Primary Nanoparticles Research Articles

Synthesis of gold nanoparticles by the spark discharge method for visible plasmonics

This work demonstrates synthesis of metal Au nanoparticles with a plasmon resonance in the visible optical region by the spark discharge method in atmosphere of argon of purity 6.0. With raising of sintering temperature from 25 to 950 °C, the morphology of synthesized Au nanoparticles changed from agglomerates to individual particles with decreasing the median size from 270 to 90 nm according to aerosol spectrometer. While by transmission electron microscopy primary nanoparticles with a gold crystalline structure with sizes in range from 5 to 120 nm were observed. Synthesized nanoparticles ensembles had broad absorption peaks with maximum in the visible optical region with peak positions approximately at 490 nm. High temperature sintered particles had a spherical shape and an additional absorption peak at approximately 640 nm.

Rapid construction of hierarchically porous metal–organic frameworks by a spray‐drying strategy for enhanced tannic acid adsorption

AbstractMetal–organic frameworks (MOFs) have attracted much attention owing to their tailored pore environment and surface functionality. However, most of the currently reported MOFs are confined to small pore sizes (<5 nm), limiting their practical applications. Here, a facile and versatile strategy for rapid construction of hierarchically porous MOFs (HP‐MOFs) by spray‐drying is reported, in which presynthesized nanosized MOFs (N‐MOFs) can be assembled to form MOF microspheres with meso/macropores resulting from the interspace among closely arranged N‐MOFs. This strategy enables the construction of multicomponent HP‐MOFs with various functions. As a proof of concept, we show that the adsorption for tannic acid (TA) can be significantly enhanced using HP‐MIL‐101(Cr). Particularly, HP‐MIL‐101‐30 (30 represents the primary nanoparticle size) exhibits a record‐high adsorption capacity (1175 mg g−1), and the adsorption rate of HP‐MIL‐101‐30 is increased by 50% compared to that of N‐MIL‐101‐30. These findings have important implications for the rapid construction of HP‐MOFs, which is beneficial for the adsorption of large molecules.

Combined Small-Angle Neutron Scattering/Small-Angle X-ray Scattering Analysis for the Characterization of Silver Nanoparticles Prepared via Photoreduction in Water-in-Oil Microemulsions.

In this study, we used small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) to investigate the formation process of silver (Ag) nanoparticles (NPs) in water-in-oil (w/o) reverse microemulsions comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT), water, and organic solvents (such as benzene, octane, and decane) by the photoreduction of silver perchlorate (AgClO4). Combining SANS and SAXS, the structural changes in the w/o microemulsions before and after the formation of Ag NPs via photoreduction were quantitatively evaluated. From the SANS experiments performed using the contrast-variation method, the size of water cores containing Ag NPs and the thickness of the AOT shells were calculated using the core-shell hard-sphere model. The size of the Ag NPs and their aggregates was calculated via SAXS analysis based on the polydisperse sphere model with a Schulz-Zimm distribution. We found that aggregates of three or four primary Ag NPs are formed by, first, the aggregation of water droplets through the entanglement of the tails of the AOT shell, followed by the self-assembly of Ag NPs into their aggregates because of particle-particle attractive interactions.

Nanoparticles for Magnetic Heating: When Two (or More) Is Better Than One.

The increasing use of magnetic nanoparticles as heating agents in biomedicine is driven by their proven utility in hyperthermia therapeutic treatments and heat-triggered drug delivery methods. The growing demand of efficient and versatile nanoheaters has prompted the creation of novel types of magnetic nanoparticle systems exploiting the magnetic interaction (exchange or dipolar in nature) between two or more constituent magnetic elements (magnetic phases, primary nanoparticles) to enhance and tune the heating power. This process occurred in parallel with the progress in the methods for the chemical synthesis of nanostructures and in the comprehension of magnetic phenomena at the nanoscale. Therefore, complex magnetic architectures have been realized that we classify as: (a) core/shell nanoparticles; (b) multicore nanoparticles; (c) linear aggregates; (d) hybrid systems; (e) mixed nanoparticle systems. After a general introduction to the magnetic heating phenomenology, we illustrate the different classes of nanoparticle systems and the strategic novelty they represent. We review some of the research works that have significantly contributed to clarify the relationship between the compositional and structural properties, as determined by the synthetic process, the magnetic properties and the heating mechanism.

In Vivo PET Imaging of Monocytes Labeled with [89Zr]Zr-PLGA-NH2 Nanoparticles in Tumor and Staphylococcus aureus Infection Models.

