Influence the dopant concentration on the photocatalytic activity: Dy3+, Eu3+ doped TiO2

NASA Astrophysics Data System (ADS)

Zikriya, Mohamed; Nadaf, Y. F.; Pramod, A. G.; Renuka, C. G.

2018-05-01

Titanium dioxide (TiO2) nanoparticles were synthesis by means of hydrothermal process from metatitanic acid. The impacts reaction temperature, stirring process and aging time on the morphology, the transfer of nanoparticles particles were characterized. The morphology of the nanoparticles was described in detail with scanning electron microscopy. In the dynamic of hydrothermal method, stirring can cut down the reaction time of change from particles to nanoparticles. As can be seen from the XRD patterns, the diffraction peaks get broadened as the Eu3+ focus is increased, proposing an orderly abatement in the grain size. The Crystallite size was calculated for pure, Dy3+ and Eu3+ doped TiO2 from diffraction plane by Sherrer's formula and it was found that 13 nm to 18 nm. From SEM images the majorities of TiO2 particles are oblate spheroid or spheroid and look looser, and some macropores could be seen on a few particles.

New insight into singlet oxygen generation at surface modified nanocrystalline TiO2--the effect of near-infrared irradiation.

PubMed

Buchalska, Marta; Labuz, Przemysław; Bujak, Łukasz; Szewczyk, Grzegorz; Sarna, Tadeusz; Maćkowski, Sebastian; Macyk, Wojciech

2013-07-14

The generation of singlet oxygen in aqueous colloids of nanocrystalline TiO2 (anatase) modified by organic chelating ligands forming surface Ti(IV) complexes was studied. Detailed studies revealed a plausible and to date unappreciated influence of near-infrared irradiation on singlet oxygen generation at the surface of TiO2. To detect (1)O2, direct and indirect methods have been applied: a photon counting technique enabling time-resolved measurements of (1)O2 phosphorescence, and fluorescence measurements of a product of singlet oxygen interaction with Singlet Oxygen Sensor Green (SOSG). Both methods proved the generation of (1)O2. Nanocrystalline TiO2 modified with salicylic acid appeared to be the most efficient photosensitizer among the tested materials. The measured quantum yield reached the value of 0.012 upon irradiation at 355 nm, while unmodified TiO2 colloids appeared to be substantially less efficient generators of singlet oxygen with the corresponding quantum yield of ca. 0.003. A photocatalytic degradation of 4-chlorophenol, proceeding through oxidation by OH˙, was also monitored. The influence of irradiation conditions (UV, vis, NIR or any combination of these spectral ranges) on the generation of both singlet oxygen and hydroxyl radicals has been tested and discussed. Simultaneous irradiation with visible and NIR light did not accelerate OH˙ formation; however, for TiO2 modified with catechol it influenced (1)O2 generation. Singlet oxygen is presumably formed according to Nosaka's mechanism comprising O2˙(-) oxidation with a strong oxidant (hole, an oxidized ligand); however, the energy transfer from NIR-excited titanium(iii) centers (trapped electrons) plays also a plausible role.

Low temperature biosynthesis of Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure exhibiting fast lithium ion conduction.

PubMed

Du, Xiaoyong; He, Wen; Zhang, Xudong; Ma, Jinyun; Wang, Chonghai; Li, Chuanshan; Yue, Yuanzheng

2013-04-01

We demonstrate a biomimetic synthesis methodology that allows us to create Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure at lower temperature. We design a 'nanocrystal-glass' configuration to build a nanoarchitecture by means of yeast cell templates self-assembly followed by the controlled in-situ biomineralization of materials on the cell wall. Electrochemically active nanocrystals are used as the lamellar building blocks of mesopores, and the semiconductive glass phase can act both as the 'glue' between nanocrystals and functionalized component. The Li2O-MgO-P2O5-TiO2 nanocrystalline glass exhibits outstanding thermal stability, high conductivity and wide potential window. This approach could be applied to many other multicomponent glass-ceramics to fabricate mesoporous conducting materials for solid-state lithium batteries. Copyright © 2012 Elsevier B.V. All rights reserved.

Red shifts of the Eg(1) Raman mode of nanocrystalline TiO2:Er monoliths grown by sol-gel process

NASA Astrophysics Data System (ADS)

Palomino-Merino, R.; Trejo-Garcia, P.; Portillo-Moreno, O.; Jiménez-Sandoval, S.; Tomás, S. A.; Zelaya-Angel, O.; Lozada-Morales, R.; Castaño, V. M.

2015-08-01

Nanocrystalline monoliths of Er doped TiO2 were prepared by the sol-gel technique, by controlling the Er-doping levels into the TiO2 precursor solution. As-prepared and annealed in air samples showed the anatase TiO2 phase. The average diameter of the nanoparticles ranged from 19 to 2.6 nm as the nominal concentration of Er varies from 0% to 7%, as revealed by EDS analysis in an electron microscope. Photo Acoustic Spectroscopy (PAS) allowed calculate the forbidden band gap, evidencing an absorption edge at around 300 nm, attributed to TiO2 and evidence of electronic transitions or Er3+. The Raman spectra, corresponding to the anatase phase, show the main phonon mode Eg(1) band position at 144 cm-1 with a red shift for the annealing samples.

Rietveld analysis of the effect of annealing atmosphere on phase evolution of nanocrystalline TiO2 powders.

PubMed

Salari, M; Rezaee, M; Chidembo, A T; Konstantinov, K; Liu, H K

2012-06-01

The structural evolution of nanocrystalline TiO2 was studied by X-ray diffraction (XRD) and the Rietveld refinement method (RRM). TiO2 powders were prepared by the sol-gel technique. Post annealing of as-synthesized powders in the temperature range from 500 degrees C to 800 degrees C under air and argon atmospheres led to the formation of TiO2 nanoparticles with mean crystallite size in the range of 37-165 nm, based on the Rietveld refinement results. It was found that the phase structure, composition, and crystallite size of the resulting particles were dependent on not only the annealing temperature, but also the annealing atmosphere. Rietveld refinement of the XRD data showed that annealing the powders under argon atmosphere promoted the polymorphic phase transformation from anatase to rutile. Field emission scanning electron microscopy (FESEM) was employed to investigate the morphology and size of the annealed powders.

One-pot synthesis and optical properties of Eu3+-doped nanocrystalline TiO2 and ZrO2

NASA Astrophysics Data System (ADS)

Julián, Beatriz; Corberán, Rosa; Cordoncillo, Eloisa; Escribano, Purificación; Viana, Bruno; Sanchez, Clément

2005-11-01

A simple and versatile one-pot sol-gel synthesis of Eu3+-doped nanocrystalline TiO2 and ZrO2 nanomaterials is reported in this paper. It consists of the controlled crystallization of Eu3+-doped TiO2 or ZrO2 nanoparticles from an initial solution containing the metal alkoxide, the lanthanide precursor, a complexing agent and a non-complexing acid. The main interest is that it could be extended to different lanthanide ions and inorganic metal oxides to prepare other multifunctional nanomaterials. The characterization by XRD, HRTEM and SAED techniques showed that the TiO2 and ZrO2 crystallization takes place at very low temperatures (60 °C) and that the crystallite size can be tailored by modifying the synthetic conditions. The optical properties of the resulting materials were studied by emission spectra and decay measurements. Both Eu3+:TiO2 and Eu3+:ZrO2 samples exhibited long lifetime values after removing organic components (τ = 0.7 and 1.3 ms, respectively), but the Eu3+:ZrO2 system is specially promising for photonic applications since its τ value is longer than some reported for other inorganic or hybrid matrices in which Eu3+ ions are complexed. This behaviour has been explained through an effective dispersion of the lanthanide ions within the ZrO2 nanocrystals.

Eco-friendly synthesis of core-shell structured (TiO2/Li2CO3) nanomaterials for low cost dye-sensitized solar cells.

PubMed

Karuppuchamy, S; Brundha, C

2016-12-01

Core-shell structured TiO 2 /Li 2 CO 3 electrode was successfully synthesized by eco-friendly solution growth technique. TiO 2 /Li 2 CO 3 electrodes were characterized using X-ray Diffractometer (XRD), Scanning electron microscopy (SEM) and photocurrent-voltage measurements. The synthesized core-shell electrode material was sensitized with tetrabutylammonium cis-di(thiocyanato)-N,N'-bis(4-carboxylato-4'-carboxylic acid-2,2'-bipyridine)ruthenate(II) (N-719). The performance of dye-sensitized solar cells (DSCs) based on N719 dye modified TiO 2 /Li 2 CO 3 electrodes was investigated. The effect of various shell thickness on the photovoltaic performance of the core-shell structured electrode is also investigated. We found that Li 2 CO 3 shells of all thicknesses perform as inert barriers which improve open-circuit voltage (V oc ) of the DSCs. The energy conversion efficiency was greatly dependent on the thickness of Li 2 CO 3 on TiO 2 film, and the highest efficiency of 3.7% was achieved at the optimum Li 2 CO 3 shell layer. Copyright © 2015 Elsevier Inc. All rights reserved.

Improved electron density through hetero-junction binary sensitized TiO2/ CdTe / D719 system as photoanode for dye sensitized solar cell

NASA Astrophysics Data System (ADS)

Pandey, A. K.; Ahmad, Muhammad Shakeel; Alizadeh, Mahdi; Rahim, Nasrudin Abd

2018-07-01

The combined effect of dual sensitization and hetero-junction symmetry has been investigated on the performance of TiO2 based dye sensitized solar cell. CdTe nanoparticles have been introduced in TiO2 matrix to function as sensitizer as well as act as hetero-junction between D719 dye and TiO2 nanoarchitecture. Four concentrations of CdTe i.e. 0.5 wt%, 2 wt%, 5 wt% and 8 wt% have been investigated. Morphological and compositional studies have been conducted using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Light absorption characteristics have been investigated by employing Uv-vis spectroscopy and the overall performance has been studied using solar simulator and electrochemical impedance spectroscopy (EIS). Performance has been found to be increased with the addition of CdTe due to high electron density and reduction in recombination reactions. An increase of 41.73% in incident photo conversion efficiency (IPCE) and 75.57% in short circuit current density (Jsc) have been recorded for the specimens containing 5 wt% CdTe compared to bare TiO2 based DSSCs. Further addition of CdTe leads to reduction in overall performance of DSSCs.

Biomolecule-controlled hydrothermal synthesis of C-N-S-tridoped TiO2 nanocrystalline photocatalysts for NO removal under simulated solar light irradiation.

PubMed

Wang, Yawen; Huang, Yu; Ho, Wingkei; Zhang, Lizhi; Zou, Zhigang; Lee, Shuncheng

2009-09-30

In this study, C-N-S-tridoped titanium dioxide (TiO(2)) nanocrystals were synthesized by using a facile hydrothermal method in the presence of a biomolecule l-cysteine. This biomolecule could not only serve as the common source for the carbon, sulfur and nitrogen tridoping, but also could control the final crystal phases and morphology. The resulting materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and UV-vis diffuse reflectance spectroscopy. XPS analysis revealed that S was incorporated into the lattice of TiO(2) through substituting oxygen atoms, N might coexist in the forms of N-Ti-O and Ti-O-N in tridoped TiO(2) and most C could form a mixed layer of carbonate species deposited on the surface of TiO(2) nanoparticles. The photocatalytic activities of the samples were tested on the removal of NO at typical indoor air level in a flow system under simulated solar light irradiation. The tridoped TiO(2) samples showed much higher removal efficiency than commercial P25 and the undoped counterpart photocatalyst. The enhanced visible light photocatalytic activity of C-N-S-tridoped TiO(2) nanocrystals was explained on the basis of characterizations. The possible formation process of the monodispersed C-N-S-tridoped anatase TiO(2) nanocrystals was also proposed. This study provides a new method to prepare visible light active TiO(2) photocatalyst.

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

PubMed

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

Home-made experiment of Dye-sensitized TiO2 Nanocrystalline Solar Cells and its education evaluation

NASA Astrophysics Data System (ADS)

Tai, M. F.; Shieh, M. C.; Chen, T. W.

2010-03-01

Dyes extracted from some natural fruits including anthocyanins absorb sunlight and effectively activate electrons of anthocyanins. Thus these activated electrons are conducted between TiO2 nanocrystals and form electric potential and current between two electrodes. The dyes can be gotten from the natural fruits, such as blackberries, raspberry, pomegranate seeds and bing cherries. This principle permits making a dye sensitized TiO2 nanocrystallines solar cell (DSSC). All required materials and tools for fabricating a home- made DSSC are easy to obtain around home. The procedures are perfect hands-on experiment as well as demonstration in K-12 schools or home settings. We have designed several protocols for fabricating DSSC and have successfully demonstrated in more than 100 activities with different level students. K-12 Students were able to build their own working DSSC's within 2-3 hours sessions and learned about alternative energy sources. These experiments can inspire students and general public about the modern technology in daily life. Low cost (low than US 3 in Taiwan)and safety are also ensured in our DSSC experiments.

Multiple electron injection dynamics in linearly-linked two dye co-sensitized nanocrystalline metal oxide electrodes for dye-sensitized solar cells.

PubMed

Shen, Qing; Ogomi, Yuhei; Park, Byung-wook; Inoue, Takafumi; Pandey, Shyam S; Miyamoto, Akari; Fujita, Shinsuke; Katayama, Kenji; Toyoda, Taro; Hayase, Shuzi

2012-04-07

Understanding the electron transfer dynamics at the interface between dye sensitizer and semiconductor nanoparticle is very important for both a fundamental study and development of dye-sensitized solar cells (DSCs), which are a potential candidate for next generation solar cells. In this study, we have characterized the ultrafast photoexcited electron dynamics in a newly produced linearly-linked two dye co-sensitized solar cell using both a transient absorption (TA) and an improved transient grating (TG) technique, in which tin(IV) 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (NcSn) and cis-diisothiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II) bis(tetrabutylammonium) (N719) are molecularly and linearly linked and are bonded to the surface of a nanocrystalline tin dioxide (SnO(2)) electrode by a metal-O-metal linkage (i.e. SnO(2)-NcSn-N719). By comparing the TA and TG kinetics of NcSn, N719, and hybrid NcSn-N719 molecules adsorbed onto both of the SnO(2) and zirconium dioxide (ZrO(2)) nanocrystalline films, the forward and backward electron transfer dynamics in SnO(2)-NcSn-N719 were clarified. We found that there are two pathways for electron injection from the linearly-linked two dye molecules (NcSn-N719) to SnO(2). The first is a stepwise electron injection, in which photoexcited electrons first transfer from N719 to NcSn with a transfer time of 0.95 ps and then transfer from NcSn to the conduction band (CB) of SnO(2) with two timescales of 1.6 ps and 4.2 ps. The second is direct photoexcited electron transfer from N719 to the CB of SnO(2) with a timescale of 20-30 ps. On the other hand, back electron transfer from SnO(2) to NcSn is on a timescale of about 2 ns, which is about three orders of magnitude slower compared to the forward electron transfer from NcSn to SnO(2). The back electron transfer from NcSn to N719 is on a timescale of about 40 ps, which is about one order slower compared to the forward electron transfer from N719 to Nc

Enhancement of electrical and optical performance of N719 by co-sensitization

NASA Astrophysics Data System (ADS)

Shikoh, Ali Sephar; Ahmad, Zubair; Touati, Farid; Al-Muhtaseb, Shaheen A.

2018-04-01

This paper deals with the electrical, optical and electrochemical properties of a metal-free dye C78H74O8 (AS-2), which has been used to improve the photo-detection properties of C58H86N8O8RuS2 (N719) based Dye sensitized photo-sensors (DSPSs). Both dyes were mixed together in various proportions and the most promising ratio N719/AS-2 (1:0.25) was selected for staining photo-anodes for DSPS integration. The fabricated DSPSs were studied in terms of electrical parameters and photodetection properties. The N719/AS-2 (1:0.25) based DSPS were found to have a reduced leakage current, increased breakdown voltage and a closer proximity to an ideal diode, as compared to the N719 based DSPS. Further, the N719/AS-2 (1:0.25) based DSPS was also found to have better linearity at high irradiance levels, thus rendering the co-sensitized device useful as a photosensor in various applications. Electrochemical Impedance Spectroscopy (EIS) analysis was also performed to explain the interfacial charge recombination process.

Photocatalytic self-cleaning TiO2 coatings on carbonatic stones

NASA Astrophysics Data System (ADS)

Bergamonti, Laura; Bondioli, Federica; Alfieri, Ilaria; Lorenzi, Andrea; Mattarozzi, Monica; Predieri, Giovanni; Lottici, Pier Paolo

2016-02-01

A self-cleaning coating based on TiO2 nanoparticles obtained by sol-gel method in an alkaline environment has been tested on different types of carbonatic stones: Botticino, Carrara and Pietra Dorata, frequently used in historic buildings. XRD and Raman measurements confirmed the nanocrystalline nature of titania in anatase form, with 5-10 nm crystal size, and evidenced a small amount of brookite. A fast photocatalytic oxidation by TiO2 coatings of the stained stones with methyl orange and methylene blue under UV lamp irradiation has been assessed. The enhancement of surface wettability due to UV-induced TiO2 hydrophilicity has been evidenced by contact angle measurements. ESEM/EDS showed a surface distribution of the coating fairly homogeneous. The coating does not introduce significant colorimetric changes of the stones and does not alter the water capillarity absorption. Thus, the alkaline nanocrystalline TiO2 is promising for self-cleaning coatings on carbonatic stones.

Influence of surfactant and annealing temperature on optical properties of sol-gel derived nano-crystalline TiO2 thin films.

PubMed

Vishwas, M; Sharma, Sudhir Kumar; Rao, K Narasimha; Mohan, S; Gowda, K V Arjuna; Chakradhar, R P S

2010-03-01

Titanium dioxide thin films have been synthesized by sol-gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 degrees C. The influence of surfactant and annealing temperature on optical properties of TiO(2) thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO(2) films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO(2) films was estimated by Tauc's method at different annealing temperature. Copyright 2010 Elsevier B.V. All rights reserved.

Structural, Optical and Ethanol Sensing Properties of Dy-Doped SnO2 Nanoparticles

NASA Astrophysics Data System (ADS)

Shaikh, F. I.; Chikhale, L. P.; Nadargi, D. Y.; Mulla, I. S.; Suryavanshi, S. S.

2018-04-01

We report a facile co-precipitation synthesis of dysprosium (Dy3+) doped tin oxide (SnO2) thick films and their use as gas sensors. The doping percentage (Dy3+) was varied from 1 mol.% to 4 mol.% with the step of 1 mol.%. As-produced material with varying doping levels were sintered in air; and by using a screen printing technique, their thick films were developed. Prior to sensing performance investigations, the films were examined for structural, morphological and compositional properties using x-ray diffraction, a field emission scanning electron microscope, a transmission electron microscope, selected area electron diffraction, energy dispersive analysis by x-rays, Fourier transform infrared spectroscopy and Raman spectroscopic techniques. The structural analyses revealed formation of single phase nanocrystalline material with tetragonal rutile structure of SnO2. The morphological analyses confirmed the nanocrystalline porous morphology of as-developed material. Elemental analysis defined the composition of material in accordance with the doping concentration. The produced sensor material exhibited good response towards different reducing gases (acetone, ethanol, LPG, and ammonia) at different operating temperatures. The present study confirms that the Dy3+ doping in SnO2 enhances the response towards ethanol with reduction in operating temperature. Particularly, 3 mol.% Dy3+ doped sensor exhibited the highest response (˜ 92%) at an operating temperature of 300°C with better selectivity, fast response (˜ 13 s) and recovery (˜ 22 s) towards ethanol.

Anomalous compression behavior of ˜12 nm nanocrystalline TiO2

NASA Astrophysics Data System (ADS)

Wang, Qiming; Li, Shourui; Peng, Fang; Lei, Li; Hu, Qiwei; Wang, Pei; Nan, Xiaolong; Liu, Jing; Zhu, Wenjun; He, Duanwei

2017-06-01

When the grain size decreases, there inevitably exists a critical size (dc) where the contribution of surface atoms to the physical properties is competitive with that of the interior atoms, giving rise to a wide variety of new phenomena. The behavior of granular materials near dc is particularly interesting because of the crossover, a continuous transition from one type of mechanism to another. In situ high-pressure x-ray diffraction experiments showed that the compression curve of nanocrystalline anatase TiO2 with grain size near dc reached a platform after about 5%-6% of deformation under hydrostatic compression. Eventually, the unit cell volume of anatase expanded at ˜14-16 GPa. We propose that the anomalous compression behavior is attributed to the formation and thickening of the stiff high density amorphous shell under high pressure, giving rise to a great arching effect at the grain boundary at the nanolevel. This process results in a remarkable difference in stress between inside and outside of the shell, generating the illusions of the hardening and the negative compressibility. This study offers a new insight into the mechanical properties of nanomaterials under extreme conditions.

Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

NASA Astrophysics Data System (ADS)

Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

2017-02-01

TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

Worm-like mesoporous TiO2 thin films templated using comb copolymer for dye-sensitized solar cells with polymer electrolyte

NASA Astrophysics Data System (ADS)

Lee, Jae Hun; Park, Cheol Hun; Jung, Jung Pyo; Kim, Jong Hak

2015-12-01

A comb copolymer consisting of hydrophobic poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate) (PBEM) and hydrophilic poly(oxyethylene methacrylate) (POEM) is synthesized via one-pot free radical polymerization. The PBEM-POEM comb copolymer is used as an agent to direct the structure toward one consisting of worm-like mesoporous TiO2 (WM-TiO2) films. The selective, preferential interaction between the titania precursor and the hydrophilic POEM chains is responsible for the formation of a well-organized worm-like mesostructure. The morphology of the WM-TiO2 films is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In particular, the effects of film thickness on the optical and electrochemical properties are systematically investigated. The introduction of the WM-TiO2 layer between the nanocrystalline TiO2 (NC-TiO2) layer and fluorine-doped tin oxide (FTO) glass results in increased transmittance of visible light due to an antireflective property, decreased interfacial resistance and suppressed charge recombination at the interfaces of NC-TiO2/FTO glass. As a result, the photovoltaic conversion efficiency of the dye-sensitized solar cell (DSSC) with a polymer electrolyte is improved from 5.3% to 6.6% at an optimum film thickness (310 nm). The obtained efficiency represents a higher efficiency for the N719-based DSSC with a solvent-free, polymer electrolyte.

TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

NASA Astrophysics Data System (ADS)

Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

2015-02-01

The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

Characterization and properties of TiO2-SnO2 nanocomposites, obtained by hydrolysis method

NASA Astrophysics Data System (ADS)

Kutuzova, Anastasiya S.; Dontsova, Tetiana A.

2018-04-01

The paper deals with the process of TiO2-SnO2 nanocomposites synthesis utilizing simple hydrolysis method with further calcination for photocatalytic applications. The obtained nanopowders contain 100, 90, 75, 65 and 25 wt% of TiO2. The synthesized nanocomposite samples were analyzed by X-ray diffraction method, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption method. The correlation between structure and morphology of the obtained nanocrystalline composite powders and their sorption and photocatalytic activity towards methylene blue degradation was established. It was found that the presence of SnO2 in the nanocomposites stabilizes the anatase phase of TiO2. Furthermore, sorption and photocatalytic properties of the obtained composites are significantly influenced not only by specific surface area, but also by pore size distribution and mesopore volume of the samples. In our opinion, the results obtained in this study have shown that the TiO2-SnO2 composites with SnO2 content that does not exceed 10% are promising for photocatalytic applications.

Frequency dependent dielectric properties of combustion synthesized Dy2Ti2O7 pyrochlore oxide

NASA Astrophysics Data System (ADS)

Jeyasingh, T.; Saji, S. K.; Kavitha, V. T.; Wariar, P. R. S.

2018-05-01

Nanocrystalline pyrochlore material Dysprosium Titanate (Dy2Ti2O7) has been synthesized through a single step optimized combustion route. The phase purity and phase formation of the combustion product has been characterized using X-Ray diffraction analysis (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. X-Ray diffraction analysis (XRD) reveal that Dy2Ti2O7 is highly crystalline in nature with cubic structure in the Fd3m space group. The microstructures and average particle size of the prepared nanopowder were examined by High Resolution Transmission Electron Microscopy (HR-TEM). The optical band gap of the Dy2Ti2O7 nanoparticles is determined from the absorption spectrum, was attributed to direct allowed transitions through optical band gap of 3.98 eV. The frequency dependent dielectric measurements have been carried out on the sintered pellet in the frequency range 1 Hz-10 MHz. The measured value of dielectric constant (ℇ') was ˜ 43 and loss tangent (tan δ) was 4×10-3 at 1 MHz, at room temperature.

Study on defect properties of nanocrystalline TiO2 during phase transition by positron annihilation lifetime

NASA Astrophysics Data System (ADS)

Zheng, F.; Liu, Y.; Liu, Z.; Dai, Y.-Q.; Fang, P.-F.; Wang, S.-J.

2012-08-01

The defect properties of nanocrystalline TiO2 were investigated by positron annihilation lifetime spectroscopy (PALS) and X-ray diffraction (XRD) as a function of annealed temperature that ranged from 300 to 850 °C. Below 500 °C, the measured positron lifetimes of τ1 (200-206 ps) and τ2 (378-402 ps) revealed the existence of mono-vacancy and vacancy-clusters at grain surface and in the micro-void of intergranular region. Between 500 and 750 °C, the phase transition from anatase to rutile was probed by the variations of positron lifetime and XRD pattern. With the increasing temperature from 500 to 850 °C, the positron lifetime τ1, τ2 and its intensity I2 sharply decreased from 200 ps, 378 ps, and 60% to 135 ps, 274 ps, and 33%, respectively. The results clearly indicate that the mono-vacancy or vacancy-clusters at grain surface and micro-voids between the grains were annealed out during the phase transition.

High efficiency dye-sensitized solar cell based on novel TiO2 nanorod/nanoparticle bilayer electrode

PubMed Central

Hafez, Hoda; Lan, Zhang; Li, Qinghua; Wu, Jihuai

2010-01-01

High light-to-energy conversion efficiency was achieved by applying novel TiO2 nanorod/nanoparticle (NR/NP) bilayer electrode in the N719 dye-sensitized solar cells. The short-circuit current density (JSC), the open-circuit voltage (VOC), the fill factor (FF), and the overall efficiency (η) were 14.45 mA/cm2, 0.756 V, 0.65, and 7.1%, respectively. The single-crystalline TiO2 NRs with length 200–500 nm and diameter 30–50 nm were prepared by simple hydrothermal methods. The dye-sensitized solar cells with pure TiO2 NR and pure TiO2 NP electrodes showed only a lower light-to-electricity conversion efficiency of 4.4% and 5.8%, respectively, compared with single-crystalline TiO2 NRs. This can be attributed to the new NR/NP bilayer design that can possess the advantages of both building blocks, ie, the high surface area of NP aggregates and rapid electron transport rate and the light scattering effect of single-crystalline NRs. PMID:24198470

3D nanostructured N-doped TiO2 photocatalysts with enhanced visible absorption.

PubMed

Cho, Sumin; Ahn, Changui; Park, Junyong; Jeon, Seokwoo

2018-05-24

Considering the environmental issues, it is essential to develop highly efficient and recyclable photocatalysts in purification systems. Conventional TiO2 nanoparticles have strong intrinsic oxidizing power and high surface area, but are difficult to collect after use and rarely absorb visible light, resulting in low photocatalytic efficiency under sunlight. Here we develop a new type of highly efficient and recyclable photocatalyst made of a three-dimensional (3D) nanostructured N-doped TiO2 monolith with enhanced visible light absorption. To prepare the sample, an ultrathin TiN layer (∼10 nm) was conformally coated using atomic layer deposition (ALD) on 3D nanostructured TiO2. Subsequent thermal annealing at low temperature (550 °C) converted TiN to anatase phase N-doped TiO2. The resulting 3D N-doped TiO2 showed ∼33% enhanced photocatalytic performance compared to pure 3D TiO2 of equivalent thickness under sunlight due to the reduced bandgap, from 3.2 eV to 2.75 eV through N-doping. The 3D N-doped TiO2 monolith could be easily collected and reused at least 5 times without any degradation in photocatalytic performance.

Influence of N2 annealing on TiO2 tubes structure and its photocatalytic activity

NASA Astrophysics Data System (ADS)

Chen, Xiaoxiang; Pan, Zhanchang; Yu, Ke; Xiao, Jun; Wu, Shoukun; Li, Jinghong; Chen, Chun; Lin, Yingsheng; Hu, Guanghui; Xu, Yanbin

2018-02-01

In this work, the TiO2 tubes (TBs) were prepared by solvothermal method. The morphology and phase structure of TiO2 TBs is significantly affected by N2 annealing temperature. XRD was used to characterize the phase structure of the as-prepared samples. The morphology and surface areas were characterized by SEM and N2 adsorption-desorption, which show that the tubes were assembled with about 100-nm nanosheets and small ball particles under 400 and 600 °C N2 annealing; when temperature reached 800 °C, the surface of tubes appeared a lot of collapse and many large holes. In addition, the surface areas of 400 °C TiO2, 600 °C TiO2, and 800 °C TiO2 TBs were significantly affected by N2 annealing. Most importantly, the UV-vis and electrochemical tests demonstrate 600 °C TiO2 TBs exhibit higher absorption intensity and photocurrent; thus, it possess on better photocatalytic activity. Therefore, the photocatalytic performance for TiO2 TBs is significantly co-affected by surface area and mix-phase. [Figure not available: see fulltext.

Photosensitization of different ruthenium(II) complex dyes on TiO 2 for photocatalytic H 2 evolution under visible-light

NASA Astrophysics Data System (ADS)

Peng, Tianyou; Dai, Ke; Yi, Huabing; Ke, Dingning; Cai, Ping; Zan, Ling

2008-07-01

Hydrogen production over dye-sensitized Pt/P25 under visible-light irradiation was investigated by using methanol or TEOA as an electron donor. Ru 2(bpy) 4L 1-PF 6 shows the best photosensitization due to its largest conjugation system, widest range of visible-light and 'antenna effect' among the used three Ru(II)-bipyridyl dyes. Ru 2(bpy) 4L 1-PF 6 loosely linked with TiO 2 also exhibit more steady and higher increases in H 2 evolution upon prolonging the irradiation time than the tightly linked N719. The dynamic equilibrium between the linkage of ground dye and divorce of oxidized dye from TiO 2 can enhance the electron-injection and hinder the backward transfer, and then improve the H 2 evolution efficiency.

The effect of TiO2 on nucleation and crystallization of a Li2O-Al2O3-SiO2 glass investigated by XANES and STEM.

PubMed

Kleebusch, Enrico; Patzig, Christian; Krause, Michael; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

2018-02-13

Glass ceramics based on Li 2 O/Al 2 O 3 /SiO 2 are of high economic importance, as they often show very low coefficients of thermal expansion. This enables a number of challenging applications, such as cooktop panels, furnace windows or telescope mirror blanks. Usually, the crystallization of the desired LAS crystal phases within the glasses must be tailored by a careful choice of crystallization schedule and type of nucleation agents to be used. The present work describes the formation of nanocrystalline TiO 2 within an LAS base composition that contains solely TiO 2 as nucleating agent. Using a combination of scanning transmission electron microscopy as well as X-ray absorption spectroscopy, it is found that a mixture of four- and six-fold coordinated Ti 4+ ions exists already within the glass. Heating of the glass to 740 °C immediately changes this ratio towards a high content of six-fold coordinated Ti, which accumulates in liquid-liquid phase-separation droplets. During the course of thermal treatment, these droplets eventually evolve into nanocrystalline TiO 2 precipitations, in which Ti 4+ is six-fold coordinated. Thus, it is shown that the nucleation of nanocrystalline TiO 2 is initiated by a gradual re-arrangement of the Ti ions in the amorphous, glassy matrix, from a four-fold towards a six-fold coordination.

Dye adsorption mechanisms in TiO2 films, and their effects on the photodynamic and photovoltaic properties in dye-sensitized solar cells.

PubMed

Hwang, Kyung-Jun; Shim, Wang-Geun; Kim, Youngjin; Kim, Gunwoo; Choi, Chulmin; Kang, Sang Ook; Cho, Dae Won

2015-09-14

The adsorption mechanism for the N719 dye on a TiO2 electrode was examined by the kinetic and diffusion models (pseudo-first order, pseudo-second order, and intra-particle diffusion models). Among these methods, the observed adsorption kinetics are well-described using the pseudo-second order model. Moreover, the film diffusion process was the main controlling step of adsorption, which was analysed using a diffusion-based model. The photodynamic properties in dye-sensitized solar cells (DSSCs) were investigated using time-resolved transient absorption techniques. The photodynamics of the oxidized N719 species were shown to be dependent on the adsorption time, and also the adsorbed concentration of N719. The photovoltaic parameters (Jsc, Voc, FF and η) of this DSSC were determined in terms of the dye adsorption amounts. The solar cell performance correlates significantly with charge recombination and dye regeneration dynamics, which are also affected by the dye adsorption amounts. Therefore, the photovoltaic performance of this DSSC can be interpreted in terms of the adsorption kinetics and the photodynamics of oxidized N719.

Photooxidative desulfurization for diesel using Fe / N - TiO2 photocatalyst

NASA Astrophysics Data System (ADS)

Khan, Muhammad Saqib; Kait, Chong Fai; Mutalib, Mohd Ibrahim Abdul

2014-10-01

A series of N - TiO2 with different mol% N was synthesized via sol-gel method and characterized using thermal gravimetric analyzer and raman spectroscopy. 0.2 wt% Fe was incorporated onto the calcined (200°C) N - TiO2 followed by calcination at 200°C, 250°C and 300°C. Photooxidative desulfurization was conducted in the presence of 0.2wt% Fe / N - TiO2 with different mol% N with and without oxidant (H2O2). Oxidative desulfurization was only achieved when H2O2 was used while without H2O2 no major effect on the sulfur removal. 0.2Fe -30N - H2O2 photocatalysts showed best performance at all calcination temperatures as compared to other mol% N - H2O2 photocatalysts. 16.45% sulfur removal was achieved using photocatalysts calcined at 300 °C.

48 CFR 719.273-2 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Section 719.273-2 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS The U.S. Agency for International Development (USAID) Mentor-Protégé Program 719.273-2 Definitions. Throughout, the term “small business” includes all categories...

Optical and Photovoltaic Properties of Thieno[3,2-b]thiophene-Based Push-Pull Organic Dyes with Different Anchoring Groups for Dye-Sensitized Solar Cells.

PubMed

Fernandes, Sara S M; Castro, M Cidália R; Pereira, Ana Isabel; Mendes, Adélio; Serpa, Carlos; Pina, João; Justino, Licínia L G; Burrows, Hugh D; Raposo, M Manuela M

2017-12-31

The effect of anchoring groups on the optical and electrochemical properties of triphenylamine-thienothiophenes, and on the photovoltaic performance of DSSCs photosensitized with the prepared dyes, was studied using newly synthesized compounds with cyanoacetic acid or rhodanine-3-acetic acid groups. Precursor aldehydes were synthesized through Suzuki cross-coupling, whereas Knoevenagel condensation of these with 2-cyanoacetic acid or rhodanine-3-acetic acid afforded the final push-pull dyes. A comprehensive photophysical study was performed in solution and in the solid state. The femtosecond time-resolved transient absorption spectra for the synthesized dyes were obtained following photoexcitation in solution and for the dyes adsorbed to TiO 2 mesoporous films. Information on conformation, electronic structure, and electron distribution was obtained by density functional theory (DFT) and time-dependent DFT calculations. Triphenylamine-thienothiophene functionalized with a cyanoacetic acid anchoring group displayed the highest conversion efficiency (3.68%) as the dye sensitizer in nanocrystalline TiO 2 solar cells. Coadsorption studies were performed for this dye with the ruthenium-based N719 dye, and they showed dye power conversion efficiencies enhanced by 20-64%. The best cell performance obtained with the coadsorbed N719 and cyanoacetic dye showed an efficiency of 6.05%.

