Nanoscale & Nanoscale Advances Blog

Electrochemistry of folded graphene edges

Adriano Ambrosi, Alessandra Bonanni and Martin Pumera
Nanoscale, 2011, C1NR10136F

Graphene  has many exciting potential applications, from solar cells to antibacterial sheets. There has been intensive research into the various properties of graphene, and it has been shown to have excellent electronic, electrochemical, optical, mechanical and thermal properties. As graphene has a planar form, it is important to consider the affects of conformational changes of the sheets such as folding and wrinkling, which can alter electrical and electrochemical properties. An important consideration here is the properties of graphene edges, as opposed to on the sheet’s surface.

Pumera and coworkers from Nanyang Technological University, Singapore, have conducted a study of the electrochemistry of folded graphene edges, and compared it to that of open edges. Folded edges have a very different structure compared to closed edges, and therefore it is natural to assume that they should possess different physical, chemical and electronic properties. Pumera et al. conclude in their paper that the electrochemical properties are superior at the open edges, discovering that the electron transfer rate is about 35 times faster at open-edged graphene structures than at folded-edged graphenes. This could be an extremely important consideration when synthesising graphene-based materials for many applications, particularly sensing and bio-sensing, as pointed out by the authors.

To read the full article, click here.

Articles from both Nanoscale and Energy & Environmental Science are listed as Thomson Reuters ISI fast-breaking papers this month.

Each month, ScienceWatch tracks which papers are ‘Fast Breaking’, i.e. have the highest percentage increase in citations, and for April both Nanoscale and Energy & Environmental Science papers are top in the Chemistry and Environmental fields, respectively.

Surprisingly, both papers are also by the same author, Frederik Krebs – so our congralutions go out to Professor Krebs!

April’s ISI fast-breaking papers

Field: Chemistry

Upscaling of polymer solar cell fabrication using full roll-to-roll processing
Frederik C. Krebs, Thomas Tromholt and Mikkel Jørgensen
Nanoscale, 2010, 2, 873-886

Field: Environment/Ecology

Manufacture, integration and demonstration of polymer solar cells in a lamp for the “Lighting Africa” initiative
Frederik C. Krebs, Torben D. Nielsen, Jan Fyenbo, Mads Wadstrøm and Marie S. Pedersen
Energy Environ. Sci., 2010, 3, 512-525

Nanoscale ‘HOT’ Communication – read it today!

Silver nanoplates on commercial copper foil were prepared by a reproducible and cost-effective wet chemical method and those can be used as a reliable surface-enhanced Raman spectroscopy substrate.

Silver nanoplates prepared by modified galvanic displacement for surface-enhanced Raman spectroscopy
Yongchao Lai, Wenxiao Pan, Dongju Zhang and Jinhua Zhan
Nanoscale, 2011, DOI: 10.1039/C0NR01030H

Issue 3 of Nanoscale is now out and we’d like to share some of the highlights with you…

The front cover features the work of Nguyen T. K. Thanh and colleagues on magnetic CoPt nanoparticles as MRI contrast agents for the detection transplanted neural stem cells. The inside front cover highlights the sonochemical formation of metal sponges by Daria V. Andreeva and co-workers.

Review
Pitfalls in the characterization of nanoporous and nanosized materials
Claudia Weidenthaler
Nanoscale, 2011, 3, 792

Feature article
Multi-scale theoretical investigation of hydrogen storage in covalent organic frameworks
Emmanuel Tylianakis, Emmanouel Klontzas and George E. Froudakis
Nanoscale, 2011, 3, 856

Communication
An enzyme-sensitive probe for photoacoustic imaging and fluorescence detection of protease activity
Xiaohu Xia, Miaoxin Yang, L. Kyle Oetjen, Yu Zhang, Qingge Li, Jingyi Chen and Younan Xia
Nanoscale, 2011, 3, 950

HOT paper
Tuning from blue to magenta the up-converted emissions of YF3:Tm3 /Yb3 nanocrystals
Marta Quintanilla, Nuria O. Núñez, Eugenio Cantelar, Manuel Ocaña and Fernando Cussó
Nanoscale, 2011, 3, 1046

A molecular brush based on conjugated polyelectrolyte (CPE) grafted with dense poly(ethylene glycol) (PEG) chains was successfully complexed with an anticancer agent, cisplatin, to form cisplatin-loaded nanoparticles (CPE-PEG-Pt), say scientists from Singapore and China.

The nanoparticles have high far-red/near-infrared fluorescence and are able to release the drug in a continuous and slow manner.

Read this exciting Nanoscale article today – hot off the press!

