Co-doped TiO2 Nanoparticles Research Articles

Synthesis of Fe- and Co-Doped TiO2 with Improved Photocatalytic Activity Under Visible Irradiation Toward Carbamazepine Degradation.

Pure TiO2 and Fe- and Co-doped TiO2 nanoparticles (NPs) as photocatalysts were synthesized using wet chemical methods (sol-gel + precipitation). Their crystalline structure and optical properties were analyzed using X-ray diffraction (XRD), Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible light (UV-Vis) diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The photocatalytic activity of the synthesized nanoparticles was evaluated through degradation of carbamazepine (CBZ) under UV-A and visible-light irradiations. The XRD and Raman analyses revealed that all synthesized nanomaterials showed only the anatase phase. The DRS results showed that the absorption edge was blue-shifted for Fe-doped TiO2 NPs. The decrease in charge recombination was evidenced from the PL investigation for both Co-doped and Fe-doped TiO2 nanomaterials. An enhancement in photocatalytic degradation of carbamazepine in aqueous suspension under both UV-A light and visible-light irradiations was observed for Fe-doped Titania NPs by comparison with pure TiO2. These results suggest that the doping cations could suppress the electron/hole recombination. Therefore, the photocatalytic activity of TiO2-based nanomaterials was enhanced.

Transforming polymorphs of Co-doped TiO2 nanoparticles: an efficient photo-electrode for dye-sensitized solar cells

Simple sol–gel assisted spin coating technique was used to prepare cobalt-doped TiO2 films for the application of dye-sensitized solar cells (DSSC). TiO2 photo-electrodes with few Co concentrations (0, 0.025, 0.05, 0.075 and 0.1 M) were prepared on conducting glass substrates. The morphology, structure and composition of the Co:TiO2 films were observed using SEM, XRD and EDAX analysis. The average crystallite size of Co:TiO2 nanoparticles obtained from diffractograms are in the range of 3–12 nm. The transformation of polymorphs from anatase to rutile and vice versa for the increasing concentrations of Co in TiO2 films is observed. The values of optical bandgap energy for Co-doped films are observed to be higher than the pure TiO2 film and the highest is for the dopant level of 0.025 M. Doping of 0.1 M Co in TiO2 enhances the power conversion efficiency of DSSC by 65% compared to pure TiO2 film, demonstrating the influence of Co doping on the functioning of DSSC.

Influence of nickel and lanthanum ions co-doping on photocatalytic properties of TiO2 for effective degradation of reactive yellow 145 in the visible region

Nickel and lanthanum co-doped TiO2 nanoparticles with different metal loading, narrow particle size distribution, and high surface area are synthesized using the sol–gel method. The nanoparticles are further characterized using different techniques like flame atomic absorption spectroscopy (FAAS), specific surface area and porosity measurements, X-ray diffraction (XRD) analysis, fourier transform infrared spectroscopy (FT-IR), UV–vis diffused reflectance spectroscopy (DRS), raman analysis, scanning electron microscopic studies (SEM), photoluminescence (PL) studies, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopic measurements (EIS). The experimental results of XRD analysis indicated that the co-doping of TiO2 with lanthanum (La) and nickel (Ni) results in an increased in the surface area of TiO2 nanoparticles accomplished by a decrease in the crystallite size from 18.00 to 10.42 nm. The appearance of a new absorption band in DRS spectra at 721 nm caused by the Ni+2 and La+3 doping is responsible for the enhancement of the photocatalytic degradation under visible light. The increased oxygen vacancies, surface defects as well as reduced recombination of charge carriers are confirmed by the PL studies. The photocatalytic experiment for Reactive Yellow-145 (RY-145) is carried out using 1.00 g/L of modified TiO2 suspension at different values of pH and temperature. The experimental results revealed that 96.5% of RY-145 is degraded after a short time of irradiation. The maximum degradation is achieved in case of nanoparticles co-doped with 5% Ni and 3% La ion. Furthermore, the adsorption experiment is also carried out to explore the adsorption of dye by photocatalytic support. The photocatalytic degradation of dye is further confirmed by measuring chemical oxygen demand (COD) values before and after degradation.

