NMR studies on Nano-Materials
EMSL Project ID
2434
Abstract
The objective of this proposal is to use the high resolution solid-state NMR to continue our study of molecularly designed nano-materials. Both the 300 and 500 MHz, possible 750 MHz solid state NMR spectrometers are required for the investigation of the conformation and dynamics of surfactant molecules in novel nano-materials. Our project is funded by DOE under the basic energy science division. Our new proposed research involves synthesis and characterization of novel templating molecules. High field NMR can be used to characterize the structures of those novel templating molecules either in self-organized forms or in organic/inorganic composites. Our earlier NMR study clearly demonstrates the co-existence of two conformational domains for surfactant on the clay type of materials. Two main resonance peaks are resolved from the backbone alkyl chains: the resonance at 30 ppm corresponding to the conformationally ordered (all-trans) domain, and the resonance at 33 ppm corresponding conformationally disordered (mixture of trans and gauche) domain. The contributions from both domains are significant even in the samples believed to be very diordered. Therefore the NMR technique allows detailed characterization and quantification of the conformational heterogeneity, which is difficult with other techniques. Furthermore, variable-temperature NMR also directly provides quantitative information on the conformational rigidity of the different domains. The relaxation time derived from the contact-time array experiments and 2D WISE suggests that the molecules in the ordered domain is as rigid as those in solid crystalline materials, and that the molecules in disordered domain is similar to those in liquid crystalline materials. Upon heating, the molecules in the disordered domain remain more or less unchanged, while the molecules in the ordered domain become disordered. However, the molecules in the clay minerals never attained the complete liquid-like behavior even after melting.We also plan to use 500 MHz NMR spectrometers to study the Al speciation in the Tank waste project which is funded by DOE under EMSL program. High field is required to obtain the high-resolution spectra for the quadruple nuclei such as 27Al. Multiple-Quantum NMR will be used to investigate the different sites within the same coordination. The Al speciation and the structure under high PH conditions can be determined using a combination of NMR and x-ray diffraction techniques.
Project Details
Project type
Capability Research
Start Date
2002-04-15
End Date
2003-05-06
Status
Closed
Released Data Link
Team
Principal Investigator