Signal Enhancement and Tuning of Surface Plasmon Resonance in Au Nanoparticle/Polyelectrolyte Ultrathin Films

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• 作者：Guoqian Jiang ; Akira Baba ; Hiroshi Ikarashi ; Risheng Xu ; Jason Locklin ; Khan Rana Kashif ; Kazunari Shinbo ; Keizo Kato ; Futao Kaneko ; Rigoberto Advincula
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：December 20, 2007
• 年：2007
• 卷：111
• 期：50
• 页码：18687 - 18694
• 全文大小：614K
• 年卷期：v.111,no.50(December 20, 2007)
• ISSN：1932-7455

文摘

Investigations on optical and dielectric properties of hybrid ultrathin layer-by-layer (LbL) films of goldnanoparticles (AuNPs) and polyelectrolytes under different pH conditions resulted in surface plasmon resonance(SPR) signal enhancement under attenuated total reflection (ATR) spectroscopy conditions. Theoreticalconsiderations on the basis of the Maxwell-Garnett theory were made to compare with experimental results.LbL films with different layer architectures were fabricated from AuNPs and two polyelectrolytes: poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on Au and Ag thin film substrates forATR. UV-vis spectroscopy and SPR spectroscopy were applied to study LbL film growth and monitor SPRshift upon pH switching. The (PAH/AuNPs)_x multilayers showed an interesting dual-responsive SPR changeas a function of pH and distance between AuNP layers and metal film. The addition of (PAH/PSS)_y layerswas found to act as an effective cushion to enhance this SPR response due to the significant swelling/shrinkingof the film. In the case of [(PAH/PSS)_y + (PAH/AuNPs)_x], both theoretical calculations and experimentalresults showed that the SPR response can either (a) move toward lower incident angle with a sharp peakshape upon swelling in pH = 2 or (b) shift to a higher angle with a broadened peak shape after contractionin pH = 10. This effect was found to be opposite to what is expected from LbL films made up of thepolyelectrolytes alone. Moreover, increasing the distance between AuNPs and the metal films also decouplesthis enhancement effect. A two-wavelength experiment (red and green lasers) was used to quantitativelydemonstrate this SPR response to pH switching. Finally, SPR imaging was employed to monitor the SPRchange with pH switching between 2 and 10 on the [(PAH/PSS)₄ + (PAH/AuNPs)₂] film. Thus, on the basisof the SPR spectroscopic and SPR imaging pH response, a reproducible and stable sensing system can besuccessfully fabricated with these films.