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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Role of High-Spin Species and Pendant Amines in Electrocatalytic Alcohol Oxidation by a Nickel Phosphine Complex

We report the development of active and efficient electrocatalysts for oxidation of alcohols using earth-abundant metals will aid the progress towards a renewable energy economy. Here we present a detailed mechanistic study of electrocatalytic benzyl alcohol oxidation by a molecular nickel complex containing pendant amines using a combination of kinetic studies, NMR spectroscopy, and density functional theory. The catalyst preferentially binds alcohol in high-spin octahedral geometry, but this complex is not readily deprotonated by exogeneous base and inhibits catalysis. Dissociation of one or more solvent ligands returns the complex to a low-spin state that can be deprotonated. Kinetic modeling indicates the off-cycle high-spin intermediate lowers the catalytic turnover frequency by a factor of eight, suggesting that substantial gains in activity can be attained by improvements to the catalyst coordination geometry. In a second finding, we demonstrate the pendant amine of the catalyst only functions as a proton relay for the potential-determining step, oxidation of a nickel hydride intermediate, but does not have a substantial impact on the overall rate for oxidation of benzyl alcohol to benzaldehyde. This result contradicts the common expectation for pendant amines to participate in rate-limiting proton transfer reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Ultrafast Imaging of Molecules with Electron Diffraction

Photoexcited molecules convert light into chemical and mechanical energy through changes in electronic and nuclear structure that take place on femtosecond timescales. Gas phase ultrafast electron diffraction (GUED) is an ideal tool to probe the nuclear geometry evolution of the molecules and complements spectroscopic methods that are mostly sensitive to the electronic state. GUED is a passive probing tool that does not alter the molecular properties during the probing process and is sensitive to the spatial distribution of charge in the molecule, including both electrons and nuclei. Improvements in temporal resolution have enabled GUED to capture coherent nuclear motions in molecules in the excited and ground electronic states with femtosecond and subangstrom resolution. Here we present the basic theory of GUED and explain what information is encoded in the diffraction signal, review how GUED has been used to observe coherent structural dynamics in recent experiments, and discuss the advantages and limitations of the method.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on U(HO2)2 by Materials Project

UO2(OH)2 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one molecular hydrogen;dihydrate molecule and one UO2 sheet oriented in the (0, 0, 1) direction. In the UO2 sheet, U6+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of U–O bond distances ranging from 2.05–2.11 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent U6+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent U6+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2000

Recent Results for AGN Observed by the Rossi X-Ray Timing Explorer

The Rossi X-ray Timing Explorer (RXTE) has produced many excellent observations of active galaxies, providing the best sensitivity in the 10 - 20 keV range so far. This presentation reports selected RTXE data for AGN in the context of the currently popular models. One is the recent result for two Seyfert 1 galaxies, NGC 5548 and IC4329a: both show the "canonical" Seyfert I X-ray spectra, with an underlying power law, plus Gaussian iron K line and Compton reflection. Interestingly, in both cases, the profile of the Fe K line does not extend as far to the red as seen in the famous NCG-6-30-15, and this indicates that the regions where the Fe K lines originate in AGN are diverse. Independently, in both objects we see a strong spectral variability of the primary continua, which soften as the sources brighten. The second result is for the heavily absorbed Seyfert 2 NGC 4945. The RXTE data confirm the strong absorption corresponding to the optical depth to electron scattering of about 2, but also reveal rapid variability of the hard (8-30 keV) X-ray emission on a time scale of a day or less. This suggests that for NGC 4945, the putative parsec-size molecular torus cannot be both geometrically and optically thick, and implies that the Cosmic X-ray Background is unlikely to be made up primarily of AGN with geometry as inferred for this object.

Madejski, G. M.↗
NASA NTRS1999

Nano-Plasticity of Single-Wall Carbon Nanotubes Under Uniaxial Compression

Nano-plasticity of thin single-wall carbon nanotubes under uniaxial compression is investigated through generalized tight-binding molecular dynamics (GTBMD) and ab-initio electronic structure methods. A novel mechanism of nano-plasticity of carbon nanotubes under uniaxial compression is observed in which bonding geometry collapses from a graphitic (sp(sup 2)) to a localized diamond like (sp(sup 3)) reconstruction. The computed critical stress (approximately equals 153 G Pa) and the shape of the resulting plastic deformation is in good agreement with recent experimental observation of collapse and fracture of compressed carbon nanotubes in polymer composites.

