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[Display omitted] • A simple single step multicomponent ugi type reaction was carried out to yield N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). • The synthesized TBFIPA was characterized using 1H NMR, 13C NMR and HRMS spectroscopic methods. • The selective & sensitive detection was identified using hypsochromic shift (lab : 335nm → 285nm) & fluorescence quenching. • The proposed mechanism is evident from Job plot, 1H NMR titration, ESI-MS data and theoretical DFT calculation. • The Cr3+ ion-selective TBFIPA was successfully applied in the design of a user-friendly silica-based portable test kits. • Also, the fluorescence quenching ability of TBFIPA in presence of Cr3+ ions are validated by imaging onion epidermal cells. • Real samples contaminated with Cr3+ ions were identified using TBFIPA with an appropriated relative error percentage. A simple single step one pot multicomponent reaction was performed to synthesize N-(tert -butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm → 285 nm) in the UV–Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (k a) obtained from Benesi-Hildebrand plot is 0.21 × 105 M−1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10−7 M and 1.56 × 10−7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe YX is a near-infrared fluorescent probe. • The probe YX can complete continuous detection Zn2+ and PPi. • The probe YX has a good application prospect in biology. • The probe can detect Zn2+ and PPi in actual samples. As the second most abundant transition metal element in the human body, zinc ions play an important role in the normal growth and development of the human body. We have successfully synthesized a near-infrared fluorescent probe with FRET effect for the detection of Zn2+. Probe DR6G has good selectivity and anti-interference ability for Zn2+. When Zn2+ is added to the probe DR6G solution, it responds completely within seconds, releasing red fluorescence with a detection limit of 2.02 × 10−8 M. As the main product of ATP hydrolysis, PPi is indispensable in various metabolic activities in cells and the human body. Due to the strong binding ability of Zn2+ and PPi, it is easy to form ZnPPi precipitation, so we added PPi to the solution to complete the Zn2+ detection, and realized the continuous detection of PPi, and the detection limit was 2.06 × 10−8 M. Since Zn2+ and PPi play an important role in vivo, it is of great practical significance to design and synthesize a fluorescent probe that can continuously detect Zn2+ and PPi. Biological experiments have shown that the probe DR6G has low cytotoxicity and can complete the detection of exogenous Zn2+ and PPi in cells and living mice in vitro. Bacterial experiments have shown that the DR6G probe also has certain research value in the field of environmental monitoring and microbiology. Due to the constant variation of the fluorescence signals of Zn2+ and PPi during detection, we designed the logic gate program. In practical applications, the probe DR6G can quantitatively detect Zn2+ in zinc-containing oral liquids and qualitatively detect PPi in toothpaste. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new asymmetrical photochromic diarylethene (DTE-HQo) exhibiting multicolour photoswitching behaviors have been successfully synthesized. • DTE-HQo can effectively distinguishes between Zn2+ and Cd2+ through visual observation due their distinct binding mode. • DTE-HQo could be applied in cell imaging. A new asymmetrical photochromic diarylethene DTE-HQo composed of a 2-hydrazinoquinoline moiety as the binding unit for ions and dithenylethene as a photoswitching trigger was reported. DTE-HQo displayed favourable photochromism upon irradiation with UV/vis light. Its fluorescent behaviour could be efficiently modulated by light, Zn2+, Cd2+ and HSO 4 −. The binding of Zn2+ induced a strong fluorescence peak at 510 nm in D TE -HQo due to the formation of a 1:2 complex [Zn2+ + 2 D TE -HQo ], resulting in a notable colour change from dark to intense white emission. Triggered by Cd2+, D TE -HQo formed a 1:1 complex [Cd2+ + D TE -HQo ], leading to an enhanced emission intensity by 21-fold with an emission peak red-shifted from 461 nm to 514 nm. Unexpectedly, [Zn2+ + 2 D TE -HQo ] underwent hydrolysis when stimulated with water, generating a yellow-emitting complex [Zn2+ + D TE -HQo ]. This color change easily distinguishes it from Cd2+ complex. Additionally, DTE-HQo showed high selectivity towards HSO 4 − and exhibited distinct "turn-on" fluorescence with a colour change from dark to bright blue upon stimulation. Moreover, the strong emission complexes of DTE-HQo with Zn2+, Cd2+ and HSO 4 − could be effectively quenched during the photocyclization process. Therefore, DTE-HQo can serve as an unimolecular multicolour photoswitching chemosensor, offering potential applications as a multifunctional probe for detecting Zn2+, Cd2+ and HSO 4 −. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, it is of great significance to develop a novel fluorescent chemosensor for Cd(II) ions detection with cost-effective, rapid, facile and applicable to environment and biological milieus. Herein, we report a new peptide-based fluorescent chemosensor DSC (Dan-Ser-Cys-NH 2) based on dipeptide (Ser-Cys-NH 2) conjugated with dansyl group, which was synthesized using solid phase peptide synthesis (SPPS) technology. As designed, DSC exhibited fluorescent "turn-on" response for Cd2+ in 100% aqueous solution over a wide range of pH values based on photoinduced electron transfer (PET). The stoichiometry binding of DSC and Cd2+ was determined to be 2:1 by Job's plot and ESI-MS analysis. Furthermore, DSC showed highly sensitive for Cd2+ and a low detection limit of 13.8 nM. What's more, DSC has cell permeability and low cytotoxicity, and fluorescence imaging experiments demonstrated that DSC was capable of monitoring Cd2+ in living HK2 cells by confocal microscopy. Graphical abstract Unlabelled Image Highlights • A novel peptide-based fluorescent chemosensor DSC was synthesized. • DSC exhibited highly selective fluorescent "turn-on" response toward Cd2+ ions. • DSC displayed highly sensitive, with Cd2+ ions detection limits of 13.8 nM. • DSC could serve as a potential chemosensor to detect Cd2+ ions in living cells. [ABSTRACT FROM AUTHOR]

