A DFT study to unravel the fluorescence mechanisms of APTES-modified carbon dots

Next Nanotechnology Pub Date : 2024-01-01 DOI:10.1016/j.nxnano.2023.100037

Varsha Lisa John , Fasila P.M. , Vinod T.P.

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Abstract

Surface passivation is a well-established method for modifying carbon dots (CDs), intended to improve their properties. We present a theoretical study employing density functional theory (DFT) and time-dependent-DFT (TD-DFT) to explain the photoluminescence (PL) mechanism of amine-modified carbon dots (CD-NH₂) [CDs modified with (3-Aminopropyl) triethoxy silane (APTES)] considering their local geometry at the terminal ends; the zig-zag (CD_ZZ-NH₂) and armchair (CD_AC-NH₂) structural orientations. The experimental evidence from our previous report suggests that the amine groups were tethered on the surface of CDs through a Si-O bond realized by the silane coupling reaction between the ethoxy group of APTES and the hydroxyl group of the CDs. The effect of pH in tweaking the PL of these systems is scrutinized in the present study. The influence of pH and structure on the bandgap of CD-NH₂ is demonstrated by analyzing the difference in HOMO-LUMO energies, the density of states (DoS) spectra, and electrostatic potentials (ESP).

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揭示 APTES 改性碳点荧光机制的 DFT 研究

表面钝化是改性碳点（CD）的一种行之有效的方法，旨在改善其性能。我们利用密度泛函理论（DFT）和时间依赖性-DFT（TD-DFT）进行了一项理论研究，以解释胺修饰碳点（CD-NH2）[用（3-氨基丙基）三乙氧基硅烷（APTES）修饰的碳点]的光致发光（PL）机理，其中考虑到了它们在末端的局部几何形状；"之 "字形（CDZZ-NH2）和扶手椅形（CDAC-NH2）结构取向。我们之前报告的实验证据表明，胺基团是通过 APTES 的乙氧基和 CD 的羟基之间的硅烷偶联反应实现的 Si-O 键拴在 CD 表面的。本研究仔细研究了 pH 值对这些体系的聚光效应的影响。通过分析 HOMO-LUMO 能量差异、状态密度（DoS）光谱和静电位（ESP），证明了 pH 值和结构对 CD-NH2 带隙的影响。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Next Nanotechnology

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