Bound pairs: Direct evidence for long-range attraction between like-charged colloids

Tata, B. V. R.; Mohanty, Priti S.; Valsakumar, M. C.

doi:10.1016/j.ssc.2008.06.026

Cited by 50 publications

(69 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Before we discuss the origin of split second peak, we would like to mention here that the split peak is genuine and does not arise due to finite thickness of the optical slice. By performing Monte Carlo simulations Tata et al 33 showed that the in-plane g͑r͒ calculated for a slice with thickness close to the optical slice is the same as that of 3D g͑r͒ of a bulk suspension. Hence, the split peak observed in 3D g͑r͒ is genuine and free from projection errors and imaging artifacts.…”

Section: Resultsmentioning

confidence: 98%

Random hcp and fcc structures in thermoresponsive microgel crystals

Brijitta

Tata

Joshi

et al. 2009

The Journal of Chemical Physics

View full text Add to dashboard Cite

Monodisperse thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) microgel particles having a diameter of 520 nm were synthesized by free-radical precipitation polymerization and centrifuged to obtain a concentrated suspension. The centrifuged mother suspension was made to self-order into a crystalline state by repeated annealing beyond the volume phase transition (VPT) of the particles. We report here the three-dimensional (3D) real space structure, determined using a confocal laser scanning microscope, of PNIPAM microgel crystal samples prepared by two different recrystallized routes: (1) solidifying a shear melted colloidal liquid (referred as as-prepared sample) and (2) slow cooling of a colloidal liquid (referred as recrystallized sample). We have recorded images of several regions of the crystal with each region containing 15 horizontal crystal planes for determining the in-plane [two-dimensional (2D)] and 3D pair-correlation functions. The 2D pair-correlation function g(r) revealed hexagonal long-range order of particles in the layers with a lattice constant of 620 nm. The analysis of stacking sequence of layers recorded on as-prepared sample has revealed the existence of stacking disorder with an average stacking probability alpha approximately 0.42. This value of alpha together with the analysis of 3D pair-correlation function determined from particle positions revealed the structure of microgel crystals in the as-prepared sample to be random hexagonal close packing. We report the first observation of a split second peak in the 3D g(r) of the microgel crystals obtained from a shear melted liquid. Upon melting the sample above VPT and recrystallizing it the split second peak disappeared and the crystals are found to have a face centered cubic (fcc) structure with alpha approximately 0.95. From simulations, the split second peak is shown to arise from the displacement of some of the B-planes from the ideal hcp positions. The present results are discussed in light of those reported for charged and hard sphere colloidal crystals and plausible reasons for observing two different structures are also explained.

show abstract

Section: Resultsmentioning

confidence: 98%

Random hcp and fcc structures in thermoresponsive microgel crystals

Brijitta

Tata

Joshi

et al. 2009

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…For example, in the recent experiment on highly deionized water by Tata et al [11], ℓ DB ≈ 500nm, λ Bj ≈ 0.7nm, andT ≈ 1/57; the system is therefore well in the low temperature limit. The problem of dilute electrolytes is therefore simple from the field theory point of view.…”

Section: Appendix B: Some General Results At Saddle Point Levelmentioning

confidence: 93%

Poisson-Boltzmann theory for two parallel uniformly charged plates

Xing

2011

Phys. Rev. E

View full text Add to dashboard Cite

We solve the nonlinear Poisson-Boltzmann equation for two parallel and likely charged plates both inside a symmetric elecrolyte, and inside a 2 : 1 asymmetric electrolyte, in terms of Weierstrass elliptic functions. From these solutions we derive the functional relation between the surface charge density, the plate separation, and the pressure between plates. For the one plate problem, we obtain exact expressions for the electrostatic potential and for the renormalized surface charge density, both in symmetric and in asymmetric electrolytes. For the two plate problems, we obtain new exact asymptotic results in various regimes.

show abstract

“…In that work, the authors take into account all the proposed artefacts to date for their measurements, demonstrating that charged glass surfaces really induce attractions between charged colloidal spheres. Moreover, Tata et al (2008) claim that their observations using confocal laser scanning of millions of charged colloidal particles establish the existence of an attractive behaviour in the electrostatic potential. Moreover, other possible electrostatic variations in these systems may appear for several reasons.…”

Section: Anomalous Effectsmentioning

confidence: 99%