A Sense of Scale is a project I orchestrated, collecting images which display the variety of research performed by the Nanoscience Group in the School of Physics and Astronomy at the University of Nottingham. With the subject matter ranging from human cells to individual atoms, the length scale of images spans from millimetres down to nanometres.

Many features of interest in nanoscience can only be explored with advanced microscopy techniques. The Nanoscience Group specialises in a range of scanning probe microscopy methods which permit observations of nanoscale objects by exploiting interactions between a sharp tip and the sample; the basis of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM).

This pattern formed when a chloroform solution containing gold nanoparticles (white) dried on a solid substrate (blue). This fingering pattern developed due to instabilities at the rim of an expanding hole. This structure is several micrometres wide, but only 2 nanometres high - the diameter of the nanoparticles.

Image width: 10 micrometres

Acquired by using AFM

This is an image of a thin polymer bilayer film; polystyrene (PS) on poly(ethylene oxide) (PEO). When heated, the PEO underlayer melts, leaving the glassy PS film in a state of mechanical stress. This stress is relaxed via buckling of the film in a periodic manner to form the wrinkles seen here.

Image width: 350 micrometres

Acquired by using optical microscopy

This is an image of a two-dimensional disordered crystal formed by small, rod-like, organic molecules. The crystal is held together via hydrogen bonding between carboxylic acid groups. The crystal is aperiodic (it has no translational order) but it exists within a periodic framework.

Image width: 33 nanometres

Acquired by using STM in liquid

These are 3T3 fibroplasts on a wrinkled polystyrene surface. The cells have been chemically stained with FITC-conjugated phalloidin (highlighting the actin cytoskeletal fibres as green) and DAPI nuclear stain (highlighting the cell nuclei as blue).

Image width: 1 millimetre

Acquired using fluorescence optical microscopy

This image of a Si(100) surface shows individual silicon atoms, paired up to form dimers which are arranged in rows. These dimers are buckled such that one silicon atom is raised slightly with respect to the other. This can be seen here as each 'bright' atom neighbours a 'dim' atom.

Image width: 4.4 nanometres

Acquired using AFM in ultra-high vacuum at 5 K (-268 C)

This composite image shows a series of STM scans of a graphite surface. The progression from a 'bad' (left) to 'good' (right) image is controlled by a genetic algorithm which alters imaging parameters, such as tunnel current and applied voltage, to optimize the image quality.

Image width: 20 nanometres (effective)

Acquired using STM

This silicon surface is known as the Si(111)-(7x7) reconstruction. After cleaving a silicon crystal in a certain direction to expose this face, atoms at the surface organise themselves into this complex arrangement to form a stable surface.

Image width: 25 nanometres

Acquired using STM in ultra-high vacuum at 77 K (-196 C)

This image shows spherulites of poly(caprolactone) (PCL) which formed after a thin film of this semicrystalline polymer was spin coated from solution. The boundary regions mark where growing spherulites meet and have run out of material to crystallize.

Image width: 50 micrometres

Acquired using AFM

The worm-like pattern seen here is formed by 2 nanometre gold nanoparticles. The area on the left has been repeatedly scanned with an AFM tip for 8 hours. Interactions between the tip and nanoparticles has resulted in a modification of the pattern; it has been coarsened with respect to the unmodified area on the right.

Image width: 2 micrometres

Acquired using AFM