Week 8 - Nanoparticle Synthesis

The past few days I've been working on my presentation for the end of this internship. I will end up giving it at least twice. Once to the research group here and once for the super-internship requirement. For today's post I'll be summarizing the synthesis of some of the particles I've been working with. 


The synthesis begins with silver nitrate (AgNO3) (Blogger doesn't let me do subscripts, I'm sorry). It's combined with PVP-40 (a polymer) with ethylene glycol as a solvent. The mixture is then slowly brought to 120 degrees Celsius. The heat and PVP-40 allows the nanoparticle to form, with the PVP-40 acting as a stabilizing agent. The main (and only) method of purification in nanoparticle synthesis is centrifugation, as the particles are too small for filters, too light for columns, and cannot be allowed to dry. 

 This first step results in our silver nanoparticles. They are small, solid pieces of silver 30 to 50 nanometers in diameter. With the addition of tetraethyl orthosilicate (TEOS) and more PVP-40 a silica (SiO2) shell is formed around our nanoparticles. The final step is the etching. In this case we heat the solution while stirring for around an hour. After a centrifuge cleaning we have finished nanorattles, meaning that the internal silver nanoparticle is free to move in the silica shell. The yield for this is typically a few mg.

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