Inagaki, S., et al., Drastic sensitivity enhancement in Si MAS NMR of zeolites and mesoporous silica materials by paramagnetic doping of Cu. Phys Chem Chem Phys, 2013.
http://www.ncbi.nlm.nih.gov/pubmed/23824320
The paramagnetic doping of Cu2+ in both mesoporous silica materials and microporous silicate crystals (zeolites) can be used effectively to enhance the signal intensity of 29Si solid state magic angle spinning NMR, as a result of shortening of the spin-lattice relaxation time, T1, by the paramagnetic effect, because of the Cu2+ electronic relaxation time in the range of 10-8 s. This leads to drastically reduced data-collection times, typically 80-fold shorter than that in mesoporous silica. We found that the estimated range of the paramagnetic effect of Cu2+ doping in porous silicates was at least 1 nm.