Simple SummaryImmune cells are increasingly used for therapy in cancer and other diseases. To better understand immune-cell kinetics, cell-tracking with highly sensitive imaging modalities is required. The aim of this study was to develop a new strategy for the in vivo tracking of a small number of cells, using positron emission tomography (PET). We labeled poly(lactic-co-glycolic acid) nanoparticles containing a primary endcap (PLGA-NH2) with the radionuclide zirconium-89. The nanoparticles were characterized for size, polydispersity index, zetapotential and radiolabel retention. Subsequently, they were used for the ex vivo radiolabeling of a monocyte cell line (THP-1). We demonstrated that these radiolabeled monocyte cells can be traced in vivo in mouse tumor and infection models.The exponential growth of research on cell-based therapy is in major need of reliable and sensitive tracking of a small number of therapeutic cells to improve our understanding of the in vivo cell-targeting properties. 111In-labeled poly(lactic-co-glycolic acid) with a primary amine endcap nanoparticles ([111In]In-PLGA-NH2 NPs) were previously used for cell labeling and in vivo tracking, using SPECT/CT imaging. However, to detect a low number of cells, a higher sensitivity of PET is preferred. Therefore, we developed 89Zr-labeled NPs for ex vivo cell labeling and in vivo cell tracking, using PET/MRI. We intrinsically and efficiently labeled PLGA-NH2 NPs with [89Zr]ZrCl4. In vitro, [89Zr]Zr-PLGA-NH2 NPs retained the radionuclide over a period of 2 weeks in PBS and human serum. THP-1 (human monocyte cell line) cells could be labeled with the NPs and retained the radionuclide over a period of 2 days, with no negative effect on cell viability (specific activity 279 ± 10 kBq/106 cells). PET/MRI imaging could detect low numbers of [89Zr]Zr-THP-1 cells (10,000 and 100,000 cells) injected subcutaneously in Matrigel. Last, in vivo tracking of the [89Zr]Zr-THP-1 cells upon intravenous injection showed specific accumulation in local intramuscular Staphylococcus aureus infection and infiltration into MDA-MB-231 tumors. In conclusion, we showed that [89Zr]Zr-PLGA-NH2 NPs can be used for immune-cell labeling and subsequent in vivo tracking of a small number of cells in different disease models.

Smart PMMA‑cerium oxide anticorrosive coatings: Effect of ceria content on structure and electrochemical properties

Organic-inorganic hybrids are considered an effective and environmentally compliant alternative to chromate-based anticorrosive coatings, currently banned due to the high toxicity of hexavalent chromium. In this work, hybrid nanocomposites based on poly(methyl methacrylate) (PMMA), covalently bonded to cerium oxide nanoparticles through the 2-hydroxyethyl methacrylate (HEMA) coupling agent, were tailored by carefully tuning the inorganic colloidal precursor to provide films with active corrosion protection for metallic substrates. Lithium hydroxide was exploited as oxidizing agent of cerium nitrate to form ceria nanoparticles. Precursor solutions and solid nanocomposites with different LiOH to Ce(NO3)3.6H2O molar ratios were analyzed using spectroscopic and electron microscopy techniques and theoretical simulations. Electrochemical impedance spectroscopy (EIS) was used to study the anticorrosive performance of the coatings on carbon steel and 7075 aluminum alloy. The results showed that increasing amounts of LiOH lead to the formation of higher ceria content and larger primary nanoparticles, ranging from 1.7 to 2.8 nm. The homogenous ~20 μm-thick coatings present excellent anticorrosive performance on carbon steel and AA7075 substrates. Coatings on carbon steel with low LiOH loading (1Li:1Ce) showed long-term durability and high impedance modulus of up to 29 GΩ cm2 after 1 day in saline solution. On the AA7075 alloy, the presence of larger cerium oxide particles at higher LiOH content (3Li:1Ce) acted as effective reservoirs of cerium ions, providing high barrier coatings (395 GΩ cm2) with active corrosion protection.

