The Experts below are selected from a list of 33669 Experts worldwide ranked by ideXlab platform
Chongwu Zhou - One of the best experts on this subject based on the ideXlab platform.
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toward optimized Light Utilization in nanowire arrays using scalable nanosphere lithography and selected area growth
Nano Letters, 2012Co-Authors: Anuj R Madaria, Ningfeng Huang, Ruijuan Li, Michelle L Povinelli, Daniel P Dapkus, Chongwu ZhouAbstract:Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal–organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show th...
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toward optimized Light Utilization in nanowire arrays using scalable nanosphere lithography and selected area growth
Nano Letters, 2012Co-Authors: Anuj R Madaria, Ningfeng Huang, Michelle L Povinelli, Daniel P Dapkus, Maoqing Yao, Chunyung Chi, Chenxi Lin, Chongwu ZhouAbstract:Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal-organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show that GaAs nanowires as short as 130 nm show reflection of <10% over the visible range of the solar spectrum. Our results indicate that a highly ordered nanowire structure is not necessary: despite the "defects" present in NSL-patterned nanowire arrays, their optical performance is similar to "defect-free" structures patterned by more costly, time-consuming EBL methods. Our scalable approach for synthesis of vertical semiconducting nanowires can have application in high-throughput and low-cost optoelectronic devices, including solar cells.
Wonyong Choi - One of the best experts on this subject based on the ideXlab platform.
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status and challenges in photocatalytic nanotechnology for cleaning air polluted with volatile organic compounds visible Light Utilization and catalyst deactivation
Environmental science. Nano, 2019Co-Authors: Seunghyun Weon, Wonyong ChoiAbstract:Photocatalysis that utilizes semiconductor nanoparticles is one of the most investigated environmental nanotechnologies. It is a promising technology for air purification because it can decompose gaseous pollutants (particularly volatile organic compounds (VOCs)) directly into harmless CO2 and H2O under ambient conditions. Photocatalysis can be particularly suitable for removing low concentration pollutants (sub-ppm levels) in indoor environments where conventional adsorption technologies are not very efficient. Although photocatalytic air purification has been extensively investigated, it still falls far short of satisfying the requirements for practical usage. This review focuses on two main critical issues for improving the applicability of photocatalytic air purification: (1) increasing visible Light activity to utilize ambient Light and (2) preventing catalyst deactivation that hinders long-term usage of photocatalysts. Literature reports on the photocatalytic degradation of VOCs using visible Light are surveyed and systematically categorized based on the type of photocatalytic materials and VOCs. Strategies taken to significantly increase the efficiency of visible Light photocatalysts are introduced. On the other hand, photocatalyst deactivation processes are discussed according to the kinds of air pollutants, and various methods of assessing the extent of photocatalyst deactivation are outlined. The development of deactivation-resistant photocatalysts and their applications to air purification are also introduced and discussed. Finally, the status and the problems of the current research on photocatalytic air purification are critically discussed and suggestions for future studies of photocatalytic air purification are made.
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Polymeric Carbon Nitride with Localized Aluminum Coordination Sites as a Durable and Efficient Photocatalyst for Visible Light Utilization
ACS Catalysis, 2018Co-Authors: Chi Hun Choi, Xinchen Wang, Wonyong ChoiAbstract:The development of efficient and yet economic photocatalysts that can utilize solar Light is crucial for the sustainable future. We report a simple approach to introduce a bidentate type of metal coordination site in polymeric carbon nitride (PCN) by an in situ keto–enol cyclization route of acetylacetone and urea to incorporate a metal chelating pyrimidine derivative into the molecular framework of PCN. The resulting new metal coordination sites provide both N- and O-complexing ligands unlike the unmodified PCN that has N-ligands only. As a proof-of-concept experiment, we introduced Al3+ ions into these coordination sites, which induced significant enhancements in visible Light photocatalytic activities for organic pollutant degradation and H2 evolution as compared to those of bulk PCN and the conventional “nitrogen pot” metal-coordinated PCN. The optimized Al loading was as low as 0.32 wt %. The photocatalytic activities sensitively depended on the Al incorporation, and the Al-incorporated sample demons...
