Gil-Guerrero Sara, Otero Nicolás, Queizán Marta, Mandado Alonso Marcos
Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain.
Sensors (Basel). 2019 Apr 21;19(8):1896. doi: 10.3390/s19081896.
In this work, the electronic and optical properties of hybrid boron-nitrogen-carbon structures (h-BNCs) with embedded graphene nanodisks are investigated. Their molecular affinity is explored using pyridine as model system and comparing the results with the corresponding isolated graphene nanodisks. Time-dependent density functional theory (TDDFT) analysis of the electronic excited states was performed in the complexes in order to characterize possible surface and charge transfer resonances in the UV region. Static and dynamic (hyper)polarizabilities were calculated with coupled-perturbed Kohn-Sham theory (CPKS) and the linear and nonlinear optical responses of the complexes were analyzed in detail using laser excitation wavelengths available for (Hyper)Raman experiments and near-to-resonance excitation wavelengths. Enhancement factors around 10 and 10 were found for the polarizability and first order hyperpolarizability, respectively. The quantum chemical simulations performed in this work point out that nanographenes embedded within hybrid h-BNC structures may serve as good platforms for enhancing the (Hyper)Raman activity of organic molecules immobilized on their surfaces and for being employed as substrates in surface enhanced (Hyper)Raman scattering (SERS and SEHRS). Besides the better selectivity and improved signal-to-noise ratio of pristine graphene with respect to metallic surfaces, the confinement of the optical response in these hybrid h-BNC systems leads to strong localized surface resonances in the UV region. Matching these resonances with laser excitation wavelengths would solve the problem of the small enhancement factors reported in Raman experiments using pristine graphene. This may be achieved by tuning the size/shape of the embedded nanographene structure.
在这项工作中，研究了嵌入石墨烯纳米盘的硼 - 氮 - 碳混合结构（h - BNCs）的电子和光学性质。使用吡啶作为模型体系来探索它们的分子亲和力，并将结果与相应的孤立石墨烯纳米盘进行比较。为了表征紫外区域可能的表面和电荷转移共振，对复合物中的电子激发态进行了含时密度泛函理论（TDDFT）分析。利用耦合微扰Kohn - Sham理论（CPKS）计算了静态和动态（超）极化率，并使用适用于（超）拉曼实验的激光激发波长和近共振激发波长详细分析了复合物的线性和非线性光学响应。发现极化率和一阶超极化率的增强因子分别约为10和10。这项工作中进行的量子化学模拟指出，嵌入在混合h - BNC结构中的纳米石墨烯可以作为增强固定在其表面的有机分子的（超）拉曼活性以及用作表面增强（超）拉曼散射（SERS和SEHRS）底物的良好平台。除了相对于金属表面原始石墨烯具有更好的选择性和改进的信噪比之外，这些混合h - BNC系统中光学响应的限制导致在紫外区域出现强烈的局域表面共振。将这些共振与激光激发波长匹配将解决使用原始石墨烯的拉曼实验中报道的增强因子较小的问题。这可以通过调整嵌入的纳米石墨烯结构的尺寸/形状来实现。
