Li Huey Tan

University of Illinois, Urbana-Champaign, Urbana, Illinois, United States

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Publications (20)202.03 Total impact

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    ABSTRACT: A systematic investigation of the effects of different DNA sequences on the morphologies of silver nanoparticles (AgNPs) grown from Ag nanocube seeds is reported. The presence of 10-mer oligo A, T and C directed AgNP growth from cubic seeds into edge-truncated octahedra of different truncation extents and truncated tetrahedral AgNPs, while AgNP in the presence of oligo G re-mained cubic. The shape and morphological evolution of the nanoparticle growth for each system is investigated using SEM and TEM and correlated with UV-Vis absorption kinetic studies. In addition, the roles of oligo C and oligo G secondary structures in modulating the morphologies of AgNPs are elucidated and the morphological evolution for each condition of AgNP growth is pro-posed. The shapes were found to be highly dependent on the binding affinity of each of the bases and the DNA secondary struc-tures, favoring the stabilization of the Ag{111} facet. The AgNPs synthesized through this method have morphologies and optical properties that can be varied by using different DNA sequences, while the DNA on these AgNPs are also stable against glutathione. The AgNP functionalization can be realized in a one-step synthesis while retaining the biorecognition ability of the DNA, which allows for programmable assembly.
    Journal of the American Chemical Society 09/2014; · 10.68 Impact Factor
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    ABSTRACT: In this review, we summarize recent progress in the application of synchrotron-based spectroscopic techniques for nucleic acid research that takes advantage of high-flux and high-brilliance electromagnetic radiation from synchrotron sources. The first section of the review focuses on the characterization of the structure and folding processes of nucleic acids using different types of synchrotron-based spectroscopies, such as X-ray absorption spectroscopy, X-ray emission spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation circular dichroism, X-ray footprinting and small-angle X-ray scattering. In the second section, the characterization of nucleic acid-based nanostructures, nucleic acid-functionalized nanomaterials and nucleic acid-lipid interactions using these spectroscopic techniques is summarized. Insights gained from these studies are described and future directions of this field are also discussed.
    Advanced Materials 09/2014; · 14.83 Impact Factor
  • Li Huey Tan, Hang Xing, Yi Lu
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    ABSTRACT: Conspectus Several properties of nanomaterials, such as morphologies (e.g., shapes and surface structures) and distance dependent properties (e.g., plasmonic and quantum confinement effects), make nanomaterials uniquely qualified as potential choices for future applications from catalysis to biomedicine. To realize the full potential of these nanomaterials, it is important to demonstrate fine control of the morphology of individual nanoparticles, as well as precise spatial control of the position, orientation, and distances between multiple nanoparticles. In addition, dynamic control of nanomaterial assembly in response to multiple stimuli, with minimal or no error, and the reversibility of the assemblies are also required. In this Account, we summarize recent progress of using DNA as a powerful programmable tool to realize the above goals. First, inspired by the discovery of genetic codes in biology, we have discovered DNA sequence combinations to control different morphologies of nanoparticles during their growth process and have shown that these effects are synergistic or competitive, depending on the sequence combination. The DNA, which guides the growth of the nanomaterial, is stable and retains its biorecognition ability. Second, by taking advantage of different reactivities of phosphorothioate and phosphodiester backbone, we have placed phosphorothioate at selective positions on different DNA nanostructures including DNA tetrahedrons. Bifunctional linkers have been used to conjugate phosphorothioate on one end and bind nanoparticles or proteins on the other end. In doing so, precise control of distances between two or more nanoparticles or proteins with nanometer resolution can be achieved. Furthermore, by developing facile methods to functionalize two hemispheres of Janus nanoparticles with two different DNA sequences regioselectively, we have demonstrated directional control of nanomaterial assembly, where DNA strands with specific hybridization serve as orthogonal linkers. Third, by using functional DNA that includes DNAzyme, aptamer, and aptazyme, dynamic control of assemblies of gold nanoparticles, quantum dots, carbon nanotubes, and iron oxide nanoparticles in response to one or more stimuli cooperatively have been achieved, resulting in colorimetric, fluorescent, electrochemical, and magnetic resonance signals for a wide range of targets, such as metal ions, small molecules, proteins, and intact cells. Fourth, by mimicking biology, we have employed DNAzymes as proofreading units to remove errors in nanoparticle assembly and further used DNAzyme cascade reactions to modify or repair DNA sequences involved in the assembly. Finally, by taking advantage of different affinities of biotin and desthiobiotin toward streptavidin, we have demonstrated reversible assembly of proteins on DNA origami.
