NMR techniques have been widely used to infer molecular structure, including surfactant aggregation. A combination of optical spectroscopy, proton NMR spectroscopy, and pulsed field gradient NMR (PFG NMR) is used to study the adsorption number for sodium dodecyl sulfate (SDS) with single-wall carbon nanotubes (SWCNTs). Distinct transitions in the NMR chemical shift of SDS are observed in the presence of SWCNTs. These transitions demonstrate that micelle formation is delayed by SWCNTs due to the adsorption of SDS on the nanotube surface. Once the nanotube surface is saturated, the free SDS concentration increases until micelle formation is observed. Therefore, the adsorption number of SDS on SWCNTs can be determined by the changes to the apparent critical micelle concentration (CMC). PFG NMR found that SDS remains strongly bound onto the nanotube. Quantitative analysis of the diffusivity of SDS allowed calculation of the adsorption number of strongly bound SDS on SWCNTs. The adsorption numbers from these techniques give the same values within experimental error, indicating that a significant fraction of the SDS interacting with nanotubes remains strongly bound for as long as 0.5 s, which is the maximum diffusion time used in the PFG NMR measurements.

Pulsed field gradient (PFG) NMR was applied to study self-diffusion of an ethane/ethene mixture and the corresponding pure gases in a mixed-matrix membrane (MMM) formed by dispersing ZIF-8 particles in 6FDA-DAM polymer. In addition to the MMM, diffusion measurements of the pure gases were also carried out for the membrane constituents, i.e. ZIF-8 particle bed and the pure polymer film. PFG NMR studies were performed at a high magnetic field of 17.6T using large magnetic field gradients up to 30T/m. The former allowed achieving sufficiently large signal-to-noise ratios, while the latter enabled diffusivity measurements to be performed for molecular displacements smaller than the size of ZIF-8 particles. As a result, the gas self-diffusivities for the diffusion inside the ZIF-8 particles dispersed in the MMM and for the diffusion inside the surrounding polymer matrix could be obtained separately. For each gas, the diffusivities inside the ZIF-8 and polymer phases of the MMM were found to be smaller than the corresponding diffusivities in the neat ZIF-8 particle bed and pure polymer film. This observation is explained by the reduced framework flexibility of ZIF-8 and the polymer chain rigidification in the MMM. The ethane and ethene diffusivities in the MMM loaded with the ethane/ethene mixture were compared with the corresponding diffusivities in the MMM loaded with a single gas. It was found that the presence of another gas component in the ZIF-8 particles dispersed in the MMM does not change the self-diffusivity inside the particles for both gases. At the same time, the self-diffusivity of the faster-diffusing sorbate (ethene) in the polymer phase of the MMM was reduced by co-adsorption of the slower-diffusing sorbate (ethane) in the MMM. The analytical expression proposed in our previous work for the long-range diffusivity in MMMs was validated for gas mixtures and pure gases based on the experimental data reported in this work.

An interdisciplinary field trip to a remote marine lab joined graduate students from fine arts and natural resource science departments to think creatively about the topic of climate change and science communication. We followed a learning cycle framework to allow the students to explore marine ecosystems and participate in scientific lectures, group discussions, and an artist-led project making abstract collages representing climate change processes. Students subsequently worked in small groups to develop environmental communication material for public visitors. We assessed the learning activity and the communication product using pre-and post-field trip participant surveys, focus group discussions, and critiques by art and communication experts of the products. Significant changes in knowledge about climate change occurred in program participants. Incorporating artists and the arts into this activity helped engage multiple senses and emphasized social interaction, as well as providing support to participants to think creatively. The production of art helped to encourage peer learning and normalize the different views among participants in communicating about climate change impacts. Students created effective communication products based on external reviews. Disciplinary differences in cultures, language, and standards challenged participating faculty, yet unanticipated outcomes such as potentially transformative learning and improved teacher evaluations resulted.

Pulsed field gradient (PFG) NMR is applied to resolve different modes of ethene self-diffusion inside a mixed-matrix membrane (MMM) consisting of ZIF-8 particles embedded in 6FDA–DAM polymer: (i) diffusion inside the ZIF-8 particles, (ii) diffusion inside the surrounding polymer matrix, and (iii) diffusion under conditions of an exchange between the particles and the polymer over length scales smaller than and comparable with the membrane thickness. This resolution is achieved using C-13 PFG NMR studies at a high magnetic field of 17.6T and large magnetic field gradients up to 30T/m. C-13 PFG NMR was also applied to measure ethene diffusion in the constituent components used in the MMM formation: a bed of ZIF-8 particles and a pure 6FDA–DAM polymer. It is shown that the comparison of all the measured diffusion data elucidates details of sorbate diffusion and diffusion mediated exchange dynamics between the ZIF-8 particles and the polymer in the MMM. An exchange model is applied to connect the long-range diffusivity measured for displacements larger than the size of ZIF-8 particles in the MMM with the diffusivities measured inside the ZIF-8 particles and the polymer.

