Strong Emissive Nanofibers of Organogels for the Detection of Volatile Acid Vapors

Abstract

Two L-phenylalanine derivatives with 5,8-bis(2-(carbazol-3-yl)vinyl)quinoxaline (PCQ) and 5,8-bis[2-(carbazol-3-yl)]-2,3-dimethylquinoxaline (DCQ) as fluorophores were synthesized, and their photophysical properties were measured and compared. The two compounds were found to gelate some organic solvents and self-assemble into 1D nanofibers in gels. The wet gel of PCQ emitted a weak orange fluorescence, but the DCQ gel had a strong green one. This result can be due to the presence of two methyl groups and the nonplanar conformation of fluorophore in DCQ. The gel film of DCQ also showed significantly stronger fluorescence than that of PCQ. Thus, the wet gel and xerogel film of DCQ were selected to study their sensing properties to acids. The yellow wet gel of DCQ transformed into a brown sol upon the addition of 0.2 equiv trifluoroacetic acid (TFA), accompanied by emission quenching. The xerogel film of DCQ rapidly responded to volatile acids, such as TFA, HCl, and HOAc. The fluorescence of the xerogel film was gradually quenched with increased concentration of volatile acid vapors. The fibrous film exhibited low detection limits for volatile acid. The detection limits of the thin films for TFA, HCl, and HOAc reached 43, 122, and 950 ppb, respectively.

Steric‐Structure‐Dependent Gel Formation, Hierarchical Structures, Rheological Behavior, and Surface Wettability

“…In contrast, a l = 35 nm hypochromatic shift in the absorptionm axima was observed in the absorption spectra of GN in DMSO in the gel state compared with the absorptionband at l = 323 nm in solution (Figure 3e), which indicated the H-type aggregation of gelator molecules in the DMSO gel. [70] The absorption of the solution andg el states of GN in 1,4-dioxane showedt he same absorption band at l = 301 nm ( Figure S2). The UV/Vis absorption spectra of GO in solution in DMF showed ac haracteristic peak at l = 265 nm that was hypsochromically shifted to l = 258 nm in the gel state (Figure 3f), which also displayed an "H-aggregated" p-p stacking in the gelation process of GO.…”

“…The absorption of GN in solution in DMF was centered at λ =303 nm and was slightly redshifted to λ =307 nm in the gel state (Figure d). In contrast, a λ =35 nm hypochromatic shift in the absorption maxima was observed in the absorption spectra of GN in DMSO in the gel state compared with the absorption band at λ =323 nm in solution (Figure e), which indicated the H‐type aggregation of gelator molecules in the DMSO gel . The absorption of the solution and gel states of GN in 1,4‐dioxane showed the same absorption band at λ =301 nm (Figure S2).…”

Polymer functionalization by luminescent supramolecular gels

“…Emission changes from yellow to blue upon exposure to aliphatic amines. The L-phenylalanine derivative with 5,8-bis[2-(carbazol-3-yl)]-2, 3-dimethylquinoxaline (DCQ) moieties (Figure 6c) 53 reportedly gels in some organic solvents and self-assembles into one-dimensional nanofibers in gels. The DCQ gel exhibits enhanced green fluorescence compared with its heated solution.…”

“…Figure 11b shows that the dye-doped Figure 6 Structures of low-molecular-weight gel-forming fluorophores. [51][52][53] Luminescent supramolecular gels H Ihara et al polymer gel film exhibits specific CD patterns based on each absorption band. The doped dyes are all non-chiral, so the CD signals are induced CD generated by statically bound chirally orientated glutamide aggregates in the polymer film.…”

Luminescent Nanofibers Fabricated from Phenanthroimidazole Derivatives by Organogelation: Fluorescence Response towards Acid with High Performance

“…The detectionl imits of PCC, PDC,a nd PSC in the nanofiberbased films for TFAw ere estimated to be 2.8 ppm, 7.4 ppm, and 0.12 ppm, respectively. [17] To furtherr eveal that the above good sensory properties were related to morphologies of the nanofiber-based films, we prepared the films based on PCC, PDC and PSC by using the spin-coatingm ethod. As shown in Figures6aand S8 d, the emission of PCC at 548 nm in spincoated film was quenched significantly upon exposuret ot he saturated vapor of TFAf or 10 s, and the film emitting green light at 365 nm becamen on-emissive induced by TFA.…”