Volume 3 Issue 9, September 2008

There are many different ways to introduce the public to nanotechnology, writes Chris Toumey. Just don't mention human hairs or the space elevator.

Researchers have set up a company to sell graphene samples to other researchers.

Researchers have used a vibrating carbon nanotube to set a new record for nanomechanical mass sensing. Could this approach — currently being pursued by three independent groups — lead to a new type of mass spectrometer?

Nanoscale formulations of selenium can effectively capture mercury vapours from spills that could otherwise contaminate the air of homes and offices.

Two independent teams have shown that it is possible to produce stable suspensions of single-layer graphene from graphite crystals using chemical techniques.

Thin films of redox-active molecules can be used to construct logic gates, which can then be linked together to create basic circuits.

Large cargos stop protein filaments from rotating as they glide along a surface coated with motor proteins, but small cargos do not.

Nanoscale mechanical resonators can make precision measurements of force, position and mass. Atomic resolution in mass sensing at room temperature has now been demonstrated with a carbon nanotube-based resonator that essentially operates as a mass spectrometer. The atomic equivalent of shot noise has also been detected.

The first samples of pristine graphene were obtained by 'peeling off' and epitaxial growth, but chemical approaches are more suited to large-scale production. Exfoliation, reintercalation and expansion of graphite can produce high-quality single-layer graphene sheets suspended in organic solvents, and these sheets can be made into large transparent films by Langmuir–Blodgett assembly.

The performance of state-of-the-art photovoltaic devices based on polymer–nanocrystal composites is still limited by the preparation of the composite films. By blending and annealing cadmium telluride nanocrystals in a polymer–fullerene matrix, high photoconductive gain can be achieved under low applied voltages.

Base-pairing drives the assembly of dye-functionalized nanoparticles that have complementary DNA strands attached. This aggregation leads to a massive enhancement of the resonant Raman signal, which may prove useful for sensing applications.

A combination of quantum dots and fluorescence-interference contrast microscopy can be used to monitor the rotation of microtubules with nanometre accuracy as they glide over motor proteins. This approach shows that the microtubules stop rotating when they pick up large cargos, but their velocity does not change.

Photoacoustic imaging offers higher spatial resolution than most optical imaging techniques, but contrast agents are needed because many diseases in their early stages do not display a natural photoacoustic contrast. Using single-walled carbon nanotubes conjugated with a peptide as a contrast agent allows the non-invasive photoacoustic imaging of tumours in animals.

Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. The dispersion and exfoliation of graphite in organic solvents can produce graphene monolayers with a yield of about 1% by weight. Moreover, these samples are free from defects and oxides, and can be used to produce semi-transparent conducting films and conducting composites.

Experiments to explore electron transport in single molecules generally involve the use of chemical linker groups at both ends of the molecule to firmly anchor it to the source and drain contacts. Here it is shown that oligo-phenylene ethynylene molecules with a single anchor group can form molecular junctions as well. The process is attributed to aromatic stacking between neighbouring molecules in nearby electrodes.