8-Hydroxyquinoline derivative as a fluorescent chemosensor for zinc ion.

8-Hydroxyquinoline derivative 1 as a fluorescent chemosensor for Zn2+ was synthesized. Because Cd2+ is often found with Zn2+ in the environment and can form fluorescent complexes with chelating fluorophores, a potentially important property of chemosensors for Zn2+ is their selectivity for Zn2+ over Cd2+. The Zn2+ or Cd2+ complexes of 1 gave an emission band from the 1:1 complex, but the fluorescence intensity for Cd2+ was a half of that for Zn2+. Ligand 1 is suited for use as a fluorescent chemosensor for Zn2+.     

Bis-azamacrocyclic anthracene as a fluorescent chemosensor for cations in aqueous solution

A bis-azamacrocyclic anthracene (L2), which has two a 12-membered cyclic tetraamine (cyclen) connected through a 9,10-dimethylanthracene spacer, has been synthesized as a new fluorescent chemosensor for detection of pH and metal cations in aqueous solution (cyclen = 1,4,7,10-tetraazacyclododecane, L2 = 9,10-bis(1,4,7,10-tetraazacyclododecane-1-ylmethyl)anthracene). The fluorescence response of L2 has been studied in comparison to that of the previously reported monoazamacrocyclic anthracene (L1 = 1-(9-anthrylmethyl)-1,4,7,10-tetraazacyclododecane). Plots of the fluorescence intensity of L2 against pH demonstrate a sigmoidal curve with pKa 7.4, which is lower than that of L1 (8.3). Potentiometric titration reveals that the increase in the L2 fluorescence requires protonation of both cyclen rings, thus resulting in the lower pKa value. L2 demonstrates impressive fluorescence response against metal cations. At basic pH, upon addition of Zn2+ or Cd2+, L1 leads to an increase in the fluorescence intensity with a 1:1 metal-intensity response. L2, however, shows a 2:1 response to Zn2+, while showing a 1:1 response to Cd2+. At neutral pH, L1 fluorescence decreases upon addition of Zn2+ or Cd2+ because of a formation of metal-anthracene pi complex. L2, however, still demonstrates a Zn2+-induced increase in intensity with a 2:1 response, while no change in intensity is observed upon Cd2+ addition. The obtained findings suggest potential utilities of L2 as a new type fluorescent chemosensor for the detection of cations in aqueous solution.     

Sensitive and Selective Fluorescent Chemosensors Combining Multiple PET Processes for Ag+ Sensing

In this work, a novel fluorescent chemosensor combining multiple photoinduced electron transfer(PET) processes for the detection of Ag⁺ ion was synthesized. The PET processes were derived from the lone electron pair of the selenium donors and the tertiary nitrogen atom of the coumarin fluorophore, which have not yet been used in the fluorescent chemosensor designed for Ag⁺ ion. Interestingly, the chemosensors showed fluorescent responses to Ag⁺ ion with a fluorescence enhancement factor of 3-5-fold by blocking the intramolecular PET quenching pathways. Furthermore, the probe exhibited high selectivity and sensitivity for Ag⁺ ion over other relevant species with detection limit down to 10 nmol/L level. The chemosensors also showed excellent performances in analyzing natural water samples. The chemosensors developed herein represent a new strategy for the PET fluorescent chemosensor design for the detection of Ag⁺ ion.     

A highly selective and sensitive inorganic/organic hybrid polymer fluorescence "turn-on" chemosensory system for iron cations

A polymer-based fluorescence "turn-on" chemosensor is demonstrated with high sensitivity and selectivity toward Fe2+ cations. This system is an inorganic/organic hybrid system in which Cu2+ is coordinated at the receptor site of a conjugated polymer sensor. The unique quenching behavior of the Cu2+ toward this conjugated polymer was used to lower the initial fluorescence intensity of the sensory system. This results in a highly sensitive and also selective sensory system toward Fe2+ as compared to other related divalent transition-metal cations in solution.     

A Selective and Sensitive "Turn-on" Fluorescent Chemosensor for Recognition of Hg(2+) Ions in Water

Based upon highly selective and irreversible Hg(2+) -promoted deprotection of the dithioacetal reaction, a new water-soluble "turn-on" fluorescent chemosensor (1) was prepared and exhibited high selectivity and sensitivity towards the Hg(2+) ion over other heavy and transition-metal ions in pure water by transforming a weakly fluorescent precursor (colorless) to a highly fluorescent aldehyde (yellow-green; see figure) with a 155-fold increase in fluorescent intensity.     

Both visual and ratiometric fluorescent sensor for Zn2+ based on spirobenzopyran platform

A ratiometric fluorescent Zn²⁺ chemosensor, SPQH, based on spirobenzopyran platform, was synthesized. In aqueous HEPES 7.4 buffer solution, upon chelation with Zn(II), SPQH demonstrates high selectivity and subnanomolar sensitivity for zinc ion with 36-fold enhancement in the NIR fluorescence output.     

