Selective Detection Of Fluoride Ions Research Articles

A novel fluorescent covalent organic framework for the selective detection of fluoride ion

A novel fluorescent covalent organic framework for the selective detection of fluoride ion

Fluoride-philic reduced graphene oxide–fluorophore anion sensors

rGO–fluorophore noncovalent conjugates efficient in the selective detection of fluoride ions in the attomolar range are presented. The high affinity of fluoride ions to rGO leads to stable graphite fluoride formation, initiating a turn-on response.

Facile fabrication of a fluorene-containing polyimide film-based fluorescent sensor for rapid and selective detection of fluoride ion

A fluorene-containing polyimide (PI) with tert-butyldimethylsiloxy (TBS) side groups (PI-TBS) was designed and readily prepared by a post-polymerization modification on hydroxyl-containing PI. When the electron-donating hydroxyl groups in PI chain are replaced with bulky non-polar TBS side groups, inter-chain charge transfer effect of the modified PI-TBS is effectively weakened, finally resulting in the fluorescent characteristic of PI-TBS. The as-obtained fluorescent PI-TBS film-based sensor for detection of fluoride ion (F−) displays the remarkable fluorescence quenching with a short response time and high selectivity over other coexistent anions, when PI-TBS film was immersed in the fluoride-containing solution. Moreover, after immersing in the fluoride-containing solution, the PI-TBS film shows a naked-eye visible color change to yellow-green from light yellow under daylight and an obvious fluorescence quenching under 365 nm UV light. The energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopic (XPS) analyses and density functional theory (DFT) calculation studies indicate that the selective fluoride-induced cleavage of the Si-O bond enhances the intramolecular charge transfer (ICT) in PI chains, leading to fluorescence quenching. This work provides a direct polymer film-based fluorescent sensor device for the fast, selective and naked-eye visible detection of F−.

Simultaneous detection and removal of fluoride from water using smart metal-organic framework-based adsorbents

• Simultaneous detection and removal of fluoride from water. • Smart MOFs-based adsorbents. • Adsorption mechanisms of fluoride by MOFs. The fluoride ion is usually added to drinking water because of its prominent role in treating osteoporosis and improving dental health. However, fluoride contents over the optimal level (>1.5 ppm) in water resources has been found to have harmful effects on human health such as bone and dental fluorosis, Alzheimer's syndrome, DNA damage, infertility, kidney failure, acute gastric problems, thyroid disorder, brain damage, and even cancer. Therefore, sensitive and selective detection of fluoride ions and their removal from drinking water are of great significance. The unique features of metal–organic frameworks (MOFs), such as chemical activities, a broad range of functionalities, high stability, and modification opportunities for specific molecule detection or adsorption, make them broadly applicable in detecting and removing fluoride ions from water. The present review summarizes recent developments for detecting and removing fluoride ions from water by MOFs. The recent progress in fluoride removal via MOFs will be discussed in depth. The actual adsorption performance of various MOFs toward fluoride will be elaborated using partition coefficient (PC), independent of operating conditions. The detection and adsorption mechanisms are fleshed out comprehensively, providing insights and a roadmap to address current challenges and shed light on future study directions.

A Simple and Efficient Schiff Base Derived Chemosensor for Selective Detection of Fluoride Ion

A new thiazole substituted chemosensor 1 has been designed and synthesized for selective detection of fluoride ions. The chemosensor 1 was characterized by 1H NMR and 13C NMR. The absorption studies of chemosensor in DMF exhibits two peaks at 283 nm and 327 nm. The anion sensing behaviour of chemosensor 1 for various anions (I-, Cl-, Br-, NO3-, HSO4-, PF6-, ClO4-) in DMF were investigated by UV-vis spectroscopy. Chemosensor 1 exhibited high degree of selectivity for fluoride ions over other anions. A good linearity in the range of 16-133 μM with 6.12 μM limit of detection value (LOD) was observed.

Colorimetric sensor based on hydrazine moiety for rapid and selective detection of fluoride ion via intramolecular charge transfer

ABSTRACT A colorimetric anion sensor (E)-3-((2-((4-(4-Methoxyphenyl)thiophen-2- yl)methyl)hydrazono)methyl)-1 H-indole ATH was synthesised and confirmed by different spectroscopic methods, such as 1 H NMR, 13 C NMR, ESI-Mass and FT-IR spectroscopy. The ATH sensor revealed the spectral change and detection in the presence of fluoride ion over the other anions such as OH−, Cl−, AcO−, I−, HSO4 −, NO3 −, Br−, S2-, CN− & NO2 −. Interestingly, sensor ATH exhibited highly selective fluoride ion detection with significant changes in the colour from light yellow to dark yellow in ACN and ACN: H2O (8:2, v/v) medium. The colorimetric sensor effectively responds to fluoride ion stimulation through deprotonation and (ICT) intramolecular charge transfer sensing mechanism. The fluoride sensing mechanism was confirmed by 1 H NMR titration and was supported by density functional theory (DFT) and electrochemical studies. In this study, the B–H plot calculates the stoichiometry and binding constant (Ka) of the host-guest complex and strong interaction between the probe ATH with fluoride ions forming a 1:2 binding ratio. Furthermore, the test strips based on the probe ATH were used to detect F- ions qualitatively and quantitatively in 100% aqueous solution.

