Efficient degradation of dye pollutants in wastewater via photocatalysis using a magnetic zinc oxide/graphene/iron oxide-based catalyst

In this paper, we present a proof-of-concept study of the enhancement of photocatalytic activity via a combined strategy of fabricating a visible-light responsive ternary heterostructure and improving overall photostability by incorporating magnetic zinc oxide/graphene/iron oxide (ZGF). A solvothermal approach was used to synthesize the catalyst. X-ray diffraction (XRD), scanning electron microscopic, energy dispersive X-ray, transmission electron microscopic, vibrating sample magnetometric, and ultraviolet–visible diffuse reflectance spectroscopic techniques were used to characterize the synthesized samples. The obtained optimal Zn(NO_(3))_(2) concentration, temperature, and heating duration were 0.10 mol/L, 600℃, and 1 h, respectively. The XRD pattern revealed the presence of peaks corresponding to zinc oxide, graphene, and iron oxide, indicating that the ZGF catalyst was effectively synthesized. Furthermore, when the developed ZGF was used for methylene blue dye degradation, the optimum irradiation time, dye concentration, catalyst dosage, irradiation intensity, and solution pH were 90 min, 10 mg/L, 0.03 g/L, 100 W, and 8.0, respectively. Therefore, the synthesized ZGF system could be used as a catalyst to degrade dyes in wastewater samples. This hybrid nanocomposite consisting of zinc oxide, graphene, and iron oxide could also be used as an effective photocatalytic degrader for various dye pollutants.

Synthesis of surface imprinted polymers based on wrinkled flower-like magnetic graphene microspheres with favorable recognition ability for BSA

Nowadays,the employing of molecular imprinting technique in the analysis and separation of proteins from complex biological samples has been widely favored by researchers.To enrich the types of surface protein imprinted materials and expand the application fields of graphene materials,novel surface molecular imprinted polymers(MIPs)based on magnetic graphene microspheres Fe_(3)O_(4)@r GO@MIPs are first synthesized in this paper.Fe_(3)O_(4)@r GO@MIPs are prepared by oxidative self-polymerization of dopamine on the surface of magnetic graphene(Fe_(3)O_(4)@r GO)composite microspheres.Bovine serum albumin(BSA)is selected as protein template.Fe_(3)O_(4)@r GO microspheres with wrinkled flower-like structure are obtained by compounding Fe_(3)O_(4)and graphene oxide in an appropriate ratio via the method of high-temperature reduction self-assembly.The microspheres exhibit promising dispersibility,high external surface area,rich pore structure,and sufficient magnetic properties.These advantages not only prevent the agglomeration of imprinted microspheres in the aqueous phase,which is conducive to contact and static adsorption,but also increase the amount of protein imprinting.Additionally,sufficient magnetic properties ensure fast and effective separation of the adsorbents.While the adsorption capacity is increased,the separation procedure becomes simple.The binding capacity of Fe_(3)O_(4)@r GO@MIPs for BSA can reach 317.58 mg/g within 60 min,and the imprinting factor(IF)is 4.24.More importantly,Fe_(3)O_(4)@r GO@MIPs can specifically recognize the target BSA from the mixed proteins and the actual sample.There is no significant decrease in the adsorption amount,IF,and magnetic properties after eight runs.It is promising to be used in the separation of proteins from the actual biological samples.

Magnetic graphene nanocomposite as an efficient catalyst for hydrogenation of nitroarenes

Graphene-Fe3O4 nanocomposite（G-Fe3O4） was synthesized by a chemical co-precipitation method which was used as an efficient catalyst for the reduction of nitroarenes with hydrazine hydrate.The method has been applied to a broad range of compounds with different properties and the yields were in the range of 75%-92%.The G-Fe3O4 catalyst can be readily recovered and reused 5 times without significant loss of the catalytic activity.

Effect of co-presence of NSAIDs with cadmium:i)evaluation of NSAIDbearing water for washing Cd from soil,ii)Cd removal from NSAIDbearing water using magnetic graphene oxide

