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Fluorescence spectra of colloidal self-assembled CdSe nano-wire on substrate of porous Al <sub/>2</sub> O <sub/>3</sub> /Au nanoparticles
摘要： We present a self-assembly method to prepare array nano-wires of colloidal CdSe quantum dots on a substrate of porous Al2O3 film modified by gold nanoparticles. The photoluminescence (PL) spectra of nanowires are in situ measured by using a scanning near-field optical microscopy (SNOM) probe tip with 100-nm aperture on the scanning near-field optical microscope. The results show that the binding sites from the edge of porous Al2O3 nanopores are combined with the carboxyl of CdSe quantum dots’ surface to form an array of CdSe nanowires in the process of losing background solvent because of the gold nanoparticles filling the nano-holes of porous Al2O3 film. Compared with the area of non-self-assembled nano-wire, the fluorescence on the Al2O3/Au/CdSe interface is significantly enhanced in the self-assembly nano-wire regions due to the electron transfer conductor effect of the gold nanoparticles’ surface. In addition, its full width at half maximum (FWHM) is also obviously widened. The method of enhancing fluorescence and energy transfer can widely be applied to photodetector, photocatalysis, optical display, optical sensing, and biomedical imaging, and so on.
关键词： porous Al2O3 film,colloidal self-assembled method,CdSe nano-wire,enhanced photoluminescence
更新于2025-11-25 10:30:42
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Multi-shelled upconversion nanostructures with enhanced photoluminescence intensity <i>via</i> successive epitaxial layer-by-layer formation (SELF) strategy for high-level anticounterfeiting
摘要： Owing to the ability to convert near-infrared (NIR) incident light into high-energy ultraviolet or visible light photons, lanthanide-doped upconversion nanoparticles (UCNPs) have attracted great attention in anticounterfeiting applications as appealing and unparalleled agents. To facilitate the efficient energy transfer and overcome the bottleneck of low upconverted photoluminescence, we report a one-pot successive epitaxial layer-by-layer formation (SELF) strategy based on ion layer adsorption and Oswald ripening to synthesize a series of high-quality monodispersed multi-shelled UCNPs with narrow size distribution (coefficient of variation less than 5 %). Up to 30 layers of uniform shell are successfully deposited by successive introduction of the shell precursor solutions, which results in fold change of 300 and 200 in upconverted emission intensities for Er3+ and Tm3+-doped multi-shelled UCNPs, respectively. Using as-prepared multi-shelled UCNPs via SELF approach in conjunction with fabricated downconversion nanoparticles (DCNPs), we develop a facile and cost-effective strategy based on dual-modal manipulation of luminescence in anticounterfeiting to provide extra high-level security protection. The genuine pattern with true information is easier to visualize with the naked eye under excitation of 980 nm near-infrared (NIR) laser, while the false information could be readily read out when exposed to ultraviolet (UV) light. Meanwhile, latent fingerprint recognition with low background interference and distinguishable details in ridge patterns is achieved taking advantage of the significantly improved brightness in multi-shelled UCNPs.
关键词： anticounterfeiting,Upconversion,enhanced photoluminescence,multi-shell,latent fingerprint
更新于2025-11-19 16:46:39
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Silicon Quantum Dots Metal Enhanced Photoluminescence by Gold Nanoparticles in Colloidal Ensembles: Effect of Surface Coating
摘要： In the present study we report the photophysical properties of colloidal ensembles of silicon quantum dots (SiD) and gold nanoparticles (AuNP), particularly focused on investigating metal-enhanced photoluminescence effects. AuNP with different sizes, (27 ± 10) and (88 ± 12) nm, and ca. 3.4 nm size SiD with different surface groups, either covered with an oxidized surface film bearing Si-OH surface groups or grafted with propylamine leading to Si-(CH2)2-CH2-NH2 terminal functionalities, were tested to evaluate gold enhancement of SiD photoluminescence. Nanoparticles were characterized by HRTEM, FTIR, XPS, ICP-AES, and gel electrophoresis, while photophysical properties of nanoparticles alone and in colloidal ensembles at different concentrations were investigated by absorption and steady-state and time-resolved photoluminescence studies, including quantum yield determinations. Enhanced absorption and photoluminescence of SiD in the presence of AuNP was evidenced, leading in the most favorable cases to ca. 10-times increase in SiD brightness. This effect depends strongly on the SiD surface coating and its interaction with citrate-capped gold surfaces, where these interactions govern particles aggregation and relative distance distributions among SiD and AuNP in the ensembles. The nature of these interactions and how they affect metal-enhanced luminescence is thoroughly discussed. The present study provides significant information on the effect of SiD surface groups and surface charge on the metal-enhanced luminescence phenomenon in colloidal aqueous suspensions.
关键词： gold nanoparticles,colloidal ensembles,metal-enhanced photoluminescence,silicon quantum dots,surface coating
更新于2025-09-23 15:21:01