Optical and Photovoltaic Properties of Thieno[3,2-b]thiophene-Based Push–Pull Organic Dyes with Different Anchoring Groups for Dye-Sensitized Solar Cells

PubMed Central

2017-01-01

The effect of anchoring groups on the optical and electrochemical properties of triphenylamine-thienothiophenes, and on the photovoltaic performance of DSSCs photosensitized with the prepared dyes, was studied using newly synthesized compounds with cyanoacetic acid or rhodanine-3-acetic acid groups. Precursor aldehydes were synthesized through Suzuki cross-coupling, whereas Knoevenagel condensation of these with 2-cyanoacetic acid or rhodanine-3-acetic acid afforded the final push–pull dyes. A comprehensive photophysical study was performed in solution and in the solid state. The femtosecond time-resolved transient absorption spectra for the synthesized dyes were obtained following photoexcitation in solution and for the dyes adsorbed to TiO2 mesoporous films. Information on conformation, electronic structure, and electron distribution was obtained by density functional theory (DFT) and time-dependent DFT calculations. Triphenylamine–thienothiophene functionalized with a cyanoacetic acid anchoring group displayed the highest conversion efficiency (3.68%) as the dye sensitizer in nanocrystalline TiO2 solar cells. Coadsorption studies were performed for this dye with the ruthenium-based N719 dye, and they showed dye power conversion efficiencies enhanced by 20–64%. The best cell performance obtained with the coadsorbed N719 and cyanoacetic dye showed an efficiency of 6.05%. PMID:29302638

Photocatalytic oxidation of propylene on La and N codoped TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Jinfeng; Li, Haiyan; Zong, Lanlan; Li, Qiuye; Wang, Xiaodong; Zhang, Min; Yang, Jianjun

2015-02-01

Lanthanum- and nitrogen-codoped TiO2 photocatalysts was synthesized using orthorhombic nanotubes titanic acid as the precursor by a simple impregnation and subsequent calcination method. The morphology, phase structure, and properties of La- and N-codoped TiO2 were well characterized by transmission electron microscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra. The La-/N-codoped TiO2 showed excellent photoactivity of propylene oxidation compared with the single-doped TiO2 and La-/N-codoped P25 TiO2 nanoparticles under visible light irradiation. The origin of the enhancement of the visible light-responsive photocatalytic activity was discussed in detail.

Unconventionally prepared TiO2/g-C3N4 photocatalysts for photocatalytic decomposition of nitrous oxide

NASA Astrophysics Data System (ADS)

Troppová, Ivana; Šihor, Marcel; Reli, Martin; Ritz, Michal; Praus, Petr; Kočí, Kamila

2018-02-01

The TiO2/g-C3N4 nanocomposites with the various TiO2:g-C3N4 weight ratios from 1:1 to 1:3 were prepared unconventionally by pressurized hot water processing in a flow regime. The parent TiO2 and g-C3N4 was prepared by thermal hydrolysis and thermal annealing, respectively. The nanocomposites as well as parent TiO2 and g-C3N4 were characterized using several complementary characterization methods and investigated in the photocatalytic decomposition of N2O under UVA (λ = 365 nm) irradiation. All the prepared TiO2/g-C3N4 nanocomposites showed higher photocatalytic activity in comparison with the pure g-C3N4 and chiefly pure TiO2. The photocatalytic activity of TiO2/g-C3N4 nanocomposites was decreasing in the following sequence: TiO2/g-C3N4 (1:3) > TiO2/g-C3N4 (1:2) > TiO2/g-C3N4 (1:1). In comparison with the parent TiO2 or g-C3N4, the TiO2/g-C3N4 nanocomposites' photocatalytic capability was significantly enhanced by coupling TiO2 with g-C3N4. The generation of TiO2/g-C3N4 Z-scheme photocatalyst mainly benefited from the effective separation of photoinduced electron-hole pairs and the extended optical absorption range. The TiO2/g-C3N4 (1:3) nanocomposite showed the best photocatalytic behavior in a consequence of the optimal weight ratio of TiO2:g-C3N4 and the lowest band gap energy from all nanocomposites. The N2O conversion in its presence was 70.6% after 20 h of UVA irradiation.

Hierarchical Honeycomb Br-, N-Codoped TiO2 with Enhanced Visible-Light Photocatalytic H2 Production.

PubMed

Zhang, Chao; Zhou, Yuming; Bao, Jiehua; Sheng, Xiaoli; Fang, Jiasheng; Zhao, Shuo; Zhang, Yiwei; Chen, Wenxia

2018-06-06

The halogen elements modification strategy of TiO 2 encounters a bottleneck in visible-light H 2 production. Herein, we have for the first time reported a hierarchical honeycomb Br-, N-codoped anatase TiO 2 catalyst (HM-Br,N/TiO 2 ) with enhanced visible-light photocatalytic H 2 production. During the synthesizing process, large amounts of meso-macroporous channels and TiO 2 nanosheets were fabricated in massive TiO 2 automatically, constructing the hierarchical honeycomb structure with large specific surface area (464 m 2 g -1 ). cetyl trimethylammonium bromide and melamine played a key role in constructing the meso-macroporous channels. Additionally, HM-Br,N/TiO 2 showed a high visible-light H 2 production rate of 2247 μmol h -1 g -1 , which is far more higher than single Br- or N-doped TiO 2 (0 or 63 μmol h -1 g -1 , respectively), thereby demonstrating the excellent synergistic effects of Br and N elements in H 2 evolution. In HM-Br,N/TiO 2 catalytic system, the codoped Br-N atoms could reduce the band gap of TiO 2 to 2.88 eV and the holes on acceptor levels (N acceptor) can passivate the electrons on donor levels (Br donor), thereby preventing charge carriers recombination significantly. Furthermore, the proposed HM-Br,N/TiO 2 fabrication strategy had a wide range of choices for N source (e.g., melamine, urea, and dicyandiamide) and it can be applied to other TiO 2 materials (e.g., P25) as well, thereby implying its great potential application in visible-light H 2 production. Finally, on the basis of experimental results, a possible photocatalytic H 2 production mechanism for HM-Br,N/TiO 2 was proposed.

Location Of Hole And Electron Traps On Nanocrystalline Anatase TiO2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mercado, Candy C.; Knorr, Fritz J.; McHale, Jeanne L.

2012-05-17

The defect photoluminescence from TiO2 nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces, and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO2 nanotubes, which we find using electron back-scattered diffraction to consist of walls which expose (110) and (100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO2 nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescencemore » of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on under-coordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO2 nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl4 surface treatment heals traps on anatase and mixed-phase TiO2 films, and reveals distinct differences in the trap-state distributions of TiO2 nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.« less

Band edge movement and structural modifications in transition metal doped TiO2 nanocrystals for the application of DSSC

NASA Astrophysics Data System (ADS)

Patle, L. B.; Huse, V. R.; Chaudhari, A. L.

2017-10-01

Nanocrystalline undoped and transition metal ion doped (TM:Cu2+, Mn2+ and Fe3+) TiO2 nanoparticles, with 1 mol% were synthesized by a simple and cost effective modified co-precipitation method at room temperature and were successfully used as photoanode for dye sensitized solar cell (DSSC). The effect of transition metal ions into TiO2 nano crystalline powder has been systematically investigated using x-ray diffraction (XRD), UV-Vis spectroscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive x-ray spectroscopy (EDX). The results of XRD confirm nanocrystalline anatase tetragonal structure of prepared undoped and TM doped TiO2 semiconductor. The influence of doping on band edge movement has been estimated using UV-visible spectroscopy. The SEM results indicate that microscopic effect of doping on morphology of the TiO2. The peaks of EDX signify incorporation of transition metal cations into TiO2 lattice. The effect of doping on flat band potential was estimated using interpolation on Mott-Schottky plot. The performances of DSSCs of undoped and doped TiO2 photoelectrodes were investigated under light illumination. In comparison with undoped and (Cu2+, Fe3+) doped TiO2 photoanodes we found that incorporation of Mn2+ into TiO2 exhibits improvement in photoconversion efficiency (η). There is increase in photoconversion efficiency of DSSCs with Mn2+ doped TiO2 by 6% as compared to that of undoped TiO2 photoanode.

Photodecomposition of volatile organic compounds using TiO2 nanoparticles.

PubMed

Jwo, Ching-Song; Chang, Ho; Kao, Mu-Jnug; Lin, Chi-Hsiang

2007-06-01

This study examined the photodecomposition of volatile organic compounds (VOCs) using TiO2 catalyst fabricated by the Submerged Arc Nanoparticle Synthesis System (SANSS). TiO2 catalyst was employed to decompose volatile organic compounds and compare with Degussa-P25 TiO2 in terms of decomposition efficiency. In the electric discharge manufacturing process, a Ti bar, applied as the electrode, was melted and vaporized under high temperature. The vaporized Ti powders were then rapidly quenched under low-temperature and low-pressure conditions in deionized water, thus nucleating and forming nanocrystalline powders uniformly dispersed in the base solvent. The average diameter of the TiO2 nanoparticles was 20 nm. X-ray diffraction analysis confirmed that the nanoparticles in the deionized water were Anatase type TiO2. It was found that gaseous toluene exposed to UV irradiation produced intermediates that were even harder to decompose. After 60-min photocomposition, Degussa-P25 TiO2 reduced the concentration of gaseous toluene to 8.18% while the concentration after decomposition by SANSS TiO2 catalyst dropped to 0.35%. Under UV irradiation at 253.7 +/- 184.9 nm, TiO2 prepared by SANSS can produce strong chemical debonding energy, thus showing great efficiency, superior to that of Degussa-P25 TiO2, in decomposing gaseous toluene and its intermediates.

Efficient dye-sensitized solar cells from mesoporous zinc oxide nanostructures sensitized by N719 dye

NASA Astrophysics Data System (ADS)

Kumara, G. R. A.; Deshapriya, U.; Ranasinghe, C. S. K.; Jayaweera, E. N.; Rajapakse, R. M. G.

2018-03-01

Dye-sensitized solar cells (DSCs) have attracted a great deal of attention due to their low-cost and high power conversion efficiencies. They usually utilize an interconnected nanoparticle layer of TiO2 as the electron transport medium. From the fundamental point of view, faster mobility of electrons in ZnO is expected to contribute to better performance in DSCs than TiO2, though the actual practical situation is quite the opposite. In this research, we addressed this problem by first applying a dense layer of ZnO on FTO followed by a mesoporous layer of interconnected ZnO nanoparticle layer, both were prepared by spray pyrolysis technique. The best cell shows a power conversion efficiency of 5.2% when the mesoporous layer thickness is 14 μm and the concentration of the N719 dye in dye coating solution is 0.3 mM, while a cell without a dense layer shows 4.2% under identical conditions. The surface concentration of dye adsorbed in the cell with a dense layer and that without a dense layer are 5.00 × 10‑7 and 3.34 × 10‑7 mol/cm2, respectively. The cell with the dense layer has an electron lifetime of 54.81 ms whereas that without the dense layer is 11.08 ms. As such, the presence of the dense layer improves DSC characteristics of ZnO-based DSCs.

An ingenious strategy of preparing TiO2/g-C3N4 heterojunction photocatalyst: In situ growth of TiO2 nanocrystals on g-C3N4 nanosheets via impregnation-calcination method

NASA Astrophysics Data System (ADS)

Zhang, Guanghui; Zhang, Tianyong; Li, Bin; Jiang, Shuang; Zhang, Xia; Hai, Li; Chen, Xingwei; Wu, Wubin

2018-03-01

An ingenious method was employed to design and fabricate the TiO2/g-C3N4 heterojunction photocatalysts in this study. The thermal oxidation etching of g-C3N4 nanosheets and the in situ growth of TiO2 nanocrystal on the surface of g-C3N4 nanosheets were completed simultaneously by the calcination process. The g-C3N4 nanosheets played a crucial role in regulating and assembling the structures and morphologies of TiO2. Furthermore, the thickness and content of g-C3N4, and the crystallinity of TiO2 in TiO2/g-C3N4 composites could be regulated and controlled by the calcination temperature. Among the resultant TiO2/g-C3N4 samples, the TiO2/g-C3N4 sample with 41.6 wt% g-C3N4 exhibited the highest photocatalytic activity. It could degrade almost all MO molecules under visible light irradiation within 3 h. Moreover, it displayed higher visible light photocatalytic performance for degrading MO solution than pure g-C3N4 and D-TiO2. The synergistic effect between TiO2 and g-C3N4 makes significant contributions to the enhancement of the visible light photocatalytic activity. In addition, the favorable photocatalytic performance of TiO2/g-C3N4 nanocomposites is also attributed to the porous structures and uniform morphologies, and large surface area. Furthermore, the resultant TiO2/g-C3N4 exhibits excellent photocatalytic stability. Radical trapping experiments indicated that rad O2- and h+ were the main reactive species during the photodegradation process under visible light irradiation. Hopefully, the results can offer new design and strategy for preparing other g-C3N4-based nanocomposites for environmental and energy applications.

Shape-dependence of the thermal and photochemical reactions of methanol on nanocrystalline anatase TiO2

NASA Astrophysics Data System (ADS)

Bennett, David A.; Cargnello, Matteo; Diroll, Benjamin T.; Murray, Christopher B.; Vohs, John M.

2016-12-01

Structure-activity relationships and the influence of particle size and shape on the partial- and photo-oxidation of methanol on nanocrystalline anatase TiO2 were investigated using temperature-programmed desorption. The study employed two distinct nanoparticle morphologies: truncated bipyramids exposing primarily {101} facets, and flatter platelets exposing primarily {001} surfaces, whose nominal sizes ranged from 10 to 25 nm. The platelets were found to be more active for thermally-driven reactions, such as coupling of methoxide groups to produce dimethyl ether, and deoxygenation to produce methane. A dependence of the reactivity of {001} facets for the coupling of methoxide groups to produce dimethyl ether on facet size was also observed. In contrast to the thermally-driven reactions, the bipyramidal nanoparticles were observed to be more active for a range of photochemical reactions, including oxidation and coupling to produce methyl formate, and photo-decomposition of surface methoxide species. This study also shows how well-defined nanocrystals can be used to help bridge the materials gap between studies of single crystal model catalysts and their high surface area industrial analogs.

Basic molten salt process-A new route for synthesis of nanocrystalline Li 4Ti 5O 12-TiO 2 anode material for Li-ion batteries using eutectic mixture of LiNO 3-LiOH-Li 2O 2

NASA Astrophysics Data System (ADS)

Rahman, M. M.; Wang, Jia-Zhao; Hassan, Mohd Faiz; Chou, Shulei; Wexler, David; Liu, Hua-Kun

A nanocrystalline Li 4Ti 5O 12-TiO 2 duplex phase has been synthesized by a simple basic molten salt process (BMSP) using an eutectic mixture of LiNO 3-LiOH-Li 2O 2 at 400-500 °C. The microstructure and morphology of the Li 4Ti 5O 12-TiO 2 product are characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The sample prepared by heat-treating at 300 °C for 3 h (S-1) reveals dense agglomerates of ultra-fine nanocrystalline Li 4Ti 5O 12; with heat treatment at 400 °C for 3 h (S-2), there is a duplex crystallite size (fine < 10 nm, and coarse > 20 nm) of Li 4Ti 5O 12-TiO 2; at 500 °C for 3 h (S-3), a much coarser and less-dense distribution of lithium titanate (crystallite size ∼15-30 nm) is observed. According to the results of electrochemical testing, the S-2 sample shows initial discharge capacities of 193 mAh g -1 at 0.2 C, 168 mAh g -1 at 0.5 C, 146 mAh g -1 at 1 C, 135 mAh g -1 at 2 C, and 117 mAh g -1 at 5 C. After 100 cycles, the discharge capacity is 138 mAh g -1 at 1 C with a capacity retention of 95%. The S-2 sample yields the best electrochemical performance in terms of charge-discharge capacity and rate capability compared with other samples. Its superior electrochemical performance can be mainly attributed to the duplex crystallite structure, composed of fine (<10 nm) and coarse (>20) nm nanoparticles, where lithium ions can be stored within the grain boundary interfaces between the spinel Li 4Ti 5O 12 and the anatase TiO 2.

Molecular and Dissociative Adsorption of Water on (TiO 2 ) n Clusters, n = 1–4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Mingyang; Straatsma, Tjerk P.; Dixon, David A.

In the low energy structures of the (TiO 2) n(H 2O) m (n ≤ 4, m ≤ 2n) and (TiO 2) 8(H 2O) m (m = 3, 7, 8) clusters were predicted using a global geometry optimization approach, with a number of new lowest energy isomers being found. Water can molecularly or dissociatively adsorb on pure and hydrated TiO 2 clusters. Dissociative adsorption is the dominant reaction for the first two H 2O adsorption reactions for n = 1, 2, and 4, for the first three H 2O adsorption reactions for n = 3, and for the first four Hmore » 2O adsorption reactions for n = 8. As more H 2O’s are added to the hydrated (TiO 2)n cluster, dissociative adsorption becomes less exothermic as all the Ti centers become 4-coordinate. Furthermore two types of bonds can be formed between the molecularly adsorbed water and TiO 2 clusters: a Lewis acid–base Ti–O(H 2) bond or an O···H hydrogen bond. The coupled cluster CCSD(T) results show that at 0 K the H 2O adsorption energy at a 4-coordinate Ti center is ~15 kcal/mol for the Lewis acid–base molecular adsorption and ~7 kcal/mol for the H-bond molecular adsorption, in comparison to that of 8–10 kcal/mol for the dissociative adsorption. The cluster size and geometry independent dehydration reaction energy, ED, for the general reaction 2(-TiOH) → -TiOTi– + H 2O at 4-coordinate Ti centers was estimated from the aggregation reaction of nTi(OH) 4 to form the monocyclic ring cluster (TiO 3H 2) n + nH 2O. E D is estimated to be -8 kcal/mol, showing that intramolecular and intermolecular dehydration reactions are intrinsically thermodynamically allowed for the hydrated (TiO 2) n clusters with all of the Ti centers 4-coordinate, which can be hindered by cluster geometry changes caused by such processes. Finally by bending force constants for the TiOTi and OTiO bonds are determined to be 7.4 and 56.0 kcal/(mol·rad 2). Infrared vibrational spectra were calculated using density functional theory, and the new bands appearing upon water adsorption

Molecular and Dissociative Adsorption of Water on (TiO 2 ) n Clusters, n = 1–4

DOE PAGES

Chen, Mingyang; Straatsma, Tjerk P.; Dixon, David A.

2015-10-20

In the low energy structures of the (TiO 2) n(H 2O) m (n ≤ 4, m ≤ 2n) and (TiO 2) 8(H 2O) m (m = 3, 7, 8) clusters were predicted using a global geometry optimization approach, with a number of new lowest energy isomers being found. Water can molecularly or dissociatively adsorb on pure and hydrated TiO 2 clusters. Dissociative adsorption is the dominant reaction for the first two H 2O adsorption reactions for n = 1, 2, and 4, for the first three H 2O adsorption reactions for n = 3, and for the first four Hmore » 2O adsorption reactions for n = 8. As more H 2O’s are added to the hydrated (TiO 2)n cluster, dissociative adsorption becomes less exothermic as all the Ti centers become 4-coordinate. Furthermore two types of bonds can be formed between the molecularly adsorbed water and TiO 2 clusters: a Lewis acid–base Ti–O(H 2) bond or an O···H hydrogen bond. The coupled cluster CCSD(T) results show that at 0 K the H 2O adsorption energy at a 4-coordinate Ti center is ~15 kcal/mol for the Lewis acid–base molecular adsorption and ~7 kcal/mol for the H-bond molecular adsorption, in comparison to that of 8–10 kcal/mol for the dissociative adsorption. The cluster size and geometry independent dehydration reaction energy, ED, for the general reaction 2(-TiOH) → -TiOTi– + H 2O at 4-coordinate Ti centers was estimated from the aggregation reaction of nTi(OH) 4 to form the monocyclic ring cluster (TiO 3H 2) n + nH 2O. E D is estimated to be -8 kcal/mol, showing that intramolecular and intermolecular dehydration reactions are intrinsically thermodynamically allowed for the hydrated (TiO 2) n clusters with all of the Ti centers 4-coordinate, which can be hindered by cluster geometry changes caused by such processes. Finally by bending force constants for the TiOTi and OTiO bonds are determined to be 7.4 and 56.0 kcal/(mol·rad 2). Infrared vibrational spectra were calculated using density functional theory, and the new bands appearing upon water adsorption

TiO2 film decorated with highly dispersed polyoxometalate nanoparticles synthesized by micelle directed method for the efficiency enhancement of dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

He, Lifei; Chen, Li; Zhao, Yue; Chen, Weilin; Shan, Chunhui; Su, Zhongmin; Wang, Enbo

2016-10-01

In this work, two kinds of polyoxometalate (POM) nanoparticles with controlled shapes and structures were synthesized by micelle directed method and then composited with TiO2 via calcination to remove the surfactants owing to the excellent electronic storage and transmission ability of POM, finally obtaining two kinds of TiO2 composites with highly dispersed and small-sized POM nanoparticles (∼1 nm). The TiO2 composites were then induced into the photoanodes of dye-sensitized (N719) solar cells (DSSCs). The separation of electron-holes becomes more favorable due to the nanostructure and high dispersion of POM which provide more active sites than pure POM tending to agglomeration. The TiO2 composite photoanodes finally yielded the power conversion efficiency (PCE) of 8.4% and 8.2%, respectively, which were 42% and 39% higher than the pristine TiO2 based anodes. In addition, the mechanisms of POM in DSSC are proposed.

Study of TiO2 particles size, dyes, and catalyst to improve the performance of DSSC

NASA Astrophysics Data System (ADS)

Saehana, Sahrul; Darsikin, Muslimin

2016-02-01

This study reports effort to improve performance of solar cells by using various natural dyes in dye-sensitized solar cell (DSSC). We applied three kind of natural dye, i.e, black rice dye, cactus dye and dragon fruit dye. We found that performance of DSSC which employ black rice dye was higher than other natural dyes. It is because the wider spectrum wavelength of black rice dyes. Its performance also compared with rhutenium dye (N719). Effect of TiO2 particle to DSSC performance was also investigated. It was concluded that smaller TiO2 particle size will increase the performance of DSSC solar cells. It was because the smaller particle size (high surface area) will load more dye. In addition, we also demonstrated the use of graphite from lead pencil as counter electrode.

Molecular level energy and electron transfer processes at nanocrystalline titanium dioxide interfaces

NASA Astrophysics Data System (ADS)

Farzad, Fereshteh

This thesis describes photo-induced molecular electron and energy transfer processes occurring at nanocrystalline semiconductor interfaces. The Introductory Chapter provides background and describes how these materials may be useful for solar energy conversion. In Chapter 2, results describing excitation of Ru(deeb)(bpy)2 2+, bis(2,2'-bipyridine)(2,2'-bipyridine-4,4 '-diethylester)ruthenium(II) hexafluorophosphate, bound to nanocrystalline TiO2 thin films, immersed in an acetonitrile bath are presented. The data indicates that light excitation forms predominately long-lived metal-to-ligand charge-transfer, MLCT, excited states under these conditions. Modeling of the data as a function of irradiance has been accomplished assuming parallel unimolecular and bimolecular excited state deactivation processes. The quantum yield for excited state formation depends on the excitation irradiance, consistent with triplet-triplet annihilation processes that occur with k > 1 x 108 s-1. Chapter 3 extends the work described in Chapter 2 to LiClO4 acetonitrile solutions. Li+ addition results in a red shift in the MLCT absorption and photoluminescence, PL, and a concentration dependent quenching of the PL intensity on TiO2. The Li+ induced spectroscopic changes were found to be reversible by varying the electrolyte composition. A second-order kinetic model quantified charge recombination transients. A model is proposed wherein Li+ ion adsorption stabilizes TiO2 acceptor states resulting in energetically more favorable interfacial electron transfer. The photophysical and photoelectrochemical properties of porous nanocrystalline anatase TiO2 electrodes modified with Ru(deeb)(bpy)2 2+, Os(deeb)(bpy)22+, and mixtures of both are described in Chapters 4 and 5. In regenerative solar cells with 0.5 M LiI/0.05 M I2 acetonitrile electrolyte, both compounds efficiently inject electrons into TiO2 producing monochromatic incident photon-to-current efficiencies (IPCE), IPCE (460 nm) = 0.70 + 0

Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

NASA Astrophysics Data System (ADS)

Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

2011-11-01

The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected.

Molecular design of TiO2 for gigantic red shift via sublattice substitution.

PubMed

Shao, Guosheng; Deng, Quanrong; Wan, Lin; Guo, Meilan; Xia, Xiaohong; Gao, Yun

2010-11-01

The effects of 3d transition metal doping in TiO2 phases have been simulated in detail. The results of modelling indicate that Mn has the biggest potential among 3d transition metals, for the reduction of energy gap and the introduction of effective intermediate bands to allow multi-band optical absorption. On the basis of theoretical formulation, we have incorporated considerable amount of Mn in nano-crystalline TiO2 materials. Mn doped samples demonstrate significant red shift in the optical absorption edge, with a secondary absorption edge corresponding to theoretically predicted intermediate bands/states. The gigantic red shift achievable in Mn-doped TiO2 is expected to extend the useful TiO2 functionalities well beyond the UV threshold via the optical absorption of both visible and infrared photon irradiance.

Photoluminescence properties of white light emitting La2O3:Dy3+ nanocrystals

NASA Astrophysics Data System (ADS)

Reenabati Devi, Konsam; Dorendrajit Singh, Shougaijam; David Singh, Th.

2018-06-01

White light emitting nanocrystalline La2O3:Dy3+ phosphors with different concentration (0.5-2 at.%) were synthesized by simple precipitation method. X-ray diffraction (XRD) pattern indicates all the samples crystallizes in the hexagonal phase. Average crystallite sizes of the samples calculated from XRD data were found to be in the range of 20-55 nm. Transmission electron microscopy, selected area electron diffraction, energy dispersive analysis of X-ray and photoluminescence (PL) of the samples are also reported. Strong PL excitation peak due to charge transfer band was observed at 230 nm. Photoluminescence emission peaks observed at 486 and 575 nm were probably attributed to 4F9/2-6H15/2 and 4F9/2-6H13/2 of Dy3+ ions respectively. Optimum luminescence intensity is found at 1 at.% Dy3+ doped La2O3 sample. Further, Commission Internationale de l'é clairage (CIE, 1931) co-ordinates and correlated color temperature (CCT) of the doped sample were calculated to investigate the phosphors' performance and technical applicability of the emitted light respectively. CCT of the 0.5 and 1 at.% samples is 5894 K (white light), within the range of vertical daylight, which makes the synthesised samples promising nanophosphor and may find application in simulating vertical daylight of the Sun.

Photoluminescence properties of white light emitting La2O3:Dy3+ nanocrystals

NASA Astrophysics Data System (ADS)

Reenabati Devi, Konsam; Dorendrajit Singh, Shougaijam; David Singh, Th.

2018-01-01

White light emitting nanocrystalline La2O3:Dy3+ phosphors with different concentration (0.5-2 at.%) were synthesized by simple precipitation method. X-ray diffraction (XRD) pattern indicates all the samples crystallizes in the hexagonal phase. Average crystallite sizes of the samples calculated from XRD data were found to be in the range of 20-55 nm. Transmission electron microscopy, selected area electron diffraction, energy dispersive analysis of X-ray and photoluminescence (PL) of the samples are also reported. Strong PL excitation peak due to charge transfer band was observed at 230 nm. Photoluminescence emission peaks observed at 486 and 575 nm were probably attributed to 4F9/2-6H15/2 and 4F9/2-6H13/2 of Dy3+ ions respectively. Optimum luminescence intensity is found at 1 at.% Dy3+ doped La2O3 sample. Further, Commission Internationale de l'é clairage (CIE, 1931) co-ordinates and correlated color temperature (CCT) of the doped sample were calculated to investigate the phosphors' performance and technical applicability of the emitted light respectively. CCT of the 0.5 and 1 at.% samples is 5894 K (white light), within the range of vertical daylight, which makes the synthesised samples promising nanophosphor and may find application in simulating vertical daylight of the Sun.

Thermoelectric Properties of Dy-Doped SrTiO3 Ceramics

NASA Astrophysics Data System (ADS)

Liu, J.; Wang, C. L.; Peng, H.; Su, W. B.; Wang, H. C.; Li, J. C.; Zhang, J. L.; Mei, L. M.

2012-11-01

Sr1- x Dy x TiO3 ( x = 0.02, 0.05, 0.10) ceramics were prepared by the reduced solid-state reaction method, and their thermoelectric properties were investigated from room temperature to 973 K. The resistivity increases with temperature, showing metallic behavior. The Seebeck coefficients tend to saturate at high temperatures, presenting narrow-band behavior, as proved by ab initio calculations of the electronic structure. The magnitudes of the Seebeck coefficient and the electrical resistivity decrease with increasing Dy content. At the same time, the thermal conductivity decreases because the lattice thermal conductivity is reduced by Dy substitution. The maximum value of the figure of merit reaches 0.25 at 973 K for the Sr0.9Dy0.1TiO3 sample.

Luminescence characteristics of Dy3+ activated Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphor

NASA Astrophysics Data System (ADS)

Wani, Javaid A.; Dhoble, N. S.; Dhoble, S. J.

2012-11-01

In this paper, we have reported a new Na 2Sr 2Mg (BO 3)2F 2:Dy 3+ thermoluminescence (TL) phosphor prepared via the wet chemical method. Prepared phosphor was characterized by X-ray powder diffraction, photoluminescence (PL), TL and scanning electronmicroscopy techniques. The scanning electronmicroscopic image of Na 2Sr 2Mg (BO 3)2F 2:Dy 3+ phosphor confirms the micron size of particles. Under the PL study, the characteristic emission spectrum of Dy 3+ corresponding to 4F 9/2→6H 15/2 (481 nm) and 4F 9/2→6H 13/2 (576 nm) transitions was observed. The TL property of the as prepared phosphor was also found to be good. TL intensity of Na 2Sr2Mg(BO 3)F 2:Dy 3+ phosphors at 0.99 kGy exposure of γ-irradiations was compared with standard CaSO 4:Dy phosphor. It was seen that TL intensity of Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphors is 1.1 times less compared with the standard CaSO 4:Dy TL dosimeter phosphor. The kinetic parameters are also discussed in detail. The values of activation energy E (eV) and frequency factor S (s -1) were found to be 0.57 eV and 1.25×106 s-1, respectively.

N incorporation and electronic structure in N-doped TiO2(110) rutile

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, Sau H.; Nachimuthu, Ponnusamy; Joly, Alan G.

2007-02-08

Epitaxial TiO2-xNx film growth under anion-rich conditions is characterized by nearly balanced incorporation rates for substitutional N (NO) and interstitial Ti (Tii). Tii donors fully compensate and stabilize N3-, but preclude the formation of p-type material. Hybridization occurs between Tii(IV) and NO3-, but the value of x is limited to ~0.02 under these conditions. Tii(IV)-NO3- states occur above the valence band maximum of pure TiO2, riving rise to enhanced optical absorption in the visible up to ~2.5 eV. Much higher NO and Tii concentrations result from using cation-rich conditions.

Preparation and photoelectrocatalytic performance of N-doped TiO2/NaY zeolite membrane composite electrode material.

PubMed

Cheng, Zhi-Lin; Han, Shuai

2016-01-01

A novel composite electrode material based on a N-doped TiO2-loaded NaY zeolite membrane (N-doped TiO2/NaY zeolite membrane) for photoelectrocatalysis was presented. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible (UV-vis) and X-ray photoelectron spectroscopy (XPS) characterization techniques were used to analyze the structure of the N-doped TiO2/NaY zeolite membrane. The XRD and SEM results verified that the N-doped TiO2 nanoparticles with the size of ca. 20 nm have been successfully loaded on the porous stainless steel-supported NaY zeolite membrane. The UV-vis result showed that the N-doped TiO2/NaY zeolite membrane exhibited a more obvious red-shift than that of N-TiO2 nanoparticles. The XPS characterization revealed that the doping of N element into TiO2 was successfully achieved. The photoelectrocatalysis performance of the N-doped TiO2/NaY zeolite membrane composite electrode material was evaluated by phenol removal and also the effects of reaction conditions on the catalytic performance were investigated. Owing to exhibiting an excellent catalytic activity and good recycling stability, the N-doped TiO2/NaY zeolite membrane composite electrode material was of promising application for photoelectrocatalysis in wastewater treatment.

On the photo-luminescence properties of sol–gel derived undoped and Dy{sup 3+} ion doped nanocrystalline Scheelite type AMoO{sub 4} (A = Ca, Sr and Ba)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jena, Paramananda; Gupta, Santosh K., E-mail: santufrnd@gmail.com; Natarajan, V.

2015-04-15

Nanocrystalline Scheelite type Dy doped AMoO{sub 4} [where A = Ba, Sr and Ca] samples were prepared by acrylamide assisted sol–gel process and characterized by XRD, FT-Raman, FTIR, SEM and photoluminescence (PL). PL of undoped sample shows blue/green emission in CaMoO{sub 4} and SrMoO{sub 4} but multicolour visible emission leading to near white light in BaMoO{sub 4} nanoparticles; the origin of which is explained. It was observed that on doping 0.5 mol% of Dy{sup 3+} in molybdate samples complete energy transfer takes place in case of SrMoO{sub 4} and BaMoO{sub 4}, but host contributed substantially in Dy doped BaMoO{sub 4}more » sample, resulting in biexponential decay. It was also observed that symmetry around Dy{sup 3+} decreases as the size of alkaline earth ion increases. Due to combined blue, yellow and red colour emission in dysprosium doped sample; all samples showed near white light emission under UV and near UV excitation.« less

TiO2 films with rich bulk oxygen vacancies prepared by electrospinning for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Li, Xiaodong; Gao, Caitian; Wang, Jiangtao; Lu, Bingan; Chen, Wanjun; Song, Jie; Zhang, Shanshan; Zhang, Zhenxing; Pan, Xiaojun; Xie, Erqing

2012-09-01

Highly transparent nanocrystalline TiO2 films have been fabricated by electrospinning (ES) technique based on a transmutation process from as-spun nanofibers with an appropriate amount of tri-ethanolamine (TEOA) added to the precursor. A possible evolution mechanism of the transparent nanocrystalline TiO2 films is proposed. It is found that the films prepared via transmutation from electrospun nanofibers possess rich bulk oxygen vacancies (BOVs, PL band at 621-640 nm) by using photoluminescence (PL) spectroscopy. Contrastively, the dominant peak in PL spectrum of the spin-coated film is the emission from surface oxygen vacancies (SOVs, PL band at 537-555 nm). The electrospun TiO2 films with rich BOVs induce large open-circuit voltage (Voc) and fill factor (FF) improvements in dye-sensitized solar cells (DSCs), and thus a large improvement of energy conversion efficiency (η). In addition, these performance advantages are maintained for a double-layer cell with a doctor-bladed ˜7 μm top layer (P25 nanometer TiO2, Degussa) and an electrospun ˜3 μm bottom layer. The double-layer cell yields a high η of 6.01%, which has increased by 14% as compared with that obtained from a 10 μm thick P25 film.

Characterization of screen-printed dye-sensitized nanocrystalline TiO2 solar cells

NASA Astrophysics Data System (ADS)

Gupta, Tapan K.; Cirignano, Leonard J.; Shah, Kanai S.; Moy, Larry P.; Kelly, David J.; Squillante, Michael R.; Entine, Gerald; Smestad, Greg P.

