Evaluation of Green-Synthesized Cuprospinel Nanoparticles as a Nanosensor for Detection of Low-Concentration Cd(II) Ion in the Aqueous Solutions by the Quartz Crystal Microbalance Method

Cd(II) heavy metal is an extremely dangerous hazardous material for both humans and the environment. Its high toxicity is the reason behind the examination of new techniques for detecting very small concentrations of Cd(II). Recently, Quartz Crystal Microbalance (QCM) has been one of the techniques that have been widely used to detect trace heavy metal ions in solutions. It is a simple, inexpensive, portable, and sensitive gravimetric sensor due to its quality sensitivity lowest to nanograms. In this work, Cuprospinel nanoparticles were synthesized through the green synthesis approach using Psidium guajava L. leaf extract as a reducing agent, which is the first scientific description to report the preparation of these nanoparticles by this method. Subsequently, the synthesized nanoparticles were subjected to the characterization of their crystallinity, structure, and morphology by the XRD, N(2) adsorption–desorption, zeta potential, DLS, AFM, SEM, and TEM analyzers. The prepared Cuprospinel nanoparticles were evaluated as a nanosensor for the detection of the very low concentration of Cd(II) ions in aqueous solutions using the QCM technique. The results of the characterization proved that the Cuprospinel nanoparticles have formed in the nanoscale with sub-spherical shapes and particles size ranging from 20 to 80 nm. The BET surface area and pore size analysis revealed that the synthesized Cuprospinel nanoparticles possess a surface area of 47.3 m(2)/g, an average pore size of 1.5 nm, and a micropore volume of 0.064 cc/g. The QCM results demonstrated the success of the Cuprospinel nanoparticles sensor in detecting the tiny amounts of Cd(II) ions in the aqueous solutions with concentrations reaching about 3.6 ng/L.