Ginger V. Shultz

Polymer-Based Solar Cells: State-of-the-Art Principles for the Design of Active Layer Components

Abstract The vision of organic photovoltaics is that of a low cost solar energy conversion platform that provides lightweight, flexible solar cells that are easily incorporated into existing infrastructure with minimal impact on land usage. Polymer solar cells have been a subject of growing research interest over the past quarter century, and are now developed to the point where they are on the verge of introduction into the market. Towards the goal of continuing to improve the performance of polymer solar cells, a number of avenues are being explored. Here, the focus is on optimization of device performance via the development of a more fundamental understanding of device parameters. The fundamental operating principle of an organic solar cell is based on the cooperative interaction of molecular or polymeric electron donors and acceptors. Here the state-of-the-art in understanding of the physical and electronic interactions between donor and acceptor components is examined, as is important for understanding future avenues of research and the ultimate potential of this technology.

The development of a tool for measuring graduate students' topic specific pedagogical content knowledge of thin layer chromatography

Graduate students play a critical role in undergraduate education at doctorate granting institutions; but generally have minimal opportunity to develop teaching expertise. Furthermore, little is known about how graduate students develop teaching expertise in this context. We investigated the development of topic-specific pedagogical content knowledge among chemistry graduate student teaching assistants (GTAs). Thin layer chromatography was selected as the topic of investigation because undergraduate students encounter it throughout organic chemistry lab and it is connected to several foundational chemistry topics. An instrument was developed to measure both content knowledge (CK) and pedagogical content knowledge (PCK) of thin layer chromatography for GTAs with a range of teaching experience. Data from the test instrument were transformed using the Rasch model and statistically analysed. Our analysis showed that graduate students at all levels of experience performed well on content knowledge questions, but even experienced GTAs demonstrated low levels of pedagogical content knowledge. Importantly, experienced GTAs demonstrated a greater proficiency than novice GTAs, which suggests that pedagogical content knowledge is developed over time.

Teaching assistants' topic-specific pedagogical content knowledge in 1H NMR spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy is an essential analytical tool in chemistry, and the technique is routinely included as a topic across the undergraduate chemistry curriculum. As a result of NMRs importance, classroom instruction of this topic has received considerable attention in chemistry education research. However, little is known about instructors’ knowledge for teaching this topic. In order to better understand this knowledge, we investigated topic-specific pedagogical content knowledge in 1H NMR spectroscopy among 20 chemistry teaching assistants at a large Midwestern university in the United States. A questionnaire was developed to provide an inferential measure of content knowledge and topic-specific pedagogical content knowledge in 1H NMR spectroscopy for participants with a range of teaching experience. Data from the questionnaire were analyzed qualitatively and quantized using a rubric. The quantitative data were transformed using the Rasch model and statistically analyzed. Results from these analyses indicate that pedagogical content knowledge increased with teaching experience in 1H NMR spectroscopy, suggesting that knowledge for teaching this topic is developed through practice. Additionally, the development of pedagogical content knowledge was found to depend upon content knowledge required for specific NMR sub-topics and problems. This finding suggests that the ultimate “grain-size,” or domain-specificity, of pedagogical content knowledge may extend to the problem level. Results from this study have implications for how instructors may cultivate knowledge for teaching NMR spectroscopy, as well as for how pedagogical content knowledge may be more effectively incorporated into instructor training programs.

Investigation of the role of writing-to-learn in promoting student understanding of light–matter interactions

Fundamental quantum chemistry concepts—quantization of energy, electronic structure, and light–matter interaction—are essential for understanding chemistry and spectroscopy, an important tool for studying molecules. However, very few studies have investigated how students learn and understand these concepts or how their learning can be supported. Drawing on the capacity of writing to support learning of difficult concepts, we designed an intervention that targeted quantum concepts in the context of the use of spectroscopy for identifying chemical composition of the Orion Nebula. A quasi-experimental design with a pre-post assessment on a control and treatment group was used to identify the gains associated with completing the WTL activity. Results from a three-tiered assessment show that WTL students significantly improved in their explanations of the concept of spectroscopic transitions and their overall confidence in their understanding. Analysis of their writing, follow-up interviews, and feedback served to explain the changes observed on the pre-post assessment.

Identifying and Remediating Student Misconceptions in Introductory Biology via Writing-to-Learn Assignments and Peer Review

Student misconceptions are an obstacle in science, technology, engineering, and mathematics courses and unless remediated may continue causing difficulties in learning as students advance in their studies. Writing-to-learn assignments (WTL) are characterized by their ability to promote in-depth conceptual learning by allowing students to explore their understanding of a topic. This study sought to determine whether and what types of misconceptions are elicited by WTL assignments and how the process of peer review and revision leads to remediation or propagation of misconceptions. We examined four WTL assignments in an introductory biology course in which students first wrote about content by applying it to a realistic scenario, then participated in a peer-review process before revising their work. Misconceptions were identified in all four assignments, with the greatest number pertaining to protein structure and function. Additionally, in certain contexts, students used scientific terminology incorrectly. Analysis of the drafts and peer-review comments generated six profiles by which misconceptions were addressed through the peer-review process. The prevalent mode of remediation arose through directed peer-review comments followed by correction during revision. It was also observed that additional misconceptions were elicited as students revised their writing in response to general peer-review suggestions.

Tetra­carbonyl­bis(η5-cyclo­penta­dienyl)bis[(dec-9-en-1-yl)diphenyl­phosphine]dimolybdenum(0)(Mo—Mo) tetra­hydro­furan disolvate

The asymmetric unit of the title compound, [Mo2(η5-C5H5)2(C22H29P)2(CO)4]·2C4H8O, contains two half-molecules of the organometallic species and two solvent molecules. Both organometallic molecules are completed by crystallographic inversion symmetry, yielding dimeric units with Mo—Mo single-bond lengths of 3.2703 (6) and 3.2548 (6) Å. Each Mo atom is also coordinated by an η5-cyclopentdienyl ligand, two carbonyl ligands, and a (dec-9-en-1-yl)diphenylphosphine ligand.

Tetracarbon­ylbis(η5-cyclo­penta­dien­yl)bis(diphenyl­phosphine)dimolybdenum(Mo—Mo) hexane solvate

The title compound, [Mo2(C5H5)2(C12H11P)2(CO)4]·C6H14, is a centrosymmetric Mo complex in which two Mo atoms are connected by an Mo—Mo bond [3.2072 (12) Å]. Each Mo atom is coordinated by an η5-cyclopentadienyl ligand, two carbonyl ligands and a diphenylphosphine ligand in a piano-stool fashion.