Photodegrade Methylene Research Articles

Lignin-Derived Sustainable Nano-Platforms: A Multifunctional Solution for an Efficient Dye Removal.

In contrast to conventional non-biobased adsorbents, lignin emerges as a cost-effective and environmentally benign alternative for water treatment. This study identifies unexpected and unpredicted multifunctional properties of lignin nanoparticles (LNPs). LNPs, which are prepared by simple physical processes, demonstrated for the first time to behave as multifunctional materials able to adsorb and photodegrade methylene blue (MB) in aqueous medium upon UV irradiation. Furthermore, the synthetic approach adopted to synthesize LNPs - and therefore their surface properties - strongly affects their performances. More specifically, LNPs obtained by solvent-antisolvent nanoprecipitation (SLNPs) show the highest MB adsorption properties (98 % removal), reaching a maximum adsorption capacity of 43.0 mg g-1, and the fastest adsorption kinetics with respect to other lignin-based adsorbents. Conversely, hydrotropic LNPs (HLNPs) exhibit exceptional photocatalytic activity, resulting in 98 % MB degradation over 6 hours of UV irradiation, combined with the ability to be easily recycled and reused. The present effort paves the way for the use of LNPs as efficient multifunctional materials able to perform concurrently adsorption and photocatalytic degradation of dye pollutants, toward the creation of a sustainable biobased water treatment platform.

Novel green synthesis approach of eco-friendly magnetic/semiconductor nanocomposites as magnetically separable and reusable photocatalyst for organic dye degradation

Eco-friendly and effective separation of photocatalytic nanoparticles from the reaction mixture is crucial to facilitate their repeated use in photocatalysis. The development of magnetic/semiconductor nanocomposites with high catalytic performance and easy separation is an efficient strategy for wastewater treatments. In this study, we explore the potential of combination of magnetic (CoFe2O4) and semiconductor (ZnS) synthesized via a green approach using Moringa oleifera leaf extract as magnetically separable photocatalysts for dye degradation. X-ray diffraction analysis confirmed the presence of the cubic spinel ferrite phase of CoFe2O4 and the cubic zinc blend phase of ZnS within the nanocomposites. The micrographs illustrated nearly spherical nanoparticles with average particle sizes of 12 nm for CoFe2O4 and 26 nm for CoFe2O4/ZnS, respectively. The presence of SO suggested the incorporation of ZnS on the surface of CoFe2O4/ZnS nanocomposites. The UV–visible spectra revealed an increase in the band gap energy from 3.7 to 4.5 eV with increasing ZnS concentrations. Magnetic properties analysis signified that the CoFe2O4/ZnS nanocomposites exhibited ferromagnetic characteristics. The optimal degradation efficiency of photodegradation methylene blue was observed for CoFe2O4/ZnS 50 %, achieving 78.3 % degradation within 80 min with intervals 20 min. The magnetically separable capability allows for the recycling of nanocomposites after three consecutive cycles. Therefore, CoFe2O4/ZnS nanocomposites emerge as promising candidates as separable photocatalysts for the removal of organic pollutants in environments.

Optimization and Mechanism Elucidation of Catalytic Photodegradation Methylene Blue by TiO2/Zeolite Coal Fly Ash Nanocomposite Under H2O2 Presence

Optimization and Mechanism Elucidation of Catalytic Photodegradation Methylene Blue by TiO2/Zeolite Coal Fly Ash Nanocomposite Under H2O2 Presence

Microstructures, Optical, magnetic Properties, and photocatalytic activity of magnetically separable and reusable ZnO-Doped Fe3O4/rGO nanocomposite synthesized via green route

