Nitrogen-doped Titanium Research Articles

THE PORE FORMATION AND DOPING PROCESS ON THE SYNTHESIS OF NITROGEN-DOPED TITANIA THROUGH SOL-GEL METHOD

The mesoporous nitrogen-doped titania (N-doped TiO2) has been synthesized through a one-step sol-gel method using dodecylamine as pore template and nitrogen source, which were performed with and without reflux. The role of aging time toward pore formation and doping process was also studied by applying 0 and 72 hours of aging time to the resulting solution after the hydrolysis step. The resulting material was characterized using X-Ray Diffraction (XRD), N2 Gas Sorption Analyzer (GSA), and X-ray Photoelectron Spectroscopy (XPS). The result showed that the reflux process played an important role in the doping process, where there is no nitrogen found in the material synthesized without reflux. The aging process also influenced the doping process, where the structure rearrangement is occurred increasing the nitrogen amount that substitutes the oxygen site in the TiO2 lattice, resulting in higher nitrogen content in the TiO2. The reflux process and aging process do not directly affect the pore formation of the TiO2 but applying both processes in the synthesis resulted in a material with a higher specific surface area and a more homogenous mesoporous size and structure

GLYCEROL-ASSISTED SOL-GEL SYNTHESIS OF NITROGEN-DOPED TITANIUM DIOXIDE FOR VISIBLE LIGHT-DRIVEN PHOTODEGRADATION OF INDOOR GASEOUS FORMALDEHYDE

In the present paper, the synthesis of nitrogen-doped titanium dioxide (N-doped TiO2) photocatalyst and its application for photodegradation of gaseous formaldehyde are reported. The N-doped TiO2 was synthesized via the glycerol-assisted sol-gel technique. The effect of various synthesis parameters such as nitrogen to titanium (N:Ti) molar ratio, calcination temperature, calcination duration and TiO2 loading was investigated on the photocatalytic properties of TiO2 and photodegradation of HCHO vapor. The characterization results obtained through different analytical techniques such as XRD, XPS, FESEM, DRUV-Vis, and BET revealed that all the N-doped TiO2 photocatalysts were anatase phase with enhanced visible light absorption, narrow bandgap (2.64–2.50 eV), and small particle sizes ranging from 23.12–25.17 nm. The surface area decreased from 252.7 m2/g to 72.3 m2/g with an increased N:Ti molar ratio. The N:Ti molar ratio plays an important role in the formation of crystalline structure and surface area and performance. The photodegradation of HCHO vapor was the highest (70.59%) when the N:Ti molar ratio was 20:1. The best photodegradation efficiency was achieved using the N-doped TiO2 calcined at 300°C for 1 h. This study signifies the importance of optimizing N:Ti molar ratio and calcination temperature for tuning the properties of the TiO2 and the enhancing photodegradation of indoor HCHO vapor under visible light irradiation.Keywords: Photocatalytic oxidation, titanium dioxide, formaldehyde, visible light, nitrogen-doped, glycerol.

Rhodamine B Photodegradation in Aqueous Solutions Containing Nitrogen Doped TiO2 and Carbon Nanotubes Composites.

In this work, new results concerning the potential of mixtures based on nitrogen doped titanium dioxide (TiO2:N) and carbon nanotubes (CNTs) as possible catalyst candidates for the rhodamine B (RhB) UV photodegradation are reported. The RhB photodegradation was evaluated by UV–VIS absorption spectroscopy using samples of TiO2:N and CNTs of the type of single-walled carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-wall carbon nanotubes (MWNTs), and single-walled carbon nanotubes functionalized with carboxyl groups (SWNT-COOH) having various concentrations of CNTs. The best photocatalytic performance was obtained for sample containing TiO2:N and 2.5 wt.% SWNTs-COOH, when approx. 85% of dye removal was achieved after 300 min. of UV irradiation. The reaction kinetics of RhB aqueous solutions containing TiO2:N/CNT mixtures followed a complex first-order kinetic model. The TiO2:N/CNTs catalyst induced higher photodegradation efficiency of RhB than TiO2:N due to the presence of CNTs, which act as adsorbent and dispersing agent and capture the photogenerated electrons of TiO2:N hindering the electron–hole recombination.

