Accurate sizing of nanoparticles using confocal correlation spectroscopy
Accurate sizing of nanoparticles using confocal correlation spectroscopy
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DOI：
10.1021/jp064865w
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发表时间：
2006-12-07
影响因子：
3.3
通讯作者：
Chiu, Daniel T.
中科院分区：
文献类型：
--
作者：
Kuyper, Christopher L.;Fujimoto, Bryant S.;Chiu, Daniel T.
在小体积中精确测量低浓度纳米颗粒的能力对于广泛的学科范围是有用的。在这里，我们描述了共焦相关光谱(CCS)，它能够测量荧光和非荧光粒子的大小，如量子点、金胶体、乳胶球和荧光珠。我们准确地测量了直径从11到300 nm的颗粒，这是一个很难探测的尺寸范围，因为存在一种偏向扩散现象，导致扩散时间或颗粒大小随着激光功率的变化而偏离。在低功率下，探测器饱和会导致模拟偏置扩散的伪影，这在探测高荧光或高散射纳米颗粒时尤其成问题。然而，在更高的功率(>；1 mW)下，共振和非共振条件下的自相关曲线都显示出一种结构，表明较长的相关时间的贡献增加，而较短的相关时间减少。我们认为，自相关曲线的这种变化是由于粒子通过探测器体积时的部分俘获。此外，当比较共振和非共振条件时，我们发现偏置扩散的影响只有很小的差别。模拟表明，偏置扩散所需的捕获电位深度为>；1k(B)T。克服了检测器饱和和偏置扩散带来的伪影，CCS特别具有优势，因为它能够在微流控通道和水微液滴的小体积特征中确定颗粒的大小。我们相信，该方法将在测量纳米颗粒和大分子体系的广泛应用中得到越来越多的应用。
The ability to accurately size low concentrations of nanoscale particles in small volumes is useful for a broad range of disciplines. Here, we characterize confocal correlation spectroscopy (CCS), which is capable of measuring the sizes of both fluorescent and nonfluorescent particles, such as quantum dots, gold colloids, latex spheres, and fluorescent beads. We accurately measured particles ranging in diameter from 11 to 300 nm, a size range that had been difficult to probe, owing to a phenomenon coined biased diffusion that causes diffusion times, or particle size, to deviate as a function of laser power. At low powers, artifacts mimicking biased diffusion are caused by saturation of the detector, which is especially problematic when probing highly fluorescent or highly scattering nanoparticles. However, at higher powers (> 1 mW), autocorrelation curves in both resonant and nonresonant conditions show a structure indicative of an increased contribution from longer correlation times coupled with a decrease in shorter correlation times. We propose that this change in the autocorrelation curve is due to the partial trapping of the particles as they transit the probe volume. Furthermore, we found only a slight difference in the effect of biased diffusion when comparing resonant and nonresonant conditions. Simulations suggest the depth of trapping potential necessary for biased diffusion is > 1k(B)T. Overcoming artifacts from detector saturation and biased diffusion, CCS is particularly advantageous due to its ability to size particles in the small volumes characteristic of microfluidic channels and aqueous microdroplets. We believe the method will find increasing use in a wide range of applications in measuring nanoparticles and macromolecular systems.