Synthesis of ZnO Nanoparticles with Tunable Surface Charge
Dr. Charles Hanna
ZnO nanoparticles (NPs) are under intense study due to their possible applications in a variety of fields, including magnetic nanoparticles studies and biological applications. The electrostatic interaction between nanoparticles (NPs)NPs and cells has been widely studied and regarded as a crucial contribution to the NP-induced cytotoxicity. Additionally, reports have risen attributing weak ferromagnetism to the surface of NPs. ZnO NPs are one of the good candidates for developing anti-cancer therapeutics because they show strong cytotoxicity to certain types of cancer cells without any appreciable toxicity to normal healthy cells under appropriate concentrations. It is highly desirable to improve the selective cytotoxicity of ZnO NPs to cancer cells by controlling their toxicity via adjusting their surface structure and charge. Here the ZnO NPs with average diameter of ~ 8 nm have been first synthesized using a modified forced hydrolysis method in diethylene glycol. The as-prepared NPs were post-treated by the aqueous solution of poly (acryl acid) (PAA) to modify their surface charge. With increasing the PAA concentration from 0 to 10 mg/1mL, theThe zeta potential, and hence surface charge, of ZnO NPs can be gradually reduced from +44.2 to -30.9 mV by coating with poly(acrylic acid) (PAA), showing the NPs surface charge is successfully tuned over a wide rangefrom high positive to very negative. The exciting results obtained here should facilitate the cancer therapy applications of ZnO and to help understand the effects of surface structure on magnetism. The PAA post-treating method developed here also provides a general approach to continuously modify the surface charge of the other kind of NPs. Here it has been successfully extended to adjust the surface charge of hematite NPs from highly positive (+49.1 mV) to very negative (-43.9 mV).The general method developed here for PAA coating may also be applied to modify the surface of other NPs.