Nanoplates/nanorods

The same approach with Ni-thiolate precursor has also successfully produced rhombohedral NiS (millerite) nanorods and triangular nanoplates with a nearly 1 1 ratio (Fig. 20.2) [5]. The lengths of nanorods are controllable through different heating conditions and range from 15 to 50 nm with aspect ratios of approximately 4. The pyrolysis temperature and the reactant concentration, when the precursor was prepared, mainly influence the rod or triangle proportions. 

One family of new materials with potential use in metal catalysis is that of metal nanostructures such as metal nanoparticles (see Metal Nanoparticles, Synthesis of and Metal Nanoparticles, Organization Applications of), nanoshells, nanowires, nanorods, nanotubes, nanobelts, and nanoplates. " For instance, it has been recently shown that Ag nanowires and nanoparticles can be produced by... 

To maximize fluorophore excitation and increase the fluorescence quantum yield, the spectral properties of the metal nanoparticles need to be optimized. While spherical colloidal nanoparticles of noble metals have been well known for many years, it is only recently that there has been an explosion of reports on the preparation and properties of anisotropically-shaped materials. As will be discussed in the following sections, a wide range of morphologies can be produced, including triangular nanoplates (nanoprisms), cubes, octahedra, nanowires, nanorods and bi-pyramids. The last few years have also seen major developments in our understanding of the growth processes involved, so that now it is possible to prepare many types of shaped p>articles in a controlled fashion. 

The term upconversion describes an effect [1] related to the emission of anti-Stokes fluorescence in the visible spectral range following excitation of certain (doped) luminophores in the near infrared (NIR). It mainly occurs with rare-earth doped solids, but also with doped transition-metal systems and combinations of both [2, 3], and relies on the sequential absorption of two or more NIR photons by the dopants. Following its discovery [1] it has been extensively studied for bulk materials both theoretically and in context with uses in solid-state lasers, infrared quantum counters, lighting or displays, and physical sensors, for example [4, 5]. Substantial efforts also have been made to prepare nanoscale materials that show more efficient upconversion emission. Meanwhile, numerous protocols are available for making nanoparticles, nanorods, nanoplates, and nanotubes. These include thermal decomposition, co-precipitation, solvothermal synthesis, combustion, and sol-gel processes [6], synthesis in liquid-solid-solutions [7, 8], and ionothermal synthesis [9]. Nanocrystal materials include oxides of zirconium and titanium, the fluorides, oxides, phosphates, oxysulfates, and oxyfluoiides of the trivalent lanthanides (Ln ), and similar compounds that may additionally contain alkaline earth ions. Wang and Liu [6] have recently reviewed the theory of upconversion and the common materials and methods used. 

Similar chemistry was used to approach 10 30nm particles of La2S3, via the solution thermolysis of La(S2CNEt2)3-phen. In this work, changes in the energy of the bandgap were attributed to a quantum size effect. When solution thermolyses of these trivalent materials were approached in the presence of air, nanoplates or nanorods of Ln202S were instead observed (Ln = Eu, Gd). ... 

Figure 5 TEM images of upconversion nanocrystals. (a), (b) Ultrasmall LaF3 Yb/Er nanoparticles prepared by Yi and Chow via coprecipitation method, (c), (d) 8-NaYF4 Yb/Er nanoparticles and nanoplates prepared by Yan et al via thermal decomposition method, (e), (f) a-NaYF4 Yb, Er nanoparticles prepared by Capobianco et al via thermal decomposition method, (g), (h) NaYF4 Yb r nanoparticles and nanorods prepared by Wang and LP via hydrothermal method. (Reproduced from Ref. 3 with permission of The Royal Society of Chemistry.)...

By thermal decomposition of the nano 2D MOCP precursors [Pb(2-pyc)(NCS)] and [Pb(3-pyc)(NCS)] (.Hpyc = pyridinecarboxylic acid) at 400°C, nanorods and nanoplates of PbS were obtained (Figure 3.4) [141]. The sizes and shapes of the nanostructures are related to the structure of the coordination polymers. An identical thermal processing on the [Pb(L4)(p3 3-NCS)(H20)] HL4 = lH-l,2,4-triazole-3-carboxylic acid) precursor has led to the formation of a mixture composed from PbS and Pb (S0 )0 nanoparticles [142]. This reveals that the composition or crystal packing of the initial MOCP may lead to different final products. 

The emerging of nanotechnology at the end of twentieth century, many new nanomaterials have been developed such as nanoparticles, nanorods, nanowires, nanotubes, and nanoplates. By using nanomaterial as reinforcing filler and incorporating it into the polymer matrix, one can obtain polymer nanocomposite. There are many review articles and textbooks devoted to this subject (Twardowski 2007 Mittal 2010, 2013). However, the researches and discussions on nanocomposites made from LCER and nanofiller are relatively few. 

At the same time, for the model catalysts, many attempts have been devoted to exploring the pure ceria as a catalyst without introducing any other element, and nanomaterials of pure ceria, including nanorods, nanoparticles, nanocubes, nanotubes, nanoplates, nanobeads, and nanowires have been prepared and studied (Bhatta et al., 2012 Hirst et al., 2009 Loschen et al., 2008 Tana et al., 2009 Wu et al., 2012 Xu et al., 2010). Lin et al. have thoroughly summarized some progresses in this field... 

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