Reconnecting Students and Faculty to Maximize Academic Integrity and Minimize Student Stress in the Virtual Classroom.

The article documents faculty experiences with the shift online due to the pandemic and provides recommendations to science, technology, engineering, and mathematics (STEM) instructors. Over 100 faculty members were surveyed on these topics and contrasted with previously reported student experiences. The online shift changed how faculty administered exams, ran courses, and acted to ensure academic integrity. For example, when exams went online, 73% of faculty reported spending more time preventing cheating. Concerning academic integrity and stress, faculty and students agreed with the exception of a few notable disconnects. Students reported greater workloads in online classes, while faculty maintained that the shift online did not change student workloads. Students perceived more online cheating than faculty. Overall, there seems to be a significant disconnect regarding faculty not realizing how much their actions may encourage or discourage cheating. Few faculty (<15%) indicated that being a tough grader or having test times too short is a motivating factor, but over 55% of students reported that these motivate students to cheat. Conversely, over 60% of students reported respect for their professors discourages them from cheating, while only 37% of faculty indicated the same. Over 70% of faculty and students indicated that fear of getting caught is a deterrent to cheating. Recommendations to reconnect include (i) faculty should use the finding that the number one deterrent of cheating is fear of getting caught; and (ii) faculty should maintain students' respect by being clear or overestimating workload requirements, carefully adjusting time for online exams, and setting clear expectations with uncomplicated exam questions consistent with the material taught.

Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions.

We report transport measurements on tunable single-molecule junctions of the organic perchlorotrityl radical molecule, contacted with gold electrodes at low temperature. The current-voltage characteristics of a subset of junctions shows zero-bias anomalies due to the Kondo effect and in addition elevated magnetoresistance (MR). Junctions without Kondo resonance reveal a much stronger MR. Furthermore, we show that the amplitude of the MR can be tuned by mechanically stretching the junction. On the basis of these findings, we attribute the high MR to an interference effect involving spin-dependent scattering at the metal-molecule interface and assign the Kondo effect to the unpaired spin located in the center of the molecule in asymmetric junctions.

Maximizing Academic Integrity While Minimizing Stress in the Virtual Classroom.

The article documents students' experiences with the shift online at the onset of the COVID-19 pandemic and provides informed recommendations to STEM instructors regarding academic integrity and student stress. Over 500 students were surveyed on these topics, including an open-ended question. Students experienced more stress and perceived a greater workload in online courses and therefore preferred in-person courses overall. Personal awareness of cheating during online exams is positively correlated with the proportion of cheating a student perceives. Fear of getting caught is the best cheating deterrent while getting a better grade makes cheating most enticing. Randomization of questions and answer choices is perceived as a highly effective tool to reduce cheating and is reported as the least stress-inducing method. Inability to backtrack and time limits cause students the most stress. Students report that multiple choice questions are the least effective question type to discourage cheating and oral exam questions cause the most stress. Use of camera and lockdown browser or being video- and audio- recorded caused the majority of student stress. Yet, nearly 60% agree that the combination of camera and lockdown browser is an effective deterrent. Recommendations: (i) Be transparent regarding academic dishonesty detection methods and penalties. (ii) Use online invigilating tools. (iii) Synchronize exams and (iv) randomize exam questions. (v) Allow backtracking. (vi) Avoid converting in-person exams to online exams; instead, explore new ways of designing exams for the online environment.

Triage and Recovery of STEM Laboratory Skills.

The global COVID-19 pandemic left universities with few options but to turn to remote learning. With much effort, STEM courses made this change in modality; however, many laboratory skills, such as measurement and handling equipment, are more difficult to teach in an online learning environment. A cohort of instructors who are part of the NSF RCN-UBE funded Sustainable, Transformative Engagement across a Multi-Institution/Multidisciplinary STEM (STEM)2 Network (a working group of faculty from two community colleges and three 4-year universities) analyzed introductory biology and chemistry courses to identify essential laboratory skills that students will need in advanced courses. Seven essential laboratory proficiencies were derived from reviewing disciplinary guiding documents such as AAAS Vision and Change in Undergraduate Biology Education, the American Society for Microbiology Recommended Curriculum Guidelines for Undergraduate Microbiology Education, and the American Chemical Society Guidelines for Chemistry: data analysis, scientific writing, proper handling and disposal of laboratory materials, discipline-specific techniques, measurement, lab safety and personal protective equipment, and interpersonal and collaborative skills. Our analysis has determined that some of these skills are difficult to develop in a remote or online setting but could be recovered with appropriate interventions. Skill recovery procedures suggested include a skills "boot camp," department or college coordinated club events, and a triage course. The authors recommend that one of these three recovery mechanisms be offered to bridge this skill gap and better prepare STEM students for upper-level science courses and the real world.

