Dual Linear Range Laser-Induced Graphene-Based Sensor for 4-Nitrophenol Detection in Water

Electrochemical sensors provide anexcellent platform for in situwater pollutant detection. Graphene-based electrochemical sensorshave been effective in the analysis of different genres of pollutants.However, the complex, chemically intensive steps of graphene fabricationand its modification pose challenges to the large-scale applicationof these sensors. Laser-induced graphene (LIG) is a promising technologywith a simple, rapid, chemical-free, mask-free, and scalable solutionto produce graphene-based electrochemical sensors. Among a diversearray of water pollutants, 4-nitrophenol (4-NP) is a critical pollutantowing to its acute toxicity and adverse health effects on humans andother living organisms. It is known to have carcinogenic, mutagenic,and teratogenic effects on aquatic life, plants, and human beingsat very low concentrations. This work demonstrated a simple nonreceptor-basedelectrochemical sensor for 4-NP detection by laser-induced graphene(LIG) printed on polyimide (PI) films. The laser irradiation of polymericfilms results in 3D porous graphene structure formation, which increasesthe electron transfer rate as well as the electrochemically activesurface area. The LIG sensor was fabricated by optimizing laser settingsand characterized by SEM, TEM, XRD, Raman spectroscopy, XPS, TGA,and EDS analysis. Using linear sweep voltammetry, the LIG sensorsdemonstrated linear behavior in two concentration ranges from 0.15to 1 & mu;M and 2.5 to 100 & mu;M with a detection limit of 95nM. A higher sensitivity was observed for the lower concentrationrange, which could be attributed to increased electrochemical sitesfor 4-NP in the porous LIG. The sensor showed good selectivity toward4-NP in the presence of its isomers and other phenolic compounds.Furthermore, it showed good selectivity in sewage samples spiked withdifferent 4-NP concentrations. The enhanced sensitivity of LIG toward4-NP at a lower concentration range could pave the way for high-performancesensors using LIG for environmental and other applications.