Facile and novel synthesis of nitrogen doped TiO2/Acid soluble collagen-polyvinyl pyrrolidone (ASC-PVP) hybrid nanocomposite for rapid and effective photodegradation of naphthalene from water under visible light irradiation

A highly efficient, eco-friendly, and visible-light-driven photocatalyst, namely nitrogen doped titanium dioxide (N-TiO2)/collagen-polyvinyl pyrrolidone (ASC-PVP) hybrid nanocomposite is prepared via facile sol–gel method. The ASC-PVP steadily covers the N-TiO2. The XPS data confirmed the oxygen vacancies and nitrogen interstitial-type doping in N-TiO2 prepared by the sol–gel route. Furthermore, the O 1s and N 1S XPS data prove that both nitrogen and oxygen atoms of ASC-PVP are participated in hydrogen bonds with N-Ti-O and/or Ti-O-N bonds in N-TiO2 nanoparticles. Moreover, the N-TiO2/ASC-PVP is shown an obvious red shift of absorption band edge and reduced recombination rate of electron-hole in comparison with N-TiO2 nanoparticles. N-TiO2/ASC-PVP was used to study photocatalytic degradation of a typical polycyclic aromatic hydrocarbon (PAHs), namely naphthalene in water under visible light irradiation. N-TiO2/ASC-PVP possessed high photocatalytic activity for the naphthalene degradation (86%) within 100 min under visible light. The inhibitory effect on the naphthalene photodegradation indicated that O2-. and h+·are the major reactive species. Also, the N-TiO2/ASC-PVP exhibited very good visible light photocatalytic efficiency for the removal of naphthalene at very low concentrations from seawater.

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

ObjectiveTo develop an aesthetic resin composite using a nitrogen-doped titanium dioxide (NTiO2) filler that possesses antimicrobial properties against cariogenic bacteria. MethodsN-TiO2 powder was manufactured by calcining commercial TiO2 with urea. Free radical release from the N-TiO2 powder under visible light irradiation was analysed using UV-Vis spectrophotometry. The N-TiO2 powder was incorporated into a dental resin and the photocatalytic activity assessed using a dye under both visible light and dark conditions. Using XTT assay to measure the cellular metabolic activity, the antibacterial properties of the N-TiO2 /resin composite discs were tested using Streptococcus mutans. ResultsDoping nitrogen of TiO2 resulted in a band gap shift towards the visible light spectrum, which enabled the powder to release reactive oxygen species when exposed to visible light. When incorporated into a dental resin, the N-TiO2/resin composite still demonstrated sustained release of reactive oxygen species, maintaining its photocatalytic activity and showing an antibacterial effect towards Streptococcus mutans under visible light conditions. SignificanceN-TiO2 filled resin composite shows great promise as a potential aesthetic resin based adhesive for orthodontic bonding.

The Influence of pH on the Nitrogen-doped TiO2 Structure and Its Photocatalytic Activity on Methylene Blue Degradation

The mesoporous nitrogen-doped titania (N-doped TiO2) has been synthesized through sol-gel method by refluxing the precursor mixture, continued by hydrolysis process, and then followed by annealing in air at the desired temperature. The pH of precursor mixture solution before hydrolysis process has been varied to study their influence on the resulting N-doped TiO2. The resulting material were characterized using X-Ray Diffraction (XRD), N2 Gas Sorption Analyzer (GSA), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and UV Vis Spectrophotometer. The XRD analysis result showed that the pH and water content played an important role on the crystal formation of the N-doped TiO­2. The result showed that a high acidity condition resulted in a favored tendency of anatase crystalline phase, while lowering acidity leaded to the rutile formation. Porosity analysis showed the significant influence of pH in the synthesis process on the pore characteristic and pore size distribution of the resulting material. The photocatalytic activity was tested on the methylene blue degradation system comparing to pure TiO2 and commercial Degussa P25 and the result showed that the synthesized N-doped TiO2 provided better photocatalytic activities.

Indium-tin oxide regulated band gap of nitrogen-doped titanium oxide thin films for visible light photocatalyst

Indium-tin oxide regulated band gap of nitrogen-doped titanium oxide thin films for visible light photocatalyst

Effect of Novel Polymer-Free Nitrogen-Doped Titanium Dioxide Film-Coated Coronary Stent Loaded With Mycophenolic Acid.

