Ratiometric Chemosensor Research Articles

A tert-Butyldiphenylsilyl-Containing Polyimide-Based Chemosensor for Sequential Detection of Fluoride Ions and Trace Water in Organic Solvents.

A tert-butyldiphenylsilyl-containing polyimide (PI-OSi) has been established as a colorimetric and ratiometric chemosensor for rapid detecting fluoride ions (F-). The UV-vis absorbance ratio value (A322/A288) of PI-OSi in a DMF solution displays a wide linear range change to F- concentrations with a detection limit (DL) value of 2.13 μM. Additionally, adding incremental amounts of F- to a DMF solution of PI-OSi shows an immediate color change to yellow and finally to green from colorless. More interestingly, the resulting PI-OSi plus F- system (PI-OSi·F) could detect trace water in DMF. The A292/A322 value of PI-OSi·F almost linearly increases with low water content, which suggests convenient quantitative sensing of trace water content in DMF. The DL value of PI-OSi·F for sensing water in DMF is determined to be 0.00149% (v/v). The solution color of PI-OSi·F returns to colorless when the water content increases, indicating that PI-OSi·F can conveniently estimate water content in DMF by naked-eye detection. The detection mechanisms confirmed by an 1H NMR study and a DFT calculation involve a F--induced desilylation reaction of PI-OSi to form phenolate anion followed by protonation with trace water. Finally, PI-OSi film was fabricated for the colorimetric detection of F- and water in CH3CN.

Room-temperature phosphorescence and fluorescence nanocomposites as a ratiometric chemosensor for high-contrast and selective detection of 2,4,6-trinitrotoluene

Reports on using complementary colours for high-contrast ratiometric assays are limited to date. In this work, graphitized carbon nitride (g-C3N4) nanosheets and mercaptoethylamine (MEA) capped Mn-doped ZnS QDs were fabricated by liquid exfoliation of bulk g-C3N4, and by a coprecipitation and postmodification strategies, respectively. Mn-doped ZnS quantum dots were deposited onto g-C3N4 nanosheets through an electrostatic self-assembly to form new nanocomposites (denoted as Mn–ZnS QDs@g-C3N4). Mn–ZnS QDs@g-C3N4 can emit a pair of complementary colour light, namely, orange room-temperature phosphorescence (RTP) at 582 nm and blue fluorescence at 450 nm. After 2,4,6-trinitrotoluene (TNT) dosing into Mn–ZnS QDs@g-C3N4 aqueous solution, and pairing with MEA to generate TNT anions capable of quenching the emission of Mn-doped ZnS QDs, the fluorescence colours of the solution changed from orange to blue across white, exhibiting unusual high-contrast fluorescence images. The developed ratiometric chemosensor showed very good linearity in the range of 0–12 μM TNT with a limit of detection of 0.56 μM and an RSD of 6.4 % (n = 5). Also, the ratiometric probe had an excellent selectivity for TNT over other nitroaromatic compounds, which was applied in the ratiometric test paper to image TNT in water, and TNT sensing under phosphorescence mode to efficiently avoid background interference. A high-contrast dual-emission platform for selective ratiometric detection of TNT was therefore established.

Coumarin‐Pyrazole Based Fluorescent Sensor for Selective Detection of Dopamine in Aqueous Medium

AbstractA rapid, efficient, selective, and sensitive ratiometric chemosensor has been developed to detect dopamine. The sensor is based on coumarin fluorophore incorporating an aldehyde binding site to detect catecholamines. Here, the fluorescence quenching was observed after the reaction of compound 6 with dopamine. This fluorescence sensor relies on rapid detection of dopamine in aqueous medium by iminium ion formation between aldehyde and amine analytes at neutral pH. The reaction product gives the emission maximum at 420 nm on excitation at 280 nm. The proposed method allows the determination of dopamine upto 9.7×10−7 M. Furthermore, this method has good selectivity and sensitivity towards dopamine.

H2O2-targeted ratiometric chemosensor with long-wavelength emission and large emission shift based on ESIPT mechanism for bioimaging application

Excessive usage of H2O2 may bring adverse impacts on ecological security and public health. It is imperative for monitoring of levels of H2O2 in ecological environment and biological systems. Herein, an ESIPT mechanism-based ratiometric chemosensor HBTH was proposed, which exhibited long-wavelength emission, superior selectivity for H2O2 in complex matrix, low detection limit in fluorescence measurement (2.99 × 10−8 M), relatively rapid response (15 min) and large emission shift (143 nm). Response mechanism of HBTH for H2O2 recognition was explored by mass spectrometry analysis and theoretical calculation. Importantly, the applicability of HBTH as a H2O2-sensitive chemosensor was confirmed by selective determination of H2O2 in actual water samples and visualizing exo/endogenous H2O2 in cells, zebrafish and mice.

Dye‐linked Upconverting Nanophosphor‐based Ratiometric Chemosensor for NIR‐excited and FRET‐mediated Ultrasensitive Detection of Sulfide Ions

AbstractIn this article, a NIR‐excited ratiometric method for selective and ultrasensitive detection of sulfide (S2−) ions in an aqueous environment is presented, which is reliant on fluorescence resonance energy transfer (FRET). The chemosensor‐design is based on an upconverting nanophosphor (UCNP)‐linked coloured complex between a rhodamine‐B derivative and stannous ions (RBD‐Sn2+). Under the excitation of NIR light, the green emission of UCNP (at 542 nm) is reabsorbed by the linked RBD‐Sn2+ complex via FRET, which in turn emits in the orange (at 582 nm). S2− ions specifically interact with the linked RBD‐Sn2+ complex and quantitatively bleach its colour, leading to reduction in FRET and consequent recovery of the green emission of UCNP. We investigated the quantitative and ratiometric detection of S2− ions in aqueous phase using this NIR‐excited FRET‐based approach. The concentration of S2− ions is quantitatively connected to the ratiometric emission signal under NIR excitation. We have found that the detection limit for S2− ions using our FRET‐based nanoprobe is around ten times lower than that of colorimetric or fluorescence‐based approaches. Owing to the use of NIR‐light as excitation source, our proposed sensor can demonstrate background‐free sensing of S2− in complex environmental and biological samples.

Spontaneous preparation of a fluorescent ratiometric chemosensor for metal ions using off-the-shelf materials.

A self-assembled chemosensor prepared using off-the-shelf materials has shown various fluorescence responses including ratiometric and simple ON-OFF switching profiles by adding different toxic metal ions. The unique fingerprint-like responses have been applied to pattern recognition of metal ions in river water for environmental analysis.

Nitrogen, sulfur, and phosphorus Co-doped carbon dots-based ratiometric chemosensor for highly selective sequential detection of Al3+ and Fe3+ ions in logic gate, cell imaging, and real sample analysis

Heteroatom-doped photoluminescent (PL) carbon dots (CDs) have recently gained attention as optical sensors due to their excellent tunable properties. In this work, we propose a one-pot hydrothermal synthesis of PL nitrogen (N), sulfur (S), and phosphorus (P) co-doped carbon dots (NSP-CDs) using glutathione and phosphoric acid (H3PO4) as precursors. The synthesized NSP-CDs were characterized using different spectroscopic and microscopic techniques, including ultraviolet–visible (UV–Vis) spectroscopy, fluorescence spectroscopy, Fourier-transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. The NSP-CDs exhibited excellent PL properties with green emission at 492 nm upon excitation at 417 nm, a high quantum yield of 26.7%, and dependent emission behavior. The as-prepared NSP-CDs were spherical with a well-monodispersed average particle size of 5.2 nm. Moreover, NSP-CDs demonstrate high PL stability toward a wider pH, high salt ionic strength, and various solvents. Furthermore, the NSP-CDs showed a three-state “off–on–off” PL response upon the sequential addition of Al3+ and Fe3+ ions, with a low limit of detection (LOD) of 10.8 nM for Al3+ and 50.7 nM for Fe3+. The NSP-CD sensor can construct an INHIBIT logic gate with Al3+ and Fe3+ ions as the chemical inputs and emissions as the output mode. Owing to an excellent tunable PL property and biocompatibility, the NSP-CDs were applied for sensing Al3+ and Fe3+ ions as well as live cell imaging. Furthermore, NSP-CDs were designed as PL sensors for detecting Al3+ and Fe3+ ions in real water show their potential application.

Ratiometric Recognition of Protons by a Multiple Tagged Designer Fluorescent Chemosensor.

Molecular architecture with different fluorophoric units can offer improved and effective recognition of biologically important analytes. We present here a new strategy for the design of ratiometric chemosensors that operate by photoinduced electron transfer (PET). This ratiometric sensor endowed with tryptophan and anthracene exhibits high sensitivity, excellent selectivity and remarkable reversibility towards recognition of H+ in methanol. This "Turn-On" type behaviour is crafted into the molecule by incorporation of bispidine entity. Effective quenching of the fluorescence of the anthracene by the adjacent amine groups of the bispidine results in negligible fluorescence from the anthracene group leading to highly sensitive recognition of protons by the compound as H+ protonate the amine functionalities giving rise to the emergence of the fluorescence from the anthracene group. This, combined with the reduction in the fluorescence from the Trp group by H+, results in highly sensitive ratiometric nature of the response especially at low [H+].

