Genesis Nanotech Headlines Are Out!


Organ on a chip organx250Genesis Nanotech Headlines Are Out! Read All About It!

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SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA

Chairman Terry: “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development.”

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on:

“Nanotechnology: Understanding How Small Solutions Drive Big Innovation.”

 

 

electron-tomography

“Great Things from Small Things!” … We Couldn’t Agree More!

 

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Dye-sensitized solar cell absorbs a broad range of visible and infrared wavelengths: Increases Efficiencies


 

Phy Org Dye Solar dyesensitizeDye-sensitized solar cells (DSSCs) rely on dyes that absorb light to mobilize a current of electrons and are a promising source of clean energy. Jishan Wu at the A*STAR Institute of Materials Research and Engineering and colleagues in Singapore have now developed zinc porphyrin dyes that harvest light in both the visible and near-infrared parts of the spectrum1. Their research suggests that chemical modification of these dyes could enhance the energy output of DSSCs.

DSSCs are easier and cheaper to manufacture than conventional silicon , but they currently have a lower efficiency. Ruthenium-based dyes have been traditionally used in DSSCs, but in 2011 researchers developed a more efficient dye based on a zinc atom surrounded by a ring-shaped molecule called a porphyrin. Solar cells using this new dye, called YD2-o-C8, convert visible light into electricity with an efficiency of up to 12.3 per cent. Wu’s team aimed to improve that efficiency by developing a zinc porphyrin dye that can also absorb .

The most successful dyes developed by Wu’s team, WW-5 and WW-6, unite a zinc porphyrin core with a system of fused carbon rings bridged by a nitrogen atom, known as an N-annulated perylene group. Solar cells containing these dyes absorbed more infrared light than YD2-o-C8 and had efficiencies of up to 10.5 per cent, matching the performance of an YD2-o-C8 cell under the same testing conditions (see image).

Phy Org Dye Solar dyesensitize

Zinc porphyrin dyes were used to create solar cells that can absorb both visible and near-infrared light. Credit: A*STAR Institute of Materials Research and Engineering 

Theoretical calculations indicate that connecting the porphyrin and perylene sections of these dyes by a carbon–carbon triple bond, which acts as an electron-rich linker, improved the flow of electrons between them. This bond also reduced the light energy needed to excite electrons in the molecule, boosting the dye’s ability to harvest infrared light.

Adding bulky chemical groups to the dyes also improved their solubility and prevented them from aggregating—something that tends to reduce the efficiency of DSSCs.

However, both WW-5 and WW-6 are slightly less efficient than YD2-o-C8 at converting visible light into electricity, and they also produce a lower voltage. “We are now trying to solve this problem through modifications based on the chemical structure of WW-5 and WW-6,” says Wu.

Comparing the results from more perylene–porphyrin should indicate ways to overcome these hurdles, and may even extend light absorption further into the infrared. “The top priority is to improve the power conversion efficiency,” says Wu. “Our target is to push the efficiency to more than 13 per cent in the near future.”

Explore further: A new way to make microstructured surfaces

More information: Luo, J., Xu, M., Li, R., Huang, K.-W., Jiang, C. et al. N-annulated perylene as an efficient electron donor for porphyrin-based dyes: Enhanced light-harvesting ability and high-efficiency Co(II/III)-based dye-sensitized solar cells. Journal of the American Chemical Society 136, 265–272 (2014). DOI: 10.1021/ja409291g

Low Cost Laser Technique Improves Electrical & Photo Conductivity in Nanomaterials


NUS Laser 49845NUS scientists use low cost technique to improve properties and functions of nanomaterials: By ‘drawing’ micropatterns on nanomaterials using a focused laser beam, scientists could modify properties of nanomaterials for effective applications in photonic and optoelectric applications

Singapore | Posted on July 22nd, 2014

Through the use of a simple, efficient and low cost technique involving a focused laser beam, two NUS research teams, led by Professor Sow Chorng Haur from the Department of Physics at the NUS Faculty of Science, demonstrated that the properties of two different types of materials can be controlled and modified, and consequently, their functionalities can be enhanced.

