Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

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Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

Digital processing of speech signals

Persistent organic pollutants (POPs) are carbon-based chemical substances that are resistant to environmental degradation and may not be completely removed through treatment processes. Their persistence can contribute to adverse health impacts on wild-life and human beings. Thus, the solar photocatalysis process has received increasing attention due to its great potential as a green and eco-friendly process for the elimination of POPs to increase the security of clean water. In this context, ZnO nanostructures have been shown to be prominent photocatalyst candidates to be used in photodegradation owing to the facts that they are low-cost, non-toxic and more efficient in the absorption across a large fraction of the solar spectrum compared to TiO 2 . There are several aspects, however, need to be taken into consideration for further development. The purpose of this paper is to review the photo-degradation mechanisms of POPs and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnO as a photocatalyst. The second objective of this review is to evaluate the immobilization of photocatalyst and suspension systems while looking into their future challenges and prospects.

A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications

Ink-jet printing is a method for directly patterning and fabricating patterns without the need for masks. To achieve this, the fluids used as inks must have the capability of being stably and accurately printed by ink-jetting. We have investigated the inter-relationship between ink-jet printability and physical fluid properties by monitoring droplet formation dynamics. The printability of the fluids was determined using the inverse (Z) of the Ohnesorge number (Oh) which relates to the viscosity, surface tension, and density of the fluid. We have experimentally defined the printable range as 4 ≤ Z ≤ 14 by considering characteristics such as single droplet formability, positional accuracy, and maximum allowable jetting frequency.

Influence of fluid physical properties on ink-jet printability.

Synthesis and size control of monodisperse copper nanoparticles by polyol method.

Direct writing of copper conductive patterns by ink-jet printing

With the aim of preparing a high performance conductive ink, we sought to control the surface chemistry of Cu nanoparticles so as to minimize surface oxidation. Specifically, the surface oxide layer on Cu nanoparticles synthesized in ambient atmosphere was minimized by adjusting the molecular weight of poly(N-vinylpyrrolidone) capping molecules, as confirmed by high resolution transmission electron microscopy and X-ray photoelectron spectroscopy analyses. In addition, we demonstrate that by minimizing the thickness of the surface oxide layer, Cu granular films with good conductivity could be obtained by sintering nanoparticle assembles. Finally, we fabricated highly conductive Cu patterns on a plastic substrate by ink-jet printing.

Controlling the Thickness of the Surface Oxide Layer on Cu Nanoparticles for the Fabrication of Conductive Structures by Ink‐Jet Printing

Spherical silver nanoparticles with various sizes and standard deviations were synthesized by the polyol process Two different synthesis methods were compared in order to investigate the influence of reaction parameters on the resulting particle size and its distribution In the precursor heating method, wherein a solution containing silver nitrate was heated to the reaction temperature, the ramping rate was determined to be a critical parameter affecting the particle size In contrast, in the precursor injection method, in which a silver nitrate aqueous solution was injected into hot ethylene glycol, because of rapid nucleation, the injection rate and the reaction temperature were important factors in terms of reducing the particle size and attaining monodispersity Silver nanoparticles with a size of 17 ? 2?nm were obtained at an injection rate of 25?ml?s?1 and a reaction temperature of 100??C

https://iopscience.iop.org/article/10.1088/0957-4484/17/16/004/pdf

Dongjo Kim

Papers

Influence of fluid physical properties on ink-jet printability.

Synthesis and size control of monodisperse copper nanoparticles by polyol method.

Direct writing of copper conductive patterns by ink-jet printing

Controlling the Thickness of the Surface Oxide Layer on Cu Nanoparticles for the Fabrication of Conductive Structures by Ink‐Jet Printing

Synthesis of silver nanoparticles using the polyol process and the influence of precursor injection.