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Analysis of the rotational fine structure of the fundamental infrared band of HCl is a standard experiment in the physical chemistry laboratory curriculum. Although the absorption band was observed by Ångstrom and Palmer as early as 1893, the first spectrum showing sufficient resolution to distinguish not only the P and R branches but also the rotational fine structure was acquired in 1919 by Elmer S. Imes, the second African American to obtain a Ph.D. in physics. This spectrum, together with those obtained by Imes for HF and HBr, was of fundamental importance in demonstrating the need for a correct quantum theory of molecules. In celebration of the recent centenary of this spectrum, a number of extensions of the spectroscopy of the hydrogen halides beyond the standard curriculum are described here, including use of the research tool PGOPHER to facilitate data analysis, use of high-resolution linelist data from the HITRAN database to investigate overtones and hot bands, estimation of the bond dissociation energy from HITRAN data using Birge-Sponer extrapolation, and simulation of rovibrational bands based on high-level calculations of the ground state potential energy curve.

Using PGOPHER and HITRAN to extend spectroscopic analysis of hydrogen halides in the undergraduate laboratory

The mutarotation kinetics and equilibrium of glucose in aqueous solution are perturbed by the presence of metal cations, with Ca2+ showing one of the strongest effects, significantly shifting the equilibrium to favor the α-anomer. In this work we quantify this effect using a combination of polarimetry and 1H NMR. In the NMR measurements we use DOSY filtering to suppress the interfering HDO peak which originates in the rapidly-exchanging glucose hydroxyl protons. NMR and polarimetry give closely comparable results on anomeric abundance, although in agreement with literature studies on the unperturbed mutarotation equilibrium in aqueous glucose solutions we find that KNMR is consistently slightly smaller than Kpol. Polarimetric measurements confirm that the effect is largely cationic in character. and show that a catalytic effect of the cation on the mutarotation rate is diminished by increased solution viscosity at higher concentrations. Computational results on the glucose-Ca2+ system indicate that the dominant ion-molecule structures in solution are relatively undistorted ones with anomeric couplings 3JHCCH that are not strongly perturbed from their values for aqueous glucose solutions.

Effect of metal cations on glucose mutarotation: Complementary studies using polarimetry and DOSY-filtered NMR

Learning from biological systems such as Silicateins and their molecular mechanisms have paved the way for controlled synthesis of inorganic materials with advanced properties and high performances. In the case of zinc oxide (ZnO), conventional production methods are environmentally damaging and wasteful with the use of toxic and/or flammable solvents and precursors, extreme alkaline conditions requiring extra processing steps to neutralize, and lack satisfactory control of desired crystal habits for high value applications. Inspired by ZnO-binding peptides, we demonstrate a bioinspired synthesis and aspect ratio control of ZnO hexagonal prisms directly at 65°C using histidine in HMTA-zinc nitrate reaction system, with no seeding or substrate, yet well-defined morphology and conversion up to 40%. Histidine interferes with zinc ions, thereby stabilizing the system, affecting the conversion and particle morphology. We are now testing the performance of histidine in other ZnO synthesis systems to enable scalability of the bioinspired route.

