Addition Of Metal Ions Research Articles

Artificial Cascade Transformation Biosystem for One-Pot Biomanufacturing of Odd-Numbered Neoagarooligosaccharides and d-Tagatose through Wiser Agarose Utilization.

The application of agarose oligosaccharides has garnered great attention, with their biological activities varying among different structures. However, it still meets a great bottleneck for the targeted production of odd-numbered neoagarooligosaccharides (NAOSs), such as neoagarotriose (NA3), due to the lack of one-step hydrolases. In this work, the α-agarase AgaA33 and β-galactosidase BgaD were synergistically used to prepare NA3 with agarose as a substrate. Additionally, an l-arabinose isomerase CaLAI from Clostridium acetobutylicum was characterized to valorize low-value byproducts (d-galactose) by forming d-tagatose, which exhibited good thermal stability without the need for additional metal ions. Under the optimal reaction conditions, the production of NA3 and d-galactose catalyzed by these three enzymes was 0.40 and 0.15 g/L, respectively. The artificial three-enzyme-based cascade transformation system not only achieved the highest production of NA3 until now but also allowed for the valorization of d-galactose, providing a wiser application route for agarose utilization.

Impact of Metal Ions, Peroxymonosulfate (PMS), and pH on Sulfolane Degradation by Pressurized Ozonation

This study investigated the degradation of sulfolane using pressurized ozonation under varying initial concentrations and the influence of different catalysts and peroxymonosulfate activation methods on the degradation efficiency. Initial sulfolane concentrations of 1 mg L−1, 20 mg L−1, and 100 mg L−1 were tested over 120 min, revealing a degradation efficiency of 73%, 41%, and 18%, respectively. The addition of various metal ions (Zn2+, Mg2+, Cu2+, Ni2+, and Co2+) demonstrated that only zinc and magnesium enhanced degradation, with zinc achieving a 92% removal efficiency and magnesium achieving 86%. Different doses of magnesium and zinc were further tested, showing optimal degradation at specific concentrations. The combination of PMS with ozonation was explored, revealing that zinc activation did not significantly enhance degradation, while NaOH activation achieved near-total degradation, with a 100 mg L−1 NaOH concentration. Varying PMS concentrations indicated that altering pH was more effective than changing PMS dosage. Finally, the impact of pH changes in both reverse osmosis water and tap water matrices confirmed that higher pH levels significantly improved degradation efficacy, achieving up to 98% removal with NaOH concentrations of 50 mg L−1 in reverse osmosis water. These results suggest that optimizing pH and catalyst type are critical for enhancing sulfolane degradation in pressurized ozonation systems.

Detection of Silver and Mercury Ions Using Naphthalimide-Based Fluorescent Probe.

A multifunctional fluorescent probe P based on a naphthalimide derivative for the detection of Ag+ and Hg2+ through a dual-signal was designed and characterized. P exhibited a large Stokes shift (107 nm), high selectivity, good sensitivity, and fast response time. By adjusting the testing medium and the order of reagent addition, multifunctional detection with P was achieved. The addition of Ag+ or Hg2+ to P solution in either ethanol or an ethanol-water mixture resulted in a significant quenching of fluorescence emission at 537 nm and caused a decrease in the absorbance at 440 nm accompanied by the appearance of a new absorption peak at around 340 nm, and there was an obvious color change from yellow to colorless. In contrast, the addition of other common metal ions and anions did not produce substantial spectral or color changes. The detection limit of probe P for Ag+ and Hg2+ was calculated to be 0.33 μM. The sensing mechanism was proposed and validated through MS and 1H NMR spectrometry methods. Additionally, P demonstrated the capability to recognize Ag+ and Hg2+ in living cells with satisfactory results.

Metal Peroxide Nanoparticles for Modulating the Tumor Microenvironment: Current Status and Recent Prospects.

