Metal Precursor Solution Research Articles

Ternary Ag3AuS2 Nanocrystals for Thin-Film Solar Cells.

The concept of clean and pollution-free energy development has promoted the rise of environmentally friendly silver-based chalcogenide nanocrystal (NC) solar cells, but currently reported silver-based NCs need complex synthesis processes at high temperatures that may bring zerovalent noble metal impurities for their high redox potentials. In this study, we report a facile synthesis of novel Ag3AuS2 NCs by injecting highly active oleylamine sulfur complexes as sulfur sources into metal precursor solutions at low temperatures of 60 °C. The obtained Ag3AuS2 NCs exhibit broad absorption spectra and high molar extinction coefficients (106 M-1 cm-1). Then, the Ag3AuS2 NCs are applied as the light-absorbing active layer in environmentally friendly thin-film solar cells. By introducing a hybrid mixture of charge acceptors and donors (NCs/P3HT hybrid film) at the interface, the device gains an absorption increment and enhanced charge extraction, achieving a final power conversion efficiency of 3.38%. This work demonstrates the enormous potential of Ag3AuS2 NCs from low-temperature preparation for photovoltaic applications.

Synthesis of Silver Nanoparticles and Silver-Gold Binary System by Galvanic Replacement in an Ultrasonic Field

The conditions for the synthesis of colloidal solutions of silver nanoparticles by galvanic replacement in an ultrasonic field and the AgAuNP binary system by galvanic replacement have been studied. It has been shown that colloidal solutions of stabilized nanoparticles with absorption maxima at 410 nm (AgNPs) and 540...560 nm (AgAuNPs) are formed in solutions of sodium polyacrylate and metal precursors of AgNO3 and H[AuCl4]. The synthesized AgAuNPs are spherical in shape and their size does not exceed 20 nm.

Electroless Deposition of Noble Metals on Rod-Shape Plant Viruses in Various Aqueous Metal Precursor Solutions.

The challenge of synthesizing noble metal nanostructures sustainably has encouraged researchers to explore biological routes for nanostructure production, such as biotemplating. Plant viruses with rod-shape morphology, such as tobacco mosaic virus (TMV) and barley stripe mosaic virus (BSMV), offer promising biotemplates to produce metal nanorods. TMV and BSMV can be incubated in aqueous metal precursor solutions to mineralize metals on the coat proteins (CPs) of the viruses. Previous studies have primarily examined palladium (Pd) mineralization on TMV and BSMV using Na2PdCl4 as the Pd precursor. There is limited scientific literature on the effect of using alternative Pd precursor solutions besides Na2PdCl4 such as K2PdCl4 and PdCl2 to mineralize Pd on TMV and BSMV. Past attempts at mineralizing other noble metals such as platinum (Pt) and gold (Au) required an initial layer of Pd to be deposited on the TMV and BSMV biotemplates. In this study, we aimed to expand the understanding of using alternative Pd precursor solutions to mineralize Pd on TMV and BSMV. Additionally, the deposition of Pt and Au onto TMV and BSMV without the need for an initial Pd mineralization layer was achieved using alternative Pt and Au precursors, including K2PtCl4 and AuCl3, respectively. Pd, Pt, and Au were successfully deposited on TMV and BSMV by incubation in aqueous solutions of Na2PdCl4, K2PdCl4, PdCl2, K2PtCl4, and AuCl3. Kinetic studies were also conducted using ultraviolet-visible (UV-vis) spectroscopy to examine the rates at which Pd, Pt, and Au precursor ions were reduced during the mineralization process, mimicking their adsorption onto TMV and BSMV CPs. BSMV adsorbed noble metal precursor ions faster than TMV as determined by UV-vis spectroscopy. While palladium nanorods (PdNRs) offer high electrical conductivity desirable for electronic applications, Pd-coated TMV and BSMV may face limitations due to their organic cores, potentially compromising conductivity. To address this, one approach is to convert the organic core into conductive amorphous carbon through thermal annealing. In this study, in situ transmission electron microscopy was utilized to thermally anneal Pd-TMV2Cys, thereby transforming them into PdNRs with amorphous carbon cores.

A bimetallic PtAu-modified carbon fiber electrochemical sensor for simultaneous and highly sensitive detection of catechol and hydroquinone in environmental water.

