Superior Antibacterial Activity of Zinc Oxide/Graphene Oxide Composites Originating from High Zinc Concentration Localized around Bacteria

Comparative toxicity evaluation of graphene oxide (GO) and zinc oxide (ZnO) nanoparticles on Drosophila melanogaster

ABSTRACTBackground:Zinc oxide (ZnO) and graphene oxide (GO) nanoparticles (NPs) have antimicrobial properties. The present study was undertaken to evaluate the effects of incorporating these NPs and their chemical and physical blends on abrasion, translucency, and microhardness of flowable composite resin.Materials and Methods:In the present in vitro study, flowable composite resin samples (Grandio Flow, VOCO, Germany) were evaluated in 5 groups and the sample size was 10 for each group of each experiment (n = 10) as follows: Group 1, without NPs; Group 2, with ZnO NPs; Group 3, with GO NPs; Group 4, containing a physical mixture of GO and ZnO; and Group 5, containing a chemical mixture of GO and ZnO NPs. In all the groups, 1 wt% of the NPs were incorporate into flowable composite resin. Abrasion, translucency, and microhardness of the samples were evaluated. Data were analyzed with analysis of variance, followed by post hoc Tukey's tests at the level of significance of P < 0.05.Results:In Groups 2, 4, and 5 (all the groups containing ZnO), a significant decrease in abrasion and microhardness of flowable composite resin was observed compared to the control group. Incorporation of NPs in all the groups resulted in a significant decrease in translucency compared to the control group.Conclusion:Incorporation of NPs into flowable composite resin resulted in a decrease in translucency. The microhardness was reduced in groups containing ZnO, but the abrasion was also reduced in these groups. The incorporation of GO did not significantly alter the abrasion and microhardness of the composite resin.

The objective of this study is to evaluate the performance and emission characteristics of a diesel engine using metallic graphene oxide (GO) and nonmetallic zinc oxide (ZnO) nanoparticles in a Mahua biodiesel blend (B20). At a concentration of 75 mg/L, both GO and ZnO nanoparticles were considered and a surfactant (CTAB) and a dispersant (TWEEN 80) were added at a 1:1 ratio for surface modification. The nanofuel samples were analyzed for stability using a spectrophotometer. The nanoparticles mixed with dispersants and surfactants have shown improved stability. In addition, the injection pressure was varied from 200 to 250 bar. Dispersion of GO and ZnO nanoparticles in BD20 improved performance parameters such as BTE and BSFC. In addition, there was a significant decrease in CO, HC, smoke, and NOx emissions. TWEEN 80-added GO and ZnO nanoparticles in B20 achieved the best results, followed by the CTAB-added nanoparticles. In addition, the operating parameters showed a favorable trend toward improvement at higher injection pressures. At 250 bar, BTE was improved by 4.24% and BSFC was reduced by 3.59% compared to diesel. Also, the CO, UHC, NOx, and smoke opacity were reduced by 47.05%, 15.12%, 18.96%, and 37.09% for B20 + ZnO75 mg/L + TWEEN75 mg/L, respectively.

Effects of graphene oxide and zinc oxide nanoparticles on growth, chlorophyll, carotenoids, proline contents and diseases of carrot

Zinc oxide (ZnO) nanoparticles (NPs) integrated with two-dimensional carbon allotropes, such as graphene oxide (GO) and reduced graphene oxide (rGO), exhibit significant potential as photocatalysts for the degradation of pollutants and antibacterial applications. In this study, ZnO NPs and ZnO nanocomposites with GO and rGO were synthesized via a simple, cost effective wet chemical technique. GO and rGO were prepared using the improved Hummer's method and chemical reduction, respectively. Structural analyses were performed using X-ray diffraction (XRD) and Raman spectroscopy. XRD analysis revealed hexagonal wurtzite-phase of ZnO NPs with an increase in the crystallite size upon the formation of composites with GO and rGO. Raman spectroscopy provided additional structural information. Scanning electron microscopy (SEM) study showed spherical shaped ZnO NPs decorating the wrinkled surfaces of GO and rGO sheets. Optical studies using UV–Visible and photoluminescence spectroscopy showed a reduced band gap and suppressed charge-carrier recombination in the nanocomposites compared with pristine ZnO. Photocatalytic evaluation using methylene blue as a pollutant demonstrated improved degradation efficiencies of 82% and 86%, for GO/ZnO and rGO/ZnO nanocomposites respectively, relative to 79% for pristine ZnO NPs within 90 min of solar light irradiation. Compared with the reported literature, the synthesized rGO/ZnO nanocomposites demonstrate comparable performance, offering the advantages of a simpler synthesis method, high degradation efficiency, shorter degradation time, and lower catalyst loading. Furthermore, antibacterial activity assays, including minimum inhibitory concentration, minimum bactericidal concentration, and zone of inhibition analyses, demonstrated enhanced antibacterial efficacy of rGO/ZnO NCs against E. coli and B. subtilis, highlighting their potential as effective antibacterial materials.