Background: The significant expansion of nanobiotechnology and nanomedicine has led to the development of innovative and effective techniques to combat various pathogens, demonstrating promising results with fewer adverse effects. Metal peroxide nanoparticles stand out among the crucial yet often overlooked types of nanomaterials, including metals. These nanoparticles are key in producing oxygen (O2) and hydrogen peroxide (H2O2) through simple chemical reactions, which are vital in treating various diseases. These compounds play a crucial role in boosting the effectiveness of different treatment methods and also possess unique properties due to the addition of metal ions. Methods: This review discusses and analyzes some of the most common metal peroxide nanoparticles, including copper peroxide (CuO2), calcium peroxide (CaO2), magnesium peroxide (MgO2), zinc peroxide (ZnO2), barium peroxide (BaO2), and titanium peroxide (TiOx) nanosystems. These nanosystems, characterized by their greater potential and treatment efficiency, are primarily needed in nanomedicine to combat various harmful pathogens. Researchers have extensively studied the effects of these peroxides in various treatments, such as catalytic nanotherapeutics, photodynamic therapy, radiation therapy, and some combination therapies. The tumor microenvironment (TME) is particularly unique, making the impact of nanomedicine less effective or even null. The presence of high levels of reactive oxygen species (ROS), hypoxia, low pH, and high glutathione levels makes them competitive against nanomedicine. Controlling the TME is a promising approach to combating cancer. Results: Metal peroxides with low biodegradability, toxicity, and side effects could reduce their effectiveness in treating the TME. It is important to consider the distribution of metal peroxides to effectively target cancer cells while avoiding harm to nearby normal cells. As a result, modifying the surface of metal peroxides is a key strategy to enhance their delivery to the TME, thereby improving their therapeutic benefits. Conclusions: This review discussed the various aspects of the TME and the importance of modifying the surface of metal peroxides to enhance their therapeutic advantages against cancer, as well as address safety concerns. Additionally, this review covered the current challenges in translating basic research findings into clinical applications of therapies based on metal peroxide nanoparticles.

Catalytic benzylation of arenes using metal-ion modified HY zeolites for sustainable synthesis

Microporous zeolites are commonly employed as catalysts for the benzylation of arenes and benzyl alcohol. However, their catalytic efficiency is often compromised by diffusion limitations, particularly in reactions involving larger arenes. In this study, we developed metal-ion modified HY zeolites using Zn, Mg, and Ni as dopants and investigated their catalytic performance in the benzylation of a range of arenes, including toluene, benzene, mesitylene, p-xylene and with benzyl alcohol (BzOH). The structural and acidic properties of the modified HY zeolites were characterized using a combination of techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, Fourier-transform infrared (FTIR) spectroscopy, ammonia temperature-programmed desorption (NH₃-TPD), and proton magic angle spinning nuclear magnetic resonance (1H MAS NMR) spectroscopy. The presence of catalytically active Brønsted acid sites (BAS) was detected by 1H MAS NMR spectroscopy and it was demonstrated that the HY zeolite's acidity is considerably modulated by the addition of metal ions. The catalytic evaluations indicated that the metal-ion modified HY zeolites exhibited superior activity compared to unmodified HY zeolite, with the catalytic performance following the order Zn/HY > Ni/HY > Mg/HY > HY for the benzylation of benzyl alcohol with mesitylene. Further investigation into the mechanism revealed that the synergistic effect of metal ions and acidity plays a crucial role in enhancing the accessibility of arenes to the surface catalytic sites and thereby improving catalytic performance. These findings underscore the importance of the metal-acidity synergy in optimizing the catalytic efficacy of modified HY zeolites for selective benzylation reactions.

Exploring the antiviral activities of the FDA-approved drug sulfadoxine and its derivatives against Chikungunya virus.