In this study, we report the development of a novel electrochemical sensor capable of the simultaneous detection of catechol (CC) and hydroquinone (HQ) through differential pulse voltammetry. The sensor is constructed using carbon fiber (CF) that has been intricately modified with bimetallic PtAu nanoparticles. The fabrication process involves subjecting CF to ultrasound treatment in an acidic mixture, resulting in the formation of activated carbon fiber (ACF). This activation step not only enhances surface roughness but also facilitates subsequent modification, ensuring the stability of the material. Bimetallic PtAu nanoparticles are then uniformly deposited onto the ACF surface through co-deposition from a metal precursor solution. The modified ACF, adorned with bimetallic PtAu nanoparticles, exhibits excellent conductivity and efficiently catalyzes both CC and HQ in a 10 mM phosphate-buffered saline solution at pH 7.0, thereby enabling their simultaneous detection. Under optimized experimental conditions, this electrochemical sensor achieves impressive detection limits of 0.019 μM for CC and 0.28 μM for HQ within the same concentration range of 0.5-50 μM, respectively. The practicality of the sensor is further demonstrated through recovery experiments using real water samples. This electrochemical sensor, with its superior performance and versatility, shows great potential for applications in analytical chemistry and environmental monitoring.

Print-Light-Synthesis for Single-Step Metal Nanoparticle Synthesis and Patterned Electrode Production.

The fabrication of thin-film electrodes, which contain metal nanoparticles and nanostructures for applications in electrochemical sensing as well as energy conversion and storage, is often based on multi-step procedures that include two main passages: (i) the synthesis and purification of nanomaterials and (ii) the fabrication of thin films by coating electrode supports with these nanomaterials. The patterning and miniaturization of thin film electrodes generally require masks or advanced patterning instrumentation. In recent years, various approaches have been presented to integrate the spatially resolved deposition of metal precursor solutions and the rapid conversion of the precursors into metal nanoparticles. To achieve the latter, high intensity light irradiation has, in particular, become suitable as it enables the photochemical, photocatalytical, and photothermal conversion of the precursors during or slightly after the precursor deposition. The conversion of the metal precursors directly on the target substrates can make the use of capping and stabilizing agents obsolete. This review focuses on hybrid platforms that comprise digital metal precursor ink printing and high intensity light irradiation for inducing metal precursor conversions into patterned metal and alloy nanoparticles. The combination of the two methods has recently been named Print-Light-Synthesis by a group of collaborators and is characterized by its sustainability in terms of low material consumption, low material waste, and reduced synthesis steps. It provides high control of precursor loading and light irradiation, both affecting and improving the fabrication of thin film electrodes.

Interzeolite Transformation of Borosilicate MWW to Metallosilicate BEA-Type Zeolites: Separated Kinetics of Structural Transformation and Metal Substitution

The synthesis of cobalt-, nickel-, and zincosilicate β zeolites (Co-BEA, Ni-BEA, and Zn-BEA, respectively) via a single-step hydrothermal interzeolite transformation of borosilicate MWW (B-MWW) with each metal precursor solution was systematically investigated. While all three metallosilicates exhibited distinct BEA structures with stable framework metal species, their structural transformation and metal substitution kinetics differed depending on the type of metal. The crystallization of Co-BEA and Ni-BEA was completed within two days, while that of Zn-BEA continued even after seven days. Apart from the crystallization kinetics, the incorporation rate of Co into the framework of the BEA structure was slower than that of the other two metals. The characteristics of the BEA structure according to the type of framework heteroatom were further demonstrated using density functional theory calculations. Despite having a comparable metal content (ca. 3 wt %), the Lewis acidities of fully crystallized Co-, Ni-, and Zn-BEA were different corresponding to the types of framework metals. These three metallosilicates showed good catalytic activity for Lewis acid-catalyzed glucose conversion, and the catalytic results were attributed to the intrinsic properties of the catalysts determined from their synthesis stage.

Toward controllable and predictable synthesis of high-entropy alloy nanocrystals

High-entropy alloy (HEA) nanocrystals have attracted extensive attention in catalysis. However, there are no effective strategies for synthesizing them in a controllable and predictable manner. With quinary HEA nanocrystals made of platinum-group metals as an example, we demonstrate that their structures with spatial compositions can be predicted by quantitatively knowing the reduction kinetics of metal precursors and entropy of mixing in the nanocrystals under dropwise addition of the mixing five-metal precursor solution. The time to reach a steady state for each precursor plays a pivotal role in determining the structures of HEA nanocrystals with homogeneous alloy and core-shell features. Compared to the commercial platinum/carbon and phase-separated counterparts, the dendritic HEA nanocrystals with a defect-rich surface show substantial enhancement in catalytic activity and durability toward both hydrogen evolution and oxidation. This quantitative study will lead to a paradigm shift in the design of HEA nanocrystals, pushing away from the trial-and-error approach.

