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Nanoparticles (NPs) are increasingly used as agrochemical components through foliar spraying such as foliage fertilizers or pesticides. However, the understanding of the mechanisms of nanoparticle absorption and translocation from the leaf surface is limited. In this study, ZnO NPs (30 nm) labeled with fluorescein isothiocyanate (FITC) were foliar applied to wheat leaf tissues to investigate the process of attachment and absorption. Using laser confocal microscopy, we observed that FITC–ZnO NPs cross the leaf epidermis through the stomata and accumulate first in the apoplast, followed by subsequent transport to mesophyll cells. The Zn concentrations in wheat leaf apoplast and cytoplasm decreased by 33.2% and 8.3% with stomatal aperture diameter reduction, respectively; the apoplastic Zn concentration is influenced more by stomatal aperture than the cytoplasmic Zn level. Scanning electron microscopy with energy-dispersive X-ray analysis was used to map Zn in the wheat leaves and data suggest a different Zn distribution for ZnO NPs and ZnSO4. Zn ions in ZnO NP-treated samples are heterogeneously distributed in comparison with those in ZnSO4-treated samples. The results indicate that the main route to cross the wheat leaf epidermis for ZnO NPs is via the stomata; then these nanoparticles accumulate and release Zn ions in the apoplast, and the released Zn ions and ZnO NPs are absorbed by mesophyll cells. Our findings demonstrate how ZnO NPs cross the wheat leaf epidermis, distribute within mesophyll tissues, and enter into plant cells, and this information is useful for the development of sustainable nano-enabled platforms for nanoscale micronutrient delivery.

Currently, over a billion people around the world lack access to clean drinking water, industrial wastewater treatment and reuse is limited, and conventional water treatment systems cannot adequately treat all contaminants of concern. Nanotechnology-enabled water treatment (NWT) has begun to emerge as a viable option to address many of the problems facing the water treatment status quo, either through cost reducing performance enhancements or filling unmet niches. Advancements in fundamental nanoscience allow unprecedented use of catalysis and energy from across the broad electromagnetic spectrum, as well as unique physicochemical properties, to purify drinking water, treat industrial wastewater, and access unconventional water supplies. However, before fully adopting NWT, it is imperative that the devices are both safe and sustainable, enhancing acceptance from consumers, government, non-government organizations, and industry. We suggest that we are in a unique window of time to “do nano right” by making key sustainability considerations very early in nano-water technology development. To this end, we have developed a framework based on three guiding research questions aimed at understanding the breadth of sustainability considerations for NWT at each of the four major life cycle stages – extraction, production, use, and end-of-life. In following this framework, researchers and product developers can design nano-enabled water treatment devices that perform well and are both safe and sustainable. By presenting the current state of sustainable NWT and specifying gaps in the literature, the present review aims to further develop NWT to be the best alternative to conventional water treatment across a variety of sectors.

Misunderstanding on the claims and statements in Hong et al. (2021) were clarified.

The use of nanomaterials in agriculture as nanofertilizers, nanopesticides, or nano-enabled sensors to increase crop yield is gaining increasing interest. Engineered nanomaterials (ENMs) can improve crop productivity by influencing fertilizer nutrient availability in soil and uptake by plants. These materials can suppress crop diseases by directly acting on pathogens through a variety of mechanisms, including the generation of reactive oxygen species (ROS). ENMs may also suppress disease indirectly by improving crop nutrition and enhancing plant defense pathways. Efficient use of ENMs may complement or replace conventional fertilizers and pesticides, subsequently reducing the environmental impact of agricultural practices. This review evaluates the current literature on ENMs used as pesticides and fertilizers, and highlights critical knowledge gaps that must be addressed to ensure sustainable application of nanotechnology in agriculture so as to achieve global food security.

Foliar spray of engineered nanoparticles (NPs) as nanofertilizers, nanopesticides, nanosensors, and nanocarriers is increasingly being employed in the agricultural industry. Foliar spraying of NPs improves the effectiveness of plant protection technologies compared to traditional soil–root application. Foliar-sprayed NPs mainly enter the leaves through stomata and are transported to different plant parts via apoplastic and symplastic pathways. Foliar NPs enhance defenses and resistance against pests and diseases and improve the yield and quality of crops. However, the mechanisms of damage caused by foliar NPs need further elucidation. Moreover, important factors limiting foliage uptake of NPs such as wax deposits on leaf surfaces, environmental factors (e.g., light, temperature, and humidity), and physical and chemical properties of NPs should be investigated to further improve this technology.