Abstract As an efficient turn-on fluorescent chemosensor for Al3+, a new coumarin derivative (CND) has been designed and synthesized by the condensation of 8-formyl-7-hydroxycoumarin with niacin hydrazide. The spectroscopic studies revealed that the sensor CND exhibited a remarkable fluorescence enhancement towards Al3+ with high selectivity and sensitivity in EtOH-HEPES (95:5, v/v, pH = 7.40), which was attributed to the photoinduced electron transfer (PET) and C N isomerization mechanism. Fluorescence titration calculations data showed that the detection limit and the association constants of CND for Al3+ were found to be 2.51 × 10−7 M and 9.64 × 104 M−1, respectively. The results of experiments, including Job's plot, 1H NMR titration and ESI-MS, revealed that the stoichiometric binding between CND and Al3+ was 1:1. The investigations of the pH dependency of CND for Al3+ detection, and the cell imaging suggested the sensor CND could be promisingly applied for the recognition of Al3+ in biological cells. Graphical Abstract Unlabelled Image Highlights • A novel coumarin-based fluorescence sensor for Al3+ was designed and synthesized. • This sensor has good selectivity and sensitivity for Al3+. • This sensor can be applied in live cells. [ABSTRACT FROM AUTHOR]

Abstract A novel fluorescent probe, phenolphthalein‑dialdehyde‑(2‑pyridyl) hydrazone (L), for sequentially detecting Al3+ and F− in almost 100% aqueous medium was successfully designed and synthesized. The probe offers two binding pockets for Al3+ to form a 1: 2 ligand/metal complex, leading to a significant fluorescence enhancement at 465 nm. Further, the in-situ formed L-Al complex acts as a secondary fluorescent chemosensor for F− by quenching the fluorescence of the complex with high selectivity. The detection limit for Al3+ and F− sensing is 2.28 nM and 0.13 μM, respectively, which are far below the World Health Organization (WHO) acceptable limits (7.41 μM for Al3+ ion and 79 μM for F−) in drinking water. The probe L was successfully applied to the detection of Al3+ and F− in cells using fluorescence microscopy. Graphical Abstract The new fluorescent probe L can be used for selective detection of Al3+ and F− in almost 100% aqueous medium and live cells. Unlabelled Image Highlights • A new fluorescent probe L was synthesized and characterized • L can be used for selective detection of Al3+ and F−. • L exhibits a fluorescence response in almost 100% aqueous medium and live cells. • The detection limit for Al3+ was as low as nano-molar level. • L was employed for imaging the Al3+ and F− in living biological cells. [ABSTRACT FROM AUTHOR]