La-Ce doped TiO2 nanocrystals: a review on synthesis, characterization and photocatalytic activity

Titanium dioxide (TiO2) is one of the best semiconductor photocatalysts due to its high stability, oxidative power, non-toxicity, low cost etc. But its photocatalytic activity is limited due to rapid recombination of photo-generated electron-hole pair, wide band gap and anatase to rutile phase transformation. These disadvantages can be eliminated by introducing dopants into the TiO2 nanocrystals. Sol-gel and hydrothermal methods can be used for the synthesis of doped and co-doped TiO2 nanocrystals. Advanced characterization techniques can be used for the study of phase structure, optical properties, thermal properties, surface area, morphological changes and photocatalytic activity of doped and co-doped TiO2 nanoparticles. Doping inhibits the anatase to rutile phase transformation and suppresses the recombination of photo-generated electron-hole pair which enhances the photocatalytic activity. Here we made a review on the synthesis, characterization and photocatalytic activity of La, Ce doped and co-doped TiO2 nanoparticles.

Synthesis of Co3+ Doped TiO2 by Co-precipitation Route and Its Gas Sensing Properties

Abstract Undoped and Co-doped TiO2 nanoparticles were synthesized by a facile co-precipitation method and calcined at 700°C. The phase identification carried out by XRD measurements and Raman spectroscopy analysis of calcined powders reveals the formation of mainly anatase phase for undoped TiO2, and 0.5 mol % Co-doped TiO2 whereas rutile phase for 1 mol % Co-doped TiO2. The sensors prepared with these powders deposited on interdigital (IDE) sensor platforms were tested toward NO2 and H2 sensing properties at 600 °C. As the undoped and 0.5 % Co-doped TiO2 reveal n-type behavior, 1 % Co-doped TiO2 shows p-type semi-conductive behavior. 1 % Co-doped TiO2 exhibits good sensing performance toward NO2 while the undoped TiO2 powder yields the best sensor performance toward H2 at 600°C. This indicates that the crystal structure of TiO2 sensing material must be adjusted depending on the nature of target gas. The results indicate that the main factor influencing high temperature gas sensor performance of nanoparticulate TiO2 is either the alteration of its electronic structure or the type of polymorphs.

Effect of silica coating on the structural and luminescent properties of Sm3+/Yb3+ or Tm3+/Yb3+ co-doped TiO2 nanoparticles

The luminescent characteristics of spherical titanium dioxide (TiO2) nanoparticles (NP's) doped with Sm3+/Yb3+ and Tm3+/Yb3+ with and without a silica coating were analyzed. These nanoparticles were synthesized using the spray pyrolysis technique and coated with silica through a wet chemical process. The Sm3+/Tm3+ and Yb3+ doping induces a triphasic poly-crystalline structure of rutile and anatase TiO2 and a Sm2Ti2O7/Tm2Ti2O7 cubic phase. A Williamson-Hall analysis was used to monitor the tensions of the NP's crystallites at the various doping concentrations and with addition of the silica shell. The luminescent spectra presented the characteristic emission peaks for the electronic energy levels transitions of the Sm3+/Tm3+ and Yb3+ ions. The Sm3+/Yb3+ co-doped NP's showed a maximum emission peak in the visible region at 612 nm, associated with 4G5/2 → 6H7/2 transitions of the Sm3+ ions. The IR emission peak at 973 nm (2F5/2 → 2F7/2) pertaining to Yb3+. For the combination of Tm3+/Yb3+, two emissions associated with Tm3+ ions were observed at 440 nm (1D2 → 3F4) and 806 nm (3H4 → 3H6). The emission at 973 nm (2F5/2 → 2F7/2) is correlated to the Yb3+ ions. Silica coating of the NP's resulted in luminescence emission intensity increase of about 4 times.

