Pyrene Derivative Emitting Red or near-Infrared Light with Monomer/Excimer Conversion and Its Application to Ratiometric Detection of Hypochlorite

Benzo[1,2-b:6,5-b']dithiophene-4,5-diamine: A New Fluorescent Probe for the High-Sensitivity and Real-Time Visual Monitoring of Phosgene

The detection of highly toxic chemicals such as phosgene is crucial for addressing the severe threats to human health and public safety posed by terrorist attacks and industrial mishaps. However, timely and precise monitoring of phosgene at a low cost remains a significant challenge. This work is the first to report a novel fluorescent system based on the Intramolecular Charge Transfer (ICT) effect, which can rapidly detect phosgene in both solution and gas phases with high sensitivity by integrating a benzo[1,2-b:6,5-b']dithiophene-4,5-diamine (BDTA) probe. Among existing detecting methods, this fluorescent system stands out as it can respond to phosgene within a mere 30 s and has a detection limit as low as 0.16 μM in solution. Furthermore, the sensing mechanism was rigorously validated through high-resolution mass spectrometry (HRMS) and density functional theory (DFT) calculations. As a result, this fluorescent probing system for phosgene can be effectively adapted for real-time, high-sensitivity sensing and used as a test strip for visual monitoring without the need for specific equipment, which will also provide a new strategy for the fluorescent detection of other toxic materials.

Modulation of AIE and Intramolecular Charge Transfer of a Pyrene-Based Probe for Discriminatory Detection and Imaging of Oligomers and Amyloid Fibrils

Oligomers and amyloid fibrils formed at different stages of protein aggregation are important biomarkers for a variety of neurodegenerative diseases including Alzheimer's and Parkinson's diseases. The development of probes for the sensitive detection of oligomeric species is important for early stage diagnosis of amyloidogenic diseases. Many small molecular dyes have been developed to probe the dynamic growth of amyloid fibrils. However, there is a lack of discriminatory detection strategies to monitor the dynamics of both oligomers and amyloid fibrils based on the differential modulation of the photophysical properties of a single dye. Here we report a pyrene-based intramolecular charge transfer (ICT) dye with large Stokes shifted red-emitting aggregation induced emission (AIE) for monitoring the dynamic populations of both oligomers and fibrils during the aggregation of hen egg white lysozyme (HEWL) protein. At the early stage of protein aggregation, the accumulation of HEWL oligomers results in a rapid and substantial increase in the red AIE intensity at 660 nm. Later, as the oligomers transform into mature fibrils, the dye exhibits a distinct photophysical change. Binding of the dye to HEWL fibrils strongly suppresses the red AIE and enhances ICT emission. This is evidenced by a gradual decrease in the AIE intensity (∼660 nm) and an increase in LE (∼490 nm) and ICT (∼540 nm) emission intensities during the later stages of protein aggregation. Thus, the dye provides simultaneous measurements of the population dynamics of both HEWL oligomers and fibrils during protein aggregation based on the discriminatory modulation of AIE and ICT of the dye. The dye also enables imaging of both HEWL oligomers and fibrils simultaneously using different emission channels in super-resolution confocal fluorescence microscopy.

Synthesis of Tough and Fluorescent Self-Healing Elastomers by Scandium-Catalyzed Terpolymerization of Pyrenylethenylstyrene, Ethylene, and Anisylpropylene

The synthesis of fluorescent self-healing polymers by the incorporation of a fluorophore-containing olefin into a polyolefin backbone through catalyst-controlled multicomponent copolymerization is of fundamental interest and practical importance, but such an approach has remained unexplored to date. Herein, we report for the first time the synthesis of tough and fluorescent self-healing polymers by sequence-controlled terpolymerization of 4-[2-(1-pyrenyl)ethenyl]styrene (Pyr), ethylene (E), and anisylpropylene (AP) using a sterically demanding half-sandwich scandium catalyst. The resulting terpolymers consisted of relatively long alternating E-alt-AP sequences, isolated Pyr units, and short E-E blocks, which exhibited excellent tensile strength, remarkable self-healability, and high fluorescence quantum yield. The excellent mechanical and self-healing properties could be attributed to the nanophase separation of the crystalline E-E segments and the hard Pyr aggregates from a flexible E-alt-AP segment matrix, in which the Pyr units not only served as an efficient fluorophore but also played an important role in forming nanodomains and enhancing the polymer mobility. Furthermore, the styrenyl C═C bond of the Pyr unit in the terpolymers could undergo [2 + 2] cycloaddition under photoirradiation, which thus enabled the fabrication of a self-healable fluorescent two-dimensional image on a terpolymer film through photolithography. This work offers an unprecedented efficient protocol for the synthesis of a brand-new family of fluorescent self-healing materials, showcasing the high potential of catalyst-controlled sequence-regular copolymerization of different olefins for the creation of novel functional polymers.

