Understanding materials with dimensions down to few nanometers is of major importance for fundamental science as well as prospective applications. Structural transformation and phononconfinement effects in the nanodiamonds (NDs) have been theoretically predicted below 3 nm size. Here we investigate the effect of size on the surface chemistry, microscopic structure, and Raman scattering of high-pressure high-temperature (HPHT) and detonation nanodiamonds (DNDs) down to 2-3 nm. The surface and size of NDs are controlled by annealing in air and ultracentrifugation resulting in three ND fractions. Particle size distribution (PSD) of the fractions is analyzed by combining dynamic light scattering (DLS), analytical ultracentrifugation (AUC), small angle X-ray scattering (SAXS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) as complementary techniques. Based on the obtained PSD we identify size-dependent and synthesis-dependent differences of NDs properties. In particular, interpretation of Raman scattering on NDs is revisited. Comprehensive comparison of detonation 3 and pure monocrystalline HPHT NDs reveals effects of diamond core size and defects, chemical and temperature (in)stability as well as limitations of current phonon confinement models. In addition, low-frequency Raman scattering in the 20 -200 cm -1 range is experimentally observed.The size dependence of this signal for both HPHT NDs and DNDs suggests that it may correspond to confined acoustic vibrational, "breathing-like" modes of NDs.
Drug-loaded polymer micelles or nanoparticles are being continuously explored in the fields of drug delivery and nanomedicine. Commonly, a simple core−shell structure is assumed, in which the core incorporates the drug and the corona provides steric shielding, colloidal stability, and prevents protein adsorption. Recently, the interactions of the dissolved drug with the micellar corona have received increasing attention. Here, using small-angle neutron scattering, we provide an in-depth study of the differences in polymer micelle morphology of a small selection of structurally closely related polymer micelles at different loadings with the model compound curcumin. This work supports a previous study using solid-state nuclear magnetic resonance spectroscopy and we confirm that the drug resides predominantly in the core of the micelle at low drug loading. As the drug loading increases, neutron scattering data suggests that an inner shell is formed, which we interpret as the corona also starting to incorporate the drug, whereas the outer shell mainly contains water and the polymer. The presented data clearly shows that a better understanding of the inner morphology and the impact of the hydrophilic block can be important parameters for improved drug loading in polymer micelles as well as provide insights into the structure− property relationship.
In this paper we describe the optimization of transmission X-ray targets by Monte-Carlo simulation for a laboratory X-ray microscopy setup. We identified two optimal target layer thicknesses (0.1 µm and 0.7 µm) for a high-resolution target and a high-flux target. Measurements show a decrease in focal spot size by one third or an increase in X-ray flux by a factor of three compared to those of a standard micro-focus target. Focal spot sizes down to 154 nm and 260 nm are achievable with the optimized targets. Simulation results for the X-ray flux match well to the experimental results, whereas the results for the focal spot sizes still show discrepancies attributed to the simplified simulation setup.
Drug loaded polymer micelles or nanoparticles are being continuously explored in the fields of drug delivery and nanomedicine. Commonly, a simple core-shell structure is assumed, in which the core incorporates the drug and the corona provides steric shielding, colloidal stability, and prevents protein adsorption. Recently, the interactions of the dissolved drug with the micellar corona have received increasing attention. Here, using small-angle neutron scattering, we provide an in-depth study of the differences in polymer micelle morphology of a small selection of structurally closely related polymer micelles at different loadings with the model compound curcumin. This work supports a previous study using solid state nuclear magnetic resonance spectroscopy and we confirm that the drug resides predominantly in the core of the micelle at low drug loading. As the drug loading increases, neutron scattering data suggests that an inner shell is formed, which we interpret as the corona also starting to incorporate the drug, whereas the outer shell mainly contains water and the polymer. The presented data clearly shows that a better understanding of the inner morphology and the impact of the hydrophilic block can be important parameters for improved drug loading in polymer micelles as well as provide insights into structure-property relationships.<br>
The self‐assembly of block copolymers has captured the interest of scientists for many decades because it can induce ordered structures and help to imitate complex structures found in nature. In contrast to proteins, nature's most functional hierarchical structures, conventional polymers are disperse in their length distribution. Here, we synthesized hydrophilic and hydrophobic polypeptoids via solid‐phase synthesis (uniform) and ring‐opening polymerization (disperse). Differential scanning calorimetry measurements showed that the uniform hydrophobic peptoids converge to a maximum of the melting temperature at a much lower chain length than their disperse analogs, showing that not only the chain length but also the dispersity has a considerable impact on the thermal properties of those homopolymers. These homopolymers were then coupled to yield amphiphilic block copolypeptoids. SAXS and AFM measurements confirm that the dispersity plays a major role in microphase separation of these macromolecules, and it appears that uniform hydrophobic blocks form more ordered structures.
Drug loaded polymer micelles or nanoparticles are being continuously explored in the fields of drug delivery and nanomedicine. Commonly, a simple core-shell structure is assumed, in which the core incorporates the drug and the corona provides steric shielding, colloidal stability, and prevents protein adsorption. Recently, the interactions of the dissolved drug with the micellar corona have received increasing attention. Here, using small-angle neutron scattering, we provide an in-depth study of the differences in polymer micelle morphology of a small selection of structurally closely related polymer micelles at different loadings with the model compound curcumin. This work supports a previous study using solid state nuclear magnetic resonance spectroscopy and we confirm that the drug resides predominantly in the core of the micelle at low drug loading. As the drug loading increases, neutron scattering data suggests that an inner shell is formed, which we interpret as the corona also starting to incorporate the drug, whereas the outer shell mainly contains water and the polymer. The presented data clearly shows that a better understanding of the inner morphology and the impact of the hydrophilic block can be important parameters for improved drug loading in polymer micelles as well as provide insights into structure-property relationships.<br>
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