Manufacturing inorganic nanoparticles using microemulsion-mediated synthesis

Nanoparticulate materials impart improved properties for the devices, systems or formulations in which they are key components. Several novel inorganic nanoparticle manufacturing techniques have been commercialised recently to compete with long-established processes that provide nanosized particles with inferior properties. However, the specific attributes of the nanoparticle products of each process differ, and the respective applications will therefore differ significantly. This article describes a manufacturing process for inorganic nanoparticles that is appreciably different from these processes, which are primarily gas-phase syntheses. It is based on microemulsion-mediated chemical precipitation of the nanoparticles, which has been widely employed as a laboratory technique to synthesise small quantities of such materials while providing excellent control over particle size, particle size homogeneity and chemical composition. Economic scale-up requires efficient collection of product particles and recycling of microemulsion components (surfactants and non-polar organic fluid) for refuse Low-cost ceramic crossflow ultrafiltration is employed for particle harvesting and fluid phase recycling. Laboratory characterisation of the process and nanoparticle products is described, and projected product costs and applications are also discussed.     

由有机和无机金属前躯体自蔓延高温合成碳包覆磁纳米粒子(英文)

介绍了一项由自蔓延高温合成(SHS)碳包覆磁纳米粒子的系统研究。采用还原剂NaN3和三种不同氧化剂-聚四氟乙烯、六氯乙烷和六氯苯,实施了SHS制备。研究了金属前躯体(Fe(CO)5或K3[Fe(CN)6])对产物的得率、反应热、形貌、结构和磁性能的影响。结果表明:有机铁前躯体和C2Cl6氧化剂反应体系可获得磁性最佳、得率最高的产物。     

Oxide glass used as inorganic template for fluorescent fluoride nanoparticles synthesis

We report an original way to synthesise single-crystal PbF₂ nanoparticles by selective chemical attack of a bulk nanocomposite oxyfluoride glass–ceramic. Free of impurities and homogeneously doped with Er³⁺ ions, the particles are of narrow size dispersion around 15 nm and weakly aggregated. The nanocrystallites emit a very intense green and blue up conversion fluorescence after infrared excitation. The doping level and the size of the particles is finely driven through the precursor glass–ceramic synthesis and composition.     

Simple synthesis of MoS2 inorganic fullerene-like nanomaterials from MoS2 amorphous nanoparticles

The amorphous MoS₂ nanoparticles have been synthesized by a simple oxidation–reduction reaction in an aqueous solution. A series of products with different morphologies, such as MoS₂ nanospheres, inorganic fullerene-like nanospheres, nanorods and Mo bended rods, can be obtained by annealing the amorphous MoS₂ nanoparticles under N₂ atmosphere under 400–1200 °C. These products have been characterized by X-ray diffraction, field emission scanning electronic microscopy, transmission electron microscopy and high-resolution transmission electron microscopy in detail. The possible transformation mechanism for the structure has been discussed based on the experimental results. In addition, the optical properties of IF-MoS₂ have also been performed by UV–vis absorption spectroscopy.     

Cellular toxicity of inorganic hydroxide nanoparticles

Layered double hydroxides (LDHs), anionic clays, have attracted increasing interest as nanovehicles for delivering genes, drugs, and bio-active molecules into cells. However, no attempts have been made to evaluate the potential undesirable effects of LDH nanoparticles. The cytotoxicity of LDHs with different chemical compositions (ZnAl- and MgAl-LDH) was systematically evaluated in various cell types, such as human normal cells, carcinoma cells, and red blood cells, by measuring cell viability, cell proliferation, membrane damage, and hemolytic effect. No significant cytotoxic effects could be seen in both cases, but ZnAl-LDH was determined to be slightly more toxic than MgAl-LDH in terms of membrane damage and hemolysis induction. It is, therefore, expected that LDHs could be promising candidates for novel inorganic drug delivery carriers.     

Novel two-step synthesis of gold nanoparticles capped with bile acid conjugates

Bile acids and their conjugates are physiologically important molecules. Syntheses and structure elucidation combined with investigation of properties and applications of bile acids and their derivatives are of academic interest. The concept of using bile acids and their conjugates in nanoscience is a novel idea, which opens up fascinating prospects. In this article, an easy and simple route for obtaining N-lithocholyl-l-(cysteine ethyl ester) (3), capable of effectively capping and stabilizing metal nanoparticles, is described. The whole synthetic route needs only two steps giving a moderate to good yield. The gold NPs are characterized by elemental analysis, UV spectroscopy, and TEM. Additionally, ¹³C CP/MAS NMR studies for different ligand/Au ratios have been performed.     

