Fabrication and characterization of graphene oxide–titanium dioxide nanocomposite for degradation of some toxic insecticides

Highly Efficient Photocatalytic Degradation of Imidacloprid Based on Iron Metal-Organic Frameworks of Mesoporous NH2-MIL-88b/Graphite Carbon Nitride Nanocomposites by Visible Light Driven in Aqueous Media

Pesticides that protect crops from insects and other pests are some of the main causes of water pollution. Imidacloprid (IMC) is the most widely used insecticide in the world and should be removed from the environment. This work aims to prepare mesoporous nanocomposites to increase the photodegradation efficiency of IMC. To improve the surface properties and enhance the photocatalytic activity, mesoporous nanocomposites with different weight ratios of graphite carbon nitride (CN = 125, 250, and 500 mg) were prepared by the solvothermal method. Mesoporous NH2-MIL-88b(Fe)/graphite carbon nitride (CN = 250 mg, NH2-MCN-2) nanocomposites showed the best photocatalytic performance. To save the time and cost of the experiments, central composite design (CCD) and response surface methodology (RSM) were used and the results were obtained as the initial concentration of IMC (20 mg L-1), amount of photocatalyst (0.76 g L-1), pH = 5, and degradation time ∼46 min. The maximum photocatalytic degradation efficiency estimated by the model was obtained at 96.31%, which is very close to the actual value of 95.47%. The mesoporous NH2-MCN-2 nanocomposite showed excellent stability and suitable reusability with a maximum degradation of 84.5% after five cycles. Results obtained from kinetic studies indicated a rate constant value of 0.08 min-1, and isotherm models showed that equilibrium data are more consistent with the Langmuir model in photocatalytic degradation. Electrochemical experiments showed significant improvement in the electron transfer rate and photocatalytic activity of the mesoporous NH2-MCN-2 nanocomposite. Different trapping agents were used to investigate the effective active species in IMC photodegradation, and it was determined that the hole (h+) and OH radical (•OH) play the main role. The possible mechanism for IMC photocatalytic degradation was suggested by Mott-Schottky (M-S) electrochemical impedance.

Environmental Application of Graphene and Its Forms for Wastewater Treatment: a Sustainable Solution Toward Improved Public Health

Public health is seriously jeopardized in developing countries due to poor sanitation and the presence of persistent pollutants in natural water bodies. Open dumping, wastewater discharge without proper treatment and atmospheric fallout of the organic and inorganic pollutants are the main causes behind the poor condition. Some of the pollutants pose a greater risk due to their toxicity and persistence. Such a class of pollutants are known as chemical contaminants of emerging concern (CECC), including antibiotics and drug residues, endocrine disruptors, pesticides and micro- and nano-plastics. Conventional treatment methods cannot treat them properly and are often associated with several disadvantages. However, the chronological development of techniques and materials for their treatment has exhibited graphene as an efficient candidate for environmental remediation. This current review considers the various graphene-based materials, their properties, advancement in synthesis methods with time and their detailed application in removing dyes, antibiotics and heavy metals. It has been discussed how graphene and its derivatives exhibit unique electronic, mechanical, structural and thermal properties. In this paper, the mechanism of adsorption and degradation using these graphene-based materials has also been discussed vividly. In addition to this, a bibliographic analysis was performed to identify the trend of research related to graphene and its derivatives in the adsorption and degradation of pollutants round the globe reflected by the publications. Therefore, this review can be instrumental in understanding the fact that further development of graphene-based materials and their mass production can provide a very effective and economical wastewater treatment method.