Abstract Hydrazino-carbothioamide, 1 , serves as a turn-on fluorescent chemosensor to Zn2+ and the mixture shows green emission (λ em 492) in presence of large number of ions with impressive limit of detection (LOD), 0.59 nM. Intense fluorescence of Zn-complex is selectively turn-off upon adding H 2 PO 4 − only to the limit of detection, 26 μM, while other anions remain silent. The sensing mechanism of 1 is established by suppressing the ESIPT of 1 and complexation with Zn2+ (CHEF) is supported by Job's plot, 1H NMR, and HR-MS data. Turn-on-off sequential detection of Zn2+ and H 2 PO 4 − also have successfully been employed for the engineering of INHIBIT molecular logic gate. The sensor is non-toxic and has been used in identifying Zn2+ in the intracellular region of African green monkey kidney cells (Vero cells). Graphical Abstract Very low detection limit (0.59 nM) is shown by green emission (492 nm) of hydrazino-carbothioamide probe on binding selectively with Zn2+ at pH, 7.2 which is specifically quenched by H 2 PO 4 − with LOD, 26 μM. This probe uses detection of Zn2+ in Vero cells and INHIBIT logic gate is constituted. Unlabelled Image Highlights • Hydrazino-carbothioamide sensor shows green emission with Zn2+. • Highly selective turn-on Zn2+ sensor shows LOD 0.59 nM. • Emission of the complex is quenched specifically upon addition of H 2 PO 4 − and LOD is 26 μM. • The sensor is non-toxic and identifies Zn2+ in the intracellular region of Vero cells. • Emission change at 492 nm with Zn2+ and H 2 PO 4 − can be described to INHIBIT logic gate. [ABSTRACT FROM AUTHOR]

Abstract A new naphthalene-quinoline based chemosensor L was prepared and structurally characterized. L exhibited excellent selectivity and sensitivity to Al3+ through distinct fluorescence enhancement (335-fold) and ratiometric detection in DMF/H 2 O (v/v, 1/9) based on the combined mechanisms of ESIPT and CHEF. The recognizing behavior of L toward Al3+ had been investigated in detail through Job's Plot, FT-IR, HNMR, and HRMS analysis. The limit of detection (LOD) for Al3+ was as low as and 3.67 × 10−8 M. L was successfully applied in real sample detection and construction of molecular logic gate. Moreover, L was verified to be of low cytotoxicity and good imaging characteristics for the detection of Al3+ in cells HSC. Graphical abstract Unlabelled Image Highlights • A naphthalene-quinoline based chemosensor L was prepared and structurally characterized. • L exhibited excellent selectivity and sensitivity to Al3+ through fluorescence enhancement (335-fold) and ratiometric detection. • The limit of detection (LOD) for Al3+ was determined as 3.67 × 10−8 M. • L was successfully applied in the detection of Al3+ in cells HSC. [ABSTRACT FROM AUTHOR]

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu 2+ was designed and synthesized. Fluorescence and UV–vis spectra studies demonstrated that L can detect Cu 2+ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu 2+ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu 2+ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu 2+ displayed L had cell permeability and detection ability for Cu 2+ in live cells. [ABSTRACT FROM AUTHOR]

An effort of a new Schiff base macrocyclic chemosensor, 1 4 ‑methyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecaphane‑2,5,8,11,14,17‑hexaene (me1) and 1 4 ,7 4 ‑dimethyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecadecaphane‑2,5,8,11,14,17‑hexaene (dm2), which enables selective sensing of Al 3+ in aqueous DMF were synthesized by a simplistic one-step condensation reaction of macrocyclic compounds. The probe me1 and dm2 characterized by elemental analysis, FT-IR, 1 H and 13 C NMR, LC-MS spectral techniques. The compounds as mentioned above subjected to FE-SEM with EDS and elemental color mapping. On addition of Al 3+ , the fluorescent probe me1 and dm2 induces turn-on responses in both absorption and sensing spectra by a PET mechanism. The receptor me1 and dm2 serve highly selective, sensitive and turn-on detection of Al 3+ . Further, they did not interfere with other cations present in biological or environmental samples. The detection limit is found to be 3 μM and 5 μM. From the view of cytotoxic activity, the ability of these compounds me1 and dm2 to inhibit the growth of KB cell lines examined. The chelating functionality of compounds me1 and dm2 examined for their inhibitory properties of KB cell, live cell images. The compounds me1 and dm2 subjected to theoretical studies by DFT-B3LYP invoking the 6-31G level of theory. The energy of the HOMO and LUMO has been established. [ABSTRACT FROM AUTHOR]

