Probing the rotational and translational diffusion and colloidal stability of nanorods is of significant fundamental interest with implications for many different applications. Recently R. Nixon-Luke and G. Bryant presented a...

Over the last decade, the interest in carbon dots, graphene dots, or similar carbon-based nanoparticles has increased considerably. This interest is based on potentially high fluorescent quantum yields, controllable excitation-dependent emission, low toxicity, and convenient reaction conditions. Carbon dots are often seen as a promising alternative to classical semiconductor quantum dots that are typically made from toxic semiconductor materials. Surprisingly, aspects like the atomic structure, composition, mechanism of formation, and precise understanding of the photophysical properties of carbon dots are still mostly unknown. The large number of different precursor systems and the variety in synthesis routes make a direct comparison of different systems difficult. To advance this, we went for a systematic approach and compared the results of four synthesis routes using two different precursor systems. We used different spectroscopy and microscopy methods including fluorescence correlation spectroscopy to characterize the different reaction products. We found that for syntheses solely based on citric acid as the precursor, we obtain particles where the emission wavelength is strongly dependent on the excitation wavelength despite relatively low quantum yields. In comparison, when urea is added as a nitrogen doping reactant, we observe vastly increased quantum yields. By making use of a combination of dialysis and column chromatography, we were able to isolate various luminescent species with high quantum yields and verify the existence of different molecular fluorophores. A detailed and consistent characterization of the reaction products during the course of purification revealed strong interactions between molecular fluorophores and larger reaction products.

Stabilization of gold nanoparticles in organic solvents is a key challenge in making them available for a wider range of material applications. Polymers are often used as stabilizing ligands because they also allow for the introduction of new properties and functionalities. Many of the established synthesis protocols for gold nanoparticles are water-based. However, the insolubility of many synthetic polymers in water renders the direct functionalization of aqueous particle dispersions with these ligands difficult. Here, we report on an approach for the functionalization of gold nanoparticles, which were prepared by aqueous synthesis, with hydrophobic polymer ligands and their characterization in nonpolar, organic dispersions. Our method employs an auxiliary ligand to first transfer gold nanoparticles from an aqueous to an organic medium. In the organic phase, the auxiliary ligand is then displaced by thiolated polystyrene ligands to form a dense polymer brush on the particle surface. We characterize the structure of the ligand shell using electron microscopy, scattering techniques, and ultracentrifugation and analyze the influence of the molecular weight of the polystyrene ligands on the structure of the polymer brush. We further investigate the colloidal stability of polystyrene-functionalized gold nanoparticles in various organic solvents. Finally, we extend the use of our protocol from small, spherical gold nanoparticles to larger gold nanorods and nanocubes.

We present the synthesis of so called amphiphilic glycomacromolecules (APGs) by using solid-phase polymer synthesis. Based on tailor made building blocks, monosdisperse APGs with varying compositions are synthesized, introducing carbohydrate...

Magnetic nanoparticles (MNPs) are widely known as valuable agents for biomedical applications. Recently, MNPs were further suggested to be used for a remote and non-invasive manipulation, where their spatial redistribution or force response in a magnetic field provides a fine-tunable stimulus to a cell. Here, we investigated the properties of two different MNPs and assessed their suitability for spatio-mechanical manipulations: semisynthetic magnetoferritin nanoparticles and fully synthetic ‘nanoflower’-shaped iron oxide nanoparticles. As well as confirming their monodispersity in terms of structure, surface potential, and magnetic response, we monitored the MNP performance in a living cell environment using fluorescence microscopy and asserted their biocompatibility. We then demonstrated facilitated spatial redistribution of magnetoferritin compared to ‘nanoflower’-NPs after microinjection, and a higher magnetic force response of these NPs compared to magnetoferritin inside a cell. Our remote manipulation assays present these tailored magnetic materials as suitable agents for applications in magnetogenetics, biomedicine, or nanomaterial research.