A conjugated fluorescent polymer sensor with amidoxime and polyfluorene entities for effective detection of uranyl ion in real samples

A conjugated oligoelectrolyte for the recognition of uranyl ion in aqueous and soil samples via RGB method

The development of selective and practically applicable sensors for monitoring trace uranyl ions (UO22+) in an aqueous medium is the biggest challenge. This study presents the development of a conjugated oligoelectrolyte-based probe (COE) for the selective detection of UO22+ ions in water bodies. The COE is a water-soluble probe having an organic backbone with two ionic pendants at the terminal points. It changes its color to a dark yellow selectively in the presence of UO22+ ions. This visible change was integrated with a smartphone RGB color quantification method. The COE displayed an RGB chemo-dosimeter to selectively monitor UO22+ ions without interference from other metal ions. In the parallel experiment, COE displays a spectrofluorimetric emission signal at λems. = 525 nm (with λexc. = 420 nm), which exhibits quenching of signal when interacted with UO22+ ions. The limit of detection (LOD) is found to be 3.07 × 10-2 µM and 4.50 µM by spectrofluorimetric and RGB color value methods, respectively. 1H NMR and XPS analysis investigated the mode of interaction, and it suggested that the quenching of the emission signal was due to the interaction between the electron-rich azomethine site of COE and UO22+ ion. The smartphone-based RGB color analysis makes COE a potential probe with reduced operation time and offers a fresh approach for the immediate, real-time detection of UO22+ ions in aqueous and soil samples.

An Intervention into the Diverse Utilities of Fluorenes: A Brobdingnagian Family

The keyword "Fluorene" search in SciFinder found more than 57,000 results, including high-impact journal articles, review articles, patents, books, proceedings, etc. Against this background, a detailed enquiry has been made by our group on various classes of fluorenes and their relevancy. For the past several decades, fluorene and its related compounds have experienced extensive studies, which are attributed to the vast range of applications they possess in various fields like sensors, polymers, OLED devices and even in the pharmaceutical industries. Since fluorene is an important member of the 'polyaromatic-hydrocarbon' family and has proved its relevancy in multidisciplinary areas, summarising those milestones might be worthwhile for future researchers. Here, we intend to highlight the key applications of fluorene derivatives in the form of a review article and have put much effort into consolidating some of their most imperative applications, including those in sensors and medicinal, optoelectronic and electrochemical fields. The manuscript divides the fluorene family into multiple subclasses, counting mono- and polyfluorenes, spirofluorenes, silicon-cored fluorenes, indenofluorenes, etc., based on their structure, and portrays all the critical properties of each class. Since fluorenes are globally accepted as outstanding candidates for numerous applications and practicalities, our effort may find crucial acceptance in the near future.

Tailor-designed carbon-based novel fluorescent architecture for nanomolar detection of radioactive elements U(VI) and Th(IV) in pH ± 5.0

Highly stable nitrogen-doped Graphene Quantum Dots (N-GQD) functionalized with Pamoic Acid (PA@N-GQD) are utilized for nanomolar detection of radioactive elements, Uranium (VI) and Thorium (IV), in pH ± 5.0. The absorption, fluorescence, crystalline nature, elemental composition, functional groups, and morphological state of as-prepared PA@N-GQD are evaluated by UV-visible absorption, photoluminescence, XRD, XPS, FTIR, HRTEM, FESEM, and AFM characterizations. The aqueous solution of PA@N-GQD is characterized by its spherical morphology, averaging 6.5 nm in size. PA@N-GQD exhibits a gradual decrease in fluorescence intensity at 438 nm (λex 344 nm) upon the addition of Uranium (VI) and Thorium (IV) ions. The selectivity, sensitivity, competitivity, pH, time effect, and reversibility studies of PA@N-GQDs have been carried out using the photoluminescence technique. The attained fluorescence Limit of Detection (LoD) of PA@N-GQD for Uranium (VI) and Thorium (IV) ions are 2.009 × 10-9 and 1.351 × 10-9 M, respectively. From the fluorescence titration studies of U(VI) and Th(IV), the binding constant, Stern-Volmer constant, Modified Stern-Volmer constant, association constant, and dissociation constants have been calculated separately. These aforementioned results indicate that the PA@N-GQD has a higher binding affinity towards Th(IV) than U(VI) in aqueous medium. This current research represents the development of advanced materials for environmental and analytical applications, specifically focusing on the precise detection and quantification of radioactive elements.

