Tao Yi

Fudan University, Shanghai, Shanghai Shi, China

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Publications (102)427.9 Total impact

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    ABSTRACT: Sn(2+) is usually added to toothpaste to prevent dental plaque and oral disease. However, studies of its physiological role and bacteriostatic mechanism are restricted by the lack of versatile Sn(2+) detection methods applicable to live cells, including Streptococcus mutans. Here we report two Sn(2+) fluorescent probes containing a rhodamine B derivative as a fluorophore, linked via the amide moiety to N,N-bis(2-hydroxyethyl)ethylenediamine () and tert-butyl carbazate group (), respectively. These probes can selectively chelate Sn(2+) and show marked fluorescence enhancement due to the ring open reaction of rhodamine induced by Sn(2+) chelation. The probes have high sensitivity and selectivity for Sn(2+) in the presence of various relevant metal ions. Particularly, both and can target lysosomes, and can probe Sn concentrations in lysosomes with rather acidic microenvironment. Furthermore, these two probes have low toxicity and can be used as imaging probes for monitoring Sn(2+) not only in live KB cells (eukaryotic) but also in Streptococcus mutans cells (prokaryotic), which is a useful tool to study the physiological function of Sn(2+) in biological systems.
    The Analyst. 08/2014;
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    ABSTRACT: Three alkynylplatinum (II) bipyridyl complexes in which two cholesterol groups are combined with a bipyridyl group via alkyl chains and amido bonds were designed and synthesized. The complexes have different lengths of ethylene glycol chains at the para-position of 1-phenylethyne. All three complexes can self-assemble to gel networks in DMSO, while only the morphology of 1a without an ether chain shows well-defined right-handed helical structures with layer packing mode. However, 1c with long ethylene glycol chains forms perfect regular left-handed helical structures in aqueous ethanol solution while the volume percentage of water is less than 5% (v/v). As the ratio of water increases, the chirality changes from a left-handed helix to a right-handed helix and the packing mode alters from the monolayer structure to the hexagonal structure. As the ratio of water further increases to greater than 50% (v/v), the structure of the assembly finally transforms to bilayer vesicles. The process of the morphology transition is traced by circular dichroism spectra, powder X-ray diffraction, SEM and TEM images. The result indicates that a polar solvent (water) acts as a trigger to change the self-assembly of the chiral structures of the complex due to the strong hydrophobic interaction between cholesterol groups and the balance of the hydrophobicity and hydrophilicity of the solvent environment.
    Soft Matter 07/2014; · 3.91 Impact Factor
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    ABSTRACT: Different luminescent single crystals of 2-(anthracen-9-yl)-4,5-diphenyl-1H-imidazole (ADPI) were obtained through the construction of different stacking modes with the aid of intermolecular interactions. Both the fluorescence and the stacking mode of the crystals can be reversibly tuned by mechanical and thermal forces to render ADPI piezochromic, which represents a unique example of reversibly controlled solid emission. The regulation of π–π stacking between the anthracene planes by mechanical and thermal forces is suggested to be the main driving force for the piezochromic character of ADPI.
    Chemical Science 07/2014; · 8.31 Impact Factor
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    ABSTRACT: Sn2+ was usually added to toothpaste to prevent dental plaque and oral disease. However, studies of its physiological role and bacteriostatic mechanism are restricted by the lack of versatile Sn2+ detection methods applicable to living cells and Streptococcus mutans. Here we report two Sn2+ fluorescent probes containing rhodamine B derivative as a fluorophore, linked via amide moiety to N, N-bis(2-hydroxyethyl)ethylenediamine (R1) and tert-butyl carbazate group (R2), respectively. These probes can selectively chelate Sn2+ and show marked fluorescent enhancement due to the ring open reaction of rhodamine induced by Sn2+ chelating. The probes have high sensitivity and selectivity for Sn2+ in the presence of various relevant metal ions. Particularly, both R1 and R2 can target lysosome and R2 can probe Sn concentrations in lysosomes with rather acidic microenvironment. Furthermore, the two probes have low toxicity and can be used as imaging probes for monitoring Sn2+ not only in living KB cell (eukaryotic cell) but also streptococcus mutans (prokaryotic cell), which is a useful tool to study the physiological function of Sn2+ in biological systems.
    The Analyst 07/2014; · 4.23 Impact Factor
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    ABSTRACT: Thiazole orange-modified diarylethene () shows weak fluorescence but no photochromism in aqueous solution. When binding with DNA, the fluorescence of is enhanced drastically and the photochromic reactivity is unlocked. This kind of DNA-responsive photoswitchable system can be used for imaging nucleic acids within cells.
