Toxicity of zinc oxide nanoparticles to the annelid <Emphasis Type="Italic">Enchytraeus crypticus</Emphasis> in agar-based exposure media

Toxicity of zinc oxide nanoparticle (ZnO-NPs) powder and water soluble salt of Zn (ZnCl₂) to the annelid Enchytraeus crypticus was tested in agarose gel. Influence of the spiking method on the resulting size of nanoparticles and on E. crypticus mortality was studied. Two methods of ZnO-NPs powder (mean particle size diameter of 10 nm) introduction into the exposure media were used. In the first method, the nano-powder was initially cryogenically ground with dry agar followed by an addition of water. The second procedure began with re-suspension of nanoparticles in demineralized water containing a dispersant (sodium pyrophosphate decahydrate). The obtained colloid was subsequently mixed with hot agar gel. Relative mortality in worms observed after 96 h of their exposure to the ZnO-NPs concentrations (all in mg of ZnO-NPs per kg of agar) of 50, 100, 200, 500 and 1000 in the cryogenically ground medium ranged between 28.9 % and 34.4 % and it did not exhibit any concentration dependence. When the second method of exposure media preparation was applied, the relative mortality ranged from 0 % to 66.6 % in the same concentration region depending on the concentration. Scanning electron microscopy (SEM) revealed the presence of large agglomerates (1–10 µm in diameter) in the media prepared by cryogenic grinding with the highest concentration of ZnO-NPs. Neither the cryogenically ground media with lower ZnO-NPs concentrations nor any media prepared from colloidal solutions contained agglomerates exceeding 100 nm, detectable by SEM. Hydrodynamic diameters of particles in the colloids used in the second method of agar preparation were measured using dynamic light scattering (DLS) and ranged between 164 nm and 240 nm. The observed toxicity was thus clearly dependent on the size of ZnO-NPs agglomerates and the technique of exposure media preparation. Experimentally detected LC₅₀ value for dissolved Zn²⁺ was 37.2 mg kg^?1 in agar. The same concentration of Zn induced an approximately 30 % mortality of E. crypticus when administered in form of cryogenically ground ZnO-NPs with agar. No observable effects were found at this ZnO-NPs concentration when the exposure medium was prepared from the colloid solution.     

Synthesis,magnetic properties and X-ray analysis of Zn0.97X0.03O nanoparticles (X = Mn,Ni, and Co) using Scherrer and size–strain plot methods

Un-doped and doped ZnO nanoparticles (Zn_0.97X_0.03O-NPs, X = Mn, Co, and Ni) were synthesized from a metal acetate precursor and acetic acid by a modified sol–gel combustion method. The compounds were synthesized at calcination temperatures of 650 °C for 1 h. The synthesized un-doped/doped ZnO-NPs were characterized by X-ray diffraction analysis (XRD) and high-magnification transmission electron microscopy (TEM). The XRD results revealed that the sample product was crystalline with a hexagonal wurtzite phase. The TEM showed ZnO-NPs nearly spherical shapes and a non-uniform shape for doped ZnO-NPs. The crystalline development in the ZnO-NPs was investigated by X-ray peak broadening. The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the un-doped and doped ZnO-NPs. Physical parameters such as strain, stress and energy density values were calculated more precisely for all reflection peaks of XRD corresponding to the wurtzite hexagonal phase of ZnO lying in the range of 20–80° from the SSP results. The vibrating sample magnetometer (VSM) was also used to study the magnetic behavior of the samples in the ceramic form. The obtained results showed that strain play an important role in peak broadening; moreover, the mean crystalline size of the un-doped and doped ZnO-NPs estimated from the TEM and the SSP method were highly inter-correlated.     