Humic acid assisted synthesis of silver nanoparticles and its application to herbicide detection

Silver nanoparticles have been synthesized by reduction of silver nitrate in the presence of humic acids (HA) which acted as capping agents. The HA protected nanoparticles were found to be sensitive to increasing concentrations of sulfurazon-ethyl herbicide in solution which induced a variation in color of the nanoparticles solution from yellow to purple. The effect of the humic acid concentration used in the nanoparticles synthesis was studied by varying the [Ag⁺:HA] ratio content from [1:1] to [1:100]. UV–Vis spectroscopy was used to monitor the extinction spectra of silver nanoparticles after the synthesis and in the herbicide sensing experiments. An average silver nanoparticles size of 5 nm was confirmed by transmission electron microscope (TEM). When exposed to increasing concentration of sulfurazon-ethyl (0, 100, 200, 300, 400, 500 ppm), the solution of nanoparticles was found to changes from yellow color to orange red and purple with increasing herbicide concentration.     

Human health hazards of persistent inorganic and carbon nanoparticles

Persistent inorganic and carbon nanoparticles are increasingly engineered for applications and may also be present in conventional materials such as carbon black. Furthermore, they may originate from conventional non particulate materials by processes such as wear and tear. Persistent inorganic and carbon nanoparticles can be hazardous to humans. Relatively much research regards the hazards of inhaled nanoparticles. These may give rise to respiratory disease and to negative effects on other organs, including the cardiovascular system. Determinants of risk of inhaled nanoparticles include: number, size, surface characteristics, shape, structure, and the formation of assemblages. These determinants should preferentially be considered in exposure metrics. A major molecular mechanism underlying the inhalation hazard of nanoparticles is the generation of reactive oxygen species, but other mechanisms such as interactions with proteins and DNA may also contribute. Health hazards may also be linked to ingestion of persistent inorganic and carbon nanoparticles, dermal exposure and exposure of the eye. Standards for workplace exposure to persistent inorganic and carbon are currently emerging and there are options for hazard reduction by elimination and substitution of hazardous nanoparticles and by engineering controls.     

Wet-chemical green synthesis of L-lysine amino acid stabilized biocompatible iron-oxide magnetic nanoparticles

In this paper, we report a novel method for the synthesis of L-Lysine (lys) amino acid coated maghemite (gamma-Fe2O3) magnetic nanoparticles (MNPs). The facile and cost effective method permitted preparation of the high-quality superparamagnetic gamma-Fe2O3 MNPs with hydrophilic and biocompatible nature. For this work, first we synthesized magnetite phase Fe3O4/lys by wet chemical method and oxidized to y-Fe2O3 in controlled oxidizing environment, as evidenced by XRD and VSM magnetometry. The crystallite size and magnetization of gamma-Fe2O3/lys MNPs was found to be 14.5 nm, 40.6 emu/gm respectively. The surface functionalization by L-lysine amino acid and metal-ligand bonding was also confirmed by FTIR spectroscopy. The hydrodynamic diameter, colloidal stability and surface charge on MNPs were characterized by DLS and zeta potential analyser.     

A new inorganic framework in the synthesis of barium carbonate nanoparticles via convenient solid state decomposition route

BaCO₃, a common mineral with important applications in industry, has been synthesized in the orthorhombic phase with a high purity. As a new precursor, barium-o-phthalate complex was applied to prepare BaCO₃ nanoparticles via solvent-free thermal decomposition route. Thermogravimetric analysis (TGA) was applied to determine the thermal behavior of the complex. The products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The best results were obtained for the sample prepared at 500 °C. Transmission electron microscopy (TEM) of this product shows “bean-like” shaped nanoparticles with an average size of 35–70 nm. The purity, composition and stoichiometry of the as-prepared sample were studied by Electron Diffraction X-ray spectroscopy (EDX) spectra.     

Hydrothermal synthesis of fluorescent silicon nanoparticles using maleic acid as surface-stabilizing ligands

Water-soluble silicon nanoparticles (SiNPs) have been synthesized with photoluminescence quantum yield more than 32% via a hydrothermal treatment of 3-aminopropyltriethoxysilane as silicon sources and maleic acid (MA) as surface-stabilizing ligands. Prepared SiNPs showed the presence of carboxylic acid groups through the incorporation of MA. The presence of 48.8 and 51.2% of Si–Si and Si–O binding was observed in the resulting carboxylic acid-functionalized SiNPs (COOH-SiNPs). As revealed by the fluorescence lifetime images, COOH-SiNPs possesses several fluorophores mainly composed of above Si–Si binding inside of single particle, which explains the excitation-dependent fluorescence emission behavior of COOH-SiNPs. Also, the presence of oxides mainly composed of Si–O binding and MA on the surface of COOH-SiNPs provides long-term stability for both fluorescence and dispersion. The potential use of COOH-SiNPs as fluorescence bioimaging agents for cellular media has been demonstrated. COOH-SiNPs showed excellent cell viability more than 91% for both MDAMB and MDCK cells even in 1,000 ppm concentration, and multicolor fluorescence imaging (blue, green, and red) of MDAMB cells was successfully accomplished with different excitation wavelengths.     