Srivastava, Deepak↗
NASA NTRSDate not supplied

Multiscale Analysis of Thermo-Mechanical Behavior of Boron Nitride-Reinforced Epoxy Nanocomposites

The effect of size, shape, morphology, and arrangement of micro constituents of Boron Nitrite (BN) nanoplatelet/epoxy composites on their properties were investigated using a multi scale approach that includes Molecular Dynamics (MD) and micromechanics. The thermo-mechanical properties of the composites were evaluated using molecular theory and the analysis showed that the elastic constants of BN/epoxy composites were not severely affected by temperature. Also, the micromechanical analysis of Generalized Method of Cells (GMC) was utilized at higher length scale to evaluate elastic properties of the composites, for different geometries and arrangements of micro constituents. The predicted results of the analysis showed that the size, aspect ratios, morphology, and the arrangements of inclusions in BN/epoxy nanocomposites all have remarkable effect on the mechanical performances of the material systems.

nanocomposites↗
NASA NTRS2020

HAWC plus Far-infrared Observations of the Magnetic Field Geometry in M51 and NGC 891

Stratospheric Observatory for Infrared Astronomy High-resolution Airborne Wideband Camera Plus polarimetry at154μm is reported for the face-on galaxy M51 and the edge-on galaxy NGC 891. For M51, the polarization vectors generally follow the spiral pattern defined by the molecular gas distribution, the far-infrared(FIR) intensity contours, and other tracers of star formation. The fractional polarization is much lower in the FIR-bright central regions than in the outer regions, and we rule out loss of grain alignment and variations in magnetic field strength as causes. When compared with existing synchrotron observations, which sample different regions with different weighting, we find the net position angles are strongly correlated, the fractional polarizations are moderately correlated, but the polarized intensities are uncorrelated. We argue that the low fractional polarization in the central regions must be due to significant numbers of highly turbulent segments across the beam and along lines of sight in the beam in the central 3 kpc of M51. For NGC 891, the FIR polarization vectors within an intensity contour of1500-MJy sr1are oriented very close to the plane of the galaxy. The FIR polarimetry is probably sampling the magnetic field geometry in NGC 891 much deeper into the disk than is possible with NIR polarimetry and radio synchrotron measurements. In some locations in NGC 891, the FIR polarization is very low, suggesting we are preferentially viewing the magnetic field mostly along the line of sight, down the length of embedded spiral arms. There is tentative evidence for a vertical field in the polarized emission off the plane of the disk.

Disk galaxies↗
DOE OSTI2025

Computing virtual dark-field X-ray microscopy images of complex discrete dislocation structures from large-scale molecular dynamics simulations

Dark-field X-ray microscopy (DFXM) is a novel diffraction-based imaging technique that non-destructively maps the local deformation from crystalline defects in bulk materials. While studies have demonstrated that DFXM can spatially map 3D defect geometries, it is still challenging to interpret DFXM images of the high-dislocation-density systems relevant to macroscopic crystal plasticity. This work develops a scalable forward model to calculate virtual DFXM images for complex discrete dislocation structure(s) (DDS) obtained from atomistic simulations. Our new DDS-DFXM model integrates a non-singular formulation for calculating the local strain from the DDS and an efficient geometrical optics algorithm for computing the DFXM image from the strain field. We apply the model to complex DDS obtained from a large-scale mol­ecular dynamics simulation of compressive loading on single-crystal silicon. Simulated DFXM images exhibit prominent contrast for dislocation features between the multiple slip systems, demonstrating the potential of DFXM to resolve features from dislocation multiplication. In conclusion, the integrated DDS-DFXM model provides a toolbox for DFXM experimental design and image interpretation in the context of bulk crystal plasticity for a range of measurements across shock plasticity and the broader materials science community.

