Liquid temperature effect on Pt-Sn electrocatalyst properties during plasma sputtering onto polyethylene glycol

Liquid temperature effect on Pt-Sn electrocatalyst properties during plasma sputtering onto polyethylene glycol | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Liquid temperature effect on Pt-Sn electrocatalyst properties during plasma sputtering onto polyethylene glycol Aïssatou DIOP, Soumya Atmane, Dilane Kevin Tagueu, Eric Millon, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8873928/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 21 Apr, 2026 Read the published version in Journal of Nanoparticle Research → Version 1 posted 9 You are reading this latest preprint version Abstract Pt-Sn nanoparticles were synthesized by magnetron sputtering of a 2-inch Pt 0.8 Sn 0.2 target into polyethylene glycol using an innovative reactor configuration designed for liquid-phase deposition. A comprehensive study was conducted to understand the influence of liquid temperature on the growth of nanoparticles under two conditions: (i) an in-situ heating of the liquid during sputtering deposition using bain-marie bath, and (ii) an ex-situ post-deposition annealing under air of the nanoparticle-liquid suspension obtained after deposition. COMSOL multiphysics simulations have revealed that the temperature of the liquid critically determines the transport regime of sputtered species inside the liquid glycol thus affecting the nanoparticle formation pathways. Complementary structural and morphological characterisations, such as transmission electron microscopy, X-ray diffraction and small angle X-ray scattering, demonstrate that temperature modulates particle size and size distribution. The in-situ heating of the liquid during the growth promotes aggregation and the emergence of interparticle correlations but do not significantly modify the size distribution of the NPs. The ex-situ annealing treatment up to 150°C of the as-deposited NPs affects their organization in solution, lightly alter their intrinsic size and can induce structural and microstructural modifications of the NPs and particularly affect the elemental distribution of Pt and Sn. These results provide new insights into temperature-controlled synthesis of alloy nanoparticles in liquids. Sputtering onto liquid magnetron sputtering nanoparticles polyethylene glycol Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Metal nanoparticles (NPs) based on noble metals such as platinum, gold and silver, combined with metals such as copper, tin or zinc are the subject of various studies on electrocatalyst reactions for the development of sustainable energy and environmental applications. The properties of NPs depend strongly on their nature, size, distribution, shape, composition, ordered, microstructure, and those of their surrounding environment, hence the importance of controlling these parameters according to the application concerned. There are currently several ways to synthesise NPs. The most used methods are the chemical routes such as electrodeposition, hydrothermal synthesis, salt reduction and chemical vapor deposition, but there are also physical methods such as pyrolysis, laser ablation, and atomic layer deposition. Each of these techniques has advantages and disadvantages both with regard the properties of the NPs and their concentration. Techniques combining DC-pulsed excitation with ultrasonic vibration [ 1 , 2 ], plasma as nanosecond-pulsed discharges in liquid (as liquid nitrogen [ 3 , 4 ]) with tip materials electrodes [ 5 ] or metallic salts [ 6 ], have emerged as pulsed-laser ablation in liquid [ 7 , 8 ], or sputtering onto a liquid (SoL) [ 9 – 13 ]. This latter deposition technique that synthesises NPs by sputtering a metal target onto a liquid substrate, allows controlling their properties, such as their shape, size, and concentration, by modifying the properties of the discharge or the properties of the host liquid [ 14 , 15 ]. In the case of a solid substrate deposition process, the heat transfer induced by ion bombardment (which emits IR radiation [ 16 ] ) causes an increase of temperature of the substrate surface, which influences the growth mechanisms and the properties such as the microstructure and phase composition of the deposited layer [ 17 , 18 ]. Similarly, when deposition is performed on a liquid, the heat released by the transmitted IR photons affects not only the temperature of the liquid but also its physicochemical properties and its evaporation, which in return affect the plasma and target surface properties. Sputtering onto liquid has therefore been the subject of various studies, highlighting the complexity of the process [ 19 ]. It has been shown that the properties of the obtained NPs depend strongly on the metal/liquid pair used as target/substrate but also on the process parameters. Discharge parameters (power, current, voltage), target/liquid distance, working pressure are known to control the flux of sputtered species, i.e., the number of species arriving on the substrate per unit of time and surface area, as well as the kinetic energy of the sputtered species [ 20 – 27 ]. There are different types of liquids used in SoL method, including silicone oil, ionic liquids, and polyols, which essentially have one thing in common: their ability to capture aggregates and stabilize the resulting NPs. They are also characterized by their low saturated vapour pressure, typically ranging from about 10 − 1 and 10 − 6 Pa at room temperature (RT), and are not easy to adapt to the process depending on their properties. Here, we have chosen to work with a polyol, the polyethylene glycol (PEG) 400, characterized by a density of 1.12, a vapour pressure below 1 Pa, a boiling temperature of 195°C and dynamic viscosity close to 100 mPa.s at 25°C (and close to 60 mPa.s at 50°C). The role of the liquid temperature during the SoL growth has been already investigated but the results are unclear [ 28 – 30 ]. This ambiguity may arise from several factors, including the intrinsic difficulty of heating a liquid under vacuum, since most studies used vacuum-compatible planar substrate heaters initially developed to heat a planar solid substrate and not a 3D liquid container. Planar heater necessary induces temperature gradient inside liquid which make the understanding of the temperature effect difficult. In addition, the specific metal-liquid affinity can strongly affect nucleation and growth mechanisms. In all case, these studies converge on the conclusion that modifying the temperature of the liquid alters both surface tension and viscosity, thereby strongly influencing the diffusive velocity of the sputtered species within the medium. Consequently, increasing the liquid temperature modifies the characteristics of the resulting nanoparticles. Higher temperatures promote the formation of larger particles with broader size distributions, due to enhanced coalescence and reduced viscosity of the medium. They also tend to modify crystallinity and alloy ordering, as reported in SoL deposition when temperature-dependent influence nucleation and growth of the nanoparticles [ 31 ]. In this study, we propose to investigate the effect of the temperature of the liquid on properties of NPs produced by SoL method using a recently developed apparatus based one a bain-marie water bath method allowing a homogeneous heating of liquid container. The experiments focus on Pt-Sn alloys which are promising electrocatalytics for oxygen reaction reduction (ORR) [ 32 ]. To provide a mechanistic understanding of the influence of liquid temperature on nanoparticle formation during SoL, we first performed a numerical investigation of nanoparticle motion in heated PEG 400 using COMSOL Multiphysics. This model quantifies the temperature-dependant evolution of thermally induced nanoparticle flows within the liquid, and serves as a basis for interpreting the experimental observations. The numerical results are then complemented by small-angle X-ray scattering (SAXS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) of Pt-Sn nanoparticles synthesised by sputtering onto liquid as a function of the liquid temperature during the deposition phase, as well as after post-synthesis annealing under ambient air at 50, 70, 100 and 150°C of the NPs obtained by SoL at RT. 2. Material and experimental methods 2.1. NPs preparation by SoL and thermal treatment Pt-Sn NPs were deposited by plasma sputtering of a 2-inch Pt 0.8 Sn 0.2 target clamped in magnetron manufactured by Kurt J. Lesker placed in a vacuum chamber consisting of a cylindrical stainless steel enclosure, 240 mm in diameter and 130 mm in height as schematised in Fig. 1 a. A 2x10 − 7 mbar base pressure is reached in 2 hours after pumping using a 80 l/s turbomolecular pump (ATP80 Adixen) and a primary without liquid, whereas only 2x10 − 5 mbar (2x10 − 3 Pa) is obtained with the presence of PEG. The substrate holder is a hollow flange that can accommodate a vial/flask filled with liquid (in this case, PEG 400) held in place by vacuum in the reactor. The borosilicate swan-neck flask can contain up to 10 ml due to its internal diameter D of 2.6 cm (5.3 cm² exchange surface) but only 8 ml is introduced inside it before pumping leading to a liquid height h of 1.5 cm (meniscus bottom). This flask-substrate collects the particles ejected from the target. During the deposition, the liquid can be heated up to 80°C in immersing vial in a container filled with water placed on a hotplate or simply by plasma irradiation during deposition. The presence of the transparent vial outside the vacuum apparatus allows real-time visualization of changes in the liquid under the influence of environmental factors using two cameras: one to observe the liquid from flask side and one to observe the liquid through the bottom side when the hotplate is removed. To synthesise the NPs, the power of the plasma generator was set at 50 W for a 2-inch target, giving a power density of 2.5 W cm − ² whereas the target voltage is monitored. The argon working pressure, the gas flow rate, the distance between the target and the liquid surface and the deposition time were set at 0.5 Pa, 10 sccm, 4 cm and 10 min, respectively. After deposition, different samples obtained by SoL at room temperature (without the bain-marie system) were annealed at different temperatures ranging from 50 to 150°C under ambient atmosphere using a conventional muffle furnace from Nabertherm (Model LT 5/13, T_max: 1300°C, controller B 180) to study possible changes in the properties of the NPs. 2.2. Numerical investigation of nanoparticles motion in heated liquid To investigate the interaction of particles within PEG liquid, a two-dimensional D x h computational domain of dimensions 26×10 mm was constructed using COMSOL Multiphysics. This domain represents a vertical cross-section of the liquid column inside the cylindrical flask. Particle transport was simulated using a particle tracking approach, in which particles are introduced below the liquid surface and driven by fluid motion induced by the resulting temperature gradient following the plasma/PEG interaction. The flow field was computed using the non-isothermal flow module implemented in COMSOL Multiphysics. Boundary conditions were applied at the liquid interfaces as shown in Fig. 1 b. No-slip conditions were imposed along the lateral and bottom boundaries corresponding to the glass walls of the flask, whereas a slip boundary condition was applied at the gas–liquid interface on the top boundary. Because at RT, the plasma heats PEG whereas convective cooling occurs at the glass walls, a cooling convective exchange coefficient of 5 W m − 1 K − 1 was selected for side and bottom boundaries. On the contrary, these boundaries are imposed to 50°C (Dirichlet boundary conditions) with the bain-marie bath regulated at 50°C. At the gas–liquid interface, an incoming energy flux density with a Gaussian distribution along the interface is imposed with a maximum of 30 mW·cm⁻² (consistent with experimentally measured values) and a standard deviation equal to D . Marangoni forces were also considered in the model to account for thermocapillary effects and to promote Marangoni-driven convection, particularly in the vicinity of the gas–liquid interface. The derivative surface tension coefficient ( γ ) was fixed at -8x10 − 5 Nm −1 K − 1 [ 33 ]. Following the establishment of the steady thermal regime and flow fields, particles were injected at a depth of 0.5 mm below the gas–liquid interface at regular intervals of 10 s over a total time of 200 s, whereas the total simulation time was fixed to 600 s (for 50°C case) and 3600 s (for RT case). All thermophysical properties were assumed to be temperature dependent. In particular, the dynamic viscosity ( η ) of PEG was modeled as an exponential function of temperature, decreasing from 115 mPa·s at 25°C to 29 mPa·s at 50°C [ 34 ]. The fluid density ( ρ ) linearly decreases between 1126 and 1101 g.cm − 3 [ 34 ], the heat capacity ( C p ) increases between 2300 and 2500 J kg − 1 K − 1 [ 35 ] and finally the thermal expansion coefficient ( α ) and the thermal conductivity ( k ) are set at 1.3x10 − 3 K − 1 .and 0.2 W m − 1 K − 1 respectively [ 36 ]). 