A new selective fluorescent sensor for Fe3+ based on a pyrazoline derivative

A selective bis-thiophene chalcone-based spectrofluorimetric sensor for Fe3

A highly selective bis thiophene-based chalcone as a chemosensor for detecting Fe3+ metal ions in DMF: H2O (9:1). This sensor was selective toward ferric ions over other metal ions with a detection limit in micromolar range.

Chalcone-based Turn-Off Chemosensor for Selective and Susceptible Detection of Fe2+ Ions: Spectroscopic and DFT Investigations

Herein, in this report we are introducing newly synthesized chalcone derivative, "(E)-1-phenyl-3-(4-((5-(((Z)-thiophen-2-ylmethylene)amino)-1,3,4-thiadiazol-2-yl)thio)phenyl)prop-2-en-1-one" (5), as a chemosensor to detect Fe2+ metal ions in HEPES buffer solution of pH 7.5. Spectroscopic techniques were used to confirm the synthesized sensor. To determine the chemical reactivity and molecular stability of the probe, a frontier molecular orbitals investigation was carried out. A molecular electrostatic potential map was investigated to know the binding site of 5 for metal ion coordination. The theoretical absorption and fluorescence emission properties were estimated and correlated with the experimental observations. The sensor showed excellent selectivity for Fe2+ compared to all other studied metal ions. The fluorescence binding studies were carried out by adding different amounts of Fe2+ ions for a fixed concentration of probe 5. The inclusion of Fe2+ ions resulted in a decrease in fluorescence intensity with a bathochromic shift of emission wavelength of 5 due to the 5-Fe2+ complexation. The binding affinity value for the probe was found to be 576.2 M-1 with the help of the Stern-Volmer plot. The Job's plot and mass spectra supported the 2:1 (5: Fe2+) stoichiometry of complex formation. The detection limit and limit of quantification of 5 for Fe2+ were calculated to be 4.79 × 10-5 M and 14.54 × 10-5 M. Further, in addition to this, the photophysical parameters such as fluorescence lifetime of 5 and 5-Fe2+ complex measured to be 0.1439 and 0.1574 ns. The quantum yield of 5 and 5-Fe2+ was found to be 0.0398 and 0.0376. All these experimental findings revealed that probe 5 has excellent selectivity and sensitivity for Fe2+ ions.

Novel pyrazoline and pyrazole "turn on" fluorescent sensors selective for Zn2+/Cd2+ at λem 480 nm and Fe3+/Fe2+ at λem 465 nm in MeCN

A small series of simple pyrazoline and pyrazole based sensors, all derived from the same chalcone precursors, were synthesised, characterised and screened for their fluorescence "turn on" properties in the presence of multiple metals. Pyrazole 8 displayed an excellent fluorescence profile with approx. 20× fold increase in λem 480 nm with Zn2+ compared to a 2.5× fold increase with Cd2+. Pyrazole 9 displayed a 30× fold increase at λem 465 nm for Fe3+ compared to Fe2+ with a Fe3+ limit of detection of 0.025 μM. The corresponding pyrazolines displayed contrasting properties with important implications for future pyrazoline and pyrazole sensor design.

Iminobenzophenone-thiophen hydrazide schiff base: a selective turn on sensor for paramagnetic Fe3+ ion and application in real sample analysis

A highly selective turn-on sensor for paramagnetic Fe³⁺ ions based on (E)-N'-((2-aminophenyl)(phenyl)methylene)thiophene-2-carbohydrazide is successfully synthesized. The sensor BPTH is significantly selective and sensitive towards Fe³⁺ ions over other interfering metal ions especially Cu²⁺ and Co²⁺ ions with a lowest limit of recognition 1.48 × 10^-7 M. The turn-on sensing mechanism involves enhanced charge transfer. Fe³⁺ ion forms strong binding with the ligand with a K_a value about 8.23 × 10⁴ M^-1 and a 1:1 stoichiometric ratio is confirmed by Job's plot experiment. With Fe³⁺ ion, the yellow ligand BPTH change to a green fluorescent and reversible with 1 equivalent of EDTA. Practical application of sensor is demonstrated in real sample analysis.

