Comparison of surface-enhanced resonance Raman scattering from unaggregated and aggregated nanoparticles
Comparison of surface-enhanced resonance Raman scattering from unaggregated and aggregated nanoparticles
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DOI：
10.1021/ac035053o
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发表时间：
2004-02-01
影响因子：
7.4
通讯作者：
Smith, WE
中科院分区：
文献类型：
--
作者：
Faulds, K;Littleford, RE;Smith, WE
探讨了激发频率和聚集状态对银纳米粒子胶体悬浮液和表面增强共振拉曼散射（SERRS）检测超痕量分析灵敏度的影响，以确定定量分析的合适条件。两种结构相似的染料，其中只有一种会引起聚集，被用作分析物而不使用外部聚集剂，从而简化了表面化学并消除了主要的误差来源。通过电位和粒度分析测量，加入非聚集性染料不会引起颗粒电荷或大小的变化，也不会产生随时间变化的聚集。在等离子体共振波长处的激发获得了最强烈的单粒子散射。分子共振在灵敏度上增加了2个数量级。聚集染料的加入导致颗粒表面电荷的减少，并开始了一个随时间变化的聚集过程。然而，在某些激发波长处，SERRS随时间的变化是恒定的，这可能是因为在动态聚集过程中，在这些波长处保持了恒定数量的活跃簇。由聚集和分子共振引起的额外增强分布在激发频率范围内。然而，电子光谱表明，等离子体共振增强在所用激发的最长波长（785 nm）是有效的，但在距离染料的最大吸光度（429 nm）很远的地方，强度会显著下降。因此，只要激发频率接近等离子体共振频率，利用单纳米颗粒悬浮液进行灵敏分析是可行的。在进行的实验中，聚集只增加了类似于6的增强，因为只有一些聚集的粒子在任何一个波长上都有活性等离子体激元，但在更复杂的情况下，获得良好增强的激发波长范围更广，从而提供了更大的灵活性。
The effect of excitation frequency and state of aggregation on the sensitivity obtained in ultratrace analysis using colloidal suspensions of silver nanoparticles and surface-enhanced resonance Raman scattering (SERRS) detection is explored to define suitable conditions for quantitative analysis. Two structurally similar dyes, only one of which causes aggregation, were used as analytes without the use of external aggregating agents, thus simplifying the surface chemistry and removing a major source of error. Addition of the nonaggregating dye caused no change in particle charge or size and no time-dependent aggregation as measured by potential and particle size analysis. The most intense single-particle scattering was obtained using excitation at the wavelength of the plasmon resonance. Molecular resonance added similar to2 orders of magnitude in sensitivity. Addition of the aggregating dye caused a reduction in surface charge of the particles and initiated a time-dependent aggregation process. However, constant SERRS with time is obtained at some excitation wavelengths probably because a constant number of clusters active at these wavelengths is maintained in the dynamic aggregation process. The additional enhancement caused by aggregation and molecular resonance is spread over a range of excitation frequencies. However, electronic spectra suggested that plasmon resonance enhancement would be effective at the longest wavelength of excitation used (785 nm), but there was a significant drop in intensity this far away from the absorbance maximum of the dye (429 nm). Thus, sensitive analysis using suspensions of single nanoparticles is feasible provided the excitation frequency used is close to that of the plasmon resonance frequency. Aggregation adds only an enhancement of similar to6 in the experiments performed since only some particles in aggregates will have an active plasmon at any one wavelength, but the range of excitation wavelengths at which good enhancement is obtained is wider giving more flexibility if more complexity.