Mawatari K, Kitamori T, Sawada T
Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
Anal Chem. 1998 Dec 1;70(23):5037-41. doi: 10.1021/ac980250m.
We have developed a thermal lens microscope for liquid-phase and surface microanalyses. By applying the thermal lens microscope to particle detection, we succeeded in detecting a pulsed photothermal signal from single-nanometer-sized particles in liquid and counting them individually. The samples were polystyrene latex particles (190 and 80 nm in diameter) and colloidal Ag particles (10 nm in diameter). To verify that the detected pulsed signals corresponded to the single-particle photothermal effects, we confirmed the items as described below using 190-nm polystyrene particles. First, no pulsed signal was generated under irradiation by either the excitation beam or the probe beam. Second, the pulse counts were proportional to the expectation value of the particles in the detection volume and zero for ultrapure water blank. Third, the pulse counts' distribution in a series of unit times had a Poisson distribution when the expectation value of the sample was much less than 1. Then, we demonstrated counting 80-nm polystyrene particles and 10-nm Ag particles in water. The pulsed signals were clearly distinguished from noise, and the signal-to-noise ratio was as large as 5. Finally, we discussed differences between the conventional thermal lens effect and the single-particle photothermal effect. Individual nanometer-sized particle detection by photothermal effect was the first demonstration.
我们开发了一种用于液相和表面微分析的热透镜显微镜。通过将热透镜显微镜应用于颗粒检测，我们成功地检测到了液体中单个纳米级颗粒的脉冲光热信号，并对其进行了单独计数。样品为聚苯乙烯乳胶颗粒（直径190和80纳米）和胶体银颗粒（直径10纳米）。为了验证检测到的脉冲信号对应于单颗粒光热效应，我们使用190纳米的聚苯乙烯颗粒对以下项目进行了确认。首先，在激发光束或探测光束照射下均未产生脉冲信号。其次，脉冲计数与检测体积内颗粒的期望值成正比，超纯水空白的脉冲计数为零。第三，当样品的期望值远小于1时，一系列单位时间内脉冲计数的分布呈泊松分布。然后，我们展示了对水中80纳米聚苯乙烯颗粒和10纳米银颗粒的计数。脉冲信号与噪声明显区分，信噪比高达5。最后，我们讨论了传统热透镜效应与单颗粒光热效应之间的差异。通过光热效应进行单个纳米级颗粒检测是首次展示。