1999-10-01

Titanium dioxide (TiO2) films have been deposited on SnO2 coated glass substrates by screen-printing. Film morphology and structure have been characterized by scanning electron microscopy, x-ray diffraction and BET analysis. Dye-sensitized TiO2 photoelectrochemical cells have been assembled and characterized. Cells sensitized with anthocyanin and a ruthenium complex have been investigated. A 0.77 cm2 ruthenium dye sensitized cell with 6.1% power conversion efficiency under Air Mass (AM1.5) conditions was obtained. Results obtained with a pure anthocyanin dye and dye extracted from blackberries were compared. Finally, a natural gel was found to improve the stability of anthocyanin sensitized cells.

Facile synthesis and characterization of N-doped TiO2/C nanocomposites with enhanced visible-light photocatalytic performance

NASA Astrophysics Data System (ADS)

Jia, Tiekun; Fu, Fang; Yu, Dongsheng; Cao, Jianliang; Sun, Guang

2018-02-01

Ultrafine anatase N-doped TiO2 nanocrystals modified with carbon (denoted as N-doped TiO2/C) were successfully prepared via a facile and low-cost approach, using titanium tetrachloride, aqueous ammonia and urea as starting materials. The phase composition, surface chemical composition, morphological structure, electronic and optical properties of the as-prepared photocatalysts were well characterized and analyzed. On the basis of Raman spectral characterization combining with the results of X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM), it could be concluded that N dopant ions were successfully introduced into TiO2 crystal lattice and carbon species were modified on the surface or between the nanoparticles to form N-doped TiO2/C nanocomposites. Compared with that of bare TiO2, the adsorption band edge of N-doped TiO2/C nanocomposites were found to have an evident red-shift toward visible light region, implying that the bandgap of N-doped TiO2/C nanocomposites is narrowed and the visible light absorption capacity is significantly enhanced due to N doping and carbon modification. The photoactivity of the as-prepared photocatalytsts was tested by the degradation of Rhodamine B (RhB) under visible light (λ > 420 nm), and the results showed that the N-doped TiO2/C nanocomposites exhibited much higher photodegradation rate than pure TiO2 and N-doped TiO2, which was mainly attributed to the synergistic effect of the enhanced light harvesting, augmented catalytic active sites and efficient separation of photogenerated electron-hole pairs.

Complex doping chemistry owing to Mn incorporation in nanocrystalline anatase TiO2 powders.

PubMed

Guo, Meilan; Gao, Yun; Shao, G

2016-01-28

Mn-doped TiO2 powders with a wide range of nominal doping levels were fabricated using a one-step hydrothermal method followed by 400 °C annealing. Anatase powders with a uniform size distribution below 10 nm were obtained. The maximum solubility of Mn in the TiO2 lattice was around 30%, beyond which the Mn3O4 compound appeared as a secondary phase. The optical absorption edges for Mn-doped anatase TiO2 were red-shifted effectively through increasing Mn content. Alloying chemistry and associated elemental valences were elaborated through combining X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and theoretical simulation in the framework of density functional theory (DFT). The results showed that the Mn species exhibited mixed valence states of 3+ and 4+ in anatase TiO2, with the latter being the key to remarkable photocatalytic performance.

Synthesis and photocatalytic activity of N-doped TiO2 produced in a solid phase reaction

NASA Astrophysics Data System (ADS)

Xin, Gang; Pan, Hongfei; Chen, Dan; Zhang, Zhihua; Wen, Bin

2013-02-01

N-doped TiO2 was synthesized by calcining a mixture of titanic acid and graphitic carbon nitride (g-C3N4) at temperatures above 500 °C. The final samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and UV-vis diffuse reflectance spectra. The photocatalytic activity of N-doped TiO2 was studied by assessing the degradation of methylene blue in an aqueous solution, under visible light and UV light irradiation. It was found that the N-doped TiO2 displayed higher photocatalytic activity than pure TiO2, under both visible and UV light.

Growth and optical properties of Dy doped and undoped n-type InSe single crystal

NASA Astrophysics Data System (ADS)

Gürbulak, B.

1999-02-01

Undoped n-InSe and Dy doped n-InSe (n-InSe : Dy) single crystals were grown by a method which is similar to direct freezing method. Ingots had no cracks and voids on the surface. There were no processes to polish and clean treatment at cleavage faces of these samples because of the natural mirror-like cleavage faces. The absorption measurements were carried out in n-InSe and n-InSe : Dy samples in the temperature range 10-320 K. The first exciton energies for n=1 were calculated as 1.331, 1.248 eV in n-InSe and were 1.326, 1.244 eV in n-InSe : Dy at 10 and 300 K, respectively. The second exciton energies for n=2 in n-InSe were calculated as 1.346, 1.336 eV and in n-InSe : Dy were 1.340, 1.332 eV at 10 and 80 K, respectively. Binding energies of n-InSe and n-InSe : Dy were calculated as 19.47 and 18.87 meV, respectively. The direct bands gap for n-InSe are 1.350, 1.267 eV and for n-InSe : Dy are 1.344, 1.263 eV at 10, 300 K, respectively.

Ga2O3 and GaN nanocrystalline film: reverse micelle assisted solvothermal synthesis and characterization.

PubMed

Sinha, Godhuli; Ganguli, Dibyendu; Chaudhuri, Subhadra

2008-03-01

Gallium oxide (beta-Ga2O3) nanoparticles were successfully deposited on quartz glass substrates using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-hexane/ethylene glycol monomethyl ether (EGME) reverse micelle-mediated solvothermal process with different omega values. The mean diameter of Ga2O3 particles was approximately 2-3 nm and found to be approximately independent of omega values of the reverse micelles. However, when the Ga2O3 nanocrystalline films were nitrided at 900 degrees C under flowing NH3 atmosphere for 1 h, the mean diameter of the resulted gallium nitride (wurtzite-GaN) nanoparticles varied from 3-9 nm. Both nanocrystalline films of Ga2O3 and GaN were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence in order to study their chemical and physical properties explicitly.

Remediation of Organic and Inorganic Arsenic Contaminated Groundwater using a Nonocrystalline TiO2 Based Adsorbent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, C.; Meng, X; Calvache, E

2009-01-01

A nanocrystalline TiO2-based adsorbent was evaluated for the simultaneous removal of As(V), As(III), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in contaminated groundwater. Batch experimental results show that As adsorption followed pseudo-second order rate kinetics. The competitive adsorption was described with the charge distribution multi-site surface complexation model (CD-MUSIC). The groundwater containing an average of 329 ?g L-1 As(III), 246 ?g L-1 As(V), 151 ?g L-1 MMA, and 202 ?g L-1 DMA was continuously passed through a TiO2 filter at an empty bed contact time of 6 min for 4 months. Approximately 11 000, 14 000, and 9900 bed volumesmore » of water had been treated before the As(III), As(V), and MMA concentration in the effluent increased to 10 ?g L-1. However, very little DMA was removed. The EXAFS results demonstrate the existence of a bidentate binuclear As(V) surface complex on spent adsorbent, indicating the oxidation of adsorbed As(III). A nanocrystalline TiO2-based adsorbent could be used for the simultaneous removal of As(V), As(III), MMA, and DMA in contaminated groundwater.« less

Rheological and volumetric properties of TiO2-ethylene glycol nanofluids

PubMed Central

2013-01-01

Homogeneous stable suspensions obtained by dispersing dry TiO2 nanoparticles in pure ethylene glycol were prepared and studied. Two types of nanocrystalline structure were analyzed, namely anatase and rutile phases, which have been characterized by scanning electron microscopy. The rheological behavior was determined for both nanofluids at nanoparticle mass concentrations up to 25%, including flow curves and frequency-dependent storage and loss moduli, using a cone-plate rotational rheometer. The effect of temperature over these flow curve tests at the highest concentration was also analyzed from 283.15 to 323.15 K. Furthermore, the influence of temperature, pressure, nanocrystalline structure, and concentration on the volumetric properties, including densities and isobaric thermal expansivities, were also analyzed. PMID:23763850

Development of high efficient visible light-driven N, S-codoped TiO2 nanowires photocatalysts

NASA Astrophysics Data System (ADS)

Zhang, Yanlin; Liu, Peihong; Wu, Honghai

2015-02-01

One-dimensional (1D) nanowire material (especially nonmetal doped 1D nanowires) synthesized by a facile way is of great significance and greatly desired as it has higher charge carrier mobility and lower carrier recombination rate. N, S-codoped TiO2 nanowires were synthesized using titanium sulfate as a precursor and isopropanol as a protective capping agent by a hydrothermal route. The obtained doped nanowires were characterized by XRD, SEM, HRTEM, SAED, XPS, BET and UV-vis absorption spectrum. The incorporation of N and S into TiO2 NWs can lead to the expansion of its lattice and remarkably lower its electron-transfer resistance. Photocatalytic activity measurement showed that the N, S-codoped TiO2 nanowires with high quantum efficiency revealed the best photocatalytic performance for atrazine degradation under visible light irradiation compared to N, S-codoped TiO2 nanoparticles and S-doped TiO2 nanowires, which was attributed to (i) the synergistic effect of N and S doping in narrowing the band gap, separating electron-hole pairs and increasing the photoinduced electrons, and (ii) extending the anatase-to-rutile transformation temperature above 600 °C.

Designing a Dy2 Single-Molecule Magnet with Two Well-Differentiated Relaxation Processes by Using a Nonsymmetric Bis-bidentate Bipyrimidine- N-Oxide Ligand: A Comparison with Mononuclear Counterparts.

PubMed

Díaz-Ortega, Ismael F; Herrera, Juan Manuel; Aravena, Daniel; Ruiz, Eliseo; Gupta, Tulika; Rajaraman, Gopalan; Nojiri, H; Colacio, Enrique

2018-06-04

Herein we report a dinuclear [(μ-mbpymNO){(tmh) 3 Dy} 2 ] (1) single-molecule magnet (SMM) showing two nonequivalent Dy III centers, which was rationally prepared from the reaction of Dy(tmh) 3 moieties (tmh = 2,2,6,6-tetramethyl-3,5-heptanedionate) and the asymmetric bis-bidentate bridging ligand 4-methylbipyrimidine (mbpymNO). Depending on whether the Dy III ions coordinate to the N^O or N^N bidentate donor sets, the Dy III sites present a NO 7 ( D 2 d geometry) or N 2 O 6 ( D 4 d ) coordination sphere. As a consequence, two different thermally activated magnetic relaxation processes are observed with anisotropy barriers of 47.8 and 54.7 K. Ab initio calculations confirm the existence of two different relaxation phenomena and allow one to assign the 47.8 and 54.7 K energy barriers to the Dy(N 2 O 6 ) and Dy(NO 7 ) sites, respectively. Two mononuclear complexes, [Dy(tta) 3 (mbpymNO)] (2) and [Dy(tmh) 3 (phenNO)] (3), have also been prepared for comparative purposes. In both cases, the Dy III center shows a NO 7 coordination sphere and SMM behavior is observed with U eff values of 71.5 K (2) and 120.7 K (3). In all three cases, ab initio calculations indicate that relaxation of the magnetization takes place mainly via the first excited-state Kramers doublet through Orbach, Raman, and thermally assisted quantum-tunnelling mechanisms. Pulse magnetization measurements reveal that the dinuclear and mononuclear complexes exhibit hysteresis loops with double- and single-step structures, respectively, thus supporting their SMM behavior.

Heterogeneous reaction of N2O5 with airborne TiO2 particles and its implication for stratospheric particle injection

NASA Astrophysics Data System (ADS)

Tang, M. J.; Telford, P. J.; Pope, F. D.; Rkiouak, L.; Abraham, N. L.; Archibald, A. T.; Braesicke, P.; Pyle, J. A.; McGregor, J.; Watson, I. M.; Cox, R. A.; Kalberer, M.

2014-06-01

Injection of aerosol particles (or their precursors) into the stratosphere to scatter solar radiation back into space has been suggested as a solar-radiation management scheme for the mitigation of global warming. TiO2 has recently been highlighted as a possible candidate particle because of its high refractive index, but its impact on stratospheric chemistry via heterogeneous reactions is as yet unknown. In this work the heterogeneous reaction of airborne sub-micrometre TiO2 particles with N2O5 has been investigated for the first time, at room temperature and different relative humidities (RH), using an atmospheric pressure aerosol flow tube. The uptake coefficient of N2O5 onto TiO2, γ(N2O5), was determined to be ~1.0 × 10-3 at low RH, increasing to ~3 × 10-3 at 60% RH. The uptake of N2O5 onto TiO2 is then included in the UKCA chemistry-climate model to assess the impact of this reaction on stratospheric chemistry. While the impact of TiO2 on the scattering of solar radiation is chosen to be similar to the aerosol from the Mt Pinatubo eruption, the impact of TiO2 injection on stratospheric N2O5 is much smaller.

Interfacial Electron Transfer at Sensitized Nanocrystalline TiO2 Electrolyte Interfaces: Influence of Surface Electric Fields and Lewis-Acidic Cations

NASA Astrophysics Data System (ADS)

Barr, Timothy J.

Interfacial electron transfer reactions facilitate charge separation and recombination in dye-sensitized solar cells (DSSCs). Understanding what controls these electron transfer reactions is necessary to develop efficient DSSCs. Gerischer proposed a theory for interfacial electron transfer where the rate constant was related to the energetic overlap between the donor and acceptor states. The present work focuses on understanding how the composition of the CH3CN electrolyte influenced this overlap. It was found that the identity of the electrolyte cation tuned the energetic position of TiO2 electron acceptor states, similar to how pH influences the flatband potential of bulk semiconductors in aqueous electrolytes. For example, the onset for absorption changes, that were attributed to electrons in the TiO2 thin film, were 0.5 V more positive in Mg2+ containing electrolyte than TBA+, where TBA+ is tetrabutylammonium. Similar studies performed on mesoporous, nanocrystalline SnO2 thin films reported a similar cation dependence, but also found evidence for electrons that did not absorb in the visible region that were termed ‘phantom electrons.’. Electron injection is known to generate surface electric fields on the order of 2 MV/cm. The rearrangement of cations in response to surface electric fields, termed screening, was investigated. It was found that magnitude of the electric field and the screening dynamics were dependent on the identity of the electrolyte cation. The rate of charge recombination to the anionic iodide/triiodide redox mediator correlated with the screening ability of the cation, and was initially thought to control charge recombination. However, it was difficult to determine whether electron diffusion or driving force were also cation dependent. Therefore, a in-lab built apparatus, termed STRiVE, was constructed that could disentangle the influence electron diffusion, driving force, and electric fields had on charge recombination. It was found

Manipulation of Dy-Mn coupling and ferrielectric phase diagram of DyMn2O5: The effect of Y substitution of Dy

NASA Astrophysics Data System (ADS)

Zhao, Z. Y.; Wang, Y. L.; Lin, L.; Liu, M. F.; Li, X.; Yan, Z. B.; Liu, J.-M.

2015-11-01

DyMn2O5 is an extraordinary example in the family of multiferroic manganites and it accommodates both the 4f and 3d magnetic ions with strong Dy-Mn (4f-3d) coupling. The electric polarization origin is believed to arise not only from the Mn spin interactions but also from the Dy-Mn coupling. Starting from proposed scenario on ferrielectricity in DyMn2O5 where the exchange-strictions associated with the Mn3+-Mn4+-Mn3+ blocks and Dy3+-Mn4+-Dy3+ blocks generate the two ferroelectric sublattices, we perform a set of characterizations on the structure, magnetism, and electric polarization of Dy1-xYxMn2O5 in order to investigate the roles of Dy-Mn coupling in manipulating the ferrielectricity. It is revealed that the non-magnetic Y substitution of Dy suppresses gradually the Dy3+ spin ordering and the Dy-Mn coupling. Consequently, the ferroelectric sublattice generated by the exchange striction associated with the Dy3+-Mn4+-Dy3+ blocks is destabilized, but the ferroelectric sublattice generated by the exchange striction associated with the Mn3+-Mn4+-Mn3+ blocks remains less perturbed, enabling the ferrielectricity-ferroelectricity transitions with the Y substitution. A phenomenological ferrielectric domain model is suggested to explain the polarization reversal induced by the Y substitution. The present work presents a possible scenario of the multiferroic mechanism in not only DyMn2O5 but probably also other RMn2O5 members with strong 4f-3d coupling.

Study of concentration-dependent cobalt ion doping of TiO2 and TiO(2-x)Nx at the nanoscale.

PubMed

Gole, James L; Prokes, Sharka M; Glembocki, O J; Wang, Junwei; Qiu, Xiaofeng; Burda, Clemens

2010-07-01

Experiments with a porous sol-gel generated TiO(2) nanocolloid and its corresponding oxynitride TiO(2-x)N(x) are carried out to evaluate those transformations which accompany additional doping with transition metals. In this study, doping with cobalt (Co(ii)) ions is evaluated using a combination of core level and VB-photoelectron and optical spectroscopy, complementing data obtained from Raman spectroscopy. Raman spectroscopy suggests that cobalt doping of porous sol-gel generated anatase TiO(2) and nitridated TiO(2-x)N(x) introduces a spinel-like structure into the TiO(2) and TiO(2-x)N(x) lattices. TEM and XPS data complemented by valence band-photoelectron spectra demonstrate that metallic cobalt clusters are not formed even at high doping levels. As evidenced by Raman spectroscopy, the creation of a spinel-like structure is commensurate with the room temperature conversion of the oxide and its oxynitride from the anatase to the rutile form. The onset of this kinetically driven process correlates with the formation of spinel sites within the TiO(2) and TiO(2-x)N(x) particles. Despite their visible light absorption, the photocatalytic activity of these cobalt seeded systems is diminished relative to the oxynitride TiO(2-x)N(x).

Photocatalytic thin films containing TiO2:N nanopowders obtained by the layer-by-layer self-assembling method

NASA Astrophysics Data System (ADS)

Rojas-Blanco, L.; Urzúa, M. D.; Ramírez-Bon, R.; Espinoza Beltrán, F. J.

2012-01-01

In this work, TiO2-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2-N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15 min.

Degradation of organic dyes using spray deposited nanocrystalline stratified WO3/TiO2 photoelectrodes under sunlight illumination

NASA Astrophysics Data System (ADS)

Hunge, Y. M.; Yadav, A. A.; Mahadik, M. A.; Bulakhe, R. N.; Shim, J. J.; Mathe, V. L.; Bhosale, C. H.

2018-02-01

The need to utilize TiO2 based metal oxide hetero nanostructures for the degradation of environmental pollutants like Rhodamine B and reactive red 152 from the wastewater using stratified WO3/TiO2 catalyst under sunlight illumination. WO3, TiO2 and stratified WO3/TiO2 catalysts were prepared by a spray pyrolysis method. It was found that the stratified WO3/TiO2 heterostructure has high crystallinity, no mixed phase formation occurs, strong optical absorption in the visible region of the solar spectrum, and large surface area. The photocatalytic activity was tested for degradation of Rhodamine B (Rh B) and reactive red 152 in an aqueous medium. TiO2 layer in stratified WO3/TiO2 catalyst helps to extend its absorption spectrum in the solar light region. Rh B and Reactive red 152is eliminated up to 98 and 94% within the 30 and 40 min respectively at optimum experimental condition by stratified WO3/TiO2. Moreover, stratified WO3/TiO2 photoelectrode has good stability and reusability than individual TiO2 and WO3 thin film in the degradation of Rh B and reactive red 152. The photoelectrocatalytic experimental results indicate that stratified WO3/TiO2 photoelectrode is a promising material for dye removal.

Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO2 Nanorod Arrays as Electron Transfer Layer.

PubMed

Zhang, Zhen-Long; Li, Jun-Feng; Wang, Xiao-Li; Qin, Jian-Qiang; Shi, Wen-Jia; Liu, Yue-Feng; Gao, Hui-Ping; Mao, Yan-Li

2017-12-01

In this paper, N-doped TiO 2 (N-TiO 2 ) nanorod arrays were synthesized with hydrothermal method, and perovskite solar cells were fabricated using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The power conversion efficiency of solar cells based on N-TiO 2 with the N doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO 2 . To get an insight into the improvement, some investigations were performed. The structure was examined with X-ray powder diffraction (XRD), and morphology was examined by scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) and Tauc plot spectra indicated the incorporation of N in TiO 2 nanorods. Absorption spectra showed higher absorption of visible light for N-TiO 2 than un-doped TiO 2 . The N doping reduced the energy band gap from 3.03 to 2.74 eV. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra displayed the faster electron transfer from perovskite layer to N-TiO 2 than to un-doped TiO 2 . Electrochemical impedance spectroscopy (EIS) showed the smaller resistance of device based on N-TiO 2 than that on un-doped TiO 2 .

Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

PubMed

Yoshida, Tomoko; Niimi, Satoshi; Yamamoto, Muneaki; Nomoto, Toyokazu; Yagi, Shinya

2015-06-01

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts. Copyright © 2015 Elsevier Inc. All rights reserved.

Trap Depth Engineering of SrSi2O2N2:Ln2+,Ln3+ (Ln2+ = Yb, Eu; Ln3+ = Dy, Ho, Er) Persistent Luminescence Materials for Information Storage Applications.

PubMed

Zhuang, Yixi; Lv, Ying; Wang, Le; Chen, Wenwei; Zhou, Tian-Liang; Takeda, Takashi; Hirosaki, Naoto; Xie, Rong-Jun

2018-01-17

Deep-trap persistent luminescence materials exhibit unique properties of energy storage and controllable photon release under additional stimulation, allowing for both wavelength and intensity multiplexing to realize high-capacity storage in the next-generation information storage system. However, the lack of suitable persistent luminescence materials with deep traps is the bottleneck of such storage technologies. In this study, we successfully developed a series of novel deep-trap persistent luminescence materials in the Ln 2+ /Ln 3+ -doped SrSi 2 O 2 N 2 system (Ln 2+ = Yb, Eu; Ln 3+ = Dy, Ho, Er) by applying the strategy of trap depth engineering. Interestingly, the trap depth can be tailored by selecting different codopants, and it monotonically increases from 0.90 to 1.18 eV in the order of Er, Ho, and Dy. This is well explained by the energy levels indicated in the host-referred binding energy scheme. The orange-red-emitting SrSi 2 O 2 N 2 :Yb,Dy and green-emitting SrSi 2 O 2 N 2 :Eu,Dy phosphors are demonstrated to be good candidates of information storage materials, which are attributed to their deep traps, narrow thermoluminescence glow bands, high emission efficiency, and excellent chemical stability. This work not only validates the suitability of deep-trap persistent luminescence materials in the information storage applications, but also broadens the avenue to explore such kinds of new materials for applications in anticounterfeiting and advanced displays.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

NASA Astrophysics Data System (ADS)

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-02-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

PubMed Central

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-01-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions. PMID:26911529

A trimetallic strategy towards ZnDyCr and ZnDyCo single-ion magnets.

PubMed

Hu, Kong-Qiu; Jiang, Xiang; Wu, Shu-Qi; Liu, Cai-Ming; Cui, Ai-Li; Kou, Hui-Zhong

2015-09-21

Two cyano- and phenoxo-bridged octanuclear complexes ZnDyCo (complex ) and ZnDyCr (complex ) with diamagnetic Zn(ii) and Co(iii) are reported. Dy(iii) is surrounded by nine oxygen atoms of two [Zn(Me2valpn)] (Me2valpn(2-) = dianion of N,N'-2,2-dimethylpropylenebis(3-methoxysalicylideneimine)) and one water molecule. Magnetic studies reveal that both exhibit single-ion magnet (SIM) behavior with the energy barrier of 85.9 K for complex and 100.9 K for complex .

Study of the Photodynamic Activity of N-Doped TiO2 Nanoparticles Conjugated with Aluminum Phthalocyanine

PubMed Central

Pan, Xiaobo; Liang, Xinyue; Yao, Longfang; Wang, Xinyi; Jing, Yueyue; Fei, Yiyan; Chen, Li

2017-01-01

TiO2 nanoparticles modified with phthalocyanines (Pc) have been proven to be a potential photosensitizer in the application of photodynamic therapy (PDT). However, the generation of reactive oxygen species (ROS) by TiO2 nanoparticles modified with Pc has not been demonstrated clearly. In this study, nitrogen-doped TiO2 conjugated with Pc (N-TiO2-Pc) were studied by means of monitoring the generation of ROS. The absorbance and photokilling effect on HeLa cells upon visible light of different regions were also studied and compared with non-doped TiO2-Pc and Pc. Both N-TiO2-Pc and TiO2-Pc can be activated by visible light and exhibited much higher photokilling effect on HeLa cells than Pc. In addition, nitrogen-doping can greatly enhance the formation of 1O2 and •O2−, while it suppresses the generation of OH•. This resulted in significant photodynamic activity. Therefore, N-TiO2-Pc can be an excellent candidate for a photosensitizer in PDT with wide-spectrum visible irradiation. PMID:29053580

Microanalytical characterization of multi-rare earth nanocrystalline magnets by TEM and APT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Y. Q.; Tang, W.; Miller, Michael K

2006-01-01

The partitioning behavior of various rare-earth (RE) elements during solidification and their segregation behavior at the grain boundaries were investigated in nanocrystalline (Y{sub 0.5}Dy{sub 0.5}{sub 2.2}Fe{sub 14}B and (Nd{sub 0.5}Y{sub 0.25}Dy{sub 0.25}){sub 1.8}Zr{sub 0.4}Co{sub 1.5}Fe{sub 12.5}B alloys by transmission electron microscopy and atom probe tomography. The best hard magnetic properties obtained are H{sub cj} = 22 kOe, B{sub r}=5.10 kG, and (BH){sub max} = 5.97 MG Oe for the Y-Dy-based alloy and H{sub cj}=10.6 kOe, B{sub r}=6.64 kG, and (BH){sub max}=9.56 MG Oe for the Y-Nd-Dy based alloy. The grain size of the Y-Dy based alloy was {approx} 50 nm.more » The Y-Nd-Dy based alloy had an overall finer, bimodal grain size. An intergranular (Y{sub 0.36}Dy{sub 0.64}){sub 6}Fe{sub 23} phase was detected in the Y-Dy based alloy. A uniform distribution of RE elements was found within the 2-14-1 grains in both alloys. The Y:(Dy+Nd) ratio in the Y-Nd-Dy alloy was lower than its nominal composition, indicating that the Y is segregating to grain boundaries or forming a second phase.« less

Preparation of flexible TiO2 photoelectrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Li, Wen-Ren; Wang, Hsiu-Hsuan; Lin, Chia-Feng; Su, Chaochin

2014-09-01

Dye-sensitized solar cells (DSSCs) based on nanocrystalline TiO2 photoelectrodes on indium tin oxide (ITO) coated polymer substrates have drawn great attention due to its lightweight, flexibility and advantages in commercial applications. However, the thermal instability of polymer substrates limits the process temperature to below 150 °C. In order to assure high and firm interparticle connection between TiO2 nanocrystals (TiO2-NC) and polymer substrates, the post-treatment of flexible TiO2 photoelectrodes (F-TiO2-PE) by mechanical compression was employed. In this work, Degussa P25 TiO2-NC was mixed with tert-butyl alcohol and DI-water to form TiO2 paste. F-TiO2-PE was then prepared by coating the TiO2 paste onto ITO coated polyethylene terephthalate (PET) substrate using doctor blade followed by low temperature sintering at 120 °C for 2 hours. To study the effect of mechanical compression, we applied 50 and 100 kg/cm2 pressure on TiO2/PET to complete the fabrication of F-TiO2-PE. The surface morphology of F-TiO2-PE was characterized using scanning electron microscopy. The resultant F-TiO2-PE sample exhibited a smooth, crack-free structure indicating the great improvement in the interparticle connection of TiO2-NC. Increase of compression pressure could lead to the increase of DSSC photoconversion efficiency. The best photoconversion efficiency of 4.19 % (open circuit voltage (Voc) = 0.79 V, short-circuit photocurrent density (Jsc) = 7.75 mA/cm2, fill factor (FF) = 0.68) was obtained for the F-TiO2-PE device, which showed great enhancement compared with the F-TiO2-PE cell without compression treatment. The effect of compression in DSSC performance was vindicated by the electrochemical impedance spectroscopy measurement.

Semiconducting and quartz microbalance (QCM) humidity sensor properties of TiO2 by sol gel calcination method

NASA Astrophysics Data System (ADS)

Yakuphanoglu, Fahrettin

2012-06-01

Titanium dioxide (TiO2) material was synthesized using the sol gel calcination method. The structural properties of the TiO2 semiconductor were investigated by atomic force microscopy. The electrical conductivity of the TiO2 was measured as a function of temperature and TiO2 exhibits a conductivity of 2.55 × 10-6 S/m at room temperature with activation energy of 104 meV. The electrical conductivity of the TiO2 at room temperature is higher than that of nanocrystalline TiO2 (3 × 10-7 S/m) and TiO2 thin film in air (5 × 10-9 S/m) and in vacuum (8.8 × 10-10 S/m). It was found that the electrical transport mechanism of the TiO2 is controlled by thermally activated mechanism. The optical band gap of the TiO2 powder sample was determined to be 3.17 eV, which is good in agreement with the bulk TiO2 (Eg = 3.2 eV). Up to our knowledge, there is no any reported data about the band gap of TiO2 nanopowder based on the diffused reflectance calculation. Quartz crystal microbalance (QCM) TiO2 humidity sensor was prepared. The sensor indicates a large frequency change with an interaction occurred between TiO2 and humidity molecules. The sensor exhibits a good repeatability when it was exposed to the moist air of 65% RH.

Improved performance of Ag-doped TiO2 synthesized by modified sol-gel method as photoanode of dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

2016-08-01

Ag-doped TiO2 with Ag content ranging from 1 to 7 mol% was synthesized by a modified sol-gel route, and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was compared with undoped TiO2 photoanode. Titanium(IV)isopropoxide was used as precursor and hexamethylenetetramine as the capping agent. XRD results show the formation of TiO2 nanoparticles with an average crystallite size of 5 nm (1 % Ag-doped TiO2) and 9 nm (undoped TiO2), respectively. The TiO2 nanopowder was used to prepare its thin film photoelectrode using doctor's blade method. Significant improvement in light-to-energy conversion efficiency was achieved when thin films of 1 % Ag-doped TiO2 were applied as photoanode in DSSC taking N719 as the sensitizer dye. As evidenced by EIS measurements, the electron lifetime of DSSC with Ag-doped TiO2 increased from 1.33 (for undoped TiO2) to 2.05 ms. The short-circuit current density ( J sc), open-circuit voltage ( V oc), fill factor (FF) and the overall energy conversion efficiency ( η) were 1.07 mA cm-2, 0.72 V, 0.73 and 0.40 %, respectively, with the use of 1 % Ag-doped TiO2 photoanode, whereas with undoped TiO2 under similar conditions, J sc = 0.63 mA cm-2, V oc = 0.70 V, fill factor 0.45 and conversion efficiency 0.14 % could be obtained. Therefore, compared with the reference DSSC containing an undoped TiO2 photoanode, the power conversion efficiency of the cell based on Ag-doped TiO2 has been remarkably enhanced by ~70 %. The substantial improvement in the device performance is attributed to the reduced band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag-doped TiO2, which ultimately resulted in improved IPCE, J SC and η values.

N,N'-Bis((6-methoxylpyridin-2-yl)methylene)-p-phenylenediimine based d(10) transition metal complexes and their utilization in co-sensitized solar cells.

PubMed

Wei, Liguo; Yang, Yulin; Fan, Ruiqing; Na, Yong; Wang, Ping; Dong, Yuwei; Yang, Bin; Cao, Wenwu

2014-08-07

N,N'-Bis((6-methoxylpyridin-2-yl)methylene)-p-phenylenediimine based four-coordinated d(10) transition metal complexes (named ML, M = Zn, Cd, Hg) were synthesized and employed as co-sensitizers and co-adsorbents in combination with a ruthenium complex N719 in dye sensitized solar cells. After co-sensitization, not only the incident-photon-to-current conversion efficiency is enhanced but also the dark current is reduced. A short circuit current density of 14.46 mA cm(-2), an open circuit voltage of 0.74 V and a fill factor of 0.62 corresponding to an overall conversion efficiency of 6.65% under AM 1.5 G solar irradiation were achieved when ZnL was used as a co-sensitizer, which are much higher than that for DSSCs only sensitized by N719 (5.22%) under the same conditions. The improvement in efficiency is attributed to the fact that N,N'-bis((6-methoxylpyridin-2-yl)methylene)-p-phenylenediimine coordinated complexes overcome the deficiency of N719 absorption in the low wavelength region of the visible spectrum, prevent its aggregation, offset competitive visible light absorption of I3(-) and reduce charge recombination due to formation of an effective cover layer of the dye molecules on the TiO2 surface. As a result, the synthesized complexes are promising candidates as co-adsorbents and co-sensitizers for highly efficient DSSCs.

Electronic properties of Cr-N codoped rutile TiO2(110) thin films

NASA Astrophysics Data System (ADS)

Cheng, Zhengwang; Zhang, Lili; Dong, Shihui; Ma, Xiaochuan; Ju, Huanxin; Zhu, Junfa; Cui, Xuefeng; Zhao, Jin; Wang, Bing

2017-12-01

We report our investigation on the electronic properties of Cr-N codoped rutile TiO2(110) single crystal thin films, homoepitaxially grown by pulsed-laser-deposition method, and characterized using scanning tunneling microscopy and spectroscopy (STM/STS), X-ray/ultraviolet photoemission spectroscopy (XPS/UPS), in combination with first-principles calculations. Our results show that the bandgap reduction of the TiO2(110) surface is mainly contributed by the delocalized states whose position is at 2.0 eV below the Fermi level, introduced by the substitutional codoped Cr-2N pair, which is evidenced by the accordance of the results between the STS spectra and the calculated DOS. The codoped Cr-N pair contributes the gap state at about 0.8 eV below the Fermi level, in consistent with the theoretical calculations. While, the monodoped Cr contributes the states either close to the valence band maximum or the conduction band minimum, which should not contribute to the bandgap reduction too much. Our experimental results joint with theoretical calculations provide an atomic view of the bandgap reduction of the rutile TiO2(110) surface, which indicates that the excess substitutional N atoms should be important to efficiently narrow the bandgap by introducing the Cr-2N pairs.

Theoretical study of electronic transfer current rate at dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

AL-Agealy, Hadi J. M.; AlMaadhede, Taif Saad; Hassooni, Mohsin A.; Sadoon, Abbas K.; Ashweik, Ahmed M.; Mahdi, Hind Abdlmajeed; Ghadhban, Rawnaq Qays

2018-05-01

In this research, we present a theoretical study of electronic transfer kinetics rate in N719/TiO2 and N719/ZnO dye-sensitized solar cells (DSSC) systems using a simple model depending on the postulate of quantum mechanics theory. The evaluation of the electronic transition current rate in DSSC systems are function of many parameters such that; the reorientation transition energies ΛSe m D y e , the transition coupling parameter ℂT(0), potential exponential effect e-(E/C-EF ) kBT , unit cell volume VSem, and temperature T. Furthermore, the analysis of electronic transfer current rate in N719/TiO2 and N719/ZnO systems show that the rate upon dye-sensitization solar cell increases with increases of transition coupling parameter, decreasing potential that building at interface a results of different material in this devices and increasing with reorientation transition energy. On the other hand, we can find the electronic transfer behavior is dependent of the dye absorption spectrum and mainly depending on the reorientation of transition energy. The replacement of the solvents in both DSSC system caused increasing of current rates dramatically depending on polarity of solvent in subset devices. This change in current rate of electron transfer were attributed to much more available of recombination sites introduced by the solvents medium. The electronic transfer current dynamics are shown to occurs in N719/TiO2 system faster many time compare to ocuures at N719/ZnO system, this indicate that TiO2 a is a good and active material compare with ZnO to using in dye sensitized solar cell devices. In contrast, the large current rate in N719/TiO2 comparing to ZnO of N719/ZnO systems indicate that using TiO2 with N719 dye lead to increasing the efficiency of DSSC.

