•Two novel coumarin-based compounds 1 and 2 were designed and synthesized.•The difference of fluorescence properties between 1 and 2 for Al3+ was clarified.•Addition of Al3+ into 1 resulted in a remarkable fluorescence enhancement and a large red-shift.•High selectivity and sensitivity of 1 towards Al3+ were observed.In this study, two novel coumarin-based compounds called 2-Acetylpyrazine (coumarin-3′-formyl) hydrazone (1) and 2-Acetylpyrazine (7′-diethylaminocoumarin-3′-formyl) hydrazone (2) have been designed, synthesized and characterized. Compound 1 showed higher selectivity and sensitivity for Al3+ over other environmentally and biologically important metal ions than compound 2, and a remarkable enhancement of compound 1 in fluorescence emission intensity at 486 nm with a large red-shift was observed in the presence of Al3+. This phenomenon was attributed to the inhibition of the photoinduced electron-transfer (PET) process upon complexation of 1 with Al3+. Thus, compound 1 could be used as a fluorescent sensor for Al3+.

•A simple naphthalene-derived Al3+-selective fluorescent chemosensor was designed and synthesized.•The binding stoichiometry between HL and Al3+ was determined to be 1:1 by the Job’s plot and ESI-MS spectrum data.•The recognition process of HL towards Al3+ was chemically reversible by adding Na2EDTA.•HL exhibited a specific fluorogenic response towards Al3+ based on multi-mechanism (PET and ESIPT) in fully aqueous solution.•The proposed sensing mechanism was investigated by the 1H NMR titration experiment in detail.A simple fluorescent chemosensor HL based on naphthalene with high selectivity and sensitivity towards Al3+ over other commonly coexisting metal cations in fully aqueous solution to enhance the potential applications of the fluorescent chemosensor was developed. HL exhibited a significant fluorescence enhancement at 475 nm in the presence of Al3+ over other competitive metal ions with a low detection limit of 0.43 μM due to the inhibition of the photo induced electron transfer (PET) and the excited-state intramolecular proton transfer (ESIPT). The 1:1 binding stoichiometry between HL and Al3+ was corroborated by the Job plot and the ESI-MS spectrum. Importantly, the reversible recognition process of HL to Al3+ will make HL could be used circularly and repeatedly in practical applications by addition of Na2EDTA. In addition, the binding behavior and sensing mechanism of HL to Al3+ were illustrated in detail by the 1H NMR titration experiment.Download high-res image (64KB)Download full-size image

•A novel coumarin-furan conjugate 1 was designed and synthesized.•Ratiometric fluorescence response of 1 to Zn2 + was observed in ethanol-water system.•Good selectivity and high sensitivity of 1 towards Zn2 + over other metal ions were obtained.•Binding mechanism for the response of 1 to Zn2 + was investigated in detail.In this study, a novel coumarin-derived compound bearing the furan moiety called 7-diethylamino-3-formylcoumarin (2′-furan formyl) hydrazone (1) has been designed, synthesized and evaluated as a Zn2 + ratiometric fluorescent probe in ethanol-water system. This probe 1 showed good selectivity and high sensitivity towards Zn2 + over other metal ions investigated, and a decrease in fluorescence emission intensity at 511 nm accompanied by an enhancement in fluorescence emission intensity at 520 nm of this probe 1 was observed in the presence of Zn2 + in ethanol-water (V : V = 9 : 1) solution, which provided ratiometric fluorescence detection of Zn2 +. Additionally, the ratiometric fluorescence response of 1 to Zn2 + was nearly completed within 0.5 min, which suggested that this probe 1 could be utilized for sensing and monitoring Zn2 + in environmental and biological systems for real-time detection.

•A novel fluorescent probe based on 1,8-naphthyridine and naphthalimide was designed and synthesized.•The probe exhibited high selectivity towards Al3+ over commonly coexistent metal ions.•The probe was chemically reversible in the presence of Na2EDTA.•The proposed binding mechanism between HL and Al3+ was investigated in detail.A novel Schiff-base, 7-acetamino-4-methyl-1,8-naphthyridine-2-carbaldehyde-(1′,8′-naphthalenedicarbonyl) hydrazone (HL) was designed, synthesized and evaluated as a fluorescent probe. The fluorescence properties of this probe towards various metal ions were investigated by UV–vis and fluorescence spectra in methanol. Test results indicated that the probe had high selectivity towards Al3+ over other commonly coexisting metal ions. Upon addition of Al3+, the fluorescence intensity at 414 nm increased significantly due to the inhibition of the PET process. The binding constant (Ka) of Al3+ binding to HL was calculated to be 5.64 × 104 M−1 from a Benesi-Hildebrand plot, and the detection limit (LOD) of HL for sensing Al3+ was calculated to be 0.13 μM. The binding stoichiometry between HL and Al3+ was determined as 1:1 by the Job’s plot. Furthermore, the probe was chemically reversible for Al3+ in methanol by the addition of Na2EDTA solution.Download high-res image (72KB)Download full-size image

•Pd/Fe3O4-PEI-RGO was synthesized by dispersion of Pd NPs and Fe3O4 NPs on GO sheets.•Pd/Fe3O4-PEI-RGO provides a sensing platform for the colorimetric detection of H2O2.•Pd/Fe3O4-PEI-RGO has the advantages of facile preservation and rapid separation.•Pd/Fe3O4-PEI-RGO has the enhanced peroxidase catalytic activity.Herein Pd/Fe3O4-PEI-RGO nanohybrid was synthesized by dispersion of Pd NPs and Fe3O4 NPs on PEI modified graphene oxide sheets. This nanohybrid was found to possess superior peroxidase-like activity, and could efficiently oxidize 3,3′,5,5′-Tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to produce a color reaction. Therefore, this provides a sensing platform for the colorimetric detection of H2O2 in solution. The linear range for H2O2 was from 0.5 to 150 μM and the limit of detection was as low as 0.1 μM. Moreover, the nanohybrids have the advantages of facile preservation and rapid separation. More importantly, comparing with the other catalysts (PEI-RGO, Fe3O4-PEI-RGO and Pd-PEI-RGO), this nanohybrid exhibits the enhanced peroxidase catalytic activity. Thus, it is expected that this nanohybrid could conveniently and efficiently detect H2O2 in the pharmaceutical, environmental and industrial fields.We reported as-synthesized Pd/Fe3O4-PEI-RGO nanohybirds as enhanced peroxidase mimetics for the colorimetric detection of H2O2 in solution.

•A novel chromone-derived compound 1 was designed and synthesized.•Good selectivity and high sensitivity of 1 towards Al3+ over other metal ions were observed.•1:1 stoichiometry between 1 and Al3+ was determined systematically.•PET and CN isomerization mechanism for the response of 1 to Al3+ was investigated.In this study, a novel chromone-derived Schiff-base ligand which was called bis(6-hydroxychromone-3-methylidene)-o-phenylenediimine (1) was designed, synthesized, and evaluated as an Al3+ “turn on” fluorescent probe. This probe 1 showed good selectivity and high sensitivity towards Al3+ in the presence of most metal ions, and a remarkable enhancement by about 30.91-fold in fluorescence emission intensity at 459 nm was observed with addition of 1 equiv of Al3+, which was attributed to the inhibition of photoinduced electron-transfer (PET) phenomenon and CN isomerization process at the excited state. Moreover, the fluorescence response of 1 to Al3+ was nearly completed within 10 min. Thus, this probe 1 could be utilized for sensing and monitoring Al3+ in environmental and biological systems for real-time detection.

•The novel ratiometric fluorescent probe (HL) responds to Al3+.•The sensing mechanism is attributed to an FRET mechanism from naphthalene to rhodamine.•The theoretical detection limit for Al3+ can reach at 8.06 × 10−8 M.In this study, a novel chemosensor (HL) for Al3+ which contains rhodamine and naphthalene moieties has been designed and synthesized. In the presence of Al3+, the receptor exhibited a strong, increasing fluorescent emission centered at 550 nm at the expense of the fluorescent emission of HL centered at 520 nm. We proposed that the addition of Al3+ triggered intramolecular fluorescence resonance energy transfer (FRET) from naphthalene to Rhodamine 6G.

