No abstract

No abstract

No abstract

A novel class of mesoporous aluminosilicate molecular sieves has been prepared by replication from carbon mesoporous molecular sieves (CMKs) using zeolite precursors and characterized by a variety of analytical and spectroscopic techniques, such as XRD, N2 adsorption/desorption, SEM/TEM, IR, hyperpolarized (HP) 129Xe, and 31P MAS NMR. These replicated mesoporous materials (RMMs), namely RMM-1 and RMM-3 prepared from CMK-1 and CMK-3, were found to exhibit mesoporous structures respectively analogous to Al-MCM-48 and Al-SBA-15 but possess unique microporous characteristics due to the presence of zeolite secondary building units in the framework. Consequently, these RMMs are also found to have superior thermal, hydrothermal, and mechanical stabilities and with improved acidic properties compared to their respective parent counterparts. The RMM-3 so prepared represents the first synthesis of protonated aluminosilicate with an SBA-15 structure prepared by a nonacidic route.

The eight vitamin E isomers [α-, β-, γ-, and δ-tocopherols (T) and α-, β-, γ-, and δ-tocotrienols (T3)] and γ-oryzanol are known to possess diverse biological activities. This study examined the contents of these compounds and their distribution in 16 commercial rice varieties in Taiwan. Results showed that the order of vitamin E, total T, total T3, and γ-oryzanol contents was rice bran > brown rice > rice husk > polished rice. γ-T3 was the highest vitamin E isomer present in all rice samples, while β-T, β-T3, δ-T, and δ-T3 were present in trace amounts. The Japonica varieties contained a higher total T, total T3, and γ-oryzanol than the Indica varieties. They also have a higher level of α-T and α-T3 but a lower level of γ-T and γ-T3 than the Indica varieties. However, no obvious difference in total T, total T3, and γ-oryzanol content was noted between black- and red-colored rice varieties.

Cadmium selenide is a II−VI semiconductor model system known for its nanoparticle preparation, growth mechanism, luminescence properties, and quantum confinement studies. For the past 2 decades, various thermodynamically stable "magic-size nanoclusters (MSCs)" of CdSe have been observed, isolated, and theoretically calculated. Nevertheless, none of the proposed structures were experimentally confirmed due to the small crystal domains beyond the diffraction limit. With a combination of nondestructive SAXS, WAXS, XRD, XPS, EXAFS, and MAS NMR techniques, we were able to verify the phase transformation, shape, size dimension, local bonding, and chemical environments of (CdSe) 13 nanoclusters, which are indicative of a paired cluster model. These experimental results are consistent with the size, shape, bond lengths, dipole moment, and charge densities of the proposed "paired-tubular geometry" predicted by computational approaches. In this article, we revisit the formation pathway of the mysterious (CdSe) 13 nanoclusters and propose a paired cluster structure model for better understanding of II−VI semiconductor nanoclusters.

No abstract

No abstract