Atomic layer deposition (ALD) has recently become the method of choice for the semiconductor industry to conformally process extremely thin insulating layers (high‐k oxides) onto large‐area silicon substrates. ALD is also a key technology for the surface modification of complex nanostructured materials. After briefly introducing ALD, this Review will focus on the various aspects of nanomaterials and their processing by ALD, including nanopores, nanowires and ‐tubes, nanopatterning and nanolaminates as well as low‐temperature ALD for organic nanostructures and biomaterials. Finally, selected examples will be given of device applications, illustrating recent innovative approaches of how ALD can be used in nanotechnology.

Mid-infrared spectroscopy is a widely used tool for material identification and secondary structure analysis in chemistry, biology and biochemistry. However, the diffraction limit prevents nanoscale protein studies. Here we introduce mapping of protein structure with 30 nm lateral resolution and sensitivity to individual protein complexes by Fourier transform infrared nanospectroscopy (nano-FTIR). We present local broadband spectra of one virus, ferritin complexes, purple membranes and insulin aggregates, which can be interpreted in terms of their α-helical and/or β-sheet structure. Applying nano-FTIR for studying insulin fibrils—a model system widely used in neurodegenerative disease research—we find clear evidence that 3-nm-thin amyloid-like fibrils contain a large amount of α-helical structure. This reveals the surprisingly high level of protein organization in the fibril’s periphery, which might explain why fibrils associate. We envision a wide application potential of nano-FTIR, including cellular receptor in vitro mapping and analysis of proteins within quaternary structures.

In nature, tiny amounts of inorganic impurities, such as metals, are incorporated in the protein structures of some biomaterials and lead to unusual mechanical properties of those materials. A desire to produce these biomimicking new materials has stimulated materials scientists, and diverse approaches have been attempted. In contrast, research to improve the mechanical properties of biomaterials themselves by direct metal incorporation into inner protein structures has rarely been tried because of the difficulty of developing a method that can infiltrate metals into biomaterials, resulting in a metal-incorporated protein matrix. We demonstrated that metals can be intentionally infiltrated into inner protein structures of biomaterials through multiple pulsed vapor-phase infiltration performed with equipment conventionally used for atomic layer deposition (ALD). We infiltrated zinc (Zn), titanium (Ti), or aluminum (Al), combined with water from corresponding ALD precursors, into spider dragline silks and observed greatly improved toughness of the resulting silks. The presence of the infiltrated metals such as Al or Ti was verified by energy-dispersive x-ray (EDX) and nuclear magnetic resonance spectra measured inside the treated silks. This result of enhanced toughness of spider silk could potentially serve as a model for a more general approach to enhance the strength and toughness of other biomaterials.

Large biomolecules are attractive templates for the synthesis of metal 1-7 and inorganic 8-10 compound nanostructures. The well-defined chemical and structural heterogeneity of the biotemplates can be exploited for the precise control of the size and shape of the formed nanostructures. Here, we demonstrate that the central channel of the tobacco mosaic virus (TMV) can be used as a template to synthesize nickel and cobalt nanowires only a few atoms in diameter, with lengths up to the micrometer range.A key issue in nanotechnology is the development of conceptually simple construction techniques for the mass fabrication of identical nanoscale structures. Conventional "top-down" fabrication techniques are both energy-intensive and wasteful because many production steps involve depositing unstructured layers and then patterning them by removing most of the deposited films. Furthermore, increasingly expensive fabrication facilities are required as the feature size decreases. The natural alternative to top-down construction is the "bottom-up" approach, in which nanoscale structures are built from their atomic and molecular constituents by self-assembly. This approach relies on the exploitation of specific intermolecular interactions and is one of the key building principles of all living organisms. It is thus obvious to search for biological structures that can be used as templates for directing the self-assembly. An ideal biological nano-object for this purpose is the tobacco mosaic virus (TMV), which is a very stable tube-shaped complex of a helical RNA composed of ca. 6400 bases and 2130 identical coat proteins. The rigid virion is 300 nm long, but linear head-to-tail aggregation results in oligomers with lengths of 600, 900 nm, and so forth.11 TMV has an outer diameter of 18 nm; a central channel with a diameter of 4 nm is clad by flexible loops of the protein structure. TMV is thus a perfect molecular nanocylinder. The well-defined chemical groups at specific locations of the coat proteins can act as ligands for metal ions. We use this chemical functionality for the growth of metal wires from metal ion solutions. TMV is first activated by the selective binding of Pd(II) or Pt(II) ions, followed by metallization with boranecontaining nickel and cobalt solutions. Nickel and cobalt wires (3 nm wide) with lengths of up to 600 nm grow selectively in the central channel.To produce TMV, which is harmless to mammals, we infected Nicotiana tabacum cv. Samsun nn plants with plasmid DNA that comprised the code for the movement and coat protein of the TMV genome as well for the replicase. Systemically infected leaves were harvested, and virions were isolated by standard methods. Each virion is composed of the RNA, a helix with an 8-nm diameter, and the coat proteins that are arranged in a helical fashion. The RNA bases fit into pockets in the coat protein structure. Both the outer surface and the channel cladding are hydrophilic, as seen by the presence of water molecules 12 and by the adsorption properties. The oute...