Lijun Tang

Single sensor for two metal ions: colorimetric recognition of Cu2+ and fluorescent recognition of Hg2+.

The first novel rhodamine B based sensor, rhodamine B hydrazide methyl 5-formyl-1H-pyrrole-2-carboxylate Schiff base (2) capable of detecting both Cu(2+) and Hg(2+) using two different detection modes has been designed and synthesized. The metal ion induced optical changes of 2 were investigated in MeOH:H(2)O (3:1) HEPES buffered solution at pH 7.4. Sensor 2 exhibits selective colorimetric recognition of Cu(2+) and fluorogenic recognition of Hg(2+) with UV-vis and fluorescence spectroscopy, respectively. Moreover, both of the Cu(2+) and Hg(2+) recognition processes are proven to be hardly influenced by other coexisting metal ions.

A highly selective and ratiometric fluorescent sensor for relay recognition of zinc(II) and sulfide ions based on modulation of excited-state intramolecular proton transfer

A new fluorescent 2-(2′-aminophenyl)benzimidazole derivatized sensor BMD was designed and synthesized. In CH3CN/H2O (2 : 8, v/v, HEPES 10 mM, pH 7.4) solution, sensor BMD displays two emission bands and exhibits a highly selective and ratiometric response to Zn2+ ions with a distinctly longer-wavelength emission blue shifted through the inhibition of the excited-state intramolecular proton transfer (ESIPT) process. BMD can clearly discriminate Zn2+ from Cd2+ and other metal ions. Moreover, the in situ generated BMD-Zn2+ solution exhibits a highly selective and ratiometric response to S2− among various anions and thiol-containing amino acids via Zn2+ displacement approach, which results in a revival of the ESIPT phenomenon of free BMD. These results demonstrate that BMD can serve as a ratiometric sensor for sequential recognition of Zn2+ and S2− in aqueous solution through inhibition and turn-on of ESIPT process.

A rhodamine-benzothiazole conjugated sensor for colorimetric, ratiometric and sequential recognition of copper(II) and sulfide in aqueous media.

A new rhodamine-benzothiazole conjugated colorimetric sensor 1 that exhibits sequential recognition to Cu(2+) and S(2-) in CH3CN/HEPES buffer (v/v=1:1, HEPES 10mM, pH=7.0) solution has been developed. Sensor 1 displays highly selective and sensitive recognition to Cu(2+) with a ratiometric behavior, and the resultant 1-Cu(2+) complex can act as a highly selective S(2-) sensor via Cu(2+) displacement approach. The Cu(2+) and S(2-) recognition processes are rapid and reversible, and the Cu(2+) and S(2-) inputs can result in an INHIBIT logic gate.

Multi-analyte, ratiometric and relay recognition of a 2,5-diphenyl-1,3,4-oxadiazole-based fluorescent sensor through modulating ESIPT

A new two dipicolyl amine (DPA) dangled 2,5-diphenyl-1,3,4-oxadiazole derivatized sensor L has been designed and synthesized. Sensor L displays excited state intramolecular proton transfer (ESIPT) properties in buffered water solution (HEPES 10 mM, pH = 7.4). L shows highly selective and ratiometric fluorescence responses to Zn2+ in a 1 : 2 binding ratio. Fluorescence spectra and 1H NMR studies demonstrate that L binds Zn2+ ions through its amide form, which promoted the ESIPT emission enhancement. The in situ generated L–2Zn2+ complex can serve as a relay recognition sensor toward PPi and S2− via further complexation and Zn2+ sequestering processes respectively. Thus, multi-analyte and relay recognition of L through modulating ESIPT has been achieved.

Quinoline benzimidazole-conjugate for the highly selective detection of Zn(II) by dual colorimetric and fluorescent turn-on responses

A quinoline benzimidazole-conjugate (QBC) has been synthesized for the highly selective detection of Zn(II) both by colorimetry and fluorimetry. Probe QBC senses Zn2+ over other cations as fluorescence ‘off–on’ behaviour in HEPES-buffered CH3CN–H2O (1 : 1, v/v, pH = 7.0) solution. A possible mechanism is proposed based on the inhibition of PET and intramolecular restricted torsional rotation through the C–C single bond between the quinoline benzimidazole-conjugate. The Chemosensor is utilized to detect Zn2+ in much real sample analysis.

