Poly(1-amino-5-chloroanthraquinone): Highly Selective and Ultrasensitive Fluorescent Chemosensor For Ferric Ion

Poly(1-amino-5-chloroanthraquinone) (PACA) was firstly synthesized by a chemically oxidative interfacial polymerization. The PACA has been developed as a fluorescent sensor for the determination of Fe(III) in semi-aqueous solution at pH 7.0. The sensor exhibited remarkably high sensitivity toward Fe³⁺ since the fluorescence of the polymer could be significantly quenched even though trace Fe³⁺ was added. The sensor showed a linear fluorescence emission response over a wide concentration range from 1.0?×?10^?10 to 1.0?×?10^?4 M, with an ultra-low detection limit of 2.0?×?10^?11 M. The quenching of the fluorescence was found to be static one due to the formation of non-fluorescent complex in the ground state.     

Interaction of Folic Acid with Mn2+ Doped CdTe/ZnS Quantum Dots: In Situ Detection of Folic Acid

To utilize the nanomaterials as an effective carrier for the drug delivery applications, it is important to study the interaction between nanomaterials and drug or biomolecules. In this study GSH functionalized Mn²⁺-doped CdTe/ZnS QDs has been utilized as a model nanomaterial due to its high luminescence property. Folic acid (FA) gradually quenches the FL of GSH functionalized Mn²⁺???doped CdTe/ZnS QDs. The Stern-Volmer quenching constant (K_sv), binding constant (K_s) and effective quenching constant (Ka) for the FA-QDs system is calculated to be 1.32?×?10⁵ M^?1, 1.92?×?10⁵ and 0.27?×?10⁵ M^?1, respectively under optimized condition (Temp. 300 K, pH 8.0, incubation time 40 min.). The effects of temperature, pH, and incubation time on FA-QDs system have also been studied. Statistical analysis of the quenched FL intensity versus FA concentration revealed a linear range from 1?×?10^?7 to 5.0?×?10^?5 for FA detection. The LOD of the current nano-sensor for FA was calculated to be 0.2 μM. The effect of common interfering metal ions and other relevant biomolecules on the detection of FA (12.0 μM) have also been investigated. L-cysteine and glutathione displayed moderate effect on FA detection. Similarly, the common metal ions (Na⁺, K⁺, Ca²⁺ and Mg²⁺) produced minute interference while Zn²⁺ Cu²⁺ and Fe³⁺ exert moderate interference. Toxic metal ions (Hg²⁺ and Pb²⁺) produced severe interferences in FA detection.

Graphical abstract

GSH-Mn²⁺ CdTe/ZnS QDs based Fluorescence Nanosensor for Folic acid

     

Concentration quenched luminescence and energy transfer analysis of Nd3+ ion doped Ba-Al-metaphosphate laser glasses

This paper reports the dopant ion (Nd³⁺) concentration effects on its luminescence properties in a new glass system based on barium-alumino-metaphosphates. Amongst the studied concentrations range of 0.276–13.31×10²⁰ ions/cm³, the glass with 2.879×10²⁰ ions/cm³ (1 mol%) Nd³⁺ concentration shows intense NIR emission from ⁴F_3/2 excited state, followed by a decrease in emission intensity for further increase in Nd³⁺ ion concentration. The observed luminescence quenching is ascribed to Nd³⁺ self-quenching through the donor-donor migration assisted cross-relaxation mechanism. The microscopic energy transfer parameters for donor-acceptor energy transfer, C _DA, and donor-donor energy migration, C _DD, have been obtained from the theoretical fittings to experimental decay curves and the spectral overlap model respectively. The C _DD parameters (×10^?39 cm⁶/sec) are found to be about three orders greater than that of C _DA (×10^?42 cm⁶/sec) for Nd³⁺ self-quenching in this host, demonstrating that the excitation energy migration among donors is due to the hopping mechanism. The energy transfer micoparameters obtained in the present study are comparable to the values reported for commercially available laser glasses LHG-8 and Q-98.     