Intensifying separation and antifouling performance of PSf membrane incorporated by GO and ZnO nanoparticles for petroleum refinery wastewater treatment

As a result of their unique and novel properties, nanocomposites have found applications in a wide variety of fields. The purpose of this study is to demonstrate the ability to synthesize nanoparticles consisting of zinc oxide (ZnO) and graphene oxide (GO) via sol–gel techniques. An x‐ray diffractometer (XRD) as well as a UV–visible spectrometer were used to determine the crystalline and optical characteristics of the prepared samples. A hexagonal wurtzite crystal structure was observed in both pure ZnO nanoparticles and those that contain GO based on XRD results. It was estimated that the average crystallite size is based on the broadening of x‐ray lines. In comparison with pure ZnO, the antimicrobial properties were enhanced when GO was incorporated with ZnO. In addition, experiments on the absorption edge indicated the presence of a red shift as a result of the incorporation of GO. When GO is incorporated in quantitative amounts, the bandgap value of pure ZnO decreased. FTIR spectra exhibit a band of absorption at 486 cm−1, which confirms Zn‐O stretching in both samples. SEM images reveal a random pattern of structural features on the surface of the prepared samples. According to the EDX spectrum, pure GO nanoparticles and those doped with ZnO contain 61%–64% zinc and 32%–34% oxygen, respectively. When annealed at a higher temperature, ZnO NPs produced more H2 with a narrower bandgap than before annealing. In addition, methyl blue (MB) was used as an example of an organic compound in order to investigate the potential photocatalytic properties of nanoparticles with ZnO doped GO. In addition to DPPH assays, ZnO nanoparticles and ZnO doped GO nanoparticles were tested for their ability to scavenge free radicals. Comparing ZnO doped GO NPs with pure ZnO, these nanoparticles showed increased antioxidant activity. Based on the increased zone of inhibition observed for pure ZnO and ZnO doped GO (5, 10, 50, and 100 mg/mL), the antibacterial activity of pure ZnO and ZnO doped GO is concentration dependent. A detailed discussion of the results of the study demonstrated that ZnO doped GO and pure ZnO are toxic in different ways depending on how long they survive in degreased Zebrafish embryos and how fast they decompose.Research HighlightsThe scope of the manuscript was under the results of the study confirmed that both nanoparticles exhibited concentration dependent antioxidative activity.Determined that 89% of methyl orange dye can be degraded photocatalytically.ZnO nanoparticles were found to be 74.86% antioxidant at a concentration of 50 g/mL in the present study.At a concentration of 50 g/mL, ZnO doped GO NPs showed 79.1% antioxidant activity.Photocatalytic degradation mechanism scheme is implicit in the photoexcited charge carrier transportation path is observed for all the samples.Survival rate of zebrafish embryos was shown to decrease with increasing concentrations of ZnO and zinc oxide plus GO nanoparticles.

