Donald Fitzmaurice

Carbon Nanotube Templated Self‐Assembly and Thermal Processing of Gold Nanowires

Gold nanowires have been produced by the self-assembly of gold nanoparticles onto multi-walled carbon nanotubes. The nanotubes were mixed with a suspension of gold nanoparticles, resulting in a dec ...

Heterosupramolecular chemistry: programmed pseudorotaxane assembly at the surface of a nanocrystal.

Gold nanocrystals, stabilized by thiols covalently bound to a dibenzo[24]crown-8 moiety, have been programmed to recognize and selectively bind dibenzylammonium cations in solution. This results in a self-organization process at the surface of a nanocrystal with the assembly of a pseudorotaxane (see picture).

Using spectroscopy to probe the band energetics of transparent nanocrystalline semiconductor films

Abstract Transparent polycrystalline semiconductor films are formed on a conducting glass substrate by sintering nanocrystallites in air at high temperatures. Incorporation in an electrochemical cell, as the working electrode, permits potentiostatic control of the Fermi energy within the semiconductor film. On applying a potential more negative than the flatband potential electrons accumulate in the conduction band. Spectral changes assigned to accumulation of free carriers and the associated Burstein shift have been characterized. Calculation of the flatband potential is possible from the measured relationship between either the free electron absorbance or the Burstein shift, and the applied potential at several different pHs. These methods are finding applications in optimization of regenerative photoelectrochemical cells based on polycrystalline semiconductor films.

Electron Accumulation in Nanostructured TiO2 (Anatase) Electrodes

If both the technological and commercial potential of nanostructured metal oxide electrodes are to be fully realized, it will be important to understand the effects of electrolyte composition on the extent of electron accumulation and the nature of charge compensation at different applied potentials. Having studied the potential dependent optical absorption spectroscopy of nanostructured TiO2 (anatase) electrodes in different electrolytes, we concluded that the extent and nature of charge accumulation and compensation depends on whether the potential applied corresponds to weak ( 40 mC cm-2) accumulation conditions, on whether the electrolyte is prepared using a protic or aprotic solvent, and on whether the ions present in the electrolyte are capable of being intercalated or not.

Photoelectrochromic heterosupramolecular assemblies

Heterosupramolecular assemblies based on modified transparent nanostructured TiO2 (anatase) membranes are described. Exposure of these heterosupramolecular assemblies to visible light causes them to turn blue. Furthermore, if a negative potential is applied to the nanostructured TiO2 membrane this blue color persists for hours. Because only those areas which have been irradiated are blue, and because the lifetime of the blue colored state depends on the potential applied to the nanostructured TiO2 membrane, applications are foreseen for these photoelectrochromic materials.

Determination of band edge energies for transparent nanocrystalline TiO2CdS sandwich electrodes prepared by electrodeposition

Abstract We describe preparation of transparent nanocrystalline semiconductor sandwich electrodes. Specifically, TiO 2 CdS and CdSTiO 2 sandwich electrodes have been prepared by electrodeposition of CdS on TiO 2 and TiO 2 on CdS, respectively. Also described are the application of optoelectrochemical techniques for determination of the energy of the conduction band edge at thesemiconductor — liquid electrolyte solution interface ( V cb ). Specifically, V cb has been determined for each semiconductor in nanocrystalline TiO 2 , CdS, TiO 2 CdS and CdSTiO 2 electrodes. For TiO 2 and CdS electrodes, V cb is −0.37 V (SCE) and −0.7 V, respectively, in aqueous solution at pH 2.0. Under similar conditions V cb forTiO 2 and CdS is −0.47 V and −0.4 V, respectively, in the corresponding TiO 2 CdS sandwich electrode. Using the results of these and similar experiments, it has been possible to prepare energy level diagrams for nanocrystalline semiconductor sandwich electrodes. Implications for potential applications of these electrodes, particularly in regenerative photoelectrochemical cells, are considered.

Heterosupramolecular optical write–read–erase device

A covalently linked ruthenium tris(bipyridyl) complex and viologen have been chemisorbed at the surface of the constituent nanocrystals of a transparent nanostructured TiO 2 film supported on conducting glass. This resulting heterosupramolecular assembly, when incorporated as the working electrode in a sealed two-electrode cell, yields a device which can be written to using blue–green light, read using red light and erased by applying a voltage.

Imaging the DNA and nanoparticle components of a self-assembled nanoscale architecture

We describe the self-assembly in solution of a nanoscale architecture from DNA and gold nanoparticles. Also described is the characterization of this nanoscale architecture by transmission electron microscopy, atomic force microscopy and near-field scanning optical microscopy. A key finding is that it is possible to image both the DNA and nanoparticle components of the nanoscale architecture.

Synthesis of Oligonucleotides Carrying Anchoring Groups and Their Use in the Preparation of Oligonucleotide–Gold Conjugates

Oligodeoxynucleotide conjugates 1–15 carrying anchoring groups such as amino, thiol, pyrrole, and carboxy groups were prepared. A post-synthetic modification protocol was developed. In this method 2′-deoxy-O4-(p-nitrophenyl)uridine-3-phosphoramidite was prepared and incorporated in oligonucleotides. After assembly, the modified nucleoside was made to react with different amines carrying the anchoring groups. At the same time, protecting groups were removed to yield the desired oligonucleotide conjugates. In a second approach, amino, thiol, and carboxylic groups were introduced into the 3′-end of the oligonucleotides by preparing solid supports loaded with the appropriate amino acids. Oligonucleotidegold conjugates were prepared and their binding properties were examined.

Heterosupramolecular Chemistry: Self‐Assembly of an Electron Donor (TiO2 Nanocrystallite)‐Acceptor (Viologen) Complex

A TiO2 nanocrystallite has been modified to recognise and selectively bind, by complementary hydrogen bonding, a uracil substrate incorporating a viologen moiety. Band-gap excitation of the self-assembled donor (TiO2 nanocrystallite)-acceptor (viologen) complex results in electron transfer. Some implications of these findings for the self-assembly of functional nanostructures containing both condensed phase and molecular components are considered.