https://zenodo.org/record/1258869/files/article.pdf

NWChem: a comprehensive and scalable open-source solution for large scale molecular simulations

Nanoparticles: Properties, applications and toxicities

Activation of persulfate (PS) and peroxymonosulfate (PMS) and application for the degradation of emerging contaminants

Combined quantum-mechanics/molecular-mechanics (QM/MM) approaches have become the method of choice for modeling reactions in biomolecular systems. Quantum-mechanical (QM) methods are required for describing chemical reactions and other electronic processes, such as charge transfer or electronic excitation. However, QM methods are restricted to systems of up to a few hundred atoms. However, the size and conformational complexity of biopolymers calls for methods capable of treating up to several 100,000 atoms and allowing for simulations over time scales of tens of nanoseconds. This is achieved by highly efficient, force-field-based molecular mechanics (MM) methods. Thus to model large biomolecules the logical approach is to combine the two techniques and to use a QM method for the chemically active region (e.g., substrates and co-factors in an enzymatic reaction) and an MM treatment for the surroundings (e.g., protein and solvent). The resulting schemes are commonly referred to as combined or hybrid QM/MM methods. They enable the modeling of reactive biomolecular systems at a reasonable computational effort while providing the necessary accuracy.

QM/MM Methods for Biomolecular Systems

Implicit Solvation Models: Equilibria, Structure, Spectra, and Dynamics.

The synthesis of palladium (Pd) and gold (Au) nanoparticles (NPs) for the treatment of groundwater has become a popular method because of its effectiveness and sustainability [1]. An effective synthesis method for the production of these NPs uses a combination of sonication and solvothermal processes [3],[4]. The as-made samples are designed to have a 2:1 Pd:Au molar ratio, and a 5wt% of Pd on carbon support, for comparison with corresponding commercial granular activated carbon (GAC) supported 5wt% Pd catalysts. In the past, we have shown that these as-made GAC supported Pd/Au NPs which have been fabricated in 24 hr were potent at degrading carcinogens like trichloroethylene (TCE) [3],[4]. Here, we have investigated the effect of formation time on carbon-supported Pd/Au NPs catalyst to potentially expedite the synthesis process. We synthesized samples in one-hour intervals between 0 and 24 hr and here compare the 1-hr and 24-hr samples. The samples were characterized using an FEI Tecnai F-20 TEM/STEM with EDS capabilities and a Shimadzu UV 3600 UV-Vis Spectrophotometer. Specifically, for TEM analysis, for better characterization, graphene was used as a support in the place of the denser, thicker GAC. In doing so, the surface of GAC is approximated to be similar to a highly defective surface of graphene. For any TCE degradation testing however, the as-made GAC-supported Pd/Au NPs have been used.

Effect of Synthesis Time of Carbon Supported Pd/Au NPs on TCE degradation

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The Importance of Complementary Information Provided by Surface Analysis, Electron Microscopy and in situ Characterization of Nanoparticles

Kinetics of carbon tetrachloride reduction at an iron rotating disk electrode

This chapter provides an overview of synthesis, characterization and property measurements techniques important for making understanding the nature of zero valent iron nanoparticles. The chemical reactivity of nanometer-sized materials can be quite different from that of either bulk forms of a material or the individual atoms and molecules that comprise it. Advances in our ability to synthesize, visualize, characterize and model these materials have created new opportunities to control the rates and products of chemical reactions in ways not previously possible. Zero valent iron (ZVI), including non-nanoparticle forms for iron, is one of the most promising remediation technologies for the removal of mobile chlorinated hydrocarbons and reducible inorganic anions for ground water. ZVI nanoparticles may have great potential to assist environmental remediation, but there are significant scientific and technological questions that remain to be answered. Understanding of ZVI reactive metal core-shell nanoparticles requires use of particles that are as well characterized and understood as possible. In this chapter we describe the issues and provide examples that include synthesis of nanoparticles, analytical characterization of the particles and finally measurements of their chemical properties.

Synthesis, Characterization, and Properties of Zero‐valent Iron Nanoparticles

Introduction There are many reports suggesting that nano-sized Fe and Fe oxides exhibit greater reactivity with reducible contaminants than micro-sized particles of the same materials. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. In particular, many studies do not clearly distinguish between massnormalized and surface-area-normalized rate constants, or do not use robust methods for calculating the latter from the former. Furthermore, secondary factors such as pH can influence comparisons between types of iron because different types of iron can produce different solution pH’s and solution pH affects contaminant reduction rates. To take such factors into account when making generalizations about relative reaction rates – without a mechanistic kinetic model more detailed than any that is current available for this system – an alternative approach is needed. Here we explore the use of a graphical tool for assessing relative rates of reactions occurring on particle surfaces.

Paul G. Tratnyek

Papers

Effect of Synthesis Time of Carbon Supported Pd/Au NPs on TCE degradation

The Importance of Complementary Information Provided by Surface Analysis, Electron Microscopy and in situ Characterization of Nanoparticles

Kinetics of carbon tetrachloride reduction at an iron rotating disk electrode

Synthesis, Characterization, and Properties of Zero‐valent Iron Nanoparticles

Nanosize effects on the kinetics of contaminant reduction by iron and iron oxides