Anna Kozina

National Autonomous University of Mexico | UNAM · Department of Physical Chemistry of the Institute of Chemistry

We study the mixtures of amphiphilic Janus and homogeneous hydrophobic particles trapped at an air/water interface. In contrast to an expected monolayer formation, bilayers of colloidal particles are produced. Despite their strong interfacial adsorption, Janus particles form the upper layer. They are not placed on top of the other particles but rat...

Hypothesis Colloids at fluid interfaces organize according to inter-particle interactions. The main contributions to an effective interaction potential are expected to be electrostatic dipole-dipole repulsion and capillary attraction due to fluid interface deformation. When these interactions are weak, a secondary minimum in the particle pair inter...

Hypothesis The anisotropic nature of colloidal particles results in orientation-dependent interactions that organize the particles into peculiar structures different from those formed by isotropic colloids. Particles with a hydrophilic hemisphere are expected to assemble in hydrophobic solvents due to the contribution of hydrophobic interactions as...

Colloidal suspensions of monodisperse spherical particles have been extensively studied since one of the main advantages of these systems is their similarity to atomic ones. This property has been used successfully in basic science to understand the equilibrium and non-equilibrium behavior of model colloids and to correlate them with their atomic c...

We report the systematic variation of the citrate-to-platinum ratio during the colloidal synthesis of platinum nanoparticles and its correlation with the resulting particle size and aggregative stability. Our study reveals that higher citrate concentrations lead to smaller particle and aggregate sizes. This decrease is the result of an interplay be...

Aggregation pathway of amyloid-β (25-35) in water affects the oxidative stress in the brain observed after administration of aggregated peptide in animals in vivo. Our studies on peptide aggregation ex situ prior to injection suggest that from the onset of peptide incubation in aqueous media, all samples exhibit the formation of fibril-like aggrega...

We perform the analysis of predictions of a classical density functional theory for associating fluids with different association strength concerned with wetting of solid surfaces. The four associating sites water-like models with non-associative square-well attraction parametrized by Clark et al. [Mol. Phys., 2006, 104, 3561] are considered. The f...

The optimization of fabrication conditions for colloidal micron-sized oblates obtained by the deformation of an oil-in-hydrogel emulsion is reported. The influence of the type of emulsion stabilizer, ultrasonication parameters, and emulsion and gel mixing conditions was explored. The best conditions with which to obtain more uniform particles were...

Rifampicin is one of the most commonly used antibiotics for treating tuberculosis, but shows low bioavailability and requires long-term administration, and hence its use may result in severe side effects. Encapsulation of rifampicin in polymeric reservoirs allows it to be administered locally and improves its pharmacological action. High rifampicin...

The use of ultrasound to generate mini-emulsions (50 nm to 1 μm in diameter) and nanoemulsions (mean droplet diameter < 200 nm) is of great relevance in drug delivery, particle synthesis and cosmetic and food industries. Therefore, it is desirable to develop new strategies to obtain new formulations faster and with less reagent consumption. Here, w...

Understanding the physical and chemical mechanisms underlying the interactions between giant micelles and photoswitchable molecules is essential because it is not evident why some photoswitchable chromophores with apparently good potential to modify micellar systems' macroscopic properties have a poor performance on UV-irradiation. We report a mech...

Citrate-stabilized palladium nanoparticles were synthesized and supported on silica spheres. Conditions affecting particle size, stability and adsorption on silica particles are explored. The catalytic activity of nanoparticles in suspension as well as on silica support was evaluated in the Sonogashira reaction for the synthesis of 1,4-bis[(trimeth...

Metabolic syndrome (MS) results from excessive consumption of high‐calorie foods and sedentary lifestyles. Clinically, insulin resistance, abdominal obesity, hyperglycemia, dyslipidemia, and hypertension are observed. MS has been considered a risk factor in the development of dementia. In the brain, a metabolically impaired environment generates ox...

Chromophores susceptible to light-induced trans-cis isomerization embedded in cylindrical micelles can modify micelles and their light-responsive performance. A small chromophore (4-(phenylazo) benzoate ion) is embedded in cylindrical micelles made of CetylTrimethylAmmonium Bromide (CTAB) and Sodium Salicylate (NaSal) in water. The microstructure i...

