Concerns arising from accidental and occasional releases of novel industrial nanomaterials to the environment and waterbodies are rapidly increasing as the production and utilization levels of nanomaterials increase every day. In particular, two-dimensional nanosheets are one of the most significant emerging classes of nanomaterials used or considered for use in numerous applications and devices. This study deals with the interactions between 2D molybdenum disulfide (MoS₂) nanosheets and beneficial soil bacteria. It was found that the log-reduction in the survival of Gram-positive Bacillus cereus was 2.8 (99.83%) and 4.9 (99.9988%) upon exposure to 16.0 mg/mL bulk MoS₂ (macroscale) and 2D MoS₂ nanosheets (nanoscale), respectively. For the case of Gram-negative Pseudomonas aeruginosa, the log-reduction values in bacterial survival were 1.9 (98.60%) and 5.4 (99.9996%) for the same concentration of bulk MoS₂ and MoS₂ nanosheets, respectively. Based on these findings, it is important to consider the potential toxicity of MoS₂ nanosheets on beneficial soil bacteria responsible for nitrate reduction and nitrogen fixation, soil formation, decomposition of dead and decayed natural materials, and transformation of toxic compounds into nontoxic compounds to adequately assess the environmental impact of 2D nanosheets and nanomaterials.

This study determined Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium survival on tomato skins as a function of sanitization treatment, under three differing contamination and sanitization scenarios. Sanitizing treatments consisted of the plant-derived antimicrobial (PDA) geraniol (0.5 wt.%) emulsified in the polymeric surfactant Pluronic F-127 (GNP), 0.5 wt.% unencapsulated geraniol (UG), 200 mg/L hypochlorous acid at pH 7.0 (HOCl), and a sterile distilled water wash (CON). Experimental contamination and sanitization scenarios tested were: (1) pathogen inoculation preceded by treatment; (2) the pathogen was inoculated onto samples twice with a sanitizing treatment applied in between inoculations; and (3) pathogen inoculation followed by sanitizing treatment. Reductions in counts of surviving pathogens were dependent on the sanitizing treatment, the storage period, or the interaction of these independent/main effects. GNP treatment yielded the greatest reductions in pathogen counts on tomato skins; pathogen survivor counts following GNP treatment were consistently statistically lower than those achieved by HOCl or UG treatments (p < 0.05). GNP treatment provided greatest pathogen reduction under differing conditions of pre- and/or post-harvest cross-contamination, and reduced hygiene-indicating microbes the most of all treatments on non-inoculated samples. Encapsulated geraniol can reduce the risk of pathogen transmission on tomato fruit, reducing food safety hazard risks for tomato consumers.

This study aimed to quantify survival in Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium isolates on melon rind surface samples achieved by sanitizer treatment under three differing melon contamination and sanitization scenarios. Sanitizing treatments consisted of the plant-derived antimicrobial (PDA) essential oil component (EOC) geraniol (0.5 wt.%) entrapped in the polymeric surfactant Pluronic F-127 (GNP), 0.5 wt.% unencapsulated geraniol (UG), 200 mg/L hypochlorous acid at pH 7.0 (HOCl), and a sterile distilled water wash (CON). The experimental contamination and sanitization scenarios tested were: (1) pathogen inoculation preceded by treatment; (2) the pathogen was inoculated onto samples twice with sanitizing treatment applied in between inoculation events; or (3) pathogen inoculation followed by sanitizing treatment. Reductions in the numbers of surviving pathogens were dependent on the sanitizing treatment, the storage period, or the interaction of these effects. GNP treatment provided the greatest reductions in surviving pathogen counts on melon rinds, but these did not regularly statistically differ from those achieved by HOCl or UG treatment. GNP treatment provided the best pathogen control under differing conditions of pre- and/or post-harvest cross-contamination and can be applied to reduce the risk of pathogen transmission on melon rinds.

Recent developments in horizontal drilling and fracking technology have had a crucial role in increased shale gas and oil production in the U.S and the world. Natural resources kept in low permeability reservoirs, namely shale formations, can be recovered by a well-designed hydraulic fracturing process. Optimization of production and efficiency in hydraulic fracturing significantly depend on properties and efficiency of fracturing fluids. This work presents a pH-responsive supramolecular assembly solution system synthesized via complexation of maleic acid with an amino-amide in an aqueous media. Our previous studies on this system have verified its significant potential to be used as displacement fluids in EOR due to its highly adjustable and reversible viscosity behavior. Herein, we investigated its potential as fracturing fluids considering its mobility control, and proppant transfer and settling capacities. The main protocol is: the viscosity of injected supramolecular solution is set to an optimum (moderate to high) value enabling both enhanced proppant transport and easy injection of the fluid, and then reduced with an external pH stimulus near fissures for proppant sedimentation and easy flowback. Flow-sweep experiments of the fracturing fluid using the supramolecular solution and proppants (silica sand) revealed that for only a 2wt.% concentration, viscosity could be varied nearly 1600 times by changing pH from ~4 to ~8, reversibly. Moreover, sedimentation studies showed that the settling rate of the silica proppants descended five orders of magnitude by increasing pH from 4 to 8 in a reversible fashion. On the other hand, our lab-scale preliminary experiments showed that these supramolecular assembly solutions both have reversible pH-responsive properties and high salinity and temperature tolerance. While degradation and breakage are observed in polymer viscosity modifiers used in hydraulic fracturing under high temperatures and sudden extreme shear stresses, supramolecular assembly solutions have ability to disassemble and re-assemble. Use of supramolecular solutions in fracturing fluids can also prevents reduction of permeability of reservoirs arising from polymer blockage during flowback period. Therefore, supramolecular solutions can be thought as self-healing polymer solutions. Briefly, supramolecular assembly solution system described here has a potential to be a novel type fracturing fluid due to its pH-tunable and reversible viscosity and proppant transfer capacity, high salt tolerance, self-healing property, and sustainability and environmental friendliness.