Solid-state, reagent-free and one-step laser-induced synthesis of graphene-supported metal nanocomposites from metal leaves and application to glucose sensing

The laser-induced method to prepare three-dimensional (3D) porous graphene has been widely used in many fields owing to its low-cost, easy operation, maskless patterning and ease of mass production. Metal nanoparticles are further introduced on the surface of 3D graphene to enhance its property. The existing methods, however, such as laser irradiation and electrodeposition of metal precursor solution, suffer from many shortcomings, including complicated procedure of metal precursor solution preparation, strict experimental control, and poor adhesion of metal nanoparticles. Herein, a solid-state, reagent-free, and one-step laser-induced strategy has been developed for the fabrication of metal nanoparticle modified-3D porous graphene nanocomposites. Commercial transfer metal leaves were covered on a polyimide film followed by direct laser irradiation to produce 3D graphene nanocomposites modified with metal nanoparticles. The proposed method is versatile and applicable to incorporate various metal nanoparticles including gold silver, platinum, palladium, and copper. Furthermore, the 3D graphene nanocomposites modified with AuAg alloy nanoparticles were successfully synthesized in both 21 Karat (K) and 18K gold leaves. Its electrochemical characterization demonstrated that the synthesized 3D graphene-AuAg alloy nanocomposites exhibited excellent electrocatalytic properties. Finally, we fabricated LIG-AuAg alloy nanocomposites as enzyme-free flexible sensors for glucose detection. The LIG-18K electrodes exhibited the superior glucose sensitivity of 1194 μA mM−1 cm−2 and low detection limits of 0.21 μM. The LIG-21K nanocomposite sensors showed two linear ranges from 1 μM to 1 mM and 2 mM–20 mM with good sensitivity. Furthermore, the flexible glucose sensor showed good stability, sensitivity, and ability to sense in blood plasma samples. The proposed one-step fabrication of reagent-free and metal alloy nanoparticles on LIG with excellent electrochemical performance opens up possibilities for diversifying potential applications of sensing, water treatment and electrocatalysis.

Characterization and Photocatalytic Performance of Newly Synthesized ZnO Nanoparticles for Environmental Organic Pollutants Removal from Water System

Most countries are facing problems of environmental pollution due to toxic organic pollutants being discharged into the environment from various man-made sources. Heterogeneous photocatalysis is a possible solution for the mentioned problem, and it has been widely applied for the removal of pollutants from aqueous solutions, thanks to its high removal efficiency and environmental friendliness. Among the commonly used metal oxides, ZnO has attracted researchers’ interests due to its ecofriendly and nontoxic nature. In this work, ZnO nanoparticles (ZnO-NPs) were prepared by the precipitation method from water (w) and ethanol solutions of the corresponding metal precursors (zinc–acetate dihydrate, A_ZnO, and zinc–nitrate hexahydrate, N_ZnO) followed by calcination at different temperatures. The structure and morphology of the prepared catalysts were characterized by different techniques (XRD, BET, and SEM). Based on the XRD results, it can be seen that the synthesized NPs possess high purity. Furthermore, at a higher calcination temperature, a higher crystal size was observed, which was more intense in the case of the ethanol solution of the precursors. The BET analysis showed macropores at the surface and also indicated that the increased temperature led to decreased surface area. Finally, SEM images showed that in the case of the water precursor solution, an irregular, rod-like shape of the NPs was observed. The photocatalytic properties of newly synthesized ZnO-NPs exposed to simulated sunlight were examined during the removal of pesticide clomazone (CLO) and the antidepressant drug amitriptyline (AMI). ZnO-NPs prepared by the precipitation method from the water solution of zinc–acetate dihydrate and calcined at 500 °C (A_ZnOw_500) showed the highest performance under simulated sunlight. Furthermore, the activity of A_ZnOw_500 and N_ZnOw_500 catalysts in the removal of three organic pollutants from water—two pesticides (sulcotrione (SUL) and CLO) and one pharmaceutical (AMI)—was also compared. Results showed that decreased photocatalytic activity was observed in the presence of N_ZnOw_500 NPs in all investigated systems. Finally, the effect of the initial pH was also examined. It was found that in the case of CLO and SUL, there was no influence of the initial pH, while in the case of AMI the kapp was slightly increased in the range from pH ~7 to pH ~10.