Said Prof Sow, “In our childhood, most of us are likely to have the experience of bringing a magnifying glass outdoors on a sunny day and tried to focus sunlight onto a piece of paper to burn the paper. Such a simple approach turns out to be a very versatile tool in research. Instead of focusing sunlight, we can focus laser beam onto a wide variety of nanomaterials and study effects of the focused laser beam has on these materials.”

NUS Laser 49845

Mesoporous silicon nanowires were scanned by a focused laser beam in two different patterns, imaged by bright-field optical microscope, as depicted by (a) and (c), as well as fluorescence microscopy, as depicted by (b) and (d). Evidently, the images hidden in boxes shown in (a) and (c) are clearly revealed under fluorescence microscopy.

Micropatterns ‘drawn’ on MoS2 films could enhance electrical conductivity and photo conductivity

Molybdenum disulfide (MoS2), a class of transition metal dichalcogenide compound, has attracted great attention as an emerging two-dimensional (2D) material due to wide recognition of its potential in and optoelectronics. One of the many fascinating properties of 2D MoS2 film is that its properties depend on the thickness of the film. In addition, its properties can be modified once the film is modified chemically. Hence one of the challenges in this field is the ability to create microdevices out of the MoS2 film comprising components with different thickness or chemical nature.

To address this technological challenge, Prof Sow, Dr Lu Junpeng, a postdoctoral candidate from the Department of Physics at the NUS Faculty of Science, as well as their team members, utilised an optical microscope-focused laser beam setup to ‘draw’ micropatterns directly onto large area MoS2 films as well as to thin the films.

With this simple and low cost approach, the scientists were able to use the focused laser beam to selectively ‘draw’ patterns onto any region of the film to modify properties of the desired area, unlike other current methods where the entire film is modified.

Interestingly, they also found that the electrical conductivity and photoconductivity of the modified material had increased by more than 10 times and about five times respectively. The research team fabricated a photodetector using laser modified MoS2 film and demonstrated the superior performance of MoS2 for such application.

This innovation was first published online in the journal ACS Nano on 24 May 2014.

Hidden images ‘drawn’ by focused laser beam on silicon nanowires could improve optical functionalities

In a related study published in the journal Scientific Reports on 13 May 2014, Prof Sow led another team of researchers from the NUS Faculty of Science, in collaboration with scientists from Hong Kong Baptist University, to investigate how ‘drawing’ micropatterns on mesoporous silicon nanowires could change the properties of nanowires and advance their applications.

The team scanned a focused laser beam rapidly onto an array of mesoporous silicon nanowires, which are closely packed like the tightly woven threads of a carpet. They found that the focused laser beam could modify the optical properties of the nanowires, causing them to emit greenish-blue fluorescence light. This is the first observation of such a laser-modified behaviour from the mesoporous silicon nanowires to be reported.

The researchers systematically studied the laser-induced modification to gain insights into establishing control over the optical properties of the mesoporous silicon nanowires. Their understanding enabled them to ‘draw’ a wide variety of micropatterns with different optical functionalities using the focused laser beam.

To put their findings to the test, the researchers engineered the functional components of the nanowires with interesting applications. The research team demonstrated that the micropatterns created at a low laser power are invisible under bright-field optical microscope, but become apparent under fluorescence microscope, indicating the feasibility of hidden images.

Further research

The fast growing field of electronics and optoelectronics demands precise material deposition with application-specific optical, electrical, chemical, and mechanical properties.

To develop materials with properties that can cater to the industry’s demands, Prof Sow, together with his team of researchers, will extend the versatile focused laser beam technique to more nanomaterials. In addition, they will look into further improving the properties of MoS2 and mesoporous silicon with different techniques.

Copyright © National University of Singapore

Bio-inspired way to grow graphene for electronic devices


BioGraphene-320Dr. Gao (left) and research assistant Ms Lim Xiao Fen working on the wafer-scale graphene growth and transfer in the Graphene Research Centre’s clean roomGraphene, a form of two-dimensional carbon, has many desirable properties that make it a promising material in many applications. However, its production especially for high-end electronics such as touch screens faces many challenges. This may soon change with a fresh approach developed by National Univ. of Singapore (NUS) researchers that mimics nature.

