A new type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) linked via triazole groups was designed and synthesized. Its sensing behavior toward metal ions was investigated by ultraviolet-visible and fluorescence spectroscopies. Addition of a Fe2+ ion to a tetrahydrofuran solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe2+ with a low limit of detection (2.03 μM) which is, to the best of our knowledge, the superior than the previously studied chemosensors for Fe2+.
Selective fluorescence turn on Zn2+ sensor with long-wavelength emission and a large Stokes shift is highly desirable in Zn2+ sensing area. We reported herein the synthesis and Zn2+ recognition properties of a new thiosemicarbazone-based fluorescent sensor L. L displays high selectivity and sensitivity toward Zn2+ over other metal ions in DMSO-H2O (1:1, v/v, HEPES 10 mM, pH = 7.4) solution with a long-wavelength emission at 572 nm and a large Stokes shift of 222 nm. Confocal fluorescence microscopy experiments demonstrate that L is cell-permeable and capable of monitoring intracellular Zn2+.
Graphical Abstract We report a new thiosemicarbazone-based fluorescent sensor (L) for selective recognition of Zn2+ with a long wavelength emission and a large Stokes shift.
A series of MZr4(PO4)6:Dy3+ (M = Ca, Sr, Ba) phosphors were prepared by the solid state diffusion method. Confirmation of the phase formation and morphological studies were performed by X-ray powder diffraction (XRD) measurements and scanning electron microscopy, respectively. Photoluminescence (PL) properties of these phosphors were thoroughly analyzed and the characteristic emissions of Dy3+ ions were found to arise from them at an excitation wavelength of 351 nm. The PL emission spectra of the three phosphors were analyzed and compared. The CIE chromaticity coordinates assured that the phosphors produced cool white-light emission and hence, they are potential candidates for UV excited white-LEDs (WLEDs).
The 2,2′-dinaphtholazobenzene molecular framework (P) was designed, synthesized and characterized. Its absorption and fluorescence properties revealed that P is a dual sensor for copper ions (Cu2+) and fluoride ions (F?) in DMSO. The colorimetric activities were clearly visible by naked eye upon the addition of the two ions. Fluorescence quenching and enhancement were observed when Cu2+ and F? ions were added respectively. Density Functional Theory (DFT) calculations were carried out to provide an insight into the interaction of guest ions (Cu2+ and F?) with P, and to explain how the molecular orbitals were affected.
Specific functionalized calix[4]arene based fluorescent chemosensor was synthesized for cations and anions binding efficiency examination. Receptor C4MA displayed strong affinity for Al3+and S2O72? with enhanced fluorescence intensity. The selective response of C4MA was investigated in the presence of different co-existing competing ions. The limit of detection (LOD) of Al3+and S2O72? was calculated as 2.8?×?10?6 M and 2.6?×?10?7 M respectively. Sensor C4MA forms (1:1) stoichiometric complex with both Al3+ and S2O72? and their binding constants were calculated as 12.1?×?104 and 8.3?×?103 respectively. Complexes were also characterized through FT-IR spectroscopy.
The solvatochromic 9-hydroxybenzo[b]quinolizinium ion is shown to operate as fluorescent probe for the detection of water in acetonitrile. The dual fluorescence of this photoacid and its dependence on the content of water in the medium enable the ratiometric analysis of the fluorescence data.
Due to the deleterious effects of mercury on human health and natural ecosystems, high reactivity, non-degradability, extreme volatility and relative water and tissue solubility, it would consider as one of the most toxic environmental pollutants among the transition metals. In the present investigation, we have tried to summarized the several organic material based fluorescent sensor including rhodamine, boron-dipyrromethene (BODIPYs), thiourea, crown-ether, coumarine, squaraines, pyrene, imidazole, triazole, anthracene, dansyl, naphthalenedimide/ naphthalene/ naphthalimide, naphthyridine, iridium (III) complexes, polymeric materials, cyclodextrin, phthalic anhydride, indole, calix [4]arene, chromenone, 1,8-naphthalimides, lysine, styrylindolium, phenothiazine, thiocarbonyl quinacridone, oxadiazole, triphenylamine–triazines, tetraphenylethene, peptidyl and semicarbazone for the trace mercury detection in the aqueous, aqueous–organic and cellular media. The present review provides a brief look over the previous development in the organic material based fluorescent sensor for mercuric ion detection. Furthermore, the ligand-metal binding stoichiometry, binding/association/dissociation constants and the detection limit by the receptors have been particularly highlighted which might be useful for the future design and development of more sensitive and robust fluorescent chemosensor/chemodosimeter for the mercuric ion detection.
