Sensor based on diamond nanoparticles and WS2 for ponceau 4R and tartrazine determination: Influence of green solvents employed for WS2 exfoliation

We report on the development of an electrochemical sensor for the simultaneous determination of ponceau 4R (P4R) and tartrazine (FR) dyes in non-alcoholic beverages. The sensor is based on the sequential modification of a glassy carbon (GC) electrode with WS2 and diamond nanoparticles (DNP). First, we have performed a computational study to select, among several eco-friendly solvents, the most adequate for exfoliating the 2D nanomaterial from bulk WS2. From this study, four solvents (triacetin, triethyl citrate, dimethylisosorbide and ethanol/water) were preselected for obtaining WS2 dispersions that were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The sensors obtained with these WS2 dispersions and DNP were tested for the determination of both dyes, finding the best results for ethanol/water. We have verified that the presence of both nanomaterials gives rise to an enhancement in the response with respect to both the bare GC and the sensor containing only one of them. The response consists of a pair of peaks corresponding to P4R ( + 0.69 V) and TR ( + 0.96 V) and a peak at around +0.2 V, coming from both dyes. After optimizing the initial potential in differential pulse voltammetric (DPV) measurements, we found that when -0.30 V is applied, the peak at + 0.2 V is only due to P4R. This lower potential value is more adequate than that at + 0.69 V to perform the determination of P4R. As a result of the capability to determine P4R at a low potential together with the synergistic effect between both nanomaterials, which leads to improved sensitivities, our methodology allows the simultaneous determination of both dyes with good analytical properties.