A New Fluorescent Chemosensor for Selective and Sensitive Detection of Mn2+ in Acidic Medium

Recently, fluorescent sensors have attracted considerable attention in their sensitive and selective determination of heavy metal ions in the aqueous acidic medium due to their advantages such as low cost and easy handling. In this study, the bathocuproine (BCP) compound was used as a fluorescent chemosensor. The selectivity and sensitivity of BCP have been investigated against some metal ions of biological and environmental importance. The results obtained from the ultraviolet-visible region (UV-vis.) and the fluorescence spectroscopy experiments revealed that the BCP sensor showed selectivity and sensitivity only to Manganese (II) ions in the experimental conditions studied. In addition, the binding stoichiometry of BCP and Mn2+ was determined to be 1:1 by the Benesi-Hildebrand method.

Synthesis of Porphyrin-Appended Pyridine as a Fluorescent Chemosensor for Cd（Ⅱ） and Hg（Ⅱ）

In this research, specific molecular sensors are classified according to the type of receptor-cation interaction, that is ligand-metal interactions. Receptors are based on a multidentate protoporphyrin-appended pyridine platform, which leaves at least a vacant coordination site for the incoming metal ions. A protoporphyrin-appended pyridine, 2,5-pyridine dicarboxyamidyl-8,13-bis（vinyl）-3,7,18,17-tetramethyl-21 H, 23 H-porphyrin（P-PTP）, was designed and synthesized. Its application as potential fluoroionophore for recognition of cadmium and mercury ions is reported. P-PTP shows chelation-enhanced fluorescence effect with Cd（Ⅱ） and Hg（Ⅱ） via the interruption of photoinduced electron transfer （PET） process, which has been utilized as the basis of the fabrication of the metal ions-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Cd（Ⅱ）- and Hg（Ⅱ）- sensitive chemosensors were investigated. It shows a linear response toward Cd（Ⅱ） and Hg（Ⅱ） in the concentration range of 1.0×10-3 to 1.0×10-7 M with a limit of detection of 1.0×10-7 M and 0.5×10-7M for Cd（Ⅱ） and Hg（Ⅱ）, respectively. The chemosensor shows good selectivity for Cd（Ⅱ） over a large number of other transition metal ions, i.e., Cu（Ⅱ）, Zn（Ⅱ） and mixed metal ions.

New rhodamine derivative as OFF-ON fluorescent chemosensor for detection of Cu^(2+)

A novel fluorescence probe for the detection of Cu2+ has been designed and synthesized, which is based on a ring-opening reaction of spirolactam triggered by Cu2+ . This probe exhibits excellent Cu2+ ion selectivity as well as significant color changes visible to the naked eye at the concentration of 0.03 mM (ca. 2.0 mg/L), the WHO (World Health Organization) recommended level (2.0 mg/L) of Cu2+ ions in drinking water. This novel rhodamine-based fluorescence probe can be directly used to detect Cu2+ with satisfactory sensitivity and selectivity in aqueous solution.

Novel Highly Selective Fluorescent Chemosensors for Hg（Ⅱ）

Based on Rhodamine,two novel fluorescent Hg2＋ chemosensors（R1,R2） were synthesized from inexpensive starting materials.They were designed and synthesized with o-aminophenol and o-phenylenediamine derivatives as the Hg2＋ chelator,the comparison between the photophysical properties of two chemosensor molecules was made.The chemosensors were designed with a photoinduced electron transfer（PET） mechanism.After binding to Hg2＋ which blocks the PET process,the fluorescence intensity of the chemosensors was enhanced by up to 15-fold.They exhibit very strong fluorescence responses to Hg2＋ and have remarkably higher selectivity for Hg2＋ than for other metal ions including K＋,Na＋,Ca2＋,Mg2＋,Cd2＋,Mn2＋,Ni2＋,Co2＋,Zn2＋,Cu2＋,Cr3＋,Fe3＋,pb2＋,Ag＋,Al3＋,Fe2＋ and Sn2＋ in Tris-HC1/sodium phosphate buffer.The fluorescence enhancement of R2 towards Hg2＋ maintains stable in wide pH span（6.4-8.8） aqueous solutions.

Hg2＋-Selective Fluorescent Chemosensor Based on Cation-π Interaction

Two sulphur-containing 4-aminonaphthalimide derivatives were investigated as Hg2＋ fluorescent chemosensors. In CH3CN, both sensors present a remarkable fluorescence enhancement to Cu2＋ and Fe3＋, but a selective fluorescence quenching to Hg2＋ among the other metal ions. A cation-π interaction between Hg〉 and the naphthalimide moiety was proposed and confirmed By the density tunetional theory（DFT）.

