Detection Of Anions Research Articles

Colorimetric detection of anionic surfactant using polydiacetylene/zinc (II)/zinc oxide nanocomposites with unique yellow-to-red color transition

Polydiacetylenes (PDAs) have extensively received attention as colorimetric sensors because of their stimulus-responsive properties. This contribution presents a simple technique to modify polydiacetylene/zinc (II) ion/zinc oxide (PDA/Zn2+/ZnO) nanocomposites for colorimetric detection of an anionic surfactant. Incorporation of cetyltrimethylammonium bromide (CTAB) into the nanocomposite structure is achieved through a simple mixing process in an aqueous medium. Interestingly, the resultant PDA/Zn2+/ZnO-CTAB sensors exhibit a unique yellow-to-red color change in response to the anionic surfactant, sodium dodecyl sulfate (SDS). Furthermore, the colorimetric detection of SDS at different concentrations can be achieved by varying the added CTAB concentrations. The detectable concentration range of SDS in this study extends from 0.3 to 7 mM. Our study offers a simple and low-cost method to fabricate colorimetric sensors for anionic surfactant detection using PDA materials.

Preparation of Ba4Lu3F17:Tb3+ fluorescent sensor and its detection for [formula omitted] and 4-NP

Quantitative detection of permanganate (MnO4‐) and 4-nitrophenol (4-NP) is essential for environmental safety. Fluorescence detection technology is one of the most widely used detection technologies, which can be used for the detection of various anions and organic pollutants. In this paper, Ba4Lu3F17:Tb3+ phosphors were successfully obtained by hydrothermal method. The morphology transition of Ba4Lu3F17 crystal from nanoparticles through octahedron to hexagonal prism was realized in the pH range of 3–11. The best luminescent samples were obtained by changing the type of additives and the doping concentration of Tb3+ ions. The obtained Ba4Lu3F17:Tb3+ has high selectivity and anti-interference for MnO4‐ and 4-NP detection, with the detection limits being 0.79 μM and 1.28 μM, respectively.

Increasing the selectivity of optical anion sensors with cationic extracting agents

ABSTRACT Anions play an important role in our life, from storing our genetic code on the polyanion DNA, to being the active ingredient in agricultural fertilisers and other industrial processes. Consequently, chemists have been designing systems that can sense anionic species through a variety of methods, such as unimolecular chromophores or sensor arrays. Nonetheless, most existing sensing approaches still have some drawbacks, particularly related to obtaining adequate selectivity and achieving sensing of anions in aqueous environments. In this manuscript, we report a liquid–liquid extraction (LLE)-based sensing approach that allows the conversion of non-selective optical anion sensors that only work in organic media, into selective sensing systems that allow detection of anions in water. We tested this approach on deprotonation-based anion sensors (alizarin, naphthol AS, 4-nitrophenol, BI-Lawsone, and chromophore 1) and hydrogen bonding-based anion sensors (1,2-diaminoanthraquinone and 4-nitro-1,2-phenylenediamine). In general, the deprotonation-based sensors could be converted from a non-selective sensor for basic anions (NCO¯, H2PO4¯, AcO¯ and F¯) to a selective sensing system for NCO¯ with the aid of carefully chosen tetraalkylammonium salts as extracting agents. On the other hand, the hydrogen-bonding based sensors could be converted to a selective sensing system for the hydrophobic anion ClO4¯ using similar tetraalkylammonium salts.

A simple Cu(II)-dppy complex for selective detection of hazardous sulfide anion in water and its application in DNA and BSA binding