A Highly Fluorescent Pyrene-Based Sensor for Selective Detection Of Fe3+ Ion in Aqueous Medium: Computational Investigations

In this work, we introduce a highly selective and sensitive fluorescent sensor based on pyrene derivative for Fe(III) ion sensing in DMSO/water media. 2-(pyrene-2-yl)-1-(pyrene-2-ylmethyl)-1H-benzo[d]imidazole (PEBD) receptor was synthesized via simple condensation reaction and confirmed by spectroscopic techniques. The receptor exhibits fluorescence quenching in the presence of Fe(III) ions at 440 nm. ESI–MS and Job’s method were used to confirm the 1:1 molar binding ratio of the receptor PEBD to Fe(III) ions. Using the Benesi-Hildebrand equation the binding constant value was determined as 8.485?×?10³ M^?1. Furthermore, the limit of detection (LOD, 3σ/K) value was found to be 1.81 µM in DMSO/water (95/5, v/v) media. According to the Environmental Protection Agency (EPA) of the United States, it is lower than the acceptable value of Fe³⁺ in drinking water (0.3 mg/L). The presence of 14 other metal ions such Co²⁺, Cr³⁺, Cu²⁺, Fe²⁺, Hg²⁺, Pb²⁺, K⁺, Ni²⁺, Mg²⁺, Cd²⁺, Ca²⁺, Mn²⁺, Al³⁺, and Zn²⁺ did not interfere with the detection of Fe(III) ions. The fluorescence life-time of the receptor PEBD with and without Fe³⁺ ion was found to be 1.097?×?10^?9 s and 0.9202?×?10^?9 s respectively. Similarly, the quantum yield of the receptor PEBD with Fe³⁺ and without Fe³⁺ ion was calculated, and found as 0.05 and 0.25 respectively. Computational studies of the receptor PEBD were carried out with density functional theory (DFT) using B3LYP/ 6-311G (d, p), LANL2DZ level of theory.

Graphical Abstract

     

Graphene Quantum Dots from Polycyclic Aromatic Hydrocarbon for Bioimaging and Sensing of Fe3+ and Hydrogen Peroxide

An easy approach for large‐scale and low‐cost synthesis of photoluminescent (PL) graphene quantum dots (GQDs) based on the carbonization of commercially available polycyclic aromatic hydrocarbon (PAH) precursors with strong acid and followed by hydrothermal reduction with hydrazine hydrate is reported. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) characterizations indicate that the size and height of GQDs are in the range of 5–10 nm and 0.5–2.5 nm, respectively. PAH, which has more benzene rings, generally forms GQDs with relatively larger size. The GQDs show high water solubility, tunable photoluminescence, low cytotoxicity, and good optical stability, which makes them promising fluorescent probes for cellular imaging. In addition, the fluorescence of GQDs shows a sensitive and selective quenching effect to Fe³⁺ with a detection limit of 5 × 10^?9m . By combination with the Fe²⁺/Fe³⁺ redox couple, the PL GQDs are able to detect oxidant, using H₂O₂ as an example. This study opens up new opportunities to make full use of GQDs because of their facile availability, cost‐effective productivity, and robust functionality.     

Sensitive and Selective PET-Based π-expanded Phenanthrimidazole Luminophore for Zn2+ Ion

