The potential of using atmospheric-pressure spark ablation for production of atomic clusters has been shown in the recent past. In this study we used this method to produce atomic clusters in Argon and investigated their chemical composition with an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF-MS). Both anionic and cationic silver and gold clusters were generated and characterised. The carrier gas was used directly from the gas cylinder without the application of any additional gas purification. As a result, the carrier gas stream contained trace impurities of N2, O2, and H2O, as well as radicals such as O, OH, and H and their ionized forms resulting from the plasma created by the sparks. The experimental results show that different reactivities towards oxygen and water traces can be observed depending on the number of metal atoms in the clusters, their polarity, as well as their compositions; e.g., Aun− shows less reactive behaviour towards oxygen and hydrogen compared to Agn−. The results also show that certain cluster types can be generated at large enough quantities by atmospheric-pressure spark ablation, which considering the low installation and operating cost of the technique can pave the way towards its exploitation for numerous technological applications.@en

The detection efficiency of Condensation Particle Counters (CPCs) reduces drastically as particle size becomes smaller than 2 nm. Increasing the supersaturation in order to enhance the detection efficiency, has limited applicability because the onset supersaturation value of droplet formation by homogeneous nucleation is very close to the heterogeneous onset supersaturation for sub-2 nm particles. In this work we introduce a new method for increasing the detection efficiency of CPCs for sub-2 nm particles, which relies mainly on controlling the spatial distribution of the supersaturation profile by simply modifying the operating temperatures of the CPC. We evaluated the new method by generating monodisperse particles in the size range of 0.98–4.50 nm and used them to characterize a TSI 3025 CPC. We achieved significant increase of the detection efficiency for sub-2 nm particles. Furthermore, we calculated the supersaturation field developed in the condenser tube with a finite element model and used it to determine the detection efficiency according to heterogeneous nucleation theory. These calculations reveal that the observed increase of the detection efficiency can be explained by the manipulation of the spatial distribution of the supersaturation field. The method introduced here can greatly improve the detection efficiency of CPCs and in the meantime further extend their use for particle sizing purposes in the sub-2-nm range.@en