Ambient temperature reduction of TiO2 surface was observed through hydrogen spillover from Pd nanoparticles with a hydrogen consumption stoichiometry of 1.4 H2:Pd up to ≤2 wt%Pd loading. This ...behavior was attributed to the formation of nanoparticles exhibiting 2D behavior for ≤2 wt%Pd loading. The 2D behavior of Pd nanoparticles were further confirmed from the relative abundance of metallic Pd in 3D, deduced from hydrogen stoichiometry of β-PdHx. EPR revealed oxygen vacancy formation, operando NMR revealed facile hydrogen spillover, and CO oxidation reaction rates systematically increased for Pd ≤ 2 wt%, indicating facile exchange of hydrogen and oxygen at 2D Pd/TiO2 interfaces.
BACKGROUND This study investigated the potential effects of Injectable Platelet-Rich Fibrin (I-PRF) on root coverage of free gingival graft surgery. MATERIAL AND METHODS A total of 40 patients with ...Miller class I or II gingival recession were included. The patients who participated in this study were randomly divided into 2 groups, including the control and experiment groups. The patients in the control group were treated only with free gingival graft (FGG). The patients in the experiment group were treated with free gingival graft and injected with I-PRF as a root surface biomodification agent (FGG+I-PRF). The patients were called back after 3 months, and the amount of exposed root surface was determined and compared to the preoperative findings. RESULTS The mean initial exposed root surface was 4.7±1.49 mm for the FGG+I-PRF group, 4.1±1.07 mm for the FGG group, and 4.4±1.31 mm for all subjects. Three months after the operation, the mean root surface coverage values of the 2 groups were 3.5±1.05 and 3.9±0.78 mm in the control and experiment groups, respectively. CONCLUSIONS The findings showed that the injection of Injectable Platelet-Rich Fibrin (I-PRF) had a positive effect on root coverage in free gingival graft surgery.
Adsorption measurements of CO
2
and H
2
O over TiO
2
surfaces in dark and under illumination were carried out to reveal the ensuing bottlenecks of the initial steps of the artificial photosynthesis ...reaction. When the adsorption isotherms of both CO
2
and H
2
O were measured under illumination, the results were comparable to isotherms measured at higher temperatures in dark. This evidence is interpreted as the presence of hot spots, due to charge carrier recombination reactions. Differential heat of adsorption measurements revealed that H
2
O adsorption on TiO
2
is stronger, and with a higher coverage than that of CO
2
. Dissociation of water is an energetically uphill reaction, and the local hot spots due to charge carrier recombination in indirect bandgap semiconductors can enhance the reaction probability. At higher temperatures, higher reaction probabilities are expected and estimated by a thermodynamic analysis for water splitting reaction. The potential role of these hot spots during natural and artificial photosynthetic reactions is discussed.
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•Sample prepared by toluene had smaller crystallite size than those of stearic acid.•After heating of the samples prepared by stearic acid, Mg2Ni9Y compound appeared.•Particle size of ...the catalyst was more effective than the amount of Mg2Ni9Y phase.•MgH2 doped with toluene desorbed 1wt% more H2 than MgH2 doped with stearic acid.
Synthesizing 2Mg–9Ni–Y catalyst was investigated by mechanical alloying of Mg, Ni, and Y elemental powder mixture and subsequent heat treatment. Accordingly, effects of milling time, process control agent (PCA) type (stearic acid and toluene), and heat treatment time on the powder microstructure, phase composition, and powder morphology were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser particle size analyzer (LPSA). Results showed that particle size of the samples prepared by toluene were smaller than those of the samples prepared by stearic acid. Also, it was found that the ternary Mg2Ni9Y compound was not formed by mechanical milling alone. This intermetallic compound was partially formed after the heat treatment of ball milled powders for 8h at 800°C. Effect of toluene on powder particle was higher than that of stearic acid. According to XRD patterns, it seems that the amount of formed Mg2Ni9Y in the samples which were ball milled for 15h using stearic acid and subsequently heat treated at 800°C for 8h was more than the powders that used toluene in the same conditions. Furthermore, results of hydrogen desorption tests of MgH2 doped with 10wt% sample prepared by toluene after the desorption time of 2500s at 300°C showed that it desorbed 1wt% more hydrogen than MgH2 doped with 10wt% sample prepared by acid stearic.
Adsorption measurements of CO.sub.2 and H.sub.2O over TiO.sub.2 surfaces in dark and under illumination were carried out to reveal the ensuing bottlenecks of the initial steps of the artificial ...photosynthesis reaction. When the adsorption isotherms of both CO.sub.2 and H.sub.2O were measured under illumination, the results were comparable to isotherms measured at higher temperatures in dark. This evidence is interpreted as the presence of hot spots, due to charge carrier recombination reactions. Differential heat of adsorption measurements revealed that H.sub.2O adsorption on TiO.sub.2 is stronger, and with a higher coverage than that of CO.sub.2. Dissociation of water is an energetically uphill reaction, and the local hot spots due to charge carrier recombination in indirect bandgap semiconductors can enhance the reaction probability. At higher temperatures, higher reaction probabilities are expected and estimated by a thermodynamic analysis for water splitting reaction. The potential role of these hot spots during natural and artificial photosynthetic reactions is discussed.
Methane activation via bromination can be a feasible route with selective synthesis of mono-bromomethane. It is known that the condensation of brominated products into higher hydrocarbons can result ...in coking and deactivation in the presence of di-bromomethane. In this study, selective production of methyl bromide was investigated over sulfated ZrO
2 included SBA-15 structures. It was observed that the higher the ZrO
2 amounts the higher the conversion, while the catalyst remained >99% selective for the monobrominated methane. Over 25
mol.% ZrO
2 included SBA-15 catalyst with a BET surface area of 246
m
2/g, methane was brominated with 69% conversion at 340
°C and only CH
3Br was selectively produced.
Economical valorization of low quality, high sulfur feedstocks is an important challenge. Most of the valorization processes start from pyrolysis, with a significant amount of evolution of sulfur ...containing compounds. This study addresses in situ and downstream sulfur capture ability of lead oxide (PbO) in comparison to zinc oxide (ZnO) during the pyrolysis of high–sulfur Tuncbilek lignite. In order to assess the role of hydrogen in sulfur capture, hydrogenation experiments were also performed. Sulfidation reaction thermodynamics of PbO and ZnO was compared to most commonly used metal oxides for sulfur capture i.e., FeO, MnO, and CaO. The equilibrium conversions indicated superior performance of PbO and ZnO towards sulfidation reactions at high temperatures. Thermodynamic superiority of PbO sulfidation encouraged us to investigate the PbO as a new sulfur sorbent for hot gas desulfurization. The experimental verification of the high temperature sulfidation ability of PbO and ZnO was performed using high–sulfur Tuncbilek lignite under semibatch conditions. The final compounds formed after each process were observed by X-ray diffractometer (XRD) and Diffuse Reflectance Infrared Fourier Transformation Spectroscopy (DRIFTS). Experiments revealed that PbO can be promising candidate as hot gas sulfur trap during pyrolysis and hydrogenation processes, while ZnO can hold up sulfur only in the presence of hydrogen. Furthermore, both PbO and ZnO show the superior sulfur capture performance in the presence of hydrogen when they were used as adsorbents located after the reactor (downstream) at ambient conditions.
•Pb and Zn oxides are thermodynamically favorable sulfur traps during pyrolysis and hydrogenation of lignite.•PbO can capture sulfur during both pyrolysis and hydrogenation processes.•ZnO sulfidation can only be possible under hydrogenation conditions in the temperature range of 40 °C −800 °C.
A low field benchtop electron spin resonance (ESR) (also referred to as electron paramagnetic resonance (EPR)) spectrometer is used to reveal paramagnetic centres such as oxygen vacancies and Ti
+3
...centres over 0.5%Pd/TiO
2
. The measurement was performed at room temperature after the sample was reduced
in situ
under mild hydrogen pressures and evacuated to P < 10
−6
Torr. The measurement was possible due to a T
1
compensation effect under vacuum: Correlation times at low pressures enabled sufficient line narrowing and detection of the ESR signal, justifying a method using benchtop spectrometers coupled to vacuum manifolds. The method justification was demonstrated using similar measurements performed on a reference compound, Mn(II) in plasticine: a measurement performed by saturation recovery technique revealed that T
1
of the signal due to Mn(II) was smaller in vacuum than its atmosphere exposed counterpart. By applying vacuum, the ESR spectra of 0.5%Pd/TiO
2
were collected at ambient temperatures, with features equivalent to the published data obtained at cryogenic temperatures.
In this study, the effects of dead volume and sweep gas flow rate on photocatalytic hydrogen production over Pt/TiO2 were examined to determine their possible impact on hydrogen production rates. ...Five different dead volumes (15, 45, 75, 190, 425 ml) under constant reaction solution and interfacial area experimented by using custom made reactors. It was found that higher dead volumes in the gas phase inversely affect the measured hydrogen production. The difference between highest and lowest H2 production rates (at steady state) among five dead volumes is found as 30 μmol/h gcat which is 24% of the highest rate. On the other hand, the difference due to sweep gas flow rates (15, 30, 45 ml/min Ar) was not as significant. It was concluded from these results that measured hydrogen production rate in photocatalytic systems depend strongly on the reactor size through gas phase dead volume and operational factors like sweep gas flowrate. The difference between highest and lowest hydrogen production rates for different dead volumes or sweep gas flow rates is too great to ignore when the average photocatalytic hydrogen production levels (∼500 μmol/h gcat) in the literature are considered. Uncertainties associated with these factors together with well-known difficulties in measurement (or reporting) of the amount of energy and the characteristics of light absorbed by the reaction solution make the comparison of results from different studies impossible. The results of this study confirm the need for standard protocols of measurement and testing in the photocatalysis field in general, and photocatalytic hydrogen production particularly.
•Transport bottlenecks during photocatalytic hydrogen production are reported.•Mass transfer between the gas and liquid phases depend on sweep gas flow rate.•Dead volume above liquid affects gas holdup & G-L interface concentration gradient.•Position of light source strongly influences incident light flux at reactive zone.•Data must be reported with gas volume, liquid volume, sweep rate & light flux.
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