Sahoo Anubhab, Dixit Tejendra, Kumari Anshu, Gupta Sharad, Kothandaraman R, Rajeev P P, Rao M S Ramachandra, Krishnan Sivarama
Department of Physics, Indian Institute of Technology Madras Chennai-600036 India +9144 2257 5898
Optoelectronics and Quantum Devices Group, Department of Electronics and Communication Engineering, Indian Institute of Information Technology Design and Manufacturing Kancheepuram Chennai-600127 India.
Nanoscale Adv. 2024 Nov 15;7(2):524-535. doi: 10.1039/d4na00793j. eCollection 2025 Jan 14.
Controlling both UV and visible emissions in ZnO quantum dots (QDs) poses a significant challenge due to the inherent introduction of defects during the growth process. We have refined the photoluminescence (PL) emission characteristics of ZnO QDs through a single-step, reagent-free femtosecond pulsed laser ablation in liquid (fs-PLAL) technique. The ratio of the near band edge (NBE) to deep-level emission (DLE), which determines the shape of the QDs' optical emission spectrum, is precisely controlled by the ablation laser pulse parameters-namely, pulse energy and temporal duration. Having established our ability to control the optical properties, we have investigated the mechanisms and physics involved in controlling optical emission. The key highlight of the work is that ablation with a fs-pulse induces substantial defect states without altering the particle size, with the extent of the effect being dependent on the pulse energy and pulse duration. The spectroscopic techniques inducing Raman spectroscopy, excitation power dependent PL and transient PL study provided deep insight into the PL emission properties of these similarly sized QDs. The improved DLE in these laser-ablated QDs is explained by a surface-recombination-layer approximation process employing steady-state and transient PL. Moreover, we have demonstrated the applicability of green emission for pH sensing within a linear range of 7-10 and highlight the inherent antibacterial properties of these QDs.
由于在生长过程中不可避免地会引入缺陷，控制氧化锌量子点（QDs）中的紫外线和可见光发射是一项重大挑战。我们通过单步、无试剂的液体飞秒脉冲激光烧蚀（fs-PLAL）技术优化了氧化锌量子点的光致发光（PL）发射特性。决定量子点光发射光谱形状的近带边（NBE）与深能级发射（DLE）的比率，可通过烧蚀激光脉冲参数精确控制，即脉冲能量和持续时间。在确定了我们控制光学性质的能力后，我们研究了控制光发射所涉及的机制和物理过程。这项工作的关键亮点在于，飞秒脉冲烧蚀会在不改变颗粒尺寸的情况下诱导大量缺陷态，其影响程度取决于脉冲能量和脉冲持续时间。拉曼光谱、激发功率依赖的PL和瞬态PL研究等光谱技术，为深入了解这些尺寸相似的量子点的PL发射特性提供了帮助。通过采用稳态和瞬态PL的表面复合层近似过程，解释了这些激光烧蚀量子点中DLE的改善情况。此外，我们展示了绿色发射在7-10的线性范围内用于pH传感的适用性，并突出了这些量子点固有的抗菌特性。