Currently, there is no antiviral licensed to treat chikungunya fever, a disease caused by the infection with Alphavirus chikungunya (CHIKV). Treatment is based on analgesic and anti-inflammatory drugs to relieve symptoms. Our study aimed to evaluate the antiviral activity of sulfadoxine (SFX), an FDA-approved drug, and its derivatives complexed with silver(I) (AgSFX), salicylaldehyde Schiff base (SFX-SL), and with both Ag and SL (AgSFX-SL) against CHIKV. The anti-CHIKV activity of SFX and its derivatives was investigated using BHK-21 cells infected with CHIKV-nanoluc, a marker virus-carrying nanoluciferase reporter. Dose-response and time of drug-addition assays were performed in order to assess the antiviral effects of the compounds, as well as in silico data and ATR-FTIR analysis for insights on their mechanisms of action. The SFX inhibited 34% of CHIKV replication, while AgSFX, SFX-SL, and AgSFX-SL enhanced anti-CHIKV activity to 84%, 89%, and 95%, respectively. AgSFX, SFX-SL, and AgSFX-SL significantly decreased viral entry and post-entry to host cells, and the latter also protected cells against infection. Additionally, molecular docking calculations and ATR-FTIR analysis demonstrated interactions of SFX-SL, AgSFX, and AgSFX-SL with CHIKV. Collectively, our findings suggest that the addition of metal ions and/or Schiff base to SFX improved its antiviral activity against CHIKV.

3D Printable κ‐Carrageenan‐Based Granular Hydrogels

Abstractκ‐carrageenan, an algae‐extracted polysaccharide known for its emulsifying properties, is widely used in food and beauty products. Because of its abundance in nature, similarity to natural glycosaminoglycans, and biocompatibility, it is a promising alternative to animal gelatin for tissue engineering. Key to the more widespread use of κ‐carrageenan for biomedical applications is its processability, which is hampered by its temperature‐dependent rheological properties. Here, a κ‐carrageenan‐based ink is introduced that can be 3D printed at room temperature through direct ink writing (DIW). This is achieved by formulating κ‐carrageenan as microgels that are covalently crosslinked through a second network, resulting in double network granular hydrogels (DNGHs). These DNGHs can be stiffened to reach stiffnesses up to 0.9 MPa under tension and 1.1 MPa under compression through the addition of metal ions and glucose. The metal/glucose reinforcement also increases the work of fracture up to 1.1 MJ m−3, exceeding that of unmodified κ‐carrageenan DNGHs 50‐fold. The potential of the ink by room temperature 3D printing cm‐sized free‐standing load‐bearing structures is demonstrated. This ink is envisaged to be a well‐suited algae‐derived alternative for the animal‐based gelatin for tissue engineering and in food applications for example as soft confectionery products.

Elucidating the Transition of 3D Morphological Evolution of Binary Alloys in Molten Salts with Metal Ion Additives.

Molten salts serve as effective high-temperature heat transfer fluids and thermal storage media used in a wide range of energy generation and storage facilities, including concentrated solar power plants, molten salt reactors and high-temperature batteries. However, at the salt-metal interfaces, a complex interplay of charge-transfer reactions involving various metal ions, generated either as fission products or through corrosion of structural materials, takes place. Simultaneously, there is a mass transport of ions or atoms within the molten salt and the parent alloys. The precise physical and chemical mechanisms leading to the diverse morphological changes in these materials remain unclear. To address this knowledge gap, this work employed a combination of synchrotron X-ray nanotomography and electron microscopy to study the morphological and chemical evolution of Ni-20Cr in molten KCl-MgCl2, while considering the influence of metal ions (Ni2+, Ce3+, and Eu3+) and variations in salt composition. Our research suggests that the interplay between interfacial diffusivity and reactivity determines the morphological evolution. The summary of the associated mass transport and reaction processes presented in this work is a step forward toward achieving a fundamental comprehension of the interactions between molten salts and alloys. Overall, the findings offer valuable insights for predicting the diverse chemical and structural alterations experienced by alloys in molten salt environments, thus aiding in the development of protective strategies for future applications involving molten salts.

Development and Characterization of a Tunable Metal-Organic Framework (MOF) for the Synthesis of a Rare Sugar D-Tagatose.