Reference
D Ding et al, Nanoscale, 2011, DOI: 10.1039/c0nr00950d

From stochastic single atomic switch to nanoscale resistive memory device

Attila Geresdi, András Halbritter, András Gyenis, Péter Makk and György Mihály

Nanoscale, 2011, DOI:10.1039/C0NR00951B

Scientists from Hungary have published some important work in Nanoscale regarding the use of solid state ionic conductors as atomic-sized junctions in non-volatile computer memory devices. By varying the size of the junctions from single-atom-sized to 10 nm, the group concluded that there is a lower size limit of 3 nm for reliable ionic nano-switches, a size which is well below the resolution of recent lithographic techniques.

In this work, Garesdi et al. created the junctions by gently touching a silver thin film with an electrochemically sharpened tungsten tip. Exposure of the silver film to air established the ionic conductor surface layer, and the nanoscale ‘point-contact’ geometry was sufficient to form a reliable switching device above the 3 nm threshold. Below this value, the switching process was much less reliable. The storage density here, even with the 3 nm limit, would be higher than current NAND flash devices and similar to the proposed bit size threshold of magnetic media which arises due to the superparamagnetic limit.

The authors provide a detailed analysis of the physical properties of the nano-junctions, as well as an explanation of the underlying mechanisms. They conclude that their ionic conductor-based devices are good candidates for non-volatile memory cells.

To read this article, click here.

Scientists in China have made a synthetic bone material using a new technique for creating polymer nanocomposites incorporated with inorganic nanoparticles.

Yuandong Dou, Kaili Lin and Jiang Chang, Nanoscale, 2011, DOI: 10.1039/C1NR10028A

Fluorescent images of the composite films

Jiang Chang and colleagues created this material after coming up with a new approach to making the  nanocomposites,  allowing them to control both the spatial distribution and orientational organisation of the nanocomponents, a known limitation of current methods of fabrication.

Their method involves using electrospinning and hot pressing techniques. They firstly homogeneously dispersed the nanoparticles within a polymer matrix solution, which was then electrospun into a patterned “nanofibrous mat” using a specifically designed “collector”. This mat was then placed between two sheets of non-woven polymer nanofibre and hot pressed to create the nanocomposite.

Because bone tissue is, generally speaking, structurally similar to these composites (they involve mineral particles preferentially oriented in a collagen matrix), the researchers tested their new fabrication method by creating an synthetic bone material by incorporating calcium silicate hydrate nanowires into a polyvinyl butyral matrix.  Their artificial material showed remarkable mechanical properties, particularly when compared with the pure polymer (for instance, the bending strength of the researchers’ material reached 188 MPa, as compared to the 86 MPa of the polymer), which also matched those of real cortical bone tissue.

You can find out more about this work by reading the article here.

Encapsulated enhanced green fluorescence protein in silica nanoparticle for cellular imaging

Zhengwei Cai, Zhangmei Ye, Xiaowei Yang, Yanli Chang, Haifang Wang, Yuanfang Liu and Aoneng Cao
Nanoscale DOI:10.1039/C0NR00956C

Scientists in China have developed a simple method of capping green fluorescent protein (GFP) in silica, which is a vital step in improving the versatility of fluorescent proteins for use as imaging probes.

Cai et al. at Shanghai University developed a covalent attachment route, which means the capping precursors are chemically bonded to the protein, rather than just providing passive encapsulation. The silica shell is then grown from the precursor layer to provide a solid and stable shell. A simple reverse emulsion method was used, and the group achieved a very high encapsulation efficiency and high protein loading. Their characterisation results suggest that encapsulating GFP in silica significantly increases its fluorescence and stability as the capping provides an effective barrier from external interference, such as protease attack, denaturants, and excessive heating.

Fluorescent probes are widely used to image biological structures and processes, both in vivo and in vitro. The main concerns in the design of these probes are their optical properties and the way they interact with their environment. For example, you may have a probe which exhibits excellent optical properties, but is toxic and therefore adversely affects the things you are trying to image. Conversely, you could have a probe which is non-toxic, but is unstable and loses its fluorescence too quickly under excitation. Traditional organic dyes suffered from various problems, including a lack of stability, broad emission profiles and toxicity issues. These have gradually been replaced with modern ‘nanoprobes’ which consist of either fluorescent nanoparticles or nanoparticulate coatings for fluorescent molecules. Of all the nanoprobes developed, fluorescent quantum dots exhibit the best optical properties, however, as they generally contain heavy metals such as cadmium, there are toxicity concerns in many applications.

The silica encapsulated fluorescent protein nanoparticles developed in this work may prove to be an exciting new probe which exhibits excellent optical and stability properties whilst avoiding problems such as toxicity and instability,

To read this article, click here.

Nanoscale DOI:10.1039/C0NR00956C