A novel fluorescence sensor for uranyl ion detection based on a dansyl-modified peptide

It is of great significance to sensitively and selectively detect uranyl ion (UO₂²⁺) in environmental and biological samples due to the high risks of UO₂²⁺ to human health. However, such suitable sensors are still scarce. A novel fluorescence sensor based on a dansyl-modified peptide, Dansyl-Glu-Glu-Pro-Glu-Trp-COOH (D-P5), was efficiently synthesized by Fmoc solid phase peptide synthesis. As the first linear peptide-based fluorescence sensor for UO₂²⁺, D-P5 exhibited high selectivity and sensitivity to UO₂²⁺ over 27 metal ions (UO₂²⁺, Cr³⁺, Cu²⁺, Ba²⁺, Hg²⁺, Pb²⁺, Co²⁺, Ag⁺, Fe³⁺, Ca²⁺, K⁺, Mg²⁺, Mn²⁺, Na⁺, Ni²⁺, Cd²⁺, Zn²⁺, Al³⁺, Dy³⁺, Er³⁺, Gd²⁺, Ho³⁺, La³⁺, Lu³⁺, Pr³⁺, Sm³⁺, Tm³⁺) by a turn-off fluorescence response in 10 mM HEPES buffer (pH 6.3). The effects of anions such as S^2-, NO₃^-, SO₄^2- CO₃^2-, HCOO^-, antioxidant ascorbic acid and 4-nitrophenyl acetate on the selectivity for UO₂²⁺ detection were also studies. D-P5 sensor could be used for detecting UO₂²⁺ in a good linear relationship with concentration in the range of 0-8.0 μM with a low limit of detection of 83.2 nM. Furthermore, the interaction of the sensor with UO₂²⁺ was characterized by ESI-MS, IR, XPS and ITC measurements. The 1:1 binding stoichiometry between the sensor and UO₂²⁺ was measured by the job's plot and further verified by ESI-MS. The binding constant of the sensor with UO₂²⁺ was calculated to be 9.8 × 10⁴ M^-1 by modified Benesi-Hildebrand equation. ITC results showed that theΔH^θ andΔS^θ for the interaction of D-P5 with UO₂²⁺ were -(7.167 ± 1.25) kJ·mol^-1 and 66.5 J·mol^-1·K^-1, respectively. Time-resolved fluorescence spectroscopy indicated that the mechanism of fluorescence quenching of D-P5 by UO₂²⁺ ion was static quenching process. In addition, this sensor displayed a good practicality for UO₂²⁺ detection in lake water sample without tedious sample pretreatment.

Simultaneous detection and separation of uranium based on a fluorescent amidoxime-functionalized covalent organic polymer

To ensure the long-term sustainable development of nuclear energy as well as the prevention and control of uranium pollution, new materials that can simultaneously detect and separate uranium are still urgently needed. Herein, a new fluorescent covalent organic polymer (COP), namely HT-COP-AO, was synthesized andemployed as both the fluorescent probe and absorbent for simultaneous uranium detection and separationconsidering its excellent fluorescence property and strong uranium coordination ability. The results showed that the fluorescence of HT-COP-AO was quickly quenched by uranium within 2 min, and the limit of detection was 0.23 µM (3σ/K). Further studies implied that uranium was coordinated with the amidoxime groups of HT-COP-AO through U-N and O = U = O bonds, which resulted in electron transfer from uranium to HT-COP-AO and quenching the fluorescence of HT-COP-AO consequently. Meanwhile, HT-COP-AO exhibited excellent absorption ability towards uranium, and the maximum absorption capacity (q_max = 401.3 mg/g) was higher than most reported amidoxime modified materials. The HT-COP-AO also showed high selectivity for both uranium detection and separation which makes it a great promising for uranium monitoring in real water samples.