•An easy-to-make Schiff-base fluorescent sensor was designed and synthesized.•The probe exhibited high selectivity and sensitivity for Zn2+ over other metal ions.•The chemosensor showed excellent restorability.•CN isomerization and PET can be used to explain the high selectivity of the probe.A new resumable Schiff-base fluorescent probe 7-methoxychromone-3-carbaldehyde-(3′-hydroxy-2′-naphthaleneformyl) hydrazone (L) was designed and synthesized for selective recognition Zn2+. With the titration and the ESI-MS spectra data, we reached the conclusion that the binding ratio between L and Zn2+ was determined to be 1. The sensor showed a strong fluorescence enhancement in ethanol system of Zn2+ (excitation 430 nm and emission 498 nm). And the enhancement may be due to CN isomerization and Photoinduced Electron Transfer (PET).Proposed binding mode for interaction of Zn2+ with L.

•The sensors show selectively response toward Al3+.•The sensors exhibit a large fluorescence enhancement in the presence of Al3+.•The detection limits reached at 10−8 M.Two Schiff-base fluorescent sensors have been synthesized, which both can act as fluorescent probes for Al3+, upon addition of Al3+, they exhibit a large fluorescence enhancement which might be attributed to the formation of 1:1 ligand-Al complexes which inhibit photoinduced electron transfer (PET) progress, and that the proposed binding modes of the sensors and Al3+ are identified by theoretical calculations.

•A multifunctional fluorescent probe for Zn2+/Cu2+ has been designed and synthesized.•The sensor shows significant fluorescence enhancement in the presence of Zn2+, due to inhibit ESIPT process.•We have successfully utilized the two metal ions (Cu2+ and Zn2+) as chemical inputs for the manufacture of INHIBIT type logic gate.In this study, a novel naphthalene schiff-base as a dual-analyte fluorescent sensor for Zn2+ and Cu2+ has been designed and synthesized. The sensor shows significant fluorescence enhancement in the presence of Zn2+, which might be attributed to inhibit ESIPT process, in contrast, its fluorescence is quenched by Cu2+ owing to its inherent to the magnetic property. More interestingly, we have successfully utilized the two metal ions (Cu2+ and Zn2+) as chemical inputs for the manufacture of INHIBIT type logic gate.

•A simple and resumable two-photon probe for Zn2+ is designed and synthesized.•The reason are attributed to the restricted CN isomerization and the inhibited (PET).•It has lower detection limit.In this study, a simple one-photon and two-photon probe, 7-(4′-(diethylamino)-2′-hydroxybenzylideneimino)-4-methyl coumarin, for Zn2+ is designed and synthesized. The sensor shows high selectivity towards Zn2+ ions with significant fluorescence intensity enhanced at 500 nm, which might be attributed to the formation of 2:1 stoichiometric L–Zn complex resulting in the restricted CN isomerization and the inhibited photo-induced electron transfer. More importantly, the reversibility of the recognition process of HL is performed by adding a Zn2+ bonding agent Na2EDTA.

•The receptor HL shows obviously enhancement of fluorescence intensity in the present of Mg2+.•The detection limit of HL for Mg2+ could reach at 10−7 M level.•HL showed a good selectivity to Mg2+ over other metal cations, especially Ca2+, which often responds together with Mg2+.A new senser Isatin-3-(7′-Methoxychromone-3′-methylidene) hydrazone based on chromone Schiff base was synthesized to detect Mg2+. The complexation behavior of chemosensor with different metal ions in ethanolic solution was studied on UV–vis absorption spectra and fluorescent spectra. Results showed that the chemosensor HL displayed a 70-fold fluorescence enhancement upon the addition of Mg2+ due to the photo-induced electron transfer (PET) effect. On the other hand, metal ions except Mg2+ did not cause significant change in either the absorption or the fluorescence spectrum of HL. In addition, HL showed a good selectivity to Mg2+ over other metal cations, especially Ca2+, which often responds together with Mg2+. Therefore, HL can act as an efficient sensor for magnesium ion.

We have developed an efficient strategy for synthesizing a strongly coupled Au/Fe3O4/GO hybrid material to improve the catalytic activity, stability, and separation capability of Au nanoparticles (NPs) and Hg2+. The hybrid material can be synthesized by the direct anchoring of Au and Fe3O4 NPs on the functional groups of GO. This approach affords strong chemical attachments between the NPs and GO, allowing this hybrid material to ultrasensitively detect Hg2+ in aqueous solutions with a detection limit as low as 0.15 nM. In addition, the deposition of Hg0 on the surface of Au/Fe3O4/GO could be quickly (within 30 min) and efficiently (>99% elimination efficiency) removed by the simple application of an external magnetic field and then Au/Fe3O4/GO could be subsequently reused at least 15 times, with the elimination efficiency remaining high (>96%).

The application of nanohybrids in water treatment by the catalytic degradation of various pollutants has attracted much attention from researchers. Here, the Pd/Fe3O4-PEI-RGO nanohybrids (1d) with high shape selectivity and high specific surface area have been synthesized by the dispersion of Pd NPs and Fe3O4 NPs on PEI modified graphene oxide sheets. These nanohybrids show superior catalytic activity toward methylene blue with a high degradation efficiency above 99% in the presence of NaBH4 in aqueous solution, which is attributed to the effects of the Pd NPs supported on reduced graphene oxide nanosheets. Meanwhile, the 1d catalyst can be easily separated from the reaction mixture by applying an external magnetic field. The catalyst was recycled nine times without showing any significant loss in its activity. Such features enable this catalyst for promising application in catalysis, environment, and new energy fields.

Recent studies have suggested that the physical and chemical properties of nanoparticles (NPs) strongly depend on local chemical composition, size, and shape. Here, we report a new precursor-mediated growth of monodisperse magnetic cobalt ferrite (CoFe2O4) NPs with controlled size and shape. CoFe2O4 NPs with near corner-grown cubic, near cubic and polyhedron shape can be successfully prepared by simply tuning the amount of iron and cobalt acetylacetonates in oleic acid. Interestingly, the product shape varies from near corner-grown cubic to starlike by only changing the reaction temperature from 320 °C to 330 °C. These CoFe2O4 NPs exhibit size and shape-dependent peroxidase-like activity towards 3,3′,5,5′-tetramethylbenzdine (TMB) in the presence of H2O2, and thus exhibited different levels of peroxidase-like activities, in the order of spherical > near corner-grown cubic > starlike > near cubic > polyhedron; this order was closely related to their particle size and crystal morphology. CoFe2O4NPs exhibited high stability in HAc–NaAc buffer (pH = 4.0) and high activity over a broad pH (2.5–6.0). Furthermore, the Michaelis constants Km value for the CoFe2O4 NPs (0.006 mM) with TMB as the substrate was lower than HRP (0.062 mM) and Fe3O4 NPs (0.010 mM). After further surface functionalization with folic acid (FA), the folate-conjugated CoFe2O4 nanoparticles allow discrimination of HeLa cells (folate receptor overexpression) from NIH-3T3 cells (without folate receptor expression). Such investigation is of great significance for peroxidase nanomimetics with enhanced activity and utilization.

•New fluorescent chemosensor was designed and synthesized.•High selectivity and sensitivity of this sensor for Al3+ was observed in ethanol.•Addition of Al3+ into this sensor gave remarkable enhanced fluorescence intensity.In this article, a simple hydrazone-based ‘‘turn on’’ fluorescent chemosensor has been designed, synthesized and evaluated. Upon addition of Al3+ ions, the sensor showed high selectivity and sensitivity with a 900-fold enhancement at 490 nm, which was attributed to the photoinduced electron-transfer (PET) and the chelation-enhanced fluorescence (CHEF). In addition, the detection limit of this sensor for Al3+ could reach 10−7 mol/L.

•The sensor shows “off–on” fluorescent responses toward Al3+ in aqueous media.•The detection limit reached at 10−6 m in near 100% aqueous media.•The sensing mechanism is attributed to ESIPT and PET.An efficient fluorescent Al3+ sensor, 2-hydroxy-1-naphthylaldehyde nicotinoyl hydrazone (HL) has been designed and synthesized. The receptor shows “off–on” fluorescent responses toward Al3+ in near 100% aqueous media. Other relevant metal ions such as Li+, Na+, K+, Ca2+, Mg2+, Cu2+, Co2+, Mn2+, Ni2+, Zn2+, Ba2+, Fe2+, Cd2+, Hg2+, Pb2+, Sc3+, Fe3+, Cr3+ caused almost no fluorescence increase. The reason for this phenomenon is that the addition of Al3+ to the solution of HL induce the formation of a 1:1 stoichiometry of the binding mode of L-Al(III) which inhibits the excited-state intramolecular proton transfer (ESIPT) and photoinduced electron transfer (PET). More importantly, the reversibility of the recognition process of HL was performed by adding a Al3+ bonding agent Na2EDTA.The sensor shows “turn-on” fluorescent responses toward Al3+ in near 100% aqueous media. The reason for this phenomenon is that the addition of Al3+ to the solution of HL result in the formation of a 1:1 stoichiometry of the binding mode of L-Al which inhibits the excited-state intramolecular proton transfer (ESIPT) and photoinduced electron transfer (PET).

