Electrodeposition (ED) and chemical bath deposition (CBD) are both solution processing methods that assemble solid materials from molecules, ions, or complexes in solution. The reactions occur on solid surfaces to produce polycrystalline and epitaxial films, porous networks, nanorods, superlattices, and composites. Both methods can be used to produce metals, semiconductors, magnetic materials, and ceramics in a wide array of architectures. Because of the low processing temperatures (often near room temperature), the techniques are ideal for producing nanostructured materials and interfaces. The methods are not only inexpensive and relatively simple, but they can often produce materials and nanostructures that cannot be accessed in ultrahigh vacuum. For example, the shape and orientation can be tuned by controlling the pH or through solution additives. Also, in ED, the departure from equilibrium can be precisely controlled through the applied potential. This issue attempts to provide understanding of the growth mechanisms—from the molecular to final structure—of interfacial electrochemical and CBD reactions. For example, the influence of solution additives and pH and the effect of external parameters such as the applied potential will be discussed. Practical applications of these films and nanostructures include photovoltaic/photoelectrochemical cells and chemical/magnetic sensors.

Most modern electrochemical and photoelectrochemical devices (e.g., solar cells, photoelectrochemical cells, fuel cells, and batteries) are composed of polycrystalline semiconductor and metal electrodes. The shape and size of the individual crystals constituting a polycrystalline electrode as well as the overall interfacial architecture have a significant effect on the overall performance of the electrode. Therefore, a method that can precisely control electrode morphologies and provide an understanding of their effects on electrode performance is critical for producing highly efficient and cost-effective electrode materials. Electrochemical synthesis is a low-cost method that can produce a variety of materials as polycrystalline electrodes with exceptional control of their morphologies. This article reviews recently developed electrochemical synthesis strategies that produce inorganic materials with various morphological features, which have a direct impact on the material's properties. This article will serve as a good foundation for those seeking a viable electrochemical route to produce electrodes having a specifically desired morphology.

Magnetism is highly sensitive to the local atomic environment, a property that is at the origin of the unique magnetic behavior induced by the large ratio of surface or interface atoms to bulk atoms in nanostructures and ultrathin films. One key property of strong relevance in technology is interface-induced perpendicular magnetization anisotropy, which often is observed in ultrathin magnetic layers of only a few atomic planes. Establishing the existence of this phenomenon required an improved control of the growth modes, and advances in its understanding required detailed structural studies coupled with sensitive magnetic characterization. While magnetic nanostructures have been mainly realized using molecular beam epitaxy, the preparation of magnetic nanostructures in the electrolytic environment has become possible, with a degree of control that is comparable to that achieved in ultrahigh vacuum. This article reviews recent studies about epitaxial ultrathin magnetic layers electrodeposited on Au(111) single crystal electrodes with emphasis on in situ structural and magnetic characterization. This article also demonstrates that surface magnetism is very sensitive to the electrochemical interface.

Nanowires composed of noble metals are attractive candidates for chemical sensors because they are both ductile and chemically stable in air. The single application where electrodeposited metal nanowires have had the largest impact is that of hydrogen gas (H2) sensing. The development of sensitive, selective, power-efficient, rapid-responding, and inexpensive H2 sensors, for the purpose of detecting leaked H2 in proximity to devices such as fuel cells, is an active area of research. In this application, a change in the dc electrical resistance of the nanowire from its background value signals the presence of H2 and provides an estimate of its concentration. Two types of nanowires have been studied for use as hydrogen sensors: Electrodeposited nanowires composed of pure palladium metal (Pd) reversibly absorb hydrogen to form a hydride according to Pd + xH2 → PdH2x. Alternatively, nanowires that transduce the presence of H2 may be prepared by decorating an inert, electrically conductive support such as a carbon nanotube or a nickel nanowire with one or more eletrodeposited palladium nanoparticles. These palladium nanoparticles impart selectivity to H2 and cause the electrical conductivity of the composite particle/support to be modulated in the presence of H2. Here we summarize recent contributions of electrodeposition to the development of nanowire-based sensors for H2.

This article discusses the state of the art of solution growth of ZnO films and nanostructures. Chemical bath deposition (CBD), hydrothermal deposition, and electrodeposition (ED) are presented, where the interplay between experimental parameters and film properties can be highlighted. All of the methods allow the growth of ZnO with high structural quality and morphologies ranging from nanorods to dense films to nanoporous structures. The growth appears to be controlled by heterogeneous nucleation in supersaturated solutions, in the bulk for CBD, and at the interface for ED. Various emerging applications are presented, from light-emitting devices to solar cells and piezoelectric microgenerators.

Epitaxial thin films of semiconductor materials are mostly formed on single crystal substrates using physical and chemical vapor phase deposition techniques. This article focuses on a much less common technique for synthesis of epitaxial thin films, chemical bath deposition (CBD) from solution, which offers a simple, inexpensive, and scalable alternative. One of the major advantages of CBD is in sequential processing, where low deposition temperatures help minimize interdiffusion. We outline the CBD pathway to epitaxial semiconductor films and provide examples for well-defined orientation relationships between film and substrate pairs in a variety of epitaxial systems. The influence of the chemical nature, structure, and orientation of the substrate on the incipient films is outlined, as well as the effect of parameters such as solution composition, bath temperature, and pH for controlling the film morphology and its consequent physical properties.

Arrays of cross-reactive sensors for the detection of multi-component chemical and biological agents have been actively developed during the past two decades. The rapid progress in this field has been driven by the need for fast online detection of a wide range of chemical and biological compounds and mixtures in different branches of industry and in medicine. Nanomaterials are ideal base materials for such sensor arrays because they are chemically versatile, can easily be fabricated, and can be integrated into existing sensing platforms to increase the sensitivity to the target agents. We present a concise though non-exhaustive didactic review of the main concepts and approaches related to the use of nanomaterials in cross-reactive sensor arrays. We focus on electronic transducers incorporating the most important classes of nanomaterials: molecularly modified metal nanoparticles, metal oxide nanoparticles, carbon nanotubes, and semiconducting nanowires. Selected examples of their integration into sensors and sensor arrays are given. We conclude with a brief discussion of the possibilities that the integration of the different types of nanomaterials into sensor arrays offer and the expected limitations.