Colorimetric Determination of Mercury(II) by Secondary Gold Nanoparticles Formation on Primary Gold Nanoparticles as an Efficient Nanozyme

Gold nanoparticles (Au-NPs) shows promise enzyme-like activity for hydrogen peroxide decomposition and produced free electrons for metal ion reduction. Thus, we focused on the design and construction of primary Au-NPs (p-Au-NPs) for decomposition hydrogen peroxide and subsequently reduction of Au3+ to form secondary Au-NPs (s-Au-NPs). Since mercury(II) as soft metal ion can make amalgam with the Au-NPs this can be applied as a boosting idea for indirect detection of mercury(II). Therefore, s-Au-NPs preparation in presence of different concentrations of mercury(II) on surface of p-Au-NPs that cause a color change by final oxidation of 3,4-diaminotoluene while s-Au-NPs/p-Au-NPs cannot oxidize 3,4-diaminotoluene marker and no color change is achieved become as a goal. This occurrence causes a colorimetric procedure, from mauve to dark wine, which facilitates determination of mercury(II) ions in a reasonable range from 2.15 to 25.12 µM with a UV–Vis spectrometer. Sensor characterized by analysis such as UV–Vis, DLS, SEM, EDS, XRD and FT-IR. At last, accuracy of the model investigated with recovery process and observed that method could be advantageously applied as a simple method for the determination of mercury (II) in real samples have been developed to monitor the water quality by tracing different amount of analyte ions in samples. The different water sample such as lake water, tap water, and any water with the necessity of checking the quality of it to help the environment for places with the lack of high-tech technology.

Single-pot solvothermal strategy toward support-free nanostructured LiBH4 featuring 12 wt% reversible hydrogen storage at 400 °C

Lithium borohydride (LiBH4) exhibits poor hydrogen storage reversibility because of phase separation between LiH and B due to foaming during thermal dehydrogenation. Herein, we report that by synthesizing nanostructured LiBH4 without any supports, the foaming and phase separation can be effectively suppressed, and consequently, the hydrogen storage reversibility of LiBH4 can be considerably improved. Using a facile single-pot solvothermal approach, a hierarchical porous nanostructured LiBH4 composed of 50–60 nm-sized primary nanoparticles is synthesized. The resulting neat nano-LiBH4 reversibly desorbs and absorbs approximately 12 wt% of H at 400 °C and under 100 bar H2. The superior hydrogen storage performance is attributed to the effective inhibition of foaming upon heating. The formation of LiH and B prior to melting, which can be associated with the largely reduced particle sizes and porous agglomeration structure, plays a crucial role in suppressing foaming. Our findings offer a new strategy for the preparation of nanoscaled freestanding borohydrides, and also important insights into the development of highly reversible metal borohydrides for hydrogen storage applications.

Mechanochemical Alkali-Metal-Salt-mediated synthesis of ZnO nanocrystals with abundant oxygen Vacancies: An efficient support for Pd-based catalyst

Zinc oxide is a key material in catalysis. Designing of ZnO crystal aggregates with the surface defect has received significant attention. Herein, we synthesized ZnO aggregates with tiny primary nanoparticles through a mechanochemistry-assisted salt-templating (potassium chloride) method. Interestingly, this KCl-templating strategy could lead to significant increase in specific surface area (SSA) of ZnO (up to 91 m2/g), whereas commercial ZnO-COM has a SSA of 5 m2/g. Meanwhile, this strategy via ZnCl2-KCl solid solution has also created a number of oxygen vacancies into ZnO aggregates. With these attractive features, as-made Pd-ZnO catalyst showed outstanding performance in methanol steam reforming, especially at low temperature (20 % Conversion and 95 % CO2 Selectivity at 150 °C). Current strategy provides a gateway for the rational design of ZnO-based catalytic materials.

Controllable dry synthesis of binder-free nanostructured platinum electrocatalysts supported on multi-walled carbon nanotubes and their performance in the oxygen reduction reaction

Different platinum nanostructures were synthesized by pulsed laser ablation (PLA) of a pure Pt target, a by-product-free and solvent-free synthesis technique. The Pt nanostructures were directly deposited on multi-walled carbon nanotubes (MWCNT) pre-grown on a stainless steel (SS) mesh by chemical vapor deposition. Performing PLA at different background gas pressures (10−5 to 10 Torr, argon) and laser pulse energies (20 to 66 mJ pulse−1) led to a range of coating morphologies containing very low Pt loadings (14 to 35 μg cm−2), from the uniform and dense nanoparticle thin coatings at low pressure to highly porous granular coatings at higher pressure. Increasing the background gas pressure led to an increase in primary Pt nanoparticle size from 2.0 ± 0.2 nm to 2.8 ± 0.8 nm. XPS results showed a positive shift in the Pt 4f7/2 binding energies with lowering the PLA pressure and laser energy, which was linked to the formation of smaller Pt nanoparticles. The presence of Pt (111), (200), (220), and (311) was confirmed by SAED patterns in the Pt nanostructures. The electrocatalytic performance of these binder-free Pt/MWCNT/SS structures was evaluated in the oxygen reduction reaction (ORR) in an alkaline medium, in both the rotating disk electrode (RDE) and gas diffusion electrode (GDE) configurations. In the RDE setup, all Pt/MWCNT/SS electrocatalysts were found to yield a higher specific ORR activity than the commercial Pt/C thin film, while in the GDE setup the Pt/MWCNT/SS electrode with the lowest Pt loading and highest surface area yielded the highest ORR specific activity.

