Sustainable Paper-Derived Laser-Induced Graphene Electrochemical Platform for Ultra-Sensitive Diazepam Detection in Forensic Investigations.

The use of benzodiazepines like diazepam (DZ) in drug-facilitated crimes necessitates the development of rapid, sensitive and portable detection methods. This study presents a sustainable, paper-derived laser-induced graphene (paper-LIG) electrochemical platform for ultrasensitive DZ detection in forensic investigations. The sensor was fabricated using a cellulose paper substrate treated with sodium tetraborate to enhance thermal stability, enabling efficient graphene conversion via optimized laser scribing. The physicochemical properties of paper-LIG were characterized using field emission scanning electron microscopy, energy-dispersive X-ray spectrometry, Raman spectroscopy, Fourier-transform infrared spectrometry, and X-ray photoelectron spectroscopy. Additionally, the effects of working and auxiliary electrode sizes on electrochemical performance were evaluated. The resulting paper-LIG electrode exhibited excellent electrochemical performance, enabling direct DZ detection in beverage samples without complex pretreatment. Using an optimized voltammetric technique, the sensor achieved a wide linear range (1-1000 μmol L-1) and a low detection limit (0.4 μmol L-1). This platform demonstrated high selectivity, reproducibility (RSD 2.2%), and recovery (96.4-102.5%), confirming its reliability for forensic applications. Its low cost, scalability, and eco-friendliness make this sensor a promising tool for rapid on-site drug screening.