The novel photoinduced electron transfer (PET) chemosensor, 1-(1-(4-methoxyphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)naphthalen-2-ol [MPPN] and its zinc complex were synthesised and characterized by electronic spectral and Frontier molecular orbital energy analysis. MPPN becomes efficient fluorescent chemosensor upon binding with metal ions and shows a strong preference toward Zn²⁺ ion. Density Functional theory (DFT) calculations reveal that luminescence of free MPPN originates from its orbital structure in which two π-orbitals (HOMO and HOMO-1) of the imidazole ring are situated between two π-orbitals (HOMO-2 and LUMO) of the naphthyl fragment. Therefore the absorption and emission processes occur between the two π- orbitals (HOMO-2 and LUMO). The two higher energy imidazole orbitals (HOMO and HOMO-1 ) serve as quenchers for the excited state of the molecule through nonradiative processes. Upon binding with Zn²⁺ ion, MPPN becomes a highly luminescent with λ_emi???421 nm. The significant enhancement of luminescence upon binding with Zn²⁺ ion is attributed to the stabilization of HOMO-2 and HOMO-1 π-orbitals of imidazole ring upon their engagement in new bonds with Zn²⁺ ion. The affinity of MPPN to zinc ion is found to be very high [K?=?6?×?10⁶ M^?1] when compared with other metals ions. The nonlinear absorption coefficient γ for MPPN is 1.9?×?10^?12 m/W and 3.9?×?10^?11 m/W for MPPN-Zn complex.     

Mechanism and enhancement of photoluminescence from silicon nanocrystals implanted in SiO2 matrix

Photoluminescence (PL) spectra of Si nanocrystals (NCs) prepared by 130 keV Si ions implantation onto SiO2 matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist of two PL peaks, originated from smaller Si NCs due to quantum confinement effect (QCE) and the interface states located at the surface of larger Si NCs. The evolution of number of dangling bonds (DBs) on Si NCs was also investigated. For hydrogen-passivated samples, a monotonic increase in PL peak intensity with the dose of implanted Si ions up to 3×1017 ions /cm2 is observed. The number of DBs on individual Si NC, the interaction between DBs at the surface of neighbouring Si NCs and their effects on the efficiency of PL are discussed.     

YIG formation in annealed iron implanted YAG

YAG and YIG crystals implanted respectively with 100 keV⁵⁷Fe²⁺ ions (1 × 10¹⁷ ions.cm^?2) and 50 keV²⁷Al ions (1.1 × 10¹⁷ ions.cm^?2) have been studied by conversion electron Mössbauer spectroscopy (CEMS) directly after implantation and after annealings in air at temperatures up to 1100°C. In both as-implanted samples iron is found mainly in three states: Fe²⁺, Fe³⁺ and small metallic precipitates. Annealing behaviour is divided into two stages: (i) up to 400°C the iron has become completely oxidized and (ii) between 400 and 850°C the epitaxial regrowth of the implanted layer takes place. During this process a part of iron ions are incorporated into octahedral and tetrahedral sites, thus making a Y₃ (Al Fe)₅ O₁₂ compound. The remaining iron part precipitates in the form of Fe₂O₃ particles.     

Synthesis and Analytical Application of a Novel Fluorescent Hg2+ Probe 3′, 6′-Bis(Diethylamino)-2-((2,4-Dimethoxybenzylidene)Amino)Spiro[Isoindoline-1,9′-Xanthene]-3-Thione

A novel probe, 3′,6′ - bis(diethylamino) -2- ((2,4-dimethoxybenzylidene)amino) spiro [isoindoline-1,9′-xanthene]-3-thione (RBS), was designed and synthesized. Its structure was characterized with elemental analysis, IR spectra and ¹H NMR. The probe displayed highly selective and sensitive recognition of Hg²⁺. Reacting with mercury ions in aqueous solution, its fluorescence intensity was enhanced significantly, while its color was changed from colorless to pink. So, a new fluorescence method of detection of Hg²⁺ was proposed. Its dynamic response concentration range and detection limit for Hg²⁺ were 5.00?×?10^?9 M to 1.00?×?10^?6 M detected and 1.83?×?10^?9 M, respectively. Satisfying results were obtained when the probe was applied to detect spiked Hg²⁺ in samples.     

