S. Mourdikoudis

Nanocrystal engineering of noble metals and metal chalcogenides: controlling the morphology, composition and crystallinity

The term “Nanocrystal Engineering” can be defined as the design and synthesis of nanocrystals with desired morphologies and compositions based on understanding and exploitation of the nucleation and growth process. It is a key process in advancing the applications of nanomaterials including biosensing, catalysis, photonics, electronics and photovoltaics. As compared to the accomplishments of organic synthesis, we are still far from the complete understanding and experimental control over the synthesis of nanocrystals with well-defined morphology. However, the last two decades of research have resulted in excellent control over the morphology and composition of noble metal and metal chalcogenide nanocrystals. In this Highlight article, we summarize various standard protocols and recent advances for the shape-controlled synthesis of such nanocrystals. From the discussion in this article, it is clear that significant progress has been made toward the design and synthesis of nanocrystals with desired shape, crystallinity and composition by controlling the nucleation and growth process using specific synthetic protocols. We hope that this Highlight article will help researchers to follow some general rules to engineer the morphology and composition of noble metal and metal chalcogenide nanocrystals to maximise their efficiency for various applications.

Inorganic engineered nanoparticles in drinking water treatment: a critical review

This review summarizes the recent research in the field of inorganic engineered nanoparticle development with direct or potential interest for drinking water treatment. The incorporation of engineered nanoparticles into drinking water treatment technologies against the removal of heavy metals, microorganisms and organic pollutants appears as a very dynamic branch of nanotechnology. Nanoparticles owe their potential to the high specific surface area and surface reactivity compared to conventional bulk materials. Depending on the mechanism of uptake, nanoparticles can be designed to establish high selectivity against specific pollutants and provide the required efficiency for application. However, despite early encouraging results, nanoparticles meet a number of limitations to get promoted and become part of large-scale water treatment plants. The most important is their availability in the required large quantities and their efficiency to fulfil the strict regulations for drinking water consumption and environmental safety. Both deal with the particle preparation cost and the cost of treatment operation with respect to the increase in supplied water price for the consumers. Under this view, this work attempts to evaluate reported studies according to their possibility to meet the reliable requirements of water technology and also suggests an experimental approach to allow validation of tested nanoparticles.

Selective Synthesis of Cu2O and Cu/Cu2O NPs: Antifungal Activity to Yeast Saccharomyces cerevisiae and DNA Interaction

A facile selective synthesis of Cu2O and heterogeneous Cu/Cu2O nanoparticles (NPs) was achieved through a solvothermal approach by Cu(NO3)2 in proportion of three different surfactants, namely, tetraethylene glycol (TEG), oleylamine (OAm) and polyoxyethylene (20) sorbitan laurate (Tween 20). Formation aspects for the spherical Cu2O@OAm (30 nm) and Cu2O@Tween (12 nm) as well as for the core-shell and semishell Cu/Cu2O@TEG NPs (7 nm) and the Cu/Cu2O@OAm (170 nm) nanorods have been proposed. The fungistatic and fungicidal activity of the newly synthesized NPs was studied in vitro against the yeast Saccharomyces cerevisiae, which constitutes a unicellular eukaryotic model microorganism in molecular and cell biology. The antifungal results, based on optical density and fluorescence measurements, clearly indicate that the composition, size, and amount of surfactant are of key importance in the antifungal properties of the NPs. Cu2O@OAm NPs exhibited the most prominent antifungal activity with 3.73 μg/mL IC(50viability) value. The isolated DNA of S. cerevisiae cells after exposure to the NPs was investigated, and binding and/or degradation phenomena were recorded that are correlated to the size and concentration of the NPs. Their activity pathway was further explored, and reactive oxygen species production and lipid peroxidation were verified mainly for Cu2O NPs.