Cadmium“Cd”is a toxic pollutant that may present in soil and water.This work evaluates:i)the use of non-steroidal anti-inflammatory drugs“NSAIDs”-bearing water for washing soil containing Cd(Ⅱ),ii)removal of Cd(Ⅱ)from NSAID-bearing water by adsorption onto magnetic graphene oxide which can be easily separated by strong magnet.The studied NSAIDs are aspirin,ketoprofen,ibuprofern and diclofenac.The Cd(Ⅱ)-NSAIDs complexes were synthesized and characterized by FT-IR.Graphene was initially oxidized by either nitric acid,or ammonium persulphate method,or Hummer's method.Magnetite was then deposited on graphene oxide to give the corresponding magnetic graphene oxides(NA-MGO,APSMGO and Hum-MGO,respectively).The effect of the following factors on Cd(Ⅱ)uptake was investigated:NSAIDs type,pH,graphene oxidation method,magnetite:graphene oxide mass ratio in the adsorbent,(Cd(Ⅱ):NSAID)molar ratio.Maximum Cd(Ⅱ)uptake was achieved using“magnetic graphene oxidized with ammonium persulphate where the mass ratio of magnetite to graphene oxide was 2:1”in the presence of diclofenac at pH6.The best Cd(Ⅱ):diclofenac molar ratio was 1:3.The maximum adsorption capacity of Cd(Ⅱ)was found to be 83 mg L1.The regeneration of the adsorbent was possible by 0.3 M HNO3 solution and 80%of adsorption efficiency was maintained after five cycles.Upon presence of coexisting ions,80%of the adsorption efficiency was maintained.Various NSAIDs-containing waters were used for washing Cd-containing soil;the maximum removal efficiencies of Cd were 18%and 16%using 5 mM diclofenac or 10 mM aspirin,respectively.Using diclofenac or aspirin-spiked real pharmaceutical wastewater gave 28%removal of Cd.The optimum adsorption method was used for removal of Cd(Ⅱ)from diclofenac-containing soil-washing water,where two successive adsorptions were needed for complete Cd uptake.

Mitochondrion targeting peptide-modified magnetic graphene oxide delivering mitoxantrone for impairment of tumor mitochondrial functions

In this study,we prepared mitochondrion targeting peptide-grafted magnetic graphene oxide(GO)nanocarriers for efficient impairment of the tumor mitochondria.The two-dimensional GOMNP-MitP nanosheets were synthesized by grafting magnetic y-Fe_(2)O_(3)to the surface of GO,followed by covalent modification of mitochondrion targeting peptide(MitP).GOMNP-MitP exhibited the high capacity of loading the anticancer drug mitoxantrone(MTX),and preferentially targeted the tumor mitochondria.With the aid of alternating magnetic field(AMF),the MTX-loading GOMNP-MitP released MTX to the mitochondria,severely impairing mitochondrial functions,including attenuation of ATP production,decrease in mitochondrial membrane potential(MMP),and further leading to activation of apoptosis.This study realized high-efficient mitochondrion-ta rgeting drug delivery for anticancer therapy by twodimensional nanoplatforms.

Reduced Graphene Oxide Coupled Magnetic CuFe2O4-TiO2 Nanoparticles with Enhanced Photocatalytic Activity for Methylene Blue Degradation

CuFe_2O_4-TiO_2/graphene nanocomposites have been prepared via a one-step hydrothermal method,and the as-prepared CuFe_2O_4-TiO_2/graphene was characterized by X-ray powder diffraction,Raman spectroscopy,scanning electron microscopy and transmission electron microscopy.The transmission electron microscopy demonstrated that CuFe_2O_4-TiO_2 nanoparticles were successfully dispersed on the graphene sheets.Photocatalytic activity of nanocomposites was evaluated in terms of degradation of methylene blue（MB） dye solution under visible light radiation.Results showed that the photocatalytic efficiency of CuFe_2O_4-TiO_2/graphene nanocomposites was higher than its individual pure oxides（CuFe_2O_4 or TiO_2） and TiO_2/graphene.The enhancing photocatalytic activity performance of the CuFe_2O_4-TiO_2/graphene nanocomposites may attributed to the mutual effect between the Cu Fe_2O_4,Ti O_2 nanoparticles and the graphene sheets.Moreover,Cu Fe_2O_4 nanoparticles have excellent magnetic property,which makes the CuFe_2O_4-TiO_2/graphene heteroarchitecture magnetically recyclable in a suspension system.

Transport and Conductance in Fibonacci Graphene Superlattices with Electric and Magnetic Potentials

We investigate the electron transport and conductance properties in Fibonacci quasi-periodic graphene superlat- rices with electrostatic barriers and magnetic vector potentials. It is found that a new Dirac point appears in the band structure of graphene superlattice and the position of the Dirac point is exactly located at the energy corresponding to the zero-averaged w^ve number. The magnetic and eleetr/c potentials modify the energy band structure and transmission spectrum in entirely diverse ways. In addition, the angular-dependent transmission is blocked by the potential barriers at certain incident angles due to the appearance of the evanescent states. The effects of lattice constants and different potentials on angular-averaged conductance are also discussed.

An electrically tunable metasurface integrated with graphene for mid-infrared light modulation

We propose a low-cost plasmonic metasurface integrated with single-layer graphene for dynamic modulation of midinfrared light. The plasmonic metasurface is composed of an array of split magnetic resonators（MRs） where a nano slit is included. Extraordinary optical transmission（EOT） through the deep subwavelength slit is observed by excitation of magnetic plasmons in the split MRs. Furthermore, the introduction of the slit provides strongly enhanced fields around the graphene layer, leading to a large tuning effect on the EOT by changing the Fermi energy of the graphene. The proposed metasurface can be utilized as an optical modulator with a broad modulation width（15 μm） or an optical switch with a high on/off ratio（〉 100）. Meanwhile, the overall thickness of the metasurface is 430 nm, which is tens of times smaller than the operating wavelength. This work may have potential applications in mid-infrared optoelectrical devices and give insights into reconfigurable flat optics and optoelectronics.

