Browsing by Author "Mensch, Arielle C."
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Item Investigation of phosphorous doping effects on polymeric carbon dots: Fluorescence, photostability, and environmental impact(Elsevier, 2017-12-05) Zhi, Bo; Gallagher, Miranda J.; Frank, Benjamin P.; Lyons, Taeyjuana; Qiu, Tian A.; Da, Joseph; Mensch, Arielle C.; Hamers, Robert J.; Rosenzweig, Zeev; Fairbrother, D. Howard; Haynes, Christy L.Carbon dots have arisen as a potential alternative to traditional quantum dots since they fluoresce but are synthesized from sustainably sourced green chemicals. Herein, fluorescent nitrogen-doped polymeric carbon dots (CDs) were synthesized by using citric acid (CA) or malic acid (MA) as carbon precursors and ethylenediamine as the nitrogen precursor. Additionally, phosphoric acid was used as a doping agent for each type of CDs to evaluate the impact of incorporating phosphorus into the nanoparticles. Thus, four kinds of doped CDs (N-doped or N, P co-doped) were obtained and named as CACDs, CA-P-CDs, MACDs, and MA-P-CDs. Quantum yield and fluorescence lifetime analysis indicate that phosphorus doping of up to c.a. 10 wt% does not induce a remarkable influence on CD photoluminescence. The photostability of the N, P co-doped MACDs (MA-P-CDs), however, was observed to increase compared to the N-doped MACDs under 350 nm UV (UV-B) exposure. Lastly, to assess the impact of this emerging nanoparticle on prokaryotes, the bacterial toxicity of these CDs was tested using Shewanella oneidensis MR-1 as a model microorganism. Interestingly, the CDs exhibited no toxicity in most cases, and in fact facilitated bacteria growth. Hence, this work suggests that CDs are potentially eco-friendly fluorescent materials.Item Redesign of hydrophobic quantum dots mitigates ligand-dependent toxicity in the nematode C. elegans(Elsevier, 2021-04) Niemuth, Nicholas J.; Williams, Denise N.; Mensch, Arielle C.; Cui, Yi; Orr, Galya; Rosenzweig, Zeev; Klaper, Rebecca D.Surface properties of engineered nanomaterials (ENMs) have been shown to influence their interaction with biological systems. However, studies to date have largely focused on hydrophilic materials, likely due to biocompatibility concerns and aqueous exposure conditions necessary for many model systems. Therefore, a knowledge gap exists in nanotoxicity literature for impacts of hydrophobic ENMs, with studies of hydrophobic materials largely limited to carbon ENMs. Here we demonstrate testing of hydrophobic quantum dots (QDs) using the nematode C. elegans, a model soil organism cultured on solid media and amenable to hydrophobic exposures. To evaluate the influence of hydrophobicity, we compared CdSe/ZnS QDs functionalized with hydrophobic trioctylphosphine oxide (TOPO) to identical QDs functionalized with hydrophilic dihydrolipoic acid-polyethylene glycol (DHLA-PEG) and alternative hydrophobic CdSe/ZnS QDs functionalized with oleic acid (OA). Results show that hydrophobic TOPO QDs are significantly more toxic than hydrophilic DHLA-PEG QDs, and substitution of TOPO with OA yields relatively non-toxic hydrophobic QDs. Fluorescence microscopy shows TOPO QDs loosely associated with the organism's cuticle, but atomic force microscopy shows no difference in cuticle structure from exposure. Importantly, TOPO ligand alone is as toxic as TOPO QDs, and our data suggests that TOPO may impact neuromuscular function, perhaps upon displacement from the QD surface. This study demonstrates the importance of examining ligand-specific impacts of hydrophobic ENMs and indicates OA-functionalized QDs as a potential alternative to TOPO QDs for reduced toxicity.