Bound Volume Number


Degree Type

Honors Capstone Project

Date of Submission

Spring 5-1-2015

Capstone Advisor

Prof. Jon Zubieta

Honors Reader

Prof. Mathew Maye

Capstone Major


Capstone College

Arts and Science

Audio/Visual Component



precipitation point, electroneutrality, polyoxomolybdate, cationic gold nanoparticles

Capstone Prize Winner


Won Capstone Funding


Honors Categories

Social Sciences

Subject Categories

Inorganic Chemistry


The electrostatic assembly of cationic gold nanoparticles (AuNPs) with core diameters of approximately 1.5 nm and 4.5 nm and the anionic sphere and wheel polyoxomolybdates (Mo-132a), (Mo‑132b), and (Mo‑154) was investigated. The AuNPs were capped with a trimethylammonium terminated ligand. Zeta potential and UV-Vis studies supported the successful assembly of the oppositely charged species. The ratio at which the precipitation of aggregates from solution occurred was consistent with the point of electroneutrality observed in the zeta potential results. The UV-Vis studies showed the loss of the surface plasmon resonance (SPR) band as this point of electroneutrality was approached.

In a study performed by Gooch, et. al. involving combining the 4.5 nm AuNP and Mo-132a and Mo-132b, it was found that a counterintuitive trend was observed. The precipitation point for the more negatively charged Mo-132b corresponded to a higher ratio than the precipitation point for Mo-132a. This trend continued in this study involving the 4.5 nm AuNP and Mo-154, where = [POM]:[AuNP] mole ratio of ≈ 8 was required to reach the point of electroneutrality and precipitation than what would be predicted through basic charge balance considerations. In the study involving the 1.5 nm AuNP, the spherical Mo‑132 Keplerates precipitated out approximately at the point where the charges on the nanoparticles and polyoxomolybdates were balanced, similar to what is observed when oppositely charged nanoparticles interact. These ratios for Mo-132a and Mo-132b were ≈ 1 and ≈ 0.6, respectively. However, the precipitation point between the smaller AuNP and Mo-154 again required less of the Mo-154 than what would be expected if it followed this trend at ≈ 0.4. Overall, these results indicate that both the shape and charge of the polyoxomolybdate and the size of the AuNP affect their interaction and precipitation point.

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Creative Commons Attribution 3.0 License
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