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Metal-enhanced fluorescence of interlaminar composite film with self-assembled quantum Dots/Au@SiO2 microarchitecture
摘要： Quantum dots fluorescence-enhanced films, which mainly consisted of CdSe@ZnS quantum dots and noble metal nanoparticles or nanorods, were formed by layer-by-layer self-assembly techniques. This particular architecture consisting of metal nanoparticles-poly (diallyl dimethylammonium chloride) (PDDA)-QDs was characterized by those fabrication processes mainly including surface-modifying the oleic acid-capped CdSe@ZnS QDs ( high quantum yield of ~89% ) with mercaptopropionic acid (MPA) to be charged negatively (-COO-) for following solution-processed assembly, adjusting the size and coating the gold nanoparticles/nanorods with silica to form suitable dielectric insulation layer and further optimize the fluorescence-enhanced performance, as well as using the cationic polyelectrolyte to control the charges between layers and form opposite charges between two adjacent layers. After optimizing the structure of the quantum dot fluorescence-enhanced films and corresponding surface plasmon enhancement effect, the enhancement factor of 10.8 in Au NPs@SiO2-PDDA-QDs complex film and that of 24.7 in Au NRs@SiO2-PDDA-QDs complex film as compared with the pure quantum dot fluorescence film were achieved, respectively. This indicated that the Au NRs@SiO2-PDDA-QDs complex film was one of the most promising potentials for further display backlight and biometric identifier application.
关键词： CdSe@ZnS quantum dots,Au@SiO2 microarchitecture,electrostatic self-assembly,metal surface plasmon enhancement,Quantum dots fluorescence-enhanced films
更新于2025-09-12 10:27:22
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Triplet Excited State Enhancement Induced by PDDA Polymer Assembled Gold Nanoparticles
摘要： Gold nanoparticles (AuNPs) have unique optical properties due to their characteristic localized surface plasmon resonances (LSPR). Upon the excitation of LSPR, AuNPs can affect the adjacent organic molecules strongly in both the ground state and the excited state. Previously, only 2~3 fold of plasmon enhancement effect on triplet state formation was displayed due to the random and uncontrollable formation of AuNP aggregates. Here, we utilize polymer PDDA to assemble AuNPs forming aggregates with strong plasmonic resonance. By means of transient UV-visible absorption spectroscopy, the triplet state of rose bengal enhanced by PDDA-AuNPs is directly monitored and the maximum enhancement is found to be ~ 10 fold. The large enhancement should be mainly resulted from the plasmon effect of AuNPs aggregates. Additionally, it is found that the triplet state enhancement effect of PDDA assembled AuNPs is sensitive to concentration of polymer and the size of AuNPs. These findings shed light on the applications of gold nanoparticles in triplet-triplet energy transfer, triplet exciton harvesting and photodynamic therapy.
关键词： PDDA polymer,Gold nanoparticles,Plasmon enhancement,Triplet excited state,Photodynamic therapy
更新于2025-09-11 14:15:04
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Resonant Plasmon-Enhanced Upconversion in Monolayers of Core-Shell Nanocrystals: Role of Shell Thickness
摘要： The upconversion luminescence (UCL) of colloidal lanthanide-doped upconversion nanocrystals (UCNCs) can be improved either by precise encapsulation of the surface by optically inert shells around the core, by an alteration of the nearby environment via metal nanoparticles, or by a combination of both. Considering their potential importance in crystalline silicon photovoltaics,the present study investigates both effects for two-dimensional arrangements of UCNCs. Using excitation light of 1500 nm wavelength, we study the variation in the upconversion luminescence from an Er3+-doped NaYF4 core as a function of the thickness of a NaLuF4 shell in colloidal solutions as well as in spin-cast-assisted self-assembled monolayers of UCNCs. The observed UCL yields and decay times of Er3+ ions of the UCNCs increase with increasing shell thickness in both cases, and nearly no variation in decay times is observed in the transition of the UCNCs from solution to film configurations. The luminescence efficiency of the UCNC monolayers is further enhanced by electron-beam-lithographic-designed Au-nanodiscs deposited either on top or buried within of the monolayer. It is observed that the improvement by the nanocrystal shells is greater than that of the Au-nanodiscs.
关键词： shell thickness,core-shell nanocystals,monolayer,upconversion,Plasmon enhancement
更新于2025-09-04 15:30:14