Insights on the Formation of Nanoparticles Prepared by Magnetron Sputtering Onto Liquids: Gold Sputtered Onto Castor Oil as a Case Study

Magnetron sputter deposition of metal targets over liquids allows producing colloidal solutions of small metal nanoparticles (NPs) without any additional reducing or stabilizing reagents. Despite that this synthetic approach is known for almost 15 years, the detailed mechanism of NP formation is still unclear. Detailed investigations must be carried out to better understand the growth mechanism and, ultimately, control the properties of the NPs. Here, the combination of the gold (Au) target and castor oil, a highly available green solvent, was chosen as a model system to investigate how different experimental parameters affect the growth of NPs. The effect of deposition time, applied sputter power, working gas pressure, and type of sputter plasma (direct current magnetron sputtering (DC-MS) vs. high-power impulse magnetron sputtering (HiPIMS)) on properties of Au NPs has been studied by UV-vis spectroscopy and transmission electron microscopy (TEM), and further supported by quantum-chemistry calculations and mass-spectrometry analysis. The mechanism of the Au NP formation includes the production of primary NPs and their subsequent aggregative growth limited by diffusion in the viscous castor oil medium. Final Au NPs have a narrow size distribution and a medium diameter of 2.4–3.2 nm when produced in DC-MS mode. The NP size can be increased up to 5.2 ± 0.8 nm by depositing in HiPIMS mode which, therefore, mimics energy and time-consuming post synthesis annealing.

Synthesis and Characterization of Porous CaCO3 Vaterite Particles by Simple Solution Method.

Appropriately engineered CaCO3 vaterite has interesting properties such as biodegradability, large surface area, and unique physical and chemical properties that allow a variety of uses in medical applications, mainly in dental material as the scaffold. In this paper, we report the synthesis of vaterite from Ca(NO3)2·4H2O without porogen to obtain a highly pure and porous microsphere for raw material of calcium phosphate as the scaffold in our future development. CaCO3 properties were investigated at two different temperatures (20 and 27 °C) and stirring speeds (800 and 1000 rpm) and at various reaction times (5, 10, 15, 30, and 60 min). The as-prepared porous CaCO3 powders were characterized by FTIR, XRD, SEM, TEM, and BET methods. The results showed that vaterite with purity 95.3%, crystallite size 23.91 nm, and porous microsphere with lowest pore diameter 3.5578 nm was obtained at reaction time 30 min, temperature reaction 20 °C, and stirring speed 800 rpm. It was emphasized that a more spherical microsphere with a smaller size and nanostructure contained multiple primary nanoparticles received at a lower stirring speed (800 rpm) at the reaction time of 30 min. One of the outstanding results of this study is the formation of the porous vaterite microsphere with a pore size of ~3.55 nm without any additional porogen or template by using a simple mixing method.

CdSe/Ag Hybrid Aerogels: Integration of Plasmonic and Excitonic Properties of Metal–Semiconductor Nanostructures via Sol–Gel Assembly

Metal–semiconductor hybrid nanomaterials (HNMs) exhibit unique properties that are distinct from individual nanostructures, leading to promising applications in optical technologies. The interfacial linkage of semiconductor and metal nanoparticles (NPs) via cogelation is an effective strategy to produce HNMs that show strong plasmon‐exciton coupling and improved physical properties. However, optical properties of these hybrids show little to no tunability. Herein, CdSe/Ag hybrid aerogels that show tunable absorption and photoluminescence (PL) are produced by cogelation of CdSe nanorods (NRs) or NPs with Ag hollow NPs. Hybrid electronic states are created by overlapping the excitonic absorption of CdSe NRs or NPs with the plasmonic absorption of Ag NPs. Physical characterization of the hybrids reveals an interconnected network of hexagonal CdSe and cubic Ag NPs, linked by Ag+ and Se2− surface species, without intervening ligands. PL spectra exhibit maxima at 640 and 720 nm for the CdSe NPs/Ag and CdSe NRs/Ag hybrids, respectively, corresponding to new radiative decay mechanisms. Time‐resolved PL data support the emergence of new radiative pathways, kinetically and energetically distinct from the excitonic and plasmonic properties of primary NPs. This new approach of metal–semiconductor hybrid formation through cogelation is intriguing for the design of high‐efficiency HNMs without detrimental PL quenching.

