Controlled hybridization of Sn-SnO₂ nanoparticles via simple-programmed microfluidic processes for tunable ultraviolet and blue emissions

Precisely controlling the microstructure and composition of each component in hybrid nanomaterials is critical for desired properties but very challenging. Herein, we demonstrate a new proof-of-concept method, or microtubing-based simple-programmed microfluidic processes (MT-SPMPs). MT-SPMPs preserve the ability for controlled hybridization by accurately adjusting the detailed microstructures and crystal phases of components using Sn-SnO₂ nanoparticles as models, by coupling the synergistic effects of complex surfactants with the precise reaction kinetics control. Consequently, uniform Sn-SnO₂ nanospheres with diameters from 2 nm to 14 nm or Sn@SnO ₂ nanorods with a diameter of 19 nm and length of 66 nm can be achieved. The SnO₂ shell thickness can be well controlled at the Bohr exciton radius range. Particularly, the defect type and density in these nanospheres and nanorods can be tuned for unique ultraviolet emission at 347 nm or enhanced blue emission at 475 nm. Analysis on the detailed microstructure and crystal-phase dependent photoluminescences indicates that the quantum mechanical dipole-forbidden rule can be effectively conquered by the formation of Sn-SnO₂ nanohybrids with controlled defects (oxygen vacancies or Sn interstitials).