scholarly journals Optical Sensing of Molecular Oxygen (O2) via Metal Oxide Photoluminescence: A Comparative Study of TiO2, SnO2 and ZnO

Chemosensors ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 163
Author(s):  
Ambra Fioravanti ◽  
Pietro Marani ◽  
Sara Morandi ◽  
Laura Giordano ◽  
Pasqualino Maddalena ◽  
...  
Keyword(s):  
Comparative Study ◽  
Molecular Oxygen ◽  
Tin Dioxide ◽  
Sno2 Nanoparticles ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Fast Response ◽  
Tio2 Sample ◽  
Surface Vacancy ◽  
Future Work

A comparative study is presented on the photoluminescence (PL) response toward molecular oxygen (O2) in tin dioxide (SnO2), zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles. The findings show that both PL enhancement and PL quenching can be observed on different materials, arguably depending on the spatial localization of the defects responsible for the PL emission in each different oxide. No significant results are evidenced for SnO2 nanoparticles. ZnO with red/orange emission shown an O2-induced PL enhancement, suggesting that the radiative emission involves holes trapped in surface vacancy oxygen centers. While the ZnO results are scientifically interesting, its performances are inferior to the ones shown by TiO2, which exhibits the most interesting response in terms of sensitivity and versatility of the response. In particular, O2 concentrations in the range of few percent and in the range of a few tenths of a part per million are both detectable through the same mixed-phase TiO2 sample, whose rutile phase gives a reversible and fast response to larger (0.4–2%) O2 concentration while its anatase phase is usable for detection in the 25–75 ppm range. The data for rutile TiO2 suggest that its surfaces host deeply trapped electrons at large densities, allowing good sensitivities and, more notably, a relatively unsaturated response at large concentrations. Future work is expected to improve the understanding and modeling of the photophysical framework that lies behind the observations.

Antimony-doped SnO2 nanoparticles-decorated TiO2 composite with enhanced electrical properties

2019 ◽  
Vol 13 (01) ◽  
pp. 1951005
Author(s):  
Xue Li ◽  
Jianhua Qian ◽  
Junhua Li ◽  
Ke Tang
Keyword(s):  
Tin Dioxide ◽  
Theoretical Calculations ◽  
Sno2 Nanoparticles ◽  
Chelating Agent ◽  
Rutile Phase ◽  
Microscopic Level ◽  
Polymeric Precursor ◽  
Precursor Method ◽  
Calcination Process ◽  
Two Stages

Antimony-doped tin dioxide (ATO)-coated TiO2 (TiO2@ATO) composite was synthesized by a polymeric precursor method with lactic acid as the chelating agent. The structural and morphological characterizations of the as-fabricatied TiO2@ATO composite were investigated by XRD, FTIR, SEM, TEM and XPS. The resistivity was also examined by electrical resistance measurements. The theoretical calculations were introduced for elucidating the change of bandgap from the microscopic level. The results showed that the lowest resistivity of TiO2@ATO composite they could be achieved was 1.69 [Formula: see text]. TiO2@ATO composite possessed a core–shell structure with the ATO shell thickness of 13–16[Formula: see text]nm. The as-prepared ATO nanoparticles were in rutile phase and with 4.3–7.0[Formula: see text]nm in diameter (calcinated at 550∘C). The ATO grain growth during the calcination process could be viewed as consisting of two stages: the activation energies were calculated to be [Formula: see text][Formula: see text]kJ/mol and [Formula: see text][Formula: see text]kJ/mol, respectively.

scholarly journals Preparation and High-Throughput Testing of TiO2-Supported Co Catalysts for Fischer‒Tropsch Synthesis

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 352
Author(s):  
Christian Schulz ◽  
Peter Kolb ◽  
Dennis Krupp ◽  
Lars Ritter ◽  
Alfred Haas ◽  
...  
Keyword(s):  
High Throughput ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Tropsch Synthesis ◽  
Performance Tests ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis ◽  
Co Catalysts ◽  
Impregnation Technique ◽  
Co Conversion

A series of Co/TiO2 catalysts was tested in a parameters field study for Fischer‒Tropsch synthesis (FTS). All catalysts were prepared by the conventional impregnation technique to obtain an industrially relevant Co content of 10 wt % or 20 wt %, respectively. In summary, 10 different TiO2 of pure anatase phase, pure rutile phase, as well as mixed rutile and anatase phase were used as supports. Performance tests were conducted with a 32-fold high-throughput setup for accelerated catalyst benchmarking; thus, 48 experiments were completed within five weeks in a relevant operation parameters field (170 °C to 233.5 °C, H2/CO ratio 1 to 2.5, and 20 bar(g)). The most promising catalyst showed a CH4 selectivity of 5.3% at a relevant CO conversion of 60% and a C5+ productivity of 2.1 gC5+/(gCo h) at 207.5 °C. These TiO2-based materials were clearly differentiated with respect to the application as supports in Co-catalyzed FTS catalysis. The most prospective candidates are available for further FTS optimization at a commercial scale.

scholarly journals Unexpected Link between the Template Purification Solvent and the Structure of Titanium Dioxide Hollow Spheres

