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Now showing items 1 - 16 of 24

  • A New Rhodamine-based Fluorescent Probe for the Discrimination of Fe3+ from Fe2+

    You, Qi-Hua   Huang, Hua-Bin   Zhuang, Zhi-Xia   Wang, Xiao-Ru   Chan, Wing-Hong  

    A new rhodamine-based fluorescent probe for the discrimination of Fe3+ from Fe2+ has been designed and investigated. The probe shows an immediate visual color change in response to Fe3+ and Cu2+, while only Fe3+ triggers the fluorescent change of the probe. The existence of large amount of other metal ions shows negligible interference in the detection of Fe3+. The association constant K-ass of 4.64x10(8)M(-2) (R-2 =3D 0.994) and 5.38x10(8)M(-2) (R-2 =3D 0.991) of the complex was derived from UV/Vis and fluorescence titration assuming 1:2 stoichiometry of probe-Fe3+ complex, respectively.
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  • FRET-based modified graphene quantum dots for direct trypsin quantification in urine

    Poon, Chung-Yan   Li, Qinghua   Zhang, Jiali   Li, Zhongping   Dong, Chuan   Lee, Albert Wai-Ming   Chan, Wing-Hong  

    A versatile nanoprobe was developed for trypsin quantification with fluorescence resonance energy transfer (FRET). Here, fluorescence graphene quantum dot is utilized as a donor while a well-designed coumarin derivative, CMR2, as an acceptor. Moreover, bovine serum albumin (BSA), as a protein model, is not only served as a linker for the FRET pair, but also a fluorescence enhancer of the quantum dots and CMR2. In the presence of trypsin, the FRET system would be destroyed when the BSA is digested by trypsin. Thus, the emission peak of the donor is regenerated and the ratio of emission peak of donor/emission peak of acceptor increased. By the ratiometric measurement of these two emission peaks, trypsin content could be determined. The detection limit of trypsin was found to be 0.7 mu g/mL, which is 0.008-fold of the average trypsin level in acute pancreatitis patient's urine suggesting a high potential for fast and low cost clinical screening. (C) 2016 Elsevier B.V. All rights reserved.
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  • A ratiometric fluorescent and colorimetric probe for selective detection of hydrazine

    Chan, Wing-Hong   Tse, Ho-Yin   Li, Qinghua   Chan, Sing-Ming   You, Qihua   Lee, Albert W M  

    A colorimetric and ratiometric fluorescent hydrazine reactive probe COUMA2 has been developed. In aqueous solution, hydrazinolysis of COUMA2 results in deacetylation affording fluorescent products displaying dual emissive peaks at 500 and 655 nm. 50 μM NH2NH2 can induce a ratiometric change of fluorescent signal from COUMA2 by a factor of 4.89.
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  • An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids.

    Zhou, Xiao-Bo   Yip, Yuk-Wang   Chan, Wing-Hong   Lee, Albert W M  

    Two mesitylene based neutral receptors 1 and 2 bearing two thiourea binding sites were constructed as fluorescent probes for sensing dicarboxylates. Their binding affinities toward dicarboxylates, aspartate and glutamate have been investigated in acetonitrile solution by fluorescence titration experiments. Both fluorescent sensors exhibited some ability to discriminate the antipodal forms of aspartate and glutamate.
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  • Both visual and ratiomenic fluorescent sensor for Zn2+ based on spirobenzopyran platform

    Zhu, Jian-Fa   Chan, Wing-Hong   Lee, Albert W. M.  

    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. (C) 2012 Elsevier Ltd. All rights reserved.
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  • A cholic acid-based fluorescent chemosenor for the detection of ATP.

