Silica nanoparticles containing a rhodamine dye and multiple gold nanorods
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Silica shells are grown around colloidally synthesized gold nanorods (AuNRs) to form core–shell particles (AuNR@SiO2) of variable occupancy, defined as the number of AuNRs per silica particle. Multiple AuNR occupancy within the silica shell, confirmed with high-resolution electron microscopy, is reflected in a redshift of the longitudinal plasmon mode of the nanorods due to multipolar coupling between AuNRs of a favored end–end orientation. In addition to the plasmon resonance that dominates their absorbance spectra, FL-AuNR@SiO2, core–shell particles incorporating a lipid probe (rhodamine-DOPE), can be monitored by their fluorescence and Raman signals. Optical and scanning electron microscopy (SEM) images are compared directly, enabling the correlation of spectroscopic characteristics with particle morphology. Raman and SEM images show that the most intense Raman signals come from aggregates of AuNRs trapped within the silica matrix. Biexponential fits to fluorescence decays indicate that competing mechanisms of quenching and fluorescence enhancement contribute to a reduced fluorescence lifetime of rhodamine-DOPE located near the AuNRs.
KeywordsGold nanorod Plasmon Silica Fluorescence Raman Rhodamine Lipid dye Core–shell
Brendan Twamley is gratefully acknowledged for acquiring SEM images. This work was supported by the National Biophotonics and Imaging Platform initiative funded under the HEA Programme for Research in Third-Level Institutions—Cycle 4. SEM was supported by the Science Foundation Ireland under Grant number 03/IN.3/1361/EC07.
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