A new N-doped carbon quantum dots (N-CQDs) fluorescent probe was synthesized via a solvent-free solid-phase carbonization method. The sensing material was characterized using various instrumental techniques, including Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The designed probe selectively detected Hg2+ ions in an ON-OFF manner and biothiols [Cysteine (Cys), Homocysteine (Hcy) and Glutathione (GSH)] in an OFF-ON mode in pure water, emitting a distinct blue-green fluorescence colour. The N-CQDs probe sensitively and selectively detected Hg2+ ions in ultrapure water as the sensing medium. The detection and quantification limits for Hg2+ ions were calculated from the standard calibration graph as 19.16 and 63.87 nM, respectively. The LOD/LOQ for Cys, Hcy and GSH were 34.81/116.35 nM, 29.67/98.91 nM, and 29.67/98.91 nM, respectively. The validation studies (selectivity, sensitivity, linearity range, precision, repeatability, intermediate precision and robustness) were performed for Hg2+ ions sensing. Finally, the N-CQDs sensor was successfully applied to real sample applications in water, food, living cells and fish samples with satisfactory results. These results demonstrated that the N-CQDs-based fluorescent sensor is well-suited for real samples with minimal interference from coexisting metal ions. In addition, the N-CQDs probe has been effectively employed in the development of cotton swabs, paper-based test kits, and a smartphone-integrated platform for detecting these analytes in real samples.

Nanoparticles (NPs) are particles that have dimensions of 100 nm or less, and they are the fundamental building blocks of nanotechnology. NPs have remarkable properties that have led to innovative applications in various fields such as medicine, electronics, agriculture, chemical catalysis, and food industry. The unique properties of NPs, such as their controlled size, shape, composition, crystallinity, and structure, are essential for their diverse applications. NPs can take different shapes, sizes, and structures, and based on their compositions, they are categorized into three classes: carbon-based, metal-based, and polymeric NPs. To expand the application of NPs in different disciplines, it is essential to synthesize these materials with specific shape, sizes, morphology, crystallinity, and chemical composition. Researchers use two primary approaches, namely "top-down" and "bottom-up" approaches, to synthesize NPs. Various methodologies such as the hydrothermal method, sol–gel technique, microemulsion method, and plant-mediated synthesis are employed for the synthesis of NPs. Researchers need to perform external and internal characterization of NPs to study their unique and extraordinary features. Characterization methods such as electron microscopy imaging (e.g., SEM, TEM, and AFM), dynamic light scattering (DLS), zeta potential measurements, X-ray diffraction (XRD) methodology, and X-ray photoelectron spectroscopy (XPS) are commonly used for this purpose. It is hoped that the comprehensive explanations of various methodologies presented here are insightful to the readers.

Materials that are plastic in nature have gained popularity worldwide thanks to a variety of applications, durability, and low cost. Different types of plastics have been vastly produced since the 1940s, and they are an essential part of our life since. Plastics pose a significant risk to ecosystem health, human health, and natural life due to their widespread use. Plastic kinds are categorized according to their size, such as micro/nanoplastics (M/N-Ps). These plastics pose more issues for living things, disrupting the natural order of things and contaminating the water, air, and soil. Plants that get exposed to M/N-Ps uptake them at high concentrations, causing their death and harming the food quantity and quality. This chapter of this book is split into three sections. The first section of the chapter will introduce the concept of M/N-Ps and their nature of existence in the environment. The section will include M/N-Ps occurrence due to decomposition in nature and secondary product release of industrial production. The second section of the chapter will discuss how these plastics interact with the soil media. This chapter will cover the effects on soil chemical properties, microbial community, and soil physical properties, which affect overall plant growth and health. The last chapter will include the interaction of M/N-Ps with terrestrial plants and organic pollutants. Due to their small size, M/N-Ps could be mobilized into plant vascular.

