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n response to the worldwide presence of per- and polyfluoroalkyl substances (PFAS) in the environment, there has been a great focus on developing effective PFAS removal technology to address this class of contaminants that pose a threat to human and environmental health. Sorbent materials have been a significant focus in PFAS remediation technology; however, the molecular-level interactions between PFAS and sorbent materials are often overlooked or not explored, despite the important role they play in sorbent performance. The objective of this perspective is to showcase how different analytical techniques can be used to provide critical insight into the fundamental interactions between PFAS molecules and sorbent materials. Herein, we discuss the power of various experimental and computational techniques to unveil the fundamental chemistry driving PFAS-sorbent interactions, revealing critical information for the development of robust remediation materials. 

Developing new technologies for removal of per- and polyfluoroalkyl substances (PFAS) from water is critical for public and environmental safety. In conjunction, suitable analytical techniques are required for understanding interactions between novel sorbent materials and PFAS to facilitate efforts on designing improved materials. In this work, six nanoscale carbon dots (CDs) are synthesized for fundamental PFAS sorption studies, and 19F NMR is introduced as a primary analytical technique to rank and understand the affinity of the synthesized CDs toward PFAS. The CDs are synthesized from various-amine rich precursors (polyethylenimine or chitosan) to yield cationic CDs and promote electrostatic interactions with anionic PFAS. The affinity of CDs toward perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and a mixture of 24 PFAS was assessed. Three main approaches were used to rank CD affinity for PFAS: Kd determination using 1D NMR and two CPMG-based methods. Based on Kd values, the PEI CDs exhibited higher affinity for PFOA than any of the chitosan-based CDs or β-cyclodextrin, while affinity for PFOS was comparable across all sorbent materials. CMPG-based experiments suggested that PEI CDs have superior affinity for PFOA and operate in a slower exchange regime with PFOA than the chitosan-based CDs. In the PFAS mixture, the PEI-CDs and top-performing chitosan-based CDs interacted strongly with PFAS of varying chain lengths and identity. These results indicate that CDs should continue to be explored for their high PFAS affinity and solidifies the power of 19F NMR techniques to provide critical molecular-level information about PFAS-sorbent interactions in suspension. 

Food insecurity is a prominent global issue. With a predicted global population of 9 billion by 2050, food production must double at a minimum to accommodate these growing numbers. One approach to combat food insecurity is targeting plant pathogens that affect crop quality and yield, resulting in an overall increase in edible food production. Plant pathogen management has previously utilized the RNA interference (RNAi) mechanism for remediation; however, its widespread use has technical limitations. In this study, silica nanoparticles (SiO2 NPs) were utilized as nanocarriers of therapeutic double-stranded ribonucleic acid (dsRNA) to enhance dsRNA delivery into plant cells, thereby activating the RNAi system and suppressing the occurrence of potato virus Y (PVY). This highly mutable pathogen causes several adverse effects in potato and other crop plants. Fast-dissolving silica (FDS) nanoparticles, mesoporous silica nanoparticles (MSNs), and ultraporous mesostructured silica nanoparticles (UMNs) with negative and positive surface charges were synthesized. After thorough characterization, nine distinct SiO2 NP formulations were loaded with dsRNA, with UMNs showing the best loading capacity. Due to the negatively charged nature of dsRNA, positively charged UMNs were favored and employed in further application experiments. Gel electrophoresis indicated that dsRNA loaded into/onto these UMNs was released over several days. Fifteen days after inoculation, greenhouse experiments with tobacco plants demonstrated that dsRNA-loaded UMNs effectively suppressed PVY. In a field study, dsRNA loaded into/onto UMNs showed a 0% disease incidence, an improvement compared to dsRNA or nanoparticle application alone. These findings reveal that UMNs are an efficient nanocarrier for delivering dsRNA against PVY, thereby increasing crop health and yield. A techno-economic analysis was performed to evaluate the economic viability of this nanomaterial for industrial commercialization. 

Reactive oxygen species (ROS) are common cellular oxidants that when overproduced by cellular stressors cause harm to cells. Detection of ROS is of utmost importance to understanding a wide variety of cellular function and toxicity mechanisms. Conventional ROS fluorescence assays involve using a single dye to visualize the ROS quantity. Herein, we describe ROS-sensitive, fluorescent-dye-incorporated carbon dots with dual fluorescence capabilities and good biocompatibility. Carbon dots (CDs) made of citric acid and urea were synthesized with incorporated cyanine-3-amine (Cy3), a bright red fluorescent dye, to create Cy3-CDs. To get Cy3 into the ROS-sensitive form, this work demonstrated that Cy3 alone and Cy3 within carbon dots can be electrochemically reduced to their colorless ROS-sensitive form. Cy3, CDs, and Cy3-CDs are all responsive to additions of superoxide, leading to an increase in the fluorescence. Overall, this work examines how O2•– and additional oxidizers interact with CDs, Cy3, and Cy3-CDs, and molecular-level hypotheses are explored that will inform the design of future carbon dot-based ROS sensors. 

