Tianduo Li

A highly selective and sensitive fluorescent sensor for the rapid detection of Hg2 + based on phenylamine-oligothiophene derivative

A fast-responsive fluorescent phenylamine-oligothiophene sensor 3TDDA was reported. This sensor exhibited highly selective and sensitive detection of Hg(2+) ion in aqueous solution (THF/CH3CN/H2O, 45/50/5, v/v) through fluorescence quenching. The detection was not affected by the coexistence of other competitive metal ions such as Na(+), K(+), Ag(+), Ca(2+), Fe(3+), Al(3+), Co(2+), Ni(2+), Zn(2+), Pb(2+), Cd(2+), Fe(2+) and Cr(3+). A stoichiometric ratio (1:1) of the sensor and Hg(2+) was determined by a Jobs plot and mole-ratio curves. The binding of sensor 3TDDA and Hg(2+) was also chemically reversible with EDTA. The detection limit was calculated as low as 4.392×10(-7) M.

Highly selective, sensitive and fast-responsive fluorescent sensor for Hg2 +

A phenylamine-oligothiophene-based fluorescent sensor 2TBEA was reported. This sensor exhibited highly selective, sensitive and rapid detection of Hg(2+) ion in THF/H2O (7/3, v/v) solution through fluorescence quenching. The detection was unaffected by the coexistence of other competitive metal cations including Na(+), K(+), Ag(+), Ca(2+), Fe(3+), Al(3+), Co(2+), Cu(2+), Ni(2+), Zn(2+), Pb(2+), Cd(2+), Fe(2+) and Cr(3+). A1:1 binding ratio for 2TBEA - Hg(2+) was demonstrated by Jobs plot and mole-ratio curves. The coordination process was chemically reversible with EDTA. The detection limit was evaluated to be as low as 6.164×10(-8)M.

New views on the reaction of primary amine and aldehyde from DFT study.

A general theoretical investigation on the reaction of primary amine with aldehyde was carried out by density functional theory. The calculation systems involve three kinds of primary amines (methylamine, vinylamine, and phenylamine) and three kinds of aldehydes (formaldehyde, acetaldehyde, and acrylaldehyde). The steric and electronic inductive effects on the reaction mechanism were studied. Results reveal that the nucleophilic attack of primary amine on aldehyde under neutral conditions leads to carbinolamines, rather than Schiff bases. The nucleophilic attack on the protonated aldehyde produces the protonated Schiff base. The steric hindrance of the aldehyde slows down the nucleophilic attack but allows enough time to abstract a H; consequently, the formation of the protonated Schiff base is preferred. During the carbinolamine protonation, the H(+) preferably locates on the amine nitrogen and then is abstracted by the hydroxyl oxygen over an energy barrier, leaving protonated Schiff base after timely water liberation. The formation of a prereaction potential energy well obviously softens the steric and electronic inductive effects on the active barrier for different reactants.

Viscometric Study of the Gelatin Solutions Ranging from Dilute to Extremely Dilute Concentrations

The viscosity of gelatin solutions with concentrations between 10−4 and 10−5 g/cm3, covering the extremely dilute zones, was studied via a photoelectric viscometer, and the effects of the electrolyte, pH, surfactant, urea, and temperature were discussed. The results showed that the reduced viscosity (ηsp/C) of gelatin exhibited a drastic increase with dilution in the extremely dilute aqueous solutions, this being a typical polyelectrolyte effect. The reduced viscosity of gelatin underwent several oscillations with varying pH; the minimum value of the viscosity was at pH = 5.0, corresponding to its isoelectric point, where gelatin exhibited antipolyelectrolyte behavior. The reduced viscosity of gelatin decreased with increasing temperature, which was due to the helix–coil transition in the gelatin solution. The temperature of the helix–coil transition was 30.0°C in gelatin aqueous solution; however the temperature of helix–coil transition decreased to 20.0°C in urea. Upon cooling, the gelatin molecules in aqueous solution underwent a coil–helix transition. Hydrophobic interactions caused chain folding in the presence of the surfactant sodium dodecylsulphate.

Facile fabrication of AIE/AIEE-active fluorescent nanoparticles based on barbituric for cell imaging applications

Four barbituric derivatives (1–4), were synthesized with obvious aggregation induced emission (AIE) or aggregation induced emission enhancement (AIEE) behaviors. The optical properties in different states and the mechanisms of the enhanced emission of 1–4 were investigated. We found that there were a large number of globular or blocky nanoparticles with average diameters from 229 to 394 nm in tetrahydrofuran (THF)/water solutions when the water fraction (fw) was 90%. The single crystal data of 2 and 4 reveal that multiple intermolecular interactions restrict the intramolecular motions, and promote the formation of a herringbone arrangement (4), thus permitting intense emission in the aggregate state. In addition, the frontier molecular orbital energy and band gap calculated by density functional theory (DFT) are consistent with the experimental results. Compound 4 is cell-permeable: upon entering the live cells, the dye molecules can accumulate in the lysosomes and turn on the fluorescence.