A new rhodamine-based fluorescent chemosensor for mercury in aqueous media

A new fluorescent ‘‘on–off' chemosensor for Hg2+initiated by a derivative of rhodamine B was designed and synthesized. Compound 1 exhibited high sensitivity and selectivity for Hg2+over other commonly coexistent metal ions in aqueous media. Upon the addition of Hg2+, the spirocyclic ring of probe is opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm is observed. The colorimetric and fluorescent response to Hg2+can be conveniently detected by the naked eye, which provides a facile method for visual detection of Hg2+. From the molecular structure and spectral results of 1, an irreversible, hydrolysis, desulfurization reaction mechanism is proposed.     

A new fluorescence chemosensor based on benzothiazole derivative for Zn2+ and its logic gate behavior

A novel benzothiazole derivative J as a fluorescent chemosensor for Zn²⁺ has been designed and synthesized. The chemosensor J exhibits high selectivity and sensitivity to Zn²⁺ as fluorescence “turn-on” behavior, which the other cations do not make sense. The detection limit calculated by fluorescence titration method was 1.64 × 10^?8 M. Furthermore, the generated J-Zn²⁺ ensemble could recover the enhanced fluorescence upon the addition of EDTA generating an “on-off-on” recycle. In addition, the test strip based on J was fabricated, which could act as a convenient and efficient Zn²⁺ test kit.     

Perylene diimide based ‘turn-on’ fluorescence sensor for detection of Pd in mixed aqueous media

A perylene diimide (PDI) based fluorescence chemosensor (PDI-1) for Pd²⁺ was prepared. PDI-1 showed a remarkable fluorescence enhancement (over 120-fold) in the presence of Pd²⁺ in mixed aqueous media with high selectivity and sensitivity. Moreover, the dramatically ‘off–on’ fluorescence response concomitantly induced the obvious color change from dark purple to brilliant pink, which could also be identified by naked eyes easily. The low limit for Pd²⁺ detection was found to be as small as 10⁻⁹ mol/L. Hence, PDI-1 is a highly promising fluorescent chemosensor for the direct determination of residual Pd²⁺ in chemical medicines and environment samples.     

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.     

水杨醛-4-甲氧基苯甲酰腙识别锌离子的研究

设计合成了荧光传感分子水杨醛-4-甲氧基苯甲酰腙(SAMB),通过IR、1HNMR和元素分析确证了其结构,利用紫外-可见吸收光谱和荧光光谱考察了其对不同阳离子的识别作用。结果表明,SAMB的荧光发射对锌离子表现出高选择性响应,且形成1∶1型配合物。乙醇中锌离子的加入导致SAMB的荧光增强328倍,而其他过渡金属离子只引起SAMB的荧光的略微增强。初步探讨了受体分子与锌离子的结合模式与荧光增强机理。     

Fluorescent peptide sensor for the selective detection of Cu

A new fluorescent peptidyl chemosensor for Cu²⁺ ions with fluorescence resonance energy transfer (FRET) capabilities has been synthesized via Fmoc solid-phase peptide synthesis. The metal chelating unit, which is flanked by the fluorophores tryptophan (donor) and dansyl chloride (acceptor), consists of the amino acids glycine and aspartic acid (Gly-Gly-Asp-Gly-Gly-Asp-Gly-Gly-Asp-Gly-Gly-Asp-Gly-Gly). Coordination of the Cu²⁺ ions to the metal chelating unit results in fluorescent quenching of both the donor and acceptor fluorophores. Although it was determined that Cu²⁺ binding causes no change in FRET efficiency, emission and Cu²⁺-induced quenching of the acceptor dye can be used to monitor the concentration of the copper ions, with a detection limit of 32 μg L⁻¹. The sensor also demonstrated sensitivity, reversibility and selectivity towards Cu²⁺ in a transition metal matrix at pH 7.0.     

基于四丹磺酰胺杯[4]芳烃的汞离子荧光化学传感器

我们方便地合成了上沿修饰四丹磺酰胺基团的杯[4]芳烃衍生物1,发现该化合物在含50％水的乙腈中显示出对汞离子高选择性和灵敏性的识别作用,竞争实验表明多数金属离子对其检测干扰较小。机理研究结果表明荧光萃灭源于由丹磺酰胺基团到汞离子的光致电子转移过程。另外,通过研究1和1-Hg2+的荧光衰减实验,以及对比双丹磺酰胺杯[4]芳烃2和单丹磺酰胺杯[4]芳烃3对汞离子的识别作用,发现化合物1的四丹磺酰胺基团具有很好的预组织和协同作用。化合物1对汞离子的检测限为3.41×10-6 mol·L-1,这可以使1成为一个潜在的汞离子荧光化学传感器。     

Novel multi-responsive fluorescence switch for Hg2+ and UV/vis lights based on diarylethene-rhodamine derivative

