Yang Zhiyong
Email Address
chmyz@nus.edu.sg
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Publication Optimizing label-free DNA electrical detection on graphene platform(2011-04-01) Dubuisson, E.; Yang, Z.; Loh, K.P.; CHEMISTRYThe anodized epitaxial graphene (EG) electrode demonstrates a high level of performance for electrochemical impedance as well as differential pulse voltammetry detection of immobilized DNA and free DNA, respectively, at solid-liquid interfaces. On the anodized EG surface, because of the presence of oxygen functionalities as well as π conjugated domains, the anchoring of the DNA probe can be achieved by either covalent grafting or noncovalent π-π stacking readily. The effect of different binding modes on the sensitivity of the impedimetric sensing was investigated. Equivalent circuit modeling shows that the sensitivity of EG to DNA hybridization is controlled by changes in the resistance of the molecular layer as well as the space charge layer. The linear dynamic detection range of EG for DNA oligonucleotides is in the range of 5.0 × 10-14 to 1 × 10-6 M. In addition, with the use of differential pulse voltammetry, single stranded DNA, fully complimentary DNA, as well as single nucleotide polymorphisms can be differentiated on anodized EG by monitoring the oxidation signals of individual nucleotide bases. © 2011 American Chemical Society.Publication Using the graphene moiré pattern for the trapping of C 60 and homoepitaxy of graphene(2012-01-24) Lu, J.; Yeo, P.S.E.; Zheng, Y.; Yang, Z.; Bao, Q.; Gan, C.K.; Loh, K.P.; CHEMISTRYFigure Persented: The graphene Moiré superstructure offers a complex landscape of humps and valleys to molecules adsorbing and diffusing on it. Using C 60 molecules as the classic hard sphere analogue, we examine its assembly and layered growth on this corrugated landscape. At the monolayer level, the cohesive interactions of C 60 molecules adsorbing on the Moiré lattice freeze the molecular rotation of C 60 trapped in the valley sites, resulting in molecular alignment of all similarly trapped C 60 molecules at room temperature. The hierarchy of adsorption potential well on the Moiré lattice causes diffusion-limited dendritic growth of C 60 films, as opposed to isotropic growth observed on a smooth surface like graphite. Due to the strong binding energy of the C 60 film, part of the dentritic C 60 films polymerize at 850 K and act as solid carbon sources for graphene homoepitaxy. Our findings point to the possibility of using periodically corrugated graphene in molecular spintronics due to its ability to trap and align organic molecules at room temperature. © 2011 American Chemical Society.Publication Carbazole isomers induce ultralong organic phosphorescence(NATURE RESEARCH, 2020) Chen, Chengjian; Chi, Zhenguo; Chong, Kok Chan; Batsanov, Andrei S; Yang, Zhan; Mao, Zhu; Yang, Zhiyong; Liu, Bin; Prof Bin Liu; CHEMISTRY; CHEMICAL & BIOMOLECULAR ENGINEERINGCommercial carbazole has been widely used to synthesize organic functional materials that have led to recent breakthroughs in ultralong organic phosphorescence , thermally activated delayed fluorescence , organic luminescent radicals and organic semiconductor lasers . However, the impact of low-concentration isomeric impurities present within commercial batches on the properties of the synthesized molecules requires further analysis. Here, we have synthesized highly pure carbazole and observed that its fluorescence is blueshifted by 54 nm with respect to commercial samples and its room-temperature ultralong phosphorescence almost disappears . We discover that such differences are due to the presence of a carbazole isomeric impurity in commercial carbazole sources, with concentrations <0.5 mol%. Ten representative carbazole derivatives synthesized from the highly pure carbazole failed to show the ultralong phosphorescence reported in the literature . However, the phosphorescence was recovered by adding 0.1 mol% isomers, which act as charge traps. Investigating the role of the isomers may therefore provide alternative insights into the mechanisms behind ultralong organic phosphorescence . 1 2,3 4 5 6 1,7–15 1,6–18