We report magnetically-separable, reusable, green-synthesized Fe3O4/rGO/ZnO, as heterogeneous catalyst for photo-Fenton degradation of organic pollutants in aqueous solution under certain treatments. Fe3O4 nanoparticles was green-synthesized using Moringa oleifera leaf extract, while rGO was synthesized utilizing Amaranthus viridis leaf extract. Fe3O4/rGO was composited under sonication treatment. Afterwards, Fe3O4/rGO was doped with ZnO with various concentration of ZnO. X-ray diffraction and selected area electron diffraction showed that Fe3O4 and ZnO had spinel cubic and hexagonal structure, respectively; another phase appeared as Fe2O3 spinel cubic structure. Crystallite size was decreased as the ZnO concentration increased. Morphology image showed almost spherical, non-uniform, and slightly dispersed particle under agglomerated condition, attaching to rGO sheets. The particle size of Fe3O4, Fe3O4/rGO, and Fe3O4/rGO/ZnO is 14.3; 14.1; and 10.4 nm, respectively. Fourier-transform infrared spectra showed metallic functional groups, such as Fe-O and Zn–O at 562–589 and 462–478 cm−1 also suggests nanocomposite formation. However, blue-shift absorption and band gap widening were observed with ZnO addition. Raman spectroscopy revealed the formation as-synthesized GO and rGO. Vibrating sample magnetometer showed that green-synthesized Fe3O4/rGO/ZnO exhibited superparamagnetic properties. Removal efficiency of photodegradation methylene blue was optimal for green-synthesized Fe3O4/rGO/ZnO under sonication treatment, reached 100 % degradation within 180 min for uptake every 30 min. Photodegradation was also analyzed using Langmuir-Hinshelwood kinetic model, resulting rate constant of 24.7 × 10−3 min−1 and half-life time of 28.1 min at optimum treatment. Reusability of photocatalytic activity after 3 cycles showed only a tiny drop in catalytic efficiency. Meanwhile, it possesses high stability in catalytic activity and structure. The green-synthesized Fe3O4/rGO/ZnO potential as an environmentally friendly reusable photocatalyst for wastewater degradation.

Magnetic Carbon Quantum Dots/Iron Oxide Composite Based on Waste Rice Noodle and Iron Oxide Scale: Preparation and Photocatalytic Capability.

To provide an economical magnetic photocatalyst and introduce an innovative approach for efficiently utilizing discarded waste rice noodle (WRN) and iron oxide scale (IOS), we initially converted WRN into carbon quantum dots (CQDs) using a hydrothermal method, simultaneously calcining IOS to obtain iron oxide (FeOx). Subsequently, we successfully synthesized a cost-effective, magnetic CQDs/FeOx photocatalytic composite for the first time by combining the resulting CQDs and FeOx. Our findings demonstrated that calcining IOS in an air atmosphere enhanced the content of photocatalytically active α-Fe2O3, while incorporating WRN-based CQDs into FeOx improved the electron-hole pair separation, resulting in increased O2 reduction and H2O oxidation. Under optimized conditions (IOS calcination temperature: 300 °C; carbon loading: 11 wt%), the CQDs/FeOx composite, utilizing WRN and IOS as its foundation, exhibited exceptional and reusable capabilities in photodegrading methylene blue and tetracycline. Remarkably, for methylene blue, it achieved an impressive degradation rate of 99.30% within 480 min, accompanied by a high degradation rate constant of 5.26 × 10-3 min-1. This composite demonstrated reusability potential for up to ten photocatalytic cycles without a significant reduction in the degradation efficiency, surpassing the performance of IOS and FeOx without CQDs. Notably, the composite exhibited strong magnetism with a saturation magnetization strength of 34.7 emu/g, which enables efficient and convenient recovery in photocatalytic applications. This characteristic is highly advantageous for the large-scale industrial utilization of photocatalytic water purification.