Properties of Structurally Excellent N-doped TiO2 Rutile

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chambers, Scott A.; Cheung, Sau H.; Shutthanandan, V.

2007-10-15

We have used plasma-assisted molecular beam epitaxy to synthesize structurally near-perfect crystalline films of TiO2-xNx rutile for the first time. These materials allow the properties of TiO2-xNx to be elucidated without the interfering effects of oxygen vacancy defects. In the absence of such defects, the extent of N incorporation in the lattice is limited to 2 ± 1 at. % of the anions. Substitutional N (NO) exhibits a -3 formal charge due to charge transfer from shallow-donor interstitial Ti(III), which forms during epitaxial growth. Hybridization between NO and adjacent lattice Ti ions occurs, resulting in new states off the topmore » of the rutile valence band and an apparent band gap reduction of ~ 0.5 eV. It is not yet known if these new states result in mobile electron-hole pair creation upon irradiation, but experiments are planned to answer this important question.« less

Sprayed nanostructured TiO2 films for efficient photocatalytic degradation of textile azo dye.

PubMed

Stambolova, Irina; Shipochka, Capital Em Cyrillicaria; Blaskov, Vladimir; Loukanov, Alexandrе; Vassilev, Sasho

2012-12-05

Spray pyrolysis procedure for preparation of nanostructured TiO(2) films with higher photocatalytic effectiveness and longer exploitation life is presented in this study. Thin films of active nanocrystalline TiO(2) were obtained from titanium isopropoxide, stabilized with acetyl acetone and characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The activity of sprayed nanostructured TiO(2) is tested for photocatalytic degradation of Reactive Black 5 dye with concentrations up to 80 ppm. Interesting result of the work is the reduction of toxicity after photocatalytic treatment of RB5 with TiO(2), which was confirmed by the lower percentage of mortality of Artemia salina. It was proved that the film thickness, conditions of post deposition treatment and the type of the substrate affected significantly the photocatalytic reaction. Taking into account that the parameters are interdependent, it is necessary to optimize the preparation conditions in order to synthesize photocatalytic active films. Copyright © 2012 Elsevier B.V. All rights reserved.

Evaluation of the photocatalytic activity of Ln3+-TiO2 nanomaterial using fluorescence technique for real wastewater treatment.

PubMed

Saif, M; Aboul-Fotouh, S M K; El-Molla, S A; Ibrahim, M M; Ismail, L F M

2014-07-15

Evaluation the photocatalytic activity of different Ln(3+) modified TiO2 nanomaterials using fluorescence based technique has rarely been reported. In the present work, xmol Ln(3+) modified TiO2 nanomaterials (Ln = Nd(3+), Sm(3+), Eu(3+), Gd(3+), Dy(3+) and Er(3+) ions; x = 0.005, 0.008, 0.01, 0.02 and 0.03) were synthesized by sol-gel method and characterized using different advanced techniques. The photocatalytic efficiency of the modified TiO2 expressed in the charge carrier separation and OH radicals formation were assigned using TiO2 fluorescence quenching and fluorescence probe methods, respectively. The obtained fluorescence measurements confirm that doping treatment significantly decreases the electron-hole recombination probability in the obtained Ln(3+)/TiO2. Moreover, the rate of OH radicals formation is increased by doping. The highly active nanoparticles (0.02Gd(3+)/TiO2 and 0.01Eu(3+)/TiO2) were applied for industrial wastewater treatment using solar radiation as a renewable energy source. Copyright © 2014 Elsevier B.V. All rights reserved.

Tempe Waste Water Degradation Using TiO2-N/Bentonite alginate Granule Photocatalyst with Ultraviolet Light Irradiation

NASA Astrophysics Data System (ADS)

Khoirun Nisaa', Aldila; Wardhani, Sri; Purwonugroho, Danar; Darjito

2018-01-01

Tempe waste water stew has high ammonia concentration which causes odor due to polluting by anaerobic decay. Free ammonia in the waste has exceeded the limit, thus endangering the aquatic environment. This research aims to determine the activity of photocatalyst granule TiO2-N/bentonite-alginate as decomposers of compounds in the photodegradation process. Photodegradation is the decomposition process of compounds by semiconductors with light. Results expected includes the photocatalyst activity of TiO2-N/bentonite-alginate granule produced by ultraviolet rays is known based on the effect of dopant N concentration on the catalyst and the effect of photocatalytic ratio toward tempe waste water. Methods proposed in this research are activation of bentonite using H2SO4 0.8 M, TiO2-N synthesize by sonication method with urea as the source of N, then TiO2-N impregnation into bentonite. Photocatalyst in granule form synthesized with alginate was then dripped with syringe pump into 3% (w/v) CaCl2. The photocatalyst characterization will be performed using XRD. The optimum tempe waste water degradation at the concentration of TiO2-N 0.4 (g/g) bentonite is 53.66%. The ratio of photocatalyst and tempe waste water, optimum at 150 mg of photocatalyst with 25 mL of waste equal to 53.66%.

Sonocatalytic degradation of humic acid by N-doped TiO2 nano-particle in aqueous solution.

PubMed

Kamani, Hossein; Nasseri, Simin; Khoobi, Mehdi; Nabizadeh Nodehi, Ramin; Mahvi, Amir Hossein

2016-01-01

Un-doped and N-doped TiO2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol-gel method, and were characterized by X-ray diffraction, field emission scanning electron microscopy, Energy dispersive X-ray analysis and UV-visible diffuse reflectance spectra techniques. Then enhancement of sonocatalytic degradation of humic acid by un-doped and N-doped TiO2 nano-particles in aqueous environment was investigated. The effects of various parameters such as initial concentration of humic acid, N-doping, and the degradation kinetics were investigated. The results of characterization techniques affirmed that the synthesis of un-doped and N-doped TiO2 nano-particles was successful. Degradation of humic acid by using different nano-particles obeyed the first-order kinetic. Among various nano-particles, N-doped TiO2 with molar doping ratio of 6 % and band gap of 2.92 eV, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56 × 10(-2) min(-1). The high degradation rate was associated with the lower band gap energy and well-formed anatase phase. The addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as N-doped TiO2 with a molar ratio of 6 %N/Ti was found the best nano-catalyst among the investigated catalysts. The sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.

PAMAM templated N,Pt co-doped TiO2 for visible light photodegradation of brilliant black.

PubMed

Nzaba, Sarre Kadia Myra; Ntsendwana, Bulelwa; Mamba, Bhekie Brilliance; Kuvarega, Alex Tawanda

2018-05-01

This study examined the photocatalytic degradation of an azo dye brilliant black (BB) using non-metal/metal co-doped TiO 2 . N,Pt co-doped TiO 2 photocatalysts were prepared by a modified sol-gel method using amine-terminated polyamidoamine dendrimer generation 0 (PG0) as a template and source of nitrogen. Structural, morphological, and textural properties were evaluated using scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM/EDX), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman spectroscopy (RS), photoluminescence (PL) and ultra-violet/visible spectroscopy (UV-Vis). The synthesized photocatalysts exhibited lower band gap energies as compared to the Degussa P-25, revealing a red shift in band gap towards the visible light absorption region. Photocatalytic activity of N,Pt co-doped TiO 2 was measured by the reaction of photocatalytic degradation of BB dye. Enhanced photodegradation efficiency of BB was achieved after 180-min reaction time with an initial concentration of 50 ppm. This was attributed to the rod-like shape of the materials, larger surface area, and enhanced absorption of visible light induced by N,Pt co-doping. The N,Pt co-doped TiO 2 also exhibited pseudo-first-order kinetic behavior with half-life and rate constant of 0.37 and 0.01984 min -1 , respectively. The mechanism of the photodegradation of BB under the visible light irradiation was proposed. The obtained results prove that co-doping of TiO 2 with N and Pt contributed to the enhanced photocatalytic performances of TiO 2 for visible light-induced photodegradation of organic contaminants for environmental remediation. Therefore, this work provides a new approach to the synthesis of PAMAM templated N,Pt co-doped TiO 2 for visible light photodegradation of brilliant black.

Effect of photocatalytic reduction of carbon dioxide by N-Zr co-doped nano TiO2.

PubMed

Zhang, Ru; Wang, Li; Kang, Zhuo; Li, Qiang; Pan, Huixian

2017-11-01

Modified sol-gel method was adopted to prepare TiO 2 , Zr-TiO 2 and N/Zr-TiO 2 composite catalyst. The as-synthesized photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunner- Emmet- Teller measurement and UV-Vis diffuse reflectance spectroscopy. And the photocatalytic performance toward CO 2 reduction was evaluated under ultraviolet light. The catalyst particles were demonstrated in the nanometer level size. When N and Zr are co-doped, on the one hand, Ti 4+ can be replaced by Zr 4  +, which leads to lattice distortion and inhibits electron-hole recombination. On the other hand, N enters into TiO 2 lattice gap to form O-Ti-N bond structure, and partial Ti 4+ are reduced to Ti 3+ . Compared with pristine TiO 2 , the specific surface area and the band gap of N/Zr-TiO 2 were improved and reduced, respectively. The N and Zr synergistically contribute to the obviously strengthened absorption intensity in visible region, as well as significantly improved photocatalytic activity. In the gas phase reactor, when the calcination temperature was 550°C, 0.125N/0.25Zr-TiO 2 composite performed the highest photocatalytic activity UV irradiation for 8 h, and the corresponding CH 4 yield was 11.837 µmol/g, which was 87.8% higher than that of pristine TiO 2 . For the visible light, the CH 4 yield was 9.003 µmol/g after 8 h irradiation, which was 83.9% higher than that of pristine TiO 2 .

Ab Initio Study of the Atomic Level Structure of the Rutile TiO2(110)-Titanium Nitride (TiN) Interface.

PubMed

Gutiérrez Moreno, José Julio; Nolan, Michael

2017-11-01

Titanium nitride (TiN) is widely used in industry as a protective coating due to its hardness and resistance to corrosion and can spontaneously form a thin oxide layer when it is exposed to air, which could modify the properties of the coating. With limited understanding of the TiO 2 -TiN interfacial system at present, this work aims to describe the structural and electronic properties of oxidized TiN based on a density functional theory (DFT) study of the rutile TiO 2 (110)-TiN(100) interface model system, also including Hubbard +U correction on Ti 3d states. The small lattice mismatch gives a good stability to the TiO 2 -TiN interface after depositing the oxide onto TiN through the formation of interfacial Ti-O bonds. Our DFT+U study shows the presence of Ti 3+ cations in the TiO 2 region, which are preferentially located next to the interface region as well as the rotation of the rutile TiO 2 octahedra in the interface structure. The DFT+U TiO 2 electronic density of states (EDOS) shows localized Ti 3+ defect states forming in the midgap between the top edge of the valence and the bottom of the conduction band. We increase the complexity of our models by the introduction of nonstoichiometric compositions. Although the vacancy formation energies for Ti in TiN (E vac (Ti) ≥ 4.03 eV) or O in the oxide (E vac (O) ≥ 3.40 eV) are quite high relative to perfect TiO 2 -TiN, defects are known to form during the oxide growth and can therefore be present after TiO 2 formation. Our results show that a structure with exchanged O and N can lie 0.82 eV higher in energy than the perfect system, suggesting the stability of structures with interdiffused O and N anions at ambient conditions. The presence of N in TiO 2 introduces N 2p states localized between the top edge of the O 2p valence states and the midgap Ti 3+ 3d states, thus reducing the band gap in the TiO 2 region for the exchanged O/N interface EDOS. The outcomes of these simulations give us a most comprehensive

Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3

PubMed Central

Buruiana, Tinca; Melinte, Violeta; Buruiana, Emil C

2017-01-01

Polymer nanocomposites containing titanium oxide nanoparticles (TiO2 NPs) combined with other inorganic components (Si–O–Si or/and γ-Fe2O3) were prepared by the dispersion of premade NPs (nanocrystalline TiO2, TiO2/SiO2, TiO2/Fe2O3, TiO2/SiO2/Fe2O3) within a photopolymerizable urethane dimethacrylate (polytetrahydrofuran-urethane dimethacrylate, PTHF-UDMA). The physicochemical characterization of nanoparticles and hybrid polymeric composites with 10 wt % NPs (S1–S4) was realized through XRD, TEM and FTIR analyses. The mean size (10–30 nm) and the crystallinity of the NPs varied as a function of the inorganic constituent. The catalytic activity of these hybrid films was tested for the photodegradation of phenol, hydroquinone and dopamine in aqueous solution under UV or visible-light irradiation. The best results were obtained for the films with TiO2/Fe2O3 or TiO2/SiO2/Fe2O3 NPs. The degradation of the mentioned model pollutants varied between 71% and 100% (after 250 min of irradiation) depending on the composition of the hybrid film tested and the light applied (UV–visible light). Also, it was established that such hybrid films can be reused at least for five cycles, without losing too much of the photocatalytic efficiency (ca. 7%). These findings could have implications in the development of new nanocatalysts. PMID:28243566

Band-engineering of TiO2 as a wide-band gap semiconductor using organic chromophore dyes

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Kartini, I.; Ramelan, A. H.; Saputri, L. N. M. Z.; Munawaroh, H.

2017-07-01

Bond-engineering as applied to semiconductor materials refers to the manipulation of the energy bands in order to control charge transfer processes in a device. When the device in question is a photoelectrochemical cell, the charges affected by drift become the focus of the study. The ideal band gap of semiconductors for enhancement of photocatalyst activity can be lowered to match with visible light absorption and the location of conduction Band (CB) should be raised to meet the reducing capacity. Otherwise, by the addition of the chromofor organic dyes, the wide-band gab can be influences by interacation resulting between TiO2 surface and the dyes. We have done the impruvisation wide-band gap of TiO2 by the addition of organic chromophore dye, and the addition of transition metal dopand. The TiO2 morphology influence the light absorption as well as the surface modification. The organic chromophore dye was syntesized by formation complexes compound of Co(PAR)(SiPA)(PAR)= 4-(2-piridylazoresorcinol), SiPA = Silyl propil amine). The result showed that the chromophore groups adsorbed onto TiO2 surface can increase the visible light absorption of wide-band gab semiconductor. Initial absorption of a chromophore will affect light penetration into the material surfaces. The use of photonic material as a solar cell shows this phenomenon clearly from the IPCE (incident photon to current conversion efficiency) measurement data. Organic chromophore dyes of Co(PAR)(SiPA) exhibited the long wavelength absorption character compared to the N719 dye (from Dyesol).

Facile decoration of TiO2 nanoparticles on graphene for solar degradation of organic dye

NASA Astrophysics Data System (ADS)

Salem, Shiva; Salem, Amin; Rezaei, Mostafa

2016-11-01

The reduced graphene oxide is interesting material for the synthesis of TiO2-based photocatalyst. In the present investigation, blackberry fruit, which contains high levels of anthocyanins and other phenolic compounds, was employed as a reducing agent mainly due to its high antioxidant capacity. The nano-crystalline TiO2 was decorated on different amounts of graphene oxide with sol-gel method and then the photocatalytic activity for degradation of cationic dye was evaluated by UV spectroscopy to achieve the optimum content of graphene oxide. The decoration of anatase nanoparticles on prepared reduced graphene oxide was investigated by X-ray diffraction, scanning and transmission electron microscopy techniques. The new composite gives significantly higher activity when is compared to the compositions fabricated by graphene oxide. The compact layer provides a large TiO2-graphene contact area and reduces the electron recombination. The decoration of TiO2 nanoparticles, 5-10 nm, on the graphene oxide reduced by blackberry juice further improves the dye removal. The results imply that the nanoparticle decoration is the key strategy to increase the degradation capacity.

Enhanced photocatalytic activity of electrospun nanofibrous TiO2/g-C3N4 heterojunction photocatalyst under simulated solar light

NASA Astrophysics Data System (ADS)

Wang, Chunlei; Hu, Liming; Chai, Bo; Yan, Juntao; Li, Jianfen

2018-02-01

Electrospun nanofibrous TiO2/g-C3N4 heterojunction photocatalysts with different TiO2 content have been synthesized via a facile electrospinning and subsequent in situ evaporation and calcination process for the first time, which are examined in terms of morphology, component content, optical properties, PL spectra, photocurrent response, EIS measurement, photocatalytic activity and mechanism. SEM images exhibit TiO2/g-C3N4-4 heterojunction photocatalyst possesses the excellent 1D structure. HRTEM and element mapping images confirm the formation of heterojunction structure. DRS tests identify that TiO2/g-C3N4-4 heterojunction exhibits the intensitive absorption in both UV and visible light region. The photoelectrochemical tests prove that the recombination between electrons and holes are effectively inhibited. Based on TG analysis and photodegradation experiments, TiO2/g-C3N4-4 heterojunction photocatalyst with TiO2 content of 29.30 wt% possesses the best photocatalytic degradation efficiency for the RhB among the g-C3N4, TiO2 and their mixture under simulated sunlight irradiation. Moreover, 1D morphology of TiO2/g-C3N4-4 heterojunction photocatalyst is in favor of separating from solution for reuse and transferring the electrons, and maintains a very high photocatalytic degradation efficiency of 96% even after four recycles experiments, which is beneficial for practical application.

Synthesis, structure, luminescent, and magnetic properties of carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2] (Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato).

PubMed

Ehama, Kiyomi; Ohmichi, Yusuke; Sakamoto, Soichiro; Fujinami, Takeshi; Matsumoto, Naohide; Mochida, Naotaka; Ishida, Takayuki; Sunatsuki, Yukinari; Tsuchimoto, Masanobu; Re, Nazzareno

2013-11-04

Carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2]·solvent were synthesized through atmospheric CO2 fixation reaction of [Zn(II)L(n)(H2O)2]·xH2O, Ln(III)(NO3)3·6H2O, and triethylamine, where Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato. Each Zn(II)2Ln(III)2 structure possessing an inversion center can be described as two di-μ-phenoxo-bridged {Zn(II)L(n)Ln(III)(NO3)} binuclear units bridged by two carbonato CO3(2-) ions. The Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of L(n) and one oxygen atom of a bridging carbonato ion at the axial site. Ln(III) ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base L(n), two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9-300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the Zn(II)2Ln(III)2 complexes are analyzed on the basis of the dicarbonato-bridged binuclear Ln(III)-Ln(III) structure, as the Zn(II) ion with d(10) electronic configuration is diamagnetic. ZnGd1 (L(1)) and ZnGd2 (L(2)) show a ferromagnetic Gd(III)-Gd(III) interaction with J(Gd-Gd) = +0.042 and +0.028 cm(-1), respectively, on the basis of the Hamiltonian H = -2J(Gd-Gd)ŜGd1·ŜGd2. The magnetic data of the Zn(II)2Ln(III)2 complexes (Ln(III) = Tb(III), Dy(III)) were analyzed by a spin Hamiltonian including the crystal field effect on the Ln(III) ions and the Ln(III)-Ln(III) magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of Zn(II)2Tb(III)2 complexes were observed, while those

Enhanced photovoltaic performance of dye-sensitized solar cells based on NaYF4:Yb(3+), Er(3+)-incorporated nanocrystalline TiO2 electrodes.

PubMed

Zhu, Guang; Wang, Hongyan; Zhang, Quanxin; Zhang, Li

2015-08-01

Near infrared to visible up-conversion of light by rare earth ion-doped phosphors (NaYF4:Yb(3+), Er(3+)) that convert multiple photons of lower energy to higher energy photons offer new possibilities for improved performance of photovoltaic devices. Here, up-conversion phosphor NaYF4:Yb(3+), Er(3+) doped nanocrystalline TiO2 films are designed and used as a electrode for dye-sensitized solar cells, and the photovoltaic performance of DSSCs based on composite electrodes are investigated. The results show the cell with NaYF4:Yb(3+), Er(3+) achieves a power conversion efficiency of 7.65% under one sun illumination (AM 1.5G, 100mWcm(-2)), which is an increase of 14% compared to the cell without NaYF4:Yb(3+), Er(3+) (6.71%). The performance improvement is attributed to the dual effects of enhanced light harvesting from extended light absorption range and increased light scattering, and lower electron transfer resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

Interface engineered construction of porous g-C3N4/TiO2 heterostructure for enhanced photocatalysis of organic pollutants

NASA Astrophysics Data System (ADS)

Li, Ya-Nan; Chen, Zhao-Yang; Wang, Min-Qiang; Zhang, Long-zhen; Bao, Shu-Juan

2018-05-01

A porous g-C3N4/TiO2 with hierarchical heterostructure has been successfully fabricated through a in situ assembling of small needle-like TiO2 on the surface of ultrathin g-C3N4 sheets. The ultrathin g-C3N4 sheets with carbon vacancies and rich hydroxyl groups were found to facilitate the nucleation and in situ growth of TiO2 and also to modulate the surface chemical activity of the g-C3N4/TiO2 hierarchical heterostructure. The as-designed photocatalytic heterojunction degraded Acid Orange with 82% efficiency after 10 min under simulated solar light, and possessed excellent cycle stability. Relative physical characterizations and photochemical experiments reveal that engineering the interface/surface of g-C3N4 plays a vital role in effectively constructing heterostructures of g-C3N4/TiO2, thus realizing efficient photoinduced electron-hole separation during photocatalytic process.

Wear-triggered self-healing behavior on the surface of nanocrystalline nickel aluminum bronze/Ti3SiC2 composites

NASA Astrophysics Data System (ADS)

Zhai, Wenzheng; Lu, Wenlong; Zhang, Po; Wang, Jian; Liu, Xiaojun; Zhou, Liping

2018-04-01

Self-healing can protect materials from diverse damages, but is intrinsically difficult in metals. This paper demonstrates a potential method through a simultaneous decomposition and oxidation of Ti3SiC2 to achieve healing of stress cracking on the surface of nickel aluminum bronze (NAB)/Ti3SiC2 nanocrystalline composites during fretting wear. At the finest nanocrystalline materials, a crack recovery would be attained at 76.5%. The repetitive fretting wear leads to a modest amount of 'flowability' of Ti3SiC2 toward the crack, facilitating crack recovery. Along with the wear-triggered self-healing, the NAB/Ti3SiC2 shows an improved tribological performance with the stable decreased friction torque due to the formation of lubrication TiO2 oxide.

Eu2+,Dy3+ codoped SrAl2O4 nanocrystalline phosphor for latent fingerprint detection in forensic applications

NASA Astrophysics Data System (ADS)

Sharma, Vishal; Das, Amrita; Kumar, Vinay

2016-01-01

In this work, europium and dysprosium doped strontium aluminate (SrAl2O4:Eu2+,Dy3+) nanophosphor is synthesized and its novel application for the detection of latent fingerprints on various contact surfaces is reported. The SrAl2O4:Eu2+,Dy3+ is synthesized using a combustion method and shows long-lasting afterglow luminescence. The powder particles are characterized using field emission scanning electron microscopy (FE-SEM), SEM-energy dispersive x-ray analysis, x-ray diffraction and photoluminescence spectrophotometry. The FE-SEM image analysis reveals that the nanoparticles are mostly 8-15 nm in size with an irregular spherical shape. This nano-structured powder was applied to fresh and aged fingerprints deposited on porous, semi-porous and non-porous contact surfaces, such as ordinary colored paper, glossy paper, glass, aluminum foil, a yellow foil chocolate wrapper, a soft drink can, a PET bottle, a compact disc and a computer mouse. The results are reproducible and show great sensitivity and high contrast in the developed fingermark regions on these surfaces. These nanophosphor particles also show a strong and long-lasting afterglow property, making them a suitable candidate for use as a fingerprint developing agent on luminescent and highly patterned surfaces. These kinds of powders have shown that they can remove the interference from background luminescence, which is not possible using ordinary luminescent fingerprinting powders.

TiO2-Containing Carbon Derived from a Metal-Organic Framework Composite: A Highly Active Catalyst for Oxidative Desulfurization.

PubMed

Bhadra, Biswa Nath; Song, Ji Yoon; Khan, Nazmul Abedin; Jhung, Sung Hwa

2017-09-13

A new metal-organic framework (MOF) composite consisting of Ti- and Zn-based MOFs (ZIF-8(x)@H 2 N-MIL-125; in brief, ZIF(x)@MOF) was designed and synthesized. The pristine MOF [H 2 N-MIL-125 (MOF)]- and an MOF-composite [ZIF(30)@MOF]-derived mesoporous carbons consisting of TiO 2 nanoparticles were prepared by pyrolysis (named MDC-P and MDC-C, respectively). MDC-C showed a higher surface area, larger pore sizes, and larger mesopore volumes than MDC-P. In addition, the TiO 2 nanoparticles on MDC-C have more uniform shapes and sizes and are smaller than those of MDC-P. The obtained MDC-C and MDC-P [together with MOF, ZIF(30)@MOF, pure/nanocrystalline TiO 2 , and activated carbon] were applied in the oxidative desulfurization reaction of dibenzothiophene in a model fuel. The MDC-C, even with a lower TiO 2 content than that of MDC-P, showed an outstanding catalytic performance, especially with a very low catalyst dose (i.e., a very high quantity of dibenzothiophene was converted per unit weight of the catalyst), fast kinetics (∼3 times faster than that for MDC-P), and a low activation energy (lower than that for any reported catalyst) for the oxidation of dibenzothiophene. The large mesopores of MDC-C and the well-dispersed/small TiO 2 might be the dominant factors for the superior catalytic conversions. The oxidative desulfurization of other sulfur-containing organic compounds with various electron densities was also studied with MDC-C to understand the mechanism of catalysis. Moreover, the MDC-C catalyst can be reused many times in the oxidative desulfurization reaction after a simple washing with acetone. Finally, composing MOFs and subsequent pyrolysis is suggested as an effective way to prepare a catalyst with well-dispersed active sites, large pores, and high mesoporosity.

Enhanced photocatalytic H2-production activity of C-dots modified g-C3N4/TiO2 nanosheets composites.

PubMed

Li, Yang; Feng, Xionghan; Lu, Zhexue; Yin, Hui; Liu, Fan; Xiang, Quanjun

2018-03-01

As a new carbon-based material, carbon dots (C-dots) have got widely preference because of its excellent electronic transfer capability. In this work, a novel ternary layered C-dots/g-C 3 N 4 /TiO 2 nanosheets (CGT) composite photocatalysts were prepared by impregnation precipitation methods. The optimal ternary CGT composite samples revealed high photocatalytic hydrogen evolution rate in triethanolamine aqueous solutions, which exceeded the rate of the optimal g-C 3 N 4 /TiO 2 composite sample by a factor of 5 times. The improved photocatalytic activity is owed to the positive effects of C-dots and layered heterojunction structure of TiO 2 nanosheets and g-C 3 N 4 sheets. C-dots in the CGT composites can serve as electron reservoirs to capture the photo-induced electrons. The well-defined layered heterojunction structure of CGT provides the intimate contact and the strong interaction of anatase TiO 2 nanosheets and g-C 3 N 4 sheets via face-to-face orientation, which restrains the recombination of photogenerated charge carriers, and thus enhances the photocatalytic H 2 -production activity. Electron paramagnetic resonance and transient photocurrent response proved the strong interaction and improved interfacial charge transfer of TiO 2 nanosheets and g-C 3 N 4 sheets, respectively. The mechanism of improving the photocatalytic H 2 -evolution activity was further confirmed by time-resolved fluorescence, electron paramagnetic resonance, transient photocurrent response and electrochemical impedance spectroscopy. Copyright © 2017 Elsevier Inc. All rights reserved.

Reddish-orange, neutral and warm white emissions in Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses

NASA Astrophysics Data System (ADS)

Rodríguez-Carvajal, David A.; Meza-Rocha, A. N.; Caldiño, U.; Lozada-Morales, R.; Álvarez, E.; Zayas, Ma. E.

2016-11-01

Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with Tesbnd Osbnd Te and Gesbnd Osbnd Ge related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370-420 nm) based LEDs. The Eu3+ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy3+ singly doped glass excited at 388 nm. The Dy3+/Eu3+ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy3+ and Eu3+ relative excitation. The Dy3+ excitation bands observed in the Dy3+/Eu3+ glass by monitoring the 611 nm Eu3+ emission, suggest that Dy3+ → Eu3+ energy transfer takes place, despite the fact that the Dy3+ emission decays in the Dy3+ and Dy3+/Eu3+ doped glass, remain without changes. The shortening of Eu3+ decay in presence of Dy3+ was attributed to an Eu3+ → Dy3+ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s-1, respectively.

The Back Scattering Micro-Raman Spectroscopy of Different Crystalline Phases of TiO2 Nanoparticles Produced by Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Malekfar, R.; Mihanyar, S.; Mozaffari, M.

2007-09-01

TiO2 is known to be one of the best photocatalysts among the semiconductors. In order to improve its photocatalytic features, it is necessary to be able to control factors such as the mean particle size, nanocrystalline system, grain shapes and diffraction. Nanocrystalline TiO2 sample powders were produced using H2O2 and Ti(OBu)4 as precursor materials and their above features were then characterized by using XRD, Raman spectroscopy and SEM. The grain size was calculated using the Debye Scherrer formula for anatase phase, 15 nm, which is in agreement with the value obtained by SEM imaging. Ti(OBu)4 was added dropwise to a very ice-cold solution of H2O2 under intensive stirring. This immediately yielded a red solution which was shortly followed by a strong exothermic reaction due to the unstable nature of the reaction at this stage. This process also involved rigorous giving off of H2O2, O2, and butyl alcohol. A yellow transparent peroxo-polytitanic (PPT) acid gel was thus prepared. This gel was then heated at 150 °C for 5 hours and was transformed into amorphous TiO2. The produced yellow powder was heated at 250 °C, 350 °C and 450 °C for one hour with a ramping up speed of 5 °C/min heating rate. It was later calcined at 550 °C, 750 °C and 950 °C for 30 minutes. By investigating the Raman spectra typically shown in figure 1 and also XRD patterns, it was confirmed that the anatase phase nanocrystalline powder, which is well known for its application as photocatalysts, was produced at the first three lower treatment temperatures mentioned above.

Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

NASA Astrophysics Data System (ADS)

Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

2018-06-01

SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm < λ < 780 nm) irradiation is used to evaluate the photocatalytic activity of the composites. Compared with pure TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.

A weak-light-responsive TiO2/g-C3N4 composite film: photocatalytic activity under low-intensity light irradiation.

PubMed

Wang, Peifang; Guo, Xiang; Rao, Lei; Wang, Chao; Guo, Yong; Zhang, Lixin

2018-05-10

A TiO 2 /g-C 3 N 4 composite photocatalytic film was prepared by in situ synthesis method and its photocatalytic capability under weak-visible-light condition was studied. The co-precursor with different ratio of melamine and TiO 2 sol-gel precursor were treated using ultrasonic mixing, physical deposition, and co-sintering method to form the smooth, white-yellow, and compact TiO 2 /g-C 3 N 4 composite films. The prepared TiO 2 /g-C 3 N 4 materials were characterized by SEM, TEM, EDS, XRD, BET, VBXPS, and UV-vis diffuse reflectance spectra. The results of composite showed that TiO 2 and g-C 3 N 4 have close interfacial connections which are favorable to charge transfer between these two semiconductors with suitable band structure, g-C 3 N 4 retard the anatase-to-rutile phase transition of TiO 2 significantly, the specific surface area were increased with g-C 3 N 4 ratio raised. Under weak-light irradiation, composite films photocatalytic experiments exhibited RhB removal efficiency approaching 90% after three recycles. Powders suspension degradation experiments revealed the removal efficiency of TiO 2 /g-C 3 N 4 (90.8%) was higher than pure TiO 2 (52.1%) and slightly lower than pure g-C 3 N 4 (96.6%). By control experiment, the enhanced photocatalysis is ascribed to the combination of TiO 2 and g-C 3 N 4 , which not only produced thin films with greater stability but also formed heterojunctions that can be favorable to charge transfer between these two semiconductors with suitable band structure. This study presents the potential application of photocatalytic film in the wastewater treatment under weak-light situation.

Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite

NASA Astrophysics Data System (ADS)

Li, Y.; Li, S. G.; Wang, J.; Li, Y.; Ma, C. H.; Zhang, L.

2014-12-01

Three TiO2 loaded composites, TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO2. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO2 content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.

Synthesis and Characterization of N-Doped Porous TiO2 Hollow Spheres and Their Photocatalytic and Optical Properties

PubMed Central

Li, Hongliang; Liu, Hui; Fu, Aiping; Wu, Guanglei; Xu, Man; Pang, Guangsheng; Guo, Peizhi; Liu, Jingquan; Zhao, Xiu Song

2016-01-01

Three kinds of N-doped mesoporous TiO2 hollow spheres with different N-doping contents, surface area, and pore size distributions were prepared based on a sol–gel synthesis and combined with a calcination process. Melamine formaldehyde (MF) microspheres have been used as sacrificial template and cetyltrimethyl ammonium bromide (CTAB) or polyvinylpyrrolidone (PVP) was selected as pore-directing agent. Core–shell intermediate spheres of titania-coated MF with diameters of 1.2–1.6 μm were fabricated by varying the volume concentration of TiO2 precursor from 1 to 3 vol %. By calcining the core–shell composite spheres at 500 °C for 3 h in air, an in situ N-doping process occurred upon the decomposition of the MF template and CTAB or PVP pore-directing surfactant. N-doped mesoporous TiO2 hollow spheres with sizes in the range of 0.4–1.2 μm and shell thickness from 40 to 110 nm were obtained. The composition and N-doping content, thermal stability, morphology, surface area and pore size distribution, wall thickness, photocatalytic activities, and optical properties of the mesoporous TiO2 hollow spheres derived from different conditions were investigated and compared based on Fourier-transformation infrared (FTIR), SEM, TEM, thermogravimetric analysis (TGA), nitrogen adsorption–desorption, and UV–vis spectrophotoscopy techniques. The influences of particle size, N-doping, porous, and hollow characteristics of the TiO2 hollow spheres on their photocatalytic activities and optical properties have been studied and discussed based on the composition analysis, structure characterization, and optical property investigation of these hollow spherical TiO2 matrices. PMID:28773967

Mechanism of room temperature oxygen sensor based on nanocrystalline TiO2 film

NASA Astrophysics Data System (ADS)

Bakri, A. S.; Sahdan, M. Z.; Nafarizal, N.; Abdullah, S. A.; Said, N. D. M.; Raship, N. A.; Sari, Y.

2018-04-01

A titanium dioxide (TiO2) thin film is proposed as the active layer for the detection of oxygen gas. The sensor is fabricated on silicon wafer using sol-gel dip coating technique with a constant withdrawal speed. The field emission scanning electron microscope image reveals that the film has a uniform structure while the x-ray diffraction analysis indicates that the film is anatase phase with tetragonal lattice structure. The film exhibit the highest intensity peak at (101) plane. The surface roughness measurement shows that the film has low surface roughness with small grain size. The electrical studies revealed that the resistivity is about 4.02 x 10-3 Ω.cm and the thickness of TiO2 film is 127.44 nm. The gas sensor measurement showed that the sensor response of the film is about 4.21% at room temperature.

One-step electrospinning synthesis of TiO2/g-C3N4 nanofibers with enhanced photocatalytic properties

NASA Astrophysics Data System (ADS)

Tang, Qian; Meng, Xianfeng; Wang, Zhiying; Zhou, Jianwei; Tang, Hua

2018-02-01

TiO2/g-C3N4 composite nanofibers have been successfully synthesized by one-step electrospinning method, using titanium (IV) n-butoxide (TNBT) and urea as raw materials. The structure and compositions of TiO2/g-C3N4 samples are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Diffuse reflectance spectroscopy (DRS), Scanning electron microscopy (SEM), Transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS) and Brunauer-Emmett-Teller (BET), respectively. The results show that the porous uniform TiO2/g-C3N4 composite nanofibers, with diameter of 100-150 nm, can be successfully prepared through electrospinning method combining 550 °C calcination process. The photocatalytic activity is evaluated by the degradation of rhodamine B (RhB) under simulated solar light. The enhanced catalytic activity is attributed predominantly to the heterojunction between TiO2 and g-C3N4, which promotes the transferring of carriers and prohibits their recombination. With the optimal doping amount of 0.6 g urea (corresponding to 3 g TNBT), the TiO2/g-C3N4 composite nanofibers exhibit the highest rate towards the photocatalytic degradation of RhB. A diagram is presented to explicate the mechanism of the whole catalytic experiment. This study might provide a promising future of applying green catalysts to solving water pollution problems.

