Competitive adsorption of sodium naphthenates and naturally occurring species at water-in-crude oil emulsion droplet surfaces

Evaluating the hydrophilic–lipophilic nature of asphaltenic oils and naphthenic amphiphiles using microemulsion models

“…It is well established that reducing the solubility of asphaltenes within the oil phase results in the formation of aggregates that are surface-active compared to their monomeric counterparts [5][6][7][8][9][10]. This surfaceactivity has been linked to the formation of asphaltene skins at the oil-water interface that contribute to the stability of emulsions [11,12].…”

Directing semiconductor nanorod assembly into 1D or 2D supercrystals by altering the surface charge

“…When ζ is higher, the Coulomb repulsion maintains the dispersion such that no aggregation occurs. There will be, however, a critical interdipole distance at which the thermal energy is sufficient to 20 overcome the repulsive barrier, roughly 23 and 47 nm for NR with ζ = 20 mV and 25 mV, respectively. Once within the attractive potential, the dipoles can align and assemble.…”

“…[2] The rods will act to minimize surface tension by orienting with their long axis parallel to the droplet surface. The energy potential of the NR at the droplet surface 45 is calculated by a modified equation following He et al, [17] -1 for the CdSetoluene, the CdSe-air and the toluene-air interfaces, respectively; [18][19][20] this gives a potential of 450 k B T, well in excess of the electrostatic potentials involved. This removes 55 the possibility of any electrostatic forces pushing the rods back into the volume.…”

“…[7,21] In both cases the equilibrium of dispersion and aggregation was deliberately modulated; 2D monolayers and not 3D supercrystals were formed from assembling NRs in the bulk. 20 In summary, correlating both the influence of inter-particle forces (charge and dipole) and the available dimensions (liquid-air 2D, bulk 3D) creates intrinsically tuneable parameters to control NR assembly. Charge can be modified relatively easily by ligand exchange and monitored by zeta 25 potential allowing a general route to predict rod organisation.…”

“…[1] In the case of dispersions of mono-disperse, 15 spherical nanocrystals, the inter-particle interactions can be tuned to form highly ordered supercrystals in the solid state when the correct balance between nanoparticle diffusion rate, solvent volatility and seeding rate is struck. [2] Of recent interest are semiconductor nanorods (NRs) where assembly 20 allows individual properties such as single electron charging, linearly polarised emission and absorption to be collectively tuned and upscaled for application in electronics, photonics and solar energy conversion. [3][4] The long axis of NRs, however, complicates assembly from solution.…”