Space, the final frontier for Graphene and 2D Materials

Several years ago Prof. Castro Neto predicted the importance of graphene and other 2D materials on space technology and exploration: “In the space business weight is a big issue from the financial and physical perspectives. The heavier the payload the higher the cost of launching rockets and accelerating them into higher speeds. Graphene and 2D materials are the lightest functional materials in the universe and hence are perfect in terms of mass density”, says Prof. Castro Neto, “and, moreover, in the absence of air and water, 2D materials never corrode and can last indefinitely.”  Prof. Castro Neto goes further “In deep space the temperatures are so low that some 2D materials superconduct reducing the energy cost of operation to a perfect zero.”

Prof Castro Neto’s dreams of making graphene a big player in the space race are becoming reality. In collaboration with Boreal Space, a US based satellite launcher, CA2DM is soon launching the first graphene devices into orbit opening a new chapter in space exploration for 2D materials.

Find out more of this exciting news here.

RPGR 2017, another successful conference!

The 9th annual Recent Progress in Graphene and Two-dimensional Materials Research Conference (RPGR2017) follows on the success of the first eight RPGR conferences held in Seoul (2009), Singapore (2010), Suwon (2011), Beijing (2012), Tokyo (2013), Taipei (2014), Australia (2015) and Korea (2016).

The conference took place in Grand Copthorne Waterfront Hotel, Singapore from 19-22 September 2017.
It was attended by 260 participants from 21 different countries. Continue Reading

Grooming young scientists in Singapore

Research work on monolayer WS2 done by Belle Sow Miaoer, a student from NUS High School of Mathematics and Science, Dr Lu Junpeng (NUS) and Professor Sow Chorng Haur (NUS) was published and highlighted in the inside cover page of Advanced Optical Materials [1].

Monolayer WS2 is a promising material in optoelectronic devices. Decoration of WS2 using gold nanoparticles (AuNPs) produces surprising results. AuNPs exhibit preferential, site-selective decorations that reveal hidden heterogeneity within the WS2. In addition, the AuNPs enhance fluorescence intensity in selected regions and even activate fluorescence emission from previously dark regions. The photoluminescence spectra become sharpened and dominated by neutral excitons.

Continue Reading

Monochalcogenides enrich library of 2D crystals

The field of two-dimensional materials is possibly one of the fastest expanding fields in material science and condensed matter research worldwide. The interest on this class of materials was boosted by the fast development of ever more efficient methods to synthesize them at atomically thin level.

Within the ever-growing library of 2D crystals, layered group-IV monochalcogenides (MC) have become an increasingly important group of materials. In particular, the binary IV-VI compounds SnS, SnSe, GeS, and GeSe, which form a subgroup with orthorhombic structure. SnS can be found in nature: its orthorhombic α phase, also known as herzenbergite, is a naturally occurring (nontoxic) mineral with an optical band gap of ≈ 1.3 eV, in the range of optimal values for solar cells (1.1 to 1.5 eV). Such properties boosted experimental and theoretical research on SnS in recent years.

Continue Reading

Gate-Tunable Giant Stark Effect in Few-Layer Black Phosphorus

Two-dimensional black phosphorus has sparked enormous research interest due to its high carrier mobility, layer-dependent direct bandgap and outstanding in-plane anisotropic property. It is one of the few 2D materials where it is possible to tune the bandgap over a wide energy range from the visible to the IR spectrum.

When a few atomic layers of BP are exposed to an electric field, a physical phenomenon known as the Stark effect is observed. In atomic spectra, the Stark effect is the shifting and splitting of atomic energy levels under the influence of an externally applied electric field. Similarly, this Stark effect causes the conduction and valence band to shift towards each other, resulting in the reduction of the bandgap of few-layer BP.

Continue Reading

CA2DM-NUS team pioneers two-dimensional polymer breakthrough that could revolutionise energy storage

The novel ultra-thin two-dimensional polymer sheet, which is the organic analogue of graphene, heralds new opportunities for long lasting sodium rechargeable batteries

Polymers, such as plastic and synthetic textiles, are very useful technological commodities that have revolutionised daily life and industries. A research team from the National University of Singapore (NUS) has successfully pushed the frontier of polymer technology further by creating novel two-dimensional (2D) graphene-like polymer sheets.

