A Boron Dipyrromethene-Based Fluorescence 'OFF-ON' Probe for Sensitive and Selective Detection of Palladium(II) Ions and Its Application in Live Cell Imaging

A novel boron dipyrromethene (BODIPY)-based fluorescent probe BDP-Pd was designed and synthesized. Upon coordination with Pd²⁺ , the emission of the probe at 508 nm significantly increased, showing an 'OFF-ON' fluorescence response. The complexation of BDP-Pd with Pd²⁺ in both acetonitrile and aqueous solution were then studied by absorption and fluorescence spectra. The binding stoichiometry between the probe and Pd²⁺ was found to be 1 : 2, and the binding constant was determined to be 8.5×10¹⁰  M^-2 and 8.2×10¹⁰  M^-2 in acetonitrile and aqueous solution, respectively. The probe exhibited a detection limit as low as 0.72 ppb toward Pd²⁺ with no obvious interference from up to 21 species of common metal ions, suggesting BDP-Pd as a sensitive and selective fluorescent probe for Pd²⁺ detection. The fast fluorescence 'OFF-ON' phenomenon of the probe upon coordination with Pd²⁺ ions could be easily observed by a hand-hold UV lamp under naked eye in solution as well as on homemade test trips. Density functional theory (DFT) calculations were carried out to give the optimized structure of complex BDP-Pd : 2Pd²⁺ and rationalize the detection mechanism through a prohibited intramolecular photoinduced electron transfer (PET) process. The bio-imaging application of the probe was investigated and it showed excellent cell permeability for fluorescent imaging of Pd²⁺ ions in A549 human non-small cell lung cancer cells.

Design and synthesis of new functionalized 8-(thiophen-2-yl)-1,2,3,4-tetrahydroquinolines as turn-off chemosensors for selective recognition of Pd2+ ions

Functionalized 8-thienyl-1,2,3,4-tetrahydroquinoline was synthesized as a fluorescent turn-off chemosensor for selective recognition of Pd²⁺ ions with a low detection limit.

A new turn-on fluorescent probe for the detection of palladium(0) and its application in living cells and zebrafish

A new “turn-on” fluorescent probe 1 for the detection of Pd⁰ has been designed and synthesized.

Highly Productive Synthesis, Characterization, and Fluorescence and Heavy Metal Ion Adsorption Properties of Poly(2,5-dimercapto-1,3,4-thiadiazole) Nanosheets

Poly(2,5-dimercapto-1,3,4-thiadiazole) (PBT) nanosheets were synthesized by chemical oxidative synthesis under mild conditions. The media, oxidant species, monomer concentrations, oxidant/monomer molar ratio, and temperature were optimized to achieve higher yields and better performance. The molecular structure, morphology, and properties of the nanosheets were analyzed by Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis), and fluorescence spectroscopies, wide-angle X-ray diffraction (WAXD), matrix-assisted laser desorption/ionization/time-of-flight (MALDI-TOF) mass spectrometry, X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), and simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC). It was found that the polymerization of 2,5-dimercapto-1,3,4-thiadiazole occurs via dehydrogenation coupling between two mercapto groups to form the ⁻S⁻S⁻ bond. PBTs show the highest polymerization yield of up to 98.47% and form uniform nanosheets with a thickness of 89~367 nm. poly(2,5-dimercapto-1,3,4-thiadiazole) polymers (PBTs) exhibit good chemical resistance, high thermostability, interesting blue-light emitting fluorescence, and wonderful heavy metal ion adsorption properties. Particularly, the PBT nanosheets having a unique synergic combination of three kinds of active ⁻S⁻, ⁻SH, and =N⁻ groups with a moderate specific area of 15.85 m² g^-1 exhibit an ultra-rapid initial adsorption rate of 10,653 mg g^-1 h^-1 and an ultrahigh adsorption capacity of up to 680.01 mg g^-1 for mercury ion, becoming ultrafast chelate nanosorbents with a high adsorption capacity. With these impressive properties, PBT nanosheets are very promising materials in the fields of water treatment, sensors, and electrodes.

A fluorescent and colorimetric probe containing oxime-ether for Pd(2+) in pure water and living cells

Palladium contamination causes potential danger to the environment, and a study of its biological safety is still on the way. Here, a fluorescent and colorimetric probe (compound 1) containing oxime-ether for Pd(2+) has been developed. 1 can detect Pd(2+) in aqueous samples with high selectivity and sensitivity. 1 can also work well in biological samples, which gives access to detect Pd(2+) in an organism.