We probe the mechanics of two different viscoelastic complex systems at a microscopic length scale. The first is made of cross-linked polymer gel, and the second consists of a polysaccharide solution, in which spherical birefringent colloidal tracers have been embedded. This method is widely known as optical microrheology. In the present work we fo...

The aggregation behavior and its influence on the intramolecular motion of three highly-conjugated solid-state molecular rotors 2-4 with alkyl groups was investigated by a combination of fluorescence spectroscopy, Transmission Electron Microscopy (TEM), X-Ray Powder Diffraction (XRPD) and variable temperature solid-state 2H Nuclear Magnetic Resonan...

Xanthan is an extracellular polysaccharide of polyanionic nature widely used in industrial processes as flow modifier. Its characterization in dilute solutions is complicated by the strong tendency to aggregation. We explore the possibility to obtain dilute xanthan solutions without aggregates. We applied some steps of the sample preparation proced...

Correction for 'Polymer-enforced crystallization of a eutectic binary hard sphere mixture' by Anna Kozina et al., Soft Matter, 2012, 8, 627-630.

Assemblies of monolayers made of colloidal silica particles trapped at the air/water interface are prepared to have an increasing capillary interaction. Fine-tuning of the strength of interaction and its orientational specificity is achieved through isotropic or anisotropic colloid surface chemical modification or by adjusting the subphase surface...

In this work the crystallization kinetics of colloidal binary mixtures with attractive interaction potential (Asakura-Oosawa) has been addressed. Parameters such as fraction of crystals, linear crystal dimension and crystal packing have been quantified in order to understand how the crystal formation is driven in terms of the depth of the attractiv...

A new inorganic material was used to produce hydrogen in situ by contact with water for reduction of unsaturated hydrocarbons. Phenylacetylene reduction into styrene and ethylbenzene was chosen as a model reduction reaction. We show that a fine control over the reaction yield and selectivity can be obtained by controlling the hydrogen release and s...

The thermal stability of antiepileptic drug phenytoin was investigated on its encapsulation in titania matrix. It was shown that the drug is stable up to 150°C, even though phenytoin melting point was previously reported to be much higher. The mechanism of phenytoin decomposition is suggested and confirmed by the experiment on heating to higher tem...

Parkinson's disease (PD) is a progressive, neurodegenerative disorder of the central nervous system. The primary symptoms of PD result from greatly reduced activity of dopamine-secreting cells due to cell death in the pars compacta region of the substantia nigra. The loss of dopamine as a result of death of dopamine neurons accounts for most of the...

We present a study of the evolution of structural properties and dynamical behaviour of colloidal complex systems, as seen by two techniques working on two different length scales. Our system consists of a binary mixture at high volume fraction of internally crosslinked polystyrene microgels dispersed in an organic solvent. In this colloidal binary...

Two types of titania matrix were investigated as a support for the prolonged drug delivery of the antidepressant fluoxetine. Sample MT was synthesized using carbon template and consisted of titania microtubes on which then fluoxetine was adsorbed. Sample SG was synthesized by the sol-gel method when the drug was added during the reaction. The morph...

The sol-gel method was used to synthesize inorganic reservoirs with encapsulated antiepileptic drug phenytoin. The drug release profile was shown to depend on the morphology and surface properties of the matrix. A parameter of the synthesis such as water/alkoxide ratio r(w) was varied in order to investigate its influence on the matrix properties a...

We carried out elaborate studies on phenytoin encapsulation within the titania matrix. We changed the parameters of the sol-gel synthesis to play with the drug-matrix interactions and titania morphology to design the release kinetics. First, we showed that hydroxyl groups of titania matrix are the main interaction sites with hydantoin ring of pheny...

We prepared a buoyancy matched binary mixture of polydisperse polystyrene microgel spheres of size ratio 0.785 and at a volume fraction of 0.567 just below the kinetic glass transition. In line with theoretical expectations, a eutectic phase behavior was observed, but only a minor fraction of the samples crystallized at all. By adding a short non-a...

Nanostructured titania reservoirs were synthesized by the sol−gel method. An antiepileptic drug phenytoin was encapsulated for the targeted drug delivery. NMR studies confirmed that the drug does not undergo substantial modifications during the sol−gel process. The water/alkoxide ratio rw was varied from 2 to 24 to evaluate the role of hydrolysis d...