Carbon quantum dots (CQD) have received considerable attention due to its advantageous characteristics of highly fluorescent nature and good biocompatibility. In this study, CQD were successfully prepared from empty fruit bunch (EFB) biochar, a renewable and sustainable resource using a facile microwave-assisted method in just minutes. The structures, morphology, and functional groups of CQD were analysed by HRTEM, FTIR and XPS analysis. CQD displayed bright blue emission upon exposure to UV irradiation. The maximum fluorescence emission of CQD was detected at 420 nm throughout the excitation wavelength 280 nm. To obtain optimum molecular structure of CQD, density functional theory (DFT) calculations were carried out using 6-31G(d) basis set which also includes a comparison of three exchange correlation functions such as B3LYP, CAM-B3LYP and wB97XD. These functionals were used to calculate the ground state molecular structure of CQD. The HOMO-LUMO gap obtained from 6 to 31G(d)/B3LYP was around 6.4 eV and is closer to the experimental band gap of 4.4 eV compared to CAM-B3LYP and wB97XD. The fluorescence quenching effect was observed when Cu²⁺ ions were added into CQD solution. The experiment results showed that the as-prepared CQD have a sensitive response to Cu²⁺ ions in the concentration range of 0–400 μM. This work not only provides insight into the properties and molecular structure of CQD obtained via a facile and scalable method, but also shows potential of a fluorescence sensor for metal ions detection.

碳量子点（CQD）由于其具有高度荧光性质和良好的生物相容性的有利特性而受到了广泛的关注。在这项研究中，仅用几分钟即可从空果束（EFB）生物炭中成功制备出CQD，EFB生物炭是一种可再生且可持续的资源，使用便捷的微波辅助方法。通过HRTEM，FTIR和XPS分析对CQD的结构，形态和官能团进行了分析。CQD在暴露于紫外线照射后显示亮蓝色发射。在整个激发波长280 nm处，在420 nm处检测到CQD的最大荧光发射。为了获得最佳的CQD分子结构，使用6-31G（d）基集进行了密度泛函理论（DFT）计算，其中还包括三个交换相关函数（如B3LYP，CAM-B3LYP和wB97XD。这些功能用于计算CQD的基态分子结构。与CAM-B3LYP和wB97XD相比，从6到31G（d）/ B3LYP获得的HOMO-LUMO间隙约为6.4 eV，并且更接近于4.4 eV的实验带隙。铜时观察到荧光猝灭作用^将2+离子添加到CQD溶液中。实验结果表明，所制备的CQD在0-400μM的浓度范围内对Cu ²⁺离子具有敏感的响应。这项工作不仅提供了对通过简便，可扩展方法获得的CQD的性质和分子结构的深入了解，而且还展示了用于金属离子检测的荧光传感器的潜力。