Novel monohydrogenphosphate ion-selective polymeric membrane sensor based on phenyl urea substituted calix[4]arene

Ion-Selective Electrode Based on a Novel Biomimetic Nicotinamide Compound for Phosphate Ion Sensor

Phosphorus is not only an import nutrient to aquatic habitats, but it also acts as a growth inhibitor in aquatic ecosystems; however, it also aggravates environmental issues, such as eutrophication. There is a growing interest in rapid phosphorus detection to manage and protect water resources. Due to the large molecular structure and high hydration energy of phosphate ions, ion-selective electrodes (ISEs) remain in their infancy for real-time measurements in terms of practical application. In this study, a newly developed ionophore based on a biomimetic nicotinamide functional group was used to detect phosphate selectively, displaying efficient binding through charge interactions and hydrogen bonds. The ISE membrane containing silicone rubber demonstrated an effective detection performance over a long period of time. With a dynamic range between 10^-6 and 10^-2 M and a limit of detection of 0.85 × 10^-6 M (26 μg/L), the newly synthesized ISE membranes demonstrated selectivity for phosphate ions over other ions, including acetate, sulfate, and chloride.

Status and advances in technologies for phosphorus species detection and characterization in natural environment- A comprehensive review

Poor recovery of phosphorus (P) across natural environment (water, soil, sediment, and biological sources) is causing rapid depletion of phosphate rocks and continuous accumulation of P in natural waters, resulting in deteriorated water quality and aquatic lives. Accurate detection and characterization of various P species using suitable analytical methods provide a comprehensive understanding of the biogeochemical cycle of P and thus help its proper management in the environment. This paper aims to provide a comprehensive review of the analytical methods used for P speciation in natural environment by dividing them into five broad categories (i.e., chemical, biological, molecular, staining microscopy, and sensors) and highlighting the suitability (i.e., targeted species, sample matrix), detection limit, advantages-limitations, and reference studies of all methods under each category. This can be useful in designing studies involving P detection and characterization across environmental matrices by providing insights about a wide range of analytical methods based on the end user application needs of individual studies.

An incisive optical recognition of monohydrogen phosphate by a fluorescein-based chemodosimeter

We herein devised an incisive chromofluorogenic chemodosimeter (FLH) for detecting HPO₄²⁻ over other phosphates, viz. H₂PO₄⁻, PO₄³⁻, and PPi.

Indigo Carmine-Cu complex probe exhibiting dual colorimetric/fluorimetric sensing for selective determination of mono hydrogen phosphate ion and its logic behavior

A new selective probe based on copper complex of Indigo Carmine (IC-Cu₂) for colorimetric, naked-eye, and fluorimetric recognition of mono hydrogen phosphate (MHP) ion in H₂O/DMSO (4:1v/v, 1.0mmolL^-1 HEPES buffer solution pH7.5) was developed. Detection limit of HPO₄^2- determination, achieved by fluorimetric and ₃lorimetric method, are 0.071 and 1.46μmolL^-1, respectively. Potential, therefore is clearly available in IC-Cu₂ complex to detect HPO₄^2- in micromolar range via dual visible color change and fluorescence response. Present method shows high selectivity toward HPO₄^2- over other phosphate species and other anions and was successfully utilized for analysis of P₂O₅ content of a fertilizer sample. The results obtained by proposed chemosensor presented good agreement with those obtained the colorimetric reference method. INHIBIT and IMPLICATION logic gates operating at molecular level have been achieved using Cu²⁺and HPO₄^2- as chemical inputs and UV-Vis absorbance signal as output.

ZnO nanorods array based field-effect transistor biosensor for phosphate detection

A promising field-effect transistor (FET) biosensor has been fabricated based on pyruvate oxidase (PyO) functionalized ZnO nanorods (ZnO NRs) array grown on seeded SiO₂/Si substrate. The direct and vertically grown ZnO NRs on the seeded SiO₂/Si substrate offers high surface area for enhanced PyO immobilization, which further helps to detect phosphate with higher specificity. Under optimum conditions, the fabricated FET biosensor provided a convenient method for phosphate detection with high sensitivity (80.57μAmM^-1cm^-2) in a wide-linear range (0.1µM-7.0mM). Additionally, it also showed very low effect of electroactive species, stability and good reproducibility. Encouraging results suggest that this approach presents a promising method to be used for field measurements to detect phosphate.