Background: Titanium is commonly used in blood-exposed medical devices because it has superior blood compatibility. Mycophenolic acid inhibits the proliferation of vascular smooth muscle cells. This study examined the effect of a non-polymer TiO2 thin film–coated stent with mycophenolic acid in a porcine coronary overstretch restenosis model. Methods: Thirty coronary arteries in 15 pigs were randomized into three groups in which the coronary arteries were treated with a TiO2 film–coated stent with mycophenolic acid (NTM, n = 10), everolimus-eluting stent with biodegradable polymer (EES, n = 10), or TiO2 film–coated stent (NT, n = 10). A histopathologic analysis was performed 28 days after the stenting. Results: There were no significant intergroup differences in injury score, internal elastic lamina area, or inflammation score. Percent area stenosis was significantly smaller in the NTM and EES groups than in the NT group (36.1 ± 13.63% vs. 31.6 ± 7.74% vs. 45.5 ± 18.96%, respectively, p = 0.0003). Fibrin score was greater in the EES group than in the NTM and NT groups [2.0 (range, 2.0–2.0) vs. 1.0 (range, 1.0–1.75) vs. 1.0 (range, 1.0–1.0), respectively, p < 0.0001]. The in-stent occlusion rate measured by micro-computed tomography demonstrated similar percent area stenosis rates on histology analysis (36.1 ± 15.10% in NTM vs. 31.6 ± 8.89% in EES vs. 45.5 ± 17.26% in NT, p < 0.05). Conclusion: The NTM more effectively reduced neointima proliferation than the NT. Moreover, the inhibitory effect of NTM on smooth muscle cell proliferation was not inferior to that of the polymer-based EES with lower fibrin deposition in this porcine coronary restenosis model.

Synergistic effects of Tin sulfide Nitrogen-doped titania Nanobelt-Modified graphitic carbon nitride nanosheets with outstanding photocatalytic activity

Designing efficient ternary nanostructures is a feasible approach for energy production under simulated solar irradiation. In this study, excellent photoexcited charge carrier separation and enhanced visible-light response were achieved with nitrogen-doped titania nanobelts (N-TNBs), whose 1D geometry facilitated the fabrication of a heterostructure with SnS2 on the surface of graphitic carbon nitride (g-C3N4). We established the design of SnS2@N-TNB and SnS2@N-TNB/g-C3N4 heterostructures by in situ hydrothermal and ultrasonication processes, and achieved commendable simulated solar light driven photocatalytic H2 generation. UV–vis diffuse reflectance spectroscopy analysis revealed a red shift in the absorption spectra of the SnS2@N-TNB and SnS2@N-TNB/g-C3N4 samples. The H2 produced via SnS2@N-TNB-10/g-C3N4 (6730.8 µmol/g/h) was 2.6 times higher than that produced by SnS2@N-TNB (2515.1 µmol/g/h), and 299 times higher than that produced by N-TNB (22.5 µmol/g/h). The improved photocatalytic H2 production was attributed to the maximum interface contact between SnS2@N-TNB and g-C3N4, and to the improved visible-light absorption and effective charge-carrier separation. Therefore, the present study provides novel insights for combining the advantages of ternary materials to improve the conversion of solar energy to H2 fuel.

Metal‐Insulator‐Insulator‐Metal Diodes with Responsivities Greater Than 30 A W−1 Based on Nitrogen‐Doped TiOx and AlOx Insulator Layers

AbstractMetal‐insulator‐insulator‐metal diodes based on nitrogen‐doped titanium dioxide (NTiOx) and aluminum oxide (NAlOx) are fabricated and characterized for the first time. Pt/TiOx‐NTiOx/Pt and Pt/TiOx‐NAlOx/Pt diodes with 30 nm of TiOx or NTiOx and 5 nm of NAlOx are compared to undoped Pt/TiOx/Pt and Pt/TiOx‐AlOx/Pt diodes of similar thickness. The nitrogen atoms are expected to modify the barrier heights and produce electron traps in the insulators. This changes the conduction mechanisms of the doped diodes, including the introduction of unidirectional, defect‐mediated Poole–Frenkel transport and trap‐assisted tunneling, which increase the performance of the doped diodes. The representative figures of merit observed for a Pt/TiOx‐NAlOx/Pt diode at 0.5 V include an asymmetry of 8.76 × 103, nonlinearity of 4, and zero‐bias responsivity of 22.3 A W−1. Zero‐bias responsivities as high as 36.8 A W−1 are obtained, which surpass the 19.4 A W−1 theoretical limit for Schottky diodes. Notably, this defect‐engineering approach is found to improve the figures of merit without an unwanted increase in diode resistance. A thinner Pt/NTiOx‐NAlOx/Al diode is also produced, which has a low zero‐bias resistance of 36 Ω, nonlinearity of 3.7, and zero‐bias responsivity of 1.7 A W−1.

