Investigation of the coupling between semiconductor quantum dots and metal nanostructures

• Main Authors: Chih-Wei Chen, 陳志瑋
• Other Authors: Yang-Fang Chen
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/33207998375003284241

博士 === 臺灣大學 === 物理研究所 === 98 === In this thesis, we have reported the physical phenomena based on the composites of semiconductors quantum dots (QDs), metallic nanoparticles (NPs), and metallic nanoclusters (NCs). In the part 1 we introduced a simple approach to investigate the tunable energy transfer effect of mixed-size CdSe quantum dots combined with elastomeric poly-dimethylsiloxane (PDMS) film. Then following the same approach, in part 2 we investigated the influence of surface plasmon of gold nanoparticles on the optical properties of CdSe QDs embed in elastomeric PDMS film. In part 3, we performed the effect of surface plasmon on highly sensitive energy transfer between the non-toxic metallic silver NPs and gold NCs. In part 4, we demonstrated a novel strategy to fabricate well aligned assembly gold nanorods. It is found that the photoluminescence of CdSe QDs on the structure can be strongly enhanced and revealed optical anisotropic properties. 1. Tunable energy transfer efficiency based on the composite of mixed CdSe quantum dots and elastomeric film We demonstrate a facile and general approach to investigate the dependence of energy transfer on the separation distance between proximal mixed-size quantum dots. Without varying the mixed concentrations, the tunable energy transfer efficiency is achieved based on the composite of mixed quantum dots and elastomeric film by utilizing the inherent nature of the flexibility of elastomeric film. To demonstrate our working principle, the composite of mixed-size CdSe quantum dots and poly-dimethylsiloxane has been studied. The results clearly show that the energy transfer process between proximal quantum dots follows the Förster resonance energy transfer, in which the dependence of the transfer efficiency E as a function of the donor-acceptor distance R obeys E = 1/[1+(R/R0)6]. 2. Tunable emission based on the composite of Au nanoparticles and CdSe quantum dots deposited on elastomeric film A simple approach to investigate the dependence of emission on the separation distance between semiconductor quantum dots and metal nanoparticles is demonstrated. Without varying the mixed concentrations, a tunable emission is achieved based on the deposition of the composite of Au nanoparticles and CdSe quantum dots on elastomeric film. By utilizing the inherent nature of the elasticity of the elastomeric film, it is found that depending on the separation distance, the emission intensity can be quenched or enhanced. The underlying mechanism can be explained quite well by the interplay between the local field excitation due to surface plasmons and electrons transfer to metal nanoparticles. 3. Highly sensitive emission sensor based on surface plasmon enhanced energy transfer between gold nanoclusters and silver nanoparticles In the study of interaction between emissive gold nanoclusters and silver nanoparticles, we explored that the emission of gold nanoclusters is very sensitive to the presence of silver nanoparticles. Quite remarkably, the quenching ratio can reach more than several hundred times. We demonstrate that the underlying mechanism can be attributed to the surface energy transfer with the quenching efficiency following the expression χ = 1/[1+(d/d0)4], where d is the distance between gold nanoclusters and silver nanoparticles, and do is the characteristic length of energy transfer. This highly sensitive behavior in the composite consisting of relatively nontoxic gold nanoclusters and silver nanoparticles may find a powerful potential in developing biomedical applications, such as biosensors and drugs delivery. 4. Surface plasmon induced optical anisotropy of CdSe quantum dots on well aligned assembly gold nanorods A simple approach that can be used to control the optical anisotropy of CdSe/ZnS quantum dots by coupling to the surface plasmon resonance of a metal grating has been demonstrated. We present well aligned assembly gold nanorods grating structure by combining polydimethylsiloxane as a stamp. It is found that CdSe quantum dots on the structure revealed optical anisotropic effect due to the resonance with the transverse surface plasmon mode. It is worth noting that the polarized direction of emission was perpendicular to the axis of grating structure. This well aligned metal structure can be developed for the application of optical devices such as optical switch and polarized light emitted diodes. The novel phenomena discovered in this thesis not only provide a more detailed understanding of nanomaterials, but also able to enhance their applications.