Molecular-Level Insight into Semiconductor Nanocrystal Surfaces.

Semiconductor nanocrystals exhibit attractive photophysical properties for use in a variety of applications. Advancing the efficiency of nanocrystal-based devices requires a deep understanding of the physical defects and electronic states that trap charge carriers. Many of these states reside at the nanocrystal surface, which acts as an interface between the semiconductor lattice and the molecular capping ligands. While a detailed structural and electronic understanding of the surface is required to optimize nanocrystal properties, these materials are at a technical disadvantage: unlike molecular structures, semiconductor nanocrystals lack a specific chemical formula and generally must be characterized as heterogeneous ensembles. Therefore, in order for the field to improve current nanocrystal-based technologies, a creative approach to gaining a "molecular-level" picture of nanocrystal surfaces is required. To this end, an expansive toolbox of experimental and computational techniques has emerged in recent years. In this Perspective, we critically evaluate the insight into surface structure and reactivity that can be gained from each of these techniques and demonstrate how their strategic combination is already advancing our molecular-level understanding of nanocrystal surface chemistry.

An actionable needs assessment for adolescents and young adults with cancer: the AYA Needs Assessment & Service Bridge (NA-SB).

PURPOSE: In the USA, many of the nearly 90,000 adolescents and young adults (AYAs) diagnosed with cancer each year do not receive services to address the full scope of needs they experience during and after cancer treatment. To facilitate a systematic and patient-centered approach to delivering services to address the unmet needs of AYAs with cancer, we developed the AYA Needs Assessment & Service Bridge (NA-SB). METHODS: To develop NA-SB, we leveraged user-centered design, an iterative process for intervention development based on prospective user (i.e., provider and AYA) engagement. Specifically, we conducted usability testing and concept mapping to refine an existing tool-the Cancer Needs Questionnaire-Young People-to promote its usability and usefulness in routine cancer practice. RESULTS: Our user-centered design process yielded a need assessment which assesses AYAs' physical, psychosocial, and practical needs. Importantly, needs in the assessment are grouped by services expected to address them, creating an intuitive and actionable link between needs and services. CONCLUSION: NA-SB has the potential to improve care coordination at the individual level by allowing cancer care programs to tailor service delivery and resource provision to the individual needs of AYAs they serve.

Exchange equilibria of carboxylate-terminated ligands at PbS nanocrystal surfaces.

Ligand exchange reactions are commonly used to alter the surface chemistry of metal chalcogenide quantum dots; however, a lack of quantifiable data for these processes limits the rational functionalization of nanomaterials. Here, we quantify the X-type ligand exchange reaction between carboxylate-terminated ligands on PbS quantum dots via1H NMR spectroscopy. Using spectroscopic handles of both the native and exchange ligand, bound and free forms of each have been quantified as a function of exchange ligand concentration. We find that the equilibrium constants for the reaction between oleate-capped PbS quantum dots and undec-10-enoic acid are 2.23 ± 0.50 and 2.14 ± 0.42 for sets of nanocrystals prepared by two different synthetic methods. X-ray photoelectron, absorbance, and emission spectroscopies indicate that the carboxylate exchange reaction does not alter the lead ion coverage of the nanocrystal surface. The quantitative equilibrium constant determined herein can be used to improve control over partial ligand exchange reactions on PbS nanocrystals.