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1.
ACS Appl Mater Interfaces ; 11(26): 23083-23092, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31252484

RESUMO

Metal-enhanced fluorescence (MEF), resulting from the near-field interaction of fluorophores with metallic nanostructures, has emerged as a powerful tool for dramatically improving the performance of fluorescence-based biomedical applications. Allowing for lower autofluorescence and minimal photoinduced damage, the development of multifunctional and multiplexed MEF platforms in the near-infrared (NIR) windows is particularly desirable. Here, a low-cost fabrication method based on nanosphere lithography is applied to produce tunable three-dimensional (3D) gold (Au) nanohole-disc arrays (Au-NHDAs). The arrays consist of nanoscale glass pillars atop nanoholes in a Au thin film: the top surfaces of the pillars are Au-covered (effectively nanodiscs), and small Au nanoparticles (nanodots) are located on the sidewalls of the pillars. This 3D hole-disc (and possibly nanodot) construct is critical to the properties of the device. The versatility of our approach is illustrated through the production of uniform and highly reproducible Au-NHDAs with controlled structural properties and tunable optical features in the NIR windows. Au-NHDAs allow for a very large NIR fluorescence enhancement (more than 400 times), which is attributed to the 3D plasmonic structure of the arrays that allows strong surface plasmon polariton and localized surface plasmon resonance coupling through glass nanogaps. By considering arrays with the same resonance peak and the same nanodisc separation distance, we show that the enhancement factor varies with nanodisc diameter. Using computational electromagnetic modeling, the electric field enhancement at 790 nm was calculated to provide insights into excitation enhancement, which occurs due to an increase in the intensity of the electric field. Fluorescence lifetime measurements indicate that the total fluorescence enhancement may depend on controlling excitation enhancement and therefore the array morphology. Our findings provide important insights into the mechanism of MEF from 3D plasmonic arrays and establish a low-cost versatile approach that could pave the way for novel NIR-MEF bioapplications.


Assuntos
Pesquisa Biomédica , Nanopartículas Metálicas/química , Nanoestruturas/química , Fluorescência , Corantes Fluorescentes/química , Corantes Fluorescentes/provisão & distribuição , Ouro/química , Nanopartículas Metálicas/uso terapêutico , Nanosferas/química , Ressonância de Plasmônio de Superfície
2.
Phys Chem Chem Phys ; 20(21): 14828-14834, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29780986

RESUMO

Zinc oxide (ZnO) nanorods (NRs) have been demonstrated as a promising platform for enhanced fluorescence-based sensing. It is, however, desirable to achieve a tuneable fluorescence enhancement with these platforms so that the fluorescence output can be adjusted based on the real need. Here we show that the fluorescence enhancement can be tuned by changing the diameter of the ZnO nanorods, simply controlled by potassium chloride (KCl) concentration during synthesis, using arrays of previously developed aligned NRs (a.k.a. aligned NR forests) and nanoflowers (NFs). Combining the experimental results obtained from ZnO nanostructures with controlled morphology and computer-aided verification, we show that the fluorescence enhancement factor increases when ZnO NRs become thicker. The fluorescence enhancement factor of NF arrays is shown to have a much stronger dependency on the rod diameter than that of aligned NR arrays. We prove that the morphology of nanostructures, which can be controlled, can be an important factor for fluorescence enhancement. Our (i) effort towards understanding the structure-property relationships of ZnO nanostructured arrays and (ii) demonstration on tuneable fluorescence enhancement by nanostructure engineering can provide some guidance towards the rational design of future fluorescence amplification platforms potentially for bio-sensing.

3.
J Phys Chem B ; 112(51): 16415-21, 2008 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-19367907

RESUMO

We report on the aggregate structure of a symmetrical A-B-A 9,9-dialkylfluorene/2-alkylaniline "coil-rod-coil" triblock copolymer (or PF/PANI11112-b-PANI11)--consisting of 2-dodecylanilines as A blocks and 9,9-di(3,7,11-trimethyldodecyl)fluorene)s as B blocks--mixed in deuterated toluene, chloroform, and methylcyclohexane. These mixtures contain micrometer scale aggregates. Small-angle neutron scattering data indicate that the interface between the aggregates and solvents manifests surface fractal-like structure. The upper and lower limit length scales which show fractal character are of the order of > 100 and 15 nm. The surface fractal dimension D(s) varies from 2.2 to 2.8. The data show that stiff polyfluorene (PF) segments (persistence length > or = 9.5 nm, diameter approximately 2 nm) of PF/PANI11112-b-PANI11 are dissolved down to the molecular level. Photoluminescence data indicate that most PF units are isolated from both polyaniline (PANi) units and each others. Together with the scattering data, this implies that the disordered interface consists of stiff isolated PF blocks linked together via domains of associated PANi blocks.

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