Site-Specific Description of the Enhanced Recognition Between Electrogenerated Nitrobenzene Anions and Dihomooxacalix[4]arene Bidentate Ureas

Electron transfer controlled hydrogen bonding was studied for a series of nitrobenzene derivative radical anions, working as large guest anions, and substituted ureas, including dihomooxacalix[4]arene bidentate urea derivatives, in order to estimate binding constants (Kb) for the hydrogen-bonding process. Results showed enhanced Kb values for the interaction with phenyl-substituted bidentate urea, which is significantly larger than for the remaining compounds, e.g., in the case of 4-methoxynitrobenzene a 28-fold larger Kb value was obtained for the urea bearing a phenyl (Kb ∼ 6888) vs tert-butyl (Kb ∼ 247) moieties. The respective nucleophilic and electrophilic characters of the participant anion radical and urea hosts were parametrized with global and local electrodonating (ω(-)) and electroaccepting (ω(+)) powers, derived from DFT calculations. ω(-) data were useful for describing trends in structure–activity relationships when comparing nitrobenzene radical anions. However, ω(+) for the host urea structures lead to unreliable explanations of the experimental data. For the latter case, local descriptors ωk(+)(r) were estimated for the atoms within the urea region in the hosts [∑kωk(+)(r)]. By compiling all the theoretical and experimental data, a Kb-predictive contour plot was built considering ω(-) for the studied anion radicals and ∑kωk(+)(r) which affords good estimations.

Bidentate urea derivatives of p-tert-butyldihomooxacalix[4]arene: neutral receptors for anion complexation

Three new bidentate ureidodihomooxacalix[4]arene derivatives (phenyl 5a, n-propyl 5b, and tert-butyl 5c) were synthesized in four steps from the parent compound p-tert-butyldihomooxacalix[4]arene and obtained in the cone conformation, as shown by NMR studies. The binding ability of these neutral receptors toward spherical, linear, trigonal planar, and tetrahedrical anions was assessed by (1)H NMR and UV-vis titrations. The structures and complexation energies of some complexes were also studied by DFT methods. The data showed that the association constants are strongly dependent on the nature of the substituent (aryl/alkyl) at the urea moiety. In general, for all the receptors, the association constants decrease with decrease of anion basicity. Ph-urea 5a is the best anion receptor, showing the strongest complexation for F(-) (log K(assoc) = 3.10 in CDCl3) and also high binding affinity for the carboxylates AcO(-) and BzO(-). Similar results were obtained by UV-vis studies and were also corroborated by DFT calculations.

An ICT based "turn on/off" quinoline armed calix[4]arene fluoroionophore: its sensing efficiency towards fluoride from waste water and Zn2+ from blood serum

A novel structurally simple calix[4]arene appended 8-amidoquinoline linked conjugate was synthesized and has been used as a turn-on fluorescence probe for Zn(2+) and turn off fluorescence probe for F(-). Moreover, this probe has been applied for Zn(2+) detection in blood serum upto 8.7 μM and fluoride detection upto 22 nM in waste water samples, using emission spectra.

Sensing and analysis of soluble phosphates in environmental samples: a review

Excess phosphate levels in water can lead to increased algal growth, eutrophication and reduced water quality. Phosphate levels in water are regulated by the EU through the Urban Waste Water Treatment Directive (annual mean total phosphorus concentrations of 1-2 mg/l) and the Water Framework Directive that will enforce "good ecological and chemical status" by 2015. Legislation is therefore driving the need for increased monitoring of soluble phosphate in water, escalating the desire for a direct, label free approach that could provide remote, continuous monitoring in real-time. The standard method for measuring soluble phosphate in water is a colourimetric technique developed in the 1960s. This colourimetric approach is difficult to adapt for on-line measurements, uses specific reagents which require safe disposal and thus incurs significant costs to the water industry when carried out on a large scale. This review considers optical and electrochemical sensors plus recent advances with synthetic receptors and molecularly imprinted polymers. Progress in the development of phosphate sensors, designed for use in a variety of disciplines, is highlighted with a view to adapting successful approaches for use in the water sector. Additional considerations include the need for long term stability, low maintenance, specificity for phosphate and the capability of measuring total phosphorus concentrations down to at least 1 mg/l, as required by legislation. A sensor that could directly measure soluble, inorganic phosphate concentrations would draw significant interest from the environment sector and other disciplines, including the agricultural, detergent and bio-medical industries.