    Accounts of Chemical Research 05/2014; · 20.83 Impact Factor
  • Li Huey Tan, Hang Xing, Hongyu Chen, Yi Lu
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    ABSTRACT: Anisotropic nanoparticles can provide considerable opportunities for assembly of nanomaterials with unique structures and properties. However, most reported anisotropic nanoparticles are either difficult to prepare, have a low yield, or difficult to functionalize. Here we report a facile one-step solution-based method to prepare anisotropic DNA-functionalized gold nanopar-ticles (a-DNA-AuNP) with 96% yield and with high DNA density (120 ± 20 strands on the gold hemisphere surface). The method is based on the competition between a thiolated hydrophilic DNA and a thiolated hydrophobic phospholipid and has been applied to prepare a-DNA-AuNP with different sizes of nanoparticles and a variety of DNA sequences. In addition, DNA strands on the a-DNA-AuNP can be exchanged with other DNA strands with a different sequence. The anisotropic nature of the a-DNA-AuNPs allows regioselective hetero- and homo-nuclear assembly with high monodispersity, as well as regioselective functionalization of two different DNA strands for more diverse applications.
    Journal of the American Chemical Society 10/2013; · 10.68 Impact Factor
  • Yu Xiang, Peiwen Wu, Li Huey Tan, Yi Lu
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    ABSTRACT: : Recent progress in using DNAzyme-functionalized gold nanoparticles (AuNPs) for biosensing is summarized in this chapter. A variety of methods, including those for attaching DNA on AuNPs, detecting metal ions and small molecules by DNAzyme-functionalized AuNPs, and intracellular applications of DNAzyme-functionalized AuNPs are discussed. DNAzyme-functionalized AuNPs will increasingly play more important roles in biosensing and many other multidisciplinary applications. This chapter covers the recent advancement in biosensing applications of DNAzyme-functionalized gold nanoparticles, including the detection of metal ions, small molecules, and intracellular imaging.
    Advances in biochemical engineering/biotechnology 09/2013; · 1.64 Impact Factor
  • Ngo Yin Wong, Hang Xing, Li Huey Tan, Yi Lu
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    ABSTRACT: While much work has been devoted to nanoscale assembly of functional materials, selective reversible assembly of components in the nanoscale pattern at selective sites has received much less attention. Exerting such a reversible control of the assembly process will make it possible to fine-tune the functional properties of the assembly and to realize more complex designs. Herein, by taking advantage of different binding affinities of biotin and desthiobiotin toward streptavidin, we demonstrate selective and reversible decoration of DNA origami tiles with streptavidin, including revealing an encrypted Morse code "NANO" and reversible exchange of uppercase letter "I" with lowercase "i". The yields of the conjugations are high (> 90%) and the process is reversible. We expect this versatile conjugation technique to be widely applicable with different nanomaterials and templates.
    Journal of the American Chemical Society 02/2013; · 10.68 Impact Factor
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    ABSTRACT: Monolayers of polymer-encapsulated Au nanoparticles with controlled density are obtained via a facile solution-based method by modulating the inter-particle repulsion and using empty polymer micelles as spacers. These Au nanoparticles are then used to catalyze the vapor transport growth of metal oxide nanowires, where distinct density-dependent growth regimes are identified.
    Small 01/2013; · 7.82 Impact Factor
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    ABSTRACT: DNA is in control: Different combinations of DNA nucleotides can control the shape and surface roughness of gold nanoparticles during their synthesis. These nanoparticles were synthesized in the presence of either homogenous oligonucleotides or mixed-base oligonucleotides using gold nanoprisms as seeds. The effect of the individual DNA bases and their combinations on shape control are shown in the figure.
    Angewandte Chemie International Edition 08/2012; 51(36):9078-82. · 11.34 Impact Factor
  • Ngo Yin Wong, Chuan Zhang, Li Huey Tan, Yi Lu
    Small 05/2011; 7(10):1427-30. · 7.82 Impact Factor
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    ABSTRACT: Gold nanoparticles are useful in biomedical applications due to their distinct optical properties and high chemical stability. Reports of the biogenic formation of gold colloids from gold complexes has also led to an increased level of interest in the biomineralization of gold. However, the mechanism responsible for biomolecule-directed gold nanoparticle formation remains unclear due to the lack of structural information about biological systems and the fast kinetics of biomimetic chemical systems in solution. Here we show that intact single crystals of lysozyme can be used to study the time-dependent, protein-directed growth of gold nanoparticles. The protein crystals slow down the growth of the gold nanoparticles, allowing detailed kinetic studies to be carried out, and permit a three-dimensional structural characterization that would be difficult to achieve in solution. Furthermore, we show that additional chemical species can be used to fine-tune the growth rate of the gold nanoparticles.
