Abstract We report an effective and simple method for separation of carbon nanodots (CNDs) by size-exclusion chromatography that yields CNDs fractions with different sizes and luminescent properties. As a result, three major types of CNDs with spectrally distinct luminescent centers were identified. The first type of luminescent particles has emission maxima at about 400–440 nm, the highest size and luminescence intensity. CNDs of the second type have a middle size and the lowest luminescence intensity with emission maxima in the range 450–470 nm. The distinctive feature of these two fractions is the excitation-dependent shift of the emission maxima to longer wavelengths. The third type of CNDs has luminescence around 520 nm with no emission shift upon the increase of excitation wavelength and the smallest size. The observed spectral variations in different fractions correlate with a change in average particle size as seen in TEM images. Size fractionation of CNDs mixture is very important to many fields, mostly for bioimaging and medicine applications because it leads to CNDs' unified distribution and behavior. Dilution of CNDs in water suspension leads to the increase of emission intensity and shifts the PL spectra to shorter wavelengths providing evidence for concentration quenching effect in CNDs.

中文翻译：

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凝胶柱分离碳纳米颗粒中光学和结构特性的分散

摘要 我们报告了一种通过尺寸排阻色谱分离碳纳米点 (CND) 的有效且简单的方法，该方法产生具有不同尺寸和发光特性的 CND 级分。结果，鉴定了具有光谱不同发光中心的三种主要类型的 CND。第一种发光粒子在约 400-440 nm 处具有发射最大值，这是最大的尺寸和发光强度。第二种类型的 CND 具有中等尺寸和最低的发光强度，发射最大值在 450-470 nm 范围内。这两个部分的显着特征是发射最大值向更长波长的激发依赖偏移。第三种类型的 CND 在 520 nm 附近发光，随着激发波长的增加和最小的尺寸没有发射偏移。观察到的不同部分的光谱变化与平均粒径的变化相关，如 TEM 图像中所见。CNDs 混合物的尺寸分级对于许多领域非常重要，主要用于生物成像和医学应用，因为它导致 CNDs 的统一分布和行为。在水悬浮液中稀释 CND 会导致发射强度增加，并将 PL 光谱移至更短的波长，这为 CND 中的浓度猝灭效应提供了证据。