Qi Lin

Double Metal Ions Competitively Control the Guest-Sensing Process: A Facile Approach to Stimuli-Responsive Supramolecular Gels

A facile approach to the design of stimuli-responsive supramolecular gels (SRSGs) termed double-metal-ion competitive coordination control is reported. By this means, the fluorescence signals and guest-selective responsiveness of the SRSGs are controlled by the competitive coordination of two different metal ions with the gelators and the target guest. To demonstrate this approach, a gelator G2 based on multiple self-assembly driving forces was synthesized. G2 could form Ca(2+) -coordinated metallogel CaG with strong aggregation-induced emission (AIE). Doping of CaG with Cu(2+) results in AIE quenching of CaG and formation of Ca(2+) - and Cu(2+) -based metallogel CaCuG. CaCuG could fluorescently detect CN(-) with specific selectivity through the competitive coordination of CN(-) with the Cu(2+) and the coordination of Ca(2+) with G2 again. This approach may open up routes to novel stimuli-responsive supramolecular materials.

Copillar[5]arene-based supramolecular polymer gels

Copillar[5]arene-based supramolecular polymer gels were obtained in acetonitrile. These supramolecular polymer gels were driven by C–H⋯π interactions, presented two phases as time goes on, and finally formed a supramolecular organic framework. Notably, the supramolecular polymer gels showed reversible gel–sol phase transitions upon heating and cooling. Moreover, the gels exhibit excellent self-healing properties.

A highly selective colorimetric chemosensor for detection of nickel ions in aqueous solution

A highly selective chemosensor LX based on quinoline was described, which could instantly detect Ni2+ in aqueous solution with specific selectivity and high sensitivity. The addition of Ni2+ to sensor LX induced a remarkable color change from yellow to red; this sensing procedure could not be interfered by other coexistent competitive cations such as Fe3+, Co2+, and Cu2+. Thus LX could be used as a potential Ni2+ colorimetric and naked-eye chemosensor. Moreover, test strips based on sensor LX were fabricated, which could act as a convenient and efficient Ni2+ test for “in-the-field” measurement of Ni2+.

A novel colorimetric HSO4(-) sensor in aqueous media.

A novel and sensitive anion receptor 3, bearing Schiff base structure, nitrophenyl azobenzol and carboxyl groups, was developed and characterized as a single chemosensor for the recognition of HSO(4)(-) anion. The different responses of UV-vis spectra and color changes of 3 could be applied to the recognition for HSO(4)(-) over other anions such as F(-), CI(-), Br(-), I(-), AcO(-), H(2)PO(4)(-) and CIO(4)(-) by the naked eye. Furthermore, the anion binding interaction of receptor-anion was also studied using UV-vis and (1)H NMR titration which revealed that 3 displayed a remarkable binding ability for the HSO(4)(-) with an association constant K(a)=6.59×10(4) M(-1). And the detection limitation of HSO(4)(-) with the receptor 3 was 2.0×10(-6) mol L(-1) in aqueous solution. Most importantly, the qualitative detection of HSO(4)(-) using receptor 3 was attempted with test kit which was made from receptor 3.

A novel 5-mercapto triazole Schiff base as a selective chromogenic chemosensor for Cu2+

A novel colorimetric cation sensor bearing phenol, thiol and HCN groups was designed and synthesized. In a DMSO/H2O (9:1, v/v) solution, the sensor exhibited highly selective recognition of Cu2+ among a range of metal ions tested. In the presence of Cu2+, solutions of the sensor underwent a dramatic color change from colorless to yellow, while the presence of other metal cations such as Zn2+, Pb2+, Cd2+, Ni2+, Co2+, Fe3+, Hg2+, Ag+ and Ca2+ had no effect on the color. The detection limit of the sensor toward Cu2+ is 8.0×10(-7) M and an association constant Ka of 4.3×10(5) M(-1) was measured. The sensing of Cu2+ by this sensor was found to be reversible, with the Cu2+-induced color being lost upon addition of EDTA.

A highly selective dual-channel Hg 2+ chemosensor based on an easy to prepare double naphthalene Schiff base

A non-sulfur chemosensor based on an easy to prepare double naphthalene Schiff base is reported for the colorimetric and fluorometric dual-channel sensing of Hg2+ ions by taking advantage of the twisted intramolecular charge transfer (TICT) mechanism. This work provides a novel approach for the selective recognition of mercury ions. Moreover, this sensor serves as a potential recyclable component in sensing materials and the complex L-Hg2+ (L = 1-[(2-naphthalenylimino)methyl]-2-naphthalenol) can therefore be used as a fluorescent sensor for iodine anions. Notably, the color changes are very significant and all the recognition and recycling processes can be observed by the naked eye.

Pillar[5]arene‐Based Supramolecular Organic Framework with Multi‐Guest Detection and Recyclable Separation Properties

The selective detection and separation of target ions or molecules is an intriguing issue. Herein, a novel supramolecular organic framework (SOF-THBP) was constructed by bis-thioacetylhydrazine functionalized pillar[5]arenes. The SOF-THBP shows a fluorescent response for Fe3+ , Cr3+ , Hg2+ and Cu2+ ions. The xerogel of SOF-THBP shows excellent recyclable separation properties for these metal ions and the absorption rates were up to 99.29 %. More interestingly, by rationally introducing these metal ions into the SOF-THBP, a series of metal-ion-coordinated SOFs (MSOFs) such as MSOF-Fe, MSOF-Hg and MSOF-Cu were constructed. These metal ions coordinated MSOFs could selectively sense F- , Br- , and l-Cys, respectively. The detection limits of these MSOFs for F- , Br- and l-Cys were about 10-8  m.

A colorimetric and fluorescent cyanide chemosensor based on dicyanovinyl derivatives: Utilization of the mechanism of intramolecular charge transfer blocking

Chemosensor (CS1) was designed and synthesized by simple green chemistry procedure. CS1 exhibited both colorimetric and fluorescence turn-off responses for cyanide (CN(-)) ion in aqueous solution. The probe showed an immediate visible color changes from yellow to colorless and green fluorescence disappearance when CN(-) was added. The mechanism of chemosensor reaction with CN(-) was studied using (1)HH NMR and (13)C NMR spectroscopies and mass spectrometry. Moreover, test strips based on the sensor were fabricated, which served as convenient and efficient CN(-) test kits.

A simple Michael acceptor type quinoline derivative for highly selective sequential recognition of CN− and Cu2+ in aqueous solution

A 2-(quinolin-2-ylmethylene) malononitrile (6) chemosensor has been designed and synthesized. The fluorogenic properties of 6 toward different anions and metal ions were investigated in DMSO/H2O (1 : 9, v/v) solution. Probe 6 exhibits high selectivity and sensitivity (5.09 × 10−8 M) to CN− as fluorescence “off–on” behavior through Michael addition. Moreover, the in situ formed 6-CN− is further utilized to sense the Cu2+ through complexation reaction with high selectivity and fluorescence quenching performance in aqueous water. Probe 6 has selectively detected CN− in real water sample, and on test strips. The FTIR, 1HNMR and ESI-MS spectroscopy supported the proposed mechanism of interaction.

A novel functionalized pillar[5]arene-based selective amino acid sensor for L-tryptophan

A novel L-tryptophan (L-Trp) fluorescent sensor (BTAP5) based on a functionalized pillar[5]arene has been developed. The sensor BTAP5 exhibits high selectivity and sensitivity (2.83 × 10−7 M) towards L-Trp in H2O/DMSO (7 : 3, v/v) solution. The recognition mechanism was studied by 1H NMR, electrospray ionization mass spectrometry and 2D NOESY.