A selective sensor for nanolevel detection of lead (II) in hazardous wastes using ionic-liquid/Schiff base/MWCNTs/nanosilica as a highly sensitive composite

An effective potentiometric sensor had been fabricated for the rapid determination of Pb²⁺ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder. The constructed nanocomposite electrode showed better sensitivity, selectivity, response time, response stability, and lifetime in comparison with typical Pb²⁺ carbon paste electrode for the successfully determination of Pb²⁺ ions in water and in waste water samples. The best response for nanocomposite electrode was obtained with electrode composition of 18% ionophore, 20% BMIM-PF₆, 49% graphite powder, 10% MWCNT, and 3% nanosilica. The new electrode exhibited a Nernstian response (29.76?±?0.10 mV decade^?1) toward Pb²⁺ ions in the range of 5?×?10^?9?C1.0?×?10^?1 mol L^?1 with a detection limit of 2.51?×?10^?9 mol L^?1. The potentiometric response of prepared sensor is independent of the pH of test solution in the pH range of 4.5?C8.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition, and heavy metal ions.     

Photoluminescence associated with impurity clusters in phosphorous doped silicon

Photoluminescence measurements as a function of excitation level and temperature are presented for Si(P) containing 7.5×10¹⁷ P atomd/cm³. The luminescence in Si(P) for intermediate concentrations in the range from 1×10¹⁶ to 2×10¹⁸ cm^?3 is interpreted in terms of recombination of trapped carriers at clusters of impurities.     

Oxygen-dependent Oxidation of Fe(II) to Fe(III) and Interaction of Fe(III) with Bovine Serum Albumin, Leading to a Hysteretic Effect on the Fluorescence of Bovine Serum Albumin

The serum albumin is the most abundant protein in blood plasma and the iron is essential for many cellular processes. However, the interaction between Fe³⁺ and haem-free serum albumin remains unclear. Here we provide evidence for the fact that haem-free BSA possesses one specific Fe³⁺-binding site. The binding of Fe³⁺ to BSA results in a significant quenching of the Trp fluorescence of BSA. The average apparent dissociation constant value for the interaction of Fe³⁺ and BSA is 3.46 × 10⁻⁸ ± 3 × 10⁻¹⁰ M at 37 °C and 3.30 × 10⁻⁸ ± 5 × 10⁻¹⁰ M at 25 °C, respectively, as determined by fluorescence titration. Addition of 50 μM Fe²⁺ to 1 μM BSA results in an obvious hysteretic effect on the fluorescence of BSA. The time-dependent fluorescence quenching of BSA by Fe²⁺ is not caused by the Fe²⁺-induced conformational change of BSA, but the oxygen-dependent oxidation of Fe²⁺ to Fe³⁺. Fe²⁺ undergoes an oxygen-dependent oxidation to Fe³⁺ under aerobic conditions, which is accelerated by the interaction of BSA with Fe³⁺ and extensively inhibited under anaerobic conditions. The results suggest that BSA may take part in non-transferrin bound iron transfer.     

Energy transfer from the singlet levels of diketones and dyes to lanthanide ions in nanoparticles consisting of their diketonate complexes