A coumarin-based sensor C1 , namely 3-acetoacetylcoumarin was designed, synthesized and applied for hydrazine detection. Hydrazinolysis of the chemosensor gives a fluorescent coumarin-pyrazole product C1 − N 2 H 4 [3-(3-methyl-1H-pyrazol-5-yl)coumarin], and thus resulting in a prominent fluorescence off-on response toward hydrazine under physiological conditions. The probe is highly selective toward hydrazine over cations, anions and other biologically/environmentally abundant analytes. The detection limit of the probe is 3.2 ppb. The sensing mechanism was supported by 1 H NMR, IR, MS and DFT calculation. The application of the fluorescent probe in monitoring intracellular hydrazine in glioma cell line U251 was also demonstrated. [ABSTRACT FROM AUTHOR]

A fluorescence probe has been designed and synthesized, and applied with a combined theoretical and experimental study. Research suggests that the probe can be used to sense Zn 2 + and Hg 2 + through selective turn-on fluorescence responses in the aqueous HEPES buffer (0.05M, pH = 7.4). The limit of detection (LOD) were determined as 1.46 × 10 − 7 M (Zn 2 + ) and 2.50 × 10 − 7 M (Hg 2 + ). Moreover, based on DFT, the geometry optimizations of probe 1, [1-Hg 2 + ] complex and [1-Zn 2 + ] complex were carried out using the Gaussian 09 program, in which the B3LYP function was used. The electronic properties of free probe 1 and the metal complexes were studied based on the Natural Bond Orbital (NBO) analyses. The probe 1 has also been successfully applied to detection of Zn 2 + and Hg 2 + in living cells. [ABSTRACT FROM AUTHOR]

A kind of biomass CDs (F-CDs) with the polysaccharide-rich precursor of Flammulina velutipes (F. velutipes) through a simple one-step hydrothermal approach, are used as fluorescent •OH-responsive sensors for sensing and intracellular imaging of •OH. [Display omitted] • Biomass CDs are synthesized with Flammulina velutipes by a hydrothermal method. • The CDs have remarkable sensitivity and selectivity for quantitative •OH assay. • The CDs can monitor intracellular •OH levels in cells by fluorescence imaging. Monitoring hydroxyl radical (•OH) fluctuation is of great importance to study some relative pathological processes and to predict early diagnosis of diseases. Efficient •OH-responsive fluorescent sensors based on carbon dots (CDs) have been reported, but most researches have focused on the new strategies for the synthesis and doping of the CDs. Herein, a kind of biomass CDs (F-CDs) with Flammulina velutipes (F. velutipes) as the carbon source was prepared by a one-step hydrothermal method without any additional modification. The prepared F-CDs have remarkable sensitivity and selectivity and there is a good linear relationship from 0 to 12 μM with a low detection limit of 95 nM for quantitative •OH assay. With excitation-independent emission, favourable biocompatibility and low toxicity, the F-CDs can penetrate cell membranes as •OH-responsive fluorescent sensors to detect intracellular •OH in A549 cells stimulated by phorbol 12-myristate 13-acetate (PMA) and successfully monitor the •OH concentration levels by the corresponding fluorescence change. Given the combined benefits of the green and eco-friendly approach, the F-CDs show promise as novel theranostics tools for early detection and treatment of related diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • BQL demonstrated a large Stokes shift (minimizing interference from autofluorescence) and a good response to viscosity (using the TICT principle). • BQL demonstrated little to no pH-dependency, polarity-dependency, or interference from other analytes. • BQL was used to monitor viscosity changes in mitochondria induced by ion carriers, and was used to report on viscosity in real time during mitophagy. Mitochondria are the sites of respiration in cells, and they participate in many indispensable biological processes. Because variations in mitochondrial viscosity can lead to dysfunctions of mitochondrial structure and function (and even induce malignant diseases), new sensors that can accurately monitor changes in mitochondrial viscosity are essential. To better investigate these changes, we report the development and evaluation of a novel benzothiophene-quinoline-based fluorescent chemosensor (BQL) that was designed especially for monitoring mitochondrial viscosity. BQL demonstrated a large Stokes shift (minimizing interference from autofluorescence) and a good response to viscosity (using the TICT principle). Moreover, BQL demonstrated little to no pH-dependency, polarity-dependency, or interference from other analytes. Thus, BQL has an excellent specificity for viscosity. BQL was used to monitor viscosity changes in mitochondria induced by ion carriers, and was used to report on viscosity in real time during mitophagy. To sum up, BQL provided a new approach for detecting viscosity in living cells and in vivo. BQL should prove to be an excellent tool for the analysis of viscosity changes in live cells. [ABSTRACT FROM AUTHOR]

