High-boiling Organic Solvents Research Articles

A new look at metal–carbon hybrids: Molecular-scale study of covalently grafted gold

The reliable integration of new nanocarbons in future molecular and hybrid electronics requires mastery of chemical binding between dissimilar materials down to the individual bond. Here, we present a detailed study of covalent grafting of aryl radicals on single crystal Au(111), and investigate their electrochemical stability and oxidative desorption. Copper underpotential deposition and Gaussian deconvolution of its current–potential trace are used to map the thermodynamic and kinetic landscape of the modified Au surface. Scanning tunnelling microscopy in a high-boiling organic solvent suggests that grafting is accompanied by vacancy island formation on the Au surface, while iodide adsorption heals these vacancies and allows high-contrast imaging of individual covalent grafts.

Increasing the Particle Size and Magnetic Property of Iron Oxide Nanoparticles through a Segregated Nucleation and Growth Process.

Iron oxide nanoparticles (IONs) with good water dispersibility were prepared by the thermal decomposition of iron acetylacetonate (Fe(acac)3) in the high-boiling organic solvent polyethylene glycol (PEG) using polyethyleneimine (PEI) as a modifier. The nucleation and growth processes of the crystals were separated during the reaction process by batch additions of the reaction material, which could inhibit the nucleation but maintain the crystal growth, and products with larger particle sizes and high saturation magnetization were obtained. The method of batch addition of the reactant prepared IONs with the largest particle size and the highest saturation magnetization compared with IONs reported using PEG as the reaction solvent. The IONs prepared by this method also retained good water dispersibility. Therefore, these IONs are potentially suitable for the magnetic separation of cells, proteins, or nucleic acids when large magnetic responses are needed.

Eco-friendly preparation of polyimide/boron nitride composite films with excellent thermal conductivity and mechanical properties

Polyimide/hexagonal boron nitride (PI/BN) composite films have attracted interest as heat dissipation materials for advanced microelectronic devices. However, conventional preparations of PI/BN composite films employ harmful and expensive high-boiling organic solvents. In this work, thermally conductive PI/BN composite films were, for the first time, prepared using a nontoxic, eco-friendly, and inexpensive aqueous solvent. BN was ultrasonically exfoliated in a mixed solvent of water and tert-butanol to obtain aqueous BN suspensions, in which a poly(amic acid) salt (PAAS) was synthesized. The PAAS/BN suspensions were then drop-casted, and thermally imidized into PI/BN composite films. The PI/BN films exhibited excellent in-plane and out-of-plane thermal conductivities (up to 15.043 W/mK and 1.142 W/mK, respectively), which is attributed to the effective exfoliation and dispersion of BN in the aqueous solvent. Furthermore, these films exhibited high tensile strength, flexibility, and thermal stability.

Solid-state nickel(0)-mediated Yamamoto coupling enabled by mechanochemistry

Abstract Herein, we report the first solid-state protocol for nickel(0)-mediated Yamamoto-coupling reactions using ball milling. A variety of aryl halides reacted efficiently in the presence of bis(cyclooctadiene)nickel(0) [Ni(cod)2] and 4,4'-di-tert-butyl-2,2'-bipyridyl under solid-state mechanochemical conditions, affording the corresponding biaryls in high yields. Considering that potentially harmful and high-boiling organic solvents are not required, the present study provides a more convenient, environmentally friendly, and sustainable alternative to conventional solution-based Yamamoto coupling. Solid-state Yamamoto-coupling polymerization and the development of a catalytic variant are also described.

