Muhammad Afiz Shahmer Muhammad Noor Afandi, Yap Wing Fen, Hazwani Suhaila Hashim, Rahayu Emilia Mohamed Khaidir, Nur Alia Sheh Omar, Wan Mohd Ebtisyam Mustaqim Mohd Daniyal, Jaafar Abdullah, Huda Abdullah, Ahmad Taufiq, Faten Bashar Kamal Eddin
In this study, the preparation of carbon quantum dots (CQDs) derived from lemon juice as a precursor using hydrothermal method is described. The optical properties of the CQDs were characterized using photoluminescence spectroscopy, which exhibited a maximum emission peak at 450 nm, with the highest intensity recorded for the sample treated at 180 °C. Fourier transform infrared spectroscopy confirmed the presence of amino, carboxylic acid, carboxyl, and hydroxyl groups in the CQDs. Transmission electron microscopy analysis revealed that the CQDs were predominantly spherical in shape, with an average particle diameter of approximately 4.73 nm. The integration of the gold/CQDs thin film with surface plasmon resonance spectroscopy enabled the detection of uric acid. Using Winspall software, the refractive index of the gold/CQDs thin film was determined to be n + ik = 1.6014 + 3.7i, with a thickness of 12.00 nm. The sensor demonstrated a linear response to uric acid concentrations up to 1 µM, achieving sensitivity values of 3.968° µM−1 and 0.4098° µM−1, along with a binding affinity constant of 6.94754 MM−1. These findings demonstrate that the gold/CQDs thin film possesses strong potential for the detection of uric acid, achieving quantitation and detection limits as low as 0.05 µM and 0.002 µM, respectively. © The Author(s) 2025.
Department of Physics, Faculty of Science, Universiti Putra Malaysia, Selangor, Serdang, 43400 UPM, Malaysia; Functional Nanotechnology Devices Laboratory, Institute of Nanoscience and Nanotechnology, Universiti Putra Malaysia, Selangor, Serdang, 43400 UPM, Malaysia; Faculty of Applied Sciences, Universiti Teknologi MARA, Cawangan Sarawak, Kota Samarahan, Sarawak, 94300, Malaysia; Physics Section, School of Distance Education, Universiti Sains Malaysia, Gelugor, Pulau Pinang, 11800, Malaysia; Department of Electrical, Electronic, and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Selangor, Bangi, 43600 UKM, Malaysia; Department of Physics, Faculty of Mathematics and Natural Science, Universitas Negeri Malang, Jl. Semarang 5, Malang, 65145, Indonesia; Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310058, China