A novel pyridyl functionalized rhodamine dye with large Stokes shift and stable fluorescence in water was facilely prepared and utilized for a Hg2+-selective probe. [Display omitted] • A Rhodamine derivative PR has been prepared with Stokes shift of 81 nm. • Probe PRHg is synthesized, presenting high selectivity and sensitivity (LOD: 8.5 nM) to Hg2+. • PRHg exhibits great potential for tracing Hg2+ in living cells. Rhodamines gain sustained attention owing to their great potential for probe design applications. Herein, the facile preparation of a new pyridyl functionalized rhodamine dye PR is reported, which has stable fluorescence signal in water with maximum emission peak at 594 nm and Stokes shift of 81 nm. Based on dye PR , a new fluorescent probe PRHg has been developed by modifying the spirolactone of PR with hydrazine hydrate so as to produce spirolactam recognizing group for sensing of Hg2+. PRHg exhibits high selectivity and sensitivity towards Hg2+ in water/ethanol (v/v = 4/1, pH = 7.0) by a specific Hg2+-binding promoted spirolactam ring opening and hydrolyzing process. And, the detection limit for Hg2+ is evaluated to be 8.5 nM. Besides, the probe can respond to Hg2+ within 40 min and over a wide pH range from 4.0 to 10.0. Moreover, PRHg (40 µM) performs low cytotoxicity to HeLa cells (over 91.0 % cell survival rate), which allows the probe to be employed for tracing intracellular Hg2+ by fluorescence imaging. [ABSTRACT FROM AUTHOR]

A simple and efficient fluorescent chemosensor for Al 3 + is reported in the paper. The chemosensor is obtained by dehydration reaction of 2-hydroxy-1-naphthaldehyde and 2-aminophenol. The chemosensor has high selectivity and sensitivity for Al 3 + and displays fluorescence “off–on” switch signal. The detection limit of the chemosensor for Al 3 + can reach 1.0 × 10 − 7 M in DMSO/H 2 O (1:9, v/v) solution. The mass spectra and Job's plot analysis confirm the 1:1 stoichiometry between chemosensor and Al 3 + . Potential utilization of the probe as an intracellular sensor of Al 3 + in human cancer (HiSa) cells is also examined by confocal fluorescence microscopy. [ABSTRACT FROM AUTHOR]

A novel fluorogenic "turn-on" sensor NPP based on naphthalimide and picolinohydrazide units was prepared for highly selective Al3+ detection. This "signal-on" probe NPP has been efficiently utilized for Al3+ detection in real samples. [Display omitted] • A novel naphthalimide-picolinohydrazide derived optical chemosensor NPP is presented for Al3+. • NPP exhibited hypersensitive toward Al3+ with rapid signal response (1 min). • Limit of detection (LOD) of NPP for Al3+ was as low as 39 nM. • NPP was efficiently utilized as a promising sensor for Al3+ detection in real samples. • NPP -coated test strips were successfully applied for quickly monitoring Al3+ ions in a visible manner. The development of high-selective chemosensors for trace Al3+ detection in the ecosystem is crucially importance due to its detrimental effects. In this work, a simple Schiff-base fluorescent probe NPP derived from naphthalimide and picolinohydrazide was rationally designed and prepared for efficient detection of Al3+. NPP exhibited prominent sensing behaviors toward Al3+ with low detection limit (LOD) (39 nM), rapid response time (1 min), strong binding affinity (4.02 × 104), good anti–interference characteristics and visual detection. Binding ratio of NPP -Al3+ complex was determined to be 1:1 by Job's plot analysis. In addition, the chelation mechanism of NPP with Al3+ ions was proposed and substantiated by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT), IR spectrum and 1H NMR titration experiments. Furthermore, this "signal-on" probe NPP was efficiently utilized as a promising indicator for Al3+ detection in environmental and biological samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] New Schiff base sensor is selectively detects Cu2+ ions by naked eye color change. [•] Fe3+ ions are also selectively detected by monitoring fluorescence emission. [•] The sensing mechanisms observed are binding and hydrolysis, respectively. [•] The binding and hydrolysis products were confirmed by 1H NMR, MS. [•] The new sensor has potential future use in biological cell imaging studies. [Copyright &y& Elsevier]