Recycling of PFSA-Based Membranes and Their Re-Application in PEM Fuel Cells

The commercialization of PEM fuel cells offers a promising opportunity to overcome our dependence on fossil fuels and provides an attractive alternative for automotive and stationary power applications.[1] However, PEMFCs are still costly in production, with the main cost factor due to the fabrication of the perfluorosulfonic acid (PFSA)-based proton exchange membrane and the noble metal catalysts.[2,3] Recycling of these components could increase the economic attractiveness of PEMFCs. However, while the high resistance of the ionomer membrane to thermal and chemical degradation is favorable for their use in fuel cells, it also makes membrane recycling a major challenge.Here, we present a newly developed recycling strategy to recover PFSA-based membranes after operation by a hydrothermal treatment. Both short side chain (SSC) and long side chain (LSC) ionomers with EWs of 800 and 1000 were investigated. In contrast to previously published methods, we were able to recover the PFSA ionomer by using water instead of high-boiling organic solvents, such as DMF or DMSO.[4,5] The recycled membranes were obtained from the recycled PFSA ionomer solution by doctor-blading. They were investigated by in-situ Raman techniques for studying the water uptake and analyzed by IR and small-angle X-ray scattering (SAXS) techniques to get a more detailed insight into their morphology. In single cell tests at standard (80 °C) and enhanced (up to 130 °C) PEMFC operating temperatures, the recycled membranes showed an increased cell performance as compared to the pristine 3M-800EW membrane. Solid-state NMR measurements confirmed that no chemical changes in the membrane occurred due to the heat-treatment process.We assume that the observed performance boost can be attributed to an increased water uptake and retention. Furthermore, a change in the polymer matrix formation may be responsible for the observed behavior, which led to an expanded water filled channel structure, where water can accumulate to facilitate proton diffusion as H3O+ through the channels. To confirm this assumption, the morphology of the recycled membranes will be investigated by in situ SAXS measurements at different temperatures and degrees of hydration.[1] I. Staffell, D. Scamman, A. Velazquez Abad, P. Balcombe, P. E. Dodds, P. Ekins, N. Shah, K. R. Ward, Energy Environ. Sci. 2019, 12, 463–491.[2] J. Fan, M. Chen, Z. Zhao, Z. Zhang, S. Ye, S. Xu, H. Wang, H. Li, Nat. Energy 2021, 6, 475–486.[3] D. Papageorgopoulos, Fuel Cell R&D Overview. 2019 Annual Merit Review and Peer Evaluation Meeting, 2019.[4] Q. Xu, X. Chen, S. Wang, C. Guo, Y. Niu, R. Zuo, Z. Yang, Y. Zhou, C. Xu, Energies 2022, 15, 8717.[5] H. F. Xu, X. Wang, Z. G. Shao, I. M. Hsing, J. Appl. Electrochem. 2002, 32, 1337–1340.

Synthesis of Sandwiched Composite Nanomagnets by Epitaxial Growth of Fe3O4 Layers on SrFe10Cr2O19 Nanoplates in High-Boiling Organic Solvent

Herein, we demonstrate the synthesis of sandwiched composite nanomagnets, which consist of hard magnetic Cr-substituted hexaferrite cores and magnetite outer layers. The hexaferrite plate-like nanoparticles, with average dimensions of 36.3 nm × 5.2 nm, were prepared via a glass crystallization method and were covered by spinel-type iron oxide via thermal decomposition of iron acetylacetonate in a hexadecane solution. The hexaferrite nanoplates act as seeds for the epitaxial growth of the magnetite, which results in uniform continuous outer layers on both sides. The thickness of the layers can be adjusted by controlling the concentration of metal ions. In this way, layers with an average thickness of 3.7 and 4.9 nm were obtained. Due to an atomically smooth interface, the magnetic composites demonstrate the exchange coupling effect, acting as single phases during remagnetization. The developed approach can be applied to any spinel-type material with matching lattice parameters and opens the way to expand the performance of hexaferrite nanomagnets due to a combination of various functional properties.

WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

Solvent‐free Reactions for the Synthesis of Indolenine‐based Squaraines and Croconaines: Comparison of Thermal Heating, Mechanochemical Milling, and IR Irradiation

Squaraines and croconaines are organic dyes characterized by intense absorption in the visible or near-infrared spectral regions with applications ranging from biology to material sciences. They are commonly synthesized by condensation reactions of oxocarbonic acids (squaric or croconic acid, respectively) with electron-rich aromatic compounds in high-boiling organic solvents. Here, a simple, cost-effective, and environmentally benign process was developed for the synthesis of indolenine-based squaraines and croconaines under solvent-free conditions. Protocols based on conventional thermal heating, mechanochemical milling, and IR-light activation were compared.

