Expression of concern: Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

Expression of concern for 'Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 13245-13255, https://doi.org/10.1039/D1RA01056E.

Biochemical and phytochemical responses of Ammi visnaga L. (Apiaceae) callus culture elicited by SiO2 and graphene Oxide-SiO2 nanoparticles.

Ammi visnaga L. is an enriched medicinal plant with medicinally important compounds. Two types of nanoparticles (NPs) including silica (SiO2) and graphene oxide bound with SiO2 (GO-SiO2) NPs at different concentrations (0, 15, 25 mg L-1) were used as elicitors to investigate their effects on callus morphology, H2O2 content, total phenolic content (TPC), total flavonoids content (TFC), ferric reducing/antioxidant power (FRAP), and few antioxidant enzymes such as catalase (CAT), guaiacol peroxidase (GPX), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO) in the callus cultures of A. visnaga. The effects of elicitation of both NPs on calli were observed using a scanning electron microscope (SEM). The 15 mg L-1 concentration of GO-SiO2 NPs produced the highest TPC (193.3 mg GAE g-1 FW), CAT (13.1 U mg-1 Protein), GPX (0.0089 U mg-1 Protein), and APX (0.079 U mg-1 Protein). Whereas, the maximum content of H2O2 (0.68 µmol g-1 FW), FRAP (0.0092 µmol mg-1), and TFC (62.27 mg QE g-1 FW) was observed at 25 mg L-1 and 15 mg L-1 of SiO2 NPs, respectively. Conclusively, in the callus culture of A. visnaga, the 15 mg L-1 concentration of GO-SiO2 NPs was the most suitable dosage for enhancing the enzymatic antioxidant activities (CAT, GPX, APX) and TPC, rather than SiO2 NPs.

Correction: Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

[This corrects the article DOI: 10.1039/D1RA01056E.].

Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

Fabricating suitable adsorbents with low-cost and high efficiency extraction for measurement of very small amounts of agricultural pesticides in food and water is playing a vital key role in personal and environmental health. Here, a new composite of zeolitic imidazolate framework-67@magnesium aluminate spinel (ZIF-67@MgAl2O4) has been fabricated by a simple method at room temperature with different weight ratios. Several techniques such as FE-SEM, BET, XRD, and TGA have been used to confirm the structural characterization of the obtained materials. The obtained ZIF-67@MgAl2O4 was utilized as an adsorbent in the solid phase microextraction technique to extract and preconcentrate the herbicide molinate (as an analyte) in aqueous solution. Corona discharge ionization-ion mobility spectrometry (CD-IMS) was applied for quantification of the analyte molecules. Extraction temperature, extraction time, stirring rate, and sample pH as the main parameters that affected the extraction proficiency were chosen and considered. Under optimal conditions, the linear dynamic range (LDR) of the various concentrations of the molinate and correlation coefficient were 10.0-100.0 µg L-1 and 0.9961, respectively. The limit of quantification (LOQ) and method detection limit (MDL) were 10.0 µg L-1 and 3.0 µg L-1, respectively. The relative standard deviation (RSD) of the ZIF-67@MgAl2O4 for extracting the molinate molecules (molinate concentration; 50 µg L-1) was calculated to be 4% and the enrichment factor (EF) was ∼5.

Investigation of heterogeneous sulfonated graphene oxide to hydrolyze cellulose and produce dark fermentative biohydrogen using Enterobacter aerogenes.

The main aim of this work was investigating the potential of sulfonated graphene oxide (sGO) for hydrolysis of cellulosic substrates and dark fermentative hydrogen production from obtained hydrolysates using E. aerogenes. Sulfonation of graphene oxide was performed using chlorosulfonic acid which showed a high acid density of 4.63 mmol/g. Influence of the reaction time (1-5 h), temperature (90-180 °C) and sGO dosage (62.5-500 mg in 25 mL reaction volume) on the hydrolysis of pretreated microcrystalline cellulose was experimented. It revealed that the yield of glucose and total reducing sugars and selectivity can reach 454.4 ± 22.20 mg/g, 682.6 ± 30.67 mg/g and 95.5%, respectively, at 150 °C for 3 h using 250 mg sGO. The maximum hydrogen efficiency of 150.0 ± 5.65 mL/g was achieved under optimized conditions, which was 2.2-fold higher than that from the pretreated MCC substrate as control in the absence of sGO (67.3 ± 8.84 mL/g).

Retention of silver nano-particles and silver ions in calcareous soils: Influence of soil properties.

The rapid production and application of silver nanoparticles (AgNPs) have led to significant release of AgNPs into the terrestrial environments. Once released into the soil, AgNPs could enter into different interactions with soil particles which play key roles in controlling the fate and transport of these nanoparticles. In spite of that, experimental studies on the retention of AgNPs in soils are very scarce. Hence, the key objective of this research was to find out the retention behavior of AgNPs and Ag(I) ions in a range of calcareous soils. A second objective was to determine the extent to which the physico-chemical properties of the soils influence the Ag retention parameters. To this end, isothermal batch experiments were used to determine the retention of Poly(vinylpyrrolidinone)-capped AgNPs (PVP-AgNPs) and Ag(I) ions by nine calcareous soils with a diversity of physico-chemical properties. The results revealed that the retention data for both PVP-AgNPs and Ag(I) ions were well described by the classical Freundlich and Langmuir isothermal equations. The retention of PVP-AgNPs and Ag(I) ions was positively correlated to clay and organic carbon (OC) contents as well as electrical conductivity (EC), pH, and cation exchange capacity (CEC) of the soils. Due to multicolinearity among the soil properties, principal component analysis (PCA) was used to group the soil properties which affect the retention of PVP-AgNPs and Ag(I) ions. Accordingly, we identified two groups of soil properties controlling retention of PVP-AgNPs and Ag(I) ions in the calcareous soils. The first group comprised soil solid phase parameters like clay, OC, and CEC, which generally control hetero-aggregation and adsorption reactions and the second group included soil solution variables such as EC and pH as well as Cl- and Ca2+ concentrations, which are supposed to mainly affect homo-aggregation and precipitation reactions.

Synthesis, characterization and catalytic oxidation of para-xylene by a manganese(III) Schiff base complex on functionalized multi-wall carbon nanotubes (MWNTs).

In the present study, hydroxyl functionalized manganese(III) Schiff-base; [Mn((OH)(2)-salophen)Cl] [(OH)(2)-salophen] = (N,N'-bis(4-hydroxysalicylidene)phenylene-1,2-diamine); has been covalently anchored on modified multi-wall carbon nanotubes (MWNTs); [Mn((OH)(2)-salophen)Cl]@MWNTs]. The new modified MWNTs have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron (XPS), thermal analysis, FT-IR spectroscopy and elemental analysis. The results suggest that the symmetrical Schiff-base is a bivalent anion with tetradentate N(2)O(2) donors derived from the phenolic oxygen and azomethine nitrogen. 4-Hydroxy salophen; [(OH)(2)-salophen], complex of manganese, grafted on the walls of MWNTs have been investigated as catalysts for the aerobic oxidation of para-xylene in the absence of added halogen promoters and using tert-butylhydroperoxide (TBHP) as the initiator at low temperatures. The major products include toluic acid, toluyl aldehyde and toluyl alcohol. The MWNTs-grafted complex did not undergo any colour change during the reaction and could be easily separated and reused many times. In contrast, the neat complex, while they were active in the first cycle, was completely destroyed during the run and changed colour. They, however, gave lower conversions compared to the grafted catalyst.