Rapid degradation of dyes in water by magnetic Fe^0/Fe_3O_4/graphene composites

Magnetic Fe^0/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption–desorption, scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FT-IR）, vibrating-sample magnetometer（VSM） measurements and X-ray photoelectron spectroscopy（XPS）. The results indicated that Fe^0/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe^0/Fe3O4/graphene and pollutants. Fe^0/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe^0/Fe3O4/graphene rapidly. After 20 min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe^0/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe^0/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water.

Preparation and application of iron oxide/persimmon tannin/graphene oxide nanocomposites for efficient adsorption of erbium from aqueous solution

Rare earth elements(REEs)are used for the developme nt of new energy materials owing to their intrinsic physicochemical property.However,excess REEs in water threaten the safety of animals,plants and humans.An efficient way to separate REEs from the water is therefore needed.In this study,a biosorbent consisting of iron oxide(Fe3 O4),persimmon tannin(PT),and graphene oxide(GO)as Fe3 O4/PT/GO was prepared,and the adsorption of trivalent erbium(Er3+)ions from aqueous solution was investigated.The adsorption process for Er3+ions conforms to pseudo-second order kinetic and the Langmuir isotherm model behavior.Thermodynamic studies indicate that the adsorption process is spontaneous and endothermic.Scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),thermogravimetric analysis(TGA).Fourier-transform infrared(FT-IR)spectroscopy;Brunauer-Emmett-Teller(BET)analysis,and vibrating sample magnetometer(VSM)were used to assess the adsorption mechanism of Er3+ions onto the Fe3 O4/PT/GO biosorbent.A combination of electrostatic interactions,redox reactivity and chelation are responsible for adsorption of Er3+ions on the Fe3 O4/PT/GO biosorbent,The magnetic Fe3 O4/PT/GO biosorbent can be easily separated under the magnetic field for effective recycle of Er3+ions from aqueous solution.Therefore,this new biomass composite holds great promise for wastewater treatment.

Fabrication of magnetic multi-template molecularly imprinted polymer composite for the selective and efficient removal of tetracyclines from water

Antibiotic contamination of the water environment has attracted much attention from researchers because of their potential hazards to humans and ecosystems.In this study,a multi-template molecularly imprinted polymer(MIP)modified mesoporous silica coated magnetic graphene oxide(MGO@MS@MIP)was prepared by the surface imprinting method via a sol-gel process and was used for the selective,efficient and simultaneous removal of tetracyclines(TCs),including doxycycline(DC),tetracycline(TC),chlorotetracycline(CTC)and oxytetracycline(OTC)from water.The synthesized MIP composite was characterized by Fourier transform infrared spectroscopy,transmission electron microscope and thermogravimetric analysis.The adsorption properties of MGO@MS@MIP for these TCs were characterized through adsorption kinetics,isotherms and selectivity tests.The MIP composite revealed larger adsorption quantities,excellent selectivity and rapid kinetics for these four tetracyclines.The adsorption process was spontaneous and endothermic and followed the Freundlich isotherm model and the pseudo-second-order kinetic model.The MGO@MS@MIP could specifically recognize DC,TC,CTC and OTC in the presence of some chemical analogs.In addition,the sorption capacity of the MIP composite did not decrease significantly after repeated application for at least five cycles.Thus,the prepared magnetic MIP composite has great potential to contribute to the effective separation and removal of tetracyclines from water.

A nanocomposite consisting of silica-coated magnetite and phenyl-functionalized graphene oxide for extraction of polycyclic aromatic hydrocarbon from aqueous matrices

In this study,graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe3O4@SiO2@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons（PAHs） from water samples.The resulting microspheres（Fe3O4@SiO2@GO-PEA） were characterized by Fourier transform-infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,CHNS elemental analysis,and vibrating sample magnetometry（VSM） techniques.The adsorbent possesses the magnetic properties of Fe3O4 nanoparticles that allow them easily to be separated by an external magnetic field.They also have the high specific surface area of graphene oxide which improves adsorption capacity.Desorption conditions,extraction time,amount of adsorbent,salt concentration,and pH were investigated and optimized.Following desorption,the PAHs were quantified by gas chromatography with flame ionization detection（GC-FID）.The limits of detection（at an S/N ratio of 3） were achieved from 0.005 to0.1 μg/L with regression coefficients（R2） higher than 0.9954.The relative standard deviations（RSDs） were below 5.8%（intraday） and 6.2%（inter-day）,respectively.The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7%and 106.7%（with RSDs of 1.6%to 8.4%,for n = 3）.The results indicated that the Fe3O4@SiO2@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.