Multifunctional Heterogeneous Ion-Exchange Membranes for Ion and Microbe Removal in Low-Salinity Water.

Here, multifunctional heterogeneous ion-exchange metal nanocomposite membranes were prepared for surface water desalination and bacterial inactivation under low-pressure (0.05 MPa) filtration conditions. Ultrafiltration (UF) heterogeneous ion exchange membranes (IEMs) were modified with different concentrations of AgNO3 and CuSO4 solutions using the intermatrix synthesis (IMS) technique to produce metal nanocomposite membranes. Scanning electron microscopy (SEM) images revealed that the metal nanoparticles (MNPs) (Ag and Cu) were uniformly distributed on the surface and the interior of the nanocomposite membranes. With increasing metal precursor solution concentration (0.01 to 0.05 mol·L-1), the metal content of Ag and Cu nanocomposite membranes increased from 0.020 to 0.084 mg·cm-2 and from 0.031 to 0.218 m·cm-2 respectively. Results showed that the hydrodynamic diameter diameters of Ag and Cu nanoparticles (NPs) increased from 62.42 to 121.10 nm and from 54.2 to 125.7 nm respectively, as the metal precursor concentration loaded increased. The leaching of metals from metal nanocomposite membranes was measured in a dead-end filtration system, and the highest leaching concentration levels were 8.72 ppb and 5.32 ppb for Ag and Cu, respectively. The salt rejection studies indicated that ionic selectivity was improved with increasing metal content. Bacterial filtration showed higher antibacterial activity for metal nanocomposite membranes, reaching 3.6 log bacterial inactivation.

Rapid synthesis of cerium-UiO-66 MOF nanoparticles for photocatalytic dye degradation.

An unprecedented synthesis method is used to form a series of Ce-UiO-66-X (X = NH2, OH, H, NO2, COOH) metal-organic frameworks by precipitation from mixed solvents, with instantaneous crystallisation on combining separate solutions of ligands and metal precursors. This allows the first direct synthesis of Ce-UiO-66-OH. Powder X-ray diffraction (PXRD) shows that all materials are pure phase with a broadened profile that indicates nano-scale crystallite domain size. The effect of different functional groups on the benzene-1,4-dicarboxylate linker within the UiO-66 structure has been investigated on degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red, and Alizarin red S) dyes under UV and visible light irradiation at room temperature. Analysis of the dye adsorption in the absence of light is accounted for using pseudo-first order kinetics, and the Ce-UiO-66-NH2, Ce-UiO-66-OH, and Ce-UiO-66-H materials display a considerable photocatalytic activity to degrade Alizarin red S and Congo red rapidly between 1 and 3 minutes. The materials show excellent photostability and recyclability under UV and visible light, with no loss of crystallinity seen by PXRD and activity maintained over 5 cycles, with 16 hours photostability for Ce-UiO-66-NH2.

Droplet‐Based Microfluidics Platform for the Synthesis of Single‐Atom Heterogeneous Catalysts

Wet chemical approaches are among the most versatile and scalable strategies for preparing single‐atom heterogeneous catalysts (SACs). However, despite their broad application, the synthesis of SACs via these routes remains largely ad hoc, with limited attention to the effect of different synthetic parameters on the stabilization of metal species. As a proof of concept, herein, a microfluidic platform is demonstrated for short‐timescale (<10 s), systematic syntheses of SACs via wet impregnation using a range of metal precursor–carrier combinations. The microfluidic environment within rapidly mixed, nanoliter droplets ensures precise control of the concentrations and residence times of the support particles in the metal precursor solutions. This enables the rapid assessment of the influence of the metal precursor concentration on the uptake and dispersion of the adsorbed metal species, as demonstrated for the synthesis of palladium and platinum SACs based on a high‐surface form of graphitic carbon nitride (C3N4). Extension to SACs based on other metals (Ni) and relevant carriers (N‐doped carbon, γ‐alumina) confirms the generality of the synthesis method. The microfluidic approach opens possibilities for high‐throughput parameter screening and mechanistic studies in the design of heterogeneous single‐atom catalysts.

