-standing debate. By using an all-optical microfluidic fluorescence method, we present experimental results for DNA and polystyrene beads over a large range of particle sizes, salt concentrations, and temperatures. The data support a unifying theory based on solvation entropy. Stated in simple terms, the Soret coefficient is given by the negative solvation entropy, divided by kT. The theory predicts the thermodiffusion of polystyrene beads and DNA without any free parameters. We assume a local thermodynamic equilibrium of the solvent molecules around the molecule. This assumption is fulfilled for moderate temperature gradients below a fluctuation criterion. For both DNA and polystyrene beads, thermophoretic motion changes sign at lower temperatures. This thermophilicity toward lower temperatures is attributed to an increasing positive entropy of hydration, whereas the generally dominating thermophobicity is explained by the negative entropy of ionic shielding. The understanding of thermodiffusion sets the stage for detailed probing of solvation properties of colloids and biomolecules. For example, we successfully determine the effective charge of DNA and beads over a size range that is not accessible with electrophoresis.DNA ͉ fluorescence ͉ microfluidic ͉ Soret ͉ thermodiffusion T hermodiffusion has been known for a long time (1), but its theoretical explanation for molecules in liquids is still under debate. The search for a theoretical understanding is motivated by the fact that thermodiffusion in water might lead to powerful all-optical screening methods for biomolecules and colloids. Equally well, thermodiffusion handles and moves molecules alloptically and therefore can complement well established methods: for example, electrophoresis or optical tweezers. For the latter, forces of optical tweezers scale with particle volume and limit this method to particles of only Ͼ500 nm. Electrophoresis does not suffer from force limitations but is difficult to miniaturize because of electrochemical reactions at the electrodes.On the other hand, thermodiffusion allows the microscale manipulation of small particles and molecules. For example, 1,000-bp DNA can be patterned arbitrarily in bulk water (Fig. 1). The temperature pattern ''DNA,'' heated by 2 K, was written into a water film with an infrared laser scanning microscope. The concentration of 1,000-bp DNA was imaged by using a fluorescent DNA tag. In an overall cooled chamber at 3°C, DNA accumulates toward the heated letters ''DNA'' (negative Soret effect), whereas at room temperature DNA is thermophobic (positive Soret effect) as seen by the dark letters.In the past, the apparent complexity of thermodiffusion prevented a full theoretical description. As seen for DNA in Fig. 1, molecules characteristically deplete from regions with an increased temperature, but they can also show the inver...

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Section: Theoretical Approachmentioning

confidence: 72%

“…Both temperature derivatives give rise to a factor ␤ ϭ 1 Ϫ (T/)Ѩ/ѨT. The effective charge Q eff is largely temperature-insensitive, which was confirmed by electrophoresis independently (28). Such a dependence would be unexpected because the strongly adsorbed ions dominate the value of the effective charge.…”

Section: Theoretical Approachmentioning

confidence: 74%

Why molecules move along a temperature gradient

Duhr

Braun

2006

Proc. Natl. Acad. Sci. U.S.A.

892

987

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“…17 which demonstrates that overcharging is obtained with multivalent ions only above a certain threshold and only at intermediate salt concentrations. Overcharging of charged particles by multivalent counterions is important for a multitude of applications and can change the sign of the electrophoretic mobility [153,154] and induce macrophase separation [99,100]. Note that the present argument is analogous to the derivation in [150].…”

Section: Overcharging By Spherical Polyionsmentioning

confidence: 77%

Statics and dynamics of strongly charged soft matter

Boroudjerdi¹,

Kim²,

Naji³

et al. 2005

Physics Reports

343

523

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Soft matter materials, such as polymers, membranes, proteins, are often electrically charged. This makes them water soluble, which is of great importance in technological application and a prerequisite for biological function. We discuss a few static and dynamic systems that are dominated by charge effects. One class comprises complexation between oppositely charged objects, for example the adsorption of charged ions or charged polymers on oppositely charged substrates of different geometry. Here the main questions are whether adsorption occurs and what the effective charge of the resulting complex is. We explicitly discuss the adsorption behavior of polyelectrolytes on substrates of planar, cylindrical and spherical geometry with specific reference to DNA adsorption on supported charged lipid layers, DNA adsorption on oppositely charged cylindrical dendro-polymers, and DNA binding on globular histone proteins, respectively. In all these systems salt plays an important role, and some of the important features can already be obtained on the linear Debye-Hückel level. The second class comprises effective interactions between similarly charged objects. Here the main theme is to understand the experimental finding that similarly and highly charged bodies attract each other in the presence of multi-valent counterions. This is demonstrated using field-theoretic arguments as well as Monte-Carlo simulations for the case of two homogeneously charged bodies. Realistic surfaces, on the other hand, are corrugated and also exhibit modulated charge distributions, which is important for static properties such as the counterion-density distribution, but has even more pronounced consequences for dynamic properties such as the counterion mobility. More pronounced dynamic effects are obtained with highly condensed charged systems in strong electric fields. Likewise, an electrostatically collapsed highly charged polymer is unfolded and oriented in strong electric fields. All charged systems occur in water, and water by itself is not a very well understood material. At the end of this review, we give a very brief and incomplete account of the behavior of water at planar surfaces. The coupling between water structure and charge effects is largely unexplored, and a few directions for future research are sketched. On an even more nanoscopic level, we demonstrate using ab-initio methods that specific interactions between oppositely charged groups (which occur when their electron orbitals start to overlap) are important and cause ion-specific effects that have recently moved into the focus of interest.

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“…Nonetheless, as soon as ion-ion correlations get relevant, mean field theories such as the PB one [29] or its linearized version (as related above in 2.1) can not explain the experimentally observed relevant effect of overcharging [30,31].…”

Section: Overcharging and Thomson Problemmentioning

confidence: 99%

Electrostatics in soft matter

Messina

2009

J. Phys.: Condens. Matter

197

216

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Abstract. Recent progress in the understanding of the effect of electrostatics in soft matter is presented. A vast amount of materials contains ions ranging from the molecular scale (e.g., electrolyte) to the meso/macroscopic one (e.g., charged colloidal particles or polyelectrolytes). Their (micro)structure and physicochemical properties are especially dictated by the famous and redoubtable long-ranged Coulomb interaction. In particular theoretical and simulational aspects, including the experimental motivations, will be discussed.

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Charging and Aggregation of Latex Particles by Oppositely Charged Dendrimers

Cited by 110 publications

References 37 publications

Why molecules move along a temperature gradient

Why molecules move along a temperature gradient

Statics and dynamics of strongly charged soft matter

Electrostatics in soft matter

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