D-tagatose is a valuable rare sugar with potential health benefits such as antiobesity, low-calorie, prebiotic, and anticancer. However, its production is mainly depending on chemical or enzymatic catalysis. Herein, a cobalt-based metal-organic framework (MOF) was developed at room temperature in an aqueous system using a self-assembly method. The L-arabinose isomerase (L-AI) was immobilized into this unique MOF by an in situ encapsulation process. The morphology and structural aspects of the MOF preparations were characterized by different analytical techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Moreover, thermogravimetric analysis (TGA) suggested the high thermal stability of the L-AI@MOF. Significantly, the immobilized catalyst exhibited enhanced catalytic efficiency (kcat/Km) of 3.22mM-1s-1 and improved turnover number (kcat) of 57.32s-1. The L-AI@MOF efficiently catalyzes the synthesis of D-tagatose from D-galactose up to the equilibrium level (~ 50%) of isomerization in heterogeneous catalysis. Interestingly, L-AI@MOF was found stable and reusable for more than five cycles without the requirement of additional metal ions during catalysis. Thus, L-AI stabilized in the MOF system demonstrated a higher catalytic activity and potential guidance for the sustainable synthesis of rare sugar D-tagatose.

Emulsion liquid membrane (ELM) enhanced by nanoparticles and ionic liquid for extracting vanadium ions from wastewater.

Emulsion liquid membrane (ELM) stands out as an extraction process that has drawn much attention due to its promising prospects in industrial wastewater treatment technology. Nevertheless, the pivotal challenge is to reach high membrane stability to overcome the obstacle of applying ELM at the industrial scale. In this study, ELM was boosted by using nanoparticles (superparamagnetic iron oxide (Fe2O3)) in the stripping phase (W1) and ionic liquid (1-methyl-3-octyl-imidazolium-hexafluorophosphate [OMIM][PF6) in the oil phase (O) for recovering/extracting vanadium from synthetic wastewater to near completion and at the same time enhancing emulsion stability to be appropriate for industrial application. The vanadium recovery/extraction percentage has been raised significantly in 3min to 99.6% when adding 0.01% (w/w) Fe2O3 NPs (20 to 50nm in size) in the internal phase (W1) and 5% (v/v) [OMIM]PF6 ionic liquid in the oil phase (O). Also, the emulsion stability was considerably improved, and the leakage percentage was reduced to 16% after 3days. The results of this study could be used in the future to remove additional heavy metal ions from industrial effluents.

Computational insights into the underlying mechanism of zinc ion-specificity of the fluorescent probe, BDA-1

Ion specificity is crucial for developing fluorescence probes. Using a recently reported optical sensor (BDA-1) of Zn2+ as a representative, we carried out extensive quantum chemical calculations on its photophysical properties using density function theory. According to the calculated optimized geometries, excitation energies and transition oscillator strengths, the weak fluorescence of BDA-1 observed in experiments is attributed to the suppression of fluorescence emission by efficient internal conversion, rather than the previously proposed photoinduced electron transfer (PET) mechanism. With the addition of Zn2+ or Cd2+ ions, the tetradentate chelates [M:BDA-1-H+]+ (M=Zn, Cd) are produced. According to frontier molecular orbital and interfragment charge transfer analyses of these complexes, PET is preferentially confirmed to occur upon photo-excitation. Notably, as one coordination bond in the excited [Cd:BDA-1-H+]+ complex is significantly weakened in comparison to that of [Zn:BDA-1-H+]+, their molecular orbital compositions in the S1 state are completely different. As a result, absorption and radiation transitions of [Zn:BDA-1-H+]+ both have considerable oscillator strength, while fluorescence radiation from the excited [Cd:BDA-1-H+]+ is doubly suppressed. This difference causes that the fluorescence intensity of BDA-1 is sensitive to the addition of metal ions, and exhibits the zinc ion-specificity.

