Fluorescence sensing is currently one of the most widely used methods for the detection of chemical and biochemical analytes. Due to its rapid and highly sensitive detection capability, fluorescence sensing is emerging as a very important technique for biological research. To improve the detection capability and resolution of luminescence sensors, it is important to enhance detection sensitivity and increase the signal-to-noise ratio. In recent literature, enhancement of luminescence intensity through coupling with surface plasmons in metallic nanostructures has been reported. It is reported in literature that the fluorescence enhancement is optimal when the nanoparticle surface plasmon resonance is tuned to the emission wavelength of the fluorophores1. Surface plasmon resonance wavelength of metal nanoparticles can be tuned by varying their particle size, height, shape, composition, particle-to-particle distance and surrounding dielectric medium. In this work, silver-cupper nanoparticles were synthesized using the pulsed laser deposition methods. Surface plasmon resonance wavelengths of these Ag-Cu nanoparticles were tuned in the visible and near infrared region by changing experimental conditions such as annealing temperature2 (Figure 1). This talk will focus on the enhancement of several fluorophores such as platinum octaethyl porphyrin (PtOEP, an important phosphorescent emitter in OLED technology and widely used for oxygen pressure sensing), Alexa fluor 488, Alexa fluor 700 (fluorescent labeling reagents) on the Ag-Cu nanoparticle platform. The surface resonance wavelength of the Ag-Cu nanoparticles will be tuned to the emission spectra of fluorophore then effect of spectral overlap studied. Distance between the fluorophore molecules and nanostructured platform is also an important parameter in fluorescence enhancement3. The study of fluorescence intensity as a function of the distance between a layer of fluorophores and nanostructured metal surface will also be presented. Preliminary results obtained so far are very encouraging with observed fluorescence correlating well with spectral overlap of the Ag-Cu nanoparticle platform.
Reference:
1 F. Tam, G. P. Goodrich, B. R. Johnson, et al., Nano Lett. 7, 496 (2007).
2 M. Hirai and A. Kumar, Journal of Applied Physics 100, 014309 (2006).
3 Y. Chen, K. Munechika, and D. S. Ginger, Nano Lett. 7, 690 (2007).
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