Interaction of Reactive Gases with Platinum Aerosol Particles at Room Temperature: Effects on Morphology and Surface Properties

Abstract

Nanoparticles produced in technical aerosol processes exhibit often dendritic structures, composed of primary particles. Surprisingly, a small but consistent discrepancy was observed between the results of common aggregation models and in situ measurements of structural parameters, such as fractal dimension or mass-mobility exponent. A phenomenon which has received little attention so far is the interaction of agglomerates with admixed gases, which might be responsible for this discrepancy. In this work, we present an analytical series, which underlines the agglomerate morphology depending on the reducing or oxidizing nature of a carrier gas for platinum particles. When hydrogen is added to openly structured particles, as investigated by tandem differential mobility analysis (DMA) and transmission electron microscopy (TEM) analysis, Pt particles compact already at room temperature, resulting in an increased fractal dimension. Aerosol Photoemission Spectroscopy (APES) was also able to demonstrate the interaction of a gas with a nanoscaled platinum surface, resulting in a changed sintering behavior for reducing and oxidizing atmospheres in comparison to nitrogen. The main message of this work is about the structural change of particles exposed to a new environment after complete particle formation. We suspect significant implications for the interpretation of agglomerate formation, as many aerosol processes involve reactive gases or slightly contaminated gases in terms of trace amounts of unintended species.

Creation of Gases with Interplanetary Oxygen Concentration at Atmospheric Pressure by Nanoparticle Aerosol Scavengers: Implications for Metal Processing from nm to mm Range

“…Hence, the interaction of a certain gas species with a particle surface is ascertainable . Details on the APES and its setup were reported elsewhere. ,, In this context, the APES was used to study the influence of residual oxygen on a model particle system, here copper nanoparticles. The results will be discussed below.…”

“…The formation of metal oxides in the gas phase implies the consumption of oxygen that is meant to be removed. The production of gas-borne nanoparticles made of oxygen-affine metals, such as aluminum or magnesium, was conducted by spark discharge synthesis, which is described in detail elsewhere. − A distinctive characteristic of spark ablation is the formation of openly structured agglomerates made of almost monodisperse primary particles ( d Primary < 15 nm). , Hence, metal agglomerates exhibit large specific surface areas, enabling interaction between residual oxygen and the freshly produced metal surface. Beyond the Al and Mg used in this work, other oxygen-getter materials such as Ti, Fe, Ca, Ni, Cu, etc.…”

Synergizing ICP-MS, STEM-EDXS, and SMPS single particle analytics exemplified by superlattice L10 Pt/Fe aerosol nanoparticles produced by spark ablation

“…From literature it is known that NPs, which appear as agglomerates with a distinct primary particle structure, exhibit an altered sintering behavior when the temperature treatment occurs in either an oxidizing or reducing gas atmosphere. 39,40 For this reason, the sintering behavior of Pt/Fe and Fe agglomerates based on SMPS data will be discussed rst, including a primary particle size evaluation for Pt/Fe by TEM imaging. The SMPS measurements aim at the detection of morphological changes in the agglomerate structure towards compact particles as the temperature increases.…”

Fabrication of Nanoparticle Agglomerate Films by Spark Ablation and Their Application in Surface-Enhanced Raman Spectroscopy

“…This method often called spark ablation only requires a controlled, atmosphericpressure gaseous environment and a pair of electrically conductive electrodes, between which a transient spark plasma creates a vapor plume from the electrodes' material, which will condense into nanoparticles [16]. By varying the electrical properties of the discharge [17][18][19][20][21][22], the geometry of the electrodes and the surrounding chamber [23][24][25][26], the properties of the electrode material [27][28][29][30], or the properties of the carrier gas [31][32][33], one can tune the characteristics of the generated particles. Since spark ablation can conveniently be used to produce multielement NPs by simply combining dissimilar alloyed or 2 of 16 compacted electrodes [34,35], this tunability even includes the crystal structure of the produced particles [29,36,37].…”