The traditional hazardous sulfide species (S2–, HS–, and H2S) are widely dispersed throughout the environment and have widespread applications in various industrial processes. Despite numerous applications, excessive exposure to sulfide species can lead to several chronic diseases. In light of the importance of sulfide detection in water, we have reported a novel water-soluble 1:2 copper complex ([CuL2]Cl2) of 2,2′-(4-(3,4-dimethoxyphenyl)pyridine-2,6-diyl)dipyrazine ligand L. The [CuL2]Cl2 receptor has been utilized for the sulfide detection in the vicinity of other anions of higher concentration (ten equivalents of F−, I−, Br−, Cl−, H2PO4−, NO3− HCO3−, OH−, CH3CO2−, SO42−, CO32−, P2O74- (PPi), SO32−, HPO42−, S2O32− (10 mM)) in water at physiological pH 7.4 (10 mM HEPES buffer) with the help of absorption spectral studies and colorimetric study. The detection limit of sulfide is calculated to be 1.13 µM. DFT calculations suggested that the most exergonic free energy (-31.99 kcal/mol) is associated with sulfide, leading to the displacement of Cu(II) ion from the [CuL2]Cl2 receptor, which well supported the experimental absorption spectral data. In addition, [CuL2]Cl2 receptor also demonstrated noteworthy interactions with Calf-Thymus DNA (CT-DNA) and bovine serum albumin (BSA).

Iodine‐DMSO Catalyzed β‐carboline Derivative Chemoselective Fluorescent Molecule for Detection of Fluoride and Cyanide Anion

AbstractIn this work, a simple and highly sensitive fluorescent receptor 1‐(p‐tolyl)‐4,9‐dihydro‐3H‐pyrido[3,4‐b]indole (receptor 1), has been synthesized for the detection of fluoride and cyanide ions. The receptor 1 was very selective towards fluoride and cyanide anions over other anions such as Cl−, Br−, I−, HSO4−, NO3−, HPO42−, and OAc−. Synthesized receptor 1 shows low detection limits 3.29 × 10−8 M for fluoride ion, which was determined by UV–vis absorption. While LOD for cyanide was observed to be 61.5 nM. Importantly, while, receptor 1 produced binding constant for fluoride and cyanide in DMSO‐H2O (1:9, v/v) was found to be 5 × 10−4M−1 and 3.28 × 10−5 M−1, respectively. The variation in the optical and fluorescence spectroscopy confirms the formation of N─H⋯F− and N─H⋯CN− hydrogen bond of the pyrrolic proton The sensing mechanism displayed by receptor 1 for fluoride and cyanide ions was confirmed by 1H‐NMR and FT‐IR spectroscopic along with density functional theory (DFT) calculations. Solution with the fluoride and cyanide ions in DMSO‐H2O (1:9, v/v) shows a color change from light yellow to blue under UV light and yellow to colorless in visible light.

Selective Chromogenic Chemosensors for Arsenite Anion: A Facile Approach to Analyzing Arsenite in Honey, Milk, and Water Samples.

In this study, two chemosensors, N5R1 and N5R2, based on 5-(4-nitrophenyl)-2-furaldehyde, with varying electron-withdrawing groups, were synthesized and effectively employed for the colorimetric selective detection of arsenite anions in a DMSO/H2O solvent mixture (8 : 2, v/v). Chemosensors N5R1 and N5R2 exhibited a distinct color change upon binding with arsenite, accompanied by a spectral shift toward the near-infrared region (Δλmax exceeding 200 nm). These chemosensors established stability between a pH range 6-12. Among them, N5R2 displayed the lowest detection limit of 17.63 ppb with a high binding constant of 2.6163×105 M-1 for arsenite. The binding mechanism involved initial hydrogen bonding between the NH binding site and the arsenite anion, followed by deprotonation and an intramolecular charge transfer (ICT) mechanism. The mechanism was confirmed through UV and 1H NMR titrations, cyclic voltammetric studies, and theoretical calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Real water samples, honey, and milk samples were successfully analyzed by both chemosensors for the sensing of arsenite.

