Synthesis and characterization of controlled-size CU nanoparticles

In industrial applications, synthesis of monodisperse catalyst particles is problematic, therefore the effect rising from the size in catalytic processes remain unexploited. In this work, copper nanoparticles with narrow size distribution were fabricated with a wet chemistry method, in higher temperature, under argon atmosphere. In this process, 3-15 nm copper nanoparticles were produced with controlled size. The free standing catalysts were characterized by and transmission electron microscopy, electro diffraction

Fabrication of size-controlled copper nanoparticles with different methods

The opportunity of using photocatalists in photocatalytical reactions is a very exciting and promising topic, thus it is one of the most popular and intensively growing research field in chemical sciences. Photocatalysis can give us alternative options for watersplitting and CO2 reduction. Copper particles with proper size and shape could be a good candidate for further application.1,2 In our work we introduce two different methods for syntetizing copper nanoparticles with different sizes. Our first method is a solvothermal synthesis in nitrate salt bath, the second is a solvochemical method in room temperature (~26°C), in latter case stabilizers are used. The precursors were water-soluble copper salts (C10H16CuO4, CuSO4) in each method, and the reductive components were oleylamine and NaBH4. During the experiments, we studied the effect of the temperature, reaction time and contcentrations of the components. According to our experience, size-controlling of copper nanoparticles is available with these synthesis methods. Our samples were investigated with Transmission Electron Microscopy and with Dynamic Light Scattering

Random networks of core-shell-like Cu-Cu2O/CuO nanowires as surface plasmon resonance-enhanced sensors

The rapid oxide formation on pristine unprotected copper surfaces limits the direct application of Cu nanomaterials in electronics and sensor assemblies with physical contacts. However, it is not clear whether the growing cuprous (Cu2O) and cupric oxides (CuO) and the formation of core-shell-like Cu-Cu2O/CuO nanowires would cause any compromise for non-contact optical measurements, where light absorption and subsequent charge oscillation and separation take place such as those in surface plasmon-assisted and photocatalytic processes, respectively. Therefore, we analyze how the surface potential of hydrothermally synthetized copper nanowires changes as a function of time in ambient conditions using Kelvin probe force microscopy in dark and under light illumination to reveal charge accumulation on the nanowires and on the supporting gold substrate. Further, we perform finite element modeling of the optical absorption to predict plasmonic behavior of the nanostructures. The results suggest that the core-shell-like Cu-Cu2O/CuO nanowires may be useful both in photocatalytic and in surface plasmon-enhanced processes. Here, by exploiting the latter, we show that regardless of the native surface oxide formation, random networks of the nanowires on gold substrates work as excellent amplification media for surface-enhanced Raman spectroscopy as demonstrated in sensing of Rhodamine 6G dye molecules

Study of 1.8 NM Pt nanoparticles anchored on different amorphous silica supports in ethanol decomposition reaction

1.8 nm Pt nanoparticles with narrow size distribution were anchored on mostly identical, amorphous silica supports (SBA-15 [1], MCF-17 [2], Silica Foam [3]) and were tested in ethanol decomposition reactions at < 573 K. The reaction on the Pt/SF (0.117 molecules·site-1 ·s-1 ) was ~2 times faster compared to Pt/MCF-17 (0.055 molecules·site-1 ·s-1 ) and Pt/SBA-15 (0.063 molecules·site-1 ·s-1 ) at 573 K. In the case of Pt/SBA-15, selectivity towards acetaldehyde was ~4 times higher (68%) compared to the Pt/MCF-17 (18%) and Pt/SF (16%) catalysts. In the case of Pt/MCF-17 and Pt/SF, the methane to acetaldehyde ratio was 0.27 and 0.24, respectively, while it was ~ 10 times higher (1.97) for Pt/SBA-15 catalyst. The ethene selectivity was ~2 times higher in the case of Pt/MCF-17 (0.99%) and Pt/SF (0.93%) compared to Pt/SBA-15 (0.41%). Pt/MCF17 and Pt/SBA-15 produces ~ 50% more hydrogen (~27%) compared to Pt/SF catalyst (21 %). Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) studies showed striking differences in the porosity, pore- and mesostructure, sintering and Pt-SiO2 interface altering effect of the silica supports as well as the Pt nanoparticles decorated catalysts which may have significant effect on the catalytic activity

Synthetisation and characterisation of platinum nanoparticles in a wide range of size

Discovering new alternative catalysts for (industrial) organic reactions is an important and challangeing task. Use of transition metals in these kind of reactions has had success since the begining of the 19th century. Development of nanostructure related methods can help us to enhance these reactions. This study showcases different methods that were developed for synthetising nanostructured platinum crystals in a wide range of size. (1-100nm) Production of smaller nanoparticles requires ethylene glycol as solvent, while more robust crystals can be formed in a watery solution. The process could be made either with the use of proctecting organic groups or without; these properties provide good flexibility considering the further usage of the nanoparticles. Characterisation of the nanoparticles involved measurements with Transmission Electron Microscopy and Dynamic Light Scattering, these methods have showed the monodisperse size distribution and spherical geometry of the nanocrystals

Investigation of Pt/SiO2 nanoparticles by solution and single particle mode ICP-MS

Pt/SiO2 nanocomposites (Stöber SiO2 support particles surface coated with 1.6 nm Pt nanoparticles) were analysed utilizing inductively coupled plasma mass spectrometry (ICP-MS) in the solution and single particle modes. Both analytical approaches were optimized and their performance compared in detail. The single particle ICP-MS approach proposed in this study is a novel approach for the determination of the surface concentration nanoparticles in nanocomposites

In-situ DRIFTS and NAP-XPS Exploration of the Complexity of CO2 Hydrogenation over Size Controlled Pt Nanoparticles Supported on Mesoporous NiO

4.8 nm Pt nanoparticles were anchored onto the surface of mesoporous nickel-oxide supports (NiO). Pt/NiO samples were compared to pristine NiO and Pt/SBA-15 silica catalysts in CO2 hydrogenation to form carbon-monoxide, methane and ethane at 473-673 K. 1 % Pt/NiO were ~20 times and ~1.5 times more active at 493 K compared to Pt/SBA-15 and NiO catalysts, respectively. However, the Pt-free NiO support has an activity of 120% compared to Pt/NiO catalysts at 673 K. In the case of 1% Pt/SBA-15 catalyst, selectivity towards methane was 13 %, while it was 90% and 98% for NiO and 1% Pt/NiO at 673 K, respectively. Exploration of the results of the reactions was performed by Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) as well as in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). In the case of pure NiO, we found that the surface of the support was mainly covered by elemental Ni under reaction condition, where the Ni/NiOx system is responsible for the high activity of Pt-free catalyst. In the case of Pt/NiO, Pt improves the reduction of NiOx towards metallic Ni. In the case of the 1 % Pt/NiO catalysts, the presence of limited amount of Pt resulted in an optimal quantity of oxidized Pt fraction at 673 K showing the presence of a Pt/PtOx/Ni/NiOx mixed phase where the different interfaces may be responsible for the high activity and selectivity towards methane. In the case of pure NiO under reaction condition, small amounts of formaldehyde as well as hydrogen perturbed CO [HnCO (n=1,2)] were detected. However, in the case of 1 % Pt/NiO catalysts, besides the absence of formaldehyde a significant amount of HnCO (n=2-3) was present on the surface responsible for the high activity and methane selectivity