2.3. Filtration and transfer of nanoparticles on carbon black (Vulcan) To perform observations with high vacuum electron microscope, the deposited material must be removed from PEG liquid. The first method consists of immersing TEM grids directly into the solution. These holey type grids, provided by SPI supplies, are copper-based and coated with a thin layer of holey carbon. They have 200 meshes and are 3 mm in size. After immersion, grids are rinsing with absolute ethanol to remove as much PEG as possible and leaving them to dry at room temperature for one hour. The second method [ 37 ] consists of adding Vulcan carbon XC 72R previously treated at 400°C in a nitrogen atmosphere to the solution consisting of PEG and NPs. This solution is then diluted with water and filtered using a filtration kit from Fischer scientific and a PVDF filtration membrane from Sigma Aldrich (pore size : 0.22 µm, thickness : 0.1 mm and diameter : 13 mm). The filter containing the particles is then dried at 80°C for 1 hour. The obtained powder is collected for characterization (microscopy and X-ray diffraction). 2.4. Characterisations methods 2.4.1. Small angle X-rays scattering (SAXS) Small-angle X-ray scattering is a technique commonly used to study the internal organization of heterogeneous materials. As X-ray diffraction, this technique involves measuring electron density variations of a multicomponent system by the collection of the X-rays scattered intensities, but in this case, at small detection angles that correspond to a nanometer scale investigation of the heterogeneities, like a dispersion of nanoparticles. In this study, SAXS measurements were performed using the Xeuss SAXS/GISAXS (grazing incidence small angle X-ray scattering)/WAXS (wide angle X-ray scattering) apparatus equipped with a 30 W X-ray source and a copper anode producing a wavelength λ = 0.154 nm (8040 eV). The data were collected in an angular range of 0.1° to 10° with a sample-detector distance of 570 mm. The detector was a Pilatus 300 K, with an active area of 83.8 x 106.5 mm², allowing fast and accurate acquisition of scattering 2D spectra. To ensure that the NPs show the characteristics of the as-deposited material without any changes due to the resting time, the PEG-NPs solution were analysed by SAXS shortly (inferior to 24h) after their synthesis. The PEG-NPs solution was introduced inside a 2 mm in diameter borosilicate glass capillary (80 mm length, 0.01 mm wall thickness from Hilgenberg GmbH) closed using wax and then placed inside the vacuum SAXS apparatus. The acquisition time was fixed to 10 hours for each capillary to obtain a high signal to noise ratio. 2D SAXS images are radially integrated over the angle defined by direct beam to obtain SAXS spectra (scattered intensity vs scattering vector). A capillary filled with pristine PEG400, free of particles, is analysed and the resulted spectrum is subtracted to all SAXS spectra. These spectra are then processed with SASView software using a hard sphere model [ 38 ] to extract structural parameters such as the NPs radius and interparticle distances. 2.4.2. High-resolution transmission electron microscopy The sample was observed using a JEOL ACCELARM 200 Cold FEG Transmission Electron Microscope equipped with Energy Dispersive X-ray Spectrometer (EDS)(Centurio JEOL). A beryllium sample holder was used. Observations were made at 200 kV in STEM mode, spot size 0.08 nm, camera length 8 cm, on Bright Field (BF) and High Angle Annular Dark Field (HAADF) detectors. A beam shower of 20 min was made prior to observation. EDS mapping was 512x512 pixels size, Dwell time, was 0,01 msec, and 75 sweep count, using spot size 0.2 nm and optimized tilt sample holder in order to maximise the signal. The EDX signal was dilate once using FiJi software for easier viewing. This characterization was carried out on the MACLE-CVL platform. The size of NPs and their distribution were determined by using ImageJ software [ 39 ]. 2.4.3. X-ray diffraction X-ray diffraction characterization was performed using a Bruker D8 Discover diffractometer equipped with a copper anticathode delivering X-ray photons at 0.154 nm wavelength and, a solid-state semiconductor detector mounted in four-circle theta-2theta orientated goniometer equipped with a ¼ Eulerian cradle and automated XYZ sample stage. In this study, a 0.2 mm pinhole is mounted whereas Κ α1 -radiation monochromator and equatorial Soller optic were not used. XRD diagrams are obtained in the Bragg-Brentano geometry 𝜃/2𝜃 using “1D mode” detector completely opened (1.92°), between 2𝜃= 20° to 60°. The data was processed using the DiffracEva software [ 40 ]. Once the diffractograms have been acquired, the lattice parameters and the size of the crystallites using the Scherrer method [ 41 , 42 ] can be obtained, taking into account that such calculations are poorly accurate for very small particles (less than 2–3 nm) and low crystallinity and therefore only provide approximate values for the size of crystallites. 3. Results and discussion 3.1. Macroscopic observations and simulations Figure 2 displays the camera pictures of flask containing 8 ml of PEG during the 50 W running sputtered deposition at RT (Fig. 2 a-c) and when water surrounding the flask is heated and regulated at 50°C (Fig. 2 d-f). The second camera located below the glass could not be used due to the presence of the heating plate for 50°C (Fig. 2 d-f). For 1 min, side views are similar for RT and 50°C with the presence of a thin dark layer close to the liquid surface and a blurred zone just below it corresponding to a probable short-range diffusion front of the sputtering materials inside PEG surface. Surprisingly the inset of Fig. 2 a indicates that sputtering material is only visible in a ring close to the lateral glass walls and not in the flask center. If deposition stopped at 1 min, this ring tends to diffuse in the center of the flask to homogenize the solution in few 10’s min. When deposition is running, diffusion front penetrates toward flask bottom. For 2 min, almost half of the 16 mm liquid height is brown, the penetration of sputtered materials being slightly greater for 50°C (penetration length of 7 mm at 50°C versus 5.5 mm at RT). For a time sputtering of 10 min, dark ring in contact to glass walls remains present at RT even if the material tends to penetrate towards to the flask center. Finally, the lateral view for 50°C (Fig. 2 f) clearly shows a dark area in the flask center indicating that sputtered material is denser in this area than in circular periphery. The comparison between experiments at RT and 50°C shows that liquid temperature directly affects the transport regime of sputtered materials inside PEG liquid. For unheated liquid, materials diffuse inside the liquid through the PEG periphery close to the glass wall. Due to the shape of the flask (swan neck), most of sputtered materials is supposed to be deposited on the center of liquid surface and not on its periphery. The observation at RT indicates that sputtering material quickly diffuses on the liquid surface toward the glass walls and then diffuses along them to bottom. For sputtering at 50°C, without bottom visualisation, it is difficult to discuss about transport of particles at this temperature. However, the presence of a dark zone in flask center on Fig. 2 f indicates that particles transport within the PEG differs from the RT case. To improve our understanding of the temperature effect on material transport, a computation based on two-dimensional modelling was performed and particle transport was simulated using non-isothermal flow model coupled with the Marangoni effect. Even if this simulation was performed up to 10 (50°C) and 60 min (RT) with a time step of 1 s, only three time-step (1, 5 and 10 min) were selected and shown on Fig. 3 for the two thermal conditions: RT with convective cooling on glass walls and Dirichlet boundary at 50°C. Moreover, the liquid mean temperatures at three positions (T bottom , T up and T side reported on Fig. 1 ) are shown on Fig. 3 d and 3 h. The particles transport is clearly different between both thermal conditions. For RT (a, b and c), red particles slide towards the lateral walls remaining on PEG liquid surface due to Marangoni forces (speed close to 0.06 mm/s), then they fall down in the vicinity of lateral walls between 5 and 10 min. In the same time, liquid temperatures increases from 25°C at t = 0 min to 37, 31 and 30°C at 10 min for T up , T side and T down respectively. All temperatures are not clearly stabilized at this time and approximatively 90 min are needed. For 50°C (d, e, f), red particles follow the same trajectories, but their speed is much higher on the surface walls (between 0.3 and 0.5 mm/s) due to Marangoni forces and even alongside walls. Particles reach vial bottom before 5 min and then start to go up along to the vial axis and reach liquid surface before 10 min, leading to semi-circular shape trajectory. For 50°C, liquid surface temperature increases up to 55°C (reached after 10 min plasma running) whereas both other temperatures (T side and T down ) are fixed to 50°C. Finally, these results of simulation seem consistent to experimental ones relative to Fig. 2 in both thermal cases. 3.2. Nanoparticle properties: size, structure and microstructure Figure 4 shows the SAXS curves as function of the scattering vector range between 0.25 and 4 nm − 1 as a function of liquid temperature during the SoL deposition (Fig. 4 a), and after an ex-situ annealing at different temperatures of samples previously obtained by SoL at RT (Fig. 4 b). All data were fitted assuming spherical NPs with a diameter following a Gaussian distribution. For Fig. 4 a, the SAXS spectrum of RT sample exhibits the characteristic signal of spherical NPs with an average diameter of 1.1 nm and a standard deviation between 0.3 nm, consistent with values commonly reported for this class of alloyed phases [ 37 , 43 , 44 ]. For the sample obtained at 50°C, a stronger overall intensity is observed which can be attributed to the presence of a larger number of NPs in the probed volume. The mean diameter starts to increase to 1.2 nm. After annealing at 70°C, the low q region of the SAXS pattern remains similar in shape to that observed at 50°C (even of continue to increase) but with a noticeably higher intensity (below 0.4 Å −1 ) suggests the appearance of a second populations of larger scattering species. At higher q, a peak is starting to appear at about 0.25 Å −1 which is be attributed to the emergence of a correlation length L cor equal to 1.8 nm. This correlation peak means that some particles are close to each other and an organisation starts to appear between them with a specific interparticle distance. At 80°C, the same behaviour is observed, with even more pronounced features with and L cor equal to 1.6 and 2.8 nm respectively. For the case of ex-situ annealing (Fig. 4 b), a similar overall trend is found, although the correlation peaks appear at higher temperatures, 100 and 150°C. The second and third curves in Fig. 4 b, corresponding to annealing at 50°C and 70°C, are well described by spherical nanoparticles model with equal to 1.1 nm. After annealing at 70°C, no correlation peak is detected. Such a peak only appears after annealing at 100°C with L cor = 2.4 nm. At 150°C, the SAXS pattern clearly reveals two distinct contributions: a strong low q signal associated with large NPs, and a high q contribution featuring a pronounced correlation peak with L cor = 2.8 nm. As already mentioned, the presence of a correlation peak at 70°C, 80°C ( in-situ ), 100 and 150°C ( ex-situ annealing) means that small particles are not randomly distribute inside liquid but that an organisation starts to appear. Figure 5 corresponds to a HRTEM image of deposited materials post-annealed at 100°C and then deposited on a grid. To quantify the local geometry