Nitrogen-doped TiO2 Nanoparticles Research Articles

3D-TNAs/N-TiO2 photoanode assisted heterogeneous electro-Fenton with a novel Fe-MOFs@CF cathode for efficient synergetic oxidation of organic contaminants

Photoelectro-catalysis (PEC) and heterogeneous electro-Fenton (HEF) reactions are two frontier research fields for real effluent treatments. In the present work, a synergetic system with integration of both PEC and HEF has been developed for pollutant removal. PEC process with lower external bias results in the efficient separation of photogenerated hole and electrons, which can also modulate the HEF catalytic performance at the counter electrode, and in other cases the active HEF reaction can in turn affect the intrinsic activity of PEC. In this system, three dimensional TiO2 nanotube arrays coupled with nitrogen doped TiO2 nanoparticles (3D-TNAs/N-TiO2) was prepared as photoanode for solar light-driven PEC process while NH2-MIL-101 loaded on carbon felt (Fe-MOFs@CF) have been used as the cathode for HEF reaction. The performances of the synergetic system showed much higher degradation efficiency, which were evaluated by degrading typical organic containments in water (with the best of∼95 % in 5 min with 2*3 cm2 electrode area). The reaction rate in the coupling system were ∼7.25 and 1.18 times higher than single PEC or HEF with a wide pH applied range, well recycled and good stability for further application in water purification.

Production of the protein-based nitrogen-doped carbon quantum dots/TiO2 nanoparticles with rapid and efficient photocatalytic degradation of hexavalent chromium

Hexavalent chromium (Cr (VI)) is a typical heavy metal ion caused numerous wastewater, and the photocatalysis is an attractive advanced treatment process for Cr (VI) removal. Biomass material bovine serum albumin and tetrabutyl titanate were used to prepare nitrogen-doped carbon quantum dots and TiO2 (N-CQDs/TiO2) nanoparticles by a facile one-step hydrothermal method. The excellent photonic conversion function of N-CQDs narrowed band gap widths of TiO2 to 2.84 eV due to the N element and the CQDs introduced to the TiO2 successfully. When the mass ratio of BSA and TiO2 was 1 and the hydrothermal reaction time was 48 h, the obtained nanoparticle can rapidly and efficiently degrade of Cr (VI) in 40 min of reaction, and the kinetic reaction rate reached 10.7 times that of pure TiO2 nanoparticles. And the Cr (VI) was reduced in 10 min by 1 mg/L nanoparticle under the pH of 2 or tartaric acid content of 1 g/L due to the electrons were transferred from N-CQDs to the TiO2 surface to achieve effective electron/hole separation and reacted with the Cr (VI) to reduce it to Cr (III). The N-CQDs/TiO2 also exhibited degradation of Congo red completely and killing of E. coli under simulated solar light.

A membrane/mediator-free high-power density dual-photoelectrode PFC aptasensor for lincomycin detection in milk and chicken

Over use of lincomycin (LIN) as antibiotic in animals can lead to multiple harmful impacts to public health, thus detection of LIN at trace level in milk and chicken sample matrixes is vital. In this work, Zinc phthalocyanine nanoparticles sensitized MoS2 (ZnPc/MoS2) was firstly developed as a novel photocathode material combined with nitrogen-doped graphene-loaded TiO2 nanoparticles (TiO2/NG) as photoanode material to construct a dual-photoelectrode photofuel cell (PFC). The as-prepared membrane/mediator-free PFC achieved excellent output performance that the maximum power density (Pmax) reached 11.83 μW cm−2. Specific aptamers are adopted as LIN recognition elements, the as-proposed self-powered aptasensor for LIN exhibited a linear scope in 10−11 –10−5 mol L−1 along with a low detection limit (3S/N) of 3.33 pmol L−1. Consequently, such high-power density dual-photoelectrode PFC aptasensor may be a reassuring candidate electrochemical sensor for the detection of trace contamination in food samples.