(Invited) Design of Catalyst Layer Structure for High Fuel Cell Performance

The low Pt electrode is an important research topic for the commercialization of polymer electrolyte fuel cell (PEFC). Platinum nanoparticles act as a catalyst for the fuel cell electrode and promote the oxygen reduction reaction (ORR). In this process, the surface properties and structure of adjacent carbon supports and ionomer binders greatly affect the Pt catalyst. Therefore, the performance of the Pt/C catalyst in the fuel cell electrode is determined not only by the intrinsic activity of the catalyst itself, but also by the interface structure between the ionomer binder and the Pt/C catalyst. It has been reported that the ORR activity of the Pt/C catalyst in the fuel cell electrode is affected by the Pt poisoning of the sulfonic acid group tethered to the Nafion backbone as well as the oxygen permeability of the ionomer binder [1]. The difference in pore characteristics of the carbon support affects the optimum ionomer content [2] and Pt utilizaton [3] in the electrode. The surface properties of the carbon support also affect ionomer distribution and ionomer thickness on the catalyst surface, thereby altering the activity of the catalyst [4]. In spite of recent studies, understanding of complicated physicochemical phenomena in the microstructure of electrode is still very limited. In this talk, we will discuss the fuel cell performance characteristics based on several electrochemical analyses according to the microstructure control of the catalyst layer. Various functional groups were introduced on the surface of Pt/C catalyst by post treatment and the catalyst layer was prepared to observe the ionomer distribution and ion transport characteristics according to functional groups. In addition, a multilayer catalyst layer having different ionomer contents in the thickness direction of the catalyst layer was prepared using an ultrasonic spraying process, and changes in hydrogen ion transfer and oxygen diffusion transfer characteristics in these catalyst layers were observed in a fuel cell. Finally, the electrochemical properties of the catalyst layer made of the ionomer dispersed in the high-boiling organic solvent will be introduced. 1. V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, A. Kongkanand, ACS Energy Lett. 3 (2018) 618. 2. Y. Liu, C. Ji, W. Gu, J. Jorne, H. A. Gasteiger, J. Electrochem. Soc. 158(6) (2011) B614. 3. Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources 315 (2016) 179. 4. A. Orfanidi, P. Madkikar, H. A. El-Sayed, G. S. Harzer, T. Kratky, H. A. Gasteiger, J. Electrochem. Soc. 164 (2017) F418.

Ionic liquid as a green solvent for ionothermal synthesis of 2D keto-enamine-linked covalent organic frameworks

Abstract Covalent organic frameworks (COFs) are usually synthesized under solvothermal conditions in a mixture of high-boiling organic solvents in a sealed system. By using a room temperature ionic liquid (IL) as a solvent, we presented the preparation of two-dimensional (2D) keto-enamine-linked COFs in an open container at ambient pressure. The as-synthesized 2D keto-enamine-linked COFs have ordered open channels and so the IL can be completely removed from the pores to provide the sole formation of crystalline 2D COFs. Not only the imidazolium-based IL acted as both solvent and catalyst, it was also recycled for further use without activity loss.

