Video Experimental Relacionado

Updated: Jun 11, 2026

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

Published on: April 28, 2016

Asignación de RMN de estado sólido 13C de resonancias de carbono en nanotubos de carbono de pared única metálicos y

Chaiwat Engtrakul¹, Mark F Davis, Kevin Mistry

¹National Renewable Energy Laboratory, Golden, Colorado 80401, USA. Chaiwat.Engtrakul@nrel.gov

Journal of the American Chemical Society

|July 3, 2010

Resumen

La espectroscopia de resonancia magnética nuclear de carbono-13 de estado sólido (13C NMR) diferencia efectivamente los nanotubos de pared única metálicos (m-SWNT) y semiconductores (s-SWNT). Esta técnica proporciona un método sensible para analizar mezclas SWNT basadas en sus distintos cambios químicos.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Nanotecnología La nanotecnología es la nanotecnología.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

Los nanotubos de pared única (SWNT) poseen propiedades electrónicas únicas determinadas por su quiralidad, lo que lleva a los tipos metálicos (m-SWNT) y semiconductores (s-SWNT).
Distinguir entre m-SWNTs y s-SWNTs es crucial para desarrollar aplicaciones específicas en electrónica y sensores.
La caracterización de la pureza y composición de SWNT en muestras mixtas sigue siendo un desafío analítico significativo.

Objetivo del estudio:

Investigar la utilidad de la espectroscopia de resonancia magnética nuclear (13C NMR) de carbono-13 en estado sólido para diferenciar las m-SWNT y las s-SWNT.
Para determinar la sensibilidad de los desplazamientos químicos de RMN 13C como una sonda para la composición de SWNT en muestras mixtas.
Establecer un método fiable para analizar mezclas de SWNT con proporciones variables de especies metálicas y semiconductoras.

Principales métodos:

Se utilizó espectroscopia de RMN de estado sólido 13C de alta resolución.
Se analizaron muestras de SWNT con una amplia gama de contenido metálico (m-SWNT) y semiconductor (s-SWNT), incluidas muestras altamente purificadas (casi 100%).
Se centró en SWNTs con diámetros de aproximadamente 1,3 nm y empleó el ajuste gaussiano para el análisis espectral.

Principales resultados:

Se ha demostrado que la RMN 13C es una sonda sensible para distinguir entre m-SWNTs y s-SWNTs en muestras mixtas.
Se observaron distintas características de desplazamiento químico de RMN 13C para m-SWNTs (aprox. 123 ppm) y s-SWNTs (aprox. 122 partes por millón).
Con éxito se ajustaron espectros de muestras de m- y s-SWNT altamente enriquecidas con un solo gaussiano, mientras que las muestras mixtas requerían dos gaussianos para un ajuste preciso.

Conclusiones:

La espectroscopia de RMN 13C en estado sólido proporciona un método robusto y sensible para caracterizar la composición de las mezclas SWNT.
Los distintos desplazamientos químicos de los carbonos m- y s-SWNT permiten una diferenciación y cuantificación confiables.
Este enfoque espectroscópico es valioso para el control de calidad y el desarrollo de materiales y dispositivos basados en SWNT.

Más Videos Relacionados

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

Published on: June 1, 2016

Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes

Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes

Published on: January 10, 2017

Videos de Conceptos Relacionados

Carbon-13 (¹³C) NMR: Overview

Carbon-13 (¹³C) NMR: Overview

Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...

¹³C NMR: ¹H–¹³C Decoupling

¹³C NMR: ¹H–¹³C Decoupling

The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...

2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)

2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)

Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...

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...

Chemical Shift: Internal References and Solvent Effects

Chemical Shift: Internal References and Solvent Effects

In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...

NMR Spectroscopy: Chemical Shift Overview

NMR Spectroscopy: Chemical Shift Overview

The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...