On the state of Mn in MnxZn1−xO nanoparticles and their surface modification with isonipecotic acid

• Published in: Journal of solid state chemistry 2017-03, Vol.247, p.43-52
• Main Authors: Jiménez-Hernández, L., Estévez-Hernández, O., Hernández, M.P., Díaz, J.A., Farías, M.F., Reguera, E.
• Format: Article
• Language: English
• Subjects: Isonipecotic acid; Mn-doped ZnO; Peroxidase conjugation; XPS; ZnO
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2016.12.022

Mn-doped ZnO (MnxZn1−xO) nanoparticles were synthesized by the co-precipitation method and coated with isonipecotic acid as capping ligand. The structure, composition and morphology of the resulting nanomaterial were investigated by energy disperse X-ray analysis, X-ray diffraction, and transmission electron microscopy data. Such measurements showed that the solid obtained contains 6at% of Mn and it is formed by a highly crystalline material with 3–5nm range of crystallite size, and only a small elongation of its cell parameter with respect to undoped ZnO wurtzite unit cell. Information on the state of manganese atom in the MnxZn1−xO nanostructures formed was obtained from X-ray photoelectron (XPS) and electron energy loss (EELS) spectroscopies. XPS and EELS spectra are composed of four peaks, corresponding to two species of Mn(II) and signals from Mn(III) and Mn(IV). Such spectral data on the state of Mn in the material studied is consistent with the mapping of Mn distribution observed in recorded transmission electron microscopy images, which reveal presence of clusters of Mn atoms. Only a fraction of doping Mn atoms were found forming a solid solution with the host ZnO structure. The functionalization of the nanoparticles system with Isonipecotic acid shows that this molecule remains anchored to the nanoparticles surface mainly through its N basic site. The availability of free carboxylate groups in the capping molecule was tested by conjugation to type IV horseradish peroxidase. State of Mn atoms in Mn-doped ZnO nanostructures prepared by the precipitation method, their capping with isonipecotic acid and subsequent conjugation to peroxidase. [Display omitted] •State of manganese in manganese-doped zinc oxide nanoparticles.•Isonipecotic acid as surface modifier of ZnO nanoparticles.•Peroxidase conjugation to ZnO nanoparticles modified with isonipecotic acid.