EPR Studies of Nanomaterials

Smirnov, Alex I.

doi:10.1002/9783527633531.ch20

Cited by 8 publications

(2 citation statements)

References 37 publications

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“…10−12 In recent years, electron paramagnetic resonance (EPR) spectroscopy and spin-probe/spin-label methods have become an important tool in the study of nanoscale materials. 13 EPR provides unique insight into the local environment around the spin probes, interactions with other electron (and nuclear) spins on a nanometer scale, and mobility on the nanosecond time scale and, as such, can provide detailed information about the short-and long-range nanostructuring of molecular-scale building blocks within complex assembled systems. Although most spectacular examples come from structural biology, 14 where EPR has been successfully used to explore protein and DNA structure, dynamics, and interactions, similar approaches were exploited to investigate other supramolecular systems, 15 e.g., colloidal structures, 16 host−guest complexes, 17 coordination cages, 18 polymer aggregates, 19 mesoporous materials, 20 and nanoparticles.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In recent years, electron paramagnetic resonance (EPR) spectroscopy and spin-probe/spin-label methods have become an important tool in the study of nanoscale materials . EPR provides unique insight into the local environment around the spin probes, interactions with other electron (and nuclear) spins on a nanometer scale, and mobility on the nanosecond time scale and, as such, can provide detailed information about the short- and long-range nanostructuring of molecular-scale building blocks within complex assembled systems.…”

Section: Introductionmentioning

confidence: 99%

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Using EPR Spectroscopy as a Unique Probe of Molecular-Scale Reorganization and Solvation in Self-Assembled Gel-Phase Materials

et al. 2014

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We describe the synthesis of spin-labeled bis-ureas which coassemble with bis-urea gelators and report on self-assembly as detected using electron paramagnetic resonance spectroscopy (EPR). Specifically, EPR detects the gel-sol transition and allows us to quantify how much spin-label is immobilized within the gel fibers and how much is present in mobile solvent pools-as controlled by temperature, gelator structure, and thermal history. EPR is also able to report on the initial self-assembly processes below the gelation threshold which are not macroscopically visible and appears to be more sensitive than NMR to intermediate-sized nongelating oligomeric species. By studying dilute solutions of gelator molecules and using either single or double spin-labels, EPR allows quantification of the initial steps of the hierarchical self-assembly process in terms of cooperativity and association constant. Finally, EPR enables us to estimate the degree of gel-fiber solvation by probing the distances between spin-labels. Comparison of experimental data against the predicted distances assuming the nanofibers are only composed of gelator molecules indicates a significant difference, which can be assigned to the presence of a quantifiable number of explicit solvent molecules. In summary, EPR provides unique data and yields powerful insight into how molecular-scale mobility and solvation impact on assembly of supramolecular gels.

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