Novel schiff base as Fe3+ sensor as well as an antioxidant and its theoretical studies

A novel Schiff base derivative L (N1-(thiophene-2-ylmethylene)benzene-1,2-diamine) was synthesized via condensation reaction of 3-thiophene carboxaldehyde and 1,2-diamino benzene. The synthesized compound was authenticated using 1 H NMR, 13 C NMR, HRMS, and IR spectroscopy. The compound L was found to be a Fe3+ sensor with the complexation ratio of 1 : 3 as revealed by Job’s plot with maximum absorption at 318 nm. The photophysical properties were studied using absorption and emission spectra. DFT and TD-DFT studies were carried out in order to support the photophysical outcomes of compound L. An antioxidant behaviour of compound L was studied using TAC, FRAP, and DPPH assays and it was found to be showing better TAC activity than the used standard i.e. gallic acid.

Fluorescence "Turn-off" Sensing of Iron (III) Ions Utilizing Pyrazoline Based Sensor: Experimental and Computational Study

A simple pyrazoline-based ''turn off'' fluorescent sensor 5-(4-methoxyphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1H-pyrazole (PFM) was synthesized and well characterized by different techniques such as FT-IR, ¹H-NMR, ¹³C-NMR, and mass spectrometry. The synthesized sensor PFM was utilized for the detection of Fe³⁺ ions. Fluorescence emission selectively quenched by Fe³⁺ ions compared to other metal ions (Mn²⁺, Al³⁺, Fe²⁺, Hg²⁺, Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, and Zn²⁺) via paramagnetic fluorescence quenching and showed good anti-interference ability over the existence of other tested metals. Under optimum conditions, the fluorescence intensity of sensor quenched by Fe³⁺ in the range of 0 to 3 μM with detection limit of 0.12 μM. Binding of Fe³⁺ ions to PFM solution were studied by fluorescent titration, revealed formation of 1:1 PFM-Fe metal complex and binding constant of complex was found to be of 1.3 × 10⁵ M^-1. Further, the fluorescent sensor has been potentially used for the detection of Fe³⁺ in environmental samples (river water, tap water, and sewage waste water) with satisfactory recovery values of 99-101%.

Designed synthesis of an sp2 carbon-conjugated fluorescent covalent organic framework for selective detection of Fe3

A new fully conjugated covalent organic framework material (COF_TFPPy-ThDAN) has been synthesized via the Knoevenagel condensation reaction using 1,3,6,8-tetra(4-formylphenyl)pyrene (TFPPy) as the chromogenic unit and 2,2'-([2,2'-bithiophene]-5,5'-diyl)diacetonitrile (ThDAN) as the linker. The COF_TFPPy-ThDAN has been successfully prepared under the optimized conditions and showed excellent crystallinity and chemical stability. Especially, it was able to maintain its crystallinity even when immersed under harsh conditions such as HCl (3 M) and NaOH (3 M). Meanwhile, COF_TFPPy-ThDAN exhibited good fluorescence properties, which could remain relatively stable under different pH conditions. Moreover, COF_TFPPy-ThDAN was further employed for the detection of Fe³⁺ with high sensitivity and selectivity with a limit of detection (LOD) of 1.26 μM. COF_TFPPy-ThDAN with high stability and fluorescence is a promising material for chemical sensing.

Experimental and Theoretical Studies of the Pyrazoline Derivative 5-(4-methylphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1H-Pyrazole and its Application for Selective Detection of Cd2+ ion as Fluorescent Sensor

A simple fluorescent chemosensor 5-(4-methylphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4, 5-dihydro-1H-pyrazole (PY) has been synthesized for the detection of Cd²⁺ ion.The fluorescent probe PY shows high selectivity for Cd²⁺in the presence of othermetal ions (Co²⁺, Cu²⁺, Hg²⁺, Mn²⁺, Zn²⁺, Fe³⁺, Pb²⁺, Ni²⁺, and Al³⁺). The fluorescence intensity of the PY has been strongly quenched with increasing concentration of Cd²⁺ (0-0.9 μM)via photoinduced electron transfer mechanism. The binding constant of Cd²⁺ to PY for the 1:1 complex isfound to be 5.3 × 10⁵ M^-1with a detection limit of 0.09 μM. The chemosensor was successfully applied for determination of Cd²⁺ in different water samples (tap, river, and bottled water) showing good recovery values in the range of 94.8-101.7% with RSD less than 3%. Density functional theory (DFT) calculations were also performed to investigate electronic and spectral characteristics which are quite agreeable with the experimental value. The results show that the synthesized fluorescent chemosensor shows good selectivity towards Cd²⁺ and can be readily applied for the detection of Cd²⁺ in real samples including water samples.