around each NPs, the widely employed Delaunay triangulation method was applied to the right-bottom corner of Fig. 5 a to connect each NPs to its nearest neighbours and result is shown in Fig. 5 b. This produces triangulations where each feature of interest is connected to its first neighbours. The obtained histogram of the segment lengths, shown in Fig. 5 c, is fitted by a lognormal curve whose maximum is reached for 3.5 nm. Long segments due to empty regions in the image only contribute to the long tail of the distribution and do not influence the measurement of the peak position. This result is in good agreement with the existence of a correlation length of 2.4 nm observed on SAXS spectra (Fig. 4 ) at a position close to 0.25 Å −1 . The larger value obtained by triangulation measurement is the result of two effects: a small statistics due to the limited image area used for the triangulation and the fact that this region has been chosen for its slightly smaller NP density in order to clearly identify individual NP positions and perform an accurate triangulation. In summary, the SAXS analyses of NPs produced at different temperatures by heating the liquid during SoL and of NPs heated ex-situ after SoL deposition at RT provide a coherent picture of the size evolution of the NPs as a function of temperature. In both cases, increasing the temperature affects the organization of the NPs in solution while increasing their intrinsic size. As the temperature rises, the particles tend to organize, resulting in the appearance of correlation peaks in the SAXS signal and conformed by HRTEM images post-treatment. However, the rate at which these structural changes occur depends on the heating method: in-situ heating promotes earlier structural transitions compared with ex-situ annealing, highlighting the importance of the monitoring nanoparticle formation under realistic synthesis conditions. X-ray diffraction measurements were performed on the sample synthesized by SoL at RT to obtain a macroscopic reference of the phases likely involved in the formation of Pt-Sn nanoparticles obtained by conventional liquid sputtering, and after an ex-situ annealing at 150°C of these NPs. The XRD experiments require a significant amount of material, obtained by filtering the solution to recover the carbon-supported nanoparticles. The amount of material in the solution is 4 mg. Thus, 50% wt of vulcanized carbon was added, i.e., 4 mg. Figure 6 shows the XRD diagrams of the vulcanized carbon (without NPs) as reference support (grey line), of the NPs obtained (yellow line) by SoL at RT, and of these NPs after annealing at 150°C (red line). Theoretical diffraction patterns of some pure compounds are also shown in the lower part of Fig. 6 . A broad peak centred around 25° is observed for each sample and, corresponds to the (002) plane of the poorly crystallized graphite phase, which is present in the vulcanized carbon (Fig. 6 , grey line) used as a support for the NPs outside the suspension. The carbon support also induces a broad peak centered at around 44°, corresponding to the 004 diffraction line of graphite (space group P6 3 mmc; COD file 9012230). The experimental diffraction peaks of NPs produced at RT located at 39.19° and 45.26° (continuous yellow line) are respectively in agreement with the (111) and (200) planes of a platinum-based phase [ 45 ]. Indeed, these two peaks could be attributed from the following two hypothesis. Firstly, the (111) and (200) peak positions may correspond to the presence of the cubic phase alloy Pt 3 Sn (space groupe Pm3m; a = 0.400 nm; COD file 1523555). In that case, it must be noticed that such a phase contains less Pt than the sputtering target used for the deposition (Pt 4 Sn 1 ) meaning that the excess of Pt should also present somewhere else. Secondly, regarding the theoretical peak positions of the (111) and (200) planes of the pure FCC cubic Pt phase (space group Fm3m; a = 0.392 nm, COD file 1011103), the 2θ values would be 39.79° and 46.24° for the (111) and (200) lines, respectively. The experimental 2θ angular positions are therefore shifted toward lower values of 2θ, indicating the formation of a solid solution based on Pt FCC cells in which Sn has been inserted or substituted in the Pt lattice. Regarding the thermodynamical phase diagram [ 46 ], such Sn incorporation do not exceed 10at.% in Pt at low temperatures (100–200°C). Given the amount of Sn expected in the NPs (20 at.%), it can be assumed that not all tin species can be inserted into the Pt lattice. That is why the presence of isolated (segregated) Sn can not be excluded as evidenced on Fig. 5 by its theoretical angular positions corresponding to the (111), (220) and (311) planes of tetragonal Sn phase. It is therefore not easy to decide between the two possibilities. Nevertheless, the asymmetrical shape of the X-ray diffraction peaks would argue in favor of the presence of two phases. Considering the (111) reflection as a single peak, the full width at half maximum is around 0.5° indicates the presence of small crystallites for which the mean size is evaluated to be approximately 2.9 nm using the Scherrer equation which is much larger that value obtained by SAXS measurement for RT. Regarding the XRD diagram of the previous NPs after annealing at 150°C (solid red line), we can observe a decrease in crystallinity (broadening and lower intensity of the peaks) compared to the NPs as deposited (solid yellow line). More interestingly, the main peak located around 39° is shifted towards higher angular values, which would mean that the phases of the as-deposited NPs evolve towards an almost pure Pt phase (transformation of Pt 3 Sn into Pt + Sn), indicating that thermal annealing leads to a segregation of Sn and modifies the microstructure of the NPs. Finally, it can not be excluded that the annealing performed in ambient atmosphere also leads to partial oxidization of the particles in addition to its amorphization and the segregation of tin. The XRD experiments provide only a macroscopic view of the structural features of the NPs possible phases, and their average size considering a homogeneous distribution of particles in form and size. For a more in-depth analysis, the microstructure of the NPs has been studied by HRTEM. The protocol used to recover NPs onto TEM grids was applied to observe the Pt-Sn NPs synthesized in PEG. Figure 7 presents HRTEM images of Pt-Sn nanoparticles deposited at RT (Figs. 7 a and 7 b) and deposited in a liquid heated at 80°C (Fig. 7 d and 7 e). Figures. 7g-h and 7j-k correspond to the sample obtained by SoL at RT followed by an ex-situ annealing at 100°C and 150°C, respectively. The size distribution (Figures. 7c, 7f, 7i and 7l) of each sample was determined by measurement of individual particles considered as spherical directly from the images. For the sample deposited at RT, well-dispersed NPs across the grid, with clearly defined interfaces are observed. The size distribution reveals a single population of NPs that can be fitted with a lognormal function, with a mean diameter around 1.6 nm and a standard deviation of 0.46 nm. When the liquid is heated during deposition at 80°C, the NPs (Figs. 7 d and 7 e) appear closer together. Despite the tendency of NPs to aggregate, and by considering only isolated particles, the size distribution obtained from 40 individual particles leads to an average diameter of 1.6 nm with a standard deviation of 0.46 nm. This value is very close to that measured for the sample obtained at RT. For the sample obtained with an ex-situ annealing at 100°C (Figs. 7 g-i), the size distribution again fitted with a lognormal function, yields an average diameter of around 1.8 nm with a standard deviation of 0.33 nm. When the temperature of annealing is increased at 150°C (Figs. 7 j-l), the size distribution is characterized by a bimodal distribution and an average size of around 2.8 nm with a standard deviation of 0.53 nm. An increase of the annealing temperature would induce an aggregation of small NPs to form NPS with a higher size. In all cases, the images in Figures. 7b, 7e, 7h and 7k display (111) lattice fringes with a d-spacing of 0.22 nm, characteristic of Pt-rich NPs. The edge of NPs are less distinct at 150°C than for the NPs prepared at RT (Fig. 7 h), which may be due to beam-induced artefacts but also to a modification of the NPs resulting in a core-shell type microstructure corresponding to a possible segregation of tin atoms on the outer part of the NPs during heating, as it has been also suggested by the XRD experiments. To go deeper insight on the effect of temperature on the elemental distribution within the Pt-Sn NPs, STEM coupled with EDX mapping has been performed on samples realized at RT followed by an annealing at 150°C (Fig. 8 ). It has first to be noted that the accuracy of high-resolution chemical analysis can be complicated by residual PEG despite multiple rinsing steps. Indeed, EDX mappings show the distribution of Pt element (Fig. 8 b) and Sn (Fig. 8 c) and unfortunately does not reveal clear heterogeneity of the NPs chemical composition after an ex-situ annealing treatment, as expected regarding the XRD analyses which indicated that a segregation of Sn at the outer part of Pt-Sn NPs could be envisaged. The different data obtained by SAXS, XRD and HRTEM experiments on Pt-Sn nanoparticles synthesizing by sputtering onto liquid PEG make it possible highlight some effects of the temperature on the structural and microstructural properties of the NPs. Firstly, the temperature of the liquid was raised during the deposition and secondly the solution was annealed in a conventional muffle furnace at ambient air at different temperatures. When the deposition is performed at RT, the NPs are mostly spherical, well crystallized with a well-defined order and a monodisperse size distribution with an average size of around 1.6 nm (versus 1.1 nm with SAXS). In the as-deposited NPs at RT, most of Pt and Sn atoms are mixed together, leading either to a compound with a well-defined composition corresponding to the cubic phase of the Pt 3 Sn alloy or to a Pt-Sn solid solution in which Sn is insert into the FCC Pt lattice. In-situ heating promotes NPs diameter increase, aggregation and the emergence of interparticle correlations. This is consistent with what is usually seen in the literature for this type of process [ 28 , 47 ]. It has been shown that changing the temperature of the liquid alters the surface tension and viscosity, which drastically changes the diffusive velocity of the species sputtered into the liquid. This leads to an increase in the size of the nanoparticles due to the increase in the number of collisions between species during nucleation and growth in the liquid. For example, in the work of Staszek et al., they shown that increasing the temperature from 5 to 20°C produce a remarkable increase in NPs average size from 12.8 nm (5°C) to 21.2 nm (20°C) [ 29 ]. In this work, rising the liquid temperature promotes atomic diffusion, which tends to increase the mobility of the nanoparticles, causing them to coalesce without altering their individual microstructure. They organize themselves and form a cluster, which induces amorphization of the overall structure. It appears therefore that the temperature may have an effect during the deposition step by SoL which is not evidenced in the present work but also modify the NPs properties as far they are deposited on the substrate during the growth. Following this path, the ex-situ annealing treatment à 150°C of the as-deposited NPs shows that a temperature, even moderate can induce structural and microstructural modifications of the NPs. Particularly, the elemental distribution of Pt and Sn is affected which induces a shift of the XRD peaks towards the 2θ higher value (Fig. 6 ) which could be the consequence of a segregation of Sn at the outer part of Pt-Sn NPs. Conclusion PtSn electrocatalyst nanoparticles were synthetized by DC magnetron sputtering of a Pt 0.8 Sn 0.2 target onto a polyethylene glycol under Ar plasma. This work highlights the influence of the liquid temperature on the properties of the NPs by comparing two thermal conditions: in-situ heating of the liquid during deposition using a bain-marie system ensuring homogeneous temperature control, and post-deposition annealing under air of the as-deposited NPs in a conventional furnace. COMSOL Multiphysics simulations and macroscopic observations show that the growth mechanism during SoL is strongly temperature-dependent, as liquid heating modifies surface