•CPF/GO-LDH is well fabricated by an exfoliation-restacking method.•The interlayer distances are discussed on the basis of electrostatic interaction.•The composite displays a sustained slow release.•CPF/GO-LDH could be potentially applied for controlled-release of the pesticide.A series of the graphene oxide-ZnAl-layered double hydroxide composites loaded with pesticide chlorpyrifos (CPF/GO-LDH) were fabricated by an exfoliation-restacking method. CPF/GO-LDH composites were characterized by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and transmission electron microscopy (TEM), thermogravimetry analysis and differential scanning calorimetry (TGA-DSC). The interlayer distances of CPF/GO-LDH with various GO/LDH mass ratios were in the range of 0.70–0.87 nm, which were analyzed on the basis of electrostatic interaction between LDH nanosheets and GO substrate. The combustion temperature of CPF in the composites was enhanced 130–170 °C. Release behaviors of CPF/GO-LDH composites in buffer solutions were investigated and analyzed. The sustainable slow releases were observed during the whole stage studied, and the release rates and equilibrium release amounts of CPF were closely dependent on release mediums and GO/LDH mass ratios. The release behaviors of CPF/GO-LDH were fitted with pseudo second-order and parabolic diffusion models. The present study suggested that the CPF/GO-LDH could be potentially applied for controlled-release of the pesticide.

Inclusion complexes were formed by including the pesticide beta-cypermethrin (BC) in sulfonated hydroxyethyl-β-cyclodextrin (SHECD) and sulfobutyl ether β-cyclodextrin (SBECD), and these complexes were then intercalated into the galleries of layered double hydroxides (LDHs) to synthesize BC/SHECD–LDH and BC/SBECD–LDH hybrids. The hybrids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry/differential thermal analysis (TGA/DTA), and scanning electron microscopy (SEM). The results showed that BC/SHECD–LDH and BC/SBECD–LDH had basal spacings of 1.64 and 2.12 nm, respectively, which were analyzed on the basis of the structural properties of cyclodextrin (CD). The combustion temperature of interlayer SHECD was increased by 140 °C through intercalation. Furthermore, the release behaviors of BC from BC/SHECD–LDH and BC/SBECD–LDH composites were investigated. The release of BC from the hybrids was faster at pH 6.8 than at pH 5.0, and the released amounts were higher at the former pH, in close correlation with the structural type of CD and the release media. The BC release kinetic processes were well-fitted with pseudo-second-order and parabolic diffusion models. BC/SHECD–LDH could potentially be applied for pesticide formulation.

A novel method was developed to make the charge-neutral and poorly water-soluble pesticide chlorpyrifos (CPF) adsolubilize into layered zinc hydroxide nitrate intercalated with dodecylbenzenesulfonate (ZHN-DBS). It included two steps: first, CPF was solubilized into the micelles formed by anionic surfactant sodium dodecylbenzenesulfonate (DBS), nonionic surfactant polyoxyethylene (10) nonyl phenyl ether (TX-10) or zwitterionic surfactant dodecyl betaine (DB), and then ZHN–DBS was poured into CPF micelles to synthesize ZHN–DBS–CPF, ZHN–TX-10–CPF, and ZHN–DB–CPF intercalated compounds. These intercalated compounds were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis and differential thermal analysis (TGA/DTA). The results showed that ZHN–DBS–CPF, ZHN–TX-10–CPF, and ZHN–DB–CPF had the basal spacings of 3.29–3.59, 2.57–2.87, and 1.97 nm, respectively, which was discussed from the intercalated mechanism. The intercalated CPF had the higher thermal stability. Release behaviors of CPF from intercalated compounds were investigated and analyzed in buffer solutions (pH 5.0 and 6.8). The results exhibited that the release rates and equilibrium release amounts of CPF were closely dependent on micelles types and release mediums. The release behaviors of ZHN–DBS–CPF and ZHN–TX-10–CPF were well described with pseudo second-order and parabolic diffusion models. The present study suggested that ZHN–DBS–CPF and ZHN–TX-10–CPF could be applied as a potential pesticide delivery system.Keywords: chlorpyrifos; layered zinc hydroxide nitrate (ZHN); micelle; release behavior; surfactant;

•Zwitterionic surfactants can be well intercalated into NiZn-layered hydroxide salts.•The relative low pH is beneficial to prepare NZL-DCB, NZL-DSB and NZL-DAP.•The higher temperature and longer time may cause presence of ZnO phase.•DCB, DSB and DAP probably form an overlapped bilayer in the gallery.Three zwitterionic surfactants, dodecyl dimethyl carboxylbetaine (DCB), dodecyl dimethyl sulfobetaine (DSB) and N-dodecyl-β-aminoprpionate (DAP), intercalated into NiZn-layered hydroxide salts (NZL-DCB, NZL-DSB and NZL-DAP) were synthesized by the coprecipitation method. The effect of surfactant content, pH, temperature and time of hydrothermal treatment on preparation was investigated and discussed. The NZL-DCB, NZL-DSB and NZL-DAP were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry analysis and differential thermal analysis (TGA/DTA). The results showed that basal spacings of NZL-DCB, NZL-DSB and NZL-DAP were around 3.45, 3.68 and 3.94 nm, respectively. DCB, DSB and DAP probably form an overlapped bilayer in the gallery. TGA/DTA data indicated that NZL-DCB, NZL-DSB and NZL-DAP displayed three loss weight stages: loss of adsorbed and structural water, dehydroxylation of matrix and decomposition of nitrate ions, decomposition and combustion of surfactants. Furthermore, chemical analysis data, BET surface area and scanning electron microscopic (SEM) were also measured and analyzed.

•Hydrogen bond interactions cause NaSal assist the percolation.•Brij-56 (TX-100) makes Peff decrease and droplets diameter increase, promoting the percolation.•Spans have little effect on percolation due mainly to their small headgroup.•Alcohol can decrease evidently the activation energy by enhancing the interfacial flexibility.Influence of salts (sodium chloride, sodium salicylate and sodium cholate) and nonionic surfactants (Brij-56, TX-100, Span-20, Span-40 and Span-60) on structure and percolation behavior of water/AOT/IPM/propanol (butanol) systems were systematically investigated using conductivity and dynamic light scattering. Percolation behavior had a distinct change with different types of salts and nonionic surfactants. Addition of sodium chloride delayed the conductivity percolation, while sodium salicylate and sodium cholate assisted the percolation. Addition of Brij-56 and TX-100 promoted evidently the conductivity percolation, whereas Spans had little effect. Conductivity behavior was further discussed from the structural properties of nonionic surfactants and salts, and the surfactant packing parameter (P). Droplets sizes were measured using dynamic light scattering to underline the effect of nonionic surfactants on P. Furthermore, ln σ had a linear correlation with temperature in the range of (278.15 to 313.15) K. No percolation threshold induced by temperature was detected among all the studied systems. Moreover, the activation energy for conductivity was also estimated and discussed according to the Arrhenius-type equation.

Effect of block copolymer polyalkoxylated butyl ether (LQ) and anionic surfactant polyoxyethylene styrenated phenol ether phosphonate (P) on stability of etofenprox in water emulsion was systematically investigated by measuring creaming stability, droplet size, viscosity, and crystallization temperature. Addition of P (LQ) enhanced markedly stability of emulsions prepared with polyoxyethylene (40) castor oil ether (EL-40) and polyoxyethylene (20) castor oil ether (EL-20). On the basis of it, we prepared the EL-40 + EL-20 + P + LQ (1) and EL-40 + EL-20 + P + LQ (2) emulsions at the fixed concentrations of EL-40 and EL-20, P and EL-20, respectively. The emulsions displayed the excellent stability, observed only a little turbid layer on the surface with time prolong. The distinct trends of droplets size and viscosity in two kinds of emulsions were well analyzed by the structural properties of surfactants (including block copolymer) and the interaction between them. Furthermore, differential scanning calorimetry (DSC) technology was first introduced to study freeze–thaw stability of pesticide emulsions. The data indicated that the freezing point shifted evidently with P and/or LQ concentration, however, the melting point had almost no change. It revealed that the EL-40 + EL-20 + P + LQ emulsions had good stability at low temperature. Combination of droplets size and viscosity measurements with DSC technology can be helpful to examine comprehensively the emulsion stability, and select surfactants and obtain pesticide emulsions with good storage and freeze–thaw stability.Effect of block copolymer polyalkoxylated butyl ether (LQ) and anionic surfactant polyoxyethylene styrenated phenol ether phosphonate (P) on the stability of etofenprox in water emulsion was systematically investigated by measuring creaming stability, droplet size, viscosity, and the crystallization temperature. The results indicated that addition of P and/or LQ to EL-40 + EL-20 emulsions exhibits good emulsion stability at room and low temperature, especially EL-40 + EL-20 + P + LQ (2) emulsions show much excellent.Highlights► Addition of P and/or LQ enhanced remarkably stability of emulsion systems. ► Droplets dimension and viscosity depended distinctly on P and/or LQ concentrations. ► Droplets dimension and viscosity together affects the freezing temperature. ► EL-40 + EL-20 + P + LQ emulsions had good stability at room and low temperature.

We have systematically investigated the effect of alcohols (ethanol, propanol, butanol, and pentanol) on the structure of the water/AOT/IPM system using conductivity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) techniques. The results show that no percolation phenomenon is observed in the water/AOT/IPM system, whereas the addition of ethanol (propanol and butanol) induces apparently percolation. The threshold water content (Wp) depends closely on the alcohol type and concentration. The effect of alcohols on the conductance behavior is discussed from the physical properties of alcohols, the interfacial flexibility, and the attractive interactions between droplets. The hydrodynamic diameter of droplets (dH) obtained from DLS increases markedly with the increase in water content (W0); however, it decreases gradually with increasing alcohol chain length and concentration. SAXS measurements display distinctly the shoulder, the low hump peaks, and the heavy tail phenomenon in the pair distance distribution function p(r) profile, which rely strongly on the alcohol species and its concentration. The gyration radius (Rg) increases with increasing W0, and decreases with the increase of alcohol chain length and concentration. Schematic diagram of the conductance mechanism of water/AOT/IPM/alcohol systems is primarily depicted. Three different phases of the discrete droplets, the oligomers, and the isolated ellipsoidal droplets existed in the different W0 ranges correspond to three different stages in the conductivity–W0 curve. Coupling the structure characteristics of reverse micelles obtained from DLS and SAXS techniques with conductivity could be greatly helpful to deeply understand the percolation mechanism of water/AOT/IPM/alcohols systems.

The effect of arabic gum (AG) and xanthan gum (XG) on the physicochemical properties of 2% pesticide avermyctin in water emulsions was systematically investigated by measuring creaming stability, droplet size, zeta potential, and rheology. Addition of AG and XG had significant influence on the physicochemical properties of emulsions. Emulsions showed high stability throughout the storage time in the AG concentration range of 0−0.14%. In contrast, addition of XG induced the apparent creaming of emulsion as the XG concentration increased from 0.011 to 0.15%, which might be well explained by the depletion flocculation of droplets. The droplet diameter increased progressively with increasing AG concentration; however, it sharply grew initially with XG concentration and reached a maximum, followed by a gradual decrease. Zeta potential increased gradually as AG concentration was lower than 0.081%, followed by a slight decrease, whereas it reduced dramatically as XG concentration increased from 0.011 to 0.040% and then remained almost unchanged. In the AG concentration range of 0−0.14%, the emulsion exhibited typical Newtonian flow behavior and the viscosity decreased a little. The XG emulsion exhibited Newtonian flow behavior at low XG concentrations (≤0.019%), whereas, non-Newtonian flow behavior was displayed at relatively high XG concentrations (>0.019%), wherein viscosity value and yield value increased gradually as XG concentration increased. In addition, the curves of shear stress versus shear rate for XG emulsion and solution were well fitted by a power law model and the Herschel−Bulkley model; the Herschel−Bulkley model fitted much better. The present study would provide useful information for the reasonable application of AG and XG in making stable pesticide emulsion.

The conductivity (σ) measurement was carried out on water/dioctyl sulfosuccinate sodium salt (DOSS)/heptanol (decanol)/toluene reverse microemulsions. Addition of toluene was distinctly observed to inhibit the conductance percolation of water/DOSS/decanol/toluene systems. The effect of additives (sodium chloride, sodium salicylate and sodium cholate) with various concentrations on the conductivity behavior of water/DOSS/heptanol (decanol)/toluene systems was also investigated and discussed. The conductivity of a water/DOSS/heptanol/toluene system was almost unchanged in the concentration ranges of sodium chloride and sodium salicylate studied, while it decreased with the increase in the sodium cholate concentration. The conductance of the water/DOSS/decanol/toluene system increased with increasing of sodium cholate and sodium salicylate concentrations, and it changed little with the sodium chloride concentration. The lnσ value exhibited a linear correlation with temperature in the range of 5–40 °C. No percolation threshold induced by temperature was detected either in the absence or in the presence of additives. Furthermore, the activation energy for conductivity was estimated and discussed according to the Arrhenius type equation. The present study would provide useful information for selecting a suitable template for nanometer materials preparation.