•The novel fluorescent probe (HL) responds to Al3+.•HL shows remarkable fluorescence enhancement in the presence of Fe3+in aqueous media.•The sensing mechanism is attributed to an FRET mechanism from coumarin to Rhodamine 6G.In this study, a novel ratiometric fluorescent sensor (HL) for Fe3+ based on the conjugation of rhodamine and coumarin has been designed and synthesized. The free sensor displays fluorescence emission at 475 nm, on the addition of Fe3+ to an aqueous solution of HL, the sensor shows significant fluorescence enhancement at 550 nm which should be attributed to an intramolecular fluorescence resonance energy transfer (FRET) mechanism from coumarin to Rhodamine 6G.

In this study, a novel ratiometric chemosensor for Al3+ (HL) which contains coumarin and naphthalene moieties has been designed and synthesized on the basis of the mechanism of internal charge transfer (ICT). On addition of Al3+, the receptor exhibits a strong, increasing fluorescent emission centered at 525 nm at the expense of the fluorescent emission of HL centered at 481 nm in ethanol and water (9:1, v/v). This phenomenon is attributed to formation of a 1:1 complex (Ka = 1.03 × 104), which inhibits internal charge transfer (ICT).

•The fluorescent probe (HL) serves as a dual analyte chemosensor and quantifies Mg2+ and Zn2+ in different systems.•In the present of Mg2+/Zn2+, HL shows a large fluorescence enhancement in acetonitrile/ethanol–water (v/v, 4:1).•The sensing mechanisms are attributed to PET process rather than the ring-opening of the rhodamine spirolactam.In this study, a naphthalene schiff-base which serves as a dual analyte chemosensor and quantifies Mg2+ and Zn2+ has been synthesized. The sensor shows “off–on” fluorescent response toward Mg2+ in acetonitrile while the detection of the sensor could be switched for Zn2+ by regulating solvents from acetonitrile to a mixture of ethanol–water (v/v, 4:1). Both of the sensing mechanisms are attributed to the formation of 1:1 ligand–metal complexes which inhibit photo-induced electron transfer (PET) process. More importantly, the reversibility of the recognition processes of HL is performed by adding a bonding agent Na2EDTA.A naphthalene schiff-base which serves as a dual analyte chemosensor and quantifies Mg2+ and Zn2+ has been synthesized. The sensor shows “off–on” fluorescent response toward Mg2+ in acetonitrile while the detection of the sensor could be switched for Zn2+ by regulating solvents acetonitrile to a mixture of ethanol–water (v/v, 4:1). Both of the sensing mechanisms are attributed to the formation of 1:1 ligand–metal complexes which inhibit photo-induced electron transfer (PET) process.

•We have designed a single fluorescent chemosensor for recognition of Al3+/Zn2+ base on ESIPT.•2-Methyl quinoline-4-carboxylic hydrazide was rarely synthesized.•HL shows a large fluorescence enhancement (120/150-fold) in the presence of Al3+ and Zn2+, respectively.•The detection limits for Al3+/Zn2+ reach at 10−7 M level.A naphthalene derivative 2-hydroxy-α-naphthaldehyde-(2′-methylquinoline-4′-formyl) hydrazone (HL) as a fluorescent chemosensor for Al3+/Zn2+ in ethanol and water (9:1, v/v) has been designed and synthesized. The receptor shows a large fluorescence enhancement at 509 nm and 543 nm in the present of Al3+ and Zn2+, respectively. The excited-state intramolecular proton transfer (ESIPT) process, coupled with photoinduced electron transfer (PET) process are proposed to explain the observed spectral response.

•2-methyl quinoline-4-carboxylic hydrazide was rarely synthesized.•We have designed a fluorescent chemosensor for recognition of Al3+ base on PET.•The sensor shows a large fluorescence enhancement in the present of Al3+.•The detection limits for Al3+ reach at 10−6 M level in aqueous solution.In this paper, a novel fluorescent Al3+-sensor (8-Hydroxyquinoline-7-aldehyde-(2′-methylquinoline-4′-formyl hydrazone, L1) based on quinoline derivative has been designed and synthesized. Compared with L1 without Al3+, the sensor L1 shows significant fluorescence enhancement in the presence of Al3+ in ethanol–water (v/v, 9:1). We hypothesize that the reason might be attributed to the formation of 1:2 ligand–metal complexes inhibiting photoinduced electron transfer (PET) progress.

•A novel hydrazone ligand based on quinoline was designed and synthesized.•The reason for no characteristic fluorescence of Sm(III) complex was discussed.•A novel ternary Sm(III) complex was synthesized by introducing 1,10-phenanthrolin.•The ternary complex showed efficient luminescence through an energy-transfer pathway.A novel ligand called 2-oxo-quinoline-3-carbaldehyde-isonicotinyl hydrazone (L) was designed and synthesized, and its Sm(III) complex was successfully prepared and characterized by X-ray diffraction. According to investigation, the Sm(III) complex didn’t exhibit characteristic fluorescence due to the mismatching energy between L and Sm(III) ion. However, when the complex was reacted with 1,10-phenanthrolin (Phen) as a secondary ligand, a novel ternary Sm(III) complex was synthesized, which showed efficient luminescence activity through an energy-transfer pathway. These results indicated that 1,10-phenanthrolin was an excellent sensitizer to Sm(III) ion.

In this study, a novel pyrazine-derived fluorescent sensor bearing the furan unit (1) has been designed, synthesized and characterized. This sensor 1 showed large enhancement in the fluorescence emission intensity at 517 nm in the presence of Al3+ and it also showed high selectivity and sensitivity for Al3+ over other common environmentally and biologically important metal ions, as the detection limit of 1 towards Al3+ could reach 10−7 mol L−1. Moreover, the enhancement of fluorescence emission intensity was attributed to the chelation-enhanced fluorescence (CHEF) phenomenon upon complexation of 1 with Al3+.

In this study, we have developed a simple fluorescent sensor, 7-(2′,4′-dihydroxybenzylideneimino)-4-methyl coumarin, which shows a high selectivity towards Al3+/Zn2+ over a wide range of metal ions. On the one hand, the fluorescence intensity of the probe shows significant fluorescence enhancement in the presence of Al3+ at 427 nm (λex = 357 nm), which might be mainly attributable to the hydrolysis of imines. On the other hand, the receptor exhibits a selective response to Zn2+ at 489 nm (λex = 405 nm), and a photoinduced electron transfer process (PET) is proposed to explain the observed spectral response.

A novel Schiff-base fluorescent sensor (HL) for Al3+ has been synthesized. The addition of Al3+ results in a significant increase of its fluorescent intensity at 420 nm in ethanol, however, other metal ions have almost no influence on the fluorescence. The reason for this phenomenon might be attributed to the formation of a 1:1 stoichiometric L–Al complex which inhibits the photo-induced electron transfer (PET) process. More importantly, the proposed binding mode of L–Al(III) is further identified by theoretical calculations.

•A multifunctional fluorescent probe for Zn2 +/Cu2 + has been designed and synthesized.•L–Cu is used for the detection of S2 − with ‘in situ’ prepared Cu2 + complex in aqueous solutions.•It has lower detection limit.A multifunctional fluorescent chemosensor 7-(diethylamino)-coumarin-3-carbaldehyde-(2’-methylquinoline-4’-formyl) hydrazone (HL) has been designed and synthesized. The sensor shows significant fluorescence enhancement in the presence of Zn2 +, which might be mainly due to the restricted –CN isomerization process. In contrast, the fluorescence of the sensor is quenched by Cu2 + attributed to the inherent paramagnetic species. More interestingly, the ‘in situ’ prepared L–Cu exhibits a selective response to S2 − based on reversible formation–separation of complex L–Cu and CuS.

•A novel bis-Schiff base fluorescent probe for Al3+ has been designed and synthesized.•The probe for Al3+ shows significant fluorescence enhancement accompany with about 40 nm blue shift on the basis of the mechanism of ICT.•The detection limit for Al3+ reached at 10−7 M level in 100% aqueous solution.In this paper, a novel bis-Schiff base fluorescent probe (HL) for Al3+ has been designed and synthesized on the basis of the mechanism of internal charge transfer (ICT). Compared with the free receptor, the fluorescence intensity of HL shows significant fluorescence enhancement accompany with about 40 nm blue shift in the presence of Al3+. More importantly, the lowest detection limit for Al3+ can reach at 10−7 M level in near 100% aqueous solution.Upon addition of Al3+, compared with the free receptor, the fluorescence intensity of HL shows significant fluorescence enhancement accompany with about 40 nm blue shift in the presence of Al3+, the reasons for this phenomenon are attributed to forms 1:1 complex which inhibit internal charge transfer process.