Zinc oxide doped on reduced graphene oxide nanosheets activated by solar radiation for degradation of organic pollutants and bacterial inactivation

Metal ion-based nanocomposite materials were recognized to exhibit a wide range of photocatalytic and biological applications. This study aims to synthesize zinc oxide doped reduced graphene oxide (ZnO/RGO) nanocomposite in sufficient quantities through the sol-gel method. The physical characters of the synthesized ZnO/RGO nanocomposite were determined by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Energy-dispersive X-ray (EDS) and Transmission electron microscopy (TEM) techniques. The TEM image results revealed rod-like morphology of the ZnO/RGO nanocomposite. The X-ray photoelectron spectral data revealed the formation of ZnO nanostructures representing the banding energy gap value of 1044.6 and 1021.5 eV positions. Moreover, ZnO/RGO nanocomposites displayed excellent photocatalytic degradation with a degradation efficiency of 98.6%. This research not only demonstrates the photocatalytic efficiency of zinc oxide-doped RGO nanosheets but also illustrates the antibacterial efficacy against two different bacterial pathogens including Gram-positive E. coli and Gram-negative S. aureus. Furthermore, this research highlights an eco-friendly and inexpensive preparation of nanocomposite material for a wide range of environmental applications.

Multidrug-resistant Aeromonas bacteria prevalence in Nile tilapia broodstock

BACKGROUND

Aeromonas hydrophila is an opportunistic pathogen. Thus, it has received significant attention mainly in the fish sectors with high production scales. Nile tilapia broodstock confined in the environment of fish hatcheries can be stressed. Hence, they are vulnerable to A. hydrophila.

RESULTS

Sequencing of the gyr B gene revealed the presence of 18 different A. hydrophila strains (kdy 10,620-10,637), which were deposited in the NCBI under accession numbers ON745861-ON745878. The median lethal doses of the isolates ranged from 2.62 × 10⁴ to 3.02 × 10⁶ CFU/mL. Antibiotic resistant genes, sulfonamide (sul1) and tetracycline (tetA) were found in the eighteen isolates. Approximately 83.3% of A. hydrophila strains were sensitive to ciprofloxacin and florfenicol. Further, eight A. hydrophila strains had high MDR indices at 0.27-0.45. All isolates presented with hemolysin activity. However, only 72.22% of them had proteolytic activity, and only 61.11% could form biofilms. Bacterial isolates harbored different pattern virulence genes, the heat-stable cytotonic enterotoxin (ast), cytotoxic enterotoxin (act), and hemolysin (hly) genes were the most prevalent. Also, a trial to inhibit bacterial growth was conducted using titanium dioxide nanoparticles (TiO₂ NPs) with three sizes (13, 32, and 123 nm). If A. hydrophila strains with a high MDR index were tested against TiO₂ NPs (20 µg/mL) for 1, 12, and 24 h, those with a small size had a greater bactericidal action than large ones. Bacterial strains were inhibited at different percentages in response to TiO₂ NP treatment.

CONCLUSIONS

Nile tilapia broodstock, mortality is associated with different A. hydrophila strains, which harbored virulent and MDR genes. Furthermore, TiO₂ NPs had bactericidal activity, thereby resulting in a considerable reduction in bacterial load.

Synergistic effects of structural, crystalline, and chemical defects on the photocatalytic performance of Y-doped ZnO for carbaryl degradation

In this study, a photocatalytic material consisting of ZnO and yttrium-doped ZnO (YZO) nanoparticles was obtained via a facile precipitation conducted under ambient pressure whereby crystalline ZnO was successfully doped with yttrium. YZO had a hexagonal wurtzite polycrystalline structure with smaller crystal and grain sizes than ZnO, which in turn meant larger specific surface area and pore volume. Chemical defects were also produced, which facilitated photocatalytic activity, because such defects can act as reaction centers. The optical band gap magnitude and the diamagnetic nature of YZO were also determined. The structural, crystalline, and chemical defects of YZO synergistically enhanced the photocatalytic degradation of carbaryl; indeed, the kinetic rate constant of this reaction catalyzed by YZO was 11.17 × 10^-2 min^-1 under natural sunlight irradiation, higher than the value measured for ZnO (8.68 × 10^-2 min^-1). Evidence thus indicates that yttrium-doping effectively modified some properties of ZnO nanoparticles so that YZO nanoparticles proved a suitable photocatalytic material for carbaryl degradation.

