From single-site tantalum complexes to nanoparticles of Ta_xN_y and TaO_xN_y supported on silica: elucidation of synthesis chemistry by dynamic nuclear polarization surface enhanced NMR spectroscopy and X-ray absorption spectroscopy

Abstract

SOMC is exploited for synthesizing very fine nanoparticles of TaxNy/TaOxNy on silica, elucidating the strategies with DNP SENS and EXAFS.

Probing the Surface Structure of Semiconductor Nanoparticles by DNP SENS with Dielectric Support Materials

“…All three silica samples had solvent enhancements less than that reported for bulk TCE, consistent with previous DNP SENS experiments on silica materials (Figure 1). 67,85,86 α-Al 2 O 3 and h-BN gave very high solvent DNP enhancements of ε C CP = 293 and ε C CP = 357, respectively (Figure 1). Powdered α-Al 2 O 3 (sapphire) is known to transmit microwaves efficiently and is the material from which DNP rotors are manufactured.…”

Surface enhanced dynamic nuclear polarization solid-state NMR spectroscopy sheds light on Brønsted–Lewis acid synergy during the zeolite catalyzed methanol-to-hydrocarbon process

“…To overcome the low-sensitivity concerns, dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) has recently gained a lot of interest from the scientic community. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] Typically, a sample is initially impregnated with a DNP agent (i.e., a nitroxide biradical) containing solution to bring it into the vicinity of the surface. 29,30,[37][38][39][40][41][42][43]45,46 The DNP agent enhances the polarization of protons of the solvent and neighbouring surface regions, which are then transferred to the surface's hetero-nuclei through cross-polarization (CP) or similar coherence magnetization transfer schemes (as illustrated in Fig.…”

A strategy to convert propane to aromatics (BTX) using TiNp4 grafted at the periphery of ZSM-5 by surface organometallic chemistry

“…This method usually leads to a well-defined singlesite catalyst with a uniform distribution of active sites. But the choice of organometallic compounds must come from an indeep analysis of the mechanism: [21][22][23] Based on the assumption that alkane aromatization occurs by dehydrogenation of the paraffin into an olefin followed by the aromatization (oligomerization, cyclisation, dehydrogenation) of the obtained olefin by an acid-catalyzed mechanism, the choice and the localization of the metal for the first step are crucial. The selection of Ti was based on the observation that among oxide-supported group IV metal hydrides, titanium hydrides are the best catalysts for low-temperature hydrogenolysis of paraffin.…”