Special Issue: Functional Nanoparticles for Environmental Contaminants Removal and Agricultural Application

Currently, increasing demands are being placed on agricultural production, presented with the challenge of finding sustainable ways to meet the needs of the world’s growing population [1]. Global warming and climate change have become a “wifi” contributing to agricultural and environmental issues, with rising global temperatures and extreme weather events leading to crop failures and impacting food security [2]. Furthermore, intensive agricultural practices and unsustainable land use are causing soil erosion, a loss of fertility, and reduced productivity [3]. Limited access to water, over-extraction, and pollution pose major challenges to agriculture, particularly in arid and semi-arid regions [4]. Additionally, the spread of pests and diseases has become increasingly challenging to control due to factors such as global trade and climate change [5].

Nanotechnology, and particularly the field of nanomaterials, holds the potential to revolutionize agriculture and the environment [6]. It can be utilized to enhance crop production efficiency [7], reduce the use of pesticides and fertilizers [8], and improve food quality [9]. Nanotechnology can also contribute to the development of novel materials that enhance irrigation efficiency, crop storage, and various other aspects of farming [10]. Moreover, nanotechnology has the potential to create sensors capable of detecting changes in soil quality, enabling farmers to make more informed decisions about land management [11]. Encouragingly, significant progress has been made in the field of nano-agriculture and environmental applications, as highlighted in our Special Issue “Functional Nanoparticles for Environmental Contaminants Removal and Agricultural Application” in Coatings.

Nanotechnology has played a positive role in agriculture. Guo et al. (2022) observed that silver nanoparticles outperformed other nanoparticles in terms of final crop seed germination percentages, and zinc nanoparticles were found to be the most effective in promoting root length growth during seed germination in a meta-analysis conducted between 1950 and 2021 [12]. Hexaconazole is a widely used, broad-spectrum, and highly efficient triazole fungicide, but its extensive use can lead to environmental disasters [13]. In response, Pan et al. (2021) applied azobenzene-modified bimodal mesoporous silica nanoparticles (BMMs-Azo) in conjunction with β-cyclodextrin to control the release of hexaconazole, reducing its environmental impact [14]. Biochar is known for its numerous surface functional groups and porous structure, which can reduce nutrient loss and enhance nutrient uptake by plants [15]. Combining Methylotrophic bacillus, colloidal biochar (containing dissolved nanoparticles), and organic fertilizer significantly increased the contents of lycopene, vitamin C, total sugar, and soluble sugar in tomato fruits by 58.40%, 46.53%, 29.45%, and 26.65%, respectively [16]. Additionally, Yang et al. (2022) demonstrated that biochar nanoparticles, acting as nanocarriers, substantially increased the fertilizer utilization of Chinese cabbage and promoted plant growth by over 50% [17]. Copper nanoparticles have widespread applications in various industries, but their effects in agriculture and the environment vary. Yang et al. (2022) observed that 5 ppm copper nanoparticles caused the slight swelling of epithelial cells in the epididymal duct of Chinese soft-shelled turtles, while higher copper ion concentrations severely damaged the epithelial structure of the epididymal tube [18]. Faraz et al. (2022) reported on the foliar application of 2–16 ppm copper oxide nanoparticles (CuO NPs) on Brassica juncea 25 days after sowing, whereby 8 ppm resulted in optimal chlorophyll content, net photosynthetic rate, leaf proline content, and antioxidant enzyme activity [19]. However, the effectiveness of this concentration may vary for other plants. Surface coating is another factor affecting the interaction of CuO NPs with plants. Deng et al. (2022) found that the foliar spraying of 300 ppm bare NPs yielded similar results to 75 ppm citric-acid-coated NPs, with Cu NPs increasing the yield by approximately 170% compared to the control [20]. Interestingly, soil amendment with both bare and coated NPs did not significantly impact the plant mass relative to untreated plants. The use of manufactured nano-objects (MNOs), including carbon nanotubes (CNTs), nanoparticles (NPs), and nanopesticides, raises concerns, as these substances can impact the life cycle and not only accumulate in soils but also in other environmental components, negatively affecting the soil biota and processes. MNOs can interfere with soil physicochemical properties and microbial metabolic activity in rhizospheric soils [21]. Notably, negatively charged CuO NPs were found to significantly reduce disease progression and increase biomass, whereas positively charged NPs and a CuSO4 salt control had little impact on plants [22]. Based on element characteristics, it has been reported that magnesium nanoparticles (Mg-NPs) are more effective in enhancing the development of ‘Superior Seedless’ berries during various growth stages (flowering, fruit set, version, and harvest) compared to sulfate magnesium (MgSO₄·7H₂O) and magnesium disodium EDTA (Mg-EDTA) [23]. As we move forward in the realm of coated nanoparticles for environmental remediation and agricultural use, recent studies have shown promise. It has been reported that β-carotene-coated chitosan nanoparticles (CNPs) have the potential to block polycyclic aromatic hydrocarbons (PAHs) and protect crops in PAH-contaminated soil. Under specific conditions of 20 °C, pH 6, and 10 mg/mL TPP, spinach biomass significantly increased, and the transfer of PAHs from the soil to the roots was reduced [24]. In agricultural activities, insecticides and pesticides can have unintended effects, and the nanofeature of higher efficiency is utilized to reduce ecotoxicity. Alginate CNPs have been employed in combination with DMT to reduce insecticide toxicity in zebrafish larvae while reducing the required dose [25]. Furthermore, CNPs can serve as a core for novel SnS₂ quantum dots with Azadirachta indica leaf extract, with coated CNPs exhibiting an enhanced removal of crystal violet dye [26]. Overall, our Special Issue reflects the cutting-edge trends in nanotechnology applications in agriculture and the environment.

