Rational Design of Highly Porous SnO2 Nanotubes Functionalized with Biomimetic Nanocatalysts for Direct Observation of Simulated Diabetes.

1D metal-oxide nanotube (NT) structures have attracted considerable attention for applications in chemical sensors due to their high surface area and unique chemical and physical properties. Moreover, bimodal pores, i.e., meso- and macro-sized pores, which are formed on the shell of NTs, can further facilitate gas penetration into the sensing layers, leading to much improved sensing properties. However, thin-walled NTs with bimodal pore distribution have been rarely fabricated due to the limitations of synthetic methods. Here, Ostwald ripening-driven electrospinning combined with sacrificial templating route using polystyrene (PS) colloid and bioinspired protein is firstly proposed for producing both bi-modal pores and catalyst-loaded thin-walled SnO₂ NTs. Homogeneous catalyst loading on porous SnO₂ NTs is achieved by the protein cage that contains catalysts and PS colloids and protein shells are thermally decomposed during calcination of electrospun fibers, resulting in the creation of dual-sized pores on NTs. Pt catalyst decorated porous SnO₂ NTs (Pt-PS_SnO₂ NTs) show exceptionally high acetone gas response, superior selectivity against other interfering gases, and very low limit of detection (10 ppb) to simulated diabetic acetone molecules. More importantly, sensor arrays assembled with developed porous SnO₂ NTs enable the direct distinction between the simulated diabetic breath and normal breath from healthy people. [ABSTRACT FROM AUTHOR]