Facile fabrication of reusable starch sponge with adjustable crosslinked networks for efficient nest-trap and in situ photodegrade methylene blue

The fabrication of reusable natural polysaccharide sponges with nanoscale dispersed photocatalysts to achieve robust photocatalytic efficiency is desirable yet challenging. Herein, inspired by the nesting behavior when fishing, we designed reusable starch sponge with chemically anchored nano-ZnO into carboxylated starch matrix by thermoplastic interfacial reactions and solvent replacement for absorbing and photodegrading methylene blue (MB) in situ. The plasticization and interfacial reactions promoted a simultaneous increase in the reactivity of the starch hydroxyl/carboxyl groups and the specific surface area of ZnO. Meanwhile, the crosslinked networks of starch sponge could be adjusted by varying the ZnO and carboxylic groups contents. The results of photodegradation experiments revealed the recyclable closed-loop process of attraction-trapping-photodegradation of MB was successfully realized, achieving the effect of killing three birds with one stone. The reusable starch sponge with homogeneous dispersion of nano-ZnO by constructing three-dimensional porous channels possessed the high enrichment capacity and the remarkable photocatalysis efficiency with 150 mg/L ZnO. Under UV irradiation, the starch sponge degraded 97 % of MB with 1.67 × 10−3 min−1 photodegradation rate constant even after five cycles, which exceeded most existing photocatalytic systems. Overall, the reusable starch sponge with adjustable structure provided new insights for multifunctional bio-based photocatalyst loading systems.

Multi-application of fennel (Foeniculum vulgaris) seed composites for the adsorption and photo-degradation of methylene blue in water

This work reports on synthesis of fennel-based composites and their feasibility to remove and photo-degrade methylene blue dye from aqueous solution. Pristine fennel seeds (PFS) was impregnated with iron(III) oxide nanoparticles (Fe2O3 NP) and iron(III)-1,2,3,4-tetracarboxylic acid (Fe-TCA) to yield the composites fennel seeds-nanoparticles (FS-NP) and fennel seeds-tetracarboxylic acid (FS-TCA), respectively. Scanning electron microscope (SEM) images revealed that the surface of the adsorbents appeared to have a rough texture with cavities. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the presence of −OH, −C=O, −COC, −COOH and −CO groups that could easily bind to the dye. The physicochemical characteristics such as cation exchange capacity (CEC) and Brunauer, Emmett and Teller (BET) surface area were enhanced after impregnation compared with PFS. The maximum adsorption capacity recorded at pH 10 for PFS was 13.2 mg/g while for FS-NP and FS-TCA was 32.8 and 42.9 mg/g, respectively This was ascribed to chemical interaction such as hydrogen bond, electrostatic attraction and π-π stacking. The isotherm and kinetic data were best described by Freundlich and pseudo-first order models. Thermodynamic parameters (∆Ho and ∆Go) showed spontaneity and endothermicity respectively. The positive values of ΔSo suggests that there was increased level of freedom at solid/liquid interface. PFS showed no activity for photocatalytic degradation properties while PF-NP and PF-TCA recorded 58.9 and 48.6% efficiencies, respectively. The data revealed that pseudo-second order described the photocatalytic processes of MB better than pseudo-first order kinetics.

Synthesis of strontium oxide nanoparticlesby probe sonication method: Its photocatalytic activity and electrochemical sensor studies

In this paper, we report on the synthesis of strontium oxide nanoparticles (SONPs) using a novel probe sonication method. Powder X-ray diffraction (PXRD) was used to characterize the physicochemical properties of the prepared materials, which confirmed that the average SrO crystallite size was 43 ​nm. The Kubelka-Monk function of diffuse reflectance spectroscopy (DRS) was used to confirm the average energy gap of SONPs (4.06 ​eV). SONPs have been successfully used in conjunction with inventive photocatalysts to remove dyes such as Methylene Blue (MB) and Acid Green (AG). MBand AG dyes were used as standard dyes to investigate the photocatalytic properties of NPs when exposed to UV light and sunlight.These nanometal oxides photodegrade methylene blue (87.70%) and acid green (71.20%) dyes with remarkable efficiency when exposed to UV light. These nanometal oxides demonstrated superior sensitivity when paracetamol was used as an analyte in cyclic voltammetry tests at various scan speeds (10 ​mV/s to 50 ​mV/s). As a result, SONPs may be useful in photocatalytic activity and electrochemical sensor applications.