N-Butyl-4-hydrazino-1,8-naphthalimide-Loaded Chitosan Self-Assembled Nanoparticles as Fluorescent Ratiometric Chemosensors for Detection of Formaldehyde

<i>N</i>-Butyl-4-hydrazino-1,8-naphthalimide-Loaded Chitosan Self-Assembled Nanoparticles as Fluorescent Ratiometric Chemosensors for Detection of Formaldehyde

Unveiling of a smartphone-mediated ratiometric chemosensor towards the nanomolar level detection of lethal CN-: combined experimental and theoretical validation with the proposition of a molecular logic circuitry.

A promising naphthalene-functionalized ratiometric chemosensor (E)-1-((naphthalen-5-yl) methylene)-2-(2,4-dinitrophenyl) hydrazine (DNMH) is unveiled in the present work. DNMH demonstrates brisk discernible colorimetric response from yellow to red in the presence of CN−, a lethal environmental contaminant, in a near-perfect aqueous medium with a LOD of 278 nM. The “key role marker” controlling the electrochemical and non-covalent H-bonding interaction between DNMH and CN− is through the commendable role of acidic –NH functionalities. Kinetic studies reveal a pseudo second order reaction rate and the formation of an unprecedented photostable adduct. The negative value of ΔG as evaluated from ITC substantiates the spontaneity of the DNMH⋯CN− interaction. The sensing mechanism was further reinforced with state-of-the-art theoretical investigations, namely DFT, TDDFT and Fukui indices (FIs). Moreover, the proposition of a reversible multi-component logic circuitry implementing Boolean functions in molecular electronics has also been triggered by the turn-over spectrophotometric response of the ditopic ions CN− and Cd2+. The cytotoxicity of DNMH towards Bacillus thuringiensis and Escherichia coli is successfully investigated via the MTT assay. Impressively, “dip stick” and “easy to prepare” test paper device and silica gel-based solid-phase CN− recognition validate the on-site analytical application of DNMH. Furthermore, the involvement of a synergistic approach between ‘chemistry beyond the molecule’ and ‘engineering’ via an exquisitely implemented smartphone-assisted colorimetric sensory prototype makes this work unprecedented among its congeners and introduces a new frontier in multitudinous material-based functional product development.

A novel fluorometric chemosensor based on imidazo[4,5-b]phenazine-2-thione for ultrasensitive detection and separation of Hg2+ in aqueous solution

We synthesized and developed 1,3-dihydro-2H-imidazo[4,5-b]phenazine-2-thione as a ratiometric chemosensor for Hg2+ recognition in a DMSO/H2O (v/v = 9:1) binary solution. We rationally introduced the phenazine imidazole group as the fluorophore and the thione moiety as the recognition site to bind Hg2+. Interestingly, the chemosensor showed an ultrasensitive response to Hg2+, and the lowest limit of detection was 0.167 nM. In addition, it can also separate Hg2+ from aqueous solutions with excellent ingestion capacity, with an adsorption ratio of up to 96%. Furthermore, ion test strips based on chemosensors were fabricated for convenient and efficient detection of Hg2+.

An AIRE-active far-red ratiometric fluorescent chemosensor for specifically sensing Zn2+ and resultant Zn2+ complex for subsequent pyrophosphate detection in almost pure aqueous media

A simple Schiff-base fluorescent chemosensor (1) was synthesized by the reaction of 3-amino-pyrazine-2-carbohydrazide and 7-diethylamino-3-formylcoumarin; the sensor 1 displayed a notable green emission at 524 nm in DMSO and an aggregation-induced ratiometric emission (AIRE) at 555 nm in an almost buffered aqueous media (0.5% DMSO content). The AIRE of 1 was quenched following binding to Zn2+ ions, while the fluorescence emission in the far-red region was evidently enhanced at 628 nm. Notably, the ratiometric signal output could be utilized to specifically distinguish Zn2+ among various metal ions. Moreover, the 1-Zn2+ complex was effectively employed as a fluorescent ratiometric chemosensor for pyrophosphate (PPi) detection. The detection limit was 3.52 μM and 2.45 μM for Zn2+ and PPi, respectively. The binding mechanism was evaluated by 1H NMR, ESI-MS, single-crystal X-ray diffraction, TEM, time-resolved fluorescence spectrophotometry, and density functional theory studies. Overall, owing to its sensitive fluorescence behavior, cell imaging studies demonstrated that this sensor is capable of sensing Zn2+ and PPi in living cells.

A reaction-based colorimetric and ratiometric chemosensor for imaging identification of HClO in live cells, mung bean sprouts, and paper strips

Hypochlorous acid (HClO) as well as its ionic form (ClO−), representative of reactive oxygen species (ROS), are essential players in all sorts of biological processes. The abnormal level of each can lead to the onset of various diseases. Besides, Sodium hypochlorite, a commonly-used bleaching agent in our daily lives, could also result in breathing and skin problems when overexposed. Therefore, developing a molecular chemosensor for sensing HClO is of biological and environmental importance. Though many such chemosensors have been reported, new HClO chemosensors with different sensing performances may still come in handy in certain situations. In this work, we have developed a new coumarin-based chemosensor, CM-hbt, for realizing both ratiometric and colorimetric imaging detection of HClO in live cells. Notably, we further explored its application in sensing HClO in plant mung beans as well as fabricated an easy-to-use paper strip apparatus for facilitating its quick detection, which is seldomly seen in other HClO chemosensors. All the analysis results confirmed the high sensitivity and selectivity of this novel chemosensor. DFT calculations were used to decipher the underlying sensing mechanism of CM-hbt. Overall, this work presents a novel chemosensor, CM-hbt, as a colorimetric and ratiometric chemosensor for realizing imaging detection of HClO in a variety of different model systems, which highlights its broad spectrum of application potentials.

Corrigendum to “A Schiff base-based ratiometric chemosensor conjugated NBD derivative with the large Stokes shift for formaldehyde detection” [Tetrahedron 76 (2020) 131411

Corrigendum to “A Schiff base-based ratiometric chemosensor conjugated NBD derivative with the large Stokes shift for formaldehyde detection” [Tetrahedron 76 (2020) 131411

A novel ratiometric and colorimetric chemosensor for highly sensitive, selective and ultrafast tracing of HClO in live cells, bacteria and zebrafish

Hypochlorous acid (HClO) along with its ionic form, hypochlorite anion (ClO−) are critical reactive oxygen species (ROS), which play vital roles in biological systems. Dysregulated production of HClO/ClO− can result in tissue damage and cause a variety of diseases. Besides, Sodium hypochlorite has been widely used as a bleaching agent for water disinfection, surface cleaning in daily life. Excessive exposure to sodium hypochlorite will lead to symptoms of severe breathing and skin problems. Therefore, developing a state-of-the-art (simple, highly sensitive, highly selective and super fast-response) sensor for tracking HClO is of biological, toxicological, and environmental importance. Though many HClO probes have been reported so far, this big aim still presents a challenge. Researchers around the world are continuing to develop new HClO probes that could improve their sensitivity, selectivity, the limit of detection, response time, easiness to use, etc. Herein, with coumarin as the fluorophore molecule, we rationally developed a novel chemosensor (CMTH) for detecting HClO with both ratiometric and colorimetric responses resulted from the oxidation reaction of CN bond. Further analysis results indicated that CMTH can realize highly sensitive with low limit of detection (256 nM, among the best of its kind) and highly selective (over a bunch of interfering analytes) imaging detection of HClO in multiple organisms with low cytotoxicity, and good cell and tissue permeability as well. In particular, compared to other fluorescent HClO probes reported so far, CMTH excels in the response time to HClO (< 40 s), being the top-notch of its kind. Besides, owing to its excellent water solubility, CMTH can also be applied to track HClO in the environmental system. Taken together, we have presented here a novel chemosensor, CMTH, as a colorimetric and ratiometric chemosensor for highly sensitive and ultrafast imaging detection of HClO in aqueous solutions, eukaryotic cells, prokaryotic bacteria and vertebrate zebrafish.

A naked-eye visible colorimetric and ratiometric chemosensor based on Schiff base for fluoride anion detection

A dual-platform colorimetric and ratiometric chemosensor, namely 6-(2-hydroxynaphthalen)-N-n-butyl-naphthalimide (HNA), based on Schiff base constructed from N-n-butyl-4-amino-1,8-naphthalimide and 2-hydroxy-1-naphthaldehyde has been designed and fabricated for detecting fluoride anion (F−) in DMSO solution. HNA is a colorimetic and ratiometric probe with superior selectivity and sensitivity. The color changes of HNA from yellow to purple was observed by the naked eyes in the presence of F−. The absorbance in the UV-Vis spectra of HNA was decreasing in 422 nm, while gradually increasing in 583 nm by adding F−. The limit of detection (LOD) of HNA for detecting F− is low to 0.61 μM and the binding model of HNA and F− is in 3:2 stoichiometry. Meanwhile, HNA can be used to detect F− in real samples. Finally, the mechanism of HNA for the detection of F− was investigated. The present work indicated that HNA would be a superior potential chemosensor in monitoring F− selectively and sensitively.

A Visual and Ratiometric Chemosensor Using Thiophene Functionalized Hydrazone for the Selective Sensing of Pb2+ and F- Ions.

Herein, a simple, efficient ratiometric chemosensor was reported for the selective sensing of Pb2+ and F- ions using thiophene functionalized hydrazone as a chemical probe. Hydrazone moiety was developed by utilizing thiophene/naphthalene as a platform for the particular recognition of cation and anion. The structures of the precursor (Z)-(1-(5-bromothiophen-2-yl)ethylidene)hydrazine (ABTH) and the final probe 1-((Z)-(((Z)-1-(5-bromothiophen-2-yl)ethylidene)hydrazono)methyl)naphthalen-2-ol (NAPABTH) were confirmed by 1H, 13C-NMR and LC-MS spectroscopic methods. The interaction of NAPABTH with Pb2+ and F- ions was visually observed by the formation of pink and dark yellow solutions, respectively. The detection limits were found to be very low for Pb2+ as 1.06ppm and for F- ions as 3.72nM. This visual detection of Pb2+/F- ions with satisfactory outcomes obtained from UV-Vis titrations. The sensing mechanistic pathways and stoichiometric ratios were obtained from DFT and Job's plot, respectively. The observed results are highly promising as highly selective chemosensor with lower detection limits for Pb2+ and F- ions. This strategy could exhibit tremendous applications for the selective sensing of heavy metal cations with rapid sensitivity for the design of new devices.

Colorimetric and ratiometric chemosensor for hydrogen sulfide based on the 1-(2-pyridylazo)-2-naphthol-zinc ions ensemble

This paper reports a colorimetric and ratiometric chemosensor for hydrogen sulfide based on the 1-(2-pyridylazo)-2-naphthol and zinc ions ensemble. The detection strategy was designed based on the hydrogen sulfide-induced dissolution of the ensemble to form more stable zinc sulfide species. Using this strategy, hydrogen sulfide can remove zinc ions from the ensemble and restore the optical signals of the indicator, 1-(2-pyridylazo)-2-naphthol. Upon addition of hydrogen sulfide to the ensemble of 1-(2-pyridylazo)-2-naphthol and zinc ions, the absorption spectra displayed decreasing absorption intensity at 511 and 541 nm and increasing absorption intensity at 398 nm; moreover, the solution exhibited an obvious color change from pink to yellow that could be observed by the naked eye. This ensemble system could detect hydrogen sulfide with a limit of detection of 1.9 µM, and other common anions did not induce distinct changes in either absorption spectra or solution colors.

Ratiometric chemosensor for differentiation of TNP from other NACs using distinct blue fluorescence and visualization of latent fingerprints

Paper strips coated with the red-fluorescent probeDMAS-TPdisplay a distinct blue fluorescence with 2,4,6-trinitrophenol andSiO2@DMAS-TPNPs to visualize latent fingerprints up to level 3.

Construction of a mitochondria-targeted ratiometric fluorescent probe for monitoring hydrazine in soil samples and culture cells

Isoniazid and its major metabolite, hydrazine (N2H4), may interfere with mitochondrial function and have negative effects on cells. Consequently, an understanding of the role of N2H4 in mitochondria is highly desirable for protecting human health. Herein, we report a novel mitochondria-targeted ratiometric fluorescent probe (Mitro-N2H4) for N2H4 detection. Mitro-N2H4 exhibited an attenuation of green emission at 521 nm and an enhancement of yellow emission at 590 nm in the presence of N2H4 because of hydrazinolysis, indicating that it can be used as a ratiometric chemosensor for N2H4 with high selectivity and sensitivity. Such on-site monitoring of N2H4 vapour using test strips and N2H4-moistened soil analysis demonstrated its advantages in potential application for the convenient sensing of N2H4. Moreover, the rationally designed probe has many potential applications for imaging N2H4 produced in situ during the metabolism of isoniazid in living cells based on the ratio of the fluorescent signal.