Real scenario of metal ion sensor: is conjugated polymer helpful to detect hazardous metal ion

Metal ions from natural and anthropogenic sources cause pollution to society and the environment is major concern in the present scenario. The deposition and contamination of metal ions in soil and water affect the biogeochemical cycles. Thus, it threatens the everyday life of living and non-living organisms. Reviews on the detection of metal ions through several techniques (Analytical methods, electrochemical techniques, and sensors) and materials (Nanoparticles, carbon dots (quantum dots), polymers, chiral molecules, metal-organic framework, carbon nanotubes, etc.) are addressed separately in the present literature. This review reveals the advantages and disadvantages of the techniques and materials for metal ion sensing with crucial factors. Furthermore, it focus on the capability of conjugated polymers (CPs) as metal ion sensors able to detect/sense hazardous metal ions from environmental samples. Six different routes can synthesize this type of CPs to get specific properties and better metal ion detecting capability in vast research areas. The metal ion detection by CP is time-independent, simple, and low cost compared to other materials/techniques. This review outlines recent literature on the conjugated polymer for cation, anion, and dual ion sensors. Over the last half decades published articles on the conjugated polymer are discussed and compared.

Platinum complexation with glutamate amino acid: Computational study

In this research work, complex formation of platinum (Pt) metal particle with the glutamate (Glu) amino acid was investigated by performing density functional theory (DFT) calculations. Such application could be very much important regarding the importance of developing metal based biosensors for biological media. To achieve the purpose of this work, two spin numbers of 0 and 1 were considered for Pt for locating separately towards neutral and anionic forms of Glu for Pt / Glu complexes formations. The obtained results of optimization and QTAIM analyses indicated various configurations for different spin numbers of Pt metal particle towards each of neutral and anionic forms of Glu. Existence of covalent bond was observed for most cases in addition to existence of weak van der Waals interactions for the complexes.

CO and NO selective adsorption by a C16Mg8O8 nanocage: A DFT Study

Density functional theory (DFT) calculations were performed to stabilize a representative C16Mg8O8 nanocage derived from C32 and Mg16O16 counterparts for selective adsorption of carbon monoxide (CO) and nitrogen monoxide (NO) gaseous molecules. After obtaining optimized structures, molecular features were evaluated for describing the model systems. Diagrams of density of states (DOS) revealed that the energy differences between frontier molecular orbital levels of the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) of the stabilized C16Mg8O8 nanocage could provide a more proper semiconductor in comparison with each of the original C32 and Mg16O16 cages. To explore the advantage of such C16Mg8O8 nanocage for CO and NO gases adsorption, molecular descriptors such as energies, geometries, and electronic structures were characterized for all possible adsorption configurations of bimolecular formation of gas . . .  nanocage. Significant changes of HOMO and LUMO levels besides the values of corresponding energy gaps of C16Mg8O8 nanocage in singular and bimolecular systems could help to recognize adsorption of each of CO and NO gaseous molecules. Furthermore, more variations of energy gaps in the process of gas . . .  nanocage bimolecular formation could lead to more sensitivity of nanocage for detection of adsorbed gases. As a consequence, the investigated C16Mg8O8 nanocage was introduced for differential recognition of CO and NO gases regarding several environmental health issues.

