Structure Differentiation of Hydrophilic Brass Nanoparticles Using a Polyol Toolbox

Orestis Antonoglou; Evangelia Founta; Vasilis Karagkounis; Eleni Pavlidou; George Litsardakis; Stefanos Mourdikoudis; Nguyen Thi Kim Thanh; Catherine Dendrinou-Samara

doi:10.3389/fchem.2019.00817

Structure Differentiation of Hydrophilic Brass Nanoparticles Using a Polyol Toolbox

Front Chem. 2019 Nov 29:7:817. doi: 10.3389/fchem.2019.00817. eCollection 2019.

Authors

Orestis Antonoglou¹, Evangelia Founta¹, Vasilis Karagkounis¹, Eleni Pavlidou², George Litsardakis³, Stefanos Mourdikoudis^{4

5}, Nguyen Thi Kim Thanh^{4

5}, Catherine Dendrinou-Samara¹

Affiliations

¹ Laboratory of Inorganic Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
² Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece.
³ Laboratory of Materials for Electrotechnics, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece.
⁴ Biophysics Group, Department of Physics and Astronomy, University College London (UCL), London, United Kingdom.
⁵ UCL Healthcare Biomagnetic and Nanomaterials Laboratories, London, United Kingdom.

Abstract

Nano-brasses are emerging as a new class of composition-dependent applicable materials. It remains a challenge to synthesize hydrophilic brass nanoparticles (NPs) and further exploit them for promising bio-applications. Based on red/ox potential of polyol and nitrate salts precursors, a series of hydrophilic brass formulations of different nanoarchitectures was prepared and characterized. Self-assembly synthesis was performed in the presence of triethylene glycol (TrEG) and nitrate precursors Cu(NO₃)₂·3H₂O and Zn(NO₃)₂·6H₂O in an autoclave system, at different temperatures, conventional or microwave-assisted heating, while a range of precursor ratios was investigated. NPs were thoroughly characterized via X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmition electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and ζ-potential to determine the crystal structure, composition, morphology, size, state of polyol coating, and aqueous colloidal stability. Distinct bimetallic α-brasses and γ-brasses, α-Cu₄₀Zn₂₅/γ-Cu₁₁Zn₂₄, α-Cu₆₃Zn₃₇, α-Cu₄₇Zn₁₀/γ-Cu₁₉Zn₂₄, and hierarchical core/shell structures, α-Cu₅₉Zn₃₀@(ZnO)₁₁, Cu₃₅Zn₁₆@(ZnO)₄₉, α-Cu₃₇Zn₁₈@(ZnO)₄₅, Cu@Zinc oxalate, were produced by each synthetic protocol as stoichiometric, copper-rich, and/or zinc-rich nanomaterials. TEM sizes were estimated at 20-40 nm for pure bimetallic particles and at 45-70 nm for hierarchical core/shell structures. Crystallite sizes for the bimetallic nanocrystals were found ca. 30-45 nm, while in the case of the core-shell structures, smaller values around 15-20 nm were calculated for the ZnO shells. Oxidation and/or fragmentation of TrEG was unveiled and attributed to the different fabrication routes and formation mechanisms. All NPs were hydrophilic with 20-30% w/w of polyol coating, non-ionic colloidal stabilization (-5 mV < ζ-potential < -13 mV) and relatively small hydrodynamic sizes (<250 nm). The polyol toolbox proved effective in tailoring the structure and composition of hydrophilic brass NPs while keeping the crystallite and hydrodynamic sizes fixed.

Keywords: bimetallic nanoparticles; copper; microwave; polyol process; solvothermal; triethylene glycol; zinc.