Effective Removal of Metal ion and Organic Compounds by Non-Functionalized rGO

Effective removal of heavy metals from water is critical for environmental safety and public health. This work presents a reduced graphene oxide (rGO) obtained simply by using gallic acid and sodium ascorbate, without any high thermal process or complex functionalization, for effective removal of heavy metals. FTIR and Raman analysis show the effective conversion of graphene oxide (GO) into rGO and a large presence of defects in rGO. Nitrogen adsorption isotherms show a specific surface area of 83.5 m2/g. We also measure the zeta-potential of the material showing a value of -52 mV, which is lower compared to the -32 mV of GO. We use our rGO to test adsorption of several ion metals (Ag (I), Cu (II), Fe (II), Mn (II), and Pb(II)), and two organic contaminants, methylene blue and hydroquinone. In general, our rGO shows strong adsorption capacity of metals and methylene blue, with adsorption capacity of qmax = 243.9 mg/g for Pb(II), which is higher than several previous reports on non-functionalized rGO. Our adsorption capacity is still lower compared to functionalized graphene oxide compounds, such as chitosan, but at the expense of more complex synthesis. To prove the effectiveness of our rGO, we show cleaning of waste water from a paper photography processing operation that contains large residual amounts of hydroquinone, sulfites, and AgBr. We achieve 100% contaminants removal for 20% contaminant concentration and 63% removal for 60% contaminant concentration. Our work shows that our simple synthesis of rGO can be a simple and low-cost route to clean residual waters, especially in disadvantaged communities with low economical resources and limited manufacturing infrastructure.

Synthesis and enhanced photocatalytic application of porous nanocomposites of (r)GO/TiO2 embedded HCP (hyper crosslinked polymer)

Nanocomposites (r)GO/TiO₂/hyper crosslinked polymer (HCP) were prepared using ultrasonic-assisted method, and identified by (SEM), (EDS), (TEM), and (XRD) techniques. This study was performed to examine the effect of various operating parameters on photocatalytic degradation of Rhodamine B (Rh.B) over (r)GO/TiO₂ embedded HCP followed by an optimization study using response surface methodology (RSM) based on Box-Behnken design (BBD). The photocatalytic activity of rGO/TiO₂/polycalix[4]resorcinarene ((r)GTP) was evaluated using the cationic dye Rhodamine B as a pollutant model under solar light (intensity = 850 W/m²) between 10 and 12 am, June, Ahvaz, Iran. Response Surface Methodology was adopted for the optimization of degradation parameters viz pH, dye concentration, and nanocomposites dosage and contact time. The optimum values for the maximum Rhodamine B (Rh B) degradation of rGO/TiO₂/polycalix (rGTP) and GTP were obtained, in which the degradation of rGTP was 100% and the degradation efficiency of GO/TiO₂/polycalix (GTP) was 70%. ANOVA analysis results demonstrated that irradiation time and nanocomposite mass were the most significant parameters. It was found that rGO/TiO₂/polycalix[4]resorcinarene (rGTP) nanocomposite displayed the best degradation yield for the dye. The results showed that the rGTP nanocomposite displayed good EIS and CV properties besides being eco-friendly and reusable. It could also show a high capacity for the elimination of the dye in the industrial wastewaters.

Rapid Microwave-Assisted Synthesis of N/TiO2/rGO Nanoparticles for the Photocatalytic Degradation of Pharmaceuticals

