Colloidal nanoparticle analysis by nanoelectrospray size spectrometry with a heated flow

A nanoelectrospray-furnace-scanning mobility particle spectrometer (SMPS) system was developed which is capable of rapidly and accurately measuring the size distributions of colloidal nanoparticles. Many colloidal suspensions require the use of nonvolatile surfactants to stabilize the suspensions. Nonvolatile materials coat colloidal particles and form residue particles during the electrospray process; thus, SMPS measurements are normally inaccurate for colloidal particles. Here, a tubular furnace reactor is used to evaporate residue nanoparticles and coatings, which allows for correct nanoparticle size measurement. Test suspensions of silver, gold, and SiO2 nanoparticles were measured in the electrospray-furnace-SMPS system. SMPS measurements and field emission scanning electron microscopy measurements were in excellent agreement for all test suspensions. High-temperature heating in the furnace was used to evaporate the nanoparticles themselves, which shifted the nanoparticle size spectra to smaller sizes, allowing for thermal analysis to be performed on colloidal suspensions in addition to size measurement.