Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany; Dermatology Clinic, University Medical Center Mainz, Langenbeckstraße 1, 55131 Mainz, Germany.
J Colloid Interface Sci. 2018 May 15;518:11-20. doi: 10.1016/j.jcis.2018.01.102. Epub 2018 Jan 31.
Carbon dot systems are highly surface sensitive fluorescent nanomaterials. In the presence of specific molecules or ions, the fluorescence properties can be strongly influenced. Often their fluorescent properties are activated or strongly enhanced through passivation agents such as polymer coatings. While several passivating polymers have been directly attached to the carbon dot systems, the interaction of carbon dot systems with the polymer surface of colloids has not been investigated as a way to activate or enhance the photoluminescent properties. Here, we show for the first time that the interaction of carbon dot systems with polymer colloids can strongly enhance the fluorescent properties of the carbon dot systems.
To introduce carbon dot - polymer nanoparticle interactions, carbon dots are either generated directly in a microwave assisted synthesis in the presence of negatively charged polystyrene nanoparticles (in situ) or synthesized in the microwave separately and mixed afterwards with polymer nanoparticles (mixing). For the carbon dot system synthesis, chitosan, 1,2-ethylenediamine, and acetic acid are used as precursors. The produced carbon dot - polymer nanoparticle system are characterized by scanning electron microscopy, transmission electron microscopy, and flow cytometry measurements, and their interaction is assessed by fluorescence spectroscopy and fluorescence lifetime measurements.
We show that depending on the synthesis route (in situ or mixing), the carbon dot systems are either covalently attached (in situ) or electrostatically bound (mixing) to the surface of the nanoparticles. Regardless of the preparation methods of the investigated carbon dot - polymer nanoparticle system and the interaction (chemical or physical) with the surface, the fluorescence intensity is strongly enhanced and the fluorescence lifetime prolonged. These findings indicate a stabilization of the radiative trap states of carbon dot systems through interaction with the surface of the particles.
碳点系统是高度表面敏感的荧光纳米材料。在特定分子或离子存在的情况下，荧光性质可以受到强烈影响。通常，通过聚合物涂层等钝化剂可以激活或强烈增强它们的荧光性质。虽然已经有几种钝化聚合物直接附着在碳点系统上，但碳点系统与胶体聚合物表面的相互作用尚未被研究作为激活或增强光致发光性质的一种方式。在这里，我们首次表明，碳点系统与聚合物胶体的相互作用可以强烈增强碳点系统的荧光性质。
为了引入碳点-聚合物纳米粒子相互作用，碳点要么在存在带负电荷的聚苯乙烯纳米粒子的微波辅助合成中直接生成（原位），要么在微波中分别合成，然后与聚合物纳米粒子混合（混合）。对于碳点系统的合成，壳聚糖、1,2-乙二胺和乙酸用作前体。通过扫描电子显微镜、透射电子显微镜和流式细胞术测量来表征所产生的碳点-聚合物纳米粒子系统，并通过荧光光谱和荧光寿命测量来评估它们的相互作用。
我们表明，根据合成途径（原位或混合），碳点系统要么通过共价键合（原位）与纳米粒子表面结合，要么通过静电结合（混合）。无论研究的碳点-聚合物纳米粒子系统的制备方法和与表面的相互作用（化学或物理）如何，荧光强度都得到了强烈增强，荧光寿命也延长了。这些发现表明，通过与粒子表面的相互作用，碳点系统的辐射陷阱状态得到了稳定。