Nanocomposites comprising nitrogen-doped TiO₂ and reduced graphene oxide (N/TiO₂/rGO), with different rGO loading qualities, were prepared by a cost-effective microwave-assisted synthesis method. The synthesized materials were broadly characterized by Raman spectroscopy, X-ray diffraction (XRD), infrared spectroscopy (FTIR), photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), electron microscopy (SEM-EDS), and nitrogen adsorption/desorption isotherms. Anatase was the only crystalline phase observed for all synthesized materials. The rGO loading did not affect the morphological properties, but it positively influenced the photocatalytic activity of the nanocomposite materials, especially at low rGO loading. Photocatalysts were evaluated via the degradation of specific organic micropollutant (OMP) pharmaceuticals: ciprofloxacin (CIP), diclofenac (DCF), and salicylic acid (SA), under different radiation sources: ultraviolet A (UVA), solar light simulator (SLS), blue visible light (BVL) and cold visible light (CVL). CIP and SA were removed effectively via the synergy of adsorption and photocatalysis, while DCF degradation was achieved solely by photocatalysis. After implementing scavenger agents, photocatalytic degradation processes mainly depended on the specific pollutant type, while irradiation sources barely defined the photocatalytic mechanism. On the other hand, changes in irradiation intensity significantly influenced the photolysis process, while photocatalysis was slightly affected, indicating that irradiation spectra are more relevant than intensity.

Enhanced Antibacterial Performance of Chitosan/Corn Starch Films Containing TiO2/Graphene for Food Packaging

Chitosan (CTS)/corn starch (CSH)/nano-TiO₂/graphene (Gr) antibacterial active packaging films were prepared by ultrasonic-assisted electrospray deposition and solution-casting methods, and the effects of the TiO₂:Gr mass ratio and ultrasonication power on their morphology and mechanical, optical, thermal, barrier, and antibacterial properties were investigated. The film fabricated at a TiO₂:Gr ratio of 6:4 and an ultrasonication power of 160 W exhibited a uniform distribution of the nanofillers in the CTS/CSH matrix and significantly enhanced the mechanical, barrier, and water-resistance properties. Furthermore, this film demonstrated superior ultraviolet and visible light-shielding characteristics as compared with those of the non-filled CTS/CSH film, while its Escherichia coli and Staphylococcus aureus inhibition efficiencies were equal to 96.67 ± 0.09% and 99.85 ± 0.13%, respectively. Therefore, the film can effectively prevent food spoilage, indicating its potential for food-packaging applications.

Challenges and effectiveness of nanotechnology-based photocatalysis for pesticides-contaminated water: A review

Pesticides have been frequently used in agricultural fields. Due to the expeditious utilization of pesticides, their excessive usage has negative impacts on the natural environment and human health. This review discusses the successful implications of nanotechnology-based photocatalysis for the removal of environmental pesticide contaminants. Notably, various nanomaterials, including TiO₂, ZnO, Fe₂O₃, nanoscale zero-valent iron, nanocomposite-based materials, have been proposed and have played a progressively essential role in wastewater treatment. In addition, a detailed review of the crucial reaction condition factors, including water matrix, pH, light source, temperature, flow rate (retention time), initial concentration of pesticides, a dosage of photocatalyst, and radical scavengers, is also highlighted. Additionally, the degradation pathway of pesticide mineralization is also elucidated. Finally, the challenges of technologies and the future of nanotechnology-based photocatalysis toward the photo-degradation of pesticides are thoroughly discussed. It is expected that those innovative extraordinary photocatalysts will significantly enhance the performance of pesticides degradation in the coming years.

Spectroscopic study of self-assembly of anti-hepatitis C virus sofosbuvir drug with bio-polymeric nanoparticles for improving the drug release effect