Preparation of N-TiO2/SiO2 composites by solvothermal method and their photocatalytic properties

In order to improve the visible light catalytic activity of titanium dioxide (TiO2) and ensure its long-term stability on the surface of concrete, an N-TiO2/SiO2 composite was prepared using tetrabutyl titanate, nitric acid, and modified SiO2 nanospheres as the precursors by a solvothermal method. The effect of nitric acid on the phase composition, morphology and photoelectric properties of the synthesized photocatalytic composites was systematically studied by various characterization methods. The results show that the optimum nitric acid/butyl titanate volume ratio is 1/6. The nitrogen-doped TiO2 nanoparticles were uniformly dispersed on the surface of spherical SiO2 with a diameter of 200 nm. The degradation rate of simulated pollutants (RhB) with pH 5 and 7 exceeded 95% within 30 min and the catalytic effect remained excellent after five repetitions without much weakening. The excellent visible photocatalytic performance can be attributed to the doping of N replacing part of the oxygen atoms in TiO2, forming the energy level of N 2p at the O 2p energy level and reducing the TiO2 energy band gap to 2.99 eV. At the same time, the better dispersion of N-TiO2/SiO2 prepared by this new synthesis method also plays an important role in the improvement of visible light photocatalytic activity.

Highly active β-NaYF4:Yb/Er-N-TiO2 nanoparticles for NIR light driven Rhodamine B degradation

Composite nanoparticles consisting upconversion nanoparticles (β-NaYF4:Yb/Er) and nitrogen doped TiO2 nanoparticles were constructed via a chemical assembly method. Efficient energy transfer was enabled since the upconverted energy matched up with the band gap of N-TiO2. This enables the resulting composite nanoparticles to possess excellent Rhodamine B (RhB) degradation activity under near infrared (NIR) light irradiation.

Architecting of an aptasensor for the staphylococcus aureus analysis by modification of the screen-printed carbon electrode with aptamer/Ag–Cs-Gr QDs/NTiO2

Given the many issues bacterial infections cause to humans and the necessity for their detection, in this work we developed a robust aptasensor for prompt, ultrasensitive, and selective analysis of staphylococcus aureus bacterium (S. aureus). A nanocomposite of Ag nanoparticles, chitosan, graphene quantum dots, and nitrogen-doped TiO2 nanoparticles (Ag–Cs-Gr QDs/NTiO2) was synthesized, and thoroughly characterized by XRD, FT-IR, and FE-SEM spectroscopic methods. The surface of screen-printed carbon electrodes modified with Ag–Cs-Gr QDs/NTiO2 nanocomposite was utilized as a compatible platform for aptamer attachment. The aptasensor accurately determined S. aureus in the dynamic range of 10–5 × 108 CFU/mL with detection limit of 3.3 CFU/mL. The monitoring of the practical performance of aptasensor in human serum samples revealed its superiority over the conventional methods (relative recovery of 96.25–103.33%). The Ag–Cs-Gr QDs/NTiO2-based aptasensor offers facile, biocompatibility, good repeatability, reproducibility (RSD = 3.66%), label free and stabile strategy for sensitive S. aureus analysis free from biomolecules interferences in actual specimens.

Predicting kinetics of water-rich permeate flux through photocatalytic mesh under visible light illumination

Membrane-based separation technologies are attractive to remediating unconventional water sources, including brackish, industrial, and municipal wastewater, due to their versatility and relatively high energy efficiency. However, membrane fouling by dissolved or suspended organic substances remains a primary challenge which can result in an irreversible decline of the permeate flux. To overcome this, membranes have been incorporated with photocatalytic materials that can degrade these organic substances deposited on the surface upon light illumination. While such photocatalytic membranes have demonstrated that they can recover their inherent permeability, less information is known about the effect of photocatalysis on the kinetics of the permeate flux. In this work, a photocatalytic mesh that can selectively permeate water while repelling oil was fabricated by coating a mixture of nitrogen-doped TiO2 (N-TiO2) and perfluorosilane-grafted SiO2 (F-SiO2) nanoparticles on a stainless steel mesh. Utilizing the photocatalytic mesh, the time-dependent evolution of the water-rich permeate flux as a result of photocatalytic degradation of the oil was studied under the visible light illumination. A mathematical model was developed that can relate the photocatalytic degradation of the organic substances deposited on a mesh surface to the evolution of the permeate flux. This model was established by integrating the Langmuir–Hinshelwood kinetics for photocatalysis and the Cassie–Baxter wettability analysis on a chemically heterogeneous mesh surface into a permeate flux relation. Consequently, the time-dependent water-rich permeate flux values are compared with those predicted by using the model. It is found that the model can predict the evolution of the water-rich permeate flux with a goodness of fit of 0.92.

