Ratiometric orange fluorescent and colorimetric highly sensitive imidazolium-bearing naphthoquinolinedione-based probes for CN- sensing in aqueous solutions and bio-samples

The widespread use of cyanide (CN^-) in industry results in contamination of various effluents such as drain, lake, and tap water, an imminent danger to the environment and human health. We prepared naphthoquinolinedione (cyclized; 1-5) and anthracenedione (un-cyclized) probes (6-7) for selective detection of CN^-. The addition of CN^- to the probe solutions (1-5) resulted in a color change from pale green to orange under 365 nm illumination. The nucleophilic addition of CN^- to C2 of the imidazolium ring of the probes is responsible for selective CN^- detection. Among all probes, 1 gave the lowest fluorescence-based LOD of 0.13 pM. In contrast, the un-cyclized probes (6 and 7) were substantially inferior to the cyclized counterparts (1 and 2, respectively) for detecting a trace amount of CN^-. The notably low LOD displayed by probe 1 was maintained in the detection of CN^- in real food samples, human fluids, and human brain cells. This is the first report studying imidazolium-bearing naphthoquinolinedione-based probes for CN^- sensing in 100% water.

Pyrene functionalized oxacalix[4]arene architecture as dual readout sensor for expeditious recognition of cyanide anion

A pyrene functionalized oxacalix[4]arene architecture (DPOC) was utilized as a fluorescence probe for selective recognition of cyanide ions. The receptor DPOC shows excellent selectivity towards cyanide ion with a red shift of 108 nm in absorption band along with a significant change in colour from light yellow to pink. The fluorescence titration experiments further confirm the lower limit of detection as 1.7µM with no significant influences of competing anions. ¹ H-NMR titration experiments support the deprotonation phenomena, as the -NH proton disappears upon successive addition of cyanide ions. The DFT calculation also indicates a certain increment of -NH bond length upon interaction with cyanide ions. The spectral properties as well as colour of DPOC-CN^- system may be reversed upon the addition of Ag⁺/ Cu²⁺ ions up to 5 consecutive cycles. Moreover, DPOC coated "test strips" were prepared for visual detection of cyanide ions.

A benzothiazole-based new fluorogenic chemosensor for the detection of CN- and its real-time application in environmental water samples and living cells

Since the cyanide ion is used in a wide range of industries and is harmful to both human health and the environment, a number of research efforts are dedicated to creating fluorescence sensors for the detection of cyanide (CN-). Herein, for the fluorescence detection of CN-, a new highly selective and sensitive sensor 2-(3-(benzo[d]thiazol-2-yl)-4-hydroxybenzylidene)-1H-indene-1,3(2H)-dione (BID) was created by conjugating a benzothiazole moiety with 1H-indene-1,3(2H)-dione. The donor and acceptor components of this hybrid receptor were covalently connected through a double bond. The nucleophilic addition of a cyanide anion to the BID inhibits the intramolecular charge transfer (ICT) transition, resulting in spectral and colour alterations in the receptor. When the solvent polarity was increased from n-hexane to methanol, this molecule exhibited a bathochromic shift in the emission wavelength (610 to 632 nm), suggesting the presence of a solvatochromic action. The sensor BID has shown strong specificity towards CN- by interrupting its internal charge transfer (ICT), resulting in a significant change in the UV-vis spectrum and a notable blue shift in the fluorescence emission spectrum. The cyanide anion (CN-) is responsible for the optical alterations observed by BID, as opposed to the other anions examined. The detection limit was 5.97 nM, significantly less than the WHO's permitted amount of CN- in drinking water. The experimental findings indicate that BID's fluorescence response to CN- is pH insensitive throughout a wide pH range of 6.0 to 12.0. The interaction mechanism between the BID and CN- ions has been studied by HRMS, 1H-NMR titration experiments, FT-IR, and DFT, which confirmed the nucleophilic addition of CN- on vinylidene and subsequent disturbance of ICT. Additionally, we demonstrated the real-time detection application of CN- in environmental water samples and live-cell imaging.

A fluorescent supramolecular gel and its application in the ultrasensitive detection of CN- by anion-π interactions

Supramolecular gels have been widely reported on account of their unique superiority and application prospects. In this work, we constructed a novel supramolecular gel (HD-G) by using hydroxy-naphthaldehyde decorated with naphthalimide in DMSO solution, which exhibited excellent selectivity and ultrasensitive sensing properties toward CN^- (the lowest detection limit is 1.82 × 10^-10 M). The sensing mechanism of this supramolecular gel takes advantage of π-π stacking interactions and anion-π interactions, which is different from the other familiar methods.

