Green chemistry & chemical stewardship certificate program: a novel,interdisciplinary approach to green chemistry and environmental health education

ABSTRACT

The Green Chemistry & Chemical Stewardship Certificate Program was designed using the Community of Inquiry (COI) model as a framework for developing curriculum that engages students across the entire program to meet interdisciplinary, professional development program outcomes. The COI framework allows faculty and course developers to develop courses that consider cognitive, social, and teaching presence as equal components of successful learning experiences. In this program, students focus on systems thinking around green chemistry, business, environmental health, chemical alternative assessment tools, and social and environmental justice. They complete a capstone project that identifies a particular environmental or human health issue associated with a chemical and suggest suitable substitutions that are less harmful but equally effective. This paper describes the program’s curriculum, partnerships, delivery modalities, and student feedback as a framework developing professional development opportunities that offer a rich interdisciplinary experience for learners.     

Supercritical fluid chromatography (SFC) of linear and cyclic components in technical silicone oils

Since technical silicone oils are widely used, high performance analysis and exact quality control are necessary. The quantity of low molecular cyclic components is of special importance for the properties of the oils. Supercritical Fluid Chromatography (SFC) provides a facility for determining such cyclic components. Accurate assignment of linear and cyclic polydimethylsiloxanes is possible by coupling SFC with mass spectrometry (MS) or by using standard materials.     

The sensitized photodehydrochlorination of poly(vinyl chloride)—II. Model compound studies

p-Cresol, a model compound for an additive shown previously to be a potent photosensitizer of dehydrochlorination in poly(vinyl chloride) PVC, has been shown to sensitize dehydrochlorination in t-butyl chloride, a model for PVC. A quantitative study of the effect of chlorinated alkanes upon the fluorescence of p-cresol in solution reveals that quenching is due to charge transfer interactions, the halogenated compound acting as electron acceptor. Since the mono-halo compound t-butyl chloride does not quench p-cresol fluorescence, it was concluded that the photosensitization occurs via the triplet state of the p-cresol, and this view was confirmed by addition of triplet quenchers. A mechanism for the reaction is proposed, initial exciplex formation being followed by electron transfer.     

Low-Fouling Fluoropolymers for Bioconjugation and In Vivo Tracking

The conjugation of hydrophilic low-fouling polymers to therapeutic molecules and particles is an effective approach to improving their aqueous stability, solubility, and pharmacokinetics. Recent concerns over the immunogenicity of poly(ethylene glycol) has highlighted the importance of identifying alternative low fouling polymers. Now, a new class of synthetic water-soluble homo-fluoropolymers are reported with a sulfoxide side-chain structure. The incorporation of fluorine enables direct imaging of the homopolymer by ¹⁹F MRI, negating the need for additional synthetic steps to attach an imaging moiety. These self-reporting fluoropolymers show outstanding imaging sensitivity and remarkable hydrophilicity, and as such are a new class of low-fouling polymer for bioconjugation and in vivo tracking.     

A 119mSn Mössbauer study of the photochemical degradation of organotin stabilised PVC

Although organotin compounds are widely used as thermal and photochemical stabilisers for PVC, their mode of action and their fate on degradation of the polymer are not yet fully understood. ^119mSn Mössbauer spectroscopy has been used to study chemical changes undergone by two commonly used stabilisers, dibutyltinbis(iso-octylthioglycollate) and dibutyltinbis(iso-octylmaleate), during irradiation of stabilised PVC in artificial sunlight. After 1000 hours' exposure, the maleate stabiliser is chemically unchanged, whereas the thioglycollate is rapidly converted to the monochloroester, Bu₂SnCl(SCH₂CO₂C₈H₁₇). Prolonged exposure of the thioglycollate stabilised polymer leads to the formation of stannic oxychloride.     

Long-lived lanthanide emission via a pH-sensitive and switchable LRET complex

Lanthanide-based luminescence resonance energy transfer (LRET) can be used as a tool to enhance lanthanide emission for time-resolved cellular imaging applications. By shortening lanthanide emission lifetimes whilst providing an alternative radiative pathway to the formally forbidden, weak lanthanide-only emission, the photon flux of such systems is increased. With this aim in mind, we investigated energy transfer in differently spaced donor–acceptor terbium–rhodamine pairs with the LRET “on” (low pH) and LRET “off” (high pH). Results informed the design, preparation and characterisation of a compound containing terbium, a spectrally-matched pH-responsive fluorophore and a receptor-targeting group. By combining these elements, we observed switchable LRET, where the targeting group sensitises lanthanide emission, resulting in an energy transfer to the rhodamine dye with an efficiency of E = 0.53. This strategy can be used to increase lanthanide emission rates for brighter optical probes.

A pH-sensitive luminescence resonance energy transfer (LRET) was explored as a method to increase photon flux in a terbium-rhodamine-receptor targeting group construct. At low pH, long-lived dye emission and shorter terbium lifetimes were observed.