共查询到20条相似文献,搜索用时 15 毫秒
1.
Yiseul Park N. Jiten Singh Dr. Kwang S. Kim Prof. Dr. Takashi Tachikawa Dr. Tetsuro Majima Prof. Dr. Wonyong Choi Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10843-10850
The development of visible‐light‐active photocatalysts is being investigated through various approaches. In this study, C60‐based sensitized photocatalysis that works through the charge transfer (CT) mechanism is proposed and tested as a new approach. By employing the water‐soluble fullerol (C60(OH)x) instead of C60, we demonstrate that the adsorbed fullerol activates TiO2 under visible‐light irradiation through the “surface–complex CT” mechanism, which is largely absent in the C60/TiO2 system. Although fullerene and its derivatives have often been utilized in TiO2‐based photochemical conversion systems as an electron transfer relay, their successful photocatalytic application as a visible‐light sensitizer of TiO2 is not well established. Fullerol/TiO2 exhibits marked visible photocatalytic activity not only for the redox conversion of 4‐chlorophenol, I?, and CrVI, but also for H2 production. The photoelectrode of fullerol/TiO2 also generates an enhanced anodic photocurrent under visible light as compared with the electrodes of bare TiO2 and C60/TiO2, which confirms that the visible‐light‐induced electron transfer from fullerol to TiO2 is particularly enhanced. The surface complexation of fullerol/TiO2 induced a visible absorption band around 400–500 nm, which was extinguished when the adsorption of fullerol was inhibited by fluorination of the surface of TiO2. The transient absorption spectroscopic measurement gave an absorption spectrum ascribed to fullerol radical cations (fullerol.+) the generation of which should be accompanied by the proposed CT. The theoretical calculation regarding the absorption spectra for the (TiO2 cluster+fullerol) model also confirmed the proposed CT, which involves excitation from HOMO (fullerol) to LUMO (TiO2 cluster) as the origin of the visible‐light absorption. 相似文献
2.
Dr. Baoshun Liu Dr. Xuelei Wang Dr. Liping Wen Prof. Dr. Xiujian Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10751-10759
The in situ open‐circuit voltages (Voc) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO2 under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO2 and from the methanol molecule. The electron injection from methanol to TiO2 is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO2 surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO2 leads to the upshift of the Fermi level of electrons in TiO2, which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano‐TiO2 is continuously changing during photocatalysis as electrons are injected from methanol to TiO2. Combined with the apparent Langmuir–Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO2 CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of Voc with time during photocatalysis. 相似文献
3.
Production of Hydrogen by Glycerol Photoreforming Using Binary Nitrogen–Metal‐Promoted N‐M‐TiO2 Photocatalysts 下载免费PDF全文
The need for renewable energy focuses attention on hydrogen obtained by using sustainable and green methods. The sustainable compound glycerol can be used for hydrogen production by heterogeneous photocatalysis. A novel approach involves the promotion of the TiO2 photocatalyst with a binary combination of nitrogen and transition metal. We report the synthesis and spectroscopic characterization of the new N‐M‐TiO2 photocatalysts (M=none, Cr, Co, Ni, Cu), and the photocatalytic reforming of glycerol to hydrogen under ambient conditions and near‐UV or visible light versus benchmark P25 TiO2. In units of activity μmol m?2 h?1, N‐Ni‐TiO2 is five‐fold more active than P25, and N‐Cu‐TiO2 is 44‐fold more active. The photocatalytic activity of N‐M‐TiO2 increases from Cr to Co and Ni, whereas the photoluminescence decreases; the change in activity is due to the modulation of charge recombination. 相似文献
4.