Pulsed field gradient (PFG) NMR was applied to measure tortuosity factors for carbon dioxide diffusion in the Knudsen and gas regimes inside monoliths of a samaria-alumina aerogel catalyst, a high porosity material containing micropores in addition to meso- and macropores. The apparent tortuosity factor obtained from PFG NMR measurements for the Knudsen diffusion in the meso- and macropores of the catalyst has an unexpectedly large value of approximately 6 if carbon dioxide adsorption in the micropores and other types of surface adsorption sites of the catalyst is ignored. At the same time, the corresponding apparent tortuosity factor in the gas regime was found to be around 2. Application of a proposed model which describes fast molecular exchange between the surface adsorption sites and the main pore volume of the catalyst yields corrected tortuosity factors which depend only on the pore system geometry. Using this model, the corrected tortuosity factors were found to be around 2 for both diffusion regimes, in agreement with the expectations based on a high porosity of the studied catalyst.

Pulsed field gradient (PFG) NMR was used to investigate the self-diffusion of carbon dioxide in alumina stabilized samaria aerogel catalyst, a promising porous catalyst for gas-phase reactions featuring high porosity and high surface area. For diffusion studies, the catalyst was prepared in two sample packing types, macroscopic monoliths (i.e., macroscopic cylindrical particles) and powder beds with particle sizes around 200 μm that are considered for catalytic applications. Studies of diffusion in these samples revealed how macroscopic packing influences the catalyst transport properties. Application of a high magnetic field of 17.6 T in the reported PFG NMR studies enabled diffusion measurements for relatively low carbon dioxide densities in the catalyst samples corresponding to a gas loading pressure of around 0.1 atm. As a result, it was possible to perform diffusion measurements for a large range of carbon dioxide loading pressures between 0.1 and 10 atm. The measured carbon dioxide diffusivities in the beds of catalyst particles are interpreted in the context of a simple diffusion-mediated exchange model previously used for zeolites and other porous materials.

In this paper, we demonstrate the potential of pulsed field gradient (PFG) NMR spectroscopy t o reveal detailed knowledge of self-diffusion of light gases and light gas mixtures in carbon molecular sieve membranes on small length scales. PFG NMR is used to investigate intra-membrane diffusion of carbon dioxide and methane for a broad range of temperatures and mean square displacements in a carbon molecular sieve membrane derived from a 6FDA/BPDA-DAM polyimide film. Diffusion is investigated with single component sorbates as well as with a carbon dioxide / methane mixture. Results obtained from these studies are compared and discussed.

In this paper we present and discuss selected results of our recent studies of sorbate self-diffusion in microporous materials. The main focus is given to transport properties of carbon molecular sieve (CMS) membranes as well as of the intergrowth of FAU-type and EMT-type zeolites. CMS membranes show promise for applications in separations of mixtures of small gas molecules, while FAU/EMT intergrowth can be used as an active and selective cracking catalyst. For both types of applications diffusion of guest molecules in the micropore networks of these materials is expected to play an important role. Diffusion studies were performed by a pulsed field gradient (PFG) NMR technique that combines advantages of high field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m). This technique has been recently introduced at the University of Florida in collaboration with the National Magnet Lab. In addition to a more conventional proton PFG NMR, also carbon-13 PFG NMR was used.

Carbon molecular sieve (CMS) membranes are promising materials for energy efficient separations of light gases. In this work, we report a detailed microscopic study of carbon dioxide and methane self-diffusion in three CMS membrane derived from 6FDA/BPDA(1:1)-DAM and Matrimid polymers. In addition to diffusion of one-component sorbates, diffusion of a carbon dioxide/methane mixture was investigated. Self-diffusion studies were performed by the multinuclear (i.e., 1H and 13C) pulsed field gradient (PFG) NMR technique which combines the advantages of high field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m). Diffusion measurements were carried out at different temperatures and for a broad range of the root-mean-square displacements of gas molecules inside the membranes. The diffusion data obtained from PFG NMR are compared with the corresponding results of membrane permeation measurements reported previously for the same membrane types. The observed differences between the transport diffusivities and self-diffusion coefficients of carbon dioxide and methane are discussed.

This work reports the direct experimental observation of lipid exchange between liquid-ordered domains and their liquid-disordered surroundings in 3-component planar-supported multibilayers (1,2-dioleoyl-sn-glycerol-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-phosphocholine/cholesterol). The measurements of lipid lateral diffusion and exchange were carried out using proton pulsed field gradient (PFG) NMR spectroscopy with high field strength (17.6 T) and high gradient amplitudes (up to 30 T/m). Application of large gradients affords the use of sufficiently small diffusion times under the condition that the width of the gradient pulses is much smaller than the diffusion time. As a result, PFG NMR studies of time-dependent diffusion behavior in lipid bilayers become possible over submicrometer length scales of displacements, which are comparable with the domain size. Comparison of the PFG NMR diffusion data and the corresponding results of dynamic Monte Carlo simulations allowed for the estimation of domain boundary permeability and domain size at temperatures near the transition temperature for the studied bilayers.