In the last century, scientists have successfully developed molecules which can be crosslinked to form one-dimensional and three-dimensional polymers. These are used to produce a wide range of technological products. However, making 2D polymers has met with little success, as most molecules are not flat and they tend to rotate in solution, making it difficult to control their linking to a 2D plane,” said Professor Loh Kian Ping, Head of 2D Materials Research in the Centre for Advanced 2D Materials at NUS. He also holds an appointment with the Department of Chemistry at the NUS Faculty of Science.


Continue Reading

2D materials for all-optical photonic devices

There is an ultimate limit for electronic miniaturization imposed by electron-electron interactions and by the Pauli exclusion principle that forbids two electrons to occupy the same quantum state. This will eventually prevent the development of denser circuitry, as well as of multiplexed or parallel schemes using electrons as information carrier units. Photons, however, can share a same logical gate, without interacting among one another, unless mediated by the supporting material and its nonlinear optical properties. This suggests that, in the near future, technology based on all-optical photonic devices will partially take over electronics and, possibly, extend classical computing in use today to include new quantum protocols and techniques. In this photon controlling photon type of devices, materials that provide efficient nonlinear optical interaction will indubitably play a central role.

Continue Reading

Science review on 2D materials and van der Waals heterostructures

Writing in Science, leading 2D materials researchers estimate that research on combining materials of just a few atomic layers in stacks called heterostructures is at the same stage that graphene was 10 years ago, and can expect the same rapid progress graphene has experienced.

Graphene was the first 2D material, isolated at The University of Manchester in 2004. Its range of superlative properties, including fantastic strength, conductivity, flexibility and transparency, has paved the way for applications ranging from water filtration to bendable smartphones; from rust-proof coatings to anti-cancer drug delivery systems.

Combining graphene with other materials, which individually have excellent characteristics complimentary to the extraordinary properties of graphene, has resulted in exciting scientific developments and could produce applications as yet beyond our imagination.     

The authors of the review article, from The University of Manchester and National University of Singapore, state that early applications could be high-mobility transistors for superfast electronics and LED devices using graphene as a transparent electrode.

However, such in the range of possible combinations of materials, researchers believe that heterostructures could deliver designer materials, made to order to meet the demands of industry.

The family of 2D crystals is expanding all the time, meaning that new possibilities for combining them in stacks can be explored.

The next challenge is to work out how to mass produce 2D materials; a similar problem that faced graphene in the early years after it was isolated.

Sir Kostya Novoselov, who together with Professor Sir Andre Geim won the Nobel prize for Physics in 2010 for demonstrating the remarkable properties of graphene, believes 2D materials are one of the most exciting and promising areas of research.

He said: “With 2D materials, we are currently where we were about 10 years ago with graphene – plenty of interesting science and unclear prospects for mass production.

“Given the fast progress of graphene technology over the past few years, we can expect similar advances in the production of heterostructures, making the science and applications more achievable.”

Co-author Professor Antonio Castro Neto, Director of the Centre for Advanced 2D Materials at the National University of Singapore, added: “In the search for revolutionary and disruptive new technologies, van der Waals heterostructures and devices based on two dimensional materials emerge as major players.

“This review covers the latest developments in one of the fastest growing fields that bridges science, materials science, and engineering.”

Source: The University of Manchester

CA2DM crosses h-index = 50 in less than 5 years

In a brief span of 5 years, the Centre for Advanced Two-Dimensional Materials (CA2DM), and its predecessor, Graphene Research Centre, has just quietly passed a milestone in academic research. This is the h-index = 50 mark which signifies that 50 of its papers have at least 50 citations by peer publications. Putting things into its proper context, what this really means is that the work of CA2DM’s scientists is being acknowledged by their peers.

Drawn from over 400 papers published to date, CA2DM’s 50 most cited articles (attached) show a breadth of diversity and strength across many topics in 2D materials like graphene oxide, transition metal dichalcogenides, biomaterials, topological semimetals, organic catalysts, and energy storage materials.