Enhanced coupling through π-stacking in imidazole-based molecular junctions.

We demonstrate that imidazole based π-π stacked dimers form strong and efficient conductance pathways in single-molecule junctions using the scanning-tunneling microscope-break junction (STM-BJ) technique and density functional theory-based calculations. We first characterize an imidazole-gold contact by measuring the conductance of imidazolyl-terminated alkanes (im-N-im, N = 3-6). We show that the conductance of these alkanes decays exponentially with increasing length, indicating that the mechanism for electron transport is through tunneling or super-exchange. We also reveal that π-π stacked dimers can be formed between imidazoles and have better coupling than through-bond tunneling. These experimental results are rationalized by calculations of molecular junction transmission using non-equilibrium Green's function formalism. This study verifies the capability of imidazole as a Au-binding ligand to form stable single- and π-stacked molecule junctions at room temperature.

Tuning the polarity of charge carriers using electron deficient thiophenes.

Thiophene-1,1-dioxide (TDO) oligomers have fascinating electronic properties. We previously used thermopower measurements to show that a change in charge carrier from hole to electron occurs with increasing length of TDO oligomers when single-molecule junctions are formed between gold electrodes. In this article, we show for the first time that the dominant conducting orbitals for thiophene/TDO oligomers of fixed length can be tuned by altering the strength of the electron acceptors incorporated into the backbone. We use the scanning tunneling microscope break-junction (STM-BJ) technique and apply a recently developed method to determine the dominant transport channel in single-molecule junctions formed with these systems. Through these measurements, we find that increasing the electron affinity of thiophene derivatives, within a family of pentamers, changes the polarity of the charge carriers systematically from holes to electrons, with some systems even showing mid-gap transport characteristics.

Single-excitation dual-color coherent lasing by tuning resonance energy transfer processes in porous structured nanowires.

Single-excitation dual-color coherent lasing was achieved in a mixed random system of a binary dye and the suspension of gold-silver porous nanowires with plenty of nanogaps. This greatly enhanced the local electromagnetic field in the visible range and guaranteed a low threshold and high Q factor (>10 000) operator for simultaneous dual-color lasing. By tuning the resonance energy transfer process in the stimulated emission, triple output modes (single chartreuse lasing, chartreuse and red dual-color lasing, and single red coherent lasing) were easily obtained. This triple-mode coherent random lasing introduces a new approach to designing multi-functional micro-optoelectronic devices for multi-color speckle-free imaging and interference.

Three-Phase Morphology of Semicrystalline Polymer Semiconductors: A Quantitative Analysis.

Quantitative morphological analysis is essential to the fundamental understanding of semiconducting polymers. Temperature modulated differential scanning calorimetry is used to determine the amount of crystalline and noncrystalline phases within regioregular poly(3-hexylthiophene) (rrP3HT). Careful optimization of the experimental conditions shows that the glass transition of rrP3HT consists of three parts corresponding to the devitrification of the side chains, mobile amorphous fraction (MAF), and rigid amorphous fraction (RAF), consecutively. Measurements taken from this, as well as from the melting transition, allows the first calculation of the degree of crystallinity, MAF and RAF, to be achieved in a single experiment for rrP3HT. This technique thus enables the morphological phases to be determined and potentially related to the performance of electronic devices made from semiconducting polymers.

Control of single-molecule junction conductance of porphyrins via a transition-metal center.

Using scanning tunneling microscope break-junction experiments and a new first-principles approach to conductance calculations, we report and explain low-bias charge transport behavior of four types of metal-porphyrin-gold molecular junctions. A nonequilibrium Green's function approach based on self-energy corrected density functional theory and optimally tuned range-separated hybrid functionals is developed and used to understand experimental trends quantitatively. Importantly, due to the localized d states of the porphyrin molecules, hybrid functionals are essential for explaining measurements; standard semilocal functionals yield qualitatively incorrect results. Comparing directly with experiments, we show that the conductance can change by nearly a factor of 2 when different metal cations are used, counter to trends expected from gas-phase ionization energies which are relatively unchanged with the metal center. Our work explains the sensitivity of the porphyrin conductance with the metal center via a detailed and quantitative portrait of the interface electronic structure and provides a new framework for understanding transport quantitatively in complex junctions involving molecules with localized d states of relevance to light harvesting and energy conversion.