Self-assembly of Sofosbuvir drug (SOF) anti-hepatitis C virus (HCV) with bio-polymeric nanoparticles such as chitosan nanoparticles (Cs NPs) and polyvinyl alcohol nanoparticles (PVA NPs), the novel composites have been characterized successfully by different analysis such as Energy-dispersive X-ray spectroscopy (EDX), Scanning electron microscopy (SEM), UV-Visible spectrophotometer (UV-Vis) and Fourier Transmittance Infrared (FT-IR). The improvement of the Sofosbuvir effect as a result of loading drug on the bio-polymer NPs surface has been detected by the UV-Vis, and fluorescence spectroscopy techniques. The improvement of SOF efficiency was revealed via studying the drug release of SOF from biopolymers NPs surface at pH 7.4, UV-Vis spectra used for the releasing process. The binding constant (K_b) value was reported at 0.000055 and 0.3613 min^-1 for Cs and PVA NPs respectively. Also, the value of K_SV was documented at 0.0014 and 7.16 min^-1 for Cs@SOF and PVA@SOF hybrid nanocomposite. The incorporation rate (k) of SOF on the surface of biopolymer nano molecules was calculated to be 0.00812 and 0.0165 min^-1 for Cs and PVA NPs, respectively. Besides the observed value of (n) was close to the unit 0.74 and 0.86 for Cs and PVA NPs, respectively. The SOF released from Cs NPs surface was documented at 0.09 mg after 24 h, while PVA NPs reported at 0.7 mg at the same time and the release efficiency is 56.5 and 73% for Cs@SOF and PVP@SOF, respectively. From the results, we suggest Cs/SOF and PVA/SOF hybrid nanocomposites have spectroscopic results that make them promising candidate drugs, but need to the clinical trials.

Sandwich nanohybrid of chitosan-polyvinyl alcohol for water treatment and Sofosbuvir drug delivery for anti-hepatitis C virus (HCV)

The incorporation between nano-polyvinyl alcohol (PVA) and nano-chitosan (Cs) to produce sandwich nanohybrid (SNH) for water treatment and improvement the adsorption of sofosbuvir drug (SOF). The photocatalytic activity and formation of reactive oxygen species (ROS) were detected with oxidation of organic dyes such as Rhodamine B (RhB), methylene blue (MB), and methyl orange (MO). The effect of SNH on the release of SOF in blood and inside the cells at pH 7.4 and pH 6.8, respectively were observed by UV-Visible spectroscopy (UV-Vis). The binding constant (K_b) was reported at 0.0035 min^-1 and the loading constant at 0.0024 min^-1, while the release efficiency was 42.6% at pH 7.4 and 74.7% at pH 6.8. The efficiency of photocatalytic activity against organic dyes MO, MB, and RhB are detected at 2.4% and 1%, and 42%, respectively. The cytotoxicity of SNH has been observed with MDA-MB-231 and HepG2 cell line with three concentrations of SNH, where the little concentration has low effect on the HepG2 and high viability, this result was reversed with the high concentration, also the yellow color due to the lysis of the cells. The antioxidant of the SNH was detected by FRAP technique.

Photocatalytic Detoxification of Some Insecticides in Aqueous Media Using TiO2 Nanocatalyst

The present study was performed to fabricate a titanium dioxide (TiO₂) nanocatalyst with proper characteristics for the removal of some insecticides (dimethoate and methomyl) from aqueous media. A TiO₂ catalyst of regular (TiO₂-commercial-/H₂O₂/UV) or nano (TiO₂-synthesized-/H₂O₂/UV) size was employed as an advanced oxidation process by combining it with H₂O₂ under light. Moreover, the total detoxification of insecticides after treatment with the most effective system (TiO₂(s)/H₂O₂/UV) was also investigated through exploring the biochemical alterations and histopathological changes in the liver and kidneys of the treated rats. Interestingly, the present study reported that degradation rates of the examined insecticides were faster using the TiO₂ catalyst of nano size. Complete degradation of the tested insecticides (100%) was achieved under the TiO₂(s)/H₂O₂/UV system after 320 min of irradiation. The half-life values of the tested insecticides under H₂O₂/TiO₂(c)/UV were 43.86 and 36.28 for dimethoate and methomyl, respectively, whereas under the H₂O₂/TiO₂(c)/UV system, the half-life values were 27.72 and 19.52 min for dimethoate and methomyl, respectively. On the other hand, no significant changes were observed in the biochemical and histopathological parameters of rats administrated with water treated with TiO₂(s)/H₂O₂/UV compared to the control, indicating low toxicity of the TiO₂ nanocatalyst-. Altogether, the advanced oxidation processes using TiO₂ nanocatalyst can be considered as a promising and effective remediation technology for the complete detoxification of methomyl and dimethoate in water. However, further future research is needed to identify the possible breakdown products and to verify the safety of the used nanomaterials.