A Review on Metal Ion Sensors Derived from Chalcone Precursor

Disclosure of new molecular probes as chromogenic and fluorogenic cation sensors is scientifically exigent work. Recently chalcone derivatives gained more attention because of their structural variability. A suitable donor and acceptor groups separated by delocalized π-orbitals display excellent chromogenic and fluorogenic properties because of intramolecular charge transfer (ICT). These designed molecular frameworks provide the coordination sites to the incoming metal ions results in small changes in the optical properties. In a typical sensing behavior, coordination leads to a large conjugation plane with the probe resulted in hypo/hyperchromic shifts or red/blue shifts. In this review, we tried to converge the reported chalcone-derived sensors and explored the design, synthesis, metal ion sensing mechanism, and practical application of the probes. We expect that this review gives a basic outline for researchers to explore the field of chalcone-based sensors further.

Carbon source self-heating: ultrafast, energy-efficient and room temperature synthesis of highly fluorescent N, S-codoped carbon dots for quantitative detection of Fe(iii) ions in biological samples

In recent years, photoluminescent (PL) carbon dots (CDs) have attracted enormous attention because of their many fascinating properties. However, the traditional synthesis routes of PL CDs usually suffer from relatively low quantum yields (QYs) and require complicated operation processes as well as lots of externally supplied energy. Herein, we report a room temperature, green, ultrafast and energy-efficient route for large scale synthesis of highly PL N, S-codoped CDs without any external energy supply. The N, S-codoped CDs are prepared through a novel carbon source self-heating strategy, using the sole precursor tetraethylenepentamine (TEPA) simultaneously as the carbon, nitrogen and heat source, triggered by the heat initiator sodium persulfate (Na2S2O8). The large amount of heat released from Na2S2O8-triggered oxidation of TEPA could effectively promote the spontaneous polymerization and carbonization of TEPA precursors themselves as well as the in situ co-doping of sulfur, which had marked synergistic effects on the fluorescence enhancement of CDs, eventually leading to the high-yield (58.0%) preparation of highly fluorescent N, S-codoped CDs (QY 26.4%) at room temperature within 2 min. Moreover, the fluorescence of N, S-codoped CDs could be selectively quenched by Fe3+ ions in the presence of EDTA, in an ultra-wide range of 0.2-600 μM, with a detection limit of 0.10 μM. Ultimately, the fluorescent nanoprobe was successfully used for the quantitative detection of Fe3+ in human serum samples, indicating its great potential for sensing and biomedical applications.

Ethanol-Precipitation-Assisted Highly Efficient Synthesis of Nitrogen-Doped Carbon Quantum Dots from Chitosan

Nitrogen-doped carbon quantum dots (NCQDs) were prepared from chitosan through a hydrothermal reaction. When ethanol precipitation was used as the purification method, a high product yield of 85.3% was obtained. A strong blue fluorescence emission with a high quantum yield (QY) of 6.6% was observed from the NCQD aqueous solution. Physical and chemical characteristics of the NCQDs were carefully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectra, X-ray photoelectron spectroscopy (XPS), and transient fluorescence spectra. Experimental results showed that diameters of the NCQDs were in the range of 2-10 nm. The carbon quantum dots possess good water dispersibility and precipitation by ethanol. When used for metal ion detection, the detection limit of the NCQDs for Fe3+ was as low as 1.57 μM. This work proposed a facile method to synthesize NCQDs from chitosan with high yield and demonstrated that carbon quantum dots derived from chitosan were promising for ion detection.

GB, Latiyan S, Jain S. Remarkably selective biocompatible turn-on fluorescent probe for detection of Fe3+ in human blood samples and cells

The robust nature of a biocompatible fluorescent probe is demonstrated, by its detection of Fe³⁺ even after repeated rounds of quenching (reversibility) by acetate in real human blood samples and cells in vitro.

Carbazole based nanoprobe for selective recognition of Fe3+ ion in aqueous medium: Spectroscopic insight