tension and viscosity, thereby altering the transport regime of sputtered species within glycol and influencing nucleation pathways. SAXS and HRTEM analyses reveal that as-deposited PtSn nanoparticles exhibit diameters around 1–2 nm, consistent with values reported in the literature for SoL synthesized Pt-based alloys. XRD confirms that the NPs are well crystallized and predominantly Pt-rich, with Sn incorporation in agreement with HRTEM-EDX observations. The combined characterisation results indicate that, in this study, increasing the temperature increases the nanoparticle diameter from 1.6 to 2.8 nm using HRTEM and from 1.2 to 1.6 nm using SAXS. Moreover, whether in-situ or ex-situ rising temperature, this latter influences nanoparticle organisation: above a certain threshold, a regular space between them is observed, and higher temperatures promote the onset of aggregation. Overall, this work demonstrates that magnetron sputtering onto a liquid is well suited for producing small and well-dispersed Pt-Sn nanoparticles in PEG, which is highly relevant for electrocatalytic applications. Moreover, both in-situ and ex-situ heating enhance diffusion within the liquid and drive nanoparticle reorganisation, offering a means to tune particle size for targeted applications. Further work will focus on electrochemical characterisation of these PtSn nanoparticles. Declarations Credit authorship contribution statement Aïssatou Diop - Original draft, Investigation, formal analysis , Soumya Atmane, liquid investigation, Dilane Kevine Tagueu - comsol multiphysics works, Eric Millon – Supervision, review & writing, Audrey Sauldubois – microscopy works, Nadjib Semmar , comsol multiphysics supervision, Loïc Gimenez – PVD technical expert, Maxime Mikikian - Delaunay triangulation investigation, Pascal Andreazza – review, Amael Caillard - supervision, project administration, funding acquisition, review & editing, writing. Declaration of competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability The data presented here will be made available on request. Acknowledgements This work is realized in the case of BHyoLOHC project (ProjetIA-22-PEHY-0016) funded by the French National Agency of Research via the PEPR Decarbonated Hydrogen. A. Caillard and A. Diop gratefully thank Christophe Coutanceau and Karine Vigier de Oliveira for scientific discussion related to PtSn nanoparticles and BHyoLOHC project management. This project has benefited from the expertise and the facilities of the Platform MACLE - CVL which was co-funded by the European Union and Centre-Val de Loire Region (FEDER). The authors acknowledge Nicolas Gouillon from ICMN for technical support during SAXS measurements. References Pootawang P, Saito N, Takai O, et al. Synthesis and characteristics of Ag/Pt bimetallic nanocomposites by arc-discharge solution plasma processing. Nanotechnology. 2012;23(39):395602. Chang H, Kao MJ, Jwo CS, et al. Preparation of Co/Ag nanocompound fluid using ASNSS with aid of ultrasonic orthogonal vibration. 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Cite Share Download PDF Status: Published Journal Publication published 21 Apr, 2026 Read the published version in Journal of Nanoparticle Research → Version 1 posted Editorial decision: Revision requested 18 Mar, 2026 Reviews received at journal 17 Mar, 2026 Reviews received at journal 10 Mar, 2026 Reviewers agreed at journal 25 Feb, 2026 Reviewers agreed at journal 18 Feb, 2026 Reviewers invited by journal 18 Feb, 2026 Editor assigned by journal 17 Feb, 2026 Submission checks completed at journal 15 Feb, 2026 First submitted to journal 13 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8873928","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":593308406,"identity":"4bd10480-0be7-4412-aa03-8724f11795be","order_by":0,"name":"Aïssatou DIOP","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Aïssatou","middleName":"","lastName":"DIOP","suffix":""},{"id":593308423,"identity":"32da4794-e58e-4ad1-b77d-1b5615ce7ba0","order_by":1,"name":"Soumya Atmane","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Soumya","middleName":"","lastName":"Atmane","suffix":""},{"id":593308424,"identity":"c60d1fa4-25da-4830-8cb4-25c57d16bd0c","order_by":2,"name":"Dilane Kevin Tagueu","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Dilane","middleName":"Kevin","lastName":"Tagueu","suffix":""},{"id":593308431,"identity":"5e475d27-6e20-4f5d-ae37-b2234498cd59","order_by":3,"name":"Eric Millon","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Eric","middleName":"","lastName":"Millon","suffix":""},{"id":593308436,"identity":"7af33da1-ea95-48aa-84a8-6971531102b1","order_by":4,"name":"Audrey Sauldubois","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Audrey","middleName":"","lastName":"Sauldubois","suffix":""},{"id":593308437,"identity":"4ebea057-5abb-43f9-8350-56e0490fcf18","order_by":5,"name":"Nadjib Semmar","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Nadjib","middleName":"","lastName":"Semmar","suffix":""},{"id":593308440,"identity":"8a73083c-0067-48b1-b703-9706efbe62d9","order_by":6,"name":"Loic Gimenez","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Loic","middleName":"","lastName":"Gimenez","suffix":""},{"id":593308443,"identity":"4b9dcdca-1a47-46e1-be68-451ec32bbb0f","order_by":7,"name":"Maxime Mikikian","email":"","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":false,"prefix":"","firstName":"Maxime","middleName":"","lastName":"Mikikian","suffix":""},{"id":593308445,"identity":"39bcdde3-c6d2-479d-9a3e-c2278e7c0c55","order_by":8,"name":"Pascal Andreazza","email":"","orcid":"","institution":"Université d’Orléans, CNRS, ICMN, UMR 7374","correspondingAuthor":false,"prefix":"","firstName":"Pascal","middleName":"","lastName":"Andreazza","suffix":""},{"id":593308448,"identity":"f5c76f9b-a4eb-4ba5-83a8-d586968661e2","order_by":9,"name":"Amaël Caillard","email":"data:image/png;base64,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","orcid":"","institution":"Université d’Orléans, CNRS, GREMI, UMR 7344","correspondingAuthor":true,"prefix":"","firstName":"Amaël","middleName":"","lastName":"Caillard","suffix":""}],"badges":[],"createdAt":"2026-02-13 16:24:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8873928/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8873928/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11051-026-06631-z","type":"published","date":"2026-04-21T15:59:12+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":103094815,"identity":"02880bcb-36db-49c7-9dc0-5188a4457a41","added_by":"auto","created_at":"2026-02-20 17:41:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":232143,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of SoL equipment with special bain-marie water bath and cameras (a); and two- dimensional computational domain defined in COMSOL multiphysics (b)\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/78a596075682c37836e9be91.png"},{"id":103094816,"identity":"741d771f-e8e3-4f68-baab-c46cee201924","added_by":"auto","created_at":"2026-02-20 17:41:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":938195,"visible":true,"origin":"","legend":"\u003cp\u003eSide and bottom (in inset) views of the glass flask containing PEG and nanoparticles during SoL experiments at RT (a, b, c) and at 50°C (d, e, f) using a water bath hold at 50°C as function of deposition running time (1, 2 and 10 min).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/1c59c6ca0024cdac25e43740.png"},{"id":103094822,"identity":"1fc587e8-afa8-4777-abfe-be0412c4fff7","added_by":"auto","created_at":"2026-02-20 17:41:33","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":817850,"visible":true,"origin":"","legend":"\u003cp\u003eCOMSOL simulation of PEG liquid speed (m s\u003csup\u003e-1\u003c/sup\u003e) submitted to a heat flux of 30 mW cm\u003csup\u003e-2\u003c/sup\u003e from the upper interface for two different thermal boundary conditions : RT (a,b,c,d) and 50°C (e,f,g,h); and three different times : 1 (a,e), 5 (b,f) and 10 min (c,g). \u0026nbsp;Time evolution of liquid mean temperatures (T\u003csub\u003ebottom\u003c/sub\u003e, T\u003csub\u003eup\u003c/sub\u003e and T\u003csub\u003eside\u003c/sub\u003e) are reported (d and h).\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/50ab3f8a4c97dd7ee9ca6ea2.jpeg"},{"id":103504139,"identity":"83ee4c32-ff42-4282-acb9-ee55209f0f94","added_by":"auto","created_at":"2026-02-26 13:17:41","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":66604,"visible":true,"origin":"","legend":"\u003cp\u003eSAXS spectra of (a) the NPs produced by SoL at RT and different temperatures of bain-marie water batch (50°C, 70°C and 80°C) and (b) of NPs obtained at RT followed with a post annealing at different temperatures (50°C, 70°C, 100°C and 150°C). Experimental data (coloured symbols) fitted curves (coloured lines) with mean NPs diameter \u0026lt;d\u0026gt; are reported on both graphs.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/f74a7fdb50f374a8f785bbed.png"},{"id":103094817,"identity":"e1b96708-c92d-4383-bdd8-f4bd922fccef","added_by":"auto","created_at":"2026-02-20 17:41:33","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":443899,"visible":true,"origin":"","legend":"\u003cp\u003eSTEM Bright Field observation of Pt-Sn NPs obtained by SoL at RT and post-annealed at 100°C (a), Delaunay triangulation method (b) and histogram of the segment lenghts (c).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/47977b423df73780487e6f7d.png"},{"id":103503965,"identity":"c9b91e68-8f94-413c-9861-73937574b22f","added_by":"auto","created_at":"2026-02-26 13:05:54","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":97965,"visible":true,"origin":"","legend":"\u003cp\u003eθ/2θ XRD diagrams of vulcanized carbon support (grey line), of Pt-Sn nanoparticles deposited by SoL at 50W and RT (yellow line) and of the latter after annealing at 150°C (red line). The theoretical angular positions of different expected phases are shown in the lower part (dash lines).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/a02a843ffb6b2e832b9b566d.png"},{"id":103094819,"identity":"6ed730e6-51e3-49c1-a664-c0fa87d1239a","added_by":"auto","created_at":"2026-02-20 17:41:33","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1003067,"visible":true,"origin":"","legend":"\u003cp\u003eSTEM BF and HAADF observation of PtSn NPs obtained by SoL at RT (a, b, c), of PtSn NPs obtained by SoL at 80 °C (d, e, f), and of PtSn NPs obtained by SoL at RT followed with an ex-situ annealing at 100°C (g, h, i) and at 150°C (j, k, l). The corresponding size distribution are also presented (c, f, i, l,).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/a8b8d1647b40e4cff5d37732.png"},{"id":103503948,"identity":"4b4a46b9-4dd0-44f7-b8e1-d928acdd943a","added_by":"auto","created_at":"2026-02-26 13:05:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":863389,"visible":true,"origin":"","legend":"\u003cp\u003eSTEM image (a) and EDX mapping of Pt (b) and Sn (c) of Pt-Sn NPs obtained by SoL at RT followed with an ex-situ annealing at 150°C\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/cc1aa6d81960612b38518101.png"},{"id":107927909,"identity":"ce46d249-9e4a-432d-a947-125787324e15","added_by":"auto","created_at":"2026-04-27 16:06:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4566338,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8873928/v1/88286a3b-6939-495d-a6ef-8871c68a410f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Liquid temperature effect on Pt-Sn electrocatalyst properties during plasma sputtering onto polyethylene glycol","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMetal nanoparticles (NPs) based on noble metals such as platinum, gold and silver, combined with metals such as copper, tin or zinc are the subject of various studies on electrocatalyst reactions for the development of sustainable energy and environmental applications. The properties of NPs depend strongly on their nature, size, distribution, shape, composition, ordered, microstructure, and those of their surrounding environment, hence the importance of controlling these parameters according to the application concerned. There are currently several ways to synthesise NPs. The most used methods are the chemical routes such as electrodeposition, hydrothermal synthesis, salt reduction and chemical vapor deposition, but there are also physical methods such as pyrolysis, laser ablation, and atomic layer deposition. Each of these techniques has advantages and disadvantages both with regard the properties of the NPs and their