Preparation of the CuCr2O4 spinel nanoparticles catalyst for selective oxidation of toluene to benzaldehyde
TL;DR: In this paper, the authors have shown that the size of the catalyst as well as the spinel phase plays a crucial role in the activity by favoring the oxidation of toluene.
About: This article is published in Green Chemistry.The article was published on 2014-04-22. It has received 98 citations till now. The article focuses on the topics: Catalyst support & Catalyst poisoning.
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TL;DR: The main purpose of this feature article is to highlight the possibilities of mechanochemical protocols in (nano)materials engineering for catalytic applications.
240 citations
TL;DR: In this paper, the effect of different reaction parameters like reaction temperature, H2O2 to aniline molar ratio, reaction time, and so forth have been studied in detail.
Abstract: Cationic surfactant cetyltrimethylammonium chloride-mediated hydrothermal preparation of CuCr2O4 spinel nanoparticles has been reported. This CuCr2O4 spinel nanoparticle catalyst has been characterized by XRD, XPS, SEM, TEM, TGA, and ICP-AES. Characterization results showed the formation of CuCr2O4 spinel nanoparticles with sizes between 25 and 50 nm. It was found that the catalyst can selectively convert aniline to azoxybenzene with H2O2 as oxidant. The effect of different reaction parameters like reaction temperature, H2O2 to aniline molar ratio, reaction time, and so forth have been studied in detail. An aniline conversion of 78% with azoxybenzene selectivity of 92% can be achieved over this catalyst at 70 °C. The catalyst did not show any leaching up to five reuses, showing the true heterogeneity of the catalyst. However, significant H2O2 decomposition occurs on the catalyst necessitating its usage in five-fold excess.
94 citations
TL;DR: In this article, a new synthesis strategy was developed to prepare Pt nanoparticles with size between 2 and 5 nm supported on CeO2 nanoparticles by the hydrothermal method in the presence of the surfactant cetyltrimethyl ammonium bromide and a polymer (PVP).
91 citations
TL;DR: In this paper, a heterogeneous catalysts comprising of silver nanoparticles supported on nanostructured tungsten oxide were applied for room temperature oxidative coupling of aniline to azoxybenzene.
87 citations
TL;DR: In this paper, a facile and scaled-up synthesis route to hierarchically nanostructured transition metal oxides with desirable properties is of great practical importance because of their excellent performance as heterogeneous catalysts in organic synthesis.
82 citations
References
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TL;DR: In this paper, a selfconsistent real-space multiple-scattering (RSMS) approach for calculations of x-ray-absorption near-edge structure (XANES) is presented and implemented in an ab initio code applicable to arbitrary aperiodic or periodic systems.
Abstract: A self-consistent real-space multiple-scattering (RSMS) approach for calculations of x-ray-absorption near-edge structure (XANES) is presented and implemented in an ab initio code applicable to arbitrary aperiodic or periodic systems This approach yields a quantitative interpretation of XANES based on simultaneous, self-consistent-field (SCF) calculations of local electronic structure and x-ray absorption spectra, which include full multiple scattering from atoms within a small cluster and the contributions of high-order MS from scatterers outside that cluster In addition, the code includes a SCF estimate of the Fermi energy and an account of orbital occupancy and charge transfer We also present a qualitative, scattering-theoretic interpretation of XANES Sample applications are presented for cubic BN, ${\mathrm{UF}}_{6},$ Pu hydrates, and distorted ${\mathrm{PbTiO}}_{3}$ Limitations and various extensions are also discussed
3,879 citations
TL;DR: This review highlights the recent progress in the chemical synthesis of bimetallic NCs and the control over morphology, size, composition, and structure of bimodal NCs as well as the exploration of their properties and applications.
