Induced Aggregation of Steric Stabilizing Anionic-Rich 2-Amino-3-chloro-5-trifluoromethylpyridine on CeO2 QDs: Surface Charge and Electro-Osmotic Flow Analysis

Manufacturing quantum dots (QDs) and their suspensions through incorporation of surface coatings can have enormous attention in manipulating surface properties such as size, shape, and structure. The surface of engineered QDs capped by the adsorption of organic matter is known for strongly influencing their physicochemical properties, which is very useful for many biomedical and technological applications. Prerequisite for any possible applications, the effect of organic matter on the surface of nanoparticles is important. In this contribution, owing to the privileged medicinal scaffolds based on the structure of pyridine derivatives, we have synthesized cerium oxide QDs with similar to 2.4 nm in size capped with anionic-rich head groups of 2amino-3-chloro-5-trifluoromethylpyridine (ACTP), and the assay is based on the steric stabilizing capping behavior of anionic rich ACTP molecules on the surface of CeO2 QDs. Aggregated QDs, obtained by adding capping agent in the reaction, have been characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and zeta potential techniques. XRD and FTIR analysis has been evaluated for the incorporation of ACTP on the surface of QDs. UV vis DRS analysis indicates the molecular aggregation predicted by dielectric confinement effect via local excitations mixed with more separated charge-transfer configurations. Under the influence of ACTP on the QDs, the electrophoretic mobility, conductivity, and current, along with average electric field, have been analyzed by electro-osmotic (EOS) flow analysis. In this scenario, it has been found that the addition of anionic head groups of ACTP molecules such as the nitrogen atom in the pyridine ring, CF3 functional groups, and Cl substitution-induced steric stabilization on CeO2 QDs (i.e., QD-to-QD interaction) has increased the ionic strength with decreasing zeta potential and promoted gradual QD aggregation. This study has thus led to a better understanding of the biophysicochemical interaction of anionic-rich ACTP molecules on the surface of CeO2 QDs and provides a physical picture of the structure and bonding of biocoated QD aggregation, which may lead to useful applications in biomedicine and designing a new material.