Improved charge-transfer resonance in graphene oxide/ZrO2 substrates for plasmonic-free SERS determination of methyl parathion

• Published in: Chemosphere (Oxford) 2023-04, Vol.320, p.138081-138081, Article 138081
• Main Authors: Vargas-Zamarripa, Marlene, Rivera, Aura A., Sierra, Uriel, Salas, Pedro, Serafín-Muñoz, Alma H., Ramírez-García, Gonzalo
• Format: Article
• Language: English
• Subjects: Charge-transfer mechanism; Chemical enhancement; Environmental monitoring; Plasmonic-free analysis; Semiconductor SERS; Water analysis
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2023.138081

This work reports a sensitive SERS substrate based on graphene oxide (GO) and quantum-sized ZrO2 nanoparticles (GO/ZrO2) for label-free determination of the organophosphate pesticide methyl parathion (MP). The enhanced light-matter interactions and the consequent SERS effect in these substrates resulted from the effective charge transfer (CT) mechanism attributed to synergistic contributions of three main factors: i) the strong molecular adherence of the MP molecules and the ZrO2 surface which allows the first layer-effect, ii) the relatively abundant surface defects in low dimensional ZrO2 semiconductor NPs, which act as intermediate electronic states that reduce the large bandgap barrier, and iii) the hindered charge recombination derived from the transference of the photoinduced holes to the GO layer. This mechanism allowed an enhancement factor of 8.78 × 104 for GO/ZrO2-based substrates, which is more than 5-fold higher than the enhancement observed for platforms without GO. A detection limit of 0.12 μM was achieved with an outstanding repeatability (variation ≤4.5%) and a linear range up to 10 μM, which is sensitive enough to determine the maximal MP concentration permissible in drinking water according to international regulations. Furthermore, recovery rates between 97.4 and 102.1% were determined in irrigation water runoffs, strawberry and black tea extracts, demonstrating the reliability of the hybrid GO/ZrO2 substrate for the organophosphate pesticides quantification in samples related to agri-food sectors and environmental monitoring. [Display omitted] •The plasmonic-free SERS substrate was validated for methyl parathion determination in irrigation water runoffs.•Charge transfer transitions are enhanced by the strong adherence between ZrO2 and the organophosphate pesticide.•Surface defects in quantum-sized ZrO2-NPs provide midgap states that boost excitation and vibronic coupling.•The photoinduced holes are transferred to the graphene oxide layer, hindering the charge recombination.•An enhancement factor of 8.78 × 104, limit of detection of 0.12 μM, and recovery rate of 102.1 ± 2.3% were determined.