Naked eye detection of anions: Dihydrazone receptor-based visual sensing

In this study, we designed and synthesized a novel colorimetric sensor for fluoride ions by integrating a thienodicarbohydrazide framework with salicylaldehyde, resulting in a unique bis-hydrazone-phenol receptor. This sensor exhibited exceptional selectivity for fluoride and acetate ions in nonaqueous environments, with detection visible to the naked eye. Upon interaction with fluoride ions, the receptor underwent a significant red shift in its UV–Visible absorption spectrum, moving from an absorption maximum at 332 nm–380 nm, signalling the recognition event. Acetate ions induced a similar shift. The binding interactions were thoroughly investigated, with a Jobs plot revealing a 1:1 receptor-anion complex formation with fluoride ions and a 1:2 complex with acetate ions. Further validation came from 1H NMR titration, which confirmed the presence of hydrogen bonding interactions between the receptor and the ions. The receptor demonstrated remarkable binding constants of 5.2 × 10⁴ M−2 for acetate and 1.6 × 10⁴ M−1 for fluoride ions, highlighting its strong and selective affinity. Fluorescence titrations further confirmed the receptor's potential as a chemo sensor, showing distinct emission changes in the presence of fluoride and acetate ions. This study not only underscores the receptor's capability for visual detection of fluoride ions in non-aqueous systems but also paves the way for its application in diverse analytical and environmental settings.

Cascade enzyme-mimicking with spatially separated gold-ceria for dual-mode detection of superoxide anions

Metal-semiconductor nanozyme of dumbbell Au-CeO2 with spatially separated heterostructure has cascade superoxide dismutase (SOD)-like and peroxidase (POD)-like activities for superoxide anions detection. It was synthesized by selective growth of CeO2 at the ends of Au nanorod (Au NR). Taking advantage of the excellent local surface plasmon resonance (LSPR) effect of Au NR, the spatially separated Au-CeO2 has a higher photothermal effect than the continuously growing core-shell structure of Au@CeO2. Meanwhile, the hot electrons of Au NR could transfer to CeO2 under 808 nm laser irradiation, changing the ratio of Ce3+/Ce4+ redox couples over CeO2 and facilitating H2O2 decomposition thus enhancing POD-like activity. Based on the SOD-like activity of Au-CeO2, superoxide anion (O2·−) can be transformed into hydrogen peroxide (H2O2). Dual-mode including absorbance and temperature sensing detection of O2·−, with the detection range from nM to μM i.e., 0.1–150 μM and LOD of 0.033 μM (S/N = 3) was achieved through the cascade catalysis and photothermal effect. The as-proposed method was applicable to both cancer and normal cell samples with satisfactory accuracy and recovery.

Dual-Hydrogen Bond Donor-Functionalized Carbon Nanotube Fibers: Enhancing Anion-Sensing Performance Through Functionalization Approaches.

In this study, chemiresistive anion sensors are developed using carbon nanotube fibers (CNTFs) functionalized with squaramide-based dual-hydrogen bond donors (SQ1 and SQ2) and systematically compared the sensing properties attained by two different functionalization methods. Model structures of the selectors are synthesized based on a squaramide motif incorporating an electron-withdrawing group. Anion-binding studies of SQ1 and SQ2 are conducted using UV-vis titrations to elucidate the anion-binding properties of the selectors. These studies revealed that the chemical interaction with acetate (AcO-) induced the deprotonation of both SQ1 and SQ2. Selectors are functionalized onto the CNTFs using either covalent or non-covalent functionalization. For covalent functionalization, SQ1 is chemically formed on the surface of the CNTFs, whereas SQ2 is non-covalently functionalized to the surface of the CNTFs assisted by poly(4-vinylpyridine). The results showed that non-covalently functionalized CNTFs exhibited a 3.6-fold higher sensor response toward 33.33mm AcO- than covalently functionalized CNTFs. The selector library is expanded using diverse selectors, such as TU- and CA-based selectors, which are non-covalently functionalized on CNTFs and presented selective AcO--sensing properties. To demonstrate on-site and real-time anion detection, anion sensors are integrated into a sensor module that transferred the sensor resistance to a smartphone via wireless communication.