X-ray imaging↗
DOE OSTI2020

Materials Data on VH17C4S4(O5F3)4 by Materials Project

VH12(S2O9)2(CF3)4H5O2 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of four fluoroform molecules; one molecular hydrogen;dihydrate molecule; and one VH12(S2O9)2 ribbon oriented in the (1, 0, 0) direction. In the VH12(S2O9)2 ribbon, V5+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of V–O bond distances ranging from 2.02–2.04 Å. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.68 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.70 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the fourth H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.69 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are two inequivalent S+3.50+ sites. In the first S+3.50+ site, S+3.50+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.46 Å) and one longer (1.48 Å) S–O bond length. In the second S+3.50+ site, S+3.50+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of S–O bond distances ranging from 1.45–1.48 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one H1+ and one S+3.50+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one S+3.50+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one H1+ and one S+3.50+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one S+3.50+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one H1+ and one S+3.50+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to one S+3.50+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one V5+ and two H1+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one V5+ and two H1+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one V5+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VH17C4S4(O5F3)4 by Materials Project

VH12(S2O9)2(CF3)4H5O2 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of four fluoroform molecules; one molecular hydrogen;dihydrate molecule; and one VH12(S2O9)2 ribbon oriented in the (1, 0, 0) direction. In the VH12(S2O9)2 ribbon, V5+ is bonded in an octahedral geometry to six O2- atoms. There are two shorter (2.03 Å) and four longer (2.04 Å) V–O bond lengths. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.61 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.67 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.69 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.62 Å) H–O bond length. In the sixth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.58 Å) H–O bond length. There are two inequivalent S+3.50+ sites. In the first S+3.50+ site, S+3.50+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.46 Å) and one longer (1.47 Å) S–O bond length. In the second S+3.50+ site, S+3.50+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.46 Å) and one longer (1.47 Å) S–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one H1+ and one S+3.50+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one H1+ and one S+3.50+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one H1+ and one S+3.50+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one H1+ and one S+3.50+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one S+3.50+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one H1+ and one S+3.50+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one V5+ and two H1+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one V5+ and two H1+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one V5+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn3P2(HO2)4 by Materials Project

(Zn3P2HO8)2(H2)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional and consists of four molecular hydrogen molecules and one Zn3P2HO8 framework. In the Zn3P2HO8 framework, there are two inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded in a trigonal planar geometry to one H and two equivalent O2- atoms. The Zn–H bond length is 1.55 Å. Both Zn–O bond lengths are 1.86 Å. In the second Zn2+ site, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with two equivalent ZnO4 tetrahedra and corners with four equivalent PO4 tetrahedra. There are a spread of Zn–O bond distances ranging from 1.94–2.03 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four equivalent ZnO4 tetrahedra. There is three shorter (1.54 Å) and one longer (1.60 Å) P–O bond length. H is bonded in a single-bond geometry to one Zn2+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one Zn2+ and one P5+ atom. In the second O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Zn2+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Zn2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Zn2+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

2D Retrieval Frameworks for Hot Jupiter Phase Curves

Spectroscopic phase curves provide unique access to the three-dimensional properties of transiting exoplanet atmospheres. However, a modeling framework must be developed to deliver accurate inferences of atmospheric properties for these complex data sets. Here, we develop an approach to retrieve temperature structures and molecular abundances from phase curve spectra at any orbital phase. In the context of a representative hot Jupiter with a large day–night temperature contrast, we examine the biases in typical one-dimensional (1D) retrievals as a function of orbital phase/geometry, compared to two-dimensional (2D) models that appropriately capture the disk-integrated phase geometry. We guide our intuition by applying our new framework on a simulated Hubble Space Telescope (HST)+Spitzer phase curve data set in which the “truth” is known, followed by an application to the spectroscopic phase curve of the canonical hot Jupiter, WASP-43b. We also demonstrate the retrieval framework on simulated James Webb Space Telescope (JWST) phase curve observations. We apply our new geometric framework to a joint fit of all spectroscopic phases, assuming longitudinal molecular abundance homogeneity, resulting in an a factor of 2 improvement in abundances precision when compared to individual phase constraints. With a 1D retrieval model on simulated HST+Spitzer data, we find strongly biased molecular abundances for CH{sub 4} and CO{sub 2} at most orbital phases. With 2D, the day and night profiles retrieved from WASP-43b remain consistent throughout the orbit. JWST retrievals show that a 2D model is strongly favored at all orbital phases. Based on our new 2D retrieval implementation, we provide recommendations on when 1D models are appropriate and when more complex phase geometries involving multiple TP profiles are required to obtain an unbiased view of tidally locked planetary atmospheres.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

A Coupled-Cluster Study of the Molecular Structure, Vibrational Spectrum, and Relative Energies of the XCN and XNC (X=F, Cl) Isomers

The XCN and XNC (X=F, Cl) isomers have been investigated using the CCSD and CCSD(T) methods in conjunction with a TZ2P basis set. Equilibrium geometries, dipole moments, harmonic frequencies, IR intensities and relative energies have been evaluated. The CCSD(T) geometries and vibrational frequencies for the XCN isomers are in good agreement with the available experimental data. The CCSD(T) results for FCN and FNC are in good agreement with the CEPA calculations of Botshwina et al., with the exception of the energy difference, which the CEPA method underestimates by about 1.2 kcal/mol. FCN and CICN are shown to be lower in energy than the FNC and ClNC isomers by 69.511.0 and 42.711.0 kcal/mol (0 K), respectively.

Lee, Timothy J.↗
DOE OSTI2020

HAWC+ Far-infrared Observations of the Magnetic Field Geometry in M51 and NGC 891

Stratospheric Observatory for Infrared Astronomy High-resolution Airborne Wideband Camera Plus polarimetry at 154 μm is reported for the face-on galaxy M51 and the edge-on galaxy NGC 891. For M51, the polarization vectors generally follow the spiral pattern defined by the molecular gas distribution, the far-infrared (FIR) intensity contours, and other tracers of star formation. The fractional polarization is much lower in the FIR-bright central regions than in the outer regions, and we rule out loss of grain alignment and variations in magnetic field strength as causes. When compared with existing synchrotron observations, which sample different regions with different weighting, we find the net position angles are strongly correlated, the fractional polarizations are moderately correlated, but the polarized intensities are uncorrelated. We argue that the low fractional polarization in the central regions must be due to significant numbers of highly turbulent segments across the beam and along lines of sight in the beam in the central 3 kpc of M51. For NGC 891, the FIR polarization vectors within an intensity contour of 1500 MJy sr{sup −1} are oriented very close to the plane of the galaxy. The FIR polarimetry is probably sampling the magnetic field geometry in NGC 891 much deeper into the disk than is possible with NIR polarimetry and radio synchrotron measurements. In some locations in NGC 891, the FIR polarization is very low, suggesting we are preferentially viewing the magnetic field mostly along the line of sight, down the length of embedded spiral arms. There is tentative evidence for a vertical field in the polarized emission off the plane of the disk.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2020

HAWC+ Far-infrared Observations of the Magnetic Field Geometry in M51 and NGC 891

Stratospheric Observatory for Infrared Astronomy High-resolution Airborne Wideband Camera Plus polarimetry at 154 μm is reported for the face-on galaxy M51 and the edge-on galaxy NGC 891. For M51, the polarization vectors generally follow the spiral pattern defined by the molecular gas distribution, the far-infrared (FIR) intensity contours, and other tracers of star formation. The fractional polarization is much lower in the FIR-bright central regions than in the outer regions, and we rule out loss of grain alignment and variations in magnetic field strength as causes. When compared with existing synchrotron observations, which sample different regions with different weighting, we find the net position angles are strongly correlated, the fractional polarizations are moderately correlated, but the polarized intensities are uncorrelated. We argue that the low fractional polarization in the central regions must be due to significant numbers of highly turbulent segments across the beam and along lines of sight in the beam in the central 3 kpc of M51. For NGC 891, the FIR polarization vectors within an intensity contour of 1500 MJy sr(exp -1) are oriented very close to the plane of the galaxy. The FIR polarimetry is probably sampling the magnetic field geometry in NGC 891 much deeper into the disk than is possible with NIR polarimetry and radio synchrotron measurements. In some locations in NGC 891, the FIR polarization is very low, suggesting we are preferentially viewing the magnetic field mostly along the line of sight, down the length of embedded spiral arms. There is tentative evidence for a vertical field in the polarized emission off the plane of the disk.

