InP Quantum Dot-Organosilicon Nanocomposites

Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343, Korea Received October 22, 2011, Accepted February 1, 2012InP quantum dot (QD)-organosilicon nanocomposites were synthesized and their photoluminescencequenching was mainly investigated because of their applicability to white LEDs (light emitting diodes). Theas-synthesized InP QDs are capped with myristic acid (MA), which are incompatible with typical siliconeencapsulants. We have introduced a new ligand, 3-aminopropyldimethylsilane (APDMS), which enablesembedding the QDs into vinyl-functionalized silicones through direct chemical bonding. The exchange ofligand from MA to APDMS does not significantly affect the UV absorbance of the InP QDs, but quenches thePL to about 10% of its original value with the relative increase in surface related emission intensities, which isexplained by stronger coordination of the APDMS ligands to the surface indium atoms. InP QD-organosiliconnanocomposites were synthesized by connecting the QDs using a short cross-linker such as 1,4-divinyl-tetramethylsilylethane (DVMSE) by the hydrosilylation reaction. The formation and changes in the opticalproperties of the InP QD-organosilicon nanocomposite were monitored by ultraviolet visible (UV-vis)absorbance and steady state photoluminescence (PL) spectroscopies. As the hydrosilylation reaction proceeds,the QD-organosilicon nanocomposite is formed and grows in size, causing an increase in the UV-visabsorbance due to the scattering effect. At the same time, the PL spectrum is red-shifted and, very interestingly,the PL is quenched gradually. Three PL quenching mechanisms are regarded as strong candidates for the PLquenching of the QD nanocomposites, namely the scattering effect, Forster resonance energy transfer (FRET)and cross-linker tension preventing the QD’s surface relaxation. Key Words : InP quantum dot, Organosilicon, Nanocomposite, PL quenching, Ligand exchangeIntroductionA semiconductor quantum dot (QD) is a nano-sized,crystalline particle consisting of hundreds to thousands ofatoms, falling in the gap between molecular cluster and bulkcrystal.