Synthesis of two Cd (II)-MOFs and fluorescence sensing of 2, 4, 6-trinitrophenol and anions

Two new Cd (II) metal-organic frameworks (MOFs), {[Cd (L)0.5]·1.2DMF·H2O} n (1) and [Cd(H2L) (1, 2-die)2] n (2) [H4L = [1, 1′:4′, 1′'-terphenyl]-2, 2′', 4, 4′'-tetracarboxylic acid, 1,2-die = 1,2-di(pyridin-4-yl) ethane], have been synthesized under hydro(solvo)thermal conditions and structurally characterized by X-ray single crystal diffraction. 1 is a three-dimensional framework (3D) formed by the connections between layers, whereas 2 is a one-dimensional (1D) chain structure. Fluorescence sensing experiments show that both 1 and 2 can detect 2, 4, 6-trinitrophenol (TNP) and 2 has a lower detection limit. The detection limits of 1 and 2 were 0.18 μmol·L-1 and 0.054 μmol·L-1, respectively. However, their detection of anions is different, 1 can selectively detect MnO4-, and the detection limit is 0.38 μmol·L-1. 2 can selectively detect CrO42-, and the detection limit is 0.84 μmol·L-1. This indicates that different nitrogen-containing ligands have significant effects on the structure and properties of MOFs. In addition, 2 was used for the detection of sulfasalazine (SECT) in aqueous solution, and the detection limit is 0.29 μmol·L-1. Finally, the mechanism of fluorescence quenching was thoroughly investigated.

Fluorescence detection of superoxide anion with CsPbBr3 perovskite quantum dots in aqueous media

Among reactive oxygen species, the superoxide radical anion (O2−) is of particular interest due to its involvement in oxidative stress-related diseases and environmental pollutants. Through solution-phase strategy mediated by ligands, colloidal spherical and water-stable perovskite quantum dots (PQDs) of cesium lead bromide (CsPbBr3) were fabricated by functionalizing with D-tartaric acid (D-TA) (namely, CsPbBr3@D-TA PQDs), exhibiting exceptional photoluminescence quantum yield of 29.88 % and intense emission peak at 522 nm when excited at 380 nm. The as-fabricated CsPbBr3@D-TA PQDs showed strong durability and displayed bright green fluorescence when exposed to 365 nm UV radiation. The emission peak of CsPbBr3 PQDs at 522 nm was completely quenched by O2−, showing wider linear range from 0.125 to 25 µM with a detection limit of 39.82 nM. Moreover, CsPbBr3@D-TA PQDs were also applied for bio-imaging of yeast cells. The CsPbBr3@D-TA PQDs-based fluorescence approach holds great potential for sensing of O2− in real samples.

Computational Justification Towards Detection of Dual Anions on a Single Molecular Platform: The Role of Solvent in Decoration of Dual Channels

ABSTRACTRatiometric optical detection of analytes is a convenient strategy as the technique is devoid of relative error and background correction. Herein, solvent‐guided ratiometric optical recognition of fluoride and bisulfate anions by a low‐cost, “off‐the‐shelf” bioactive molecule, harmane (HRH) is thoroughly explored. Interestingly, solvent plays a dynamic role in the selective recognition of the dual anions via the dual channels of HRH in an intelligent manner. The probe displays high‐fidelity recognition behavior towards fluoride ion in an aprotic solvent (acetonitrile) and towards bisulfate ion in a protic environment (acetonitrile/water; 5:1; v/v). Both the channels of HRH are very selective for a particular anion (F−/HSO4−) in a specific solvent. Organized and comprehensive theoretical calculation denotes that hydrogen bonding between the acidic pyrrolic proton of HRH and fluoride for the first channel and the acidic proton of bisulfate and the pyridinic nitrogen for the second channel of HRH led to the formation of a hydrogen‐bonded ion pair (HBIP). Consequently, significant optical changes are observed in the visible region, which is convenient for real‐life detection of F− and HSO4− independently. The essential role of solvent in tuning the dual channels of HRH is an important artifact in the literature of fundamental photochemistry.

