Ryan C. Nieuwendaal

The high-temperature CO₂ adsorption performance of ethylenediamine- (EN) and cysteamine-functionalized (CYS) UiO-67 metal–organic frameworks were evaluated and compared to that of the parent framework. CO₂ adsorption capacities and uptake kinetics were measured under a pure CO₂ atmosphere from 26 °C to 80 °C using thermogravimetric analysis. While functionalization reduced adsorption capacities at room temperature due to decreased accessible pore volume, both UiO-67-EN and UiO-67-CYS exhibited significantly improved performance at elevated temperatures, which is desirable for capture under flue-gas conditions. Unmodified UiO-67 retained only 17.9% of its initial adsorption capacity upon heating from 26 °C to 80 °C, whereas UiO-67-EN and UiO-67-CYS retained 52.3% and 61.2% of their initial capacities, respectively. At 80 °C, UiO-67-EN and UiO-67-CYS exhibited CO₂ adsorption capacities of 0.26(4) and 0.32(9) mmol g⁻¹, representing 2.06-fold and 2.57-fold improvements over the parent framework. Enhanced adsorption kinetics were also observed, with UiO-67-EN and UiO-67-CYS displaying 2.81-fold and 3.95-fold increases, respectively, in initial CO₂ uptake rates at 80 °C relative to unmodified UiO-67. Cyclic sorption-desorption studies demonstrated sustained high-temperature performance, with UiO-67-CYS retaining an adsorption capacity of 0.18(9) mmol g⁻¹ after 100 cycles at 80 °C. These results demonstrate that amine- and thiol-functionalization of UiO-67 significantly improves CO₂ capture capacity, uptake kinetics, and remain stable under elevated-temperature conditions.

An optimal methodology for locating and tracking cellulose nanofibers (CNFs) in vitro and in vivo is crucial to evaluate the environmental health and safety properties of these nanomaterials. Here, we report the use of a new boron-dipyrromethene (BODIPY) reactive fluorescent probe, meso-DichlorotriazineEthyl BODIPY (mDTEB), tailor-made for labeling CNFs used in simulated or in vivo ingestion exposure studies. Time-correlated single photon counting (TCSPC) fluorescence lifetime imaging microscopy (FLIM) was used to confirm covalent attachment and purity of mDTEB-labeled CNFs. The photoluminescence properties of mDTEB-labeled CNFs, characterized using fluorescence spectroscopy, include excellent stability over a wide pH range (pH2 to pH10) and high quantum yield, which provides detection at low (μM) concentrations. FLIM analysis also showed that lignin-like impurities present on the CNF reduce the fluorescence of the mDTEB-labeled CNF, via quenching. Therefore, the chemical composition and the methods of CNF production affect subsequent studies. An in vitro triculture, small intestinal, epithelial model was used to assess the toxicity of ingested mDTEB-labeled CNFs. Zebrafish (Danio rerio) were used to assess in vivo environmental toxicity studies. No cytotoxicity was observed for CNFs, or mDTEB-labeled CNFs, either in the triculture cells or in the zebrafish embryos.

Organic materials that exhibit high charge conductivities have potential uses in a number of electronics application areas, such as photovoltaics and flat panel displays and what once was a perpetual “on the horizon” class of materials, organic electronics are finding many real-world uses in a number of flexible electronics applications such as wearable sensors. However, regardless of the applied technology, precise knowledge of the morphologies of the organic molecules that comprise the active material are critical to optimizing the functionality. Solid-state NMR is a powerful analytical tool for deciphering local structures in complex morphologies and measuring molecular dynamics in dynamically heterogeneous materials. In this review, we cover recent solid-state NMR works that have focused on organic electronics materials such as polythiophenes, polyphenylene vinylenes, polyfluorenes, and a number of donor–acceptor polymers with applications in organic electronics, namely organic thin film transistors, organic light emitting diodes, and organic photovoltaics.

Triblock polyelectrolyte gels were characterized by small-angle neutron scattering (SANS) and dynamic light scattering (DLS). The oppositely charged end blocks self-assemble into polyelectrolyte complex cores, while the neutral poly(ethylene oxide) middle block bridges adjacent cores. The size of the polyelectrolyte complex core does not change with temperature. However, the neutral middle block displays a temperature-dependent conformation. The liquid-like order of the complex core within the gel phase leads to stretched bridging chains that approach their unperturbed dimensions with increasing concentration. A stretch ratio for bridging chains was defined as the ratio between stretched and unperturbed dimensions. A further reduction in the chain stretching occurs with increasing temperature due to solvent quality. DLS observes multiple modes consistent with a collective diffusion (fast mode) and diffusion of clusters (slow mode). The dynamics of these clusters are at length scales associated with the SANS excess scattering, but with relaxation time near the crossover frequency observed by mechanical spectroscopy.

Hydrogels are of intense recent interest in connection with biomedical applications ranging from 3-D cell cultures and stem cell differentiation to regenerative medicine, controlled drug delivery, and tissue engineering. This prototypical form of soft matter has many emerging material science applications outside the medical field. The physical processes underlying this type of solidification are incompletely understood, and this limits design efforts aimed at optimizing these materials for applications. We address this general problem by applying multiple techniques (e.g., NMR, dynamic light scattering, small angle neutron scattering, rheological measurements) to the case of a peptide derivative hydrogelator (molecule 1, NapFFKYp) over a broad range of concentration and temperature to characterize both the formation of individual nanofibers and the fiber network. We believe that a better understanding of the hierarchical self-assembly process and control over the final morphology of this kind of material should have broad significance for biological and medicinal applications utilizing hydrogels.

Several techniques are presented for characterizing the order of semiconducting polymers on different length scales, including: differential scanning calorimetry; solid-state nuclear magnetic resonance spectroscopy; transmission electron microscopy; and grazing incidence scattering. As the behavior of highly conjugated polymers can differ distinctly from the more classic, highly saturated polymers for which some of these techniques were originally developed (e.g. polyethylene), the hazards and pitfalls associated with applying these techniques to semiconducting polymers are also discussed.