Peihua Zhu

Morphology-controlled self-assembly of a ferrocene–porphyrin based NO2 gas sensor: tuning the semiconducting nature via solvent–solute interaction

A novel unsymmetrical ferrocene–porphyrin derivative, namely 5-(4-ferrocamidophenyl)-10,15,20-triphenylporphyrin (H2FcPor), is designed, synthesized and characterized. The self-assembly properties of this novel ferrocene–porphyrin in methanol and n-hexane are comparatively investigated by scanning electron microscopy (SEM), the X-ray diffraction (XRD) technique, Fourier transform infrared (FT-IR) spectroscopy and electronic absorption spectroscopy. Intermolecular π–π interaction in cooperation with the solvent–solute interaction and the absence or presence of intermolecular hydrogen bonding leads to the formation of nanospheres and nanobelts in methanol and n-hexane, respectively. When applied as gas sensors, both the nanospheres and the nanobelts exhibit excellent gas sensitivity, and good stability and selectivity at room temperature for NO2 detection. Under the same measurement conditions, the detection limit and recovery times of nanobelt gas sensors are lower and faster than those for nanosphere gas sensors. Surprisingly, the nanospheres exhibit a normal n-type gas-sensing response to NO2, while the nanobelts display p-type gas-sensing behaviour in different NO2 concentration ranges. The abnormal sensing behavior with transition from n- to p-type NO2 sensing is tuned by solvent–porphyrin molecule interaction and molecular packing mode for the first time.

Room temperature NO2 sensor based on highly ordered porphyrin nanotubes.

Highly ordered nanotubes of 5, 10, 15, 20-tetrakis(4-aminophenyl)porphyrin zinc (ZnTAP) are fabricated by using nanoporous anodized aluminum oxide (AAO) membrane as the template. Electronic absorption spectra, fluorescence spectra, transmission electron microscope (TEM), scanning electronic microscopy (SEM), low-angle X-ray diffraction (XRD) techniques are adopted to characterize these nanotubes. The highly ordered nanotubes of ZnTAP show good conductivity and present an efficient gas sensor platform for the ultrasensitive detection of NO2 under room temperature. The proposed sensor shows high sensitivity, reproducibility and fast response/recovery behavior, and provides a promising avenue for improving the sensing performance.

Comparative NO2-sensing in cobalt and metal-free porphyrin nanotubes

In the present study, the nanotubes of 5-(4-hydroxyphenyl)-10, 15, 20-tri(4-chlorophenyl) porphyrin (p-HTClPP) (1) and 5-(4-hydroxyphenyl)-10, 15, 20-tri(4-chlorophenyl) porphyrin cobalt (p-HTClPPCo) (2) were successfully prepared by using anodize alumina oxide (AAO) template method. The p-HTClPP and p-HTClPPCo nanotubes have been confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electronic absorption spectra, fluorescence spectroscopy, fourier transform infrared spectroscopy (FT-IR), low-angle X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) techniques. Both p-HTClPPCo and p-HTClPP nanotubes showed excellent sensitivity, reproducibility and selectivity toward NO2. Especially the prepared sensor of p-HTClPPCo nanotubes exhibited faster response/recovery characteristics and lower detection limit of NO2 (up to 500ppb) than that of p-HTClPP nanotubes, which pave a new avenue in the gas sensitive field.