Influences of marine biofouling on the potential responses of polymeric membrane ion-selective electrodes

Using polymeric membrane ion-selective electrodes (ISEs) for reliable long-term marine environmental observations is still a challenge due to the formation of biofilms on electrode surfaces. Unfortunately, the contributions of the specific biofilm components to sensor failure have not been studied. Herein, the influences of the specific biofilm components on the performance of the neutral carrier-based polymeric membrane ISEs are systematically investigated in terms of sensitivity, selectivity, and stability. More importantly, the spatial distributions of these foulants in the fouled sensing membrane phase are studied by confocal laser scanning microscopy for the first time to give insight into the fouling mechanisms. Three typical biochemicals (i.e., proteins, polysaccharides, microbial lipids) in biofilms are selected as the representative foulants. The poly (vinyl chloride)-based CO32--ISEs and K+-ISEs/Ca2+-ISEs have been selected as the model sensors for detection of anions and cations, respectively. Experiments show that depending on the type of the biofoulants, the adsorption of the foulants on the polymeric membrane surface and/or their extraction into the organic membrane phase could occur and induce a change in the potential responses. This study provides a deep insight into the influences of the specific biofilm components on the polymeric membrane ISEs, which is of importance for development of the polymeric membrane marine sensors with high antifouling capabilities for long-term marine monitoring.

Stochastic Sensing of Chloride Anions Using an α-Hemolysin Pore with a semiaza-Bambusuril Adapter.

Pores containing molecular adapters provide internal selective binding sites, thereby allowing the stochastic sensing of analytes. Herein, we demonstrate that semiaza-bambusuril (BU) acts as a non-covalent molecular adapter when lodged within the lumen of the wild-type α-hemolysin (WT-αHL) protein pore. Because the bambusurils are recognized as anion receptors, the anion binding site within the adapter-nanopore complex allows the detection of chloride anions, thus converting a non-selective pore into an anion sensor.

Exploiting cyanide anion detection in food samples and for constructing logic gates by turn-off fluorescent chemosensor

A high-performance turn-off fluorescent chemosensor MSAP was developed for the selective sensing of cyanide anion without any interferences from other competing anions. MSAP's spectral responses to cyanide anion have been investigated by UV–vis and fluorescence spectroscopy. The limit of detection of cyanide anion was about 2.8 μM, which is much less than the WHO acceptable threshold level. The binding stoichiometry between the MSAP and cyanide anion was about 1:1, which was well augmented by Job`s plot. The quenching constant between MSAP and CN− ion calculated from the Stern-Volmer equation was about 8.7351×104M−1. The proposed detection mechanism of MSAP for the sensing of cyanide anion was further demonstrated by 1H NMR titration, ESI-MS and by density functional theory (DFT) studies. At last, probe MSAP was fruitfully exploited to analyse the presence of cyanide ion in diverse food samples and a XOR molecular logic gate was fabricated.

Structure and Kinetics of Organic Acid Radicals Formed in Reaction with •OH Radicals.

The study investigated •OH-derived radicals from certain organic acids employed in nuclear fuel processing and separation using EPR spectroscopy and quantum chemistry methods. Hydroxyl radicals were generated through a Fenton-like reaction within the EPR resonator under both acidic and basic conditions, allowing for the detection of neutral and radical anions, respectively. The spectral assignment and analysis were conducted using a combination of literature data and quantum chemical calculations employing DFT theory with B3LYP or LPBE functionals and the L2a_3 basis set. The reaction of the •OH radical with lactic and glycolic acids yielded primary C-centered radicals through hydrogen abstraction from these acids. In contrast, the •OH radical exclusively generated secondary radicals from oxalic acid, whereas for citric acid, it resulted in both primary and secondary species induced by decarboxylation. The EPR spectrum of acetohydroxamic acid, upon reaction with the •OH radical, displayed a complex pattern featuring primary •N-type and N-O•-type radicals. The decay pathways of the generated radicals were primarily attributed to radical-radical reactions, with the extracted reaction rate constants generally falling within the typical range observed for such reactions. The EPR parameters calculated for potential radicals using B3LYP and LPBE functionals with L2a_3 basis set demonstrated good accuracy for neutral radicals, albeit requiring minor adjustments for radical anions.