A novel dual channel six-membered spirorhodamine for Cu2+ and ClO- depending on solvent and application in real samples and bioimaging

To reveal the solvent dependence of six-membered rhodamine spirocycles (SMRS), a new probe SM-RB has been synthesized and investigated the spectral properties in different solvents upon the addition of various metal ions and anions. SM-RB exhibited high selectivity for Cu2+ in CH3CN/HEPES and ClO- in C2H5OH/HEPES solutions, respectively. The spectral changes of SM-RB in the presence of ClO- in C2H5OH/HEPES solution were much less than that of Cu2+ in CH3CN/HEPES. The detection limit of Cu2+ was as low as 36 nM (fl) in CH3CN/HEPES. The kinetic equilibration time (8 s) indicated that the two solvent systems did not delay the spectral response speed to Cu2+ and ClO-. Solvent systems influenced the pKa value of SM-RB in CH3CN/HEPES and C2H5OH/HEPES. The pKa value of SM-RB was 4.34 (±0.7) (Abs) and 4.75 (±0.14) (Fl) in CH3CN/H2O, but can’t be exactly calculated by pH titration in C2H5OH/H2O. The reversibility and Job plot of SM-RB were investigated to propose the response mechanism of SM-RB with Cu2+ and ClO- in the two solvent systems. Finally, SM-RB not only can be used for the quantitative detection of copper ions in grape peel, but also can real-time monitor the fluctuation of Cu2+ in lysosomal pools.

Versatile Solvatochromic fluorophores based on Schiff bases for colorimetric detection of metal ions

In recent years, fluorescent probes have been extensively studied as powerful tools for the effective assessment of toxic metal ions due to their high sensitivity, selectivity, capability for real-time and non-invasive monitoring, and versatility. In this paper, novel fluorescent probes based on Schiff bases, namely 2-((1E,2E)-1-(6-chlorobenzo[d]thiazol-2-ylimino)-3-(4-(dimethylamino)phenyl)allyl)phenol (1) and 2-((1E,2E)-3-(4-(dimethylamino)phenyl)-1-(4-methylbenzo[d]thiazol-2-ylimino)allyl)phenol (2), were synthesized and characterized. The optical properties of these probes were examined across a spectrum of fourteen solvents with varying polarities, revealing significant solvatochromic effects on both absorption and fluorescence spectra. The analysis delineated a discernible difference in dipole moment between electronic ground and excited states, with molecules exhibiting enhanced stabilization in singlet excited states. Subsequently, a straightforward method was devised for the selective and sensitive detection of diverse metal ions in aqueous solutions, including K+, V3+, Cr3+, Fe3+, Co2+, Ni2+, Cu2+, Se6+, Cd2+, Ba2+, and Hg2+, through naked eye observation, UV–Visible, and fluorimetric measurements. Notably, the UV–Vis spectra of probes 1 and 2 manifested a significant red shift upon the addition of metal ions, indicative of potential ligand-to-metal charge-transfer (LMCT) phenomena, with the exception of Ni2+, Cu2+, and Se6+ions. The observed alterations in optical absorption and fluorescence emission contributed to the probes' heightened selectivity and sensitivity, obviating the necessity for sample pretreatment. Competitive assays underscored the probes' preference for Cr3+ and V3+ ions over other common metal ions. Furthermore, Job's plot analysis suggested a 1:1 ligand-to-metal molar ratio binding. The investigated Schiff bases exhibited elevated binding constants (Ka), low detection limits, and limits of quantification, alongside diminished fluorescence quantum yield. Leveraging fluorescence quenching, facile paper-based sensor strips coated with Schiff bases facilitated prompt, qualitative, and quantitative in situ detection of metal ions in aqueous solutions across a broad concentration spectrum, discernible to the naked eye under UV light.

A hydrogel based on Fe(II)-GMP demonstrates tunable emission, self-healing mechanical strength and Fenton chemistry-mediated notable antibacterial properties.