Bioimaging of a chromenoquinoline-based ratiometric fluorescent probe for detecting ClO. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023;303:123256. [PMID: 37579661 DOI: 10.1016/j.saa.2023.123256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Hypochlorous acid (HClO) is a reactive oxygen species and a relatively strong antibacterial substance in the immune defense system. The normal concentration of HClO in the human body is approximately 200 μM, and its high concentration can cause tissue damage and some diseases. Herein, a chromenoquinoline-based ratiometric fluorescent probe was developed to detect and quantify HClO. The developed Probe 1 exhibited the advantages of large Stokes shift (137 nm), high synthetic yield (84.7 %), simple synthesis method, short response time (<4 min), low detection limit (5.1 nM), and low toxicity. The probe was successfully validated in live cells and zebrafish.

Bis-cyanostilbene based fluorescent materials: A rational design of AIE active probe for hypochlorite sensing

In the present investigation cyanostilbene based molecular probes, PCS and PCO, bearing N,N-dimethylthiocarbamate and N,N-dimethylcarbamoyal groups, respectively, have been synthesised. These probes exhibit AIEE activity in their aggregated state in the mixed solvent system of THF: H2O by way of turning on their emission, which has also been observed in powder, neat thin films and hybrid polymer films. While the probe PCO is silent to ClO-, PCS exhibits a significant response towards ClO- rationalised on the basis of HOCl specific oxidation of thiocarbamate, which is also extended to detect ClO- in water samples. Additionally, applicability of the test strips of PCS for rapid on-site detection of ClO- has been demonstrated. The experimental results are supplemented by the theoretical calculations wherever possible.

Monitoring of Hypochlorite Level in Fruits, Vegetables, and Dairy Products: A BODIPY-Based Fluorescent Probe for the Rapid and Highly Selective Detection of Hypochlorite

Hypochlorite/hypochlorous acid (ClO^-/HOCl), among the diverse reactive oxygen species, plays a vital role in various biological processes. Besides, ClO^- is widely known as a sanitizer for fruits, vegetables, and fresh-cut produce, killing bacteria and pathogens. However, excessive level of ClO^- can lead to the oxidation of biomolecules such as DNA, RNA, and proteins, threatening vital organs. Therefore, reliable and effective methods are of utmost importance to monitor trace amounts of ClO^-. In this work, a novel BODIPY-based fluorescent probe bearing thiophene and a malononitrile moiety (BOD-CN) was designed and constructed to efficiently detect ClO^-, which exhibited distinct features such as excellent selectivity, sensitivity (LOD = 83.3 nM), and rapid response (<30 s). Importantly, the probe successfully detected ClO^- in various spiked water, milk, vegetable, and fruit samples. In all, BOD-CN offers a clearly promising approach to describe the quality of ClO^--added dairy products, water, fresh vegetables, and fruits.

Design of a large Stokes shift ratiometric fluorescent sensor with hypochlorite detection towards the potential application as invisible security ink

Hypochlorite (ClO^-) as a well-known highly reactive oxygen species (ROS), is widely used as preservative and household disinfectant in daily life. Although many fluorescence imaging sensors for ClO^- have been reported, the development of ClO^- ratio fluorescence sensors with large Stokes shift is still quite limited. This sensor shows obvious benefits including minimizing environmental intervention and improving signal-to-noise ratio. In the present project, we report an innovative conjugated pyrene-based system, 1-B, as a chlorine fluorescence sensor. The detector exhibits ratio detection performance, large Stokes and emission shifts. Furthermore, the system has desired sensitivity as well as selectivity for ClO^-. Based on these excellent properties, the sensor 1-B was successfully used as ink to encrypt patterns and anti-counterfeiting information through inkjet printing technology. Compared with the existing probes, the probe shows some superior characteristics, which provides a promising tool for exploring the role of ClO^- response sensor in the field of anti-counterfeiting.