A fluorescent probe for fluoride ion based on 2-aminopyridyl-bridged calix[6]arene

An 2-anfinopyddyl-bddged calix[6]arene on the upper rim fixed in cone conformation （3） was successfully synthesized and its highly selective recognition towards fluoride ion was proved by fluorescent and 1H NMR titration experiments.

Time-resolved Luminescence-based Chemosensor for Fluoride Anion

A new europium complex is descried as a time-resolved luminescence-based sensor for fluoride anion. The sensor is selective even in the presence of intensive background fluorescence.

Fluorescence Enhancement of Polyamine Derivatives of 1,8-Naphthalimide with Transition Metal Ions

A series of fluorescent chemosensors 1-3 were synthesized to detect transition metal ions. At the room temperature, fluorescence intensities of these chemosensors in acetonitrile without transition metal ions were found to be very weak, due to the process of the efficient intramolecular photoinduced electron transfer （PET）. However, after addition of the transition metal ions, the chemoscnsor 1-3 exhibits obvious fluorescence enhancement. Moreover, the intensity of the fluorescence emission of chemosensors increases significantly in the presence of Zn^2＋ and Cd^2＋. The fluorescent chemosensors with different polyamine as receptors show diverse affinity abilities to the transition metal ions and signal the receptor-metal ion interaction by the intensity change of fluorescence emission.

Detection of Picric Acid by Terpy-Based Metallo- Supramolecular Fluorescent Coordination Polymers in Aqueous Media

The synthesis of two linear terpy-based metallo-supramolecular fluorescent coordination polymers through 1 ： 1 complexation of Zn^2＋ and Cd^2＋ ions with ditopic terpyridine ligand was reported. The dispersibility of P1 and P2 was significantly improved in organic solvent and water through the introduction of hydrophilic oligo-ethyoxy side chain. Two polymers displayed yellow light emission both in solution and the solid state due to the intra-ligand charge transfer （ILCT） between the d^10 metal ions and the conjugated spacer unit. These coordination polymers were explored as fluorescent chemosensors for detecting picric acid in aqueous media, displaying high sensitivity and good selectivity. In addition, test strips were prepared from these polymers and exhibited the practical potential of detecting the NACs pollutants in the outdoor water for public safety and security.

Naphthalimide as Highly Selective Fluorescent Sensor for Ag^＋ Ions

The naphthalimide derivative. NA1 was synthesized, which consists of a bis（2-（ethylthio）ethyl）amine group binding cations and naphthalimide unit as chromogenic and fluorogenic signaling subunit. Absorption and emission spectra and the effect of polarity of solvents and pH values were studied. The photo-induced electron transfer （PET） occurred from the donor of bis（2-（ethylthio）ethyl）amine group to the naphthalimide fluorophore. The present study demonstrates that NA1 is a viable candidate as a fluorescent receptor for a new Ag^＋ ion sensor. This silver ion chemosensor can discriminate Ag^＋ ion well among heavy metal ions by an enhancement of the fluorescence intensity in ethanol-water （1 ： 9, V ： V）. And NA1 is also a pH-sensor because the fluorescence of the compound varies with the pH values.

A New Biphenylcarbonitrile Based Fluorescent Sensor for Zn2＋ Ions and Application in Living Ceils

A new and efficient fluorescent sensor 4＇-hydroxy-3＇-[（4-antipyrineimino）methyl]-4-biphenylcarboni- trile（L） was prepared for the selective detection of Zn2＋ in aqueous ethanol medium. When excited at 419 nm, the fluorescent intensity of sensor L at 507 nm was remarkably increased more than 54-fold after adding Zn2＋ ions. The strong green emission of the solution can be easily identified by naked eye tinder UV light. Thus, sensor L behaves as a naked eye fluorescent ＂turn on＂ detector for Zn2＋ ions. The fluorescence enhancement might be attributed to the in- hibition of excited state intramolecular proton transfer（ESIPT） and C==N isomerization as well as the chelation en- hanced fluorescence（CHEF） effect. The complex solution of sensor L with Zn2＋ ions exhibited reversibility with ethylene diamine tetraacetic acid（EDTA） and the probe could be recycled for further use. Notably, sensor L could clearly distinguish Zn2＋ from Cd2＋. The interaction of sensor L with zinc ions was investigated by means of FTIR, 1H NMR and HRMS spectroscopy. Furthermore, sensor L has been applied for cell imaging studies.

Highly sensitive and selective chemosensor for Cu～(2+) detection based on a N-propargyl rhodamine 6G-hydrazide derivative

A novel fluorescence ＂turnon＂ probe for CH^2＋ detection has been designed based on a Cu^2＋ triggered spirolactam ringopening reaction. The synthetic probe is a doubleresponsive fluorescent and colorimetric Cu^2＋specific sensor. In aqueous solution, it exhibits high selectivity and excellent sensitivity. With a significant color change visible to the naked eye at the concentration of 3 I.tM （ca. 0.19 mg/L）, about one magnitude lower than the WHO （World Health Organization） recommended level （2.0 mg/L） for Cu^2＋ions in drinking water, the probe could be used to monitor Cu^2＋ ions in drinking water.

