Effect of leavening agent on structural and photocatalytic properties of ZnO nanorods

In the present work, we have demonstrated a simple, facile, one-step, rapid and cost effective synthesis of ZnO nanorods through the thermal decomposition of zinc acetate and leavening agent (NaHCO₃). The silver nanoparticles (AgNPs) were deposited on the surface of ZnO nanorods by photocatalytic reduction of Ag (I) to Ag(0). As synthesized ZnO nanorods and Ag–ZnO nanocomposites were characterized by using X-ray Diffraction, field emission scanning electron microscope, high-resolution transmission electron microscope and diffuse reflectance spectroscopy. The photocatalytic activities of the ZnO nanorods and Ag–ZnO nanocomposites were evaluated for the photodegradation of Methyl Orange (MO) under UV and sunlight irradiation. The use of common leavening agent helps to prevent the aggregation of ZnO nanorods, further it hinders crystallite growth and narrowing the diameter of nanorods by the evolution of carbon dioxide during calcination. The ZnO nanorods and Ag–ZnO nanocomposite exhibited an enhanced photocatalytic activity and separation of photogenerated electron and hole pairs. Due to effect of leavening agent and AgNPs deposited on surface of ZnO nanorods finds best catalyst for the 99% degradation of MO within 30 min compared to ZnO.     

Preparation of TiO2, Ag-doped TiO2 nanoparticle and TiO2–SBA-15 nanocomposites using simple aqueous solution-based chemical method and study of their photocatalytical activity

Nanocrystalline TiO₂, Ag-doped TiO₂ and TiO₂–SBA-15 nanocomposites have been synthesised using a simple aqueous solution-based chemical method. Nanocrystalline TiO₂ was synthesised by calcining the precursor prepared by using ethylenediamine tetraacetic acid and TiCl₃ in aqueous medium. Formation of crystalline phase (anatase, rutile or mixed phase) and crystallite size were found to be dependent on calcination temperature. To enhance the photocatalytic activity, Ag-doped TiO₂ was synthesised by doping of Ag during the synthesis step of TiO₂. TiO₂–SBA-15 nanocomposites were synthesised by impregnation method. Pure anatase TiO₂ nanoparticle was formed in the amorphous matrix of the silicate SBA-15, even though the loading of the TiO₂ in the silicate matrix was as low as 5?wt%. The synthesised materials were characterised using thermal analysis, powder X-ray diffraction method, surface area and porosimetry analysis, diffuse reflectance analysis and transmission electron microscopy. The photocatalytic property of the synthesised materials was investigated towards the degradation of methyl orange under sunlight exposure and monitored by UV–visible spectrophotometer. Ag-doped TiO₂ exhibited enhanced photocatalytic activity than undoped TiO₂. TiO₂–SBA-15 nanocomposites showed impressive photocatalytic activity even with 10?wt% TiO₂ loading.     

Photodegradation process of Eosin Y using ZnO/SnO2 nanocomposites as photocatalysts: experimental study and neural network modeling

A series of coupled ZnO/SnO₂ nanocomposites were prepared with different molar ratios (1:10, 1:2, 2:1, and 10:1), using a homogeneous co-precipitation method. The structural properties were evaluated by different techniques: XRD, UVDR, SEM, N₂ adsorption, and IR. The photocatalytic activity of the samples was tested with the main goal of Eosin Y degradation from wastewaters. The prepared nanocomposites/systems exhibit higher photocatalytic activity than a single semiconductor photocatalyst and ZnO can effectively improve the photocatalytic efficiency of SnO₂ under UV illumination. A direct neural network modeling methodology, based on feed-forward neural networks, was performed in order to evaluate the efficiency of the photodegradation process of Eosin Y, depending of the reaction conditions. The developed model considered the following parameters with significant influence on the approached process: crystallite size, surface area, absorbtion edge, TOC values, time of reaction, and catalyst concentration as inputs and the final dye concentration as output. Accurate results were obtained in the validation phase of the neural model: relative average error under 4 % and a correlation between experimental and simulation data of 0.999.     

Nanostructured mesoporous Au/TiO2 for photocatalytic degradation of a textile dye: the effect of size similarity of the deposited Au with that of TiO2 pores

Mesoporous Au/TiO₂ nanocomposites with different Au particle size (7.3–11.8 nm) were synthesized via deposition–precipitation method. The synthesized nanocomposites have been characterized by XRD, TEM, XPS, DLS, ICP-OES, N₂ sorpometry, and UV–Vis spectroscopy. Au/TiO₂ showed higher quantum yield and greater photocatalytic efficiency compared to pure TiO₂ under both ultraviolet and sunlight illumination. The increase of the photocatalytic efficiency of TiO₂ upon deposition with gold nanoparticles, Au NPs, is due to the interface electron transfer from Au nanoparticles to TiO₂ under visible light illumination and from TiO₂ to Au nanoparticles under UV illumination. For the first time, the effect of Au particle sizes when it is very similar to the interparticles pores of TiO₂ has been investigated. The highest reaction rate (5.7 × 10^?2 min^?1) and degradation efficiency of Safranin-O (SO) dye (97 %) were observed when the deposited gold nanoparticles are the smallest among the studied samples (sAu/TiO₂). In spite of blocking a high percentage of the TiO₂ pores, the sAu/TiO₂ sample demonstrated a complete degradation of SO dye in 50 min which is more efficient than any other reported catalysts in the literature.     

Enhanced photocatalytic activity of BiFeO3 particles by surface decoration with Ag nanoparticles

BiFeO₃ particles with different morphologies and sizes were synthesized via a hydrothermal process, where the morphology and size was tailored by using different KOH concentrations in precursor solution. The samples prepared at n(KOH) = 3, 4.5, 6, and 7.5 M are composed, respectively, of octahedron-shaped particles (500–600 nm), cube-like particles (200–500 nm), irregular spherical agglomerates (9–16 μm) formed from disk-like grains with diameter of 1.4–2.8 μm and thickness of 0.2 μm, and cuboid-shaped particles with length-to-width ratio of 1.4:1–3.5:1 and width size ranging from 80 to 280 nm. Ag nanoparticles were deposited on the surface of BiFeO₃ particles by a chemical reduction method to produce Ag@BiFeO₃ nanocomposites. The photocatalytic activity of prepared samples was evaluated by degrading rhodamine B under simulated sunlight irradiation. It is demonstrated that Ag-decorated BiFeO₃ particles exhibit an enhanced photocatalytic activity compared to bare BiFeO₃ particles. This can be explained by the effective transfer of photogenerated electrons from the conduction band of BiFeO₃ to Ag nanoparticles and hence increased availability of holes for the photocatalytic reaction. Hydroxyl radicals were detected by the photoluminescence technique using terephthalic acid as a probe molecule and are found to be produced over the irradiated BiFeO₃ and Ag@BiFeO₃ photocatalysts; especially, an enhanced yield is observed for the latter.     

Improved photodegradation activity of SnO<Subscript>2</Subscript> nanopowder against methyl orange dye through Ag doping

Silver doped tin oxide (SnO₂:Ag) nanopowders were synthesized by a simple soft chemical route with 0, 5, 10 and 15 wt% concentrations of Ag. The structural, morphological, optical, photoluminescence and photocatalytic properties of the synthesized samples were studied and the results obtained are reported in this paper. XRD studies confirm the polycrystalline nature of the synthesized samples. The undoped and doped samples exhibit a strong (1 0 1) preferential growth. Decreased crystallite size is observed with Ag doping. Nanosized grains were observed for the doped samples. Peak related to Sn–O–Sn lattice vibration is observed for both the undoped and doped samples in the FTIR spectra. Peaks related to oxygen vacancies were observed at 362 and 499 nm for all the samples in the PL spectra. Enhanced photocatalytic activity was observed for the doped samples and the SnO₂:Ag nanopowder with 10 wt% Ag doping concentration exhibited maximum photodegradation efficiency against the degradation of methyl orange dye.     

A facile one step synthesis of SnO<Subscript>2</Subscript>/CuO and CuO/SnO<Subscript>2</Subscript> nanocomposites: photocatalytic application

Here novel photocatalysts, SnO₂/CuO and CuO/SnO₂ nanocomposites were successfully synthesized by chemical method at room temperature. X-ray Diffraction (XRD), transmission electron microscopy (TEM), Fourier transform Infrared (FT-IR), UV–Visible (UV–Vis) and photoluminescence (PL) spectroscopy were utilized for characterization of the nanocomposites. The photocatalytic activity of the nanocomposites was investigated. The hybrid nanocomposites exhibited high photocatalytic activity as evident from the degradation of methylene blue (MB) dye. The result revealed substantial degradation of the MB dye (92 and 69.5% degradation of SnO₂/CuO and CuO/SnO₂, respectively) under visible light illumination with short period of 30 min. Their large conduction band potential difference and the inner electrostatic field formed in the p–n heterojunction provide a strong driving force for the photogenerated electrons to move from Cu₂O to SnO₂ under visible light illumination. The excellent photodegradation of methylene blue suggested that the heterostructured SnO₂/CuO nanocomposite possessed higher charge separation and photodegradation abilities than CuO/SnO₂ nanocomposite under visible light irradiation.     

Structural analysis of graphene oxide/silver nanocomposites: optical properties,electrochemical sensing and photocatalytic activity

In the present study, graphene oxide/silver (GO/Ag) nanocomposites were synthesized via a facile simple one pot chemical reduction method using ethylene glycol/sodium borohydrate (EG/NaBH₄) as solvent and reducing agent. GO was selected as a substrate and stabilizer to prepare GO/Ag nanocomposites. The synthesized GO/Ag nanocomposites were characterized by a series of techniques. Highly monodispersed stable crystalline silver nanoparticles having a face-centered cubic (fcc) phase were confirmed by X-ray powder diffraction (XRD) on GO signature. Scanning electron microscopy images showed that Ag nanoparticles are deposited on the GO sheet with a narrow size distribution. Transmission electron microscopy observations revealed that large numbers of Ag nanoparticles were uniformly distributed on GO sheet and well separated with an average size of 18 nm. Ultraviolet–visible (UV–Vis) spectroscopic results showed the peak of GO and surface plasmon resonance (SPR) of Ag nanoparticles. The SPR property of GO/Ag nanocomposites showed that there was an interaction between Ag nanoparticles and GO sheet. The intensities of the Raman signal of GO/Ag nanocomposites are gradually increased with attachment of Ag nanoparticles i.e. there is surface-enhanced Raman scattering activity. Electrochemical investigations indicated that the nanocomposites possessed an excellent performance for detecting towards 4-nitrophenol. An application of the obtained GO/Ag nanocomposites as a catalyst in the reduction of 4-nitrophenol to 4-aminophenol by NaBH₄ was demonstrated. The GO/Ag nanocomposites exhibited high activity and stability for the catalytic reduction of 4-nitrophenol. The prepared GO/Ag nanocomposites act as photo-catalysts.     

Solar light induced rhodamine B degradation assisted by TiO2–Zn–Al LDH based photocatalysts

A series of TiO₂/Zn–Al layered double hydroxides (LDHs) based composites were synthesized and their photocatalytic efficiency in rhodamine B photodegradation reaction under solar light irradiation was tested. The aim of this study was to develop photocatalysts based on TiO₂/Zn–Al layered double hydroxides that can be activated by solar light irradiation. The influence of TiO₂ doping (1, 2 and 3 mass%) on the photocatalytic properties of developed TiO₂/Zn–Al LDHs nanocomposites was studied. Different photocatalytic behaviour of composites was interpreted in correlation to their structural, textural, morphological properties and kinetic parameters. All nanocomposites were active in the selected reaction. It was observed that the presence of Zn₂TiO₄ coupled with the ZnO phase contributes to the activity provoked by solar light irradiation. The photodegradation follows the pseudo first-order kinetics in accordance with the Langmuir–Hinshelwood model. The kinetic study suggested that the applied synthesis methodology resulted in homogeneous distribution of TiO₂ and other active components on the photocatalyst surface leading to better accessibility of active sites. The developed synthesis method enables favourable interactions among active phases. Novel TiO₂/LDH based photocatalysts are advantageous considering the low-cost and simple preparation, ensuring high photodegradation efficiency, making them appealing for the application in the field of water treatment.     

A novel single-step synthesis of N-doped TiO2 via a sonochemical method

A novel single-step synthetic method for the preparation of anatase N-doped TiO₂ nanocrystalline at low temperature has been devoleped. The N-doped anatase TiO₂ nanoparticles were synthesized by sonication of the solution of tetraisopropyl titanium and urea in water and isopropyl alcohol at 80 °C for 150 min. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis absorption spectrum. The product structure depends on the reaction temperature and reaction time. The photocatalytic activity of the as-prepared photocatalyst was evaluated via the photodegradation of an azo dye direct sky blue 5B. The results show that the N-doped TiO₂ nanocrystalline prepared via sonication exhibit an excellent photocatalytic activity under UV light and simulated sunlight.     

Facile preparation of Ag–Ag<Subscript>2</Subscript>S hetero-dendrites with high visible light photocatalytic activity

A stable and highly efficient Ag–Ag₂S hetero-dendrites (HDs) photocatalyst has been obtained via an extremely facile electrodeposition and subsequently in situ sulfuration route. The SEM and TEM show well-defined uniform dendrites morphology with an average diameter about 30 nm. In addition, the absorption spectra of Ag–Ag₂S HDs exhibit strong absorption in both visible and NIR regions. The EIS indicates that the low charge transfer resistance of Ag–Ag₂S HDs enhances the photocatalytic activity. The prepared HDs-4 photocatalyst with moderate degree of vulcanization shows excellent activity for degradation the methylene blue (MB) under the sunlight irradiation owing to the suitable ratios of Ag–Ag₂S. The enhanced photocatalytic activity could be attributed to the favorable synergistic effects between Ag and Ag₂S materials, such as huge extended absorption of solar light, low charge transfer resistance and high electron–hole separation efficiency. Moreover, radical scavenger experiments confirmed that superoxide radicals and holes were the main reactive species for MB degradation. Meanwhile, the Ag–Ag₂S HDs displays good photocatalytic stability after being recycled five times.     

Multifunctional performance of gC<Subscript>3</Subscript>N<Subscript>4</Subscript>-BiFeO<Subscript>3</Subscript>-Cu<Subscript>2</Subscript>O hybrid nanocomposites for magnetic separable photocatalytic and antibacterial activity

Highly active gC₃N₄-BiFeO₃-Cu₂O nanocomposites were successfully prepared via a facile, cost effective and eco-friendly method of hydrothermally wet precipitation combined with ultrasonic dispersion process. The prepared samples were characterized by XRD, FTIR, HRSEM, EDS, TEM, UV–Vis DRS, PL, VSM, BET and electrochemical properties. By means of these analysis for examine the crystal phase, nanostructure, band gap and light-harvesting properties were carried out. UV-DRS spectra indicate that the bandgap of g-C₃N₄ (2.7 eV) reduced to 2.59 and 2.21 eV by mixed with corresponds to BiFeO₃ and BiFeO₃/Cu₂O nanomaterials. The ideal photocatalytic activity of the gC₃N₄-BiFeO₃-Cu₂O nanocomposites, where RhB dye under visible light irradiation which was up to 4.36 and 2.52 times as the higher photodegradation ability to compare pristine g-C₃N₄ and gC₃N₄-BiFeO₃ catalyst. The magnetization was confirmed by VSM studies, and hence, after the photocatalytic reaction, the magnetically separable catalyst can be quickly separated from the water by an external magnetic field. The superior photocatalytic performance is due to the synergistic effect on the interface of BiFeO₃/Cu₂O in the gC₃N₄-BiFeO₃-Cu₂O nanocomposites has reduced the bandgap which enables high separation efficiency of the charge carrier, suppressed recombination rate and their high surface area. Moreover, the chief gC₃N₄-BiFeO₃-Cu₂O catalyst can exhibited the lesser charge transfer resistance (impedance), enhances of photocurrent responses, whereas exposed to the development of photocatalytic appearance and more charge carrier ability. Also, the antibacterial activity of the gC₃N₄-BiFeO₃-Cu₂O nanocomposite has showing a well deactivation in both G⁺ (S. aureus) and G^? (E. coli) bacteria’s whereas compare to other prepared samples.     

Modification of nano-TiO2 by doping with nitrogen and fluorine and study acetaldehyde removal under visible light irradiation

P25–TiO₂ nanoparticles were doped with fluorine, nitrogen, and their combination. Samples of N-doped, F-doped, and N–F-codoped TiO₂ were prepared by physical and chemical treatments. The products were characterized by X-ray diffraction, Fourier transform infrared, Brunauer–Emmett–Teller technique, and ultraviolet–visible diffuse reflectance spectroscopy. It was revealed that absorption spectra of N-doped, F-doped, and F–N-codoped TiO₂ were extended to the visible region wavelengths, and the photocatalytic experiments showed enhancement of acetaldehyde removal under visible light irradiation. The photocatalytic activity of the powders was evaluated through the process of acetaldehyde degradation under visible light scattering in a continuous stirred tank reactor. F–N-codoped nano-TiO₂ calcinated at 500 °C possessed the highest photocatalytic activity. The photocatalytic kinetic consumption of acetaldehyde was studied on N–F–TiO₂ powders under 80 W Hg lamp irradiation, and a Langmuir-type kinetic model was developed for the reaction with appropriate kinetic parameters.     

Synthesis and investigation of SnS<Subscript>2</Subscript>/RGO nanocomposites with different GO concentrations: structure and optical properties,photocatalytic performance

In this study, we report the synthesis of tin disulfide/reduced graphrene oxide (SnS₂/RGO) nanocomposites by a simple one-step hydrothermal method. In order to investigate the effect of RGO on the structure and optical properties and photocatalytic activity of the products a series of nanocomposites was prepared with different concentrations of GO. The samples were examined using X-ray diffraction, field emission scanning electron microscopy (FESEM), Raman spectroscopy, UV–Vis spectroscopy and photoluminescence techniques. The results confirmed the growth of SnS₂ with the hexagonal phase. FESEM analysis showed that the hexagonal tin disulfide nanoplates are uniformly dispersed on the surface of the graphene oxide sheets. The optical examination of SnS₂ and SnS₂/RGO nanocomposites indicated that the band gaps of all nanocomposites are greater than that of SnS₂ due to the quantum confinement effect. The photocatalytic activity of the SnS₂/RGO nanocomposites was investigated for degradation of the acid orange 7 dye under visible light. It was observed that all nanocomposites have a higher photocatalytic activity for the degradation in comparison with pure SnS₂. The optimum concentration of GO in SnS₂/RGO nanocomposite for achieving the highest photocatalytic efficiency (81%) was determined as 2 mg ml^?1 during 180 min.     

Different combinations of Fe3O4 microsphere,Polypyrrole and silver as core–shell nanocomposites for adsorption and photocatalytic application

Several core–shell nanocomposites composed of Fe₃O₄ microspheres, Polypyrrole and silver were fabricated here by a series of wet chemical methods. The as-prepared nanocomposites were further used in adsorption and photodegradation of azo dyes. The chemical properties of the products were characterized by a series of techniques and equipment. The adsorption and photocatalytic activities of the obtained core–shell heterostructure were studied by controlled experiments. It was found that Fe₃O₄@PPy nanostructure exhibited the highest removal abilities towards organic dyes in aqueous solution among the as-prepared samples. The final removal ratio is 86.2% and 80.4% for Methyl Orange and Orange II aqueous solutions, respectively. Deposition of Ag nanoparticles was employed here to investigate the transportation and separation of photo-induced charges on the surface or interface of Fe₃O₄@PPy under UV illumination.     

Enhanced photocatalytic degradation for thiophene by Ag/α-MoO<Subscript>3</Subscript> heterojunction under visible-light irradiation

Ag/α-MoO₃ heterojunctions were prepared by a photoreduction process and characterized using XRD, TEM, UV–Vis-DRS, EDS, XPS, PL, EIS and PT. Ag/α-MoO₃ heterojunctions exhibited excellent photocatalytic oxidative desulfurization activity for thiophene under visible-light irradiation. The removal efficiency of 5% Ag/α-MoO₃ composites could get to 98.3% with 1.5 g L^?1 amount of catalyst used under visible-light irradiation for 270 min, which is 2.5 times as high as that of pure α-MoO₃ nanobelts. The stability of as-prepared Ag/α-MoO₃ heterojunctions were investigated through recycling run experiment, which the desulfurization rate of 5 wt% Ag/α-MoO₃ for thiophen still remained 92.8% after five consecutive cycles. Furthermore, the active species trapping experiment confirmed that h⁺ and ^·O₂ ^? were the main active in photocatalytic degradation process for thiophene. Additionally, the mechanism of the enhanced photocatalytic activity for Ag/α-MoO₃ was proposed. These features demonstrate that the Ag/α-MoO₃ heterojunctions have great application potential for refractory pollutants’ removal from fuel oil.     

Sonochemical synthesis, characterization, and photocatalytic properties of Bi2−x Sb x WO6 nanorods

We report an efficient route for the sonochemical synthesis of Bi_2?x Sb _x WO₆ (x = 0, 0.01, 0.02, 0.05, 0.1, and 2) nanorods using bismuth nitrate/antimony chloride and sodium tungstate as precursors. The products obtained have been characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–Vis diffuse reflectance spectroscopy. The photoactivities of all the samples for the Rhodamine-B (RhB) photodegradation were investigated systematically under UV and visible light irradiation. The results of the photocatalytic degradation of RhB in aqueous solution showed that 2–5 % antimony ion doping greatly improved the photocatalytic efficiency of sonochemically synthesized Bi₂WO₆ nanorods under both UV and visible radiation compared to its undoped counterpart. Among all the samples, the Sb₂WO₆ nanorods exhibited the highest photodegradation efficiency since 86 % of RhB could be photodegraded in 90 min under UV radiation. The stability of the photocatalysts was ascertained using FT-IR and Raman spectroscopy.     

Structural and Photocatalytic Activity of Mesoporous N-Doped TiO2 with Band-to-Band Visible Light Absorption Ability

White colored N-doped TiO₂ and a neat TiO₂ powder were synthesized via sol–gel method. Prepared samples were characterized by means of x-ray diffractions, Brunauer–Emmet–Teller and Barrett–Joyner–Halenda methods, x-ray photoelectron spectroscopy, ultraviolet-visible analysis, scanning electron microscopy, and energy dispersive x-ray spectroscopy. Both of the N-doped TiO₂ and neat TiO₂ consisted of anatase phase of titania with mesoporous nature and according to XPS analysis prepared N-doped TiO₂ is a substitutional nitrogen containing sample. The band gap of N-doped TiO₂ and neat TiO₂ were estimated from ultraviolet-visible spectroscopy data to be 2.7 and 3.2 eV, respectively. Prepared substitutional N-doped TiO₂ featured steep light absorption edge with an approximately parallel characteristic of its absorption edge to that neat TiO₂. This is due to its band-to-band visible light absorption ability. Synthesized N-doped TiO₂ had a large surface area value of 193 m²/g and high photon absorption ability causing superior photocatalytic properties towards Congo red azo dye compared to neat TiO₂ either under ultraviolet or visible light illumination.     

TiO2–Cu photocatalysts: a study on the long- and short-range chemical environment of the dopant

In this study, the short- and long-range chemical environments of Cu dopant in TiO₂ photocatalyst have been investigated. The Cu-doped and undoped TiO₂ specimens were prepared by the sol–gel approach employing CuSO₄·5H₂O and Ti(O-iPr)₄ precursors and subjecting the dried gels to thermal treatment at 400 and 500 °C. The photocatalytic activity, investigated by methylene blue degradation under sunlight irradiation, showed a significantly higher efficiency of Cu-doped samples than that of pure TiO₂. The X-ray diffraction results showed the presence of anatase phase for samples prepared at 400 and 500 °C. No crystalline CuSO₄ phase was detected below 500 °C. It was also found that doping decreases the crystallite size in the (004) and (101) directions. Infrared spectroscopy results indicated that the chemical environment of sulfate changes as a function of thermal treatment, and UV–vis spectra showed that the band gap decreases with thermal treatment and Cu doping, showing the lowest value for the 400 °C sample. X-ray absorption fine structure measurements and analysis refinements revealed that even after thermal treatment and photocatalytic assays, the Cu²⁺ local order is similar to that of CuSO₄, containing, however, oxygen vacancies. X-ray photoelectron spectroscopy data, limited to the near surface region of the catalyst, evidenced, besides CuSO₄, the presence of Cu¹⁺ and CuO phases, indicating the active role of Cu in the TiO₂ lattice.     

Novel continuous single-step synthesis of nitrogen-modified TiO2 by flame spray pyrolysis for photocatalytic degradation of phenol in visible light

A novel rapid and continuous process has developed for the synthesis of nitrogen-doped TiO₂ (N-TiO₂) with flame spray pyrolysis (FSP) method. The nitrogen incorporation into TiO₂ was achieved by a facile modification (addition of dilute nitric acid) in the precursor for the synthesis. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The doping of nitrogen into the TiO₂ was confirmed by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX) spectroscopy. The UV–vis spectra of the modified catalysts (with primary N source) exhibited band-gap narrowing for 4N-TiO₂ with band gap energy of 2.89 eV, which may be due to the presence of nitrogen in TiO₂ structure. The introduction of secondary N-source (urea) into TiO₂ crystal lattice results in additional reduction of the band gap energy to 2.68 eV and shows a significant improvement of visible light absorption. The N-TiO₂ nanoparticles modified by using secondary N-source showed significant photocatalytic activity under visible light much higher than TiO₂. The higher activity is attributed to the synergetic interaction of nitrogen with the TiO₂ lattice. The lowering of the band-gap energy for the flame made N-doped TiO₂ materials implies that the nitrogen doping in TiO₂ by aerosol method is highly effective in extending the optical response of TiO₂ in the visible region. The nitrogen atomic percentage has increased monotonically (0.09%–0.15%) with the increase in primary nitrogen source (nitric acid), and significantly boosted to 0.97% when secondary nitrogen source (urea) was introduced. The highest rate of phenol degradation was obtained for catalysts with secondary N source due to increase in N content in the catalyst.