Colorimetric sensors for discriminatory detection of arsenite ions: Application in milk, honey and water samples and molecular logic gates

Millions of people are exposed to dangerous arsenic levels in drinking water, highlighting the urgent need for affordable, continuous on-site arsenic monitoring methods. It is crucial to specifically detect arsenite among inorganic arsenic anions because it is more poisonous than arsenate. Addressing these concerns, the present study developed 5-(4-nitrophenyl)-2-furaldehyde based two colorimetric chemosensors, N5R3 and N5R4, with different signaling groups for the selective detection of arsenite anions over arsenate in DMSO/H2O (6:4, v/v). The red-shift in the UV–Vis absorption spectra supported the distinct color changes of sensors N5R3 and N5R4 displayed upon binding with arsenite. Sensors demonstrated stability over a pH range of 6 to 12 and exhibited stability over a considerable time period. Among the chemosensors, N5R3 exhibited the lowest detection limit of 7.41 ppb with a high binding constant of 2.9976 × 106 M−1 for arsenite. The 1:1 binding interactions between the chemosensors and arsenite were confirmed using B-H plot and Job’s plot analysis. The intramolecular charge transfer (ICT) mechanism for detecting arsenite was proposed through UV and 1H NMR titrations, electrochemical studies, mass spectral analysis and DFT calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Both chemosensors efficiently recognized arsenite in real water, honey, and milk samples.

Three fluorescent probes based on Cd-MOFs for highly selective, sensitive and stable detection of antibiotics, anions and cations in water

It is essential to explore methods for detecting environmental pollutants to address the issue of pollution. Three novel Cd-based MOFs fluorescent sensors, namely [Cd1.5(TPT)0.5(BTC)H2O·DMF] (CUST-541), [Cd(TPT)(5-NTPA)·H2O] (CUST-542), and [Cd1.5(TPTZ)1.5(BTC)H2O·H2O] (CUST-543) (TPTZ = 2,4,6-Tris(2-pyridyl)-1,3,5-triazine; H3BTC = Trimesic acid; 5-NTPA = 5-Nitroisophthalic acid; TPT = 2,4,6-tri-4-pyridyl-1,3,5-triazine) were successfully compounded under solvent thermal conditions. Single-crystal X-ray diffraction analyses revealed that the crystal structures of CUST-541 and CUST-542 were found to have similar C2/c space group, while CUST-543 was in the monoclinic system with the P2/c space group. We have tested different types of antibiotics, cations, and anions, and found that the MOFs have very low LOD for NFT, Cu2+, and CrO42-. The LODs of NFT, Cu2+, and CrO42- for crystals are 0.53 μM, 0.38 μM, and 2.36 μM, respectively. Furthermore, this method is characterized by its low detection limit, rapid response time, wide linear range, and reproducible luminescence sensitivity.

Preparation of tetra-imidazolium salt and sensing for fluoride anion

One tetra-imidazolium salt (2) based on quinoxaline was prepared and characterized, and the detection of anions by compound 2 as a chemosensor was researched through fluorescence spectra, UV/Vis spectra, 1H NMR titrations, MS and IR spectra. The experimental results displayed that sensor 2 can selectively recognize F− through the instrument or the naked eyes (the color changed from colorless to brown in visible light). The high K value (6.4 × 104 M−1) for 2 F− indicated that 2 had strong bonding force to F−. The low detection limit (1.84 × 10−7 mol/L) indicated that the detection of F− by 2 was sensitive.

Stochastic Sensing of Chloride Anions Using an α‐Hemolysin Pore with a semiaza‐Bambusuril Adapter

AbstractPores containing molecular adapters provide internal selective binding sites, thereby allowing the stochastic sensing of analytes. Herein, we demonstrate that semiaza‐bambusuril (BU) acts as a non‐covalent molecular adapter when lodged within the lumen of the wild‐type α‐hemolysin (WT‐αHL) protein pore. Because the bambusurils are recognized as anion receptors, the anion binding site within the adapter‐nanopore complex allows the detection of chloride anions, thus converting a non‐selective pore into an anion sensor.