A highly selective ‘off-on’ fluorescence chemosensor for Cr(III)

An ‘off-on’ fluorescence chemosensor for the selective signalling of Cr(III) has been designed exploiting the guest-induced inhibition of the photoinduced electron transfer signalling mechanism. The system shows an approximately 17-fold Cr(III)-selective chelation-enhanced fluorescence response in tetrahydrofuran and the system is highly selective against the background of environmentally and biologically relevant metal ions.     

Isophorone‐boronate ester: A simple chemosensor for optical detection of fluoride anion

A highly selective isophorone‐boronate ester based chemosensor, ( 1 ) , having a dicyanovinyl moiety as a convenient colorimetric probe, has been designed. Different types of anionic analyte such as CH₃COO^?, ClO₄^?, Cl^?, F^?, PF₆^?, Br^? and HSO₄^? were tested and among them only highly nucleophilic F^? anion displayed significant response towards the sensor. Addition of the fluoride anion across the boron atom disrupts the π‐conjugation thereby shifts the absorption wavelength towards the redshift region due to the decrease in the HOMO‐LUMO energy gap and a colour change from yellow to blue is observed under visible light condition. The detection limit of this probe was calculated to be 3.25 × 10^—8 M for fluoride anion. The binding constants and the detection limits of the sensor were calculated using absorption titration studies. The silica gel TLC strips dip‐coated by the chemosensor ( 1 ) revealed a colour change from yellow to brick red to naked eye.     

F-Induced ‘turn-on’ fluorescent chemosensor based on 1,3-alt thiacalix[4]arene

A new thiacalix[4]arene based fluorescent sensor 1 bearing two naphthyl groups has been synthesized in 1,3-alternate conformation. In the absence of fluoride ion, the receptor 1 is in ‘off-state’ showing no fluorescence emission. The presence of fluoride ion triggered the fluorescence emission to ‘on-state’. The receptor shows pronounced selectivity for fluoride ions. In THF, the presence of F⁻ ions induces the formation of a 1:1 (G:H) complex.     

A ‘turn-on’ fluorescent chemosensor based on rhodamine-N-(3-aminopropyl)-imidazole for detection of Al ions

A novel N-(3-aminopropyl)-imidazole-appended rhodamine-based fluorescent chemosensor was synthesized. The sensing behavior and selectivity of the synthesized chemosensor toward metal cations were studied by UV/vis and fluorescence spectroscopy. The chemosensor recognized Al³⁺ ions by a significantly enhanced fluorescence and a visible color change due to opening of the spirolactam ring triggered by the addition of Al³⁺ ions.     

新型金属羰基红外化学传感器的合成及对氟离子的识别性能

将N-(4-甲基苯基)-N′-甲基脲与中间体三氨三羰基合铬反应,合成了一种新型的红外化学传感器分子——N-(4-甲基苯基)-N′-甲基脲三羰基铬;利用元素分析、红外光谱、核磁共振波谱及电子轰击质谱分析了其组成和结构;采用傅立叶变换红外光谱初步研究了该金属羰基化合物对氟离子的红外识别与传感性能.结果表明,在质子型介质乙醇中,随着氟离子的加入,该金属羰基化合物的特征吸收峰向低波数方向显著偏移;其对氟离子的红外识别检测下限可达10-6 mol.L-1.     

A benzothiazole-based receptor-immobilised silica nanoparticle as chemosensor for Hg2+

Fluorogenic benzothiazole-based receptor has been easily immobilised onto filter paper and silica nanoparticle by sol-gel reaction. The sensing ability of the benzothiazole-immobilised thin layer filter paper chromatography (TLC-1) was evaluated on the basis of fluorescent changes caused by metal ions that were dropped onto the TLC plate. The TLC-1 exhibited a high affinity and selectivity for Hg²⁺ over other competing metal ions. Therefore, the TLC-1 holds promise as a portable sensor for the detection of Hg²⁺ in aqueous solution. Furthermore, the adsorption capacity of a column packed with SiO₂-1 was evaluated by the application of metal ions under various experimental conditions, such as pH, flow rate and concentration. The SiO2-1 column removed 98% of Hg²⁺ from drinking water containing 10 ppb of Hg²⁺. The adsorption capacity of the SiO₂-1 column was not strongly affected by pH and flow rates.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