A new turn on Pd(2+)-specific fluorescence probe and its use as an imaging reagent for cellular uptake in Hct116 cells

A new coumarin-rhodamine conjugate is used as a specific probe for Pd(2+) ions and this could even delineate Pd(II) from Pd(0) or Pd(IV) in aqueous buffer medium (pH ∼ 7). Laser confocal microscopic studies reveal that efficient cellular internalization of this reagent helps in imaging the cellular uptake of Pd(2+) as low as 0.1 ppm in Hct 116 cells. This reagent could even be used for estimation of Pd(2+) in human urine samples.

A simple and effective fluorescent probe based on rhodamine B for determining Pd2+ ions in aqueous solution

It is demonstrated that the mechanism of the probe to Pd²⁺ and images under a UV lamp.

Synthesis and characterization on novel fluorescent sensors for Pd2+/Pd0 with high selectivity

Novel chemosensors based on triaryl 1H-imidazo[4,5-b]pyrazine with high selectivity for palladium (Pd⁰/Pd²⁺) detection have been synthesized simply.

Current developments in fluorescent PET (photoinduced electron transfer) sensors and switches

A fluorophore can be combined with a receptor according to a molecular engineering design in order to yield fluorescent sensing and switching devices.

An azodye–rhodamine-based fluorescent and colorimetric probe specific for the detection of Pd2+ in aqueous ethanolic solution: synthesis, XRD characterization, computational studies and imaging in live cells

An azodye–rhodamine hybrid colorimetric fluorescent probe (L) has been designed and synthesized.

Colourimetric and fluorescent probes for the optical detection of palladium ions

In recent years, the development of optical probes to analyse trace palladium ions (Pd(2+)) has attracted great attention because of the residual palladium released by catalytic converters or from various Pd-catalysed reactions. These residual palladium ions may cause potential health hazards. This review provides a brief introduction to the new methods used to determine trace amounts of Pd(2+), which then mainly focuses on the different reporting systems and unique mechanisms of the colourimetric and fluorescent probes used to detect Pd(2+), including Pd(2+) complex formation or Pd-catalysed reactions.

Construction of a near-infrared fluorescence turn-on and ratiometric probe for imaging palladium in living cells

A new NIR fluorescent probe, NIR-Pd, for palladium species was designed and synthesized, based on a HD NIR fluorophore and deprotection of aryl propargyl ethers by palladium. The probe NIR-Pd displayed either a large NIR fluorescence turn-on or ratiometric response to palladium with high sensitivity and selectivity. Additionally, the novel NIR probe can monitor palladium species in live HeLa cells by NIR fluorescence imaging.

Integration of the 1,2,3-triazole "click" motif as a potent signalling element in metal ion responsive fluorescent probes

In a systematic approach we synthesized a new series of fluorescent probes incorporating donor-acceptor (D-A) substituted 1,2,3-triazoles as conjugative π-linkers between the alkali metal ion receptor N-phenylaza-[18]crown-6 and different fluorophoric groups with different electron-acceptor properties (4-naphthalimide, meso-phenyl-BODIPY and 9-anthracene) and investigated their performance in organic and aqueous environments (physiological conditions). In the charge-transfer (CT) type probes 1, 2 and 7, the fluorescence is almost completely quenched by intramolecular CT (ICT) processes involving charge-separated states. In the presence of Na(+) and K(+) ICT is interrupted, which resulted in a lighting-up of the fluorescence in acetonitrile. Among the investigated fluoroionophores, compound 7, which contains a 9-anthracenyl moiety as the electron-accepting fluorophore, is the only probe which retains light-up features in water and works as a highly K(+)/Na(+)-selective probe under simulated physiological conditions. Virtually decoupled BODIPY-based 6 and photoinduced electron transfer (PET) type probes 3-5, where the 10-substituted anthracen-9-yl fluorophores are connected to the 1,2,3-triazole through a methylene spacer, show strong ion-induced fluorescence enhancement in acetonitrile, but not under physiological conditions. Electrochemical studies and theoretical calculations were used to assess and support the underlying mechanisms for the new ICT and PET 1,2,3-triazole fluoroionophores.