Zero-valent iron nanoparticles (ZVI NPs) have been employed in environmental and biomedical applications. These nanoparticles are used in the remediation of soil and water contaminated with heavy metals, and ZVI NPs can be used in the biomedical sector, as drug delivery system due to the large surface area-to-volume ratio. However, their toxicity should be better investigated. In this study, green tea extract was used to synthesize ZVI NPs. The green tea-synthesized nanoparticles (GT-ZVI NPs) were characterized by dynamic light scattering (DLS), X-ray diffraction, Fourier transform infrared spectroscopy and atomic force microscopy. DLS analysis revealed that the nanoparticles have average hydrodynamic size of 104 nm. The results indicated the presence of organic matter derived from green tea extract on the surface of GT-ZVI NPs. The average size of the nanoparticles at solid state was found to be 32 nm. The cytotoxicity of GT-ZVI NPs (1–150 µg/mL) was determined on tumoral (human chondrosarcoma line, SW1353 cells) and non-tumoral (Vero fibroblast cell line) by quantitative cell viability analysis and cell morphological evaluation. GT-ZVI NPs exerted more cytotoxic effect on tumoral line compared to non-tumoral cell line. The viability of SW1353 cells was higher than 75% upon incubation with GT-ZVI NPs, at concentrations in the range of 1–60 µg/mL. At nanoparticle concentrations of 100 and 150 µg/mL, the viability of SW1353 cells decreased 69 and 62%, respectively. These results indicate that these nanoparticles might find important applications in cancer treatment with less toxicity to normal cells.
The revolutionary nanotechnology has generated environment safety concerns due to accumulation and toxicity behavior of nanomaterials. Given the wide application of various nanomaterials in daily products of our life, their environmental release is exceedingly obvious. Moreover, soil is the major sink for nanomaterials after their intentional or inadvertent release into the environment. Enormous attempts have apparently been made to study the impact of nanomaterials in the soil environment. Besides that, our understanding is inadequate due to disparities among results and effects of nanomaterials ranging from lethal, sub-lethal, to non-toxic. Subsequently, interpreting the real potential of nanomaterials to affect the soil environment and associated ecological processes is a challenging task. The interactions of different nanomaterials within different soil environments are crucial to authenticate toxicity behavior. Correspondingly, a global perspective is required for a comprehensive understanding of the environmental impact of nanomaterials. Therefore, we propose the need for a global database of “Nanomaterials in the soil environment” based on the estimates of nanomaterials flow among the three major components, viz. soil, soil microbes, and plants. Since the soil ecosystem is the foundation for many ecological processes supporting aboveground plant community and humankind, there is a need for this global database to precisely address the environmental issues. We propose that the empirical data from this global database would be helpful in bridging the knowledge gaps in the right way. Moreover, through this challenging task, soil policy can be developed to regulate nanomaterials usage and to protect soil health and associated biodiversity.
This paper presents life cycle analysis of the container-based single-family housing and combines energy analysis and optimization, life cycle assessment and life cycle costing. The proposed models include the container code (CC), designed to Canadian national building code as reference model, and an improved container (IC) incorporating passive solar technologies. Utilizing passive design strategies results in approximately 79% reduction in annual operational energy consumption for the improved case. The life cycle assessment considers the total energy use and global warming potential over 60-year lifespan. Three life cycle phases are considered: pre-use, use and operation, and end of life. As a result of envelope upgrade, the IC offers 77% reduction in life cycle energy use and global warming potential (GWP) than the CC. However, the envelope upgrade requiring greater energy intensity through industrial processing of additional building materials led to higher environmental impact, approximately 65,370 kWh of embodied energy and 20 t of CO2 eq of GWP embodied carbon emissions for the improved container at pre-use phase. In terms of life cycle cost, IC shows less than 10% total cost savings as compared to CC. This study, however, proves that integrating passive solar design techniques in building not only results in reduced energy consumption but rather translates to reduction in life cycle environmental impacts and life cycle cost building systems, which is, in this case, a modular container housing.
