Skip to Main Content
 

Global Search Box

 
 
 

ETD Abstract Container

Abstract Header

Green Synthesis and Gold Alloying of Silver Molecular Nanoparticles

Bhattarai, Badri, Bhattarai

Abstract Details

2018, Doctor of Philosophy, University of Toledo, Chemistry.
Noble metal nanoparticles have been extensively studied for use in applications in a diverse range of fields such as optoelectronics, catalysis, sensing, medicine, etc. due to their unique properties that arise as a result of their dimensions. Metal nanoparticles of size less than 3 nm exhibit molecular properties, unlike larger nanoparticles. These molecular nanoparticles are excellent model systems to study the chemistry of nanomaterials at the molecular level as their molecular formulae, crystal structure, chemical composition, electronic structures etc. can be experimentally measured and theoretically calculated. In addition, knowledge of their thermodynamic stability and mechanisms of formation can be leveraged in developing green synthetic routes in order to produce safer products that widen the range of applications, and to develop safer processes that increase manufacturability and decrease waste. Even though nanoparticle research is more focused on the end product and their properties, rather than the process, we have taken a different route of dismantling the M4Ag44(p-MBA)30 nanoparticle synthesis and developing a green route with significantly improved efficiency and an 89% yield. The need of solvent, which contributed to 98% of the waste, was kept to a minimum by using a stoichiometric silver-thiolate polymer as a precursor to intimately mix the metal atoms and ligands, and by forming a paste using a small amount of liquid to promote mass transport. The process mass intensity (PMI), a green metric defined by material input over product output, was decreased by almost 18-fold compared to the solution-phase synthesis. Some toxic chemicals were also removed or replaced throughout the process. This method is very effective for thermodynamically favorable products, and should be useful for other systems too. Alloying of metal nanoparticles is advantageous to achieve new properties. For example, gold-silver bimetallic NPs can be more stable than silver NPs and have better optical properties than gold NPs. Here we have studied the alloying process in M4AuxAg44-x(p-MBA)30 alloy nanoparticles, where 0 = x = 12, and M is a countercation. Two methods were used to synthesize M4AuxAg44-x(p-MBA)30 alloy nanoparticles: (i) co-reduction of gold-thiolate and silver-thiolate with alkali borohydride, and (ii) galvanic-exchange reaction between gold-thiolate and M4Ag44(p-MBA)30 nanoparticles in order to substitute silver with gold. The major findings were: (i) the number of gold atoms incorporated in the alloy was always less than the gold input, (ii) only up to twelve gold atoms were incorporated, (iii) gold prefers to stay at the innermost core energetically in alloy nanoparticles, as shown by the x-ray crystal structure of M4Au12Ag32(p-MBA)30 alloy nanoparticles, (iv) gold atom distributions were generally Gaussian, and (v) addition of gold in silver nanoparticles to create alloys increases the stability against oxidation.
Terry Bigioni (Committee Chair)
Joseph A. R. Schmidt (Committee Member)
Dragan Isailovic (Committee Member)
Nikolas Podraza (Committee Member)
166 p.

Recommended Citations

Citations

  • Bhattarai, Bhattarai, B. (2018). Green Synthesis and Gold Alloying of Silver Molecular Nanoparticles [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533312041161417

    APA Style (7th edition)

  • Bhattarai, Bhattarai, Badri. Green Synthesis and Gold Alloying of Silver Molecular Nanoparticles. 2018. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533312041161417.

    MLA Style (8th edition)

  • Bhattarai, Bhattarai, Badri. "Green Synthesis and Gold Alloying of Silver Molecular Nanoparticles." Doctoral dissertation, University of Toledo, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533312041161417

    Chicago Manual of Style (17th edition)