Nanoscale & Nanoscale Advances Blog

Scientists in China have developed a quick and easy procedure for preparing 3D graphene in water, enhancing graphene’s properties so that it can be used in supercapacitors, to store hydrogen and as a catalyst support.

Graphene, a single sheet of carbon atoms patterned in a honeycomb lattice can, via self-assembly, form 1D and 2D structures that have many potential applications. However, the graphene obtained is usually small, which limits its use as a functional material. 3D microporous and mesoporous carbon materials (hydrogels and aerogels) are lightweight; have high porosities and storage capacities; large surface areas; high electrical conductivity and thermal stability. Preparing such structures is challenging under mild conditions and current methods are not scalable or cost efficient.

Lifeng Yan and colleagues at the University of Science and Technology of China, Heifei, have prepared 3D graphene structures by self-assembly from graphene oxide using mild chemical reduction in water at 95 degrees Celsius at atmospheric pressure without stirring. The graphene shapes were controlled by using reactor vessels of differing shapes. The team were able to produce cylinder-, pear- and sphere-like shapes. ‘The process is quite simple – any macroscopic 3D graphene shapes can be prepared at room temperature and pressure,’ explains Yan.

In tests, the team found that the materials had high electrical conductivity, and high mechanical and thermal stability. The values for specific capacitance were similar to graphene hydrogels prepared by a hydrothermal method. The materials’ mechanical stability, measured by a compression test, was comparable to chemically cross-linked polymer hydrogels.  

Yan’s team plans to investigate the applications of their materials in super-capacitance, biosensors and catalysis, as well as preparing different types of novel 3D graphene composites.  

‘These macroscopic multi-pore materials will be very interesting if they can be used for reducing greenhouse gases by developing new catalysts,’ says Xiaobo He, an expert in graphene materials at Louisiana State University, US.

Carl Saxton

Read the Nanoscale paper in full:

In situ self-assembly of mild chemical reduction graphene for three-dimensional architectures
Wufeng Chen and Lifeng Yan, Nanoscale, 2011
DOI: 10.1039/c1nr10355e

A Nanoscale Communication on optical imaging of ligand-protein binding has been featured in C&EN this week.

The work by Nancy Xu uses the PHOTON method to map single ligand molecules in single protein–ligand complexes.

Read the ‘HOT’ Nanoscale Communication today:

Multicolored nanometre-resolution mapping of single protein–ligand binding complexes using far-field photostable optical nanoscopy (PHOTON)
Tao Huang and Xiao-Hong Nancy Xu
Nanoscale, 2011, DOI: 10.1039/C1NR10182J

Issue 4, 2011 of Nanoscale is now online, here are just some of the highlights…

Review
Electrostatics at the nanoscale
David A. Walker, Bartlomiej Kowalczyk, Monica Olvera de la Cruz and Bartosz A. Grzybowski, Nanoscale, 2011, 3, 1316

Feature article
Supramolecular assembly/reassembly processes: molecular motors and dynamers operating at surfaces
Artur Ciesielski and Paolo Samorì, Nanoscale, 2011, 3, 1397

‘HOT’ Communication
A simple and scalable graphene patterning method and its application in CdSe nanobelt/graphene Schottky junction solar cells
Yu Ye, Lin Gan, Lun Dai, Yu Dai, Xuefeng Guo, Hu Meng, Bin Yu, Zujin Shi, Kuanping Shang and Guogang Qin, Nanoscale, 2011, 3, 1477

Issue 4’s front cover features the review by Luis M. Liz-Marzán on controlled assembly of plasmonic colloidal nanoparticle clusters (DOI: 10.1039/C0NR00804D).

Browse the whole issue today online.

Scientists in China have developed a simple method for time-lapse imaging of single molecule reactions in situ by using DNA origami as a reaction surface.

The team recorded the whole dynamic process of the streptavidin–biotin binding reaction. They found that at a streptavidin concentration of 7.6 nM, the binding ratio increased steadily up to nearly 100% within 30 minutes.

This novel single-molecule reaction detection method, at the nanometre scale, may prove useful to study other macromolecule behavior and reaction kinetics, say the researchers.

Reference:
N Wu, X Zhou, D M Czajkowsky, M Ye, D Zeng, Y Fu, C Fan, J Hu and B Li, Nanoscale, 2011, DOI: 10.1039/ c1nr10181a

A team from Canada and the US has demonstrated that InP/ZnS quantum dots show low levels of cytotoxicity in cell lines related to reactive oxygen species production.

Indium phosphide quantum dots have emerged as a less hazardous alternative to cadmium-based particles, but their cytotoxicity has not been well examined, says the team, until now. Although their constituent elements are of very low toxicity to cells in culture, they nonetheless exhibit phototoxicity related to generation of reactive oxygen species by excited electrons and/or holes interacting with water and molecular oxygen, they add.

Using spin-trap electron paramagnetic resonance spectroscopy and reporter assays, the researchers found a considerable amount of superoxide and a small amount of hydroxyl radical formed under visible illumination of biocompatible InP quantum dots with a single ZnS shell, comparable to what is seen with CdTe. A double thickness shell reduces the reactive oxygen species concentration approximately two-fold. Survival assays in five cell lines correspondingly indicate a distinct reduction in toxicity with the double shell InP quantum dots. Toxicity varies significantly across cell lines according to the efficiency of uptake, being overall significantly less than what is seen with CdTe or CdSe/ZnS.

This indicates that InP quantum dots are a useful alternative to cadmium-containing quantum dots, while remaining capable of electron-transfer processes that may be undesirable or which may be exploited for photosensitisation applications, concludes the team.

Read the Nanoscale article today:
H Chibli, L Carlini, S Park, N M Dimitrijevic and J L Nadeau, Nanoscale, 2011
DOI: 10.1039/c1nr10131e