Preparation and Photoelectric Properties of C-LaFeO3 Composites

The C spheres synthesized by a hydrothermal method were used as a C source, which was doped with LaFeO3 to obtain C-LaFeO3 composites with different C contents (5%, 10%, 15%, and 20%). The effects of C content on the structure, morphology, and photoelectric properties of LaFeO3 were investigated experimentally. The results show that C doping does not change the crystal structure of LaFeO3. The proper amount of C doping improves the photocatalytic and electrochemical activities of the composites. However, excessive C reduces the photocatalytic and electrochemical activities of the C-LaFeO3 composites. Comparing the different C contents, when the C content is 15%, the photocatalytic performance of C-LaFeO3 photodegrading methylene blue solution (MB) under visible light is the best, reaching an efficiency of 97%. In addition, electrochemical tests in a 6 M KOH electrolyte solution demonstrate that C doping significantly improves the redox reaction capacity, and the specific capacitance of 15% C-LaFeO3 (466.08) F/g) at a current density of 0.5 A/g is about 2.5 times that of LaFeO3 (180.10 F/g). Furthermore, EIS studies show that that the ion diffusion resistance of the 15% C-LaFeO3 electrode decreased, which is indicative of good electrochemical performance.

Dual Plasmon Resonances and Tunable Electric Field in Structure-Adjustable Au Nanoflowers for Improved SERS and Photocatalysis.

Flower-like metallic nanocrystals have shown great potential in the fields of nanophononics and energy conversion owing to their unique optical properties and particular structures. Herein, colloid Au nanoflowers with different numbers of petals were prepared by a steerable template process. The structure-adjustable Au nanoflowers possessed double plasmon resonances, tunable electric fields, and greatly enhanced SERS and photocatalytic activity. In the extinction spectra, Au nanoflowers had a strong electric dipole resonance located around 530 to 550 nm. Meanwhile, a longitudinal plasmon resonance (730~760 nm) was obtained when the number of petals of Au nanoflowers increased to two or more. Numerical simulations verified that the strong electric fields of Au nanoflowers were located at the interface between the Au nanosphere and Au nanopetals, caused by the strong plasmon coupling. They could be further tuned by adding more Au nanopetals. Meanwhile, much stronger electric fields of Au nanoflowers with two or more petals were identified under longitudinal plasmon excitation. With these characteristics, Au nanoflowers showed excellent SERS and photocatalytic performances, which were highly dependent on the number of petals. Four-petal Au nanoflowers possessed the highest SERS activity on detecting Rhodamine B (excited both at 532 and 785 nm) and the strongest photocatalytic activity toward photodegrading methylene blue under visible light irradiation, caused by the strong multi-interfacial plasmon coupling and longitudinal plasmon resonance.

Fabrication of asymmetric zinc oxide/carbon nanotubes coated polysulfone photocatalytic nanocomposite membrane for fouling mitigation

AbstractMembrane filtration is a favorable option in water reclamation from contaminated water source, nevertheless, inevitable membrane fouling which greatly shortens membrane longevity and separation efficiency. The paper aimed to mitigate the membrane fouling through the formation of an asymmetric PSF‐ZnO/CNTs photocatalytic nanocomposite membrane. Instead of direct blending the photocatalyst into polymer matrix, the asymmetric nanocomposite membrane was prepared with prior formation of a self‐assembled ZnO/CNTs photocatalyst layer through wet‐processing technique followed with coating of PSF support layer via phase inversion method. The morphology of the nanocomposite membrane was characterized to confirm the formation of the asymmetric structure. The effect of ZnO/CNTs photocatalyst loading on the pore characteristic and antifouling properties of the PSF‐ZnO/CNTs nanocomposite membrane in dye remediation were assessed. The incorporation of ZnO/CNTs layer was found to endows the membrane with ability to photodegrade methylene blue. The PSF‐ZnO/CNTs membrane with 0.038 g ZnO/CNTs photocatalyst loading (M5) showed the greatest flux recovery ratio (98.46%) and the lowest irreversible fouling ratio (1.54%) while exhibited decent water permeability about 29.99 L/m2h without compromise the methylene blue rejection rate (91.04%).