Abstract: Bimetallic nanocrystals (NCs) with core/shell, heterostructure, or inter-metallic and alloyed structures are emerging as more important materials than monometallic NCs They are expected to display not only a combination of the properties associated with two distinct metals, but also new properties and capabilities due to a synergy between the two metals More importantly, bimetallic NCs usually show composition-dependent surface structure and atomic segregation behavior, and therefore more interesting applied potentials in various fields including electronics, engineering, and catalysis Compared with monometallic NCs, preparation of bimetallic NCs is much more complicated and difficult to be achieved In recent years, researchers from many groups have made great efforts in this area This review highlights the recent progress in the chemical synthesis of bimetallic NCs The control over morphology, size, composition, and structure of bimetallic NCs as well as the exploration of their properties and applications are discussed
983 citations
TL;DR: Two independent techniques are used to obtain the background function for the x-ray-absorption fine structure (XAFS) of pure Pb at energies that are normally inaccessible because they are in the edge, and one of the presented methods of background removal can be employed for general XAFS analysis, and is easily automated.
Abstract: Two independent techniques are used to obtain the background function for the x-ray-absorption fine structure (XAFS) of pure Pb at energies that are normally inaccessible because they are in the edge. The results of the two techniques are shown to give the same \ensuremath{\chi}(k) above a threshold energy in the absorption edge, where the background is 70% of the edge step. The reliability of the XAFS starting at unprecedentedly low k values (1.5 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$ above the Fermi energy) allows sensitive tests of several details of theoretical XAFS calculations. Electron-hole-excitation losses in addition to the plasmon-pole loss term are shown to be important, and the Hedin-Lundqvist many-body self-energy is found to be superior to that of Dirac-Hara for pure Pb. One of the presented methods of background removal can be employed for general XAFS analysis, and is easily automated.
788 citations
TL;DR: It is reported here that supported gold-palladium nanoparticles on carbon or TiO2 are active for the oxidation of the primary carbon-hydrogen bonds in toluene and related molecules, giving high selectivities to benzyl benzoate under mild solvent-free conditions.
Abstract: Selective oxidation of primary carbon-hydrogen bonds with oxygen is of crucial importance for the sustainable exploitation of available feedstocks. To date, heterogeneous catalysts have either shown low activity and/or selectivity or have required activated oxygen donors. We report here that supported gold-palladium (Au-Pd) nanoparticles on carbon or TiO2 are active for the oxidation of the primary carbon-hydrogen bonds in toluene and related molecules, giving high selectivities to benzyl benzoate under mild solvent-free conditions. Differences between the catalytic activity of the Au-Pd nanoparticles on carbon and TiO2 supports are rationalized in terms of the particle/support wetting behavior and the availability of exposed corner/edge sites.
678 citations
TL;DR: In this article, the authors show that individual lanthanide-doped upconverting nanoparticles (UCNPs) with multiple Yb3+ and Er3+ dopants exhibit bright anti-Stokes visible upconverted luminescence with exceptional photostability when excited by a 980nm continuous wave laser.
Abstract: The development of probes for single-molecule imaging has dramatically facilitated the study of individual molecules in cells and other complex environments. Single-molecule probes ideally exhibit good brightness, uninterrupted emission, resistance to photobleaching, and minimal spectral overlap with cellular autofluorescence. However, most single-molecule probes are imperfect in several of these aspects, and none have been shown to possess all of these characteristics. Here we show that individual lanthanide-doped upconverting nanoparticles (UCNPs)—specifically, hexagonal phase NaYF4 (β-NaYF4) nanocrystals with multiple Yb3+ and Er3+ dopants—emit bright anti-Stokes visible upconverted luminescence with exceptional photostability when excited by a 980-nm continuous wave laser. Individual UCNPs exhibit no on/off emission behavior, or “blinking,” down to the millisecond timescale, and no loss of intensity following an hour of continuous excitation. Amphiphilic polymer coatings permit the transfer of hydrophobic UCNPs into water, resulting in individual water-soluble nanoparticles with undiminished photophysical characteristics. These UCNPs are endocytosed by cells and show strong upconverted luminescence, with no measurable anti-Stokes background autofluorescence, suggesting that UCNPs are ideally suited for single-molecule imaging experiments.
619 citations