A TD-DFT study of a class of D-π-A fluorescent probes for detection of typical oxidants

A deep understanding of the fluorescence response mechanisms is the foundation for design-oriented strategies for D-π-A probes for trace hazardous chemicals. Here, from the perspective of electronegativity regulation of the π-bridge recognition site, an electron-donation modulation strategy involving various comprehensive evaluations of the optical and chemical properties is proposed through a series of theoretical analyses. Due to the preferential combined interaction between the π-bridge recognition site and MnO₄^-, high electrophilic reactivity and feasible chemical reaction energy barrier, a high-performance filter paper chip and hydrogel chip for the detection of aqueous and air-suspended environmental KMnO₄ was achieved. We expect the present modulation strategy will facilitate efficient fluorescent probe design and provide a universal methodology for the exploration of functional D-π-A molecules.

Recent Advances in Excimer-Based Fluorescence Probes for Biological Applications

The fluorescent probe is a powerful tool for biological sensing and optical imaging, which can directly display analytes at the molecular level. It provides not only direct visualization of biological structures and processes, but also the capability of drug delivery systems regarding the target therapy. Conventional fluorescent probes are mainly based on monomer emission which has two distinguishing shortcomings in practice: small Stokes shifts and short lifetimes. Compared with monomer-based emission, excimer-based fluorescent probes have large Stokes shifts and long lifetimes which benefit biological applications. Recent progress in excimer-based fluorescent sensors (organic small molecules only) for biological applications are highlighted in this review, including materials and mechanisms as well as their representative applications. The progress suggests that excimer-based fluorescent probes have advantages and potential for bioanalytical applications.

Methyl position affect the fluorescence performance of HBT derivatives for the detection of hypochlorite under alkaline condition

Five fluorescent derivatives of hydroxyphenyl-benzothiazole (HBT) with different methyl positions at the hydroxyphenyl group were synthesized with good yield. Their reactivity and fluorescent response to hypochlorite were carefully studied. It was found that the HBT derivatives with meta-methyl (3-HBT or 5-HBT) showed the highest reactivity to hypochlorite under basic conditions, accompanied by the most efficient fluorescence quenching, whereas HBT derivatives with ortho or para methyl exhibited the least reactivity to hypochlorite. The LUMO and HOMO of 3-HBT were further verified to explain the fluorescence behavior by density functional theory (DFT) calculation. The excellent selectivity of 3-HBT toward hypochlorite against other reactive oxygen species (ROS) was also evaluated under the same conditions. The compounds emit bright green fluorescence in a solid-state, which is convenient for designing sensing devices for hypochlorite in water samples. Thus, the HBT derivatives with meta methyl (3-HBT) were successfully applied to fabricate paper sensors for the quantification of hypochlorite in tap water. Hence, the fluorescent 3-HBT exhibits great promise as a selective and sensitive hypochlorite probe in chemical and biological applications.

FAP-α-Instructed Coumarin Excimer Formation for High Contrast Fluorescence Imaging of Tumor

Emissive excimers, which are formed by planar polycyclic aromatic fluorophores (e.g., coumarin), enable high contrast tumor imaging. However, it is still challenging to "turn on" excimer fluorescence in physiological dilute solutions. The biocompatible CBT-Cys click condensation reaction enables both intra- and intermolecular aggregations of the as-loaded fluorophores on the probe molecules, which may promote the generation of emissive excimers in a synergistic manner. As a proof-of-concept, we herein design a fluorescence probe Cbz-Gly-Pro-Cys(StBu)-Lys(coumarin)-CBT (Cbz-GPC(StBu)K(Cou)-CBT), which can be activated by FAP-α under tumor-inherent reduction conditions, undergo a CBT-Cys click reaction, and self-assemble into coumarin nanoparticle Cou-CBT-NP to "turn on" the excimer fluorescence. In vitro and in vivo studies validate that this "smart" probe realizes efficient excimer fluorescence imaging of FAP-α-overexpressed tumor cells with high contrast and enhanced accumulation, respectively. We anticipate that this probe can be applied for diagnosis of FAP-α-related diseases in the clinic in near future.

