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

Based on fundamental chemistry, biotechnology and materials science have developed over the past three decades into today's powerful disciplines which allow the engineering of advanced technical devices and the industrial production of active substances for pharmaceutical and biomedical applications. This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology. This novel and highly interdisciplinary field of chemistry is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles, as well as to the various aspects of molecular cloning, recombinant DNA and protein technology, and immunology. Evolutionary optimized biomolecules such as nucleic acids, proteins, and supramolecular complexes of these components, are utilized in the production of nanostructured and mesoscopic architectures from organic and inorganic materials. The highly developed instruments and techniques of today's materials research are used for basic and applied studies of fundamental biological processes.

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Nanoparticles, Proteins, and Nucleic Acids: Biotechnology Meets Materials Science

Recent research in the field of nanometre-scale electronics has focused on two fundamental issues: the operating principles of small-scale devices, and schemes that lead to their realization and eventual integration into useful circuits. Experimental studies on molecular1 to submicrometre2 quantum dots and on the electrical transport in carbon nanotubes3,4,5 have confirmed theoretical predictions6,7,8 of an increasing role for charging effects as the device size diminishes. Nevertheless, the construction of nanometre-scale circuits from such devices remains problematic, largely owing to the difficulties of achieving inter-element wiring and electrical interfacing to macroscopic electrodes. The use of molecular recognition processes and the self-assembly of molecules into supramolecular structures9,10 might help overcome these difficulties. In this context, DNA has the appropriate molecular-recognition11 and mechanical12,13,14,15,16 properties, but poor electrical characteristics prevent its direct use in electrical circuits. Here we describe a two-step procedure that may allow the application of DNA to the construction of functional circuits. In our scheme, hybridization of the DNA molecule with surface-bound oligonucleotides is first used to stretch it between two gold electrodes; the DNA molecule is then used as a template for the vectorial growth of a 12 µm long, 100 nm wide conductive silver wire. The experiment confirms that the recognition capabilities of DNA can be exploited for the targeted attachment of functional wires.

DNA-templated assembly and electrode attachment of a conducting silver wire

Molecular recognition between complementary strands of DNA allows construction on a nanometre length scale. For example, DNA tags may be used to organize the assembly of colloidal particles, and DNA templates can direct the growth of semiconductor nanocrystals and metal wires. As a structural material in its own right, DNA can be used to make ordered static arrays of tiles, linked rings and polyhedra. The construction of active devices is also possible--for example, a nanomechanical switch, whose conformation is changed by inducing a transition in the chirality of the DNA double helix. Melting of chemically modified DNA has been induced by optical absorption, and conformational changes caused by the binding of oligonucleotides or other small groups have been shown to change the enzymatic activity of ribozymes. Here we report the construction of a DNA machine in which the DNA is used not only as a structural material, but also as 'fuel'. The machine, made from three strands of DNA, has the form of a pair of tweezers. It may be closed and opened by addition of auxiliary strands of 'fuel' DNA; each cycle produces a duplex DNA waste product.

A DNA-fuelled molecular machine made of DNA

Supramolecular nanotube architectures based on amphiphilic molecules.

We have developed a method of semiconductor nanostructure fabrication relying on the size and shape of a polynucleotide to dictate the overall structure of an assembly of individual nanoparticles. This is exemplified by our use of the 3455‐basepair circular plasmid DNA molecule pUCLeu4 which, when anchored to a suitably derivatized substrate, yields an array of semiconductor nanoparticles matching the shape of the biopolymer stabilizer. The viability of the methodology was confirmed using data from high resolution transmission electron microscopy, selected area electron diffraction, and linear optical absorption spectroscopy. This is a unique demonstration of the self‐assembly of mesoscale semiconductor nanostructures using biological macromolecules as templates.

Dictation of the shape of mesoscale semiconductor nanoparticle assemblies by plasmid DNA

We report here a comparison of the ability of the monodentate Lewis base n-propylamine and the bidentate molecule ethylenediamine to quench the photoluminescence of light-emitting silicon in three different structural environments. These include porous silicon fabricated from p-type substrates; porous silicon from n-type substrates, and Si nanocrystallites derived from porous silicon. Both types of porous Si substrates were characterized by conventional transmission electron microscopy, while the Si nanocrystallites were characterized by high-resolution transmission electron microscopy. The fractional changes in photoluminescence as a consequence of amine addition were measured and fitted to a static equilibrium model from which adduct formation constants were calculated. It is found that the Si lumophores embedded in the porous oxides on n- and p-type substrates interact similarly with n-propylamine and ethylenediamine; however, ultrasonic extraction of the nanocrystalline Si fragments from the porous ox...

A Comparison of Porous Silicon and Silicon Nanocrystallite Photoluminescence Quenching with Amines

Scanning tunneling microscopy (STM) has been used to obtain images and current–voltage (I–V) curves of carbon nanotubes produced by arc discharge of carbon electrodes. The STM I–V curves indicate that carbon nanotubes with diameters from 2.0 to 5.1 nm have a metallic density of states. Using STM, we also observe nanometer‐size graphene sheets which are four graphite layers thick. The STM images of carbon nanotubes are in good agreement with transmission electron microscope images.

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Scanning tunneling microscopy current-voltage characteristics of carbon nanotubes

In this work, we report a method for the incorporation of rare‐earth oxides onto silicon surfaces. This process uses a high‐energy dc spark to convert salts of rare‐earth ions such as europium and erbium to the corresponding oxide phase(s) with concomitant formation of a porous layer. Scanning electron micrographs of the silicon substrate show an irregular, pitted surface morphology for those areas exposed to spark processing. Photoluminescence, infrared spectroscopy, and electron microscopy of the spark‐processed regions of the Si substrate are clearly consistent with the formation of the desired luminescent oxide phase.

Formation of rare‐earth oxide doped silicon by spark processing

Porous silicon light emitting diodes with distinct red and orange electroluminescent (EL) regions have been fabricated. Red luminescence is obtained by sonication of the as-formed orange-emitting porous silicon layers. While the red luminescence in the as-formed substrate is unstable in air or under irradiation, deposition of a thin layer of poly(9-vinyl cabazole) (PVK) by spin-coating effectively circumvents the oxidation process. The overall EL efficiency of the red and orange regions can be improved by depositing a thin film of a 1 :1 (w/w) mixture of PVK and PBD [2-(4-biphenylyl)-5-(4-tert-butyl-phenyl)-1, 3, 4-oxadiazole] on the porous Si surface.

Young Gyu Rho

Papers

Dictation of the shape of mesoscale semiconductor nanoparticle assemblies by plasmid DNA

A Comparison of Porous Silicon and Silicon Nanocrystallite Photoluminescence Quenching with Amines

Scanning tunneling microscopy current-voltage characteristics of carbon nanotubes

Formation of rare‐earth oxide doped silicon by spark processing

Fabrication of a Porous Silicon Diode Possessing Distinct Red and Orange Electroluminescent Regions