Glyphosate: ZnO Nanocrystal Interaction Controlled by pH Changes

The study of the interaction of the herbicide glyphosate with zinc oxide (ZnO) nanocrystals (NCs) was investigated under controlled pH conditions. These changes alter the various chemical groups' vibrational frequencies of the glyphosate molecule according to the infrared spectra. Scanning electron microscopy (SEM), and atomic force microscopy (AFM) images suggest that the pH changes promote specific conformational changes due to the protonation of glyphosate. Then, the glyphosate is organized as a mycelium around ZnO NCs at neutral pH. Also, as the pH varies from acidic to alkaline, new crystal structures occur, which goes from star-like to volcano-like shapes. For an efficient quantification of glyphosate using ZnO NCs, it is essential to correlate the pH to its method. The acidic medium is recommended for optical methods, while the basic medium is more suitable for gravimetric methods, and neutral pH is ideal for spectroscopic analysis in FTIR and Raman. Therefore, in this study, we demonstrated that tuning pH could change the identification method to improve accuracy.