Two-dimensional (2D) materials have attracted increasing research interest because of the abundant choice of materials with diverse and tunable electronic, optical, and chemical properties. Moreover, 2D material based heterostructures combining several individual 2D materials provide unique platforms to create an almost infinite number of materials and show exotic physical phenomena as well as new properties and applications. To achieve these high expectations, methods for the scalable preparation of 2D materials and 2D heterostructures of high quality and low cost must be developed. Chemical vapor deposition (CVD) is a powerful method which may meet the above requirements, and has been extensively used to grow 2D materials and their heterostructures in recent years, despite several challenges remaining. In this review of the challenges in the CVD growth of 2D materials, we highlight recent advances in the controlled growth of single crystal 2D materials, with an emphasis on semiconducting transition meta...

Chemical Vapor Deposition Growth and Applications of Two-Dimensional Materials and Their Heterostructures

Flexible and wearable electronics are attracting wide attention due to their potential applications in wearable human health monitoring and care systems. Carbon materials have combined superiorities such as good electrical conductivity, intrinsic and structural flexibility, light weight, high chemical and thermal stability, ease of chemical functionalization, as well as potential mass production, enabling them to be promising candidate materials for flexible and wearable electronics. Consequently, great efforts are devoted to the controlled fabrication of carbon materials with rationally designed structures for applications in next-generation electronics. Herein, the latest advances in the rational design and controlled fabrication of carbon materials toward applications in flexible and wearable electronics are reviewed. Various carbon materials (carbon nanotubes, graphene, natural-biomaterial-derived carbon, etc.) with controlled micro/nanostructures and designed macroscopic morphologies for high-performance flexible electronics are introduced. The fabrication strategies, working mechanism, performance, and applications of carbon-based flexible devices are reviewed and discussed, including strain/pressure sensors, temperature/humidity sensors, electrochemical sensors, flexible conductive electrodes/wires, and flexible power devices. Furthermore, the integration of multiple devices toward multifunctional wearable systems is briefly reviewed. Finally, the existing challenges and future opportunities in this field are summarized.

Advanced Carbon for Flexible and Wearable Electronics.

Wearable biosensors have received tremendous attention over the past decade owing to their great potential in predictive analytics and treatment toward personalized medicine. Flexible electronics could serve as an ideal platform for personalized wearable devices because of their unique properties such as light weight, low cost, high flexibility and great conformability. Unlike most reported flexible sensors that mainly track physical activities and vital signs, the new generation of wearable and flexible chemical sensors enables real-time, continuous and fast detection of accessible biomarkers from the human body, and allows for the collection of large-scale information about the individual's dynamic health status at the molecular level. In this article, we review and highlight recent advances in wearable and flexible sensors toward continuous and non-invasive molecular analysis in sweat, tears, saliva, interstitial fluid, blood, wound exudate as well as exhaled breath. The flexible platforms, sensing mechanisms, and device and system configurations employed for continuous monitoring are summarized. We also discuss the key challenges and opportunities of the wearable and flexible chemical sensors that lie ahead.

Wearable and flexible electronics for continuous molecular monitoring.

The chemical production of graphene as well as its controlled wet chemical modification is a challenge for synthetic chemists. Furthermore, the characterization of reaction products requires sophisticated analytical methods. In this Review we first describe the structure of graphene and graphene oxide and then outline the most important synthetic methods that are used for the production of these carbon-based nanomaterials. We summarize the state-of-the-art for their chemical functionalization by noncovalent and covalent approaches. We put special emphasis on the differentiation of the terms graphite, graphene, graphite oxide, and graphene oxide. An improved fundamental knowledge of the structure and the chemical properties of graphene and graphene oxide is an important prerequisite for the development of practical applications.

Chemistry with graphene and graphene oxide-challenges for synthetic chemists.