A simple Al3+ sensor, 8-acetyl-7-hydroxy-4-methylcoumarin (AHMC), was synthesized. It can display an excellent fluorescence “turn-on” response to Al3+ over other common metal ions in methanol–water media. Theoretical calculations have also been carried out to understand the configuration of the AHMC–Al complex and rationalize experimental absorption data.

A new Zn(II) complex was synthesized based on a new Salen-type tetradentate N2O2 bisoxime chelate ligand (H2L) derived from 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and 1,2-bis(aminooxy)ethane. Single-crystal X-ray diffraction analysis reveals that the structure of the Zn(II) complex features a three-dimensional (3D) cyclic supramolecular system via intermolecular hydrogen bonds. Moreover, the solid-state photoluminescent properties demonstrate that the Zn(II) complex exhibits unusual luminescence mechanochromism tuned by CH3OH.

In this study, a simple fluorescent sensor 2-hydroxybenzcarbaldehyde-(2-methylquinoline-4-formyl) hydrazone (HL) has been designed, synthesized and characterized by 1H-NMR, IR, ESI-MS. Upon addition of Al3+, HL shows a large fluorescence enhancement (220-fold) at 484 nm. The reasons for this phenomenon are attributed to formation of a 1:1 complex (Ka = 5.6 × 104), which inhibits the excited-state intramolecular proton transfer (ESIPT) process and photo-induced electron transfer (PET) process. Other metal ions including Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Hg2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+ and Zn2+, have almost no influence on the fluorescence. The lowest detection limit for Al3+ is calculated to be 7.2 × 10−7 M in ethanol.

•HL shows strong fluorescence enhancement (125-fold) in aqueous media.•It has good water-solubility and lower detection limit.•PET and ICT are proposed to explain the observed spectral response.An efficient fluorescent Al3+ receptor, 4-N,N-diethylaminosalicylicaldehyde -(2′-methylquinoline-4-formyl) hydrazone (HL) has been synthesized and characterized by physico-chemical and spectroscopic tools. Upon addition of Al3+ to an aqueous solution of HL, it shows 125-fold enhancement of fluorescence intensity at 550 nm. Photoinduced electron transfer (PET) process, coupled with the intramolecular charge transfer (ICT) process, are proposed to explain the observed spectral response. The lowest detection limit for Al3+ is determined as 6 × 10−7 M in ethanol and water (4:1, v/v).

•We have designed a new chemosensor for aluminum ions.•2-Methyl quinoline-4-carboxylic hydrazide was rarely synthesized.•L shows a large fluorescence enhancement with turn-on over 200-fold in ethanol.•It has lower detection limit.A fluorescence probe, 8-formyl-7-hydroxyl-4-methyl coumarin – (2′-methylquinoline-4-formyl) hydrazone (L) has been synthesized. The chemosensor is found preferential binding to Al3+ in presence of other competitive ions with associated changes in its optical and fluorescence spectra behavior. Upon addition of Al3+ to a solution of L, it shows 200-fold enhancement of fluorescence intensity which might be attributed to form a 2:1 stoichiometry of the binding mode of LAl(III) and the chelation enhanced fluorescence (CHEF) process at 479 nm in ethanol. The lowest detection limit for Al3+ is determined as 8.2 × 10−7 M.

•The new Schiff-base ligand (1) was easily synthesized and widely available.•The compound 1 exhibited a high selectivity and sensitivity toward Al3+ in ethanol.•The detection limit of 1 to Al3+ was up to 0.67 ppb.•Potential utilization of 1 as intracellular sensors of Al3+ ions was also examined.A new Schiff-base ligand (1) with good fluorescence response to Al3+, derived from 2-oxo-quinoline-3-carbaldehyde and nicotinic hydrazide, had been synthesized and investigated in this paper. Spectroscopic investigation revealed that the compound 1 exhibited a high selectivity and sensitivity toward Al(III) ions over other commonly coexisting metal ions in ethanol, and the detection limit of Al3+ ions is at the parts per billion level. The mass spectra and Job’s plot confirmed the 1:1 stoichiometry between 1 and Al3+. Potential utilization of 1 as intracellular sensors of Al3+ ions in human cancer (HeLa) cells was also examined by confocal fluorescence microscopy.

A highly selective and sensitive fluorescent turn-on chemosensor methyl pyrazinylketone benzoyl hydrazone (MPBH) was synthesized by a facile one-step Schiff base reaction. MPBH which owns a quite simple structure showed a high selectivity for Al3+ over other metal ions in ethanol. Due to the formation of a 1:1 complex between MPBH and the aluminum ions, a significant fluorescence enhancement with a turn-on ratio over 800-fold was achieved. The detection limit of MPBH for Al3+ reached at 10−7 M level.Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The fluorescent chemosensor was synthesized by a facile one-step reaction. ► The structure of the fluorescent chemosensor is quite simple with a molecular weight at 240. ► The fluorescent chemosensor showed high selectivity for Al3+ from fluorescence “off” to fluorescence “on”. ► The detection limit of the fluorescent chemosensor reached at 10−7 M level, pointing to the high sensitivity.

•A novel fluorescein-coumarin conjugate Schiff-base has been synthesized.•The compound exhibits high sensitivity and selectivity for Zn2+.•The Schiff-base ligand can be synthesized easily.A novel fluorescent sensor, 7-hydroxy-4-methylcoumarin-8-carbaldehyde-(fluorescein) hydrazone was designed and synthesized for selective recognition of Zn2+ in HEPES buffer medium of PH 7.4. This reagent could be used as a probe for Zn2+ by monitoring changes in the absorption and the fluorescence spectral patterns. More importantly, this sensor displays an extreme selectivity, sensitivity and color change for Zn2+ over other earth- and transition metal ions, which was mainly due to the spirolactam ring-opening power of Zn2+. Upon the addition of Zn2+, an overall emission change of 33-fold was observed and the detection limit was low as 6.54 ppb. Photoinduced electron transfer process, coupled with the intramolecular charge transfer process, are proposed to explain the observed spectral response.

A novel sensor, 7-Hydroxy-4-methylcoumarin-8-carbaldehyde-(rhodamine) hydrazone (l) has been synthesized and investigated as a fluorescence chemosensor for Ca2+ in acetonitrile. The compound is found preferential binding to Ca2+ in presence of large excess of other competitive ions with associated changes in its optical and fluorescence spectral behavior. Upon the addition of Ca2+, an overall emission change of 64-fold was observed. Photoinduced electron transfer (PET) process, coupled with the intramolecular charge transfer (ICT) process, are proposed to explain the observed spectral response.Highlights► A novel fluorescent sensor based on rhodamine and coumarin has been synthesized to detect Ca2+. ► Sensesor shows high sensitivity and selectivity to Ca2+ with detection limit of 30 ppb.► The sensor can distinguish Ca2+ and Mg2+ effectively.

A novel and facile strategy was firstly developed to synthesize an efficient magnetic resonance imaging contrast agent via linking the Gd-complex (Gd-DTPA) onto the surfaces of ferroferric oxide nanoparticles. The new contrast agent is easily soluble in water media and shows better targeting ability on the liver organ. In addition, the synthesized contrast agent shows excellent magnetic resonance contrast behavior with longitudinal relaxivity value of 62.58 mM−1 s−1 and emits strong bright fluorescence in the cellular environment. Furthermore, the new magnetic resonance imaging contrast agent is superparamagnetic at room temperature and has no apparent cytotoxicity on human HeLa cells.Graphical AbstractThe contrast agent was prepared by linking Gd-complex onto Fe3O4 NPs surface, which exhibits excellent MR contrast behavior with longitudinal relaxivity value of 62.58 mM−1 s−1 and bright fluorescence in cellular environment.Highlights► A new strategy was developed to synthesize a contrast agent based on Fe3O4 nanoparticles. ► The contrast agent shows a higher relaxation value than the previous traditional contrast agents, and strong selectivity on the liver organ in mice. ► The contrast agent has no cytotoxicity and can emit bright fluorescence in cellular environment.