Novel Silver and Bismuth Tungstate-Based Nanostructures Synthesized by a Green Route and Their Application to Dye Photodegradation

Organic dyes constitute one of the main pollutants existing in wastewater, perturbing aquatic life and causing environmental problems. Photocatalytic oxidation represents an alternative process for effective and easy degradation of dyes. In this study, the synthesis of novel silver and bismuth tungstate-based nanostructures with high photocatalytic activity for photodegrading methylene blue (MB) dye is described. The novel, as-prepared, Ag8W4O16/AgBiW2O8/Bi2WO6 photocatalyst improved MB decomposition efficiency achieving a photodegradation of 82.50% within 40 min under UV irradiation. Herein, the holes (h+) are the main oxidative species in the MB degradation process. Moreover, the photocatalytic mechanisms of MB degradation by using the AgBiW2O8/Bi2WO6 and Ag8W4O16/AgBiW2O8/Bi2WO6 heterojunctions is postulated. The synthesis is conducted by a green and combined methodology that includes the use of a metathesis reaction (double displacement reaction)/molten salt procedure. This methodology is simple, effective, high-yield (95%), and intermediate temperature, carried out in normal atmospheric conditions and using simple equipment. The particles were obtained in NaNO3 at 350 °C (2 h) showing spherical-like shapes with sizes from 10 to 59 nm according to the Ag content in samples. SBET and Dp values obtained for samples varied from 8.1 to 10.2 m2 g−1 and 17.67 to 32.15 nm, respectively. The Ag load in samples showed an important role in the phase composition of photocatalysts obtaining AgBiW2O8/Bi2WO6 and Ag8W4O16/AgBiW2O8/Bi2WO6-type heterostructures.

Synthesis, structure, and characterization of RbNdGe2O6 as a novel visible-light-driven catalyst for photodegradation methylene blue

A novel lanthanide germanate, namely RbNdGe2O6, has been successfully synthesized by high-temperature solid-state reaction in open air atmosphere for the first time. Single crystal X-ray diffraction indicates a 3D framework composed of 1D neodymium oxygen chains connected with cyclogermanate Ge3O9 units with Rb+ located in the internal space. X-ray powder diffraction coupled with Rietveld refinement reveals the sample’s phase purity we have prepared. Thermal behavior analysis shows RbNdGe2O6 is very stable, it doesn’t decomposition until heated up to 998 ​°C. UV–visible absorption and diffuse reflection spectrum feature characteristic absorption bands of f-electron transition and an optical bandgap value of 4.65 ​eV. Magnetic susceptibilities measurement gives significant antiferromagnetic interactions between magnetic centers. The photodegradation experiments were performed to evaluate photocatalytic activities of RbNdGe2O6. By using P25 as a reference, RbNdGe2O6 features to be an effective visible-light-driven catalyst in photodegrading methylene blue. Although the BET value of RbNdGe2O6 is only 3% that of P25, the photocatalytic activity reaches 0.55 times that of P25. Furthermore, the proposed photocatalytic mechanism which dominated by holes was further verified by adding ammonium oxalate as a quencher.

Enhanced Photocatalytic Performance of Hierarchical ZnFe2O4/g-C3N4 Heterojunction Composite Microspheres

Semiconductor photocatalysts with suitable band gap for fair response to visible light and efficient separation of electron–hole pairs, are the key to practical application of photocatalytic technology. Magnetically separable hierarchical ZnFe2O4/g-C3N4 composite photocatalysts were prepared by a facile solvothermal method combined with a subsequent annealing process. The composite microspheres were composed of ZnFe2O4 nanoparticles, whose diameter was restricted due to the confined space effect from g-C3N4 nanosheets. ZnFe2O4/g-C3N4 heterojunction structures led to the improvement of the efficiency for photodegrading methylene blue and rhodamine B under visible light, where the kinetic constant over ZnFe2O4/CN-150 photocatalyst was more than ten times larger than that over pure ZnFe2O4. The photogenerated electrons from g-C3N4 surfaces could easily migrate to ZnFe2O4, leading to efficient separation of electron–hole pairs. Also, the composite photocatalyst possessed a chemical stability against photocorrosion and a magnetic property, which made it magnetically separable and reusable conveniently.