Genotoxic and Cytotoxic Properties of Zinc Oxide Nanoparticles Phyto-Fabricated from the Obscure Morning Glory Plant Ipomoea obscura (L.) Ker Gawl

The study was undertaken to investigate the antioxidant, genotoxic, and cytotoxic potentialities of phyto-fabricated zinc oxide nanoparticles (ZnO-NPs) from Ipomoea obscura (L.) Ker Gawl. aqueous leaf extract. The UV-visible spectral analysis of the ZnO-NPs showed an absorption peak at 304 nm with a bandgap energy of 3.54 eV, which are characteristics of zinc nanoparticles. Moreover, the particles were of nano-size (~24.26 nm) with 88.11% purity and were agglomerated as observed through Scanning Electron Microscopy (SEM). The phyto-fabricated ZnO-NPs offered radical scavenging activity (RSA) in a dose-dependent manner with an IC₅₀ of 0.45 mg mL⁻¹. In addition, the genotoxicity studies of ZnO-NPs carried out on onion root tips revealed that the particles were able to significantly inhibit the cell division at the mitotic stage with a mitotic index of 39.49%. Further, the cytotoxic studies on HT-29 cells showed that the phyto-fabricated ZnO-NPs could arrest the cell division as early as in the G0/G1 phase (with 92.14%) with 73.14% cells showing early apoptotic symptoms after 24 h of incubation. The results of the study affirm the ability of phyto-fabricated ZnO-NPs from aqueous leaf extract of I. obscura is beneficial in the cytotoxic application.     

Effect of different capping agents on physicochemical and antimicrobial properties of ZnO nanoparticles

This research aims to investigate the influence of soluble starch; lactose; carboxymethyl cellulose; urea; and polyvinylpyrrolidone on synthesis of zinc oxide nanoparticles (ZnO-NPs). Zinc acetate was used as a precursor under alkaline conditions to produce ZnO-NPs as a low-cost and efficient antimicrobial and UV-blocking agent. Characterization and antimicrobial functional properties of prepared nanoparticles were investigated and reported using FTIR, TGA, XRD, TEM, analysis, as well as antimicrobial assay, respectively. The results revealed that the thermal decomposition profile, size of ZnO-NPs, IR spectra, as well as antimicrobial activity of the prepared ZnO-NPs is governed by the type of capping agents. Crystallinity analysis showed identical patterns in peak intensities and width irrespective of the used capping agents. On the other hand, the obtained results disclosed that using soluble starch as a capping agent results in attaining lower particle size of 3–5 nm and higher antimicrobial efficacy as compared with the other capping agents.     

Ameliorating the Adverse Effects of Tomato mosaic tobamovirus Infecting Tomato Plants in Egypt by Boosting Immunity in Tomato Plants Using Zinc Oxide Nanoparticles

Tomato mosaic virus (ToMV) is one of the economically damageable Tobamovirus infecting the tomato in Egypt that has caused significant losses. It is therefore of great interest to trigger systemic resistance to ToMV. In this endeavor, we aimed to explore the capacity of ZnO-NPs (zinc oxide nanoparticles) to trigger tomato plant resistance against ToMV. Effects of ZnO-NPs on tomato (Solanum lycopersicum L.) growth indices and antioxidant defense system activity under ToMV stress were investigated. Noticeably that treatment with ZnO-NPs showed remarkably increased growth indices, photosynthetic attributes, and enzymatic and non-enzymatic antioxidants compared to the challenge control. Interestingly, oxidative damage caused by ToMV was reduced by reducing malondialdehyde, H₂O₂, and O₂ levels. Overall, ZnO-NPs offer a safe and economic antiviral agent against ToMV.     