Palladium Nanoparticle-Loaded Cellulose Paper: A Highly Efficient, Robust, and Recyclable Self-Assembled Composite Catalytic System

We present a novel strategy based on the immobilization of palladium nanoparticles (Pd NPs) on filter paper for development of a catalytic system with high efficiency and recyclability. Oleylamine-capped Pd nanoparticles, dispersed in an organic solvent, strongly adsorb on cellulose filter paper, which shows a great ability to wick fluids due to its microfiber structure. Strong van der Waals forces and hydrophobic interactions between the particles and the substrate lead to nanoparticle immobilization, with no desorption upon further immersion in any solvent. The prepared Pd NP-loaded paper substrates were tested for several model reactions such as the oxidative homocoupling of arylboronic acids, the Suzuki cross-coupling reaction, and nitro-to-amine reduction, and they display efficient catalytic activity and excellent recyclability and reusability. This approach of using NP-loaded paper substrates as reusable catalysts is expected to open doors for new types of catalytic support for practical applications.

Morphology influence on nanoscale magnetism of Co nanoparticles: Experimental and theoretical aspects of exchange bias

Co-based nanostructures ranging from core-shell to hollow nanoparticles were produced by varying the reaction time and the chemical environment during the thermal decomposition of Co2(CO)8. Both structural characterization and kinetic model simulation illustrate that the diffusivities of Co and oxygen determine the growth ratio and the final morphology of the nanoparticles. Exchange coupling between Co and Co-oxide in core/shell nanoparticles induced a shift of field-cooled hysteresis loops that is proportional to the shell thickness, as verified by numerical studies. The increased nanocomplexity when going from core/shell to hollow particles, also leads to the appearance of hysteresis above 300 K due to an enhancement of the surface anisotropy resulting from the additional spin-disordered surfaces.

Structure and vacancy distribution in copper telluride nanoparticles influence plasmonic activity in the near-infrared

Copper chalcogenides find applications in different domains including photonics, photothermal therapy and photovoltaics. CuTe nanocrystals have been proposed as an alternative to noble metal particles for plasmonics. Although it is known that deviations from stoichiometry are a prerequisite for plasmonic activity in the near-infrared, an accurate description of the material and its (optical) properties is hindered by an insufficient understanding of the atomic structure and the influence of defects, especially for materials in their nanocrystalline form. We demonstrate that the structure of Cu1.5±xTe nanocrystals can be determined using electron diffraction tomography. Real-space high-resolution electron tomography directly reveals the three-dimensional distribution of vacancies in the structure. Through first-principles density functional theory, we furthermore demonstrate that the influence of these vacancies on the optical properties of the nanocrystals is determined. Since our methodology is applicable to a variety of crystalline nanostructured materials, it is expected to provide unique insights concerning structure–property correlations.

OXIDATION PROCESS OF Fe NANOPARTICLES

The natural oxidation process is studied in the case of 15 nm iron nanoparticles produced by the thermal decomposition of Fe(CO)5. X-ray diffraction spectra of the nanoparticles at different timescales after exposure to air revealed the instant oxidation of iron and the formation of wustite and magnetite. Wustite mainly occupies the interior of nanoparticles, as evidenced by microscopy, but is slowly transformed to a spinel structure. The shape, the dispersion and the role of surfactant were investigated by conventional microscopy and Fourier Transformed-Infrared (FT-IR) spectroscopy. Magnetic hysteresis loops confirmed the expected variation of magnetic properties till the steady state.

Real and reciprocal space electron tomography reveals structure and vacancies

Tom Willhammar1, Kadir Sentosun2, Stefanos Mourdikoudis3, Bart Goris2, Marnik Bercx2, Dirk Lamoen2, Bart Partoens2, Luis M. LizMarzan4, Sara Bals2, Gustaaf van Tendeloo2 1Department Of Materials And Environmental Chemistry, Stockholm, Sweden, 2EMAT, University of Antwerp, Antwerp, Belgium, 3Departamento de Quimica Fisica, Universidade de Vigo, Vigo, Spain, 4Bionanoplasmonics Laboratory, CIC biomaGUNE, San Sebastian, Spain E-mail: tom.willhammar@mmk.su.se