Browsing by Author "Pu, Ying-Chih"

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A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities
(2014-08-07)
Lu, Yi-Hsuan
;
Lin, Wei-Hao
;
Yang, Chao-Yao
;
Chiu, Yi-Hsuan
;
Pu, Ying-Chih
An environmentally benign antisolvent method has been developed to prepare Cu2+-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu2+ ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu2+ introduction, resulting in the formation of Cu2+-doped ZnO nanocrystals. The as-prepared Cu2+-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu2+ may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu2+-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu2+. A further increase in the Cu2+ concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu2+. The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu2+-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu2+ doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems.
A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities
(2014-08-07)
Lu, Yi-Hsuan
;
Lin, Wei-Hao
;
Yang, Chao-Yao
;
Chiu, Yi-Hsuan
;
Pu, Ying-Chih
An environmentally benign antisolvent method has been developed to prepare Cu2+-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu2+ ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu2+ introduction, resulting in the formation of Cu2+-doped ZnO nanocrystals. The as-prepared Cu2+-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu2+ may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu2+-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu2+. A further increase in the Cu2+ concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu2+. The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu2+-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu2+ doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems.
Ag-Nanoparticle-Decorated SiO2 Nanospheres Exhibiting Remarkable Plasmon-Mediated Photocatalytic Properties
(2012-09-06)
Chen, Kuang-Hsiu
;
Pu, Ying-Chih
;
Chang, Kao-Der
;
Liang, Yi-Fan
;
Liu, Chia-Ming
We demonstrated for the first time that Ag-nanoparticle-decorated SiO2 nanospheres (NSs) may display noticeable photocatalytic activities upon surface plasmon resonance (SPR) excitation. The samples were prepared by reacting SiO2 NSs with AgNO3 in the seed-mediated growth process, from which the Ag particle size and decoration density can be readily controlled. The dependence of the SPR-mediated photocatalytic performance of Ag-decorated SiO2 NSs on the Ag morphology was investigated and presented. The as-prepared Ag-decorated SiO2 NSs showed a significantly red shifted and relatively broad SPR absorption when compared with the individually dispersed Ag nanoparticles. Owing to the considerably broad SPR absorption that spanned from the visible to the near-infrared region, Ag-decorated SiO2 NSs surpassed N-doped P-25 TiO2 powder and individually dispersed Ag nanoparticles in photocatalytic activity, demonstrating their potential as an active photocatalyst in nearly all the current photocatalysis applications. Furthermore, the result of performance evaluation under natural sunlight shows that the present Ag-decorated SiO2 NSs can be used as highly efficient photocatalysts that may practically harvest energy from sunlight. The current study provides a new paradigm for designing plasmonic metal nanostructures that can effectively absorb the entire solar spectrum and beyond for solar fuel generation.
Au Nanostructure-Decorated TiO2 Nanowires Exhibiting Photoactivity Across Entire UV-visible Region for Photoelectrochemical Water Splitting
(2013-08-01)
Pu, Ying-Chih
;
Wang, Gongming
;
Chang, Kao-Der
;
Ling, Yichuan
;
Lin, Yin-Kai
Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV visible light for solar fuel production.
Au-Cd1-xZnxS core-alloyed shell nanocrystals: boosting the interfacial charge dynamics by adjusting the shell composition
(2018-09-28)
Pu, Ying-Chih
;
Chen, Wei-Ta
;
Fang, Mei-Jing
;
Chen, Yu-Lin
;
Tsai, Kai-An
Au-Cd1-xZnxS core-shell nanocrystals (NCs) with controllable shell compositions (from x = 0 to x = 0.37) were synthesized by using the hot-injection method. By increasing the mole fraction of ZnS in the Cd1-xZnxS shell, the conduction band of Cd1-xZnxS can be cathodically shifted to cause an increase of energy difference between the conduction band level of the Cd1-xZnxS shell and the Fermi level of the Au core, thereby enlarging the driving force of interfacial electron transfer to enhance the photoelectrochemical (PEC) efficiency. The interfacial charge dynamics of the samples were examined by time-resolved photoluminescence (TRPL) spectroscopy. The results showed that the interfacial electron transfer rate constant (k(et)) from the Cd1-xZnxS shell to the Au core was increased by 2 orders of magnitude, from 2.41 x 10(7) to 4.91 x 10(9) s(-1) as the mole fraction of ZnS increased from 0 to 0.37. Furthermore, PEC characterization, including Mott-Schottky analysis and photovoltage decay measurements, illustrated that gradually introducing ZnS into the shell composition of Au-Cd1-xZnxS NCs can modify the band structure and enhance the effectiveness of interfacial ET for advancing the PEC properties. The practical use of Au-Cd1-xZnxS NCs in PEC methanol oxidation was also demonstrated, revealing their promising potential as viable photoelectrodes for various PEC applications. The present study delivers an alternative approach of modulating the interfacial ET dynamics of core-shell MSNs by means of shell composition adjustment. The illustrations provide an empirical guideline to the intelligent design of core-shell metal-semiconductor nanoheterostructures (MSNs) for the desired PEC applications.
