Correlation between scattering properties of silver particle arrays and fluorescence enhancement - PubMed (original) (raw)

Correlation between scattering properties of silver particle arrays and fluorescence enhancement

Henryk Szmacinski et al. Appl Spectrosc. 2008 Jul.

Abstract

We report on the nanofabrication of patterned silver particle arrays using electron-beam lithography and the evaluation of their optical properties using backscattering and fluorescence spectroscopy. The silver particles varied in size from 100 to 250 nm and were in the shape of circles, squares, and triangles. Three inter-particle separations, 40, 65, and 90 nm as measured from the side of one particle to the side of the next particle, were used. We observed distinctive patterns of backscattering and fluorescence intensity depending on the particle size, inter-particle spacing, and excitation/emission wavelength used. Our approach allows for a study of the correlation between the backscattering intensities and fluorescence enhancement of silver particle arrays, which can be used to optimize the arrays for multi-fluorophore configuration for advanced sensing designs.

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Figures

Fig. 1

Geometry of a silver array with three inter-particle separations (40, 65, and 90 nm from side to side) and seven particle sizes from 100 to 250 nm. The particle thickness was 75 nm.

Fig. 2

SEM images of entire sub-arrays of Ag particles of (A) circular and (B) triangular shapes at a magnification of 10.00K×. See Table I for details on particle size and spacing. (C, D) High magnification of 70K× shows that the shapes of particles are well defined.

Fig. 3

Experimental configuration for measurement of the backscattering and fluorescence images. The excitation/emission conditions are 488/500–550 nm for FITC and 633/>660 nm for Cy5. The layer of proteins labeled with FITC and Cy 5 is not shown.

Fig. 4

(Left) Measured backscattered images of Ag periodic arrays with three particle shapes, (A) square, (B) circular, and (C) triangular at an incident light wavelength of 488 nm. (Right) Relative backscattering calculated versus glass substrate for particle spacing of 40, 65, and 90 nm. The error bars represent the standard deviation calculated from average values of three sub-arrays with identical particle geometrical configurations. The solid lines are drawn as guides.

Fig. 5

(Left) Fluorescence images of FITC on Ag periodic arrays with three particle shapes, (A) square, (B) circular, and (C) triangular. (Right) Enhanced fluorescence of FITC (versus signal on glass substrate) calculated as average values from images. The solid lines are drawn as guides.

Fig. 6

(Left) Backscattering of incident light of 633 nm on Ag particle arrays. (Right) Fluorescence enhancement of Cy5 on Ag particle arrays; (A) square, (B) circular, (C) triangular. The solid lines are drawn as guides.

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Correlation between scattering properties of silver particle arrays and fluorescence enhancement - PubMed (original) (raw)