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Polymeric Carbon Nitride with Localized Aluminum Coordination Sites as a Durable and Efficient Photocatalyst for Visible Light Utilization
2018Co-Authors: Chi Hun Choi, Xinchen Wang, Lihua Lin, Suji Gim, Shinbi Lee, Hyungjun Kim, Wonyong ChoiAbstract:The development of efficient and yet economic photocatalysts that can utilize solar Light is crucial for the sustainable future. We report a simple approach to introduce a bidentate type of metal coordination site in polymeric carbon nitride (PCN) by an in situ keto–enol cyclization route of acetylacetone and urea to incorporate a metal chelating pyrimidine derivative into the molecular framework of PCN. The resulting new metal coordination sites provide both N- and O-complexing ligands unlike the unmodified PCN that has N-ligands only. As a proof-of-concept experiment, we introduced Al3+ ions into these coordination sites, which induced significant enhancements in visible Light photocatalytic activities for organic pollutant degradation and H2 evolution as compared to those of bulk PCN and the conventional “nitrogen pot” metal-coordinated PCN. The optimized Al loading was as low as 0.32 wt %. The photocatalytic activities sensitively depended on the Al incorporation, and the Al-incorporated sample demonstrated an excellent stability in water with showing little sign of metal leaching. While the aluminum ions complexed in the nitrogen pot little influenced the photocatalytic activity, Al3+ ions complexed by both N and O ligands in the alternative coordination sites significantly enhanced the photocatalytic activity of PCN. This study demonstrates a facile and scalable synthesis of PCN with alternative metal coordination sites for efficient solar energy conversion
Shichao Liao - One of the best experts on this subject based on the ideXlab platform.
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biomimetic electron transport via multiredox shuttles from photosystem ii to a photoelectrochemical cell for solar water splitting
Energy and Environmental Science, 2017Co-Authors: Wangyin Wang, Chunmei Ding, Zhiliang Wang, Shichao LiaoAbstract:A bio-hybrid system integrating photosystem II (PSII) with artificial photocatalysts is considered as a platform to understand the solar-to-chemical energy conversion process. However, the electron transfer from PSII to artificial components remains inefficient, which hinders the favorable conversion performance. Herein, a CdS–PSII hybrid photoelectrochemical (PEC) cell is proposed for overall water splitting, where PSII and the CdS-based PEC cell are connected by an ordered multi-step electron transfer pathway comprising two redox shuttles quinone/hydroquinone and ferricyanide/ferrocyanide coupled by a graphite-based galvanic cell. The hybrid system allows overall water splitting with 8.5 μmol O2 h−1 and 17.7 μmol H2 h−1 under simulated solar Light, corresponding to a solar-to-hydrogen efficiency of 0.34%. Moreover, the tandem Light absorption from CdS to PSII both improves the Light Utilization efficiency and prolongs the lifetime of PSII. This work may inspire new approaches to achieve Z-scheme water splitting in the field of artificial photosynthesis.
Anuj R Madaria - One of the best experts on this subject based on the ideXlab platform.
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toward optimized Light Utilization in nanowire arrays using scalable nanosphere lithography and selected area growth
Nano Letters, 2012Co-Authors: Anuj R Madaria, Ningfeng Huang, Ruijuan Li, Michelle L Povinelli, Daniel P Dapkus, Chongwu ZhouAbstract:Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal–organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show th...
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toward optimized Light Utilization in nanowire arrays using scalable nanosphere lithography and selected area growth
Nano Letters, 2012Co-Authors: Anuj R Madaria, Ningfeng Huang, Michelle L Povinelli, Daniel P Dapkus, Maoqing Yao, Chunyung Chi, Chenxi Lin, Chongwu ZhouAbstract:Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal-organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show that GaAs nanowires as short as 130 nm show reflection of <10% over the visible range of the solar spectrum. Our results indicate that a highly ordered nanowire structure is not necessary: despite the "defects" present in NSL-patterned nanowire arrays, their optical performance is similar to "defect-free" structures patterned by more costly, time-consuming EBL methods. Our scalable approach for synthesis of vertical semiconducting nanowires can have application in high-throughput and low-cost optoelectronic devices, including solar cells.
Shuyan Song - One of the best experts on this subject based on the ideXlab platform.
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preparation of carbon rich g c3n4 nanosheets with enhanced visible Light Utilization for efficient photocatalytic hydrogen production
Small, 2017Co-Authors: Man Yang, Yan Xing, Xianchun Liu, Yang Yang, Xiao Wang, Shuyan SongAbstract:Exfoliation of layered bulk g-C3N4 (CNB) to thin g-C3N4 sheets in nanodomains has attracted much attention in photocatalysis because of the intriguing properties of nanoscaled g-C3N4. This study shows that carbon-rich g-C3N4 nanosheets (CNSC) can be easily prepared by self-modification of polymeric melon units through successively thermally treating bulk g-C3N4 in an air and N2 atmosphere. The prepared CNSC not only retain the outstanding properties of nanosheets, such as large surface area, high aspect ratios, and short charges diffusion distance, but also overcome the drawback of enlarged bandgap caused by the quantum size effect, resulting in an enhanced Utilization of visible Light and photoinduced electron delocalization ability. Therefore, the as-prepared CNSC show a high hydrogen evolution rate of 39.6 µmol h−1 with a turnover number of 24.98 in 1 h at λ > 400 nm. Under irradiation by longer wavelength of Light (λ > 420 nm), CNSC still exhibit a superior hydrogen evolution rate, which is 72.9 and 5.4 times higher than that of bulk g-C3N4 and g-C3N4 nanosheets, respectively.