Aiping Gao

Strong Blue Emissive Supramolecular Self-Assembly System Based on Naphthalimide Derivatives and Its Ability of Detection and Removal of 2,4,6-Trinitrophenol

Two simple and novel gelators (G-P with pyridine and G-B with benzene) with different C-4 substitution groups on naphthalimide derivatives have been designed and characterized. Two gelators could form organogels in some solvents or mixed solvents. The self-assembly processes of G-P in a mixed solvent of acetonitrile/H2O (1/1, v/v) and G-B in acetonitrile were studied by means of electron microscopy and spectroscopy. The organogel of G-P in the mixed solvent of acetonitrile/H2O (1/1, v/v) formed an intertwined fiber network, and its emission spectrum had an obvious blue shift compared with that of solution. By contrast, the organogel of G-B in acetonitrile formed a straight fiber, and its emission had an obvious red shift compared with that of solution. G-P and G-B were employed in detecting nitroaromatic compounds because of their electron-rich property. G-P is more sensitive and selective toward 2,4,6-trinitrophenol (TNP) compared with G-B. The sensing mechanisms were investigated by 1H NMR spectroscopic experiments and theoretical calculations. From these experimental results, it is proposed that electron transfer occurs from the electron-rich G-P molecule to the electron-deficient TNP because of the possibility of complex formation between G-P and TNP. The G-P molecule could detect TNP in water, organic solvent media, as well as using test strips. It is worth mentioning that the organogel G-P can not only detect TNP but also remove TNP from the solution into the organogel system.

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

A series of bicholesteryl-based gelators with different central linker atoms C, N, and O (abbreviated to GC, GN, and GO, respectively) have been designed and synthesized. The self-assembly processes of these gelators were investigated by using gelation tests, field-emission scanning electron microscopy, field-emission transmission electron microscopy, UV/Vis absorption, IR spectroscopy, X-ray diffraction, rheology, and contact-angle experiments. The gelation ability, self-assembly morphology, rheological, and surface-wettability properties of these gelators strongly depend on the central linker atom of the gelator molecule. Specifically, GC and GN can form gels in three different solvents, whereas GO can only form a gel in N,N-dimethylformamide (DMF). Morphologies from nanofibers and nanosheets to nanospheres and nanotubes can be obtained with different central atoms. Gels of GC, GN, and GO formed in the same solvent (DMF) have different tolerances to external forces. All xerogels gave a hydrophobic surface with contact angles that ranged from 121 to 152°. Quantum-chemical calculations indicate that the GC, GN, and GO molecules have very different steric structures. The results demonstrate that the central linker atom can efficiently modulate the molecular steric structure and thus regulate the supramolecular self-assembly process and properties of gelators.

Bis-naphthalimides self-assembly organogel formation and application in detection of p-phenylenediamine

Two new gelators containing bis-naphthalimides group were designed and synthesized. The gelator 1b could form gels in DMF and mixed solvent of DMSO/H2O (10/1, v/v). The self-assembly processes of 1b in two kinds of solvents were detailedly investigated by UV-vis, fluorescence, infrared spectroscopy, field emission scanning electron microscope (FE-SEM), X-ray diffraction and contact angle experiments. The experiment results showed the hydrogen bonding was the main force for the gel formation. The gel 1b formed in mixed solvent of DMSO/H2O (10/1, v/v) possessed of the ability of distinguishing of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine. At the same time, the gelator 1b could selectively and sensitively detect p-phenylenediamine in solution with the detection limit of 8.961×10-8ML-1. The detection experiment was also confirmed by DFT theoretical calculations. This research would expand the supramolecular self-assembly materials application in sensor field and offer a new detection method for organic amines.

Superhydrophobic surface formation and modulation in a biphenyltetracarboxylic dianhydride derivative self-assembly system via changing alkyl chain lengths

A series of organogelators (C4, C6, C12 and C18) based on biphenyltetracarboxylic dianhydride derivative were designed and synthesized. The organogels could be obtained via self-assembly of the biphenyltetracarboxylic dianhydride derivatives in some frequently-used solvents. The organogels were thoroughly characterized using various microscopic techniques including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV-vis and fluorescence spectra, contact angle. Interestingly, superhydrophobic surface was formed via the self-assembly of compound C12 in petroleum ether and exhibited the lotus-effect. The surface wettability could be modulated via changing alkyl chain lengths. The π–π stacking and van der Waals force were possible the main driving forces for gel formation. This gel system held promise for soft materials application in upscale superhydrophobic surface materials.

