Mobility distributions of Sub 5 nm singly self-charged water soluble and non-soluble particles from a heated NiCr wire in clean dry air

Sub 5 nm particles are more and more detected, measured and monitored since few years. They appear in many fields including combustion, atmosphere, automotive industry, filtration, horizontal ellipsis They are studied because of the development during the last decades, of their different instrumentation in terms of generation, classification, detection and counting (CPCs, PSMs, DMAs, and mass spectrometers). These instruments need to be calibrated with stable sources of particles down to 1 nm. Electrospray source plays a major role in the generation of singly charged ions, soluble in water or alcohols from 1 to 1.8 nm. Unfortunately, clusters larger than 1.8 nm produced with electrospray atomization are multi charged. Charge reduction with a neutralizer or bipolar electrospray source are then required to bring their electrical charge to unity. Heated wires have shown their ability to produce non-soluble hydrophobic singly self-charged particles from 1.3 nm to 20 nm without any external device to bring their electrical charge to unity. The heated wire method have been widely used with noble and inert gases (N-2, He, Ar) to produce clean and pure nanoparticles. The present work focuses on the generation in air of hydrophobic nickel chrome oxides and hydrophilic and water-soluble chlorides particles. The study focuses on the generation of sub 5 nm. A high flow and high resolution DMA is used for this purpose. The method produces concentrations up to 5 10(4) p/cc after classification with a DMA. The generation presents a long-term high stability in terms of concentration. The losses and rate of agglomeration inside the chamber and in the DMA are not taken into account. The results given in the article are the distributions available after classification and ready to be used. Copyright (c) 2022 University Paris Est Creteil