Synthesis and optical properties of AgInS2 nanoparticles

Ternary chalcogenide Ag-In quantum dots (QDs) are more environmentally friendly than known Cd-, Pb- and P-containing nanoparticles. Here we review the literature on colloidal synthesis methods, properties, and promising fields for the application of AgInS2 quantum dots. Similar to the QDs of lead and cadmium chalcogenides, the most accurate control over the structure and morphology of AgInS2 QDs is achieved by using the method of introducing precursors into high-boiling organic solvents. However, to realize the potential applications of ternary quantum dots, in particular as luminescent biomarkers, the quantum dots must be soluble in polar solvents, especially water. The transfer of quantum dots into aqueous solutions is usually accomplished by exchanging primary lyophilic ligands with smaller bifunctional molecules, such as thioglycolic (or mercapto­propionic) acids, which can passivate the surface of the quantum dots while making them soluble in the polar environment. Methods of colloidal synthesis of AgInS2 / ZnS quantum dots can be classified into the following types: Injection of ions into a high-boiling solvent Synthesis in a mixture of solvents Synthesis in the aquatic environment Methods for the synthesis of AgInS2 QDs in both aqueous solution and organic solvent medium are described. Examples of application of quantum dots for biomedical purposes and in photovoltaic and sensory devices are given. Quantum dots have high photostability and brightness, are characterized by a wide range of absorption and narrow spectral bands of radiation, ie meet most of the criteria for fluorescent materials and biosensors for imaging cancer cells in antitumor therapy, immunofluorescent labeling of proteins, detection of toxins s, visualize intracellular structures, etc. Quantum dots of tertiary chalcogenides, in particular CuInS2 and AgInS2, may be an alternative to quantum dots of binary lead and cadmium chalcogenides for use in light-emitting and light-absorbing systems, such as LEDs, sensors and solar absorbers.

Controlling the Morphology of Au-Pd Heterodimer Nanoparticles by Surface Ligands.

Controlling the morphology of noble-metal nanoparticles is mandatory to tune specific properties such as catalytic and optical behavior. Heterodimers consisting of two noble metals have been synthesized, so far mostly in aqueous media using selective surfactants or chemical etching strategies. We report a facile synthesis for Au@Pd and Pd@Au heterodimer nanoparticles (NPs) with morphologies ranging from segregated domains (heteroparticles) to core-shell structures by applying a seed-mediated growth process with Au and Pd seed nanoparticles in 1-octadecene (ODE), which is a high-boiling organic solvent. The as-synthesized oleylamine (OAm) functionalized Au NPs led to the formation of OAm-Au@Pd heteroparticles with a "windmill" morphology, having an Au core and Pd "blades". The multiply twinned structure of the Au seed particles (⌀ ≈ 9-11 nm) is associated with a reduced barrier for heterogeneous nucleation. This leads to island growth of bimetallic Au@Pd heteroparticles with less-regular morphologies. The reaction process can be controlled by tuning the surface chemistry with organic ligands. Functionalization of Au NPs (Ø ≈ 9-11 nm) with 1-octadecanethiol (ODT) led to the formation of ODT-Au@Pd NPs with a closed Pd shell through a strong ligand-metal binding, which is accompanied by a redistribution of the electron density. Experiments with varied Pd content revealed surface epitaxial growth of Pd on Au. For OAm-Pd and ODT-Pd seed particles, faceted, Au-rich domain NPs and impeded core-shell NPs were obtained, respectively. This is related to the high surface energy of the small Pd seed particles (⌀ ≈ 5-7 nm). The metal distribution of all bimetallic NPs was analyzed by extended (aberration-corrected) transmission electron microscopy (HR-TEM, HAADF-STEM, EDX mapping, ED). The Au and Pd NPs, as well as the ODT-Au@Pd and OAm-Pd@Au heteroparticles, catalyze the reduction of 4-nitrophenol to 4-aminophenol with borohydride. The catalytic activity is dictated by the particle structure. OAm-Au@Pd heteroparticles with faceted Au domains had the highest activity because of a mixed Au-Pd surface structure, while ODT-Au@Pd NPs, where the active Au core is covered by a Pd shell, had the lowest activity.

Phase Directing Ability of an Ionic Liquid Solvent for the Synthesis of HER-Active Ni2P Nanocrystals

An ionic liquid (IL) solvent was used to synthesize small, phase-pure nickel phosphide (Ni2P) nanocrystals. In contrast, under analogous reaction conditions, substitution of the IL for the common high-boiling organic solvent 1-octadecene (ODE) results in phase-impure nanocrystals. The 5 nm Ni2P nanocrystals prepared in IL were electrocatalytically active toward the hydrogen evolution reaction. The synthesis in IL was also extended to alloyed Ni2–xCoxP nanocrystals, where 0.5 ≤ x ≤ 1.5.

