We investigated the thermoelectric properties of metalloporphyrins connected by thiol anchor groups to gold electrodes. By varying the transition metal-centre over the family Mn, Co, Ni, Cu, Fe, and Zn we are able to tune the molecular energy levels relative to the Fermi energy of the electrodes. The resulting single-molecule room-temperature thermopowers range from almost zero for Co and Cu centres, to +80 μV K⁻¹ and +230 μV K⁻¹ for Ni and Zn respectively. In contrast, the thermopowers with Mn(II) or Fe(II) metal centres are negative and lie in the range −280 to −260 μV K⁻¹. Complexing these with a counter anion to form Fe(III) and Mn(III) changes both the sign and magnitude of their thermopowers to +218 and +95 respectively. The room-temperature power factors of Mn(II), Mn(III), Fe(III), Zn and Fe(II) porphyrins are predicted to be 5.9 × 10⁻⁵ W m⁻¹ K⁻², 5.4 × 10⁻⁴ W m⁻¹ K⁻², 9.5 × 10⁻⁴ W m⁻¹ K⁻², 1.6 × 10⁻⁴ W m⁻¹ K⁻² and 2.3 × 10⁻⁴ W m⁻¹ K⁻² respectively, which makes these attractive materials for molecular-scale thermoelectric devices.

Using density functional theory combined with a Green’s function scattering approach, we examine the thermoelectric properties of hetero-nanoribbons formed from alternating lengths of graphene and boron nitride. In such structures, the boron nitride acts as a tunnel barrier, which weakly couples states in the graphene, to form mini-bands. In un-doped nanoribbons, the mini bands are symmetrically positioned relative to the Fermi energy and do not enhance thermoelectric performance significantly. In contrast, when the ribbons are doped by electron donating or electron accepting adsorbates, the thermopower S and electronic figure of merit are enhanced and either positive or negative thermopowers can be obtained. In the most favourable case, doping with the electron donor tetrathiafulvalene increases the room-temperature thermopower to −284 μ v K ⁻¹ and doping by the electron acceptor tetracyanoethylene increases S to 210 μ v K ⁻¹ . After including both electron and phonon contributions to the thermal conductance, figures of merit ZT up to of order 0.9 are obtained.

We investigate the molecular sensing properties of carbon nanotube–boron nitride–carbon nanotube (CNT–BN–CNT) junctions.

We demonstrate a technique for creating unique forms of pure sp2-bonded carbon and unprecedented heteromolecules. These new structures, which we refer to as sculpturenes, are formed by sculpting selected shapes from bilayer graphene, heterobilayers, or multilayered materials and allowing the shapes to spontaneously reconstruct. The simplest sculpturene is topologically equivalent to a torus, with dimensions comparable to those of fullerenes. The topology of these new molecular structures is stable against atomic-scale defects. We demonstrate that sculpturenes can form the basic building blocks of hollow, multiconnected structures, with potential applications to nanofluidics and nanoelectronics.