Engineered Nanoparticles with Decoupled Photocatalysis and Wettability for Membrane-Based Desalination and Separation of Oil-Saline Water Mixtures.

Membrane-based separation technologies are the cornerstone of remediating unconventional water sources, including brackish and industrial or municipal wastewater, as they are relatively energy-efficient and versatile. However, membrane fouling by dissolved and suspended substances in the feed stream remains a primary challenge that currently prevents these membranes from being used in real practices. Thus, we directly address this challenge by applying a superhydrophilic and oleophobic coating to a commercial membrane surface which can be utilized to separate and desalinate an oil and saline water mixture, in addition to photocatalytically degrading the organic substances. We fabricated the photocatalytic membrane by coating a commercial membrane with an ultraviolet (UV) light-curable adhesive. Then, we sprayed it with a mixture of photocatalytic nitrogen-doped titania (N-TiO2) and perfluoro silane-grafted silica (F-SiO2) nanoparticles. The membrane was placed under a UV light, which resulted in a chemically heterogeneous surface with intercalating high and low surface energy regions (i.e., N-TiO2 and F-SiO2, respectively) that were securely bound to the commercial membrane surface. We demonstrated that the coated membrane could be utilized for continuous separation and desalination of an oil–saline water mixture and for simultaneous photocatalytic degradation of the organic substances adsorbed on the membrane surface upon visible light irradiation.

Inactivation of pathogens by visible light photocatalysis with nitrogen-doped TiO2 and tourmaline-nitrogen co-doped TiO2

• Effective photo-inactivation of bacteria, mycobacteria, and fungi were achieved. • Tourmaline acts as an efficient co-catalyst improved N-TiO 2 for photo-inactivation. • Key variables affecting S. aureus photo-inactivation were systemically evaluated. • Inactivation kinetics of S. aureus are well described by LMH model. • Hydroxyl radicals are the major radicals govern the photo-inactivation processes. Four types of pathogens, namely, Staphylococcus aureus ( S. aureus , gram-positive bacteria), Escherichia coli ( E. coli , gram-negative bacteria), Mycobacterium avium ( M. avium, mycobacteria), and Candida albicans ( C. albicans , fungi), are common microorganisms that cause serious human health issues. However, searching for an efficient material for inactivating pathogens via visible light driven photocatalysts remains a challenge. An attempt was made to compare the photocatalytic performance using nano-sized nitrogen-doped titanium oxide (N-TiO 2 ) and tourmaline-nitrogen-co-doped titanium oxide (T-N-TiO 2 ) for inactivation of pathogens under visible light irradiation. S. aureus was used to compare the photocatalytic inactivation performance of N-TiO 2 and T-N-TiO 2 . The findings showed that photocatalyst dosage, initial microbial concentration, and visible light intensity are the key factors affecting photocatalytic inactivation process for both photocatalysts. A 2-log-inactivation of S. aureus under 7.25 mW/cm 2 visible light irradiation via T-N-TiO 2 was achieved within 3 h, which is shorter than the inactivation via N-TiO 2 (4 h). TEM observations had proved that both visible-light-induced photocatalysis could cause severe damage to the cell membrane. The results of electron paramagnetic resonance also indicated that more hydroxyl radicals generated in the T-N-TiO 2 photo-inactivation system allowed a better inactivation performance of the visible-light-induced T-N-TiO 2 . This is the first work exploring that Light-responsive Modified Hom’s model (LHM) is able to simulate photocatalytic inactivation of S. aureus . T-N-TiO 2 composite was firstly evaluated for its efficacy of photocatalytic inaction of S. aureus , E. coli, and M. avium , and an increasing order of time was required for complete inactivation as follows: S. aureus < E. coli < M. avium < C. albicans. We have found that the inactivation efficiency of tested pathogens using T-N-TiO 2 is the highest as compared with literature works. Overall, T-N-TiO 2 exhibits a better inactivation efficiency than that of N-TiO 2 in all the tested pathogens.

