Small- and wide-angle X-ray scattering (SWAXS) has been used to investigate the effect that water has on the nanoscale structure of protic ionic liquids (PILs) along with their precursor Brønsted acids and bases. The series of PILs consisted of primary, secondary, and tertiary alkylammonium cations in conjunction with formate, nitrate, or glycolate anions. Significant differences were observed for these systems. The nanoscale aggregates present in neat protic ionic liquids were shown to be stable in size on dilution to high concentrations of water, indicating that the water is localized in the ionic region and has little effect on the nonpolar domains. The Brønsted acid-water solutions did not display nanostructure at any water concentration. Primary amine Brønsted bases formed aggregates in water, which generally displayed characteristics of poorly structured microemulsions or a form of bicontinuous phase. Exceptions were butyl- and pentylamine with high water concentrations, for which the SWAXS patterns fitted well to the Teubner-Strey model for microemulsions. Brønsted base amines containing multiple alkyl chains or hydroxyl groups did not display nanostructure at any water concentration. IR spectroscopy was used to investigate the nature of water in the various solutions. For low PIL concentrations, the water was predominately present as bulk water for PIL molar fractions less than 0.4-0.5. At high PIL concentrations, in addition to the bulk water, there was a significant proportion of perturbed water, which is water influenced in some way by the cations and anions. The molecular state of the water in the studied amines was predominately present as bulk water, with smaller contributions from perturbed water than was seen in the PILs.
The development of biomedical nanoparticulate materials for use in diagnostics is a delicate balance between performance, particle size, shape, and stability. To identify materials that satisfy all of the criteria it is useful to employ automated high-throughput (HT) techniques for the study of these materials. The structure and performance of surfactant templated mesoporous silica is very sensitive to a wide number of variables. Variables, such as the concentration of the structure-directing agent, the cosolvent and dopant ions and also the temperature and concentration of quenching all have an influence on the structure, surface chemistry, and therefore, the performance of the mesoporous silica nanoparticles generated. Using an automated robotic synthetic platform, a technique has been developed for the high-throughput preparation of mesoporous silica and gadolinium-doped silicate (gadoliniosilicate) nanoparticulate MRI contrast agents. Twelve identical repeats of both the mesoporous silica and gadolinosilicate were synthesized to investigate the reproducibility of the HT technique. Very good reproducibility in the production of the mesoporous silica and the gadolinosilcate materials was obtained using the developed method. The performance of the gadolinosilicate materials was comparable as a T(1) agent to the commercial MRI contrast agents. This HT methodology is highly reproducible and an effective tool that can be translated to the discovery of any sol-gel derived nanomaterial.
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