Ni-doped and Ni/Cr co-doped TiO2 nanotubes for enhancement of photocatalytic degradation of methylene blue

Ni-doped and Ni/Cr co-doped TiO2 nanotubes were successfully synthesized using a novel hydrothermal method. The surface and bulk properties of as-synthesized nanopowders were characterized using various microstructural and optical techniques. The photocatalytic ability of these nanopowders was investigated systematically for the decomposition of methylene blue dye (MB) under visible light illumination. The morphological results revealed the structural transformation of TiO2 nanotubes to nanosheets, and further to a mixture of nanosheet/nanotube on doping with Ni and co-doping of Ni/Cr, respectively. Moreover, the Ni doping causes an optical absorption edge shifts towards lower wavelengths, while doping by Ni/Cr results to an optical absorption edge shifts towards higher wavelength in comparison to TiO2-nanotubes. Also, Ni-doping and Ni/Cr co-doping strongly affects the Raman vibrational modes owing to the changes in interplanar distance, crystallite size, dislocation density, and crystal microstrains. Among the undoped, doped and co-doped TiO2 nanoparticles, the 6Ni/4Cr co-doped TiO2 exhibited a higher efficiency of 95.6% and excellent stability towards the photocatalytic degradation of MB. It is attributed to the availability of many carriers for the efficient photo-oxidation within the UV-Vis optical absorption range. Also, the photocatalytic reaction kinetics and degradation mechanism of MB were discussed.

Hydrothermal and sol-gel low-temperature synthesis of tin, silver co-doped TiO2 nanoparticles with enhanced photocatalytic efficiency: artificial neural network modelling

Pure anatase TiO2 nanoparticles with various Ag and Sn contents were synthesized by hydrothermal and sol-gel low-temperature methods. Structural and morphological characterizations of synthesized nanoparticles were performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and N2 adsorption/desorption isotherm and brunauer-emmett-teller (BET) techniques. The effect of synthesis procedure on the crystalline structure, crystal size, surface area, pore size distribution and photocatalytic activity of synthesized samples were studied. The photocatalytic activity was tested vs. degradation of methylene blue (MB) under black light radiation. Ag/Sn-TiO2 nanoparticles synthesized by hydrothermal method showed higher photoactivity during the degradation of MB under black light irradiation because of being enhanced in the specific surface area, total pore volume, and its reduction in the crystallite size. An artificial neural network (ANN) comprising four input variables (mol% of dopant ions, photocatalyst dosage, initial dye concentration, and pH of the solution), eight neurons and an output variable (degradation efficiency %) was optimized, tested and validated for MB degradation by Ag/Sn-TiO2 nanoparticles synthesized via hydrothermal method. The results showed that the predicted data from the designed ANN model are in good agreement with the experimental data with a correlation coefficient (R2) of 0.979. A 98.9% photodegradation efficiency of MB was achieved by utilizing 0.07 mol% Ag and 0.03 mol% Sn co-doped TiO2 at pH = 12.

Coprecipitation synthesis of N, Fe doped anatase TiO2 nanoparticles and photocatalytic mechanism

N, Fe single doped and co-doped anatase TiO2 nanoparticles were successfully prepared by coprecipitation method using TiCl4, NH4OH, Fe(NO3)3·9H2O as raw materials and polyvinyl alcohol as dispersant. The samples were characterized by TG-DSC, FTIR, XRD, FESEM, EDS, XPS, and UV–Vis to investigate the influence of doping concentration on the thermal effect, crystal structure, morphology, composition, energy band gap and photocatalytic activity of TiO2 nanoparticles. Results indicated that TiO2 nanoparticles doped with 0.15 at.% N and 0.3 at.% Fe showed the best photocatalytic activity. N, Fe co-doping had a synergistic effect: (1) The transformation inhibition of anatase to rutile phase was achieved, leading to formation of high crystallized monophasic anatase TiO2; (2) The bandgap narrowing effect was significant, increasing the light absorption range; (3) The small grain size of ~ 10 nm in diameter was obtained, resulting in effective separation of photo-induced electrons and holes.

Synthesis and photocatalytic activity of transition metal and rare earth element co-doped TiO2 nano particles

The intrinsic and co-doped nano TiO2 particles were synthesized by sol-gel method. The crystal structure was characterized by X-ray diffraction and high-resolution electron microscopy. An obviously shift toward longer wavelengths direction can be observed in the UV-visible absorption spectra, and the band gap can be estimated to be 2.4 eV. The response range of the TiO2 photocatalyst can be widened from UV to visible light. The results of photocatalysis study show that co-doped nano TiO2 shows good photocatalytic performance. The transition metal and rare earth element co-doped TiO2 nano particles will be a very attractive candidate for the wastewater degradation and environmental protection.