A “turn-on” fluorescent probe based on BODIPY dyes for highly selective detection of fluoride ions

In the present paper, a novel difluoroboron dipyrromethene-based (BODIPY) fluorescent probe with a conjugated hydrazone group, named BDBH, was developed for the detection of F− with high selectivity and sensitivity. After addition of tetrabutylammonium fluoride (TBAF) into a BDBH solution, the fluorescence was “turned on”, which displayed an 80-fold increasement of emission intensity. The wavelengths of excitation and emission were 518 nm and 613 nm respectively, which were free from the background interference. The titration of 1H NMR (Nuclear Magnetic Resonance) indicated that the interaction involved hydrogen-bonding formation between the acidic H of –NH–CO group and F− at low concentration and deprotonation of N–H group at increasing concentration of fluoride. The theoretical calculations verified that once F− interacted with BDBH, the planarity and conjugation of BDBH enhanced, which resulted in a strong fluorescence emission at 613 nm. Furthermore, confocal fluorescence images of BDBH-incubated HeLa cells verified its potential application as an “off-on” sensor to monitor F− in living cells.

Development of indole-based fluorescent probe for detection of fluoride and cell imaging of HepG2

A fluorescent probe IDS based on indole ring was designed and synthesized. It has been successfully developed for highly selective detection of fluoride ions with a low detection of 1.3 ppb. Besides, the probe IDS was used for fluorescence imaging of F− in HepG2 cells and detected the concentration of fluoride ions in the environmental water samples and urine sample. These applications suggested that IDS was a sensitive probe in research and potential for the diagnosis of endemic fluorosis.

Non-covalently functionalised rGO–fluorescein unit for selective detection of fluoride ions

The combination of reduced Graphene oxide and Fluorescein dye serves as a highly selective optical switch for sensing fluoride ion via colorimetric and fluorimetric modes. A turn off stage viz., quenching of optical signal of fluorescein was observed by the formation of a supramolecular assembly between reduced graphene oxide (host matrix) and the dye (indicator). This OFF stage was turned ON instantly with the advent of fluoride ion (guest), with high selectivity. The limit of detection values obtained are 4.2 ppm and 1.7 ppb respectively, via colourimetric and fluorimetric strategy. Solid state test strips of the sensor unit could detect fluoride in aqueous media at concentration down to 3 ppm with the help of UV source.

Colorimetric and fluorimetric chemosensor based on upper rim-functionalized calix[4]arene for selective detection of fluoride ion

A new colorimetric and fluorescent chemosensor for fluoride anion based on calix [4]arene bearing four sulfonamide-fluorenone subunits on the upper rim was conveniently synthesized. It showed a remarkable color change as well as the fluorescence quenching upon addition of F- even in the presence of a wide range of anions in DMSO. The binding property of L with F- was studied by a combination of various spectroscopic techniques, such as absorption and emission titration, Job's plot and 1H NMR titration. It is anticipated that this design with functional group attached to upper rim of calix[4]arene platform can provide a new approach for the development of F- chemosensor.

Turn-on fluorescence sensor for selective detection of fluoride ion and its molecular logic gates behavior

Loutonin based emissive probe (L) for the dual sensing of fluoride (F−) and bisulphate (HSO4−) anions in aqueous media. The development is based on reports that the interaction between fluoride and loutonin based fluorescent probe exhibits rapid and remarkable color changes in both colorimetrically as well as fluorimetrically. More amusingly, on the introduction of bisulphate ion into the medium containing loutonin fluoride ion complex (L-F−) which shows both the color and fluorescence has been recovered. The limit of detection for fluoride ions by the probe was determined as 8.62 × 10−7 M by fluorescence titrations. Further the probe L can be employed for the removal of fluoride ions. The need for a dual anion detection system with such an outstanding reversible and reproducible process characteristics led us to consider loutonin as a feasible nominee for the construction of molecular keypad lock and molecular logic circuits. The fluorescence change of loutonin after appendage of fluoride ions is mainly due to the hydrogen bonding interaction. Further, the probe could be potentially incorporated into the test strips and silica gel plates, with better selectivity for fluoride and bisulphate anions in aqueous media.

Precisely controlling fluorescence enhancement and high-contrast colorimetric assay in OFF-ON fluoride sensing based on a diketopyrrolopyrrole boronate ester

Fluoride sensing has been an interesting and vital problem owing to the negative influences of fluoride in the human body when taken in excessive amounts. Herein, we report the diketopyrrolopyrrole boronate ester as a potential chemosensor for fluorescent analysis and selective detection of fluoride ion. Quantitative analysis demonstrates that the emission peaks increases step-by-step at 592 and 641 nm in proportion with the increase of fluoride equivalents. Simultaneously, the color change is rapid and from sky blue to pink. The limit of detection is 1.58 × 10−5 M of fluoride anion, indicating a lower limit than the requirement of the World Health Organization. Furthermore, freshly cleaned test papers show an excellent selectivity at a low cost and the color change is similar to the results in solution. In addition, the morphology and the recognition mechanism have also been proposed. The results show that the diketopyrrolopyrrole boronate ester can be effective as a novel fluorescent and colorimetric sensor for fluoride, which opens the opportunity for the design and synthesis of new smart materials and sensors with precisely controlling fluorescence enhancement.

Mitochondrial-targeted near-infrared fluorescence probe for selective detection of fluoride ions in living cells

Fluoride ions (F−), as a strongest electron withdrawing anion of the smallest size, have played an indispensable role in biological systems. Here a mitochondria-targeted near-infrared (NIR) fluorescent probe (Mito-FP) is developed for selective detection of F− in living cells. Mito-FP is designed using a NIR hemicyanine as a fluorophore and tert-butyldimethylsilyl (TBDMS) as a recognition site which is linked to the fluorophore via a 4-hydroxylbenzyl alcohol self-immolative linker. Mito-FP is essentially nonfluorescent. F− can specifically cleave the Si–O bond which triggers the elimination of the quinone methide intermediate and generates the initial NIR hemicyanine fluorophore with distinct intramolecular charge transfer and activated fluorescence signal. The Mito-FP probe is responsive to the concentrations of F− in the range of 10–120 μM with an estimated limit of detection of 3.2 μM. Mito-FP also exhibits high selectivity toward F− with good stability in the physiological pH conditions. Mito-FP is successfully introduced to detect and image F− in HeLa cells. Moreover, Mito-FP is also demonstrated to exhibit excellent mitochondrial-targeting ability. This NIR fluorescence probe could provide a useful tool for studying F− in mitochondria.

A pyrene based colorimetric chemosensor for CO2 gas detection triggered by fluoride ion

A pyrene derivative (KB-3) was synthesized and demonstrated as a colorimetric and ratiometric chemosensor for selective detection of fluoride ion with the detection limit of 391 nM. The mechanism of fluoride ion detection is due to the complete deprotonation of NH proton in KB-3 as revealed by 1H NMR studies. Further, the deprotonated KB-3 is demonstrated for perceptive detection of CO2 gas down to 0.1 ml. Moreover, detection of fluoride using KB-3 is explored to develop INHIBIT type logic gate at molecular level.

Dopamine integrated B, N, S doped CQD nanoprobe for rapid and selective detection of fluoride ion

A simple fluorescence turn on sensor for the detection of fluoride ion in totally aqueous medium has been developed by integrating boronic acid functionalized carbon quantum dot (BNSCQD) and dopamine. The intense emission of BNSCQD is quenched due to photoelectron transfer (PET) from BNSCQD to dopamine. A remarkable enhancement of emission intensity in presence of F− is achieved due to high reactivity of F− towards boron centre of the BNSCQD-dopamine complex and hence restricting PET between BNSCQD and dopamine. The LOD of our sensor is 0.7 pM. The sensor is not cytotoxic and could be utilised to trace fluoride level changes in human serum as well as in living cells.

A novel fluorescent off-on probe for the sensitive and selective detection of fluoride ions.

A highly sensitive and selective fluorescent probe for fluoride ions has been developed by incorporating the dimethylphosphinothionyl group as a recognition moiety into the fluorophore of coumarin. The detection mechanism is based on the fluoride ion-triggered cleavage of the dimethylphosphinothionyl group, followed by the release of coumarin, which leads to a large fluorescence enhancement at 455 nm (λex = 385 nm). Under the optimized conditions, the fluorescence enhancement of the probe is directly proportional to the concentration of fluoride ions in the range of 0–30 μM with a detection limit of 0.29 μM, which is much lower than the maximum content of fluoride ions guided by WHO. Notably, satisfying results have been obtained by utilizing the probe to determine fluoride ions in real-water samples and commercially available toothpaste samples. The proposed probe is rather simple and may be useful in the detection of fluoride ions in more real samples.