    Wang, Hao   Chan, Wing-Hong  

    A novel ditopic cholic acid-based fluorescent chemosensor for ATP, 1a, was designed and synthesized. Its interactions with phosphates, AMP, ADP, ATP, CTP, GTP, and TTP have been investigated. When ATP was added to a 1:1 aqueous CH3CN solution of the sensor at pH 7.4, a significant decrease in fluorescence of 1a was observed, whereas other guest molecules showed a much smaller effect. The complex between 1a and ATP was confirmed through combined UV, 1H, 13C and 31P NMR spectroscopic methods. The uniqueness of the new sensor is that it binds with ATP 33-124 times more selectively than other nucleotides, as evidenced from the respective binding constants. 1a is a highly sensitive sensing probe; as little as 30 nM ATP can cause 15% fluorescence quenching of the sensor.
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  • A quinolinyl antipyrine based fluorescence sensor for Zn2+ and its application in bioimaging

    You, Qi-Hua   Chan, Pui-Shan   Chan, Wing-Hong   Hau, Sam C. K.   Lee, Albert W. M.   Mak, N. K.   Mak, Thomas C. W.   Wong, Ricky N. S.  

    By incorporating 4-aminoantipyrine moiety onto 8-aminoquinoline with a suitable spacer, a highly selective and sensitive fluorescent Zn2+ sensor, QPA, was designed and constructed. In 25% ACN-HEPES buffer pH 7.0 solution, QPA exhibited 10.6-fold fluorescence enhancement at 500 nm upon addition of Zn2+. The limit of detection (LOD) was calculated to be 1.3 x 10(-7) M according to fluorescence titration. The 1 : 1 binding mode of the metal complex was established by combined UV-vis, fluorescence and HRMS spectroscopic method. The membrane permeability of QPA to living cells and bioimaging of Zn2+ are demonstrated.
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  • Inhibition of beta 1-40 amyloid fibrillation with N-acetyl-L-cysteine capped quantum dots

    Xiao, Lehui   Zhao, Dan   Chan, Wing-Hong   Choi, Martin M. F.   Li, Hung-Wing  

    One of the primary factors that induce Alzheimer's disease (A beta) is the deposition of beta-amyloid (A beta). The A# molecules can self-assemble to form neurotoxic aggregates with various morphologies, such as dimers, oligomers, protofibrils and fibrils. For this aspect, we demonstrated that the amyloid fibrillation can be inhibited by quenching the nucleation and elongation processes with a low concentration of water dispersed N-acetyl-L-cysteine capped quantum dots (NAC-QDs). Based on the concentration dependence of NAC-QDs on the seeded fibril growth, there is a remarkable inhibition effect when the NAC-QDs concentration is increased by 100-fold from 10(-9) to 10(-7) m. The NAC-QDs concentration required to show inhibition effect is much lower than that of the amyloid peptide concentration (50 mu m). The step-like change suggests that the inhibition effect of NAC-QDs displays a threshold response. The inhibition is likely due to the intermolecular attractive interactions such as the hydrogen bonding between NAC-QDs and amyloid fibrils resulting in the blockage of the active elongation sites on the fibrils. (C) 2009 Elsevier Ltd. All rights reserved.
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  • Ratiometric fluorescent probe for enantioselective detection of D-cysteine in aqueous solution

    Zhou, Xiao-bo   Chan, Wing-Hong   Lee, Albert W. M.   Yeung, Chi-Chung  

    A ratiometric fluorescent probe based on a Cd(2+)-ACAQ complex was designed and demonstrated for the chemo- and enantioselective detection of cysteine in 99:1 buffered HEPES:ACN solutions. Under the measuring conditions, the sensor demonstrates high selectivity toward Cys against Hcy and GSH, and an enantioselectivity of 3.35 can be achieved for antipodal forms of Cys.
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  • Cholic acid-based fluorescent sensor for mercuric and methyl mercuric ion in aqueous solutions

    Wang, Hao   Chan, Wing-Hong  

    Cholic acid-based fluorescent PET sensor probe 1, bearing a pair of dithiocarbamate pendants as the receptive site and anthracene moiety as the signal displaying unit, was designed and synthesized. The sensor probe not only shows high selectivity and sensitivity to Hg2+ in aqueous acetonitrile solution, but also responds moderately to MeHg+. A distinctive OFF-ON type signaling of up to 10-fold enhancement was observed for this new sensor probe toward Hg2+. (c) 2007 Elsevier Ltd. All rights reserved.
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  • Effect of surface-functionalized nanoparticles on the elongation phase of beta-amyloid (1-40) fibrillogenesis