Breakdown of interference rules in azulene, a nonalternant hydrocarbon.

We have designed and synthesized five azulene derivatives containing gold-binding groups at different points of connectivity within the azulene core to probe the effects of quantum interference through single-molecule conductance measurements. We compare conducting paths through the 5-membered ring, 7-membered ring, and across the long axis of azulene. We find that changing the points of connectivity in the azulene impacts the optical properties (as determined from UV-vis absorption spectra) and the conductivity. Importantly, we show here that simple models cannot be used to predict quantum interference characteristics of nonalternant hydrocarbons. As an exemplary case, we show that azulene derivatives that are predicted to exhibit destructive interference based on widely accepted atom-counting models show a significant conductance at low biases. Although simple models to predict the low-bias conductance do not hold with all azulene derivatives, we demonstrate that the measured conductance trend for all molecules studied actually agrees with predictions based on the more complete GW calculations for model systems.

Bandgap engineering through controlled oxidation of polythiophenes.

The use of Rozen's reagent (HOF⋅CH3 CN) to convert polythiophenes to polymers containing thiophene-1,1-dioxide (TDO) is described. The oxidation of polythiophenes can be controlled with this potent, yet orthogonal reagent under mild conditions. The oxidation of poly(3-alkylthiophenes) proceeds at room temperature in a matter of minutes, introducing up to 60 % TDO moieties in the polymer backbone. The resulting polymers have a markedly low-lying lowest unoccupied molecular orbital (LUMO), consequently exhibiting a small bandgap. This approach demonstrates that modulating the backbone electronic structure of well-defined polymers, rather than varying the monomers, is an efficient means of tuning the electronic properties of conjugated polymers.

Cascade-pumped random lasers with coherent emission formed by Ag-Au porous nanowires.

A series of sequentially cascade-pumped random lasers is reported. It consists of three random lasers in which the Ag-Au bimetallic porous nanowires play the role of scatterers, and the gain materials are coumarin 440 (C440), coumarin 153 (C153), and rhodamine 6G (R6G), respectively. The random laser with C440 is first pumped by a 355 nm pulsed laser. The emission of C440 pumps the C153, and the emission of C153 pumps the R6G sequentially. Low-threshold coherent emissions from the three random lasers are observed. The cascade-pumped random lasers can be achieved easily with low cost and can be used in applications conveniently.

Unusual molecular conformations in fluorinated, contorted hexabenzocoronenes.

Fluorinated, contorted hexabenzocoronenes (HBCs) have been synthesized in a facile manner via Suzuki-Miyaura coupling of fluorinated phenyl boronic acids followed by photocyclization and Scholl cyclization. In addition to the molecular conformation observed in previous HBC derivatives, close-contact fluorine-fluorine intramolecular interactions result in a metastable conformation not previously observed. Heating the metastable HBCs above 100 °C irreversibly converts them to the stable conformation, suggesting that the metastable conformation arises from a kinetically arrested state during cyclization.

High rates and substrate selectivities in water by polyvinylimidazoles as transaminase enzyme mimics with hydrophobically bound pyridoxamine derivatives as coenzyme mimics.

Free-radical polymers of 4-vinylimidazole and copolymers with 1-dodecyl-4-vinylimidazole were used as enzyme mimics to transaminate pyruvic acid to alanine, phenylpyruvic acid to phenylalanine, and indole-3-pyruvic acid to tryptophan in water at pH 7.5 and 20 degrees C using pyridoxamines carrying hydrophobic side chains as coenzyme mimics. The best enzyme mimic accelerated the transamination of indole-3-pyruvic acid by a factor of 4 million relative to the rate without the polymer, a higher rate ratio than we had previously achieved with a polyaziridine-based enzyme mimic. The properties of various polyvinylimidazoles were compared, including those prepared with the RAFT modification of the polymerization process.

Dendrimers in solution can have their remote catalytic groups folded back into the core: enantioselective transaminations by dendritic enzyme mimics-II.

PAMAM dendrimers with double thioether arms have been synthesized with a pyridoxamine core and terminal chiral amino groups. Transamination to afford natural isomers of phenylalanine and alanine induced enantioselectivity by the peripheral chiral caps, supporting a computer model that indicates folding of dendrimer chains back into the core.

Enantioselective Transaminations by Dendrimeric Enzyme Mimics.

PAMAM dendrimers have been constructed with a pyridoxamine core, and chiral capping amino groups. Transamination to form phenylalanine and alanine from their related ketoacids produced enantioselectivities induced by the formally remote chiral caps, supporting computer models that indicate folding of the dendrimer chains back into the core region.