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN- with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN- on the vinyl CC bond has been successfully confirmed by the optical measurements, 1H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19μM, which is much lower than the maximum permission concentration in drinking water (1.9μM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN- in field measurements.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2 + in ~ 100% aqueous media and application to real samples

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu2+ was developed. Sensor ADA showed high selectivity and sensitivity toward Cu2+ in ~100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu2+ recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu2+ in drinking water set by U.S. Environmental Protection Agency (~20μM) and the World Health Organization (~30μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu2+ with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.

A dual-responsive colorimetric and fluorescent chemosensor based on diketopyrrolopyrrole derivative for naked-eye detection of Fe3 + and its practical application

A novel dual-responsive colorimetric and fluorescent chemosensor L based on diketopyrrolopyrrole derivative for Fe3+ detection was designed and synthesized. In presence of Fe3+, sensor L displayed strong colorimetric response as amaranth to rose pink and significant fluorescence enhancement and chromogenic change, which served as a naked-eye indicator by an obvious color change from purple to red. The binding constant for L-Fe3+ complex was found as 2.4×104 with the lower detection limit of 14.3nM. The sensing mechanism was investigated in detail by fluorescence measurements, IR and 1H NMR spectra. Sensor L for Fe3+ detection also exhibited high anti-interference performance, good reversibility, wide pH response range and instantaneous response time. Furthermore, the sensor L has been used to quantify Fe3+ ions in practical water samples with good recovery.

Detection of nitroaromatic explosives by a 3D hyperbranched σ–π conjugated polymer based on a POSS scaffold

A three-dimensional hyperbranched polymer (3D-HP) with σ–π conjugated PDMPS (poly(dichloromethylphenylsilane)s) units covalently bonded to a polyhedral oligosilsesquioxane (POSS) scaffold was prepared by a one-step “thiol–ene click chemistry” reaction. Compared with POSS-based organic polymers, the 3D-HP with a flexible Si–Si chain showed enhanced solubility. This 3D hyperbranched polymer exhibited outstanding thermal stability and optimal photophysical properties. For probing nitroaromatics (NACs), the 3D-HP showed excellent sensitivity (Ksv = 2.83 × 104 M−1) against the presence of a tetrahydrofuran (THF) solution of 2,4,6-trinitrotoluene (TNT). In addition, the 3D-HP coated on glass films exposed to saturated DNT vapor exhibited a high quenching efficiency (ηEP) of the fluorescence of 3D-HP film, which was drastically suppressed (82%) for 300 s. The excellent fluorescent quenching performance of the 3D-HP can be attributed to the following points: (i) hyperbranched conjugated polymers afford multi-dimensional transport pathways for excitons migration; (ii) there exists in the polymer high electron affinity and rapid electron delocalization of σ–π conjugated polysilanes; (iii) noncovalent interactions between the electropositive δ+ Si atoms of σ–π conjugated polysilanes and N and/or O atoms of electron-deficient nitroaromatics (NACs) facilitate the adsorption of NACs. Furthermore, the bulky octathiol-POSS units in the 3D-HP can improve the permeability of the film sensor. This 3D hyperbranched σ–π conjugated polymer 3D-HP has the potential to be used to prepare sensitive, selective, and stable sensors for the detection of NACs explosives.

Rheological Behavior of Gelatin/1-Allyl-3-Methylimidazolium Chloride Solutions

Gelatin/1-allyl-3-methylimidazolium chloride solutions with different gelatin concentrations were prepared by using the ionic liquid 1-allyl-3-methylimidazolium chloride [AMIM]Cl as a solvent. Rheological properties of the gelatin ionic liquid solutions were investigated by steady shear and oscillatory shear measurements. In the steady shear measurements, all gelatin solutions showed a shear-thinning behavior at low shear rates, which we suggest reflect the characteristics of solvent [AMIM]Cl. In the oscillatory shear measurements, the effects of concentration and temperature on solution viscoelasticity were determined. The results show that the storage modulus G′ of gelatin solutions was essentially independent of gelatin concentration and temperature at all frequencies, while the solution viscosity greatly depended on polymer concentration and temperature. The loss modulus G″ increased with increase in concentration and decreased with rising temperature. This indicated that physical origins of elastic and dissipative behaviors were completely different. The influence of dissolved gelatin on the elasticity of solutions seemed to be minor.