    Chan, Ho-Man   Xiao, Lehui   Yeung, Kai-Ming   Ho, See-Lok   Zhao, Dan   Chan, Wing-Hong  

    The influence of nanoparticles of various sizes and surface functionalities on the self-assembling fibrillogenesis of beta-amyloid (1-40) peptide was investigated. Functionalized nanoparticles including quantum dots and gold nanoparticles were co-incubated with monomeric A beta(1-40) peptides under seed-mediated growth method to study their influences on the elongation phase of the fibrillogenesis. It is observed that charge-to-surface area ratio of the nanoparticles and the functional moiety and electrostatic charges of the conjugated ligands on the particle surfaces took crucial regulatory role in the A beta(1-40) fibrillogenesis. (C) 2012 Elsevier Ltd. All rights reserved.
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  • A FRET fluorescent chemosensor SPAQ for Zn(2+) based on a dyad bearing spiropyran and 8-aminoquinoline unit

    Zhu, Jian-Fa   Yuan, Han   Chan, Wing-Hong   Lee, Albert W. M.  

    A novel FRET fluorescent sensor SPAQ containing 8-aminoquinoline (donor) and spiropyran derivative (acceptor) was designed and synthesized for detecting Zn(2+). The probe successfully exhibited a fluorescence turn on and ratiometric response for Zn(2+) in ethanol solution with high selectivity. Upon excitation at 370 nm, the modulation of the emission intensity of SPAQ at 645 and 470 nm were achieved in the presence of Zn(2+) by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. (C) 2010 Elsevier Ltd. All rights reserved.
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  • CaSH Organocatalysis: Enantioselective Friedel-Crafts Alkylation of Indoles with alpha,beta-Unsaturated Aldehydes

    Tian, Tian   Pei, Bao-Jian   Li, Qing-Hua   He, Hao   Chen, Ling-Yan   Zhou, Xiang   Chan, Wing-Hong   Lee, Albert W. M.  

    Enantioselective Friedel-Crafts alkylation of indole with alpha,beta-unsaturated aldehyde was catalyzed by camphor sulfonyl hydrazine (CaSH) with good enantioselectivity (81-88%).
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  • Pervaporation of aqueous ethanol solution through poly(amidesulfonamide)s (PASAs) membranes

    Chan, Wing-Hong   Ng, Ching-Fai   Lam-Leung, Suei-Yee   He, Xumin  

    Symmetric non-porous membranes derived from five poly(amidesulfonamide)s were prepared for the separation of ethanol-water mixtures by the use of the pervaporation technique. It was found that water preferentially permeated through all PASA membranes in all ranges of feed compositions. The relationship between the polymer structure and its pervaporation performance will be discussed. The dependence of permeation rate on the feed composition was explained by the ‘carrier-mediated’ mechanism. The effect of temperature on the pervaporation characteristics of the materials was investigated in details. Experimental results revealed that the polymer based on the diamino monomer containing the piperazine moiety and isophthaloyl chloride emerged as the best system in terms of separation factor and permeation rate in the dehydration of ethanol.
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  • Hg2+ sensing in aqueous solutions: an intramolecular charge transfer emission quenching fluorescent chemosensors

    Cheung, Sin-Man   Chan, Wing-Hong  

    Compounds 4a and 4b, comprising an anthracene moiety as the fluorophore and a pair of dithiocarbamate functionalities as ligating groups, were designed as fluorescent chemosensors for Hg(II). In aqueous solvent systems, upon excitation, in addition to the normal emission bands of locally excited (LE) state of anthracene, both compounds show a prominent pH-independent intramolecular charge transfer (ICT) emissive band, which can be modulated by Hg2+ binding. The systems can be exploited to develop a fluorescent sensitive probe for Hg2+. (c) 2006 Elsevier Ltd. All rights reserved.
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  • Water–alcohol separation by pervaporation through chemically modified poly(amidesulfonamide)s

    Chan, Wing-Hong   Ng, Ching-Fai   Lam-Leung, Suei-Yee   He, Xumin  

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