Soft landing of polyatomic anions onto three-dimensional semiconductive and conductive substrates

Soft landing of well-characterized polyoxometalate anions, PW12O403- (WPOM) and PMo12O403- (MoPOM), was carried out to explore the distribution of anions in the semiconducting 10 and 6 mu m-long vertically aligned TiO2 nanotubes as well as 300 mu m-long conductive vertically aligned carbon nanotubes (VACNTs). The distribution of soft-landed anions on the surfaces and their penetration into the nanotubes were studied using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). We observe that soft landed anions generate microaggregates on the TiO2 nanotubes and only reside in the top 1.5 mu m of the nanotube height. Meanwhile, soft landed anions are uniformly distributed on top of VACNTs and penetrate into the top 40 mu m of the sample. We propose that both the aggregation and limited penetration of POM anions into TiO2 nanotubes is attributed to the lower conductivity of this substrate as compared to VACNTs. This study provides first insights into the controlled modification of three dimensional (3D) semiconductive and conductive interfaces using soft landing of mass-selected polyatomic ions, which is of interest to the rational design of 3D interfaces for electronics and energy applications.

Automated summary

Soft landing of well-characterized polyoxometalate anions, PW12O403- (WPOM) and PMo12O403- (MoPOM), on vertically aligned TiO2 nanotubes and carbon nanotubes was conducted. The distribution of anions on the surfaces and their penetration into the nanotubes were studied using EDX and SEM. The results showed that the anions formed microaggregates on the TiO2 nanotubes and only resided in the top 1.5 μm, while they were uniformly distributed on the carbon nanotubes and penetrated into the top 40 μm. The limited penetration in TiO2 nanotubes was attributed to the lower conductivity of this substrate compared to carbon nanotubes. This study provides valuable insights into the controlled modification of 3D semiconductor and conductive interfaces using soft landing of mass-selected polyatomic ions.