Enhanced ZIF-8-enabled colorimetric CO2 sensing through dye-precursor synthesis

The accumulation of carbon dioxide (CO2) within enclosed spaces, along with volatile organic compounds, under certain humidity, temperature, and ventilation conditions is associated with detrimental human health symptoms such as fatigue. Color-based chemical sensing is a promising approach to detect CO2 levels relevant to indoor air quality through producing fast, quantifiable output visible to the naked eye. In a prior work, a colorimetric gas sensor was fabricated through synthesizing the metal-organic framework, ZIF-8, as the adsorbent, followed by post-synthetic mixing with a dye, phenol red (PSP), and primary amine, ethylenediamine (ED). While this sensor (termed PSP-ED/ZIF-8) maintained its structural integrity in atmospheric conditions and exhibited an increasing fuchsia-to-yellow color change with increasing CO2 levels in dry environment, the colorimetric response greatly suffered in the presence of humid CO2. In this work, a significantly improved colorimetric CO2 sensor (referred to as ED/PSP:ZIF-8) is accomplished through directly incorporating phenol red in the ZIF-8 metal and linker precursor solutions and then blending with ethylenediamine. MATLAB-generated color distributions and in-situ ultraviolet-visible (UV-Vis) spectroscopic studies quantitatively demonstrate an enhanced colorimetric gas response of ED/PSP:ZIF-8 compared to that of PSP-ED/ZIF-8 across an important range of CO2 for indoor air quality monitoring (500 – 3500 ppm) and across a range of humidity. The new sensor also exhibits high selectivity to CO2 compared to select volatile organic compounds, such as acetone and ethanol, which contribute to human health symptoms experienced indoors. The enhanced performance is attributed to the proposed incorporation of phenol red within ZIF-8, while maintaining the chemical stability of the MOF.

Enhancing oxygen reduction reaction performance in acidic media via bimetal Fe and Cr synergistic effects

Currently, it is a great challenge to improve the stability of Fe-based oxygen reduction reaction (ORR) catalysts in acidic medium, because the Fenton reaction between Fe-based catalyst and H2O2 will reduce the stability of the catalyst. In this study, Fe, Cr and nitrogen-doped carbon (FeCr-N-C) was synthesized via co-impregnation of biomass walnut shells with metal precursor solutions. The FeCr-N-C catalyst has an onset potential of 0.88 V vs. RHE and outperforms the Fe-N-C catalyst in acidic media. Moreover, FeCr-N-C shows negligible activity decay (ΔE1/2 = 14 mV) in 0.1 M HClO4 after 20 000 cycles. The experimental results proved that the bimetal synergism can produce low yield of H2O2 (<2%), which might attribute to variations of local electronic structure. The reactive oxygen species of the catalyst were analyzed by Ultraviolet-visible (UV-Vis) absorption spectra. It was proved that the presence of bimetal inhibited the Fenton reaction between Fe2+/Fe3+ and H2O2, and further improved the stability of the catalysts. Hence, this study proposes an efficient strategy to facilitate the practical application of Fe-based catalysts in acidic media.

Thermoplasmonic laser-induced backside wet etching

The article is devoted to one of the effective technologies for processing solid transparent materials—thermoplasmonic laser-induced backside wet etching (TP LIBWE). This technology involves aqueous solutions of metal precursors as a working medium. The dependence of the efficiency of sapphire TP LIBWE micromachining on the parameters of laser action is studied with the aqueous solution of the AgNO3 precursor as a working media. The near-optimal range of laser intensities from the point of the etching speed and quality is found. Utilizing the optoacoustic methods, high-speed video, and an optical integrating sphere, the initial stage of the TP LIBWE process is studied in detail. A four-stage model of the TP LIBWE beginning process is proposed, which explains the effects from the beginning of Ag nanoparticle formation in the region of laser exposure to the transition of the TP LIBWE process to a stationary laser microstructuring mode. It is shown that effective microstructuring occurs due to the appearance on the sapphire surface of a thin modified layer in the region of laser action. This thin modified layer is an amorphous Al2O3 with numerous plasmonic Ag nanoparticles inside it and at the sapphire/liquid interface.

