Graphene-Activated Optoplasmonic Nanomembrane Cavities for Photodegradation Detection Yin Yin, †,‡ Jinbo Pang, § Jiawei Wang,* ,†,⊥,# Xueyi Lu, † Qi Hao, † Ehsan Saei Ghareh Naz, † Xinxing Zhou, ∥ Libo Ma,* ,† and Oliver G. Schmidt †,⊥,# † Institute for Integrative Nanosciences and § Institute for Complex Materials, IFW Dresden, 01069 Dresden, Germany ‡ School of Materials Science and Engineering, Jiangsu University, 212013 Zhenjiang, China ∥ Synergetic Innovation Center for Quantum Effects and Applications, School of Physics and Electronics, Hunan Normal University, 410081 Changsha, China ⊥ Material Systems for Nanoelectronics, Technische Universitä t Chemnitz, 09107 Chemnitz, Germany # Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Technische Universitä t Chemnitz, Rosenbergstr. 6, 09126 Chemnitz, Germany * S Supporting Information ABSTRACT: Graphene, with its excellent chemical stability, biocompatibility, and capability of electric field enhancement, has a great potential in optical and optoelectronic applications with superior performances by integrating with conventional optical and plasmonic devices. Here, we design and demonstrate graphene-activated optoplasmonic cavities based on rolled-up nanomembranes, which are employed for in situ monitoring the photodegradation dynamics of organic dye molecules on the molecular level in real time. The presence of the graphene layer significantly enhances the electric field of hybrid optoplasmonic modes at the cavity surface, enabling a highly sensitive surface detection. The degradation of rhodamine 6G molecules on the graphene-activated sensor surface is triggered by localized laser irradiation and monitored by measuring the optical resonance shift. Our demonstration paves the way for real-time, high-precision analysis of photodegradation by resonance-based optical sensors, which promises the comprehensive understanding of degradation mechanism and exploration of effective photocatalysts. KEYWORDS: graphene, optoplasmonic sensors, whispering gallery modes, photocatalysts, photodegradation P hotocatalytic degradation as a fundamental physicochem- ical process has attracted increasing attention in accelerating pollutant degradation and energy conversion. 1−5 In comparison with conventional biological and physical treatments, the photodegradation method is efficient, econom- ical, and environment-friendly. Thus, it is of high interest to investigate the degradation technique including the generation, mechanism, and detection of the physicochemical process. Conventional methods for the detection of degradation dynamics rely on the measurement of absorbance spectra or photocurrent densities. 2 However, it is still challenging to accurately monitor the photodegradation of organic com- pounds on the molecular level and realize spatially resolved information in a sub-micrometer-sized area. Over the past two decades, miniaturized optical sensors have been extensively explored for damage-free, real-time, and label-free detection in the biological/chemical analysis. 6−13 Among various optical sensors, whispering-gallery-mode (WGM) microcavities have been proved a powerful platform with ultrahigh accuracy and resolution down to single molecules/particles. 6,7,12,13 More- over, the strategy of combining plasmonic nanostructures and WGM microcavities has further improved the sensing performance due to enhanced field localization, 14−18 which, in turn, has enabled the detection of single proteins and ions. 19,20 Therefore, it is highly desired to apply the optoplasmonic WGM microcavities for detecting degradation and pushing down the limit of detection (LOD). Graphene, as a chemically stable and biocompatible two- dimensional (2D) material, has provided a fantastic platform to investigate and exploit optoplasmonic sensing. 21−28 In particular, the flat single-atom-layered hexagonal structure with a high charge density is capable of absorbing tiny molecules through strong π−π stacking, which leads to a chemically enhanced sensing capability. 21 In addition, the plasmonically enhanced localized electric field can be further strengthened by the charge transfer from graphene to the noble-metal surface, which facilitates the sensitivity improve- ment. 23−25 Here, we propose and demonstrate graphene- Received: January 13, 2019 Accepted: April 8, 2019 Published: April 9, 2019 Research Article www.acsami.org Cite This: ACS Appl. Mater. Interfaces 2019, 11, 15891-15897 © 2019 American Chemical Society 15891 DOI: 10.1021/acsami.9b00733 ACS Appl. Mater. Interfaces 2019, 11, 15891−15897 Downloaded via UNIV OF JINAN on May 1, 2019 at 06:10:17 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.