Photocatalytic degradation of amoxicillin from aqueous solutions by titanium dioxide nanoparticles loaded on graphene oxide

The photocatalytic degradation of amoxicillin (AMX) by titanium dioxide nanoparticles loaded on graphene oxide (GO/TiO₂) was evaluated under UV light. Experimental results showed that key parameters such as initial pH, GO/TiO₂ dosage, UV intensity, and initial AMX concentration had a significant effect on AMX degradation. Compared to the photolysis and adsorption processes, the AMX degradation efficiency was obtained to be more than 99% at conditions including pH of 6, the GO/TiO₂ dosage of 0.4 g/L, the AMX concentration of 50 mg/L, and the intensity of 36 W. Trapping tests showed that all three hydroxyl radical (OH^•), superoxide radical (O₂^•-), and hole (h⁺) were produced in the photocatalytic process; however, h⁺ plays a major role in AMX degradation. Under UV irradiation, GO/TiO₂ showed excellent stability and recyclability for 4 consecutive reaction cycles. The analysis of total organic carbon (TOC) suggested that AMX could be well degraded into CO₂ and H₂O. The formation of NH₄⁺, NO₃^-, and SO₄^2- as a result of AMX degradation confirmed the good mineralization of AMX in the GO/TiO₂/UV process. The toxicity of the inlet and outlet samples of the process has been investigated by cultivation of Escherichia coli and Streptococcus faecalis, and the results showed that the condition is suitable for the growth of organisms. The photocatalytic degradation mechanism was proposed based on trapping and comparative tests. Based on the results, the GO/TiO₂/UV process can be considered as a promising technique for AMX degradation due to photocatalyst stability, high mineralization efficiency, and effluent low toxicity.

A novel graphene oxide decorated with halloysite nanotubes (HNTs/GO) composite used for the removal of levofloxacin and ciprofloxacin in a wide pH range

A novel HNTs/GO composite used for the removal of levofloxacin and ciprofloxacin in a wide pH range.

Transparent floatable magnetic alginate sphere used as photocatalysts carrier for improving photocatalytic efficiency and recycling convenience

Practical application of powder photocatalysts is far from satisfying due to their low photon utilization, inconvenient recovery and potential environmental risk. In this study, an easily recoverable, environmentally friendly and highly transparent floatable magnetic photocatalyst carrier was prepared based on biopolymer alginate and Fe₃O₄ particles. Further, three different types of photocatalysts were chosen as model semiconductor photocatalysts and loaded on the shell of the carriers. The freeze process facilitated the formation of internal cavities that enhanced floating ability and transparency of the spheres. Meanwhile, the excellent floating performance offered massive reaction sites for pollutants reacting with photocatalysts, O₂ and photons on the air/water interface. Photodegradation results showed all three floatable hybrid photocatalysts exhibited enhanced photocatalytic efficiencies compared to the virgin photocatalysts. In short, the carrier can integrate excellent floating ability, environmental friendliness and full recycling with good stability, and it can greatly improve the photocatalytic efficiency of various powder semiconductor photocatalysts.

Recent Strategies for Environmental Remediation of Organochlorine Pesticides

The amount of organochlorine pesticides in soil and water continues to increase; their presence has surpassed maximum acceptable concentrations. Thus, the development of different removal strategies has stimulated a new research drive in environmental remediation. Different techniques such as adsorption, bioremediation, phytoremediation and ozonation have been explored. These techniques aim at either degrading or removal of the organochlorine pesticides from the environment but have different drawbacks. Heterogeneous photocatalysis is a relatively new technique that has become popular due to its ability to completely degrade different toxic pollutants—instead of transferring them from one medium to another. The process is driven by a renewable energy source, and semiconductor nanomaterials are used to construct the light energy harvesting assemblies due to their rich surface states, large surface areas and different morphologies compared to their corresponding bulk materials. These make it a green alternative that is cost-effective for organochlorine pesticides degradation. This has also opened up new ways to utilize semiconductors and solar energy for environmental remediation. Herein, the focus of this review is on environmental remediation of organochlorine pesticides, the different techniques of their removal from the environment, the advantages and disadvantages of the different techniques and the use of specific semiconductors as photocatalysts.

