Optimizing the preparation of laser-derived 3D porous graphene electrodes for modification-free sensing of heavy metal ions†

Abstract

Heavy metallic cations are prevalent in the environment and have detrimental effects on human health and flora. Research into methods for their detection is increasing. Laser-derived graphene electrodes (LDGEs) have gained popularity in electrochemical applications owing to their straightforward preparation, cost-effectiveness, porous structure, high specific surface area, and advantageous electronic properties. In this study, we showed that the fine-tuning of laser beam parameters, such as power and speed, as well as the electrochemical detection parameters, allowed detecting heavy metal ions, specifically Cd²⁺ and Pb²⁺, using carefully optimized porous LDGEs, without the need of adding any other metals such as Bi³⁺. The optimal LDGEs, respectively fabricated with a laser power and speed of 6.4 W and 30 cm s⁻¹ were characterized using electrochemical measurements, digital imaging, scanning electron microscopy, and Raman spectroscopy, confirming the 3D porous structure. The LDGEs were then subjected to square-wave anodic stripping voltammetry for the simultaneous detection of Cd²⁺ and Pb²⁺ in a 0.1 M acetate-buffered solution at pH 4. The key metrics for the LDGE-based sensor were as follows: sensitivities of 0.45 (Cd²⁺) and 0.93 (Pb²⁺) μA ppb⁻¹ cm⁻², linear ranges spanning from 25 to 1000 ppb (Cd²⁺) and 10 to 500 ppb (Pb²⁺), and detection limits of 6.13 ppb (Cd²⁺) and 2.96 ppb (Pb²⁺) (at S/N = 3).The electrochemical sensor could simultaneously detect Cd²⁺ and Pb²⁺ in real samples, including ore and tap water. This underscores the applicability and versatility of the optimized LDGEs for heavy-metal ion detection in complex environmental matrices.