Supramolecular hydrogels serve as an excellent platform to enable in situ reactive oxygen species (ROS) generation while maintaining controlled localized conditions, thereby mitigating cytotoxicity. Herein, we demonstrate hydrogel formation using guanosine-5'-monophosphate (GMP) with tetra(4-carboxylphenyl) ethylene (1) to exhibit aggregation-induced emission (AIE) and tunable mechanical strength in the presence of divalent metal ions such as Ca2+, Mg2+, and Fe2+. The addition of divalent metal ions leads to structural transformation in the metallogels (M-1GMP). Furthermore, the incorporation of Fe2+ ions into the hydrogel (Fe-1GMP) promotes the Fenton reaction that could be upregulated upon adding ascorbic acid (AA), demonstrating antibacterial efficacy via ROS generation. In vitro studies on AA-loaded Fe-1GMP demonstrate excellent bacterial killing efficacy against E. coli, S. aureus and vancomycin-resistant enterococci (VRE) strains. Finally, in vivo studies involving topical administration of Fe-1GMP to Balb/c mice with skin infections further suggest the potential antibacterial efficacy of the hydrogel. Taken together, the hydrogel with its unique combination of mechanical tunability, ROS generation capability and antibacterial efficacy can be used for biomedical applications, particularly in wound healing and infection control.

Viscosity reduction of xanthan gum through free radical mechanisms mediated by ascorbic acid

Xanthan gum (XG) is a widely used thickener known for its high viscosity and excellent stability. However, the presence of ascorbic acid (AA) leads to a clear decrease in its viscosity, thereby affecting the application of xanthan gum in food products containing AA. Therefore, the aim of this study was to uncover the mechanism by which AA reduces the viscosity of xanthan gum. Ascorbic acid (0.1 mmol/L) caused a viscosity loss reaching up to 96% for xanthan gum solutions (2 g/L). The reaction was further enhanced by heating at 60 °C for 1 h without stirring, a weakly acidic system at pH 5.4, and the addition of hydrogen peroxide or metal ions (Fe2+ and Cu2+). Interestingly, AA induction produces free radicals and changes in their content correlate with a decrease in XG viscosity. Moreover, removing dissolved oxygen by heating and nitrogen purging treatment effectively reduced AA-derived free radical levels and prevented the decrease in XG viscosity. The decrease in viscosity of XG caused by AA involved its free radicals generated through an oxygen-dependent pathway.

Metal Ions Trigger the Gelation of Cysteine‐Containing Peptide‐Appended Coordination Cages

AbstractWe report a series of coordination cages that incorporate peptide chains at their vertices, prepared through subcomponent self‐assembly. Three distinct heterochiral tripeptide subcomponents were incorporated, each exhibiting an L−D−L stereoconfiguration. Through this approach, we prepared and characterized three tetrahedral metal‐peptide cages that incorporate thiol and methylthio groups. The gelation of these cages was probed through the binding of additional metal ions, with the metal‐peptide cages acting as junctions, owing to the presence of sulfur atoms on the peripheral peptides. Gels were obtained with cages bearing cysteine at the C‐terminus. Our strategy for developing functional metal‐coordinated supramolecular gels with a modular design may result in the development of materials useful for chemical separations or drug delivery.

Metal Ions Trigger the Gelation of Cysteine-Containing Peptide-Appended Coordination Cages.

We report a series of coordination cages that incorporate peptide chains at their vertices, prepared through subcomponent self-assembly. Three distinct heterochiral tripeptide subcomponents were incorporated, each exhibiting an L-D-L stereoconfiguration. Through this approach, we prepared and characterized three tetrahedral metal-peptide cages that incorporate thiol and methylthio groups. The gelation of these cages was probed through the binding of additional metal ions, with the metal-peptide cages acting as junctions, owing to the presence of sulfur atoms on the peripheral peptides. Gels were obtained with cages bearing cysteine at the C-terminus. Our strategy for developing functional metal-coordinated supramolecular gels with a modular design may result in the development of materials useful for chemical separations or drug delivery.