One-Pot Production of Pt–Ni Alloy Nanodendrites on Ceria Nanosheet Supporting Materials with High Electrocatalytic Performance Toward Methanol Oxidation and Oxygen Reduction

To create better fuel cell catalysts, effective approaches to generate hybrid materials comprised of intimately connected metal nanocatalysts and nonstoichiometric metal oxides with finely regulated topologies are very desirable. The production of closely connected metal (PtNi alloy)–metal oxide (CeOx, ceria) hybrid nanostructures is reported here using a simple one-pot synthesis technique. Heating a mixed metal (Pt, Ni, and Ce) precursor solution in oleylamine/oleic acid resulted in well-defined PtNi/ceria hybrids, in which PtNi alloy nanodendrites with multiple branches are evenly spread over small-grained ceria nanosheets. The ceria nanosheets in the hybrids have a large number of oxygen vacancies and a high conductivity due to their small grain size. In comparison to carbon-supported counterparts and a commercial catalyst, the prepared PtNi/ceria hybrids exhibited outstanding electrocatalytic activity and stability for both methanol oxidation and oxygen reduction reactions, which can be attributed to the synergistic effects of the Ni component and ceria on the enhancement of the electrocatalytic function. The current technique will be used to create the best multicomponent catalysts for specific processes.

Iron and copper nanoparticles inside and outside carbon nanotubes: Nanoconfinement, migration, interaction and catalytic performance in Fischer-Tropsch synthesis

Carbon materials have attracted increasing attention as supports for metal catalysts. Iron-containing carbon nanotubes often promoted with copper have found application in Fischer-Tropsch synthesis, which provides an alternative way for conversion of renewable feedstocks to chemicals and fuels. In carbon nanotubes, the active phase can be nanoconfined inside the channels or localized on the outer surface. In most of previous work, the distribution of metal nanoparticles inside or outside carbon nanotubes is considered to be immobile during the catalyst activation or catalytic reaction.In this paper, we uncovered remarkable mobility of both iron and copper species in the bimetallic catalysts between inner carbon nanotube channels and outer surface, which occurs in carbon monoxide and syngas, while almost no migration of iron species proceeds in the monometallic catalysts. This mobility is enhanced by noticeable fragility and defects in carbon nanotubes, which appear on their impregnation with the acid solutions of metal precursors and precursor decomposition. Remarkable mobility of iron and copper species in bimetallic catalysts affects the genesis of iron active sites, and enhances interaction of iron with the promoter. In the bimetallic iron-copper catalysts, the major increase in the activity was attributed to a higher reaction turnover frequency over iron surface sites located in a close proximity with copper.

Synthesis of nanostructured FePt systems

The paper compares some characteristics of nanoparticles of the FePt system obtained by the method of joint reduction of solutions of metal precursors using different reducing agents: an alkaline solution of hydrazine hydrate and sodium tetrahydroborate. The method of transmission electron microscopy is used to analyze the shape and morphology of the obtained nanosized particles, according to the data obtained by the methods of X-ray diffraction, phase analysis is carried out and the main X-ray structural parameters are evaluated. Thermal analysis in combination with mass spectrometry is used to characterize the state and purity of the surface of nanoparticles. It is shown in the work that nanoscale FePt systems obtained using the reductants selected in the work have similar physicochemical characteristics.