concentration. Techniques combining DC-pulsed excitation with ultrasonic vibration [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], plasma as nanosecond-pulsed discharges in liquid (as liquid nitrogen [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]) with tip materials electrodes [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] or metallic salts [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], have emerged as pulsed-laser ablation in liquid [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], or sputtering onto a liquid (SoL) [\u003cspan additionalcitationids=\"CR10 CR11 CR12\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. This latter deposition technique that synthesises NPs by sputtering a metal target onto a liquid substrate, allows controlling their properties, such as their shape, size, and concentration, by modifying the properties of the discharge or the properties of the host liquid [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the case of a solid substrate deposition process, the heat transfer induced by ion bombardment (which emits IR radiation [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] ) causes an increase of temperature of the substrate surface, which influences the growth mechanisms and the properties such as the microstructure and phase composition of the deposited layer [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Similarly, when deposition is performed on a liquid, the heat released by the transmitted IR photons affects not only the temperature of the liquid but also its physicochemical properties and its evaporation, which in return affect the plasma and target surface properties. Sputtering onto liquid has therefore been the subject of various studies, highlighting the complexity of the process [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. It has been shown that the properties of the obtained NPs depend strongly on the metal/liquid pair used as target/substrate but also on the process parameters. Discharge parameters (power, current, voltage), target/liquid distance, working pressure are known to control the flux of sputtered species, i.e., the number of species arriving on the substrate per unit of time and surface area, as well as the kinetic energy of the sputtered species [\u003cspan additionalcitationids=\"CR21 CR22 CR23 CR24 CR25 CR26\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. There are different types of liquids used in SoL method, including silicone oil, ionic liquids, and polyols, which essentially have one thing in common: their ability to capture aggregates and stabilize the resulting NPs. They are also characterized by their low saturated vapour pressure, typically ranging from about 10\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e Pa at room temperature (RT), and are not easy to adapt to the process depending on their properties. Here, we have chosen to work with a polyol, the polyethylene glycol (PEG) 400, characterized by a density of 1.12, a vapour pressure below 1 Pa, a boiling temperature of 195\u0026deg;C and dynamic viscosity close to 100 mPa.s at 25\u0026deg;C (and close to 60 mPa.s at 50\u0026deg;C). The role of the liquid temperature during the SoL growth has been already investigated but the results are unclear [\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. This ambiguity may arise from several factors, including the intrinsic difficulty of heating a liquid under vacuum, since most studies used vacuum-compatible planar substrate heaters initially developed to heat a planar solid substrate and not a 3D liquid container. Planar heater necessary induces temperature gradient inside liquid which make the understanding of the temperature effect difficult. In addition, the specific metal-liquid affinity can strongly affect nucleation and growth mechanisms. In all case, these studies converge on the conclusion that modifying the temperature of the liquid alters both surface tension and viscosity, thereby strongly influencing the diffusive velocity of the sputtered species within the medium. Consequently, increasing the liquid temperature modifies the characteristics of the resulting nanoparticles. Higher temperatures promote the formation of larger particles with broader size distributions, due to enhanced coalescence and reduced viscosity of the medium. They also tend to modify crystallinity and alloy ordering, as reported in SoL deposition when temperature-dependent influence nucleation and growth of the nanoparticles [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, we propose to investigate the effect of the temperature of the liquid on properties of NPs produced by SoL method using a recently developed apparatus based one a bain-marie water bath method allowing a homogeneous heating of liquid container. The experiments focus on Pt-Sn alloys which are promising electrocatalytics for oxygen reaction reduction (ORR) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. To provide a mechanistic understanding of the influence of liquid temperature on nanoparticle formation during SoL, we first performed a numerical investigation of nanoparticle motion in heated PEG 400 using COMSOL Multiphysics. This model quantifies the temperature-dependant evolution of thermally induced nanoparticle flows within the liquid, and serves as a basis for interpreting the experimental observations. The numerical results are then complemented by small-angle X-ray scattering (SAXS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) of Pt-Sn nanoparticles synthesised by sputtering onto liquid as a function of the liquid temperature during the deposition phase, as well as after post-synthesis annealing under ambient air at 50, 70, 100 and 150\u0026deg;C of the NPs obtained by SoL at RT.\u003c/p\u003e"},{"header":"2. Material and experimental methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. NPs preparation by SoL and thermal treatment\u003c/h2\u003e \u003cp\u003ePt-Sn NPs were deposited by plasma sputtering of a 2-inch Pt\u003csub\u003e0.8\u003c/sub\u003eSn\u003csub\u003e0.2\u003c/sub\u003e target clamped in magnetron manufactured by Kurt J. Lesker placed in a vacuum chamber consisting of a cylindrical stainless steel enclosure, 240 mm in diameter and 130 mm in height as schematised in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. A 2x10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e mbar base pressure is reached in 2 hours after pumping using a 80 l/s turbomolecular pump (ATP80 Adixen) and a primary without liquid, whereas only 2x10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e mbar (2x10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Pa) is obtained with the presence of PEG. The substrate holder is a hollow flange that can accommodate a vial/flask filled with liquid (in this case, PEG 400) held in place by vacuum in the reactor. The borosilicate swan-neck flask can contain up to 10 ml due to its internal diameter \u003cem\u003eD\u003c/em\u003e of 2.6 cm (5.3 cm\u0026sup2; exchange surface) but only 8 ml is introduced inside it before pumping leading to a liquid height \u003cem\u003eh\u003c/em\u003e of 1.5 cm (meniscus bottom). This flask-substrate collects the particles ejected from the target. During the deposition, the liquid can be heated up to 80\u0026deg;C in immersing vial in a container filled with water placed on a hotplate or simply by plasma irradiation during deposition. The presence of the transparent vial outside the vacuum apparatus allows real-time visualization of changes in the liquid under the influence of environmental factors using two cameras: one to observe the liquid from flask side and one to observe the liquid through the bottom side when the hotplate is removed. To synthesise the NPs, the power of the plasma generator was set at 50 W for a 2-inch target, giving a power density of 2.5 W cm\u003csup\u003e\u0026minus;\u003c/sup\u003e\u0026sup2; whereas the target voltage is monitored. The argon working pressure, the gas flow rate, the distance between the target and the liquid surface and the deposition time were set at 0.5 Pa, 10 sccm, 4 cm and 10 min, respectively. After deposition, different samples obtained by SoL at room temperature (without the bain-marie system) were annealed at different temperatures ranging from 50 to 150\u0026deg;C under ambient atmosphere using a conventional muffle furnace from Nabertherm (Model LT 5/13, T_max: 1300\u0026deg;C, controller B 180) to study possible changes in the properties of the NPs.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Numerical investigation of nanoparticles motion in heated liquid\u003c/h2\u003e \u003cp\u003eTo investigate the interaction of particles within PEG liquid, a two-dimensional \u003cem\u003eD\u003c/em\u003e x \u003cem\u003eh\u003c/em\u003e computational domain of dimensions 26\u0026times;10 mm was constructed using COMSOL Multiphysics. This domain represents a vertical cross-section of the liquid column inside the cylindrical flask. Particle transport was simulated using a particle tracking approach, in which particles are introduced below the liquid surface and driven by fluid motion induced by the resulting temperature gradient following the plasma/PEG interaction.\u003c/p\u003e \u003cp\u003eThe flow field was computed using the non-isothermal flow module implemented in COMSOL Multiphysics. Boundary conditions were applied at the liquid interfaces as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb. No-slip conditions were imposed along the lateral and bottom boundaries corresponding to the glass walls of the flask, whereas a slip boundary condition was applied at the gas\u0026ndash;liquid interface on the top boundary. Because at RT, the plasma heats PEG whereas convective cooling occurs at the glass walls, a cooling convective exchange coefficient of 5 W m\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e K\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was selected for side and bottom boundaries. On the contrary, these boundaries are imposed to 50\u0026deg;C (Dirichlet boundary conditions) with the bain-marie bath regulated at 50\u0026deg;C. At the gas\u0026ndash;liquid interface, an incoming energy flux density with a Gaussian distribution along the interface is imposed with a maximum of 30 mW\u0026middot;cm⁻\u0026sup2; (consistent with experimentally measured values) and a standard deviation equal to \u003cem\u003eD\u003c/em\u003e. Marangoni forces were also considered in the model to account for thermocapillary effects and to promote Marangoni-driven convection, particularly in the vicinity of the gas\u0026ndash;liquid interface. The derivative surface tension coefficient (\u003cem\u003eγ\u003c/em\u003e) was fixed at -8x10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e Nm\u003csup\u003e\u0026minus;1\u003c/sup\u003eK\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Following the establishment of the steady thermal regime and flow fields, particles were injected at a depth of 0.5 mm below the gas\u0026ndash;liquid interface at regular intervals of 10 s over a total time of 200 s, whereas the total simulation time was fixed to 600 s (for 50\u0026deg;C case) and 3600 s (for RT case). All thermophysical properties were assumed to be temperature dependent. In particular, the dynamic viscosity (\u003cem\u003eη\u003c/em\u003e) of PEG was modeled as an exponential function of temperature, decreasing from 115 mPa\u0026middot;s at 25\u0026deg;C to 29 mPa\u0026middot;s at 50\u0026deg;C [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The fluid density (\u003cem\u003eρ\u003c/em\u003e) linearly decreases between 1126 and 1101 g.cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], the heat capacity (\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ep\u003c/em\u003e\u003c/sub\u003e) increases between 2300 and 2500 J kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e K\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] and finally the thermal expansion coefficient (\u003cem\u003eα\u003c/em\u003e) and the thermal conductivity (\u003cem\u003ek\u003c/em\u003e) are set at 1.3x10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e K\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.and 0.2 W m\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e K\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Filtration and transfer of nanoparticles on carbon black (Vulcan)\u003c/h2\u003e \u003cp\u003eTo perform observations with high vacuum electron microscope, the deposited material must be removed from PEG liquid. The first method consists of immersing TEM grids directly into the solution. These holey type grids, provided by SPI supplies, are copper-based and coated with a thin layer of holey carbon. They have 200 meshes and are 3 mm in size. After immersion, grids are rinsing with absolute ethanol to remove as much PEG as possible and leaving them to dry at room temperature for one hour. The second method [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] consists of adding Vulcan carbon XC 72R previously treated at 400\u0026deg;C in a nitrogen atmosphere to the solution consisting of PEG and NPs. This solution is then diluted with water and filtered using a filtration kit from Fischer scientific and a PVDF filtration membrane from Sigma Aldrich (pore size : 0.22 \u0026micro;m, thickness : 0.1 mm and diameter : 13 mm). The filter containing the particles is then dried at 80\u0026deg;C for 1 hour. The obtained powder is collected for characterization (microscopy and X-ray diffraction).