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

Sensitive and visual detection of p-phenylenediamine by using dialdehyde cellulose membrane as a solid matrix

A novel method was developed for the sensitive and visual detection of p-phenylenediamine (PPD) via immobilizing the target specie PPD on dialdehyde cellulose membrane (DCM) followed by the reaction with salicylaldehyde. The obtained solid fluorescent membrane (S-PPD-DCM) emitted yellow fluorescence under 365 nm UV light. DCM was not only used as a solid matrix but also played a vital role in the enrichment of PPD. Experimental variables influencing the fluorescence signal were investigated and optimized. Under the optimum conditions, a detection limit of 5.35 μg L^-1 was obtained and two linear ranges were observed at 10-100 and 100-1000 μg L^-1, respectively. Moreover, the fluorescence of the resultant membrane can still be visualized by naked eye when PPD concentration was 50 μg L^-1. The detection of PPD was hardly affected by the coexistence of 1 mg L^-1 of o-phenylenediamine, m-phenylenediamine or phenylamine, exhibiting good selectivity. The developed method involved in a two-step Schiff base reaction and enhanced the fluorescence emission via blocking nonradiative intramolecular rotation decay of the excited molecules. It was applied to determine the PPD in spiked hair dye with satisfactory results.

Th4+ tuned aggregation-induced emission: A novel strategy for sequential ultrasensitive detection and separation of Th4+ and Hg2

A novel strategy, Th⁴⁺ tuned aggregation-induced emission, for sequential ultrasensitive detection and separation of Th⁴⁺ and Hg²⁺ was developed successfully. For demonstration this strategy, we designed and synthesized two tripodal gelators TH (tri-(isoniazid-4-yl)-functionalized trimesic acylhydrazine) and TA (tri-(pyridine-4-yl)-functionalized trimesic amide). The TH and TA could assemble into a stable supramolecular polymer hydrogel THTA-G in DMSO/H₂O (3.3:6.7, v/v) binary-solution. The THTA-G does not show aggregation-induced emission (AIE) effect. However, after addition of Th⁴⁺ into the THTA-G, the obtained metallogel THTA-GTh shows strong green AIE effect, which indicated that Th⁴⁺ could tune the gel generation of AIE effect. Interestingly, the THTA-G could ultrasensitive fluorescently detect Th⁴⁺, and the corresponding metallogel THTA-GTh could ultrasensitively detect Hg²⁺. The detection limits of THTA-G and THTA-GTh for Th⁴⁺ and Hg²⁺ are 8.61 × 10^-11 mol/L and 1.08 × 10^-11 mol/L, respectively. Additionally, the xerogels of THTA-G and THTA-GTh could separate Th⁴⁺ and Hg²⁺ from aqueous solution with excellent ingestion capacity, and the THTA-G could be used as a writable smart light-emitting material.

Polymeric Ionic Liquid-Based Fluorescent Amphiphilic Block Copolymer Micelle for Selective and Sensitive Detection of p-Phenylenediamine

A highly sensitive and selective detection of p-phenylenediamine (PPD) is achieved by a fluorescence sensor, which is constructed by encapsulating the hydrophobic fluorescent 1-pyrenecarboxaldehyde (Py-CHO) into a polymeric ionic liquid (PIL)-based amphiphilic block copolymer (BCP) micelle. The amine-aldehyde condensation reaction between PPD and Py-CHO leads to the fluorescence quenching of Py-CHO, giving rise to the basis for the quantitative detection of PPD. The core cavity of the micelle formed by the self-assembly of PIL provides an excellent hydrophobic environment for the accommodation of fluorescent Py-CHO, offering significant improved sensitivity and selectivity for PPD detection. The amount of PIL in fabricating the amphiphilic BCP micelle, the BCP-Py-CHO micelle concentration, and the detection pH condition are investigated to obtain the best performance of this sensor. The accurate detection of PPD is achieved in the range of 0.02-10 μmol L^-1 under optimal conditions, and the detection limit is 0.007 μmol L^-1 (3σ/ s). The developed sensor is successfully applied to the determination of PPD contents in hair dyes, spiked water, and urine samples.

Self-assembly of sugar based glyco-lipids: Gelation studies of partially protected d-glucose derivatives

A series of sugar-based glycolipid derivatives were prepared by N-glycosylamines, and their organogelation property has been analyzed. We have observed the efficient gelation for some of the anilines substituted glycolipids derivatives in different aromatic and aliphatic solvents. It was found that the gelation occurred predominantly in aliphatic solvents with CGC of 0.8% (w/v) attributed to the presence of long alkyl chain in the glycolipids. The structural and morphological properties of the xerogels were investigated by NMR, powder XRD, and FE-SEM respectively. Furthermore, the thermal stability was analyzed by DSC.

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.

Supramolecular gel from self-assembly of a C3-symmetrical discotic molecular bearing pillar[5]arene

A novel C₃-symmetric benzene-1,3,5-tricarboxamide (BTAs) decorated with three identical pillar[5]arene tails was designed, synthesized and characterized. The compound can gelate acetonitrile at low concentration (0.2 wt%) upon sonication at room temperature, but a precipitate was obtained by a conventional heating-cooling process. Scanning electron microscopy revealed that the gel and precipitate were constructed by entangled, high-aspect-ratio flexible bundles of nanofibrils. UV-vis spectroscopy, circular dichroism, Fourier transform infrared microscopy and powder X-ray diffraction showed that the compound formed chiral, elongated, columnar aggregates with nanofiber morphology by a combination of intermolecular hydrogen bonding between the N-H and C[double bond, length as m-dash]O of amides, π-π stacking (H-aggregates) and hydrophobic interactions of peripheral groups.