Films of crystalline WO3 nanosheets oriented perpendicular to tungsten substrates were grown by a surfactant-free hydrothermal method, followed by sintering. The films exhibit photoelectrochemical oxygen evolution at low overpotential.

In the present study, we report new water-soluble cell fluorescence imaging and contrast agents that are based on DTPA-AMC(7-amino-4-methyl coumarin)-Eu3+ and DTPA-AMC(7-amino-4-methyl coumarin)-Gd3+ compounds conjugated to Fe3O4 NPs via a PEG-NH2 linker. The novel Fe3O4 NP-conjugates present two main advantages for cell fluorescence labelling: water solubility and targeting ability. The in vitro experiments demonstrate that water-soluble Fe3O4 NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Eu3+ has excellent cell permeating activity. Moreover, the relaxation rate test of Fe3O4 NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Gd3+ shows a higher T1 relaxation effect than traditional DTPA-Gd3+ MRI agents. According to in vivo liver MRI experiments, better contrast of the liver was achieved after addition of Fe3O4 NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Gd3+. The results will provide a significant guide for researchers exploring the biomedical applications of superparamagnetic Fe3O4 NPs.

In the article, a novel fluorescent probe for the copper cation based on fluorescence quenching mechanism was designed. It exhibited high selectivity for Cu(II) over other common metal ions in aqueous media. Furthermore the coordination between Cu(II) and the organic molecule sensor fabricated an interesting 1D chain coordination polymer framework.

A novel fluorescein derivative, synthesized by the reaction of fluorescein hydrazide and 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, was evaluated as a chemoselective metal ion sensor. Addition of Cu2+ to an aqueous solution of the fluorescein derivative resulted in a rapid color change from colorless to deep yellow together with a distinctive change in UV–vis absorption spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The stoichiometry of the reaction and association constant of the fluorescein derivative with Cu2+ are described. Experimental results indicate that the fluorescein derivative could provide a rapid, selective and sensitive response to Cu2+, and could be used as a potential Cu2+ colorimetric chemosensor in aqueous solution.

The controlled growth of highly ordered, [211]-oriented FeOOH nanowire arrays on various substrates, such as Pt, W, Ti, and fluoride-doped tin oxide (FTO) glass, was achieved by a solvothermal method in aqueous acetonitrile solutions at 80–120 °C, following by annealing to form α-Fe2O3 nanowires with their [110] direction perpendicular to the substrate. Adjusting the reaction pH and temperature enables control of the nanowire length. In particular, the pH has a dramatic effect on the nanowire growth, with low pH resulting in the growth of longer wires because of the acid-catalyzed hydrolysis of acetonitrile. Photoactive hematite was prepared by diffusing Ti or Sn into the nanowires during thermal annealing. Processing parameters that influenced the photoelectrochemical performance of these nanowire arrays, including the annealing regime, temperature, and length of nanowires, are discussed in detail. The Ti- and Sn-doped one-dimensional [110]-oriented α-Fe2O3 nanowire arrays provide an effective pathway for electron transport, demonstrating increased photocurrents, up to 1.3 mA/cm2 under air mass 1.5 global (AM 1.5G) illumination, in photoelectrochemical water oxidation.

In the paper, a novel fluorescent sensor (1) based on 8-hydroxyquinoline carbaldehyde Schiff-base was synthesized and characterized. This fluorescent sensor exhibited high selectivity for Al3+ over other metal ions with the detection limit reaching below 10− 7 M under weak acid aqueous conditions. These suggested that 1 could be served as a highly selective and sensitive fluorescence sensor for aluminum ion in acid medium.A novel fluorescent sensor (1) based on 8-hydroxyquinoline carbaldehyde Schiff-base was synthesized and characterized. This fluorescent sensor exhibited high selectivity for Al3+ over other metal ions with the detection limit reaching below 10− 7 M under weak acid aqueous conditions.Research Highlights►A novel 8-hydroxyquinoline carbaldehyde Schiff-base is synthesized. ►The Schiff-base exhibits higher selectivity and sensitivity for Al3+ in acid aqueous medium. ►The fluorescence sensor can be synthesized and performed easily.

A new fluorescent Zn2+ chemosensor, 8-(7′-Hydroxy-4′-methylcoumarin-8′-yl-) methyleneiminoquinoline (L) was designed and synthesized. This complex could act as highly sensitive and selective fluorescent probe for Zn2+ in THF (tetrahydrofuran). However, other metal ions gave little fluorescence change.A new fluorescent Zn2+ chemosensor, 8-(7′-Hydroxy-4′-methylcoumarin-8′-yl-) methyleneiminoquinoline (L) was designed and synthesized. This complex could act as highly sensitive and selective fluorescent probe for Zn2+ in THF.Research Highlights► A novel coumarin Schiff-base is synthesized. ► The compound exhibits higher selectivity and sensitivity for Zn2+ than other metal ions. ► The Schiff-base ligand can be synthesized easily.

A Schiff base derived from 2-oxo-quinoline-3-carbaldehyde-4-aminophenazone and its Cu(II), Zn(II) and Ni(II) complexes were synthesized. The molecular structures of the Zn(II) and Ni(II) complexes were determined by X-ray crystal diffraction. The DNA-binding modes of the compounds were investigated by spectroscopic methods, viscosity measurements and ethidium bromide-DNA displacement experiments. The experimental evidence indicated the compounds interact with calf thymus DNA through intercalation. Additionally, the compounds exhibited potential antioxidant properties in in vitro studies, and the Cu(II) complex was the most effective. The solid-state fluorescence properties of the Zn(II) complex were studied.

Three novel 2-oxo-quinoline-3-carbaldehyde Schiff-bases and their Cu(II) complexes were synthesized. The molecular structures of Cu(II) complexes were determined by X-ray crystal diffraction. The DNA-binding modes of the complexes were also investigated by UV–vis absorption spectrum, fluorescence spectrum, viscosity measurement and EB–DNA displacement experiment. The experimental evidences indicated that the ligands and Cu(II) complexes could interact with CT-DNA (calf-thymus DNA) through intercalation, respectively. Comparative cytotoxic activities of ligands and Cu(II) complexes were also determined by MTT [3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide] and SRB (sulforhodamine B) methods. The results showed that the three Cu(II) complexes exhibited more effective cytotoxic activity against HL60 cells and HeLa cells than corresponding ligands. Also, CuL3 showed higher cytotoxic activity than CuL1 and CuL2.Three new Cu(II) Schiff-bases complexes were synthesized and characterized. The study revealed that the Cu(II) complexes could bind to CT-DNA through intercalation and showed higher cytotoxicity than corresponding ligands.

3-Carbaldehyde chromone thiosemicarbazone (L) and its transition metal complexes were synthesized and characterized systematically. Crystal structures of Zn(II) and Ni(II) complexes were determined by single crystal X-ray diffraction analysis. Zn(II) complex exhibits blue fluorescence under UV light and its fluorescent property in solid state was investigated. Interactions of ligand and Cu(II), Zn(II) and Ni(II) complexes with DNA were investigated by spectral and viscosity studies, indicating the compounds bind to DNA via intercalation and Zn(II) complex binds to DNA most strongly. Antioxidant tests in vitro show the compounds possess significant antioxidant activity against superoxide and hydroxyl radicals, and the scavenging effects of Cu(II) complex are stronger than Zn(II), Ni(II) complexes and some standard antioxidants, such as mannitol and vitamin C.3-Carbaldehyde chromone thiosemicarbazone and its Copper (II), Zinc (II) and Nickel (II) complexes were synthesized and characterized. Their DNA binding properties and antioxidant activity were investigated systematically.

3-Carbaldehyde-chromone semicarbazone (L) and its Cu(II), Zn(II), Ni(II) complexes were synthesized and characterized on the basis of crystal structure and other structural characterization methods. The metal ions and Schiff base ligand can form mononuclear five-coordination complexes with 1:1 metal-to-ligand stoichiometry at the metal ions as centres. The transition metal complexes may be used as potential anticancer drugs, because they bind to calf thymus DNA via an intercalation binding mode with the binding constants at the order of magnitude 105–106 M− 1, and the metal complexes present stronger DNA binding affinities than the free ligand alone. In addition, the antioxidant activities of the ligand and its metal complexes were investigated through scavenging effects for superoxide anion and hydroxyl radical in vitro, indicating that the compounds show stronger antioxidant activities than some standard antioxidants, such as mannitol and vitamin C.The transition metal ions and Schiff base ligand can form mononuclear five-coordination complexes with 1:1 metal-to-ligand stoichiometry at the metal ions as centres. Their biological activities, such as DNA binding properties and antioxidant activities were investigated systematically.

Herein, we report for the first time on the preparation of four Paeonol Schiff-base ligands: 1,2-Bis(2-hydroxy-4-methoxy-α-methylbenzylideneimino) ethane (H2L1), 2-hydroxy-4-methoxy-α-methylbenzylidene (benzoyl) hydrazone (HL2), 2-hydroxy-4-methoxyacetophenone-ethanolamine Schiff-base (HL3), and 2-hydroxy-4-methoxyacetophenone(2′-hydroxybenzoyl) hydrazone (H2L4), and their Cu(II) complexes, of which the structure of C11N2O6H14Cu(CuL3.NO3) was confirmed by X-ray diffraction. Antioxidant activities of four Cu(II) complexes were studied by the standard non-enzymatic NBT method and Fenton system, used to produce superoxide anion radicals and hydroxyl radicals, respectively. The results show these Cu(II) complexes have excellent antioxidant activities. DNA-binding and in vitro cytotoxicity experiments were utilized to further investigate the biological activities of C11N2O6H14Cu(CuL3.NO3). These results support C11N2O6H14Cu as a potential candidate for biological use because it shows not only high antioxidant and moderate DNA-binding activities, but also good tumor cell cytotoxicity activities in human cell lines carcinomas Hep-2 (larynx), for the range of concentrations tested.Biological activities of copper (II) complexes with four different Paeonol-based Schiff-base ligands were intensively evaluated.

A new bis Schiff-base ligand (1,2-(2′-oxoquinoline-3′-yl-methylideneimino)ethane, QSB) derived from 2-oxo-quinoline-3-carbaldehyde and ethylene diamine was synthesized and characterized by 1H-NMR. Spectroscopic investigation revealed that the compound exhibited a high selectivity toward Zn(II) ion over other metal ions in acetonitrile solution. In addition, the crystal structure showed that the coordination form of QSB and Zn(II) was 1:1.A novel bis Schiff-base fluorescent chemosensor (1,2-(2′-oxoquinoline-3′-yl-methylideneimino)ethane) was synthesized and characterized. The high selectivity for Zn(II) was investigated systemically by UV-Vis and fluorescence spectra.

A novel Schiff-base ligand (H5L), hesperetin-2-hydroxy benzoyl hydrazone, and its copper (II), zinc (II) and nickel (II) complexes (M·H3L) [M(II) = Cu, Zn, Ni], have been synthesized and characterized. The ligand and Zn (II) complex exhibit green and blue fluorescence under UV light and the fluorescent properties of the ligand and Zn (II) complex in solid state and different solutions were investigated. In addition, DNA binding properties of the ligand and its metal complexes have been investigated by electronic absorption spectroscopy, fluorescence spectra, ethidium bromide displacement experiments, iodide quenching experiments, salt effect and viscosity measurements. Results suggest that all the compounds bind to DNA via an intercalation binding mode. Furthermore, the antioxidant activity of the ligand and its metal complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro. The metal complexes were found to possess potent antioxidant activity and be better than the free ligand alone and some standard antioxidants like vitamin C and mannitol.

X-ray crystal and other structural analyses indicate that Dy(III) and every ligand can form a binuclear Dy(III) complex with nine-coordination and 1:1 metal-to-ligand stoichiometry at the Dy(III) center. All the ligands and Dy(III) complexes can bind to Calf thymus DNA through intercalations with the binding constants at the order of magnitude 105–107 M−1, but Dy(III) complexes present stronger affinities to DNA than ligands. All the ligands and Dy(III) complexes can be used as potential anticancer drugs. All the ligands and Dy(III) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals but complex containing active phenolic hydroxyl group shows stronger scavenging effects for hydroxyl radicals and complex containing N-heteroaromatic substituent shows stronger scavenging effects for superoxide radicals.The ORTEP illustrations of [DyL1(NO3)(DMF)2]2 complex. Dimerization of this monomeric unit occurs through the phenolate oxygen atoms leading to a central four-membered (DyO)2-ring.

A novel chromone Schiff base, 7-methoxychromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone (L) and its Ln(III) complexes (Ln = La, Eu) were synthesized and characterized. The crystal structure of the La(III) complex was determined by single-crystal X-ray diffraction: crystallized in the orthorhombic system, space group Pbcn, Z = 8, a = 14.595(2) Å, b = 20.055(3) Å, c = 30.078(5) Å, R1 = 0.0657. Fluorescence titration spectra, electronic absorption titration spectra, EB displacement and viscosity measurement indicated that both the ligand and the complexes can bind to DNA via the intercalation mode, and that the binding affinity of the La(III) complex is higher than that of the Eu(III) complex and of the ligand (L). The antioxidant activity experiments show that these compounds also exhibit good antioxidant activities against OH and O2−. Moreover, the Eu(III) complex exhibits characteristic fluorescence of europium ion in different organic solvents.A novel Schiff base ligand, 7-methoxychromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone, and its La(III) and Eu(III) complexes were synthesized and their DNA-binding abilities, antioxidant activities and fluorescence properties were investigated in detail.

Novel Ln(III) complexes with hesperetin-4-one-(benzoyl) hydrazone (H4L) have been synthesized and characterized. Electronic absorption spectroscopy, fluorescence spectra, ethidium bromide displacement experiments, iodide quenching experiments, salt effect and viscosity measurements indicate that the ligand and Ln(III) complexes, especially the Nd(III) complex, strongly bind to calf thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constants of the Nd(III) complex and ligand with DNA were 2.39 × 106 and 2.70 × 105 M−1, respectively. Furthermore, the antioxidant activity of the ligand and Ln(III) complexes was determined by superoxide and hydroxyl radical scavenging method in vitro, which indicate that the ligand and Ln(III) complexes have the activity to suppress O2− and HO and the Ln(III) complexes exhibit more effective antioxidant activity than the ligand alone.Hesperetin-4-one-(benzoyl) hydrazone, and its Ln(III) complexes [Ln(III) = La, Sm, Dy, Yb and Nd] were synthesized and characterized. Their DNA binding properties and antioxidant activity were investigated systematically.

Two novel 2-oxo-quinoline-3-carbaldehyde (4′-hydroxybenzoyl) hydrazone, thiosemicarbazone ligands and its corresponding Cu(2+) complexes were synthesized, and the two complexes’ structures were determined by X-ray single crystal diffraction. The interaction of the two Cu(2+) complexes with calf thymus DNA (CT-DNA) was investigated by electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurement. The experimental evidences indicated that the two water-soluble Cu(2+) complexes could strongly bind to CT-DNA via an intercalation mechanism. The intrinsic binding constants of complexes 1 and 2 with CT-DNA were 7.31 × 106 and 2.33 × 106 M−1, respectively. Furthermore, the antioxidant activities (hydroxyl radical and superoxide) of the two water-soluble metal complexes were determined by hydroxyl radical and superoxide scavenging method in vitro.Two novel Schiff-bases ligands, 2-oxo-quinoline-3-carbaldehyde (4′-hydroxybenzoyl) hydrazone, thiosemicarbazone, and its Cu(2+) complexes were synthesized and their DNA-binding abilities, antioxidant activities were investigated in detail.

Eu(III) and every newly synthesized ligand can form a binuclear Eu(III) complex with a 1:1 metal to ligand stoichiometry and nine-coordinate at Eu(III) center. Every ligand acts as a dibasic tetradentate ligand, binding to Eu(III) through the phenolate oxygen atom, nitrogen atom of quinolinato unit, the CN group (methylene) and −O–CN– group (enolized and deprotonated from OC–NH– group) of the aroylhydrazine side chain. One DMF (N,N-dimethylformamide) molecule is binding orthogonally to the ligand-plane from one side to the metal ion, while another DMF and a nitrate anion (bidentate) are binding from the other. Dimerization of the monomeric unit occurs through the phenolate oxygen atoms leading to a central planar four-membered (EuO)2 ring. On the other hand, all the ligands and Eu(III) complexes may be used as potential anticancer drugs, binding to Calf thymus DNA through intercalations at the order of magnitude 105–107 M−1. All the ligands and Eu(III) complexes are strong scavengers of hydroxyl radicals and superoxide radicals, but Eu(III) complex containing active phenolic hydroxyl group shows stronger scavenging effects for hydroxyl radicals than others, and Eu(III) complex containing N-heteroaromatic substituent shows stronger scavenging effects for superoxide radicals than others.

