Qing Hua Wang

Qing Hua Wang
Arizona State University | ASU · Department of Materials Science and Engineering

PhD

About

72
Publications
27,233
Reads
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15,555
Citations
Additional affiliations
August 2014 - present
Arizona State University
Position
  • Professor (Assistant)
October 2010 - June 2014
Massachusetts Institute of Technology
Position
  • PostDoc Position
September 2005 - August 2010
Northwestern University
Position
  • Graduate Research Fellow
Education
September 2005 - August 2010
Northwestern University
Field of study
  • Materials Science and Engineering
September 2001 - May 2005
University of Toronto
Field of study
  • Engineering Science

Publications

Publications (72)
Article
Full-text available
Magnetism in two-dimensional (2D) van der Waals (vdW) materials has recently emerged as one of the most promising areas in condensed matter research, with many exciting emerging properties and significant potential for applications ranging from topological magnonics to low-power spintronics, quantum computing, and optical communications. In the bri...
Article
Full-text available
There is increasing interest in the study of chiral degrees of freedom occurring in matter and in electromagnetic fields. Opportunities in quantum sciences will likely exploit two main areas that are the focus of this Review: (1) recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterial...
Article
Due to its outstanding electrical, thermal, and mechanical properties, graphene (Gr) has been extensively studied in recent years as nanofiller for metallic nanocomposites. However, the manufacture of metallic nanocomposites with Gr as a nanofiller is still challenging especially for three-dimensional (3D) architectures. This study explores an elec...
Article
Metal diborides are a class of ceramic materials with crystal structures consisting of hexagonal sheets of boron atoms alternating with planes of metal atoms held together with mixed character ionic/covalent bonds. Many of the metal diborides are ultrahigh-temperature ceramics such as HfB2, TaB2, and ZrB2, which have melting points above 3000 °C, h...
Article
Antibiotic-resistant bacteria are a significant and growing threat to human health. Recently, two-dimensional (2D) nanomaterials have shown antimicrobial activity and have the potential to be used as new approaches to treating antibiotic resistant bacteria. In this Research Article, we exfoliate transition metal dichalcogenide (TMDC) nanosheets usi...
Article
Non-van der Waals (non-vdW) solids are emerging sources of two-dimensional (2D) nanosheets that can be produced via liquid-phase exfoliation (LPE), and are beginning to expand our understanding of 2D and quasi-2D materials. Recently, nanosheets formed by LPE processing of bulk metal diborides, a diverse family of layered non-vdW ceramic materials,...
Article
Liquid phase exfoliation (LPE) is a method that can be used to produce bulk quantities of two-dimensional (2D) nanosheets from layered van der Waals (vdW) materials. In recent years, LPE...
Preprint
Full-text available
The interest in chiral degrees of freedom occurring in matter and in electromagnetic fields is experiencing a renaissance driven by recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials. The CISS effect underpins the fact that charge transport through nanoscopic chiral structures h...
Article
Full-text available
This Special Issue of Chemistry–A European Journal is dedicated to the Chemical Functionalization of 2D Materials, and features some great contributions from experts in the field of 2D materials. This issue was originally assembled to support the Symposium G “Chemical Functionalization of 2D Materials” at the European Materials Research Society (E‐...
Article
Full-text available
The removal of heavy metal contaminants from water is important for public health, and recently many two-dimensional (2D) materials with high specific surface areas are being studied as promising new active components in water purification. In particular, 2D MoS 2 nanosheets have been used for the removal of various heavy metals, but usually in eit...
Preprint
The metal diborides are a class of ceramic materials with crystal structures consisting of hexagonal sheets of boron atoms alternating with planes of metal atoms held together with mixed character ionic/covalent bonds. Many of the metal diborides are ultrahigh temperature ceramics like HfB$_2$, TaB$_2$, and ZrB$_2$, which have melting points above...
Article
The authors present a fabrication process for the development of high-frequency (>30 GHz) on-wafer graphene devices with the use of titanium sacrificial layers. Graphene patterning requires chemical processes that have deleterious effects on graphene resulting in very low yield. The authors prevent delamination of the delicate graphene from the sub...
Article
Layered chalcogenides are a diverse class of crystalline materials that consist of various covalently bound building blocks held together by van der Waals forces. Among these materials are the transition metal dichalcogenides (TMDCs) which can be exfoliated into two-dimensional (2D) nanosheets, and the pnictogen chalcogenides (PCs) which can be exf...
Article
The two-dimensional transition-metal dichalcogenide molybdenum disulfide (MoS 2 ) has been intensely studied in the past several years due to its exceptional electronic, optical, and chemical properties in a wide range of applications. The chemical functionalization of MoS 2 allows its properties and interfacial interactions to be tuned and control...