Phthalocyanine-Conjugated Upconversion NaYF4 :Yb3+ /Er3+ @SiO2 Nanospheres for NIR-Triggered Photodynamic Therapy in a Tumor Mouse Model.

Photodynamic therapy (PDT) has garnered immense attention as a minimally invasive clinical treatment modality for malignant cancers. However, its low penetration depth and photodamage of living tissues by UV and visible light, which activate a photosensitizer, limit the application of PDT. In this study, monodisperse NaYF4 :Yb3+ /Er3+ nanospheres 20 nm in diameter, that serve as near-infrared (NIR)-to-visible light converters and activators of a photosensitizer, were synthesized by high-temperature co-precipitation of lanthanide chlorides in a high-boiling organic solvent (octadec-1-ene). The nanoparticles were coated with a thin shell (≈3 nm) of homogenous silica via the hydrolysis and condensation of tetramethyl orthosilicate. The NaYF4 :Yb3+ /Er3+ @SiO2 particles were further functionalized by methacrylate-terminated groups via 3-(trimethoxysilyl)propyl methacrylate. To introduce a large number of reactive amino groups on the particle surface, methacrylate-terminated NaYF4 :Yb3+ /Er3+ @SiO2 nanospheres were modified with a branched polyethyleneimine (PEI) via Michael addition. Aluminum carboxyphthalocyanine (Al Pc-COOH) was then conjugated to NaYF4 :Yb3+ /Er3+ @SiO2 -PEI nanospheres via carbodiimide chemistry. The resulting NaYF4 :Yb3+ /Er3+ @SiO2 -PEI-Pc particles were finally modified with succinimidyl ester of poly(ethylene glycol) (PEG) in order to alleviate their future uptake by the reticuloendothelial system. Upon 980 nm irradiation, the intensive red emission of NaYF4 :Yb3+ /Er3+ @SiO2 -PEI-Pc-PEG nanoparticles completely vanished, indicating efficient energy transfer from the nanoparticles to Al Pc-COOH, which generates singlet oxygen (1 O2 ). Last but not least, NaYF4 :Yb3+ /Er3+ @SiO2 -PEI-Pc-PEG nanospheres were intratumorally administered into mammary carcinoma MDA-MB-231 growing subcutaneously in athymic nude mice. Extensive necrosis developed at the tumor site of all mice 24-48 h after irradiation by laser at 980 nm wavelength. The results demonstrate that the NaYF4 :Yb3+ /Er3+ @SiO2 -PEI-Pc-PEG nanospheres have great potential as a novel NIR-triggered PDT nanoplatform for deep-tissue cancer therapy.

