Synthesis of Pure and Fe-Doped TiO$_2$ Nanoparticles via Electrospray-Assisted Flame Spray Pyrolysis for Antimicrobial Applications

We report a straightforward aerosol-based approach to synthesizing pure and Fe-doped TiO$_2$ nanoparticles by continuous electrospray-assisted flame spray pyrolysis (EAFSP). Initially, pure TiO$_2$ nanoparticles were prepared by electrospraying titanium diisopropoxide bis(acetylacetonate) (TDIP) at varying concentrations onto a grounded flame. In this regard, various in situ (phase Doppler anemometry, high-speed camera, and scanning mobility particle sizer) and ex situ (small-angle X-ray scattering, transmission electron microscopy, and BET adsorption isotherms) diagnostics were applied for the analysis of the in-flight droplet characteristics in the spray, such as droplet μ-explosions, as well as primary and agglomerate nanoparticle evolution within the process and the particulate product. Moreover, single-particle ICP-MS (inductively coupled plasma–mass spectrometry) in situ measurements have been conducted to get insight into the process that causes various particle morphologies and to open up the option of an in situ determination of the particle formation route. Subsequently, the EAFSP method was utilized to produce Fe-doped TiO$_2$ nanoparticles. ... mehrThe influences of the Fe$^{3+}$ dopant concentration on the particle size, crystal structure, crystallite sizes, phase formation, oxygen vacancy defects, and optical gaps were systematically investigated. The presented EAFSP synthesis, in contrast to conventional flame spray pyrolysis (FSP) with gas atomization of the solvent/precursor, eliminates the need for dispersion gas and complex solvents, making it a more efficient and environmentally friendly method for nanoparticle synthesis. Finally, we studied the application potential of EAFSP-synthesized pure and Fe-doped TiO$_2$ nanoparticles for fighting bacteria resistant to an antibiotic, here spectinomycin-resistant Escherichia coli. A clear inhibitory effect of the Fe-doped TiO$_2$ nanoparticles could be observed during the growth of bacteria in the liquid medium, up to 99.4%. These results point out the high potential of the designed Fe-doped TiO$_2$ nanoparticles to act as antimicrobial agents and treatments against infections.