A simple carbazole based nanoprobe prepared by reprecipitation method shows selective sensing behavior for Fe³⁺ ion in aqueous medium. The prepared SDS capped 9-phenyl carbazole nanoparticles (9-PCzNPs) has narrower particle size distribution with an average diameter 35nm and zeta potential of -34.3mV predicted a good stability with negative surface charge over the nanoparticles. The Field Emission Scanning Electron Microscopy (FE-SEM) image showed cubic shape morphology of nanoparticles. The aqueous suspension of SDS capped 9-phenyl carbazole nanoparticles exhibited aggregation induced enhanced red shifted intense emission in comparison with the emission arising from dilute solution of 9-phenyl carbazole in DCM. The cation recognition test based on fluorescence change shows Fe³⁺ ion induce significant fluorescence quenching, however remaining cations responds negligibly. The obtained quenching data fit into Stern-Volmer relation in the concentration range of 0.0-1.0μg·mL^-1 of Fe³⁺ ion solution and the detection limit is 0.0811μg·mL^-1. The probable mechanism of fluorescence quenching of SDS capped 9-PCzNPs is because of adsorption of Fe³⁺ ion over the negatively charged surface of NPs through electrostatic interaction. Thus the proposed method was successfully applied for the detection of Fe³⁺ ion in environmental water sample.

Molecular characteristics of a fluorescent chemosensor for the recognition of ferric ion based on photoresponsive azobenzene derivative

Metal ion recognition is of great significance in biological and environmental detection. So far, there is very few research related to the ferric ion sensing based on photoresponsive azobenzene derivatives. In this work, we report a highly selective fluorescent "turn-off" sensor for Fe³⁺ ions and the molecular sensing characteristics based on an azobenzene derivative, N-(3,4,5-octanoxyphenyl)-N'-4-[(4-hydroxyphenyl)azophenyl]1,3,4-oxadiazole (AOB-t8). The binding association constant was determined to be 6.07×10³M^-1 in ethanol and the stoichiometry ratio of 2:2 was obtained from Job's plot and MS spectra. The AOB-t8 might be likely to form the dimer structure through the chelation of ferric ion with the azobenzene moiety. Meanwhile, it was found that the photoisomerization property of AOB-t8 was regulated by the binding with Fe³⁺. With the chelation of Fe³⁺, the regulated molecular rigidity and the perturbed of electronic state and molecular geometry was suggested to be responsible for the accelerated isomerization of AOB-t8 to UV irradiation and the increased fluorescence lifetime of both trans- and cis-AOB-t8-Fe(III). Moreover, the reversible sensing of AOB-t8 was successfully observed by releasing the iron ion from AOB-t8-Fe(III) with the addition of citric acid.

Highly Sensitive and Selective Detection of Nanomolar Ferric Ions Using Dopamine Functionalized Graphene Quantum Dots

The good stability, low cytotoxicity, and excellent photoluminescence property of graphene quantum dots (GQDs) make them an emerging class of promising materials in various application fields ranging from sensor to drug delivery. In the present work, the dopamine-functionalized GQDs (DA-GQDs) with stably bright blue fluorescence were successfully synthesized for low level Fe(3+) ions detection. The as-synthesized GQDs are uniform in size with narrow-distributed particle size of 4.5 ± 0.6 nm and high quantum yield of 10.2%. The amide linkage of GQDs with dopamine, confirmed by using XPS and FTIR spectra, results in the specific interaction between Fe(3+) and catechol moiety of dopamine at the interfaces for highly sensitive and selective detection of Fe(3+). A linear range of 20 nM to 2 μM with a detection limit of 7.6 nM is obtained for Fe(3+) detection by DA-GQDs. The selectivity of DA-GQDs sensing probe is significantly excellent in the presence of other interfering metal ions. In addition, the reaction mechanism for Fe(3+) detection based on the complexation and oxidation of dopamine has been proposed and validated. Results obtained in this study clearly demonstrate the superiority of surface functionalized GQDs to Fe(3+) detection, which can pave an avenue for the development of high performance and robust sensing probes for detection of metal ions and other organic metabolites in environmental and biomedical applications.

Nitrogen and Phosphorus Co-Doped Carbon Nanodots as a Novel Fluorescent Probe for Highly Sensitive Detection of Fe(3+) in Human Serum and Living Cells

Chemical doping with heteroatoms can effectively modulate physicochemical and photochemical properties of carbon dots (CDs). However, the development of multi heteroatoms codoped carbon nanodots is still in its early stage. In this work, a facile hydrothermal synthesis strategy was applied to synthesize multi heteroatoms (nitrogen and phosphorus) codoped carbon nanodots (N,P-CDs) using glucose as carbon source, and ammonia, phosphoric acid as dopant, respectively. Compared with CDs, the multi heteroatoms doped CDs resulted in dramatic improvement in the electronic characteristics and surface chemical activities. Therefore, the N,P-CDs prepared as described above exhibited a strong blue emission and a sensitive response to Fe(3+). The N,P-CDs based fluorescent sensor was then applied to sensitively determine Fe(3+) with a detection limit of 1.8 nM. Notably, the prepared N,P-CDs possessed negligible cytotoxicity, excellent biocompatibility, and high photostability. It was also applied for label-free detection of Fe(3+) in complex biological samples and the fluorescence imaging of intracellular Fe(3+), which indicated its potential applications in clinical diagnosis and other biologically related study.