Bioinspired synthesis of nanomaterials: Case study of zinc oxide

Individuals with medical implants are often at risk of developing life-threatening thrombi on the surface of these devices. Fibrinogen (Fgn) facilitates platelet recruitment by laterally aggregating at its αC domains into interconnected fibers that provide structure for thrombi. Thus, one method of preventing thrombogenesis is by inhibiting this process. The calculated optimal adsorption cites of the in silico human Fgn NJm on a hydrophobic thermoplastic surface model were congruent with existing literature, suggesting that on a polystyrene (PS) surface, Fgn is positioned with its αC domain exposed. Allowing a molecule to bind to the exposed αC domain will prevent the Fgn proteins from laterally aggregating. This study generated an in vitro bovine model of fiber formation on a hydrophobic PS surface to investigate the proficiency of a hydrophilic 14-peptide sequence derived from the Aα635-648 region of fibronectin, P-12 (PSHISKYILRWRPK), in achieving that end. Various amounts of bovine Fgn and P-12 were plated on PS and submerged in phosphate-buffered saline at various intervals. 100 μg/mL of Fgn acted as the monolayer that would initiate fibrin cluster formation, an additional 4 mg/mL of Fgn that, uninterrupted, would aggregate to form fibers, and 10μM of P-12 were added to investigate its impact on Fgn polymerization. Large fibers were observed in the absence of P-12, supporting the previous reports that the αC domains of the monolayer were opened by the hydrophobic interaction. Significantly smaller fibers were present when the P-12 was added alongside the surface monolayer, suggesting P-12 displaced certain sections, while minimal fiber formation occurred when P-12 was added afterward, which suggests that P-12 binds with Fgn to prevent the formation of fibrin clusters. This experiment confirms that P-12 blocks the ability of Fgn to execute fiber formation and that P-12 can displace Fgn from surfaces. If medical implants are manufactured with hydrophobic surfaces, this study suggests the introduction of P-12 can be used to mitigate thrombosis.

Development of a short peptide to prevent non-thrombogenic clot formation on hydrophobic surfaces

Electrocatalytic synthesis of H2O2 via two-electron oxygen reduction reaction (2e- ORR) has attracted tremendous interest in diversified fields, including wafer cleaning, paper manufacturing, and public sanitation. However, developing inexpensive, highly active, and selective catalysts is still a challenge for the large-scale electroproduction of H2O2. Here, we report a fluorine and sulfur dual-doping strategy for metal-free nanofibers to achieve comparable performances to metal-based catalysts. The optimized F/S dual-doping catalysts can afford an onset potential of 0.814 V versus reversible hydrogen electrode (RHE) and highly enhanced H2O2 selectivity of nearly 100%, superior to most of the recently reported carbon-based and metal-based counterparts. Experimental and theoretical computation results demonstrate that the manipulated free energy profiles and reduced energy barrier originate from the synergistic effect of intermolecular charge transfer coupled with electron spin redistribution in the adjacent carbon active sites, owing to the fluorine and sulfur heteroatom doping, respectively. This work can open the door to the design and implementation of inexpensive, large-scale, and highly efficient catalysts for the electroproduction of H2O2, and enjoys versatility to be extended to other catalytic fields, such as CO2 reduction, water splitting, and ammonia production.

Highly active and selective metal-free nanofibers for H2O2 electroproduction via F/S dual-doping

The COVID-19 pandemic has impacted the Green Chemistry Teaching and Learning Community. In 2020, universities and schools were forced to move towards online education. Digital technologies offer opportunities that facilitate some educational methods; however, they also can become barriers for an Inclusive Green Chemistry Education. Thousands of deaf students faced many difficulties with online teaching tools in Brazil. Unfortunately, this migration from face-to-face teaching to remote teaching increased the dropout rate among students in schools. Many reasons for this increase in dropouts were reported, for example non-attendance of a sign language interpreter and the absence of inclusive teaching methods. This urgent reality requires a pedagogical rethink. From this perspective, this work proposed and evaluated strategies to promote interactions between hearing teachers and deaf students during online classes of chemistry. Our method was applied to high school students in a public college in Brazil. Chemistry teachers and translator-interpreters of Brazilian Sign Language (Libras) planned the lessons. They worked together for more interactive and visual classes. Visualization tools are important to teach chemistry, according to Mahaffy's model. Our project was divided into five stages: survey questions (1), case study (2), visual-educational activity (3), interactions with social media (4) and (5) final test, which were approved by the Research Ethics Committee. Results showed that Libras is essential for communication. We confirmed a positive impact on the learning of students and an effective interest into sustainable development. Using social media ensured a constant communication with students. In conclusion, our inclusive methodology allowed introducing some principles of Green Chemistry in high school classes online. We helped deaf students to stay focused and develop metacognitive skills during the COVID-19 pandemic. An inclusion of participants was possible with a Systems Thinking perspective. We hope that new inclusive approaches should be a priority for Green Chemistry Teaching and Learning Community.

American Chemical Society

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