silicon and aluminum-phosphate

Scalar couplings, recoupled or full dipolar interactions can be used to characterize multinuclear structural molecular motifs in solids, by counting the neighbouring spins in solid-state NMR, opening new ways for the differentiation of overlapping spectral responses which is a limiting factor in many high resolution experiments carried out on disordered systems.

Topics: Aluminum; Aluminum Compounds; Aluminum Silicates; Calcium; Magnetic Resonance Spectroscopy; Models, Chemical; Oxygen; Phosphates; Quantum Theory; Reference Standards; Silicon

The recently introduced concept of soft pulse added mixing (SPAM) is used in two-dimensional heteronuclear correlation (HETCOR) NMR experiments between half-integer quadrupolar and spin-1/2 nuclei. The experiments employ multiple quantum magic angle spinning (MQMAS) to remove the second order quadrupolar broadening and cross polarization (CP) or refocused INEPT for magnetization transfer. By using previously unexploited coherence pathways, the efficiency of SPAM-MQ-HETCOR NMR is increased by a factor of almost two without additional optimization. The sensitivity gain is demonstrated on a test sample, AlPO(4)-14, using CP and INEPT to correlate (27)Al and (31)P nuclei. SPAM-3Q-HETCOR is then applied to generate (27)Al-(31)P spectra of the devitrified 41Na(2)O-20.5Al(2)O(3)-38.5P(2)O(5) glass and the silicoaluminophosphate ECR-40. Finally, the method allowed the acquisition of the first high resolution solid-state correlation spectra between (27)Al and (29)Si.

Topics: Aluminum; Aluminum Compounds; Nuclear Magnetic Resonance, Biomolecular; Oxygen Radioisotopes; Phosphates; Phosphorus; Silicon

Silicon-free and silicon-rich large-pore aluminophosphate VPI-5, synthesized with various contents of AIPO-H3 impurity, was studied by Bloch decay (BD) and cross polarization (CP) NMR under magic angle spinning (MAS). The 1H-->31P CP peaks were considerably stronger from AIPO-H3 than from VPI-5. A detailed examination of the CP kinetics and a careful comparison of the CP and BD spectra are prerequisites for the unequivocal interpretation of 1H-->31P CP in porous aluminophosphates.

Topics: Aluminum Compounds; Chemical Phenomena; Chemistry, Physical; Magnetic Resonance Spectroscopy; Phosphates; Silicon; Surface-Active Agents