Nitrogen-Doped Titanium Dioxide Mixed with Calcium Peroxide and Methylcellulose for Dental Bleaching under Visible Light Activation

The available tooth whitening products in the market contain high concentrations of hydrogen peroxide (H2O2) as an active ingredient. Therefore, in order to curb the high H2O2 concentration and instability of liquid H2O2, this study evaluated the efficacy and cytotoxicity of the bleaching gel composed of 10% calcium peroxide (CaO2) and visible-light-activating nitrogen-doped titanium dioxide (N-TiO2) with methyl cellulose as a thickener. Extracted bovine teeth were discolored using coffee and black tea stain solution and were divided into two groups (n = 6). Bleaching was performed thrice on each tooth specimen in both the groups, with one minute of visible light irradiation during each bleaching time. The CIELAB L*a*b* values were measured pre- and post-bleaching. The N-TiO2 calcinated at 350 °C demonstrated a shift towards the visible light region by narrowing the band gap energy from 3.23 eV to 2.85 eV. The brightness (ΔL) and color difference (ΔE) increased as bleaching progressed each time in both the groups. ANOVA results showed that the number of bleaching significantly affected ΔE (p < 0.05). The formulated bleaching gel exhibits good biocompatibility and non-toxicity upon exposure to 3T3 cells. Our findings showed that CaO2-based bleaching gel at neutral pH could be a stable, safe, and effective substitute for tooth whitening products currently available in the market.

Photocatalytic removal of naphthalene (C10H8 ) from aqueous environments using sulfur and nitrogen doped titanium dioxide (TiO2 -N-S) coated on glass microbullets in presence of sunlight

Background and aims: Due to their toxicity and carcinogenic effects, polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (C10H8 ) are regarded as hazardous compounds for both humans and the environment, and it is essential to remove these contaminants from the environment. The present study aimed to remove naphthalene from a synthetic aqueous environment using sulfur and nitrogen doped titanium dioxide (TiO2 -N-S) nanoparticles (NPs) immobilized on glass microbullets under sunlight. Methods: In this experimental study, TiO2 -N-S NPs were synthesized using sol-gel process. The structure of NPs was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and differential reflectance spectroscopy (DRS). In addition, using statistical analyses, the effects of parameters such as the initial concentration of naphthalene, pH, contact time, and the optimal conditions on naphthalene removal were investigated. Results: XRD patterns and SEM images of the samples confirmed the size of synthesized particles in nanometer. The EDX and DRS spectra analysis showed the presence of two elements (sulfur and nitrogen) and the optical photocatalytic activity in the visible region, respectively. The maximum level of naphthalene removal in the presence of sunlight was obtained to be about 93.55% using a concentration of 0.25 g of thiourea immobilized on glass microbullets at pH=5 and contact time of 90 minutes. Conclusion: The rate of naphthalene removal using the immobilized TiO2 -N-S on glass microbullets was 93.55% in optimal conditions. Therefore, this method has an effective potential for naphthalene removal, and can be used to remove naphthalene from industrial wastewater.

Formation of Nitrogen Doped Titanium Dioxide Surface Layer on NiTi Shape Memory Alloy.

