Signal enhancement and tuning of surface plasmon resonance in Au nanoparticle/polyelectrolyte ultrathin films
Signal enhancement and tuning of surface plasmon resonance in Au nanoparticle/polyelectrolyte ultrathin films
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DOI：
10.1021/jp075986e
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发表时间：
2007-12-20
影响因子：
3.7
通讯作者：
Advincula, Rigoberto
中科院分区：
文献类型：
--
作者：
Jiang, Guoqian;Baba, Akira;Advincula, Rigoberto
在衰减全反射(ATR)光谱条件下，研究了不同pH条件下金纳米粒子(AuNPs)/聚电解质复合超薄薄膜(LBL)的光学和介电特性，发现表面等离子体共振(SPR)信号增强。在Maxwell-Garnett理论的基础上进行了理论考虑，并与实验结果进行了比较。利用金纳米粒子和聚烯丙基胺盐酸盐(PAH)和聚苯乙烯磺酸盐(PSS)两种聚电解质在Au和Ag薄膜衬底上制备了不同层结构的LBL薄膜，用于ATR。用UV-Vis光谱和SPR光谱研究了LBL薄膜的生长和pH变化时的SPR漂移。(PAH/AuNPs)(X)多层膜表现出有趣的双响应SPR随pH和AuNP层与金属膜之间的距离的变化。由于薄膜的显著膨胀/收缩，(PAH/PSS)(Y)层的添加被发现作为有效的缓冲来增强这种SPR响应。在[(PAH/PSS)(Y)+(PAH/AuNPs)(X)]的情况下，理论计算和实验结果都表明，SPR响应可以(A)在pH=2的溶胀时向较小的入射角移动，峰形锐利，或者(B)在pH=10的收缩后向较高的角度移动，峰形加宽。这一效应与由聚电解质单独组成的LBL薄膜的预期结果相反。此外，增大Au纳米颗粒与金属膜之间的距离也会使这种增强效应解耦。一个双波长实验(红光和绿光)被用来定量地展示这种SPR对pH切换的响应。最后，利用SPR成像技术监测[(PAH/PSS)(4)+(PAH/AuNPs)(2)]膜上pH在2~10范围内的SPR变化。因此，在SPR光谱和SPR成像pH响应的基础上，利用这些薄膜可以成功地制造出可重复性和稳定性的传感系统。
Investigations on optical and dielectric properties of hybrid ultrathin layer-by-layer (LbL) films of gold nanoparticles (AuNPs) and polyelectrolytes under different pH conditions resulted in surface plasmon resonance (SPR) signal enhancement under attenuated total reflection (ATR) spectroscopy conditions. Theoretical considerations 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 for ATR. UV-vis spectroscopy and SPR spectroscopy were applied to study LbL film growth and monitor SPR shift upon pH switching. The (PAH/AuNPs)(x) multilayers showed an interesting dual-responsive SPR change as a function of pH and distance between AuNP layers and metal film. The addition of (PAH/PSS)(y) layers was found to act as an effective cushion to enhance this SPR response due to the significant swelling/shrinking of the film. In the case of [(PAH/PSS)(y) + (PAH/AuNPs)(x)], both theoretical calculations and experimental results showed that the SPR response can either (a) move toward lower incident angle with a sharp peak shape upon swelling in pH = 2 or (b) shift to a higher angle with a broadened peak shape after contraction in pH = 10. This effect was found to be opposite to what is expected from LbL films made up of the polyelectrolytes alone. Moreover, increasing the distance between AuNPs and the metal films also decouples this enhancement effect. A two-wavelength experiment (red and green lasers) was used to quantitatively demonstrate this SPR response to pH switching. Finally, SPR imaging was employed to monitor the SPR change with pH switching between 2 and 10 on the [(PAH/PSS)(4) + (PAH/AuNPs)(2)] film. Thus, on the basis of the SPR spectroscopic and SPR imaging pH response, a reproducible and stable sensing system can be successfully fabricated with these films.