Preparation of metal selenide nanocrystals with hot-injection method

Nanomaterials have received extensive and growing research interests due to their unique properties and potential applications in various fields. They have contributed immensely to modern materials science and technology during the last three decades. Among various types of functional nanomaterials, metal selenide nanocrystals have attracted considerable attention because of their special properties. These nanomaterials have been applied in a wide range, such as medicine, electronics, photonics, energy conversion and storage devices, etc. Interestingly, when metals are chemically combined with selenide in the form of nanocrystals, they exhibit semiconductor-like electronic properties. These metal selenide nanocrystals have attracted significant attention in recent years due to their potential applications in solar energy conversion and storage, which are the most important challenges to be addressed to meet the world’s rising demand for clean energy in the future. Hot-injection method is an effective method for the synthesis of metal selenide nanocrystals. The success of this approach lies in the use of non-ionic precursors in high-boiling organic solvents. This makes it possible to grow the nanocrystals relatively slowly at a high temperature, which yields defect-free, well-passivated nanocrystals. The anther important aspect of this method is the separation of the nucleation and growth stages. Due to this, a high degree of monodispersity can be achieved. The fundamental principle of hot-injection method with concrete steps has been introduced. This review surveys the recent progress of the preparation of metal selenide nanocrystals by hot-injection method in terms of binary metal selenide nanocrystals, ternary metal selenide nanocrystals, quaternary, and multinary metal selenide nanocrystals. For binary metal selenide nanocrystals, four important binary metal selenide nanocrystals including CdSe, ZnSe, PbSe, and Sb2Se3 nanocrystals are discussed. Then the achievement of synthesis for CuInSe2 and CuGaSe2 nanocrystals by hot-injection method and their application in photovoltaic field are systematically cataloged as well. And the progress in preparation for CuInGaSe2 and Cu2ZnSnSe4 nanocrystals by hot-injection method has been clarified clearly. Organoselenide chemicals are generally toxic and unstable. The replacement of phosphine containing compounds in the synthesis process of metal selenide nanocrystals via hot-injection method has received considerable attention in recent years. Many attempts have been made to replace trioctylphosphine (TOP) as a medium for delivering selenium in these reactions, but each alternative possesses has significant limitations. This review mainly emphasizes on the recent advances toward the development of methods to achieve “green Se precursor” with high activity and “facile green synthesis” of metal selenide nanocrystals involved in various approaches. Two kinds of different schemes for synthesis and utilization “green Se precursor” are described. Finally, technical challenges and future trends are presented for synthesis of high quality metal selenide nanocrystals, in terms of composition-tunable and structure-controllable multinary metal selenide nanocrystals, green synthesis, industrial production and large-scale application.

A simple neridronate-based surface coating strategy for upconversion nanoparticles: highly colloidally stable 125I-radiolabeled NaYF4:Yb3+/Er3+@PEG nanoparticles for multimodal in vivo tissue imaging.

In this report, monodisperse upconversion NaYF4:Yb3+/Er3+ nanoparticles with superior optical properties were synthesized by the oleic acid-stabilized high-temperature co-precipitation of lanthanide chlorides in octadec-1-ene as a high-boiling organic solvent. To render the particles with biocompatibility and colloidal stability in bioanalytically relevant phosphate buffered saline (PBS), they were modified by using in-house synthesized poly(ethylene glycol)-neridronate (PEG-Ner), a bisphosponate. The NaYF4:Yb3+/Er3+@PEG nanoparticles showed excellent long-term stability in PBS and/or albumin without any aggregation or morphology transformation. The in vitro cytotoxicity of the nanoparticles was evaluated using primary fibroblasts (HF) and a cell line derived from human cervical carcinoma (HeLa). The particles were subsequently modified by using Bolton-Hunter-hydroxybisphosphonate to enable radiolabeling with 125I for single-photon emission computed tomography/computed tomography (SPECT/CT) bimodal imaging to monitor the biodistribution of the nanoparticles in non-tumor mice. The bimodal upconversion 125I-radiolabeled NaYF4:Yb3+/Er3+@PEG nanoparticles are prospective for near-infrared (NIR) photothermal/photodynamic and SPECT/CT cancer theranostics.

RGDS- and TAT-Conjugated Upconversion of NaYF4:Yb(3+)/Er(3+)&SiO2 Nanoparticles: In Vitro Human Epithelioid Cervix Carcinoma Cellular Uptake, Imaging, and Targeting.