Pterin-based highly selective,ratiometric, and sensitive ‘naked-eye’ sensor for acetate

The design and synthesis of a new pterin-based ratiometric and sensitive ‘naked-eye’ sensor R for highly selective recognition of acetate are reported. The acidic lactam NH and the NH of 2-N-pivaloyl group of receptor R along with 2,4-dinitrophenyl hydrazone group having the other acidic NH moiety lead to the binding of acetate anion in a 1:2 ratio by change of spectroscopic behavior on complexation (UV–vis and ¹H NMR studies) which is also proven by Job plot. The sharp color change from light yellow to violet promises R to be a useful chromogenic ratiometric sensor for acetate amongst other common anions.     

A hydrophilic fluorescent polymer containing naphthalimide moiety as chemosensor for microbioreactors

A novel hydrophilic copolymer P(NI-HEMA) containing the pendant group of naphthalimide moiety has been prepared. In the aqueous buffer solution, its film on the glass substrate shows an obvious fluorescence change and excellent linear relevance in the pH range of 5.8–8.0. Specifically, using the isobestic point at 406 nm as excitation wavelength can avoid the UV irradiation and the tedious calibration process. The film stability and hydrophilicity of copolymer P(NI-HEMA) were studied. Because of the easy synthesis, low price and high linear relevance to pH, the hydrophilic chemosensor film of P(NI-HEMA) could be potentially applied as a low-cost pH indicator for high-throughput bioprocessing in microreactors. Supported by the National Natural Science Foundation of China (Grant No. 20672036), Program for Shanghai Shuguang Project (Grant No. 07SG34), and New Century Excellent Talents in University (Grant No. NCET-06-0418)     

A metal–organic gel‐based fluorescent chemosensor for selective Al3+ detection

As an important metal element, aluminium has a significant impact on the environment and human health, and thus the detection of Al³⁺ has become the subject of much research. We synthesized a Ni(II)‐based metal–organic gel (Ni‐MOG), which can serve as an Al³⁺ fluorescence sensor with high selectivity and sensitivity, the limit of detection being calculated to be 0.5 μM. In addition, a composite film was further fabricated by hybridization of this Ni‐MOG with poly(vinyl alcohol). The composite film produced a rapid fluorescence response to Al³⁺ solutions at concentrations above 5 × 10^?5 M in 5 min. The Ni‐MOG composite film can also be successfully applied for the sensitive detection of Al³⁺ in real samples of tap water and seawater. The effective detection of Al³⁺ described in this contribution provides a new insight into water quality monitoring and has promising application value.     

A novel selective fluorescent chemosensor for Cu（Ⅱ）

A novel fluorescence enhancement Cu~(2 ) chemosensor derived from coumarin was prepared.Emission study found that it exhibits evident Cu~(2 )-amplified fluorescence prior to Co~(2 ),Pb~(2 ),Mg~(2 ),Mn~(2 ),Ni~(2 ),Zn~(2 ),Fe~(3 ),Ag~ and Cd~(2 ),and the largest emission enhancement factor is about 9 at a ratio of 2:1 (chemosensor 1/Cu~(2 )).     

A new fluorescent chemosensor for anion based on an artificial cyclic tetrapeptide

A cyclic tetrapeptide composed of alternating glycine and 8-amino-4-iso-butoxyquinoline-2-carboxylic acid was designed and synthesized. Its complexation properties with anions were performed by fluorescence spectroscopy and ¹H NMR method.     

A highly selective turn-on fluorescent chemosensor for copper(II) ion

A new pyrene derivative (1) containing a diaminomaleonitrile moiety exhibits high selectivity for Cu²⁺ detection. Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu²⁺. However, the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Fe³⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in fluorescence values for the system. The apparent association constant (K_a) of Cu²⁺ binding in chemosensor 1 was found to be 5.55×10³ M⁻¹. The maximum fluorescence enhancement caused by Cu²⁺ binding in chemosensor 1 was observed over the pH range 5-7.5.     

