Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons by Nitromethane within Ionic Liquid Added Aqueous Anionic Micellar Solution

Abstract

Applicability of nitromethane as selective fluorescence quenching agent for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is examined for eight PAHs dissolved in aqueous micellar sodium dodecyl sulfate (SDS) media in the absence and presence of varying wt % of water-miscible ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]). Alternant PAHs follow quenching sphere-of-action model, whereas nonalternant PAHs demonstrate simple linear Stern–Volmer type quenching behavior. Nitromethane quenched fluorescence emission of both the alternant and nonalternant PAHs dissolved in aqueous SDS micellar media where the selectivity of the nitromethane as the quencher is lost. However, the nitromethane begins to retain its selectivity in quenching fluorescence from alternant PAHs over that from the nonalternant PAHs as soon as small amount of IL [bmim][BF4] (ca. 0.5 wt %) is added to anionic SDS solution. The dual role of IL is demonstrated where initially at lower concentrations it works as an electrolyte helping to establish quenching selectivity of nitromethane and at higher concentrations as a cosolvent where quenching of nonalternant PAH fluorescence again starts to become significant due to the changes in the physicochemical properties of the micellar assemblies. Use of IL as an effective additive to the aqueous anionic micelle media for PAH separation and analysis is amply demonstrated.

Solvent Effect on Structural Elucidation of Photoluminescent Graphitic Carbon Nanodots

“…Previous studies have shown that nitromethane, on the other hand, is known to quench the fluorescence emission of alternant polycyclic aromatic hydrocarbons (PAHs) such as anthracene, pyrene, and larger PAHs and not quench the fluorescence emission of nonalternant PAHs such as fluoranthene. 37,38 Quenching of emission of CNDs in nitromethane, therefore, points to the alternant nature of the emissive polycyclic aromatic structure of the CNDs (see Figure 2). Quenching of PL emission in nitromethane is caused by the excited core that generated diffusive excitons that result in ultrafast electron transfer to nitromethane.…”

A Comprehensive Review of Novel Emerging Electrolytes for Supercapacitors: Aqueous and Organic Electrolytes Versus Ionic Liquid-Based Electrolytes

“…ILs have a wide range of applications. ILs are used as catalysts, − pharmaceuticals, − biopolymer processing, − stabilization of biomolecules, , CO 2 capture, , sensors, antimicrobial, in batteries, as solvents, − in separation and detection of polycyclic aromatic hydrocarbons, and in supercapacitors as electrolyte. , Mainly their use as a solvent has a specific emphasis. In synthesis or any organic reactions, organic solvents are used which are highly volatile, and some are flammable.…”

Fluorescence Quenching of Dipyrenylalkanes by an Electron/Charge Acceptor

“…The formation and dynamics of such intramolecular excimers is an active area of research. − In such systems, pyrene is perhaps the most common fluorophore due to the favorable properties of this fluorophore such as high fluorescence quantum yield, long radiative decay time, structured monomeric band combined with structureless excimer band, etc . Several groups have investigated various aspects of the intramolecular excimer formation by pyrenyl groups such as pyrene location and site on the molecular scaffold, role of solvent and temperature, and effect of external additives, among others. − Nitromethane as an external quencher of pyrene fluorescence, with excited pyrene as the electron/charge donor and nitromethane as the electron/charge acceptor, is well-established. ,− In this work, we have employed the quenching behavior of nitromethane toward pyrene to investigate the effect of this quencher on the fluorescence of the monomer and the intramolecular excimer of the two dipyrenylalkanes, 1,3-bis­(1-pyrenyl)­propane [1Py(3)­1Py] and 1,10-bis­(1-pyrenyl)­decane [1Py(10)­1Py] (structures are given in Figure ), where the two pyrenyl functionalities are separated by short (i.e., propyl) and long (i.e., decyl) alkyl chains, respectively, in four different solventsnonpolar (cyclohexane (CH)), polar-aprotic (acetonitrile (ACN)), polar-protic (ethanol (EtOH)), and chlorinated (dichloromethane (DCM))under ambient conditions.…”