Very high third-order nonlinear optical activities of intrazeolite PbS quantum dots.
Zeolite-intercalated semiconductor quantum dots (QDs) have long been proposed to give very high third-order nonlinear optical (3NLO) responses. However, measurements of their 3NLO responses have not been possible due to the lack of methods to prepare optically transparent QD-incorporating zeolite films supported on optically transparent substrates and to confine QDs only within zeolite interiors. We found that the zeolite-Y films grown on indium-tin-oxide-coated glass plates (Ygs) remain firmly bonded to the substrates during ion exchange with Pb2+ ions, drying, and formation of PbS QDs by treating Pb2+ ions with H2S. A series of Ygs encapsulating different numbers (n = 0, 8, 14, 23, and 33) of PbS in a unit cell [(PbS)n-Yg] were prepared. The PbS QDs were expelled by adsorbed moisture to the external surfaces, and the expelled QDs formed large QDs. Coating of the (PbS)n-Ygs with octadecyltrimethoxysilane results in effective confinement of the QDs within the internal pores. The zeolite-encapsulated PbS QDs showed remarkably high 3NLO activities at 532 and 1064 nm which are unparalleled by other PbS QDs dispersed in other matrixes.
Kim
Hyun Sung
HS
Center for Microcrystal Assembly, Department of Chemistry, Sogang University, Seoul 121-742, Korea.
Lee
Myoung Hee
MH
Jeong
Nak Cheon
NC
Lee
Seung Mook
SM
Rhee
Bum Ku
BK
Yoon
Kyung Byung
KB