Highly selective and sensitive colorimetric chemosensor based on tricarboyanine for detection of Ag^(+) in industrial wastewater

An efficient fluorescent probe 1 based on tricarbocyanine derivative was designed and synthesized,which can detect Ag^(+) in real industrial wastewater.UV-V is absorption and fluorescent emission spectra of probe 1 were carried out and indicated this probe can bind Ag^(+) via complexation reaction,then leading to a remarkable color change from blue to light red.Furthermore,probe 1 showed high sensitive performance and excellent selectivity toward Ag^(+) over other common metal ions in neutral pH.The sensing mechanism was proposed and further confirmed by ^(1)H NMR,which demonstrate analyte-induced destruction of the π-electron system could be shorten by the disruption of the pull-push π-conjugation system in probe 1.Moreover,a test strip was prepared by filter paper immersing in probe 1 solution,which further provide its potential application for trace Ag^(+) detection in real industrial wastewater.

A Highly Sensitive and Selective Fluorescence Chemosensor for Cu^2＋ and Zn^2＋ Based on Solvent Effect

A novel fluorescence chemosensor 1 based on （R）-binaphthyl-salen can exhibit highly sensitive and selective recognition responses toward Cu^2＋ by ＂turn-off＂ fluorescence quench type in THF/H20, and Zn^2＋ by ＂turn-on＂ fluorescence enhancement type in CHC13/CH3CN, respectively, suggesting that solvents can dramatically affect the responsive properties of salen-based chemosensor. In addition, Cu^2＋ can lead to the most pronounced changes of CD spectra without the influence of solvents, which indicates this kind chemosensor can also be used as a sole Cu^2＋ probe based on CD spectra.

Fluorescence chemosensors with pyrene and their interaction with nucleotide phosphate

A group of fluorescence chemosensor with pyrene, compounds (I), (II) and (III), were synthesized. The fluorescence spectra and the lifetime of these compounds were carefully measured. The fluorescence quenching spectra of pyrenyl butyric acid, compounds (I), (II) and (III) by different nucleotide phosphates, AMP ADP, ATP, dTTP, were also recorded and studied. The quenching and the stability constants were calculated by Stern-Volmer equation and eq. (2), respectively. The mechanism of interaction between fluorescence chemosensor and nucleotide phosphate was didscussed based on the comparison of the results obtained with the CPK model of free molecules of these com-pounds in the ground state.

Structure-property relationship on aggregation-induced emission properties of simple azine-based AIEgens and its application in metal ions detection

In recent twenty years,aggregation-induced emission(AIE),due to its excellent application prospect,has aroused widespread interests.The development of novel and easy to make AIE luminogens(AIEgens)is an attractive subject.For this purpose,it is very important to study the structure-property relationship of AIEgens.Because azine derivatives are easy to synthesis and some of them have nice AIE properties,herein,a series of azine derivatives(ADs)were employed as models to study the influence of different functional groups,electronic effects and structures on the AIE properties of azine derivatives.The AIE mechanism were studied by single crystal analysis,density functional theory(DFT)calculations and so on.The results indicated that the o-hydroxyl aryl substituted azine compounds could show good AIE properties.Meanwhile,the AIE properties of o-hydroxyl aryl substituted azine compounds were also influenced by the electronic effects of the aryl groups in the azine compounds.The o-hydroxyl groups could form intramolecular hydrogen bond with imine group,which play key role to restrict the intramolecular rotation of the aryl groups and act as base stone for the AIE process of this kind compounds.The HOMO-LUMO energy gaps of o-hydroxyl substituted azine are smaller than other homologous compounds,which is agree with the proposed AIE mechanism.Finally,thanks to the AIE properties,the o-hydroxy-substituted azines could be used as efficient Al^(3+)and Cu^(2+)fluorescent chemosensors in different conditions.In addition,test strips based on AD10 has been prepared,which can conveniently detect Cu^(2+)in industrial wastewater.This research supplied a way for the design of novel easy to make AIEgens through simple azine derivatives.

Colorimetric and Highly Selective Fluorescence ＂Turn-on＂ De-tection of Cr^3＋ by Using a Simple Schiff Base Sensor

A simple 8-quinolinecarboxaldehyde derived antipyrine Schiff base （QA） was synthesized and characterized, which exhibited high selectivity to Cr^3＋ over other metal cations. The Cr^3＋ recognition of QA could be achieved by means of fluorescense and absorption spectra, moreover, the obvious color change from colorless to yellowish is easily observed by naked-eyes. The binding constant of QA to Cr^3＋ was evaluated by spectral titration and the binding model was in 1 ： 1 stoichiometry measured by Job＇s plot.