Publications by authors named "Ramona Mhanna"

Magnetic colloidal chains are a microrobotic system with promising applications due to their versatility, biocompatibility, and ease of manipulation under magnetic fields. Their synthesis involves kinetic pathways that control chain quality, length, and flexibility, a process performed by first aligning superparamagnetic particles under a one-dimensional magnetic field and then chemically linking them using a four-armed maleimide-functionalized poly(ethylene glycol). Here, we systematically vary the concentration of the poly(ethylene glycol) linkers, the reaction temperature, and the magnetic field strength to study their impact on the physical properties of synthesized chains, including the chain length distribution, reaction temperature, and bending modulus.

View Article and Find Full Text PDF

Binary liquid mixtures can exhibit nanosegregation, albeit being fully miscible and homogeneous at the macroscopic scale. This tendency can be amplified by geometrical nanoconfinement, leading to remarkable properties. This work investigates the molecular dynamics of -butanol (TBA)-toluene (TOL) mixtures confined in silica nanochannels by quasielastic neutron scattering and molecular dynamics simulation.

View Article and Find Full Text PDF

Small angle X-ray scattering with in situ shear was employed to study the assembly and ordering of dispersions of gold nanorods within wormlike micelle solutions formed by the surfactant cetylpyridinium chloride (CPyCl) and counter-ion sodium salicylate (NaSal). Above a threshold CPyCl concentration but below the isotropic-to-nematic transition of the micelles, the nanorods self-assembled under quiescent conditions into isotropically oriented domains with hexagonal order. Under steady shear at rates between 0.

View Article and Find Full Text PDF

The confinement of liquid mixtures in porous channels provides new insight into fluid ordering at the nanoscale. In this study, we address a phenomenon of microphase separation, which appears as a novel fascinating confinement effect for fully miscible binary liquids. We investigate the structure of tert-butanol-toluene mixtures confined in the straight and mono-dispersed cylindrical nanochannels of SBA-15 mesoporous silicates (D = 8.

View Article and Find Full Text PDF

MCM-41 nanoporous silicas show a very high selectivity for monoalcohols over aprotic molecules during adsorption of a binary mixture in the gas phase. We present here an original use of gravimetric vapour sorption isotherms to characterize the role played by the alcohol hydrogen-bonding network in the adsorption process. Beyond simple selectivity, vapour sorption isotherms measured for various compositions help to completely unravel at the molecular level the step by step adsorption mechanism of the binary system in the nanoporous solid, from the first monolayers to the complete liquid condensation.

View Article and Find Full Text PDF

Synopsis of recent research by authors named "Ramona Mhanna"

  • - Ramona Mhanna's research focuses on the manipulation and understanding of nanoscale materials and their interactions, particularly in the context of magnetic colloides and confined liquids.
  • - Key findings demonstrate the impact of controlling synthesis parameters on the properties of magnetic colloidal chains, as well as insights into the dynamics of binary liquid mixtures when confined in nanopores, which exhibit unconventional behavior such as nanosegregation and microphase separation.
  • - Her studies utilize advanced techniques like small angle X-ray scattering, gravimetric vapor sorption, and molecular dynamics simulations to investigate material behaviors and phase transitions at the nanoscale, contributing to applications in areas such as microrobotics and material science.