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 112
Author(s):  
Tamás Gyulavári ◽  
Kata Kovács ◽  
Klára Magyari ◽  
Kornélia Baán ◽  
Anna Szabó ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Photocatalytic Activity ◽  
Phase Composition ◽  
Anatase Phase ◽  
Hollow Spheres ◽  
Rutile Phase ◽  
Carbon Sphere ◽  
Carbon Spheres ◽  
Carbonate Species ◽  
Determining Factor

Carbon spheres were applied as templates to synthesize titanium dioxide hollow spheres. The templates were purified with either ethanol or acetone, and the effects of this treatment on the properties of the resulting titania were investigated. The photocatalytic activity of the catalysts was measured via the decomposition of phenol model pollutant under visible light irradiation. It was found that the solvent used for the purification of the carbon spheres had a surprisingly large impact on the crystal phase composition, morphology, and photocatalytic activity. Using ethanol resulted in a predominantly rutile phase titanium dioxide with regular morphology and higher photocatalytic activity (r0,phenol = 3.9 × 10−9 M∙s−1) than that containing mainly anatase phase prepared using acetone (r0,phenol = 1.2 × 10−9 M∙s−1), surpassing the photocatalytic activity of all investigated references. Based on infrared spectroscopy measurements, it was found that the carbon sphere templates had different surface properties that could result in the appearance of carbonate species in the titania lattice. The presence or absence of these species was found to be the determining factor in the development of the titania’s properties.

In Situ High-Temperature Transmission Electron Microscopy Observations of the Formation of Nanocrystalline TiC from Nanocrystalline Anatase (TiO2)

1998 ◽  
Vol 4 (3) ◽  
pp. 269-277 ◽  
Author(s):  
A. Agrawal ◽  
J. Cizeron ◽  
V.L. Colvin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Solid Phase ◽  
Anatase Phase ◽  
High Resolution Electron Microscopy ◽  
Rutile Phase ◽  
Transmission Electron ◽  
New Phase

In this work, the high-temperature behavior of nanocrystalline TiO2 is studied using in situ transmission electron microscopy (TEM). These nanoparticles are made using wet chemical techniques that generate the anatase phase of TiO2 with average grain sizes of 6 nm. X-ray diffraction studies of nanophase TiO2 indicate the material undergoes a solid-solid phase transformation to the stable rutile phase between 600° and 900°C. This phase transition is not observed in the TEM samples, which remain anatase up to temperatures as high as 1000°C. Above 1000°C, nanoparticles become mobile on the amorphous carbon grid and by 1300°C, all anatase diffraction is lost and larger (50 nm) single crystals of a new phase are present. This new phase is identified as TiC both from high-resolution electron microscopy after heat treatment and electron diffraction collected during in situ heating experiments. Video images of the particle motion in situ show the nanoparticles diffusing and interacting with the underlying grid material as the reaction from TiO2 to TiC proceeds.

Fast response acetone-sensing properties of SnO2 nanoparticles prepared by the sol-gel method

2021 ◽  
Vol 93 (3) ◽  
pp. 30401
Author(s):  
Jiaxing Wang ◽  
Hai Yu ◽  
Yong Zhang
Keyword(s):  
High Performance ◽  
Gas Sensing ◽  
Sno2 Nanoparticles ◽  
Sol Gel ◽  
Fast Response ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Short Recovery Time ◽  
Acetone Gas Detection

SnO2 nanoparticle architectures were successfully synthesized using a sol-gel method and developed for acetone gas detection. The morphology and structure of the particles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SnO2 nanoparticle architectures were configured as high-performance sensors to detect acetone and showed a very fast response time (<1 s), a short recovery time (10 s), good repeatability and high selectivity at a relatively low working temperature. Thus, SnO2 nanoparticles should be promising candidates for designing and fabricating acetone gas sensors with good gas sensing performance. The possible gas sensing mechanism is also presented.

scholarly journals Fabrication, N-doping Mechanism and Evaluation of N-doped TiO2 Thin Films Based on Laser Ablation Method

2009 ◽  
Vol 2 (1) ◽  
pp. 17-23 ◽  
Author(s):  
S. Somekawa ◽  
Y. Kusumoto ◽  
H. Yang ◽  
M. Abdulla-Al-Mamun ◽  
B. Ahmmad
Keyword(s):  
Crystal Structure ◽  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Laser Ablation ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Laser Ablation Method ◽  
Dye Decomposition ◽  
N Doping ◽  
Keywords Laser

The relation among the change of the crystal structure, the amount of doped N and the photocatalytic activity for the decomposition of methylene blue was studied. The N-doping was promoted by the change of the crystal structure from the rutile phase to the anatase phase. The photocatalytic activity for the decomposition of methylene blue was enhanced by an increase in the amount of anatase crystals and doped N. Keywords: Laser ablation; N-doping process; Crystal change; N-doped TiO2 thin film; Dye decomposition. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i1.2992        J. Sci. Res. 2 (1), 17-23 (2010) 

scholarly journals Solid Acids from Persulphated and Perchlorated Physical Mixtures of Zirconium and Titanium Hydroxides

2002 ◽  
Vol 20 (10) ◽  
pp. 977-993
Author(s):  
Gamal M.S. El Shafei ◽  
Christine A. Philip
Keyword(s):  
Tetragonal Phase ◽  
Anatase Phase ◽  
Nitrogen Adsorption ◽  
Rutile Phase ◽  
Acid Sites ◽  
Solid Acids ◽  
Monoclinic Zirconia ◽  
Anion Adsorption ◽  
Physical Mixtures ◽  
Structural Aspects

Calcination at 650°C of a physical mixture of zirconium and titanium hydroxides led to the formation of the corresponding oxides, monoclinic zirconia and anatase. The adsorption of perchlorate or persulphate anions (as 0.05, 0.1, 0.2 or 0.4 M aqueous solutions) before calcination did not inhibit crystallization; however, perchlorate anions activated the formation of rutile in addition to the predominant anatase phase. Indeed, the adsorption of perchlorated anions prior to calcination allowed the thermodynamically less stable tetragonal phase of zirconia to be detected in addition to monoclinic zirconia at ambient temperature. In contrast, the adsorption of persulphate anions before calcination stabilized the tetragonal phase with no rutile phase being detected in this case. Infrared spectroscopy showed that adsorbed S2O82– anions were held more strongly by the solid than ClO4− anions which tended to decompose when the solid was calcined. The acidities of the solid acids produced because of S2O82– or ClO4−anion adsorption were studied via the adsorption of pyridine (pKa = 5.3) from cyclohexane solution. The amounts and strengths of the acid sites formed during persulphate treatment were higher than those resulting from perchlorate adsorption. The strength of the acid sites formed on samples calcined before loading with S2O82– or ClO4− anions showed no significant differences. Variations detected in the structural aspects arising from S2O82– or ClO4− anion adsorption were reflected in the texture as assessed by nitrogen adsorption at −196°C.

Photo Catalytic Activity of Anatase TiO2/PVA Film Coated Glass Plate

2012 ◽  
Vol 584 ◽  
pp. 396-400 ◽  
Author(s):  
Aravind Naga Revuru ◽  
Nagarajan Padmavathy ◽  
Angappan Sheela ◽  
Swamiappan Sasikumar
Keyword(s):  
Methylene Blue ◽  
Dye Degradation ◽  
Anatase Phase ◽  
Glass Plate ◽  
Photocatalytic Decomposition ◽  
Blue Dye ◽  
Methylene Blue Dye ◽  
Contributing Factors ◽  
Tio2 Sample ◽  
Tlc Plates

The major cause of surface and ground water contamination is due to effluent from dyeing industries. The discharged effluent chemicals inhibit light penetration into water bodies and some are considered to be carcinogenic. In this study, the photocatalytic decomposition of the synthetic dye, methylene blue was investigated in the presence of activated TiO2. The TiO2 sample was characterized by using XRD to analyze the presence of anatase and rutile phases. The dye degradation was monitored as a change in absorbance by UV-Visible spectrophotometer. The contributing factors towards dye degradation include both the dye concentration as well as the quantity of TiO2 used. Different quantities of TiO2 in anatase phase was taken and activated under UV radiation for 15 min. and subsequently coated on to TLC plates using 5% polyvinyl alcohol as a binding agent. This photocatalytic plate was kept in the methylene blue dye solution and exposed to sunlight. The results shows that 57% of the 30ppm methylene blue dye gets degraded within 75min., when exposed to UV activated TiO2 in presence of natural sunlight.

Probing the Phase Transition in Nanocrystalline TiO2 Powders by Positron Lifetime (PAL) Technique

2011 ◽  
Vol 319-320 ◽  
pp. 151-159 ◽  
Author(s):  
E.M. Hassan ◽  
Basma A.A. Balboul ◽  
M.A. Abdel-Rahman
Keyword(s):  
Positron Annihilation ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
Positron Annihilation Lifetime ◽  
Nanocrystallite Size ◽  
Heat Treated ◽  
Degussa P25

Positron annihilation techniques (PAT) have recently been successfully employed for the characterization of phase transitions in metals and compounds. In the present study, positron annihilation lifetime (PAL) measurements have been carried out on a nanocrystalline titania (TiO2) in the form of powders that had been heat-treated at temperatures ranging from 300 to 1273K. The PAL spectra were analyzed into two lifetime components. The shorter lifetime τ1 (185-300 ps) is attributed to positron annihilation in vacancies and the longer lifetime τ1 (400-580 ps) to positrons in microviods at interfaces. The rutile phase of TiO2 powders was utilized as a reference in order to compare their behavior with the commercially supplied and widely available anatase phase (Degussa P25). The influence of the heat-treatment upon the nanostructure during the transition of the anatase to rutile phase were also investigated by X-ray diffraction (XRD), TEM and BET surface area methods. Understanding of this effect is expected to enhance our knowledge of the morphology and nanocrystallite size of TiO2 powders and their T-dependence, and hence their physical properties.

Sign in / Sign up

Export Citation Format

Share Document