Sonochemical Catalyst Synthesis for HER and OER

Improvements on catalysts for electrochemical energy conversion is highly important if technologies such as fuel cells and electrolyzers are to become economically viable in the future. These improvements typically lie in the optimization of the catalyst’s particle size and available surface area, which means that nucleation and growth conditions during the synthesis must be controlled precisely. Common ways of producing such catalysts today involve chemical reduction methods were reducing agents like NaBH4 or ethylene glycol are used to reduce metal salts to their metallic state [1]. Even though such methods are fast and scalable, few ways are available for careful control over the nucleation and growth of the nanoparticles.To allow for better control over the nucleation and growth of nanoparticles, a sonochemical synthesis method can be employed instead [1]. In sonochemistry, high power ultrasound is applied to an aqueous metal precursor solution resulting in the formation of H-radicals and OH-radicals in the cavitation bubbles [1]. The highly reactive radicals will diffuse into the solution and reduce the metal ions to metallic nanoparticles. The nucleation and growth conditions can therefore simply be manipulated by controlling the rate of radical formation which is directly related to the ultrasound parameters. Several studies have found that the radical formation rate (or the metal reduction rate) is affected by the ultrasound frequency [2][3], ultrasound power [3], solution temperature [3], types of dissolved gasses [3], types of alcohols used [4], and types of surfactants used [5]. The ease of changing these parameters therefore ensures that nanoparticles of optimal sizes can be produced.In this project we have started to investigate exactly how ultrasound parameters influence the radical formation rate in aqueous systems. This information can therefore be used to synthesize electrocatalysts optimized for HER and OER. Initial investigations of how Ni- and Fe -precursors are affected by ultrasound have also been performed. Sonochemical assisted synthesis of NiFe nanoparticles with NaBH4 was also assessed as a potential hybrid solution.The results from the investigations of the ultrasound parameters suggested that the addition of ethanol effectively leads to a scavenging of the primary radicals in the solution. Consequently, more radicals become available for reducing metal ions, and the reduction rate increases. Higher ultrasonic power and lower ultrasonic frequency (580 kHz was the lowest frequency used in the experiment) increase the radical formation, which is supported by previous findings [2][3]. The effect of dissolved gasses showed that O2 saturation gave the highest radical yield. However, this can be traced to the sonolysis of O2 itself which lead to additional radical formation from the dissolved gas, and not just from the water vapor in the cavitation bubbles [3]. The ideal solution temperature was found to be dependent on the type of dissolved gas, with Ar exhibiting a higher ideal temperature than O2.The initial investigations of Ni- and Fe-precursors showed that the sonochemical reduction was not appreciable in the short time frame which was used (30 min). Longer sonication times will be attempted in future works.For the sonochemical assisted synthesis, NaBH4 was added as a reducing agent to aid the reduction, and an ultrasonic bath was used as the ultrasound source (42 kHz). Physical characterization of the resulting particles showed a significant decrease in the particle size due to the application of ultrasound. However, these changes were attributed to the mechanical effects most dominant at lower ultrasonic frequencies. Similar experiments will be attempted at higher frequencies to observe if the chemical effects of ultrasound act similarly.References Bruno G. Pollet. “The use of ultrasound for the fabrication of fuel cell materials”. International Journal of Hydrogen Energy 35.21 (2010). VIII symposium of the Mexican Hydrogen Society, pp. 11986–12004K Okitsu et al. “Sonochemical synthesis of gold nanoparticles: effects of ultrasound frequency”. The journal of physical chemistry. B109.44 (2005), p. 20673S Merouani et al. “Sensitivity of free radicals production in acoustically driven bubble to the ultrasonic frequency and nature of dissolved gases”. Ultrasonics – Sonochemistry 22.2 (2015), pp. 41–50Rachel A Caruso et al. “Sonochemical formation of colloidal platinum”. Colloids and Surfaces A: Physicochemical and Engineering Aspects 169.1-3 (2000), pp. 219–225K Okitsu et al. “Sonochemical preparation of ultrafine palladium particles”. Chemistry of Materials (USA) 8.2 (1996), pp. 315–317

Сравнение методов синтеза наноструктурированной системы FePt

In this work, using the example of the synthesis of nanoparticles of the mutual FePt system, obtained in an aqueous medium by the method of co-reduction of solutions of metal precursors, the effect of reducing agents is considered: an alkaline solution of hydrazine hydrate and sodium tetrahydroborate in combination with a stabilizer of sodium-potassium tartrate. The main characteristics of the obtained nanosized particles of the iron-platinum system were studied by means of a complex of physicochemical methods of analysis. The shape and morphology of the obtained nanosized particles were studied by transmission electron microscopy, phase analysis and X-ray structural parameters – by X-ray diffraction methods. It was approached to reveal the dependence of the particle size on the type of reducing agent used. It was found that nanosized FePt particles obtained with different reducing agents have similar physicochemical characteristics. The use of sodium tetrahydroborate, in the presence of a stabilizer sodium-potassium tartrate, allowed to obtain more dispersed particles with a size of 14.3±2.1 nm. FePt nanoparticles reduced by hydrazine hydrate were characterized by large sizes of 16.7±4.0 nm, and the particles form large dense agglomerates. Chemical analysis showed that when reducing with sodium tetrahydroborate, the target product contained 0.4 mol. % boron. When reducing FePt nanoparticles with hydrazine hydrate, it was found that the target product was contaminated with iron oxide, which was also confirmed by X-ray phase analysis. X-ray diffraction analysis showed that the iron-platinum nanosystem was represented by a solid-solution phase with a face-centred cubic lattice. The parameters of the crystal lattice were estimated, 3.908 Å and 3.894 Å, respectively, for FePt nanoparticles obtained using NaBH4 and N2H4∙H2O.