Performance of TiO2, Cu-TiO2, and N-TiO2 nanoparticles sensitization with natural dyes for dye sensitized solar cells

In this work, the eucalyptus and teak leave extracts are used as natural dyes for dye-sensitized solar cells (DSSCs). The TiO2, copper doped -TiO2 (Cu-TiO2), and nitrogen doped-TiO2 (N-TiO2) nanoparticles were synthesized by using the sol–gel method. The structural, morphological and elemental properties of the prepared samples were tested by X-ray diffractometer (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). XRD revealed the anatase-TiO2 phase and calculated crystallite sizes are 10, 11.23, and 13.97 nm, correspondingly. SEM micrograph shows the spherical shaped nanoparticles with less agglomeration and primary elements (Ti, O, Cu, N) confirmed by EDS spectra. Further, the nanoparticles used as a photoanode in DSSC device with natural dyes and studied their performance.

Effect of Nitrogen Doping on Photocatalytic Activity of TiO2

Nitrogen doped TiO2 nanoparticles (N-doped TiO2) in different mol percentage (2-6 mol%) of nitrogen with anatase phase, have been prepared by using EDTA-glycol method. Samples were characterized by various physico-chemical techniques. Physico-chemical characterization revealed that crystallite size, surface hydroxylation, and tuning of optical band gap towards visible region of catalyst increases with increase in dopant concentration upto 4.0 mol% in TiO2 host lattice. Thereafter, the samples were used to photocatalytic degradation of the organic dye methylene blue (MB) under sunlight irradiation directly. The progress of photodegradation reaction was monitored by UV-visible spectroscopy. During photocatalytic reaction, the effect of calcination temperature, amount of catalyst, initial concentration of dye and the effect of pH on the rate of degradation reaction was also studied. It is clearly shown that N doping in TiO2 results in the enhancement of the degradation ability of MB in UV-visible light.

Modeling and Experimental Studies on Adsorption and Photocatalytic Performance of Nitrogen-Doped TiO2 Prepared via the Sol–Gel Method

Nitrogen-doped TiO2 has a great potential as a photocatalyst under visible light irradiation with applications in the removal of air and water pollutants, and the treatment of bacterial contaminations. In this study, nitrogen-doped TiO2 nanoparticles were synthesized via the sol–gel method and a post-annealing heat treatment approach. The effects of annealing treatment on the photocatalyst crystalline size and degree of crystallinity were analyzed. Methylene blue dye was used as the model water contaminant for the evaluation of the photoactivity of the synthesized nitrogen-doped TiO2 nanoparticles. The degradation of methylene blue was attributed to three mechanisms, i.e., adsorption, photocatalysis, and direct light photolysis. A kinetic model was developed to distinguish the impact of these three different mechanisms on the removal of contaminants. Adsorption and photocatalysis are heterogeneous processes for removing water organic contaminants. The characterization analysis demonstrates that they are relevant to the microstructures and surface chemical compositions of nitrogen-doped TiO2 photocatalysts. The processing–structure–performance relationship helped to determine the optimal processing parameters for nitrogen-doped TiO2 photocatalyst to achieve the best performance. While we used methylene blue as the model contaminant, the generalized quantitative model framework developed in this study can be extended to other types of contaminants after proper calibration.

Synthesis of N-TiO2@NH2-MIL-88(Fe) Core-shell Structure for Efficient Fenton Effect Assisted Methylene Blue Degradation Under Visible Light

Core-shell TiO2-based photocatalysts with specific composition, morphology, and functionality have attracted considerable attention for their excellent degradation properties on organic pollutants via a photocatalytic oxidation process. Herein, a N-TiO2@NH2-MIL-88(Fe) core-shell structure was prepared by coating NH2-MIL-88(Fe) on nitrogen-doped TiO2(N-TiO2) nanoparticles. Introduction of heteroatom nitrogen to pure TiO2 expands the spectral response range, leading to enhanced quantum efficiency of photocatalyst. Furthermore, loading NH2-MIL-88(Fe) on N-TiO2 improved the adsorption ability of the nanocomposites due to the porous tunnels of NH2-MIL-88(Fe). The resulted core-shell N-TiO2@NH2-MIL-88(Fe) nanocomposites realized the transfer of photo excited electrons from N-TiO2 to NH2-MIL-88(Fe) rapidly, partially reduced Fe3+ to Fe2+ in NH2-MIL-88(Fe), and further enhanced the Fenton effect on efficiently degrading methylene blue dye(MB) under visible light(λ≽420 nm) with the assistance of H2O2.

Facile Synthesis of Anatase–Rutile Diphase N-doped TiO2 Nanoparticles with Excellent Visible Light Photocatalytic Activity

To further boost the charge separation and photocatalytic activity of TiO2 under visible light, the anatase–rutile mixed-phase nitrogen-doped (N-doped) TiO2 nanoparticles were successfully synthesized through a facile one-step calcining procedure using TiN as raw materials. The crystal phases, morphologies, chemical compositions, textural structures, and optical properties of as-obtained N-doped TiO2 were characterized by the corresponding analytical techniques. The photocatalytic activities of as-fabricated samples were evaluated by degrading 4-chlorophenol (4-CP) and methylene blue (MB) aqueous solution under visible light irradiation. The results revealed that the ratio of rutile to anatase increased with the improvement of sintering temperature, and the sample prepared at 500 °C had the best photocatalytic activity. This might be because it possessed the most appropriate rutile/anatase proportion as well as the nitrogen doping. The transient photocurrent responses, photoluminescence spectra (PL) measurements, and active species trapping experiments were implemented to disclose the photocatalytic mechanism. This work will provide a further insight into the synthesis of highly efficient N-doped TiO2 photocatalysts for organic contaminant removal.

Nitrogen-Doped Titanium Dioxide Nanoparticles Modified by An Electron Beam for Improving Human Breast Cancer Detection by Raman Spectroscopy: A Preliminary Study.

Titanium dioxide (TiO2) is commonly used as a pigment in paints, paper products, polymer compositions, and cosmetic products, and even as a food additive or drug coating material. In recent times, it has also been used in photovoltaic cells, semiconductors, biomedical devices, and air purification. In this paper, the potential application of nitrogen-doped TiO2 nanoparticles modified by an electron beam for improving human breast cancer detection by Raman spectroscopy is presented. Raman spectroscopy (RS) is a promising noninvasive analytical technique in cancer detection that enables us to retrieve a molecular signature of the biochemical composition of cancerous tissue. However, RS still has some challenges in signal detection, mainly related to strong concurrent background fluorescence from the analyzed tissue. The Raman signal scattering is several orders of magnitude smaller than the fluorescence intensity, and strong fluorescence masks a much weaker Raman signal. The Raman results demonstrate that the N-doped TiO2 electron beam-irradiated nanoparticles amplify the Raman scattering. The intrinsic properties of the adsorbed molecules from human breast tissue and the surface properties of the N-doped TiO2 electron beam-irradiated nanoparticles (the excited electron–hole pair at the surface) have a significant effect on the enhanced Raman signal intensity.

In situ growth of TiO2 nanoparticles on nitrogen-doped Ti3C2 with isopropyl amine toward enhanced photocatalytic activity

Construction of heterojunction and nitrogen doping is an effective approach for synthesizing photocatalysts with high quantum yield and efficient electron-hole separation. 2D MXene Ti3C2 has been considered a good carbonaceous nanomaterial for designing heterojunction, while the original surface groups and stacked structure limit the electron-hole separation. Herein, a hybrid of nitrogen-doped Ti3C2 nanosheets and TiO2 nanoparticles (NPs) composed of TiO2 NPs in situ growing on isopropyl amine (iPA) modified Ti3C2 (iN-Ti3C2) was developed for the first time. The novel iN-Ti3C2/TiO2 hybrid exhibited an excellent ultraviolet-light photodegradation of methylene blue (MB), with a degradation rate (0.02642 min−1) significantly higher than that of pure TiO2 NPs, bulk-Ti3C2/TiO2, dimethyl sulfoxide modified Ti3C2/TiO2 hybrid, and hydrazine monohydrate modified Ti3C2/TiO2 hybrid. The formation of heterojunction between iN-Ti3C2 and TiO2 and its role in the photocatalysis were systematically analyzed using various characterization techniques and density functional theory calculation. The iPA modification exfoliated Ti3C2 and doped N on Ti3C2 nanosheets; the in situ grown TiO2 NPs formed efficient heterojunctions with the nanosheets; the N-doping facilitated electron migration in Ti3C2 and inhibited the recombination of photogenerated electron-hole pairs; •OH dominated the photodegradation of MB. This work provides a new approach of constructing efficient photocatalysts for the treatment of organics-polluted water.

Multifunctional quaternized chitosan@surface plasmon resonance Ag/N-TiO2 core-shell microsphere for synergistic adsorption-photothermal catalysis degradation of low-temperature wastewater and bacteriostasis under visible light

Abstract Chitosan are deemed as a promising candidate to environmentally friendly materials owing to the inexpensive, biodegradable and rich reserves. Nevertheless, the application of chitosan materials still confronts chemical instability and low mechanical strength. In this study, we grow ultrafine nitrogen-doped TiO2 nanoparticles (chitosan as nitrogen source) on the surface of hollow quaternized chitosan by electrostatic self-assembly, giving a unique core-shell structure. Then, Ag nanoparticles is deposited on the surface of quaternized chitosan@N-TiO2 via a simple photo-deposition process. Our investigations indicate that chitosan has a great adsorption-photothermal catalysis degradation for low-temperature sodium dodecylbenzene sulfonate (SDBS) wastewater and gram-negative (E. coli) under visible light. The degradation rate of SDBS wastewater can reach 96.4% within 180 min and E. coli can be inactivated within 120 min. The outstanding degradation performance of QCS@Ag-TiO2 is ascribed to the synergistic effect of the active site of quaternized chitosan, nitrogen doping and surface plasmon resonance of Ag nanoparticles. Our work provides a promising design to combine adsorption and photothermal catalysis to prepare a multifunctional material.

Bleaching of stained resin using nitrogen doped-TiO2 nanoparticles

H₂O₂가 치아미백에 많이 사용되고 있다. 본 연구는 레이저 광조사 하에서 질소가 도핑된 이산화티탄 (N-doped TiO₂) 나노입자로 착색된 레진을 얼마나 미백시키는지를 평가한 것이다. 이를 위하여 시료를 졸-겔 방법으로 제조하고 광흡수도와 XRD를 평가하였다. 액상의 methylene blue와 분말입자를 함유한 젤을 이용하여 착색된 레진의 색변화를 측정하였다. 광조사를 위하여 파장이 다른 빛을 사용하였다. 그 결과 N-doped TiO₂는 보통의 TiO₂에 비하여 400 nm 이후에서 높은 흡수도를 보였고 N-doped TiO₂는 TiN 구조를 기반으로 새로운 루틸구조가 관찰되었다. 레이저가 조사되는 환경에서 methylene blue 용액과 착색된 레진은 3% H₂O₂를 함유한 N-TiO₂ 나노입자에 의해서 15% H₂O₂보다 더 큰 흡수도 감소와 색변화를 보였다.

Research Synthesis of La3+ Doped TiO2 Nanoparticles by Hydrothermal Method, Study on Photocatalytic Activity of Decomposition of Methylene Blue under Ultraviolet Irradiation

In this study, with the aim of improving the photocatalytic efficiency of TiO2, we studied the synthesis of La3+ doped TiO2 (with doped rates 1%, 2.5%, 5% mol/mol compared to Ti4+) by hydrothermal method. The hydrothermal condition was set at 180 °C for 12 hours. Material characteristics were investigated by XRD, SEM and solid UV-Vis methods. The results show that, all prepared materials have a crystal particle size of about nano-meters, small and smooth (4.5¸6.5 nm). La3+ doped TiO2 samples had a shift towards longer wavelengths (l» 400¸500 nm) compared to non-doped TiO2 sample (l£ 380 nm). The band gap energy (Eg) of La3+ doped TiO2 samples was reduced to 3.04¸3.10 eV . The yield of MB degradation of La3+ doped TiO2 at 5% mol/mol reached the highest ~93% after 60 minutes under ultraviolet irradiation.
 Keywords
 Anatase TiO2, photocatalysis, La3+ doped TiO2, hydrothermal method, ultraviolet irradiation. 
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Grafting of N-doped titania nanoparticles synthesized by the plasma-assisted method on textile surface for sunlight photocatalytic self-cleaning applications

The surface of textile fibers were coated with nitrogen-doped TiO2 nanoparticles obtained from an aqueous solution of TiCl3 via a plasma-assisted oxi-precipitation process at atmospheric pressure. The photocatalytic activities hence self-cleaning properties of the coated fabrics were investigated. The structural analysis was characterized by FTIR, Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy; while the surface morphology was investigated by scanning electron microscopy (SEM). As a result, it was demonstrated that visible, efficient photocatalyst with both anatase and rutile TiO2 phases and average grain size of 8–12 nm were synthesized and grafted durably onto the textile even after three successive washes in hard conditions. The coated fabrics exhibited a stable and promising photocatalytic property and therefore could be a good candidate to manufacture long life self-cleaning clothes under visible light irradiation (daylight source).

Influence of nitrogen doping on TiO2 nanoparticles synthesized by pneumatic spray pyrolysis method

Improving the photon harvesting efficiency of dye sensitized solar cells (DSSCs) employing TiO2 photo-anode has been the major issue since 1991. So it is very important to discover new techniques that will enhance the properties of TiO2 nanoparticles (NPs) which will then prevent recombination of the photo-generated electron hole pairs and as well as improving the visible absorption properties of the TiO2. This will in turn improve the performance of the DSSC photo-electrode. The optical, electronic and structural properties of TiO2 NPs rely on factors like morphology, surface area, particle size and the presence of beneficial defects caused by dopants. This study focuses on the fabrication and characterization of nitrogen doped TiO2 (NPs) prepared by pneumatic spray pyrolysis (PSP) technique. The un-doped and nitrogen doped TiO2 NPs were prepared using titanium butoxide as a precursor and urea as the dopant. The morphological and structural properties of PSP synthesized NPs were evaluated using SEM, EDX, Raman Spectroscopy (RS), XRD and FTIR. SEM analysis revealed that the presence of nitrogen dopant results in a significant change in the surface morphology of the PSP synthesized NPs. RS revealed the presence of Raman vibrational modes and symmetry at 158 (Eg(1)), 208 (Eg(2)), 258 (B1g), 255 (B1g) 396 (B1g), 514 (A1g + B1g(2)) and 640 (Eg(3)) belonging to a mixed Anatase-Rutile phase. XRD analysis revealed that the PSP synthesized NPs have particles sizes of 10.90 nm, 11.31 nm, 11.93 nm and 14.14 nm for un-doped TiO2, 0.005 M TiO2, 0.015 M TiO2 and 0.025 M TiO2 NPs respectively. FTIR spectra of the PSP fabricated samples exhibited a peak at 616.22 cm−1 that is assigned to Ti–O vibrational stretching of the anatase phase of TiO2. UV–vis spectroscopy revealed a decrease in energy band gap with increase in dopant level for the TiO2 samples prepared.

Synthesis and enhanced photocatalytic activity of nitrogen-doped triphasic TiO2 nanoparticles

TiO2 nanoparticles of the single anatase phase, binary anatase–brookite phases, and ternary anatase–brookite–rutile phases were synthesized using an HNO3-catalyzed hydrothermal process. The types and amounts of phases varied depending on the hydrothermal synthesis conditions. The results revealed that N dissolves in different amounts and chemical states, depending on the phases present and their proportions in the nanoparticles. Brookite and rutile nanoparticles oriented through one direction were found to be crystallized by the surface transformation from anatase. Photocatalytic activity tests, evaluated by degradation of methylene blue (MB) under ultraviolet (UV) and visible light illumination, revealed that the N-doped TiO2 nanoparticles containing a ternary-phase mixture had the best photocatalytic activity. The MB degradation of the visible light–active nanoparticles was three times better than that of a commercially available well-known TiO2 powder, P25 under UV illumination. The enhanced photoactivity was attributed to the following: i) a high surface area, ii) suppression of the recombination of electron–hole pairs with ternary-phase mixture crystallized in heterojunctions, iii) larger anatase phase content, and iv) narrower band gap and facilitation of charge separation by dissolved N atoms.