Cysteine as an electrosteric stabilizer
Researchers using the XSD 20-BM-B beamline at the APS are finding cysteine to be an excellent electrosteric stabilizer for zinc oxide (ZnO) nanoparticles (NPs) enabling the preparation of dispersions with particle sizes on the level of the primary particle size.
Zinc oxide (ZnO) nanoparticles (NPs) were stabilized in water using the amino acid L-cysteine. A transparent dispersion was obtained with an agglomerate size on the level of the primary particles. The dispersion was characterized by dynamic light scattering (DLS), pH dependent zeta potential measurements, high resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, photoluminescence (PL) spectroscopy and X-ray absorption fine structure (EXAFS, XANES) spectroscopy.
Cysteine acts as a source for sulfur to form a ZnS shell around the ZnO core and as a stabilizer for these core-shell NPs. A large effect on the photoluminescent properties is observed: the intensity of the defect luminescence (DL) emission decreases by more than two orders of magnitude, the intensity of the near band edge (NBE) emission increases by 20% and the NBE wavelength decreases with increasing cysteine concentration corresponding to a blue shift of about 35 nm due to the Burstein-Moss effect.
Alice Sandmann, Alexander Kompch, Viktor Mackert, Christian H. Liebscher and Markus Winterer, “Interaction of L-cysteine with ZnO: Structure, Surface Chemistry and Optical Properties,” Langmuir, Just Accepted Manuscript. DOI: 10.1021/la504968m, Published May 8, 2015.