A water-soluble highly sensitive and selective fluorescent sensor for Hg2+ based on 2-(2-(8-hydroxyquinolin)-yl)benzimidazole via ligand-to-metal charge transfer (LMCT)

A water-soluble fluorescent sensor (L) based on 2-(2-(8-hydroxyquinolin)-yl)benzimidazole has been synthesized and characterized. Sensor L displays highly selective and sensitive recognition of Hg2+ with a fluorescence “ON–OFF” response in buffered aqueous solution (1% dimethyl sulfoxide (DMSO), Tris–HCl 10 mM, pH = 7.4). X-ray crystal structure of the L–Hg2+ complex reveals that the oxygen and nitrogen atoms of 8-hydroxyquinoline and the imine N atom of the benzimidazole unit (N1) bind Hg2+ through a 1 : 1 binding stoichiometry. The fluorescence quenching mechanism is qualitatively evaluated by quantum chemical calculations which show that the fluorescence quenching phenomenon is caused by ligand-to-metal charge transfer (LMCT) in the excited state.

A new hydroxynaphthyl benzothiazole derived fluorescent probe for highly selective and sensitive Cu(2+) detection.

A new reactive probe, 1-(benzo[d]thiazol-2-yl)naphthalen-2-yl-picolinate (BTNP), was designed and synthesized. BTNP acts as a highly selective probe to Cu(2+) in DMSO/H2O (7/3, v/v, Tris-HCl 10mM, pH=7.4) solution based on Cu(2+) catalyzed hydrolysis of the picolinate ester moiety in BTNP, which leads to the formation of an ESIPT active product with dual wavelength emission enhancement. The probe also possesses the advantages of simple synthesis, rapid response and high sensitivity. The pseudo-first-order reaction rate constant was calculated to be 0.205min(-1). Moreover, application of BTNP to Cu(2+) detection in living cells and real water samples was also explored.

A novel benzothiazole-based enaminone as a fluorescent probe for highly selective and sensitive detection of CN−

A novel benzothiazole derived enaminone BTP as a fluorescent probe for CN− recognition has been developed. In DMSO/H2O (95/5, v/v, HEPES 10 mM, pH = 7.4) solution, BTP exhibits high selectivity toward CN− among various anions through colorimetric and fluorescence dual channel changes. On treatment with CN−, BTP displays a blue shifted fluorescence enhancement and a naked eye observable color change from orange to yellow green. Moreover, the CN− sensing event possesses an excellent anti-interference ability over other anions. Sensing mechanism investigations prove that the CN− recognition process undergoes a typical nucleophilic addition of CN− to the enaminone formed BTP. Simple test paper experiments evidenced the practicability of BTP for CN− detection.

A new dual chromo- and fluorogenic chemosensor for Fe 3+ in aqueous solution

A new rhodamine-based chemosensor 2, which shows a reversible dual fluorogenic and chromo-response to Fe3+ in MeOH-HEPES buffer (10 mM, pH 7.4) (3:1 v/v), has been developed. The free solution of 2 is colourless and nonfluo-rescent which changes to pink with a strong fluorescence in the presence of Fe3+. Other metal ions (Hg2+, Ag+, Pb2+, Sr2+, Ba2+, Cd2+, Ni2+, Co2+, Fe2+, Mn2+, Cu2+, Zn2+, Ce3+, Cr3+, Mg2+, K+ and Na+) had no significant effect.

Highly Selective Fluorescent Recognition of Pyrophosphate in Water by a New Chemosensing Ensemble

AbstractA new chemosensing ensemble that displays sensitive and selective fluorescent recognition of pyrophosphate in water at pH 7.4 has been developed. The ensemble is constructed by a copper complex (receptor) and eosin Y (indicator), the constructed ensemble is capable of highly selectively discriminate pyrophosphate from other common existing anions such as CH3COO−, HSO4−, NO3−, H2PO4−, HPO42−, PO43−, NCS−, I−, Cl−, Br−, F−as well as some structurally similar carboxylates such as citrate, tartrate, oxalate, malonate, succinate and glutarate. FigureA new chemosensing ensemble that can effectively differentiate pyrophosphate from common existing anions and structurally similar carboxylate anions in 100% aqueous solution at physiological pH has been developed.