Poly(acrylic acid)-stabilized colloidal gold nanoparticles: synthesis and properties

Combining the intriguing optical properties of gold nanoparticles with the inherent physical and dynamic properties of polymers can give rise to interesting hybrid nanomaterials. In this study, we report the synthesis of poly(acrylic acid) (PAA)-capped gold nanoparticles. The polyelectrolyte-wrapped gold nanoparticles were fully characterized and studied via a combination of techniques, i.e. UV-vis and infrared spectroscopy, dark field optical microscopy, SEM imaging, dynamic light scattering and zeta potential measurements. Although PAA-capped nanoparticles have been previously reported, this study revealed some interesting aspects of the colloidal stability and morphological change of the polymer coating on the nanoparticle surface in an electrolytic environment, at various pH values and at different temperatures.     

Mechanochemical synthesis of nanoparticles

The results of recent investigation of the mechanochemical synthesis of inorganic nanoparticles are reviewed. It was demonstrated that, by selecting suitable chemical reaction paths, stoichiometry of starting materials and milling conditions, mechanochemical processing can be used to synthesise a wide range of nanocrystalline particles dispersed within a soluble salt matrix. Selective removal of the matrix phase by washing the resulting powder with appropriate solvents can yield nanoparticles of the desired phase. This technique has been shown to have advantages over other methods of producing nanoparticles in terms of low cost, small particle sizes, low agglomeration, narrow size distributions and uniformity of crystal structure and morphology.     

Microfluidic synthesis of Fe nanoparticles

A microfluidic reactor process is demonstrated for the synthesis of worm-like Fe nanoparticles (NPs) at room temperature. These high aspect ratio shaped Fe NPs can be further transformed into large ellipsoid species with refined crystal structures and increased aggregation by way of a sonication process, evidenced by their transmission electron microscope (TEM) images, selected area electron diffraction (SAED), X-ray Diffraction (XRD), X-ray absorption near K-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS). Due to the compensation effects on the magnetic properties of NPs from their increased size, enhanced magnetic coupling, refined crystal structure and the reduced aspect ratio, the sonication-treated Fe NPs show a slightly enlarged coercivity (Hc), an enhanced saturation magnetization (Ms) and a slight suppress in the increased blocking temperature (Tb).     

钯纳米颗粒的形貌控制合成

为优化钯纳米颗粒的化学还原法制备工艺,本文以氯钯酸(H₂PdCl₄)为前驱体,抗坏血酸(C₆H₈O₆)为还原剂,聚丙烯酸钠(PAAS)为表面活性剂制备钯纳米颗粒。采用正交实验探究不同工艺参数对钯纳米颗粒粒径和形貌的影响。通过 X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)及电化学工作站对制备产物的结构、物相、形貌、电催化性能进行了表征。结果表明:在相同的工艺体系下,通过温度的改变,40 ℃条件下可以得到粒径大小为64.5 nm,球形度较好,分散性高的钯纳米颗粒;90 ℃条件下可以得到粒径大小为45.9 nm的立方体钯纳米颗粒。所制备的球形和立方体钯纳米颗粒对甲酸的电氧化催化活性分别为商业钯黑的1.57倍和1.49倍,在催化剂制备领域有广泛的应用前景。     

Machine learning-guided synthesis of advanced inorganic materials

Synthesis of materials with minimum number of trials is of paramount importance towards the acceleration of advanced materials development. The enormous complexity involved in existing multi-variable synthesis methods leads to high uncertainty, numerous trials and exorbitant cost. Recently, machine learning (ML) has demonstrated tremendous potential for material discovery and property enhancement. Here, we extend the application of ML to guide material synthesis process through the establishment of the methodology including model construction, optimization, and progressive adaptive model (PAM). Two representative multi-variable systems are studied. A classification ML model on chemical vapor grown MoS₂ is developed, capable of optimizing the synthesis conditions to achieve a higher success rate. And a regression model is constructed on the hydrothermal-grown carbon quantum dots, to enhance the process-related properties such as the photoluminescence quantum yield. The importance of synthesis parameters on experimental outcomes is particularly extracted from the constructed ML models. Furthermore, off-line analysis shows that enhancement of the experimental outcome with minimized number of trials can be achieved with the effective feedback loops in PAM, suggesting the great potential of involving ML to guide new material synthesis at the beginning stage. This work serves as a proof of concept for using ML in facilitating the synthesis of inorganic materials, thereby revealing the feasibility and remarkable capability of ML in opening up a new promising window for accelerating material development.     

Hot-wire synthesis of Si nanoparticles

The viability of producing silicon nanoparticles using the HWCVD process is investigated. A system is assembled and particles are produced from silane at pressures between 0.2 and 48 mbar, with hydrogen dilutions of 0-80%, at a total flow rate of 50 sccm and with a tungsten filament maintained at 1650 °C. The as-prepared powder varies in colour from yellowish to dark brown and is deposited on all surfaces inside the reaction chamber. The material is a highly porous agglomeration of nanoparticles of primary size in the order of 40 nm, with a narrow size distribution. The nanoparticles produced are mostly amorphous, hydrogenated and have a partially oxidised surface.