The current research investigates the effects of adding metallic graphene oxide (GO) and non-metallic zinc oxide (ZnO) nanoparticles to Mahua biodiesel blend (B20) on the combustion parameters of a diesel engine. GO and ZnO nanoparticles were utilized at a concentration of 75 mg/L, combined with a 1:1 mixture of the surfactant CTAB and the dispersant TWEEN 80. When nanoparticles were introduced to blended biofuel, combustion parameters such as cumulative heart rate, mean gas temperature, mass percent burnt, and rise of pressure increase (RoPR) greatly improved at higher injection pressures. When compared to clean diesel, utilizing B20+ZnO Nanoparticles+ NIS dispersant at 250 bar resulted in 6%, 15%, 7%, and 7.6% improvements in CHRR, MGT, MFB, and RoPR, respectively. The correlation coefficient (R2) for B20+ZnO NPs+ NIS (1:1) for CHRR, MGT, MFB and RoPR is 0.975, 0.978, 0.966 and 0.9883 when compared to GO nanoparticle inclusions, considering it as optimum combination and an efficient fuel. When compared to other fuel samples, the CHRR, MGT, MFB and RoPR for B20+ZnO NPs+ NIS are 2.484%, 3.2%, 2.6% and 1.25% higher, respectively, according to a statistical analysis conducted by design expert.

The eco‐friendly synthesis and thorough characterization of a ternary nanocomposite graphene oxide (GO), zinc oxide (ZnO), and silver nanoparticles (AgNPs) were investigated. Rosemary extract was utilized as a green reducing and oxidizing agent, enabling sustainable nanoparticle synthesis. Gas Chromatography‐Mass Spectrometry (GC‐MS) analysis identified active compounds facilitating nanoparticle formation, such as Globule, Ylangenal, trans‐Caryophyllene, and others. UV–vis spectroscopy confirmed the successful synthesis of AgNPs, ZnO, and GO, with characteristic peaks observed at 408, 360, and 233 nm, respectively. Fourier Transform Infrared (FTIR) spectroscopy revealed functional groups indicative of electrostatic interactions between components. X‐Ray Diffraction (XRD) analysis validated the crystallinity of ZnO and AgNPs, showing hexagonal wurtzite and face‐centered cubic structures, respectively, with average particle sizes of 24.6 nm (ZnO), 31.9 nm (AgNPs), and 18.37 nm for the composite. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images revealed morphological features, including GO sheets and AgNP and ZnO agglomerates, confirming the composite's structural integrity. Zeta potential measurements indicated high colloidal stability (−36.2 mV), attributed to the dominant influence of GO. Raman spectroscopy demonstrated structural improvements in GO upon composite formation, with a decreased ID/IG ratio (from 0.93 to 0.89), suggesting reduced defects. This comprehensive study highlights the synergistic properties of GO‐ZnO‐Ag nanocomposites, offering enhanced functionality for biomedical and biological applications.

Recently, nanoimprint lithography (NIL) has gained great attention as an effective patterning technology in the fields of light emitting diodes (LEDs), solar cells, and other optical devices, because of its simplicity and cost effectiveness. The aim of this study is the development of an imprint resin containing dispersed zinc oxide (ZnO) nano-particles that is applicable in the UV NIL process. UV NIL uses conventional monomer-based resins, which contain a UV initiator, but restricts the use of imprinted structures in optical devices due to their relatively low refractive index. In order to resolve this problem, an imprint resin containing dispersed ZnO nano-particles was prepared, using which submicron-scale structures were fabricated by the UV NIL process. The haziness of submicron-scale ZnO nano-particle resin structures and the refractive index of the ZnO nano-particle dispersion resin were measured to analyze the optical properties of the ZnO nano-particle dispersion resin and the resulting structures.

The present study endeavors toward the investigation on the bioactivity of nanofibrous scaffolds manufactured by the electrospinning process. Nanofibrous composite scaffolds of PCL with 45S5 bioactive glass and metal oxide nanoparticles were developed and characterized. The effects of incorporating silver (Ag), graphene oxide (GO), and zinc oxide (ZnO) nanoparticles into PCL/bioglass nanofibrous scaffolds on its geometry and physiochemical, morphological, mechanical, and biological properties were studied. The incorporation of GO and ZnO alters the fiber diameter, suggesting the methodology for controlling the porosity of the scaffolds. The results of FTIR and XRD confirm the structure of bioglass, Ag, GO and ZnO nanoparticles. The in vitro degradation studies in SBF solution provide evidence for the enhancement in the rate of apatite formation by the inclusion of nanoparticles as compared with PCL/BG scaffolds. The assessment of mechanical properties suggests the tensile strength was increased from 1.61 to 5 MPa in PCL/BG/ZnO system when compared with pristine PCL. The cell viability is also observed to be improved from 72% to 91% and 104% for PCL/BG/GO and PCL/BG/ZnO, respectively. The hemolytic activity studies confirm that all scaffolds are nonhemolytic in nature and PCL/BG/ZnO exhibits the least hemolytic activity of 0.65% among the other composite scaffolds, suggesting the better blood compatibility. The present study evidently shows the fact that incorporation of GO and ZnO nanoparticles with PCL in addition to BG accelerates the bioactivity and improves the mechanical strength of the scaffold.

