Ligand exchange is frequently used to introduce new functional groups on the surface of inorganic nanoparticles or clusters while preserving the core size. For one of the smallest clusters, triphenylphosphine (TPP)-stabilized undecagold, there are conflicting reports in the literature regarding whether core size is retained or significant growth occurs during exchange with thiol ligands. During an investigation of these differences in reactivity, two distinct forms of undecagold were isolated. The X-ray structures of the two forms, Au11(PPh3)7Cl3 and [Au11(PPh3)8Cl2]Cl, differ only in the number of TPP ligands bound to the core. Syntheses were developed to produce each of the two forms, and their spectroscopic features correlated with the structures. Ligand exchange on [Au11(PPh3)8Cl2]Cl yields only small clusters, whereas exchange on Au11(PPh3)7Cl3 (or mixtures of the two forms) yields the larger Au25 cluster. The distinctive features in the optical spectra of the two forms made it possible to evaluate which of the cluster forms were used in the previously published papers and clarify the origin of the differences in reactivity that had been reported. The results confirm that reactions of clusters and nanoparticles may be influenced by small variations in the arrangement of ligands and suggest that the role of the ligand shell in stabilizing intermediates during ligand exchange may be essential to preventing particle growth or coalescence.

As one approach to moving beyond transmitting "inert" ideas to chemistry students, we use the term "teaching f rom rich contexts" to describe implementations of case studies or context-based learning based on systems thinking that provide deep and rich opportunities for learning crosscutting concepts through contexts. This approach nurtures the use of higher-order cognitive skills to connect concepts and apply the knowledge gained to new contexts. We describe the approach used to design a set of resources that model how rich contexts can be used to facilitate learning of general chemistry topics. The Visualizing the Chemistry of Climate Change (VC3) initiative provides an exemplar for introducing students in general chemistry courses to a set of core chemistry concepts, while infusing rich contexts drawn from sustainability science literacy. Climate change, one of the defining sustainability challenges of our century, with deep and broad connections to chemistry curriculum and crosscutting concepts, was selected as a rich context to introduce four topics (isotopes, acids−bases, gases, and thermochemistry) into undergraduate general chemistry courses. The creation and assessment of VC3 resources for general chemistry was implemented in seven steps: (i) mapping the correlation between climate literacy principles and core first-year university chemistry content, (ii) documenting underlying science conceptions, (iii) developing an inventory of chemistry concepts related to climate change and validating instruments that make use of the inventory to assess understanding, (iv) articulating learning outcomes for each topic, (v) developing and testing peer-reviewed interactive digital learning objects related to climate literacy principles with particular relevance to undergraduate chemistry, (vi) piloting the materials with first-year students and measuring the change in student understanding of both chemistry and climate science concepts, and (vii) disseminating the interactive resources for use by chemistry educators and students. A novel feature of the approach was to design resources (step v) based on tripartite sets of learning outcomes (step iv) for each chemistry and climate concept, with each knowledge outcome accompanied by an outcome describing the evidential basis for that knowledge, and a third outcome highlighting the relevance of that knowledge for students.

Precise in situ measurements are becoming more important as we seek to identify and harness the unique properties of novel nanomaterials, yet key challenges remain in determining structures with current analytical approaches. We report here an in situ multitechnique approach that permits the real-time measurement of the sizes of nanoparticles in flowing solutions. A series of ligand-stabilized Au nanoparticle standards (d CORE = 0.8−5 nm) was analyzed by simultaneous small-angle X-ray scattering (SAXS) and UV−vis spectroscopy in a microscale flow system. A specially designed observation cell provided access to both measurements at an identical location in the flow system and allowed for the correlation of SAXS and TEM analyses. Comparison of flow-based UV−vis data to those obtained ex situ provided a bridge between in situ SAXS and ex situ TEM measurements. Average core size from both techniques matched closely for each sample, while polydispersity values from SAXS measurements were smaller than those from TEM. By correlating in situ and ex situ measurements for well-defined nanoparticle standards, these experiments form the basis of a powerful approach to assess nanoparticle core size within flowing microscale systems.

Climate change is one of the most critical problems facing citizens today. Chemistry faculty are presented with the problem of making general chemistry content simultaneously relevant and interesting. Using climate science to teach chemistry allows faculty to help students learn chemistry content in a rich context. Concepts related to electromagnetic radiation and gases can be taught using an understanding of climate change and how greenhouse gases work. However, it would be important to know the level of prior knowledge that the students bring to the course and their confidence in that knowledge. Thus, a two-tiered instrument was developed to measure student understanding of climate change, the behavior of gases, and the mechanism of radiative forcing by greenhouse gases. The instrument was implemented iteratively at two institutions to allow for revision and replication. The final form of the instrument may be used in general chemistry classes or interdisciplinary courses to shape and guide instruction.

We describe two new greener alkene bromination reactions that offer enhanced laboratory safety and convey important green chemistry concepts, in addition to illustrating the chemistry of alkenes. The two alternative reactions, one involving pyridinium tribromide and a second using hydrogen peroxide and hydrobromic acid, are compared to the traditional bromination of stilbene through the application of green metrics, including atom economy, percent experimental atom economy, E factor, and effective mass yield. The use of these metrics to guide experiment evaluation and optimization in the teaching lab environment is examined. The development of these new experiments provides (i) an ideal case study for demonstrating the process of on-going evaluation and modification of experiments that leads toward more environmentally benign educational materials for the undergraduate organic teaching laboratory and (ii) a concrete example useful for introducing the practical use of metrics to students as a part of their laboratory experience. A green debromination procedure is also described that allows for simple and economical recycling of the starting material.