Regulation effects on naphthalimide self-assembly system by terminal pyridine isomers and the coordination of metal ions

Three novel naphthalimide-based gelators (NAPP, NAMP and NAOP) linked three different amines: 4-(aminomethyl)pyridine, 3-(aminomethyl)pyridine, or 2-(aminomethyl)pyridine were designed and synthesized. NAPP, NAMP and NAOP could self-assemble into fluorescent gels in some solvents and formed a variety of morphologies. The self-assembly behaviors of three gelators in DMSO/H2O (10/1, v/v) were characterized by UV–vis absorption, fluorescence, Fourier transform infrared (FTIR), X-ray diffractions (XRD) and water contact angle experiment, and the effect of different N sites in pyridine in this self-assembly system was investigated. On the base of coordination ability of pyridine groups to metal ions, the self-assembly process could be regulated by the addition of metal ions. NAPP, NAMP and NAOP solutions had highly selective and ultrafast fluorescence detection capabilities for Fe3+ with a low limit of detection. The self-assembly structure and surface wettability of the gel self-assembly system could be adjusted by adding metal ions. The hydrophobic surface of xerogels NAPP and NAMP is transformed into a hydrophilic surface at the present of Fe3+. And the hydrophilic and hydrophobic surfaces of NAPP and NAMP could realize the transformation of hydrophilic and hydrophobic surfaces by the coordination of metal ions. This study provided a way for regulating the self-assembly process by the distance between the N site on pyridine and the amide segment and metal coordination.

Pyridine-2,6-Dicarboxylic Acid As a Facile and Highly Selective "Turn-Off" Fluorimetric Chemosensor for Detection of Cu (II) Ions in Aqueous Media.

Copper metal is third most abundant trace element in human body. Determination of Cu (II) ions is a burning topic in field of environment protection and food safety because of its significant impact on ecosystem. In this study, 2,6-pyridine dicarboxylic acid (PDA) has been explored as "turn-off" florescent probe for florescent detection of Cu (II) ions. This sensor showed highly selective complexing ability towards Cu (II) ions. Addition of aqueous solution of Cu (II) ions remarkably quenched the fluorescence intensity of PDA while, on contrary, there was no any prominent fluorescence quenching interference on addition of various metal ions. The binding mode of PDA and Cu (II) ions was determined as stoichiometry of 1:1 and it was further confirmed by single crystal XRD analysis. Mechanisms of static and dynamic quenching were confirmed by stern-volmer plot. Limit of detection (LOD) and limit of quantification (LOQ) for Cu (II) ions was calculated as 3.6 µM and 1.23 µM respectively, which is far below the acceptable value (31.5µM) according to the World Health Organization. The use of the sensor for detection of Cu (II) ions in real samples in aqueous media was also performed.

A band gap and photoluminescence properties engineering in BaO semiconductor for ultraviolet (UV) photodetector applications: A comprehensive role of co-doping

We report on ultra-violet (UV) photodetectors based on BaO nanoparticles by the detailed investigation of band gap and photoluminescence properties. The BaO nanomaterials were fabricated by the modified sol–gel technique. The innovation of co-doping can modulate the photoluminescence or sensing properties by narrowing the band gap related to enhancing the high carrier concentration, higher electronic lifetime, and low carriers recombination. It is investigated that the BaO nanoparticles with co-doping reveals a highly reduced band gap and exceptional photoluminescence properties as compared to the pristine BaO nanoparticles due to hindering carrier,s recombination for Ultra-violet (UV) photodetectors. The optical studies revealed that the addition of co-dopants in BaO host material creates new energy sites, so the band gap declines up to 1.31 eV as compared to that of pristine BaO (1.36 eV). The photoluminescence properties recorded with photoluminescence (PL) spectroscopy were recorded which revealed the decrease in PL intensity due to the hindering of carriers recombination with the addition of co-dopant metal ions. Furthermore, the inclusion of co-dopant metals results in an improvement in electrical conductivity because of a decline in carrier recombination, according to an I-V characteristic study. This factor contributes to enhance the photoluminescence properties of BaO which, in turn, contributes to enhance the sensing capability of the photodetector device. These obtained features modify optoelectronic properties are far superior as compared to that of previously reported literature on BaO nanomaterials, and the synthesized BaO semiconductor material becomes a potential candidate for efficient use in the ultraviolet (UV) photodetectors device applications.