Huanglongbing (HLB, aka citrus greening), one of the most devastating diseases of citrus, has wreaked havoc on the global citrus industry in recent decades. The culprit behind such a gloomy scenario is the phloem-limited bacteria "Candidatus Liberibacter asiaticus" (CLas), which are transmitted via psyllid. To date, there are no effective long-termcommercialized control measures for HLB, making it increasingly difficult to prevent the disease spread. To combat HLB effectively, introduction of multipronged management strategies towards controlling CLas population within the phloem system is deemed necessary. This article presents a comprehensive review of up-to-date scientific information about HLB, including currently available management practices and unprecedented challenges associated with the disease control. Additionally, a triangular disease management approach has been introduced targeting pathogen, host, and vector. Pathogen-targeting approaches include (i) inhibition of important proteins of CLas, (ii) use of the most efficient antimicrobial or immunity-inducing compounds to suppress the growth of CLas, and (iii) use of tools to suppress or kill the CLas. Approaches for targeting the host include (i) improvement of the host immune system, (ii) effective use of transgenic variety to build the host's resistance against CLas, and (iii) induction of systemic acquired resistance. Strategies for targeting the vector include (i) chemical and biological control and (ii) eradication of HLB-affected trees. Finally, a hypothetical model for integrated disease management has been discussed to mitigate the HLB pandemic.

Novel ZnS/CuS nanocomposites with different mole ratios were successfully prepared by the cation exchange reaction and characterized by AAS, FTIR, SEM, and EDX. The catalytic activities of ZnS/CuS nanocomposites were evaluated against the oxidation of thymol (T) at room temperature in acetonitrile. The obtained ZnS/CuS (20% and 50% Cu) nanocomposites exhibited excellent catalytic activity (100% conversion and selectivity in 60 min. and 20 min., respectively) using tert-butyl hydroperoxide (TBHP) as an oxidant. Recycling studies of the nanocomposite showed high conversion values throughout four catalytic cycles (four cycles with 98% conversion in 4 h).

Nanoscale nutrients are promising for improving crop performance.

Defect engineering at the surface of zinc oxide sub-5 nm nanoparticles provides a systemic nanotherapeutic with significant field efficacy against citrus HLB disease.

Different Cu formulations and soil pre-incubation regime can significantly impact the short-term availability of Cu in soil.

A multifunctional surface, subsurface and systemic therapeutic (MS3T) formulation comprised of two bactericides, both didecyldimethylammonium chloride (DDAC) and a zinc (Zn)-chelate, was developed as an alternative to copper pesticides for crop protection. Agricultural grade chemicals were used to prepare MS3T formulations. Minimal inhibitory concentration (MIC) was determined to be tested in vitro against Xanthomonas alfalfae subsp. citrumelonis (herein called Xa), Escherichia coli (E. coli), and Pseudomonas syringae (Ps). Assessment of the phytotoxic potential was carried out on tomato under greenhouse conditions. Moreover, field trials were conducted during three consecutive years on grapefruit (Chrysopelea paradise) groves to evaluate efficacy against citrus canker (Xanthomonas citri subsp. citri), scab (Elsinoe fawcetti), and melanose (Diaporthe citri). In addition to disease control, improvements to both fruit yield and quality were observed likely due to the nutritional activity of MS3T via the sustained release of plant nutrients (Zn and nitrogen). Zn residues of leaf tissues were analyzed via atomic absorption spectroscopy (AAS) at various time points before and after MS3T foliar applications throughout the duration of the 2018 field trial. Field trial results demonstrated MS3T to be an effective alternative to copper (Cu)-based formulations for the control of citrus canker.

A hybrid core–shell silica nanoparticle system integrating Cu nanoclusters and Quat combats resistance development of Xanthomonas perforans responsible for bacterial spot disease of tomatoes.