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Characterisations methods\u003c/h2\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.4.1. Small angle X-rays scattering (SAXS)\u003c/h2\u003e \u003cp\u003eSmall-angle X-ray scattering is a technique commonly used to study the internal organization of heterogeneous materials. As X-ray diffraction, this technique involves measuring electron density variations of a multicomponent system by the collection of the X-rays scattered intensities, but in this case, at small detection angles that correspond to a nanometer scale investigation of the heterogeneities, like a dispersion of nanoparticles. In this study, SAXS measurements were performed using the Xeuss SAXS/GISAXS (grazing incidence small angle X-ray scattering)/WAXS (wide angle X-ray scattering) apparatus equipped with a 30 W X-ray source and a copper anode producing a wavelength λ\u0026thinsp;=\u0026thinsp;0.154 nm (8040 eV). The data were collected in an angular range of 0.1\u0026deg; to 10\u0026deg; with a sample-detector distance of 570 mm. The detector was a Pilatus 300 K, with an active area of 83.8 x 106.5 mm\u0026sup2;, allowing fast and accurate acquisition of scattering 2D spectra. To ensure that the NPs show the characteristics of the as-deposited material without any changes due to the resting time, the PEG-NPs solution were analysed by SAXS shortly (inferior to 24h) after their synthesis. The PEG-NPs solution was introduced inside a 2 mm in diameter borosilicate glass capillary (80 mm length, 0.01 mm wall thickness from Hilgenberg GmbH) closed using wax and then placed inside the vacuum SAXS apparatus. The acquisition time was fixed to 10 hours for each capillary to obtain a high signal to noise ratio. 2D SAXS images are radially integrated over the angle defined by direct beam to obtain SAXS spectra (scattered intensity vs scattering vector). A capillary filled with pristine PEG400, free of particles, is analysed and the resulted spectrum is subtracted to all SAXS spectra. These spectra are then processed with SASView software using a hard sphere model [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] to extract structural parameters such as the NPs radius and interparticle distances.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.4.2. High-resolution transmission electron microscopy\u003c/h2\u003e \u003cp\u003eThe sample was observed using a JEOL ACCELARM 200 Cold FEG Transmission Electron Microscope equipped with Energy Dispersive X-ray Spectrometer (EDS)(Centurio JEOL). A beryllium sample holder was used. Observations were made at 200 kV in STEM mode, spot size 0.08 nm, camera length 8 cm, on Bright Field (BF) and High Angle Annular Dark Field (HAADF) detectors. A beam shower of 20 min was made prior to observation. EDS mapping was 512x512 pixels size, Dwell time, was 0,01 msec, and 75 sweep count, using spot size 0.2 nm and optimized tilt sample holder in order to maximise the signal. The EDX signal was dilate once using FiJi software for easier viewing. This characterization was carried out on the MACLE-CVL platform. The size of NPs and their distribution were determined by using ImageJ software [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.4.3. X-ray diffraction\u003c/h2\u003e \u003cp\u003eX-ray diffraction characterization was performed using a Bruker D8 Discover diffractometer equipped with a copper anticathode delivering X-ray photons at 0.154 nm wavelength and, a solid-state semiconductor detector mounted in four-circle theta-2theta orientated goniometer equipped with a \u0026frac14; Eulerian cradle and automated XYZ sample stage. In this study, a 0.2 mm pinhole is mounted whereas Κ\u003csub\u003eα1\u003c/sub\u003e-radiation monochromator and equatorial Soller optic were not used. XRD diagrams are obtained in the Bragg-Brentano geometry \u0026#120579;/2\u0026#120579; using \u0026ldquo;1D mode\u0026rdquo; detector completely opened (1.92\u0026deg;), between 2\u0026#120579;= 20\u0026deg; to 60\u0026deg;. The data was processed using the DiffracEva software [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Once the diffractograms have been acquired, the lattice parameters and the size of the crystallites using the Scherrer method [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e] can be obtained, taking into account that such calculations are poorly accurate for very small particles (less than 2\u0026ndash;3 nm) and low crystallinity and therefore only provide approximate values for the size of crystallites.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Macroscopic observations and simulations\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e displays the camera pictures of flask containing 8 ml of PEG during the 50 W running sputtered deposition at RT (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-c) and when water surrounding the flask is heated and regulated at 50\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed-f). The second camera located below the glass could not be used due to the presence of the heating plate for 50\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed-f). For 1 min, side views are similar for RT and 50\u0026deg;C with the presence of a thin dark layer close to the liquid surface and a blurred zone just below it corresponding to a probable short-range diffusion front of the sputtering materials inside PEG surface. Surprisingly the inset of Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea indicates that sputtering material is only visible in a ring close to the lateral glass walls and not in the flask center. If deposition stopped at 1 min, this ring tends to diffuse in the center of the flask to homogenize the solution in few 10\u0026rsquo;s min. When deposition is running, diffusion front penetrates toward flask bottom. For 2 min, almost half of the 16 mm liquid height is brown, the penetration of sputtered materials being slightly greater for 50\u0026deg;C (penetration length of 7 mm at 50\u0026deg;C versus 5.5 mm at RT). For a time sputtering of 10 min, dark ring in contact to glass walls remains present at RT even if the material tends to penetrate towards to the flask center. Finally, the lateral view for 50\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef) clearly shows a dark area in the flask center indicating that sputtered material is denser in this area than in circular periphery. The comparison between experiments at RT and 50\u0026deg;C shows that liquid temperature directly affects the transport regime of sputtered materials inside PEG liquid. For unheated liquid, materials diffuse inside the liquid through the PEG periphery close to the glass wall. Due to the shape of the flask (swan neck), most of sputtered materials is supposed to be deposited on the center of liquid surface and not on its periphery. The observation at RT indicates that sputtering material quickly diffuses on the liquid surface toward the glass walls and then diffuses along them to bottom. For sputtering at 50\u0026deg;C, without bottom visualisation, it is difficult to discuss about transport of particles at this temperature. However, the presence of a dark zone in flask center on Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef indicates that particles transport within the PEG differs from the RT case. To improve our understanding of the temperature effect on material transport, a computation based on two-dimensional modelling was performed and particle transport was simulated using non-isothermal flow model coupled with the Marangoni effect.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eEven if this simulation was performed up to 10 (50\u0026deg;C) and 60 min (RT) with a time step of 1 s, only three time-step (1, 5 and 10 min) were selected and shown on Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e for the two thermal conditions: RT with convective cooling on glass walls and Dirichlet boundary at 50\u0026deg;C. Moreover, the liquid mean temperatures at three positions (T\u003csub\u003ebottom\u003c/sub\u003e, T\u003csub\u003eup\u003c/sub\u003e and T\u003csub\u003eside\u003c/sub\u003e reported on Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) are shown on Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh. The particles transport is clearly different between both thermal conditions. For RT (a, b and c), red particles slide towards the lateral walls remaining on PEG liquid surface due to Marangoni forces (speed close to 0.06 mm/s), then they fall down in the vicinity of lateral walls between 5 and 10 min. In the same time, liquid temperatures increases from 25\u0026deg;C at t\u0026thinsp;=\u0026thinsp;0 min to 37, 31 and 30\u0026deg;C at 10 min for T\u003csub\u003eup\u003c/sub\u003e, T\u003csub\u003eside\u003c/sub\u003e and T\u003csub\u003edown\u003c/sub\u003e respectively. All temperatures are not clearly stabilized at this time and approximatively 90 min are needed. For 50\u0026deg;C (d, e, f), red particles follow the same trajectories, but their speed is much higher on the surface walls (between 0.3 and 0.5 mm/s) due to Marangoni forces and even alongside walls. Particles reach vial bottom before 5 min and then start to go up along to the vial axis and reach liquid surface before 10 min, leading to semi-circular shape trajectory. For 50\u0026deg;C, liquid surface temperature increases up to 55\u0026deg;C (reached after 10 min plasma running) whereas both other temperatures (T\u003csub\u003eside\u003c/sub\u003e and T\u003csub\u003edown\u003c/sub\u003e) are fixed to 50\u0026deg;C. Finally, these results of simulation seem consistent to experimental ones relative to Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e in both thermal cases.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Nanoparticle properties: size, structure and microstructure\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the SAXS curves as function of the scattering vector range between 0.25 and 4 nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as a function of liquid temperature during the SoL deposition (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea), and after an ex-situ annealing at different temperatures of samples previously obtained by SoL at RT (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). All data were fitted assuming spherical NPs with a diameter following a Gaussian distribution. For Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the SAXS spectrum of RT sample exhibits the characteristic signal of spherical NPs with an average diameter\u0026thinsp;\u0026lt;\u0026thinsp;d\u0026gt; of 1.1 nm and a standard deviation between 0.3 nm, consistent with values commonly reported for this class of alloyed phases [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. For the sample obtained at 50\u0026deg;C, a stronger overall intensity is observed which can be attributed to the presence of a larger number of NPs in the probed volume. The mean diameter starts to increase to 1.2 nm. After annealing at 70\u0026deg;C, the low q region of the SAXS pattern remains similar in shape to that observed at 50\u0026deg;C (even of \u0026lt;\u0026thinsp;d\u0026gt; continue to increase) but with a noticeably higher intensity (below 0.4 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e) suggests the appearance of a second populations of larger scattering species. At higher q, a peak is starting to appear at about 0.25 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e which is be attributed to the emergence of a correlation length L\u003csub\u003ecor\u003c/sub\u003e equal to 1.8 nm. This correlation peak means that some particles are close to each other and an organisation starts to appear between them with a specific interparticle distance. At 80\u0026deg;C, the same behaviour is observed, with even more pronounced features with \u0026lt;\u0026thinsp;d\u0026gt; and L\u003csub\u003ecor\u003c/sub\u003e equal to 1.6 and 2.8 nm respectively. For the case of ex-situ annealing (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), a similar overall trend is found, although the correlation peaks appear at higher temperatures, 100 and 150\u0026deg;C. The second and third curves in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, corresponding to annealing at 50\u0026deg;C and 70\u0026deg;C, are well described by spherical nanoparticles model with \u0026lt;\u0026thinsp;d\u0026gt; equal to 1.1 nm. After annealing at 70\u0026deg;C, no correlation peak is detected. Such a peak only appears after annealing at 100\u0026deg;C with L\u003csub\u003ecor\u003c/sub\u003e = 2.4 nm. At 150\u0026deg;C, the SAXS pattern clearly reveals two distinct contributions: a strong low q signal associated with large NPs, and a high q contribution featuring a pronounced correlation peak with L\u003csub\u003ecor\u003c/sub\u003e = 2.8 nm.