    Nature Nanotechnology 02/2011; 6(2):93-7. · 31.17 Impact Factor
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    ABSTRACT: Understanding detailed electric near-field distributions around noble metal nanostructures is crucial to the rational design of metallic substrates for maximizing surface-enhanced Raman scattering (SERS) efficiency. We obtain SERS signals from specific regions such as the ends, the sides and the entire surfaces of gold nanorod by chemisorbing analytes on the respective areas. Different SERS intensities from designated surfaces reflect their electric near-field intensities and thus the distributions. Our experimental results show that approximately 65% of the SERS enhancement emanated from the ends of gold nanorods which occupies only 28% of the total surface area, quantitatively exhibiting the strongly localized electric field around the ends. The reliability and generality of the investigation is confirmed by employing analytes with different chemical characteristics: positively and negatively charged, neutral, hydrophobic and hydrophilic ligands, which are selectively adsorbed on the different sites. Numerical simulations of the electric near-field distributions around the nanorod are in well agreement with our experimental results. In addition, we observed that the SERS intensities of colloidal gold nanospheres are independent of surface areas being functionalized by analytes, indicating a homogenous electric near-field distribution around gold nanospheres.
    Nanoscale 02/2011; 3(4):1575-81. · 6.73 Impact Factor
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    ABSTRACT: A central theme in nanotechnology is to advance the fundamental understanding of nanoscale component assembly, thereby allowing rational structural design that may lead to materials with novel properties and functions. Nanoparticles (NPs) are often regarded as 'artificial atoms', but their 'reactions' are not readily controllable. Here, we demonstrate a complete nanoreaction system whereby colloidal NPs are rationally assembled and purified. Two types of functionalized gold NPs (A and B) are bonded to give specific products AB, AB(2), AB(3) and AB(4). The stoichiometry control is realized by fine-tuning the charge repulsion among the B-NPs. The products are protected by a polymer, which allows their isolation in high purity. The integration of hetero-assembly, stoichiometry control, protection scheme and separation method may provide a scalable way to fabricate sophisticated nanostructures.
    Nature Communications 10/2010; 1:87. · 10.74 Impact Factor
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    ABSTRACT: Controlled alignment of streptavidin (STV), myoglobin, and nanoparticles with nanometer resolution has been achieved via backbone-modified phosphorothioate DNA and biotin- and maleimide-containing bifunctional linkers. Introducing triplet biotin modifications in three adjacent PSs significantly increased the STV conjugation yield. By placing phosphorothioate modifications at multiple positions of a double stranded DNA template, monomer, dimer, and trimer STV-DNA assemblies were formed with the STVs placed at controlled positions. The activity of the conjugated protein has been demonstrated by binding biotinylated AuNPs onto STV-DNA complexes, indicating the use of the system as a template for the formation of AuNP dimers and trimers with STVs separated by distances of 10-30 nm. Furthermore, a melting temperature experiment carried out with an STV-dsDNA assembly showed that the bifunctional-linker-modified PS-DNA system is much more stable than base-modified conjugation systems. This method allows for high yield, nanoscale-precision conjugation of multiple proteins to DNA. The linker can be designed to conjugate any proteins and nanomaterials specifically for a wide range of applications.
    Journal of the American Chemical Society 07/2010; 132(26):8906-8. · 10.68 Impact Factor
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    ABSTRACT: Here, we report the ensemble-averaged measurement of SERS hot spots EF from spatially isolated colloidal nanoclusters. This approach was achieved by well-defined Au@Ag core-shell NP dimers and trimers-the simplest structure to investigate SERS hot spots phenomenon. These hot spots units with similar nature were made up of uniform Au@Ag NPs attached by a close-paking Raman reporter monolayer, then stabilized by polymer encapsulation and enriched to high purity by differential centrifugation. To our knowledge this study is the most approximate description of SERS hot spots nanostructures for colloidal ensemble-averaged EF measurement. The calculated averaged EFs are 5.6�?103 for monomer and 0.7�?106 for hot spot in dimer. It indicated the SERS intensity of the molecule in gap region is higher than that in the outside region by factor of 125.
    01/2010;
  • Tao Chen, Li Huey Tan, Hongyu Chen