Experimental and theoretical DFT+D investigations regarding to various morphology of cuprous oxide nanoparticles: Growth mechanism of ionic liquid-assisted synthesis and photocatalytic activities

Under assistance of ionic liquid, the Cu2O crystal was successfully synthesized by a simple solution-phase method with several morphologies, including octahedrals, truncated octahedrals, facet-etched octahedrals, particle-coated octahedrals and aggregated spheres. The morphology of Cu2O crystals can easily be modified by tuning the adding amounts of ionic liquid 1-ethyl-3-methylimidazolium bromide. A possible growth mechanism for the crystal products can be suggested based on the DFT+D calculation and experiments. Under visible-light irradiation (λ>420nm), the obtained Cu2O samples show an outstanding performance during photodegrading methylene blue (MB) dye. The higher photocatalytic activity for MB photodegradation by the Cu2O facet-etched octahedrals comparing to octahedrals can be attributed to the formation of surface heterojunction between (100) and (111) facets. Therefore, the ionic liquid-assisted solution-phase syntheses would be potentially useful in the fields of catalyst production for photodegrading hazardous pollutants.

Co, N-Doped TiO2 Coated r-GO as a photo catalyst for Enhanced photo catalytic Activity

A highly efficient Cobalt(Co) and Nitrogen (N) doped TiO2/Reduced Graphene oxide(RGO) hybrid nano catalyst was synthesized by sol-gel and hydrothermal method. The Co, N-doped/RGO (CNDTR) hybrid catalyst shows enhanced visible light photocatalytic degradation of methylene blue dye. The average particle size of the Co, N-doped TiO2 /RGO (CNDTR) catalyst is about 25 nm. The morphology of the samples observed indicates irregular shaped particles deposited on the graphene sheets. The photo catalytic activities of the samples were evaluated through photo degradation Methylene blue dye under visible light irradiation. Doping of Co and N cause the red shift of the absorption onset of TiO2 to the visible region and enhance the photo catalytic activity. Compared with the Co, N-doped TiO2 (CNDT) sample Co, N -Doped TiO2 /RGO(CNDTR) exhibited the highest photocatalytic activity, This can be ascribed to the synergistic effect of the N and Co co-doping along with increased surface area of the samples due to RGO.

Plasmonic Ag2MoO4/AgBr/Ag composite: Excellent photocatalytic performance and possible photocatalytic mechanism

Plasmonic Ag2MoO4/AgBr/Ag composite is fabricated by in-situ ion exchange and reduction methods at room temperature. The samples are characterized by X-ray diffraction (XRD), UV–vis diffuse reflectance (DRS), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM) and photoluminescence (PL) measurements. The results show that butterfly-like Ag2MoO4 nanosheets served as the precursor, and Ag2MoO4/AgBr/Ag is formed in phase transformation with MoO42− displaced by Br−. The ternary Ag2MoO4/AgBr/Ag composite photocatalysts show greatly enhanced photocatalytic activity in photodegrading methylene blue (MB) under visible light irradiation compared with AgBr and Ag2MoO4. The pseudo-first-order rate constant kapp of Ag2MoO4/AgBr/Ag is 0.602min−1, which is 11.6 and 18.3 times as high as that of AgBr and Ag2MoO4, respectively. Meanwhile, the efficiency of degradation still kept 90% after ten times cyclic experiments. Eventually, possible photocatalytic mechanism was proposed.