The energy transfer from the S ₁ levels of p-phenylbenzoyltrifluoroacetone (PhBTA) and dyes to different Ln³⁺ ions is studied in nanoparticles (NPs) composed of complexes of this diketone with Ln³⁺ and 1,10-phenanthroline (phen) and doped with dye molecules. The quenching rate constants in the NPs consisting from complexes of Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Ho³⁺, Er³⁺, and Tm³⁺ are determined from the data on the quenching of sensitized (cofluorescence) and ordinary fluorescence of coumarin 30 (C30) and rhodamine 6G (R6G). The quenching rate constants vary from ≤5 × 10¹¹ to 10¹³ s^?1 for the fluorescence quenching of PhBTA by different Ln³⁺ ions, while the quenching of dye fluorescence occurs at rates of the order of 10⁹ s^?1. In the case of complexes with the Pr³⁺ ions, the fluorescence quenching of PhBTA in NPs composed of its complexes is accompanied by sensitized luminescence of Pr³⁺. The quenching observed is due to a nonradiative energy transfer from the S ₁ states of ligands and dyes to these ions. It is shown that in NPs composed of complexes with Eu³⁺, Yb³⁺, and Sm³⁺ the cofluorescence of C30 is quenched via the electron-transfer mechanism. The study of quenching of cofluorescence and fluorescence of dyes in NPs composed of mixed complexes of La³⁺ and Nd³⁺ (Ho³⁺) shows that the observed quenching of fluorescence and cofluorescence is governed mainly by the quenching of the S ₁ state of dyes when the Nd³⁺ (Ho³⁺) content does not exceed 5–10% and by the quenching of the S ₁ state of a ligand when the Nd³⁺ (Ho³⁺) content exceeds 50%. It is assumed that the high rate constant of energy transfer from the S ₁ level of ligands to ions Pr³⁺, Nd³⁺, Ho³⁺, Er³⁺, and Tm³⁺ in NPs composed of beta-diketonate complexes is caused by exchange interactions.     

Synthesis of Water Dispersible Fluorescent Carbon Nanocrystals from <Emphasis Type="Italic">Syzygium cumini</Emphasis> Fruits for the Detection of Fe<Superscript>3+</Superscript> Ion in Water and Biological Samples and Imaging of <Emphasis Type="Italic">Fusarium avenaceum</Emphasis> Cells

In this work, water dispersible fluorescent carbon nanocrystals (NCs) were synthesized by a simple, green and low cost hydrothermal method using Syzygium cumini (jamun) as a carbon source at 180 °C for 6 h. The average size of carbon NCs was found to be 2.1 ± 0.5 nm and shown bright blue fluorescence when excited at 365 nm under UV lamp. The carbon NCs were characterized by spectroscopic (UV-visible and fluorescence, Fourier transform infrared and dynamic light scattering) and high resolution transmission electron microscopic techniques. The quantum yield of carbon NCs was found to be ~5.9 % at 438 nm emission wavelength when excited at 360 nm. It was noticed that none of the metal ions quenched the fluorescence intensity of carbon NCs at 438 nm except for Fe³⁺, indicating the formation of Fe³⁺ ion-carbon NCs complexes. The linear range was observed in the concentration range of 0.01–100 μM with the corresponding detection limits of 0.001 μM, respectively. Furthermore, the carbon NCs were used as probes for imaging of fungal (Fusarium avenaceum) cells.     

A Novel Highly Sensitive and Selective Fluorescent Sensor for Imaging Copper (II) in Living Cells

In this work, we designed and synthesized a novel quinolin-based derivative which exhibited signaling behaviors for Cu²⁺. Upon the addition of Cu²⁺ to the solution of the molecule, it displayed an obvious fluorescence quenching in a linear fashion due to the formation of a 1:1 metal–ligand complex. This fluorescent sensor exhibited a rare sensitivity toward Cu(II) (the level of magnitude could be 6?×?10^?8), a rapid response (<10 s) and also high selectivity toward Cu²⁺ over other metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Fe³⁺, Mn²⁺, Hg²⁺, Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, Zn²⁺ and Al³⁺. Simultaneously, the cell imaging experiments and filter paper test demonstrated its extensive applicability.     

Temperature and concentration quenching of mid-IR photoluminescence in iron doped ZnSe and ZnS laser crystals

Concentration dependences of the mid-IR kinetic of luminescence at ⁵E?⁵T₂ transition in Fe:ZnSe and Fe:ZnS laser samples were studied in 14–300 K temperature ranges. Radiation lifetime in Fe:ZnSe samples measured using low doped samples with iron concentration 0.1×10¹⁸ cm^?3 was estimated to be 57 μs. The magnetic susceptibility for higher doped (C_Fe=38 and 112×10¹⁸ cm^?3) Fe:ZnSe samples was found to consist of a paramagnetic Curie–Weiss behavior arising from the weakly interacting Fe²⁺ ions and a diamagnetic ZnSe contribution plus a temperature-independent, field-dependent contribution possibly arising from very small amounts of aggregated Fe.     