    Chemical communications (Cambridge, England). 07/2014;
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    ABSTRACT: In this review, we focus on the types of smart supramolecular gels whose self-assembly processes are affected or even triggered by physical forces including sonication and mechanical stress (mechanical force). The types of gels that are responsive to sonication and mechanical stress are examined and summarised. The gels exhibit non-covalent interactions among the gelator molecules and show dynamic and reversible properties controlled by the stimuli. Upon stimulation, the gelators cause instant and in situ gelation of organic solvents or water with different modes and outcomes of self-assembly. On the other hand, sonication and mechanical stress, as external factors, can give rise to dynamic changes in microscopic morphology, optical properties, etc. Certain thixotropic supramolecular gels exhibit perfect self-healing characteristics. The driving forces and the mechanism of the self-assembly process and the responsive outcome of morphological and spectroscopic changes are discussed. Those supramolecular gels responding to sonication and mechanical stress offer a wide range of applications in fields such as smart and adaptive materials, switches, drug control and release, and tissue engineering.
    Chemical Society Reviews 04/2014; · 24.89 Impact Factor
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    ABSTRACT: A kind of novel hydrogelator based on (-)-menthol, a traditional cooling compound, tailed by an amino acid derivate through an alkyl chain, has been designed and synthesized. The hydrogelator containing an l-lysine can form a stable hydrogel with thixotropic character in a large pH range. An interesting feature is that the viscoelastic character of the hydrogel can be enhanced by mechanical force. The mechanism of the self-assembly process was investigated by means of IR, SEM, AFM and X-ray diffraction. The formation of three dimensional multiporous networks through acid base interactions and strong double hydrogen bonding between amino acids is proposed to be the driving force for the construction of the stable hydrogel. As a result, the hydrogelator can further gelate aqueous solutions of some confirmed antibacterial agents such as Zn(2+) and a series of water soluble organic antibiotic medicines like lincomycin, amoxicillin, etc., in such a unique way that the concentration of the antibacterial agents loaded into the hydrogel can be tuned to a large extent. The antimicrobial susceptibility of the hydrogels loaded with Zn(2+) or lincomycin is much more effective than that of the corresponding aqueous solution tested by the Oxford cup method. Furthermore, the hydrogelator is completely innoxious to living cells by measurement of MTT assay. Thus, the hydrogel can be developed as a universal carrier for antibacterial agents and may also be widely used in the fields of cell culture, tissue engineering, or drug delivery systems.
    Soft Matter 04/2014; 10(17):3077-85. · 3.91 Impact Factor
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    ABSTRACT: A naphthalimide-naphthyridine derivative has been synthesized for the detection of hydroxyl radicals. It can distinguish hydroxyl radicals from other reactive oxygen species with high selectivity and short response time. Moreover, it has no cellular toxicity, and can be effectively used for intracellular detection of hydroxyl radicals.
    Chemical Communications 03/2014; · 6.38 Impact Factor
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    ABSTRACT: Low molecular weight two-component gels were obtained from naphthalene diimide undecanoic acid mixed with several aliphatic and aromatic diamines. The gelation properties, structural characteristics and fluorescence of these two-component gels were studied via scanning electron microscopy, X-ray diffraction and spectroscopy. Specifically, the gel containing diaminoanthraquinone (DAQ) was sensitive to nitrite anions. The absorbance and emission intensity of the gel in the visible range obviously decreased upon addition of an aqueous solution of sodium nitrite. The faded gel collapsed and changed to a sediment after detection and the organic acid could be recycled. Te NO2− detection with the gel provides a convenient method of nitrite analysis that is visible to the “naked eye”.
    J. Mater. Chem. C. 02/2014; 2(10).
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    ABSTRACT: Upconversion luminescence (UCL) is an anti-Stokes process whereby low-energy photons are converted to higher-energy ones. UCL imaging for cells and animal tissues has attracted substantial attention in recent years because of the unique abilities of upconversion materials, which can minimize the background interference from the autofluorescence of biosamples and enhance tissue penetration. This protocol describes a step-by-step guide for the fabrication of UCL probes, including lanthanide-based upconversion nanoparticles (Ln-UCNPs) with a particle size of ∼20 nm (NaYF4/NaLuF4: Yb, Er/Tm) and triplet-triplet annihilation-based UCNPs (TTA-UCNPs) with a particle size of ∼10 nm (palladium octaethylporphyrin as sensitizer and 9,10-diphenylanthracene as annihilator). We also describe the characterization of the UCL nanoprobes (via transmission electron microscopy and UCL emission spectroscopy) and functionalization (via silica coating and ligand exchange), as well as applications for UCL bioimaging of living cells (HeLa cells) and small animals (nude mice and Kunming mice). The setup of a laser-scanning UCL microscope and a UCL imaging system is also presented. Compared with a normal imaging setup, we adopted longer-wavelength excitation lasers and short-pass filters. The synthesis of hydrophilic UCNP for application in UCL bioimaging requires ∼15 d.
