Properties of Al2O3 Thin Films Grown by PE-ALD at Low Temperature Using H2O and O2 Plasma Oxidants

Al2O3 layers with thicknesses in the 25–120 nm range were deposited by plasma enhanced atomic layer deposition at 70 °C. Trimethylaluminum was used as organometallic precursor, O2 and H2O as oxidant agents and Ar as a purge gas. The deposition cycle consisted of 50 ms TMA pulse/10 s purge time/6 s of plasma oxidation at 200 W/10 s purge time. The optical constants and thicknesses of the grown layers were determined by spectroscopic ellipsometry, while the roughness was measured by atomic force microscopy, giving RMS values in the 0.29–0.32 nm range for films deposited under different conditions and having different thicknesses. High transmittance, ~90%, was measured by UV–Vis spectroscopy. X-ray photoelectron spectroscopy revealed that, with both types of oxidants, the obtained films are close to stoichiometric composition and, with high purity, no carbon was detected. Electrical characterization showed good insulating properties of both types of films, though the H2O oxidant leads to better I-V characteristics.

Combination of Au-Ag Plasmonic Nanoparticles of Varied Compositions with Carbon Nitride for Enhanced Photocatalytic Degradation of Ibuprofen under Visible Light

Au-Ag/g-C3N4 nanohybrids 2–3 were synthesized by the one-pot self-reduction of the organometallic precursor [Au2Ag2(C6F5)4(OEt2)2]n in the presence of graphitic carbon nitride (g-C3N4), leading to two populations of alloyed Au-Ag nanoparticles (NPs) of different size and composition on the surface of g-C3N4, i.e., Ag-enriched Au-Ag NPs of smaller size and Au-enriched Au-Ag NPs of larger size. The combination of these two types of plasmonic NPs with g-C3N4 semiconductor displays enhanced photocatalytic properties towards the degradation of ibuprofen under visible light by the increased charge carrier separation provided by the inclusion of the plasmonic NPs on g-C3N4.

Facile Synthesis of Colloidal Zn3X2 (X = P, As) Quantum Dots: Transformation into (InyZn1-y)3X2 via Cation-Exchange Reactions

We firstly synthesized uniform Zn3X2 (X=P, As) quantum dots (QDs) using stable, environmentally friendly zinc precursor instead of organometallic precursor such as Me2Zn or Et2Zn, and controlled the QD size...

Improved Plasmonic Au-Ag/TiO2/rGO Photocatalyst through Entire Visible Range Absorption, Charge Separation and High Adsorption Ability.

Small size AuAg colloidal nanoparticles (AuAg NPs) are prepared through the mild decomposition of the organometallic precursor [Au2Ag2(C6F5)4(OEt2)2]n in THF, using polyvinylpirrolidone (PVP) as stabilizing polymer. These nanoparticles are directly...

Organometallic Nanoparticles Ligated by NHCs: Synthesis, Surface Chemistry and Ligand Effects

Over the last 20 years, the use of metallic nanoparticles (MNPs) in catalysis has awakened a great interest in the scientific community, mainly due to the many advantages of this kind of nanostructures in catalytic applications. MNPs exhibit the characteristic stability of heterogeneous catalysts, but with a higher active surface area than conventional metallic materials. However, despite their higher activity, MNPs present a wide variety of active sites, which makes it difficult to control their selectivity in catalytic processes. An efficient way to modulate the activity/selectivity of MNPs is the use of coordinating ligands, which transforms the MNP surface, subsequently modifying the nanoparticle catalytic properties. In relation to this, the use of N-heterocyclic carbenes (NHC) as stabilizing ligands has demonstrated to be an effective tool to modify the size, stability, solubility and catalytic reactivity of MNPs. Although NHC-stabilized MNPs can be prepared by different synthetic methods, this review is centered on those prepared by an organometallic approach. Here, an organometallic precursor is decomposed under H2 in the presence of non-stoichiometric amounts of the corresponding NHC-ligand. The resulting organometallic nanoparticles present a clean surface, which makes them perfect candidates for catalytic applications and surface studies. In short, this revision study emphasizes the great versatility of NHC ligands as MNP stabilizers, as well as their influence on catalysis.

Hydrophobically Coated Superparamagnetic Iron Oxides Nanoparticles Incorporated into Polymer-Based Nanocapsules Dispersed in Water

This paper reports the characterization of iron oxide magnetic nanoparticles obtained via the thermal decomposition of an organometallic precursor, which were then loaded into nanocapsules prepared via the emulsification process in the presence of an amphiphilic derivative of chitosan. The applied synthetic method led to the formation of a hydrophobic layer on the surface of nanoparticles that enabled their loading in the hydrophobic liquid inside of the polymer-based capsules. The average diameter of nanoparticles was determined to be equal to 15 nm, and they were thoroughly characterized using X-ray diffraction (XRD), magnetometry, and Mössbauer spectroscopy. A core–shell structure consisting of a wüstite core and maghemite-like shell was revealed, resulting in an exchange bias effect and a considerable magnetocrystalline anisotropy at low temperatures and a superparamagnetic behavior at room temperature. Importantly, superparamagnetic behavior was observed for the aqueous dispersion of the nanocapsules loaded with the superparamagnetic nanoparticles, and the dispersion was shown to be very stable (at least 48 weeks). The results were analyzed and discussed with respect to the potential future applications of these nanoparticles and nanocapsules based on biopolymers as platforms designed for the magnetically navigated transport of encapsulated hydrophobic substances.