Laser Induced Temperature Perturbation on Ultramicroelectrodes: Unsupported Solutions in Nonaqueous Methanol

Temperature dependence studies of electrochemical parameters provide insight into electron transfer processes. In cases where adding excess electrolyte experimental causes complications colloidal systems, organic or biological samples it is preferable to deal with the high resistivity of the medium. We validate the use of unsupported and weakly supported solutions in thermoelectrochemical experiments. The temperature dependence of the diffusion coefficient allows calibration of the steady-state current to measure changes when a continuous wave (CW) ultraviolet laser, λ=325 nm, illuminates an ultramicroelectrode (UME) from the front. Calibrating the steady-state current ratios before and after heating with a thermostatic bath allows temperature measurements within an accuracy of 0.6 K. The solutions are without supporting electrolytes in methanol, a volatile solvent, and we use a model that accurately describes the viscosity and temperature dependence of the solvent. We calculated the temperature and derived an equation to estimate the temperature measurement error. A numeric method yields satisfactory results, considering the changes for both diffusion coefficients and viscosity explicitly, and predict the thermostatic temperature bath, agreeing with the theoretical model's error. In unsupported solutions, the ferrocene diffusion coefficient and the iodide apparent diffusion coefficient follow the expected increase with temperature. Under CW laser illumination ΔT=4±1 K.

Particle anisotropy tunes emergent behavior in active colloidal systems

Studies of active particle systems have demonstrated that particle anisotropy can impact the collective behavior of a system. However, systems studied to date have served as one-off demonstrations of concept,...

Spectral Properties of Foams and Emulsions

The optical and spectral properties of foams and emulsions provide information about their micro-/nanostructures, chemical and time stability and molecular data of their components. Foams and emulsions are collections of different kinds of bubbles or drops with particular properties. A summary of various surfactant and emulsifier types is performed here, as well as an overview of methods for producing foams and emulsions. Absorption, reflectance, and vibrational spectroscopy (Fourier Transform Infrared spectroscopy-FTIR, Raman spectroscopy) studies are detailed in connection with the spectral characterization techniques of colloidal systems. Diffusing Wave Spectroscopy (DWS) data for foams and emulsions are likewise introduced. The utility of spectroscopic approaches has grown as processing power and analysis capabilities have improved. In addition, lasers offer advantages due to the specific properties of the emitted beams which allow focusing on very small volumes and enable accurate, fast, and high spatial resolution sample characterization. Emulsions and foams provide exceptional sensitive bases for measuring low concentrations of molecules down to the level of traces using spectroscopy techniques, thus opening new horizons in microfluidics.

Polyphenols as Antioxidants for Extending Food Shelf-Life and in the Prevention of Health Diseases: Encapsulation and Interfacial Phenomena

Toxicity caused by the exposure to human-made chemicals and environmental conditions has become a major health concern because they may significantly increase the formation of reactive oxygen species (ROS), negatively affecting the endogenous antioxidant defense. Living systems have evolved complex antioxidant mechanisms to protect cells from oxidative conditions. Although oxidative stress contributes to various pathologies, the intake of molecules such as polyphenols, obtained from natural sources, may limit their effects because of their antioxidant and antimicrobial properties against lipid peroxidation and against a broad range of foodborne pathogens. Ingestion of polyphenol-rich foods, such as fruits and vegetables, help to reduce the harmful effects of ROS, but the use of supramolecular and nanomaterials as delivery systems has emerged as an efficient method to improve their pharmacological and therapeutic effects. Suitable exogenous polyphenolic antioxidants should be readily absorbed and delivered to sites where pathological oxidative damage may take place, for instance, intracellular locations. Many potential antioxidants have a poor bioavailability, but they can be encapsulated to improve their ideal solubility and permeability profile. Development of effective antioxidant strategies requires the creation of new nanoscale drug delivery systems to significantly reduce oxidative stress. In this review we provide an overview of the oxidative stress process, highlight some properties of ROS, and discuss the role of natural polyphenols as bioactives in controlling the overproduction of ROS and bacterial and fungal growth, paying special attention to their encapsulation in suitable delivery systems and to their location in colloidal systems where interfaces play a crucial role.

Stable aqueous dispersions of bare and double layer functionalized superparamagnetic iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have attracted the particular interest of scientists from various disciplines since their obtaining to the present day. The physicochemical and pharmacokinetic properties of SPIONs-containing magnetic nanofluids, and their applicability in biomedicine, largely depend on the stability of the colloidal system, particle size, size distribution, net magnetic moment, phase composition, and type and properties of stabilizers. Also, in some cases, when using magnetic nanoparticles for biomedical purposes, it is necessary that the stabilizing ligands of nanoparticles should not significantly change the magnetic properties. From this point of view, the preparation of stable colloidal systems containing bare iron oxide nanoparticles (BIONs) in water at physiological pH attracts particular attention and becomes increasingly popular in scientific circles. This study is focused on the development of the synthesis of aqueous suspensions of SPIONs stabilized with various organic molecules (oleic acid [OA] and poly(ethylene glycol) monooleate - with molecular weights 460 and 860) using a modified controlled chemical coprecipitation reaction, as well as stable nanofluids containing BIONs in an aqueous medium at neutral pH (near-physiological). The obtained samples were characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy, small-angle x-ray scattering (SAXS), dynamic light scattering (DLS), electrophoretic light scattering (ELS), and Vibrating Sample Magnetometry.

Colloidal Stability of Silica-Modified Magnetite Nanoparticles: Comparison of Various Dispersion Techniques

The production of stable and homogeneous batches during nanoparticle fabrication is challenging. Surface charging, as a stability determinant, was estimated for 3-aminopropyltriethoxysilane (APTES) coated pre-formed magnetite nanoparticles (MNPs). An important consideration for preparing stable and homogenous MNPs colloidal systems is the dispersion stage of pre-formed samples, which makes it feasible to increase the MNP reactive binding sites, to enhance functionality. The results gave evidence that the samples that had undergone stirring had a higher loading capacity towards polyanions, in terms of filler content, compared to the sonicated ones. These later results were likely due to the harsh effects of sonication (extremely high temperature and pressure in the cavities formed at the interfaces), which induced the destruction of the MNPs.

Modeling of colloidal systems in technological processes

The article describes the main methods of mathematical modeling of industrial free-dispersed systems. The method of constructing the regression equation by the method of linear and nonlinear installation of coefficients is proposed. The fundamentals of tensor and harmonic approaches to the analysis of disperse systems are considered, which allow optimizing the equations of material and energy balance in the conditions of industrial operation of dispersions.

Digital sovereignty of Russia based on the element base of topological nanostructures on a solid surface induced by laser radiation

The purpose of this work is to develop breakthrough technologies and technology transfer in the field of topological photonics, nanoelectronics and new materials with controlled functional and structural characteristics using a unique line of the Vladimir State University (VlSU) equipment (within the framework of the corresponding created structures - Centre of collective use, Center for Structural Materials Science and Breakthrough Engineering Physical Technologies, Center for Engineering Competencies, etc.) for carrying out work in the direction of high-tech industrial sectors. The report deals with the following issues on this topic: basic physical and scientific and technical principles, methods for measuring laser-induced structures on the surface of materials in real time, obtaining surface nanostructures on solid materials by deposition from colloidal systems using a two-stage scheme with laser ablation, modeling macroscopic quantum states in the functional properties of laser-induced 4d-topological nanoclusters in thin films on a solid surface and experimental demonstration of the work of real prototypes.