The chemical production of graphene as well as its controlled wet- chemical modification is a challenge for synthetic chemists and the characterization of reaction products requires sophisticated analytic methods. In this review we first describe the structure of graphene and graphene oxide. We then outline the most important synthetic methods which are used for the production of these carbon based nanomaterials. We summarize the state-of-the-art for their chemical functionalization by non-covalent and covalent approaches. We put special emphasis on the differentiation of the terms graphite, graphene, graphite oxide and graphene oxide. An improved fundamental knowledge about the structure and the chemical properties of graphene and graphene oxide is an important prerequisite for the development of practical applications.

Chemistry with Graphene and Graphene Oxide - Challenges for Synthetic Chemists

Sensors allow an electronic device to become a gateway between the digital and physical worlds, and sensor materials with unprecedented performance can create new applications and new avenues for user interaction. Graphene oxide can be exploited in humidity and temperature sensors with a number of convenient features such as flexibility, transparency and suitability for large-scale manufacturing. Here we show that the two-dimensional nature of graphene oxide and its superpermeability to water combine to enable humidity sensors with unprecedented response speed (∼30 ms response and recovery times). This opens the door to various applications, such as touchless user interfaces, which we demonstrate with a ‘whistling’ recognition analysis.

Ultrafast Graphene Oxide Humidity Sensors

We compare three different carbon nanoarchitectures used to produce standard coin cell batteries: graphene monolayer, graphite paper and graphene foam. The batteries' electrochemical performances are characterised using cyclic voltammetry, constant-current discharge and dynamic galvanostatic techniques. Even though graphene is the fundamental building block of graphite its properties are intrinsically different when used in batteries because there is no ion intercalation in graphene. The nanoarchitecture of the graphene electrode is shown to have a strong influence over the battery's electrochemical performance. This provides a versatile way to design various battery electrodes on different demands.

Graphene nanoarchitecture in batteries

An apparatus and method of forming an apparatus, the apparatus comprising: a graphene field effect transistor where the graphene field effect transistor comprises a graphene channel and quantum dots provided overlaying the graphene channel, wherein the quantum dots comprise a first layer comprising quantum dots connected to a first ligand and a second layer comprising quantum dots connected to a second ligand, and wherein the first ligand is configured to cause the first layer to have a first refractive index and the second ligand is configured to cause the second layer to have a second refractive index wherein the second refractive index is different to the first refractive index

An apparatus and method of forming an apparatus comprising a graphene field effect transistor

An apparatus (517) comprising first and second plasmonic nanoparticles (502a, 502b) connected to one another by a deformable member (518), the first and second plasmonic nanoparticles each configured to exhibit a respective plasmon resonance when exposed to incident electromagnetic radiation (203), wherein, in a first configuration, the first and second plasmonic nanoparticles are in sufficient proximity to one another that their respective plasmon resonances can interact to produce a resulting plasmon resonance, and wherein mechanical deformation of the deformable member causes a variation in the relative position of the plasmonic nanoparticles to a second configuration to produce a detectable change in the resulting plasmon resonance of the first configuration which can be used to determine said mechanical deformation.

A mechanical deformation sensor based on plasmonic nanoparticles

An apparatus ( 10 ) comprising a substrate ( 2 ) and an antenna ( 20 ). The antenna (20) comprising a first conductive element ( 21 ) having a first electrical length and connected to a first antenna terminal ( 31 ) and a second conductive element ( 22 ) having a second electrical length connected to a second antenna terminal ( 32 ), wherein at least the first conductive element is supported by a first portion of the substrate ( 11 ) and wherein at least the first portion of the substrate is configured to deform from a first configuration to a second configuration to: change the first electrical length of the first conductive element relative to the second electrical length of the second conductive element; and add or remove at least one operational resonant mode of the antenna.

Nadine Harris

Papers

Ultrafast Graphene Oxide Humidity Sensors

Graphene nanoarchitecture in batteries

An apparatus and method of forming an apparatus comprising a graphene field effect transistor

A mechanical deformation sensor based on plasmonic nanoparticles

Apparatus comprising an antenna having conductive elements