Bharathi Ganapathi, Nataraj Devaraj, Premkumar Sellan, Saravanan Padmanaban, Thangadurai Daniel T, Khyzhun Oleg Yu, Senthilkumar Kittusamy, Kathiresan Ramasamy, Kolandaivel Ponmalai, Gupta Mukul, Phase Deodatta
Quantum Materials & Energy Devices (QM-ED) Laboratory, Department of Physics, Bharathiar University Coimbatore TN India
UGC-CPEPA Centre for Advanced Studies in Physics for the Development of Solar Energy Materials and Devices, Department of Physics, Bharathiar University Coimbatore TN India.
RSC Adv. 2020 Jul 16;10(45):26613-26630. doi: 10.1039/d0ra04549g. eCollection 2020 Jul 15.
Graphene-nanostructured systems, such as graphene quantum dots (GQDs), are well known for their interesting light-emitting characteristics and are being applied to a variety of luminescence-based applications. The emission properties of GQDs are complex. Therefore, understanding the science of the photophysics of coupled quantum systems (like quantum clusters) is still challenging. In this regard, we have successfully prepared two different types of GQD clusters, and explored their photophysical properties in detail. By co-relating the structure and photophysics, it was possible to understand the emission behavior of the cluster in detail. This gave new insight into understanding the clustering effect on the emission behaviour. The results clearly indicated that although GQDs are well connected, the local discontinuity in the structure prohibits the dynamics of photoexcited charge carriers going from one domain to another. Therefore, an excitation-sensitive dual emission was possible. Emission yield values of about 18% each were recorded at the blue and green emission wavelengths at a particular excitation energy. This meant that the choice of emission color was decided by the excitation energy. Through systematic analysis, it was found that both intrinsic and extrinsic effects contributed to the blue emission, whereas only the intrinsic effect contributed to the green emission. These excitation-sensitive dual emissive GQD clusters were then used to sense Fe and Cr ions in the nanomolar range. While the Cr ions were able to quench both blue and green emissions, the Fe ions quenched blue emission only. The insensitivity of the Fe ions in the quenching of the green emission was also understood through quantum chemical calculations.
石墨烯纳米结构系统，如石墨烯量子点（GQD），以其有趣的发光特性而闻名，并正被应用于各种基于发光的应用中。GQD的发射特性很复杂。因此，理解耦合量子系统（如量子簇）的光物理科学仍然具有挑战性。在这方面，我们成功制备了两种不同类型的GQD簇，并详细探索了它们的光物理性质。通过将结构与光物理相关联，能够详细了解簇的发射行为。这为理解聚类对发射行为的影响提供了新的见解。结果清楚地表明，尽管GQD连接良好，但结构中的局部不连续性阻止了光激发电荷载流子从一个域转移到另一个域。因此，实现了激发敏感的双发射。在特定激发能量下，蓝色和绿色发射波长处的发射产率值分别约为18%。这意味着发射颜色的选择由激发能量决定。通过系统分析发现，内在和外在效应都对蓝色发射有贡献，而只有内在效应导致绿色发射。然后，这些激发敏感的双发射GQD簇被用于检测纳摩尔范围内的铁和铬离子。虽然铬离子能够淬灭蓝色和绿色发射，但铁离子仅淬灭蓝色发射。通过量子化学计算也理解了铁离子对绿色发射淬灭的不敏感性。