    Nature Protocol 10/2013; 8(10):2033-44. · 8.36 Impact Factor
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    ABSTRACT: Phosphorescent nanospheres of a carboxyl-functionalized iridium complex ([Ir(ppy)2(Hdcbpy)], ppy: 2-phenylpyridine; Hdcbpy: 4-carboxy-2,2'-bipyridyl-4'-carboxylate) were prepared by a conventional precipitation method. Driven by hydrogen bond interaction between carboxylic groups of the complex and the guest molecule tris(imidazoline), these nanospheres can be transformed into 1-dimensional nanowires in the presence of tris(imidazoline) at the concentration of the iridium complex higher than 4.8 mM, while nanowires change back to nanospheres with the diameter obviously smaller than that of the sole complex of [Ir(ppy)2(Hdcbpy)]. The interaction between carboxylic groups and tris(imidazoline) molecules was confirmed by FT-IR spectra. The structures of the nanowires and nanospheres were further studied by XRD diffraction analysis. With the morphological transformation from nanospheres to nanowires, the phosphorescence of nanostructures was blue shifted from 590 to 564 nm.
    Dalton Transactions 02/2013; · 3.81 Impact Factor
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    ABSTRACT: Two organometallic terpyridyl platinum gelators containing hydrophobic cholesterol with or without large steric hindrance were synthesized and characterized. The complex with three bulky tert-butyl groups (1a) can form a stable gel in several kinds of solvent, such as alcohol, ethyl acetate and toluene with ultrasound irradiation. These sonicated gels display different colour and emission properties compared with their related solutions and precipitates. The intensity of the photoluminescence in gel or solid state of 1a is obviously enhanced by aggregation. The morphology, as well as the surface wettability of 1a can also be reversibly adjusted by sonication and heating. However, the complex without three bulky tert-butyl groups (1b) has poorer solubility and gelation capability, and lower luminescence quantum yield due to strong intermolecular π–π stacking and metal–metal interaction. The spectral and structural variation was characterized by UV-visible and fluorescence spectra, SEM and TEM images, and XRD analysis. The mechanism of the molecularly self-assembled pattern indicates that the large steric hindrance is the reason for the different gelation capabilities and emission properties of the two complexes. Sonication may change the molecular conformation of 1a and promote the ionic dipolar interaction and hydrophobic interactions for gelation, and thus switch the optical properties of the complex in the aggregated state.
    J. Mater. Chem. C. 02/2013; 1(9):1753-1762.
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    ABSTRACT: Two guanosine analogues have been designed and synthesized by connecting one () or three adamantane branches (). The compound containing a single adamantane branch formed G-quartets in acetonitrile solution, and was then transformed into a G-ribbon gel at concentrations higher than the critical gelation concentration. In contrast, the compound with three adamantane branches precipitated after a heating-cooling process. By means of circular dichroism and UV/visible spectra, NMR, SEM, and structural studies, the mechanism of the formation of the G-quartets and G-ribbon gel, as well as the difference in the self-assembly modes of the two compounds, have been fully elucidated. Compound firstly self-assembled into G-quartets in solutions in the concentration range 5.0 × 10(-4) to 1.0 × 10(-2) M, and these G-quartets were transformed into a G-ribbon on further increasing the concentration. Gelation occurred when the G-ribbon self-assembled into a hexagonal columnar structure with the help of intermolecular hydrogen-bonding and hydrophobic interactions. This gel was sensitive to sonication and underwent a morphology change from a columnar structure to a flower-like structure composed of flakes. In contrast, due to steric hindrance, compound only assembled into a spherical structure based on hydrophobic interactions.
    Organic & Biomolecular Chemistry 01/2013; · 3.57 Impact Factor
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    ABSTRACT: In this work, film structure was obtained by self-assembly of fluorescein derivative via sol–gel process. The self-assembly structure and the formation mechanism had been studied and certified by scanning electron microscopy, IR, UV–vis, fluorescence and X-ray diffraction experiment data. The UV–vis absorption and emission spectra of the compound 1 were changed with the change of the pH value in the solution state. This gelator had certain selectivity for pH value and formed gels.
