3-mercaptopropionic acid surface modification of Cu-doped ZnO nanoparticles: Their properties and peroxidase conjugation

• State of copper in copper-doped zinc oxide nanoparticles.
• 3-Mercaptopropionic acid as surface modifier of ZnO nanoparticles.
• Peroxidase conjugation to ZnO nanoparticles modified with 3-mercaptopropionic acid.

Cu-doped ZnO (CuxZn1-xO) nanoparticles have been prepared by a co-precipitation method followed by their surface modification with 3-mercaptopropionic acid (MPA). The nature and morphology of the resulting nanostructures were established from X-ray diffraction, transmission electron microscopy and X-ray fluorescence spectroscopy data. Such measurements showed highly crystalline material with nanostructure size of about 3–5 nm and with the indicated chemical composition. Information on the state of copper atom in the CuxZn1-xO structure was obtained from X-ray photoelectron and UV–vis spectroscopies, and magnetic measurements. These techniques together with infrared and photoluminescence spectroscopies were used to study the surface modification of CuxZn1-xO with 3-mercaptopropionic acid. The zinc oxide nanostructures under study display colored light emission. Such fluorescent features and their stability in aqueous media are highly desirable in many potential applications, including biological labels for specific targeting in bioimaging probes and for recognition studies in biosensing applications. The viability of the MPA surface modified CuxZn1-xO nanoparticles to form a surface complex with biomolecules was demonstrated by their conjugation to peroxidase, a molecule with a high versatility for biological assays.

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