NiTi shape memory alloys are increasingly being used as bone and cardiac implants. The oxide layer of nanometric thickness spontaneously formed on their surface does not sufficiently protect from nickel transition into surrounding tissues, and its presence, even in a small amount, can be harmful to the human organism. In order to limit this disadvantageous phenomenon, there are several surface engineering techniques used, including oxidation methods. Due to the usually complex shapes of implants, one of the most prospective methods is low-temperature plasma oxidation. This article presents the role of cathode sputtering in the formation of a titanium dioxide surface layer, specifically rutile. The surface of the NiTi shape memory alloy was modified using low-temperature glow discharge plasma oxidation processes, which were carried out in two variants: oxidation using an argon + oxygen (80% vol.) reactive atmosphere and the less chemically active argon + air (80% vol.), but with a preliminary cathode sputtering process in the Ar + N2 (1:1) plasma. This paper presents the structure (STEM), chemical composition (EDS, SIMS), surface topography (optical profilometer, Atomic Force Microscopy—AFM) and antibacterial properties of nanocrystalline TiO2 diffusive surface layers. It is shown that prior cathodic sputtering in argon-nitrogen plasma almost doubled the thickness of the produced nitrogen-doped titanium dioxide layers despite using air instead of oxygen. The (TiOxNy)2 diffusive surface layer showed a high level of resistance to E. coli colonization in comparison with NiTi, which indicates the possibility of using this surface layer in the modification of NiTi implants’ properties.

Synthesis and Characterization of Pure and Nitrogen Doped Titanium Oxide Nanocrystallites for Visible Light Photocatalytic Applications

The pure and nitrogen doped titanium oxide (TiO2) nanocrystallites were synthesized using sol-gel technique. The synthesized nanoparticles were characterized to examine the microstructural, optical and photocatalytic properties. The XRD studies of pure and doped TiO2 showed the formation of polycrystalline tetragonal structure with anatase phase. The crystallite sizes were calculated and found to be 17 and 15 nm for the pure and N-doped TiO2, respectively. FTIR studies indicated that the N-doped TiO2 bands are stronger compared with pure TiO2, indicating the more hydroxyl groups. FESEM studies showed the uniform formation of TiO2 nanocrystallites and spherical in shape with agglomeration. The photoluminescence spectra of the samples show emission peaks, indicating the band to band shift having the energy gap of 2.9 eV. The photocatalytic performance of the nanocatalyst was studied using methylene blue dye under visible light irradiation for 90 min. The photocatalytic efficiency of 66.9% and 85.8% is obtained for the pure and N-doped TiO2, respectively.

Tuning surface d charge of Ni-Ru alloys for unprecedented catalytic activity towards hydrogen generation from ammonia borane hydrolysis

The central task in efficient heterogeneous catalysis process lies in exploring catalysts with simultaneous superior performance and low cost. The construction of active sites based on low content of noble and non-noble metals is regard as a promising but challenging strategy for the rational design of catalysts. Herein, we report that a NiRu alloy anchored on surface of nitrogen-doped carbon-coated titanium dioxide showed the highest catalytic activity (2.51 × 105 mL·min−1·gRu−1) for NH3BH3 hydrolysis at 298 K. The unprecedented activity is beyond previous reports. The alloy effect in NiRu alloy and the metal-support interaction between alloy and composite support tune the surface d charge. From experimental and DFT simulation results, the optimized surface d charge is positively corresponding to the low active energy in water and ammonia borane molecule activation. This study opens up a new way for the rational design of highly effective non-noble metal heterogeneous catalysts.

Visible Light Driven Degradation of Terephthalic Acid: Optimization of Energy Demand by Light Modulation Techniques

