Browsing by Author "Pati, Paramjeet"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Room temperature seed mediated growth of gold nanoparticles: mechanistic investigations and life cycle assesment
    Leng, Weinan; Pati, Paramjeet; Vikesland, Peter J. (The Royal Society of Chemistry, 2015-08-04)
    In this study, we report the first room temperature seed-mediated synthesis of gold nanoparticles (AuNPs) in the presence of citrate and a gold salt. In contrast to citrate-reduction in boiling water, these mild reaction conditions provide expanded capacity to probe the mechanism of seed-mediated growth following gold salt addition. Moreover, comparative life cycle assessment indicates significant reductions in the environmental impacts for the room temperature synthesis. For this study, highly uniform gold seeds with Z-average diameter of 17.7 +/- 0.8 nm and a polydispersity index of 0.03 +/- 0.01 were prepared by a pH controlled protocol. We investigated the AuNP growth mechanism via time resolved UV-vis spectroscopy, dynamic light scattering, and transmission electron microscopy. This study indicates that citrate and its oxidation byproduct acetone dicarboxylate serve to bridge and gather Au(iii) ions around gold nanoparticle seeds in the initial growth step.
  • Thumbnail Image
    Sustainable Nanotechnology: Life Cycle Thinking in Gold Nanoparticle Production and Recycling
    Pati, Paramjeet (Virginia Tech, 2015-09-01)
    Nanotechnology has enormous potential to transform a wide variety of sectors, e.g., energy, electronics, healthcare, and environmental sustainability. At the same time, there are concerns about the health and environmental impacts of nanotechnology and uncertainties about the fate and toxicity of nanomaterials. Life cycle assessment (LCA), a quantitative framework for evaluating the cumulative environmental impacts associated with all stages of a material or process, has emerged as a decision-support tool for analyzing the environmental burdens of nanotechnology. The objective of this research was to combine laboratory techniques with LCA modeling to reduce the life cycle impacts of gold nanoparticle (AuNP) production. The LCA studies were focused on three aspects of AuNP synthesis: 1) the use of bio-based ("green") reducing agents; 2) the potential for recycling gold from nanomaterial waste; and, 3) the reduction of the life cycle impacts of AuNP production by conducting the synthesis at reduced temperature. The LCA models developed for AuNPs can inform future nanotechnology-focused LCA studies. Comparative LCA showed that in some cases, the environmental impacts associated with green synthesis methods may be worse than those of conventional synthesis approaches. The main driver of the environmental burdens associated with AuNP synthesis is the large embodied energy of gold, and so-called green synthesis methods do not offset those impacts. In addition, the reaction yield, which is seldom reported in the literature for green synthesis of nanomaterials, was found to greatly influence the life cycle impacts of AuNP synthesis. Gold from nanomaterial waste was successfully recovered by using host-guest inclusion complex formation facilitated by alpha-cyclodextrin. This recycling approach involved room temperature conditions and did not require the toxic cyanide or mercury commonly used in the selective recovery of gold. A major advantage offered by this approach for selective gold recovery over conventional approaches is that the recovery does not involve the use of toxic cyanide or mercury. To reduce the energy footprint of citrate-reduced AuNP synthesis, the synthesis was conducted at room temperature. LCA models showed significant reduction in the energy footprint. The findings of this research can inform future LCAs of other nanomaterials.
  • Thumbnail Image
    Waste not want not: life cycle implications of gold recovery and recycling from nanowaste
    Pati, Paramjeet; McGinnis, Sean; Vikesland, Peter J. (Royal Society of Chemistry, 2016-08-24)
    Commercial-scale applications of nanotechnology are rapidly increasing. Enhanced production of nanomaterials and nano-enabled products and their resultant disposal lead to concomitant increases in the volume of nanomaterial wastes (i.e., nanowaste). Many nanotechnologies employ resource-limited materials, such as precious metals and rare earth elements that ultimately end up as nanowaste. To make nanotechnology more sustainable it is essential to develop strategies to recover these high-value, resource-limited materials. To address this complex issue, we developed laboratory-scale methods to recover nanowaste gold. To this end, α-cyclodextrin facilitated host–guest inclusion complex formation involving second-sphere coordination of [AuBr4]− and [K(OH2)6]+ was used for gold recovery and the recovered gold was then used to produce new nanoparticles. To quantify the environmental impacts of this gold recycling process we then produced life cycle assessments to compare nanoparticulate gold production scenarios with and without recycling. The LCA results indicate that recovery and recycling of nanowaste gold can significantly reduce the environmental impacts of gold nanoparticle synthesis.