Highly Efficient Low-Temperature N-Doped TiO2 Catalysts for Visible Light Photocatalytic Applications

PubMed Central

Mahy, Julien G.; Cerfontaine, Vincent; Devred, François; Gaigneaux, Eric M.; Heinrichs, Benoît; Lambert, Stéphanie D.

2018-01-01

In this paper, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO2 nanoparticles of 6–8 nm are formed, with a specific surface area between 200 and 275 m2·g−1. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles of 6–8 nm with a specific surface area between 185 and 240 m2·g−1 are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO2 materials through Ti–O–N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material. This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity 4 times higher than commercial P25. PMID:29642626

Field induced 4f5d [Re(salen)]2O3[Dy(hfac)3(H2O)]2 single molecule magnet.

PubMed

Pointillart, Fabrice; Bernot, K; Sessoli, R; Gatteschi, D

2010-05-03

The reaction between the mononuclear [ReO(salen)(OMe)] (salen(2-) = N,N'-ethan-1,2-diylbis(salicylidenamine) dianion) and Dy(hfac)(3).2H(2)O (hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate anion) complexes lead to the formation of a compound with the formula {[Re(salen)](2)O(3)[Dy(hfac)(3)(H(2)O)](2)}(CHCl(3))(2)(CH(2)Cl(2))(2) noted (Dy(2)Re(2)). This compound has been characterized by single crystal and powder X-ray diffraction and has been found isostructural to the Y(III) derivative (Y(2)Re(2)) that we previously reported. The cyclic voltammetry demonstrates the redox activity of the system. The characterization of both static and dynamic magnetic properties is reported. Static magnetic data has been analyzed after the cancellation of the crystal field contribution by two different methods. Weak ferromagnetic exchange interactions between the Dy(III) ions are highlighted. The compound Dy(2)Re(2) displays slow relaxation of the magnetization when an external magnetic field is applied. Alternating current susceptibility shows a thermally activated behavior with pre-exponential factors of 7.13 (+/-0.10) x 10(-6) and 5.76 (+/-0.27) x 10(-7) s, and energy barriers of 4.19 (+/-0.02) and 8.52 (+/-0.55) K respectively for low and high temperature regimes.

Preparation, stabilization and characterization of TiO(2) on thin polyethylene films (LDPE). Photocatalytic applications.

PubMed

Zhiyong, Yu; Mielczarski, E; Mielczarski, J; Laub, D; Buffat, Ph; Klehm, U; Albers, P; Lee, K; Kulik, A; Kiwi-Minsker, L; Renken, A; Kiwi, J

2007-02-01

An innovative way to fix preformed nanocrystalline TiO(2) on low-density polyethylene film (LDPE-TiO(2)) is presented. The LDPE-TiO(2) film was able to mediate the complete photodiscoloration of Orange II using about seven times less catalyst than a TiO(2) suspension and proceeded with a photonic efficiency of approximately 0.02. The catalyst shows photostability over long operational periods during the photodiscoloration of the azo dye Orange II. The LDPE-TiO(2) catalyst leads to full dye discoloration under simulated solar light but only to a 30% TOC reduction since long-lived intermediates generated in solution seem to preclude full mineralization of the dye. Physical insight is provided into the mechanism of stabilization of the LDPE-TiO(2) composite during the photocatalytic process by X-ray photoelectron spectroscopy (XPS). The adherence of TiO(2) on LDPE is investigated by electron microscopy (EM) and atomic force microscopy (AFM). The thickness of the TiO(2) film is seen to vary between 1.25 and 1.69 microm for an unused LDPE-TiO(2) film and between 1.31 and 1.50 microm for a sample irradiated 10h during Orange II discoloration pointing out to a higher compactness of the TiO(2) film after the photocatalysis.

Visible light photocatalytic antibacterial activity of Ni-doped and N-doped TiO2 on Staphylococcus aureus and Escherichia coli bacteria.

PubMed

Ananpattarachai, Jirapat; Boonto, Yuphada; Kajitvichyanukul, Puangrat

2016-03-01

The Ni-doped and N-doped TiO2 nanoparticles were investigated for their antibacterial activities on Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. Their morphological features and characteristics such as particle size, surface area, and visible light absorbing capacity were compared and discussed. Scanning electron microscopy, X-ray diffraction, and UV-visible spectrophotometry were used to characterize both materials. The inactivation of E. coli (as an example of Gram-negative bacteria) and S. aureus (as an example of Gram-positive bacteria) with Ni-doped and N-doped TiO2 was investigated in the absence and presence of visible light. Antibacterial activity tests were conducted using undoped, Ni-doped, and N-doped TiO2. The N-doped TiO2 nanoparticles show higher antibacterial activity than Ni-doped TiO2. The band gap narrowing of N-doped TiO2 can induce more visible light absorption and leads to the superb antibacterial properties of this material. The complete inactivation time for E. coli at an initial cell concentration of 2.7 × 10(4) CFU/mL was 420 min which is longer than the 360 min required for S. aureus inactivation. The rate of inactivation of S. aureus using the doped TiO2 nanoparticles in the presence of visible light is greater than that of E. coli. The median lethal dose (LD50) values of S. aureus and E. coli by antibacterial activity under an 18-W visible light intensity were 80 and 350 mg/ml for N-doped TiO2, respectively.

15 CFR 719.19 - Settlement.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Settlement. 719.19 Section 719.19 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.19...

15 CFR 719.7 - Representation.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Representation. 719.7 Section 719.7 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.7...

15 CFR 719.11 - Subpoenas.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Subpoenas. 719.11 Section 719.11 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.11...

15 CFR 719.11 - Subpoenas.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Subpoenas. 719.11 Section 719.11 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.11...

15 CFR 719.19 - Settlement.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Settlement. 719.19 Section 719.19 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.19...

15 CFR 719.14 - Hearings.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Hearings. 719.14 Section 719.14 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.14...

15 CFR 719.7 - Representation.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Representation. 719.7 Section 719.7 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.7...

15 CFR 719.18 - Decisions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Decisions. 719.18 Section 719.18 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.18...

15 CFR 719.18 - Decisions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Decisions. 719.18 Section 719.18 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.18...

15 CFR 719.10 - Discovery.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Discovery. 719.10 Section 719.10 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.10...

Enhanced visible light activity on direct contact Z-scheme g-C3N4-TiO2 photocatalyst

NASA Astrophysics Data System (ADS)

Li, Juan; Zhang, Min; Li, Qiuye; Yang, Jianjun

2017-01-01

Direct contact Z-scheme g-C3N4-TiO2 nanocomposites without an electron mediator are prepared via simple annealing the mixture of bulk g-C3N4 and nanotube titanic acid (NTA) in air at 600 °C for 2 h. In the process of annealing, the bulk g-C3N4 transformed to ultra-thin g-C3N4 nanosheets, and NTA converted to a novel anatase TiO2, then the two components formed a close interaction. The XPS result reveals that some amount of nitrogen is doped into this novel-TiO2, and g-C3N4 nanosheets exist in the composites. The results of XRD, TEM and TG indicate that the thickness of g-C3N4 nanosheets is very thin. The ESR spectrum shows the existence of Ti3+ and single-electron-trapped oxygen vacancy in the 30%g-C3N4-TiO2 composites. In photocatalytic activity test, the 30%g-C3N4-TiO2 nanocomposites showed an excellent photo-oxidation activity of propylene under visible light irradiation (λ≥ 420 nm), and the removal efficiency of propylene reached as high as 56.6%, and the activity kept nearly 82% after four consecutive recycles. Photoluminescence (PL) result using terephthalic acid (TA) as a probe molecule indicated that the g-C3N4-TiO2 nanocomposites displayed a Z-sheme photocatalytic reaction system and this should be the main reason for the high photocatalytic activity. A possible photocatalytic mechanism was proposed on the basis of PL result and transient photocurrent-time curves.

Tunable photovoltaic performance of preferentially oriented rutile TiO2 nanorod photoanode based dye sensitized solar cells with quasi-state electrolyte

NASA Astrophysics Data System (ADS)

Sabari Girisun, T. C.; Jeganathan, C.; Pavithra, N.; Anandan, S.

2018-02-01

Photoanodes made of highly oriented TiO2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 μm, 121 nm, 15.32), 8 h (4 μm, 185 nm, 22.70), 12 h (5.6 μm, 242 nm, 27.24) and 16 h (8 μm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current-voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (Jsc = 5.99 mA cm-2, Voc = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO2 NRs (8 μm, 254 nm).

Rapid fabrication of mesoporous TiO2 thin films by pulsed fibre laser for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hadi, Aseel; Alhabradi, Mansour; Chen, Qian; Liu, Hong; Guo, Wei; Curioni, Michele; Cernik, Robert; Liu, Zhu

2018-01-01

In this paper we demonstrate for the first time that a fibre laser with a wavelength of 1070 nm and a pulse width of milliseconds can be applied to generate mesoporous nanocrystalline (nc) TiO2 thin films on ITO coated glass in ambient atmosphere, by complete vaporisation of organic binder and inter-connection of TiO2 nanoparticles, without thermally damaging the ITO layer and the glass substrate. The fabrication of the mesoporous TiO2 thin films was achieved by stationary laser beam irradiation of 1 min. The dye sensitized solar cell (DSSC) with the laser-sintered TiO2 photoanode reached higher power conversion efficiency (PCE) of 3.20% for the TiO2 film thickness of 6 μm compared with 2.99% for the furnace-sintered. Electrochemical impedance spectroscopy studies revealed that the laser sintering under the optimised condition effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films. The use of the fibre laser with over 40% wall-plug efficiency offers an economically-feasible, industrial viable solution to the major challenge of rapid fabrication of large scale, mass production of mesoporous metal oxide thin film based solar energy systems, potentially for perovskite and monolithic tandem solar cells, in the future.

48 CFR 719.271-2 - The USAID Office of Small and Disadvantaged Business Utilization (SDB).

Code of Federal Regulations, 2014 CFR

2014-10-01

... and Disadvantaged Business Utilization (SDB). 719.271-2 Section 719.271-2 Federal Acquisition... Policies 719.271-2 The USAID Office of Small and Disadvantaged Business Utilization (SDB). (a) SDB is... business enterprises) program. (b) SDB, headed by the Director SDB, who also serves as the Minority...

48 CFR 719.271-2 - The USAID Office of Small and Disadvantaged Business Utilization (SDB).

Code of Federal Regulations, 2010 CFR

2010-10-01

... and Disadvantaged Business Utilization (SDB). 719.271-2 Section 719.271-2 Federal Acquisition... Policies 719.271-2 The USAID Office of Small and Disadvantaged Business Utilization (SDB). (a) SDB is... business enterprises) program. (b) SDB, headed by the Director SDB, who also serves as the Minority...

48 CFR 719.271-2 - The USAID Office of Small and Disadvantaged Business Utilization (SDB).

Code of Federal Regulations, 2013 CFR

2013-10-01

... and Disadvantaged Business Utilization (SDB). 719.271-2 Section 719.271-2 Federal Acquisition... Policies 719.271-2 The USAID Office of Small and Disadvantaged Business Utilization (SDB). (a) SDB is... business enterprises) program. (b) SDB, headed by the Director SDB, who also serves as the Minority...

48 CFR 719.271-2 - The USAID Office of Small and Disadvantaged Business Utilization (SDB).

Code of Federal Regulations, 2011 CFR

2011-10-01

... and Disadvantaged Business Utilization (SDB). 719.271-2 Section 719.271-2 Federal Acquisition... Policies 719.271-2 The USAID Office of Small and Disadvantaged Business Utilization (SDB). (a) SDB is... business enterprises) program. (b) SDB, headed by the Director SDB, who also serves as the Minority...

48 CFR 719.271-2 - The USAID Office of Small and Disadvantaged Business Utilization (SDB).

Code of Federal Regulations, 2012 CFR

2012-10-01

... and Disadvantaged Business Utilization (SDB). 719.271-2 Section 719.271-2 Federal Acquisition... Policies 719.271-2 The USAID Office of Small and Disadvantaged Business Utilization (SDB). (a) SDB is... business enterprises) program. (b) SDB, headed by the Director SDB, who also serves as the Minority...

Selective arc-discharge synthesis of Dy2S-clusterfullerenes and their isomer-dependent single molecule magnetism.

PubMed

Chen, Chia-Hsiang; Krylov, Denis S; Avdoshenko, Stanislav M; Liu, Fupin; Spree, Lukas; Yadav, Ravi; Alvertis, Antonis; Hozoi, Liviu; Nenkov, Konstantin; Kostanyan, Aram; Greber, Thomas; Wolter, Anja U B; Popov, Alexey A

2017-09-01

A method for the selective synthesis of sulfide clusterfullerenes Dy 2 S@C 2 n is developed. Addition of methane to the reactive atmosphere reduces the formation of empty fullerenes in the arc-discharge synthesis, whereas the use of Dy 2 S 3 as a source of metal and sulfur affords sulfide clusterfullerenes as the main fullerene products along with smaller amounts of carbide clusterfullerenes. Two isomers of Dy 2 S@C 82 with C s (6) and C 3v (8) cage symmetry, Dy 2 S@C 72 - C s (10528), and a carbide clusterfullerene Dy 2 C 2 @C 82 - C s (6) were isolated. The molecular structure of both Dy 2 S@C 82 isomers was elucidated by single-crystal X-ray diffraction. SQUID magnetometry demonstrates that all of these clusterfullerenes exhibit hysteresis of magnetization, with Dy 2 S@C 82 - C 3v (8) being the strongest single molecule magnet in the series. DC- and AC-susceptibility measurements were used to determine magnetization relaxation times in the temperature range from 1.6 K to 70 K. Unprecedented magnetization relaxation dynamics with three consequent Orbach processes and energy barriers of 10.5, 48, and 1232 K are determined for Dy 2 S@C 82 - C 3v (8). Dy 2 S@C 82 - C s (6) exhibits faster relaxation of magnetization with two barriers of 15.2 and 523 K. Ab initio calculations were used to interpret experimental data and compare the Dy-sulfide clusterfullerenes to other Dy-clusterfullerenes. The smallest and largest barriers are ascribed to the exchange/dipolar barrier and relaxation via crystal-field states, respectively, whereas an intermediate energy barrier of 48 K in Dy 2 S@C 82 - C 3v (8) is assigned to the local phonon mode, corresponding to the librational motion of the Dy 2 S cluster inside the carbon cage.

Effect of TiO2 on the Gas Sensing Features of TiO2/PANi Nanocomposites

PubMed Central

Huyen, Duong Ngoc; Tung, Nguyen Trong; Thien, Nguyen Duc; Thanh, Le Hai

2011-01-01

A nanocomposite of titanium dioxide (TiO2) and polyaniline (PANi) was synthesized by in-situ chemical polymerization using aniline (ANi) monomer and TiCl4 as precursors. SEM pictures show that the nanocomposite was created in the form of long PANi chains decorated with TiO2 nanoparticles. FTIR, Raman and UV-Vis spectra reveal that the PANi component undergoes an electronic structure modification as a result of the TiO2 and PANi interaction. The electrical resistor of the nanocomposite is highly sensitive to oxygen and NH3 gas, accounting for the physical adsorption of these gases. A nanocomposite with around 55% TiO2 shows an oxygen sensitivity of 600–700%, 20–25 times higher than that of neat PANi. The n-p contacts between TiO2 nanoparticles and PANi matrix give rise to variety of shallow donors and acceptor levels in the PANi band gap which enhance the physical adsorption of gas molecules. PMID:22319389

Amphiphilic block-graft copolymer templates for organized mesoporous TiO2 films in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lim, Jung Yup; Lee, Chang Soo; Lee, Jung Min; Ahn, Joonmo; Cho, Hyung Hee; Kim, Jong Hak

2016-01-01

Amphiphilic block-graft copolymers composed of poly(styrene-b-butadiene-b-styrene) (SBS) backbone and poly(oxyethylene methacrylate) (POEM) side chains are synthesized and combined with hydrophilically preformed TiO2 (Pre-TiO2), which works as a structural binder as well as titania source. This results in the formation of crack free, 6-μm-thick, organized mesoporous TiO2 (OM-TiO2) films via one-step doctor-blading based on self-assembly of SBS-g-POEM as well as preferential interaction of POEM chains with Pre-TiO2. SBS-g-POEM with different numbers of ethylene oxide repeating units, SBS-g-POEM(500) and SBS-g-POEM(950), are used to form OM-TiO2(500) and OM-TiO2(950), respectively. The efficiencies of dye-sensitized solar cells (DSSCs) with a quasi-solid-state polymer electrolyte reach 5.7% and 5.8% at 100 mW/cm2 for OM-TiO2(500) and OM-TiO2(950), respectively. The surface area of OM-TiO2(950) was greater than that of OM-TiO2(500) but the light reflectance was lower in the former, which is responsible for similar efficiency. Both DSSCs exhibit much higher efficiency than one (4.8%) with randomly-organized particulate TiO2 (Ran-TiO2), which is attributed to the higher dye loading, reduced charge recombination and improved pore infiltration of OM-TiO2. When utilizing poly((1-(4-ethenylphenyl)methyl)-3-butyl-imidazolium iodide) (PEBII) and mesoporous TiO2 spheres as the solid electrolyte and the scattering layer, the efficiency increases up to 7.5%, one of the highest values for N719-based solid-state DSSCs.

A simple and low temperature process for super-hydrophilic rutile TiO 2 thin films growth

NASA Astrophysics Data System (ADS)

Mane, R. S.; Joo, Oh-Shim; Min, Sun-Ki; Lokhande, C. D.; Han, Sung-Hwan

2006-11-01

We investigate an environmentally friendly aqueous solution system for rutile TiO2 violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO2 with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO2 films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.

Mesoporous TiO2 Bragg Stack Templated by Graft Copolymer for Dye-sensitized Solar Cells

PubMed Central

Park, Jung Tae; Chi, Won Seok; Kim, Sang Jin; Lee, Daeyeon; Kim, Jong Hak

2014-01-01

Organized mesoporous TiO2 Bragg stacks (om-TiO2 BS) consisting of alternating high and low refractive index organized mesoporous TiO2 (om-TiO2) films were prepared to enhance dye loading, light harvesting, electron transport, and electrolyte pore-infiltration in dye-sensitized solar cells (DSSCs). The om-TiO2 films were synthesized via a sol-gel reaction using amphiphilic graft copolymers consisting of poly(vinyl chloride) backbones and poly(oxyethylene methacrylate) side chains, i.e., PVC-g-POEM as templates. To generate high and low index films, the refractive index of om-TiO2 film was tuned by controlling the grafting ratio of PVC-g-POEM via atomic transfer radical polymerization (ATRP). A polymerized ionic liquid (PIL)-based DSSC fabricated with a 1.2-μm-thick om-TiO2 BS-based photoanode exhibited an efficiency of 4.3%, which is much higher than that of conventional DSSCs with a nanocrystalline TiO2 layer (nc-TiO2 layer) (1.7%). A PIL-based DSSC with a heterostructured photoanode consisting of 400-nm-thick organized mesoporous TiO2 interfacial (om-TiO2 IF) layer, 7-μm-thick nc-TiO2, and 1.2-μm-thick om-TiO2 BS as the bottom, middle and top layers, respectively, exhibited an excellent efficiency of 7.5%, which is much higher than that of nanocrystaline TiO2 photoanode (3.5%). PMID:24980936

Preparation and photocatalytic activity of nitrogen-doped TiO2 hollow nanospheres

NASA Astrophysics Data System (ADS)

Cho, Hyung-Joon; Hwang, Poong-Gok; Jung, Dongwoon

2011-12-01

TiO2 hollow nanospheres were prepared using silicon oxide as a template. N-doped titanium oxide hollow spheres, TiO2-xNx were synthesized by reacting TiO2 hollow spheres with thiourea at 500 °C. XRD and XPS data showed that oxygen was successfully substituted by nitrogen through the nitrogen-doping reaction, and finally N-doped TiO2 hollow spheres were formed. The N-doped TiO2 hollow spheres showed new absorption shoulder in visible light region so that they were expected to exhibit photocatalytic activity in the visible light. The photocatalytic activity of N-doped TiO2 hollow spheres under visible light was similar to that of normal spherical TiO2-xNx in spite of the structural difference.

Porous immobilized C coated N doped TiO2 containing in-situ generated polyenes for enhanced visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Sabri, N. A.; Nawi, M. A.; Nawawi, W. I.

2015-10-01

Carbon coated nitrogen-doped Degussa P25TiO2 (or C,N-P25TiO2) was successfully immobilized on a glass plate using epoxidized natural rubber (ENR-50) and polyvinyl chloride (PVC) as the organic binders. Photo-etching of the fabricated system for 10 h oxidized its PVC binder into polyenes as well as forming a highly porous surface. The band gap energy (Eg) of the photo-etched immobilized photocatalyst system (C,N-P25TiO2/ENR/PVC-10 h) was reduced from 2.91 to 2.86 eV. Its photocatalytic activity was studied via photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under a 45 W visible light fluorescent lamp. C,N-P25TiO2/ENR/PVC-10 h with polyenes performed better than its slurry counterpart under visible light irradiation where the conjugated double bonds acted as photo sensitizers. The immobilized C,N-P25TiO2/ENR/PVC-10 h has excellent reusability and sustainable with an average k value of 0.056 ± 0.011 min-1 and average percent removal of 99.18 ± 0.54%.

Electrospinning processed nanofibrous TiO2 membranes for photovoltaic applications

NASA Astrophysics Data System (ADS)

Onozuka, Katsuhiro; Ding, Bin; Tsuge, Yosuke; Naka, Takayuki; Yamazaki, Michiyo; Sugi, Shinichiro; Ohno, Shingo; Yoshikawa, Masato; Shiratori, Seimei

2006-02-01

We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO2 membranes as electrode materials. A thin TiO2 film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF4 aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO2 film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO2 membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO2 membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N'-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO2 film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO2 membranes. The efficiency of the fibrous TiO2 photoelectrode with the average membrane thickness of 3.9 µm has a maximum value of 4.14%.

Photocatalytic behaviour of WO3/TiO2-N for diclofenac degradation using simulated solar radiation as an activation source.

PubMed

Cordero-García, A; Turnes Palomino, G; Hinojosa-Reyes, L; Guzmán-Mar, J L; Maya-Teviño, L; Hernández-Ramírez, A

2017-02-01

In this study, the photocatalytic removal of an emerging contaminant, diclofenac (DCF) sodium, was performed using the nitrogen-doped WO 3 /TiO 2 -coupled oxide catalyst (WO 3 /TiO 2 -N). The catalyst synthesis was accomplished by a sol-gel method using tetrabutyl orthotitanate (C 16 H 36 O 4 Ti), ammonium p-tungstate [(NH 4 ) 10 H 2 W 12 O 42 ·4H 2 O] and ammonium nitrate (NH 4 NO 3 ) as the nitrogen source. For comparison, TiO 2 and WO 3 /TiO 2 were also prepared under similar conditions. Analysis by X-ray diffraction (XRD), N 2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-Vis spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the synthesized materials. The photocatalytic efficiency of the semiconductors was determined in a batch reactor irradiated with simulated solar light. Residual and mineralized DCF were quantified by high-performance liquid chromatography, total organic carbon analysis and ion exchange chromatography. The results indicated that the tungsten atoms were dispersed on the surface of TiO 2 as WO 3 . The partial substitution of oxygen by nitrogen atoms into the lattice of TiO 2 was an important factor to improve the photocatalytic efficiency of WO 3 /TiO 2 . Therefore, the best photocatalytic activity was obtained with the WO 3 /TiO 2 -N 0.18 catalyst, reaching 100% DCF transformation at 250 kJ m -2 and complete mineralization at 400 kJ m -2 of solar-accumulated energy.

Characterization and Comparison of Photocatalytic Activity Silver Ion doped on TiO2(TiO2/Ag+) and Silver Ion doped on Black TiO2(Black TiO2/Ag+)

NASA Astrophysics Data System (ADS)

Kim, Jin Yi; Sim, Ho Hyung; Song, Sinae; Noh, Yeoung Ah; Lee, Hong Woon; Taik Kim, Hee

2018-03-01

Titanium dioxide (TiO2) is one of the representative ceramic materials containing photocatalyst, optic and antibacterial activity. The hydroxyl radical in TiO2 applies to the intensive oxidizing agent, hence TiO2 is suitable to use photocatalytic materials. Black TiO2was prepared through reduction of amorphous TiO2 conducting under H2 which leads to color changes. Its black color is proven that absorbs 100% light across the whole-visible light, drawing enhancement of photocatalytic property. In this study, we aimed to compare the photocatalytic activity of silver ion doped on TiO2(TiO2/Ag+) and silver ion doped on black TiO2(black TiO2/Ag+) under visible light range. TiO2/Ag+ was fabricated following steps. 1) TiO2 was synthesized by a sol-gel method from Titanium tetraisopropoxide (TTIP). 2) Then AgNO3 was added during an aging process step for silver ion doping on the surface of TiO2. Moreover, Black TiO2/Ag+ was obtained same as TiO2/Ag+ except for calcination under H2. The samples were characterized X-ray diffraction (XRD), UV-visible reflectance (UV-vis DRS), and Methylene Blue degradation test. XRD analysis confirmed morphology of TiO2. The band gap of black TiO2/Ag+ was confirmed (2.6 eV) through UV-vis DRS, which was lower than TiO2/Ag+ (2.9 eV). The photocatalytic effect was conducted by methylene blue degradation test. It demonstrated that black TiO2/Ag+ had a photocatalytic effect under UV light also visible light.

Precise identification and manipulation of adsorption geometry of donor-π-acceptor dye on nanocrystalline TiO₂ films for improved photovoltaics.

PubMed

Zhang, Fan; Ma, Wei; Jiao, Yang; Wang, Jingchuan; Shan, Xinyan; Li, Hui; Lu, Xinghua; Meng, Sheng

2014-12-24

Adsorption geometry of dye molecules on nanocrystalline TiO2 plays a central role in dye-sensitized solar cells, enabling effective sunlight absorption, fast electron injection, optimized interface band offsets, and stable photovoltaic performance. However, precise determination of dye binding geometry and proportion has been challenging due to complexity and sensitivity at interfaces. Here employing combined vibrational spectrometry and density functional calculations, we identify typical adsorption configurations of widely adopted cyanoacrylic donor-π bridge-acceptor dyes on nanocrystalline TiO2. Binding mode switching from bidentate bridging to hydrogen-bonded monodentate configuration with Ti-N bonding has been observed when dye-sensitizing solution becomes more basic. Raman and infrared spectroscopy measurements confirm this configuration switch and determine quantitatively the proportion of competing binding geometries, with vibration peaks assigned using density functional theory calculations. We further found that the proportion of dye-binding configurations can be manipulated by adjusting pH value of dye-sensitizing solutions. Controlling molecular adsorption density and configurations led to enhanced energy conversion efficiency from 2.4% to 6.1% for the fabricated dye-sensitized solar cells, providing a simple method to improve photovoltaic performance by suppressing unfavorable binding configurations in solar cell applications.

Combined Embedding of N/F-Doping and CaCO3 Surface Modification in the TiO2 Photoanode for Dye-Sensitized Solar Cells.

PubMed

Park, Su Kyung; Yun, Tae Kwan; Bae, Jae Young

2016-03-01

N/F-doping and CaCO3 surface modification was carried out in TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect of the N/F doped TiO2 and the CaCO3 coating showed a great increase of the short-circuit current (J(sc)), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 7.00% of a commercial TiO2 photoelectrode to 7.90% of an uncoated N/F-doped electrode, and to 9.09% of a N/F-doped and CaCO3 surface modified electrode. An enhanced photoresponse in N/F-doped TiO2 nanoparticles generate more photo-excited electrons, as supported by measured UV-Vis diffuse reflectance spectra. A successive CaCO3 surface modification then forms a barrier on the surface of the N/F-doped TiO2 particles; the higher basicity of the CaCO3 modified TiO2 facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.

TiO2 Nanostructure Synthesized by Sol-Gel for Dye Sensitized Solar Cells as Renewable Energy Source

NASA Astrophysics Data System (ADS)

Ramelan, A. H.; Wahyuningsih, S.; Saputro, S.; Supriyanto, E.; Hanif, Q. A.

2017-02-01

The use of renewable materials as a constituent of a smart alternative energy such as the use of natural dyes for light harvesting needs to be developed. Synthesis of anatase titanium dioxide (TiO2) and fabrication Dye-Sensitized Solar Cell (DSSC) using dye-based of anthocyanin from purple sweet potato (Ipomoea batatas L.) as a photosensitizer had been done. Synthesis TiO2 through sol-gel process with the addition of triblock copolymer Pluronic F127 template was controlled at pH 3 whereas calcination was carried out at a temperature of 500 °C, 550 °C and 600 °C. The obtained TiO2 were analyzed by XRD, SAA, and SEM. The conclusion is anatase TiO2 obtained until annealing up to 600 °C. Self-assembly Pluronic F127 triblock copolymer capable of restraining the growth of TiO2 crystals. Retention growth of TiO2 mesoporous produces material character that can be used as builders photoanode DSSC with natural sensitizer anthocyanin from purple sweet potatoes. Based on the analysis of X-ray diffraction patterns and surface area analyser, the higher the calcination temperature the greater the size of the anatase crystals is obtained, however, the smaller its surface area. Purple sweet potato anthocyanin’s dyed on to TiO2 was obtained a good enough performance for DSSC’s and gain the optimum performance from DSSC’s system built with mesoporous TiO2 annealed 550 °C using flavylium form anthocyanin.

Black TiO2 nanobelts/g-C3N4 nanosheets Laminated Heterojunctions with Efficient Visible-Light-Driven Photocatalytic Performance

PubMed Central

Shen, Liyan; Xing, Zipeng; Zou, Jinlong; Li, Zhenzi; Wu, Xiaoyan; Zhang, Yuchi; Zhu, Qi; Yang, Shilin; Zhou, Wei

2017-01-01

Black TiO2 nanobelts/g-C3N4 nanosheets laminated heterojunctions (b-TiO2/g-C3N4) as visible-light-driven photocatalysts are fabricated through a simple hydrothermal-calcination process and an in-situ solid-state chemical reduction approach, followed by the mild thermal treatment (350 °C) in argon atmosphere. The prepared samples are evidently investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption, and UV-visible diffuse reflectance spectroscopy, respectively. The results show that special laminated heterojunctions are formed between black TiO2 nanobelts and g-C3N4 nanosheets, which favor the separation of photogenerated electron-hole pairs. Furthermore, the presence of Ti3+ and g-C3N4 greatly enhance the absorption of visible light. The resultant b-TiO2/g-C3N4 materials exhibit higher photocatalytic activity than that of g-C3N4, TiO2, b-TiO2 and TiO2/g-C3N4 for degradation of methyl orange (95%) and hydrogen evolution (555.8 μmol h−1 g−1) under visible light irradiation. The apparent reaction rate constant (k) of b-TiO2/g-C3N4 is ~9 times higher than that of pristine TiO2. Therefore, the high-efficient laminated heterojunction composites will have potential applications in fields of environment and energy. PMID:28165021

Evolutionary search for novel superhard phases, or can TiO2 be the hardest oxide? (Invited)

NASA Astrophysics Data System (ADS)

Oganov, A. R.; Lyakhov, A. O.

2010-12-01

Synthesis of novel superhard materials, frequently achieved with high-pressure experimental techniques, is a difficult task. Study of such materials, usually first obtained in very small quantities, is complicated, and this field is full of controversies and artefacts (see, e.g. [1]). Hardness was long believed to be an exceedingly difficult property to model or predict; however, a number of simple models have recently been proposed and shown to yield surprisingly accurate results (see reviews in [2]). We have found [3] a way to further improve these models, by augmenting them with bond-valence model and graph theory. Combining such models with our structure prediction method [4], we have developed a powerful [5] approach for computational design of novel superhard materials. Using this method, we recently addressed [3] the previously proposed [6] possibility that C3N4 may be harder than diamond, and the claim [7] that TiO2-cotunnite is the hardest oxide with the Vickers hardness of 38 GPa. Our results unequivocally suggest that the latter suggestion is incorrect. No TiO2 polymorph can attain hardness greater than 17 GPa [3], i.e. all possible structures of TiO2 are softer than common corundum (Al2O3). Furthermore, TiO2-cotunnite is dynamically unstable at atmospheric pressure [8]. REFERENCES: [1] Oganov A.R., Solozhenko V.L., Kurakevych O.O., Gatti C., Ma Y., Chen J., Liu Z., and Hemley R.J., http://arxiv.org/abs/ 0908.2126 (2009). [2] Theory of Superhard Materials (Special Issue), J. Superhard Materials, issue 3 (2010). [3] Lyakhov A.O., Oganov A.R., in prep. (2010). [4] Oganov A.R., Glass C.W., J. Chem. Phys. 124, 244704 (2006). [5] Oganov A.R., Lyakhov A.O., J. Superhard Mater. 32, 143-147 (2010). [6] Liu A.Y., Cohen M.L., Science 245, 841-842 (1989). [7] Dubrovinsky L.S., Dubrovinskaia N.A., et al., Nature 410, 653-654 (2001). [8] Kim D.Y., et al., Appl. Phys. Lett. 90, 171903 (2007).

In situ construction of g-C3N4/TiO2 heterojunction films with enhanced photocatalytic activity over magnetic-driven rotating frame

NASA Astrophysics Data System (ADS)

Pan, Chao; Jia, Jia; Hu, Xiaoyun; Fan, Jun; Liu, Enzhou

2018-02-01

Corn-shaped TiO2 nanofilms were fabricated by a glycerol-assisted hydrothermal method, and then g-C3N4 was deposited on the surface of TiO2 films using melamine as precursor under air atmosphere by an in site microwave-heating technique. The investigations indicate that microwave-heating process is a facile strategy to obtain g-C3N4 by thermal polymerization of melamine, which can achieve in situ constructing of g-C3N4/TiO2 heterojunction films with high stability. The as-prepared TiO2 films with crack and holes have visible light scattering capability, and the scattering light overlaps with the intrinsic absorption of g-C3N4, leading to an absorption plateau in the range of 400-550 nm. Besides, a magnetic-driven rotating frame was developed to enhance the mass transfer processes during the photocatalytic water splitting. The result shows that g-C3N4/TiO2 films exhibit excellent activities under simulated-sunlight irradiation, in addition to the enhanced mass transfer, the overlapped visible light absorption, stable contact and effective charge transfer between g-C3N4 and TiO2 can facilitate the hydrogen production and light utilization efficiency as well. The hydrogen production rate can reach 13.8 mmol h-1 m-2 over g-C3N4/TiO2 films prepared using 0.5 g of melamine and 16.0 cm2 of TiO2.

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

NASA Astrophysics Data System (ADS)

Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

2013-12-01

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

PubMed Central

2013-01-01

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail. PMID:24369051

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors.

PubMed

Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

2013-12-26

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

Ultrasound with low intensity assisted the synthesis of nanocrystalline TiO2 without calcination.