Effect of Citrate on the Size and the Magnetic Properties of Primary Fe3O4 Nanoparticles and Their Aggregates

The size, size distribution and magnetic properties of magnetite nanoparticles (NPs) prepared by co-precipitation without citrate, in the presence of citrate and citrate adsorbed post-synthesis were studied by X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), Electron Paramagnetic Resonance (EPR) and magnetization measurements. The aim of this investigation was to clarify the effect of citrate ions on the size and magnetic properties of magnetite NPs. The size of the primary NPs, as determined by analysing the width of diffraction peaks using various methods, was ca. 10 nm for bare magnetite NPs and with citrate adsorbed post-synthesis, whereas it was around 5 nm for the NPs co-precipitated in the presence of citrate. DLS measurements show that the three types of NPs form aggregates (100–200 nm in diameter) but the dispersions of the citrate-coated NPs are more stable against sedimentation than those of bare NPs. The sizes and size distributions determined by XRD are in good agreement with those of the magnetic domains obtained by fitting of the magnetization vs. magnetic field intensity curves. Magnetization vs. magnetic field intensity curves show that the three kinds of sample are superparamagnetic.

Biocompatible Superparamagnetic Europium-Doped Iron Oxide Nanoparticle Clusters as Multifunctional Nanoprobes for Multimodal In Vivo Imaging.

Magnetic nanoparticle clusters composed of primary magnetic nanoparticles can not only significantly enhance the magnetic properties of the assembly but also retain the superparamagnetic properties of the individual primary nanoparticle, which is of great significance for promoting the development of multifunctional advanced materials. Herein, water-soluble biocompatible and superparamagnetic europium-doped iron oxide nanoparticle clusters (EuIO NCs) were directly synthesized by a simple one-pot method. The obtained EuIO NCs have excellent water solubility, colloidal stability, and biocompatibility. Europium doping significantly improved the contrast enhancement effect of EuIO NCs in T1-weighted MR imaging. In addition, EuIO NCs can be functionalized by active molecules, and the rhodamine123-functionalized EuIO NCs have long circulation time and excellent fluorescence imaging performance in vivo. This study provides a simple strategy for the design and construction of a novel multifunctional magnetic nanoplatform and provides solutions for the development of multimodal imaging probes and the diagnosis of disease.

Study of densification mechanisms during Spark Plasma Sintering of co-precipitated Ho:Lu2O3 nanopowders: Application to transparent ceramics for lasers

This work was focused on the determination of densification mechanisms during Spark Plasma Sintering (SPS) of Ho:Lu2O3 nanopowders. Strong variation of the stress exponent n was evidenced during the sintering process. At low relative density (i.e. ρ < 66 %), n = 3 and powder particles rearrangement and coalescence take place because of high value of effective stress and low size of primary nanoparticles. Then, for ρ between 66 % and 85 %, the stress exponent decreases to n = 2 then n = 1. Such values were related to Rachinger then Lifshitz sliding mechanisms, the last one was associated with an average activation energy of 565 kJ.mol−1. At the final densification stage (ρ > 85 %), the stress exponent suddenly increases to 4 in accordance with a power-law creep. From these investigations, an optimized thermomechanical cycle was proposed to obtain highly transparent Ho:Lu2O3 ceramics suitable for laser applications.

Processing Chitosan for Preparing Chitosan-Functionalized Nanoparticles by Polyelectrolyte Adsorption.

Chitosan-coated nanoparticles are a promising class of drug delivery vehicles that have been studied as tools for improving the gastrointestinal delivery of therapeutics. Here we present an analysis of chitosan-coated nanoparticles with an emphasis on characterizing the chitosan polymer properties. Cationic nanoparticles are produced by adsorbing a layer of chitosan HCl on an anionic (-40 mV ζ-potential) polyacrylic acid (PAA) coated primary nanoparticle. Commercially available chitosan (90% deacetylated) must be processed into a nearly completely deacetylated HCl salt form (99% deacetylation); otherwise, primary nanoparticle aggregation occurs. Deacetylated chitosan HCl produces stable, cationic (+35 mV ζ-potential) nanoparticles within 10% of the original anionic particle hydrodynamic diameter at a 1:2 molar ratio of chitosan glucosamine HCl monomers to PAA acrylic acid monomers.