Mitochondria-Targeted Ratiometric Chemdosimeter to Detect Hypochlorite Acid for Monitoring the Drug-Damaged Liver and Kidney

Liver and kidney injury caused by drug toxicity is a serious threat to human health. Acetaminophenol (APAP), as a common antipyretic and analgesic drug, inevitably causes injury. When it is overused, hypochlorous acid (HClO) is excessively generated due to metabolic abnormalities, resulting in the accumulation of HClO in the mitochondria of liver and kidney tissues and causing damage. In this study, we designed a series of HClO responsive ratiometric chemdosimeter NRH-X (NRH-O, NRH-S, and NRH-C) to evaluate liver and kidney injury, and found that NRH-O has a specific sensitive response to HClO. NRH-O can not only monitor the variations of endogenous HClO content of living cells by fluorescence ratio changes in the mitochondria but also detect the upregulation of HClO induced by APAP. In addition, NRH-O can also be used for anatomic diagnosis of liver and kidney injury by fluorescence ratio imaging of HClO in the tissues of inflammatory mice.

A benzothiazole-based fluorescent and colorimetric probe for the detection of ClO- and its application to zebrafish and water sample

A benzothiazole-based fluorescent and colorimetric chemosensor BZD ((E)-2-(benzo[d]thiazol-2-yl)-5-((4-(diethylamino)-2-hydroxybenzylidene)amino)phenol) was applied for detecting ClO^-. BZD showed fluorescence quenching and color variation for ClO^- via oxidative reaction between ClO^- and the imine bond. It could effectively detect ClO^- over various competitive analytes. Detection limit for ClO^- was calculated to be 1.74 μM by fluorescent method and 16.44 μM by colorimetric one, respectively. Additionally, BZD could be utilized for sensing ClO^- in zebrafish, real water sample and paper strip. The photophysical characteristics and sensing mechanism of BZD to ClO^- were studied by fluorescent and UV-visible spectroscopy, NMR titration, and ESI-mass spectrometry.

Comparative studies on the absorption and fluorescence responses of hemicyanine to HSO3-, CN-, HS- and ClO. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022;269:120781. [PMID: 34968839 DOI: 10.1016/j.saa.2021.120781]

A fluorescent probe Hcy-Im bearing an indolium-hemicyanine structure was designed and synthesized to compare its responses to four anions, namely HSO₃^-, CN^-, HS^- and ClO^-. The results disclosed that Hcy-Im reacted with all these four anions in 5% DMSO-PBS buffer with different speeds and spectral changes. Hcy-Im responded to HSO₃^- markedly quicker than CN^- and HS^-, and it responded to CN^- a little quicker than HS^- while the response to ClO^- was much slower than the other three anions. The detection limits for these four anions were calculated to be 0.15 μM, 1.32 μM, 2.07 μM and 2.29 μM, respectively. The characteristic conjugated CN⁺ and CC bonds in Hcy-Im were responsible for the responses towards these four anions via a Michael addition-rearrangement reaction, a 1, 2-addition reaction or an oxidation reaction. These different sensing mechanisms were verified by ¹HNMR and HRMS. Thus, it could be inferred that hemicyanine-based fluorescent probe could detect HSO₃^- sensitively and selectively while the interference of HSO₃^- should not be neglected when it was used for the detection of CN^-, HS^- and ClO^-. Moreover, as HSO₃^-, HS^- and ClO^- are anions endogenously generated in human bodies, enough attention should be paid to the presence of physiological level of these three anions in certain tissues when hemicyanine-based fluorescent probe is applied for the detection of biorelevant analytes in biological samples.

