1,721,036 research outputs found
Plasma within templates: Molding flexible nanocrystal solids into multifunctional architectures
No full textRecently, there has been a great deal of progress in the synthesis of colloidal nanocrystals with tailored physical and chemical properties through control of size and shape, chemical composition, and surface functionalization (Alivisatos, A. P. Science 1996, 271 (5251), 933-937; Burda, C.; Chen, X. B.; Narayanan, R.; El-Sayed, M. A. Chem. Rev. 2005, 105 (4), 1025-1102). Nanocrystals are thus ideal building blocks for hierarchical self-assembly of topologically complex, multifunctional architectures with properties tuneable at each level of the hierarchy. Here, we present a method, which combines template-assisted self-assembly of nanocrystals with plasma polymerization (Cademartiri, L.; von Freymann, G.; Arsenault, A. C.; Bertolotti, J.; Wiersma, D. S.; Kitaev, V.; Ozin, G. A. Small 2005, 1 (12), 1184-1187) to realize hierarchical architectures that both retain the properties of the nanocrystals and offer multifunctionality. As examples, we describe CoFe2O4-PbS mixed nanocrystal nanorods, which photoluminesce, and align and move in unison with an applied magnetic field and PbS nanocrystal inverse opals, which emit and Bragg diffract near-infrared light. Such hierarchical nanocrystal architectures can be envisioned to spawn new nanotechnologies that integrate multiple functionalities into a single construct
Emerging strategies for the synthesis of highly monodisperse colloidal nanostructures
No full textThis short perspective describes recent developments in the synthesis of nanoscale colloids from sparingly soluble precursors. These strategies, which we dubbed 'heterogeneous nanocrystal syntheses' owing to the presence of a precursor in a non-colloidal solid state, have demonstrated the ability to generate new colloidal shapes, a superior monodispersity and a remarkable ability to delay the onset of Ostwald ripening, when compared with more traditional and purely colloidal strategies. We review the key contributions to this emerging area of research and discuss in detail the remarkable number of differences between these syntheses and the widely used homogeneous organometallic syntheses for making nanoscale colloids
Recent advances in the synthesis of colloidal nanowires
No full textWe review critically the advances in the synthesis of colloidal nanowires that have occurred over the past three years, with a focus on those that produced very thin (or "ultrathin") nanowires (similar to 2-3 nm in diameter or less). We discuss the importance of these ultrathin nanowires, especially in light of the emerging evidence of their topological properties and their potential similarities with polymers
Ultrathin Nanowires - A Materials Chemistry Perspective
No full textThe recent years have seen an explosive interest in one-dimensional nanostructures,([1]) as testified by the number of citations this field has accured; as customary, its blossoming was enabled by chemical breakthrough that allowed the reproducible and affordable synthesis of such structures. ([2,3]) The limitations of those syntheses was in the diameter of the nanowires that it could produce (hardly < 10 nm), and in the use of expensive and low-yield techniques, such as chemical vapor deposition (CVD). This paper attempts to summarize the very recent chemical breakthroughs that have allowed the production of ultrathin nanowires, often in solution, and often in gram-scale quantities. By no means is this a comprehensive coverage of the field, which can in part be found in other excellent reviews,([1,2,4-6]) but a selection of those contributions that we feel would most help put this emerging field in perspective. We will review the various synthetic strategies, their pros and cons, and we will give our best guesses as to the future directions of the field and what we can expect from it
Growth of Colloidal Nanocrystals by Liquid-Like Coalescence**
Full text linkWe here describe, model, and predict the growth kinetics of amine-capped PbS colloidal nanoparticles in the absence of supersaturation. The particles grow by coalescence rather than by Ostwald ripening. A comparison of different models indicates that the effective activation energy of coalescence (67.65 kJ mol−1) is associated with two terms: a term proportional to the contact area between the ligand shells of two colliding particles, and a constant term. Our Brownian dynamics simulations show (i) how the remarkably low activation energy (or large rate constants) are most likely due to the large difference in size between the particles and their mean free path of diffusion, and (ii) how the low polydispersity is the likely result of the suppression of collision rates between rare populations due to crowding. The model successfully predicts the growth kinetics of nanoparticles, therefore enabling the precise control of the average particle size without the need of supersaturation
Flexible One-Dimensional Nanostructures: A Review
No full textThis review discusses the recent reports on one-dimensional (1D) nanostructures with unusual flexibility. We discuss the importance that flexibility could have in future applications of nanowires and other nanostructures, and detail the two main approaches that have been followed to this day to synthesize highly flexible 1D nanostructures. One approach is based on making crystals in which one or two dimensions of the structure are comparable in size with the unit cell. Such thinness has been shown to provide unusual flexibility. The other approach conjoins hard nanostructures with flexible joints. Copyright (C) 2015, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved
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