Kah Meng Yam

@article{ISI:001095847100002,
title = {Symmetry-driven half-integer conductance quantization in Cobalt-fulvalene sandwich nanowire},
author = {Zhuoling Jiang and Kah-Meng Yam and Yee Sin Ang and Na Guo and Yongjie Zhang and Hao Wang and Chun Zhang},
doi = {10.1038/s41524-023-01151-z},
times_cited = {0},
year = {2023},
date = {2023-10-21},
journal = {NPJ COMPUTATIONAL MATERIALS},
volume = {9},
number = {1},
publisher = {NATURE PORTFOLIO},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Precise manipulation and monitoring spin transport in one-dimensional (1D) systems is a long-sought goal in the field of nano-spintronics. Based on first-principles calculations, we report the observation of half-integer conductance quantization in the Cobalt-fulvalene sandwich nanowire. Compared with a pure monatomic Cobalt wire, the introduction of fulvalene molecules leads to three important features: Firstly, the strong coupling between the fulvalene and the Cobalt prevents the contamination of the ambient air, ensuring both chemical and physical stabilities; Secondly, the fulvalene symmetry-selectively filters out most of the d-type orbitals of the Cobalt while leaving a single d-type orbital to form an open spin channel around the Fermi level, which offers a mechanism to achieve the observed half-integer conductance; Thirdly, it maintains a superexchange coupling between adjacent Co atoms to achieve a high Curie temperature. Spin transport calculations show that this half-metallic nanowire can serve as a perfect spin filter or a spin valve device, thus revealing the potential of Cobalt-fulvalene sandwich nanowire as a promising building block of high-performance spintronics technology.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000676091000001,
title = {Zero-Valent Palladium Single-Atoms Catalysts Confined in Black Phosphorus for Efficient Semi-Hydrogenation},
author = {Cheng Chen and Wei Ou and Kah-Meng Yam and Shibo Xi and Xiaoxu Zhao and Si Chen and Jing Li and Pin Lyu and Lu Ma and Yonghua Du and Wei Yu and Hanyan Fang and Chuanhao Yao and Xiao Hai and Haomin Xu and Ming Joo Koh and Stephen J Pennycook and Junling Lu and Ming Lin and Chenliang Su and Chun Zhang and Jiong Lu},
doi = {10.1002/adma.202008471},
times_cited = {79},
issn = {0935-9648},
year = {2021},
date = {2021-07-23},
journal = {ADVANCED MATERIALS},
volume = {33},
number = {35},
publisher = {WILEY-V C H VERLAG GMBH},
address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
abstract = {Single-atom catalysts (SACs) represent a new frontier in heterogeneous catalysis due to their remarkable catalytic properties and maximized atomic utilization. However, single atoms often bond to the support with polarized electron density and thus exhibit a high valence state, limiting their catalytic scopes in many chemical transformations. Here, it is demonstrated that 2D black phosphorus (BP) acts as giant phosphorus (P) ligand to confine a high density of single atoms (e.g., Pd-1, Pt-1) via atomic layer deposition. Unlike other 2D materials, BP with relatively low electronegativity and buckled structure favors the strong confinement of robust zero-valent palladium SACs in the vacancy site. Metallic Pd-1/BP SAC shows a highly selective semi-hydrogenation of phenylacetylene toward styrene, distinct from metallic Pd nanoparticles that facilitate the formation of fully hydrogenated products. Density functional theory calculations reveal that Pd atom forms covalent-like bonding with adjacent P atoms, wherein H atoms tend to adsorb, aiding the dissociative adsorption of H-2. Zero-valent Pd in the confined space favors a larger energy gain for the synthesis of partially hydrogenated product over the fully hydrogenated one. This work provides a new route toward the synthesis of zero-valent SACs on BP for organic transformations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000563746200029,
title = {Enhancing Reactivity of SiC-Supported Graphene by Engineering Intercalated Metal Atoms at the Interface},
author = {Kah-Meng Yam and Na Guo and Zhuoling Jiang and Shulong Li and Chun Zhang},
doi = {10.1021/acs.jpcc.0c05286},
times_cited = {5},
issn = {1932-7447},
year = {2020},
date = {2020-08-20},
journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
volume = {124},
number = {33},
pages = {18126-18131},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Controlling the reactivity of graphene with effective yet practical physical/chemical methods has been known to be the key for many applications of graphene including graphene-based solid-state catalysis. Here, by state-of-art ab initio modeling, we present a new avenue to enhance reactivity and catalytic activity of graphene that is supported on a SiC substrate. We show that intercalated metal atoms (e.g., Ru atoms) at the SiC-graphene interface form a self-assembled two-dimensional monolayer with hexagonal lattice, and by controlling the concentration of the metal atoms, the reactivity of the supported graphene could be greatly enhanced, resulting in the chemisorption of O-2 molecule on graphene. Detailed analysis revealed that the O-2 chemisorption originates from the charge transfer of nearly one electron from the activated graphene to the O-2 2 pi* orbital. We further show that the activated graphene can be an excellent catalyst toward CO oxidation reaction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000430331400002,
