I am interested in synthesis, modification, characterisation, and application of high aspect ratio nanoparticles (particularly carbon nanotubes and oxide nanorods). These materials have unique and often extraordinary combinations of properties; the question is to what extent these properties can be manifested in assemblies at a macroscopic scale. We have developed and studied a wide variety of pure and composite systems based on nanotube/nanorods for both structural and functional applications across a range of length scales. The key challenges in almost all cases, is the synthesis of high quality material, introduction of the appropriate surface/interface chemistry, and assembly/processing into higher order structures. We have tackled these problems in situations as diverse as nanofibre-reinforced fibres and foams, hybrid photovoltaics, and supercapacitors.
I am co-director of the MRes in Nanomaterials at Imperial College, along with underdraduate teaching in inorganic, solid state, and materials chemistry, and a regular guest lecturer in Cranfield’s MPhil in Micro and Nanotechnology. I am also one of the external examiners for the Cambridge University Micro- and Nanotecnolohy Enterprise MPhil. I have helped organise a number of nano-related meetings, most recently the Nanotube summer school on Cargese last summer.
Two Transmission Electron Micrographs of titanium dioxide nanorods, in the two different polymorphs anatase and rutile. Titanium dioxide particles are already used on a massive scale in a wide range of applications; the next generation particles shown have smaller sizes, higher surface areas, and greater perfection than conventional materials. The high aspect ratio allows the creation of open networks with high connectivity, accessibility, and robustness. Preliminary data shows that they could be useful in photovoltaics or catalysis.
Ben F. Cottam, Siva Krishnadasan, Andrew J. deMello, John C. deMello and Milo S. P. Shaffer, Accelerated synthesis of titanium oxide nanostructures using microfluidic chip, Lab on a chip, 7, 167-169, 2007, DOI: 10.1039/b616068a [PDF file]
This paper contains the first report of nanorod synthesis in a microfluidic environment. Although the reaction did not display increased monodispersity compared to the usual bulk product, the enhanced mixing conditions accelerated the reaction dramatically. These structures are very promising for a wide range of applications, including (as we have recently demonstrated) photovoltaics.
K. Koziol, M. Shaffer, A.H. Windle, Three dimensional internal order in MWCNTs grown by CVD, Adv Mat, 17,.6, 760-763, 2005 (Inside Cover) [PDF file]
Carbon nanotubes can have a variety of structures, usually characterised in terms of a characteristic helicity or chirality (defined by the angle between one of the graphite lattice vectors and the tube axis). The helicity is important because it determines the electronic properties (metal or semiconductor); unfortunately, current synthesis methods generate a mixture of helicities even amongst the shells of an individual multi-wall nanotube. In this paper, we report the apparent synthesis of multi- wall nanotubes with uniform (high symmetry) helicities by the addition of nitrogen. The resulting nanotubes have a surprisingly degree of three dimensional crystallinity, an observation that we have explored in detail in a later paper, published in Small 2006.
P. Werner, F. Wõllecke, V. Altstädt, J K.W. Sandler, M Shaffer, Carbon nanofibres allow foaming of semicrystalline PEEK, Advanced Materials 17(23), (2005), 2864-286 [PDF file]
This paper reports the first data on the extensional viscosity of polymer melts containing nanofibres; interestingly, the behaviour is quite different to the more conventional shear viscosity. As a result we were able to propose a general strategy of using nanofibres, not only to improve the properties of the eventual nanocomposite, but to enable the processing of otherwise difficult systems. In this paper, we describe the first nanofibre-reinforced foams, as well as producing high quality foams using PEEK, a polymer that cannot normally be easily foamed.