A spectroscopic probe for hypochlorous acid detection

A spectroscopic probe CMBT was synthesized and characterized. CMBT showed the specific recognition for HClO based on the turn-on blue fluorescence and naked-eye change from pink to colorless. NMR, IR, HRMS-ESI, and spectral analysis suggested that colorimetric and fluorescent change of CMBT to HClO originated from the conversion of CMBT to starting material coumarin-aldehyde 1 caused by the oxidization of HClO, which was responsible for the fluorescence recovery. The detection limit was calculated to be 1.61 μM and 6.58 μM for fluorescence and UV-vis analysis with a range up to 1 mM. HClO's fluorescence detection was successfully achieved in tap and river water samples. The prepared convenient paper test strips showed a distinct color change in varying concentrations of HClO. A multi-input molecular logic circuit was constructed.

Facile synthesis of an ambient stable pyreno[4,5-b]pyrrole monoanion and pyreno[4,5-b:9,10-b']dipyrrole dianion: from serendipity to design

The stability of singly or multiply negatively charged π-conjugated organic compounds is greatly influenced by their electronic delocalization. Herein, we report a strategic methodology for isolation of a mysterious compound. The isolated compounds, a pyreno[4,5-b]pyrrole monoanion and pyreno[4,5-b:9,10-b′]dipyrrole dianion, were highly stable under ambient conditions due to high delocalization of the negative charge over multiple electron deficient C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N groups and pyrene π-scaffolds and allowed purification by column chromatography. To our knowledge, this is the first report on TCNE type reductive condensation of malononitrile involving pyrene di- and tetraone and formation of pyrenopyrrole. All compounds were characterized by spectroscopic methods and X-ray crystallography. A UV-vis spectroscopic study shows an intense low energy absorption band with a large absorption coefficient (ε).

An ambient stable pyreno[4,5-b]pyrrole monoanion and pyreno[4,5-b:9,10-b′]dipyrrole dianion have been isolated and characterized, showing a low energy intense absorption band with the absorption coefficient reaching 7.1 × 10⁴ dm³ mol⁻¹ cm⁻¹.

A phenanthridine-based probe for selective detection of hypochlorite ions

A novel oxime-based fluorescent chemosensor (E)-2-(4′-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1′-biphenyl]-4-yl)ethen-1-ol (PBO) has been developed for the fluorimetric detection of hypochlorite ion (OCl−).

Two-photon ratiometric fluorescent probe for imaging of hypochlorous acid in acute lung injury and its remediation effect

Acute lung injury (ALI) is a pulmonary inflammatory disease with high morbidity and mortality rates. However, owing to the unknown etiology and rapid progression of the disease, the diagnosis of ALI is full of challenges with no effective treatment. Since the inflammatory response and oxidative stress played vital roles in the development of ALI, we herein developed the largest emission cross-shift (△λ = 145 nm) two-photon ratiometric fluorescent probe of TPRS-HOCl with high selectivity and short response time toward hypochlorous acid (HOCl) for exploring the relevance between the degree of ALI and HOCl concentration in the development process of the disease. In addition, the inhibition effect of HOCl during different treatment periods was also evaluated. Moreover, the tendency of imaging results was basically in accordance with that of hematoxylin and eosin (H&E) staining and the treatment effect became better in the early stage when using N-acetylcysteine (NAC), demonstrating the sensitivity of TPRS-HOCl toward ALI response. Thus, TPRS-HOCl has great potential to diagnose ALI in the early stage and guide for effective treatment.

A TICT + AIE based fluorescent probe for ultrafast response of hypochlorite in living cells and mouse

Hypochlorite (HClO/ClO^-), an important reactive oxygen species (ROS), plays a significant role in the human immune system. Thus, developing a fast and efficient method for detecting ClO^- is quite necessary. Herein, we designed and synthesized a fluorescent probe TPB-CN based on twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) characteristics. The probe could respond to ClO^- with an ultrafast response velocity (<2 s). The detection limit was calculated to be 6.198 nM. In addition, probe TPB-CN was successfully applied for detecting ClO^- in living cells and mouse.

Development of a new water-soluble fluorescence probe for hypochlorous acid detection in drinking water

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A responsive small-molecule fluorescence probe is developed for hypochlorous acid (HOCl) detection.

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The new probe has good solubility and stability in water, can rapidly and selectively respond to HOCl in pure aqueous solution.

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HOCl-triggered specific reaction leads to a blue shift of UV–vis absorption and enhancement in fluorescence that are recorded for HOCl detection.

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The application of this probe for HOCl detection in drinking water samples is demonstrated.

Responsive small-molecule fluorescence probe specific for target analyte detection is an emerging technology for food safety and quality analysis. In this work, we report a new water soluble small-molecule fluorescence probe (PG) for the detection of hypochlorous acid (HOCl) in drinking water samples. Probe PG was developed by coupling of a glucosamine into 10-methyl-10H-phenothiazine fluorophore with a HOCl-responsive C=N bond. The thioether is another recognition site that can be oxidized to be sulfoxide in water. Due to the specific reactions triggered by HOCl, probe PG’s absorption band is blue shifted from 388 to 340 nm, and fluorescence at 488 nm is more than 55-fold enhanced. Probe PG features high fluorescence stability in PBS buffer with varied pH, fast response and high selectivity to HOCl. The application of the probe PG for HOCl detection in real-world samples is demonstrated by HOCl detection in drinking water, including tap water, purified water, and spring water samples. The recoveries of this method for HOCl detection in drinking water are in the range of 99.17–102.3%. This work thus provides a new method for HOCl detection in drinking water with high precision and accuracy.

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.

Achieving Organic Smart Fluorophores by Controlling the Balance between Intermolecular Interactions and External Stimuli

Organic smart fluorophores (OSFs) are highly desirable over the past decades because of their potential applications in advanced photonic devices. However, it is still difficult and challenging to obtain such materials with tunable photophysical properties and high emission efficiency based on robust construction strategies. Therefore, we proposed a simple and efficient strategy for constructing OSFs by balancing the competition between intermolecular interactions and external stimuli via molecular structure design. In this work, four pyrene derivatives (T1-Py, T4-Py, T12-Py, and S12-Py) with tunable stimuli-responsive properties were designed and synthesized. The tunable intermolecular interactions in solution states were successfully demonstrated by the molecular structure and solution concentration-dependent luminescence properties. The effect of alkyl chain length on molecular packing in solid states was investigated by polarized optical microscopy and powder and single-crystal X-ray diffraction; the results show that with the increase in molecular chain length, the molecular packing of the compounds gradually changed from π-π stacked compact mode to X-crossing stacked loose mode, which leads to different stimuli-responsive phenomena of these compounds. The strategy provided herein facilitates the construction of multistimuli-responsive (thermochromism, mechanochromism, and vapochromism) OSFs with adjustable emission color. Harnessing the heat-responsive luminescence properties and great solubility of T12-Py, the optical information anticounterfeiting based on temperature was demonstrated by printing different concentrations of T12-Py solution on filter papers. Much more, this research may provide broad implications for the design of organic smart materials based on intermolecular interactions.

Amphiphilic Diazapyrenes with Multiple Stimuli-Responsive Properties

A series of amphiphilic diazapyrenes exhibiting switchable fluorescence under the stimulus of mechanical force or water vapor are reported for the first time. Comprehensive studies of their photophysical properties in different states based on UV-Vis absorption, FL emission, FT-IR spectroscopy, and XRD analysis have revealed a stimuli-induced excimer-based sensing mechanism. The relationship between molecular structures and optical responsive properties of these diazapyrene derivatives is illustrated. Moreover, the unique fluorescent, stimuli-responsive behaviors of these diazapyrene compounds in the solid state are used to fabricate sensory films for successively and orthogonally sensing mechanical force and water vapor. In contrast to the well-established knowledge on the transformation between the pyrene monomer and excimer, our study offers valuable information about the unknown diazapyrene excimers and demonstrates their potential applications in biocompatible force sensors, data storage, and humidity sensors.

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.