Ground heat exchangers in conjunction with shallow geothermal energy system applications have received significant attention in the case of renewable energy. Soil thermal properties such as thermal conductivity and specific or volumetric heat capacity are important aspects for the design of such systems, affecting the performance. They can be obtained with the use of empirical prediction models, laboratory tests and/or in situ tests. Laboratory tests can be performed either under steady-state or under transient conditions and have the advantage of requiring small volumes of soil and producing fast results. There are many types of heat probes commercially available, with limited—though—comparative assessment available in the literature. The current paper deals with the assessment of ground characteristics of seven samples of soil and rock collected from a certain area in the Mediterranean island of Cyprus. Such properties are the thermal conductivity, the thermal diffusivity, the volumetric heat capacity, but there are some other physical properties also. The laboratory testing was done under transient conditions and included measurements taken by two needle probes and one surface probe from two different commercial apparatuses. Comparison of the obtained results for the thermal properties of the samples was made and was also supported by numerical simulations using the COMSOL Multiphysics software through a finite element analysis method on the convection–diffusion equation for heat transfer. Laboratory testing on physical properties of the samples such as moisture content, specific gravity, permeability and particle size distribution was also performed, yielding useful results related to the assessment of the thermal properties.
Huanglonbing, or citrus greening, is the most serious disease of citrus which cause large economic losses. One of the strategies to avoid the spread of the disease is the control of Diaphorina citri psyllid, its insect vector, by the application of insecticides. Development of nanoinsecticides, which are less harmful to the environment and more efficient (in terms of cost and performance) than the existing formulations, is a current challenge. In this work, nanocarriers composed of chitosan–tripolyphosphate (by ionic gelification approach) and poly-ε-caprolactone (PCL)–chitosan (by double-emulsion–solvent evaporation method) for thiametoxam insecticide were developed and characterized. Toxicological assessments using Raphidocelis subcapta, Artemia salina and Caernohabditis elegans were performed comparing PCL–chitosan nanoparticle and PCL–chitosan loaded thiamethoxam in comparison to commercial pesticide. The nanoparticles obtained from optimized conditions resulted in positive charged nanoparticles, with medium dispersity. The double-emulsion method resulted in smaller nanoparticles (313.5 ± 7 nm) and increased encapsulation efficiency (36.6 ± 0.2%) in comparison to chitosan–tripolyphosphate nanoparticles. The lower encapsulation efficiency was observed in chitosan–tripolyphosphate, impairing agricultural applications. The EC50 values (mg L−1) of Raphidocelis subcapitata and C. elegans obtained for poly-ε-caprolactone with thiamethoxam were 56.15 (18.91–131.21) and 66.07 (1.20–274.14), respectively, and poly-ε-caprolactone without thiamethoxam 94.26 (22.42–166.10) and 214.63 (139.08–494.3), respectively. No toxicity was found in Artemia salina. Our results indicate that nanoparticles (with and without thiamethoxam) were more toxic to soil organisms (C. elegan) than commercial formulations.
Traditional methods to incorporate metals into graphene oxide (GO) usually require toxic reagents or high temperatures. This study proposes an innovative and sustainable method to incorporate silver (Ag) into graphene oxide using electron beam and evaluate its antibacterial activities. The method is based on green synthesis, without toxic reagents or hazardous wastes, and can be carried out at room temperature, in short reaction times. To synthesize the Ag/rGO nanocomposite, a water/isopropanol solution with dispersed graphene oxide and silver nitrate was submitted to a dose range from 150 to 400 kGy. The product was characterized by thermogravimetry analysis, X-ray diffraction and transmission electron microscopy. The antibacterial activity of Ag/rGO was observed against Gram-negative Escherichia coli by plate count method and atomic force microscopy. The results showed that concentrations as low as 100 μg/mL of produced Ag/rGO were enough to inactivate the cells.