Polymers containing quantum dots (QDs) are considered crucial components of next-generation consumer items, but ambiguity remains regarding how these compounds may negatively affect public health and the environment.
Study: Surface defects and particle size determine transport of CdSe quantum dots out of plastics and into the environment. Image Credit:Van Pympk/Shutterstock.com
A pre-proof paper from the Journal of Hazardous Materials examines how the transport of quantum dots out of polymeric materials and into the environment relates to their surface and size properties.
Polymer Nanocomposites (PNCs): Overview and Significance
Integrating nanostructured additives such as quantum dots into polymers is a method of producing innovative hybrid compounds such as polymer nanocomposites (PNCs) with improved thermal, physical, and optical characteristics.
PNCs have numerous applications in manufacturing essential products within aerospace and automotive materials, fire retardants, energy storage systems, packaged foods, and medical equipment.
Polymer-to-Liquid Transfer of Quantum Dots in PNCs
Sustainable PNC production necessitates assessing if nanoparticles such as quantum dots migrate into the external environment. The transmission of quantum dots into the nearby liquid environment is particularly important for PNCs utilized in medical equipment or food processing applications.
Several investigations on polymer-to-liquid transport phenomena in PNCs have revealed that the nanomaterial mass transmitted from these PNCs into the liquid environment is minimal but variable in volume and shape due to differences in nanofiller characteristics, external environment, polymer type, and testing conditions.
Despite these advances, the interface chemistry of quantum dots that drive deterioration and transport dynamics, as well as the variables that control these reactions, remain unknown. As a result, it is impossible to determine whether two nominally equivalent PNCs would create more quantum dot exposure to the environment given the same set of working parameters.
Limitations of Previously Used Quantum Dots Transport Models
Theoretical frameworks can aid in the understanding of how quantum dots move from polymeric materials into the environment. While there are various transport models for small molecules, there are only a few significant models in the literature that are explicitly created for nanoparticle compounds, such as quantum dots.
One of the most pressing issues concerning the risk analysis of nanocomposite materials is the absence of data-supported theoretical frameworks for forecasting the movement of quantum dots from PNCs to the external environment.
More knowledge of nanofiller mass transfer characteristics via theory and experiments can greatly enhance PNC manufacturing and design principles, improving sustainability and lowering the negative effects of next-generation PNCs on the environment.
Highlights of the Current Study
In this study, the researchers created a PNC class utilizing low-density polyethylene (LDPE) as a polymer host and cadmium selenide (CdSe) quantum dots in an assortment of sizes. Because quantum dots are widely available, cover a size range of 1-10 nm, and have minimal size dispersibility, they are suitable models for researching nanoparticle movement from PNCs to the surrounding environment.
The photoluminescence (PL) and composition of the produced PNCs were evaluated to understand how integrating quantum dots in LDPE impacts their interface stoichiometry and surface fault concentration. Various migration studies were carried out to correlate the speed of quantum dot movement with the initial quantum dot diameter and surface reactivity.
This information was then utilized to create a semi-empirical model for predicting the transfer of quantum dots out of polymeric materials and into the surrounding fluid environment.
The researchers observed an inverse relationship between the mass of migratory quantum dots and their original diameter due to smaller particles having a greater specific surface area.
This work also introduced the first theoretical framework capable of modeling the complicated migration process of quantum dots. These models were effectively applied to substrates with a wide variety of starting quantum dots sizes and PNC storage durations. To simulate the movement of quantum dots across polymer and environment interfaces, the framework combines the time-dependent mass expulsion of quantum dots with the diffusion equation under simple boundary conditions.
Based on these findings, it is reasonable to conclude that the theoretical framework developed in this study could be a useful and functional tool for assessing quantum dots migration risks to human health and the environment. This framework can also provide new insights into the physical and chemical processes of the nanomaterials movement phenomena that would be challenging to accomplish using only experimental approaches.
Duncan, T. V. et al. (2022). Surface defects and particle size determine transport of CdSe quantum dots out of plastics and into the environment. Journal of Hazardous Materials. Available at: https://doi.org/10.1016/j.jhazmat.2022.12968