Hexadentate ligand L and its Ln3+ complexes EuLCl3 (1), TbLCl3 (2), SmLCl3 (3) are synthesised. All these complexes are well characterized for their photophysical properties such as luminescence lifetime decay(τ) and overall quantum yield(Φ). These complexes being water soluble, depicts their intense metal centred luminescence. Effect of pH on these complexes suggest that their emission intensities are stable in the pH range 4–9 and show their compatibility to function in the physiological pH.
Nanocomposites with thermo and photo-switchable fluorescent properties were synthesized via mini-emulsion polymerization based on spiropyran and methyl methacrylate monomer. The photophysical behavior of fluorescence nanocomposites was investigated by fluorescence spectrophotometry in different temperature, UV-light and time of exposure. It was found that methyl methacrylate polymer is capable of acting as a protective layer and play a critical role in improving the photostability of colorants. The nanocomposites exhibited excellent fluorescent thermo-switching action with respect to the free spiro molecule.
Solvent free synthesis of 6,7-dihydroxy-3-(3-chlorophenyl) coumarin (CFHC) was designed and obtained by the interaction of 2-(2,4,5-trimethoxyphenyl)-1-(3-chlorophenyl)acrylonitrile with pyridinium hydrochloride in the presence of silica gel by using microwave irradiation. The characterization of CFHC was confirmed by FT-IR, 1H, 13C, 13C–APT and 2D HETCOR spectroscopy methods. The optical behavior of CFHC towards metal ions was investigated by UV-visible and fluorescence spectroscopy. CFHC showed “on–off” type fluorescence response towards Cu2+ with high selectivity in aqueous solution (CH3CN/H2O, 9/1, v/v). Once binding with Cu2+, CFHC-Cu2+ complex also displayed high selectivity for sulfide, resulting in “off–on” type sensing of sulfide anion.
Graphical abstract Visual fluorescence changes upon addition of various metal ions (5.0 eq.) to CFHC in CH3CN/H2O (90:10, v/v) under UV excitation (365 nm)
A bis(naphthalimide-piperazine) derivative (1) was synthesized as a pH-sensitive Off-On fluorescent probe. Operation mechanism of 1 is based on photo-induced electron transfer (PET) and its pH-dependent optical changes were investigated by using absorption and fluorescence spectroscopy. In the pH range of 11–4.5, this probe undergoes PET process from the piperazine to the naphthalimide moiety, leading to a fluorescence quenching. However, in the pH range of 4.5–1, the PET is inhibited to give a fluorescence enhancement. Moreover, the fluorescence ‘turn-on’ response of 1 is highly selective for protons (H+) over other metal cations, biomolecules and it shows a good reversibility between acidic and basic conditions.
Arsenic (As3+) is a hazardous and ubiquitous element; hence the quantitative detection of arsenic in various kinds of environmental sample is an important issue. Herein, we reported L-cysteine capped CdTe Quantum dot based optical sensor for the fluorometric detection of arsenic (III) in real water sample. The method is based on the fluorescence quenching of QDs with the addition of arsenic solution that caused the reduction in fluorescence intensity due to strong interaction between As3+ and L-cysteine to form As(Cys)3. The calibration curve was linear over 2.0 nM-0.5 μM arsenic with limit of detection (LOD) of 2.0 nM, correlation coefficient (r2) of 0.9698, and relative standard deviation (RSD %) of 5.2%. The Stern-Volmer constant for the quenching of CdTe QDs with As3+ at optimized condition was evaluated to be 1.17 × 108 L mol?1 s?1. The feasibility of the sensor has been analyzed by checking the inference of common metal ions available in the water such as K+, Na+, Mg2+, Ca2+, Ba2+, Cu2+, Ni2+, Zn2+, Al3+, Co2+, Cr2+, Fe3+ and its higher oxidation state As5+.