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs already mentioned, the presence of a correlation peak at 70\u0026deg;C, 80\u0026deg;C (\u003cem\u003ein-situ\u003c/em\u003e), 100 and 150\u0026deg;C (\u003cem\u003eex-situ\u003c/em\u003e annealing) means that small particles are not randomly distribute inside liquid but that an organisation starts to appear. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e corresponds to a HRTEM image of deposited materials post-annealed at 100\u0026deg;C and then deposited on a grid. To quantify the local geometry around each NPs, the widely employed Delaunay triangulation method was applied to the right-bottom corner of Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea to connect each NPs to its nearest neighbours and result is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. This produces triangulations where each feature of interest is connected to its first neighbours. The obtained histogram of the segment lengths, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, is fitted by a lognormal curve whose maximum is reached for 3.5 nm. Long segments due to empty regions in the image only contribute to the long tail of the distribution and do not influence the measurement of the peak position. This result is in good agreement with the existence of a correlation length of 2.4 nm observed on SAXS spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) at a position close to 0.25 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e. The larger value obtained by triangulation measurement is the result of two effects: a small statistics due to the limited image area used for the triangulation and the fact that this region has been chosen for its slightly smaller NP density in order to clearly identify individual NP positions and perform an accurate triangulation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn summary, the SAXS analyses of NPs produced at different temperatures by heating the liquid during SoL and of NPs heated \u003cem\u003eex-situ\u003c/em\u003e after SoL deposition at RT provide a coherent picture of the size evolution of the NPs as a function of temperature. In both cases, increasing the temperature affects the organization of the NPs in solution while increasing their intrinsic size. As the temperature rises, the particles tend to organize, resulting in the appearance of correlation peaks in the SAXS signal and conformed by HRTEM images post-treatment. However, the rate at which these structural changes occur depends on the heating method: \u003cem\u003ein-situ\u003c/em\u003e heating promotes earlier structural transitions compared with \u003cem\u003eex-situ\u003c/em\u003e annealing, highlighting the importance of the monitoring nanoparticle formation under realistic synthesis conditions.\u003c/p\u003e \u003cp\u003eX-ray diffraction measurements were performed on the sample synthesized by SoL at RT to obtain a macroscopic reference of the phases likely involved in the formation of Pt-Sn nanoparticles obtained by conventional liquid sputtering, and after an \u003cem\u003eex-situ\u003c/em\u003e annealing at 150\u0026deg;C of these NPs. The XRD experiments require a significant amount of material, obtained by filtering the solution to recover the carbon-supported nanoparticles. The amount of material in the solution is 4 mg. Thus, 50% wt of vulcanized carbon was added, i.e., 4 mg. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the XRD diagrams of the vulcanized carbon (without NPs) as reference support (grey line), of the NPs obtained (yellow line) by SoL at RT, and of these NPs after annealing at 150\u0026deg;C (red line). Theoretical diffraction patterns of some pure compounds are also shown in the lower part of Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. A broad peak centred around 25\u0026deg; is observed for each sample and, corresponds to the (002) plane of the poorly crystallized graphite phase, which is present in the vulcanized carbon (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, grey line) used as a support for the NPs outside the suspension. The carbon support also induces a broad peak centered at around 44\u0026deg;, corresponding to the 004 diffraction line of graphite (space group P6\u003csub\u003e3\u003c/sub\u003emmc; COD file 9012230). The experimental diffraction peaks of NPs produced at RT located at 39.19\u0026deg; and 45.26\u0026deg; (continuous yellow line) are respectively in agreement with the (111) and (200) planes of a platinum-based phase [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Indeed, these two peaks could be attributed from the following two hypothesis. Firstly, the (111) and (200) peak positions may correspond to the presence of the cubic phase alloy Pt\u003csub\u003e3\u003c/sub\u003eSn (space groupe Pm3m; a\u0026thinsp;=\u0026thinsp;0.400 nm; COD file 1523555). In that case, it must be noticed that such a phase contains less Pt than the sputtering target used for the deposition (Pt\u003csub\u003e4\u003c/sub\u003eSn\u003csub\u003e1\u003c/sub\u003e) meaning that the excess of Pt should also present somewhere else. Secondly, regarding the theoretical peak positions of the (111) and (200) planes of the pure FCC cubic Pt phase (space group Fm3m; a\u0026thinsp;=\u0026thinsp;0.392 nm, COD file 1011103), the 2θ values would be 39.79\u0026deg; and 46.24\u0026deg; for the (111) and (200) lines, respectively. The experimental 2θ angular positions are therefore shifted toward lower values of 2θ, indicating the formation of a solid solution based on Pt FCC cells in which Sn has been inserted or substituted in the Pt lattice. Regarding the thermodynamical phase diagram [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e], such Sn incorporation do not exceed 10at.% in Pt at low temperatures (100\u0026ndash;200\u0026deg;C). Given the amount of Sn expected in the NPs (20 at.%), it can be assumed that not all tin species can be inserted into the Pt lattice. That is why the presence of isolated (segregated) Sn can not be excluded as evidenced on Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e by its theoretical angular positions corresponding to the (111), (220) and (311) planes of tetragonal Sn phase. It is therefore not easy to decide between the two possibilities. Nevertheless, the asymmetrical shape of the X-ray diffraction peaks would argue in favor of the presence of two phases. Considering the (111) reflection as a single peak, the full width at half maximum is around 0.5\u0026deg; indicates the presence of small crystallites for which the mean size is evaluated to be approximately 2.9 nm using the Scherrer equation which is much larger that value obtained by SAXS measurement for RT.\u003c/p\u003e \u003cp\u003eRegarding the XRD diagram of the previous NPs after annealing at 150\u0026deg;C (solid red line), we can observe a decrease in crystallinity (broadening and lower intensity of the peaks) compared to the NPs as deposited (solid yellow line). More interestingly, the main peak located around 39\u0026deg; is shifted towards higher angular values, which would mean that the phases of the as-deposited NPs evolve towards an almost pure Pt phase (transformation of Pt\u003csub\u003e3\u003c/sub\u003eSn into Pt\u0026thinsp;+\u0026thinsp;Sn), indicating that thermal annealing leads to a segregation of Sn and modifies the microstructure of the NPs. Finally, it can not be excluded that the annealing performed in ambient atmosphere also leads to partial oxidization of the particles in addition to its amorphization and the segregation of tin.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe XRD experiments provide only a macroscopic view of the structural features of the NPs possible phases, and their average size considering a homogeneous distribution of particles in form and size. For a more in-depth analysis, the microstructure of the NPs has been studied by HRTEM. The protocol used to recover NPs onto TEM grids was applied to observe the Pt-Sn NPs synthesized in PEG. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e presents HRTEM images of Pt-Sn nanoparticles deposited at RT (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb) and deposited in a liquid heated at 80\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ee). Figures. 7g-h and 7j-k correspond to the sample obtained by SoL at RT followed by an \u003cem\u003eex-situ\u003c/em\u003e annealing at 100\u0026deg;C and 150\u0026deg;C, respectively. The size distribution (Figures. 7c, 7f, 7i and 7l) of each sample was determined by measurement of individual particles considered as spherical directly from the images. For the sample deposited at RT, well-dispersed NPs across the grid, with clearly defined interfaces are observed. The size distribution reveals a single population of NPs that can be fitted with a lognormal function, with a mean diameter around 1.6 nm and a standard deviation of 0.46 nm.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhen the liquid is heated during deposition at 80\u0026deg;C, the NPs (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ee) appear closer together. Despite the tendency of NPs to aggregate, and by considering only isolated particles, the size distribution obtained from 40 individual particles leads to an average diameter of 1.6 nm with a standard deviation of 0.46 nm. This value is very close to that measured for the sample obtained at RT. For the sample obtained with an \u003cem\u003eex-situ\u003c/em\u003e annealing at 100\u0026deg;C (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg-i), the size distribution again fitted with a lognormal function, yields an average diameter of around 1.8 nm with a standard deviation of 0.33 nm. When the temperature of annealing is increased at 150\u0026deg;C (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ej-l), the size distribution is characterized by a bimodal distribution and an average size of around 2.8 nm with a standard deviation of 0.53 nm. An increase of the annealing temperature would induce an aggregation of small NPs to form NPS with a higher size. In all cases, the images in Figures. 7b, 7e, 7h and 7k display (111) lattice fringes with a d-spacing of 0.22 nm, characteristic of Pt-rich NPs. The edge of NPs are less distinct at 150\u0026deg;C than for the NPs prepared at RT (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eh), which may be due to beam-induced artefacts but also to a modification of the NPs resulting in a core-shell type microstructure corresponding to a possible segregation of tin atoms on the outer part of the NPs during heating, as it has been also suggested by the XRD experiments. To go deeper insight on the effect of temperature on the elemental distribution within the Pt-Sn NPs, STEM coupled with EDX mapping has been performed on samples realized at RT followed by an annealing at 150\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). It has first to be noted that the accuracy of high-resolution chemical analysis can be complicated by residual PEG despite multiple rinsing steps. Indeed, EDX mappings show the distribution of Pt element (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb) and Sn (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec) and unfortunately does not reveal clear heterogeneity of the NPs chemical composition after an ex-situ annealing treatment, as expected regarding the XRD analyses which indicated that a segregation of Sn at the outer part of Pt-Sn NPs could be envisaged.