Abstract
The surface cation composition of nanoscale metal oxides critically determines the properties of various functional chemical processes including inhomogeneous catalysts and molecular sensors. Here we employ a gradual modulation of cation composition on a ZnO/(Cu1−xZnx)O heterostructured nanowire surface to study the effect of surface cation composition (Cu/Zn) on the adsorption and chemical transformation behaviors of volatile carbonyl compounds (nonanal: biomarker). Controlling cation diffusion at the ZnO(core)/CuO(shell) nanowire interface allows us to continuously manipulate the surface Cu/Zn ratio of ZnO/(Cu1−xZnx)O heterostructured nanowires, while keeping the nanowire morphology. We found that surface exposed copper significantly suppresses the adsorption of nonanal, which is not consistent with our initial expectation since the Lewis acidity of Cu2+ is strong enough and comparable to that of Zn2+. In addition, an increase of the Cu/Zn ratio on the nanowire surface suppresses the aldol condensation reaction of nonanal. Surface spectroscopic analysis and theoretical simulations reveal that the nonanal molecules adsorbed at surface Cu2+ sites are not activated, and a coordination-saturated in-plane square geometry of surface Cu2+ is responsible for the observed weak molecular adsorption behaviors. This inactive surface Cu2+ well explains the mechanism of suppressed surface aldol condensation reactions by preventing the neighboring of activated nonanal molecules. We apply this tailored cation composition surface for electrical molecular sensing of nonanal and successfully demonstrate the improvements of durability and recovery time as a consequence of controlled surface molecular behaviors.
Highlights
The surface cation composition of nanoscale metal oxides is well known to signi cantly affect the surface molecularEdge Article successfully demonstrated with a controllable surface cation composition.[15,16,17] As such these approaches allow us to widely and systematically control the surface cation composition of nanoscale metal oxides while keeping their macroscopic morphology.Here we demonstrate a gradual modulation of the surface cation composition of heterostructured metal oxide nanowires via cation diffusion
We demonstrated a gradual modulation of the surface cation composition of ZnO/(Cu1ÀxZnx)O heterostructured nanowires by cation diffusion and investigated the effect of the surface cation composition on the adsorption and chemical transformation behaviors of nonanal
The gradual modulation of the surface Cu/Zn ratio was successfully achieved by preserving the macroscopic morphology
Summary
The surface cation composition of nanoscale metal oxides is well known to signi cantly affect the surface molecularEdge Article successfully demonstrated with a controllable surface cation composition.[15,16,17] As such these approaches allow us to widely and systematically control the surface cation composition of nanoscale metal oxides while keeping their macroscopic morphology.Here we demonstrate a gradual modulation of the surface cation composition of heterostructured metal oxide nanowires via cation diffusion. We employ a gradual modulation of cation composition on a ZnO/(Cu1ÀxZnx)O heterostructured nanowire surface to study the effect of surface cation composition (Cu/Zn) on the adsorption and chemical transformation behaviors of volatile carbonyl compounds (nonanal: biomarker).
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