• Elastomers and Composites
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• v.54 no.2
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• pp.149-155
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• 2019

Controlled mass transport in response to stimuli is essential for drug carriers. The complexity of the signaling system under physiological conditions has led researchers to develop precise nanocontainers that respond to stimuli in the physiological environment. Owing to several reasons, soft nanocontainers such as liposomes and micelles have been investigated for use as drug delivery systems. However, such carriers often suffer from the undesired leakage of drug molecules. In contrast, inorganic nanocontainers are robust, and their surfaces can be easily functionalized. For example, mesoporous silica nanoparticles equipped with gatekeeper molecules are increasingly being used for the controlled release of drug molecules in response to the desired stimuli. Since the development of the first hybrid nanocontainer comprising molecular machines, multiple versions of such gatekeeper systems featuring significantly improved stability and precise response to stimuli have been reported. In this study, various methods for incorporating photoresponsive nanocontainers with porous channels are developed.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1357-1360
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• 2011

• Bulletin of the Korean Chemical Society
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• v.22 no.9
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• pp.1023-1029
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• 2001

The positions of Kr atoms encapsulated in the molecular-dimensioned cavities of fully dehydrated zeolite A of unit-cell composition Cs3Na8HSi12Al12O48 (Cs3-A) have been determined. Cs3-A was exposed to 1025 atm of krypton gas at 400 $^{\circ}C$ for four days, followed by cooling at pressure to encapsulate Kr atoms. The resulting crystal structure of Cs3-A(6Kr) (a = $12.247(2)\AA$, R1 = 0.078, and R2 = 0.085) has been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at $21(1)^{\circ}C$ and 1 atm. In the crystal structure of Cs3-A(6Kr), six Kr atoms per unit cell are distributed over three crystallographically distinct positions: each unit cell contains one Kr atom at Kr(1) on a threefold axis in the sodalite unit, three at Kr(2) opposite four-rings in the large cavity, and two at Kr(3) on threefold axes in the large cavity. Relatively strong interactions of Kr atoms at Kr(1) and Kr(3) with Na+ ions of six-rings are observed: Na-Kr(1) = 3.6(1) $\AA$ and Na-Kr(3) = $3.08(5)\AA.$ In each sodalite unit, one Kr atom at Kr(1) was displaced $0.74\AA$ from the center of the sodalite unit toward a Na+ ion, where it can be polarized by the electrostatic field of the zeolite, avoiding the center of the sodalite unit which by symmetry has no electrostatic field. In each large cavity, five Kr atoms were found, forming a trigonal-bipyramid arrangement with three Kr(2) atoms at equatorial positions and two Kr(3) atoms at axial positions. With various reasonable distances and angles, the existence of Kr5 cluster was proposed (Kr(2)-Kr(3) = $4.78(6)\AA$ and Kr(2)-Kr(2) = $5.94(7)\AA$, Kr(2)-Kr(3)-Kr(2) = 76.9(3), Kr(3)-Kr(2)-Kr(3) = 88(1), and Kr(2)-Kr(2)-Kr(2) = $60^{\circ}).$ These arrangements of the encapsulated Kr atoms in the large cavity are stabilized by alternating dipoles induced on Kr(2) by four-ring oxygens and Kr(3) by six-ring Na+ ions, respectively.