As of this writing, 16% of the 50 papers have garnered more than 300 citations each with the highest just tipping over the 1000 mark. These papers are published in a broad range of well-known academic journals such as Nature (2), Science (6), Nature’s sister journals, e.g. Nature Nanotechnology (2) and Nature Communications (8), ACS Nano (6), Nano Letters (6) and others like Advanced Materials (2).

Papers in two specific areas of research stand out amongst the 50 in being classified by the Web of ScienceTM as both Hot Papers and Highly Cited Papers. Generally, they have had the most citations within the shortest space of time since publication when benchmarked against peer papers. The two areas are black phosphorus (3) and Weyl semimetals (3). The key scientists that carry out seminal work on black phosphorus are Professor Antonio H Castro Neto and Dr Alexandra Carvalho. CA2DM’s leading researcher on Weyl semimetals and the related topological insulators is Assistant Prof Hsin Lin.

As an indicator of their profundity and prolificacy, Professors Castro Neto and Loh Kian Ping have the honour of the most number of highly cited papers in a diverse array of topics. Two fast-rising researchers with highly cited papers in this group are Assistant Professor Goki Eda (transition metal dichalcogenides) and Associate Professor Christian Nijhuis (plasmonics).

In conclusion, as CA2DM crosses over this significant landmark, it is poised to take a firm grasp on its leading position in 2D materials research, moving towards even more groundbreaking work.


Choreographing the dance of electrons

NUS scientists have discovered how to manipulate many body states in thin semiconductors by encapsulating them in atomically thin materials and changing the electric field

Scientists at the National University of Singapore (NUS) have demonstrated a new way of controlling many body states in correlated electron systems by confining them in a device made out of atomically thin materials, and applying external electric and magnetic fields. This research, published on 23 December 2015 in the prestigious scientific journal Nature, was led by Professor Antonio Castro Neto and his research team at the Centre for Advanced 2D Materials (CA2DM) of the NUS Faculty of Science.

Almost all modern technology like motors, light bulbs and semiconductor chips runs on electricity, harnessing the flow of electrons through devices. Explained Prof Castro Neto, “Not only are electrons small and fast, they naturally repel each other due to their electric charge. They obey the strange laws of quantum physics, making it difficult to control their motion directly.”

To control electron behaviour, many semi-conductor materials require chemical doping, where small amounts of a foreign material are embedded in the material to either release or absorb electrons, creating a change in the electron concentration that can in turn be used to drive currents.

However, chemical doping has limitations as a research technique, since it causes irreversible chemical change in the material being studied. The foreign atoms embedded into the material also disrupt its natural ordering, often masking important electronic states of the pure material.

The NUS research team was able to replicate the effects of chemical doping in this study by using only external electric and magnetic fields applied to an atomically thin material, titanium diselenide (TiSe2), encapsulated with boron-nitride (hBN). The researchers were able to control the behaviour of the electrons accurately and reversibly, making measurements that had been theoretical up to now. The thinness of the two materials was crucial, confining the electrons within the material to a two-dimensional layer, over which the electric and magnetic fields had a strong, uniform effect.

“In particular, we could also drive the material into a state called superconductivity, in which electrons move throughout the material without any heat or energy loss,” Prof Castro Neto said.

Because they are atomically thin, two-dimensional superconducting materials would have advantages over traditional superconductors, in applications such as smaller, portable magnetic resonance imaging (MRI) machines.

One specific goal of the NUS research team is to develop high-temperature two-dimensional superconducting materials. Current materials require an extremely cold temperature of -270°C to function, ruling out exciting applications such as lossless electrical lines, levitating trains and MRI machines.

The technique, which took the researchers two years to develop, will enable new experiments that shine light on high-temperature superconductivity and other solid-state phenomena of interest. With a wide range of materials awaiting testing, electric field doping greatly widens the possibilities of solid-state science.

Original Publication: L. J. Li et al. Controlling many-body states by the electric-field effect in a two-dimensional material, Nature (2015). DOI: 10.1038/nature16175

Commentary in Nature Nanotechnology: Peter Abbamonte, 2D superconductivity: Electric tuning of many-body states, Nature Nanotechnology (2016). DOI:10.1038/nnano.2016.7

Media coverage as of December 27th