Swelling has great influences on the structure stability and separation performance of graphene oxide laminate membranes (GOLMs) for water desalination and purification. Herein, we report cross-linked GOLMs from GO assembled with cationic tetrakis(1-methyl-pyridinium-4-yl)porphyrin (TMPyP) by a vacuum-assisted strategy. The concave nonoxide regions (G regions) of GO are used as cross-linking sites for the first time to precisely control the channel size for water permeation and salt ion retention. Channels around 1 nm are constructed by modulating the assembly ratio of TMPyP/GO, and these cross-linked GOLMs show high salt rejection.

Nanofibers with distinct luminescent property were facilely fabricated by electrospinning from porphyrinated polyimide and demonstrated as a kind of novel sensory material for trace detection of TNT vapor (10 ppb). Covalently bonding of porphyrin fluorophores into the polyimide main chains reduces the aggregation-caused fluorescence self-quenching of porphyrin and improves the physicochemical stability of the polyimide nanofibers. The large surface area-to-volume ratio and hence good gas accessibility endow the porphyrinated nanofibers with much more remarkable fluorescent quenching behavior toward trace TNT vapor than its spin-coating dense film counterparter. Besides TNT, 2,4-dinitrotoluene (DNT), 2,4,6-trinitrophenol (PA) and nitrobenzene (NB) could also quench the fluorescence of the porphyrinated nanofibers, but the quenching efficiency is much lower than that of TNT. An apparent binding affinity constant of (2.37 ± 0.19) × 107 L/mol was calculated from SPR analysis, confirming that the porphyrinated nanofibers is a promising alternative for TNT detection.

A novel sensor fabricated from the nanofibrous membrane of porphyrinated polyimide (PPI) for the rapid detection of trace amount of hydrogen chloride (HCl) gas is described. Covalently bonding of the porphyrin fluorophores into polyimide main chains overcomes the disadvantage of porphyrin aggregation and improves the physicochemical stability of polyimide simultaneously. The dual chromo- and fluorogenic responses of the nanofibrous membrane upon exposure to HCl gas are interpreted in terms of the out-of-plane distortion of porphyrin macrocycle, which ultimately affects its optical properties. UV–vis and fluorescence spectroscopies were used to further study the protonation of porphyrin moieties in polyimide. With large amount of available surface area and hence good gas accessibility, the nanofibrous membrane of porphyrinated polyimide shows unusually high sensitivity and fast response time in sensing application. An apparent binding affinity constant of (1.05 ± 0.23) × 104 L mol−1 was calculated from surface plasmon resonance (SPR) analysis, confirming that the porphyrinated nanofibrous membrane is an applicable material for constructing HCl-sensitive gas sensor.

A series of copolymers based on diaminotetraphenylporphyrin (DATPP), oxidianiline (ODA), and pyromellitic dianhydride (PMDA) were synthesized. The resulting copoly(amic acid)s (CPAAs) were electrospun into uniform nanofibers. Subsequently, copolyimide (CPI) nanofibers were obtained from the CPAA nanofibers by thermal imidization. The morphologies and luminescence of these nanofibers were characterized by field emission scanning electron microscopy (FESEM) and confocal laser scanning microscopy (CLSM). It was found from the CLSM analyses that fluorescence quenching took place after the nanofibers were imidized. This could be attributed to the photoinduced electron transfer from excited porphyrin units to diimide acceptor groups. Thermogravimetric (TG) analyses indicated the CPI nanofibers possessed excellent thermal stability. This kind of CPI nanofibers with high temperature resistance and unique photoelectric properties could be potential materials for optical switches, catalysis, nonlinear optics, and molecular wires used in normal and especially in high temperature circumstances.

•Polyimide/MWCNTS nanofibers are electrospun for enzyme immobilization.•The retention activity of immobilized HRP is obviously improved by MWCNTS.•Electron transfer among “HRP I”, “HRP II” and MWCNTs is facilitated.Carbon nanotubes are widely applied in electronics, which offers great potential for enhancing the activity of redox enzyme. In this work, polyimide (PI) was blended with multiwalled carbon nanotubes (MWCNTs) and then electrospun into nanofibers for the immobilization of horseradish peroxidase (HRP), a redox enzyme. SEM and TEM were used to characterize the surface morphology of the PI/MWCNTs nanofibers and to analyze the protruding parts induced by the blending of MWCNT. The results indicate that, compared to the virgin PI nanofibers, the blending of MWCNTs increases the retention activity of immobilized HRP from 2.38% to 12.50%. Circular dichroism and UV–vis molecular absorption spectrometry were used to explore the interactions between HRP and MWCNTs. It seems that MWCNTs increase the enzyme activity by the facilitation of electron transfer among the catalytic intermediates “HRP I”, “HRP II” and MWCNTs.Download full-size image