Rhodamine-Based Fluorescent Probe for Al³⁺ through Time-Dependent PET–CHEF–FRET Processes and Its Cell Staining Application

Rhodamine-diformyl <i>p</i>-cresol conjugate (L) has been developed as a novel Al³⁺-selective fluorometric and colorimetric sensor based on the FRET mechanism for the first time. L can selectively detect Al³⁺ through time-dependent PET–CHEF and FRET processes. This phenomenon is nicely reflected from ¹H NMR, fluorescence lifetime, and fluorescence cell imaging studies. The probe can detect Al³⁺ as low as 5 × 10^–9 M in HEPES-buffered EtOH:water (0.1 M, 4:1, v/v, pH 7.4). The probe shows pH-dependent emission properties viz. an intense red emission (585 nm) at acidic pH and an intense green fluorescence (535 nm) at basic pH. Thus, L can also be used as a pH sensor via tunable wavelength

Antipyrine Based Arsenate Selective Fluorescent Probe for Living Cell Imaging

Condensation of salicylaldehyde and 4-aminoantipyrine has yielded a new fluorescent probe (<b>APSAL</b>) capable of detecting intracellular arsenate at the micromolar level for the first time. The structure of the probe has been established by different spectroscopic techniques and confirmed from X-ray crystallography. Common anions, viz., F^–, Cl^–, Br^–, I^–, N₃^–, NCO^–, NO₂^–, NO₃^–, SCN^–, CN^–, CH₃COO^–, SO₄^2‑, ClO₄^–, and HPO₄^2‑ do not interfere. The binding constant of <b>APSAL</b> for H₂AsO₄^– has been determined using the Benesi–Hildebrand equation as 8.9 × 10³ M^–1. Fluorescence quantum yield of <b>APSAL</b> (0.016) increases more than 12 times upon binding arsenate ion

Nickel(II)-Induced Excimer Formation of a Naphthalene-Based Fluorescent Probe for Living Cell Imaging

Ni²⁺-induced intramolecular excimer formation of a naphthalene-based novel fluorescent probe, 1-[(naphthalen-3-yl)­methylthio]-2-[(naphthalen-6-yl)­methylthio]­ethane (<b>L</b>), has been investigated for the first time and nicely demonstrated by excitation spectra, a fluorescence lifetime experiment, and ¹H NMR titration. The addition of Ni²⁺ to a solution of <b>L</b> (DMSO:water = 1:1, v/v; λ_em = 345 nm, λ_ex = 280 nm) quenched its monomer emission, with subsequent enhancement of the excimer intensity (at 430 nm) with an isoemissive point at 381 nm. The fluorescence lifetime of free <b>L</b> (0.3912 ns) is much lower than that of the nickel­(2+) complex (1.1329 ns). <b>L</b> could detect Ni²⁺ as low as 1 × 10^–6 M with a fairly strong binding constant, 2.0 × 10⁴ M^–1. Ni²⁺-contaminated living cells of plant origin could be imaged using a fluorescence microscope

Nickel(II)-Induced Excimer Formation of a Naphthalene-Based Fluorescent Probe for Living Cell Imaging

Ni²⁺-induced intramolecular excimer formation of a naphthalene-based novel fluorescent probe, 1-[(naphthalen-3-yl)­methylthio]-2-[(naphthalen-6-yl)­methylthio]­ethane (<b>L</b>), has been investigated for the first time and nicely demonstrated by excitation spectra, a fluorescence lifetime experiment, and ¹H NMR titration. The addition of Ni²⁺ to a solution of <b>L</b> (DMSO:water = 1:1, v/v; λ_em = 345 nm, λ_ex = 280 nm) quenched its monomer emission, with subsequent enhancement of the excimer intensity (at 430 nm) with an isoemissive point at 381 nm. The fluorescence lifetime of free <b>L</b> (0.3912 ns) is much lower than that of the nickel­(2+) complex (1.1329 ns). <b>L</b> could detect Ni²⁺ as low as 1 × 10^–6 M with a fairly strong binding constant, 2.0 × 10⁴ M^–1. Ni²⁺-contaminated living cells of plant origin could be imaged using a fluorescence microscope