Article
TiO2 nanomaterials with platelet or nanosheet morphologies can offer improved properties for photocatalytic applications, but established methods to produce them typically require structure-directing agents since anatase-phase TiO2 does not have a layered structure. In the present work, the preparation of TiO2 nanosheets by the chemical oxidation o...
Article
Two-dimensional semiconducting transition metal dichalcogenides (TMDCs) like molybdenum disulfide (MoS2) are generating significant excitement due to their unique electronic, chemical, and optical properties. Covalent chemical functionalization represents a critical tool for tuning the properties of TMDCs for use in many applications. However, the...
Article
Single molecule tunnel junctions (SMTJs) can provide important physical insights into electronic and vibrational phenomena at the molecular scale. However, observations and analysis are typically confined to sufficiently low temperatures as to suppress molecular motion and the resulting stochastic fluctuations in the tunneling current. In this work...
Article
Full-text available
Hybrid van der Waals (vdW) heterostructures composed of two-dimensional (2D) layered materials and self-assembled organic molecules are promising systems for electronic and optoelectronic applications with enhanced properties and performance. Control of molecular assembly is therefore paramount to fundamentally understand the nucleation, ordering,...
Article
Nanostructured transition metal oxides (TMOs) have intriguing electrochemical and physical properties that make them useful in a variety of electrochemical applications. Here, we report the synthesis of MoO3 and WO3 nanoscrolls from atomically thin layers of two-dimensional (2D) MoS2 and WS2 by atmospheric air plasma treatment. These structures wit...
Article
Full-text available
The participation of graphene in electron transfer chemistry, where an electron is transferred between graphene and other species, encompasses many important processes that have shown versatility and potential for use in important applications. Examples of these processes range from covalent functionalization of graphene to modify its properties an...
Article
Single-layer graphene (SLG) membranes have great promise as ultrahigh flux, high selectivity membranes for gas mixture separations due to their single atom thickness. It remains a central question whether SLG membranes of a requisite area can exist under an imposed pressure drop and temperatures needed for industrial gas separation. An additional c...
Article
Despite the unique properties of black phosphorus (BP) and phosphorene, including high carrier mobility and in-plane anisotropy, their stability has been hampered by significant crystal deterioration upon exposure to oxygen and water. Herein, we investigate the chemical stability of MoS2-passivated black phosphorus (BP) or bilayer (2L) phosphorene...
Article
In the pursuit of two-dimensional (2D) materials beyond graphene, enormous advances have been made in exploring the exciting and useful properties of transition metal dichalcogenides (TMDCs)-such as a permanent band gap in the visible range and the transition from indirect to direct band gap due to 2D quantum confinement-and their potential for a w...
Article
Atomically thin MoS2 is of great interest for electronic and optoelectronic applications because of its unique two-dimensional (2D) quantum confinement; however, the scaling of optoelectronic properties of MoS2 and its junctions with metals as a function of layer number as well the spatial variation of these properties remain unaddressed. In this w...
Article
Spatially propagating reaction waves are central to a variety of energy applications, such as high temperature solid phase or combustion synthesis, and thermopower waves. In this paper, we identify and study a previously unreported property of such waves, specifically that they can generate temperatures far in excess of the adiabatic limit. We show...
Article
Field-effect transistor (FET) devices comprised of a MoS2-graphene heterostructure can combine the advantages of high carrier mobility in graphene with the permanent band gap of MoS2 for digital applications. Herein, we investigate the electron transfer, photoluminescence, and gate-controlled carrier transport in such a heterostructure. We show tha...
Article
Low dimensional materials are those that possess at least one physical boundary small enough to confine the electrons or phonons. This quantum confinement reduces the dimensionality of the material and imparts unique and novel properties that are not seen in their bulk forms. Examples include quantum dots (0-D), carbon nanotubes (1-D), and graphene...
Article
Two novel, asymmetric methanofullerenes are presented, which self-assemble in cyclohexane upon thermal cycling to 80 °C. We show that, through the introduction of a dipeptide sequence to one terminus of the dendritic methanofullerene, it is possible to transform the assembly behavior of these molecules from poorly formed aggregates to high-aspect-r...
Conference Paper
Full-text available
A significant advantage of graphene as a biosensor is its potential to display a continuum of independent and aligned sensors at a specific interface. Here, we demonstrate a nanoscale version of a micro-physiometer – a device that measures cellular metabolic activity from the local acidification rate. Graphene can function as an array of independen...
Conference Paper
Two-dimensional (2D) materials have unique quantum-confined properties in a form that is highly processable. Graphene, the prototypical 2D nanomaterial, is a single atomic layer of carbon with extraordinary properties including exceptionally high electronic carrier mobilities, thermal conductivity, and mechanical strength. Graphene-based applicatio...