Graphene oxide in the remediation of norfloxacin from aqueous matrix: simultaneous adsorption and degradation process

In the present study, the simultaneous adsorption degradation of norfloxacin (NOR) by graphene oxide from aqueous matrix was verified. Graphene oxide (GO, ~ 8 layers) was prepared using modified Hummers method through the oxidation/exfoliation of expanded graphite. Spectroscopic techniques confirmed the NOR adsorption onto GO surface and the partial antibiotic degradation promoted by hydroxyl radicals derived from GO. Furthermore, the mass spectra after the adsorption-degradation processes showed NOR degradation intermediates that was compared and confirmed by other studies. The nanomaterial showed a removal capacity of 374.9 ± 29.8 mg g-1, observing greater contribution from the NOR in the zwitterionic form and removals up to 94.8%. The intraparticle diffusion process, assessed by Boyd's model and Fick's law, presented a greater contribution in the removal process, reaching the equilibrium 30 min after the beginning. In addition, the temperature increase would disadvantage the process, which was considered thermodynamically viable throughout the evaluated temperature range. Finally, the process was scaled-up in a single stage batch adsorber considering a NOR removal efficiency of 95%. This resulted in mass requirement of 63.6 g of GO in order to treat 0.5 m3 of contaminated water. In general, the simultaneous adsorption-degradation process was considered innovative and promising in pharmaceutical compounds remediation.

Preparation of Reduced Graphene Oxide Aerogel and Its Adsorption for Pb(II)

In this study, reduced graphene oxide (rGO) aerogels were successfully prepared using a facile hydrothermal method and determined with Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area, and scanning electron microscopy. The rGO aerogels were used to remove Pb(II) from aqueous solution, and the adsorption performance of rGO aerogels was investigated. In addition, the adsorption-desorption cycle experiments were carried out to evaluate the recyclability and stability of rGO aerogels. The adsorption data were consistent with the pseudo-second-order kinetic model and Langmuir isotherm model. The experimental results showed that rGO aerogels have good adsorption capacity for Pb(II) and can be utilized for wastewater treatment.

Absorption Behavior of Graphene Nanoplates toward Oils and Organic Solvents in Contaminated Water

In this work, graphene nanoplates (GNPs) were successfully prepared via direct chemical exfoliation from natural graphite. The properties of prepared GNPs were investigated using scanning electron microscopy and X-ray diffraction. The resultant GNPs had a low bulk density of 0.015 g mL−1, C content of 99.6%, a lateral diameter of 5–15 µm, and thickness of <15 nm, respectively. The absorption capacity of the GNPs for a range of oils and organic solvents including pump oil, polydimethylsiloxane oil (PDMS), dioctyl phthalates (DOP) oil, olive oil, bean oil, mazut oil, xylene, ethanol, and ethylene glycol (EG) was evaluated. The effects of the sorption conditions such as the absorption time (sorption kinetics), temperature, and aging manner (static, stirring, and ultrasonic) on the absorption capability of the GNPs were also investigated. It could be seen that the GNPs revealed extremely high absorption capacities for oil and organic solvents, reaching 21–42 times their own weight only after 2 min of absorption at room temperature, which were found to be much higher than those shown by various commercially available absorbents.