Antibacterial polyethylene - Ethylene vinyl acetate polymeric blend by incorporation of zinc oxide nanoparticles

In this work, a Low-Density Polyethylene (LDPE) - Ethylene Vinyl Acetate (EVA) polymeric blend with antimicrobial activity was obtained. The main objective was to develop an antibacterial LDPE-EVA polymeric blend from the incorporation of antibacterial nanoparticles to increase the antimicrobial and sanitary safety of this polymeric blend when applied in the manufacture of medical products. The antibacterial activity was obtained from the incorporation of zinc oxide nanoparticles (ZnO-NPs) in the LDPE-EVA polymeric blends and the thermal properties were evaluated by differential scanning calorimetry and the mechanical properties by tensile stress tests for different percentages of ZnO-NPs. Scanning electron microscopy was used to study the morphological characteristics of the ZnO-NPs and also the characteristics of the distribution of nanoparticles in the polymer blends. The dispersive energy of x-ray fluorescence spectroscopy was used to study the chemical composition of the nanoparticles. Microbiological tests were performed to evaluate the antibacterial activity of the LDPE-EVA polymeric blends without and with ZnO-NPs against the bacteria Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative). The results obtained were excellent for the future application of the antibacterial LDPE-EVA polymeric blends to the manufacture of medical products. The Young's modulus values decreased and the tensile strength values showed small reductions and the thermal properties of the LDPE-EVA were not modified. However, the antibacterial activity of LDPE-EVA with 4 wt% of ZnO-NPs was excellent, eliminating the gram-positive bacteria in just 2 h and the gram-negative bacteria in just 2.5 h on their surfaces.     

Biosynthesis of Zinc Oxide Nanoparticles from Acacia nilotica (L.) Extract to Overcome Carbapenem-Resistant Klebsiella Pneumoniae

Recently, concerns have been raised globally about antimicrobial resistance, the prevalence of which has increased significantly. Carbapenem-resistant Klebsiella pneumoniae (KPC) is considered one of the most common resistant bacteria, which has spread to ICUs in Saudi Arabia. This study was established to investigate the antibacterial activity of biosynthesized zinc oxide nanoparticles (ZnO-NPs) against KPC in vitro and in vivo. In this study, we used the aqueous extract of Acacia nilotica (L.) fruits to mediate the synthesis of ZnO-NPs. The nanoparticles produced were characterized by UV-vis spectroscopy, zetasizer and zeta potential analyses, X-ray diffraction (XRD) spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The antimicrobial activity of ZnO-NPs against KPC was determined via the well diffusion method, and determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the results showed low MIC and MBC when compared with the MIC and MBC of Imipenem and Meropenem antibiotics. The results of in vitro analysis were supported by the results upon applying ZnO-NP ointment to promote wound closure of rats, which showed better wound healing than the results with imipenem ointment. The biosynthesized ZnO-NPs showed good potential for use against bacteria due to their small size, applicability, and low toxicity to human cells.     

Preparation,characterization, and permeability of novel poly (lactic acid)-based blends filled with thymol and ZnO

Novel thin sheets based on poly (lactic acid)/poly (caprolactone)/thermoplastic starch ternary blends were fabricated by incorporating thymol, zinc oxide nanoparticles (ZnO-NPs) and thymol/ZnO-NPs at different concentrations (6, 9, 12 wt% thymol and 1, 3, 5 wt% ZnO). The gas/water vapor barrier properties of the nanocomposites comprising the effects of polar and non-polar molecules and their leading mechanisms were thoroughly discussed. Moreover, the localization preference of ZnO-NPs, morphology along with mechanical, and thermal properties of the nanocomposites were investigated. A significant improvement of 58% in the water vapor impermeability by 5 wt% ZnO and 12 wt% thymol loading was achieved. Finally, the fitting of the Maxwell model on the experimental data revealed that this model cannot correctly predict the permeation behavior of ZnO-filled nanocomposites. Results suggested that these nanocomposites could be capable of being used as the packaging materials with high barrier performance.     

