The Experts below are selected from a list of 4245 Experts worldwide ranked by ideXlab platform
Damien Jeannerat - One of the best experts on this subject based on the ideXlab platform.
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high precision Heteronuclear 2D NMR experiments using 10 ppm spectral window to resolve carbon overlap
Chemical Communications, 2009Co-Authors: Bruno Vitorge, Stefan Bieri, Munir Humam, Philippe Christen, Kurt Hostettmann, Orlando Munoz, Sandra Loss, Damien JeanneratAbstract:The acquisition of a complementary Heteronuclear 2D NMR experiment with 10-ppm carbon window allows chemists to improve by a factor 20–25 the spectral resolution and determine carbon chemical shifts with five figures from 2D spectra.
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computer optimized spectral aliasing in the indirect dimension of 1h 13c Heteronuclear 2D NMR experiments a new algorithm and examples of applications to small molecules
Journal of Magnetic Resonance, 2007Co-Authors: Damien JeanneratAbstract:A new algorithm for optimizing spectral width in the indirect dimension of Heteronuclear 2D experiments is introduced. It takes a list of carbon chemical shifts as input and calculates the optimal spectral width and number of time increments to use in the carbon dimension of 2D experiments such as HSQC, HMBC, etc. When using optimized conditions where signals are better distributed along the carbon dimension, the number of time increments needed to resolve all of the signals is reduced by one to two orders of magnitude. This decreases the experimental time by the same factors and makes the acquisition of spectra such as HSQC-TOCSY, HSQC-NOESY, etc. more practical. The new algorithm allows users to limit the maximal t(1) evolution time when relaxation is a concern, and can take lists of carbons that do not need to be resolved. For any carbon, insights regarding the position of signals in the proton dimension increase the efficiency of the optimization by allowing the overlap of pairs of carbons with incompatible proton dispersions. The application of a second optimization using a fully-resolved spectrum as a source of proton dispersion for the carbons allows the number of time increments to be reduced further. Application to cyclosporine A shows that the time taken to acquire fully resolved HSQC spectra can be 126 times less than would be required in a full-width spectrum with the same resolution. The most interesting applications concern experiments where series of HSQC-based experiments have to be acquired, for example in relaxation time measurements. It is shown that the acquisition of quickly acquired series of selective-TOCSY-HSQC can facilitate assignment in carbohydrates. Computer-optimized spectral aliasing (COSA) generally requires no modification of the pulse sequence and can therefore be easily applied by non specialists.
Michael P Hanrahan - One of the best experts on this subject based on the ideXlab platform.
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probing the surface structure of semiconductor nanoparticles by dnp sens with dielectric support materials
Journal of the American Chemical Society, 2019Co-Authors: Michael P Hanrahan, Yunhua Chen, Rafael Blomefernandez, Jennifer L Stein, Gregory F Pach, Marquix A S Adamson, Nathan R Neale, Brandi M CossairtAbstract:Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by 1-2 orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride (h-BN) to disperse the NPs doubles DNP enhancements and absolute sensitivity in comparison to standard protocols with mesoporous silica. Alternatively, precipitating the NPs as powders, mixing them with h-BN, and then impregnating the powdered mixture with radical solution leads to further 4-fold sensitivity enhancements by increasing the concentration of NPs in the final sample. This modified procedure provides a factor of 9 improvement in NMR sensitivity in comparison to previously established DNP SENS procedures, enabling challenging homonuclear and Heteronuclear 2D NMR experiments on CdS, Si, and Cd3P2 NPs. These experiments allow NMR signals from the surface, subsurface, and core sites to be observed and assigned. For example, we demonstrate the acquisition of DNP-enhanced 2D 113Cd-113Cd correlation NMR experiments on CdS NPs and natural isotropic abundance 2D 13C-29Si HETCOR of functionalized Si NPs. These experiments provide a critical understanding of NP surface structures.
Brandi M Cossairt - One of the best experts on this subject based on the ideXlab platform.
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probing the surface structure of semiconductor nanoparticles by dnp sens with dielectric support materials
Journal of the American Chemical Society, 2019Co-Authors: Michael P Hanrahan, Yunhua Chen, Rafael Blomefernandez, Jennifer L Stein, Gregory F Pach, Marquix A S Adamson, Nathan R Neale, Brandi M CossairtAbstract:Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by 1-2 orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride (h-BN) to disperse the NPs doubles DNP enhancements and absolute sensitivity in comparison to standard protocols with mesoporous silica. Alternatively, precipitating the NPs as powders, mixing them with h-BN, and then impregnating the powdered mixture with radical solution leads to further 4-fold sensitivity enhancements by increasing the concentration of NPs in the final sample. This modified procedure provides a factor of 9 improvement in NMR sensitivity in comparison to previously established DNP SENS procedures, enabling challenging homonuclear and Heteronuclear 2D NMR experiments on CdS, Si, and Cd3P2 NPs. These experiments allow NMR signals from the surface, subsurface, and core sites to be observed and assigned. For example, we demonstrate the acquisition of DNP-enhanced 2D 113Cd-113Cd correlation NMR experiments on CdS NPs and natural isotropic abundance 2D 13C-29Si HETCOR of functionalized Si NPs. These experiments provide a critical understanding of NP surface structures.
Yunhua Chen - One of the best experts on this subject based on the ideXlab platform.
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probing the surface structure of semiconductor nanoparticles by dnp sens with dielectric support materials
Journal of the American Chemical Society, 2019Co-Authors: Michael P Hanrahan, Yunhua Chen, Rafael Blomefernandez, Jennifer L Stein, Gregory F Pach, Marquix A S Adamson, Nathan R Neale, Brandi M CossairtAbstract:Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by 1-2 orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride (h-BN) to disperse the NPs doubles DNP enhancements and absolute sensitivity in comparison to standard protocols with mesoporous silica. Alternatively, precipitating the NPs as powders, mixing them with h-BN, and then impregnating the powdered mixture with radical solution leads to further 4-fold sensitivity enhancements by increasing the concentration of NPs in the final sample. This modified procedure provides a factor of 9 improvement in NMR sensitivity in comparison to previously established DNP SENS procedures, enabling challenging homonuclear and Heteronuclear 2D NMR experiments on CdS, Si, and Cd3P2 NPs. These experiments allow NMR signals from the surface, subsurface, and core sites to be observed and assigned. For example, we demonstrate the acquisition of DNP-enhanced 2D 113Cd-113Cd correlation NMR experiments on CdS NPs and natural isotropic abundance 2D 13C-29Si HETCOR of functionalized Si NPs. These experiments provide a critical understanding of NP surface structures.
Bruno Vitorge - One of the best experts on this subject based on the ideXlab platform.
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high precision Heteronuclear 2D NMR experiments using 10 ppm spectral window to resolve carbon overlap
Chemical Communications, 2009Co-Authors: Bruno Vitorge, Stefan Bieri, Munir Humam, Philippe Christen, Kurt Hostettmann, Orlando Munoz, Sandra Loss, Damien JeanneratAbstract:The acquisition of a complementary Heteronuclear 2D NMR experiment with 10-ppm carbon window allows chemists to improve by a factor 20–25 the spectral resolution and determine carbon chemical shifts with five figures from 2D spectra.