Starting NaYF4:Yb(3+)/Er(3+) nanoparticles with size tuned from 24 to 33 nm were prepared by high-temperature coprecipitation of lanthanide chlorides in high-boiling organic solvents. To enhance colloidal stability in aqueous medium, an aminosilica shell was introduced on the surface by hydrolysis and condensation of tetramethyl orthosilicate and (3-aminopropyl)trimethoxysilane using a reverse microemulsion technique; to form alkyne groups, reaction with 4-pentynoic acid followed. Finally, the cell adhesive and cell penetrating azidopentanoyl-GGGRGDSGGGY-NH2 (RGDS) and azidopentanoyl-GGGRKKRRQRRR-NH2 (TAT) peptides were conjugated to the upconversion particles via Cu(I)-catalyzed alkyne-azide cycloaddition. The concentrations of the peptides bound to the nanoparticle surfaces and amount of adsorbed residual Cu(I) catalyst were determined using an (125)I-radiolabeled RGDS peptide and a (64)Cu(I)-doped catalyst, respectively. Targeting and uptake of the RGDS- and TAT-conjugated NaYF4:Yb(3+)/Er(3+)&SiO2 nanoparticles by human cervix carcinoma HeLa cells were monitored by confocal microscopy. RGDS-conjugated nanoparticle probes were mainly localized on the cell plasma membrane due to specific binding of the peptide to the corresponding integrins. In contrast, the TAT-conjugated nanoparticles were able to cross the cell membrane and accumulate in the cell cytoplasm. Thus, this new peptide bioconjugation approach supported both extra- and intracellular nanoparticle uptake, enabling targeting and imaging of the specific tumor phenotypes.

Impact of heating mode in synthesis of monodisperse iron-oxide nanoparticles via oleate decomposition

The present work introduces the optimization of a synthetic procedure for oleate-coated iron-oxide nanoparticles by the thermal decomposition of Fe oleate dried at 30 and 70 °C in high-boiling organic solvents. The attention is focused on the temperature of the thermal decomposition, the nature of organic solvent, heating rate and the mode of the heating. In particular, heating on Wood alloy with simultaneous bubbling of argon through the reaction mixture versus the heating on mantel with magnetic stirring is highlighted as a route to improve the monodispersity of the nanoparticles. The effect of heating mode and rate on the nanoparticles size is estimated. The obtained tendencies point to the heating mode and rate as additional factors affecting the kinetic separation between nucleation and nanoparticle growth processes.

Solvothermal synthesis of nanodispersed yttrium-aluminum garnet

A new method of synthesis of nanodispersed yttrium-aluminum garnet (YAG, Y3Al5O12) consisting in the solvothermal treatment of a mixture of the respective elements of chlorides and aluminum isopropylate in high-boiling organic solvents (diphenyloxide, oleic acid, stearic acid, and oleylamine) at 250–300°C and under atmospheric pressure has been developed. Subsequent precursor treatment allows fabrication of YAG at temperatures as low as 850°C. The synthesized compounds have been investigated by the methods of IR spectroscopy, X-ray diffraction and complex thermal analysis, and electron microphotography.

Insights into the Thermal Decomposition of Co(II) Oleate for the Shape-Controlled Synthesis of Wurtzite-Type CoO Nanocrystals

Fatty acid salts of transition metals are known to undergo thermal decomposition in high-boiling organic solvents. Although it is a straightforward, promising approach for generating colloidal metal oxide nanocrystals in high yield, its widespread implementation is hindered by irreproducibility. Subtle structural variations and impurities are often introduced during preparation of the carboxylate precursors, which exhibit strong influence on thermal decomposition, and the resulting nucleation and growth of oxide nanocrystals. Here, we studied the colloidal synthesis of wurtzite-type CoO (wz-CoO) nanostructures via thermal decomposition of Co(II) oleate complex [Co(OL)]2. Using Fourier transform infrared spectroscopy, we discovered that the conventional method for preparing [Co(OL)]2 gives rise to an isolable impurity containing a free hydroxide moiety. Furthermore, [Co(OL)]2 did not thermally decompose within the expected temperature range when the impurity was removed. In contrast, pencil-shaped wz-CoO nanorods were synthesized when no measures were taken to remove the impurity, suggesting that the hydroxide functionality may facilitate the thermal decomposition. These insights enabled us to prepare size-and shape-controlled wz-CoO nanocrystals using purified [Co(OL)]2 solutions, by incorporating additives that mimic the action of the hydroxide impurity. We also demonstrate a simplified pathway to wz-CoO nanocrystals that does not require chemical additives for thermolysis.