Pengfei Wang Yueshuang Mao Lina Li Zhurui Shen Xiao Luo Kaifeng Wu Pengfei An Haitao Wang Lina Su Yi Li Sihui Zhan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11451-11456
A highly efficient Z‐scheme photocatalytic system constructed with 1D CdS and 2D CoS2 exhibited high photocatalytic hydrogen‐evolution activity of 5.54 mmol h?1 g?1 with an apparent quantum efficiency of 10.2 % at 420 nm. More importantly, its interfacial charge migration pathway was unraveled: The electrons are efficiently transferred from CdS to CoS2 through a transition atomic layer connected by Co–S5.8 coordination, thus resulting in more photogenerated carriers participating in surface reactions. Furthermore, the charge‐trapping and charge‐transfer processes were investigated by transient absorption spectroscopy, which gave an estimated charge‐separation yield of approximately 91.5 % and a charge‐separated‐state lifetime of approximately (5.2±0.5) ns in CdS/CoS2. This study elucidates the key role of interfacial atomic layers in heterojunctions and will facilitate the development of more efficient Z‐scheme photocatalytic systems. 相似文献
5.
Yi‐Tao Liu Xingxing Chen Jianyong Yu Bin Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19079-19083
Developing noble‐metal‐free electrocatalysts is important to industrially viable ammonia synthesis through the nitrogen reduction reaction (NRR). However, the present transition‐metal electrocatalysts still suffer from low activity and Faradaic efficiency due to poor interfacial reaction kinetics. Herein, an interface‐engineered heterojunction, composed of CoS nanosheets anchored on a TiO2 nanofibrous membrane, is developed. The TiO2 nanofibrous membrane can uniformly confine the CoS nanosheets against agglomeration, and contribute substantially to the NRR performance. The intimate coupling between CoS and TiO2 enables easy charge transfer, resulting in fast reaction kinetics at the heterointerface. The conductivity and structural integrity of the heterojunction are further enhanced by carbon nanoplating. The resulting C@CoS@TiO2 electrocatalyst achieves a high ammonia yield (8.09×10?10 mol s?1 cm?2) and Faradaic efficiency (28.6 %), as well as long‐term durability. 相似文献
6.
Prolonged Hot Electron Dynamics in Plasmonic‐Metal/Semiconductor Heterostructures with Implications for Solar Photocatalysis 下载免费PDF全文
Joseph S. DuChene Brendan C. Sweeny Dr. Aaron C. Johnston‐Peck Dr. Dong Su Dr. Eric A. Stach Prof. Dr. Wei David Wei 《Angewandte Chemie (International ed. in English)》2014,53(30):7887-7891
Ideal solar‐to‐fuel photocatalysts must effectively harvest sunlight to generate significant quantities of long‐lived charge carriers necessary for chemical reactions. Here we demonstrate the merits of augmenting traditional photoelectrochemical cells with plasmonic nanoparticles to satisfy these daunting photocatalytic requirements. Electrochemical techniques were employed to elucidate the mechanics of plasmon‐mediated electron transfer within Au/TiO2 heterostructures under visible‐light (λ>515 nm) irradiation in solution. Significantly, we discovered that these transferred electrons displayed excited‐state lifetimes two orders of magnitude longer than those of electrons photogenerated directly within TiO2 via UV excitation. These long‐lived electrons further enable visible‐light‐driven H2 evolution from water, heralding a new photocatalytic paradigm for solar energy conversion. 相似文献
7.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(3):819-823
Redox‐inactive metal ions are one of the most important co‐factors involved in dioxygen activation and formation reactions by metalloenzymes. In this study, we have shown that the logarithm of the rate constants of electron‐transfer and C−H bond activation reactions by nonheme iron(III)–peroxo complexes binding redox‐inactive metal ions, [(TMC)FeIII(O2)]+‐Mn + (Mn +=Sc3+, Y3+, Lu3+, and La3+), increases linearly with the increase of the Lewis acidity of the redox‐inactive metal ions (ΔE ), which is determined from the gzz values of EPR spectra of O2.−‐Mn + complexes. In contrast, the logarithm of the rate constants of the [(TMC)FeIII(O2)]+‐Mn + complexes in nucleophilic reactions with aldehydes decreases linearly as the ΔE value increases. Thus, the Lewis acidity of the redox‐inactive metal ions bound to the mononuclear nonheme iron(III)–peroxo complex modulates the reactivity of the [(TMC)FeIII(O2)]+‐Mn + complexes in electron‐transfer, electrophilic, and nucleophilic reactions. 相似文献
8.
