Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

Attempts to infer DNA electron transfer from fluorescence quenching measurements1,2,3,4,5,6,7,8,9 on DNA strands doped with donor and acceptor molecules have spurred intense debate10,11 over the question of whether or not this important biomolecule is able to conduct electrical charges. More recently, first electrical transport measurements on micrometre-long DNA ‘ropes’12, and also on large numbers of DNA molecules in films13, have indicated that DNA behaves as a good linear conductor. Here we present measurements of electrical transport through individual 10.4-nm-long, double-stranded poly(G)-poly(C) DNA molecules connected to two metal nanoelectrodes, that indicate, by contrast, large-bandgap semiconducting behaviour. We obtain nonlinear current–voltage curves that exhibit a voltage gap at low applied bias. This is observed in air as well as in vacuum down to cryogenic temperatures. The voltage dependence of the differential conductance exhibits a peak structure, which is suggestive of the charge carrier transport being mediated by the molecular energy bands of DNA.

Direct measurement of electrical transport through DNA molecules

Work function, electronegativity, and electrochemical behaviour of metals: III. Electrolytic hydrogen evolution in acid solutions

Emulsions stabilized with solid nanoparticles: Pickering emulsions

Catalytic removal of NO

Semiconductivity of organic substances. Part 9.—Nucleic acid in the dry state

The semiconductivity of organic substances. Part 6.—A range of proteins

Type I aluminium films deposited at 0 °C were of relatively low area, ca. 1000 cm 2 , stable and with a certain porosity since CO uptake was proportional to film weight. Thus a film area could be determined from its weight, since at saturation CO molecules occupy 0·75 of the total surface area given by the B.E.T. method (established for higher area type II films). It was found that H 2 and N 2 were not chemisorbed, N 2 O and NO reacted giving surface oxide, C 2 H 4 gave a slow reversible adsorption, and CO gave a slow irreversible adsorption, rate proportional to p/g , where p is the gas pressure, g the quantity of gas taken up by the film. The kinetics of oxygen uptake were followed in the range 10 -2 to 10 -3 mm Hg pressure. The first two monolayers were taken up too rapidly for kinetic measurement, and thereafter gas uptake followed the direct logarithmic law, until about 7 A of film had been formed d g /d t = a e -γg/RT p 0·6 , where a and γ are constants. The rate-determining step is considered to be a place exchange of surface oxygen with underlying aluminium atoms, stimulated by reversibly chemisorbed oxygen atoms. As the film thickens it changes from covalent amorphous to ionic spinel character, and the activation energy for place exchange increases. The process of film growth in the ionic film (thickness > ca . 10 A) involves electron tunnelling and cation migration.

Daniel D. Eley

Papers

Semiconductivity of organic substances. Part 9.—Nucleic acid in the dry state

The semiconductivity of organic substances. Part 6.—A range of proteins

Adsorption and oxide formation on aluminium films

Emulsions of water in asphaltene-containing oils 1. Droplet size distribution and emulsification rates

Semiconductivity of organic substances. Part 7.—The polyamides