Brownian Diffusion of Individual Janus Nanoparticles at Water/Oil Interfaces

Abstract

Janus nanoparticles could exhibit a higher interfacial activity and adsorb stronger to fluid interfaces than homogeneous nanoparticles of similar sizes. However, little is known about the interfacial diffusion of Janus nanoparticles and how it compares to that of homogeneous ones. Here, we employed fluorescence correlation spectroscopy to study the lateral diffusion of ligand-grafted Janus nanoparticles adsorbed at water/oil interfaces. We found that the diffusion was significantly slower than that of homogeneous nanoparticles. We carried out dissipative particle dynamic simulations to study the mechanism of interfacial slowdown. Good agreement between experimental and simulation results has been obtained only provided that the flexibility of ligands grafted on the nanoparticle surface was taken into account. The polymeric ligands were deformed and oriented at an interface so that the effective radius of Janus nanoparticles is larger than the nominal one obtained by measuring the diffusion in bulk solution. These findings highlight further the critical importance of the ligands grafted on Janus nanoparticles for applications involving nanoparticle adsorption at an interface, such as oil recovery or two-dimensional self-assembly.

Tracking of Nanoparticle Diffusion at a Liquid–Liquid Interface Adsorbed by Nonionic Surfactants

“…Moreover, the thermally activated fluctuations of the interface could cause the contact line deformation of microparticles, providing additional viscous drag to slow down the diffusion. , According to the Young–Laplace equation, the deformation should be vanishingly small when the particle size is ∼10 nm . However, the diffusion of individual homogeneous and Janus particles at a pristine flat or curved interface was still slower than the predictions of the modified Stokes–Einstein relation and hydrodynamic theories. − Simulations showed that the deformation and orientation of ligands grafted on the nanoparticle surface result in an effective radius larger than the nominal one, leading to apparent slowing diffusion. − While these studies promoted the conventional wisdom, a detailed picture of nanoparticle interfacial diffusion at a surfactant-laden interface remains elusive but important and relevant to the surfactant-assistant Pickering emulsion.…”

Reducing the Solvent Quality Gives Rise to the Outward Migration of a Star Polymer in Poiseuille Flow

“…For example, the star polymer displayed a tumbling motion when f is small, consistent with the linear chain. − Interestingly, the tank-treading motion was observed when further increasing the value of f , , which is a unique property of the star polymer. The advances in microfluidic technology , and the molecular fluorescence technology − enable the experimental observation and manipulation of molecules, polymers, and colloidal particles migration in microfluidic tubes. The center-of-mass distribution of the polymer was found to distribute nonuniformly along with Poiseuille flow in a microfluidic tube; the shear stress and wall hydrodynamic interaction can induce transverse migration along the direction perpendicular to the flow. ,, The linear polymer is observed to move toward the tube center in which the center-of-mass distribution appears a crater-shaped peak at the center. ,− Interestingly, the transverse migration of star polymers showed similar enrichment around the tube centerline.…”

Aptamer conjugated polydopamine-coated gold nanoparticles as a dual-action nanoplatform targeting β-amyloid peptide for Alzheimer's disease therapy

“…Compared with other inhibitors, nanomaterials have attracted extensive attention due to their good physicochemical properties, such as small size, low density, high surface/volume ratio, easy functionalization and the possibility of crossing the blood-brain barrier. [21][22][23] In the past decade, nanomaterials have been reported as potential therapeutic agents to prevent and treat amyloidrelated diseases. [24][25][26][27] Various nanomaterials such as graphene, quantum dots, carbon nanotubes, and fullerenes were prepared and have been demonstrated to effectively inhibit amyloid fibrillation.…”