title = {Light controllable catalytic activity of Au clusters decorated with photochromic molecules},
author = {Na Guo and Kah Meng Yam and Chun Zhang},
doi = {10.1088/1361-6528/aabac3},
times_cited = {4},
issn = {0957-4484},
year = {2018},
date = {2018-06-15},
journal = {NANOTECHNOLOGY},
volume = {29},
number = {24},
publisher = {IOP PUBLISHING LTD},
address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND},
abstract = {By ab initio calculations, we show that when decorated with a photochromic molecule, the catalytic activity of an Au nanocluster can be reversibly controlled by light. The combination of a photochromic thiol-pentacarbonyl azobenzene (TPA) molecule and an Au-8 cluster is chosen as a model catalyst. The TPA molecule has two configurations (trans and cis) that can be reversibly converted to each other upon photo-excitation. Our calculations show that when the TPA takes the trans configuration, the combined system (trans-Au-8) is an excellent catalyst for CO oxidation. The reaction barrier of the catalyzed CO oxidation is less than 0.4 eV. While, the reaction barrier of CO oxidation catalyzed by cis-Au-8 is very high (> 2.7 eV), indicating that the catalyst is inactive. These results pave the way for a new class of light controllable nanoscale catalysts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000430331400001,
title = {Two-dimensional Cu_{2}Si sheet: a promising electrode material for nanoscale electronics},
author = {Kah Meng Yam and Na Guo and Chun Zhang},
doi = {10.1088/1361-6528/aabb45},
times_cited = {9},
issn = {0957-4484},
year = {2018},
date = {2018-06-15},
journal = {NANOTECHNOLOGY},
volume = {29},
number = {24},
publisher = {IOP PUBLISHING LTD},
address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND},
abstract = {Building electronic devices on top of two-dimensional (2D) materials has recently become one of most interesting topics in nanoelectronics. Finding high-performance 2D electrode materials is one central issue in 2D nanoelectronics. In the current study, based on first-principles calculations, we compare the electronic and transport properties of two nanoscale devices. One device consists of two single-atom-thick planar Cu2Si electrodes, and a nickel phthalocyanine (NiPc) molecule in the middle. The other device is made of often-used graphene electrodes and a NiPc molecule. Planer Cu2Si is a new type of 2D material that was recently predicted to exist and be stable under room temperature [11]. We found that at low bias voltages, the electric current through the Cu2Si-NiPc-Cu2Si junction is about three orders higher than that through graphene-NiPc-graphene. Detailed analysis shows that the surprisingly high conductivity of Cu2Si-NiPc-Cu2Si originates from the mixing of the Cu2Si state near Fermi energy and the highest occupied molecular orbital of NiPc. These results suggest that 2D Cu2Si may be an excellent candidate for electrode materials for future nanoscale devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000424020000001,
title = {N-doped ZnO nanosheets: towards high performance two dimensional catalysts},
author = {Na Guo and Kah Meng Yam and Xiaolu Wang and Chun Zhang},
doi = {10.1088/1361-6528/aaa77c},
times_cited = {4},
issn = {0957-4484},
year = {2018},
date = {2018-03-09},
journal = {NANOTECHNOLOGY},
volume = {29},
number = {10},
publisher = {IOP PUBLISHING LTD},
address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND},
abstract = {Recently, catalytic activity of atomically thin two dimensional (2D) materials has attracted great interest. In this paper, via first principles calculations, we show for the first time that N-doped 2D one-atom-thick ZnO nanosheets exhibit high catalytic activity towards CO oxidation. A pristine 2D ZnO nanosheet is chemically inert and as a result, CO and O-2 molecules do not chemically bind on the nanosheet. Our calculations predict that the N doping activates the ZnO sheet, leading to strong CO and O-2 adsorptions. We further show that the CO oxidation catalyzed by the N-doped 2D ZnO sheet has a low reaction barrier around 0.5 eV. Besides high catalytic activity, the N-doped 2D ZnO sheet also demonstrates intriguing electronic and magnetic properties. These findings provide new opportunities for the future development of high performance 2D catalysts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000423628600001,
title = {Substrate engineering of graphene reactivity: towards high-performance graphene-based catalysts},
