Tao Yi

Fudan University, Shanghai, Shanghai Shi, China

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Publications (94)385.07 Total impact

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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: 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: 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
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    ABSTRACT: A pyrene-functionalized cationic oligopeptide 1 efficiently binds to double-stranded DNA, as shown by different spectrophotochemical studies. Upon binding, the conformation of 1 changes from a folded to an extended form, which leads to a distinct change in the fluorescence properties. Thus, 1 functions as a molecular peptide beacon, and as it is easily taken up by cells, 1 can also be used for imaging of nucleic acids within cells.
    Journal of the American Chemical Society 02/2012; 134(4):1958-61. · 10.68 Impact Factor
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    ABSTRACT: Phenol substituted 1,8-naphthalimide derivatives acting as a donor and an iridium(III) complex which emits orange light acting as an acceptor were synthesized to fabricate a novel white-light-emitting two-component gel. The intermolecular energy transfer between the two components plays a crucial role in providing the tuneable emission in the mixed gels. The emission of white light can be obtained by carefully tuning the ratio of the two components. These gels are ideal constituents for the design of supramolecular light-harvesting materials, which afford a novel approach to displaying information in soft materials with tuneable optical properties. Furthermore, the two-component gel can respond to cysteine with an obvious change in luminescence that is visible to the naked eye.
    Journal of Materials Chemistry 01/2012; 22(6):2650-2657. · 5.97 Impact Factor
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    ABSTRACT: Mixed polydiacetylene (PDA) liposomes functionalized on their surface with a fluorescent pentalysine peptide derivative and histidine in a ratio of 1:9 can identify bacterial lipopolysaccharide (LPS). Upon photopolymerization of the self-assembled liposomes the initial fluorescence of the peptide-diacetylene amphiphiles is quenched. Interaction with LPS in aqueous solution or on the surface of E. coli DH5α restores the fluorescence. This increase in fluorescence is selective for LPS relative to other negatively charged analytes including nucleotides and ctDNA. This simple turn-on fluorescent sensor allows detecting LPS even at low micromolar concentrations.
    Journal of the American Chemical Society 06/2011; 133(25):9720-3. · 10.68 Impact Factor
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    ABSTRACT: A novel method of rare-earth cation-assisted ligand assembly has been developed to provide upconversion nanophosphors with T(1)-enhanced magnetic resonance (MR), radioactivity, and targeted recognition properties, making these nanoparticles potential candidates for multimodal bioimaging. The process of modifying the surface of the nanophosphors has been confirmed by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, energy-dispersive X-ray analysis, and so on. The versatility of this surface modification approach for incorporating functional molecules and fabricating fluorine-18-labeled magnetic-upconversion nanophosphors as multimodal bioprobes has been demonstrated by targeted cell imaging, in vivo upconversion luminescence, MR imaging, and positron emission tomography imaging of whole-body small animals.
    ACS Nano 03/2011; 5(4):3146-57. · 12.06 Impact Factor
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    ABSTRACT: A novel diarylethene-based iridium(III) complex was synthesized as a phosphorescence probe for monitoring living cells. The switchable phosphorescence complex in solution and within living cells was controlled by two distinguishable visible-light irradiations, which suggests that this complex can be developed as a promising probe with weak photodamage for biological samples.
    Chemistry - An Asian Journal 03/2011; 6(5):1263-8. · 4.57 Impact Factor
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    ABSTRACT: Switchable supramolecular self-assemblies on the basis of interaction between melamine group containing photochromic diarylethene unit (DTE) and naphthalimide derivate (1) were designed and fabricated. 1 can gelate several aprotic solvents with different morphologies. The gel turned into partial gel in ethyl acetate with the addition of DTE as a guest molecule. Both the absorption and fluorescence spectra of the assembly can be reversibly switched by alternating UV/visible light irradiation. Meanwhile, the morphology of the coassembly of 1(2)·DTE changed to film from original pieces of gel 1 in ethyl acetate. When 1(2)·DTE was irradiated by UV light, the film morphology was converted into aggregated flakes. Moreover, the surface wettability of the complex can also be switched by light irradiation. The photochromic diarylethene unit is able to modulate the fluorescence and morphology of the assembled system only by virtue of light irradiation. Therefore, these results provide further insights into fluorescence and morphology controlling, especially application in upscale smart responsive materials.
    Langmuir 03/2011; 27(8):5090-7. · 4.19 Impact Factor
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    ABSTRACT: A novel BOPIM (boron 2-(2-pyridyl)imidazole complex) dye 1 was facilely synthesized by treatment of previously reported 2-(2′-pyridyl)imidazole with BF3·Et2O under basic condition. The bromination of BOPIM dye 1 by NBS gives an unexpected product 2-(2′-pyridyl)-4,5-dibromoimidazole (L2) with no BF2 group. The desired brominated boron complex 2 was obtained by treating L2 with BF3·Et2O. The photophysical properties of these two compounds are thoroughly studied in various solvents. Compound 1 formed aggregates in non-polar solvents, inducing abnormal emission in long-wavelength region. Both 1 and 2 show moderate fluorescent intensity and comparatively large Stokes shift, especially for compound 2 (fluorescent quantum yield is more than 0.30, and Stokes shift is over 70nm in all adopted solvents) due to its p, π-conjugated effect, which makes BOPIM a valuable building block for synthesis of multi-functional materials.
    Journal of Fluorine Chemistry - J FLUORINE CHEM. 01/2011; 132(9):612-616.
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    ABSTRACT: Two novel niclosamide derivatives were synthesized by adding polyethylene glycol groups of differing lengths to a niclosamide core. The modified niclosamide derivatives were characterized using 1H NMR and HRMS spectra. Anti-cercarial bioactivity results showed that the niclosamide derivative constructed to float on the surface of the water was able to kill cercariae when the number of hydrophilic groups was >3. A fluorescent niclosamide derivative containing naphthalimide was further synthesized to observe the interaction between the cercaricide and Schistosoma japonicum cercariae. Confocal fluorescence microscopy revealed that the fluorescent niclosamide derivative could easily penetrate into the cercarial body beyond the circulatory system leading to the rapid death of cercariae.
    Dyes and Pigments - DYE PIGMENT. 01/2011; 88(3):326-332.