Several studies have explored the effects of copper nanoparticles (NPs) on different edible plants. However, no studies on bell pepper (Capsicum annum L.) plants have been reported. In this study, plants were grown for a full life-cycle assessment (90 days of exposure) in natural soil amended with nano CuO (nCuO), bulk CuO (bCuO), and ionic copper (CuCl2) at 0, 125, 250, and 500 mg kg−1. Based on our experimental findings, none of the treatments significantly affected stem elongation, plant dry biomass, foliar area, leaf chlorophyll content, and fruit productivity of bell pepper. However, ionic copper significantly decreased the gas exchange parameters, evapotranspiration, stomatal conductance, and photosynthesis by an average of 41%, 59%, and 38%, respectively, compared to the other treatments at select concentrations (p ≤ 0.05). The ICP-OES data showed that, except for bCuO at 500 mg kg−1, at 250 mg kg−1 and above, the three compounds significantly increased root Cu (196%, 184%, and 184%) with respect to the control. Only at 500 mg kg−1, ionic Cu gave significantly higher root Cu compared to the other Cu treatments. Additionally, at 125 mg kg−1, leaf P was 41% lower for nCuO, compared to the bCuO treatment. At 500 mg kg−1, nCuO reduced Zn by 55% in leaves and 47% in fruits, compared to the control (p ≤ 0.05); however, it is premature to assert that the reduction in fruit Zn compromises the nutritional quality of bell pepper. Overall, this investigation showed that, at the concentrations tested, nCuO presented low toxicity to bell pepper, with rare differences between nano and bulk treatment responses.

Titanium dioxide nanoparticles (nano-TiO2), one of the most produced engineered nanoparticles (ENPs), are used in pigments, photocatalysis, food additives, and personal care products. This broad variety of applications has led to the unusual and widespread distribution of nano-TiO2 in several environmental sectors, with different effects on living organisms. In the last decade, several publications have shown fragments of information about the interaction, detection, uptake, and translocation of nano-TiO2 in plants. This review includes a discussion of the current knowledge about factors affecting the interaction of nano-TiO2 with soil and plants. We also discuss the role of particle size, crystal phase, surface coating, and techniques employed to study the interaction of these nanoparticles with plants. Concluding results from synchrotron based, microscopic, physiological, and biochemical analyses of plants exposed to nano-TiO2 are presented. However, the current information leaves no doubt that there are still many aspects in need of additional investigations to fully understand the effects of nano-TiO2 in plants. For instance, little is known about the transgenerational effects of nano-TiO2 exposure and the changes at agronomical and physiological levels. The effects of such ENPs in proteins and other metabolites are also not well understood. In addition, more information is needed about the interaction of nano-TiO2 with other ENPs-and-organic co-contaminates and the effects of plants. Since nano-TiO2 have been found in edible tissues, it is expected that they will be in the food chain; thus, studies on their trophic transfer are required. The authors hope that, besides contributing to a better understanding of current data about the effects of nano-TiO2 in soil and plants, this review will help to drive future investigations and will contribute to the general knowledge on the environmental interactions of engineered nanomaterials.

The effects of soil properties on nanomaterial (NM) interactions with plants are not well understood. Bean (Phaseolus vulgaris) plants were grown to maturity in natural soil (NS) or organic matter (OM)-enriched soil (ES) amended with either uncoated (Z-COTE), hydrophobically-coated (Z-COTE HP1) ZnO NMs, bulk ZnO, or ZnCl2 at 0–500 mg kg−1. At harvest, yield and seed nutrient composition were assessed. The soil × compound interaction reduced the maturation time by about 25 days and increased the seed yield (∼155%) in ES, compared to NS. In NS, ZnCl2 at 125 mg kg−1 produced 10% less seed protein than the control, and disregarding the concentration, seeds from ZnCl2 showed the highest relative sugar content (102%, compared with the other compounds), while in NS, seeds from Z-COTE HP1 accumulated the highest relative sugar content (44% more than Z-COTE and ZnCl2). In addition, seeds from ES + Z-COTE HP1 had 19% less Zn than the rest of the compounds. In ES, the OM enrichment and reduction in pH enhanced the accumulation of Zn (38%), K (64%), S (44%), P (83%), Mg (86%), Ca (70%), Fe (89%), and Mn (85%), but reduced Mo under Z-COTE HP1 and ZnCl2, in comparison to NS seeds. Compared to the controls, ZnCl2 at 500 mg kg−1 reduced the K content in NS and ES (25% and 13%) but increased the P content in NS (66%). In general, Z-COTE and Z-COTE HP1 affected seed nutritional elements in a similar manner. However, the results indicate that the effects of ZnO NMs in bean plants vary with soil composition.

Nanotechnology enabled water treatment is a promising approach to enhance the effectiveness and efficiency of purifying water in many areas of the world. Nanotechnology offers significant opportunities to revolutionize approaches towards drinking water treatment by enhancing the multifunctionality and versatility of treatment systems while reducing reliance on stoichiometric chemical addition (thus minimizing associated waste streams), shrinking large facilities with relatively long hydraulic contact times and minimizing energy intensive processes. The unique material properties that emerge at the nano-scale enable solutions to treat pollutants in water for which existing technologies are inefficient or ineffective. This perspective describes the rationale, opportunities and barriers for translating this nascent technology from promising bench-scale discoveries to full-scale commercialization and production of safe drinking water.