Synthesis and characterization of Pd nanoparticles for plastic plasmonic sensing applications

Licentiate thesis, 2019

It is well known that hydrogen mixed with air forms a highly flammable mixture. There is an urgent need for selective and accurate sensors, since hydrogen very often serves as a fuel or energy storage medium. Given the fact that even the smallest leak can lead to an explosion, it is very important for sensors to be reliable and safe, i.e. not ignite the gas themselves. Sensors with an optical read-out are under current interest, hence nanoparticles are examined towards this goal.

As a response to the above, this thesis discusses the synthesis of palladium nanoparticles with a standard surfactant as a stabilizer together with their characterization. Nanoforms of palladium are a perfect platform for hydrogen sensing, forming a hydride when exposed to hydrogen, making them very selective. However, there are compounds which strongly influence hydrogen sensing and often obscure the activity of palladium nanoparticles. Four common capping agents utilized in palladium nanoparticles synthesis were investigated to address this issue: hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC), tetraoctylammonium bromide (TOAB), polyvinylpyrrolidone (PVP).

Palladium nanoparticles were applied towards hydrogen sensing giving promising results. In order to achieve the goal to create a hydrogen sensor, nanoparticles were successfully incorporated into a poly(methyl methacrylate) (PMMA) polymer matrix. The created nanocomposite serves as a platform for two hydrogen sensing devices with plasmonic optical read-outs. On top of that it was found that among all four tested capping agents for palladium nanoparticles, PVP enhances hydrogen absorption kinetics whereas CTAB, CTAC and TOAB decrease absorption kinetics.