Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2020 Apr 2;5(14):8355–8361. doi: 10.1021/acsomega.0c00874

17O Solid-State NMR Studies of Ta2O5 Nanorods

Meng Xu 1, Junchao Chen 1, Yujie Wen 1, Jia-Huan Du 1, Zhiye Lin 1, Luming Peng 1,*
PMCID: PMC7161065  PMID: 32309746

Abstract

graphic file with name ao0c00874_0008.jpg

17O solid-state NMR spectroscopy was used to study the structure of Ta2O5 nanorods for the first time. Although the observations of oxygen ions in the “bulk” part of the Ta2O5 nanorods can be achieved with conventional high-temperature enrichment with 17O2, low-temperature isotopic labeling with H217O generated samples whose surfaces are selectively enriched, leading to surface-only detection of oxygen species. By applying 17O–1H double-resonance NMR techniques and 1H NMR spectroscopy, surface hydroxyl species and adsorbed water can also be studied. The results form the basis for further understanding of the structure–property relationship of Ta2O5 nanomaterials.

Introduction

Tantalum oxide (Ta2O5) is a wide bandgap semiconductor with high refractive indexes, low absorption, and large dielectric constants that has a variety of important applications, including catalysts,1 gas sensors,2 coating,3 photographic glasses,3,4 as well as storage capacitors.5−8 Ta2O5 nanomaterials, which have a larger surface area than their bulk counterparts, are good catalysts and catalytic supports.9−15 Particularly, Ta2O5 nanorods have potential for providing solutions to the current energy- and environment-related problems because these materials show excellent catalytic properties, including photocatalytic hydrogen production,16 photodegradation of rhodamine B,17 and methylene blue.18

In order to develop structure–property relations and improve the catalytic performances, detailed surface structure information of oxide nanomaterials is required; however, much is still not well-understood. Conventional approaches such as X-ray diffraction (XRD) fail because long-range order is interrupted on the surface of oxide nanomaterials, and only short-range order is present. Despite the fact that surface sites can be observed directly, microscopy-based techniques can hardly provide local chemical and bonding information, and the volumes investigated by such methods may not be representative of the whole sample. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful method that provides rich information on the local structure of solids, and all the nuclei in the samples are studied; therefore, it provides complementary information to XRD and microscopy and should be ideal for investigating the surface structure of oxide nanostructures. Despite this, only a very limited number of studies have focused on investigations of nanomaterials with solid-state NMR spectroscopy,19−21 presumably due to the lack of an appropriate technique to select the surface of nanomaterials, which is often only a relatively small fraction of the whole sample.

For solid-state NMR spectroscopy of Ta2O5-based materials, both 17O and 181Ta nuclei can give NMR signals in principle. However, 181Ta is associated with one of the largest known quadrupole moments, leading to very broad linewidths, and very few papers have been published on 181Ta solid-state NMR spectroscopy.22 To the best of our knowledge, no 181Ta solid-state NMR spectrum has been reported on Ta2O5. With a much smaller quadrupole moment, 17O should be the choice of the nucleus for the investigations of Ta2O5. Furthermore, 17O has a wide chemical shift range of more than 1000 ppm; thus it is a very sensitive structural probe for oxygen containing materials. The major challenge in the application of 17O NMR may be the very low natural abundance of 17O (0.037%); thus expensive isotopic labeling is often required. Nonetheless, 17O solid-state NMR should be able to provide a lot of information on the structure of Ta2O5 materials, and previous studies show that two environments corresponding to 2- and 3-coordinated O ions can be distinguished according to NMR shifts.23−28 However, to the best of our knowledge, 17O NMR has not been applied to study the structure of Ta2O5 nanomaterials.

Recently, our group developed a new approach to select the surface by uneven isotopic labeling and investigate oxide nanostructures including CeO2/TiO2 as examples.29−37 Oxygen ions at different facets or layers can be distinguished according to the 17O NMR parameters (mostly chemical shifts). Furthermore, detailed information on the surface reconstruction and presence of different types of defects can also be obtained. In this study, we apply 17O solid-state NMR spectroscopy to study the structure of Ta2O5 nanorods, with emphasis on the surface structure.

Results and Discussion

The XRD pattern of the material calcined at 500 °C shows that all of the diffraction peaks can be indexed to the hexagonal phase Ta2O5 (JCPDS no. 19-1299), which is stable at a relatively low temperature (Figure 1a).9 The absence of the peak at around 44.8°, which corresponds the (340) plane in the orthorhombic phase of Ta2O5 confirms that the sample is pure hexagonal Ta2O5. The color of the material is white, indicating that the oxygen vacancy concentration (if any) is low.38 The high-resolution transmission electron microscope (HRTEM) images of the material show that the morphology can be described as bundles of nanorods (Figure 1b). The average diameter of the each individual nanorod is approximately 6–7 nm. The N2 adsorption/desorption isotherms and the pore size distribution of the sample are shown in Figure 1c,d A relatively large surface area of 57.6 m2·g–1 is obtained from this data, which consistent with the small diameter of Ta2O5 nanorods, while the average pore size is determined as 7.5 nm.

Figure 1.

Figure 1

Open in a new tab

(a) XRD pattern of Ta2O5 nanorods calcined at 500 °C in comparison to the diffraction peaks of the hexagonal phase Ta2O5 (JCPDS no. 19-1299). (b) HRTEM images of Ta2O5 nanorods. (c) N2 adsorption/desorption isotherms and (d) pore size distribution curves of Ta2O5 nanorods calcined at 500 °C.

First, single-pulse 17O MAS NMR experiments were performed to study Ta2O5 nanorods. For NR-17O2-500, which was 17O-labeled with conventional high temperature enrichment with 17O2, two well-resolved resonances centered at around 466 and 311 ppm are observed and can be assigned to oxygen ions with different coordination numbers, OTa2 and OTa3, respectively (Figure 2), according to previous investigations on Ta2O5 materials.23−28 Because of the high enrichment temperature of 500 °C, the majority of the signals arise from the “bulk part” of the Ta2O5 nanorods.29−31,33 A very small peak at 378 ppm, owing to 17O in the zirconia rotor, can also be observed in this sample as well as other samples.

Figure 2.

Figure 2

Open in a new tab

17O MAS NMR spectra of Ta2O5 nanorods. Recycle delays were optimized according to the sample and the detailed experimental parameters are shown in Table S1. Spinning sidebands from the resonances at approx. 450 and 300 ppm are marked with “*” and “#“, respectively.

The spectra obtained for Ta2O5 nanorods enriched with H217O at lower temperatures show different features. A major resonance centered at 445 ppm and a much smaller resonance at approx. 297 ppm are observed for NR-H217O-RT-5 along with several lower frequency peaks. A similar spectrum is observed for NR-H217O-RT-30, while the centers of gravity of the high and medium frequency peaks move to a slightly higher shift at 450 and 300 ppm, respectively, and the latter has a higher relative intensity. Another lower resonance with a peak maximum at 175 ppm can also be observed. At a higher thermal treatment temperature, the 17O NMR spectrum of NR-H217O-120-30 shows two resonances centered at 457 and 315 ppm, while the relative intensity of the peak at 315 ppm is a lot stronger than the two samples labeled with 17O at room temperature. At room temperature, 17O cannot diffuse into the “bulk part” of the nanorods; therefore, the peaks at 445–450 ppm observed for NR-H217O-RT-5 and NR-H217O-RT-30 should arise from surface OTa2 species, while the resonances at 297–300 ppm can be attributed to surface/subsurface OTa3 sites. This observation suggests that the isotopic exchange can occur rapidly between the surface oxygen ions of Ta2O5 nanorods and adsorbed water at room temperature, leading to selective observation of the surface species. The peak at 450 ppm in the spectrum of NR-H217O-RT-30 has a much shorter longitudinal relaxation time compared to the signal at 466 ppm in the data of NR-17O2-500 (Figure S1), indicating that the surface species (OTa2) can be selected by using shorter recycle delays. Meanwhile, the much weaker relative intensity of the OTa3 peak indicates that the concentration of OTa3 is smaller at the surface and/or the reactivity of OTa3 groups with water is much lower at room temperature. Comparing the data obtained for NR-H217O-RT-5 and NR-H217O-RT-30, a shorter isotopic exchange time may result in even higher NMR observation selectivity for OTa2. There is a change of around 20 ppm to higher frequency (445–466 ppm) for the peak due to OTa2, from the sample labeled at room temperature (NR-H217O-RT-5) to the sample enriched at 500 °C (NR-17O2-500). It implies that the surface OTa2 species may be associated with a slightly lower chemical shift compared to OTa2 in the bulk. The lower frequency peaks with maxima in the range of around 110–220 ppm are probably owing to surface hydroxyl sites and/or adsorbed water, according to the chemical shifts. Usually adsorbed water has a smaller chemical shift compared to hydroxyl species.30,32 For NR-H217O-120-30, the lower frequency peaks are weaker while the peak at 315 ppm increases in intensity compared to the samples enriched at room temperature, suggesting that hydroxyl species and/or adsorbed water may be removed at 120 °C, and/or they are converted to other species. However, these peaks are broad presumably because of large quadrupolar coupling constants of the OH environment, which is usually as large as 6–8 MHz.29,30,39−43 Therefore, these broad peaks may be hard to observe in a single pulse experiment due to the wavy baseline, and the overlapping with the spinning sidebands of the major resonance of OTa2 also makes such observations difficult.

17O spin echo MAS NMR experiments were performed for the samples enriched with H217O in order to flatten the baseline of the spectra, assist the spectral assignments, and confirm the presence of the low frequency resonances (Figure 3). For NR-H217O-RT-5, a large resonance at 445 ppm with a small peak at 300 ppm can be observed as in the single pulse NMR data. It is also clear that there are some resonances in the frequency range of approx. −150 to 250 ppm, although they still overlap with the spinning sidebands of the peaks because of OTa2 and OTa3. The spectrum obtained for NR-H217O-RT-30 is very similar, and the peak for the surface OTa2 is observed at a slightly higher frequency of 452 ppm. In contrast, the intensity of the resonances in the lower frequency decreases significantly in NR-H217O-120-30, which is consistent with the single pulse NMR data, indicating the concentrations of such species decrease at a high temperature of 120 °C. The 17O spin echo NMR spectrum of NR-H217O-120-30 also exhibits a major resonance at 457 ppm and a peak at 315 ppm, and the fraction of the latter is higher compared to the two samples enriched at room temperature. These data confirm the small shifts to higher frequencies for the peaks at around 450 ppm when the enrichment temperatures are higher. Therefore, the surface OTa2 species should be associated with a smaller chemical shift compared to the bulk. In addition, only slightly more 17OTa3 species should be generated during the thermal treatment at 120 °C because oxygen diffusion in Ta2O5 should still be very limited at this relatively low temperature.

Figure 3.

Figure 3

Open in a new tab

17O spin echo MAS NMR spectra of Ta2O5 nanorods. Recycle delays: 1.0 s (NR-H217O-120-30), 0.1 s (NR-H217O-RT-5, NR-H217O-RT-30); Spinning rate: 12 kHz (NR-H217O-RT-5), 14 kHz (NR-H217O-RT-30, NR-H217O-120-30). Spinning sidebands from the resonances at approx. 450 and 300 ppm are marked with “*” and “#“, respectively.

The nature of the low frequency peaks at −150 to 250 ppm is further investigated with 17O–1H rotational echo double resonance (REDOR) NMR spectroscopy,44 which is a powerful technique to measure the heteronuclear dipolar coupling, a function of internuclear distance and in this case, 17O–1H. Compared to the “control” spectrum, the “double resonance” spectrum shows weaker spectral intensities for NR-H217O-RT-5, reflecting the interference of 17O spin echo formation induced by nearby 1H (Figure 4). The decrease in the intensities for the peaks due to OTa2 (445 ppm) and OTa3 (300 ppm), as shown in the “difference” spectrum, is only roughly 20%, implying these species are not very close to H. On the other hand, the resonances at −150 to 250 ppm are associated with a very large spectral intensity decrease in the “double resonance” spectrum. Considering there are still contributions from spinning sidebands for the signals in the “double resonance” experiment, a REDOR fraction of approx. 80% is estimated. According to the previous studies for a variety of materials, including acidic zeolites,39−41 layered double hydroxides,43 as well as ceria and anatase titania nanomaterials,29,30 such large REDOR effect with a small recoupling time of 0.167 ms suggests that the resonances in this region arise from oxygen with very short O–H distances, specifically, when O is directly bound to H. Therefore, the spectral assignment of the low frequency signals to surface hydroxyl species or water is confirmed.

Figure 4.

Figure 4

Open in a new tab

17O–1H REDOR NMR of Ta2O5 nanorods (NR-H217O-RT-5). Recycle delay: 0.1 s; Spinning rate: 12 kHz; Dipolar recoupling time: 0.167 ms (two rotor periods). Spinning sidebands from the resonances at approx. 450 and 300 ppm are marked with “*” and “#“, respectively. The shaded area represents the region for the hydroxyl species and/or adsorbed water.

Numerical line shape simulations were performed for the REDOR differences to further explore the hydroxyl and/or adsorbed water species. If a single species (e.g., one hydroxyl site) is considered (Figure 5), the simulated quadrupolar coupling constant, CQ, is 10.4 MHz, which is too big for any hydroxyl environment in inorganic materials (Table S2).42,45 Therefore, there are more than one OH species in the Ta2O5 nanorods. Two sites were considered, and a possible simulation is shown in Figure 6. In such a case, the values of CQs can be in the common range for hydroxyl species (Table S3). The high chemical shifts (285 and 190 ppm) used in this simulation indicate that the two species are surface hydroxyl groups. However, significant spectral intensity comes from negative NMR shifts, implying there is water adsorbed on the surface.30 This result shows that there should be different hydroxyl and adsorbed water species on the surface, which are associated with complicated local environments. However, further analysis is not attempted because of the relatively poor signal/noise ratios in the 17O–1H REDOR differences. Nonetheless, all the different oxygen containing species, including surface OTa2 and surface/subsurface OTa3 sites, as well as surface hydroxyl species and adsorbed water, can be investigated with 17O NMR spectroscopy.

Figure 5.

Figure 5

Open in a new tab

Simulation of the 17O NMR spectrum (red) considering a single site in comparison to the 17O–1H REDOR difference (blue) of NR-H217O-RT-5. Simulated NMR parameters are shown in Table S3.

Figure 6.

Figure 6

Open in a new tab

Simulations of the 17O NMR spectrum considering two possible sites in comparison to the 17O–1H REDOR difference of NR-H217O-RT-5. The simulations are shown at the bottom, and the sum of two simulations is shown in the middle (red) while the experimental data is on top (blue). Simulated NMR parameters are shown in Table S4.

Finally, 1H spin echo MAS NMR spectroscopy was used to investigate the surface hydroxyl species and adsorbed water (Figure 7). A relatively sharp resonance at 5.2 ppm with a broad shoulder at 7.4 ppm along with a sharp and intense peak at 1.9 ppm can be observed in the 1H NMR spectrum of NR-H217O-RT-5. According to the chemical shift, the peak at 5.2 ppm can be ascribed to adsorbed water, while the resonances at 1.9 and 7.4 ppm can be assigned to the terminal and bridging hydroxyl species, respectively.31,46 The peak at 5.2 ppm almost disappears in the spectrum of NR-H217O-120-30, indicating that water is removed at a relatively high temperature of 120 °C. At the same time, a significant decrease in the spectral intensity can be observed for the signal at 1.9 ppm, while the intensity of the broad peak at 7.4 ppm does not change much. Combined with the 17O NMR observation that the spectral intensity of the peak due to OTa3 increases while the intensity of lower frequency resonances owing to hydroxyl species and/or adsorbed water decreases in NR-H217O-120-30, it can be concluded that terminal hydroxyl species react with each other to generate more surface OTa3 groups, and the resulting water is removed under vacuum. For NR-17O2-500, the intensities of the peaks arising from both terminal and bridging hydroxyl species further decrease and become very weak. Considering the broad linewidth of the hydroxyl species, this result is consistent with the absence of such peaks in 17O single pulse NMR data for NR-17O2-500.

Figure 7.

Figure 7

Open in a new tab

1H spin echo NMR spectra of Ta2O5 nanorods. Recycle delays: 2.0 s (NR-17O2-500, NR-H217O-120-30), 0.2 s (NR-H217O-RT-5); spinning rate: 14 kHz (NR-17O2-500, NR-H217O-120-30), 12 kHz (NR-H217O-RT-5).

Conclusions

For the first time, 17O solid-state NMR spectroscopy was applied to investigate the structure of Ta2O5 nanorods. Surface selective labeling of OTa2 sites can be achieved with the help of low-temperature enrichment with H217O, allowing surface-only detection in 17O NMR spectroscopy. Surface hydroxyl species and adsorbed water can also be observed with 17O and 1H NMR, while their nature is confirmed with 17O–1H REDOR NMR data. Combined 17O and 1H NMR results show that terminal hydroxyl groups react with each other and generate OTa3 sites at elevated temperatures. These results will be helpful for investigating the functions of different oxygen ions of Ta2O5 nanorods in catalysis and related applications.

Materials and Methods

Material Preparation

Ta2O5 nanorods were prepared according to the method reported previously.11 In a typical synthesis procedure, 0.55 g Ta(C2H5O)5 was mixed with 4 mL of toluene in a 10 mL glass bottle. After that, the glass bottle was put into a Teflon-lined hydrothermal reaction vessel filled with 8 mL of water. Then, the vessel was heated to 220 °C for 20 h before it was allowed to cool down to room temperature. The resulting precipitates were centrifuged and washed with distilled water as well as ethanol for 3 times each. Finally, the powders were dehydrated at 60 °C for 24 h to obtain Ta2O5 nanorods.

17O Enrichment Procedures

In order to enrich Ta2O5 nanorods with 17O, Ta2O5 nanorods were enriched using similar methods followed in the literature.29−31 The as-prepared sample was first heated at a ramping rate of 5 °C·min–1 from room temperature to 500 °C for 3 h under vacuum before the sample was allowed to cool to room temperature. For the non-selective isotopic labeling involving 17O2, 90% 17O-enriched O2 gas was introduced to the samples via a vacuum line, and the mixture was heated at 500 °C for 12 h. The resulting 17O–Ta2O5 is denoted as NR-17O2-500. The nanorods were also enriched by using H217O for surface-selective enrichment. After introducing 90% 17O-enriched water to the powders at room temperature, the mixtures were kept at room temperature for 5 and 30 min before they were exposed to vacuum to remove additional water. The resulting samples are denoted as NR-H217O-RT-5 and NR-H217O-RT-30, respectively. The mixture was also heated at 120 °C for 30 min before exposing to vacuum, and the sample is denoted as NR-H217O-120-30.

Characterization

The XRD data was collected on a Shimadzu XRD-6000 diffractometer, using a Cu Kα source (λ = 1.54178 Å) operating at 40 kV and 40 mA, with a scanning rate of 4°·min–1 in the 2θ range from 20 to 80°. High-resolution transmission electron microscopy (HRTEM) images were obtained on a JEOL JEM-2100 instrument with an accelerating voltage of 200 kV. The Brunauer–Emmett–Teller specific surface area was measured by nitrogen adsorption at −196 °C using a Micromeritics Tristar 3020 apparatus. The pore size distribution was derived from the desorption branches of the isotherm with the Barrett–Joyner–Halenda method. Room temperature 1H and 17O MAS NMR experiments were performed on a 9.4 T Bruker Avance III spectrometer with a 4.0 mm MAS probe operating at 400.0 and 54.2 MHz, respectively. All the samples were packed inside the rotors in the N2 glove box and spun at a MAS rate of 12 kHz or 14 kHz. 17O single pulse NMR data were collected using a short π/18 pulse of 0.5 μs. 17O spin echo NMR spectra were acquired with a rotor-synchronized Hahn echo sequence (π/6-τ-π/3-τ-acq, τ = one rotor period) using a π/6 pulse of 1.4 μs. 1H and 17O chemical shifts were externally referenced to adamantane and H2O at 1.92 and 0.0 ppm, respectively. 17O NMR line shape simulations were performed with the Wsolids package developed by Dr. K. Eichele.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (NSFC) (91745202, 21972066, and 21573103) and the NSFC–Royal Society Joint Program (21661130149). L.P. thanks the Royal Society and the Newton Fund for Royal Society—Newton Advanced Fellowship. This work was also supported by a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.0c00874.

  • Relaxation NMR data and NMR parameters for acquiring and simulating the spectra (PDF)

The authors declare no competing financial interest.

Supplementary Material

ao0c00874_si_001.pdf (169.5KB, pdf)

References

  1. Zhang P.; Zhang J.; Gong J. Tantalum-based semiconductors for solar water splitting. Chem. Soc. Rev. 2014, 43, 4395–4422. 10.1039/c3cs60438a. [DOI] [PubMed] [Google Scholar]
  2. Mikolajick T.; Kühnhold R.; Ryssel H. The pH-sensing properties of tantalum pentoxide films fabricated by metal organic low pressure chemical vapor deposition. Sens. Actuators, B 1997, 44, 262. 10.1016/s0925-4005(97)00166-4. [DOI] [Google Scholar]
  3. Fairbrother F.The Chemistry of Niobium and Tantalum; Elsevier: NY, 1967; pp 1–28. [Google Scholar]
  4. Musikant S.Optical Materials: An Introduction to Selection and Application; CRC Press, 1985; p 28. [Google Scholar]
  5. Chaneliere C.; Autran J. L.; Devine R. A. B.; Balland B. Tantalum pentoxide (Ta2O5) thin films for advanced dielectric applications. Mater. Sci. Eng. 1998, 22, 269–322. 10.1016/s0927-796x(97)00023-5. [DOI] [Google Scholar]
  6. Wang X.; Liu J.; Bai W.; Kwong D.-L. A Novel MONOS-Type Nonvolatile Memory Using High-<tex>$kappa$</tex>Dielectrics for Improved Data Retention and Programming Speed. IEEE T. Electron Dev. 2004, 51, 597. 10.1109/ted.2004.824684. [DOI] [Google Scholar]
  7. Zhu H.; Yuan H.; Li H.; Richter C. A.; Kirillov O.; Ioannou D. E.; Li Q. Design and Fabrication of Ta$_{2}$O $_{5}$ Stacks for Discrete Multibit Memory Application. IEEE Trans. Nanotechnol. 2013, 12, 1151–1157. 10.1109/tnano.2013.2281817. [DOI] [Google Scholar]
  8. Lee M.-J.; Lee C. B.; Lee D.; Lee S. R.; Chang M.; Hur J. H.; Kim Y.-B.; Kim C.-J.; Seo D. H.; Seo S.; Chung U.-I.; Yoo I.-K.; Kim K. A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5–x/TaO2–x bilayer structures. Nat. Mater. 2011, 10, 625. 10.1038/nmat3070. [DOI] [PubMed] [Google Scholar]
  9. Krishnaprasanth A.; Seetha M. Solvent free synthesis of Ta2O5 nanoparticles and their photocatalytic properties. AIP Adv. 2018, 8, 055017. 10.1063/1.5019423. [DOI] [Google Scholar]
  10. Zhang R. H.; Zhao T. S.; Wu M. C.; Jiang H. R.; Zeng L. Mesoporous ultrafine Ta2O5 nanoparticle with abundant oxygen vacancies as a novel and efficient catalyst for non-aqueous Li-O2 batteries. Electrochim. Acta 2018, 271, 232–241. 10.1016/j.electacta.2018.03.164. [DOI] [Google Scholar]
  11. Yu X.; Wei Y.; Li Z.; Liu J. One-step synthesis of the single crystal Ta2O5 nanowires with superior hydrogen production activity. Mater. Lett. 2017, 191, 150–153. 10.1016/j.matlet.2016.12.079. [DOI] [Google Scholar]
  12. Zhang N.; Li L.; Li G. Nanosized amorphous tantalum oxide: a highly efficient photocatalyst for hydrogen evolution. Res. Chem. Intermed. 2017, 43, 5011–5024. 10.1007/s11164-017-3052-y. [DOI] [Google Scholar]
  13. Gonçalves R. V.; Wojcieszak R.; Uberman P. M.; Eberhardt D.; Teixeira-Neto E.; Teixeira S. R.; Rossi L. M. Catalytic abatement of CO over highly stable Pt supported on Ta2O5 nanotubes. Catal. Commun. 2014, 48, 50–54. 10.1016/j.catcom.2014.01.020. [DOI] [Google Scholar]
  14. Zhang M.; Hou P.; Wang Z.; Kang P. Nitrogen-Doped Ta2 O5 Nanocomposites for the Electrocatalytic Reduction of Carbon Dioxide to CO with Photoassistance. ChemElectroChem 2018, 5, 799–804. 10.1002/celc.201701353. [DOI] [Google Scholar]
  15. Momeni M. M.; Mirhosseini M.; Chavoshi M.; Hakimizade A. The effect of anodizing voltage on morphology and photocatalytic activity of tantalum oxide nanostructure. J. Mater. Sci.: Mater. Electron. 2016, 27, 3941–3947. 10.1007/s10854-015-4246-y. [DOI] [Google Scholar]
  16. Duan J.; Shi W.; Xu L.; Mou G.; Xin Q.; Guan J. Hierarchical nanostructures of fluorinated and naked Ta2O5 single crystalline nanorods: hydrothermal preparation, formation mechanism and photocatalytic activity for H2 production. Chem. Commun. 2012, 48, 7301–7303. 10.1039/c2cc33211f. [DOI] [PubMed] [Google Scholar]
  17. Li J.; Dai W.; Yan J.; Wu G.; Li L.; Guan N. Hydrothermal synthesis and photocatalytic properties of tantalum pentoxide nanorods. Chin. J. Catal. 2015, 36, 432–438. 10.1016/s1872-2067(14)60215-1. [DOI] [Google Scholar]
  18. Momeni M. M.; Mirhosseini M.; Chavoshi M. Growth and characterization of Ta2O5 nanorod and WTa2O5 nanowire films on the tantalum substrates by a facile one-step hydrothermal method. Ceram. Int. 2016, 42, 9133–9138. 10.1016/j.ceramint.2016.03.002. [DOI] [Google Scholar]
  19. Berrettini M. G.; Braun G.; Hu J. G.; Strouse G. F. NMR analysis of surfaces and interfaces in 2-nm CdSe. J. Am. Chem. Soc. 2004, 126, 7063–7070. 10.1021/ja037228h. [DOI] [PubMed] [Google Scholar]
  20. Roming M.; Feldmann C.; Avadhut Y. S. SchmedtCharacterization of Noncrystalline Nanomaterials: NMR of Zinc Phosphate as a Case Study. Chem. Mater. 2008, 20, 5787–5795. 10.1021/cm800805f. [DOI] [Google Scholar]
  21. Hanrahan M. P.; Fought E. L.; Windus T. L.; Wheeler L. M.; Anderson N. C.; Neale N. R.; Rossini A. J. Characterization of silicon nanocrystal surfaces by multidimensional Solid-State NMR spectroscopy. Chem. Mater. 2017, 29, 10339–10351. 10.1021/acs.chemmater.7b03306. [DOI] [Google Scholar]
  22. Lapina O. B.; Khabibulin D. F.; Shubin A. A.; Terskikh V. V. Practical aspects of 51V and 93Nb solid-state NMR spectroscopy and applications to oxide materials. Prog. Nucl. Magn. Reson. Spectrosc. 2008, 53, 128–191. 10.1016/j.pnmrs.2007.12.001. [DOI] [Google Scholar]
  23. Pickup D. M.; Mountjoy G.; Holland M. A.; Wallidge G. W.; Newport R. J.; Smith M. E. Structure of (Ta2O5)x(SiO2)1 – x xerogels (x = 0.05, 0.11, 0.18, 0.25 and 1.0) from FTIR, 29Si and 17O MAS NMR and EXAFS. J. Mater. Chem. 2000, 10, 1887–1894. 10.1039/b000947o. [DOI] [Google Scholar]
  24. Julián B.; Gervais C.; Rager M.-N.; Maquet J.; Cordoncillo E.; Escribano P.; Babonneau F.; Sanchez C. Solid-State17O NMR Characterization of PDMS–MxOy(M = Ge(IV), Ti(IV), Zr(IV), Nb(V), and Ta(V)) Organic–Inorganic Nanocomposites. Chem. Mater. 2004, 16, 521–529. 10.1021/cm034958f. [DOI] [Google Scholar]
  25. Anderson T. M.; Rodriguez M. A.; Bonhomme F.; Bixler J. N.; Alam T. M.; Nyman M. An aqueous route to [Ta6O19]8- and solid-state studies of isostructural niobium and tantalum oxide complexes. Dalton Trans. 2007, 4517–4522. 10.1039/b707636c. [DOI] [PubMed] [Google Scholar]
  26. Rao Y.; Kemp T. F.; Trudeau M.; Smith M. E.; Antonelli D. M. 17O and15N Solid State NMR Studies on Ligand-Assisted Templating and Oxygen Coordination in the Walls of Mesoporous Nb, Ta and Ti Oxides. J. Am. Chem. Soc. 2008, 130, 15726–15731. 10.1021/ja8056387. [DOI] [PubMed] [Google Scholar]
  27. Kim N.; Stebbins J. F. Structure of Amorphous Tantalum Oxide and Titania-Doped Tantala:17O NMR Results for Sol-Gel and Ion-Beam-Sputtered Materials. Chem. Mater. 2011, 23, 3460–3465. 10.1021/cm200630m. [DOI] [Google Scholar]
  28. Kim N.; Stebbins J. F. Effects of annealing on the structure of ion beam sputtered amorphous tantalum oxide: Oxygen-17 NMR spectra and relaxation times. J. Non-Cryst. Solids 2013, 378, 158–162. 10.1016/j.jnoncrysol.2013.07.003. [DOI] [Google Scholar]
  29. Wang M.; Wu X.-P.; Zheng S.; Zhao L.; Li L.; Shen L.; Gao Y.; Xue N.; Guo X.; Huang W.; Gan Z.; Blanc F.; Yu Z.; Ke X.; Gong X.-Q.; Grey C. P.; Peng L. Identification of different oxygen species in oxide nanostructures with 17O solid-state NMR spectroscopy. Sci. Adv. 2015, 1, e1400133 10.1126/sciadv.1400133. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Li Y.; Wu X.; Jiang N.; Lin M.; Shen L.; Sun H.; Wang Y.; Wang M.; Ke X.; Yu Z.; Gao F.; Dong L.; Guo X.; Hou W.; Ding W.; Gong X.; Grey C. P.; Peng L. Distinguishing faceted oxide nanocrystals with 17O solid-state NMR spectroscopy. Nat. Commun. 2017, 8, 581. 10.1038/s41467-017-00603-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Chen J.; Wu X.; Hope M. A.; Qian K.; Halat D. M.; Liu T.; Li Y.; Shen L.; Ke X.; Wen Y.; Du J.; Magusin P. C. M. M.; Paul S.; Ding W.; Gong X.; Grey C. P.; Peng L. Polar surface structure of oxide nanocrystals revealed with solid-state NMR spectroscopy. Nat. Commun. 2019, 10, 5420. 10.1038/s41467-019-13424-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Shen L.; Peng L. 17O solid-state NMR studies of oxygen-containing catalysts. Chin. J. Catal. 2015, 36, 1494–1504. 10.1016/s1872-2067(15)60931-7. [DOI] [Google Scholar]
  33. Shen L.; Wu X.-P.; Wang Y.; Wang M.; Chen J.; Li Y.; Huo H.; Hou W.; Ding W.; Gong X.-Q.; Peng L. 17O Solid-State NMR Studies of ZrO2 Nanoparticles. J. Phys. Chem. C 2019, 123, 4158–4167. 10.1021/acs.jpcc.8b11091. [DOI] [Google Scholar]
  34. Du J.-H.; Peng L. Recent progress in investigations of surface structure and properties of solid oxide materials with nuclear magnetic resonance spectroscopy. Chin. Chem. Lett. 2018, 29, 747–751. 10.1016/j.cclet.2018.02.012. [DOI] [Google Scholar]
  35. Li Y.; Wu X.; Liu C.; Wang M.; Song B.; Yu G.; Yang G.; Hou W.; Gong X.-Q.; Peng L. NMR and EPR studies of partially reduced TiO2. Acta Phys. Sin. 2020, 36, 1905021. [Google Scholar]
  36. Wang Y.; Yang C.; Wen Y.; Chen J.; Du J.; Peng L. Analysis of the concentrations of surface Ni ions in Ni/CeO2 with 17O solid-state NMR spectroscopy. Chin. J. Magn. Reson. 2020, 37, 52–60. [Google Scholar]
  37. Shen L.; Wang Y.; Du J. H.; Chen K.; Lin Z.; Wen Y.; Hung I.; Gan Z.; Peng L.. Probing Interactions of γ-Alumina with Water via Multinuclear Solid-State NMR Spectroscopy. ChemCatChem. 2020, 12, DOI: 10.1002/cctc.201901838. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Patnaik P.Handbook of Inorganic Chemicals; McGraw-Hill: NY, 2002; pp 911–912. [Google Scholar]
  39. Peng L.; Liu Y.; Kim N.; Readman J. E.; Grey C. P. Detection of Brønsted acid sites in zeolite HY with high-field 17O-MAS-NMR techniques. Nat. Mater. 2005, 4, 216–219. 10.1038/nmat1332. [DOI] [PubMed] [Google Scholar]
  40. Peng L.; Huo H.; Liu Y.; Grey C. P. 17O Magic Angle Spinning NMR Studies of Brønsted Acid Sites in Zeolites HY and HZSM-5. J. Am. Chem. Soc. 2007, 129, 335–346. 10.1021/ja064922z. [DOI] [PubMed] [Google Scholar]
  41. Huo H.; Peng L.; Gan Z.; Grey C. P. Solid-State MAS NMR Studies of Brønsted Acid Sites in Zeolite H-Mordenite. J. Am. Chem. Soc. 2012, 134, 9708–9720. 10.1021/ja301963e. [DOI] [PubMed] [Google Scholar]
  42. Ashbrook S. E.; Smith M. E. Solid state17O NMR-an introduction to the background principles and applications to inorganic materials. Chem. Soc. Rev. 2006, 35, 718. 10.1039/b514051j. [DOI] [PubMed] [Google Scholar]
  43. Zhao L.; Qi Z.; Blanc F.; Yu G.; Wang M.; Xue N.; Ke X.; Guo X.; Ding W.; Grey C. P.; Peng L. Investigating Local Structure in Layered Double Hydroxides with17O NMR Spectroscopy. Adv. Funct. Mater. 2014, 24, 1696–1702. 10.1002/adfm.201301157. [DOI] [Google Scholar]
  44. Gullion T.; Schaefer J. Rotational-echo double-resonance NMR. J. Magn. Reson. 1989, 81, 196–200. 10.1016/0022-2364(89)90280-1. [DOI] [PubMed] [Google Scholar]
  45. Wu G. Solid-state 17O NMR studies of organic and biological molecules. Prog. Nucl. Magn. Reson. Spectrosc. 2008, 52, 118–169. 10.1016/j.pnmrs.2007.07.004. [DOI] [PubMed] [Google Scholar]
  46. Mogilevsky G.; Karwacki C. J.; Peterson G. W.; Wagner G. W. Surface hydroxyl concentration on Zr(OH)4 quantified by 1H MAS NMR. Chem. Phys. Lett. 2011, 511, 384–388. 10.1016/j.cplett.2011.06.072. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ao0c00874_si_001.pdf (169.5KB, pdf)

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES