Ionic Probe Research Articles

An ion synergism fluorescence probe via Cu2+ triggered competition interaction to detect glyphosate

The widespread use of glyphosate (Gly) poses significant risks to environmental and human health, underscoring the urgent need for its sensitive and rapid detection. In this work, we innovated by developing a novel material, ionic liquids, which formed the ionic probe “[P66614]2[2,3-DHN]-Cu2+ (PDHN-Cu2+)” through coordination with Cu2+. This probe capitalized on the distinctive fluorescence quenching properties of ionic liquids in the presence of Cu2+, driven by synergistic interactions between anions and cations. Glyphosate disrupted the PDHN-Cu2+ coordination structure due to its stronger affinity for Cu2+, triggering a “turn-on” fluorescence response. Impressively, PDHN-Cu2+ enabled the sensitive detection of glyphosate within just one minute, achieving a detection limit as low as 71.4 nM and excellent recovery rates of 97-103% in diverse samples. This groundbreaking approach, utilizing ionic probes, lays a robust foundation for the accurate and real-time monitoring of pesticides, employing a strategy based on synergism and competitive coordination.

Ionic liquid-based chemodosimetric probe: the selective detection and removal of bisulfite from a pure aqueous system and potential uses in biosensing

This study reveals a cost-effective and recyclable ionic liquid probe for monitoring and mitigating bisulfite in water. It is effective in bio-sensing and real sample bisulfite quantifications, highlighting its dual purpose capability.

Development of a High-Throughput Mass Spectrometry-Based SARS-CoV-2 Immunoassay.

The serious impact of the Covid-19 pandemic underscores the need for rapid, reliable, and high-throughput diagnosis methods for infection. Current analytical methods, either point-of-care or centralized detection, are not able to satisfy the requirements of patient-friendly testing, high demand, and reliability of results. Here, we propose a two-point separation on-demand diagnostic strategy that uses laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) and adopts a stable yet cleavable ionic probe as a mass reporter. The use of this reporter enables ultrasensitive, interruptible, storable, restorable, and high-throughput on-demand detection. We describe a demonstration of the concept whereby we (i) design and synthesize a laser-cleavable reporter (DTPA), (ii) conjugate the reporter onto an antibody and verify the function of the conjugate, (iii) detect with good turnaround and high sensitivity the conjugated reporter, (iv) analyze quantitatively by using a laser-cleavable internal standard, and (v) identify negative and positive samples containing the spike protein. The protocol has excellent sensitivity (amol for the SARS-CoV-2 Spike S1 subunit antibody) without any amplification. This strategy is also applicable for the detection of other disease antigens besides SARS-CoV-2.

Selective detection of ionic liquid fluorescence probes for visual colorimetry of different metal ions

At present, the fast distinction of different metal ions in pure water media is not only a great challenge, but also drives the protection of water quality in environmental water bodies. In this paper, a novel ionic liquid fluorescent probe Glycolic Acid-L-Arginine (GA-L-Arg) was rationally created and designed through an in-depth study of ionic liquids. It is also used as an innovative multi-ion fluorescent probe for colorimetric detection and separate identification of Fe3+ and Co2+ in aqueous solutions of various metal ions. GA-L-Arg has excellent water solubility due to the strong hydrophilicity of Glycolic Acid and L-Arginine. The probe showed high sensitivity, extremely significant selectivity, and great pH stability for Fe3+ and Co2+ in pure water. The GA-L-Arg structure and the mechanism of Fe3+ and Co2+ detection were analyzed by infrared spectroscopic characterization and quantum chemical calculations. More importantly, the distinct colorimetric partitioning of Fe3+ and Co2+ was performed by the unique extraction of Fe3+ in the presence of the fluorescent probe and buffer solution.

Hydrothermal Synthesis of Functionalized Carbon Nanodots and Their Clusters as Ionic Probe for High Sensitivity and Selectivity for Sulfate Anions with Excellent Detection Level.

Nitrogen-doped carbon nanodots (CNDs) were synthesized and utilized as sensing probes to detect different anions and metallic ions within aqueous solutions. The pristine CNDs were developed through a one-pot hydrothermal synthesis. o-Phenylenediamine was used as the precursor. A similar hydrothermal synthesis technique in the presence of polyethylene glycol (PEG) was adopted to form the PEG-coated CND clusters (CND-100k). Through photoluminescence (PL) quenching, both CND and PEG-coated CND suspensions display ultra-high sensitivity and selectivity towards HSO4- anions (Stern-Volmer quenching constant (KSV) value: 0.021 ppm-1 for CND and 0.062 ppm-1 for CND-100k) with an ultra-low detection limit (LOD value: 0.57 ppm for the CND and 0.19 ppm for CND-100k) in the liquid phase. The quenching mechanism of N-doped CNDs towards HSO4- ions involves forming the bidentate as well as the monodentate hydrogen bonding with the sulfate anionic moieties. The detection mechanism of metallic ions analyzed through the Stern-Volmer formulation reveals that the CND suspension is well suited for the detection of Fe3+ (KSV value: 0.043 ppm-1) and Fe2+ (KSV value: 0.0191 ppm-1) ions, whereas Hg2+ (KSV value: 0.078 ppm-1) sensing can be precisely performed by the PEG-coated CND clusters. Accordingly, the CND suspensions developed in this work can be employed as high-performance PL probes for detecting various anions and metallic ions in the liquid phase.

Atomic and ionic hydrogen flux probe for quantitative in-situ monitoring of hydrogen recycling

A new combination diagnostic as a hydrogen recycling monitor in harsh conditions is proposed. Combining permeation membrane probe with a Langmuir probe provides a possibility to measure both atomic and ionic hydrogen fluxes to plasma facing components. A brief overview of permeation probes is given. The range of measurable H fluxes is from 1016 to more than 1020Hm−2s−1. Time response of the permeation probe is ∼0.1−0.5 s. A method to address disadvantages of permeation probes is proposed. This includes an introduction of a preparation chamber for Ar-plasma cleaning of the membrane and absolute calibration with a visible spectroscopy. The hydrogen recombination coefficient, evaluated in such calibration, is ku=5.9×10−30m4s−1, which agrees well with previous research.

Real-time monitoring of mercury(II) in water and food samples using a quinoline-based ionic probe

Herein, a novel ionic fluorescent probe for mercury(II) detection is presented consisting of a functional quinoline-based IL. Interestingly, the probe displayed high sensitivity (0.8 nM) and selectivity through the regulation function of electrostatic attraction, where its performance was significantly superior to that of quinoline probes without negative charge. Furthermore, the probe was found to exhibit two different fluorescent signals and colorimetric signals in the presence of different concentrations of mercury(II), which was consistent with the reaction mechanisms of the generation of large conjugated systems and the formation of anion-mercury(II) complexes. Moreover, this probe could be further loaded on a simple filter paper to serve as a visual paper sensor due to its adequate response time of less than 5 s. This regulation function strategy of electrostatic attraction has excellent potential for use in the precise detection of targeted analytes in real complex samples with improved accuracy and selectivity.

Fluorescent and Colorimetric Ionic Probe Based on Fluorescein for the Rapid and On-Site Detection of Paraquat in Vegetables and the Environment.

Detection of pesticide paraquat (PQ) is of considerable significance to ensure food safety, and its rapid and on-site detection is still a challenge. Aimed at the ion characteristics of PQ, an "enrichment and detection" strategy was proposed to improve the sensitivity through electrostatic attractions, and the ion characteristic of probes was adopted to increase the portability through avoiding aggregation-caused quenching effects in the paper strips. Herein, a novel anion-functionalized ionic liquid (IL) probe with a large conjugated plane and rich π-electrons ([Fluo][P66614]2) was designed as a fluorescent and colorimetric dual-channel probe to sensitively and rapidly detect trace amounts of PQ in vegetables and the environment. The proposed probe exhibited good linearity with a detection limit of 64.0 nM in the PQ concentration range of 0.3-7.0 μM (fluorometry) and 0.1 μM in that of 0.1-8.0 μM (colorimetry), respectively. In addition, it displayed a rapid fluorescence quenching response from green to dark (<5 s) and excellent anti-interference (among 23 other pesticides) due to dual effects of electrostatic attraction and π-π stacking. Most importantly, the lipophilic IL probe could be applied in real vegetables and environmental samples with a satisfying recovery rate of 98-103% and assembled into a handy paper strip that achieved the visual semiquantitative detection of PQ. This ionic probe provides a feasible approach for rapidly and conveniently detecting PQ for ensuring agricultural and food safety and opens a new avenue to detect ion-responsive analytes in real complex samples by an "enrichment and detection" strategy.

Malaria Diagnosis Using Paper-Based Immunoassay for Clinical Blood Sampling and Analysis by a Miniature Mass Spectrometer.

In this work, we have developed a paper-based microfluidic device capable of remote biofluid collection followed by an analysis of the dried clinical samples using a miniature mass spectrometer. We have evaluated a portable mass spectrometer as a possible surveillance platform by analyzing the clinical malaria samples (whole blood) collected from Ghana. We synthesized pH-sensitive ionic probes and coupled them with monoclonal antibodies specific to the Plasmodium falciparum histidine-rich protein 2 (PfHRP2) malaria antigen. We then used the antibody-ionic probe conjugates in a paper-based immunoassay to capture PfHRP2 antigen from untreated whole blood. After the immunoassay, the bound ionic probes were cleaved, and the released mass tags were analyzed through an on-chip paper spray mass spectrometry strategy. During process optimization, we determined the detection limit for PfHRP2 in untreated human serum to be 0.216 nmol/L when using the miniature mass spectrometer. This sensitivity is comparable to the World Health Organization's suggested threshold of 0.227 nmol/L for PfHRP2, proving that our method will be applicable to diagnose symptomatic malaria infection (≥200 parasites per μL blood). The paper device can be stored at room temperature for at least 25 days without affecting the clinical outcome, with each stored paper chip offering good repeatability and reproducibility (RSD = 4-12%). The stability and sensitivity of the developed paper-based immunoassay platform will allow miniature mass spectrometers to be used for point-of-care malaria detection as well as in large-scale surveillance screening to aid eradication programs.

Dynamics in tris(pentafluoroethyl)trifluorophosphate (FAP) anion based ionic liquids: A 2D-IR study with tungsten hexacarbonyl

Ultrafast two-dimensional infrared spectroscopy (2D-IR) measurements for tungsten hexacarbonyl, W(CO)6, has been performed in two fluoroalkylphosphate ([FAP])-based ultrahigh hydrophobic, ionic liquids, namely, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate ([EMIM][FAP]) and 1-(hexyl)-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) to probe their local structure and dynamics. To understand the effect of FAP anion on the dynamics, a relatively less hydrophobic [PF6-] anion has been introduced in the form of [HMIM][PF6]. While the linear IR spectra records some influence of anion in terms of spectral shifts, the alkyl chain length of the cation seems to have no significant influence on the spectral peak position; and even the spectral broadening is found to be in the similar range. Further, vibrational population relaxation dynamics and vibrational anisotropy decay also does not show any significant variation due to difference in constituent of these ionic liquids as well as its solvent properties, such as, viscosity. Finally, 2D-IR spectra show large variation in the spectral shapes with waiting times, which qualitatively remains similar in all the tested ionic liquids. The frequency-fluctuation correlation function measured from 2D-IR spectra displays a bi-exponential decay with the shorter time-constant dependent on the identity of the anion, and has been attributed to the ion-rattling motion, whereas, the longer component has been found to be invariant with the identity of ionic liquid, and has been attributed to ion-cage motions which is in line with previous MD simulations as well as previous experimental measurements, using ionic vibrational probe. Overall, 2D-IR spectroscopy, in combination with this neutral and hydrophobic probe, W(CO)6 provides a unique opportunity to understand the local structural dynamics of this ultrahigh hydrophobic ionic liquid which are otherwise not accessible by hitherto explored ionic vibrational probes.

An ESIPT-ICT steered naphthylthioic-based ionic probe with dual emissive channels exhibiting CHEF and CHEQ effects.

A naphthylthioic-based emissive probe (M) bearing a hydroxyl and amine group was designed and synthesized via a one-step Schiff base reaction process. The probe was characterized spectroscopically using 1H NMR, UV-Vis and fluorescence spectrophotometers. The probe turned out to be spectroscopically and colorimetrically selective and sensitive to multiple cations and anions. Interestingly, the probe displayed characteristics of excited-state intramolecular proton transfer (ESIPT)-driven dual emissive channels; experiencing fluorescence enhancement upon the molar additions of Al3+ as well as the anions used, events presumably ascribed to chelation fluorescence enhancement (CHEF), hydrogen bonding and deprotonation effects. Moreover, the fluorometric titration with Hg2+ resulted in ratiometric spectral behaviors of M, with the disappearance of the peak at 450 nm, concomitant with the appearance of a new peak at 520 nm, distinguished by a clear isosbestic point, the same behaviors exhibited by Sn2+ and Ag+ analytes towards M. The introduction of all other cations used, resulted in fluorescence quenching, attributable to chelation enhanced fluorescence quenching (CHEQ), thereby inhibiting the ESIPT process. The experiments were all carried out in the aqueous environment medium of DMSO-H2O (9 : 1) at ambient temperature. Theoretical density functional theory calculations were carried out to gain insight into the interaction of M with cations and anions, and their influence on the HOMO-LUMO energy gaps.

Water-soluble ionic liquid as a fluorescent probe towards distinct binding and detection of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol in aqueous medium

Owing to the escalating threat of criminal activities and pollution aroused by 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP), development of a proficient sensor for the detection of these explosives is highly demanded. Herein, a water-soluble ionic liquid-tagged fluorescent probe, 1-ethyl-3-(3-formyl-4-hydroxybenzyl)-1H-benzimidazol-3-ium chloride (EB-IL) has been designed and synthesized for the detection of TNT and TNP in 100% aqueous medium. The EB-IL fluorescent probe displayed strong cyan-blue fluorescence at 500 nm which gets quenched upon the addition of TNT/TNP over other concomitant nitro-compounds. The distinct binding response of EB-IL towards TNT could be due to the formation of hydrogen bonding between the acidic proton of benzimidazolium (C2–H) and nitro group of TNT. Meanwhile, the selective binding of TNP with EB-IL could be due to the exchange of counter Cl− anion of EB-IL with picrate anion. The fluorescence quenching of EB-IL by TNT could be attributed to the resonance energy transfer (RET) and that of TNP is ascribed to the anion-exchange process. The developed sensor is extremely selective and sensitive towards TNT and TNP with high quenching constants of 1.94 × 105 M−1 and 2.32 × 106 M−1 and shows a lower detection limit of 159 nM and 282 nM, respectively.

Multiresponsive Polymer Nanoparticles Based on Disulfide Bonds

A disulfide polymer that is triggerable by ultrasound, UV, and redox in aqueous solution and can self-assemble with ionic probe molecules into again multitriggerable assemblies is presented. It is created by oxidative coupling of a branched insoluble thiol to water-soluble ionic thiols. The synthesis via a nanoprecipitation technique results in charged macromolecule particles with adjustable sizes between a few tens and a few hundred nanometers stable in aqueous solution. Macromolecules of different compositions form with pentaerythritol tetrakis(3-mercaptopropionate) as insoluble cross-linkers yielding the polymer backbone, while mercaptopropionic acid, mercaptosuccinic acid, or aminoethane thiol in varying amounts is coupled to the backbone. Molecular and nanoscale switchability of the disulfide macromolecule with UV light, redox potential, and ultrasound is demonstrated. The anionic character of the polymer particles is exploited by electrostatic self-assembly with the tetra-cationic 5,10,15,20-tetrakis-(N-methyl-4-pyridyl)porphyrin and its zinc-metalated derivative, yielding supramolecular composite structures as a model system for delivery. The new type of polymer particles in aqueous solution may pave an alternative way toward multiresponsive and functional materials with potential in medicine and material science.

Ratiometric fluorescent detection of hypochlorite in aqueous solution and living cells using an ionic probe with aggregation-induced emission feature

Abstract Fluorescent sensors have attracted great research attention for detection of various target substrates in environment and living organisms. However, there are still of some issues when using traditional organic probes owing to their poor water dispersibility and aggregation caused quenching effect. In this paper, we designed and synthesized an ionic fluorescent probe (named as TPY) with aggregation-induced emission (AIE) feature and explored its potential sensor performance towards hypochlorite in aqueous solution and living organisms. The results demonstrated that TPY can detect hypochlorite with excellent selectivity, outstanding sensitivity and fast response time. The reaction mechanism should be ascribed to the reaction between hypochlorite and TPY, that was evidenced by a number of characterization techniques, such as UV–vis/fluorescence spectroscopy, 1H NMR and mass spectroscopy. Most importantly, owing to its amphiphilicity and AIE feature, the probe could be well dispersed in aqueous solution and showed enhanced fluorescence, which endow it good sensor performance in both aqueous solution and living organisms. Finally, the biological assays confirmed that TPY has low toxicity and good biocompatibility, which could be used to detect hypochlorite in living cells. We trust this work will provide some new ideas for designing fluorescent probes with better performance for chemo/biosensors.

How different are the dynamics of nanoconfined water?

We unravel the combined effects of confinement and surface interactions by studying the position dependent, time-resolved dynamic response functions in nano-containers of different shapes. Spectroscopic signatures are additionally studied through solvation dynamics by placing ionic and dipolar probes at varying distances from the enclosing surface. We find that the confined water molecules exhibit exotic dynamical features and stark differences from that in the bulk liquid. We employ atomistic molecular dynamics simulation to obtain the solvation time correlation function, non-Gaussian parameter, and non-linear response function that reveal the existence of heterogeneous and non-exponential dynamics with a strong sensitivity to both the size and the shape of the enclosure. Importantly, the slower long-time decay constant exhibits a non-monotonic spatial dependence. The initial ultrafast component is reminiscent of the same in the bulk, but it is found to have a different origin in the present systems. We perform shell-wise analyses to understand the microscopic origin of these observations and the range of the propagation of the surface induced effects.

PH- and redox-responsive hybrid porous CaCO3 microparticles based on cyclodextrin for loading three probes all at once

Drug molecules are often insoluble or poorly soluble in physiological medium and they may accumulate in fat tissues leading to drawbacks for the patient's recovery. Moreover to avoid side-effects, selective release of the drug is of major interest. In this context, we propose to combine the advantageous features of both porous and negatively charged surfaces of calcium carbonate (CaCO3) particles and host molecules (cyclodextrin, CD) for developing carrier enabling the loading of both hydrophobic and hydrophilic (ionic) several molecules all at once. Porous calcium carbonate particles present highly benefits for biological purposes because of their large surface area and their high stability in neutral media. CD presents the advantage of owing hydrophilic exterior and a less polar cavity in the center. For instance, hydrophobic drug/CD can form inclusion complexes in aqueous media. We have loaded a hydrophobic molecule, namely tocopherol acetate, inside the CD cavity and an ionic probe (rhodamine b) inside the porosity of the CaCO3. A controlled and selective release of the probe is finally evidenced according to the pH of the medium (pH 5 and 7.4). We also propose an approach combining the thiol/disulfide chemistry and the layer-by-layer process to load a third probe which is then selectively released under reducing conditions. Our strategy enables thus to easily load three probes all at once and to control their release according to the applied stimulus (pH or redox condition).

Design of functionalized fluorescent ionic liquid and its application for achieving significant improvements in Al3+ detecting

Specific fluorophore was introduced into ionic liquid based on its tunability, thus a kind of novel fluorescent ionic liquid probe [P66614][HQS] was designed, synthesized and characterized. Compared with non-fluorescent HQS, ionic liquid [P66614][HQS] emitted a certain amount of fluorescence, which could be attributed to the well-delocalized frontier orbitals and its charge transfer character, as demonstrated by quantum chemical calculation. Considering the interaction of [P66614][HQS] with metal ions, the application for detecting specific substance as a chemical sensor, such as Al3+ was investigated. Compared with the traditional probe HQS, significant improvements in Al3+ detecting was achieved by [P66614][HQS] with stronger binding ability, better sensitivity and selectivity. The better performance of [P66614][HQS] was contributed to the changed charge distribution, leading to the stronger binding interaction. We believe that this new fluorescent ionic liquid exhibited unique properties in detecting Al3+ in aqueous solution, which would broaden the application of ionic liquids.

Synthesis of Poly-Amino Acid Ionic Liquid Up-Conversion Fluorescent Probe and its Application in Fe(II)/Fe(III) Speciation Analysis.

The poly amino acid ionic liquid (poly-1-vinyl-3-butylimidazolium glutamate acid, p-1-VbmGlu), with a stable up-conversion fluorescence(UCF) probe, was firstly prepared and the synthesis conditions were optimized. The UCF were found to be specifically quenched by Fe(III), but not respond to Fe(II). In H2O2 medium, Fe(II) posed strong quenching effect on the UFC owing to Fe(III) produced by redox between H2O2.and Fe(II). Therefore p-1-VbmGlu was employed as a UFC for Fe(II)/Fe(III) speciation analysis under the control of H2O2. The detection limits of Fe(II)/Fe(III) were 6.16ng/mL and 4.48ng/mL, with relative standard deviations of 1.1% and 2.0%, respectively. This method was successfully utilized in the analysis of Fe(II)/Fe(III) in multiple real samples.

A Simple Red Emitting "Turn-On" Optical Relay Detector for Al3+ and CN-. Application in the Real Sample and RAW264.7 Cell Imaging.

A quantitative and qualitative fluorogenic molecular probe (R) has been designed and synthesized using Rhodamine-B hydrazide and 3,5-dibromo salicylaldehyde. The probe R has been applied for detection of ionic species and probe R turned out to be a prominent distinguisher among divalent and trivalent cations Al3+, Cr3+ and Fe3+ via the fluorometric response in acetonitrile medium. Colorimetric changes were observed for trivalent cations and Cu2+. Among all trivalent cations, Al3+ is possessing relay recognition for CN- even in the presence of other interfering anions with optimum precision. The association constant and the detection limit for R-Al3+ are 4.5 × 106M-1 and 17.9nM respectively. On the other hand, R + Al3++CN- exhibits an association constant and detection limit of 5.77 × 105M-1 and 4.6nM respectively. The stoichiometry of Al3+ binding with R is found to be 1:1. Quantum efficiency of probe R, R + Al3+ and R + Al3++CN- are found to be 0.2, 0.88 and 0.04 respectively. The receptor showed excellent real-time applicability for commercially available antiperspirant and apple seeds extract. The efficiency of the receptor further extended for fluorescent imaging of Al3+ and CN- in RAW264.7 cells.

Fabrication of hybrid PVA-PVC/SnZnOx/SWCNTs nanocomposites as Sn2+ ionic probe for environmental safety

ABSTRACTNew hybrid nanocomposites (NCs) based poly(vinyl alcohol) (PVA), poly(vinyl chloride) (PVC), mixed SnZnOx nanocube and single walled carbon nanotube (SWCNTs) have been fabricated by solution dispersion method with the help of ultrasonic irradiation. A fixed amount of SnZnOx and different loading of SWCNTs nanoparticles (NP)s are added successfully during the fabrication process. The SnZnOx nanocubes are synthesized using the wet-chemical procedure. Here, results from XRD, FTIR, TEM, and FE-SEM techniques are examined to provide the fundamental information necessary to fabricate PVA-PVC and their NCs. Morphology findings of SnZnOx and SWCNTs incorporated in the PVA-PCV matrix prove the appearance of nanoparticle in the films. Additionally, thermal and electrochemical behavior of the fabricated NCs have been studied by thermogravimetric technique and electrochemical measurements, respectively. An effectual electrochemical sensor using PVA-PVC/SnZnOx/SWCNTs(3)/binder/GCE assembly selective to Sn2+ ion is fabricated with conductive nafion (5%). The PVA-PVC/SnZnOx/SWCNTs(3) NCs give a good detection of Sn2+ ion and it shows a linear response over the large linear dynamic range (LDR) concentration of 0.1 nM ~ 0.01 mM . The linear relationship slope of (current vs. concentration) is examined to calculate the sensitivity (42.11 µAµM−1cm−2) and detection limit (44.36 ± 2.22 pM) of proposed Sn2+ ionic sensor probe. It has been significantly detected the selective Sn2+ ion from environmental real samples. The insights stated in this manuscript provide a clear understanding of the variable keys involved in the improvement of heavy metal ionic sensor for the application of safety environment in broad scale.