Kyle A. Mandla Michael L. Neville Curtis E. Moore Arnold L. Rheingold Joshua S. Figueroa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15473-15477
Relative to other cyclic poly‐phosphorus species (that is, cyclo‐Pn), the planar cyclo‐P4 group is unique in its requirement of two additional electrons to achieve aromaticity. These electrons are supplied from one or more metal centers. However, the degree of charge transfer is dependent on the nature of the metal fragment. Unique examples of dianionic mononuclear η4‐P4 complexes are presented that can be viewed as the simple coordination of the [cyclo‐P4]2? dianion to a neutral metal fragment. Treatment of the neutral, molybdenum cyclo‐P4 complexes Mo(η4‐P4)I2(CO)(CNArDipp2)2 and Mo(η4‐P4)(CO)2(CNArDipp2)2 with KC8 produces the dianionic, three‐legged piano stool complexes, [Mo(η4‐P4)(CO)(CNArDipp2)2]2? and [Mo(η4‐P4)(CO)2(CNArDipp2)]2?, respectively. Structural, spectroscopic, and computational studies reveal a similarity to the classic η6‐benzene complex (η6‐C6H6)Mo(CO)3 regarding the metal‐center valence state and electronic population of the planar‐cyclic ligand π system. 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(49):15756-15760
The M1 form of vanadium dioxide, which exhibits a reversible insulator–metal transition above room temperature, has been incorporated into nanoscale heterostructures through solution‐phase epitaxial growth on the tips of rutile TiO2 nanorods. Four distinct classes of VO2‐TiO2‐VO2 nanorod heterostructures are accessible by modulating the growth conditions. Each type of VO2‐TiO2‐VO2 nanostructure has a different insulator–metal transition temperature that depends on the VO2 domain sizes and the TiO2‐VO2 interfacial strain characteristics. 相似文献
10.
Qingbing Xia Yang Huang Jin Xiao Lei Wang Zeheng Lin Weijie Li Hui Liu Qinfen Gu Hua Kun Liu Shu‐Lei Chou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4062-4066
Structural modulation and surface engineering have remarkable advantages for fast and efficient charge storage. Herein, we present a phosphorus modulation strategy which simultaneously realizes surface structural disorder with interior atomic‐level P‐doping to boost the Na+ storage kinetics of TiO2. It is found that the P‐modulated TiO2 nanocrystals exhibit a favourable electronic structure, and enhanced structural stability, Na+ transfer kinetics, as well as surface electrochemical reactivity, resulting in a genuine zero‐strain characteristic with only approximately 0.1 % volume variation during Na+ insertion/extraction, and exceptional Na+ storage performance including an ultrahigh rate capability of 210 mAh g?1 at 50 C and a strong long‐term cycling stability without significant capacity decay up to 5000 cycles at 30 C. 相似文献
11.
Mapping of the Photoinduced Electron Traps in TiO2 by Picosecond X‐ray Absorption Spectroscopy 下载免费PDF全文
Dr. M. Hannelore Rittmann‐Frank Dr. Chris J. Milne Dr. Jochen Rittmann Dr. Marco Reinhard Dr. Thomas J. Penfold Prof. Majed Chergui 《Angewandte Chemie (International ed. in English)》2014,53(23):5858-5862
Titanium dioxide (TiO2) is the most popular material for applications in solar‐energy conversion and photocatalysis, both of which rely on the creation, transport, and trapping of charges (holes and electrons). The nature and lifetime of electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X‐ray absorption spectroscopy at the Ti K‐edge and the Ru L3‐edge to address this issue for photoexcited bare and N719‐dye‐sensitized anatase and amorphous TiO2 nanoparticles. Our results show that 100 ps after photoexcitation, the electrons are trapped deep in the defect‐rich surface shell in the case of anatase TiO2, whereas they are inside the bulk in the case of amorphous TiO2. In the case of dye‐sensitized anatase or amorphous TiO2, the electrons are trapped at the outer surface. Only two traps were identified in all cases, with lifetimes in the range of nanoseconds to tens of nanoseconds. 相似文献
12.