Capping agents are often used for controlling the size, aggregation, and properties of nanoparticles. To guide the design of improved nanomaterials for targeted performance, one can use mechanistic insights into the interactions between capping agents and nanoparticles. Here, we employ density functional theory (DFT), reactive force-field molecular dynamics (ReaxFF MD) simulations, and optical spectroscopy to study the interactions between salicylate, as a model capping agent, and zinc oxide (ZnO) nanoparticles. We find that salicylate strongly interacts with the nanoparticle via the formation of O-Zn bonds in a distorted six-membered coordination ring structure. We describe the mechanisms of capping of ZnO nanoparticles by salicylate via three different binding modes. Simulations indicate that salicylate undergoes dissociative adsorption at the highly active surface Zn sites via a hydrogen-transfer process, thereby forming a tridentate configuration. The water-mediated interaction also facilitates the dissociative adsorption, leading to two salicylate O atoms coordinating with a surface Zn atom, while the other salicylate O atom bonds with another surface Zn atom. For molecular adsorption, binding free energies indicate that salicylate binds more strongly to ZnO, often in a bidentate configuration, than water does. The formation of the salicylate-ZnO complex is substantiated by UV-visible and Fourier transform infrared spectra. We find that the C.O stretching mode of salicylate becomes softened when it interacts with the nanoparticle, suggesting chemisorption of salicylate on ZnO. Although DFT predicts strong interaction between salicylate and ZnO, ReaxFF MD simulation indicates the moderate interaction between these two components in aqueous solution. Water molecules in close contact with the nanoparticle surface undergo dissociation, thus resulting in a surface hydroxyl, a reactive oxygen species that may influence the nanoparticle's catalytic properties. The atomic-level information provided here can guide the selection process of salicylate as an appropriate agent for ZnO nanoparticle synthesis when strong interactions of particles with capping agents are required.

Zinkicide is a systemic bactericidal formulation containing protein-size fluorescent zinc oxide-based nanoparticles (nano-ZnO). Previous studies have shown that Zinkicide is effective in controlling citrus diseases. Its field performance as an antimicrobial agent has been linked to the bioavailability of zinc ions (Zn2+) at the target site. It is therefore important to monitor Zn2+ release from Zinkicide so that application rates and frequency can be estimated. In this study, we present a simplistic approach designed to monitor Zinkicide nanoparticle dissolution rates in water and acidic buffer solutions using traditional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The evolution of nano-ZnO in the polyacrylamide gel scaffolds was studied by exciting the sample with UV light and detecting the fluorescence of nano-ZnO. Fluorescence intensities measured with this assay allowed for quantitative analysis of molecular weight changes of nano-ZnO in citrate buffer, a surrogate of citrus juice. Our results demonstrated that citrate buffer induced the greatest degradation of Zinkicide. Fluorescence intensity fluctuations were observed over time, indicating interactions of citrate with the surface of nano-ZnO. These findings provide a new approach to quantify the dissolution of nanoparticles in simulated environments, even when other analytical methods lack sensitivity because of the small size of the system (≈4 nm).

Phloem-limited bacterial "Candidatus Liberibacter" species are associated with incurable plant diseases worldwide. Antimicrobial treatments for these pathogens are challenging due to the difficulty of reaching the vascular tissue they occupy at bactericidal concentrations. Here, in vitro antimicrobial mechanisms of Zinkicide TMN110 (ZnK), a nonphytotoxic zinc oxide (ZnO)-based nanoformulation, were compared to those of bulk ZnO (b-ZnO) using as a model the only culturable species of the genus, Liberibacter crescens Minimum bactericidal concentration (MBC) determination and time-kill assays showed that ZnK has a bactericidal effect against L. crescens, whereas b-ZnO is bacteriostatic. When ZnK was used at the MBC (150 ppm), its antimicrobial mechanisms included an increase in Zn solubility, generation of intracellular reactive oxygen species, lipid peroxidation, and cell membrane disruption; all of these were of greater intensity than those of b-ZnO. Inhibition of biofilms, which are important during insect vector colonization, was stronger by ZnK than by b-ZnO at concentrations between 2.5 and 10 ppm in batch cultures; however, neither ZnK nor b-ZnO removed L. crescens preformed biofilms when applied between 100 and 400 ppm. In microfluidic chambers simulating source-to-sink phloem movement, ZnK significantly outperformed b-ZnO in Zn mobilization and bactericidal activity against L. crescens planktonic cells in sink reservoirs. In microfluidic chamber assays assessing antibiofilm activity, ZnK displayed a significantly enhanced bactericidal activity against L. crescens individual attached cells as well as preformed biofilms compared to that of b-ZnO. The superior mobility and antimicrobial activity of ZnK in microenvironments make this formulation a promising product to control plant diseases caused by "Candidatus Liberibacter" species and other plant vascular pathogens.IMPORTANCE "Candidatus Liberibacter" species are associated with incurable plant diseases that have caused billions of dollars of losses for United States and world agriculture. Chemical control of these pathogens is complicated, because their life cycle combines intracellular vascular stages in plant hosts with transmission by highly mobile insect vectors. To date, "Candidatus Liberibacter" species are mostly unculturable, except for Liberibacter crescens, a member of the genus that has been used as a model for in vitro assays. Here, we evaluated the potential of Zinkicide (ZnK) as an antimicrobial against "Candidatus Liberibacter" species in batch cultures and under flow conditions, using L. crescens as a biological model. ZnK displayed bactericidal activity against L. crescens in batch cultures and showed increased mobility and bactericidal activity in microfluidic devices resembling "Candidatus Liberibacter" species natural habitats. ZnK performance observed here against L. crescens makes this compound a promising candidate to control plant diseases caused by vascular pathogens.