Au-decorated Na(x)H(2-x)Ti(3)O(7) nanobelts exhibiting remarkable photocatalytic properties under visible-light illumination
(2010-06-18)
Pu, Ying-Chih
;
Chen, Yu-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated for the first time that Na-intercalated H(2)Ti(3)O(7) (Na(x)H(2-x)Ti(3)O(7)) NBs, prepared in the typical alkaline hydrothermal process, can effectively absorb visible light to carry out photocatalytic reactions. With the capability of effective light absorption in visible range, Na(x)H(2-x)Ti(3)O(7) NBs performed much better in the photoclegradation of thionine than the other three counterpart products including H(2)Ti(3)O(7), mixed Na(2)Ti(6)O(13)/TiO(2) and anatase TiO(2) under visible-light irradiations. As compared to the relevant commercial products like P-25 TiO(2) and Na(2)Ti(3)O(7) powders, the as-synthesized Na(x)H(2-x)Ti(3)O(7) NBs exhibited superior photocatalytic efficiency under UV illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for Na(x)H(2-x)Ti(3)O(7) NBs when Au nanoparticles of suitable amount were deposited on their surfaces. This improvement is due to the band offsets between Na(x)H(2-x)Ti(3)O(7) and Au, which may promote charge carrier separation to favor the photocatalysis. The recycling test reveals that Au-decorated Na(x)H(2-x)Ti(3)O(7) NBs could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the current Au-decorated Na(x)H(2-x)Ti(3)O(7) NBs can be used as highly efficient photocatalysts which may practically harvest energy from sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Au-decorated NaxH2-xTi3O7 nanobelts exhibiting remarkable photocatalytic properties under visible-light illumination
(2010-06-18)
Pu, Ying-Chih
;
Chen, Yu-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated for the first time that Na-intercalated H2Ti3O7 (NaxH2-xTi3O7) NBs, prepared in the typical alkaline hydrothermal process, can effectively absorb visible light to carry out photocatalytic reactions. With the capability of effective light absorption in visible range, NaxH2-xTi3O7 NBs performed much better in the photoclegradation of thionine than the other three counterpart products including H2Ti3O7, mixed Na2Ti6O13/TiO2 and anatase TiO2 under visible-light irradiations. As compared to the relevant commercial products like P-25 TiO2 and Na2Ti3O7 powders, the as-synthesized NaxH2-xTi3O7 NBs exhibited superior photocatalytic efficiency under UV illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for NaxH2-xTi3O7 NBs when Au nanoparticles of suitable amount were deposited on their surfaces. This improvement is due to the band offsets between NaxH2-xTi3O7 and Au, which may promote charge carrier separation to favor the photocatalysis. The recycling test reveals that Au-decorated NaxH2-xTi3O7 NBs could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the current Au-decorated NaxH2-xTi3O7 NBs can be used as highly efficient photocatalysts which may practically harvest energy from sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Au/ZnS core/shell nanocrystals as an efficient anode photocatalyst in direct methanol fuel cells
(2013)
Chen, Wei-Ta
;
Lin, Yin-Kai
;
Yang, Ting-Ting
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
Au/ZnS core/shell nanocrystals with controllable shell thicknesses were synthesized using a cysteine-assisted hydrothermal method. Incorporating Au/ZnS nanocrystals into the traditional Pt-catalyzed half-cell reaction led to a 43.3% increase in methanol oxidation current under light illumination, demonstrating their promising potential for metal/semiconductor hybrid nanocrystals as the anode photocatalyst in direct methanol fuel cells.
Graphene quantum dots conjugated with polymers for two-photon properties under two-photon excitation
(2016)
Kuo, Wen-Shuo
;
Hsu, Chih-Li Lilian
;
Chen, Hua-Han
;
Chang, Chia-Yuan
;
Kao, Hui-Fang
Few studies have investigated the two-photon properties of graphene quantum dots (GQDs) and GQD-conjugated polymers. The results of the present study revealed that conjugated polymers containing nitrogen and sulfur atoms caused higher quantum confinement of emissive energy to be trapped on the surface of nanomaterials, resulting in a high-photoluminescence quantum yield and notable two-photon properties. Additionally, the nanomaterials generated no reactive oxygen species-dependent oxidative stress on cells and served as promising two-photon contrast probes.
Interfacial charge carrier dynamics of cuprous oxide-reduced graphene oxide (Cu2O-rGO) nanoheterostructures and their related visible-light-driven photocatalysis
(2017-05-05)
Pu, Ying-Chih
;
Chou, Hsin-Ying
;
Kuo, Wen-Shuo
;
Wei, Kung-Hwa
;
Hsu, Yung-Jung
We demonstrated a facile and green preparation of cuprous oxide-reduced graphene oxide (Cu2O-rGO) nanoheterostructures through a photochemical reaction. The density of Cu2O nanocubes (NCs) grown on the rGO surface can be well controlled by modulating the concentration of GO employed in the reaction. Because of the relatively low potential of Fermi level of rGO, the photoexcited electrons on the conduction band (CB) of Cu2O NCs preferentially transfer to rGO, simultaneously leaVing photogenerated holes on the valence band (VB) of Cu2O, resulting in the notable charge carrier separation properties. Time-resolved photoluminescence (TRPL) spectra were collected to quantitatively analyze the electron transfer rate constant (k(cet)) between Cu2O NCs and rGO, and the dependence of the k(et) on the rGO constituent in Cu2O-rGO nanoheterostructures. Among all the samples tested, the Cu2O-rGO nanoheterostructure with the rGO constituent of 2 wt.% (denoted as Cu2O-rGO-2) displayed the largest k(et) as well as the most pronounced charge separation property. The optimized Cu2O-rGO-2 showed the best methyl orange (MO) photocatalytic degradation performance, which was highly consistent with the trend of the obtained k(et) results. As compared with relevant commercial products, such as N-doped P-25 TiO2 and commercial Cu2O powders, the Cu2O-rGO-2 exhibited superior efficiency toward MO degradation under visible light illumination, illustrating its potential for applications in relevant photodlectric conversion processes. The recycling trial showed that the Cu2O-rGO has promising potential for use in the long-term course of photocatalysis to degrade organic pollutants. Furthermore, the photo catalytic efficiency evaluated under natural sunlight demonstrated that the present Cu2O-rGO nanoheterostructure could effectively harvest the energy of solar spectrum and converted it into the chemical energy for organic pollutants degradation. The current study could provide great insights into the design of semiconductor/graphene composites which exhibit remarkable charge separation properties for practical applications in the organic pollutants photodegradation, solar fuel generation as well as photovoltaic devices. (C) 2016 Elsevier B.V. All rights reserved.
Interfacial Charge Carrier Dynamics of the Three-Component In2O3-TiO2-Pt Heterojunction System
(2012-02-02)
Chen, Yu-Chih
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The interfacial charge carrier dynamics of the three-component semiconductor semiconductor-metal heterojunction system were investigated and presented for the first time. The samples were prepared by selectively depositing Pt nanoparticles on the TiO2 surface of In2O3-decorated TiO2 nanobelts (In2O3-TiO2 nanobelts (NBs)) using the typical photodeposition method. For In2O3-TiO2 NBs, because of the difference in band structures between In2O3 and TiO2, the photoexcited electrons of In2O3 nanocrystals would preferentially transfer to TiO2 NBs to cause charge carrier separation. With the introduction of Pt on TiO2 surface, a fluent electron transfer from In2O3, through TiO2, and eventually to Pt was achieved, giving rise to the increasingly pronounced charge separation property for the as-prepared In2O3-TiO2-Pt NBs. The remarkable charge separation of the samples was revealed with the corresponding photocurrent measurements. Time-resolved photoluminescence spectra were measured to quantitatively analyze the electron transfer event between In2O3 and TiO2 for In2O3-TiO2 NBs and its dependence on Pt deposition. Upon the deposition of Pt, In2O3-TiO2 NBs showed an increased apparent electron-scavenging rate constant, fundamentally consistent with the result of their performance evaluation in photocatalysis. The current study provides a new paradigm for designing highly efficient three-component nanoheterojunction photocatalysts which can effectively produce chemical energy from absorbing light.
Luminance enhancement in quantum dot light-emitting diodes fabricated with Field's metal as the cathode
(2017-03-08)
Basilio, Carlos
;
Oliva, Jorge
;
Lopez-Luke, Tzarara
;
Pu, Ying-Chih
;
Zhang, Jin Z.
This work reports the fabrication and characterization of blue-green quantum dot light-emitting diodes (QD-LEDs) by using core/shell/shell Cd1-xZnxSe/ZnSe/ZnS quantum dots. Poly [(9,9-bis(3'-(N, N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) was introduced in order to enhance the electron injection and also acted as a protecting layer during the deposition of the cathode (a Field's metal sheet) on the organic/inorganic active layers at low temperature (63 degrees C). This procedure permitted us to eliminate the process of thermal evaporation for the deposition of metallic cathodes, which is typically used in the fabrication of OLEDs. The performance of devices made with an aluminum cathode was compared with that of devices which employed Field's metal (FM) as the cathode. We found that the luminance and efficiency of devices with FM was similar to 70% higher with respect to those that employed aluminum as the cathode and their consumption of current was similar up to 13 V. We also demonstrated that the simultaneous presence of 1,2-ethanedethiol (EDT) and PFN enhanced the luminance in our devices and improved the current injection in QD-LEDs. Hence, the architecture for QD-LEDs presented in this work could be useful for the fabrication of low-cost luminescent devices.
Modulation of charge carrier dynamics of NaxH2-xTi3O7-Au-Cu2O Z-scheme nanoheterostructures through size effect
(2015-02-01)
Pu, Ying-Chih
;
Lin, Wei-Hao
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
For the first time we presented the interfacial charge carrier dynamics for three-component semiconductor-metal-semiconductor Z-scheme nanoheterostructure system. The samples were prepared by selectively depositing a thin layer of Cu2O on the Au surface of Au nanoparticle-decorated NaxH2-xTi3O7 nanobelts (denoted as ST-Au NBs) using the photodeposition method. For ST-Au-Cu2O NB heterostructures, the embedded Au may act as carrier-transfer mediator to promote the electron transfer from the conduction band of ST to the valence band of Cu2O. This vectorial charge transfer would give rise to electron accumulation at Cu2O and hole concentration at ST, which achieved superior charge carrier separation over the two-component counterparts of ST-Au and ST-Cu2O. The quantum size effect was significant in the deposited Cu2O, which was exploited to tune the band structure of Cu2O, modulate the charge carrier dynamics of ST-Au-Cu2O NBs, and thereby enhance the resultant photocatalytic performance. Time-resolved photoluminescence spectra were measured to quantitatively analyze the electron transfer event between ST and Au for ST-Au-Cu2O NBs, which was found dependent on the Cu2O shell thickness. As the Cu2O thickness decreased, ST-Au-Cu2O NBs showed an increased electron-scavenging rate constant due to the increased driving force of electron transfer. The carrier dynamics results were fundamentally consistent with those of the performance evaluation in photocatalysis, in which ST-Au-Cu2O NBs exhibited enhanced photocatalytic efficiency as the Cu2O thickness decreased. Systematic understanding of the interfacial charge dynamics of Z-scheme mechanism shall pave the way for the realization of artificial photosynthesis by using heterogeneous photocatalysts, where the effectiveness of charge separation and the merit of high redox powers are determinant. (C) 2014 Elsevier B.V. All rights reserved.
Multicolored Cd1-xZnxSe quantum dots with type-I core/shell structure: single-step synthesis and their use as light emitting diodes
(2014)
Pu, Ying-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We developed a single-step hot-injection process to synthesize Cd1-xZnxSe quantum dots (QDs) with tunable emission wavelengths. The multiple emission colors of the Cd1-xZnxSe QDs resulted from the variation in their compositions (x value) with the reaction time. Because of the higher reactivity of the Cd precursor, QDs whose composition was rich in CdSe were generated at the beginning of the reaction. As the reaction proceeded, the later-formed ZnSe shell was simultaneously alloyed with the core, giving rise to a progressive alloying treatment for the grown QDs. During the reaction period, the emission color of the Cd1-xZnxSe QDs shifted from red to orange, to yellow, to green and finally to blue. A light emitting diode (LED) composed of multilayers of ITO/poly(3,4-ethylenedioxythiophene): poly-(4-styrenesulfonate)/poly(3-hexylthiophene) blended with Cd1-xZnxSe QDs/Al was fabricated to test the electroluminescence (EL) properties of the QDs. The EL results show high color purity for the emission from LED devices containing Cd1-xZnxSe QDs, revealing that the as-synthesized QDs can be easily processed and integrated into a light-emitting device without using a complicated procedure. The findings from the present work also demonstrate the advantage of using the current single-step synthetic approach to obtain a batch of Cd1-xZnxSe QDs that may emit different colors in prototype LEDs.
Optical Properties and Exciton Dynamics of Alloyed Core/Shell/Shell Cd1-xZnxSe/ZnSe/ZnS Quantum Dots
(2013-04-24)
Fitzmorris, Bob C.
;
Pu, Ying-Chih
;
Cooper, Jason K.
;
Lin, Yi-Fang
;
Hsu, Yung-Jung
In this study we introduce a new method for the onepot synthesis of core/shell/shell alloyed Cd1-xZnxSe/ZnSe/ZnS QDs and examine the effect of the shell coating on the optical properties and exciton dynamics of the alloy core. The photoluminescence (PL) quantum yield is greatly enhanced after shell growth, from 9.6% to 63%. The exciton dynamics were studied by time correlated single photon counting (TCSPC) and fit using integrated singular value decomposition global fitting (i-SVD-GF), which showed the biexponential observed lifetimes on the nanosecond time scale remain the same after shell growth. Using ultrafast transient absorption (TA) spectroscopy and SVD-GF, we have determined that surface passivation by ZnSe and ZnSe/ZnS shells reduces nonradiative recombination primarily on the picosecond time scale. These findings are helpful in directing the development of the next generation of QDs for biological labeling and other applications.
Studies on the annealing and antibacterial properties of the silver-embedded aluminum/silica nanospheres
(2014-06-17)
Pan, Ko-Ying
;
Chien, Chia-Hung
;
Pu, Ying-Chih
;
Liu, Chia-Ming
;
Hsu, Yung-Jung
Substantial silver-embedded aluminum/silica nanospheres with uniform diameter and morphology were successfully synthesized by sol-gel technique. After various annealing temperatures, the surface mechanisms of each sample were analyzed using scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscopy. The chemical durability examinations and antibacterial tests of each sample were also carried out for the confirmation of its practical usage. Based on the result of the above analyses, the silver-embedded aluminum/silica nanospheres are eligible for fabricating antibacterial utensils.
Studies on the photocatalysis of core-shelled SiO2-Ag nanospheres by controlled surface plasmon resonance under visible light
(2014-08-30)
Pan, Ko-Ying
;
Liang, Yi-Fan
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
;
Yeh, Jien-Wei
Abundant core-shelled silica-silver nanospheres with uniform diameter and morphology were successfully synthesized by Stober and seed-mediated method, in sequence. By the different additions of glucose, the silver nanoparticles were deposited on silica spheres by redox reaction, which well controlled in the range from 10 to 50 nm. The surface plasmon resonance absorption band shifted toward infra-red region and became broader gradually during the dimensions of silver nanoparticles were increased in the growth range. The amazing data imply that using core-shelled silica-silver nanospheres efficiently enhances the degradation of the organic pollutants under solar energy, which means the core-shelled silica-silver nanospheres is not only a cost-effective route but an energy-saving way to our planet. (C) 2014 Elsevier B.V. All rights reserved.
Studies on the photocatalysis of core-shelled SiO2-Ag nanospheres by controlled surface plasmon resonance under visible light
(2014-08-30)
Pan, Ko-Ying
;
Liang, Yi-Fan
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
;
Yeh, Jien-Wei
Abundant core-shelled silica-silver nanospheres with uniform diameter and morphology were successfully synthesized by Stober and seed-mediated method, in sequence. By the different additions of glucose, the silver nanoparticles were deposited on silica spheres by redox reaction, which well controlled in the range from 10 to 50 nm. The surface plasmon resonance absorption band shifted toward infra-red region and became broader gradually during the dimensions of silver nanoparticles were increased in the growth range. The amazing data imply that using core-shelled silica-silver nanospheres efficiently enhances the degradation of the organic pollutants under solar energy, which means the core-shelled silica-silver nanospheres is not only a cost-effective route but an energy-saving way to our planet. (C) 2014 Elsevier B.V. All rights reserved.
Surface Passivation of TiO2 Nanowires Using a Facile Precursor-Treatment Approach for Photoelectrochemical Water Oxidation
(2014-07-10)
Pu, Ying-Chih
;
Ling, Yichuan
;
Chang, Kao-Der
;
Liu, Chia-Ming
;
Zhang, Jin Z.
We developed a facile precursor-treatment approach for effective surface passivation of rutile TiO2 nanowire photoanode to improve its performance in photoelectrochernical (PEC) water oxidation. The approach was demonstrated by treating rutile TiO2 nanowires with titanium precursor solutions (TiCl4, Ti(OBu)(4), or Ti(OiP)(4)) followed by a postannealing process, which resulted in the additional deposition of anatase TiO2 layer on the nanowire surface. Compared to pristine TiO2, all the precursor-treated TiO2 nanowire electrodes exhibited a significantly enhanced photocurrent density under white light illumination. Among the three precursor-treated samples, Ti(OBu)(4)-treated TiO2 nanowires achieved the largest enhancement of photocurrent generation, which is approximately a 3-fold increase over pristine TiO2. Monochromatic incident photon-to-electron conversion efficiency (IPCE) measurements showed that the improvement of PEC performance was dominated by the enhanced photoactivity of TiO2 in the UV region. The photovoltage and electrochemical impedance spectroscopy (EIS) measurements showed that the enhanced photoactivity can be attributed to the improved charge transfer as a result of effective surface state passivation. This work demonstrates a facile, low-cost, and efficient method for preparing highly photoactive TiO2 nanowire electrodes for PEC water oxidation. This approach could also potentially be used for other photoconversion applications, such as TiO2 based dye-sensitized solar cells, as well as photocatalytic systems.
Surface Passivation of TiO2 Nanowires Using a Facile Precursor-Treatment Approach for Photoelectrochemical Water Oxidation
(2014-07-10)
Pu, Ying-Chih
;
Ling, Yichuan
;
Chang, Kao-Der
;
Liu, Chia-Ming
;
Zhang, Jin Z.
We developed a facile precursor-treatment approach for effective surface passivation of rutile TiO2 nanowire photoanode to improve its performance in photoelectrochernical (PEC) water oxidation. The approach was demonstrated by treating rutile TiO2 nanowires with titanium precursor solutions (TiCl4, Ti(OBu)(4), or Ti(OiP)(4)) followed by a postannealing process, which resulted in the additional deposition of anatase TiO2 layer on the nanowire surface. Compared to pristine TiO2, all the precursor-treated TiO2 nanowire electrodes exhibited a significantly enhanced photocurrent density under white light illumination. Among the three precursor-treated samples, Ti(OBu)(4)-treated TiO2 nanowires achieved the largest enhancement of photocurrent generation, which is approximately a 3-fold increase over pristine TiO2. Monochromatic incident photon-to-electron conversion efficiency (IPCE) measurements showed that the improvement of PEC performance was dominated by the enhanced photoactivity of TiO2 in the UV region. The photovoltage and electrochemical impedance spectroscopy (EIS) measurements showed that the enhanced photoactivity can be attributed to the improved charge transfer as a result of effective surface state passivation. This work demonstrates a facile, low-cost, and efficient method for preparing highly photoactive TiO2 nanowire electrodes for PEC water oxidation. This approach could also potentially be used for other photoconversion applications, such as TiO2 based dye-sensitized solar cells, as well as photocatalytic systems.