Adaptive reorganization of 2D molecular nanoporous network induced by coadsorbed guest molecule.

The ordered array of nanovoids in nanoporous networks, such as honeycomb, Kagome, and square, provides a molecular template for the accommodation of "guest molecules". Compared with the commonly studied guest molecules featuring high symmetry evenly incorporated into the template, guest molecules featuring lower symmetry are rare to report. Herein, we report the formation of a distinct patterned superlattice of guest molecules by selective trapping of guest molecules into the honeycomb network of trimesic acid (TMA). Two distinct surface patterns have been achieved by the guest inclusion induced adaptive reconstruction of a 2D molecular nanoporous network. The honeycomb networks can synergetically tune the arrangement upon inclusion of the guest molecules with different core size but similar peripherals groups, resulting in a trihexagonal Kagome or triangular patterns.

Gold nanorod arrays with good reproducibility for high-performance surface-enhanced Raman scattering.

We have attempted to develop surface-enhanced Raman scattering (SERS) substrates by the use of two-dimensional (2D) Au nanorod arrays and to characterize the SERS-active sites of the Au nanostructures. We prepared two different types of 2D Au nanorod arrays by means of the anodic aluminum oxide (AAO) template-assisted nanofabrication. In the template-embedded array (type I) an Au nanorod fills up the AAO pore, while in the annularly spaced array (type II) an Au nanorod keeps approximately 20 nm away from the pore wall. The strongest SERS effect was observed for both types of substrates with an Au nanorod diameter of approximately 66 nm. With respect to the bare AAO template, the NaOH-etched (unetched) type I substrate with the 66 nm Au nanorod showed 115-fold (63-fold) enhancement in Raman scattering, corresponding to a SERS enhancement factor of 10(7)-10(9). For the unetched and ordered Au naonorod arrays, the SERS-active sites localized around the rod end, whereas for the NaOH-etched and partially aggregated Au nanorods, hot spots for SERS were found in the interstices between rod tips. The type II substrate allowed the effect of rod length on the SERS response to be investigated, and the SERS response was observed to vary very little with the rod length increase (250-1000 nm), indicating that majority of the signal originates at the rod end. A comparison between the analytes all-trans-beta-carotene and pyridine suggests that, for both types of substrates, the electromagnetic enhancement is predominant over the chemical enhancement. This work demonstrates that the unetched type I substrate is highly SERS effective, for which the fabrication protocol is advantageous in its simplicity and reproducibility.

Inclusion complex of spironaphthoxazine with gamma-cyclodextrin and its photochromism study.

An environmentally benign transparent photochromic film, 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]-naphtho[2,1-b][1,4]oxazine] (SPO) /gamma-cyclodextrin (gamma-CD), was prepared using the cast-coating method, and the nanocavity effect of gamma-CD on the photochromism of SPO was studied. The film mainly consists of the inclusion complex SPO@gamma-CD, which has been verified by EA, TGA, XRD, MS, and ICD to comprise a 1:1 host-guest stoichiometry. The film shows normal photochromism. The decoloration of photomerocyanine (PMC) fits biexponential decay: PMCs located in the cavity of gamma-CD decay with a rate constant of 6.0 x 10(-2) s(-1), which is nearly one order faster than those PMCs outside of the cavity.