Highly selective fluorescence sensors for the fluoride anion based on carboxylate-bridged diiron complexes

The diiron–sulfur clusters bearing urea and anthracene units showed rapid and selective recognition for the fluoride ion.

Synthesis of novel boron chelate complexes and proposed mechanism of new rearrangement

We synthesized novel boron chelate complexes by the reaction of pyrazoline derivatives and boron trifluoride diethyl etherate followed by a new rearrangement. The structures of the compounds were characterized by IR, NMR and HRMS, especially, a typical compound 3c was confirmed by X-ray single crystal analysis. We proposed a mechanism of the rearrangement. Moreover, the absorption and fluorescence spectroscopy of these compounds were measured.

A new pyrazoline-based fluorescent sensor for Al3+ in aqueous solution

A new pyrazoline-based fluorescent sensor was synthesized and the structure was confirmed by single crystal X-ray diffraction. The sensor responds to Al(3+) with high selectivity among a series of cations in aqueous methanol. This sensor forms a 1:1 complex with Al(3+) and displays fluorescent quenching.

Sulfur-doped graphene quantum dots as a novel fluorescent probe for highly selective and sensitive detection of Fe(3+)

Sulfur-doped graphene quantum dots (S-GQDs) with stable blue-green fluorescence were synthesized by one-step electrolysis of graphite in sodium p-toluenesulfonate aqueous solution. Compared with GQDs, the S-GQDs drastically improved the electronic properties and surface chemical reactivities, which exhibited a sensitive response to Fe(3+). Therefore, the S-GQDs were used as an efficient fluorescent probe for highly selective detection of Fe(3+). Upon increasing of Fe(3+) concentration ranging from 0.01 to 0.70 μM, the fluorescence intensity of S-GQDs gradually decreased and reached a plateau at 0.90 μM. The difference in the fluorescence intensity of S-GQDs before and after adding Fe(3+) was proportional to the concentration of Fe(3+), and the calibration curve displayed linear regions over the range of 0-0.70 μM. The detection limit was 4.2 nM. Finally, this novel fluorescent probe was successfully applied to the direct analysis of Fe(3+) in human serum, which presents potential applications in clinical diagnosis and may open a new way to the design of effective fluorescence probes for other biologically related targets.

Quantum mechanical and spectroscopic (FT-IR, 13C, 1H NMR and UV) investigations of 2-(5-(4-Chlorophenyl)-3-(pyridin-2-yl)-4,5-dihydropyrazol-1-yl)benzo[d]thiazole by DFT method

The electronic, NMR, vibrational, structural properties of a new pyrazoline derivative: 2-(5-(4-Chlorophenyl)-3-(pyridine-2-yl)-4,5-dihydropyrazol-1-yl)benzo[d]thiazole has been studied using Gaussian 09 software package. Using VEDA 4 program we have reported the PED potential energy distribution of normal mode of vibrations of the title compound. We have also reported the (1)H and (13)C NMR chemical shifts of the title compound using B3LYP level of theory with 6-311++G(2d,2p) basis set. Using time dependent (TD-DFT) approach electronic properties such as HOMO and LUMO energies, electronic spectrum of the title compound has been studied and reported. NBO analysis and MEP surface mapping has also been calculated and reported using ab initio methods.

A new Rhodamine B-based 'on-off' chemical sensor with high selectivity and sensitivity toward Fe(3+) and its imaging in living cells

A new fluorescent chemosensor based on a Rhodamine B and pyrrole conjugate (RBPY) has been designed and synthesized. UV-vis absorption and fluorescence spectroscopic studies show that RBPY exhibits a high selectivity and sensitivity toward Fe(3+) among many other metal cations in a MeOH/H2O solution (3:2, v/v, pH 7.10, HEPES buffer, 0.1mM) by forming a 1:1 complex with Fe(3+). Furthermore, results reveal that the formation of the RBPY-Fe(3+) complex is fully reversible in the presence of sulfide anions and could also be used as an efficient sensor for S(2-). Importantly, fluorescence microscopy experiments further demonstrated that RBPY can be utilized as a fluorescent probe for the detection of Fe(3+) in human liver (L-02) cells.