Coumarin Probe for Selective Detection of Fluoride Ions in Aqueous Solution and Its Bioimaging in Live Cells.

We have synthesized novel coumarin-based fluorescent chemosensors for detection of fluoride ions in aqueous solution. The detection mechanism relied on a fluoride-mediated desilylation triggering fluorogenic reaction and a strong interaction between fluoride and the silicon center. In this work, the hydroxyl-decorated coumarins containing oxysilyl moiety have been synthesized through the aldehyde-functionalized coumarins. The optical responses toward fluoride, as well as aqueous stability studies of both aldehyde and hydroxyl functionalized coumarins, have been investigated. Due to the highest fluorescence enhancement upon the addition of fluoride and good stability in aqueous solution, the hydroxyl-decorated coumarin connected with the bulky tert-butyldiphenyloxysilyl group (-OSitBuPh2) has been selected for further investigation of its potential as a fluoride sensor. This hydroxyl-decorated coumarin can selectively sense fluoride ions in aqueous media (contain 0.8% MeCN) with desirable response times (40 min). The limit of detection of this compound was determined as 0.043 ppm, satisfying the standard fluoride level (0.7 ppm) in drinking water recommended by U.S. Department of Health and Human Services. The application of this silyl-capped coumarin derivative for fluoride analysis in collected water samples displayed satisfactory analytical accuracy (<5% error). Finally, this compound was successfully employed in fluorescence bioimaging of fluoride ions in human liver cancer cells, indicating its excellent cell permeability, ability to retain inside the living cells, and good stability under physiological conditions.

Chromo-luminescent selective detection of fluoride ions by a copper(II) bis(terpyridine) complex solution via a displacement approach

Herein, for the first time, we have reported a copper(ii) bis(terpyridine) complex solution for instant 'naked eye' chromo-luminescent selective detection of fluoride ions in an acetonitrile medium at micromolar concentration. The copper complex [Cu(ii) (L)2] (NO3)2 [where L = 4'-(4-N,N'-dimethylaminophenyl)-2,2':6',2''-terpyridine] was characterized by mass spectroscopy and the terpyridine ligand by 1H NMR spectroscopy. The complex solution selectively discriminates F- ions from other anions such as AcO-, Br-, Cl-, CN-, H2PO4-, HSO4-, and I- in acetonitrile media via exceptional optical changes. The optical changes were evaluated by UV-visible and fluorescence techniques. Studies on the binding characteristics of the copper complex solution with fluoride ions revealed a displacement of copper ions from the complex solution as CuF2 resulting in the significant optical changes. Furthermore, displacement of Cu(ii) from the complex was established by means of mass spectroscopy in the presence of 20 equivalents of fluoride ions. The limit of detection (LOD) was found to be 5.07 μM which is within the permissible range of fluoride ions in drinking water set by the World Health Organization (WHO).

Functionalized π Stacks of Hexabenzoperylenes as a Platform for Chemical and Biological Sensing

Summary One challenge in tailoring organic semiconductors for sensing applications is that the introduction of reactive groups or binding sites usually impairs π-π interactions. To meet this challenge, this study puts forth an unusual type of π stacking that allows a variety of functional groups to be grafted onto organic semiconductors without sacrificing π-π interactions in the solid state. As a result of this type of π stacking, the self-assembly of functionalized hexabenzoperylenes (HBPs) provides a general sensing platform for various chemical and biological species. This supramolecular platform, in a device integrating an organic field-effect transistor channel and a microfluidic channel, has enabled highly sensitive and selective detection of fluoride ions and streptavidin in water when HBPs are equipped with a cleavable Si–O bond and a biotin moiety, respectively.

A “Turn-On” fluorescent probe for sensitive and selective detection of fluoride ions based on aggregation-induced emission

Based on the fluorophore of 2-(2′-hydroxyphenyl)benzothiazole (HBT) with aggregation-induced emission (AIE) properties, a highly selective and sensitive fluorescent probe PBT towards F− was investigated. “Turn-On” fluorescence type signaling was realized by employing fluoride-selective cleavage of the latent thiophosphinated probe in mixed aqueous media. The probe is designed in such a way that the excited state intramolecular proton transfer (ESIPT) of the HBT moiety becomes blocked. The chemodosimetric approach of F− to the probe results in the recovery of the ESIPT by removal of a free AIE-active HBT moiety through a subsequent hydrolysis process. The F− detection limit of the probe was 3.8 nM in the dynamic range of 0.5 μM to 10 μM. In addition, the proposed probe has been used to detect F− in water samples and toothpaste samples with satisfying results.