Article
Full-text available
Covalently bonding groups to the walls of carbon nanotubes has been previously observed to quench their photoluminescence. Now, it has been shown that, if you get the chemistry just right, their photoluminescence can in fact be significantly brightened by introducing defects through functionalization.
Article
Thermopower waves convert chemical energy into electrical power using nanostructured thermal conduits like carbon nanotubes (CNTs) by taking advantage of their high thermal conductivity to propagate the heat released by an exothermic reaction of a fuel layer coated around the conduit. Electron–phonon coupling in the CNTs then leads to an electrical...
Article
Self-propagating exothermic chemical reactions can generate electrical pulses when guided along a conductive conduit such as a carbon nanotube. However, these thermopower waves are not described by an existing theory to explain the origin of power generation or why its magnitude exceeds the predictions of the Seebeck effect. In this work, we presen...
Article
Transition metal oxides (TMOs) are a fascinating class of materials due to their wide ranging electronic, chemical and mechanical properties. Additionally, they are gaining increasing attention for their thermoelectric (TE) properties due to their high temperature stability, tunable electronic and phonon transport properties and well established sy...
Article
Polydimethylsiloxane (PDMS) is commonly used in research for microfluidic devices and for making elastomeric stamps for soft lithography. Its biocompatibility and nontoxicitiy also allow it to be used in personal care, food, and medical products. Herein we report a phenomenon observed when patch clamp, a technique normally used to study biological...
Article
Full-text available
The vision for graphene and other two-dimensional electronics is the direct production of nanoelectronic circuits and barrier materials from a single precursor sheet. DNA origami and single-stranded tiles are powerful methods to encode complex shapes within a DNA sequence, but their translation to patterning other nanomaterials has been limited. He...
Article
A central question in graphene chemistry is to what extent chemical modification can control an electronically accessible band gap in monolayer and bilayer graphene (MLG and BLG). Density functional theory predicts gaps in covalently functionalized graphene as high as 2 eV, while this approach neglects the fact that lattice symmetry breaking occurs...
Article
Full-text available
The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickne...
Conference Paper
We fabricate and study junctions between single walled carbon nanotubes (SWNTs) and monolayer graphene for the first time. A single layer graphene (SLG) sheet grown by chemical vapor deposition (CVD) was transferred onto a Si/SiO2 wafer with aligned CVD-grown SWNTs. Raman spectroscopic mapping is used to identify metallic-SWNT/SLG junctions, and we...
Article
We develop a theory to model the van der Waals interactions between liquid and graphene, including quantifying the wetting behavior of a graphene-coated surface. Molecular dynamics simulations and contact angle measurements were also carried out to test the theory. We show that graphene is only partially transparent to wetting and that the predicte...
Article
Full-text available
Graphene is an atomically thin, two-dimensional allotrope of carbon with exceptionally high carrier mobilities, thermal conductivity, and mechanical strength. From a chemist's perspective, graphene can be regarded as a large polycyclic aromatic molecule and as a surface without a bulk contribution. Consequently, chemistries typically performed on o...
Article
Full-text available
Graphene has exceptional electronic, optical, mechanical and thermal properties, which provide it with great potential for use in electronic, optoelectronic and sensing applications. The chemical functionalization of graphene has been investigated with a view to controlling its electronic properties and interactions with other materials. Covalent m...
Article
The chemical functionalization of graphene enables control over electronic properties and sensor recognition sites. However, its study is confounded by an unusually strong influence of the underlying substrate. In this paper, we show a stark difference in the rate of electron transfer chemistry with aryl diazonium salts on monolayer graphene suppor...
Article
Manipulation of transport hysteresis on graphene transistors and understanding electron transfer between graphene and polar/ionic adsorbates are important for the development of graphene-based sensor devices and nonvolatile memory electronics. We have investigated the effects of commonly used surfactants for graphene dispersion in aqueous solution...
Article
Controlling the electrical properties of graphene is of particular interest for future electronic, optoelectronics and sensing applications. We investigate the doping effect of different chemical functional groups covalently attached to CVD-grown graphene devices with a polymer electrolyte top-gate. The covalent reaction is based on a diazonium che...
Article
Understanding the role of polar and ionic adsorbates on the transport characteristics of graphene transistors is important for the development of graphene-based sensor devices and printable electronics using graphene solutions. We have investigated the effects of commonly used surfactants for graphene dispersion in aqueous solution on transport cha...
Article
Because covalent chemistry can diminish the optical and electronic properties of single-walled carbon nanotubes (SWCNTs), there is significant interest in developing methods of controllably functionalizing the nanotube sidewall. To date, most attempts at obtaining such control have focused on reaction stoichiometry or strength of oxidative treatmen...
