He Zhengyi, Yu Lingyan, Wang Gang, Ye Caichao, Feng Xiaoqiang, Zheng Li, Yang Siwei, Zhang Guanglin, Wei Genwang, Liu Zhiduo, Xue Zhongying, Ding Guqiao
Department of Microelectronic Science and Engineering, School of Physical Science and Technology, Ningbo University, Ningbo, Zhejiang 315211, People's Republic of China.
Academy for Advanced Interdisciplinary Studies and Guangdong Provincial Key Laboratory of Computational Science and Material Design, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People's Republic of China.
ACS Appl Mater Interfaces. 2022 Mar 30;14(12):14764-14773. doi: 10.1021/acsami.2c00584. Epub 2022 Mar 21.
Three-dimensional graphene (3D-graphene) is used in surface-enhanced Raman spectroscopy (SERS) because of its plasmonic nanoresonator structure and good ability to interact with light. However, a thin (3-5 nm) layer of amorphous carbon (AC) inevitably appears as a template layer between the 3D-graphene and object substrate when the 3D-graphene layer is synthesized, weakening the enhancement factor. Herein, two-dimensional graphene (2D-graphene) is employed as a template layer to directly synthesize 3D-graphene on a germanium (Ge) substrate via plasma-assisted chemical vapor deposition, bypassing the formation of an AC layer. The interaction and photoinduced charge transfer ability of the 3D-graphene/Ge heterojunction with incident light are improved. Moreover, the high density of electronic states close to the Fermi level of the heterojunction induces the adsorbed probe molecules to efficiently couple to the 3D-graphene-based SERS substrate. Our experimental results imply that the lowest concentrations of rhodamine 6G and rhodamine B that can be detected on the 3D/2D-graphene/Ge SERS substrate correspond to 10 M; for methylene blue, it is 10 M. The detection limits of the 3D/2D-graphene/Ge SERS substrate with respect to 3-hydroxytyramine hydrochloride and melamine (in milk) are both less than 1 ppm. This work may provide a viable and convenient alternative method for preparing 3D-graphene SERS substrates. It also constitutes a new approach to developing SERS substrates with remarkable performance levels.
三维石墨烯（3D-石墨烯）因其等离子体纳米谐振器结构以及与光良好的相互作用能力而被用于表面增强拉曼光谱（SERS）。然而，在合成3D-石墨烯层时，不可避免地会在3D-石墨烯与目标衬底之间出现一层薄（3 - 5纳米）的非晶碳（AC）作为模板层，这会削弱增强因子。在此，二维石墨烯（2D-石墨烯）被用作模板层，通过等离子体辅助化学气相沉积在锗（Ge）衬底上直接合成3D-石墨烯，从而避免了AC层的形成。3D-石墨烯/Ge异质结与入射光的相互作用以及光致电荷转移能力得到了改善。此外，异质结费米能级附近的高电子态密度促使吸附的探针分子有效地耦合到基于3D-石墨烯的SERS衬底上。我们的实验结果表明，在3D/2D-石墨烯/Ge SERS衬底上可检测到的罗丹明6G和罗丹明B的最低浓度对应于10⁻¹¹ M；对于亚甲基蓝，为10⁻¹² M。3D/2D-石墨烯/Ge SERS衬底对盐酸3-羟基酪胺和三聚氰胺（在牛奶中）的检测限均小于1 ppm。这项工作可能为制备3D-石墨烯SERS衬底提供一种可行且便捷的替代方法。它还构成了一种开发具有卓越性能水平的SERS衬底的新途径。