Influence of graphene oxide on the dielectric properties of biogenically synthesized ZnO nanoparticles

The development of active and stable heterogeneous Fenton-like catalysts have emerged as an alternative to overcome the practical limitations related to the homogeneous Fenton catalyst, where various iron species and/or iron oxides are immobilised within the structure of different catalyst supports. Clay, alumina, zeolite and carbonaceous materials such as activated carbon and carbon nanotubes have been used as catalyst supports of choice by the scientific community. However, there is a knowledge gap associated with using high aspect ratio 2D (dimension) graphene oxide (GO) as an alternative catalyst support. Of particular interest, it is postulated that the structure and functionalities of GO as a support confers to the resultant catalyst overall catalytic activity beyond the conventional Fenton catalysts. In this thesis, the structural and physicochemical properties of resultant catalyst with their corresponding catalytic activity were systematically investigated. To this end, the synergistic interaction between GO and immobilised iron oxide nanoparticles (Fe3O4 NPs) was proposed for an oxidative degradation of synthetic dye acid orange 7 (AO7), which is a major water pollutant from textile production. The GO‒Fe3O4 nanocomposites were initially synthesised through a facile one-pot method by co-precipitating irons salts onto GO sheets in a basic solution. The formation of GO‒Fe3O4 was postulated as follows: (i) Fe3+/ Fe2+ ions are adsorbed and coordinated by the carboxyl groups (C=O) of GO sheets, (ii) hydrolysed ions form nanoclusters on GO sheets when NaOH is introduced, (iii) followed by condensation of the nanoclusters to form Fe3O4 nuclei, and (iv) further nucleation and growth of Fe3O4 crystallites on GO sheets were due to the redox reaction as the pH is increased to 10. The incorporation of GO led to an enhancement on the catalytic activity of the nanocomposites with 76% AO7 removal over the control catalysts of Fe3O4 NPs and GO sheets, which corresponds to 48 and 22%, respectively. Further improvements on the catalytic activity of GO‒Fe3O4 were performed by modifying the synthesis through pre-hydrolysing iron salts prior to GO addition at pH 4 with various GO loadings. The key finding of this new method is the formation of two sets of different mesoporous structure. At low GO loadings ≤10 wt%, GO–Fe3O4 nanocomposites resulted in high surface area up to 409 m2 g-1, in tandem with high 92‒98% degradation of AO7. By contrast, GO loadings >10 wt% led to reduced surface area and lower GO‒Fe3O4 activity (60%). The presence of strong interfacial interactions (Fe–O–C bonds) in the nanocomposites contributed to the superior degradation of AO7, in tandem with structural-morphological features. The operational conditions of heterogeneous Fenton-like reaction were evaluated and modelled as a function of nanocomposites dosage, pH, temperature, oxidant and dye concentrations. Best results showed a fast 80% degradation in ~20 min, whilst ~98% of AO7 was successfully removed after 180 min of reaction time. Optimal conditions were determined for nanocomposites (GO(5wt%)‒Fe3O4) at the catalyst dosage of 0.2 g L-1, initial pH of 3 and 22 mM of H2O2 concentration at 298 K. The kinetics for the oxidative degradation of AO7 was found to be a pseudo-first-order reaction following the Langmuir-Hinshelwood mechanism. A noteworthy finding was the high activity (>98%) and recyclability of GO‒Fe3O4 over 7 cycles whilst the Fe3O4 NPs exhibited a severe loss of activity (~0%) at the 5th cycle. It was found that the ratio of Fe3+/Fe2+ for GO‒Fe3O4 remained almost constant over the 7 cycles, contrary to Fe3O4 NPs which underwent a significant Fe2+ decrease. The synergistic effect of GO in the GO‒Fe3O4 nanocomposite was able to accelerate the ≡Fe3+/≡Fe2+ redox cycles for the fast reduction of ≡Fe3+ to ≡Fe2+ which is actively participating in the decomposition of adsorbed H2O2 into HO• radicals during catalysis. The X-ray photoelectron spectroscopy (XPS) analysis of spent GO‒Fe3O4 showed that the sp2 carbon domains (C=C) slightly decreased after every cycle, thus suggesting some degree of oxidation of the carbon basal plane. It is therefore postulated that the unusual stability in the GO‒Fe3O4 is attributed to a donor-acceptor mechanism of the nanocomposites, in which the electrons donated from the oxidation of the GO are used for the regeneration of ≡Fe2+ and thus maintaining the Fe3+/Fe2+ ratio. Finally, the partial substitution of zinc (Zn) into Fe3O4 in the presence of GO was investigated, in view of the UV photocatalyst properties of zinc oxides. A slight change on the physicochemical properties of GO–Fe3-xZnxO4 lead to an increase in photocatalytic activity, where x=0.2 gave the higher degradation of AO7 in the UV-assisted Fenton-like reactions at 60 min reaction. It was found that the activity of the catalyst without GO always gave lower values ~30% of AO7 removal. Therefore, GO has proven again its beneficial use as an active component in the case of UV-assisted Fenton-like reaction as well.

