Next Article in Journal
Trial of an All-Ceramic SnO2 Gas Sensor Equipped with CaCu3Ru4O12 Heater and Electrode
Previous Article in Journal
An Approach for Measuring the Dielectric Strength of OLED Materials
Article Menu
Issue 6 (June) cover image

Export Article

Open AccessArticle
Materials 2018, 11(6), 980; https://doi.org/10.3390/ma11060980

Protective Carbon Overlayers from 2,3-Naphthalenediol Pyrolysis on Mesoporous SiO2 and Al2O3 Analyzed by Solid-State NMR

1
Department of Chemistry, Brandeis University, Waltham, MA 02453, USA
2
Department of Chemical & Biological Engineering and Center for Microengineered Materials, University of New Mexico, Albuquerque, NM 87131, USA
*
Author to whom correspondence should be addressed.
Received: 5 April 2018 / Revised: 1 June 2018 / Accepted: 5 June 2018 / Published: 9 June 2018
Full-Text   |   PDF [1326 KB, uploaded 9 June 2018]   |  

Abstract

Hydrothermally stable carbon overlayers can protect mesoporous oxides (SiO2 and Al2O3) from hydrolysis during aqueous-phase catalysis. Overlayers made at 800 °C by pyrolysis of 2,3-naphthalenediol deposited out of acetone solution were analyzed by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Power absorption due to sample conductivity was prevented by diluting the sample in nonconductive and background-free tricalcium phosphate. While pyrolysis on SiO2 produced a predominantly aromatic carbon film, at least 15% of nonaromatic carbon (sp3-hybridized C as well as C=O) was observed on γ-Al2O3. These species were not derived from residual solvent, according to spectra of the same material treated at 400 °C. The sp3-hybridized C exhibited weak couplings to hydrogen, short spin-lattice relaxation times, and unusually large shift anisotropies, which are characteristics of tetrahedral carbon with high concentrations of unpaired electrons. Moderate heat treatment at 400 °C on SiO2 and Al2O3 resulted in yellow-brown and nearly black samples, respectively, but the darker color on Al2O3 did not correspond to more extensive carbonization. Aromatic carbon bonded to hydrogen remained predominant and the peaks of naphthalenediol were still recognizable; however, some of the chemical shifts differed by up to 5 ppm, indicating significant differences in local structure. On SiO2, additional sharp peaks were detected and attributed to 1/3 of the 2,3-naphthalene molecules undergoing fast, nearly isotropic motions. View Full-Text
Keywords: NMR of conductive materials; carbon-coated mesoporous oxides; structure of carbon overlayers NMR of conductive materials; carbon-coated mesoporous oxides; structure of carbon overlayers
Figures

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Supplementary material

SciFeed

Share & Cite This Article

MDPI and ACS Style

Duan, P.; Cao, X.; Pham, H.; Datye, A.; Schmidt-Rohr, K. Protective Carbon Overlayers from 2,3-Naphthalenediol Pyrolysis on Mesoporous SiO2 and Al2O3 Analyzed by Solid-State NMR. Materials 2018, 11, 980.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Materials EISSN 1996-1944 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top