Joshi Pratik, Shukla Shubhangi, Gupta Siddharth, Riley Parand R, Narayan Jagdish, Narayan Roger
Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907, United States.
Intel Corporation, Rolner Acres Campus 3, Hillsboro, Oregon 97124, United States.
ACS Appl Mater Interfaces. 2022 Aug 17;14(32):37149-37160. doi: 10.1021/acsami.2c09096. Epub 2022 Aug 5.
The existence of point defects, holes, and corrugations (macroscopic defects) induces high catalytic potential in graphene and its derivatives. We report a systematic approach for microscopic and macroscopic defect density optimization in excimer laser-induced reduced graphene oxide by varying the laser energy density and pulse number to achieve a record detection limit of 7.15 nM for peroxide sensing. A quantitative estimation of point defect densities was obtained using Raman spectroscopy and confirmed with electrochemical sensing measurements. Laser annealing (LA) at 0.6 J cm led to the formation of highly reduced graphene oxide (GO) by liquid-phase regrowth of molten carbon with the presence of dangling bonds, making it catalytically active. Hall-effect measurements yielded a mobility of ∼200 cm V s. An additional increase in the number of pulses at 0.6 J cm resulted in deoxygenation through the solid-state route, leading to the formation of holey graphene structure. The average hole size showed a hierarchical increase, with the number of pulses characterized with multiple microscopy techniques, including scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The exposure of edge sites due to high hole density after 10 pulses supported the formation of proximal diffusion layers, which led to facile mass transfer and improvement in the detection limit from 25.4 mM to 7.15 nM for peroxide sensing. However, LA at 1 J cm with 1 pulse resulted in a high melt lifetime of molten carbon and the formation of GO characterized by a high resistivity of 3 × 10 Ω-cm, which was not ideal for sensing applications. The rapid thermal annealing technique using a batch furnace to generate holey graphene results in structure with uneven hole sizes. However, holey graphene formation using the LA technique is scalable with better control over hole size and density. This study will pave the path for cost-efficient and high-performance holey graphene sensors for advanced sensing applications.
点缺陷、孔洞和波纹（宏观缺陷）的存在赋予了石墨烯及其衍生物高催化潜力。我们报告了一种系统方法，通过改变激光能量密度和脉冲数，对准分子激光诱导还原氧化石墨烯中的微观和宏观缺陷密度进行优化，以实现过氧化物传感7.15 nM的创纪录检测限。利用拉曼光谱获得了点缺陷密度的定量估计，并通过电化学传感测量得到证实。在0.6 J/cm²进行激光退火（LA），通过液态碳的再生长和悬键的存在，导致形成高度还原的氧化石墨烯（GO），使其具有催化活性。霍尔效应测量得到的迁移率约为200 cm² V⁻¹ s⁻¹。在0.6 J/cm²时脉冲数的进一步增加导致通过固态途径脱氧，形成多孔石墨烯结构。平均孔径呈分级增加，用多种显微镜技术（包括扫描电子显微镜、原子力显微镜和透射电子显微镜）对脉冲数进行了表征。10次脉冲后由于高空洞密度导致边缘位点暴露，支持了近端扩散层的形成，这导致传质容易，并将过氧化物传感的检测限从25.4 mM提高到7.15 nM。然而，在1 J/cm²下进行1次脉冲的激光退火导致液态碳的高熔体寿命，并形成了具有3×10⁶ Ω·cm高电阻率的氧化石墨烯，这对于传感应用并不理想。使用间歇炉的快速热退火技术生成多孔石墨烯会导致孔尺寸不均匀的结构。然而，使用激光退火技术形成多孔石墨烯具有可扩展性，对孔尺寸和密度有更好的控制。这项研究将为用于先进传感应用的经济高效且高性能的多孔石墨烯传感器铺平道路。