Study on enhanced photocatalytic activity of magnetically recoverable Fe3O4@C@TiO2 nanocomposites with core–shell nanostructure

A novel and simple approach for the fabrication of Fe3O4@C@TiO2 nanocomposites with a good core–shell structure has been successfully constructed. The as-synthesized core–shell structure is composed of a magnetic core, an interlayer of carbon, and an outer TiO2 shell. In this method, the carbon middle layer could provide negatively charged for the TiO2 coating without the surfactants. The as-obtained core–shell structure composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray photoelectron spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG), N2 adsorption–desorption isotherm analyses and the magnetization measurement (SQUID). The TEM images showed that the thickness of TiO2 shell could be controlled by varying tertrabutyl titanate (TBOT) content in the ethanol/acetonitrile mixed solvents. Photocatalytic property of Fe3O4@C@TiO2 nanocomposites were evaluated by photodegradation methylene blue (MB). The results showed that the well-designed nanocomposites exhibited a higher photoactivity than Fe3O4@TiO2 nanocomposites. Moreover, this photocatalyst can be easily recovered by an external magnetic field and remain stable photocatalytic activity after five cycles. The presence of carbon interlayer can avoid the occurrence of photodissolution. Therefore, the photocatalytic activity of titania would not deteriorate seriously, which played key role for the enhanced photocatalytic activity.

Synthesis and characterization of carbon nanotubes-treated Ag@TiO2 core–shell nanocomposites with highly enhanced photocatalytic performance

The monodispersed, uniform Ag@TiO2 core–shell nanoparticles were successfully synthesized using Ag nanoparticles as colloid seeds and tetrabutyl titanate (TBOT) as Ti source through the simple solvothermal process. The acid vapor treated multi-walled carbon nanotubes (CNTs) were introduced into Ag@TiO2 core–shell system to obtain CNTs-loaded Ag@TiO2 nanocomposites (CNTs-Ag@TiO2) through a simple dipping method. Characterization of the composites was performed using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and High-resolution TEM (HRTEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS) and the X-ray photoelectron spectroscopy (XPS). Photocatalytic property of CNTs-Ag@TiO2 nanocomposites was investigated by photodegradation methylene blue (MB) solution under Xenon arc lamp and compared with Ag@TiO2, TiO2 and CNTs-TiO2 nanoparticles. The result showed that the photocatalysis property of CNTs-Ag@TiO2 nanocomposites was higher than other comparative particles. The presence of CNTs in the Ag@TiO2 nanocomposites could enhance the photocatalytic property owing to CNTs were good electron acceptors, can accept the excited electrons photo-initiated in the TiO2 particles and the Fermi level of the Ag is situated close to the conduction band edge of TiO2. Thus the electrons excited into the conduction band of TiO2 by UV–visible light irradiation are transferred to the surface of CNTs and Ag core easily. Therefore, recombination time of the electron–hole pair was prolonged, which was the key of enhance the photocatalytic activity.

Enhanced photoelectrochemical properties of TiO2 by codoping with tungsten and silver

The Tungsten (W) and Silver (Ag) codoped TiO2 samples were successfully synthesized by hydrothermal method without any post calcination. To understand the correlation between electronic structure and photocatalytic properties, the synthesized samples were characterized using X-ray diffraction, Brunauer–Emmett–Teller specific surface area, transmission electron microscopy, ultra-violet–visible absorption spectra, and X-ray photoelectron spectroscopy (XPS), and the photocatalytic properties were evaluated under visible light irradiations. Codoping could not induce any changes in the phase and all the synthesized samples displayed pure anatase phase with spherical morphology. Visible light absorptions of the codoped samples were dramatically improved compared to the corresponding mono-doped samples. XPS analysis indicated that the dopant atoms successfully entered the TiO2 network. Results from the visible light photodegradation experiments showed that tungsten-silver codoped TiO2 possessed strong ability in photo-degrading methylene blue compared to tungsten doped TiO2 and silver doped TiO2, which was attributed to the smaller particle size, higher specific surface area, enhanced visible light absorption, and improved separation of photogenerated carriers.