Article
Epitaxial graphene, grown by thermal decomposition of the SIC (0001) surface, is a promising material for future applications due to its unique and superlative electronic properties. However, the innate chemical passivity of graphene presents challenges for integration with other materials for device applications. Here, we present structural charac...
Article
With exceptional carrier mobilities, mechanical strength, and optical transparency, graphene is a leading material for next-generation electronic devices. However, for most applications, graphene will need to be integrated with other materials, which motivates efforts to understand and tune its surface chemistry. In particular, the modification of...
Article
Graphene from two different preparative routes was successfully functionalized with 4-propargyloxybenzenediazonium tetrafluoroborate in order to study a subsequent attachment by click chemistry (1,3-dipolar azide-alkyne cycloaddition) of a short chain polyethylene glycol with terminal carboxylic end group (PEG-COOH). The reaction steps were studied...
Article
Full-text available
Bilayer and trilayer graphene with controlled stacking is emerging as one of the most promising candidates for post-silicon nanoelectronics. However, it is not yet possible to produce large quantities of bilayer or trilayer graphene with controlled stacking, as is required for many applications. Here, we demonstrate a solution-phase technique for t...
Article
Conductive atomic force microscope (cAFM) nanopatterning is demonstrated on epitaxial graphene on SiC (0001) under ambient conditions. Nanopatterning kinetics and chemistry suggest that ambient cAFM nanopatterning induces local oxidization with the surface, interface, and bulk layers of epitaxial graphene on SiC (0001) playing distinct roles in the...
Article
The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer depo...
Article
Nanoscale control of surface chemistry holds promise for tailoring the electronic, optical, and chemical properties of graphene. Toward this end, the nanofabrication of sub-5-nm heteromolecular organic nanostructures is demonstrated on epitaxial graphene using room temperature ultrahigh vacuum scanning tunneling microscopy. In particular, monolayer...
Conference Paper
Graphene has emerged as one of the leading materials in condensed matter physics due to its superlative electrical and mechanical properties. With an eye towards expanding its functionality and applications, this paper highlights efforts to tailor the surface chemistry of graphene via organic functionalization. At the molecular scale, ultra-high va...
Article
Full-text available
Scanning tunneling microscopy (STM), atomic force microscopy (AFM), lateral force microscopy (LFM), and conductive AFM (cAFM) are employed to characterize epitaxial graphene on SiC(0001). Of particular interest are substrates that possess single-layer and bilayer graphene domains, which form during thermal decomposition of silicon from SiC(0001). S...
Article
The chemical functionalization of graphene in ultra-high vacuum (UHV) with monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) has been characterized with scanning tunneling microscopy (STM). The molecules self-assemble into stable, well-ordered monolayers that are arranged in a herringbone phase with extended domains spanning hundr...
Article
Full-text available
Graphene, a two-dimensional sheet of carbon atoms, is a promising material for next-generation technology because of its advantageous electronic properties, such as extremely high carrier mobilities. However, chemical functionalization schemes are needed to integrate graphene with the diverse range of materials required for device applications. In...
Article
Carbon-based nanoelectronic materials have attracted significant attention due to their potential to enable and/or improve applications such as transistors, transparent conductors, solar cells, and biosensors. This paper delineates chemical strategies for enhancing the electronic and optical properties of these promising nanomaterials. For example,...
Article
Orthogonal, interconnected inorganic and organic one-dimensional nanostructures have been fabricated by parallel self-assembly on the Si(100) surface and investigated using room temperature ultrahigh vacuum scanning tunneling microscopy. In particular, bismuth nanowires were self-assembled on the clean Si(100)-2 x 1 surface perpendicular to the Si...
Article
The cover picture shows Ga nanoclusters in a well-ordered, self-assembled array on the Si(111) − 7 × 7 surface. Ultrahigh vacuum scanning tunneling microscopy was used to simultaneously image the topography and the local density of states (LDOS) of this system. The image is a 10 nm × 10 nm region with the LDOS plotted as a color map over the topogr...
Article
A study was conducted to observe atomically resolved, delocalized two-dimensional charge redistribution associated with Ga nanocluster arrays on the Si(111)-7×7 surface. The study used the topographic scanning tunneling microscopy (STM) images and spatial maps of the differential tunneling conductance to measure the surface local density of states...
Conference Paper
Full-text available
An algorithm is proposed for the robust localization of a vehicle using both displacement tracking and sound localization. The displacement tracking is performed by optical encoders that enable the turn angle and the movement distance of the vehicle to be estimated. The sound localization utilizes a speaker mounted on the vehicle and an array of 24...
Article
Full-text available
An algorithm for the robust localization of a vehicle using both displacement tracking and sound localization is proposed. The displacement tracking is performed by optical encoders that enable the turn angle and the movement distance of the vehicle to be estimated. The sound localization utilizes a speaker mounted on the vehicle and an array of 24...