Insight into the mechanism of the photoluminescence of carbon nanoparticles derived from cryogenic studies†,Nanoscale

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Insight into the mechanism of the photoluminescence of carbon nanoparticles derived from cryogenic studies†
Nanoscale ( IF 5.8 ) Pub Date : 2018-04-23 00:00:00 , DOI: 10.1039/c8nr02296h
Yuriy Malyukin _{1,

2,

3,

4} , Oleg Viagin _{1,

2,

3,

4} , Pavel Maksimchuk _{1,

2,

3,

4} , Mariia Dekaliuk _{4,

5,

6} , Alexander Demchenko _{4,

5,

6}

Affiliation

The unexpected discovery of the photoluminescence of carbon nanoparticles attracted the attention of many researchers and resulted in their use in a variety of applications. However, the origin of their emission is still obscure, and the majority of the discussions on the subject focus on their molecular and/or excitonic emissive states. We performed cryogenic studies down to 10 K and did not observe any signatures of suppressed molecular relaxation – the spectra remained broad, showing large unaltered Stokes shifts and temperature-independent emission intensities and lifetimes below 80 K with a weak dependence above this value. We demonstrated that the most general features of carbon nanoparticles, the very large Stokes shifts and considerable differences between the absorption and excitation spectra, are the result of the formation of a dynamic defect, the self-trapped Frenkel exciton. It looks like the distorted domain of the H-aggregate due to the exciton–lattice interaction and the local overheating caused by the exciton relaxation. In addition, at low temperatures the long-lifetime spectral component was found and was attributed to phosphorescence. The obtained results strongly support the excitonic nature of the fluorescence of nanocarbon materials.

中文翻译：

深入了解低温研究产生的碳纳米颗粒的光致发光机理†

碳纳米粒子的光致发光的意外发现吸引了许多研究人员的注意力，并导致其在各种应用中的使用。然而，它们发射的起源仍然不清楚，并且关于该主题的大多数讨论都集中在它们的分子和/或激子发射态。我们进行了低至10 K的低温研究，没有观察到抑制分子弛豫的任何迹象-光谱仍然很宽，显示出较大的不变斯托克斯位移和与温度无关的发射强度，寿命低于80 K，高于此值时则具有较弱的依赖性。我们证明了碳纳米颗粒的最一般特征，非常大的斯托克斯位移以及吸收光谱和激发光谱之间的巨大差异，是动态缺陷（自陷Frenkel激子）形成的结果。由于激子与晶格的相互作用以及激子弛豫引起的局部过热，它看起来像是H骨料的扭曲畴。另外，在低温下，发现了长寿命的光谱成分，并归因于磷光。所获得的结果强烈支持纳米碳材料的荧光的激子性质。

更新日期：2018-04-23

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