A new multi-responsive fluorescent switch DTE-Pip-Rho 1O has been designed and synthesized in this study. For this molecule, the reactive site of spirolactam ring is far away from the diarylethene unit through the intramolecular piperazine. It exhibited high selectivity and sensitivity to Hg²⁺ in addition to obvious color change (colorless-pink) and fluorescence “off-on” (dark-orange) during this process. It is believed that the color change is due to Hg²⁺-assisted hydrolysis of rhodamine hydrazide. Therefore, the new molecule can be used as colorimentric and fluorescent chemosensor for Hg²⁺ with high selectivity. The detection limits of absorbance and fluorescence for Hg²⁺ were calculated to be 1.15?μM and 1.16?μM, respectively. The resulting DTE-Pip-Rho 1O-Hg²⁺ could also function as a reversible fluorescence photo-switch in response to UV/vis light owing to FRET mechanism. Moreover, it has been demonstrated that the photo-switchable system displayed excellent fatigue resistance and remarkable anti-photobleaching capability.     

"Off-On" based fluorescent chemosensor for Cu2+ in aqueous media and living cells

A novel Cu²⁺-specific “off-on” fluorescent chemosensor of naphthalimide modified rhodamine B (naphthalimide modified rhodamine B chemosensor, NRC) was designed and synthesized, based on the equilibrium between the spirolactam (non-fluorescence) and the ring-opened amide (fluorescence). The chemosensor NRC showed high Cu²⁺-selective fluorescence enhancement over commonly coexistent metal ions or anions in neutral aqueous media. The limit of detection (LOD) based on 3 × δ_blank/k was obtained as low as 0.18 μM of Cu²⁺, as well as an excellent linearity of 0.05-4.5 μM (R = 0.999), indicating the chemosensor of high sensitivity and wide quantitation range. And also the coordination mode with 1:1 stoichiometry was proposed between NRC and Cu²⁺. In addition, the effects of pH, co-existing metal ions and anions, and the reversibility were investigated in detail. It was also demonstrated that the NRC could be used as an excellent “off-on” fluorescent chemosensor for the measurement of Cu²⁺ in living cells with satisfying results, which further displayed its valuable applications in biological systems.     

Supramolecular assembly of a new squaraine and β-cyclodextrin for detection of thiol-containing amino acids in water

A new unsymmetrical aniline-based squaraine (SQ2) bearing binding unit of Hg²⁺ ion was designed and synthesised. SQ2 can form 1:2 inclusion complex with β-cyclodextrin, and the resulting complex, which undergoes absorption and fluorescence bleaching upon binding Hg²⁺, can serve as a turn-on colorimetric or fluorescent chemosensor in organic solvent-free aqueous solution for thiol-containing amino acids with high selectivity and tunable measuring range.     

Reversible "off-on" fluorescent chemosensor for Hg2+ based on rhodamine derivative

A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg(2+) with high selectivity. The structure of chemosensor 1 was characterized by IR, (1)H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg(2+) in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg(2+) complex with the Hg(2+)-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg(2+) ions and TBAI (tetrabutylammonium iodide) titration experiments.     

识别过渡金属离子的1,8-萘二甲酰亚胺多胺衍生物荧光传感器的研究

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 e±cient intramolecular photoinduced electron transfer (PET). However, after addition of the transition metal ions, the chemosensor 1-3 exhibits obvious fluorescence enhancement. Moreover, the intensity of the fluorescence emission of chemosensors increases significantly in the presence of Zn2+ and Cd2+. The fluorescent chemosensors with different polyamine as receptors show diverse a±nity abilities to the transition metal ions and signal the receptor-metal ion interaction by the intensity change of fluorescence emission.     

1-乙酰基-3-(2-羟基-4,6-二甲氧基苯基)-5-芳基-2-吡唑啉的合成及Cu2+荧光探针行为

设计合成了6个1-乙酰基-3-(2-羟基-4,6二甲氧基苯基)-5-芳基-2-吡唑啉化合物4a～4f.测试了它们的紫外光谱和荧光光谱,研究了其对铜离子的选择性识别作用.结果表明,化合物4f作为铜离子荧光探针,受常见离子干扰较小,对于铜离子有着较高的选择性和较低的检出限.     

一种新型酰肼腙类受体的合成与阳离子识别

设计合成了荧光传感分子2-吡啶甲醛-4-乙氧基苯甲酰肼腙(PAEB),采用红外光谱法、氢核磁共振和元素分析法对其结构进行了表征,用紫外可见吸收光谱和荧光发射光谱研究了PAEB对不同金属离子的配位作用的机理。结果表明:PAEB与锌(Ⅱ)形成物质的量的比为1比1配合物。由于此配合物的形成,在发射波长470nm(激发波长为400nm)处出现明显的荧光增强,且对锌(Ⅱ)而言具有较高的选择性。初步探讨了受体分子与锌(Ⅱ)的荧光增强机理。