| Summary: | The environmental fate and transport of engineered nanomaterials have been broadly investigated and evaluated in many published studies. Silver nanoparticles (AgNPs) represent one of the most widely manufactured nanomaterials. They are currently being incorporated into a wide range of consumer products due to their purported antimicrobial properties. However, either the AgNPs themselves or dissolved Ag+ ions has a significant potential for the environmental release. The safety issues for nanoparticles are continuously being tested because of their potential danger to the environment and human health. Studies have explored the toxicity of AgNPs to a variety of organisms and have shown such toxicity is primarily driven by Ag+ ion release. Dissolution of nanoparticles is an important process that alters their properties and is a critical step in determining their safety. Therefore, studying nanoparticles' dissolution can help in the current move towards safer design and application of nanoparticles. This research endeavor sought to acquire comprehensive kinetic data of AgNP dissolution to aid in the development of quantitative risk assessments of AgNP fate.
To evaluate the dissolution process in the absence of nanoparticle aggregation, AgNP arrays were produced on glass substrates using nanosphere lithography (NSL). Changes in the size and shape of the prepared AgNP arrays were monitored during the dissolution process by atomic force microscopy (AFM). The dissolution of AgNP is affected by both internal and external factors. First, surface coating effects were investigated by using three different coating agents (BSA, PEG1000, and PEG5000). Capping agent effects nanoparticle transformation rate by blocking reactants from the nanoparticle surface. Coatings prevented dissolution to different extents due to the various way they were attached to the AgNP surface. Evidence for the existence of bonds between the coating agents and the AgNPs was obtained by surface enhanced Raman spectroscopy. Moreover, to study the size effects on AgNP dissolution, small, medium, and large sized AgNPs were used. The surrounding medium and temperature were the two variables that were included in the size effects study. Relationships were established between medium concentration and dissolution rate for three different sized AgNP samples. By using the Arrhenius equation to plot the reaction constant vs. reaction temperature, the activation energy of AgNPs of different sizes were obtained and compared. === Doctor of Philosophy === Nanomaterials, defined as materials with at least one characteristic dimension less than 100 nm, often have useful attributes that are distinct from the bulk material. The novel physical, chemical, and biological properties enable the promising applications in various manufacturing industry. Silver nanoparticles (AgNPs) represent one of the most widely manufactured nanomaterials and has been used as the antimicrobial agent in a wide range of consumer products. However, either the AgNPs themselves or dissolved Ag+ ions has a significant potential for the environmental release. The environmental fate and transport of AgNPs drawn considerable attentions because of the potential danger to environment and human health. Dissolution of nanoparticles is an important process that alters their properties and is a critical step in determining their safety. Ag+ ions migrate from the nanoparticle surface to the bulk solution when an AgNP dissolves. Studying nanoparticles' dissolution can help in the current move towards safer design and application of nanoparticles.
This research aimed to acquire comprehensive kinetic data of AgNP dissolution to aid in the development of quantitative risk assessments of AgNP fate. AgNP arrays were produced on glass substrates using nanosphere lithography (NSL) and changes in the size and shape during the dissolution process were monitored by atomic force microscopy (AFM). First, surface coating effects were investigated by using three different coating agents. Coatings prevented dissolution to different extents due to the various way they were attached to the AgNP surface. Moreover, small, medium, and large sized AgNPs were used to study the size effects on AgNP dissolution. The surrounding medium concentration and temperature were the two variables that were included in the size effects study.
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