    Supramolecular Chemistry 01/2013; 25(12). · 1.55 Impact Factor
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    ABSTRACT: A series of new platinum-acetylide complexes containing ethynyl-pyrene moieties as the main skeleton were synthesized and characterized. The investigation of the absorption and emission spectra of these complexes revealed that the extension of the molecular size with the introduction of different numbered platinum-acetylide fragments can efficiently tune the absorption and emission bands from the UV to the longer wavelength region. Moreover, the gelation properties of these complexes were investigated by the "stable-to-inversion-of-a-test-tube" method. Most newly designed platinum-acetylide compounds presented a stable gel-formation property in some of the tested solvents. The morphology of the xerogels was investigated by scanning electron microscopy (SEM). Furthermore, the concentration- and temperature-dependent absorption and emission properties of these complexes were investigated, which support the formation of J-type assemblies during the aggregation process. More importantly, it was found that the complexes 4 a-C6, 4 a, and 4 a-C18 with four platinum-acetylide fragments presented potential applications as luminescent organometallic gels.
    Chemistry 11/2012; · 5.93 Impact Factor
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    ABSTRACT: Organic nanofibres were made by self-assembly of a simple gelator containing fluorene. The ratio of the length and diameter of the fibres strongly depends on the concentration of the gel. By the help of two reference molecules and spectral data, the mechanism of the nanofibre formation was investigated. An appropriate cooperation of hydrogen bonds, ππ interactions and steric hindrance is the key to the formation of the gel and nanofibres.
    CrystEngComm 10/2012; 14(23):8057-8062. · 3.88 Impact Factor
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    ABSTRACT: A naphthalimide-rhodamine B derivative was synthesized as a fluorescence turn-ON chemodosimeter for Sn(4+). A colour change and marked enhancement of fluorescence was found in the presence of Sn(4+), Cu(2+) and Cr(3+) due to the ring open reaction of rhodamine and a fluorescence resonance energy transfer process. Addition of the strong chelating agent ethylenediaminetetraacetic acid disodium salt (EDTA) partly released the cation from the complex with Sn(4+) and restored the yellow fluorescence. In addition, the compound can be used as a fluorescent probe for Sn(4+) in biological systems and may act as a tool with which to study the physiological functions of tin or pathogenesis in the human body.
    Organic & Biomolecular Chemistry 07/2012; 10(33):6740-6. · 3.57 Impact Factor
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    ABSTRACT: Novel BOPIM (boron 2-(2′-pyridyl)imidazole complex) derivatives with large Stokes shift were efficiently synthesized through two-step reactions, starting from commercially available 2-pyridinecarboxaldehyde and α-diketone. The dyes exhibit high fluorescent intensity in solution and also in solid state due to the intermolecular non-planar interactions. According to X-ray single crystal measurements, the non-covalent interactions (such as C–H⋯F–B, etc.) play important role in inhibiting planar π–π stacking, and the existence of terminal phenyl rings increases the electronic density of π system, which facilitates the charge transfer from the electron-donating π system to the electron-accepting boron moiety. DFT calculation based on X-ray crystallographic analysis was carried out for compound 2, giving consistent results with photophysical measurements.
    Tetrahedron. 06/2012; 68(25):5037–5041.
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    ABSTRACT: A novel low weight molecular gelator was designed and synthesized which can gelate several polar solvents with different morphologies. It is interesting that it exchanges morphology between a three-dimensional gel network and vesicles in ethanol via treatment with ultrasound and a heating-cooling process, through supramolecular self-assembly in a certain concentration range. The mechanism of the self-assembly process was investigated by IR, X-ray diffraction and rheological experiments. The results show that the gelator molecules self-assemble in a parallel manner into a lamella structure and the lamellas further aggregate into a gel network or vesicles at room temperature with or without the ultrasonic stimulation.
    Soft Matter 03/2012; 8(16):4494-4498. · 3.91 Impact Factor
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    ABSTRACT: A distinct and well-defined nano/micro-ring structure has been obtained from the gelation process in an asymmetric peptide-based organogel. The size of the ring can be tuned in a facile manner by varying the concentration and solvent of the gel, as well as with a sonication stimulus. The gel responds to mechanical stimulus by the ring separating into a biased arc structure to expel the solvent molecules from the gel network, resulting in a gel to sol transition. The gel can self-heal again after resting and this process is reversible many times. Thus a reversible rheological switch upon alternate shaking and resting is performed via the distinct ring disintegration and reconstitution of the gel network. It was interesting to note that the gelation also takes place by a simple shaking–resting process in a solvent/solid system at room temperature without a heating–cooling process.
    Soft Matter 02/2012; 8(12):3329-3334. · 3.91 Impact Factor