Hierarchical 1 T-MoS2/MoOx@NC microspheres as advanced anode materials for potassium/sodium-ion batteries

Metallic MoS2 (1 T-MoS2) is expected as a new anode to effectively storage K+/Na+ due to the merits of high capacity, large layer distance and good metallic conductivity. The main bottleneck of 1 T-MoS2 anode stems from the structure pulverization caused by the large volume changes upon cycling, leading to the rapid capacity fading. Herein, hierarchical N-doped carbon modified 1 T-MoS2/MoOx microspheres (1 T-MoS2/MoOx@NC) assembled by some primary nanoparticles are first fabricated by a facile solvothermal synthesis and followed annealing treatment. As anode materials for potassium-ion batteries, 1 T-MoS2/MoOx@NC delivers the outstanding rate capability (257.9/128.8 mAh g−1 at 0.05/0.5 A g−1) and exceptional long-term cycle life up to 400 cycles. 1 T-MoS2/MoOx@NC as anode materials for sodium-ion batteries also shows high reversible capacity and outstanding cyclic stability (473.8 mAh g−1 over 1300 cycles at 2 A g−1). The related kinetics tests have been used to explain the excellent potassium/sodium storage performances. Meanwhile, the 1 T-MoS2/MoOx@NC//Na3V2(PO4)3 full cell for SIBs has been assembled, which exhibits good electrochemical performances. The discharge capacity can keep at 163.5 mAh g−1 after 300 cycles at 0.5 A g−1. The excellent potassium/sodium storage performances are mainly attributed to the particular hierarchical structure as well as the synergistic effect of 1 T-MoS2, MoOx and N-doped carbon.

Fabrication of Conductive and Gas-Sensing Microstructures Using Focused Deposition of Copper Nanoparticles Synthesized by Spark Discharge

Solvent-free aerosol jet printing has been investigated for fabricating metallic and semiconductor (gas-sensitive) microstructures based on copper nanoparticles on alumina, borosilicate glass, and silicon substrates. The synthesis of nanoparticles was carried out using a spark discharge directly in the printing process without the stage of preparing nano-ink. Printed lines with a width of 100–150 µm and a height of 5–7 µm were formed from submicron agglomerates consisting of primary nanoparticles 10.8 ± 4.9 nm in size with an amorphous oxide shell. The electrical resistivity, surface morphology, and shrinkage of printed lines were investigated depending on the reduction sintering temperature. Sintering of copper oxides of nanoparticles began at a temperature of 450 °C in a hydrogen atmosphere with shrinkage at the level of 45–60%. Moreover, aerosol heat treatment was used to obtain highly conductive lines by increasing the packing density of deposited nanoparticles, providing in-situ transformation of submicron agglomerates into spherical nanoparticles with a size of 20–50 nm. Copper lines of spherical nanoparticles demonstrated excellent resistivity at 5 μΩ·cm, about three times higher than that of bulk copper. In turn, semiconductor microstructures based on unsintered agglomerates of oxidized copper have a fairly high sensitivity to NH3 and CO. Values of response of the sensor based on non-sintered oxidized copper nanoparticles to ammonia and carbon monoxide concentration of 40 ppm were about 20% and 80%, respectively.

Influence of the sintering temperature on morphology of alloy germanium-tin nanoparticles synthesized by spark discharge

Alloy GeSn airborne nanoparticles (NP) with the rate of atomic content of Sn to Ge 30 % were produced by spark discharge during simultaneous erosion of germanium and tin electrodes in atmosphere of argon of purity 6.0. Then NP were moved by gas flow to a tube furnace, which were mounted directly after discharge chamber, and sintered at temperatures from 25 to 750 °C. The change of morphology, element composition and crystal structure of NP were investigated using transmission electron microscopy (TEM) with energy dispersive X-ray analysis (EDX), aerosol spectrometer and Fourier-transform infrared spectroscopy (FTIR). Agglomerates of predominantly amorphous primary NP with the mean size of 7 nm were obtained at low sintering temperatures of the tube furnace (25 and 200 °C). High temperature (550 and 750 °C) flow-through thermal sintering of NP agglomerates resulted in production of individual crystal NP with an average size of 28 nm with various crystal structures.