Effect of ZnO Nanofiller on Structural and Electrochemical Performance Improvement of Solid Polymer Electrolytes Based on Polyvinyl Alcohol–Cellulose Acetate–Potassium Carbonate Composites

In this study, a solution casting method was used to prepare solid polymer electrolytes (SPEs) based on a polymer blend comprising polyvinyl alcohol (PVA), cellulose acetate (CA), and potassium carbonate (K₂CO₃) as a conducting salt, and zinc oxide nanoparticles (ZnO-NPs) as a nanofiller. The prepared electrolytes were physicochemically and electrochemically characterized, and their semi-crystalline nature was established using XRD and FESEM. The addition of ZnO to the polymer–salt combination resulted in a substantial increase in ionic conductivity, which was investigated using impedance analysis. The size of the semicircles in the Cole–Cole plots shrank as the amount of nanofiller increased, showing a decrease in bulk resistance that might be ascribed to an increase in ions due to the strong action of the ZnO-NPs. The sample with 10 wt % ZnO-NPs was found to produce the highest ionic conductivity, potential window, and lowest activation energy (E_a) of 3.70 × 10^–3 Scm^–1, 3.24 V, and 6.08 × 10^–4 eV, respectively. The temperature–frequency dependence of conductivity was found to approximately follow the Arrhenius model, which established that the electrolytes in this study are thermally activated. Hence, it can be concluded that, based on the improved conductivity observed, SPEs based on a PVA-CA-K₂CO₃/ZnO-NPs composite could be applicable in all-solid-state energy storage devices.     

Green Synthesized Zinc Oxide Nanoparticles Based on Cestrum diurnum L. of Potential Antiviral Activity against Human Corona 229-E Virus

SARS-CoV-2 has caused more than 596 million infections and 6 million fatalities globally. Looking for urgent medication for prevention, treatment, and rehabilitation is obligatory. Plant extracts and green synthesized nanoparticles have numerous biological activities, including antiviral activity. HPLC analysis of C. dirnum L. leaf extract showed that catechin, ferulic acid, chlorogenic acid, and syringic acid were the most major compounds, with concentrations of 1425.16, 1004.68, 207.46, and 158.95 µg/g, respectively. Zinc nanoparticles were biosynthesized using zinc acetate and C. dirnum extract. TEM analysis revealed that the particle size of ZnO-NPs varied between 3.406 and 4.857 nm. An XRD study showed the existence of hexagonal crystals of ZnO-NPs with an average size of 12.11 nm. Both ZnO-NPs (IC₅₀ = 7.01 and CC₅₀ = 145.77) and C. dirnum L. extract (IC₅₀ = 61.15 and CC₅₀ = 145.87 µg/mL) showed antiviral activity against HCOV-229E, but their combination (IC₅₀ = 2.41 and CC₅₀ = 179.23) showed higher activity than both. Molecular docking was used to investigate the affinity of some metabolites against the HCOV-229E main protease. Chlorogenic acid, solanidine, and catchin showed high affinity (−7.13, −6.95, and −6.52), compared to the ligand MDP (−5.66 Kcal/mol). Cestrum dinurum extract and ZnO-NPs combination should be subjected to further studies to be used as an antiviral drug.     

Influence of the particle size on the antibacterial activity of green synthesized zinc oxide nanoparticles using Dysphania ambrosioides extract,supported by molecular docking analysis

Bacteria-associated infections have increased in recent years due to treatment resistance developed by these microorganisms. Due to the high antibacterial capacity associated with their nanometric size, nanoparticles, such as zinc oxide (ZnO), have proven to be an alternative for general medical procedures. One of the methodologies to synthesize them is green synthesis, where the most commonly used resources are plant species. Using Dysphania ambrosioides extract at various synthesis temperatures (200, 400, 600, and 800 °C), zinc oxide nanoparticles (ZnO-NPs) with average sizes ranging from 7 to 130 nm, quasi-spherical shapes, and hexagonal prism shapes were synthesized. Larger sizes were obtained by increasing the synthesis temperature. The ZnO crystalline phase was confirmed by X-ray diffraction and transmission electron microscopy. The sizes and shapes were observed by field emission scanning electron microscopy. The Zn-O bond vibration was identified by Fourier transform infrared spectroscopy. Thermogravimetry showed the stability of ZnO-NPs. The antibacterial evaluations, disk diffusion test, and minimum bactericidal concentration, demonstrated the influence of particle size. The smaller the nanoparticle size, the higher the inhibition for all pathogenic strains: Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, and dental pathogens: Streptococcus mutans, Streptococcus sanguinis, Porphyromonas gingivalis, and Prevotella intermedia. The molecular docking study showed a favorable interaction between ZnO-NPs and some proteins in Gram-positive and Gram-negative bacteria, such as TagF in Staphylococcus epidermidis and AcrAB-TolC in Escherichia coli, which led to proposing them as possible targets of nanoparticles.     