Theoretical study on a chemosensor for fluoride anion‐based on a urea derivative

The sensing mechanism of the N‐Phenyl‐N′‐(3‐quinolinyl)urea (PQU) chemosensor for fluoride anion has been investigated by density functional theory/time‐dependent density function theory. The double intermolecular hydrogen bonds are formed between the three anions (X^??F^?, AcO^?, Cl^?) and the urea fragment of PQU. In the S₀ states, the H_b? X^? hydrogen bonds are slightly stronger than the H_a? X^? hydrogen bonds and the fluoride‐induced deprotonation occurs at the N? H_b position rather than at the N? H_a position. Consequently, the absorption peaks, including an intramolecular charge transfer transition and a ππ* transition, are significantly red‐shifted. Thermodynamic calculations confirm that the deprotonation in the ground state is favorable in energy only when excess fluoride anion exists. Along with the S₀ → S₁ transition, the H_a? X^? hydrogen bonds strengthen and the H_b? X^? hydrogen bonds weaken. However, the emission spectra of [PQU‐H_b]^?, instead of [PQU‐H_a]^?, are observed upon addition of fluoride anion. © 2013 Wiley Periodicals, Inc.     

A new fluorescent chemosensor for transition metal cations and on/off molecular switch controlled by pH

A new fluorescent chemosensor with imidazole as ionophore was synthesized by the selective derivation of calixarene, which can effectively recognize Cu²⁺ and Zn²⁺ leading to different fluoroscopic behaviors in CH₃OH-H₂O. This system could be considered as a molecular switch. By modulating the pH of the solution, on-off-on fluorescent switching is carried out upon combinatory addition of acid, base and Cu²⁺.     

A highly efficient and selective probe for F- detection based on 1H-imidazo[4,5-b]phenazine derivative

A new colorimetric and fluorimetric chemosensor for F detection based on 1H-imidazo[4,5-b]phenazine derivative has been designed and synthesized.It shows excellent fluorescent specific selectivity and sensitivity for F in DMSO solution.Upon addition of F to the solution of probe 1,a remarkable color change from yellow to red could be observed easily by the naked-eye.The detection limit of this probe toward F is 6.2 10 6mol/L.Analysis by1 H NMR proved that the imidazolyl N–H could be hydrogen-bonded with added fluoride anions,and results in the difference of colors.     

Fluorescence turn-on chemosensor for Hg<Superscript>2+</Superscript> based on a rhodamine derivative and its application in bioimaging

A fluorescence turn-on chemosensor based on rhodamine B derivative (FD10) has been developed as a highly sensitive chemosensor for Hg²⁺. A prominent fluorescence enhancement was measured in the presence of Hg²⁺, which was in agreement with the changes in the absorption spectrum. Furthermore, by means of laser scanning fluorescence microscopy experiments, it was demonstrated that FD10 was cell-permeable and could be used as a fluorescent probe for monitoring Hg²⁺ in living cells. Supported by the National Natural Science Foundation of China (Grant No. 20801015) and Shanghai Leading Academic Discipline Project (Grant No. B108)     

A new fluorescent as well as chromogenic chemosensor for anions based on an anthracene carbamate derivative

A new fluorescent as well as chromogenic anion sensor, 1,8-anthradiol bis(N-phenylcarbamate) 2, was synthesized. It exhibits new selective red-shifted absorption and fluorescence bands with F⁻ and AcO⁻, which could be attributed to the anthracene moiety directly involved in the bonding interaction with the anions.     

DDTC-Na-based colorimetric chemosensor for the sensing of cyanide in water

Sodium diethyldithiocarbamate (DDTC-Na) was demonstrated to be a new colorimetric cyanide chemosensor by utilizing an indirect trick. First, some copper ions were added to the colorless aqueous solution of DDTC-Na. Then, the resultant brown solution was studied upon the addition of different anions, including Cl⁻, I⁻, IO₃⁻, SO₄²⁻, NO₂⁻, Br⁻, H₂PO₄⁻, F⁻, SCN⁻, HSO₄⁻, ClO₄⁻ and CN⁻. It was observed by naked eyes that the brown solution changed to colorless immediately after the addition of the trace cyanide, but there were no changes towards other anions, making DDTC-Na a good selective cyanide chemosensor in pure water. Supported by the National Natural Science Foundation of China (Grant Nos. 20674059 & 20402011)