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Photoluminescence of carbon dots from mesoporous silica

机译：中孔二氧化硅碳点的光致发光

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Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy similar to 1200 cm(-1) is close to the energy of C-O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time similar to 0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation. (C) 2016 Elsevier B.V. All rights reserved.
机译：在从室温到液氦的各种温度范围和各种激发条件下研究了碳点的光物理性质。使用中孔二氧化硅颗粒作为反应器，以（3-氨基丙基）三乙氧基硅烷（APTES）作为前体合成碳点（CD）。 CD的光致发光光谱显示出对激发波长的强烈依赖性，并显示出明显的不均匀展宽。样品温度的降低揭示了光谱的双峰结构，这与辐射跃迁的振动结构有关。类似于1200 cm（-1）的振动能量接近C-O拉伸振动的能量。观察到碳点的长寿命磷光，其衰减时间在T = 80 K时类似于0.2 s。荧光和磷光光谱显示为光谱分离的。发射的长寿命成分归因于光学上禁止的三重态-单重态跃迁。发现单重态三重态分裂的值约为0.3eV。揭示了碳点发光的光诱导极化。线性偏振的程度取决于激发光和发射光的波长。该效应表明点中光学偶极跃迁具有隐藏的各向异性，并证明了在电子能量弛豫期间偶极子取向的损失。 （C）2016 Elsevier B.V.保留所有权利。

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