Highly sensitive fluorescent probe for selective detection of hypochlorite ions using nitrogen-fluorine co-doped carbon nanodots

Hypochlorite ions (ClO^-) are widely used in bleaching agents and disinfectants. However, high concentrations of chloride species are harmful to human health. Therefore, effective methods for the detection of ClO^- ions are required. In this study, using 4-fluorophthalic acid and glycine, nitrogen-fluorine co-doped carbon nanodots (N,F-CDs) were synthesized by one-pot hydrothermal synthesis for use as a fluorescent probe for the fluorometric detection of ClO^- in aqueous media, based on the inhibition of n → π* transitions. The excitation and emission peak centers of the N,F-CDs are at 387 and 545 nm, respectively. The N,F-CDs show a fast quenching response (<1 min) for ClO^- and can be used in a wide pH range (pH 4-13). Under optimal conditions, the fluorescence intensity decreased with increase in the ClO^- concentration from 0 to 35 μM, and a low limit of detection (9.6 nM) was achieved. This probe possesses excellent selectivity and high sensitivity and was used to analyze standardized samples of piped water, achieving a satisfactory recovery. Thus, this nitrogen-fluorine co-doped nanodot probe is promising for the detection of pollutants.

Probing Transient DNA Conformation Changes with an Intercalative Fluorescent Excimer

Variation of DNA conformation is important in regulating gene expression and mediating drug-DNA interactions. However, directly probing transient DNA conformation changes is challenging owing to the dynamic nature of this process. We show a label-free fluorescence method to monitor transient DNA conformation changes in DNA structures with various lengths and shapes using a DNA intercalator, K21. K21 can form transient excimers on the surface of DNA; the ratiometric emission of monomer and excimer correlate to DNA transient conformation stability in numerous DNA structures, including i-motifs, G-quadruplex structures, and single nucleotide mutation at random position. We analyzed the conformation dynamics of a single plasmid before and after enzyme digestion with confocal fluorescence microscopy. This method provides a label-free fluorescence strategy to probe transient conformation changes of DNA structures and has potential in uncovering transient genomic processes in living cells.

One-step construction of a novel AIE probe based on diaminomaleonitrile and its application in double-detection of hypochlorites and formaldehyde gas

A novel and efficient probe with AIE property was designed and synthesized for application in double-detection of hypochlorites and formaldehyde gas.

Malononitrile as the 'double-edged sword' of passivation-activation regulating two ICT to highly sensitive and accurate ratiometric fluorescent detection for hypochlorous acid in biological system

Hypochlorous acid (HOCl) as one of the most important reactive oxygen species in the organism, its role is more and more recognized. In fact, in recent years, various HOCl fluorescent probes have been developed unprecedentively based on various mechanisms. However, because most of the mechanisms are based on the oxidation characteristics of HOCl, the excellent detection performance of probes depends on the activation ability of some functional groups to reaction sites. The C[bond, double bond]C bond in the probe is often oxidized by HOCl to realize HOCl detection. However, due to the break of conjugated structure, the probe often present as a quenchable or turning on fluorescence emission. In this work, malononitrile was introduced as the "double-edged sword" of passivation-activation when in HOCl fluorescent probe was designed. Passivation-activation regulated two ICT (Intermolecular Charge Transfer, ICT) processes to ratiometric fluorescent detection for HOCl. Highly sensitive and accurate detection realized efficient application in biological imaging.

Preparation of 1, 3, 6, 8-Pyrenesulfonic Acid Tetrasodium Salt Dye-Doped Silica Nanoparticles and Their Application in Water-Based Anti-Counterfeit Ink

In order to improve the luminescent stability of water-based anti-counterfeit ink, a new fluorescent material is prepared by doping dye into silica nanoparticles. Water soluble anionic dye 1, 3, 6, 8-pyrenesulfonic acid sodium salt (PTSA) is selected as the dopant. In this work, PTSA is successfully trapped into silica nanoparticles (SiNPs) by the reverse microemulsion method using cationic polyelectrolyte poly (dimethyl diallyl ammonium chloride; PDADMAC) as a bridge. The UV absorption spectra, fluorescence emission spectra and fluorescent decay curves are used to describe the luminescent properties of the PTSA-doped silica nanoparticles (PTSA-SiNPs). In addition, the as-prepared PTSA-SiNPs and polyurethane waterborne emulsion are used to prepare water-based anti-counterfeit ink, and fluorescent patterns are successfully printed through screen-printing. The samples printed by the ink exhibit desirable fluorescence properties, heat stability, robust photostability, and a fluorescent anti-counterfeit effect, which makes the PTSA-SiNPs promising luminescent materials for anti-counterfeit applications.