Two novel pyrene containing monomeric and dimeric Schiff base derivatives PCS1 and PCS2 have been synthesized via one-pot reaction and their nano-J-type aggregation induced emission enhancement (AIEE) was well demonstrated using UV-Vis/PL, transmission electron microscopy (TEM), dynamic light scattering (DLS), time resolved photoluminescence (TRPL), and live cell imaging studies. In contrast to PCS2, PCS1 in CH₃CN exhibits fluorescence “off–on” sensor selectivity towards transition trivalent metal ions (Fe³⁺, Cr³⁺ and Al³⁺) among other metals, via PET inhibition with excimer PCS1–PCS1* formation. The 2 : 1 stoichiometry of PCS1⋯M³⁺ (M = Fe/Cr/Al) sensor complexes was calculated from Job's plots based on their PL titrations. In addition, the binding sites of PCS1⋯M³⁺ sensor complexes were well recognised from the ¹H NMR titrations and supported by ESI(+ve) mass and FTIR analysis. Additionally, fluorescence reversibilities of PCS1⋯M³⁺ were observed via consequent addition of M³⁺ ions and PMDTA, respectively. Furthermore, the detection limits (LODs) and the association constant (K_a) values of PCS1⋯M³⁺ complexes were calculated using standard deviation and linear fittings. Likewise, quantum yield (Φ) measurements, TEM analysis, determination of the effect of pH, density functional theory (DFT) and time resolved photoluminescence (TRPL) studies were performed for the PCS1⋯M³⁺ sensor complexes. More importantly, confocal fluorescence microscopy imaging of Raw264.7 cells showed that PCS1 could be used as an effective fluorescent probe for detecting transition trivalent metal ions (Fe³⁺, Cr³⁺, and Al³⁺) in living cells. Impressively, both PCS1 and PCS2 showed “off–on” sensing at highly acidic pH values (1–3) with live cell applications.

A simple anthracene-based AP probe was synthesized to detect Cu²⁺ ions, via the photoinduced electron transfer mechanism, in live cells.

Two rhodamine hydrazine derivatives Rh1 and Rh2 with catechol and ether functionalities have been synthesized and utilized towards sequential colorimetric detections of Cu(II) and pyrophosphate (PPi) ions in CH₃CN–H₂O (v/v = 9 : 1, 5 mM Tris–HCl, pH 7.4) semi-aqueous medium. Notably, Rh1 and Rh2 are the first example of colorimetric rhodamine-based probes for the sequential detections of Cu²⁺ ion and PPi anion. Based on the significant colorimetric responses (from colorless to pink) of Rh1 and Rh2 to Cu²⁺ ions, the detection limits were estimated as low as 1.22 × 10⁻⁸ M and 8.0 × 10⁻⁷ M, respectively, which signified the utilities of designed probes towards facile detections of Cu²⁺ ions. Furthermore, upon the successive addition of PPi ion to Rh1–Cu²⁺ and Rh2–Cu²⁺ complexes, it has been altered and restored to its origin of Rh1 and Rh2 via re-coordination of PPi to Cu²⁺ ion, which was confirmed by color changes from pink to colorless. Moreover, computational DFT calculations provided more insights into HOMO–LUMO structures of rhodamine derivatives and their copper complexes. Additionally, the solid state strip-based colorimetric detections of Cu²⁺ ion were supplemented as a real time application.

In this work, a simple method was developed to simultaneously fabricate silver nanoparticles (AgNPs) and modify their surfaces with recognition functional groups for colorimetric detection of Cu2+ ions. To prepare the AgNPs with proper functional group on their surface for detection of Cu2+ ions, photochemical reaction was employed and a photoactive species of tyrosine (Tyr) was used to trigger the photoreduction of AgNPs, while the oxidized Tyr (TyrOx) was used to functionalize the AgNPs surface at the same time. To understand the behaviors, the prepared color AgNPs colloidal solution was characterized by UV-visible spectrometer, FT-IR spectrometer, dynamic light scattering (DLS), X-ray photoelectron spectrometer (XPS) and density functional theory (DFT). Based on DFT calculation results, TyrOx was adsorbed on the surface of AgNPs by the quinone ring and its functional group of amino acid was freely exposed to the aqueous media for rapid interaction of Cu2+ ions. Based on detection of different metal ions, TyrOx@AgNPs were selective to interact with Cu2+ ions through formation of highly stable Cu2+-TyrOx@AgNPs complexes. The evidence in formation of Cu2+-TyrOx@AgNPs complex could be obtained through the red shift of the surface plasmonic resonance (SPR) band of TyrOx@AgNPs located at 557 nm, which gives a color change from light yellow to brown color allowing visual identification of Cu2+ ions for rapid screening purposes. For quantitative analysis, a band intensity ratio of A557/(A404-A557) was constructed to correlate with the concentration of Cu2+ ions. A linear range up to 10 μM with a detection limit close to 150 nM was found.

A novel chromogenic anion receptor 1 based on acylhydrazone and pyrazole has been designed and synthesized. Receptor 1 forms stable 1 : 1 complexes with dihydrogen phosphate and other halide anions in DMSO solution.

Vanadium compounds exhibit anti-tumor properties and insulin-like activity, but an excess is toxic. Development of a selective fluorescent chemosensor for the detection of vanadyl ions has not been reported so far. For the first time, we have reported an effective fluorescent chemosensor C1 for selective recognition and detection of vanadyl ions. C1 was evaluated as a turn “ON” fluorescent chemosensor for vanadyl ions (VO²⁺) based on a photoinduced electron transfer (PET) mechanism. The association constant for the complex C1–VO²⁺ was found to be 4.19 × 10⁴ M⁻¹. C1 also behaves as a NOT molecular logic gate where H⁺ and VO²⁺ were given as inputs. The proposed binding mode between C1 and vanadyl ions was explained using DFT calculations.