Environmental catalysis has garnered significant attention for its clean methods of producing useful chemicals and facilitating various chemical processes. This approach can decompose and eliminate organic pollutants from aqueous environments while enabling the production of valuable chemicals [27]. Liu et al. (2023) synthesized novel N-doped biochar nanoparticles through the one-step pyrolysis of algal sludge without external nitrogen sources, yielding a highly active and cost-effective carbon-based catalyst capable of activating new oxidants for contaminant removal [28]. Additionally, Liu et al. (2022) found that Sedum plumbizincicola nanoparticles can effectively remove Bisphenol A (BPA) from complex wastewater, demonstrating stable and efficient reactions [29]. Nanoscale schwertmannite (nano-SWT) was prepared using an indoor temperature synthesis method with the assistance of polyvinylpyrrolidone, and nano-SWT was found to be effective in reducing sulfamethoxazole in the presence of Fenton-like catalysts using hydrogen peroxide (H₂O₂) [30]. Currently, Fenton catalysts are widely employed in conjunction with nanoparticles for environmental contaminant removal. Manganese tetroxide (Mn3O4) nanoparticles have been reported to simultaneously degrade estriol and 17α-ethinylestradiol (E3/EE2) with removal efficiencies of 97.5% and 96.4% for E3 and EE2, respectively, using Fenton-like catalysts [31]. Copper–iron peroxide nanoparticles (CFp NPs) have been designed for tumor-microenvironment-mediated synergistic therapy in a heterogeneous chemodynamic therapy system. CFp NPs generate oxygen during catalysis and exhibit a tumor-microenvironment-responsive T1 magnetic resonance imaging contrast enhancement, aiding in tumor oxygenation and in vivo tumor monitoring [32]. Furthermore, it has been reported that S-doped carbon and Fe7S8 nanoparticles interact effectively for the high-efficiency removal of antibiotics through a Fenton-like degradation process. Within 40 min under neutral pH conditions, amoxicillin, norfloxacin, and tetracycline hydrochloride were removed at rates of 98.9%, 97.8%, and 99.3%, respectively, with the catalyst demonstrating excellent cycle stability [33]. At the same time, with the oxygen atoms in the sulfonic acid group cooperating with Ag+ to form a synergistic complexation, a novel magnetic fluorescent nanoprobe (Fe₃O₄@ZnS@MPS(MFNPs)) was designed for Ag+ detection in aquatic media [34]. These findings underscore the significant progress made in leveraging nanomaterials and catalytic processes for cleaner and more efficient environmental solutions, offering promise for a sustainable future.

In conclusion, the advancements in nano-agriculture and environmental applications are evident from the research covered in the Special Issue “Functional Nanoparticles for Environmental Contaminants Removal and Agricultural Application” in Coatings. Noteworthy examples include the use of silver nanoparticles to enhance crop seed germination and the application of azobenzene-modified bimodal mesoporous silica nanoparticles to control the release of the fungicide hexaconazole, thereby reducing environmental impacts. While nanotechnology presents exciting prospects, it is crucial to consider its potential ecological effects and develop responsible applications. Overall, the progress in nanotechnology applications in agriculture and the environment underscores the field’s potential to contribute to a more sustainable future.