Naked-eye colorimetric and turn-on fluorescent Schiff base sensor for cyanide and aluminum (III) detection in food samples and cell imaging applications

A new efficient Schiff base sensor SB3 for fluorescent and colorimetric "naked-eye" "turn-on" sensing of cyanide anion (CN^-) with excellent sensitivity and selectivity was developed. The 4,4'-(perfluoropropane-2,2-diyl)bisphenol group and two phenyl groups were covalently linked by two C = N bonds to extend the conjugation length. The four hydroxyl groups can improve the water solubility of the SB3 sensor. The SB3 sensor exhibited high specificity towards CN^- by interrupting its intramolecular charge transfer, resulting in a color change and remarkable "turn-on" green fluorescence emission. The sensing mechanism is caused by the nucleophilic addition of CN- toward imine groups of the SB3 sensor, leading to breaks of the conjugation, fluorescent spectral changes, and color change. It was confirmed by ¹H NMR titration and Mass spectra. The detection limits for CN^- and Al³⁺obtained by fluorescence spectrum are 0.80 µM and 0.25 µM, respectively. The SB3 sensor can act as an efficient chemical sensor for detecting the CN^- and Al³⁺ ions under common environmental and physiological conditions (pH 5-12). Besides, the sensor can also detect CN^- in food materials (such as sprouting potatoes and cassava flour) and imaging CN^-in living cells with strong "turn-on" fluorescence at 490 nm. SB3 is an excellent CN^- sensor that exhibits some advantages, including easy synthesis, distinct fluorescence and color change, high selectivity, low detection limit, and good anti-interference ability to analyze solution and food samples, together with fluorescence cell imaging.

Adsorption of Metallic Ions on Amidoxime-Chitosan/Cellulose Hydrogels

Adsorption using natural compounds is an attractive separation technique for recovering heavy metals from aqueous media. Although chitosan, which is a natural polysaccharide, is an environmentally benign adsorbent, it dissolves in an acidic aqueous medium. In this study, we prepared adsorbents consisting of chitosan modified with amidoxime groups for improving metal adsorptivity, and cellulose for improving gel stability using an ionic liquid, and examined their adsorption characteristics for metal ions. The prepared amidoxime-chitosan/cellulose hydrogels had a mechanical strength without cross-linking. All the investigated metals were adsorbed on the amidoxime-chitosan/cellulose hydrogels in the following adsorptivity order: Cu ≈ Ag > Ni > Zn. The adsorptivity of the metal ions increased with pH due to a proton exchange reaction. From the Langmuir adsorption isotherm, the Langmuir constant for Cu exceeded those of other metals because amidoxime has higher Cu affinity. The pseudo-second-order reaction model best described the adsorption kinetics with metal chelate formation being the rate-determining step. Because amidoxime-chitosan/cellulose hydrogels had higher physical stability and higher Cu selectivity, they were found to be a promising, environmentally benign adsorbent.

Direct halosulfonylation of alkynes: an overview

The difunctionalization reactions of easily available and inexpensive alkynes have emerged as a reliable, powerful, and step-economical approach for the construction of highly substituted complex alkenes in a one-pot manner, without the need for isolation of intermediates. A wide variety of transformations based on this concept have been successfully achieved for the preparation of synthetically and biologically important β-halovinyl sulfone scaffolds. In this Review, we summarize the recent advances and developments in this field and present a comprehensive overview of halosulfonylation of alkyne substrates with emphasis on the mechanistic features of the reactions.

Comparing coordination uranyl(vi) complexes with 2-(1H-imidazo[4,5-b]phenazin-2-yl)phenol and derivatives

Four derivatives of 2-(1H-imidazo[4,5-b]phenazin-2-yl)phenol have been synthesized and characterized structurally using X-ray crystallography. Coordination complexes with uranyl (UO₂²⁺) and copper (Cu²⁺) were prepared and absorption/emission spectra detailed. We observed increased fluorescence upon uranyl binding, in stark contrast to rapid quenching observed with the addition of copper. These phenomena have been further examined by DFT computational methods.

An indolino-spironaphthooxazine probe for colorimetric detection of ferric ions in drinking water

The sensing performance of a novel indolino-spironaphthooxazine derivative (SPNO), 6′(3,4-dihydroisoquinolin-2(1H)-yl)-3,3-dimethyl-1-phenethylspiro[indoline-2,3′-naphtho[2,1-b][1,4]oxazine], was investigated for rapid colorimetric detection of ferric ions (Fe³⁺) in drinking water.