In this study the researcher reports a novel, one step synthesized rod-like nanoparticles of cerium (III)—tetraphenylporphyrin sandwich complex as a spectrofluorometric sensor to measure trace amount of Hg (II) and Cu (II) metal ions. Moreover, the synthesized fluorescent probe was able to detect higher amounts (>10?4 M) of Hg (II) in aqueous media by changing the color which can also be used as a selective mercury naked-eye sensor. The selectivity and sensitivity of the sensor based on its fluorescence quenching in the presence of Hg (II) and Cu (II) were studied according to the Stern-Volmer equation. The detection limit of the sensor was 16 nM for Hg (II) and about 2.34 μM for Cu (II) ions.
In this paper, we report on the results of spectrofluorimetric study of new fluorescent sensor based on [Zn2L2] doped in ethyl cellulose. The sensor optical signal is based on the rapid fluorescence quenching in the presence of acetone vapor. The acetone vapor detection limit in a gas mixture by means of sensor based on [Zn2L2] doped in ethyl cellulose is 1.68 ppb. Being highly sensitive to the acetone acetone presence, instant in response and easy to use, the sensor can find an application for the noninvasive diagnostics of diabetes as well as for the monitoring of the content of acetone acetone in the air at industrial and laboratory facilities.
Our present investigation aims at the synthesis and application of new, symmetric bridged bis-pyrazolone based acid dyes. The bis-pyrazolone compounds were accomplished from bis- hydrazine of 4,4′-Diaminostilbene-2,2′-disulfonic acid and ethyl acetoacetate. The bis-pyrazolones have been coupled with diazonium salts of o-hydroxyl aromatic amines which resulted in ligand dyes. The intermediate ligand dyes were treated with 3d transition metals to achieve the targeted metal complex acid dyes. The structures of investigated compounds were confirmed with the help of spectroscopic techniques. Dyes were applied on leather and their application parameters including their light fastness, wash fastness and rubbing fastness were determined.
The etiology of Parkinson’s disease involves the interplay between the environmental and genetic factors. Here in this study human α-synuclein upon exposure to 100 μM pendimethalin for 12 h in vitro passes through a partially folded state which proceeds to the aggregated state and terminally ends in the fibrillar phase. Variations in the ANS fluorescence intensities led to the detection of intermediate and aggregated states at 6 and 10 h respectively. Far-UV CD analysis depicted significant α-helical content for intermediate state at 6 h in presence of 100 μM pendimethalin. Further increasing the incubation time to 12 h resulted in a predominant β-sheet content which was confirmed to be fibrillar by TEM. Turbidity, Rayleigh scattering analysis, Congo red assay and ThT measurements supported the TEM data i.e. the formation of fibrillar structure of human α-synuclein upon 12 h incubation. Thus, our observation could suggest a possible underlying molecular basis for Parkinson’s disease.
A label -free DNAzyme amplified biosensor is found to be highly selective and sensitive towards fluorescent detection of Pb2+ ions in aqueous media. The DNAzyme complex has designed by the hybridization of the enzyme and substrate strand. In the presence of Pb2+, the DNAzyme activated and cleaved the substrate strand of RNA site (rA) into two oligonucleotide fragments. Further, the free fragment was hybridized with a complementary strand on the surface of MBs. After magnetic separation, SYBER Green I was added and readily intercalate with the dsDNA to gives a bright fluorescence signal with intensity directly proportional to the concentration of Pb2+ions. A detection limit of 5 nM in Pb2+ the detection range 0 to 500 nM was obtained. This label- free fluorescent biosensor has been successfully applied to the determination of environmental water samples. Then results open up the possibility for real-time quantitative detection of Pb2+ with convenient potential applications in the biological and environmental field.