[Display omitted] • Rhodol-derived turn-on fluorescent chemosensor EBI-NO 2 was synthesized using a one-step method. • The chemosensor had high selectivity towards NTR, and its detection limit was as low as 0.6 ng/mL. • The reaction mechanism was verified using MS, molecular docking and theoretical calculations. • The chemosensor was successfully applied in real-time monitoring of NTR produced during growth of Escherichia coli (BL21) and in visualization of NTR in oral cancer cells (Cal-27) under hypoxia. The detection of intracellular nitroreductase (NTR) activity is important for the study of hypoxia in organisms. In the present study, a Rhodol-derived fluorescent chemosensor (Rhod-NO 2) was synthesized in a one-step procedure. Rhod-NO 2 exhibits 110-fold fluorescence enhancement in the presence of NTR. Moreover, Rhod-NO 2 demonstrates high NTR selectivity and sensitivity (LOD, 0.6 ng/mL). The mode of Rhod-NO 2 binding to NTR was also revealed by molecular docking. In addition, the reaction and luminescence mechanisms were evaluated by MS and TDDFT theoretical calculations, respectively. Finally, Rhod-NO 2 was successfully applied to monitor NTR production during Escherichia coli (E. coli) growth, and to visually analyze NTR production in malignant oral cancer cells under hypoxia. Thus, Rhod-NO 2 represents a new molecular tool to further understanding of the biological function of NTR. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel colorimetric and fluorescent chemosensor based on diaminopyrimidine (DAPCS) was designed and synthesized. • DAPCS was applied for the highly selective and ultra-sensitive detection of Cu2+ ion in aqueous media and living cell. • The probe DAPCS for Cu2+ showed a linear correlation, and LOD was calculated as 0.014 µM. • DAPCS-based test strips were fabricated and applied to the detection of Cu2+ ions in solutions. In this paper, a new and effective diaminopyrimidine-based chemosensor (DAPCS) was developed for the highly selective and ultra-sensitive detection of Cu2+ ion in aqueous media and living cell. Characterization and structure determining of DAPCS was determined by UV–Vis, FTIR and NMR analyses. It is observed that DAPCS and Cu (II) forms a ligand to metal charge transfer (LMCT) complex which produces distinguishable red color. The results also indicate that the DAPCS easily interacts with Cu2+ ion to form a 1:1 stoichiometry complex (DAPCS -Cu2+), resulting in a bathochromic shift in absorption maximum (429 nm to 449 nm) and remarkable quenching fluorescence intensity at the wavelength of 501 nm in DMSO-H 2 O solution. Furthermore, the detection limit of DAPCS towards Cu2+ was calculated to be 3.19 µM. Meanwhile, DAPCS was applied as fluorescent probe for detection of Cu2+ ions with the detection limit of 0.014 µM. The optimal pH range of probe DAPCS for quantitative analysis of Cu2+ ions was 9–11, which renders it suitable for detection of Cu2+ under physiological conditions. Additionally, the DAPCS could be applied to detect Cu2+ in real water samples and in HeLa cells, indicating the practical uses of DAPCS in real analyses. [ABSTRACT FROM AUTHOR]

As a colorimetric and fluorescent turn-on sensor to Al3+, N′-(2-hydroxybenzylidene)isoquinoline-3-carbohydrazide (HL) has been easily synthesized. The fluorescence intensity increases by 273 times in the presence of Al3+ at 458 nm. Meanwhile, the experiment data indicate that the limit of detection for Al3+ is 1.11 × 10−9 M. Remarkably, the blue fluorescence signal of HL-Al3+ could be specially observed by the naked eye under UV light and is significantly different from those of other metal ions. Fluorescence switch based on the control of Al3+ and EDTA proved HL could act as a reversible chemosensor. According to ESI-MS result and the Job's plots, the 2:1 coordination complex formed by HL and Al3+ could be produced. Density functional theory calculations were performed to illustrate the structures of HL and complex. The cell imaging experiment indicates that HL can be applied for monitoring intracellular Al3+ levels in cells. Unlabelled Image • A new chemosensor HL for the colorimetric and fluorescent detection of Al3+ was designed. • HL displays high selectivity and sensitivity, with 273-fold enhancement and detection limits down to 1.11 × 10-9 M. • HL has cell membrane permeability and can detect Al3+ in cells. • The binding mode of HL and Al3+ was studied using density functional theory. [ABSTRACT FROM AUTHOR]