Organogel of fluorescein-based derivative formation in the selected pH value

In this work, film structure was obtained by self-assembly of fluorescein derivative via sol–gel process. The self-assembly structure and the formation mechanism had been studied and certified by scanning electron microscopy, IR, UV–vis, fluorescence and X-ray diffraction experiment data. The UV–vis absorption and emission spectra of the compound 1 were changed with the change of the pH value in the solution state. This gelator had certain selectivity for pH value and formed gels.

Regulation gel formation, hierarchical structures and surface wettability via isomeride effect in supramolecular organogel system

A new serial of gelators with two cholesteryl groups based on o-phenylenediamine, m-phenylenediamine and p-phenylenediamine were synthesized, and their organogelation ability was evaluated. We found that G-o could form gels in DMF, DMSO and ethyl acetate, G-m and G-p could only gel DMF and 1,4-dioxane. The organogels were thoroughly characterized using various microscopic techniques including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV-Vis spectrum, FT-IR spectrum and contact angle. The gelation ability, morphology, self-assembly mode and materials surface wettability all could be tuned via isomeride effect in self-assembly system. Interestingly, superhydrophobic surface was formed via the self-assembly of compound G-p in 1,4-dioxane and exhibited very high adsorption capacity for water. This gel system provided new method for modulation self-assembly process in supramolecular field.

Organogel formation based on bis-urea derivative

In this work, a new gelator containing urea group was synthesised which had excellent gelation ability and could form organogel in 12 frequently used solvents. Varisized fibre structures were obtained by self-assembly via sol-gel process. The self-assembly structure and the formation mechanism had been studied and certified by scanning electron microscopy, UV–vis, IR and XRD experiment data. The ‘H-aggregate’ self-assembly mode was adopted in organogel system. H-bonding and π–π stacking were the main driving force for the organogel formation. The self-assembly structures could be adjusted by the solvents.

Melamine tunable effect in a lenalidomide-based supramolecular self-assembly system via hydrogen bonding

In this study, a new gelator containing lenalidomide and cholesterol groups was synthesized, which could form stable gels in 1,4-dioxane and mixed solvents of DMF/H2O (v/v, 1/1). The self-assembly process was studied and certified by field emission scanning electron microscopy, UV-vis, IR, XRD, and CA. Based on the results obtained from the abovementioned analyses, the self-assembly structure, aggregation pattern, and surface wettability could be tuned via the addition of melamine due to intermolecular hydrogen bonding between compound 1 and melamine (MA). The irregular lumpy and the closely packed fiber structures could be turned into microbelt and sparse fiber structures after the addition of MA, respectively. Moreover, the hydrophobicity of the xerogel film of 1-MA was obviously increased. The mechanical strength of gel 1-MA was obvisously enhanced due to the addition of MA. The UV-vis, IR, and XRD experiment results showed that the self-assembly process and mode of 1 was changed due to the addition of MA through intermolecular hydrogen bonding between 1 and MA. Therefore, these results provide a method for the regulation of the self-assembly process via intermolecular noncovalent interaction.

Formation of hydrophobic surface using a bis-urea derived organogel

A bis-urea derived gelator 1 was synthesised with a high yield via a simple organic reaction. The gelator could form organogel in four kinds of solvents. The organogels obtained from four kinds of solvents were systematically investigated by FESEM, UV–Vis, PL, IR, XRD and water contact angle experiments. It was interesting that the self-assembly process of gelator 1 could be tuned by solvents. The film structure and fibre were formed in different solvents. At the same time, the different morphologies all displayed hydrophobicity. Especially, the contact angle of the fibre obtained from organogel in DMF was up to 147°. This research would provide a good pattern for preparation of a special hydrophobic surface through supramolecular self-assembly.

Microsphere-to-nanotube transition via in situ sonication triggered in a supramolecular self-assembly system based on triphenylamine derivative

Abstract A new gelator 1 containing triphenylamine was designed and synthesized, and formed stable gel in ethyl acetate. The self-assembly process of molecule 1 was thoroughly investigated. The solid microsphere structure formed in gel 1 could be turned into nanotube in the transition process of gel to gel via sonication. At the same time, the intermolecular hydrogen bond of self-assembly system was obviously enhanced under sonication. The XRD and water contact angle experiments results of xerogel 1 before and after sonication showed great difference. The hydrophobicity of xerogel 1 film was obviously decreased with the change of contact angle from 142° to 129° after sonication at 100 W for one minute. From the results, it was possible that the solid microsphere was re-dissolved and further reassembled into nanotube. To our knowledge, it was the first example that the solid sphere structure was changed into nanotube in self-assembly system via sonication.