RESUMEN
The interactions between gold nanoparticles, their surface ligands and the solvent critically influence the properties of these nanoparticles. Although spectroscopic and scattering techniques have been used to investigate their ensemble structure, a comprehensive understanding of these processes at the nanoscale remains challenging. Electron microscopy makes it possible to characterize the local structure and composition but is limited by insufficient contrast, electron beam sensitivity and the requirement for ultrahigh-vacuum conditions, which prevent the investigation of dynamic aspects. Here we show that, by exploiting high-quality graphene liquid cells, we can overcome these limitations and investigate the structure of the ligand shell around gold nanoparticles and at the ligand-gold interface in a liquid environment. Using this graphene liquid cell, we visualize the anisotropy, composition and dynamics of ligand distribution on gold nanorod surfaces. Our results indicate a micellar model for surfactant organization. This work provides a reliable and direct visualization of ligand distribution around colloidal nanoparticles.
RESUMEN
This project aimed to develop a comprehensive set of evaluation tools to assess the accessibility and inclusion of families with children on the autism spectrum in cultural institutions. A stakeholder team conducted interviews, reviewed museum artifacts, and observed museum programming. An evaluation toolkit was constructed by incorporating best practices from current literature and collected data. Tools were piloted and revised after being implemented in the museum context. The Toolkit to Increase Accessibility and Inclusion for Children on the Autism Spectrum and with Sensory Processing Differences in Cultural Institutions was developed with five unique tools, the Dimensions of Accessibility framework, and further resources to provide a self-assessment of cultural institutions. The toolkit can be used broadly across many types of institutions and self-assessment can lead to proactive development of public spaces, institutions, and programming that is accessible and inclusive of diverse groups of people, beyond families with children on the autism spectrum.
RESUMEN
In situ TEM is a valuable technique to offer novel insights in the behavior of nanomaterials under various conditions. However, interpretation of in situ experiments is not straightforward since the electron beam can impact the outcome of such measurements. For example, ligands surrounding metal nanoparticles transform into a protective carbon layer upon electron beam irradiation and may impact the apparent thermal stability during in situ heating experiments. In this work, we explore the effect of different treatments typically proposed to remove such ligands. We found that plasma treatment prior to heating experiments for Au nanorods and nanostars increased the apparent thermal stability of the nanoparticles, while an activated carbon treatment resulted in a decrease of the observed thermal stability. Treatment with HCl barely changed the experimental outcome. These results demonstrate the importance of carefully selecting pre-treatments procedures during in situ heating experiments.