Triarylamine‐Cored Dendritic Molecular Gel for Efficient Colorometric, Fluorometric, and Impedometeric Detection of Picric Acid

Abstract

Detection of nitroaromatics at ultralow concentration is a major security concern in defense, forensics, and environmental science. To this end, a new triarylamine-cored dendritic gelator (OGR) was synthesized, which produced thermoreversible, thixotropic, and fluorescent gels in n-octanol. On gelation, both π-π* transitions and the emission peak of the gelator show redshifts with a 4.5-fold increase of fluorescence intensity in the gel state indicating J-aggregation. The nitrogen lone-pair electrons of OGR make it a donor, and electron transfer occurs to acceptor nitroaromatics causing fluorescence quenching, which is further promoted due to its acidity. The Stern-Volmer rate constants measured for different nitroaromatics showed that it senses picric acid (PA) best. The contact-mode technique with OGR-treated paper strips can allow naked-eye detection of PA under UV light down to 10 m concentration within 30 s. Reusability of the gel is achieved by treating OGR@PA with NaOH solution. Impedance spectroscopic results indicated a decrease of both charge-transport resistance and Warburg impedance on successive addition of PA. The limits of detection of PA determined from fluorescence and impedance measurements match well. Thus, the OGR gel is a reusable, low-cost, specific sensor for PA by naked-eye colorimetric, fluorescence, and impedance techniques.

Development of Polythiophene–Tripeptide Covalent Conjugates Showing Excellent Structure-Dependent Photophysical and Photocurrent Properties

“…Aside from AIE, there is also a phenomenon commonly known as aggregation-induced quenching (AIQ) that occurs at higher concentrations. 52 In the present polymeric conjugates, at concentrations above 0.08 mg/mL in DMF, there is AIQ. For the case of AIQ, the decrease of fluorescence intensity is due the conversion of photonic energy into thermal energy, causing deactivation of the excited state via a non-radiative decay path, and it makes the system non-emissive in the aggregated state.…”

“…Aside from AIE, there is also a phenomenon commonly known as aggregation-induced quenching (AIQ) that occurs at higher concentrations . In the present polymeric conjugates, at concentrations above 0.08 mg/mL in DMF, there is AIQ.…”

Aggregation‐Induced Emission‐Active Gels: Fabrications, Functions, and Applications

“…Thus, Figure shows the chemical structures of typical AIE‐active LMWGs based on Schiff bases and ESIPT systems. More specifically, typical AIE‐active LMWGs based on Schiff bases are 97 , 98 and 99 , [ 104 ] 100 , [ 105 ] 101 , [ 106 ] 102 , [ 107 ] 103 , [ 108 ] 104 , [ 109 ] 105 , [ 110 ] 106 , [ 111 ] 107 , [ 112 ] 108 , [ 113 ] 109 , [ 114 ] 110 , [ 115 ] 111 , [ 116 ] 112 , [ 117 ] 113 , [ 118 ] and 114 . [ 119 ] Moreover, some aromatic thioether‐based systems have also recently been reported to exhibit the AIE effect.…”

Multistimuli-Responsive Fluorescent Organogelator Based on Triphenylamine-Substituted Acylhydrazone Derivative

“…TPAH-B8 was synthesized by having 3,4-bis(octyloxy)benzhydrazide 64 (785.2 mg, 0.002 mol) reacting with 4-(N,N-diphenylamino)benzaldehyde (546.7 mg, 0.002 mol) in ethanol (100 mL) under reflux condition for 10 h (Scheme 2). 14 The crude product was further purified by recrystallization from ethyl acetate− cyclohexane (v/v = 3:1) mixed solvents to get pure product as a pale-yellow powder (1052.2 mg, 81.2%). The melting point is 157 °C confirmed by DSC.…”

“…In recent years, stimuli-responsive luminescent materials have attracted widespread attention due to their potential applications in sensors, data storage, optical devices, drug delivery, cell imaging, etc. − Among these materials, the fluorescent low-molecular-weight organogelators with the stimuli-responsive property have attracted the special interest of researchers. − This is because the supramolecular structures formed by the fluorescent low-molecular-weight organogelators through noncovalent bonds (such as hydrogen bonds, π–π interactions, van der Waals forces, etc.) can produce obvious responses to external stimuli and have multichannel response characteristics including fluorescence change, color variation, phase transition, etc. − …”