Inspired by how beetles and tree frogs keep their feet attached to submerged leaves, the findings published recently in Nature revealed a new method that allows both the growth and transfer steps of graphene on a silicon wafer. This technique enables the graphene to be applied in photonics and electronics, for devices such as optoelectronic modulators, transistors, on-chip biosensors and tunnelling barriers.

Professor Loh Kian Ping, Head of the NUS Department of Chemistry, led a team to come up with the one-step method to grow and transfer high-quality graphene on silicon and other stiff substrates. This promises the use of graphene in high-value areas where no technique currently exists to grow and transfer graphene with minimal defects for use in semiconductors.

Prof Loh, who is also a Principal Investigator with the Graphene Research Centre at NUS Faculty of Science, explained: “Although there are many potential applications for flexible graphene, it must be remembered that to date, most semiconductors operate on “stiff” substrates such as silicon and quartz.”

Thus, a transfer method with the direct growth of graphene film on silicon wafer is needed for enabling multiple optoelectronic applications, he said.

In the process called “face-to-face transfer”, Dr. Gao Libo, the first author who is with the Graphene Research Centre, grew graphene on a copper catalyst layer coating a silicon substrate. After growth, the copper is etched away while the graphene is held in place by bubbles that form capillary bridges, similar to those seen around the feet of beetles and tree frogs attached to submerged leaves. The capillary bridges help to attach the graphene to the silicon surface and prevent its delamination during the etching of the copper catalyst.

The novel technique can potentially be deployed in batch-processed semiconductor production lines, such as the fabrication of large-scale integrated circuits on silicon wafers.

The researchers will be fine-tuning the process to optimise the high throughput production of large diameter graphene on silicon, as well as target specific graphene-enabled applications on silicon. They are also looking at applying the techniques to other two-dimensional films.

Source: National Univ. of Singapore

Integration Of Photonic And Electronic Components


QDOTS imagesCAKXSY1K 8Better integration of photonic and electronic components in nanoscale devices may now become possible, thanks to work by Khuong Phuong Ong and Hong-Son Chu from the A*A*STAR Institute of High Performance Computing and their co-workers in Singapore and the US. From computer simulations, they have identified that the compound BiFeO3 has the potential to be used to efficiently couple light to electrical charges through light-induced electron oscillations known as plasmons. The researchers propose that this coupling could be activated, controlled and switched off, on demand, by applying an electrical field to an active plasmonic device based on this material. If such a device were realized on a very small footprint it would give scientists a versatile tool for connecting components that manipulate light or electric currents.

poles

Thin poles standing in water barely affect waves rolling past them. Similarly, nanostructured devices typically do not interact with light waves

Many devices used in everyday life — whether they be televisions, mobile phones or barcode scanners — are based on the manipulation of electric currents and light. At the micro- and nano-scales, however, it is typically challenging to integrate electronic components with photonic components. At these small dimensions, the wavelengths of light become long relative to the size of the device. Consequently, the light waves are barely detectable by the device, just as passing waves simply roll past thin poles in a water body (see image).

“The fact that, in theory, the properties of BiFeO3 [could] be [so readily controlled] by applying an electric field makes it a promising material for high-performance plasmonic devices,” explains Ong. He says that they expected such favorable properties after they had calculated the behavior of the material. But when they studied the behavior of the proposed BiFeO3-based device, they found that it could outperform devices based on BaTiO3, which is one of the best materials currently used for such applications.

Like BaTiO3, BiFeO3 can be fabricated relatively easily and cheaply. The new material is therefore a particularly promising candidate for device applications. Ong, Chu and their collaborators will now explore that potential. “We will design BiFeO3 nanostructures optimized for applications such as optical devices for data communication, sensing and solar-energy conversion,” says Ong.

According to Ong and Chu, an important step on the path to producing practical devices will be assessing the compatibility of BiFeO3-based structures with standard technologies, which typically use materials known as metal-oxide semiconductors. This future work will involve collaborations with experimental groups at the A*STAR Institute of Materials Research and Engineering and at the National University of Singapore.

 

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance