In situ picosecond transient diffuse reflectance spectroscopy of opaque TiO2 systems under microwave irradiation and influence of oxygen vacancies on the UV-driven/microwave-assisted TiO2 photocatalysis

Horikoshi, Satoshi; Tsutsumi, Hideya; Matsuzaki, Hiroyuki; Furube, Akihiro; Emeline, Alexei V.; Serpone, Nick

doi:10.1039/c4tc02748e

Cited by 31 publications

(21 citation statements)

References 55 publications

(70 reference statements)

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“…The next question is, where does the microwave affect Evonik P25 TiO2 particles? Transient decay kinetics at 550 nm for all three samples were determined in situ using a 150 ps Nd-YAG pulsed laser system (10 Hz) and a Xe flash lamp (2 ms pulses) probe while samples were being microwave-irradiated (2.45 GHz) [26] (Figure 4). The transient(s) absorbing at the probe wavelength displayed double exponential decay kinetics: a fast decay that occurred within ca.…”

Section: Coupled Microwave/photoassisted Methods For Environmental Rementioning

confidence: 99%

“…To achieve some of the above points, we have examined photocatalyzed reactions enhanced by microwaves for nearly two decades during which we demonstrated the microwave effect by simultaneously irradiating the metal-oxide photocatalyst TiO2 with UV light and microwave radiation in reactions taking place during wastewater treatments, something that could not and cannot be achieved by conventional heating [7]. As a non-thermal effect, the microwave effect in photocatalyzed reactions was demonstrated by establishing that the lifetime and utilization efficiency of electrons excited by UV light in the photocatalyst are enhanced by the microwave radiation [8]. Other researchers have also investigated such phenomena.…”

Section: Introductionmentioning

confidence: 93%

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Elucidation of Electromagnetic Wave Effect and Outgoing of Future Trend in Microwave Chemistry and Biology

Horikoshi¹

2019

Proceedings 17th International Conference on Microwave and High Frequency Heating

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The German chemist Theodor Grotthuss was the first to formulate the first law of photochemistry in 1817; he postulated that a reaction could be driven by light when the energy of light is absorbed by molecules [1]. After that, photochemistry has greatly contributed to the development of photography. In addition, second laws of photochemistry (Stark-Einstein law) was enacted, and these two laws have elevated photochemistry as an academic (science) discipline over the last one hundred years. In addition, because of advances in light sources and various devices (engineering), such materials and processes as photocatalysts, organic solar cells, photopolymerization, quantum dots, and photochromism (among others) are currently being applied in various other fields. The next significant surge in chemistry is microwave chemistry wherein microwaves, which represent electromagnetic waves other than light, were introduced as a driving force in the chemical reaction domain in the late 1980s. There are three characteristics in this chemistry when using microwaves. The first is the high heating efficiency caused by the energy of the microwaves that directly reach and are absorbed by the substance. The second is the selectivity with which a specific substrate is heated, while the third characteristic is the enhancement of chemical syntheses by the microwaves’ electromagnetic wave energy, often referred to as the microwave effect (or non-thermal effect). The phenomenon of the microwave effect (third characteristic) impacting chemical reactions has been summarized in much of the relevant literature, however, the reason why the microwave effect has not been clarified to anyone’s satisfaction is that the term microwave effect in microwave chemistry includes numerous factors. In order to fix microwaves in the chemical field, it is urgent to develop laws of “microwavechemistry”, and to do it is necessary to systematization against the phenomenas of electromagnetic waves for materials and reactions. One of the reasons for the dramatic growth in photochemistry is the development of high power laser technology. In recent years, coherent semiconductor generator with the generating high power microwaves have become easy to get, so “microwavechemistry” can proceed to the next stage. We examined that the phenomena as microwave electromagnetic waves in chemical reactions by using a semiconductor generator and a power sensor. And, it clarified that the reaction rate and yield of a very small part of the chemical reaction change with the unique phenomenon to electromagnetic waves [2]. On the other hand, generally, as plants, enzymes, biological substances temperature rises, it inhibits growth and reaction. This phenomenon was used to overcome the electromagnetic wave effect. We have succeeded in improving these activities by irradiating weak microwaves which do not increase these temperatures [3]. If microwave heating is given to them, it will work negatively. In this invited presentation, it introduces the possibility of electromagnetic wave effect(s) in these and explain its industrial application.

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Section: Coupled Microwave/photoassisted Methods For Environmental Rementioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

Elucidation of Electromagnetic Wave Effect and Outgoing of Future Trend in Microwave Chemistry and Biology

Horikoshi¹

2019

Proceedings 17th International Conference on Microwave and High Frequency Heating

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“…We reported that this new MDEL is effective for the disinfection E. coli of water and the decomposition of 2,4-dichlorophenoxyacetic acid 2,4-D in water 16 . We have also reported that photocatalytic TiO 2 oxidation reaction significantly improved when the photocatalyst is simultaneously irradiated by microwaves and UV light 17 because electron transfer inside the TiO 2 photocatalyst is optically optimized by microwaves 18 . Therefore, when MDELs are used as the light source, microwave and ultraviolet rays can be simultaneously used to irradiate the photocatalyst so that an enhanced decomposition of wastewater can be obtained with a simple apparatus 7 .…”

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confidence: 90%

Microwave Discharge Electrodeless Lamps (MDELs). Part XI. Photolytic, Chemical Oxidation, and Photocatalytic Treatment of Aqueous Urea Solution with a Novel MDEL Photoreactor

2018

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Decomposition of urea in aqueous solution was carried out using a microwave discharge electrodeless lamp (MDEL) consisting of two photoreactors with a triple tube structure that generate vacuum-UV/UV light and reactive oxygen species (ROS) using microwaves (MW) as an energy source. The rate of decomposition of urea was highest under acidic conditions (pH 4) compared with those at pH 7 and 10. When used in combination with dispersed TiO, a photocatalyst, high decomposition efficiency was achieved with less power consumption. Moreover, decomposition efficiency more than two times higher than that of ozone oxidation and sodium hypochlorite oxidation could be realized.

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“…According to Horikoshi and Serpone 23 , the crystal distortion of P25 is significant enough that the resonance of the microwaves with P25 titania stimulates electron transfer within the photocatalyst when exposed to microwave radiation 24,25 . To confirm this hypothesis, an experiment was devised in which pure anatase and pure rutile were mixed in a proportion of 80/20 same as with the anatase/ rutile ratio of P25 in water for 2 h, and sonicated at high frequency in an ultrasound bath for 30 min at 35 .…”

Section: Wettability Efficiency With the Microwave-/photoassisted Metmentioning

confidence: 99%

Microwave-/UV-assisted Enhancement of the Wettability of Photoactive TiO2 Substrates Coated on an Inactive Ti/i-TiO2 Base

et al. 2019

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In situ picosecond transient diffuse reflectance spectroscopy of opaque TiO₂ systems under microwave irradiation and influence of oxygen vacancies on the UV-driven/microwave-assisted TiO₂ photocatalysis

Abstract: Effect of microwave radiation on pristine TiO2 and oxygen-vacancy rich titania, Vo-TiO2.

Cited by 31 publications

References 55 publications

Elucidation of Electromagnetic Wave Effect and Outgoing of Future Trend in Microwave Chemistry and Biology

Elucidation of Electromagnetic Wave Effect and Outgoing of Future Trend in Microwave Chemistry and Biology

Microwave Discharge Electrodeless Lamps (MDELs). Part XI. Photolytic, Chemical Oxidation, and Photocatalytic Treatment of Aqueous Urea Solution with a Novel MDEL Photoreactor

Microwave-/UV-assisted Enhancement of the Wettability of Photoactive TiO<sub>2</sub> Substrates Coated on an Inactive Ti/i-TiO<sub>2</sub> Base

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