A hesperetin Schiff base ligand (H4L) and its complexes, [H3CuL·OAc]·H2O and [H3ZnL·OAc]·2H2O, have been synthesized and characterized on the basis of elemental analysis, molar conductivity, 1H NMR, mass spectra, UV–Vis spectra and IR spectra. The binding of these two complexes and the ligand to DNA has been investigated by ultraviolet absorption spectroscopy, fluorescence spectroscopy and viscosity measurements. The experiments indicate that all the compounds can bind to DNA through an intercalative mode and the complexes intercalate into DNA more deeply than that of the ligand. In addition, the antioxidative activity was also determined. The 50% inhibition obtained for the ligand and its complexes demonstrates that, compared to the ligand, the complexes exhibit higher antioxidative activity in the suppression of O2- and HO.A novel hesperetin Schiff base ligand and its complexes were synthesized and characterized. DNA binding studies show that the ligand and its complexes can strongly bind to DNA via an intercalation mode and the complexes can bind to DNA more deeply than the ligand.

Nd(III) and four Schiff-base ligands can form binuclear nine-coordination [NdL1–4(NO3)(DMF)2]2 complexes with 1:1 metal-to-ligand stoichiometry at Nd(III) center. All the ligands and Nd(III) complexes may be used as potential anticancer drugs, binding to Calf thymus DNA through intercalations with the binding constants at the order of magnitude 105–106 M−1. In addition, Nd(III) complexes present stronger affinities to DNA than ligands. All the ligands and Nd(III) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals.The nine-coordination crystal structure of binucleae [NdL1(NO3)(DMF)2]2 complex with 1:1 metal-to-ligand stoichiometry. Dimerization of this monomeric unit occurs through the phenolate oxygen atoms leading to a central planar four-membered (NdO)2 ring.

An original Schiff-base type fluorescent chemosensor 1-phenyl-3-methyl-5-hydroxypyrazole-4-carbaldehyde(benzoyl)hydrazone (H2L) for Cu2+ has been designed and synthesized. An obvious fluorescence quenching only for Cu2+ demonstrates that ligand H2L exhibits high selectivity and efficient signaling behavior toward micromolar concentration of Cu2+ compared with other metal ions. At the same time, the coordination form between ligand and Cu2+ is elucidated via crystal structure.A new ligand 1-phenyl-3-methyl-5-hydroxypyrazole-4-carbaldhyde(benzoyl) hydrazone was synthesized and studied as ion fluorescent chemosensor, which exhibited high sensitivity and selectivity for Cu2+.

Water-soluble Ni(II) and Cu(II) complexes of a flexible Schiff-base ligand have been synthesized, and the Ni(II) complex was characterized by X-ray crystallography. The interactions of the two complexes with calf thymus DNA were investigated by spectroscopic and viscosity measurements in water. The results suggest that the two complexes bind to DNA within the groove. Antioxidant experiments against OH• and O2−• show that these two complexes have excellent ability to scavenge O2−•, and the Cu(II) complex exhibits better activity than the Ni(II) complex.

X-ray crystal and other structural analyses indicate that Yb(III) and all four newly synthesized ligands can form a binuclear Yb(III) complex with a 1:1 metal to ligand stoichiometry by octacoordination at the Yb(III) center. Investigations of DNA binding properties show that all the ligands and Yb(III) complexes can bind to Calf thymus DNA through intercalations with the binding constants at the order of magnitude 105–107 M−1, but Yb(III) complexes present stronger affinities to DNA than ligands. All the ligands and Yb(III) complexes may be used as potential anticancer drugs. Investigations of antioxidation properties show that all the ligands and Yb(III) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals but Yb(III) complexes show stronger scavenging effects for hydroxyl radicals than ligands.

The neutral mononuclear Ln(III) complexes (Ln = La, Sm) with 7-methoxychrom-one-3-carbaldehyde-isonicotinoyl hydrazone ligand (L) have been synthesized, characterized and investigated their interactions with calf-thymus DNA. The results show that the binding affinity of the La(III) complex is stronger than that of the Sm(III) complex and that of the ligand (L). Furthermore, the antioxidant activities of the ligand (L) and its Ln(III) complexes (Ln = La, Sm) were studied in detail.

The synthesis of three Paeonol Schiff base ligand and their Zn(II) complexes are reported. The complexes were fully characterized by IR, 1H NMR, elemental analysis and molar conductivity. The experiment results show the three Zn(II) complexes can emit bright fluorescence at room temperature in DMF solution and solid state. The fluorescence quantum yields (Φ) of three Schiff base ligands and their Zn(II) complexes were calculated using quinine sulfate as the reference with a known ΦR of 0.546 in 1.0N sulfuric acid. Furthermore, in order to develop these Zn(II) complexes’ biological value, the antioxidant activities against hydroxyl radicals (OH) were evaluated. The results show the three complexes possess excellent ability to scavenge hydroxyl radicals.

A new chromone derivative (6-ethoxy chromone-3-carbaldehyde benzoyl hydrazone) ligand (L) and its two transition metal complexes [Zn(II) complex and Ni(II) complex] have been prepared and characterized on the basis of elemental analysis, molar conductivity, mass spectra, UV–vis spectra and IR spectra. The Zn(II) complex exhibits light blue fluorescence under UV light, and the fluorescent properties of Zn(II) complex and the ligand in solid state and in different solutions (MeOH, DMF, THF and H2O) were investigated. In addition, the interactions of the Zn(II) complex and the ligand with calf thymus DNA were investigated using UV–vis absorption, fluorescence, circular dichroic spectral methods and viscosity measurement. It was founded that both two compounds, especially the Zn(II) complex, strongly bind with calf thymus DNA, presumably via an intercalation mechanism.

A novel 6-ethoxy chromone-3-carbaldehyde benzoyl hydrazone (L) and its Ln(III) complexes, [Ln = Sm (1), Eu (2), Gd (3), Tb (4)], have been synthesized and characterized. The fluorescence properties of the Eu(III) and Sm(III) complexes in solid state and Eu(III) complex in different solutions (DMF, DMSO, methanol and acetonitrile) were investigated. At the same time, the DNA-binding properties of the two complexes are investigated using UV-Vis absorption spectroscopy, fluorescence spectroscopy, viscosity measurement. All the experimental evidences indicate that the two complexes can bind to CT-DNA via an intercalation mechanism. Furthermore, antioxidant activity tests in vitro showed that the complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction.

A novel Schiff base ligand (L = 7-methoxychromone-3-carbaldehyde benzoyl hydrazone) and its La(III) and Eu(III) complexes have been successfully prepared. The crystal structure of [LaL2(NO3)3]·H2O was characterized by X-ray crystallography. It crystallizes in monoclinic, space group C2/c with crystallographic data: a = 27.7173(17) Å, b = 10.0002(6) Å, c = 14.7884(9) Å, β = 102.6870(10)° and Z = 4. In the structure, the La(III) ion satisfies 12 coordination and three nitrate coordinate as bidentate ligand. The biological experiments show that the ligand and its two complexes can strongly bind to DNA through intercalation mode, and the three compounds also exhibit good antioxidant activities against OH• and O2−•. Moreover, it is found that the Eu(III) complex exhibits characteristic fluorescence of europium ion in different organic solvent.

The Schiff base, H2L, was derived from 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and diethenetriamine. The crystal structure of [NiL(C2H5OH)]·H2O obtained from ethanol solution was determined by X-ray diffraction analysis. The coordination geometry of Ni(II) ion is a distorted octahedron with three oxygen atoms and three nitrogen atoms. Under the excitation of ultraviolet light, strong fluorescence of solid Zn(II) complex was observed. In addition, the fluorescence enhancement was obtained in the presence of Zn2+ in THF solution of the ligand, indicating that H2L may be a potential fluorescent sensor for Zn2+.

A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand (L) and its Ln(III) complexes, [Ln = La(1) and Sm(2)], have been prepared and characterized. The crystal and molecular structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Antioxidative activity tests in vitro showed that L and its complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction and also oxygen free radicals, and that the effect of the La(III) complex 1 is stronger than that of mannitol and the other compounds. The compounds were tested against tumor cell lines including HL-60 and A-549. The data shows that the suppression rate of complexes 1 and 2 against the tested tumor cells are superior to the free ligand (L). The interactions of complexes 1 and 2, and L, with calf thymus DNA were investigated by UV–visible (UV–vis), fluorescence, denaturation experiments and viscosity measurements. Experimental results indicated that complexes 1 and 2, and L can bind to DNA via the intercalation mode, and that the binding affinity of complex 1 is higher than that of complex 2 and of free ligand (L). The intrinsic binding constants of complexes 1 and 2, and L were (7.62 ± 0.56) × 106, (3.70 ± 0.47) × 106 and (2.41 ± 0.46) × 106 M−1, respectively.

