서강대학교

목차

Aligned Inclusion of Hemicyanine Dyes into Silica Zeolite Films for Second Harmonic Generation
Silicalite-1 films (thickness = 400 nm) supported on both sides of glass plates (SL/G) were prepared and hemicyanine dyes (HC-n) with different alkyl chain lengths (n, n = 3, 6, 9, 12, 15, 18, 22, and 24) were included into the silicalite-1 films by dipping SL/Gs into each methanol solution of HC-n (1 mM) for 1 d. The included numbers of HC-n per channel (NC) generally decreased with increasing n, i.e., they were 6.4, 23.1, 15.4, 8.2, 5.7, 3.5, 0.9 and 1.2 molecules per channel, respectively. The d33 value gradually increased with increasing n but decreased when n > 18, i.e., they were 1.12, 0.50, 2.25, 3.59, 4.99, 5.30, 1.71, and 2.57 pmV-1, respectively. However, d33/NC progressively increased with increasing n. The d31 values were ~100 times smaller than the corresponding d33 values, and the average d33/d31 ratio was 109, which is higher than those of Langmuir-Blodgett (LB) films and poled polymers of nonlinear optical (NLO) dyes, by ~2-5 and ~30-50 times, respectively. The estimated average tilted angle of the dyes with respect to the channel direction was 7.7？, and the calculated average order parameter was 0.97, which is ~480 times higher than the values observed from poled polymers. The degree of uniform alignment (DUA) generally increased with increasing n. The progressive increase of both DUA and d33/NC with n is attributed to the increase in the tendency of HC-n to enter hydrophobic silicalite-1 channels with the hydrophobic alkyl chain first. More than 134-fold increase in DUA was observed upon increasing n from 6 to 24. The DUA of HC-24 in the silicalie-1 film was concluded to be close to 1. Although the observed d33 values were lower than the LB films of NLO dyes due to very small dye densities of the films, this methodology bears a great potential to be developed into the methods for preparing practically viable NLO films.

Chapter 2.
Aligned Inclusion of n-Propionic Acid-Tethering Hemicyanine into Silica Zeolite Film for Second Harmonic Generation
Propionic acid-tethering hemicyanine dye (HC-2-CO2H) was included into the channels of silicalite-1 films (thickness = 400 nm) supported on glass plates (SL/Gs, 2 ？ 2 cm2) by dipping SL/Gs into aqueous solutions (20 mL) of HC-2-CO2H (0.1 mM) and tetrabutylammonium hydroxide (TBAOH), in which the concentration TBAOH [TBAOH] varied from 0 to 3.0 mM. Upon increasing [TBAOH], the SHG value of the film increased from 1.1% (0 mM) to 16.0% (？ 2.0 mM), with respect to that of a reference (a 3-mm thick quartz plate whose surface normal is the y-axis) while the included number of HC-2-CO2H molecules per channel (NC) remained constant (~16). The above results show that the degree of uniform orientation of the dye in the silicalite channels increases by ~4 times upon increasing [TBAOH] from 0 to 2.0 mM. An independent measurement of the absolute dipole moment of the HC-2-CO2H-including SL/Gs prepared at [TBAOH] = 2.0 mM revealed that a large portion of HC-2-CO2H molecules are aligned within the channels with the propionic-acid part pointing toward the entrance of the channels, indicating that TBA ion acts as the orientation-controlling agent during the inclusion of HC-2-CO2H into the silicalite channels.


Subject II. Z-scan
Chapter 3.
It has long been proposed that zeolite-intercalated semiconductor quantum dots (QDs) would give very high third-order nonlinear optical (3O-NLO) responses. However, the measurements of their 3O-NLO responses have not been possible due to the lack of methods to prepare optically transparent zeolite films supported on optically transparent substrates and to intercalate and confine QDs within zeolite nanopores only. Herein, we report a method to prepare optically transparent zeolite-Y films supported on optically transparent glass, a method to prepare PbS or PbSe QD clusters (QDCs) confined only within zeolite-Y supercages. We also report the remarkable fact that the intercalated PbS and PbSe QDCs give extremely high 3O-NLO responses that are unparalleled by the conventional QD/matrix composite systems. This report also opens the door to the practical applications of optically transparent zeolite films supported on an optically transparent substrate and to the use of zeolite-intercalated QDs and QDCs for various other purposes.