Video Experimental Relacionado

Updated: Jul 17, 2026

The Evolution of Silica Nanoparticle-polyester Coatings on Surfaces Exposed to Sunlight

The Evolution of Silica Nanoparticle-polyester Coatings on Surfaces Exposed to Sunlight

Published on: October 11, 2016

19F Cuantificación por RMN de MAS de los sitios hidroxilo accesibles en las superficies de fibra de vidrio

Roderick A Fry¹, Natia Tsomaia, Carlo G Pantano

¹Departments of Chemistry and of Materials Science and Engineering, The Pennsylvania State University, Materials Research Institute, University Park, PA 16802, USA.

Journal of the American Chemical Society

|February 27, 2003

Resumen

La espectroscopia de resonancia magnética nuclear (RMN) de estado sólido 19F cuantifica los sitios hidroxilo en las fibras de vidrio. Este método utiliza una sonda de flúor-19 para analizar grupos hidroxilo superficiales accesibles, incluso en materiales de baja superficie.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Química Analítica La Química Analítica es la
Química de las superficies.

Sus antecedentes:

La caracterización de sitios hidroxilo en materiales de baja superficie es un desafío.
La espectroscopia de Resonancia Magnética Nuclear (RMN) ofrece el potencial para el análisis cuantitativo de la superficie.
La RMN con fluoro-19 (19F) es particularmente adecuada debido a sus propiedades nucleares.

Objetivo del estudio:

Investigar cuantitativamente los sitios hidroxilo accesibles en las fibras de vidrio de baja superficie.
Adaptar las técnicas de RMN de estado sólido 19F para el análisis de superficies de materiales difíciles.
Establecer un método para determinar la cobertura de hidroxilo en las superficies de fibra de vidrio.

Principales métodos:

Se utilizó la espectroscopia de resonancia magnética nuclear (RMN) de estado sólido 19F.
Se empleó la unión covalente de (3,3,3-trifluoropropil) dimetilclorosilano como una sonda 19F.
Aplicó técnicas de giro de ángulo mágico (MAS) de alta velocidad (>15 kHz) para mejorar la resolución espectral.
Calibrado utilizando modelos de geles de sílice con diferentes superficies y tamaños de poros.

Principales resultados:

Cuantificó con éxito sitios de hidroxilo accesibles en fibras de vidrio con superficies tan bajas como 0,2 m2/g.
Las mediciones de las coberturas accesibles de hidroxilo en el rango de 0.8-1.3 OH/nm2.
Se identificaron distintas resonancias de RMN que corresponden a diferentes entornos de unión (confinado vs. a granel).

Conclusiones:

La RMN 19F en estado sólido es una técnica viable para la cuantificación del sitio hidroxilo en fibras de vidrio de baja superficie.
El método proporciona información sobre las propiedades de la superficie como la rugosidad y la microporosidad.
Este enfoque permite la caracterización detallada de la superficie de materiales difíciles.

Más Videos Relacionados

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy

Published on: August 13, 2019

Fabrication of polydimethylsiloxane (PDMS)-Based Flexible Surface-Enhanced Raman Scattering (SERS) Substrate for Ultrasensitive Detection

Fabrication of polydimethylsiloxane (PDMS)-Based Flexible Surface-Enhanced Raman Scattering (SERS) Substrate for Ultrasensitive Detection

Published on: November 17, 2023

Videos de Conceptos Relacionados

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...

NMR Spectroscopy of Aromatic Compounds

NMR Spectroscopy of Aromatic Compounds

Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...

NMR Spectroscopy of Benzene Derivatives

NMR Spectroscopy of Benzene Derivatives

Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling constants depend...

¹H NMR Signal Integration: Overview

¹H NMR Signal Integration: Overview

The intensity of a signal, which can be represented by the area under the peak, depends on the number of protons contributing to that signal. The area under each peak is shown as a vertical line called an integral, with the integral value listed under it, as seen in the proton NMR spectrum of benzyl acetate. Each integral value is divided by the smallest integral value to obtain the ratio of the number of protons producing each signal. The ratio reveals the relative number of protons and not...

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.