Ethanol

Amberlite^®IR120 strong acid cation exchange resin, 5-ALA and acetylacetone were purchased from the Sigma-Aldrich, USA. Hydrochloride acid was purchased from Fluka, Switzerland. Ammonium hydroxide was purchased from Thermo-Fisher, USA. Activated carbon was ordered from Alfa Aesar, USA. Phosphoric acid was purchased from Merck, USA. Acetone, diethyl ether, ethanol, and methanol were purchased from ECHO, Taiwan. 4-Dimethylaminobenaldehyde (DMAB) was ordered from ACROS Organics™. Perchloric acid and sodium acetate were purchased from SHOWA, Japan.

Aniline (99%, Alfa aesar, Lancashire, UK) distilled before use, ammonium peroxodisulfate (APS) (J. T. Baker, Randor, PA, USA)), N-methyl-2-pyrrolidone (uniregion bio-tech, Taoyuan, Taiwan), Resorcinol (98%, Sigma Aldrich, Saint Louis, MI, USA), hydrochloric acid (HCl, 37%, Honey well Riedel-de Haen, New Taipei, Taiwan), sodium carbonate (99.5%, Sigma Aldrich, Saint Louis, MI, USA), ammonium hydroxide solution (NH₄OH, 28%, Honey well Riedel-de Haen, New Taipei, Taiwan) and ethanol (ECHO, Miaoli, Taiwan) were used as received without further purification.
DMSO-d6 was used to perform ¹H-NMR spectra on a Bruker 300 spectrometer. FTIR spectra ranging from 4000 to 650 cm⁻¹ were recorded on FT/IR-4100 spectrometer at a resolution 4.0 cm⁻¹. Scanning electron microscopy (SEM), (Hitachi S-2300) was used for examining the surface morphologies of the materials while the surface area and pore volume were determined by N₂ adsorption–desorption isotherm (BET). Hitachi U-2000 UV-Visible spectrometer and Waters GPC-150CV (Waters, Shanghai, China) were used for UV-Vis spectroscopy and molecular weight determination. Electro-spinning facility and gas-sensing devices were constructed in our lab.