Aims: The aim of this work was to investigate the impact of light modulation parameters on the degradation of terephthalic acid, an organic model pollutant, within a heterogeneous photocatalytic system under visible light. For this purpose, a fixed bed photocatalytic reactor, irradiated by white-light LEDs matrix controlled by a system for light dimming, was used. The bed consisted of a nitrogen-doped titania photocatalyst deposited on polystyrene pellets. Background: Wastewater containing TPA can be treated into conventional aerobic biological units. However, the mineralization of TPA is slow and inefficient and its presence negatively influences the biodegradation efficiency because this pollutant inhibits microbial growth. Nowadays, innovative technologies named advanced oxidation processes (AOPs), such as heterogeneous photocatalysis with UV and visible light, ozonation, and Fenton oxidation, have gained popularity for effective organic destruction of TPA from wastewater. The heterogeneous photocatalytic oxidation process of the TPA under visible light is the most advantageous process in terms of both fixed and operating costs. Objective: In this work, the successful application of light modulation techniques for degradation of TPA using a photocatalytic system with supported visible active photocatalysts (N-doped TiO2) immobilized on polystyrene pellets is reported. In particular, sinusoidal lighting has been used analyzing the influence of the period of oscillation and the amplitude of light modulation on the reaction kinetics, in such a way as to minimize the times and energy costs for the process. Methods: To evaluate the influence of light modulation on the efficiency of the TPA removal, a discontinuous system composed of a Recirculating Photocatalytic Fixed Bed Reactor (RPFBR) irradiated by a matrix of white light LEDs was used. The flat geometry of the photoreactor guarantees the efficient excitation of the photocatalyst. An amount of 250 mL of aqueous solution with the initial TPA concentration of 12.5 ppm was applied in the photocatalytic tests lasting 180 min of irradiation fixed or sinusoidal modulated. Results: The results show that the variation of the oscillation period of the sinusoidal modulation has a pertinent influence on the photodegradation of TPA and a maximum value of the apparent kinetic constant, 0.0045 min-1 is found when the period of oscillation is 0.24 s. The sinusoidal modulation with optimal amplitude occurs with current between 50-200 mA, that shows the highest value of the apparent kinetic constant equal to 0.0046 min-1. The optimal sinusoidal modulation, as a consequence is with current between 50-200 mA and period of 0.24 s. From the data collected from the tests, it is possible to evaluate the energy cost necessary to obtain the reduction of 90% of the terephthalic acid in 1 m3 of polluted water for each modulation (E E/O), and compare these values with other tests for TPA degradation reported in the literature. The internal comparison with the three systems of literature shows that the optima sinusoidal modulation of LEDs matrix permits a strong reduction in the electrical energy consumption. Conclusion: Photocatalytic tests have demonstrated the improvement of the process energy efficiency using the light modulation technique. A further confirmation of the advantage of light modulation was obtained by comparing the energy costs required for the abatement of 90% of the terephthalic acid in 1m 3 of the photocatalytic system. Finally, a mathematical model for photocatalytic degradation of terephthalic acid within the recirculating fixed bed photocatalytic reactor, irradiated by white-light LEDs was developed.

Nitrogen-doped titanium dioxide nanorod array memristors with synaptic features and tunable memory lifetime for neuromorphic computing

Titanium dioxide memristors are promising next generation devices for neuromorphic computing, which can mimic synapses of human brain. With respect to meet satisfactory performance, gradual conductance changes and stability of cycling are essential. In this work, nitrogen-doped titanium dioxide nanorod arrays (N-TiO2 NARs) memristors with high performance have been fabricated using a hydrothermal process. The X-ray photo electron spectra confirm the existence of Ti‒N bonds, with uniform distribution of nitrogen confirmed by elemental mapping. The bidirectional gradually changing conductance and endurance of over 8000 cycles have been achieved. The ratio of high resistance state (HRS) and low resistance state (LRS) exceeds 16. The synaptic features, such as potentiation, depression, paired pulse facilitation (PPF), experience-learning and STDP have been achieved using continuous sweeping voltage and pulse trains respectively. It is possible to emulate the learning processes by stimulating the memristor using pulses of different amplitude, duration and interval. By manipulating the stimulation pulse duration, voltage and current compliance, memory lifetimes (MLTs) can be tuned from seconds to tens of thousands of seconds. These transitional processes are associated with anion vacancy creation/accumulation and diffusion. Those synaptic features and tunable MLTs provide a promising approach for neuromorphic computing.

Photocatalytic degradation of vehicular exhaust by nitrogen-doped titanium dioxide modified pavement material

The increasing number of motor vehicles on roads is correspondingly augmenting obnoxious aerial exhaust pollution. Herein, this study reports the introduction of nitrogen-doped titanium dioxide (N-TiO2) as new pavement materials with enhanced photocatalytic degradation efficiency for vehicular exhaust. The structure and bandgap of the prepared N-TiO2 were simulated in Cambridge sequential total energy package (CASTEP) and verified by microscopic experiments (X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope, Ultraviolet (UV)–visible diffuse reflectance spectra). Meanwhile, this study evaluated its photocatalytic degradation efficiency in tests using carbon monoxide (CO) and nitrogen oxide (NO) as model exhaust fumes with various operating parameters optimized. In the end, the suitability of photocatalytic exhaust gas degradation fog sealing technique was compared to three pavement grades (stone mastic asphalt-13, asphalt concrete-13, and open-graded friction course-13), and the results showed that the N-TiO2 is more suitable for stone mastic asphalt pavement.