A bisphenol based fluorescence "turn-on" chemosensor 4,4′-(propane-2,2-diyl)bis(2-((E)-(2-(benzo[d]thiazol-2-yl)hydrazineyldene)methyl)phenol) (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The chemo-sensing behavior of BHMP has been established through absorption, fluorescence, NMR, and mass spectroscopic techniques. The probe BHMP selectively detects zinc ions over other metal ions and the resulting BHMP + Zn2+ ensemble serves as a secondary probe for the detection of pyrophosphate (PPi) anion specifically over other anions. The spectroscopic studies reveal the fluorescence enhancement of BHMP in association with Zn2+ ions was quenched in the presence of pyrophosphate (PPi) anions. A probable mechanism of this selective sensing behavior was described on the basis of "OFF-ON-OFF" strategy for detection of both cations and anions. Moreover, the biological applicability of the chemosensor BHMP was examined via cell imaging studies. A bisphenol based fluorescence "turn-on" chemosensor (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The probe BHMP selectively detects zinc ions over other metal ions and the resulting Zn2+-BHMP ensemble serves as a secondary probe for the detection of PPi anion. The biological applicability of the chemosensor BHMP was examined via cell imaging studies. Unlabelled Image • The probe BHMP selectively detects zinc ions and the resulting Zn2+- BHMP ensemble is applied for the detection of PPi ions. • The probe detects Zn2+ and PPi ions with low detection limit of 0.28 and 0.87 nM respectively. • The probe was successfully applied to detect Zn2+ and PPi ions in live cells. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent pH sensor was facilely constructed by covalent modification of amino-terminated silicon nanodots (SiND) with pH-sensitive fluorescein isothiocyanate (FITC). After optimization, the SiND-FITC(40:1) material with a SiND:FITC initial mass ratio of 40:1 was selected for the sensing of hydrogen ions. It was observed that the material inherits the unique features of SiND and FITC, and there is significant improvement of SiND acid−base stability, which is a favorable factor in terms of providing fluorescence reference signal. The SiND-FITC(40:1) material displays not only high pH sensitivity, but also good stability and anti-interference ability, and the response process is highly reversible. Deploying the SiND-FITC(40:1) material, we have made available a simple, sensitive, and precise approach for pH sensing. In aqueous solutions, the I 517 /I 466 fluorescence intensity ratio of SiND-FITC(40:1) increases linearly in the pH range of 5.40–7.76. This dual emission nanosensor was successfully applied for pH sensing and cellular fluorescence imaging. Unlabelled Image • Water-soluble silicon nanodots could be synthesized in large-scale. • Facile covalent modification of the silicon nanodots with FITC was achieved. • An efficacious method for ratiometric pH sensing and imaging was proposed. [ABSTRACT FROM AUTHOR]

An efficient and stable fluorescent sensor is described for the detection and imaging of thiols. It is making use of silicon quantum dots (SiQDs) which can be rapidly prepared. They were characterized by transmission electron microscopy, X-ray power diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry. The SiQDs have an absorption maximum at 300 nm and displayed blue-green fluorescence with excitation/emission maxima at 410/480 nm. A mixture of SiQDs and 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) exhibits strong fluorescence emission which however is quenched within 30 s of incubation with thiols. This is assumed to be due to an inner filter effect caused by the reaction of DTNB and thiols. The following thiols were tested: cysteine, homocysteine, and glutathione. The sensor has a linear response in the 3–100 μM thiol concentration range, and the LODs are between 0.80 and 0.96 μM. The sensor displays low cytotoxicity and was applied to fluorescence imaging of MCF-7 cells and Hela cells where it demonstrated excellent biocompatibility. Unlabelled Image • A sensor based on silicon quantum dots was in response to thiols. • Response time of 30 s with excellent selectivity towards thiols was achieved. • The sensor was effective for thiols detection in fetal bovine serum samples. • The sensor was applied in intracellular thiols imaging in living cells. [ABSTRACT FROM AUTHOR]