Accumulation of toxic copper in soil and development of copper-resistant pests are emerging challenges currently faced by the agricultural community worldwide. As an alternative, we have developed a ternary zinc chelate solution (TSOL) pesticide where zinc ions are the primary active ingredient. The material is composed of zinc, urea, and hydrogen peroxide. Urea was chosen as it is widely used as a plant fertilizer and can also bind to both zinc and hydrogen peroxide. No phytotoxicity was observed with TSOL on Meyer lemon (Citrus × meyeri) seedlings at a field spray rate of 800 μg/mL Zn metal concentration. Antimicrobial studies showed that TSOL exhibited improved killing efficacy against Escherichia coli and Xanthomonas alfalfae compared to Zn ions alone. Citrus canker field trials in a grapefruit (Chrysopelea paradisi) grove over three years showed that TSOL provided comparable disease protection to copper products at an equivalent or lower metal content.

Nosocomial infections pose serious health concerns with over 2 million reported annually in the United States. Many of these infections are associated with bacterial resistance to antibiotics and hence, alternative treatments are critically needed. The objective of this study was to assess the antimicrobial efficacy of a gallium (Ga)-based particle coated with N-Acetyl Cysteine (Ga-NAC) against Pseudomonas aeruginosa PAO1. Our studies showed the Minimum Inhibitory Concentration (MIC) of PAO1 treated with Ga-NAC was 1 µg/mL. Cytotoxicity of Ga-NAC against multiple cell lines was determined with no cytotoxicity observed up to concentrations of 2000 µg/mL (metal concentration), indicating a high therapeutic window. To elucidate potential antibacterial modes of action, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), infrared spectroscopy, and atomic force microscopy (AFM) were used. The results suggest improved Ga3+ interaction with PAO1 through Ga-NAC particles. No significant change in cell membrane chemistry or roughening was detected. As cell membrane integrity remained intact, the antimicrobial mode of action was linked to cellular internalization of Ga and subsequent iron metabolic disruption. Furthermore, Ga-NAC inhibited and disrupted biofilms seen with crystal violet assay and microscopy. Our findings suggest the Ga-NAC particle can potentially be used as an alternative to antibiotics for treatment of Pseudomonas aeruginosa infections.

A number of mitigation techniques exist to reduce the emissions of pollutant gases and greenhouse gases (GHGs) from anaerobic storage of livestock manure. Nanoparticle (NP) application is a promising mitigating treatment option for pollutant gases, but limited research is available on the mode of NP application and their effectiveness in gaseous emission reduction. In this study, zinc silica nanogel (ZnSNL), copper silica nanogel (CuSNL), and N-acetyl cysteine (NACL) coated zinc oxide quantum dot (Qdot) NPs were compared to a control lacking NPs. All three NPs tested significantly reduced gas production and concentrations compared to non-treated manure. Overall, cumulative gas volumes were reduced by 92.73%–95.83%, and concentrations reduced by 48.98%–99.75% for H2S, and 20.24%–99.82% for GHGs. Thus, application of NPs is a potential treatment option for mitigating pollutant and GHG emissions from anaerobically stored manure.