Biosynthesis of Zinc Oxide Nanoparticles Using Leaf Extract of Passiflora subpeltata: Characterization and Antibacterial Activity Against Escherichia coli Isolated from Poultry Faeces

The current study was undertaken to investigate the antibacterial (against molecular characterized E. coli isolated from poultry faeces) potential of biosynthesized zinc oxide nanoparticles (ZnO-NPs) from Passiflora subpeltata Ortega aqueous leaf extract. The biosynthesized nanoparticles were subjected to physico-chemical characterization to study shape, size and purity by UV–Vis spectroscopy, X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Transmission Electron Microscopy (TEM). The molecular identification of isolated E. coli from faeces samples was carried out by using 16–23s rRNA primers. The results of the physico-chemical characterization revealed that the biosynthesized nanoparticles were of 93.7% purity with an average size between 45 and 50 nm. The ZnO-NPs offered significant inhibition against the isolated Gram-negative E. coli with MIC at 62.5 µg mL^?1 concentration. The antibacterial potential of ZnO NPs against E. coli has also been investigated by the cell viability test, and further the effects of ZnO NPs on bacterial morphological structures was analysed by SEM and TEM.

     

An efficient synthesis of naphtha[1,2-e]oxazinone and 14-substituted-14H-dibenzo[a,j]xanthene derivatives promoted by zinc oxide nanoparticle under thermal and solvent-free conditions

A general synthetic route to the synthesis of 1,2-dihydro-1-arylnaphtho[1,2-e][1,3]oxazine-3-one and 14-substituted-14H-dibenzo[a,j]xanthenes derivatives has been developed using ZnO-NPs under thermal and solvent-free conditions. The union of 2-naphthol, aldehyde, urea enabling the synthesis of naphtho[1,2-e][1,3]oxazinone and 2-naphthol, aldehyde gave dibenzo[a,j]xanthenes in excellent yields. This method provides several advantages like simple work-up, environmentally benign, and shorter reaction times along with high yields.     

Amperometric determination of xanthine in fish meat by zinc oxide nanoparticle/chitosan/multiwalled carbon nanotube/polyaniline composite film bound xanthine oxidase

Xanthine oxidase (XOD) was immobilized on a composite film of zinc oxide nanoparticle/chitosan/carboxylated multiwalled carbon nanotube/polyaniline (ZnO-NP/CHIT/c-MWCNT/PANI) electrodeposited over the surface of a platinum (Pt) electrode. A xanthine biosensor was fabricated using XOD/ZnO-NP/CHIT/c-MWCNT/PANI/Pt as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through a potentiostat. The ZnO-NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the enzyme electrode was characterized by cyclic voltammetry, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 4 s at 0.5 V potential, pH 7.0, 35 °C and linear range 0.1-100 μM with a detection limit of 0.1 μM. The enzyme electrode was employed for determination of xanthine in fish meat during storage. The electrode lost 30% of its initial activity after 80 uses over one month, when stored at 4 °C.     

