Nanocomposites In Water Research Articles

Effect of silica nanospheres silanized by functional silanes on the physicochemical and mechanical properties of Bis-GMA/TEGDMA dental composite resin by photocuring synthesis

This investigation focused on the contribution of various silane blends, used as coupling agents, to the ultimate performance of dental nanocomposite dimethacrylate photocurable resins. Initially, the surface of silica nanospheres was silanized with three different silane coupling agents: γ-MPS, APTES, and OTMS, with the grafting rate serving as the index. Fourier Transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) verified the modification of nanosilica. Through orthogonal test experiments on the three silane coupling agents, the optimal modifier concentration, temperature, and time were determined. Subsequently, 15 wt% organomodified SiO2 nanospheres were incorporated into Bis-GMA/TEGDMA (70/30 by wt%) based resins via a photocuring process. Scanning electron microscopy (SEM) findings revealed a relatively vague interface between inorganic fillers and resins in the polymer composite, especially when reactive silanes like γ-MPS and their corresponding blends were used. The combination of SiO2 and γ-MPS functional silane blend provided the highest flexural properties and the lowest solubility after storing the nanocomposite in water for 1 week at 37 °C. With these methods, composite resins containing 15 wt% MPS-SiO2 nanospheres in a Bis-GMA/TEGDMA (70/30 by wt%) mixture exhibited the best comprehensive properties, making them a promising choice for achieving long-term durable restorations in clinical therapies.

Solar catalytic CO2 reduction over POM-entrapped zeolites decorated with TiO2 nanocomposites in water: Highly efficient and selective production of CH3OH via Z-scheme charge separation

Polyoxometalate (POM)-entrapped zeolite Y decorated with AgNTiO2 nanocomposies (AgNTiO2 @POM-Zeolite) were fabricated as inorganic co-photocatalytic systems, and their structures were characterized by XRD, FESEM, TEM, XPS, DRS, and ICPAES analysis. The incident-photon-to-electron conversion efficiency (IPCE) of the thin film of AgNTiO2 @POM-Zeolite was observed to be higher than that of AgNTiO2-POM to confirm the photoinduced charge separation between AgNTiO2 and POM across the zeolites, and its action spectrum was shifted toward longer wavelength to be resolved into two bands as the optical absorption spectrum. The photocatalytic water splitting by AgNTiO2 @POM-Zeolite was also observed to produce O2 with a negligible amount of H2 in contrast to inefficient water splitting by zeolite-free AgNTiO2 nanochains or AgNTiO2-POM, indicating that zeolite plays important role in facile transportation of protons. These results imply that the AgNTiO2 @POM-Zeolite is totally inorganic artificial photosynthetic system for the proton-assisted Z-scheme electron transport between AgNTiO2 nanochains and POM across zeolite surface via stepwise excitation with two visible lights. Accordingly, under simulated solar illumination, the photocatalytic reduction of CO2 in water was observed to show over 95% selectivity of CH3OH and O2 production with much higher conversion rate (240μmol/g cat/h) than ever reported. The newly designed photocatalysts are useful for highly efficient production of solar chemical fuels as well as mitigation of CO2.

Insight into adsorption performance and mechanism of Congo red dye onto ZnFe2O4@ZIF-8 nanocomposite in water

Nowadays, the water contamination of organic dyes generated from the textile industries is increasingly considered an alarming situation. Because dyeing wastewaters are toxic and carcinogenic, it is important to remove textile dyes by feasible techniques, typically adsorption. Herein, we report the production of zinc ferrite-loaded zeolitic imidazolate framework-8, or ZFO@ZIF-8 by a tunable hydrothermal method and use this composite as an adsorbent to purify water containing Congo red dye (CR). Well-defined ZFO@ZIF-8 possessed a SBET of 145.9 m2 g–1, a total mesoporous volume of 0.54 cm3 g–1 and an average pore size of 14.4 nm. The adsorption of CR over ZFO@ZIF-8 was investigated under contact time (0–180 min), concentration (5–30 mg L–1), dosage (0.1–1.0 g L–1), pH (3–11). The highest removal efficiency, nearly 95 % was obtained at a CR concentration of 5 mg L–1, a ZFO@ZIF-8 dosage of 0.5 g L–1, pH 5, and 180 min. CR adsorbed by ZFO@ZIF-8 was a mono-layer process, giving a maximum value of 66.45 mg g–1. A FTIR examination confirmed the involvement of electrostatic, π–π, and H bonding interactions in the CR adsorption. Interestingly, the ZFO@ZIF-8 composite was reusable at least 6 cycles, remaining an efficiency of 84 % in the final cycle. Therefore, this composite should be a promising adsorbent against organic textile dyes.

Numerical investigation of heat source induced thermal slip effect on trihybrid nanofluid flow over a stretching surface

The fluid flow model is evaluated with the mass and energy transfer through the trihybrid nanofluid (Thnf) past a stretching permeable sheet. The proficiency of the nanofluid could be more effective, improved and stable by introducing nanoparticles with various thermal and rheological properties. The trihybrid nanoliquid has been prepared by the dispersion of silver (Ag), cobalt ferrite (CoFe2O4), and magnesium oxide (MgO) nanocomposites in water. The consequences of Darcy-Forchheimer are engaged in the momentum equation, to evaluate the permeability effect. The fluid flow is expressed in the form system of PDEs with effect of natural convection, magnetic field and heat source. Which are converted into a non-dimensional set of ODE by using similarity variables substitutions. Moreover, the numerical approach PCM (parametric continuation method) is used to deal the derived set of ODEs. The results are relatively compared to the existing study for accuracy purposes. It has been noted that the Thnf has higher thermal conductivity than ordinary and hybrid nanoliquid. The velocity field rises with the mounting values of the thermal Grashof number. The velocity curve drops with the effect of a power law, Forchheimer's, and porosity parameters.

Synthesis and Characterization of Dental Nanocomposite Resins Reinforced with Dual Organomodified Silica/Clay Nanofiller Systems.

Quaternary ammonium (QA) compounds have been widely studied as potential disinfectants in dental restorative materials. The present work investigates whether the gradual displacement of nanosilica by QA-clay nanoparticles may have an impact on the physicochemical and mechanical properties of dental nanocomposite resins. For this purpose, Bis-GMA/TEGDMA-based composite resins were initially synthesized by incorporating 3-(trimethoxysilyl)propyl methacrylate (γ-MPS)-modified nanosilica/QA-clay nanoparticles at 60/0, 55/5, 50/10, 40/20, and 30/30 wt% filler loadings. Their structural characterization was performed by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The degree of double bond conversion (DC) over time and the polymerization shrinkage were determined with Fourier transform infrared spectroscopy (FTIR) and a linear variable displacement transducer (LVDT), respectively. Mechanical properties as well as water sorption and solubility parameters were also evaluated after storage of nanocomposites in water for 7 days at 37 °C. Spectral data revealed intercalated clay configurations along with areas characterized by silica-clay clusters for clay loadings up to 30 wt%. Furthermore, the insertion of 10 wt% QA-clay enhanced the auto-acceleration effect also sustaining the ultimate (DC), reduced the setting contraction and solubility, and, finally, yielded flexural modulus and strength very close to those of the control nanocomposite resin. The acquired results could herald the advanced design of dental restorative materials appropriate for contemporary clinical applications.

A Green and Ecofriendly Catalytic System for One-Pot Three-Component Synthesis of 5-Substituted 1H-Tetrazoles Under Microwave Irradiation

In this research work, the high-yielding and simple synthesis of 5-substituted 1H-tetrazoles derivatives through the one-pot three-component reaction of aldehydes, hydroxylamine hydrochloride and sodium azide catalyzed by MNPs-Picolylamine-Cu(OAc)2 nanocomposite in water under microwave irradiation has been reported. The MNPs-Picolylamine-Cu(OAc)2 nanocomposite is successfully fabricated through the immobilization of copper (II) acetate stabilized on magnetic Fe3O4 nanoparticles modified with Picolylamine [MNPs-Picolylamine-Cu(OAc)2] and then is well analyzed by various techniques such as FT-IR, XRD, TGA, SEM, TEM, EDS, VSM and ICP-OES. At the end of the reaction, the MNPs-Picolylamine-Cu(OAc)2 catalyst can be easily recycled and reused and the products obtained had high efficiency and purity.

Green Synthesis and Antioxidant Activity Investigation of New Thiazinotriazines: Reduction of Organic Pollutant Using Fe3O4/TiO2/CuO@MWCNTs MNCs

The Petasites hybridus rhizome water extract was used as a green media for the preparation of the Fe3O4/TiO2/CuO@MWCNTs magnetic nanocomposites (Fe3O4/TiO2/CuO@Multi-Walled Carbon Nanotubes) and its activity was evaluated by using it in the one-pot multicomponent reaction of isatoic anhydrides, electron deficient acetylenic compounds, α-haloketones, ammonium acetate, isothiocyanates and hydrazoyl chloride in aqueous media at room temperature for the production of novel derivatives of thiazinotriazines in excellent yields. Moreover, reduction of organic pollutants such 4-nitrophenol (4-NP) was performed by synthesized Fe3O4/TiO2/CuO@MWCNTs magnetic nanocomposites in water at room temperature. The outcomes showed this catalyst decreased organic pollutants in few seconds. The synthesized thiazinotriazines have OH and NH functional groups that have acidic hydrogen and show high antioxidant activity. The employed process for the production of thiazinotriazines has some benefits such as short time of reactions, excellent efficiency of product, easy separation of catalyst and products. HIGHLIGHTS In medicinal chemistry, the heterocyclic compounds have a well-known subject due to having wide area of biological activities of these compounds. Therefore these compounds are very important and for the synthesis of these compounds existed many procedures. Multicomponent reactions (MCRs) is one of the process for the preparation of biological activities heterocyclic compounds with many benefits such as having atom economic, an useful and excellent efficiency in the generation of heterocyclic compounds relative to many stage reactions for preparation of organic compounds The present procedure avoids the use of toxic solvent. Benzazepines, which have a seven-membered aza-heterocyclic fused aromatic ring, are of interest because of their biological activity and use as building blocks for natural product synthesis and drug discovery.

Striking dual functionality of iron pyrite-graphene oxide nanocomposites in water treating and water splitting reactions

In this study, we report a simple one-pot solvothermal route of FeS2 (pyrite)/GO (graphene oxide) nanocomposites that exhibit outstanding physicochemical properties as efficient catalysts towards dual functionality of water treating and water-splitting applications. The FeS2/GO (FSG) nanocomposites of varying FeS2 to GO weight ratios were prepared and characterized for physicochemical properties. The introduction of GO mediated the morphology and structural properties to aligned FeS2 spherical nanoparticles within the GO network compared with pristine FeS2 cubical nanostructures. In water treatment applications, the synthesized FSG nanocomposite with FeS2 to GO ratio of 4:3 was highly effective for the complete degradation (∼99%), significant mineralization (>70%), and complete detoxification of antibiotic amoxicillin (AMCT) under the optimal solar-Fenton treatment when compared to bare FeS2, and other FSG nanocomposites. Radical scavenging experiments, leaching profile for iron (Fe) species (total Fe, Fe(II), and Fe(III)), decomposition profile of hydrogen peroxide, and HO• generation in the reaction medium helps to postulate the possible reaction mechanisms for AMCT degradation. The greatly enhanced catalytic performance of FeS2/GO was correlated with efficient recycling of Fe(II)/Fe(III), higher solar-light absorptivity due to the GO existence, and synergistic coupling of FeS2 and GO evidenced through the strong formation of Fe-O chemical bonds as confirmed by Fourier-transform infrared spectroscopy. Finally, the nanocomposites achieved enhanced apparent quantum efficiency for hydrogen generation through a water-splitting reaction. The reaction mechanism of FSG nanocomposite for water-splitting was proposed accordingly. Overall, this work could provide new insights for developing potential nanocomposite materials for widespread energy generation and environmental remediation applications.

Effect of Silica Nanoparticles Silanized by Functional/Functional or Functional/Non-Functional Silanes on the Physicochemical and Mechanical Properties of Dental Nanocomposite Resins

Dental nanocomposite resins have been proposed as potential restorative materials that are inevitably challenged with dynamic oral conditions. This investigation focused on the contribution of miscellaneous silane blends, used as coupling agents, to the ultimate performance of dental nanocomposite dimethacrylate resins. Herein, silica nanoparticles were initially silanized with functional/functional or functional/non-fuctional silane mixtures (50/50 wt/wt). Fourier transforms infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) verified the modification of nanosilica. The organomodified nanoparticles were then inserted into Bis-GMA/TEGDMA based resins by hand spatulation process. Scanning electron microscopy (SEM) findings revealed a broad distribution of fillers in the polymer network when reactive silanes and their corresponding blends were used. Furthermore, optical profilometry results showed that the presence of functional/non-functional mixtures can produce relatively smooth composite surfaces. Polymerization shrinkage was found to be limited upon the decrease of the degree of conversion regarding all the tested silane mixtures. The functional/functional silane blend assured the highest flexural properties and the lowest solubility after the storage of the nanocomposite in water for 1 week at 37 °C. The above experimental data could contribute to the proper designing of dental nanocomposite resins which may fit the modern clinical applications.

Polypyrrole modified bentonite nanocomposite and its application in high-efficiency removal of Cr(VI)

The disposal of Cr(VI) contamination in water urgently required an optimal material, nanocomposite of chloride-doped polypyrrole/bentonite (Cl-PPy/BT) was synthesized successfully through in situ polymerization to achieve synergistic reduction and adsorptive removal of Cr(VI). The adsorbent property was characterized methodically. The Cr(VI) adsorption results indicated that introduction of Cl-PPy significantly favored the performance of bentonite, with maximum adsorption capacities of 314.5–454.9 mg g-1 at 25–55 °C. These capacities are much higher than those of many other organoclays (16.4–185.2 mg g-1). Additionally, the removal efficiency of Cr(VI) by Cl-PPy/BT was respectively 3.4-fold and 5.4-fold higher than those of Cl-PPy and bentonite at Cr(VI) concentration of 100 mg L-1, indicating the strong synergistic effect between bentonite and Cl-PPy. This is because Cl-PPy and BT could well resist the aggregation of each other, and therefore resulted in a loose-packed structure and good exposure of active sites. The adsorption kinetics were well described by the pseudo-second-order kinetic model, suggesting the existence of chemical adsorption process; while the thermodynamic fitting results demonstrated the existence of physical adsorption process. Furthermore, the intraparticle diffusion model indicated that the adsorption was controlled by both film and intraparticle diffusion. The combination of fitting results and instrumental analysis results suggested that electrostatic interactions between Cr(VI) and -NH+- of polypyrrole, ion exchange between Cr(VI) and Cl- as well as reduction of Cr(VI) to Cr(III) by -NH- contributed to the Cr(VI) removal. The results maybe give some new insight about the removal of Cr(VI) with negative charge by polypyrrole/bentonite nanocomposites in water.

Synthesis of porous secondary metal-doped MOFs for removal of Rhodamine B from water: Role of secondary metal on efficiency and kinetics

Metal-organic frameworks (MOFs) are newly introduced category of porous compounds reflected as proficient and economic to exclude organic dyes from water. In the present work, a metal doping strategy in MOFs has been introduced to enhance the efficiency of porous MOFs for adsorption of environmentally detrimental rhodamine B (Rh-B). The porous ZIF-67 and metal-doped MOFs (Fe@ZIF-67) having Fe metal composition 1%, 3% and 5% were fabricated by in situ doping strategy during a simple solvothermal synthesis of ZIF-67. The spectroscopic characterization showed that limited metal-doping did not affect the characteristic features of MOFs like structural topology, porosity and surface area. The highest observed adsorption amount of Fe@ZIF-67 (5%) calculated with Langmuir model was 135.14 mg. g−1, considerably higher as compared to pristine ZIF-67 (85.69 mg. g−1) and other synthesized MOFs. The adsorption experiments data was well fitted by Langmuir model (R2 = 0.998) clarified that the adsorption process of Rh-B was monolayer and specified a stronger electrostatic interaction between Rh-B and porous Fe@ZIF-67 with 5% Fe, which was reliable with the observation from the effects of pH and ionic strength. The results showed that 47.71, 64.52 and 79.92% of rhodamine B dye removed by Fe@ZIF-67 (1%), Fe@ZIF-67 (3%) and Fe@ZIF-67 (5%) respectively with 240 minutes contact time. The recycling experiments also disclosed high stability of the Fe-doped MOFs. Up to 92% adsorption efficiency was examined after four regeneration cycles. All of the outcomes shown a pronounced prospective of the synthesized Fe@ZIF-67 nanocomposite in water treatment/purification in the industry.

Synthesis of color-responsive polydiacetylene assemblies and polydiacetylene/zinc(II) ion/zinc oxide nanocomposites in water, toluene and mixed solvents: Toward large-scale production

Polydiacetylenes (PDAs) are well-known materials that can be utilized as colorimetric sensors of various stimuli. PDA-based materials are normally synthesized via a self-assembly in an aqueous medium. In this study, we explored important experimental parameters including concentration, incubating temperature, and solvent media, that affected the self-assembly of monocarboxylic PDA and reversible thermochromic PDA/Zn2+/ZnO nanocomposites. The critical concentration (C*), the lowest concentration for topotactic photopolymerization in each system, was determined. We achieved, for the first time, direct synthesis of PDA/Zn2+/ZnO nanocomposites in toluene. Furthermore, it was possible to synthesize the nanocomposites at ambient conditions, simplifying the process for large-scale production. The addition of co-solvent, ethanol, resulted in a significant increase in blue-phase concentration. The presence of ethanol in the solvent medium also caused the morphological change from sheet-like to ribbon-like structures. The ability to synthesize the nanocomposite in nonpolar media allowed the fabrication of solid-state sensors by mixing with various polymers such as polyethylene, polystyrene, poly(methyl methacrylate), and poly(4-vinylpyridine). Reversible thermochromic smart inks were prepared by simple mixing with acrylic paint. Our study extends the utilization of PDA-based materials as colorimetric sensors.

Non enzymatic electrochemical detection of paraoxon methyl using zinc oxide graphene nanocomposite in water and food samples

Highly toxic nature of organophosphorous compounds necessitates their sensing for the safety of humans. Non enzymatic electrochemical sensors are advantageous compared to enzymatic ones as they are sensitive, simple, stable and inexpensive. Herein, we have synthesized a nanocomposite of ZnO supported on graphene nanosheets (ZnO-G) and studied its applicability as an electrode material for the electrochemical sensing of organophosphate, paraoxon-methyl. Nanocomposite prepared was characterized for structural and morphological details using X-ray diffraction (XRD), BET surface area analyser and field emission scanning electron microscopic (FESEM) techniques. The sensing applicability was tested using electrochemical techniques like cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, peak current was linearly proportional to the concentration of paraoxon-methyl in the range of 0.002–0.04 µg/ml and 0.06–1.0 µg/ml with the sensitivities of 118.0nA/mM.cm2 and 35.7nA/mM.cm2 respectively and detection limit of 1.6 ng/ml. In comparison, solar reduced graphene oxide (SRGO) showed linear range of 0.05–1 µg/ml with the detection limit of 10.2 ng/ml and sensitivity of 55.3nA/mM.cm2. High performance of ZnO-G is attributed to the unique morphology and modified properties of the nanocomposite. The nanocomposite prepared has also been tested for its applicability in real samples of tap water, waste water, cabbage and tomatoes. This study confirms the excellent selectivity, reproducibility, repeatability and stability exhibited by the nanocomposite ZnO-G sample for paraoxon methyl sensing in non-enzymatic mode.

Significant fluorescence intensity of excitation dependent emission at longer wavelength of graphite-ZnO nanocomposite in water: A cyanide sensor

Significant fluorescence intensity of excitation dependent emission at longer wavelength of graphite-ZnO nanocomposite in water: A cyanide sensor

A new type of SnO2@β-Fe(Zr)OOH hollow nanosphere as a bifunctional adsorbent for removing nitrate from water: kinetics, isotherm, and thermodynamic studies

A SnO2@β-Fe(Zr)OOH nanocomposite, β-FeOOH doped with Zr on SnO2 hollow spheres, was synthesized by two-step hydrothermal method to solve the problem of nitrate pollution in sewage. The structure and properties of samples which synthesized in this work were analyzed by means of XRD, SEM, TEM, XPS, BET and Zeta potential systematically. Moreover, the effects of initial nitrate concentration, pH, time and temperature on nitrate removal were also investigated. The amount of nitrate nitrogen adsorbed by the SnO2@β-Fe(Zr)OOH nanocomposite was 14.0 mg/g in the first 30 min. Based on the analysis of the nitrate adsorption kinetic model of SnO2@β-Fe(Zr)OOH nanocomposite in water, the adsorption was in line with the second-order kinetic model and belonged to chemical adsorption. It showed that the Langmuir adsorption isotherm model fitting results are superior to the Freundlich isothermal adsorption model through fitting the adsorption isotherm. With the increase of temperature, the maximum adsorption capacity showed the same trend, which indicated that the adsorption process is an endothermic process. In addition, adsorption thermodynamic studies were carried out to prove that the reaction process is a spontaneous reaction. After six adsorption–desorption cycles, the composite still has an adsorption capacity of 80%.

Long-Term Sorption and Solubility of Zirconia-Impregnated PMMA Nanocomposite in Water and Artificial Saliva.

Exposure of denture base acrylic resins to the oral environment and storage media for extended periods of time results in sorption of saliva or water, leading to a reduction in physical properties and thus clinical service life. The purpose of this in vitro study was to assess the sorption and solubility of high-impact heat-polymerised denture base acrylic resin (HI PMMA) impregnated with zirconia nanoparticles after being stored for 180 days in distilled water (DW) and artificial saliva (AS). The specimens were divided into six groups for each storage medium, according to the concentration of zirconia nanoparticles (0, 1.5, 3.0, 5.0, 7.0, and 10.0 wt.%). Data were statistically analysed for sorption and solubility using one-way and two-way ANOVA statistical tests. Sorption in DW and AS for all groups containing zirconia showed sorption values lower than the control group at 90 days, though not significantly different (p > 0.05) compared to the control group. For both the DW and AS groups, the lowest solubility value was measured in the group containing 3 wt.% zirconia, however, there was no significant difference compared to the control group except when observing 10 wt.% zirconia in AS, which showed a significantly higher solubility (p < 0.05). High-impact PMMA, impregnated with low concentrations of ZrO2, showed the lowest sorption and solubility in both media, but was not significantly different compared to pure HI PMMA.

Green synthesise of CuO@Fe 3 O 4 @Xantan nanocomposites and its application in enhanced oil recovery by considering IFT and wettability behaviours

Enhanced oil recovery (EOR) makes use of various chemical processes to extract additional oil from reservoirs, often already under production. In this study, authors investigated the role of the CuO@Fe3O4@xanthan nanocomposite (NCs) in EOR by the focus of the interfacial tension (IFT) and wettability alteration mechanisms. This NCs is synthesized from Artocarpus altilis extract using a simple, economical and green method. The prepared NCs is identified using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Nanofluids are prepared from dispersing the synthesised NCs in water at different concentrations in order to be used in the density, viscosity, conductivity, IFT and contact angle measurements. The results showed an improvement in the values of IFT and contact angle. The IFT of oil/water is increased from 22 to 24 mN/m with increasing the concentration of the NCs from 250 to 2000 ppm. While, the wettability of the carbonate rock is remained water-wet, wherein the contact angle is raised from 28° to 58° with increasing the NCs concetration from 250 to 2000 ppm. Overall, the IFT and contact angle are only reduced when 250 ppm NCs was added to water from 28.3 mN/m and 132.6° mN/m to 22 and 34.5°.

Simultaneous magnetic solid phase extraction of acidic and basic pesticides using triazine-based polymeric network modified magnetic nanoparticles/graphene oxide nanocomposite in water and food samples

In this work, a triazine-based polymeric network modified magnetic nanoparticles/graphene oxide (TPN/Fe3O4 NPs/GO) nanocomposite was successfully synthesized and used as an effective nanosorbent in simultaneous magnetic solid phase extraction of basic and acidic pesticides from food and water samples by HPLC-UV. Imidacloprid (IMI) and 2,4-dichlorophenoxyacetic acid (2,4-D) were selected as model basic and acidic pesticides, respectively. The synthesized TPN/Fe3O4/GO was characterized by field emission-scanning electron microscopy (FE-SEM), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA). Some parameters that affect the extraction efficiency such as pH of solution, sorbent amount, salt amount, extraction time, desorption solvent volume and desorption time were optimized by central composite design. However, type of desorption solvent and sample volume were optimized by one variable at a time method. Under optimum conditions, the calibration curve was linear in the range of 0.5–500 μg L−1 and 5.0–500 μg L−1 for IMI and 2,4-D, respectively. The limits of detection (LODs) for IMI and 2,4-D were 0.17 and 1.7 μg L−1, respectively. Also, the limits of quantification (LOQs) for IMI and 2,4-D were 0.5 and 5.0 μg L−1, respectively. The relative standard deviations (RSDs) were <8.6% (n = 6). The proposed method was successfully applied for extraction and determination of IMI and 2,4-D in cucumber, tomato and water samples and satisfactory results (recoveries ≥90%) were obtained.

Green synthesis of thiiranes from epoxides catalyzed by magnetically separable CuFe2O4/Mg(OH)2 nanocomposite in water under benign conditions

The magnetically separable CuFe2O4/Mg(OH)2 nanocomposite was prepared and characterized by FT-IR, XRD, SEM, EDS, and VSM techniques. The synthesized nanoparticles were used as a new and efficient heterogeneous catalyst for the conversion of various epoxides to the corresponding thiiranes with thiourea in water solvent at room temperature. The reactions were completed within 1–3.7 h to give thiiranes in 70–99% yields. The applied CuFe2O4/Mg(OH)2 nanocomposite was separated easily using an external magnet and reused for several times without any considerable loss of activity.

Fenitrothion sensing with reduced graphene oxide decorated fumed silica nanocomposite modified glassy carbon electrode

In this study, a nanocomposite was prepared via reducing graphene oxide on fumed silica (FS) surface to develop a modified electrode for the determination of fenitrothion (FNT). Reduced graphene oxide (RGO) decorated FS (FS@RGO) was used to modify glassy carbon (GC) electrode. The modified electrode decreased the overpotential of FNT (80 mV) and increased prominently the reduction peak current of FNT (9 times). Scanning electron microscopy, energy dispersive X-ray, X-ray diffraction and Raman spectroscopy analyses revealed that the FS@RGO nanocomposite was successfully synthesized. The presence of FS on FS@RGO structure prevented the agglomeration and allowed the homogeneous distribution of the nanocomposite in water, which was a drawback for RGO. Moreover, the presence of FS brings additional functionality to FS@RGO nanocomposite, which increases the adsorption and electron transfer rate of FNT. The GC/FS@RGO electrode showed a linear response in a wide range of FNT concentration (0.005–1.0 μM) and a very low limit of detection (0.00019 μM). The performance of the GC/FS@RGO electrode was evaluated by performing recovery studies in river water, urine, raisin extract, tomato extract and orange extract. Acceptable recovery values between 92.3% and 112.2% were obtained during the analysis of FNT-spiked samples.