Nanoparticle surface chemistry characteristics are key factors that determine their behavior upon interaction with different organisms. In particular, electrostatic interactions between nanoparticles and plant-type organisms have been well-characterized; however, the impact of the degree of hydrophobicity remains largely unexplored. Here, ultraporous mesostructured silica nanoparticles (UMNs) were functionalized with different ratios of chlorotrimethylsilane (TMS) to 2-[methoxy(polyethyleneoxy)9–12propyl]trimethoxysilane (PEG) to systematically tune their hydrophobicity, and were subsequently used to interrogate how the degree of hydrophobicity affects nanoparticle interactions at the biointerface of the green alga, Raphidocelis subcapitata. Using high-content imaging and phenotypic profiling, the levels of UMN internalization, subcellular trafficking, and their associated phenotypic and physiological impacts were quantified. Increasing the PEG content on the surface of the UMNs, which decreased particle hydrophobicity, was found to significantly enhance levels of internalization, but did not alter translocation within the cells. Colocalization analyses indicated a strong association between UMNs and F-actin filaments after 1–24 hours of exposure, which was independent of PEG content and degree of UMN hydrophobicity, as there was no significant difference between particle types. However, after 48 hours, cells appeared to have incorporated a portion of UMNs into their cell walls while depositing the remainder into vacuolated spaces. Lastly, UMNs had a significant impact on phenotype complexity, with specific metrics including enhanced chlorophyll production and shifts in cell cycle progression; however, no growth inhibition was observed after 72 hours. Overall, using this approach, it was found that tuning the degree of UMN hydrophobicity had a significant impact on the levels of internalization. However, once inside the cells, the degree of hydrophobicity did not have a significant impact on translocation, phenotype, or physiological response as each particle type elicited similar cellular responses. 

Vacuum infiltration of nanoparticles into soybean seeds can promote crop health and yields while reducing environmental impact. 

Reactive oxygen species (ROS) can be quantified using fluorescence, electrochemical, and electron paramagnetic resonance spectroscopy techniques. Detection of ROS is critical in a wide range of chemical and biological systems. 

Nanoparticles (NPs) are increasingly being used in medical, electronic, energy, and agricultural applications due to their unique properties that often arise due to the high surface area-to-volume ratio. However, this characteristic along with the high reactivity of NPs make these materials highly dynamic in environmental settings. Thus, several transformations can take place when these materials enter the environment that determines their transport, toxicity, and fate of them in our environment. These transformations, and more specifically oxidative dissolution and sulfidation, are directly impacted by the characteristics that a NP has in addition to the surrounding environmental conditions. Therefore, this review aims to summarize how NP characteristics (size, coatings, etc.) and other important environmentally relevant conditions (oxic/anoxic waters, natural organic matter, etc.) impact the oxidative dissolution and sulfidation of several metal and metal oxide NPs. The impact of these factors is crucial to understanding and predicting the environmental risks of these materials in a wide range of applications. 

pH-responsive polymeric nanoparticles are an exciting class of stimuli-responsive materials that can respond to changes in pH and, as a result, have been developed for numerous applications in biomedicine, such as the loading and delivery of various cargoes. One common transformation is nanoparticle swelling due to the protonation or deprotonation of specific side chain moieties in the polymer structure. When the pH trigger is removed, the swelling can be reversed, and this process can be continually cycled by adjusting the pH. In this work, we are leveraging this swelling–deswelling–reswelling mechanism to develop a simple, fast, and easy loading strategy for a class of cross-linked polymeric nanoparticles, poly-2-(diethylamino) ethyl methacrylate (pDEAEMA), that can reversibly swell below pH 7.3, and a dye, rhodamine B isothiocyanate (RITC), as a proof-of-concept cargo molecule while comparing to poly(methyl methacrylate) (pMMA) nanoparticles as a nonswelling control. A free radical polymerization was used to generate pDEAEMA nanoparticles at three different sizes by varying the synthesis temperature. Their pH-dependent swelling and deswelling were extensively characterized using dynamic light scattering and transmission electron microscopy, which revealed a reversible increase in size for pDEAEMA nanoparticles in acidic media, whereas pMMA nanoparticles remain constant. Following dye loading, pDEAEMA nanoparticles show significant fluorescence intensity when compared to pMMA nanoparticles, suggesting that the reversible swelling is key for successful loading. Upon acidic treatment, there is a significant decrease in the fluorescence intensity when compared to the dye-loaded nanoparticles in basic media, which could be due to dilution of the dye when released in the acidic medium solution. Interestingly, nanoparticle size had no impact on dye loading properties, suggesting that the dye molecules only go so far into the polymer nanoparticle. Additionally, confocal microscopy images reveal pDEAEMA nanoparticles with higher RITC fluorescence intensity in acidic media but a lower RITC fluorescence intensity in basic media, while pMMA nanoparticles show no differences. Together, these results showcase a size reversibility-driven cargo loading mechanism that has the potential to be applied to other beneficial cargoes and for various applications.