Precise size separation of water-soluble red-to-near-infrared-luminescent silicon quantum dots by gel electrophoresis
Precise size separation of water-soluble red-to-near-infrared-luminescent silicon quantum dots by gel electrophoresis
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DOI：
10.1039/d0nr02764b
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发表时间：
2020-04-28
期刊：
影响因子：
6.7
通讯作者：
Sugimoto, Hiroshi
中科院分区：
文献类型：
--
作者：
Fujii, Minoru;Minami, Akiko;Sugimoto, Hiroshi
凝胶电泳法是分离和分析DNA、RNA和蛋白质等大分子的标准方法，首次应用于硅(Si)量子点(QD)的尺寸分离。在所研究的硅量子点中，同时掺杂了硼(B)和磷(P)。共掺杂使硅量子点表面产生负电势，使其分散在水中。研究了在不同温度(950℃-1200℃)下生长的不同B、P浓度的Si量子点。结果表明，天然聚丙烯酰胺凝胶电泳法可以将共掺杂的硅量子点按大小进行分离。凝胶电泳法能够将大小不同的量子点固定在固体基质中，这使得对大小纯化的硅量子点进行详细分析成为可能。例如，对1100℃下生长的硅量子点干凝胶的光致发光研究表明，发光最大值在1.4 eV左右的硅量子点溶液的光致发光光谱可以分成15个以上的光谱，最大光致发光根据迁移距离的不同从1.2到1.8 eV变化。研究发现，光致发光峰能量与迁移距离之间的关系依赖于Si量子点的生长温度以及B和P的浓度。对于不同杂质浓度和不同生长温度的样品，在较宽的能量范围内，荧光光谱的半高宽(FWHM)与峰值能量之间的关系有明显的趋势。半高宽随峰值能量的增加而增大，比未掺杂的硅量子点的半高宽大近一倍。共掺硅量子点较大的PL半高宽表明，由于带电杂质的存在，激子在共掺硅量子点中进一步局域化。
Gel electrophoresis, which is a standard method for separation and analysis of macromolecules such as DNA, RNA and proteins, is applied for the first time to silicon (Si) quantum dots (QDs) for size separation. In the Si QDs studied, boron (B) and phosphorus (P) are simultaneously doped. Codoping induces a negative potential on the surface of a Si QD and makes it dispersible in water. Si QDs with different B and P concentrations and grown at different temperatures (950 degrees C-1200 degrees C) are studied. It is shown that native polyacrylamide gel electrophoresis can separate codoped Si QDs by size. The capability of gel electrophoresis to immobilize size-separated QDs in a solid matrix makes detailed analyses of size-purified Si QDs possible. For example, the photoluminescence (PL) studies of the dried gel of Si QDs grown at 1100 degrees C demonstrate that a PL spectrum of a Si QD solution with the PL maximum around 1.4 eV can be separated into more than 15 spectra with the PL maximum changing from 1.2 to 1.8 eV depending on the migration distance. It is found that the relationship between the PL peak energy and the migration distance depends on the growth temperature of Si QDs as well as the B and P concentration. For all the samples with different impurity concentrations and grown at different temperatures, a clear trend is observed in the relationship between the full width at half maximum (FWHM) and the peak energy of the PL spectra in a wide energy range. The FWHM increases with the increasing peak energy and it is nearly twice larger than those observed for undoped Si QDs. The large PL FWHM of codoped Si QDs suggests that excitons are further localized in codoped Si QDs due to the existence of charged impurities.