Micellization of Cetyltrimethylammonium Bromide (CTAB) in Mixed Solvents and in the Presence of Potassium Bromide

Physico-chemical properties of the association of cetyltrimethylammonium bromide and bovine serum albumin mixture in aqueous-organic mixed solvents

Herein, we have investigated the association behavior of bovine serum albumin (BSA) and cetyltrimethylammonium bromide (CTAB) using the conductivity method in H₂O and H₂O + organic mixed solvents at different temperatures. The association phenomenon was detected from the deviation of the conductivity changes with enhancing the surfactant concentration and changes of numerous physico-chemical properties, such as CMC, α, β and thermodynamic variables (∆G⁰_m, ∆H⁰_m and ∆S⁰_m). The values of CMC for the CTAB + BSA system in 10 % (v/v) solvents follow the trend: CMC_water < CMC_water+DMSO < CMC_water+AN < CMC_water+DX < CMC_water+DMF. The interaction of BSA with CTAB is notably influenced due to a change of temperature and extent of hydration of BSA and surfactant. The obtained values of -∆G⁰_m manifest that the association of BSA and CTAB mixture is a spontaneous process, while the values of -∆G⁰_m in presence of 10 % (v/v) aq. organic solvents come out in the given sequence: -∆G_m^o (H₂O + DMSO) > ∆G_m^o (H₂O + DMF) > -∆G_m^o (H₂O + DX) > -∆G_m^o (H₂O + AN). The H-bonding, ion-dipole, along with the hydrophobic interactions, are believed to be the binding interactions between BSA and CTAB in the study media.

Ligand-Dependent Coalescence Behaviors of Gold Nanoparticles Studied by Multichamber Graphene Liquid Cell Transmission Electron Microscopy

The formation mechanism of colloidal nanoparticles is complex because significant nonclassical pathways coexist with the conventional nucleation and growth processes. Particularly, the coalescence of the growing clusters determines the final morphology and crystallinity of the synthesized nanoparticles. However, the experimental investigation of the coalescence mechanism is a challenge because the process is highly kinetic and correlates with surface ligands that dynamically modify the surface energy and the interparticle interactions of nanoparticles. Here, we employ quantitative in situ TEM with multichamber graphene liquid cell to observe the coalescence processes occurring in the synthesis of gold nanoparticles in different ligand systems, thus affording us an insight into their ligand-dependent coalescence kinetics. The analyses of numerous liquid-phase TEM trajectories of the coalescence and MD simulations of the ligand shells demonstrate that enhanced ligand mobility, employing a heterogeneous ligand mixture, results in the rapid nanoparticle pairing approach and a fast post-merging structural relaxation.