A new ligand, 2-carboxybenzaldehyde-(4’-hydroxy)benzoylhydrazone(H2L) and its ZnII and NiII complexes have been synthesized and characterized on the basis of elemental analyses, molar conductivities, 1H-NMR, IR spectra and thermal analyses. In addition, DNA-binding properties of these two metal complexes were investigated using spectrometric titrations, ethidium bromide displacement experiments, and viscosity measurements. The results show that the two complexes, especially the NiII complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constants of the ZnII and NiII complexes with DNA are 2.46 × 105 and 7.94 × 105 M−1, respectively.

2-Carboxybenzaldehydeisonicotinoylhydrazone (HL), and its three lanthanide complexes, LnL3·4H2O [Ln = La(1), Sm(2), Eu(3)], have been synthesized and characterized on the basis of elemental analyses, molar conductivities, IR spectra and thermal analyses. In addition, the DNA-binding properties of the ligand and its complexes have been investigated by absorption, fluorescence and viscosity measurements. The experimental results indicated that the complexes (2) and (3) can bind to DNA, but the ligand and the complex (1) cannot; the binding affinity of the complex (3) is higher than that of the complex (2) and the intrinsic binding constant Kb of the complex (3) is 7.86 × 104 M−1.

A new Naringenin Schiff-base ligand (H3L) and its complex, [La(H2L)2(NO3)·3H2O], have been synthesized and characterized on the basis of elemental analyses, molar conductivities, mass spectra, 1H NMR, thermogravimetry/differential thermal analysis (TG–DTA), UV spectra, and IR spectra. Spectrometric titrations, ethidium bromide displacement experiments, and viscosity measurements indicate that the two compounds, especially the La(III) complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constants of the La(III) complex and ligand with DNA were 1.83 × 107 and 9.46 × 105 M−1, respectively. Comparative cytotoxic activities of the La(III) complex and ligand were also determined by MTT [3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide] and SRB (sulforhodamine B) methods. The results showed that the La(III) complex had significant cytotoxic activity against the tested cells.A new Naringenin Schiff-base ligand and its La(III) complex have been synthesized and characterized. Spectrometric titration and viscosity measurements indicate that two compounds strongly bind with calf-thymus DNA, presumably via an intercalation mechanism.

Phthalazin-1(2H)-one was prepared by a novel route. The La(III)-complex of phthalazin-1(2H)-one, [La(NO3)3 · 4H2O · C8H7N2O] · H2O, was synthesized and characterized on the basis of elemental analysis, thermal analyses (TG/DTA) and X-ray crystallography. In the complex, the coordination number of the La(III) ion is eleven. The interaction of the ligand and its complex with calf thymus DNA was investigated by spectrophotometric methods and viscosity measurements, respectively. Experimental results indicated that phthalazin-1(2H)-one and the complex can bind to DNA by intercalation modes, but the binding affinity of La(III)-complex is higher than that of the ligand. Comparative antitumor activities of La(III)-complex was investigated by HL-60 and A-549. IC50 = 2.6 × 10−8, 3.3 × 10−5 mg/mL are given.Phthalazin-1(2H)-one was prepared by a novel route, its La(III)-complex, [La(NO3)3 · 4H2O · C8H7N2O] · H2O, was synthesized and characterized on X-ray crystallography. Comparative antitumor activities of La(III)-complex was investigated by HL-60 and A-549. IC50 = 2.6 × 10−8, 3.3 × 10−5 mg/mL are given.

•New fluorescent chemosensor was designed and synthesized.•High selectivity and sensitivity of this sensor for Al3+ was observed in ethanol.•Addition of Al3+ into this sensor gave remarkable enhanced fluorescence intensity.In this article, a simple hydrazone-based ‘‘turn on’’ fluorescent chemosensor has been designed, synthesized and evaluated. Upon addition of Al3+ ions, the sensor showed high selectivity and sensitivity with a 900-fold enhancement at 490 nm, which was attributed to the photoinduced electron-transfer (PET) and the chelation-enhanced fluorescence (CHEF). In addition, the detection limit of this sensor for Al3+ could reach 10−7 mol/L.

Films of crystalline WO3 nanosheets oriented perpendicular to tungsten substrates were grown by a surfactant-free hydrothermal method, followed by sintering. The films exhibit photoelectrochemical oxygen evolution at low overpotential.

A novel Schiff-base fluorescent sensor (HL) for Al3+ has been synthesized. The addition of Al3+ results in a significant increase of its fluorescent intensity at 420 nm in ethanol, however, other metal ions have almost no influence on the fluorescence. The reason for this phenomenon might be attributed to the formation of a 1:1 stoichiometric L–Al complex which inhibits the photo-induced electron transfer (PET) process. More importantly, the proposed binding mode of L–Al(III) is further identified by theoretical calculations.

A simple Al3+ sensor, 8-acetyl-7-hydroxy-4-methylcoumarin (AHMC), was synthesized. It can display an excellent fluorescence “turn-on” response to Al3+ over other common metal ions in methanol–water media. Theoretical calculations have also been carried out to understand the configuration of the AHMC–Al complex and rationalize experimental absorption data.

In the article, a novel fluorescent probe for the copper cation based on fluorescence quenching mechanism was designed. It exhibited high selectivity for Cu(II) over other common metal ions in aqueous media. Furthermore the coordination between Cu(II) and the organic molecule sensor fabricated an interesting 1D chain coordination polymer framework.

A new Zn(II) complex was synthesized based on a new Salen-type tetradentate N2O2 bisoxime chelate ligand (H2L) derived from 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and 1,2-bis(aminooxy)ethane. Single-crystal X-ray diffraction analysis reveals that the structure of the Zn(II) complex features a three-dimensional (3D) cyclic supramolecular system via intermolecular hydrogen bonds. Moreover, the solid-state photoluminescent properties demonstrate that the Zn(II) complex exhibits unusual luminescence mechanochromism tuned by CH3OH.

The application of nanohybrids in water treatment by the catalytic degradation of various pollutants has attracted much attention from researchers. Here, the Pd/Fe3O4-PEI-RGO nanohybrids (1d) with high shape selectivity and high specific surface area have been synthesized by the dispersion of Pd NPs and Fe3O4 NPs on PEI modified graphene oxide sheets. These nanohybrids show superior catalytic activity toward methylene blue with a high degradation efficiency above 99% in the presence of NaBH4 in aqueous solution, which is attributed to the effects of the Pd NPs supported on reduced graphene oxide nanosheets. Meanwhile, the 1d catalyst can be easily separated from the reaction mixture by applying an external magnetic field. The catalyst was recycled nine times without showing any significant loss in its activity. Such features enable this catalyst for promising application in catalysis, environment, and new energy fields.

In this study, a simple fluorescent sensor 2-hydroxybenzcarbaldehyde-(2-methylquinoline-4-formyl) hydrazone (HL) has been designed, synthesized and characterized by 1H-NMR, IR, ESI-MS. Upon addition of Al3+, HL shows a large fluorescence enhancement (220-fold) at 484 nm. The reasons for this phenomenon are attributed to formation of a 1:1 complex (Ka = 5.6 × 104), which inhibits the excited-state intramolecular proton transfer (ESIPT) process and photo-induced electron transfer (PET) process. Other metal ions including Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Hg2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+ and Zn2+, have almost no influence on the fluorescence. The lowest detection limit for Al3+ is calculated to be 7.2 × 10−7 M in ethanol.

In the present study, we report new water-soluble cell fluorescence imaging and contrast agents that are based on DTPA-AMC(7-amino-4-methyl coumarin)-Eu3+ and DTPA-AMC(7-amino-4-methyl coumarin)-Gd3+ compounds conjugated to Fe3O4 NPs via a PEG-NH2 linker. The novel Fe3O4 NP-conjugates present two main advantages for cell fluorescence labelling: water solubility and targeting ability. The in vitro experiments demonstrate that water-soluble Fe3O4 NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Eu3+ has excellent cell permeating activity. Moreover, the relaxation rate test of Fe3O4 NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Gd3+ shows a higher T1 relaxation effect than traditional DTPA-Gd3+ MRI agents. According to in vivo liver MRI experiments, better contrast of the liver was achieved after addition of Fe3O4 NPs-DBI-PEG-NH-DTPA-AMC(7-amino-4-methyl coumarin)-Gd3+. The results will provide a significant guide for researchers exploring the biomedical applications of superparamagnetic Fe3O4 NPs.