Surfactant modulated aggregation induced enhancement of emission (AIEE)--a simple demonstration to maximize sensor activity

Dual-channel ratiometric recognition of Al3+ and F- ions through an ESIPT-ESICT signalling mechanism

An optical probe 1 has been synthesized comprising naphthalimide unit conjugated with Schiff base, exhibiting excited state intramolecular proton transfer and intramolecular charge transfer as a potential sensor for Al³⁺ and F^- ions using standard spectroscopic techniques. The probe 1 exhibited local and charge-transfer excitation at 340 nm and 460 nm, respectively. On excitation at 460 nm, probe 1 displayed two emission bands at 510 nm and 610 nm, accompanied by Stokes' shift of 50 nm and 150 nm, respectively. The solvatochromic effect and theoretical calculation depicted that the representative emissions resulted from the ESICT/ESIPT phenomenon. Upon addition of Al³⁺ ions, the charge transfer excitation at 460 nm was enhanced ratiometrically to local excitation at 340 nm and showed a color change from orange to yellow. Similarily, probe 1.Al³⁺ displayed emission enhancement at 540 nm in H₂O/CH₃CN (1:9; v/v) and showed a color change from yellow to blue-green emission. Following the detection of Al³⁺ ions, hydrolysis of probe 1 to its reacting precursors was observed. The detection of Al³⁺ ions was also demonstrated in surfactant-containing water. The limit of detection (LOD) of probe 1 (H₂O/CH₃CN (1:9; v/v)) towards Al³⁺ ions was measured to be 3.2 × 10^-8 M. The probe 1 displayed a ratiometric absorption response towards F^- ions with a new peak at 570 nm and showed a color change from orange to purple. The probe 1.F^- displayed a decrease in emission at 635 nm. The LOD of probe 1 (CH₃CN) towards F^- ions was measured to be 7.5 × 10^-7 M.

Surfactant Aggregates Encapsulating and Modulating: An Effective Way to Generate Selective and Discriminative Fluorescent Sensors

The heterogeneous structure and dynamic balancing nature of surfactant aggregates make them attractive in developing fluorescent sensors. They can provide a number of advantages, e.g., enhanced fluorescence stability and quantum yield, detection capability in aqueous solutions, and easy operation. Thus, various strategies have been used to construct surfactant aggregate-based fluorescent sensors. Surfactant aggregates play various roles in different strategies and realize multiple sensing behaviors. Many new functions have been discovered for surfactant aggregates in constructing fluorescent sensors. In this feature article, we briefly summarize the development of surfactant aggregate-based fluorescent sensors and their applications in three different types of sensing: selective sensing, multiple analyte sensing, and cross-reactive sensing. For each type of sensing, the design strategies and the roles of surfactant aggregates are particularly introduced. An understanding of these aspects will help to expand the applications of surfactant assemblies in the sensing field.

A turn-on near-infrared fluorescence probe with aggregation-induced emission based on dibenzo[a,c]phenazine for detection of superoxide anions and its application in cell imaging

A new turn-on near-infrared fluorescence probe (BDP) based on dibenzo[a,c]phenazine for superoxide anion detection with aggregation-induced emission properties as well as a desirable large Stokes shift was designed and synthesized. After BDP reacted with superoxide, the initial diphenyl-phosphinyl groups of BDP were cleaved, resulting in the production of the pyridinium modified fluorophore (BD) with near-infrared emission. The fluorescent sensor BDP has a high selectivity for superoxide anions over some other intracellular ROSs, reductants, metal ions and amino acids. When HepG2 cells undergo apoptosis and inflammation, BDP is a good probe to keep track of the endogenous superoxide anion level by confocal laser scanning microscopic imaging.

A new multi-analyte fluorogenic sensor for efficient detection of Al3+and Zn2+ions based on ESIPT and CHEF features

The synthesized ESIPT based fluorogenic chemosensor, H₂L, selectively detects Zn²⁺and Al³⁺in a MeOH–H₂O (4/1, v/v, pH = 7.2) medium.

A rhodamine based turn-on chemosensor for Fe3+ in aqueous medium and interactions of its Fe3+ complex with HSA

A novel hexa-coordinating rhodamine-based chemosensor, HL6, selectively and rapidly recognizes Fe³⁺ in the presence of a number of metal cations, numerous anions and amino acids in purely aqueous medium with live cell imaging applications.