Biosynthesized Zinc Oxide Nanoparticles as Efficient Photocatalytic and Antimicrobial Agent

This work reports an innovative, effortless and inexpensive method for the preparation of ZnO nanoparticles by green approach using leaf extract of Piper betleas a reducing-stabilizing negotiator. The prepared ZnO NPs were characterized through XRD, FTIR, UV–Visible spectroscopy, and EDX etc. The band gap energy of the sample was estimated as 3.41 eV which is larger than the bulk ZnO (E_g?=?3.37 eV). The observed blue shift is attributed to the quantum confinement of excitons. FTIR analysis showed the presence of alkaloids, flavonoids, polyphenols, and terpenoid. TEM analysis showed that each nanoparticle comprised of 1 to 2 nano-crystallites. Photocatalytic activity results revealed that ZnO-NPs prepared through green synthesis route were found to be efficient in the degradation of toxic reactive red dye with degradation efficiency of 96.4% having high photodegradation rate-constant of 1.6?×?10^–2 min^?1. As an antimicrobial agent, the ZnO NPs are effective against both gram-positive (Bacillus subtilis) and negative bacteria (Escherichia coli), with the zones of clearance as 16.4 and 14.3 mm, respectively. Therefore, present research signifies an effective approach to utilize as-prepared ZnO NPs as efficient photocatalysts as well as antimicrobial agent.

     

Identification and removal of sulfhydryl groups from wastewaters

Thiols represent a source of environmental pollution especially wastewater. This work proposed to study the elaboration of cellulose acetate polymer-based membranes for their application in the removal of a sulfhydryl groups of real biological treated wastewaters. The addition of nanoparticles to membranes improves the water purification capacity by promoting a good separation of sulfur, more particularly by ZnO-NPs. We used ultrafiltration membrane-assisted ZnO and TiO₂ NPs application on real effluents from different biological treatment plants. We identified the hydrosulfite (thiol) group in wastewater and we used membrane processes ultrafiltration technique for sulfur removal. We evaluated the degradation of sulfur in biological treatment plants in Tunisia: The urban wastewater treatment plant or the conventional plant of Rades Malienne is a secondary biological wastewater treatment plant noted STEP1. The rural wastewater treatment plant based vertical flow planted with Phragmites australis from the Grombalia region noted STEP2 and rural wastewater treatment plant based horizontal flow planted with Phragmites australis from the Grombalia region noted STEP3. STEP1 is found to be more loaded with sulfur. Application of AC-ZnO membrane gives 99.07% and 99.55% of sulfur removal from wastewater of STEP1 and STEP3. STEP3 is 50 times less charged on sulfur than STEP1. We suggested that when the sulfur content is high, this leads to an increase in mineral elements. This could be explained by the interactions between thiols and the major elements that cause mineral pollution.     

Enhanced bactericidal and in vivo wound healing potential of biosynthesized zinc oxide nanoparticles from psyllium mucilage

The multifunctional zinc oxide nanoparticles are synthesized using a cost-effective, efficient, eco-friendly, simple, and clean synthesis approach. Herein, we reported the antibacterial and wound healing potential of zinc oxide nanoparticles (ZnO-NPs) prepared using psyllium gel (PG) as the reducing and stabilizing agent. The PG-mediated zinc oxide nanoparticles (PG-ZnO-NPs) were characterized using UV–Vis, photoluminescence (PL), FTIR, XRD, Raman, and SEM. UV–Vis spectral studies confirmed the surface plasmonic resonance (SPR) band at 364 nm. PL results demonstrated the fluorescent or emission nature of PG-ZnO-NPs. FTIR analysis confirmed characteristic peaks at 873.82 and 619.88 cm⁻¹ due to the tetrahedral coordination of zinc and the formation of the Zn-O bond. XRD and Raman confirm the formation of PG-ZnO-NPs, whereas SEM analysis revealed PG-ZnO-NPs are rod-shaped, having hexagonal prism-like bases, and EDX exhibited the elemental composition of PG-ZnO-NPs. The as-synthesized PG-ZnO-NPs possessed prominent microbicidal potential against gram-positive (Bacillus subtilis and Bacillus licheniformis) and gram-negative (Escherichia coli and Salmonella shigella) bacterial strains in terms of zone of inhibition (ZOI), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). In vivo biological investigations with mice show that the synthesized PG-ZnO-NPs possess outstanding biocompatibility and wound healing potential. PG-ZnO-NPs dressing significantly speeds up full-thickness wound repair by triggering a decrease in MMP-1 and MMP-2 and escalating the mRNA levels of collagen types (I & III) and fibronectin. Thus, our work validates that the inclusion of PG-ZnO-NPs in dressing shows excellent potential for acute wound management.     