Preparation, characterization, and photocatalytic activity under UV and visible light of Co, Mn, and Ni mono-doped and (P,Mo) and (P,W) co-doped TiO2 nanoparticles: a comparative study.

In this work, TiO2-based nanomaterials have been successfully synthesized by doping TiO2 with Co, Mn, and Ni and by co-doping it with (P,Mo) or (P,W). The structural, optical, and morphological properties of the synthesized nanomaterials have been investigated using various techniques such as XRD, FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, XPS, and SEM-EDS. The obtained results showed that the crystalline structure of the doped TiO2-based nanomaterials depends strongly on the nature of the doping ions. The obtained band gap energy of TiO2 co-doped with (P,Mo) changes to a level below the band gap energy of TiO2 anatase indicating a high ability to absorb visible light. The obtained photocatalytic activity results of methyl orange degradation showed that, under visible light, the mono-doping of TiO2 with Co and its co-doping with (P,Mo) or (P,W) improve significantly the photocatalytic activity of TiO2 in comparison with undoped TiO2. The activity order obtained under UV-A irradiation for the used photocatalysts is TiO2 > > 1%Ni-TiO2 > 1%Co-TiO2 > 30%(P,Mo)-TiO2 ≈ 30%(P,W)TiO2 > 1%Mn-TiO2 while under visible light, it is 1%Co-TiO2 > 30%(P,Mo)-TiO2 > 30%(P,W)TiO2 ≈ TiO2 > 1%Ni-TiO2 > 1%Mn-TiO2. The high photocatalytic activity observed for these samples could be the result of a synergetic effect of the high visible light absorption capacity and the low recombination rate of photoexcited electrons and holes.

Sol–gel Synthesized Co-Doped Anatase TiO2 Nanoparticles: Structural, Optical, and Magnetic Characterization

A simple sol–gel method was used to synthesize cobalt doped TiO2 nanoparticles. TiO2 (titania) nanoparticles with Co doping concentration within the range 0, 2, 4, 6 and 8 mol% were prepared. For the purpose of samples characterization under the effect of changing the Co concentration on structural, optical, surface morphology and magnetic properties of the samples X-ray diffraction (XRD), Fourier transform infrared, UV/Vis/NIR diffuse reflectance spectroscopy (DRS), UV–visible absorption, transmission electron microscopy, and vibrating sample magnetometer (VSM) system techniques were employed. The XRD results confirmed the formation of TiO2 (titania) nanoparticles in anatase phase for all the undoped and Co-doped samples. The microstructure studies of the samples confirmed the incorporation of Co ions into the host titania matrix is occurring via substitution for the Ti sites. All the investigated samples exhibited a room temperature ferromagnetic behavior as observed by VSM measurements with non-monotonic dependence of FM characteristic parameters on Co concentration. The samples showed optical energy gap (Eg) values ~ 3.59 eV with an extension of the band gap into the visible light region with Co doping as confirmed by DRS study. The absorption band shows shift from 510 nm to 720 nm as Co concentration in the samples increased.

Effective La-Na Co-Doped TiO₂ Nano-Particles for Dye Adsorption: Synthesis, Characterization and Study on Adsorption Kinetics.

The mesoporous La-Na co-doped TiO2 nanoparticles (NPs) have been synthesized by non-aqueous, solvent-controlled, sol-gel route. The substitutional doping of large sized Na+1 and La+3 at Ti4+ is confirmed by X-ray diffraction (XRD) and further supported by Transmission Electron Microscopy (TEM) and X-ray Photo-electron Spectroscopy (XPS). The consequent increase in adsorbed hydroxyl groups at surface of La-Na co-doped TiO2 results in decrease in pHIEP, which makes nanoparticle surface more prone to cationic methylene blue (MB) dye adsorption. The MB dye removal was examined by different metal doping, pH, contact time, NPs dose, initial dye concentration and temperature. Maximum dye removal percentage was achieved at pH 7.0. The kinetic analysis suggests adsorption dynamics is best described by pseudo second-order kinetic model. Langmuir adsorption isotherm studies revealed endothermic monolayer adsorption of Methylene Blue dye.

Effect of synthesis method on NS-TiO2 photocatalytic performance

In this study, highly visible-light photoactive nitrogen and sulfur co-doped TiO2 nanoparticles and nanosheets were synthesized via sol-gel and hydrothermal methods, respectively. The photocatalytic activity of N,S-TiO2 photocatalysts were evaluated and compared by degradation of non-steroidal anti-inflammatory drugs, ibuprofen(IBP) and naproxen (NPX), under simulated solar light. The sol-gel method developed a mesoporous structure N,S-TiO2 nanoparticle which contains both anatase and rutile phases with large BET surface area (132 m2/g). N,S-TiO2 nanosheets with pure anatase phase, with larger mesoporous structure and a smaller BET surface area (64 m2/g) was formed via hydrothermal method. NS-TiO2 nanoparticles were coated on UVC-treated polycarbonate (PC) (NS-TiO2@PC) by simple deposition method. The results showed that under identical condition, N,S-TiO2 nanoparticles can degrade 85% and 99.3% of ibuprofen and naproxen while 71.6% of IBP and 99.1% of NPX were degraded by N,S-TiO2 nanosheets. Optimization results showed that maximum degradation efficiency was achieved at the optimum conditions: irradiation intensity 8.36 mW/cm2 (for ibuprofen) and 10 mW/cm2 (for naproxen), initial drugs concentration 10 mg/L and reaction time 121 min. Under this condition, the maximum degradation efficiency of 83% and 100% were achieved for ibuprofen and naproxen, respectively. The results of this study elucidate co-doped NS-TiO2 nanoparticles prepared by sol-gel methods are photocatalytically more effective and practically easier to reproduce for the practical application, both in terms of energy saving and cost reduction. The energy cost analysis indicated that sol-gel method for synthesis of N,S-TiO2 is more cost effective.

Photocatalytic Degradation of Bisphenol-A using N, Co Codoped TiO2 Catalyst under Solar Light

Advanced oxidation processes (AOPs) including heterogeneous photocatalysis has proven as one of the best technique for waste-water treatment. Photocatalytic process using semiconductor like TiO2 based heterogeneous photocatalysis is a promising method for the treatment of toxic pollutants. In the present study, visible-light photoactive cobalt and nitrogen co-doped TiO2 nanoparticles were synthesized via wet impregnation method. The photocatalysts were characterized using X-ray diffraction (XRD), Raman Spectra, Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), UV-vis spectrophotometer and X-ray photoelectron spectrophotometer (XPS). The photocatalytic activitiy of prepared (N, Co)-codoped TiO2 on the mineralization of Bisphenol-A (BPA) under visible light irradiation was studied and the results were compared to commercial TiO2 (Degussa P25). The results demonstrated that 1.5% Co and 0.5% N – codoped TiO2 samples revealed higher activity than commercial TiO2. Total organic carbon (TOC) removal was observed to be 97%, which indicate the complete mineralization of BPA. GC-MS analysis was carried to find out the possible intermediates formed and reaction pathway.

Free-standing N,Co-codoped TiO2 nanoparticles for LiO2-based Li–O2 batteries

N and Co co-doped TiO2 nanoparticles grown on carbon fibers are employed to facilitate the formation and stabilization of LiO2.

Synthesis, characterisation and investigation of enhanced photocatalytic activity of Sm<SUP align="right">+3</SUP>, Ni<SUP align="right">+2</SUP> co-doped TiO<SUB align="right">2 nanoparticles on the degradation of azo dyes in visible region

Pure and samarium-nickel co-doped TiO2 nanoparticles with different Sm contents were synthesised by sol-gel method. The synthesised nanoparticles were characterised using different techniques. It is revealed from experimental results that the doping of TiO2 with samarium and nickel not only increase the surface area of mesoporous TiO2 but also decrease the particle size (17.0 nm to 8.01 nm by increasing Sm+3 contents). Diffuse-reflectance spectroscopic studies showed the slight red shift in band-gap transitions and appearance of the new absorption band in the visible region (719 nm) caused by Ni+2 and Sm+3 doping. The photocatalytic degradation of azo dyes (Reactive Red-195 and Reactive Black-08) was carried out in visible region using modified TiO2 at different pH values. Results revealed that 99% of RR-195 and 75.33% RB-08 were degraded after 10-20 minutes of irradiation. Maximum degradation was achieved in case of nanoparticles co-doped with 5% Ni and 3% Sm.

Synthesis and characterization of Nb-La co-doped TiO2 nanoparticles by sol-gel process for dye-sensitized solar cells

One of the main challenges of the current photovoltaic systems is improving the performance of the dye-sensitized solar cells (DSSCs). The deliberate insertion of impurity ions into the TiO2 crystal lattice as an electron transporting material in DSSCs might be an effective method for improving the electronic properties of TiO2, which leads to enhancing the photovoltaic efficiency. Recently, co-doping has become a promising strategy that can be used for effective tuning of the electronic properties. In the present study, this method was applied as a novel approach to synthesize Lanthanum-Niobium(La,Nb)-codoped TiO2 nanocrystals via the Pechini sol-gel technique. According to the results, the x-ray diffraction investigation approved the anatase phase formation of (Nb-La)-codoped TiO2 nanoparticles. In addition, the field-emission scanning electron microscopy (FESEM) showed the nanoparticles were semi-spherical and approximately 30 nm in size. The photovoltaic parameters of the assembled dye-sensitized solar cells were tested via current density-voltage measurement, exhibiting an enhancement through introducing 2% mol Nb-La ions into the TiO2 crystal lattice. The electrochemical impedance spectroscopy showed that the charge transfer process occurred faster at the FTO/TiO2 interface, which was attributed to the reduction of charge recombination and enhanced electron conductivity.

Adsorption studies of Cr(VI) and Cu(II) metal ions from aqueous solutions by synthesized Ag and Mg co-doped TiO2 nanoparticles

ABSTRACTThis communication provides the eliminating of heavy metals from water resources using Ag-Mg/TiO2 nanoparticles. The nanoparticles with a size of 15 nm were prepared using sol-gel technique and used for the removal of Cr(VI) and Cu(II) from waste waters. Batch sorption studies were carried out to investigate the adsorption of the above metal ions for a concentration range of 0.1–10 mg/L. The maximum sorption capacity values were found to be 2.42 mg/g for Cr(VI) and 2.03 mg/g for Cu(II) at a concentration of 0.1 ppm. The mechanism of adsorption was also investigated. The results showed that both Freundlich and Dubinin–Radushkevitch isotherms were found to be the best fit for the adsorption of metals. The results from kinetic data reveal that the pseudo-second-order and Reichenberg film diffusion models were found to be well fit for the experimental data. The value of the thermodynamic parameter ΔH° revealed the endothermic adsorption process and negative value of ΔG° shows the feasibility and spontaneity of material–anion interaction. In addition, the method is considered to be simple and cost-effective, and shows excellent adsorption removal properties on heavy metals for industrial applications.

Biosynthesized Co-doped TiO2 nanoparticles based anode for lithium-ion battery application and investigating the influence of dopant concentrations on its performance

TiO2 is a good alternative anode material for lithium-ion battery application because of its incomparable high structural stability and safety during the charge/discharge cycles. However, the low intrinsic conductivity of TiO2 has been a limiting factor affecting its cycling and rate capability performance. Here in this work, we present Co-doped TiO2 nanoparticles based anode with good reversibility, cycling stability and rate capability performance for its envisaged application in lithium-ion battery. The Co-doped TiO2 nanoparticles with different Co concentrations (3%, 5%, and 7%) are synthesized using simple and economic biomediated green approach, wherein TiCl4 and Co precursors are allowed to react in Bengal gram bean extract containing biomolecules which act as natural capping agents to control the size of nanoparticles. Among the pure TiO2 and different Co-doped TiO2 samples, the 7% Co-doped TiO2 anode show the highest capacity of 167 mAh g−1 (88.3%) after 100 cycles at the 0.5C current density. The Co-doped TiO2 shows higher and stable coulombic efficiency up to 100 GCD cycles indicating good reversibility. Based on the results, it is expected that the Co-doped TiO2 nanoparticles might be contributing to the enhanced electronic conductivity providing an efficient pathway for fast electron transfer.