This work aimed is to synthesis a well dispersed zinc oxide (ZnO) nanoparticles (NPs) decorated on graphene oxide (GO) nanosheet with a practical way by using sol-gel technique. Zinc acetate dehydrate (Zn(CH3COO) 2·2H2O) was used as precursor of ZnO and absolute ethanol as solvent. 1 weight percent (wt%), 5 wt%, 10 wt%, and 20 wt% of ZnO was decorated on GO nanosheet. A series of analysis was carried out to characterize the synthesized ZnO-decorated GO nanocomposite material. The results of XRD analysis show some long area of peak at 25° to 80° allocate for ZnO in the ZnO-decorated GO nanocomposite material. By performing zeta potential analysis, the findings show that there was increment of negative surface charge on ZnO-decorated GO nanocomposite material. The experiment result also found that the hydrodynamic particle size of ZnO-decorated GO nanocomposite material become larger when high ZnO loaded. FESEM micrographs demonstrated that spherical-shaped of ZnO NPs appeared on the GO nanosheet with further proved by EDX where the content of ZnO-decorated GO nanocomposite material was composed by 71.3 wt% of C, 17 wt% of O, and additional element of 11.7 wt% of Zn. Thus, it can summarize that the synthesized ZnO-decorated GO nanocomposite material was high in purity. The findings in this study proved that ZnO NPs loading in ZnO-decorated GO nanocomposite material were successfully synthesized by sol-gel method. A ZnO-decorated GO nanocomposite material with layering ZnO NPs on GO nanosheet was produced.

ZnO nanoparticles have drawn a widespread attention recently due to their novel properties which contribute to various applications especially in gas sensing and optoelectronic devices. This paper presents a surfactant-assisted complex wet chemical method for the controlled preparation of Zinc Oxide (ZnO) nanoparticles using zinc acetate as starting material. Here, the spherical ZnO nanoparticles with average size of less than 50 nm were successfully synthesized and their optical properties were analysed. In order to maximize its efficiency, surface modification with surfactants is vital as ZnO nanoparticles easily agglomerate. The effects of the surfactant on the average particle size and morphology of the ZnO nanoparticles were investigated using X-ray diffraction. Well dispersed ZnO nanoparticles with a uniform size distribution were obtained using Poly Vinyl Alcohol (PVA) as a surfactant. The addition of surfactants controlled the particle size and reduced the formation of agglomerates and at the same time helped to produce more homogenous and uniformly dispersed particles.