Zinkicide is a bactericidal nanoparticle that combats Citrus Greening with exceptional field efficacy. Bactericidal nanoparticle detection is important for surpassing EPA criteria and bringing biocide products to market; however quantitative analysis on Zinkicide degradation in particular is currently lacking. Here, we have developed a protocol using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) to monitor and track bactericidal nanoparticles in varying solutions, including water and acidic buffer mimicking citrus pH. The nanoparticle detection was performed using UV fluorescent imaging of polyacrylamide gels. This assay is a cost‐effective and relatively simple approach for detecting and quantifying the intensity, concentration, and molecular weight change of nanoparticles. We observed intensity fluctuations of Zinkicide over time, indicating that the capping agent of the nanoparticle may be affected. Our results show that citric acid buffer induces the greatest degradation of Zinkicide evidenced by molecular weight changes. These findings are beneficial for general tracking and detection of bactericidal quantum dots. Support or Funding Information The authors would like thank the Kang Lab members for their continued support and assistance. This study was supported by the UCF start‐up fund (Kang). Authors acknowledge the UCF Materials Innovation and Sustainable Agriculture Center for facilities and technical support. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

This study compares the rainfastness of nine forms of Cu, including nano and conventional Cu-based fungicide formulations, as well as their salt or bulk equivalents. Rainfastness is the ability to resist wash-off; it is a key property for improving pesticide formulations and for assessing the potential transfer of pesticides to the soil. A new protocol was developed to characterise losses of Cu from treated leaves. It consisted of dipping the leaves in rainwater and then in an acid/ethanol mixture followed by size fractionation. The proportion of Cu lost by wash-off from citrus leaves ranged from <2% (Tribasic, nCuO or Cu(OH)(2)) up to 93% (CuSO4) of the initial amount of Cu applied. Intermediate Cu losses were observed for formulations with silica (nano)particles (9-14% of applied Cu), Kocide (22 %), ChampDP (31 %), and a formulation with graphene oxide (47 %). Smaller particles generally resulted in less wash-off, possibly due to stronger attachment to the leaf surface, but other factors such as the particle shape and solubility also played an essential role. The retention of nCuO to the leaves was particularly high, and the exact mechanisms involved (e.g. foliar uptake) deserve further work. Most of the Cu was washed off in its ionic form (>74 %). Two Cu formulations (one commercial formulation and the formulation with graphene oxide) also showed wash off in significant proportions of Cu (similar to 17 %) in the nano-sized fraction. This study provides essential information on the amounts and forms of Cu that may reach the soil after the application of Cu-based agrochemicals. The great diversity in behaviour across the range of formulations considered highlights the need for more systematic research to fully exploit the potential improvements of current agrochemicals through (nano)formulation technologies.

Novel technological applications in catalysis and bactericidal formulation have emerged for zinc oxide (ZnO) nanoparticles owing to their ability to generate reactive oxygen species by fostering H2O dissociation. Rational improvement of those properties requires a mechanistic understanding of ZnO nanoparticle reactivity, which is currently lacking. Here, we determine the structural and electronic properties of nanometer-sized ZnO, determine the binding energetics of H2O adsorption, and compare to an extended macroscopic surface. We show that the electronic density of states of ZnO nanoparticles is size-dependent, exhibiting a decreasing bandgap with the increase of nanoparticle diameter. The electronic states near the Fermi energy dominantly arise from O 2p states, which are spatially localized on "reactive" surface O atoms on the nanoparticle edges that are doubly coordinated. The frontier electronic states localized at the low coordinated atoms induce a spontaneous dissociation of H2O at the nanoparticle edges. The surface Zn and O atoms have inhomogeneous electronic and geometrical/topological properties, thus providing nonequivalent sites for dissociative and molecular H2O adsorption. The free energy of H2O binding is dominated by the electronic DFT interaction energy, which is site-dependent and correlated with the Bader charge of surface Zn atom. Entropy is found to stabilize the bound form, because the increase in the vibrational contribution is greater than the decrease in the translational and rotational contribution, whereas solvation stabilizes the unbound state. The absence of rough edges on an extended, macroscopic ZnO surface prevents spontaneous dissociation of a single H2O. This study underlies the importance of coupling geometrical and electronic degrees of freedom in determining the reactivity of nanoparticles and provides a simple elucidation of the superior catalytic activity of ZnO nanoparticles compared to ZnO in macroscopic forms.