PubMed

Ghows, Narjes; Entezari, Mohamad H

2010-06-01

A novel method has been developed for the preparation of nano-sized TiO(2) with anatase phase. Nanoparticles with diameter about 6 nm were prepared at a relatively low temperature (75 degrees C) and short time. The synthesis was carried out by the hydrolysis of titanium tetra-isopropoxide (TTIP) in the presence of water, ethanol, and dispersant under ultrasonic irradiation (500 kHz) at low intensity. The results show that variables such as water/ethanol ratio, irradiation time, and temperature have a great influence on the particle size and crystalline phases of TiO(2) nanoparticles. Characterization of the product was carried out by different techniques such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV-vis spectroscopy. (c) 2010 Elsevier B.V. All rights reserved.

Impedance analysis and dielectric response of anatase TiO2 nanoparticles codoped with Mn and Co ions

NASA Astrophysics Data System (ADS)

Kumar, Anand; Kashyap, Manish K.; Sabharwal, Namita; Kumar, Sarvesh; Kumar, Ashok; Kumar, Parmod; Asokan, K.

2017-11-01

In order to elucidate the effect of transition metal (TM) doping, the impedance and dielectric responses of Co and/or Mn-doped TiO2 nanocrystalline powder samples with 3% doping concentration synthesized via sol gel technique, have been analyzed. X-ray diffraction (XRD) analysis confirms the formation of tetragonal TiO2 anatase phase for all studied samples without any extra impurity phase peaks. The variation in the grain size measured from field emission scanning electron microscope (FESEM) measurements for all the samples are in accordance with the change in crystallite size as obtained from XRD. The DC resistivity for pure TiO2 nanoparticles is the highest while codoped samples exhibit low resistivity. The temperature dependent dielectric constant and dielectric loss possess step like enhancement and show the relaxation behavior. At room temperature, the dielectric function and dielectric loss decrease rapidly with increase in frequency and become almost constant at the higher frequencies. Such a decrease in dielectric loss is suitable for energy storage devices.

Carbamazepine degradation using a N-doped TiO2 coated photocatalytic membrane reactor: Influence of physical parameters.

PubMed

Horovitz, Inna; Avisar, Dror; Baker, Mark A; Grilli, Rossana; Lozzi, Luca; Di Camillo, Daniela; Mamane, Hadas

2016-06-05

Commercial α-Al2O3 photocatalytic membranes with a pore size of 200 and 800-nm were coated with N-doped TiO2 photocatalytic film using a sol-gel technique for concurrent bottom-up filtration and photocatalytic oxidation. X-ray diffraction confirmed that the deposited N-doped TiO2 films are in the form of anatase with 78-84% coverage of the membrane surface. The concentration of N found by X-ray photoelectron spectroscopy was in the range of 0.3-0.9 atomic percentage. Membrane permeability after coating decreased by 50% and 12% for the 200- and 800-nm membrane substrates, respectively. The impact of operational parameters on the photocatalytic activity (PCA) of the N-doped TiO2-coated membranes was examined in a laboratory flow cell based on degradation of the model micropollutant carbamazepine, using a solar simulator as the light source. The significant gap in degradation rate between flow through the membrane and flow on the surface of the membrane was attributed both to the hydraulic effect and in-pore PCA. N-doped TiO2-coated membranes showed enhanced activity for UV wavelengths, in addition to activity under visible light. Experiments of PCA under varying flow rates concluded that the process is in the mass-transfer control regime. Carbamazepine removal rate increased with temperature, despite the decrease in dissolved oxygen concentration. Copyright © 2016 Elsevier B.V. All rights reserved.

g-C3N4 modified TiO2 nanosheets with enhanced photoelectric conversion efficiency in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Xu, Jian; Wang, Guanxi; Fan, Jiajie; Liu, Baoshun; Cao, Shaowen; Yu, Jiaguo

2015-01-01

Dye-sensitized solar cells (DSSCs) were fabricated by using g-C3N4 modified TiO2 nanosheets (CTS) as photoanode materials in this research. A thin layer of g-C3N4 was coated on the surface of TiO2 nanosheets by simply heating the mixture of TiO2 nanosheets and urea, which led to the formation of TiO2@g-C3N4 nanosheet heterostructure. The experimental results showed that the photoelectric conversion efficiency of DSSCs was obviously improved after modified by g-C3N4. The measurements of I-V characteristic indicated that the introduction of g-C3N4 could increase both the open circuit voltage and short-circuit photocurrent density. Along with the analysis of electrochemical impedance spectroscopy, it is considered that the thin layer of g-C3N4 can act as the blocking layer for electron backward recombination with electrolyte, which can be used as the functional material to increase the DSSC performance.

Tunable photovoltaic performance of preferentially oriented rutile TiO2 nanorod photoanode based dye sensitized solar cells with quasi-state electrolyte.

PubMed

Girisun, T C Sabari; Jeganathan, C; Pavithra, N; Anandan, S

2018-01-23

Photoanodes made of highly oriented TiO 2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO 2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 μm, 121 nm, 15.32), 8 h (4 μm, 185 nm, 22.70), 12 h (5.6 μm, 242 nm, 27.24) and 16 h (8 μm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO 2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current-voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (J sc  = 5.99 mA cm -2 , V oc  = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO 2 NRs (8 μm, 254 nm).

Transition metal ions effect on the properties and photocatalytic activity of nanocrystalline TiO2 prepared in an ionic liquid.

PubMed

Ghasemi, S; Rahimnejad, S; Setayesh, S Rahman; Rohani, S; Gholami, M R

2009-12-30

TiO(2) and transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn) doped TiO(2) nanoparticles were synthesized by the sol-gel method using 2-hydroxylethylammonium formate as an ionic liquid. All the prepared samples were calcined at 500 degrees C and characterized by X-ray diffraction (XRD), BET surface area determination, energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS), and Fourier transformed infrared (FT-IR) techniques. The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO(2). Dopant ions in the TiO(2) structure caused significant absorption shift into the visible region. The results of photodegradation of Acid Blue92 (AB92) in aqueous medium under UV light showed that photocatalytic activity of TiO(2) nanoparticles was significantly enhanced by the presence of some transition metal ions. Chemical Oxygen Demand (COD) of dye solutions were done at regular intervals gave a good idea about mineralization of dye.

Boosting Photovoltaic Performance of Dye-Sensitized Solar Cells Using Silver Nanoparticle-Decorated N,S-Co-Doped-TiO2 Photoanode

PubMed Central

Lim, Su Pei; Pandikumar, Alagarsamy; Lim, Hong Ngee; Ramaraj, Ramasamy; Huang, Nay Ming

2015-01-01

A silver nanoparticle-decorated N,S-co-doped TiO2 nanocomposite was successfully prepared and used as an efficient photoanode in high-performance dye-sensitized solar cells (DSSCs) with N719 dye. The DSSCs assembled with the N,S-TiO2@Ag-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 8.22%, which was better than that of a DSSC photoanode composed of unmodified TiO2 (2.57%) under full sunlight illumination (100 mWcm−2, AM 1.5 G). This enhanced efficiency was mainly attributed to the reduced band gap energy, improved interfacial charge transfer, and retarded charge recombination process. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content with N,S-TiO2 was found to be 20 wt%. Because of the enhanced solar energy conversion efficiency of the N,S-TiO2@Ag nanocomposite, it should be considered as a potential photoanode for high-performance DSSCs. PMID:26146362

15 CFR 719.9 - Summary decision.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Summary decision. 719.9 Section 719.9 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.9...

15 CFR 719.9 - Summary decision.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Summary decision. 719.9 Section 719.9 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ENFORCEMENT § 719.9...

10 CFR 71.9 - Employee protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

.... An employee's engagement in protected activities does not automatically render him or her immune from... 10 Energy 2 2010-01-01 2010-01-01 false Employee protection. 71.9 Section 71.9 Energy NUCLEAR... § 71.9 Employee protection. (a) Discrimination by a Commission licensee, certificate holder, an...

10 CFR 71.9 - Employee protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

.... An employee's engagement in protected activities does not automatically render him or her immune from... 10 Energy 2 2011-01-01 2011-01-01 false Employee protection. 71.9 Section 71.9 Energy NUCLEAR... § 71.9 Employee protection. (a) Discrimination by a Commission licensee, certificate holder, an...

Nanostructured N-doped TiO2 marigold flowers for an efficient solar hydrogen production from H2S

NASA Astrophysics Data System (ADS)

Chaudhari, Nilima S.; Warule, Sambhaji S.; Dhanmane, Sushil A.; Kulkarni, Milind V.; Valant, Matjaz; Kale, Bharat B.

2013-09-01

Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ~2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m2 g-1). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and production of hydrogen under solar light. The maximum hydrogen evolution obtained is higher than other known N-TiO2 systems. It is noteworthy that photohydrogen production using the unique marigold flowers of N-TiO2 from abundant H2S under solar light is hitherto unattempted. The proposed synthesis method can also be utilized to design other hierarchical nanostructured N-doped metal oxides.Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ~2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m2 g-1). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and

Microcystin-LR removal from aqueous solutions using a magnetically separable N-doped TiO2 nanocomposite under visible light irradiation

EPA Science Inventory

The performance of magnetically separable N-doped TiO2 was found to be significantly improved when compared with a non-magnetic N-doped TiO2 for the aqueous removal of cyanotoxin Microcystin-LR. The observed enhanced photocatalytic activity may be related to the presence of ferri...

Mesoporous inverse opal TiO2 film as light scattering layer for dye-sensitized solar cell.

PubMed

Jin, Mingshi; Kim, Sung Soo; Yoon, Minyoung; Li, Zhenghua; Lee, Yoon Yun; Kim, Ji Man

2012-01-01

The light harvesting efficiency of dye-sensitized solar cells was enhanced by using a scattering layer. Such as sphere type TiO2, inverse photonic crystal TiO2, hollow spherical TiO2. Among these materials, the TiO2 with inverse photonic crystal (IPC) structure, synthesized by self-assembly using spherical templates, has attracted much attention due to their photonic crystal characteristics and light scattering effects. However, when applied in the DSSCs, the surface area of IPC is very low that caused insufficient adsorption amount of dye molecules. In the present work, a scattering layer with mesoporous inverse photonic crystal (MIPC) TiO2 film was fabricated by the sol-gel reactions with surfactant-assisted sol-gel method using poly(methyl methacrylate) as the template and titanium (IV) isopropoxide as the TiO2 precursor. After removing the PMMA and surfactant, a highly ordered macroporous structure with mesopores were successfully obtained. The surface area and total pore volume of the MIPC were 82 m2/g and 0.31 cm3/g, respectively, which is much larger than those of the IPC. The DSSCs with the scattering layer of MIPC film exhibited 18 and 10% higher photo-conversion efficiency than those of cells only with a nano-crystalline TiO2 film and with scattering layer of IPC film. From UV-visible spectra of dye solutions, the MIPC film showed a higher amount of absorbed dye molecules than those of the reference and IPC films. Accordingly, an increase in the photo-current density through abundant adsorption of the dye, coupled with inherent light scattering ability can improve overall photo-conversion efficiency.

Preparation of anatase TiO2 nanoparticles using low hydrothermal temperature for dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Sofyan, N.; Ridhova, A.; Yuwono, A. H.; Udhiarto, A.

2018-03-01

One device being developed as an alternative source of renewable energy by utilizing solar energy source is dye-sensitized solar cells (DSSC). This device works using simple photosynthetic-electrochemical principle in the molecular level. In this device, the inorganic oxide semiconductor of titanium dioxide (TiO2) has a great potential for the absorption of the photon energy from the solar energy source, especially in the form of TiO2 nanoparticle structure. This nanoparticle structure is expected to improve the performance of DSSC because the surface area to weight ratio of this nanostructures is very large. In this study, the synthesis of TiO2 nanoparticle from its precursors has been performed along with the fabrication of the DSSC device. Effort to improve the size of nanocrystalline anatase TiO2 was accomplished by low hydrothermal treatment at various temperatures whereas the crystallinity of the anatase phase in the structure was performed by calcination process. Characterization of the materials was performed using X-ray Diffraction (XRD) and scanning electron microscope (SEM), while the DSSC performance was examined through a high precision current versus voltage (I-V) curve analyzer. The results showed that pure anatase TiO2 nanoparticles could be obtained at low hydrothermal of 100, 125, and 150 °C followed by calcination at 450 °C. The best performance of photocurrent-voltage characteristic was given by TiO2 hydrothermally synthesized at 150 °C with power conversion efficiency (PCE) of 4.40 %, whereas the standard TiO2 nanoparticles has PCE only 4.02 %. This result is very promising in terms low temperature and thus low cost of anatase TiO2 semiconductor preparation for DSSC application.

Impact of bimetal electrodes on dielectric properties of TiO2 and Al-doped TiO2 films.

PubMed

Kim, Seong Keun; Han, Sora; Jeon, Woojin; Yoon, Jung Ho; Han, Jeong Hwan; Lee, Woongkyu; Hwang, Cheol Seong

2012-09-26

Rutile structured Al-doped TiO(2) (ATO) and TiO(2) films were grown on bimetal electrodes (thin Ru/thick TiN, Pt, and Ir) for high-performance capacitors. The work function of the top Ru layer decreased on TiN and increased on Pt and Ir when it was thinner than ~2 nm, suggesting that the lower metal within the electrodes influences the work function of the very thin Ru layer. The use of the lower electrode with a high work function for bottom electrode eventually improves the leakage current properties of the capacitor at a very thin Ru top layer (≤2 nm) because of the increased Schottky barrier height at the interface between the dielectric and the bottom electrode. The thin Ru layer was necessary to achieve the rutile structured ATO and TiO(2) dielectric films.

Photo degradation of methyl orange by attapulgite-SnO2-TiO2 nanocomposites.

PubMed

Zhang, Lili; Lv, Fujian; Zhang, Weiguang; Li, Rongqing; Zhong, Hui; Zhao, Yijiang; Zhang, Yu; Wang, Xin

2009-11-15

Photocatalytic removal of methyl orange under ultraviolet radiation has been studied using attapulgite (ATT) composites, which were synthesized by depositing SnO(2)-TiO(2) hybrid oxides on the surface of ATT to form a composite photocatalyst (denoted ATT-SnO(2)-TiO(2)) using an in situ sol-gel technique. Results showed that SnO(2)-TiO(2) nanocomposite particles with average size of about 10nm were loaded successfully on to the surface of ATT fibers and were widely dispersed. Correspondingly, the photocatalytic activity of ATT was improved significantly by loading SnO(2)-TiO(2). The photoactivity of the composite photocatalyst decreased in the sequence ATT-SnO(2)-TiO(2)>ATT-SnO(2)>ATT-TiO(2)>ATT. In order to achieve the best photocatalyst, the molar ratio of SnO(2) and TiO(2) in the ATT-SnO(2)-TiO(2) composites was adjusted to give a series with proportions r=n(Ti)/(n(Ti)+n(Sn))=0.0, 0.25, 0.33, 0.50, 0.67, 0.75, 0.80, 0.82, 0.86, 1.0. Results indicated that the proportion of SnO(2) and TiO(2) had a critical effect on the photocatalytic activity, which increased as the content of TiO(2) increased to r0.82. The highest degradation rate of methyl orange was 99% within 30 min obtained by using ATT-SnO(2)-TiO(2) with r=0.82. The repeated use of the composite photocatalyst was also confirmed.

THERMALLY STABLE NANOCRYSTALLINE TIO2 PHOTOCATALYSTS SYNTHESIZED VIA SOL-GEL METHODS MODIFIED WITH IONIC LIQUID AND SURFACTANT MOLECULES

EPA Science Inventory

Recently, sol-gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO₂ particles via an alkoxide sol-gel method employing a water-immi...

Differentially expressed genes in the silk gland of silkworm (Bombyx mori) treated with TiO2 NPs.

PubMed

Xue, Bin; Li, Fanchi; Hu, Jingsheng; Tian, Jianghai; Li, Jinxin; Cheng, Xiaoyu; Hu, Jiahuan; Li, Bing

2017-05-05

Silk gland is a silkworm organ where silk proteins are synthesized and secreted. Dietary supplement of TiO 2 nanoparticles (NPs) promotes silk protein synthesis in silkworms. In this study, digital gene expression (DGE) tag was used to analyze the gene expression profile of the posterior silk gland of silkworms that were fed with TiO 2 NPs. In total, 5,702,823 and 6,150,719 clean tags, 55,096 and 74,715 distinct tags were detected in TiO 2 NPs treated and control groups, respectively. Compared with the control, TiO 2 NPs treated silkworms showed 306 differentially expressed genes, including 137 upregulated genes and 169 downregulated genes. Of these differentially expressed genes, 106 genes were related to silk protein synthesis, among which 97 genes were upregulated and 9 genes were downregulated. Pathway mapping using the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that 20 pathways were significantly enriched in TiO 2 NPs treated silkworms, and the metabolic pathway-related genes were the most significantly enriched. The DGE results were verified by qRT-PCR analysis of eight differentially expressed genes. The DGE and qRT-PCR results were consistent for all three upregulated genes and three of the five downregulated genes, but the expression trends of the remaining two genes were different between qRT-PCR and DGE analysis. This study enhances our understanding of the mechanism of TiO 2 NPs promoted silk protein synthesis. Copyright © 2017 Elsevier B.V. All rights reserved.

Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

PubMed

Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

2008-08-01

Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

Unique bar-like sulfur-doped C3N4/TiO2 nanocomposite: Excellent visible light driven photocatalytic activity and mechanism study

NASA Astrophysics Data System (ADS)

Zhao, Yu; Xu, Shiping; Sun, Xiang; Xu, Xing; Gao, Baoyu

2018-04-01

In this work, a nanocomposite of TiO2 nanoparticles coupled with sulfur-doped C3N4 (S-C3N4) laminated layer was successfully fabricated using a facile impregnation method and the nanocomposite exhibited superior photocatalytic activity in pollutant removal under visible light irradiation, compared to bare TiO2, g-C3N4 and binary C3N4-TiO2 nanocomposite. The enhanced photocatalytic activity was benefited from the efficient migration and transformation of electron-hole (e--h+) pairs, improved visible light absorption capability, and relatively large specific surface area induce by sulfur doping. Interestingly, the introduction of sulfur changes regulated the morphology of g-C3N4 leading to the formation of ultrathin g-C3N4 layer nanosheet assemblies and unique bar-like g-C3N4/TiO2 nanocomposite, which is beneficial for the outstanding performance of the product. In addition, trapping experiment was carried out to identify the main active species in the photocatalytic reaction over the S-C3N4/TiO2 photocatalyst, and functional mechanism of the composite was proposed. This work may provide new ideas for the fabrication and utilization of highly efficient photocatalyst with excellent visible light response in environmental purification applications.

Photocatalytic activity of Ti3+ self-doped dark TiO2 ultrafine nanorods, grey SiO2 nanotwin crystalline, and their composite under visible light

NASA Astrophysics Data System (ADS)

Zhang, Renhui; Yang, Yingchang; Leng, Senlin; Wang, Qing

2018-04-01

Efficient electron-holes separation is of crucial importance for the improvement of photocatalytic activity for photocatalytic reaction. In this work, dark TiO2 (D-TiO2) nanorods, grey SiO2 (G-SiO2) and D-TiO2/G-SiO2 composite with surface defects are synthesized. We report that the efficiency of photo-generated electrons and holes separation is well enhanced by introducing G-SiO2 into D-TiO2 lattice. Using first-principles method, we find that surface defects (O or Si vacancy) can be conducive to improving the optical absorption under visible-light region. Combination of the experimental results, for D-TiO2/G-SiO2 composite, the surface defects of TiO2 nanocrystallines can significantly improve the photocatalytic efficiency.

Effect of TiO2, ZrO2, and TiO2-ZrO2 on the performance of CuO-ZnO catalyst for CO2 hydrogenation to methanol

NASA Astrophysics Data System (ADS)

Xiao, Jie; Mao, Dongsen; Guo, Xiaoming; Yu, Jun

2015-05-01

The influence of TiO2, ZrO2, and TiO2-ZrO2 mixed oxide on the catalytic performance of CuO-ZnO catalyst in the methanol synthesis from CO2 hydrogenation was studied. The catalysts were prepared by oxalate co-precipitation method and characterized by TGA, N2 adsorption, XRD, reactive N2O adsorption, XPS, H2-TPR, H2-TPD, and CO2-TPD techniques. Characterization results reveal that all the additives improve the CuO dispersion in the catalyst body and increase the Cu surface area and adsorption capacities of CO2 and H2. The results of catalytic test reveal that the additives increase both the CO2 conversion and methanol selectivity, and TiO2-ZrO2 mixed oxide is more effective than single components of TiO2 or ZrO2. Moreover, the activity of methanol synthesis is correlated directly with CO2 adsorption capacity over the catalysts.

2.4 μm diode-pumped Dy2+:CaF2 laser

NASA Astrophysics Data System (ADS)

Švejkar, Richard; Papashvili, Alexander G.; Šulc, Jan; Němec, Michal; Jelínková, Helena; Doroshenko, Maxim E.; Batygov, Sergei H.; Osiko, Vyacheslav V.

2018-01-01

In this work, a cryogenic cooled, longitudinal diode-pumped Dy2+ :CaF2 laser was investigated for the first time. The temperature dependence of the spectroscopy and the laser properties of Dy2+ :CaF2 are presented. The tested Dy2+ :CaF2 crystal was a longitudinal pump in a near-IR region (926 nm) by laser diode radiation. The maximal mean output power and slope efficiency at 78 K during the pulse regime of the laser were 57.5 mW and 7%, respectively. Furthermore, the CW regime was successfully tested and a maximum output power of 0.37 W was obtained for the absorbed pumping power 5.7 W. The emission laser wavelength was 2367 nm.

Acid-assisted hydrothermal synthesis of nanocrystalline TiO2 from titanate nanotubes: influence of acids on the photodegradation of gaseous toluene.

PubMed

Chen, Kunyang; Zhu, Lizhong; Yang, Kun

2015-01-01

In order to efficiently remove volatile organic compounds (VOCs) from indoor air, one-dimensional titanate nanotubes (TiNTs) were hydrothermally treated to prepare TiO2 nanocrystals with different crystalline phases, shapes and sizes. The influences of various acids such as CH3COOH, HNO3, HCl, HF and H2SO4 used in the treatment were separately compared to optimize the performance of the TiO2 nanocrystals. Compared with the strong and corrosive inorganic acids, CH3COOH was not only safer and more environmentally friendly, but also more efficient in promoting the photocatalytic activity of the obtained TiO2. It was observed that the anatase TiO2 synthesized in 15 mol/L CH3COOH solution exhibited the highest photodegradation rate of gaseous toluene (94%), exceeding that of P25 (44%) by a factor of more than two. The improved photocatalytic activity was attributed to the small crystallite size and surface modification by CH3COOH. The influence of relative humidity (20%-80%) on the performance of TiO2 nanocrystals was also studied. The anatase TiO2 synthesized in 15 mol/L CH3COOH solution was more tolerant to moisture than the other TiO2 nanocrystals and P25. Copyright © 2014. Published by Elsevier B.V.

Characterization of N3 dye adsorption on TiO2 using quartz-crystal microbalance with dissipation monitoring

NASA Astrophysics Data System (ADS)

Wayment-Steele, Hannah K.; Johnson, Lewis E.; Dixon, Matthew C.; Johal, Malkiat S.

2013-09-01

Understanding the kinetics of dye adsorption on semiconductors is crucial for designing dye-sensitized solar cells (DSSCs) with enhanced efficiency. Harms et al. recently applied the Quartz-Crystal Microbalance with Dissipation Monitoring (QCM-D) to study in situ dye adsorption on flat TiO2 surfaces. QCM-D measures adsorption in real time and therefore allows one to determine the kinetics of the process. In this work, we characterize the adsorption of N3, a commercial RuBipy dye, using the native oxide layer of a titanium sensor to simulate the TiO2 substrate of a DSSC. We report equilibrium constants that are in agreement with previous absorbance studies of N3 adsorption, and therefore demonstrate the native oxide layer of a titanium sensor as a valid and readily available planar TiO2 morphology to study dye adsorption.

A facile photoassisted route to synthesis N, F-codoped oxygen-deficient TiO2 with enhanced photocatalytic performance under visible light irradiation

NASA Astrophysics Data System (ADS)

Kang, Xiaolan; Han, Ying; Song, Xuezhi; Tan, Zhenquan

2018-03-01

Herein, we report a facile and economical photoassisted strategy for synthesizing the highly active N, F-codoped oxygen-deficient TiO2 with coexposed {001} and {101} facets. NH4TiOF3 mesocrystals were used to act as the resource of dopants and the intermediate to fabricate TiO2 with highly active {001} facets. Comprehensive analysis based on X-ray photoelectron spectroscopy, transmission electron microscopy and electron spin resonances manifested that F, N and oxygen vacancies were simultaneously introduced to TiO2 through the photoassisted process. The test of phenol and Rhodamine B (RhB) degradation under visible light demonstrates that the as-prepared N, F codoped oxygen-deficient TiO2 exhibits higher photocatalytic activity than its references. The increased photocatalytic performances results from the synergetic effect of the induced Vo's and N, F codoping in TiO2 with co-exposed {001} and {101} facets, favoring the visible light utilization as well as the separation of photogenerated carriers. This strategy is expected to provide a new insight into the design of high performance photocatalysts.

Role of Adsorbed Water on Charge Carrier Dynamics in Photoexcited TiO2

PubMed Central

2017-01-01

Overall photocatalytic water splitting is one of the most sought after processes for sustainable solar-to-chemical energy conversion. The efficiency of this process strongly depends on charge carrier recombination and interaction with surface adsorbates at different time scales. Here, we investigated how hydration of TiO2 P25 affects dynamics of photogenerated electrons at the millisecond to minute time scale characteristic for chemical reactions. We used rapid scan diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS). The decay of photogenerated electron absorption was substantially slower in the presence of associated water. For hydrated samples, the charge carrier recombination rates followed an Arrhenius-type behavior in the temperature range of 273–423 K; these became temperature-independent when the material was dehydrated at temperatures above 423 K or cooled below 273 K. A DFT+U analysis revealed that hydrogen bonding with adsorbed water stabilizes surface-trapped holes at anatase TiO2(101) facet and lowers the barriers for hole migration. Hence, hole mobility should be higher in the hydrated material than in the dehydrated system. This demonstrates that adsorbed associated water can efficiently stabilize photogenerated charge carriers in nanocrystalline TiO2 and suppress their recombination at the time scale up to minutes. PMID:28413570

Structural, Morphological, Optical and Photocatalytic Properties of Y, N-Doped and Codoped TiO2 Thin Films

PubMed Central

Hamden, Zeineb; Conceição, David; Boufi, Sami; Vieira Ferreira, Luís Filipe; Bouattour, Soraa

2017-01-01

Pure TiO2, Y-N single-doped and codoped TiO2 powders and thin films deposited on glass beads were successfully prepared using dip-coating and sol-gel methods. The samples were analyzed using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, ground state diffuse reflectance absorption and scanning electron microscopy (SEM). According to the GXRD patterns and micro-Raman spectra, only the anatase form of TiO2 was made evident. Ground state diffuse reflectance absorption studies showed that doping with N or codoping with N and Y led to an increase of the band gap. Laser induced luminescence analysis revealed a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic activity of supported catalysts, toward the degradation of toluidine, revealed a meaningful enhancement upon codoping samples at a level of 2% (atomic ratio). The photocatalytic activity of the material and its reactivity can be attributed to a reduced, but significant, direct photoexcitation of the semiconductor by the halogen lamp, together with a charge-transfer-complex mechanism, or with the formation of surface oxygen vacancies by the N dopant atoms. PMID:28772962

n/p-Type changeable semiconductor TiO2 prepared from NTA

NASA Astrophysics Data System (ADS)

Li, Qiuye; Wang, Xiaodong; Jin, Zhensheng; Yang, Dagang; Zhang, Shunli; Guo, Xinyong; Yang, Jianjun; Zhang, Zhijun

2007-10-01

A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400-700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400-700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation (λ≥420 nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light (λ=365 nm, E photon=3.40 eV).

Low-Temperature Desorption of N2O from NO on Rutile TiO2(110)-1x1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Boseong; Li, Zhenjun; Kay, Bruce D.

2014-05-08

We find that NO dosed on rutile TiO2(110)-1×1 at substrate temperatures as low as 50 K readily reacts to produce N2O which desorbs promptly from the surface leaving an oxygen adatom behind. The desorption rate of N2O reaches a maximum value after 1 – 2 sec at an NO flux of 1.2 ×1014 NO/cm2∙sec and then decreases rapidly as the initially clean, reduced TiO2(110) surface with ~5% oxygen vacancies (VO’s) becomes covered with oxygen adatoms and unreacted NO. The maximum desorption rate is also found to increase as the substrate temperature is raised up to about 100 K. Interestingly, themore » N2O desorption during the low-temperature (LT) NO dose is strongly suppressed when molecular oxygen is predosed, whereas it persists on the surface with VO’s passivated by surface hydroxyls. Our results show that the surface charge, not the VO sites, plays a dominant role in the LT N2O desorption induced by a facile NO reduction at such low temperatures.« less

LED and low level laser therapy association in tooth bleaching using a novel low concentration H2O2/N-doped TiO2 bleaching agent

NASA Astrophysics Data System (ADS)

Bezerra Dias, Hércules; Teixeira Carrera, Emanuelle; Freitas Bortolatto, Janaína; Ferrarezi de Andrade, Marcelo; Nara de Souza Rastelli, Alessandra

2016-01-01

Since low concentration bleaching agents containing N-doped TiO2 nanoparticles have been introduced as an alternative to conventional agents, it is important to verify their efficacy and the hypersensitivity effect in clinical practice. Six volunteer patients were evaluated for color change and hypersensitivity after bleaching using 35% H2O2 (one session of two 12 min applications) and 6% H2O2/N-doped TiO2 (one session of three 12 min applications) and after low level laser therapy application (LLLT) (780 nm, 40 mW, 10 J.cm-2, 10 s). Based on this case study, the nanobleaching agent provided better or similar aesthetic results than the conventional agent under high concentration, and its association with LLLT satisfactorily decreased the hypersensitivity. The 6% H2O2/N-doped TiO2 agent could be used instead of conventional in-office bleaching agents under high concentrations to fulfill the rising patient demand for aesthetics.

Influence of different TiO2 blocking films on the photovoltaic performance of perovskite solar cells

NASA Astrophysics Data System (ADS)

Zhang, Chenxi; Luo, Yudan; Chen, Xiaohong; Ou-Yang, Wei; Chen, Yiwei; Sun, Zhuo; Huang, Sumei

2016-12-01

Organolead trihalide perovskite materials have been successfully used as light absorbers in efficient photovoltaic (PV) cells. Cell structures based on mesoscopic metal oxides and planar heterojunctions have already demonstrated very impressive and brisk advances, holding great potential to grow into a mature PV technology. High power conversion efficiency (PCE) values have been obtained from the mesoscopic configuration in which a few hundred nano-meter thick mesoporous scaffold (e.g. TiO2 or Al2O3) infiltrated by perovskite absorber was sandwiched between the electron and hole transport layers. A uniform and compact hole-blocking layer is necessary for high efficient perovskite-based thin film solar cells. In this study, we investigated the characteristics of TiO2 compact layer using various methods and its effects on the PV performance of perovskite solar cells. TiO2 compact layer was prepared by a sol-gel method based on titanium isopropoxide and HCl, spin-coating of titanium diisopropoxide bis (acetylacetonate), screen-printing of Dyesol's bocking layer titania paste, and a chemical bath deposition (CBD) technique via hydrolysis of TiCl4, respectively. The morphological and micro-structural properties of the formed compact TiO2 layers were characterized by scanning electronic microscopy and X-ray diffraction. The analyses of devices performance characteristics showed that surface morphologies of TiO2 compact films played a critical role in affecting the efficiencies. The nanocrystalline TiO2 film deposited via the CBD route acts as the most efficient hole-blocking layer and achieves the best performance in perovskite solar cells. The CBD-based TiO2 compact and dense layer offers a small series resistance and a large recombination resistance inside the device, and makes it possible to achieve a high power conversion efficiency of 12.80%.

10 CFR 719.2 - What are the definitions of terms used in this part?

Code of Federal Regulations, 2011 CFR

2011-01-01

... Energy, including the National Nuclear Security Administration. Department counsel means the individual... 10 Energy 4 2011-01-01 2011-01-01 false What are the definitions of terms used in this part? 719.2 Section 719.2 Energy DEPARTMENT OF ENERGY CONTRACTOR LEGAL MANAGEMENT REQUIREMENTS General Provisions...

10 CFR 719.2 - What are the definitions of terms used in this part?

Code of Federal Regulations, 2012 CFR

2012-01-01

... Energy, including the National Nuclear Security Administration. Department counsel means the individual... 10 Energy 4 2012-01-01 2012-01-01 false What are the definitions of terms used in this part? 719.2 Section 719.2 Energy DEPARTMENT OF ENERGY CONTRACTOR LEGAL MANAGEMENT REQUIREMENTS General Provisions...

10 CFR 719.2 - What are the definitions of terms used in this part?

Code of Federal Regulations, 2010 CFR

2010-01-01

... Energy, including the National Nuclear Security Administration. Department counsel means the individual... 10 Energy 4 2010-01-01 2010-01-01 false What are the definitions of terms used in this part? 719.2 Section 719.2 Energy DEPARTMENT OF ENERGY CONTRACTOR LEGAL MANAGEMENT REQUIREMENTS General Provisions...

10 CFR 719.2 - What are the definitions of terms used in this part?

Code of Federal Regulations, 2013 CFR

2013-01-01

... Energy, including the National Nuclear Security Administration. Department counsel means the individual... 10 Energy 4 2013-01-01 2013-01-01 false What are the definitions of terms used in this part? 719.2 Section 719.2 Energy DEPARTMENT OF ENERGY CONTRACTOR LEGAL MANAGEMENT REQUIREMENTS General Provisions...

Characterization of N,C-codoped TiO 2 films prepared by reactive DC magnetron sputtering

NASA Astrophysics Data System (ADS)

Wu, Kee-Rong; Hung, Chung-Hsuang

2009-12-01

Titanium dioxide (TiO 2) films are deposited by codoping nitrogen and carbon on indium tin oxide-coated substrates as visible light (Vis)-enabled catalysts. The X-ray diffraction peak intensity of the preferential orientation in (2 1 1) plane declines when the topmost 1.0 μm layer of the film is ground off. The decrease in the crystallite size and the crystallinity of anatase TiO 2 film is also evidenced by a shift towards the high wave number and broadening of the Raman spectra. Low doping concentrations of N (1.3%) and C (1.8%) are estimated by X-ray photoelectron spectroscopy (XPS) which displays an N 1 s peak at 396.8 eV and a C 1 s peak at 282.1 eV, respectively. This is attributed to the substitution of the oxygen sites with nitrogen and carbon, which is believed to be responsible for the Vis photocatalytic activity into a wavelength of >500 nm. The cross-sectional transmission electron microscopy images show larger pores at the grain boundaries and in larger columnar crystals than in the undoped TiO 2 film. All of these results indicate that porosity, crystallinity and shift in the preferential orientation are more pronounced close to the surface than close to the bottom of the sample. Wettability upon measurement of the water contact angle, methylene blue degradation and radical formation tests under both ultraviolet and Vis irradiation demonstrate that the topmost surface renders not only a larger reactive surface area but also a better carrier transport route than the rest of the film, improving its photocatalytic activity. These results show that surface porosity of the film is dominant than the tailoring of the photocatalytic activities of N,C-codoped TiO 2 catalysts.

10 CFR 719.2 - What are the definitions of terms used in this part?

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 4 2014-01-01 2014-01-01 false What are the definitions of terms used in this part? 719.2 Section 719.2 Energy DEPARTMENT OF ENERGY CONTRACTOR LEGAL MANAGEMENT REQUIREMENTS General Provisions.... Days means calendar days. Department means the Department of Energy (DOE), including the National...