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    ABSTRACT: A variety of nanocomposites between metallic nanoparticles and polymers were produced. The attachment pattern of polymer micelles on the metal nanostructures evolved from the full coverage to partially engulfing, i. e. Janus (two-faced) nanoparticles, through tuning the ligand combinations. The basic principle for this achievement is that the surface feature is dictated by competitive chemisorption of hydrophobic and hydrophilic ligands forming segregated patches on the nanostructures, which results in directional self-assembly of amphiphilic diblock copolymer on the hydrophobic ligand coated surface, while leaving the hydrophilic ligand modified surface exposed to the aqueous solution. The generality of this strategy has been demonstrated by creating a broad range of nanocomposties with different metallic cores, different ligand combinations and various amphiphilic diblock copolymers. Also, we further extend this concept for the creation of hollow polymeric structures with openings (at nanoscale), the investigation of the surface-enhanced Raman scattering site distributions on nanospheres and nanorods, and the controlled organization of the nanoparticles into dimers or oligomers.
    01/2010;
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    ABSTRACT: A templated fabrication of open nanocavities is reported, where rational control of partial polymer attachment on sacrificial metal cores introduces openings in the polymer shells. This approach provides a facile means to modify the structural features of polymer nanocavities by manipulating the surface chemistry of colloidal nanoparticles. In particular, the anisotropic geometry of gold nanorods is exploited to promote the anisotropic polymer attachment, such that two diametric openings occurred in the polymer shell. After etching the gold nanorods, this approach yields open nanochannels that are tunable in both diameter and length. The synthetic scope of the anisotropic core/shell nanoparticles is expanded, supporting the previously proposed mechanism. We demonstrate that reducing the symmetry of nano-objects could open up new ways to create structural features using simple assembly and etching techniques. The thermostability of the open polymer nanostructures is also investigated.
    ACS Nano 10/2009; 3(11):3469-74. · 12.03 Impact Factor
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    ABSTRACT: An effective method was developed for separating gold-nanoparticle clusters in high resolution; dimer and trimer samples were obtained with 95% and 81% purity, respectively.
    Journal of the American Chemical Society 05/2009; 131(12):4218-9. · 10.68 Impact Factor
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    ABSTRACT: Triple-layer (Au@Ag)@polypyrrole core-shell nanoparticles are fabricated by a one-step synthesis involving simultaneous reduction of AgNO3 and polymerization of pyrrole in the presence of Au nanoparticles; the Ag layer in the resulting nanoparticles is etched to give a (Au@H2O)@polypyrrole yolk-shell structure.
    Chemical Communications 05/2009; · 6.38 Impact Factor
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    ABSTRACT: Controls in coating gold nanoparticles with conductive polymers are reported, where uniform core/shell nanoparticles with tailored core aggregation and shell thickness are unambiguously demonstrated. In the presence of sodium dodecylsulfate (SDS), the adsorption and in situ polymerization of aniline or pyrrole on the surface of gold nanoparticles gives uniform polymer shells. A typical single encapsulation of 10 nm gold nanoparticles gave 99.1% monomers out of 1074 particles surveyed. The shell growth was found to be kinetically controlled; polyaniline was successively grown on 22 nm gold nanoparticles by multiple growth cycles, giving shell thicknesses of 14, 31, 61 and 92 nm, respectively. We show that the aggregation of gold nanoparticles can be controllably promoted in this system, by simply timing SDS addition, to give linearly aggregated cores of 2–20 particles. The in situ formation of conductive polymer shells has allowed the isolation and unambiguous characterization of these nanochains for the first time. The one-step, “mix-and-wait” synthesis solely utilizes inexpensive starting materials and is, therefore, well-suited for fabrication of large quantities of core/shell nanoparticles. The core/shell nanoparticles form stable colloidal suspensions and can be readily purified by centrifugation.
    Journal of Materials Chemistry 01/2009; 19(20). · 6.63 Impact Factor
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    ABSTRACT: Controlled partial attachment of polymer on gold nanoparticles breaks the symmetry of their surface functionalities, allowing tailored assembly of the nanoparticles.
    Journal of the American Chemical Society 10/2008; 130(36):11858-9. · 10.68 Impact Factor

Publication Stats

214 Citations
202.03 Total Impact Points

Institutions

  • 2010–2014
    • University of Illinois, Urbana-Champaign
      • • Department of Chemistry
      • • Department of Materials Science and Engineering
      Urbana, Illinois, United States
  • 2008–2013
    • Nanyang Technological University
      • • Division of Chemistry and Biological Chemistry (CBC)
      • • School of Physical and Mathematical Sciences
      Tumasik, Singapore