Structure Sensitivity of Carbon-Nitrogen Ring Opening: Impact of Platinum Particle Size from below 1 to 5 nm upon Pyrrole Hydrogenation Product Selectivity over Monodisperse Platinum Nanoparticles Loaded onto Mesoporous Silica
Well-defined platinum nanoparticles between 0.8 and 5.0 nm were prepared using dendrimer and polymer capping agents and supported onto mesoporous SBA-15 silica. Using these model catalysts, pyrrole hydrogenation was demonstrated to be structure sensitive because ring opening occurred more easily over larger particles compared to smaller ones. The phenomenon is caused by surface roughness or electronic effects that change with particle size.
"From this image, the average particle size and a distribution were determined to be 2.84 ± 0.61 nm by measuring the size of 100 particles and statistically analysing the resulting histograms. This particle size and deviation agreed with the literature results     for this synthesis approach. "
[Show abstract][Hide abstract] ABSTRACT: Pt nanoparticles/TiO2 catalysts were prepared and evaluated for UV-photocatalytic degradation ofphenol and 2-chlorophenol (2-CP) in synthetic wastewater solutions. The catalysts were synthesized by immobilizing colloidal Pt nanoparticles onto titanium dioxide (rutile TiO2). Analytical techniques, such as standard Brunauer-Emmett-Teller isotherms, X-ray diffraction, transmission electron microscope, were utillized for investigating the specific surface area, structure, and particle size distribution of the catalysts and its components. The photocatalytic activities of both phenol and 2-CP solutions were studied in a 1L batch photoreactor independently, under 450 W UV irradiation. Samples were drawn at regular intervals and residual concentration of phenol and 2-CP in the samples was analysed using an UV-visible spectrophotometer. Parameters controlling the photocatalytic process, including catalyst concentration, solution pH, and initial phenol (2-CP) concentration, were investigated. The obtained results revealed that Pt/TiO2 showed higher photocatalytic degradation for both phenol and 2-CP pollutants in solution (as compared to the rutile TiO2). The degradation efficiencies of 87.7% and 100% were obtained for phenol and 2-CP, respectively, under optimized conditions (0.5 g/L catalyst with a pollutant concentration of 50 mg/L after irradiation time of 180 min).
[Show abstract][Hide abstract] ABSTRACT: Methods for synthesizing metal, metal oxide, and metal halide nanoparticles (NPs) in the presence of dendrimers and dendrons
are discussed in this review. There are numerous reviews describing dendrimers and their properties and applications in various
areas of nanotechnologies, which indicates the growing interest of researchers in this unique class of monodisperse and highly
branched macromolecules with highly ordered and controlled structures. The special magnetic, optical, and electronic properties
of dendrimer (dendron) nanocomposites with NPs determine their prospects for application in medicine [54–58], in catalysis
[32, 58–60], as molecular sensors [61–65], etc. Dendrimers successfully stabilize NPs, playing the role of a template (i.e.,
NPs are formed inside the dendrimer) or surfactants. In the latter case, dendrimers are stabilizing molecules, so the NPs
are formed between the dendrimers. Functional dendrons can be also used as stabilizing molecules (1) directly during NP formation
or (2) upon the subsequent functionalization of NPs via the replacement of the initial surfactants with dendrons. The unique
advantages of dendrimers are completely fulfilled in those cases when the dendrimer design or reaction conditions allow either
(1) the formation of very small NP sizes (for example, functional nanoclusters of gold and silver) or (2) control of the NP
sizes, when dendrimer generation or other conditions vary, allowing one to control the properties of nanocomposites. Because
the dendrimer (dendron) structure strongly differs from the structure of traditional surfactants, this leads to an opportunity
of the targeted variation of solubility, functionality, and morphology of the nanocomposites based on dendrimers (dendrons)
even when a dendrimer (dendron) plays the role of a surfactant.
Nanotechnologies in Russia 10/2009; 4(9):576-608. DOI:10.1134/S1995078009090031
[Show abstract][Hide abstract] ABSTRACT: A novel copper-mediated solvothermal method was proposed for synthesizing colloidal spheres of a new composition, palladium
iodide (PdI2). Typical procedure was designed to involve the introduction of cupric chloride (CuCl2) as weak oxidant. CuCl2 was found to be essential for preventing the easy formation of palladium deposits as well as facilitating the synthesis and
assembly. Under the co-effect of CuCl2 and the surfactant of polyvinylpyrrolidone (PVP), neutral PdI2 colloidal spheres with narrow size distribution were successfully produced. Such ion-assisted synthetic method is believed
to be prospective in producing well-constructed nanostructures.
Keywordscolloidal sphere–palladium iodide–copper-mediated synthesis–solvothermal method–self-assembly
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