N-Doped TiO2-Coated Ceramic Membrane for Carbamazepine Degradation in Different Water Qualities

PubMed Central

Luster, Enbal; Avisar, Dror; Horovitz, Inna; Lozzi, Luca; Baker, Mark A.; Grilli, Rossana; Mamane, Hadas

2017-01-01

The photocatalytic degradation of the model pollutant carbamazepine (CBZ) was investigated under simulated solar irradiation with an N-doped TiO2-coated Al2O3 photocatalytic membrane, using different water types. The photocatalytic membrane combines photocatalysis and membrane filtration in a single step. The impact of each individual constituent such as acidity, alkalinity, dissolved organic matter (DOM), divalent cations (Mg2+ and Ca2+), and Cl− on the degradation of CBZ was examined. CBZ in water was efficiently degraded by an N-doped TiO2-coated Al2O3 membrane. However, elements added to the water, which simulate the constituents of natural water, had an impact on the CBZ degradation. Water alkalinity inhibited CBZ degradation mostly due to increase in pH while radical scavenging by carbonate was more dominant at higher values (>200 mg/L as CaCO3). A negative effect of Ca2+ addition on photocatalytic degradation was found only in combination with phosphate buffer, probably caused by deposition of CaHPO4 or CaHPO4·2H2O on the catalyst surface. The presence of Cl− and Mg2+ ions had no effect on CBZ degradation. DOM significantly inhibited CBZ degradation for all tested background organic compounds. The photocatalytic activity of N-doped TiO2-coated Al2O3 membranes gradually decreased after continuous use; however, it was successfully regenerated by 0.1% HCl chemical cleaning. Nevertheless, dissolution of metals like Al and Ti should be monitored following acid cleaning. PMID:28758982

Single-molecule magnetism in a family of {Co(III)2Dy(III)2} butterfly complexes: effects of ligand replacement on the dynamics of magnetic relaxation.

PubMed

Langley, Stuart K; Ungur, Liviu; Chilton, Nicholas F; Moubaraki, Boujemaa; Chibotaru, Liviu F; Murray, Keith S

2014-05-05

The synthesis and structural characterization of four related heterometallic complexes of formulas [Dy(III)2Co(III)2(OMe)2(teaH)2(O2CPh)4(MeOH)4](NO3)2·MeOH·H2O (1a) and [Dy(III)2Co(III)2(OMe)2(teaH)2(O2CPh)4(MeOH)2(NO3)2]·MeOH·H2O (1b), [Dy(III)2Co(III)2(OMe)2(dea)2(O2CPh)4(MeOH)4](NO3)2 (2), [Dy(III)2Co(III)2(OMe)2(mdea)2(O2CPh)4(NO3)2] (3), and [Dy(III)2Co(III)2(OMe)2(bdea)2(O2CPh)4(MeOH)4](NO3)2·0.5MeOH·H2O (4a) and [Dy(III)2Co(III)2(OMe)2(bdea)2(O2CPh)4(MeOH)2(NO3)2]·MeOH·1.5H2O (4b) are reported (teaH3 = triethanolamine, deaH2 = diethanolamine, mdeaH2 = N-methyldiethanolamine, and bdeaH2 = N-n-butyldiethanolamine). Compounds 1 (≡ 1a and 1b) and 4 (≡ 4a and 4b) both display two unique molecules within the same crystal and all compounds display a butterfly type core, with the Dy(III) ions occupying the central body positions and the diamagnetic Co(III) ions the outer wing-tip sites. Compounds 1-4 were investigated via direct current and alternating current magnetic susceptibility measurements, and it was found that each complex displayed single-molecule magnet (SMM) behavior. All four compounds display unique coordination and geometric environments around the Dy(III) ions and it was found that each displays a different anisotropy barrier. Ab initio calculations were performed on 1-4 and these determined the low lying electronic structure of each Dy(III) ion and the magnetic interactions for each cluster. It was found that there was a strong correlation between the calculated energy gap between the ground and first excited states of the single-ion ligand-field split Dy(III) levels and the experimentally observed anisotropy barrier. Furthermore, the transverse g factors found for the Dy(III) ions, defining the tunnelling rates within the ground Kramers doublets, are largest for 1, which agrees with the experimental observation of the shortest relaxation time in the high-temperature domain for this complex. The magnetic exchange between the Dy

Photoinduced underwater superoleophobicity of TiO2 thin films.

PubMed

Sawai, Yusuke; Nishimoto, Shunsuke; Kameshima, Yoshikazu; Fujii, Eiji; Miyake, Michihiro

2013-06-11

The photoinduced wettabilities of water, n-hexadecane, dodecane, and n-heptane on a flat TiO2 surface prepared by a sol-gel method-based coating were investigated. An amphiphilic surface produced by UV irradiation exhibited underwater superoleophobicity with an extremely high static oil contact angle (CA) of over 160°. The TiO2 surface almost completely repelled the oil droplet in water. A robust TiO2 surface with no fragile nanomicrostructure was fabricated on a Ti mesh with a pore size of approximately 150 μm. The fabricated mesh was found to be applicable as an oil/water separation filter.

Synergetic effect of Ti 3+ and oxygen doping on enhancing photoelectrochemical and photocatalytic properties of TiO 2/g-C 3N 4 heterojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kai; Huang, Zhenyu; Zeng, Xiaoqiao

To improve the utilization of visible light and reduce photogenerated electron/hole recombination, Ti 3+ self-doped TiO 2/oxygen-doped graphitic carbon nitride (Ti 3+-TiO 2/O-g-C 3N 4) heterojunctions were prepared via hydrothermal treatment of a mixture of g-C 3N 4 and titanium oxohydride sol obtained from the reaction of TiH 2 with H 2O 2. In this way, exfoliated O-g-C 3N 4 and Ti 3+-TiO 2 nanoparticles were obtained. Simultaneously, strong bonding was formed between Ti 3+-TiO 2 nanoparticles and exfoliated O-g-C 3N 4 during the hydrothermal process. Charge transfer and recombination processes were characterized by transient photocurrent responses, electrochemical impedance test,more » and photoluminescence spectroscopy. The photocatalytic performances were investigated through rhodamine B degradation test under an irradiation source based on 30 W cold visible-light-emitting diode. The highest visible-light photoelectrochemical and photocatalytic activities were observed from the heterojunction with 1:2 mass ratio of Ti 3+-TiO 2 to O-g-C 3N 4. The photodegradation reaction rate constant based on this heterojuction is 0.0356 min -1, which is 3.87 and 4.56 times higher than those of pristine Ti 3+-TiO 2 and pure g-C 3N 4, respectively. Here, the remarkably high photoelectrochemical and photocatalytic performances of the heterojunctions are mainly attributed to the synergetic effect of efficient photogenerated electron-hole separation, decreased electron transfer resistance from interfacial chemical hydroxy residue bonds, and oxidizing groups originating from Ti 3+-TiO 2 and O-g-C 3N 4.« less

Synergetic Effect of Ti3+ and Oxygen Doping on Enhancing Photoelectrochemical and Photocatalytic Properties of TiO2/g-C3N4 Heterojunctions.

PubMed

Li, Kai; Huang, Zhenyu; Zeng, Xiaoqiao; Huang, Baibiao; Gao, Shanmin; Lu, Jun

2017-04-05

To improve the utilization of visible light and reduce photogenerated electron/hole recombination, Ti 3+ self-doped TiO 2 /oxygen-doped graphitic carbon nitride (Ti 3+ -TiO 2 /O-g-C 3 N 4 ) heterojunctions were prepared via hydrothermal treatment of a mixture of g-C 3 N 4 and titanium oxohydride sol obtained from the reaction of TiH 2 with H 2 O 2 . In this way, exfoliated O-g-C 3 N 4 and Ti 3+ -TiO 2 nanoparticles were obtained. Simultaneously, strong bonding was formed between Ti 3+ -TiO 2 nanoparticles and exfoliated O-g-C 3 N 4 during the hydrothermal process. Charge transfer and recombination processes were characterized by transient photocurrent responses, electrochemical impedance test, and photoluminescence spectroscopy. The photocatalytic performances were investigated through rhodamine B degradation test under an irradiation source based on 30 W cold visible-light-emitting diode. The highest visible-light photoelectrochemical and photocatalytic activities were observed from the heterojunction with 1:2 mass ratio of Ti 3+ -TiO 2 to O-g-C 3 N 4 . The photodegradation reaction rate constant based on this heterojuction is 0.0356 min -1 , which is 3.87 and 4.56 times higher than those of pristine Ti 3+ -TiO 2 and pure g-C 3 N 4 , respectively. The remarkably high photoelectrochemical and photocatalytic performances of the heterojunctions are mainly attributed to the synergetic effect of efficient photogenerated electron-hole separation, decreased electron transfer resistance from interfacial chemical hydroxy residue bonds, and oxidizing groups originating from Ti 3+ -TiO 2 and O-g-C 3 N 4 .

Synergetic effect of Ti 3+ and oxygen doping on enhancing photoelectrochemical and photocatalytic properties of TiO 2/g-C 3N 4 heterojunctions

DOE PAGES

Li, Kai; Huang, Zhenyu; Zeng, Xiaoqiao; ...

2017-03-07

To improve the utilization of visible light and reduce photogenerated electron/hole recombination, Ti 3+ self-doped TiO 2/oxygen-doped graphitic carbon nitride (Ti 3+-TiO 2/O-g-C 3N 4) heterojunctions were prepared via hydrothermal treatment of a mixture of g-C 3N 4 and titanium oxohydride sol obtained from the reaction of TiH 2 with H 2O 2. In this way, exfoliated O-g-C 3N 4 and Ti 3+-TiO 2 nanoparticles were obtained. Simultaneously, strong bonding was formed between Ti 3+-TiO 2 nanoparticles and exfoliated O-g-C 3N 4 during the hydrothermal process. Charge transfer and recombination processes were characterized by transient photocurrent responses, electrochemical impedance test,more » and photoluminescence spectroscopy. The photocatalytic performances were investigated through rhodamine B degradation test under an irradiation source based on 30 W cold visible-light-emitting diode. The highest visible-light photoelectrochemical and photocatalytic activities were observed from the heterojunction with 1:2 mass ratio of Ti 3+-TiO 2 to O-g-C 3N 4. The photodegradation reaction rate constant based on this heterojuction is 0.0356 min -1, which is 3.87 and 4.56 times higher than those of pristine Ti 3+-TiO 2 and pure g-C 3N 4, respectively. Here, the remarkably high photoelectrochemical and photocatalytic performances of the heterojunctions are mainly attributed to the synergetic effect of efficient photogenerated electron-hole separation, decreased electron transfer resistance from interfacial chemical hydroxy residue bonds, and oxidizing groups originating from Ti 3+-TiO 2 and O-g-C 3N 4.« less

MoSe2 modified TiO2 nanotube arrays with superior photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Zhang, Yaping; Zhu, Haifeng; Yu, Lianqing; He, Jiandong; Huang, Chengxing

2018-04-01

TiO2 nanotube arrays (TNTs) are first prepared by anodization Ti foils in ethylene glycol electrolyte. Then, MoSe2 deposites electrochemically on TNTs. The as-synthesized MoSe2/TiO2 composite has a much higher photocurrent density of 1.07 mA cm‑2 at 0 V than pure TNTs of 0.38 mA cm‑2, which suggests that the MoSe2/TiO2 composite film has optimum photoelectrocatalysis properties. The electron transport resistances of the MoSe2/TiO2 decreases to half of pure TiO2, at 295.6 ohm/cm2. Both photocurrent-time and Mott-Schottky plots indicate MoSe2 a p-type semiconductor characteristics. MoSe2/TiO2 composite can achieve a maximum 5 orders of magnitude enhancement in carrier density (4.650 × 1027 cm‑3) than that of pure TiO2 arrays. It can be attributed to p-n heterojunction formed between MoSe2 and TiO2, and the composite can be potentially applied in photoelectrochemical, photocatalysis fields.

Enhanced nitrogen selectivity for nitrate reduction on Cu-nZVI by TiO2 photocatalysts under UV irradiation

NASA Astrophysics Data System (ADS)

Krasae, Nalinee; Wantala, Kitirote

2016-09-01

The aims of this work were to study the effect of Cu-nZVI with and without TiO2 on nitrate reduction and to study the pathway of nitrate reduction utilizing to nitrogen gas. The chemical and physical properties of Cu-nZVI and Cu-nZVI/TiO2 such as specific surface area, crystalline phase, oxidation state of Cu and Fe and morphology were determined by N2 adsorption-desorption Brunauer-Emmett-Teller (BET) analytical technique, X-ray diffraction (XRD), X-ray Absorption Near Edge Structure (XANES) technique and Transmittance Electron Microscopy (TEM). The full factorial design (FFD) was used in this experiment for the effect of Cu-nZVI with and without TiO2, where the initial solution pH was varied at 4, 5.5, and 7 and initial nitrate concentration was varied at 50, 75, and 100 ppm. Finally, the pathway of nitrate reduction was examined to calculate the nitrogen gas selectivity. The specific area of Cu-nZVI and Cu-nZVI/TiO2 was found to be about 4 and 36 m2/g, respectively. The XRD pattern of Fe0 in Cu-nZVI was found at 45° (2θ), whereas Cu-nZVI/TiO2 cannot be observed. TEM images can confirm the position of the core and the shell of nZVI for Fe0 and ferric oxide. Cu-nZVI/TiO2 proved to have higher activity in nitrogen reduction performance than that without TiO2 and nitrate can be completely degraded in both of solution pH of 4 and 7 in 75 ppm of initial nitrate concentration. It can be highlighted that the nitrogen gas selectivity of Cu-nZVI/TiO2 greater than 82% was found at an initial solution pH of 4 and 7. The main effects of Cu-nZVI with and without TiO2 and the initial nitrate concentration on nitrate reduction were significant. The interaction between solution pH and initial nitrate concentration and the interaction of all effects at a reaction time of 15 min on nitrate reduction were also significant.

Effect of substrate surface treatment on electrochemically assisted photocatalytic activity of N-S co-doped TiO2 films

NASA Astrophysics Data System (ADS)

Parada-Gamboa, N. J.; Pedraza-Avella, J. A.; Meléndez, A. M.

2017-01-01

To investigate whether different metal surface treatments, performed on meshes of stainless steel 304 and titanium, affect the photocatalytic activity (PCA) of supported modified anodic TiO2 films, metallic substrates were coated with titanium isopropoxide sol-gel precursor modified with thiourea. Substrates were pretreated by some of the following techniques: a) sandblasting, b) pickling, c) hydroxylation and d) passivation. The as-prepared electrode materials were characterized by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and voltammetry in the dark and under light UVA irradiation. PCA of modified N-S-TiO2 electrodes was evaluated by electrochemically assisted photocatalytic degradation of methyl orange. The results of XPS revealed that N and S were incorporated into the lattice of TiO2. FESEM showed that surface roughness and thickness of films varies depending on surface treatment. Voltammetric and XPS characterization of N-S co-doped TiO2 films supported on stainless steel revealed that their surface contains alpha-Fe2O3/FeOOH. Accordingly, iron contamination of the films coming from stainless steel was detrimental to the degradation of methyl orange. Prior to sol-gel coating process, sandblasting followed by nitric acid passivation for stainless steel or hydrofluoric acid pickling process in the case of titanium improved the PCA of N-S co-doped TiO2 films.

Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

NASA Astrophysics Data System (ADS)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Influence of immersion cycles during n-β-Bi2O3 sensitization on the photoelectrochemical behaviour of N-F-codoped TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Hoyos, Lina J.; Rivera, Diego F.; Gualdrón-Reyes, Andrés F.; Ospina, Rogelio; Rodríguez-Pereira, Jhonatan; Ropero-Vega, Jose L.; Niño-Gómez, Martha E.

2017-11-01

Sensitization of TiO2 nanotube (TNT)-based photoanodes with narrow-band gap semiconductors is an important alternative to improving the photoelectrochemical properties of the material. However, the interaction between the sensitizer and TNT is not understood deeply enough to relate charge carrier transport into the composite photoanode with its photoactivity. In this contribution, we studied the photoelectrochemical behaviour of N-F-self codoped TiO2 nanotubes (N-F-TNTs) that were grown by anodization of titanium plates and sensitized with β-Bi2O3 by immersing the TNTs into a Bi2O3 sol solution by dip-coating. The number of immersion cycles was varied. The as-fabricated photoanodes were characterized by FESEM, GIXRD, DRS and XPS, while their photoelectrochemical and semiconducting properties were investigated by photovoltammetry, electrochemical impedance spectroscopy and Mott-Schottky analysis in 0.1 M HClO4. The photoelectrocatalytic activity of the composite photoanodes was evaluated for glycerol oxidation under acidic and alkaline conditions. The N-F-TNTs exhibit a well-oriented structure after β-Bi2O3 deposition. The presence of substitutions of both N and F, identified by XPS, indicates the self-doping of the TNTs during anodization. The visible-light harvesting of the N-F-TNT photoanode was enhanced after three -immersion cycles during β-Bi2O3 sensitization, establishing an adequate n-n heterojunction at the N-F-TNT/Bi2O3 interface. In addition, bismuth migration from the sensitizer to the TNT lattice was promoted during thermal treatment, forming Bi-N-F-tridoping of TNT (Bi-N-F-TNT). The suitable band alignment between TNT and β-Bi2O3 and incorporation of the Bi3+ energy levels into TiO2 facilitate charge carrier separation and electron transport throughout the cell. Nevertheless, increasing the number of immersion cycles over three creates an excess of Bi3+ species at the N-F-TNT/β-Bi2O3 interface, producing an energetic barrier that hinders electron

Electrochemical and in vitro behavior of the nanosized composites of Ti-6Al-4V and TiO2 fabricated by friction stir process

NASA Astrophysics Data System (ADS)

Zhang, Chengjian; Ding, Zihao; Xie, Lechun; Zhang, Lai-Chang; Wu, Laizhi; Fu, Yuanfei; Wang, Liqiang; Lu, Weijie

2017-11-01

Although Ti-6Al-4V has been widely used in biomaterial field. Compared with other classes of materials, it still encounters some problems such as low surface hardness and relative low biocompatibility. To solve these problems friction stir processing (FSP) was applied to fabricate a nanosized composite layer of TiO2 and Ti-6Al-4V. Uniform distribution of TiO2 particles with some clusters on the surface of alloy can be observed. Due to severe plastic deformation and stirring heat, nanocrystallines and amorphous TiO2 can be observed in stir zone. FSPed samples show significant improvement in surface microhardness and biocompatibility due to its modified structure compared with original sample. In addition, through corrosion behaviors of the samples in simulated body fluid, it is found that FSP can enhance whilst TiO2 reduces the possibility and corrosion rate of material in environment of human body.

Comparisons of lanthanide/actinide +2 ions in a tris(aryloxide)arene coordination environment† †Electronic supplementary information (ESI) available: Additional computational details, spectroscopic information, crystallographic data collection, structure solution, and refinement (PDF), X-ray diffraction details of compounds 1-Ln (Ln = Nd, Gd, Dy, and Er), 2-Nd, 2-Ln/3-Ln (Ln = Gd, Dy, Er), 2-Dy/4-Dy, and 5-Dy/6-Dy. CCDC (CIF, 1538987–1538995 and 1566075 for 2-Dy/3-Dy), and DFT-optimized structural coordinates for 2-Nd and 2-Gd. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc02337e Click here for additional data file. Click here for additional data file. Click here for additional data file.

PubMed Central

Fieser, Megan E.; Palumbo, Chad T.; La Pierre, Henry S.; Halter, Dominik P.; Voora, Vamsee K.; Ziller, Joseph W.

2017-01-01

A new series of Ln3+ and Ln2+ complexes has been synthesized using the tris(aryloxide)arene ligand system, ((Ad,MeArO)3mes)3–, recently used to isolate a complex of U2+. The triphenol precursor, (Ad,MeArOH)3mes, reacts with the Ln3+ amides, Ln(NR2)3 (R = SiMe3), to form a series of [((Ad,MeArO)3mes)Ln] complexes, 1-Ln. Crystallographic characterization was achieved for Ln = Nd, Gd, Dy, and Er. The complexes 1-Ln can be reduced with potassium graphite in the presence of 2.2.2-cryptand (crypt) to form highly absorbing solutions with properties consistent with Ln2+ complexes, [K(crypt)][((Ad,MeArO)3mes)Ln], 2-Ln. The synthesis of the Nd2+ complex [K(crypt)][((Ad,MeArO)3mes)Nd], 2-Nd, was unambiguously confirmed by X-ray crystallography. In the case of the other lanthanides, crystals were found to contain mixtures of 2-Ln co-crystallized with either a Ln3+ hydride complex, [K(crypt)][((Ad,MeArO)3mes)LnH], 3-Ln, for Ln = Gd, Dy, and Er, or a hydroxide complex, [K(crypt)][((Ad,MeArO)3mes)Ln(OH)], 4-Ln, for Ln = Dy. A Dy2+ complex with 18-crown-6 as the potassium chelator, [K(18-crown-6)(THF)2][((Ad,MeArO)3mes)Dy], 5-Dy, was isolated as a co-crystallized mixture with the Dy3+ hydride complex, [K(18-crown-6)(THF)2][((Ad,MeArO)3mes)DyH], 6-Dy. Structural comparisons of 1-Ln and 2-Ln are presented with respect to their uranium analogs and correlated with density functional theory calculations on their electronic structures. PMID:29163894

Effect of Ligand Substitution around the Dy(III) on the SMM Properties of Dual-Luminescent Zn-Dy and Zn-Dy-Zn Complexes with Large Anisotropy Energy Barriers: A Combined Theoretical and Experimental Magnetostructural Study.

PubMed

Costes, Jean Pierre; Titos-Padilla, Silvia; Oyarzabal, Itziar; Gupta, Tulika; Duhayon, Carine; Rajaraman, Gopalan; Colacio, Enrique

2016-05-02

The new dinuclear Zn(II)-Dy(III) and trinuclear Zn(II)-Dy(III)-Zn(II) complexes of formula [(LZnBrDy(ovan) (NO3)(H2O)](H2O)·0.5(MeOH) (1) and [(L(1)ZnBr)2Dy(MeOH)2](ClO4) (3) (L and L(1) are the dideprotonated forms of the N,N'-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato and 2-{(E)-[(3-{[(2E,3E)-3-(hydroxyimino)butan-2-ylidene ]amino}-2,2-dimethylpropyl)imino]methyl}-6-methoxyphenol Schiff base compartmental ligands, respectively) have been prepared and magnetostructurally characterized. The X-ray structure of 1 indicates that the Dy(III) ion exhibits a DyO9 coordination sphere, which is made from four O atoms coming from the compartmental ligand (two methoxy terminal groups and two phenoxido bridging groups connecting Zn(II) and Dy(III) ions), other four atoms belonging to the chelating nitrato and ovanillin ligands, and the last one coming to the coordinated water molecule. The structure of 3 shows the central Dy(III) ion surrounded by two L(1)Zn units, so that the Dy(III) and Zn(II) ions are linked by phenoxido/oximato bridging groups. The Dy ion is eight-coordinated by the six O atoms afforded by two L(1) ligands and two O atoms coming from two methanol molecules. Alternating current (AC) dynamic magnetic measurements of 1, 3, and the previously reported dinuclear [LZnClDy(thd)2] (2) complex (where thd = 2,2,6,6-tetramethyl-3,5-heptanedionato ligand) indicate single molecule magnet (SMM) behavior for all these complexes with large thermal energy barriers for the reversal of the magnetization and butterfly-shaped hysteresis loops at 2 K. Ab initio calculations on 1-3 show a pure Ising ground state for all of them, which induces almost completely suppressed quantum tunnelling magnetization (QTM), and thermally assisted quantum tunnelling magnetization (TA-QTM) relaxations via the first excited Kramers doublet, leading to large energy barriers, thus supporting the observation of SMM behavior. The comparison between the experimental and theoretical

The Effects of Anchor Groups on (1) TiO2-Catalyzed Photooxidation and (2) Linker-Assisted Assembly on TiO2

NASA Astrophysics Data System (ADS)

Anderson, Ian Mark

Quantum dot-sensitized solar cells (QDSSCs) are a popular target for research due to their potential for highly efficient, easily tuned absorption. Typically, light is absorbed by quantum dots attached to a semiconductor substrate, such as TiO2, via bifunctional linker molecules. This research aims to create a patterned monolayer of linker molecules on a TiO2 film, which would in turn allow the attachment of a patterned layer of quantum dots. One method for the creation of a patterned monolayer is the functionalization of a TiO2 film with a linker molecule, followed by illumination with a laser at 355 nm. This initiates a TiO 2-catalyzed oxidation reaction, causing loss of surface coverage. A second linker molecule can then be adsorbed onto the TiO2 surface in the illuminated area. Towards that end, the behaviors of carboxylic and phosphonic acids adsorbed on TiO2 have been studied. TiO2 films were functionalized by immersion in solutions a single adsorbate and surface coverage was determined by IR spectroscopy. It is shown that phosphonic acids attain higher surface coverage than carboxylic acids, and will displace them from TiO2 when in a polar solvent. Alkyl chain lengths, which can influence stabilities of monolayers, are shown not to have an effect on this relationship. Equilibrium binding data for the adsorption of n-hexadecanoic acid to TiO2 from a THF solution are presented. It is shown that solvent polarity can affect monolayer stability; carboxylates and phosphonates undergo more desorption into polar solvents than nonpolar. Through illumination, it was possible to remove nearly all adsorbed linkers from TiO2. However, the illuminated areas were found not to be receptive to attachment by a second adsorbate. A possible reason for this behavior is presented. I also report on the synthesis and characterization of a straight-chain, thiol-terminated phosphonic acid. Initial experiments involving monolayer formation and quantum dot attachment are presented

15 CFR 719.14 - Hearings.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Hearings. 719.14 Section 719.14 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF... hearing and of any other oral proceedings will be taken by reporter or by electronic recording, and filed...

15 CFR 719.10 - Discovery.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 15 Commerce and Foreign Trade 2 2013-01-01 2013-01-01 false Discovery. 719.10 Section 719.10... Discovery. (a) General. The parties are encouraged to engage in voluntary discovery regarding any matter... the Federal Rules of Civil Procedure relating to discovery apply to the extent consistent with this...

15 CFR 719.10 - Discovery.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 15 Commerce and Foreign Trade 2 2012-01-01 2012-01-01 false Discovery. 719.10 Section 719.10... Discovery. (a) General. The parties are encouraged to engage in voluntary discovery regarding any matter... the Federal Rules of Civil Procedure relating to discovery apply to the extent consistent with this...

15 CFR 719.10 - Discovery.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 15 Commerce and Foreign Trade 2 2014-01-01 2014-01-01 false Discovery. 719.10 Section 719.10... Discovery. (a) General. The parties are encouraged to engage in voluntary discovery regarding any matter... the Federal Rules of Civil Procedure relating to discovery apply to the extent consistent with this...

15 CFR 719.10 - Discovery.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Discovery. 719.10 Section 719.10... Discovery. (a) General. The parties are encouraged to engage in voluntary discovery regarding any matter... the Federal Rules of Civil Procedure relating to discovery apply to the extent consistent with this...

Preparation and enhanced daylight-induced photocatalytic activity of C,N,S-tridoped titanium dioxide powders.

PubMed

Zhou, Minghua; Yu, Jiaguo

2008-04-15

A simple method for preparing highly daylight-induced photoactive nanocrystalline C,N,S-tridoped TiO2 powders was developed by a solid-phase reaction. The as-prepared TiO2 powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra, N2 adsorption-desorption measurements and transmission electron microscopy (TEM). The photocatalytic activity was evaluated by the photocatalytic oxidation of formaldehyde under daylight irradiation in air. The results show that daylight-induced photocatalytic activities of the as-prepared TiO2 powders were improved by C,N,S-tridoping. The C,N,S-tridoped TiO2 powders exhibited stronger absorption in the near UV and visible-light region with red shift in the band-gap transition. When the molar ratio of CS(NH2)2 to xerogel TiO2 powders (prepared by hydrolysis of Ti(OC4H9)4 in distilled water) (R) was kept in 3, the daylight-induced photocatalytic activities of the as-prepared C,N,S-tridoped TiO2 powders were about more than six times greater than that of Degussa P25 and un-doped TiO2 powders. The high activities of the C,N,S-tridoped TiO2 can be attributed to the results of the synergetic effects of strong absorption in the near UV and visible-light region, red shift in adsorption edge and two phase structures of un-doped TiO2 and C,N,S-tridoped TiO2.

Determination of crystal-field energy levels and temperature dependence of magnetic susceptibility for Dy3+ in [Dy2Pd] heterometallic complex.

PubMed

Karbowiak, Mirosław; Rudowicz, Czesław; Ishida, Takayuki

2013-11-18

This study is the first in a series of experimental and theoretical investigations of the crystal-field (CF) energy levels obtained from optical electronic spectra for selected heterometallic 4f-3d compounds intensively studied for the development of novel single-molecule magnets (SMMs). An intriguing question is why the [{Dy(III)(hfac)3}2Cu(II)(dpk)2] (abbreviated as [Dy2Cu]; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, Hdpk = di-2-pyridyl ketoxime) has antiferromagnetic coupling, whereas [Gd2Cu] and heavy [Ln2Cu] systems usually show ferromagnetic coupling. As the first step to explain this peculiarity, the recently synthesized complex, [Dy2Pd], is investigated. This complex is isostructural with [Dy2Cu] yet contains the diamagnetic Pd ion instead of the magnetic Cu(II) ion. Experimental energy levels of Dy(3+) ions in the powder [Dy2Pd] sample were determined from the 4.2 K absorption spectra. CF analysis was performed yielding the fitted free ion and CF parameters. The number of freely varied parameters was restricted using the superposition model. The fittings yield very satisfactory agreement between the experimental and the calculated energy levels (rms = 12.0 cm(-1)). The energies and exact composition of the state vector for the ground multiplet (6)H(15/2) of Dy(3+) are determined. These results are used for the simulation of the temperature dependence of the magnetic susceptibility, which enables the theoretical interpretation of the experimentally measured magnetic susceptibility in the range 1.8-300 K for the [Dy2Pd] complex. This study provides background for the subsequent investigation of the magnetic exchange interactions in the pertinent heterometallic complexes.

Room temperature one-step synthesis of microarrays of N-doped flower-like anatase TiO2 composed of well-defined multilayer nanoflakes by Ti anodization

NASA Astrophysics Data System (ADS)

Wang, Chenglin; Wang, Mengye; Xie, Kunpeng; Wu, Qi; Sun, Lan; Lin, Zhiqun; Lin, Changjian

2011-07-01

Microarrays of N-doped flower-like TiO2 composed of well-defined multilayer nanoflakes were synthesized at room temperature by electrochemical anodization of Ti in NH4F aqueous solution. The TiO2 flowers were of good anatase crystallinity. The effects of anodizing time, applied voltage and NH4F concentration on the flower-like morphology were systematically examined. It was found that the morphologies of the anodized Ti were related to the anodizing time and NH4F concentration. The size and density of the TiO2 flowers could be tuned by changing the applied voltage. The obtained N-doped flower-like TiO2 microarrays exhibited intense absorption in wavelengths ranging from 320 to 800 nm. Under both UV and visible light irradiation, the photocatalytic activity of the N-doped flower-like TiO2 microarrays in the oxidation of methyl orange showed a significant increase compared with that of commercial P25 TiO2 film.

Room temperature one-step synthesis of microarrays of N-doped flower-like anatase TiO2 composed of well-defined multilayer nanoflakes by Ti anodization.

PubMed

Wang, Chenglin; Wang, Mengye; Xie, Kunpeng; Wu, Qi; Sun, Lan; Lin, Zhiqun; Lin, Changjian

2011-07-29

Microarrays of N-doped flower-like TiO(2) composed of well-defined multilayer nanoflakes were synthesized at room temperature by electrochemical anodization of Ti in NH(4)F aqueous solution. The TiO(2) flowers were of good anatase crystallinity. The effects of anodizing time, applied voltage and NH(4)F concentration on the flower-like morphology were systematically examined. It was found that the morphologies of the anodized Ti were related to the anodizing time and NH(4)F concentration. The size and density of the TiO(2) flowers could be tuned by changing the applied voltage. The obtained N-doped flower-like TiO(2) microarrays exhibited intense absorption in wavelengths ranging from 320 to 800 nm. Under both UV and visible light irradiation, the photocatalytic activity of the N-doped flower-like TiO(2) microarrays in the oxidation of methyl orange showed a significant increase compared with that of commercial P25 TiO(2) film.

Thermo and mechanoluminescence of Dy3+ activated K2Mg2(SO4)3 phosphor

NASA Astrophysics Data System (ADS)

Panigrahi, A. K.; Dhoble, S. J.; Kher, R. S.; Moharil, S. V.

2003-08-01

A solid state diffusion method for the preparation of (K2 : Dy)Mg2(SO4)3 and (K2 : Dy,P)Mg2(SO4)3 phosphors is reported. Thermoluminescence (TL) and mechanoluminescence (ML) characteristics are studied. TL, shown by the (K2 : Dy,P)Mg2(SO4)3 phosphor is 60% as intense as the conventional CaSO4 : Dy phosphor used in the TLD of ionization radiation. It has a linear TL dose response and a negligible fading. These properties of (K2 : Dy,P)Mg2(SO4)3 should be suitable in dosimetry of ionization radiation using TL technique. ML of (K2 : Dy)Mg2(SO4)3 shows one peak which has been observed in ML intensity versus time curve. The ML peak shows the recombination of electrons with free radicals (anion radicals produced by γ-irradiation) released from traps during the mechanical pressure applied on the Dy activated K2Mg2(SO4)3 phosphor. This ML mechanism is proposed for γ-irradiated sulfate based phosphors. It has been found that the total light output, i.e. ML intensity, increases with concentration of dopant, strain rate and irradiation dose of the phosphor. Mechanoluminescence and ML emission spectra of (K2 : Dy)Mg2(SO4)3 were recorded for better understanding of the ML process. The TL and ML measurements have also been performed to elucidate the mechanism of ML. Some correlation between ML and TL has also been found.

N719 dye-sensitized organophotocatalysis: enantioselective tandem Michael addition/oxyamination of aldehydes.

PubMed

Yoon, Hyo-Sang; Ho, Xuan-Huong; Jang, Jiyeon; Lee, Hwa-Jung; Kim, Seung-Joo; Jang, Hye-Young

2012-07-06

A remarkably efficient photosensitizer, N719 dye, was used in asymmetric tandem Michael addition/oxyamination of aldehydes, rendering α,β-substituted aldehydes in good yields with excellent levels of enantioselectivity and diastereoselectivity. This is the first report of a multiorganocatalytic reaction involving iminium catalysis and photoinduced singly occupied molecular orbital (SOMO) catalysis. This reaction is expected to expand the scope of tandem organocatalytic reactions.

Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity.

PubMed

Faraji, Masoud; Mohaghegh, Neda; Abedini, Amir

2018-01-01

A series of g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plates were fabricated via simple dipping of TiO 2 nanotubes/Ti in a solution containing SnCl 2 and g-C 3 N 4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C 3 N 4 -SnO 2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO 2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis illuminations. Detailed characterization and results of photocatalytic and antibacterial activity tests revealed that semiconductor coupling significantly affected the photocatalyst properties synthesized and hence their photocatalytic and antibacterial activities. Modification of TiO 2 nanotubes/Ti plates with g-C 3 N 4 -SnO 2 deposits resulted in enhanced photocatalytic activities in both chemical and microbial systems. The g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate exhibited the highest photocatalytic and antibacterial activity, probably due to the heterojunction between g-C 3 N 4 -SnO 2 and TiO 2 nanotubes/Ti in the ternary composite plate and thus lower electron/hole recombination rate. Based on the obtained results, a photocatalytic and an antibacterial mechanism for the degradation of E. coli bacteria and chemical pollutants over g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate were proposed and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

In-Situ-Reduced Synthesis of Ti 3+ Self-Doped TiO 2 /g-C 3 N 4 Heterojunctions with High Photocatalytic Performance under LED Light Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kai; Gao, Shanmin; Wang, Qingyao

2015-04-27

A simple one-step calcination route was used to prepare Ti3+ self-doped TiO2/g-C3N4 heterojunctions by mixture of H2Ti3O7 and melamine. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) technologies were used to characterize the structure, crystallinity, morphology, and chemical state of the as-prepared samples. The absorption of the prepared Ti3+ self-doped TiO2/g-C3N4 heterojunctions shifted to a longer wavelength region in comparison with pristine TiO2 and g-C3N4. The photocatalytic activities of the heterojunctions were studied by degrading methylene blue under a 30more » W visible-light-emitting diode irradiation source. The visible-light photocatalytic activities enhanced by the prepared Ti3+ self-doped TiO2/g-C3N4 heterojunctions were observed and proved to be better than that of pure TiO2 and g-C3N4. The photocatalysis mechanism was investigated and discussed. The intensive separation efficiency of photogenerated electron-hole in the prepared heterojunction was confirmed by photoluminescence (PL) spectra. The removal rate constant reached 0.038 min(-1) for the 22.3 wt % Ti3+ self-doped TiO2/g-C3N4 heterojunction, which was 26.76 and 7.6 times higher than that of pure TiO2 and g-C3N4, respectively. The established heterojunction between the interfaces of TiO2 nanoparticles and g-C3N4 nanosheets as well as introduced Ti3+ led to the rapid electron transfer rate and improved photoinduced electron-hole pair's separation efficiency, resulting in the improved photocatalytic performance of the Ti3+ self-doped TiO2/g-C3N4 heterojunctions.« less

Correlation of Structure, Tunable Colors, and Lifetimes of (Sr, Ca, Ba)Al2O4:Eu2+, Dy3+ Phosphors

PubMed Central

Xie, Qidi; Li, Bowen; He, Xin; Zhang, Mei; Chen, Yan; Zeng, Qingguang

2017-01-01

(Sr, Ca, Ba)Al2O4:Eu2+, Dy3+ phosphors were prepared via a high temperature solid-state reaction method. The correlation of phase structure, optical properties and lifetimes of the phosphors are investigated in this work. For the (Sr, Ca)Al2O4:Eu2+, Dy3+ phosphors, the different phase formation from monoclinic SrAl2O4 phase to hexagonal SrAl2O4 phase to monoclinic CaAl2O4 phase was observed when the Ca content increased. The emission color of SrAl2O4:Eu2+, Dy3+ phosphors varied from green to blue. For the (Sr, Ba)Al2O4:Eu2+, Dy3+ phosphors, different phase formation from the monoclinic SrAl2O4 phase to the hexagonal BaAl2O4 phase was observed, along with a shift of emission wavelength from 520 nm to 500 nm. More interestingly, the decay time of SrAl2O4:Eu2+, Dy3+ changed due to the different phase formations. Lifetime can be dramatically shortened by the substitution of Sr2+ with Ba2+ cations, resulting in improving the performance of the alternating current light emitting diode (AC-LED). Finally, intense LEDs are successfully obtained by combining these phosphors with Ga(In)N near UV chips. PMID:29057839

Properties of TiO2 thin films and a study of the TiO2-GaAs interface

NASA Technical Reports Server (NTRS)

Chen, C. Y.; Littlejohn, M. A.

1977-01-01

Titanium dioxide (TiO2) films prepared by chemical vapor deposition were investigated in this study for the purpose of the application in the GaAs metal-insulator-semiconductor field-effect transistor. The degree of crystallization increases with the deposition temperature. The current-voltage study, utilizing an Al-TiO2-Al MIM structure, reveals that the d-c conduction through the TiO2 film is dominated by the bulk-limited Poole-Frenkel emission mechanism. The dependence of the resistivity of the TiO2 films on the deposition environment is also shown. The results of the capacitance-voltage study indicate that an inversion layer in an n-type substrate can be achieved in the MIS capacitor if the TiO2 films are deposited at a temperature higher than 275 C. A process of low temperature deposition followed by the pattern definition and a higher temperature annealing is suggested for device fabrications. A model, based on the assumption that the surface state densities are continuously distributed in energy within the forbidden band gap, is proposed to interpret the lack of an inversion layer in the Al-TiO2-GaAs MIS structure with the TiO2 films deposited at 200 C.

Enhanced photocatalytic degradation of Amaranth dye on mesoporous anatase TiO2: evidence of C-N, N[double bond, length as m-dash]N bond cleavage and identification of new intermediates.

PubMed

Naik, Amarja P; Salkar, Akshay V; Majik, Mahesh S; Morajkar, Pranay P

2017-07-01

The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO 2 under sunlight. Mesoporous anatase TiO 2 of a high photocatalytic activity has been synthesized using a sol-gel method and its photocatalytic activity for the degradation of Amaranth dye has been evaluated with respect to Degussa P25. The effect of bi-dentate complexing agents like oxalic acid, ethylene glycol and urea on the surface properties of TiO 2 catalyst has been investigated using TG-DTA, FTIR, HR-TEM, SAED, PXRD, EDS, UV-DRS, PL, BET N 2 adsorption-desorption isotherm studies and BJH analysis. The influence of catalyst properties such as the mesoporous network, pore volume and surface area on the kinetics of degradation of Amaranth as a function of irradiation time under natural sunlight has been monitored using UV-Vis spectroscopy. The highest rate constant value of 0.069 min -1 was obtained for the photocatalytic degradation of Amaranth using TiO 2 synthesized via a urea assisted sol-gel synthesis method. The effect of the reaction conditions such as pH, TiO 2 concentration and Amaranth concentration on the photodegradation rate has been investigated. The enhanced photocatalytic activity of synthesized TiO 2 in comparison with P25 is attributed to the mesoporous nature of the catalyst leading to increased pore diameter, pore volume, surface area and enhanced charge carrier separation efficiency. New intermediates of photocatalytic degradation of Amaranth, namely, sodium-3-hydroxynaphthalene-2,7-disulphonate, 3-hydroxynaphthalene, sodium-4-aminonaphthalenesulphonate and sodium-4-aminobenzenesulphonate have been identified using LC-ESI-MS for the very first time, providing direct evidence for simultaneous bond cleavage pathways (-C-N-) and (-N[double bond, length as m-dash]N-). A new plausible mechanism of TiO 2 catalysed photodegradation of Amaranth along with the comparison of its toxicity to that of its degradation

15 CFR 719.14 - Hearings.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 15 Commerce and Foreign Trade 2 2014-01-01 2014-01-01 false Hearings. 719.14 Section 719.14... Hearings. (a) Scheduling. Upon receipt of a written and dated request for a hearing, the ALJ shall, by agreement with all the parties or upon notice to all parties of at least 30 days, schedule a hearing. All...

Molecular assembly and magnetic dynamics of two novel Dy6 and Dy8 aggregates.

PubMed

Guo, Yun-Nan; Chen, Xiao-Hua; Xue, Shufang; Tang, Jinkui

2012-04-02

Complexation of dysprosium(III) with the heterodonor chelating ligand o-vanillin picolinoylhydrazone (H(2)ovph) in the presence of a carbonato ligand affords two novel Dy(6) and Dy(8) clusters, namely, [Dy(6)(ovph)(4)(Hpvph)(2)Cl(4)(H(2)O)(2)(CO(3))(2)]·CH(3)OH·H(2)O·CH(3)CN (2) and [Dy(8)(ovph)(8)(CO(3))(4)(H(2)O)(8)]·12CH(3)CN·6H(2)O (3). Compound 2 is composed of three petals of the Dy(2) units linked by two carbonato ligands, forming a triangular prism arrangement, while compound 3 possesses an octanuclear core with an unprecedented tub conformation, in which Dy(ovph) fragments are attached to the sides of the carbonato core. The static and dynamic magnetic properties are reported and discussed. In the Dy(6) aggregate, three Dy(2) "skeletons", having been well preserved (see the scheme), contribute to the single-molecule-magnet behavior with a relatively slow tunneling rate, while the Dy(8) cluster only exhibits a rather small relaxation barrier.

Thermoelectric Properties of Self Assembled TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 W/mK2 at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Thermoelectric Properties of Self Assemble TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 (mu)W/m sq K at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Observation of Significant enhancement in the efficiency of a DSSC by InN nanoparticles over TiO 2-nanoparticle films

NASA Astrophysics Data System (ADS)

Wang, Tsai-Te; Raghunath, P.; Lu, Yun-Fang; Liu, Yu-Chang; Chiou, Chwei-Huawn; Lin, M. C.

2011-06-01

We have studied the effect of InN deposited over TiO2 nanoparticle (NP) films on the performance of dye-sensitized solar cells (DSSCs) using N3 dye with I/I3- electrolyte. A 10-20% increase in efficiency was observed for InN deposited, N3 sensitized 5-8.5 μm thick TiO2 films as compared to similar non-treated films. The deposition of InN was carried out in the temperature range of 573-723 K organometallic chemical vapor deposition (OMCVD). Spectral shifts and DFT calculations with a model anchoring group (R‧COOH) both suggest binding of the N3 dye directly to both InN and the InN/TiO2 sites.

15 CFR 719.15 - Procedural stipulations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Procedural stipulations. 719.15 Section 719.15 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...

15 CFR 719.13 - Prehearing conference.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Prehearing conference. 719.13 Section 719.13 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...

15 CFR 719.13 - Prehearing conference.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Prehearing conference. 719.13 Section 719.13 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...

15 CFR 719.15 - Procedural stipulations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Procedural stipulations. 719.15 Section 719.15 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS...

Fabrication of Ce/N co-doped TiO2/diatomite granule catalyst and its improved visible-light-driven photoactivity.

PubMed

Chen, Yan; Liu, Kuiren

2017-02-15

Eliminating antibiotic remnants in aquatic environment has become one of the hottest topics among current research works. Thus, we prepared Ce, N co-doped TiO 2 /diatomite granule (CNTD-G) catalyst to provide a new method. As one typical antibiotics, oxytetracycline (OTC) was selected as the target pollutant to be degradated under visible light irradiation. The carrier diatomite helped the spread of TiO 2 nanoparticles onto its surface, and inhibited their agglomeration. The synergy of Ce and N dopants highly improved the visible-light-driven photoactivity of TiO 2 . The optimal doping amount and degradation conditions were determined. Besides, the effects of impurity ions were also investigated, including cations: Ca 2+ , Mg 2+ ; or anions: NO 3 - , SO 4 2- and PO 4 3- . The intermediates generated during degradation process were studied, and the mechanism of the photodegradation process was proposed. CNTD-G could be easily collected from the reactor, and showed excellent recyclability. Copyright © 2016 Elsevier B.V. All rights reserved.

Dilution-triggered SMM behavior under zero field in a luminescent Zn2Dy2 tetranuclear complex incorporating carbonato-bridging ligands derived from atmospheric CO2 fixation.

PubMed

Titos-Padilla, Silvia; Ruiz, José; Herrera, Juan Manuel; Brechin, Euan K; Wersndorfer, Wolfgang; Lloret, Francesc; Colacio, Enrique

2013-08-19

The synthesis, structure, magnetic, and luminescence properties of the Zn2Dy2 tetranuclear complex of formula {(μ3-CO3)2[Zn(μ-L)Dy(NO3)]2}·4CH3OH (1), where H2L is the compartmental ligand N,N',N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine, are reported. The carbonate anions that bridge two Zn(μ-L)Dy units come from the atmospheric CO2 fixation in a basic medium. Fast quantum tunneling relaxation of the magnetization (QTM) is very effective in this compound, so that single-molecule magnet (SMM) behavior is only observed in the presence of an applied dc field of 1000 Oe, which is able to partly suppress the QTM relaxation process. At variance, a 1:10 Dy:Y magnetic diluted sample, namely, 1', exhibits SMM behavior at zero applied direct-current (dc) field with about 3 times higher thermal energy barrier than that in 1 (U(eff) = 68 K), thus demonstrating the important role of intermolecular dipolar interactions in favoring the fast QTM relaxation process. When a dc field of 1000 Oe is applied to 1', the QTM is almost fully suppressed, the reversal of the magnetization slightly slows, and U(eff) increases to 78 K. The dilution results combined with micro-SQUID magnetization measurements clearly indicate that the SMM behavior comes from single-ion relaxation of the Dy(3+) ions. Analysis of the relaxation data points out that a Raman relaxation process could significantly affect the Orbach relaxation process, reducing the thermal energy barrier U(eff) for slow relaxation of the magnetization.

Phase transition at N = 92 in 158Dy

NASA Astrophysics Data System (ADS)

Gupta, J. B.

2016-09-01

Beyond the shape phase transition from the spherical vibrator to the deformed rotor regime at N = 90, the interplay of β- and γ-degrees of freedom becomes important, which affects the relative positions of the Kπ = 0+β- and Kπ = 2+γ-bands. In the microscopic approach of the dynamic pairing plus quadrupole model, a correlation of the strength of the quadrupole force and the formation of the β- and γ-bands in 158Dy is described. The role of the potential energy surface is illustrated. The E2 transition rates in the lower three K-bands and the multi-phonon bands with Kπ = 0+, 2+ and 4+ are well reproduced. The absolute B(E2, 2i+ = 0 2+) (i = 2, 3) serves as a good measure of the quadrupole strength. The role of the single particle Nilsson orbits is also described.

15 CFR 719.12 - Matters protected against disclosure.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 15 Commerce and Foreign Trade 2 2014-01-01 2014-01-01 false Matters protected against disclosure. 719.12 Section 719.12 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade... ENFORCEMENT § 719.12 Matters protected against disclosure. (a) Protective measures. The ALJ may limit...

Atomic layer deposition TiO 2-Al 2O 3 stack: An improved gate dielectric on Ga-polar GaN metal oxide semiconductor capacitors

DOE PAGES

Wei, Daming; Edgar, James H.; Briggs, Dayrl P.; ...

2014-10-15

This research focuses on the benefits and properties of TiO 2-Al 2O 3 nano-stack thin films deposited on Ga 2O 3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO 2, 7.1 nm Al 2O 3 and 2 nm Ga 2O 3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectronmore » spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O 2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO 2-Al 2O 3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al 2O 3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 10 11 cm -2. The gate leakage current density (J=2.81× 10 -8 A/cm 2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO 2/Al 2O 3 for serving as the gate oxide on Ga 2O 3/GaN based MOS devices.« less

Atomic layer deposition TiO 2-Al 2O 3 stack: An improved gate dielectric on Ga-polar GaN metal oxide semiconductor capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Daming; Edgar, James H.; Briggs, Dayrl P.

This research focuses on the benefits and properties of TiO 2-Al 2O 3 nano-stack thin films deposited on Ga 2O 3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO 2, 7.1 nm Al 2O 3 and 2 nm Ga 2O 3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectronmore » spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O 2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO 2-Al 2O 3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al 2O 3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 10 11 cm -2. The gate leakage current density (J=2.81× 10 -8 A/cm 2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO 2/Al 2O 3 for serving as the gate oxide on Ga 2O 3/GaN based MOS devices.« less

Design and construction of hierarchical TiO2 nanorod arrays by combining layer-by-layer and hydrothermal crystallization techniques for electrochromic application

NASA Astrophysics Data System (ADS)

Chen, Yongbo; Li, Xiaomin; Bi, Zhijie; He, Xiaoli; Li, Guanjie; Xu, Xiaoke; Gao, Xiangdong

2018-05-01

The hierarchical TiO2 (H-TiO2) nanorod arrays (NRAs) composed of single-crystalline nanorods and nanocrystals were finely designed and successfully constructed for electrochromic (EC) application. By combining layer-by-layer (LBL) method and hydrothermal crystallization technique, the superfine nanocrystals (5-7 nm), which can provide abundant active sites and facilitate ion insertion/extraction during EC reactions, were uniformly and conformally assembled on the surface of single-crystalline TiO2 (SC-TiO2) NRAs. The as-formed H-TiO2 NRAs integrate the advantages of one-dimensional NRAs with fast kinetics and superfine nanocrystals with high ion capacity, showing highly enhanced EC performance. Large optical contrast (40.3%), shorter coloring/bleaching time (22/4 s), high coloration efficiency (11.2 cm2 C-1), and excellent cycling stability can be achieved in H-TiO2 NRAs, superior to the pristine SC-TiO2 NRAs and nanocrystalline TiO2 films. This work provides a feasible and well-designed strategy to explore high-performance materials for EC application.

Temperature and magnetic field induced multiple magnetic transitions in DyAg(2).

PubMed

Arora, Parul; Chattopadhyay, M K; Sharath Chandra, L S; Sharma, V K; Roy, S B

2011-02-09

The magnetic properties of the rare-earth intermetallic compound DyAg(2) are studied in detail with the help of magnetization and heat capacity measurements. It is shown that the multiple magnetic phase transitions can be induced in DyAg(2) both by temperature and magnetic field. The detailed magnetic phase diagram of DyAg(2) is determined experimentally. It was already known that DyAg(2) undergoes an incommensurate to commensurate antiferromagnetic phase transition close to 10 K. The present experimental results highlight the first order nature of this phase transition, and show that this transition can be induced by magnetic field as well. It is further shown that another isothermal magnetic field induced transition or metamagnetic transition exhibited by DyAg(2) at still lower temperatures is also of first order nature. The multiple magnetic phase transitions in DyAg(2) give rise to large peaks in the temperature dependence of the heat capacity below 17 K, which indicates its potential as a magnetic regenerator material for cryocooler related applications. In addition it is found that because of the presence of the temperature and field induced magnetic phase transitions, and because of short range magnetic correlations deep inside the paramagnetic regime, DyAg(2) exhibits a fairly large magnetocaloric effect over a wide temperature window, e.g., between 10 and 60 K.

Effect of particle size of TiO2 and additive materials to improve dye sensitized solar cells efficiency

NASA Astrophysics Data System (ADS)

Ali, Falah H.; Alwan, Dheyaa B.

2018-05-01

It became a great interest Dye-sensitized solar cells (DSSC) as a successful alternative to silicon solar cells in terms of cost and simplicity. These cells rely on a semi-conductive material of electricity TiO2 nanocrystalline which encapsulates glass electrodes from the connected side at a temperature 450°C. In this work, the effect of nanoparticle size shows the size of atoms. The smaller the size of the atoms, the greater the surface area and thus the sufficient absorption of the dye and the stimulation of electrons, where increasing surface area increases efficiency. Then a limited amount was added and at a certain concentration, which led to a reasonable improvement in efficiency. According to this procedure commercially available TiO2 (10 nm,25 nm,33 nm, 50 nm) standard. A TiO2 paste was prepared by mixing commercial TiO2, ethanol, distilled water, F:SnO2 (FTO film thickness 14 μm) conductive glasses. By using Dr. Blade method we got films with appropriate thicknesses, then by using several particle sizes (10 nm, 25 nm, 33 nm, 50 nm),many efficiencies were founded (2.39 %, 2.1 %,1.85 %,1.65%) respectively. Improved solar cell efficiency after addition of several chemical materials and the best that got is Cu (NO3)2. Efficiency became for (10 nm) (2.61 %, 2.34 %,2.1%,1.85%) respectively under 40 mW/cm2.

N-doped hollow urchin-like anatase TiO2@C composite as a novel anode for Li-ion batteries

NASA Astrophysics Data System (ADS)

Xing, Yalan; Wang, Shengbin; Fang, Baizeng; Song, Ge; Wilkinson, David P.; Zhang, Shichao

2018-05-01

N-doped hollow urchin-like anatase TiO2 spheres (HUTSs) with carbon coating (HUTS@C) are prepared through a facile and scalable hydrothermal reaction followed by coating of polypyrrole and carbonization. The HUTS is composed of radially grown anatase nanorods and possesses an enhanced percentage of exposed {001} facets compared with P25 TiO2 nanoparticles. After the carbon coating, the HUTS@C retains the hollow nanostructure although covered with an N-doped carbon layer. As an anode for Li-ion batteries, the HUTS@C delivers a higher capacity of 165.1 mAh g-1 at 1C after 200 cycles and better rate capability (111.7 mAh g-1 at 10C) than the HUTS. Further electrochemical studies reveal that the HUTS@C has a better electrochemical reversibility, lower charge-transfer resistance, and higher Li-ion diffusion coefficient due to its unique nanosctructure including the hollow core, anatase phase of TiO2 microspheres with high exposed {001} facets and the N-doped carbon layer, which facilitates mass transport and enhances electrical conductivity.

PREFACE: International Conference on Dynamics of Systems on the Nanoscale (DySoN 2012)

NASA Astrophysics Data System (ADS)

Solov'yov, Andrey V.

2013-06-01

Conference logo The Second International Conference 'Dynamics of Systems on the Nanoscale' (DySoN 2012) took place in Saint Petersburg, Russia between 30 September and 4 October 2012. The venue was the Courtyard by Marriott St Petersburg Vasilievsky Hotel, 2nd line of Vasilievsky Island 61/30A, 199178. The conference was organized by the Frankfurt Institute for Advanced Studies - Goethe University, A F Ioffe Physical-Technical Institute and Saint Petersburg State Polytechnic University. This DySoN conference has been built upon a series of International Symposia 'Atomic Cluster Collisions: structure and dynamics from the nuclear to the biological scale' (ISACC 2003, ISACC 2007, ISACC 2008, ISACC 2009 and ISACC 2011). During these meetings it has become clear that there is a need for an interdisciplinary conference covering a broader range of topics than just atomic cluster collisions, related to the Dynamics of Systems on a Nanoscale. Therefore, in 2010 it was decided to launch a new conference series under the title 'Dynamics of Systems on the Nanoscale'. The first DySoN conference took place at the National Research Council, Rome, Italy in 2010. The DySoN 2012 is the second conference in this series. The DySoN 2012 Conference promoted the growth and exchange of interdisciplinary scientific information on the structure, formation and dynamics of animate and inanimate matter on the nanometer scale. There are many examples of complex many-body systems of micro- and nanometer scale size exhibiting unique features, properties and functions. These systems may have very different nature and origin, e.g. atomic and molecular clusters, nanoobjects, ensembles of nanoparticles, nanostructures, biomolecules, biomolecular and mesoscopic systems. A detailed understanding of the structure and dynamics of these systems on the nanometer scale is an important fundamental task, the solution of which is necessary in numerous applications of nano- and biotechnology, material science

Adsorption properties and photocatalytic activity of TiO2/activated carbon fiber composite

NASA Astrophysics Data System (ADS)

Yao, Shuhua; Song, Shuangping; Shi, Zhongliang

2014-06-01

Photocatalysts of titanium dioxide (TiO2) and TiO2/activated carbon fiber (TiO2/ACF) composite were prepared by sol-gel method, followed by calcining the pure TiO2 sols and the TiO2/ACF sols at 500°C for 2 h in a N2 atmosphere, respectively. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms measurement. Batch experiments were conducted to study the adsorption property of TiO2/ACF composite using methylene blue as adsorbate. The adsorption data obtained from different batch experiments were analyzed using pseudo-second-order kinetic model, the experimental data can be adequately described by the pseudo-second-order equation. The photodecomposition behavior of TiO2/ACF was investigated in aqueous solution using methylene blue as target pollutant. It was found that methylene blue could be removed rapidly from water by TiO2/ACF, the photocatalytic decomposition was obviously improved when the photocatalyst was used. Kinetics analysis revealed that the photocatalytic decomposition reaction can be described well by a first-order rate equation.

TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

NASA Astrophysics Data System (ADS)

Ghalamboran, Milad; Saedi, Yasin

2016-03-01

The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

Life or death by NFκB, Losartan promotes survival in dy2J/dy2J mouse of MDC1A

PubMed Central

Elbaz, M; Yanay, N; Laban, S; Rabie, M; Mitrani-Rosenbaum, S; Nevo, Y

2015-01-01

Inflammation and fibrosis are well-defined mechanisms involved in the pathogenesis of the incurable Laminin α2-deficient congenital muscular dystrophy (MDC1A), while apoptosis mechanism is barely discussed. Our previous study showed treatment with Losartan, an angiotensin II type I receptor antagonist, improved muscle strength and reduced fibrosis through transforming growth factor beta (TGF-β) and mitogen-activated protein kinases (MAPK) signaling inhibition in the dy2J/dy2J mouse model of MDC1A. Here we show for the first time that Losartan treatment up-regulates and shifts the nuclear factor kappa B (NFκB) signaling pathway to favor survival versus apoptosis/damage in this animal model. Losartan treatment was associated with significantly increased serum tumor necrosis factor alpha (TNF-α) level, p65 nuclei accumulation, and decreased muscle IκB-β protein level, indicating NFκB activation. Moreover, NFκB anti-apoptotic target genes TNF receptor-associated factor 1 (TRAF1), TNF receptor-associated factor 2 (TRAF2), cellular inhibitor of apoptosis (cIAP2), and Ferritin heavy chain (FTH1) were increased following Losartan treatment. Losartan induced protein expression toward a pro-survival profile as BCL-2 expression levels were increased and Caspase-3 expression levels were decreased. Muscle apoptosis reduction was further confirmed using terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) assay. Thus, along with TGF-β and MAPK signaling, NFκB serves as an important regulatory pathway which following Losartan treatment promotes survival in the dy2J/dy2J mouse model of MDC1A. PMID:25766329

Synthesis and characterization of a mixed phase of anatase TiO2 and TiO2(B) by low pressure chemical vapour deposition (LPCVD) for high photocatalytic activity

NASA Astrophysics Data System (ADS)

Chimupala, Y.; Hyett, G.; Simpson, R.; Brydson, R.

2014-06-01

This project is concerned with enhancing photocatalytic activity by preparing a mixed phase of nano-sized TiO2. TiO2 thin films were synthesized by using Low Pressure Chemical Vapour Deposition (LPCVD). Titanium isopropoxide and N2 gas were used as the precursor and carrier gas respectively. The effects of reaction temperature, carrier gas flow rate and deposited area were studied. TiO2 thin films with nano-sized TiO2 particles were obtained under suitable conditions and SEM, TEM, powder XRD and Raman spectroscopy were employed to characterize the phase and physical appearance of synthesized materials. Preliminary results show that a dual phase (TiO2(B) and anatase) thin film nanopowder was successfully prepared by LPCVD with needle- and polygonal plate-shape crystallites respectively. This thin film deposit produced a preferred orientation of TiO2(B) needles in the [001] direction of average crystallite size 50-80 nm in length and 5-10 nm in width, whilst the crystallite size of anatase polygonal-plates was around 200 nm. The optimal LPCVD condition for preparing this mixed phase of TiO2 was 600°C with a 1 mL/s N2 flow rate.

Influence of TiCl4 post-treatment condition on TiO2 electrode for enhancement photovoltaic efficiency of dye-sensitized solar cells.

PubMed

Eom, Tae Sung; Kim, Kyung Hwan; Bark, Chung Wung; Choi, Hyung Wook

2014-10-01

Titanium tetrachloride (TiCl4) treatment processed by chemical bath deposition is usually adopted as pre- and post-treatment for nanocrystalline titanium dioxide (TiO2) film deposition in the dye-sensitized solar cells (DSSCs) technology. TiCl4 post-treatment is a widely known method capable of improving the performance of dye-sensitized solar cells. In this work, the effect of TiCl4 post-treatment on the TiO2 electrode is proposed and compared to the untreated film. A TiO2 passivating layer was deposited on FTO glass by RF magnetron sputtering. The TiO2 sol prepared sol-gel method, nanoporous TiO2 upper layer was deposited by screen printing method on the passivating layer. TiCl4 post-treatment was deposited on the substrate by hydrolysis of TiCl4 aqueous solution. Crystalline structure was adjusted by various TiCl4 concentration and dipping time: 20 mM-150 mM and 30 min-120 min. The conversion efficiency was measured by solar simulator (100 mW/cm2). The dye-sensitized solar cell using TiCl4 post-treatment was measured the maximum conversion efficiency of 5.04% due to electron transport effectively. As a result, the DSSCs based on TiCl4 post-treatment showed better photovoltaic performance than cells made purely of TiO2 nanoparticles. The relative DSSCs devices are characterized in terms of short circuit current density, open circuit voltage, fill factor, conversion efficiency.

Influence of Au and TiO2 structures on hydrogen dissociation over TiO2/Au(100)

NASA Astrophysics Data System (ADS)

Nakamura, I.; Mantoku, H.; Furukawa, T.; Takahashi, A.; Fujitani, T.

2012-11-01

We performed H2-D2 exchange reactions over TiOx/Au(100) and compared the observed reaction kinetics with those reported for TiOx/Au(111) in order to clarify the influence of the Au and TiO2 structures on dissociation of H2 molecules. Low energy electron diffraction observations showed that the TiO2 produced on Au(100) was disordered, in contrast to the comparatively ordered TiO2 structure formed on Au(111). The activation energies and the turnover frequencies for HD formation over TiO2/Au(100) agreed well with those for TiO2/Au(111), clearly indicating that the hydrogen dissociation sites created over TiO2/Au(100) were the perimeter interface between stoichiometric TiO2 and Au, as was previously concluded for TiO2/Au(111). We concluded that the creation of active sites for hydrogen dissociation was independent of the Au and TiO2 structures consisting perimeter interface, and that local bonds that formed between Au and O atoms of stoichiometric TiO2 were essential for the creation of active sites.

7 CFR 58.719 - Coloring.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 3 2010-01-01 2010-01-01 false Coloring. 58.719 Section 58.719 Agriculture... Material § 58.719 Coloring. Coloring shall be Annatto or any other cheese or butter color which is approved by the Food and Drug Administration. ...

7 CFR 58.719 - Coloring.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 3 2011-01-01 2011-01-01 false Coloring. 58.719 Section 58.719 Agriculture... Material § 58.719 Coloring. Coloring shall be Annatto or any other cheese or butter color which is approved by the Food and Drug Administration. ...

48 CFR 719.273-8 - Developmental assistance.

Code of Federal Regulations, 2011 CFR

2011-10-01

.... 719.273-8 Section 719.273-8 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS The U.S. Agency for International Development... relating to— (1) Financial management; (2) Organizational management; (3) Overall business management...

Effect of band gap engineering in anionic-doped TiO2 photocatalyst

NASA Astrophysics Data System (ADS)

Samsudin, Emy Marlina; Abd Hamid, Sharifah Bee

2017-01-01

A simple yet promising strategy to modify TiO2 band gap was achieved via dopants incorporation which influences the photo-responsiveness of the photocatalyst. The mesoporous TiO2 was successfully mono-doped and co-doped with nitrogen and fluorine dopants. The results indicate that band gap engineering does not necessarily requires oxygen substitution with nitrogen or/and fluorine, but from the formation of additional mid band and Ti3+ impurities states. The formation of oxygen vacancies as a result of modified color centres and Ti3+ ions facilitates solar light absorption and influences the transfer, migration and trapping of the photo-excited charge carriers. The synergy of dopants in co-doped TiO2 shows better optical properties relative to single N and F doped TiO2 with c.a 0.95 eV band gap reduction. Evidenced from XPS, the synergy between N and F in the co-doped TiO2 uplifts the valence band towards the conduction band. However, the photoluminescence data reveals poorer electrons and holes separation as compared to F-doped TiO2. This observation suggests that efficient solar light harvesting was achievable via N and F co-doping, but excessive defects could act as charge carriers trapping sites.

Effect of SiN x diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol-gel dip coating and reactive magnetron sputtering.

PubMed

Ghazzal, Mohamed Nawfal; Aubry, Eric; Chaoui, Nouari; Robert, Didier

2015-01-01

We investigate the effect of the thickness of the silicon nitride (SiN x ) diffusion barrier on the structural and photocatalytic efficiency of TiO2 films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO2 films produced using soft chemistry (sol-gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiN x diffusion barrier. Increasing the thickness of the SiN x diffusion barrier induced a gradual decrease of the crystallite size of TiO2 films obtained by the sol-gel process. However, TiO2 obtained using the reactive sputtering method showed no dependence on the thickness of the SiN x barrier diffusion. The SiN x barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO2 films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO2 films obtained by each process was discussed.

Synthesis and visible light photoactivity of anatase Ag, and garlic loaded TiO2 nanocrystalline catalyst

EPA Science Inventory

An excellent visible light activated Ag and S doped TiO2 nanocatalyst was prepared by using AgNO3 and garlic (Allium sativum) as Ag+ and sulfur sources, respectively. The catalyst resisted the change from anatase to rutile phase even at calcination at 700 oC. The photocatalytic e...

Evaluation of the exchange interaction and crystal fields in a prototype Dy2 SMM

NASA Astrophysics Data System (ADS)

Zhang, Qing; Sarachik, Myriam; Baker, Michael; Chen, Yizhang; Kent, Andrew; Pineda, Eufemio; McInnes, Eric

In order to gain an understanding of the INS and magnetization data obtained for Dy2, the simplest member of a newly synthesized family of dysprosium-based molecular magnets, we report on calculations of the magnetic behavior of a Dy2 cluster with the formula [hqH2][Dy2(hq)4(NO3)3].MeOH. The molecular complex contains one high symmetry Dy(III) ion and one low symmetry Dy(III) ion. Our calculations suggest that exchange coupling between the two ions controls the behavior of the magnetization at low temperature, while the crystal field of the low symmetry Dy(III) ion controls the behavior at higher temperature. A point charge electrostatic model, based on crystallographic coordinates, provides a starting point for the determination of the crystal field. Parameters in these calculations are adjusted to provide best fits to inelastic neutron scattering data (INS) and low temperature magnetometry: the INS measurements access crystal field energies and low temperature magnetization probes the Dy-Dy exchange interaction. Work supported by ARO W911NF-13-1-1025 (CCNY) and NSF-DMR-1309202 (NYU).

Natural disease history of the dy2J mouse model of laminin α2 (merosin)-deficient congenital muscular dystrophy.

PubMed

Pasteuning-Vuhman, S; Putker, K; Tanganyika-de Winter, C L; Boertje-van der Meulen, J W; van Vliet, L; Overzier, M; Plomp, J J; Aartsma-Rus, A; van Putten, M

2018-01-01

Merosin deficient congenital muscular dystrophy 1A (MDC1A) is a very rare autosomal recessive disorder caused by mutations in the LAMA2 gene leading to severe and progressive muscle weakness and atrophy. Although over 350 causative mutations have been identified for MDC1A, no treatment is yet available. There are many therapeutic approaches in development, but the lack of natural history data of the mouse model and standardized outcome measures makes it difficult to transit these pre-clinical findings to clinical trials. Therefore, in the present study, we collected natural history data and assessed pre-clinical outcome measures for the dy2J/dy2J mouse model using standardized operating procedures available from the TREAT-NMD Alliance. Wild type and dy2J/dy2J mice were subjected to five different functional tests from the age of four to 32 weeks. Non-tested control groups were taken along to assess whether the functional test regime interfered with muscle pathology. Respiratory function, body weights and creatine kinase levels were recorded. Lastly, skeletal muscles were collected for further histopathological and gene expression analyses. Muscle function of dy2J/dy2J mice was severely impaired at four weeks of age and all mice lost the ability to use their hind limbs. Moreover, respiratory function was altered in dy2J/dy2J mice. Interestingly, the respiration rate was decreased and declined with age, whereas the respiration amplitude was increased in dy2J/dy2J mice when compared to wild type mice. Creatine kinase levels were comparable to wild type mice. Muscle histopathology and gene expression analysis revealed that there was a specific regional distribution pattern of muscle damage in dy2J/dy2J mice. Gastrocnemius appeared to be the most severely affected muscle with a high proportion of atrophic fibers, increased fibrosis and inflammation. By contrast, triceps was affected moderately and diaphragm only mildly. Our study presents a complete natural history