Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Aydar Atnagulov dissertation.pdf (9.82 MB)

ETD Abstract Container

Abstract Header

Application of Mass Spectrometry to the Characterization of Core and Ligand Shell Modifications of Silver Molecular Nanoparticles

Atnagulov, Aydar
http://orcid.org/0000-0001-7146-2534
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501860803445199

Abstract Details

2017, Doctor of Philosophy, University of Toledo, Chemistry.
Small silver nanoparticles, also called molecular nanoparticles (MNPs) or nanoclusters, are of great research interest due to potential applications in valuable fields such as biomedicine and catalysis. In the past decade, several groups reported successful formulae determination and crystal structures of the various species in this class of materials. Knowing such information is of crucial importance to start testing how slight modifications of both metal core and ligand shell affect the stability and properties of molecular nanoparticles. Among the techniques employed for characterization of MNPs, mass spectrometry plays a vital role. Soft ionization techniques such as matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI), developed primarily for bioanalytical applications, became indispensable for the analysis of MNPs, most of which are labile during the ionization process. Mass spectrometry also provides the high precision required to measure the precise numbers of metal atoms, ligands and charges and thereby determine the formulae of these molecules. While modified samples often resemble a statistical distribution of a product mixture, individual products can be successfully discriminated by their mass using tandem mass spectrometry and singled out such that their behavior in the gas phase can be studied. The all-silver M4Ag44(p-MBA)30 cluster was used as a model system, where M is a monocationic counterion and p-MBA is para-mercaptobenzoic acid, which serves as a protecting ligand. Metal core modifications were carried out by substituting gold for silver to form M4AuxAg44-x(p-MBA)30 clusters. Gold was chosen as a second metal due to some of its properties being similar to those of silver, including its electronic structure and atomic size. Co-reduction and galvanic exchange were the two methods used for the preparation of the bimetallic product. The range of product composition was determined, and the most thermodynamically favorable sites of heteroatoms within the nanoparticle structure were established. Moreover, chemical properties such as stability, reactivity, and fragmentation were studied as a function of product composition. Thermodynamic and kinetic barriers were evaluated for the aforementioned reactions. The role of ligands in nanoparticle stability and structural outcome of the synthesis was investigated using the same model system, M4Ag44(p-MBA)30. Several parameters including the length of an aliphatic chain between a sulfur atom and a phenyl ring, introduction of bulky groups, and aromaticity, were varied aiming to find the characteristics required for synthesis of M4Ag44(SR)30 (SR = thiolate). It has been found that ligands can be divided into two categories that produce orthogonal sets of nanoparticles. Such a division is based on the aliphatic or aromatic character of the carbon atom directly bonded to the sulfur atom of the thiol group. The outcomes obtained by the method of direct synthesis have been confirmed by using a ligand exchange, which is a softer modification technique. The limits of miscibility of ligands belonging to two different classes were tested on M4Ag44(SR)30 nanoparticle using p-MBA and glutathione. Mass spectrometry provides means to control the purity of the synthetic product and to identify potentially interesting by-products. When M4Ag44(SR)30 was synthesized using para-tert-butylbenzenethiol (TBBT), another MNP, with the molecular formula of M3Ag17(TBBT)12, was identified in the product. The synthesis was further optimized to yield primarily M3Ag17(TBBT)12. The small size of the nanoparticle, structural analysis of other silver and gold MNPs, and use of computational chemistry allowed for the rational prediction of the structure of this nanoparticle. The structure prediction was supported using heteroatom substitution as a structural probe. The inorganic part of the predicted structure was later found to be identical to that of the experimentally determined structure.
Terry Bigioni (Committee Chair)
Cora Lind-Kovacs (Committee Member)
Dragan Isailovic (Committee Member)
Nikolas Podraza (Committee Member)
136 p.
Analytical Chemistry; Chemistry; Materials Science; Physical Chemistry
noble metal nanoparticles; molecular nanoparticles; mass spectrometry; silver;

Recommended Citations

Citations

  • Atnagulov, A. (2017). Application of Mass Spectrometry to the Characterization of Core and Ligand Shell Modifications of Silver Molecular Nanoparticles [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501860803445199

    APA Style (7th edition)

  • Atnagulov, Aydar. Application of Mass Spectrometry to the Characterization of Core and Ligand Shell Modifications of Silver Molecular Nanoparticles. 2017. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501860803445199.

    MLA Style (8th edition)

  • Atnagulov, Aydar. "Application of Mass Spectrometry to the Characterization of Core and Ligand Shell Modifications of Silver Molecular Nanoparticles." Doctoral dissertation, University of Toledo, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501860803445199

    Chicago Manual of Style (17th edition)

toledo1501860803445199
407
© 2017, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.