Tailoring Ca-Based Nanoparticles by Polyol Process for Use as Nematicidals and pH Adjusters in Agriculture

Abstract

The remarkable progress in nanotechnology has extended the application of inorganic nanoparticles (NPs) in the agriculture sector, as both economically sustainable and environmentally sound alternatives. Root knot nematodes are undoubtedly a foremost problem of agriculture and research strives to develop effective materials to tackle this issue. Herein, the microwave-assisted selective polyol synthesis of different compositions of Cabased NPs, Ca(OH)2, Ca(OH)2/CaCO3 and CaCO3 is reported and the products were evaluated as nematicides and pH adjusters. Two precursors (CaCl2 and Ca(NO3)2) and three polyols (1,2-propylene glycol (PG), tetraethylene glycol (TEG), polyethylene glycol (PEG 8000)) that differ in their red/ox potential have been utilized to provide selectivity over composition. Based on the utilized polyols, NPs are produced as inorganic/organic hybrid formulations with a biocompatible organic coating that provides increased colloidal stability and controlled release of active components. Characterization of NPs has been carried out by XRD, TGA, FTIR, TEM and pH-metry. Each composition exhibited different pH changing ability, an essential feature for agrochemical applications. The in vitro nematicidal activity of Ca(OH)2, Ca(OH)2/CaCO3 and CaCO3 NPs was evaluated on second stage juveniles (J2) of two Meloidogyne species (Meloidogyne incognita & Meloidogyne javanica) based on nematode paralysis experiments. Results unveiled nematicidal activity for all evaluated Ca-based NPs, while Ca(OH)2 and CaCO3 NPs appeared to be the most and the least effective one, respectively. The nematicidal effect appears to be boosted by the release of [OH]anions, as indicated by pHmetric measurements, displaying the crucial role of [OH]anions in their nematicidal activity.

Structure Differentiation of Hydrophilic Brass Nanoparticles Using a Polyol Toolbox

“…Furthermore, most of the inorganic metal salt precursors are well-dissolved in these media, and organometallic precursors can be avoided. It has previously been reported in the literature (Caizer and Stefănescu, 2002; Stefănescu et al, 2007; Biacchi and Schaak, 2011; Carroll et al, 2011; Dong et al, 2015b; Teichert et al, 2018) and recently by us (Vamvakidis et al, 2015; Antonoglou et al, 2017, 2018; Giannousi et al, 2019; Tryfon et al, 2019) that synthetic conditions like polyol properties (structure, molecular weight, reducing ability, and capping capacity), reaction temperature, utilized precursors, and synthetic route affect the final structure and features of the nanostructures.…”

“…This is verified by lattice parameter (a = b = c in the fcc lattice) values, estimated at 3.6159 Å (0.0028) and 3.6087 Å (0.0018) for BM1 and BM2, respectively, where the increase is attributed to the zinc doping of the fcc lattice. Additionally, in the case of BM2, Zn oxalate (#37-0718) was produced and is clearly distinct from the graphitic crystallite of BM1 (Figure 2C) (Dong et al, 2015b; Antonoglou et al, 2017, 2018; Tryfon et al, 2019). By utilizing the quantitative option of MDI's Jade, the % wt crystal composition is calculated at 65% α-brass and 35% γ-brass for BM1 and 50% Cu and 50% zinc oxalate for BM2.…”

“…Reduction and/or hydrolysis reactions can take place and favor the formation of metallic and/or oxide NPs, respectively (Poul et al, 2003). The fabrication mechanism follows the formation of polyol-metal complexes that decompose, giving rise to the nucleation and growth of brass BMNPs (Biacchi and Schaak, 2011; Carroll et al, 2011; Antonoglou et al, 2017, 2018; Teichert et al, 2018; Giannousi et al, 2019; Tryfon et al, 2019). Both the formation and decomposition of these intermediate polyol-metal complexes are very sensitive to synthetic regulations.…”

“…Both the formation and decomposition of these intermediate polyol-metal complexes are very sensitive to synthetic regulations. Oxidation of TrEG occurs during the synthesis as seen in Scheme 1 where one-end and/or two-end oxidation as well as fragmentation paths can be followed (Caizer and Stefănescu, 2002; Stefănescu et al, 2007; Dong et al, 2015b; Vamvakidis et al, 2015; Antonoglou et al, 2017; Tryfon et al, 2019). As the heating method, ramp heating step, reaction temperature and hold time change, different oxidized forms and intermediates can be present, and finally different products are isolated.…”

“…Peaks of interest are examined in the 2.000–900 cm −1 region where ν-C = O (1.700–1.600 cm −1 ), ν-CH 2 (1.500–1.400 cm −1 ), ν-CH 3 (1.400–1.300 cm −1 ), and ν- C-O-C (1.200–1.000 cm −1 ) bonds are reflected. All samples displayed a broad large peak at 1.700–1.600 cm −1 region that is attributed to the plethora of oxidized forms of TrEG coming from one-end and/or two-end oxidized forms, such as aldehydic, ketonic, carboxylic, oxalate groups on the surface of BMNPs (Caizer and Stefănescu, 2002; Stefănescu et al, 2007; Dong et al, 2015b; Vamvakidis et al, 2015; Antonoglou et al, 2017; Tryfon et al, 2019). Broad peaks indicate that NPs can simultaneously be functionalized with more than one type of ligand.…”