Linear tri-pillar[5]arene-based acceptor for efficiently separate paraquat from water through collaboration effect

Paraquat, one of non-selective herbicides, is widely used in agricultural production. However, it can cause death of people or animals quickly owing to its fatal toxicity. In the present work, for efficient separation and removal of the paraquat, a concept "employ collaboration effect to enhance the Host-Guest interactions" was rationally introduced into the design of paraquat adsorbent material. According to this concept, a novel linear tri-pillar[5]arene-based acceptor molecule was synthesized. Interestingly, the acceptor shows outstanding adsorption properties for paraquat through the collaboration effect of the adjacent pillar[5]arene moieties in the linear tri-pillar[5]arene acceptor. Compared with other adsorbents such as activated carbon and single-pillar[5]arene-based adsorbent materials, the linear tri-pillar[5]arene acceptor shows higher adsorption rate for paraquat. Additionally, the linear tri-pillar[5]arene acceptor was applied to adsorb the commercial pesticide paraquat sample in water with adsorption rate of 98%. Therefore, the linear tri-pillar[5]arene acceptor could serve as a paraquat adsorbent material and convey greatly potential application in the field of removal of paraquat. The concept "employ collaboration effect to enhance the Host-Guest interactions" is a useful way for the development of adsorption materials.

A novel supramolecular polymer gel-based long-alkyl-chain-functionalized coumarin acylhydrazone for the sequential detection and separation of toxic ions

A novel approach for the detection and separation of toxic ions was successfully developed via the introduction of competitive reactions into a long-alkyl-chained acylhydrazone-based coumarin supramolecular polymer, chemosensor OGC (3%, n-BuOH/H₂O), which showed sequential detection and separation of CN^-, Fe³⁺ and S^2-, Ag⁺ in the gel state with high selectivity and sensitivity. Moreover, the ion-responsive films were prepared for the convenient and continuous detection of CN^-, Fe³⁺ and S^2-, Ag⁺ in water solution.

A novel pillar[5]arene-based emission enhanced supramolecular sensor for dual-channel selective detection and separation of Hg2+

We constructed a supramolecular sensor (APRA–G) via a host–guest inclusion interaction between a rhodamine hydrazide-functionalized pillar[5]arene (APRA) and a bipyridine salt guest (G), which formed a stable dimer.

Novel cyanide supramolecular fluorescent chemosensor constructed from a quinoline hydrazone functionalized-pillar[5]arene

Herein, we report a simple and novel approach for the design of fluorescent chemosensor through the self-assembly of functionalized monomer molecules. According to these approach, a novel supramolecular fluorescent chemosensor (SPMS) was successfully constructed by self-assembly of a quinoline hydrazone functionalized pillar[5]arene monomer PM. Interestingly, upon the addition of CN^-, the solution of SPMS instantly shows dramatic fluorescent enhancement and emitting bright blue emission. Meanwhile, the fluorescence quantum yields show distinct increase from 0.0582 of SPMS to 0.3952 of SPMS + CN^-. The detection limit (LOD) of SPMS for CN^- is 9.70 × 10^-8 M, which indicated high sensitivity. Moreover, the SPMS is selective for CN^- even in the presence of other anions, the fluorescent detection process of SPMS for CN^- was not interfered by other competitive anions (F^-, Cl^-, Br^-, I^-, N₃^-, OH^-, SCN^-, HSO₄^-, AcO^-, H₂PO₄^- and ClO₄^-). Notably, in the CN^- sensing process, the self-assembly structure of the supramolecular chemosensor SPMS didn't show any disassembly. This work provides a novel approach for instant detection of CN^- through a self-assembled supramolecular fluorescent chemosensor in aqueous system. Moreover, the test strips based on SPMS were fabricated, which could serve as convenient and efficient CN^- test kits.

A novel long-alkyl-chained acylhydrazone-based supramolecular polymer gel for the ultrasensitive detection and separation of multianalytes

By rationally introducing multi-self-assembly driving forces and coordination binding sites into the same molecule, a designed functional gelator, G, was synthesized. Next, a novel supramolecular polymer material, OGV (1% DMSO), was constructed and used for the ultrasensitive detection and separation of multianalytes in gel states. Interestingly, OGV showed a fluorescent ultrasensitive response for the Hg2+ and Fe3+ ions in water. Moreover, by introducing these metal ions into the OGV, stable metal ion-coordinated supramolecular metallogels (HgG and FeG) were formed, which could sense CN- and H2PO4- in water with high selectivity and sensitivity.

A hydrazono-quinoline-based chemosensor sensing In3+ and Zn2+via fluorescence turn-on and ClO−via color change in aqueous solution

A multi-target sensor, based on hydrazono-quinoline, was developed for fluorescence turn-on detection of In³⁺ and Zn²⁺ and colorimetric detection of ClO⁻.

A multi-stimuli responsive metallosupramolecular polypseudorotaxane gel constructed by self-assembly of a pillar[5]arene-based pseudo[3]rotaxane via zinc ion coordination and its application for highly sensitive fluorescence recognition of metal ions

A novel pillar[5]arene-based metallosupramolecular polypseudorotaxane gel has been successfully prepared.