author = {Na Guo and Kah Meng Yam and Chun Zhang},
doi = {10.1038/s41699-017-0046-y},
times_cited = {70},
year = {2018},
date = {2018-01-17},
journal = {NPJ 2D MATERIALS AND APPLICATIONS},
volume = {2},
publisher = {NATURE RESEARCH},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Graphene-based solid-state catalysis is an emerging direction in research on graphene, which opens new opportunities in graphene applications and thus has attracted enormous interests recently. A central issue in graphene-based catalysis is the lack of an effective yet practical way to activate the chemically inert graphene, which is largely due to the difficulties in the direct treatment of graphene (such as doping transition metal elements and introducing particular type of vacancies). Here we report a way to overcome these difficulties by promoting the reactivity and catalytic activity of graphene via substrate engineering. With thorough first-principles investigations, we demonstrate that when introduce a defect, either a substitutional impurity atom (e.g. Au, Cu, Ag, Zn) or a single vacancy, in the underlying Ru (0001) substrate, the reactivity of the supported graphene can be greatly enhanced, resulting in the chemical adsorption of O-2 molecules on graphene. The origin of the O-2 chemical adsorption is found to be the impurity-or vacancy-induced significant charge transfer from the graphene-Ru (0001) contact region to the 2 pi* orbital of the O-2 molecule. We then further show that the charge transfer also leads to high catalytic activity of graphene for chemical reaction of CO oxidation. According to our calculations, the catalyzed CO oxidation takes place in Eley-Rideal (ER) mechanism with low reaction barriers (around 0.5 eV), suggesting that the substrate engineering is an effective way to turn the supported graphene into an excellent catalyst that has potential for large-scale industrial applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000390320300004,
title = {Spin-dependent electron transport through a Mn-phthalocyanine molecule - A steady-state density functional theory (SS-DFT) study},
author = {Shuanglong Liu and Yongjie Xi and Na Guo and Kah Meng Yam and Chun Zhang},
doi = {10.1139/cjc-2016-0280},
times_cited = {8},
issn = {0008-4042},
year = {2016},
date = {2016-12-01},
journal = {CANADIAN JOURNAL OF CHEMISTRY},
volume = {94},
number = {12},
pages = {1002-1005},
publisher = {CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS},
address = {65 AURIGA DR, SUITE 203, OTTAWA, ON K2E 7W6, CANADA},
abstract = {We generalize the recently proposed steady-state density functional theory (SS-DFT) to spin-dependent cases and theoretically investigate the electronic and transport properties of a Mn-phthalocyanine molecule sandwiched between two graphene nanoribbon leads. The junction filters spin-up (minority spin) electrons while allowing spin-down (majority spin) electrons to pass with a filtering efficiency of about 99.5% at low biases. The spin-down electrons are found to tunnel through the junction via the HOMO orbital of the Mn-phthalocyanine molecule. Detailed analysis of the spin-dependent electron tunneling mechanism as well as the electronic/magnetic properties of the junction is presented.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:000385572000001,
title = {Oscillating edge states in one-dimensional MoS_{2} nanowires},
author = {Hai Xu and Shuanglong Liu and Zijing Ding and Sherman J R Tan and Kah Meng Yam and Yang Bao and Chang Tai Nai and Man-Fai Ng and Jiong Lu and Chun Zhang and Kian Ping Loh},
doi = {10.1038/ncomms12904},
times_cited = {69},
issn = {2041-1723},
year = {2016},
date = {2016-10-04},
journal = {NATURE COMMUNICATIONS},
volume = {7},
publisher = {NATURE PUBLISHING GROUP},
address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND},
abstract = {Reducing the dimensionality of transition metal dichalcogenides to one dimension opens it to structural and electronic modulation related to charge density wave and quantum correlation effects arising from edge states. The greater flexibility of a molecular scale nanowire allows a strain-imposing substrate to exert structural and electronic modulation on it, leading to an interplay between the curvature-induced influences and intrinsic ground-state topology. Herein, the templated growth of MoS2 nanowire arrays consisting of the smallest stoichiometric MoS2 building blocks is investigated using scanning tunnelling microscopy and non-contact atomic force microscopy. Our results show that lattice strain imposed on a nanowire causes the energy of the edge states to oscillate periodically along its length in phase with the period of the substrate topographical modulation. This periodic oscillation vanishes when individual MoS2 nanowires join to form a wider nanoribbon, revealing that the strain-induced modulation depends on in-plane rigidity, which increases with system size.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}