Terry Jay Jones↗
DOE OSTI2021

Modeling protein structures from predicted contacts with modern molecular dynamics potentials: accuracy, sensitivity, and refinement

Protein structure prediction has become increasingly popular and successful in recent years. An essential step for fragment-free, template-free methods is the generation of a final three-dimensional protein model from a set of predicted amino acid contacts that are often described by interresidue pairwise atomic distances. Here we explore the use of modern, open-source molecular dynamics (MD) engines, which have been continually developed over the last three decades with all-atom Hamiltonians to model biomolecular structure and dynamics, to generate accurate protein structures starting from a set of inferred pairwise distances. Additionally, the ability of MD empirical physical potentials to correct inaccuracies in the predicted geometries is tested. We rigorously characterize the effect of modeling parameters on results, the effect of different amounts of error in the predicted distances on the final structures, and test the ability of post-processing analysis to sort the best models out of a set of statistical replicas. We find that with exact distances and with noisy distances, the method can produce excellent structural models, and that the molecular dynamics force field seems to help correct errors in distance predictions, resisting the effects of applied noise.

Davidson, Russ↗
DOE OSTI2023

Modulating the Extent of Anisotropic Cuprophilicity via High Pressure with Piezochromic Luminescence Sensitization

We report metallophilicity has been widely studied as a fundamental supramolecular interaction. However, the extent and directionality thereof remain controversial. A major obstacle lies in the difficulty to separately control the geometry and chemical composition. Herein, we address this challenge by modulating metallophilicity with mechanical pressure. Using a multinuclear Cu(I) complex as model system, we report anomalous anisotropies of (supra)molecular structures, vibrations, and interaction energies upon isotropic compression as well as concomitant (essentially turn-on) piezochromic luminescence enhancement with ~10 3 modulation. The in situ characterizations indicate opposite behaviors of contact distances and cuprophilic interactions for intermolecular vs intramolecular Cu-Cu pairs under pressure. Theoretical calculations break down the attractive and repulsive forces associated with cuprophilicity, its spontaneous 4p-3d hybridization origin, and direction-dependent interaction strength. The use of isotropic mechanical force reveals the intrinsic anisotropy of metallophilicity in multinuclear systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Metal–Organic Framework-Based Microfluidic Impedance Sensor Platform for Ultrasensitive Detection of Perfluorooctanesulfonate

The growing global concerns to public health from human exposure to perfluorooctanesulfonate (PFOS) requires rapid, sensitive, in-situ detection where current, state-of-the-art techniques are yet to adequately meet sensitivity and selectivity standards of the real-world. This work presents, for the first time, a synergistic approach for the targeted affinity-based capture of PFOS using a porous sorbent probe that enhances detection sensitivity by embedding it on a microfluidic conductive platform. This novel sorbent-containing platform functions as an electrochemical sensor to directly measure PFOS concentration through a proportional change in electrical response (increase in impedance). The extremely high surface area and pore volume of mesoporous metal-organic framework (MOF) Cr-MIL-101 is used as the probe for targeted PFOS capture based on the affinity of the chromium center towards both the fluorine tail groups as well as the sulfonate functionalities as demonstrated by spectroscopic (NMR and XPS) and microscopic (TEM) studies. Answering the need for an ultrasensitive PFOS detection technique, we are embedding these MOF capture probes inside a microfluidic channel, sandwiched between interdigitated microelectrodes (IDµE). The nanoporous geometry increases the signal to noise ratio of interdigitated microelectrodes tremendously increasing sensitivity; this in combination with the ability of the capture probes to interact with the PFOS at the molecular level and effectively transduce that response electrochemically has allowed us achieve a PFOS detection limit of 0.5 ng/L, which is unprecedented for in-situ analytical PFOS sensors and even comparable to quantification limits achieved using state-of-the-art ex situ techniques.

36 MATERIALS SCIENCE↗