Direct electrochemistry of glucose oxidase and sensing glucose using a screen-printed carbon electrode modified with graphite nanosheets and zinc oxide nanoparticles

We have studied the direct electrochemistry of glucose oxidase (GOx) immobilized on electrochemically fabricated graphite nanosheets (GNs) and zinc oxide nanoparticles (ZnO) that were deposited on a screen printed carbon electrode (SPCE). The GNs/ZnO composite was characterized by using scanning electron microscopy and elemental analysis. The GOx immobilized on the modified electrode shows a well-defined redox couple at a formal potential of −0.4 V. The enhanced direct electrochemistry of GOx (compared to electrodes without ZnO or without GNs) indicates a fast electron transfer at this kind of electrode, with a heterogeneous electron transfer rate constant (K_s) of 3.75 s⁻¹. The fast electron transfer is attributed to the high conductivity and large edge plane defects of GNs and good conductivity of ZnO-NPs. The modified electrode displays a linear response to glucose in concentrations from 0.3 to 4.5 mM, and the sensitivity is 30.07 μA mM⁻¹ cm⁻². The sensor exhibits a high selectivity, good repeatability and reproducibility, and long term stability.

Graphical representation for the fabrication of GNs/ZnO composite modified SPCE and the immobilization of GOx

     

Removal of dithioterethiol (DTT) from water by membranes of cellulose acetate (AC) and AC doped ZnO and TiO2 nanoparticles

Dithioterethiol (DTT) is a typical example of substances that contain sulfur with adverse effects on human health. Membranes-based cellulose acetate is used for the separation processes of thiols after the addition of ZnO and TiO₂ nanoparticles. The measurement of permeability allows us to estimate the efficiency of membrane cleaning. The permeability increases from 8.82 L.h^?1.m^?2.bar^?1 for CA membrane to 20.77 L.h^?1.m^?2.bar^?1 for CA-TiO₂ and 21.96 L.h^?1.m^?2.bar^?1 for CA-ZnO membranes. For the permeability values of DTT, we noted that the CA-ZnO membrane has the highest permeability (50.66 L.h^?1.m^?2.bar^?1). The CA-ZnO membrane changes from nanofiltration to ultrafiltration membrane. On the other hand, for the CA-TiO₂ modified membrane, the permeability decreases to 6.00 L.h^?1.m^?2.bar^?1. The CA-TiO₂ membrane is in the category of reverse osmosis membranes. This variation is explained by the interaction between nanoparticles and DTT. The contact angles of the incorporated membranes decrease progressively with the addition of TiO₂ or ZnO-NPs. The low contact angle with water means high hydrophilicity, indicated that the addition of TiO₂ and ZnO improved the hydrophilicity of the membranes. The CA membrane had the highest contact angle with water of 92.64 ± 1.5°. After the addition of 0.1 g of TiO₂ or ZnO, the contact angle of CA-TiO₂ and CA-ZnO was reduced to 86.7 ± 0.2° and 70.51 ± 1.5°, respectively. Both TiO₂ and ZnO caused strong hydrophilicity of membranes. From the elimination rates of DTT, it is concluded that there are optimal conditions of (1) Pressure P = 2 bars, (2) pH = 10 and (3) DTT concentration = 2 mM.