Schiff base centered fluorescent organic compound 1,1′-[(1E,2E)-hydrazine-1,2-diylidenedi(E)methylylidene]- dinaphthalen-2-ol (HN) was synthesized followed by spectral characterization viz., NMR, IR and Mass spectroscopy. The fluorescent nanoparticles of HN prepared using reprecipitation method shows red shifted aggregation induced enhanced emission (AIEE) with respect to HN solution in acetone. The average particle size of nanoparticles (HNNPs) is of 67.2 nm shows sphere shape morphology. The surfactant cetyltrimethyl ammonium bromide (CTAB) used to stabilize HNNPs induces positive charge surface with zeta potential of 11.6 mV. The positive charge of HNNPs responsible to adsorb oppositely charged analyte on its surface with binding interactions. The fluorescence experiments performed with and without addition of different analytes to the aqueous suspension of HNNPs shows selective fluorescence quenching of HNNPs by D-Penicillamine (D-PA). The effect of other coexisting analytes does not affect the selective sensing behavior of D-PA. The mechanism of binding between HNNPs and D-PA was discussed on the basis of electrostatic interaction and adsorption phenomenon. The results interpreted by using DLS-Zeta sizer, Fluorescence lifetime measurements, conductometric titration supports the electrostatic adsorption between HNNPs and D-PA. The method has extremely low limit of detection (LOD) value 0.021 ppm is of significant as compared to reported methods. The proposed fluorescence quenching method was effectively used for quantitative estimation of D-PA from pharmaceutical medicine.
Graphical Abstract The fluorescence quenching based selective recognition of D-Penicillamine (D-PA) by using Schiff base centered fluorescent organic nanoparticles was developed and successfully applied to quantitative determination of D-PA from pharmaceutical samples viz. capsule and tablet.
Two chemiluminescent compounds containing 2,5-di(thien-2-yl)pyrrole and pyridazine units, namely 5,7-di(thiophen-2-yl)-2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione (5) and 6-phenyl-5,7-di(thiophen-2-yl)-2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione (6), were successfully synthesized and electrochemically polymerized. The compounds have chemiluminescent properties and glow in the presence of hydrogen peroxide in basic medium. The intensity of the glow can be increased dramatically by using Fe3+ ions, hemin (1.0 ppm) or blood samples (1.0 ppm) as catalyst. The compounds 5 and 6 have one well-defined irreversible oxidation peak at 1.08 V and 1.33 V vs Ag/AgCl, respectively. Electrochemical polymerization of both 5 and 6 were carried out successfully by repeating potential scanning in the presence of BF3. Et2O in an electrolyte solution of 0.1 M LiClO4 dissolved in acetonitrile. The electronic band gaps (Eg) of the polymers P5 and P6 were found to be 2.02 eV and 2.16 eV, respectively. On the other hand, the corresponding polymers are electroactive and exhibited electrochromic features.
An increasingly wide variety of fluorescent compounds is used in biotechnology, genomics, immunoassays, array technologies, imaging, and drug discovery. Therefore, synthesis of fluorophores with novel structural features can be interesting and useful in various fields. In this paper, four new fluorescent heterocyclic compounds with high quantum yields are introduced. These new fluorophores are synthesized in moderate to high yields via regioselective nitration of 3-alkyl-8-(4-chlorophenyl)-3 H-imidazo[4′,5′:3,4]benzo[c]isoxazoles. The latter compounds are obtained from the reaction of 1-alkyl-5-nitro-1 H-benzoimidazoles with (4-chlorophenyl)acetonitrile in basic MeOH solution. Physical spectral (UV-vis, IR, 1HNMR, 13C NMR, NOESY and fluorescence) and analytical data have established the structures of synthesized compounds. The fluorescence properties of new fluorescent heterocyclic compounds are studied. The fluorescence of all compounds is very intense and fluorescence quantum yields are high (> 0.52). Density functional theory (DFT) calculations are performed to provide the optimized geometries, relevant frontier orbitals and the prediction of 1H NMR chemical shifts for confirming the exact structure of fluorescent compounds. Calculated electronic absorption spectra were also obtained by time-dependent density functional theory (TD-DFT) method.
