Translational and rotational diffusion coefficients in nanofluids from polarized dynamic light scattering

Nanofluids representing nanometer-sized solid particles dispersed in liquids are of interest in many fields of process and energy engineering, e.g., heat transfer, catalysis, and the design of functionalized materials [1]. The physical, chemical, optical, and electronic properties of nanofluids are strongly driven by the size, shape, surface potential, and concentration of the nanoparticles. For the analysis of diffusive processes in nanofluids allowing access to, e.g., particle size and its distribution, dynamic light scattering (DLS) is the state-of-the-art technique. It is based on the analysis of microscopic fluctuations originating from the random thermal movement of particles in the continuous liquid phase at macroscopic thermodynamic equilibrium. For anisotropic particles or particle aggregates, besides translational diffusion also rotational diffusion occurs. To obtain the sum of the orientation-averaged translational (DT) and rotational (DR) diffusivities by depolarized DLS [2], a homodyne detection scheme is usually applied which can hardly be fulfilled in the experimental realization. Furthermore, the experiments are restricted to limited ranges for temperature, particle concentration, and viscosity

Особенности построения дискретных моделей тел с кинематически генерируемыми поверхностями

В роботі досліджується питання створення керованих геометричних і скінченно-елементних моделей тіл з поверхнями складної форми. Вивчені можливості їх застосування в єдиному циклі синтезу геометрії тіл, обмежених кінетично генерованими поверхнями, та аналізу їх напружено-деформованого стану.The paper concerns a question of creating controlled geometrical and finite-element models of bodies with complicated boundary. The ways of their application in the united cycle of bodies` geometry synthesis and analysis of their stain-stress state are studied for the case when the solids are bounded by kinematically generated surfaces

Advantages and Limitations of Integrated Flagellin Adjuvants for HIV-Based Nanoparticle B-Cell Vaccines

The great advantage of virus-like particle (VLP) nano-vaccines is their structural identity to wild-type viruses, ensuring that antigen-specific B-cells encounter viral proteins in their natural conformation. “Wild-type” viral nanoparticles can be further genetically or biochemically functionalized with biomolecules (antigens and adjuvants). Flagellin is a potent inducer of innate immunity and it has demonstrated adjuvant effectiveness due to its affinity for toll-like receptor 5 (TLR5). In contrast to most TLR ligands, flagellin is a protein and can induce an immune response against itself. To avoid side-effects, we incorporated a less inflammatory and less immunogenic form of flagellin as an adjuvant into HIV-based nanoparticle B-cell-targeting vaccines that display either the HIV-1 envelope protein (Env) or a model antigen, hen egg lysozyme (HEL). While flagellin significantly enhanced HEL-specific IgG responses, anti-Env antibody responses were suppressed. We demonstrated that flagellin did not activate B-cells directly in vitro, but might compete for CD4+ T-cell help in vivo. Therefore, we hypothesize that in the context of VLP-based B-cell nano-vaccines, flagellin serves as an antigen itself and may outcompete a less immunogenic antigen with its antibody response. In contrast, in combination with a strong immunogen, the adjuvant activity of flagellin may dominate over its immunogenicity

Photobleaching and stabilization of carbon nanodots produced by solvothermal synthesis

In this work we performed a detailed investigation of the photostability of bottom-up produced carbon nanodots (CDs) prepared from citric acid and urea by solvothermal synthesis. Analytical ultracentrifugation (AUC) reveals that the CDs have a hydrodynamic diameter of <1 nm and a very narrow size distribution. In the community it is widely assumed that CDs are photo-stable. In contrast, we found that CDs exposed to UV-irradiation exhibit noteworthy fluorescence degeneration compared to freshly prepared CDs or CDs stored in the dark, indicating that fluorescence bleaching is caused by a photochemical process. We found that fluorescence intensity decay due to exposure to UV-irradiation is accelerated in the presence of oxygen and identified the surface status of CDs as the decisive factor of fluorescence bleaching of CDs. Based on a discussion on the underlying mechanisms we show how to avoid photobleaching of CDs

Combined continuous nanoparticle synthesis with chromatographic size classification

&lt;p&gt;In this paper, we report a combination of the continuous flow synthesis of gold nanoparticles (AuNPs) with subsequent purification and narrowing of the particle size distribution (PSD) by size-exclusion chromatography (SEC) by adapting the flow rates of synthesis and classification. First, we show scalability of chromatographic classification with respect to column dimension and the absence of irreversible nanoparticle adhesion on the column material. Two different syntheses lead to a large and widely distributed and a small and narrowly distributed AuNP dispersion, which are classified by a semipreparative column. The PSDs of individual fractions are characterized by analytical SEC. The broadly distributed AuNP dispersion was classified into three fractions with distinct PSDs. For the narrowly distributed AuNPs, the separation is almost independent of the mobile phase flow rate: coarse and fine fractions with almost identical PSDs and separation efficiency curves are observed irrespective of the flow rate. Even NP samples with narrow PSDs can be classified into multiple fractions with tailored PSDs while simultaneously removing dissolved impurities from the dispersion. With our study, we demonstrate the potential of a direct combination of continuous NP synthesis with chromatographic classification for the optimization of final PSDs and the simultaneous purification of nanoparticulate dispersions.&lt;/p&gt;&lt;p&gt;Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)– Project-ID 416229255 – SFB 1411&lt;/p&gt

Translational and rotational diffusion coefficients in nanofluids from polarized dynamic light scattering

Nanofluids representing nanometer-sized solid particles dispersed in liquids are of interest in many fields of process and energy engineering, e.g., heat transfer, catalysis, and the design of functionalized materials [1]. The physical, chemical, optical, and electronic properties of nanofluids are strongly driven by the size, shape, surface potential, and concentration of the nanoparticles. For the analysis of diffusive processes in nanofluids allowing access to, e.g., particle size and its distribution, dynamic light scattering (DLS) is the state-of-the-art technique. It is based on the analysis of microscopic fluctuations originating from the random thermal movement of particles in the continuous liquid phase at macroscopic thermodynamic equilibrium. For anisotropic particles or particle aggregates, besides translational diffusion also rotational diffusion occurs. To obtain the sum of the orientation-averaged translational (DT) and rotational (DR) diffusivities by depolarized DLS [2], a homodyne detection scheme is usually applied which can hardly be fulfilled in the experimental realization. Furthermore, the experiments are restricted to limited ranges for temperature, particle concentration, and viscosity

Translational and rotational diffusion coefficients in nanofluids from polarized dynamic light scattering

Nanofluids representing nanometer-sized solid particles dispersed in liquids are of interest in many fields of process and energy engineering, e.g., heat transfer, catalysis, and the design of functionalized materials [1]. The physical, chemical, optical, and electronic properties of nanofluids are strongly driven by the size, shape, surface potential, and concentration of the nanoparticles. For the analysis of diffusive processes in nanofluids allowing access to, e.g., particle size and its distribution, dynamic light scattering (DLS) is the state-of-the-art technique. It is based on the analysis of microscopic fluctuations originating from the random thermal movement of particles in the continuous liquid phase at macroscopic thermodynamic equilibrium. For anisotropic particles or particle aggregates, besides translational diffusion also rotational diffusion occurs. To obtain the sum of the orientation-averaged translational (DT) and rotational (DR) diffusivities by depolarized DLS [2], a homodyne detection scheme is usually applied which can hardly be fulfilled in the experimental realization. Furthermore, the experiments are restricted to limited ranges for temperature, particle concentration, and viscosity