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe different data obtained by SAXS, XRD and HRTEM experiments on Pt-Sn nanoparticles synthesizing by sputtering onto liquid PEG make it possible highlight some effects of the temperature on the structural and microstructural properties of the NPs. Firstly, the temperature of the liquid was raised during the deposition and secondly the solution was annealed in a conventional muffle furnace at ambient air at different temperatures. When the deposition is performed at RT, the NPs are mostly spherical, well crystallized with a well-defined order and a monodisperse size distribution with an average size of around 1.6 nm (versus 1.1 nm with SAXS). In the as-deposited NPs at RT, most of Pt and Sn atoms are mixed together, leading either to a compound with a well-defined composition corresponding to the cubic phase of the Pt\u003csub\u003e3\u003c/sub\u003eSn alloy or to a Pt-Sn solid solution in which Sn is insert into the FCC Pt lattice. In-situ heating promotes NPs diameter increase, aggregation and the emergence of interparticle correlations. This is consistent with what is usually seen in the literature for this type of process [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. It has been shown that changing the temperature of the liquid alters the surface tension and viscosity, which drastically changes the diffusive velocity of the species sputtered into the liquid. This leads to an increase in the size of the nanoparticles due to the increase in the number of collisions between species during nucleation and growth in the liquid. For example, in the work of Staszek et al., they shown that increasing the temperature from 5 to 20\u0026deg;C produce a remarkable increase in NPs average size from 12.8 nm (5\u0026deg;C) to 21.2 nm (20\u0026deg;C) [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In this work, rising the liquid temperature promotes atomic diffusion, which tends to increase the mobility of the nanoparticles, causing them to coalesce without altering their individual microstructure. They organize themselves and form a cluster, which induces amorphization of the overall structure. It appears therefore that the temperature may have an effect during the deposition step by SoL which is not evidenced in the present work but also modify the NPs properties as far they are deposited on the substrate during the growth. Following this path, the \u003cem\u003eex-situ\u003c/em\u003e annealing treatment \u0026agrave; 150\u0026deg;C of the as-deposited NPs shows that a temperature, even moderate can induce structural and microstructural modifications of the NPs. Particularly, the elemental distribution of Pt and Sn is affected which induces a shift of the XRD peaks towards the 2θ higher value (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) which could be the consequence of a segregation of Sn at the outer part of Pt-Sn NPs.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003ePtSn electrocatalyst nanoparticles were synthetized by DC magnetron sputtering of a Pt\u003csub\u003e0.8\u003c/sub\u003eSn\u003csub\u003e0.2\u003c/sub\u003e target onto a polyethylene glycol under Ar plasma. This work highlights the influence of the liquid temperature on the properties of the NPs by comparing two thermal conditions: \u003cem\u003ein-situ\u003c/em\u003e heating of the liquid during deposition using a bain-marie system ensuring homogeneous temperature control, and post-deposition annealing under air of the as-deposited NPs in a conventional furnace. COMSOL Multiphysics simulations and macroscopic observations show that the growth mechanism during SoL is strongly temperature-dependent, as liquid heating modifies surface tension and viscosity, thereby altering the transport regime of sputtered species within glycol and influencing nucleation pathways. SAXS and HRTEM analyses reveal that as-deposited PtSn nanoparticles exhibit diameters around 1\u0026ndash;2 nm, consistent with values reported in the literature for SoL synthesized Pt-based alloys. XRD confirms that the NPs are well crystallized and predominantly Pt-rich, with Sn incorporation in agreement with HRTEM-EDX observations. The combined characterisation results indicate that, in this study, increasing the temperature increases the nanoparticle diameter from 1.6 to 2.8 nm using HRTEM and from 1.2 to 1.6 nm using SAXS. Moreover, whether \u003cem\u003ein-situ\u003c/em\u003e or \u003cem\u003eex-situ\u003c/em\u003e rising temperature, this latter influences nanoparticle organisation: above a certain threshold, a regular space between them is observed, and higher temperatures promote the onset of aggregation.\u003c/p\u003e \u003cp\u003eOverall, this work demonstrates that magnetron sputtering onto a liquid is well suited for producing small and well-dispersed Pt-Sn nanoparticles in PEG, which is highly relevant for electrocatalytic applications. Moreover, both \u003cem\u003ein-situ\u003c/em\u003e and \u003cem\u003eex-situ\u003c/em\u003e heating enhance diffusion within the liquid and drive nanoparticle reorganisation, offering a means to tune particle size for targeted applications. Further work will focus on electrochemical characterisation of these PtSn nanoparticles.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCredit authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAïssatou Diop\u003c/strong\u003e - Original draft, Investigation, formal analysis , \u003cstrong\u003eSoumya Atmane,\u0026nbsp;\u003c/strong\u003eliquid investigation, \u003cstrong\u003eDilane Kevine Tagueu -\u003c/strong\u003e comsol multiphysics works, \u003cstrong\u003eEric Millon\u003c/strong\u003e – Supervision, review \u0026amp; writing, \u003cstrong\u003eAudrey Sauldubois\u003c/strong\u003e – microscopy works, \u003cstrong\u003eNadjib Semmar\u003c/strong\u003e, comsol multiphysics supervision, \u003cstrong\u003eLoïc Gimenez\u003c/strong\u003e – PVD technical expert, \u003cstrong\u003eMaxime Mikikian\u003c/strong\u003e - Delaunay triangulation investigation, \u003cstrong\u003ePascal Andreazza\u003c/strong\u003e\u003csup\u003e\u0026nbsp;\u003c/sup\u003e– review, \u003cstrong\u003eAmael Caillard\u003c/strong\u003e - supervision, project administration, funding acquisition, review \u0026amp; editing, writing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data presented here will be made available on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work is realized in the case of BHyoLOHC project (ProjetIA-22-PEHY-0016) funded by the French National Agency of Research via the PEPR Decarbonated Hydrogen. A. Caillard and A. Diop gratefully thank Christophe Coutanceau and Karine Vigier de Oliveira for scientific discussion related to PtSn nanoparticles and BHyoLOHC project management. This project has benefited from the expertise and the facilities of the Platform MACLE - CVL which was co-funded by the European Union and Centre-Val de Loire Region (FEDER). The authors acknowledge Nicolas Gouillon from ICMN for technical support during SAXS measurements.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePootawang P, Saito N, Takai O, et al. Synthesis and characteristics of Ag/Pt bimetallic nanocomposites by arc-discharge solution plasma processing. Nanotechnology. 2012;23(39):395602.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChang H, Kao MJ, Jwo CS, et al. Preparation of Co/Ag nanocompound fluid using ASNSS with aid of ultrasonic orthogonal vibration. 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Metals Park, OH: ASM International; 1990.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHatakeyama Y, Judai K, Onishi K, et al. Anion and cation effects on the size control of Au nanoparticles prepared by sputter deposition in imidazolium-based ionic liquids. Phys Chem Chem Phys. 2016;18(4):2339\u0026ndash;2349.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-nanoparticle-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nano","sideBox":"Learn more about [Journal of Nanoparticle Research](http://link.springer.com/journal/11051)","snPcode":"11051","submissionUrl":"https://submission.nature.com/new-submission/11051/3","title":"Journal of Nanoparticle Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Sputtering onto liquid, magnetron sputtering, nanoparticles, polyethylene glycol","lastPublishedDoi":"10.21203/rs.3.rs-8873928/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8873928/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePt-Sn nanoparticles were synthesized by magnetron sputtering of a 2-inch Pt\u003csub\u003e0.8\u003c/sub\u003eSn\u003csub\u003e0.2\u003c/sub\u003e target into polyethylene glycol using an innovative reactor configuration designed for liquid-phase deposition. A comprehensive study was conducted to understand the influence of liquid temperature on the growth of nanoparticles under two conditions: (i) an \u003cem\u003ein-situ\u003c/em\u003e heating of the liquid during sputtering deposition using bain-marie bath, and (ii) an \u003cem\u003eex-situ\u003c/em\u003e post-deposition annealing under air of the nanoparticle-liquid suspension obtained after deposition. COMSOL multiphysics simulations have revealed that the temperature of the liquid critically determines the transport regime of sputtered species inside the liquid glycol thus affecting the nanoparticle formation pathways. Complementary structural and morphological characterisations, such as transmission electron microscopy, X-ray diffraction and small angle X-ray scattering, demonstrate that temperature modulates particle size and size distribution. The \u003cem\u003ein-situ\u003c/em\u003e heating of the liquid during the growth promotes aggregation and the emergence of interparticle correlations but do not significantly modify the size distribution of the NPs. The \u003cem\u003eex-situ\u003c/em\u003e annealing treatment up to 150\u0026deg;C of the as-deposited NPs affects their organization in solution, lightly alter their intrinsic size and can induce structural and microstructural modifications of the NPs and particularly affect the elemental distribution of Pt and Sn. These results provide new insights into temperature-controlled synthesis of alloy nanoparticles in liquids.\u003c/p\u003e","manuscriptTitle":"Liquid temperature effect on Pt-Sn electrocatalyst properties during plasma sputtering onto polyethylene glycol","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-20 17:41:28","doi":"10.21203/rs.3.rs-8873928/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-18T07:49:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-17T22:01:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-10T16:18:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"48936725194245926689127472352976998119","date":"2026-02-25T05:56:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80422135138254360924077169748554905316","date":"2026-02-18T12:15:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-18T07:49:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-17T21:40:21+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-15T22:18:24+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Nanoparticle Research","date":"2026-02-13T16:10:59+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-nanoparticle-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nano","sideBox":"Learn more about [Journal of Nanoparticle Research](http://link.springer.com/journal/11051)","snPcode":"11051","submissionUrl":"https://submission.nature.com/new-submission/11051/3","title":"Journal of Nanoparticle Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"811d0f73-26d9-4ab0-8f3a-ef43eafff6b9","owner":[],"postedDate":"February 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-27T16:04:12+00:00","versionOfRecord":{"articleIdentity":"rs-8873928","link":"https://doi.org/10.1007/s11051-026-06631-z","journal":{"identity":"journal-of-nanoparticle-research","isVorOnly":false,"title":"Journal of Nanoparticle Research"},"publishedOn":"2026-04-21 15:59:12","publishedOnDateReadable":"April 21st, 2026"},"versionCreatedAt":"2026-02-20 17:41:28","video":"","vorDoi":"10.1007/s11051-026-06631-z","vorDoiUrl":"https://doi.org/10.1007/s11051-026-06631-z","workflowStages":[]},"version":"v1","identity":"rs-8873928","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8873928","identity":"rs-8873928","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}