Synthesis and Characterization of New Light Emitter Symmetrical Phenoxazinium Salt and Its Potential Application as Sensor for Assessment of Hg2+

The sensitization of the excited triplet state of a novel symmetrical Bis(dialkylamino)phenoxazinium salt was developed in the presence of Hg²⁺. This effect was used to determine the concentration of Hg²⁺ in different water samples. The phenoxazinium salt sensor was characterized by different spectroscopic tools such as: UV, FTIR, NMR and fluorescence spectra. The sensor has an emission band at 347 nm in DMSO. Hg²⁺ in DMSO at pH 5.6 can remarkably quench the fluorescence intensity of the sensor at 347 nm and a new band was appeared at 436 nm due to the strong complex formation between Hg²⁺ and sensor. The quenching of the band intensity at 347 and the enhancement of the intensity of the new band at 436 were used to determine the Hg²⁺ in different waste water samples. The dynamic range found for the determination of Hg²⁺ concentration is 8.7?×?10^-10 – 1.4?×?10^-6 mol L^?1 with a detection limit of 5.8?×?10^?10 mol L^?1 and quantification detection limit of 1.8?×?10^-9 mol L^-1.     

Metallophilic Bond‐Induced Quenching of Delayed Fluorescence in Au25@BSA Nanoclusters

The metallophilic bond is a weak interaction between closed‐shell ions and has been widely used a probe for various sensing of toxic chemicals for environmental safety concerns. Here, the interaction between Au nanoclusters (NCs) and metallic ions (mercury (Hg²⁺) and copper (Cu²⁺) ions) is explored using steady‐state and time‐resolved luminescence and transient absorption measurements. For Hg²⁺ ions, the delayed fluorescence (DF) of bovine serum albumin (BSA) protected Au₂₅ (Au₂₅@BSA) NCs is quenched via an effective triplet state electron transfer through the metallophilic bond. However, the Cu²⁺ ions do not alter the DF in Au₂₅@BSA NCs because of the absence of the metallophilic interaction. Furthermore, for Au₈@BSA and Au₁₀@histidine, in which there are no Au⁺ ions on the surface, the fluorescence is not quenched by Hg²⁺ ions. Such a novel triplet electron transfer process through metallophilic bonds are observed and reported for the first time. The reduction of the reverse intersystem crossing is the crucial for Hg²⁺ ion sensing in the fluorescent Au₂₅@BSA NCs.     

Optical properties of Yb3+ ions in fluorophosphate glasses for 1.0 μm solid-state infrared lasers

Yb³⁺-doped fluorophosphate glasses were prepared by melt-quenching technique and characterized their spectroscopic properties to assess the laser performance parameters. The magnitude of absorption (emission) cross-sections at 975 nm for all the studied Yb³⁺-doped glasses is found to be in the range of 0.29–1.50 × 10^?20 (0.59–1.99 × 10^?20 cm²) which is much higher than those of commercial Kigre QX/Yb: 1.06 × 10^?20 (0.5 × 10^?20 cm²) laser glass. The luminescence lifetimes of ²F_5/2 level decrease (1.15–0.45 ms) with increase in Yb₂O₃ concentration (0.1–4.0 mol%). Effect of OH^? content on luminescence properties of Yb³⁺ ions has also been investigated. The effect of radiative trapping has been discussed by using McCumber (McC) and Fuchtbauer–Ladenburge (F–L) methods. The product of experimental lifetimes and emission cross-sections for 0.1 mol% Yb₂O₃-doped glass is found to be 2.28 × 10^?20 cm² ms which indicates that the higher energy storage and extraction capability could be possible. The detailed spectroscopic results suggest that the studied glasses can be considered for high-power and ultrashort pulse laser applications.