Amperometric sandwich immunoassay for determination of myeloperoxidase by using gold nanoparticles encapsulated in graphitized mesoporous carbon

An ultrasensitive sandwich-type electrochemical immunosensor was developed for the amperometric determination of serum myeloperoxidase (MPO). The method is making use of (a) gold nanoparticles encapsulated in graphitized mesoporous carbons (AuNP@GMC); and (b) horseradish peroxidase (HRP) labeled secondary antibody (HRP@Ab₂) immobilized on AuNP@GMC. MPO capture antibody (Ab₁) was immobilized on the electrode modified with an AuNP-graphene oxide nanocomposite. The sandwich immunoreaction leads to the formation of the complex composed of Ab₁, MPO, and HRP@Ab₂. An amplified electrochemical signal is produced by electrocatalytic reduction of H₂O₂ (at a typical voltage of -0.18 V vs. Ag/AgCl) in the presence of enzymatically oxidized thionine. The peak current of thionine was measured using differential pulse voltammetry. Under optimized steady-state conditions, the reduction peak increases in the 1 to 300 pg.mL^-1 MPO concentration range, and the detection limit is 0.1 pg.mL^-1 (at S/N = 3). Graphical abstract Schematic presentation of AuNP-GO based sandwich-type electrochemical immunoassay for the determination of myeloperoxidase by using gold nanoparticles encapsulated in graphitized mesoporous carbons (AuNP@GMC) as a carrier for horseradish peroxidase (HRP) labeled secondary antibody (HRP@Ab₂).

Simple, selective detection and efficient removal of toxic lead and silver metal ions using Acid Red 94

Toward the goal of detecting toxic elements and removing them from drinking water, we report herein the utilization of Acid Red 94 (AR94) in sensing the hazardous metal ions in water. Among the various examined metal ions (Ag⁺, Pb²⁺, K⁺, Mn²⁺, Zn²⁺, La³⁺, Hg²⁺, Ca²⁺, Cd²⁺, Co²⁺, and Ni²⁺), the UV-visible absorption spectra showed high selectivity and sensitivity for toxic silver and lead metal ions in an aqueous solution. The observed absorption spectral changes and the rapid color changes confirm complex formation between AR94 and both Ag⁺ and Pb²⁺ metal ions. The emission measurements showed the significant fluorescence quenching of the singlet excited state of AR94 in the presence of Ag⁺ and Pb²⁺ metal ions suggesting the formation of an irradiative dye-metal complex under the prevailing experimental conditions. In order to remove the accumulated complexes of AR94 with silver metal ions, safe and harmless mesoporous titanium dioxide was utilized efficiently in removing the complexes with adsorption capacities of 91% at 30 minutes. These findings suggest a simple, fast and efficient method for both detecting silver in water, and removing the formed AR94-metal complexes in water. In addition, AR94 is shown to be a good sensor for the presence of Ag and Pb nanoparticles, NPs, in aqueous solution. The absorption and emission spectra of AR94 showed significant changes that may be rationalized by the strong electromagnetic coupling induced by NPs plasmonic effects. These findings render AR94 a sensitive and selective sensor and a visual indicator for the qualitative and quantitative detection of silver ions, lead ions and their nanoparticles.

Graphene oxide decorated with zinc oxide nanoflower, silver and titanium dioxide nanoparticles: fabrication, characterization, DNA interaction, and antibacterial activity

The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined. The fabricated nanocomposites were characterized by various techniques including X-ray diffraction, ultraviolet-visible light absorption and fluorescence spectroscopy, Brunauer–Emmett–Teller theory analysis, Fourier transform infrared, and scanning electron microscopy. The antibacterial activity of the GO–metal oxide nanocomposites against two Gram-positive and two Gram-negative bacteria was examined by using the standard counting plate methodology. The results showed that the fabricated nanocomposites on the surface of GO could inhibit the growth of microbial adhered cells, and consequently prevent the process of biofilm formation in food packaging and medical devices. To confirm the antibacterial activity of the examined GO-nanocomposites, we examined their interactions with bovine serum albumin (BSA) and circulating tumor DNA (ctDNA) by steady-state fluorescence spectroscopy. Upon addition of different amounts of fabricated GO-nanocomposites, the fluorescence intensities of the singlet states of BSA and ctDNA were considerably quenched. The higher quenching was observed in the case of GO–Ag–TiO₂@ZnO nanocomposite compared with other control composites.

The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined.