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Ink-jet Printing of Hollow SnO2 Nanospheres for Gas Sensing Applications



Hollow tin-oxide (SnO2) nanospheres were synthesized by coating, carbon nanospheres (CNs) as hard templates, with a tin(IV) sol obtained by partial hydrolysis of [Sn(OBut)4] under ambient conditions. Formation of crystalline SnO2 spheres upon calcination was confirmed by powder X-ray diffraction data, whereas the hollow interiors of SnO2 particles were verified by scanning and transmission electron microscopy of both intact and broken spheres. The shell of SnO2 nanospheres sintered at 700°C consisted of a single layer of nanocrystallites (~6 nm) self-assembled in a ball-like superlattice. Tin-oxide hollow spheres showed an average diameter of 150 nm and could be homogeneously dispersed in water/ethylene glycol (50:50 vol%) mixture to form stable inorganic inks viable for their use in commercial ink-jet printers demonstrated by printing porous ceramic structures on an interdigitated sensor chip. The integration of large surface and nanoscopic voids in the final structures imparted higher sensitivity to the as-printed sensors toward both oxidizing (nitrogen dioxide) and reducing gases (methane and ethanol), which validates the enormous potential of printable inorganics in functional applications.