Constructing Ordered Three‐Dimensional TiO2 Channels for Enhanced Visible‐Light Photocatalytic Performance in CO2 Conversion Induced by Au Nanoparticles 下载免费PDF全文
Dr. Hairong Xue Prof. Dr. Tao Wang Hao Gong Hu Guo Xiaoli Fan Bin Gao Yaya Feng Prof. Dr. Xianguang Meng Prof. Dr. Xianli Huang Prof. Dr. Jianping He 《化学:亚洲杂志》2018,13(5):577-583
As a typical photocatalyst for CO2 reduction, practical applications of TiO2 still suffer from low photocatalytic efficiency and limited visible‐light absorption. Herein, a novel Au‐nanoparticle (NP)‐decorated ordered mesoporous TiO2 (OMT) composite (OMT‐Au) was successfully fabricated, in which Au NPs were uniformly dispersed on the OMT. Due to the surface plasmon resonance (SPR) effect derived from the excited Au NPs, the TiO2 shows high photocatalytic performance for CO2 reduction under visible light. The ordered mesoporous TiO2 exhibits superior material and structure, with a high surface area that offers more catalytically active sites. More importantly, the three‐dimensional transport channels ensure the smooth flow of gas molecules, highly efficient CO2 adsorption, and the fast and steady transmission of hot electrons excited from the Au NPs, which lead to a further improvement in the photocatalytic performance. These results highlight the possibility of improving the photocatalysis for CO2 reduction under visible light by constructing OMT‐based Au‐SPR‐induced photocatalysts. 相似文献
13.
Aleksandr Savateev Nadezda V. Tarakina Volker Strauss Tanveer Hussain Katharina ten Brummelhuis Jos Manuel Snchez Vadillo Yevheniia Markushyna Stefano Mazzanti Alexander P. Tyutyunnik Ralf Walczak Martin Oschatz Dirk M. Guldi Amir Karton Markus Antonietti 《Angewandte Chemie (International ed. in English)》2020,59(35):15061-15068
Polymeric carbon nitride materials have been used in numerous light‐to‐energy conversion applications ranging from photocatalysis to optoelectronics. For a new application and modelling, we first refined the crystal structure of potassium poly(heptazine imide) (K‐PHI)—a benchmark carbon nitride material in photocatalysis—by means of X‐ray powder diffraction and transmission electron microscopy. Using the crystal structure of K‐PHI, periodic DFT calculations were performed to calculate the density‐of‐states (DOS) and localize intra band states (IBS). IBS were found to be responsible for the enhanced K‐PHI absorption in the near IR region, to serve as electron traps, and to be useful in energy transfer reactions. Once excited with visible light, carbon nitrides, in addition to the direct recombination, can also undergo singlet–triplet intersystem crossing. We utilized the K‐PHI centered triplet excited states to trigger a cascade of energy transfer reactions and, in turn, to sensitize, for example, singlet oxygen (1O2) as a starting point to synthesis up to 25 different N‐rich heterocycles. 相似文献
14.
Jialong Duan Yuanyuan Zhao Yudi Wang Xiya Yang Qunwei Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16293-16297
The all‐inorganic CsPbBr3 perovskite solar cell (PSC) is a promising solution to balance the high efficiency and poor stability of state‐of‐the‐art organic–inorganic PSCs. Setting inorganic hole‐transporting layers at the perovskite/electrode interface decreases charge carrier recombination without sacrificing superiority in air. Now, M‐substituted, p‐type inorganic Cu(Cr,M)O2 (M=Ba2+, Ca2+, or Ni2+) nanocrystals with enhanced hole‐transporting characteristics by increasing interstitial oxygen effectively extract holes from perovskite. The all‐inorganic CsPbBr3 PSC with a device structure of FTO/c‐TiO2/m‐TiO2/CsPbBr3/Cu(Cr,M)O2/carbon achieves an efficiency up to 10.18 % and it increases to 10.79 % by doping Sm3+ ions into perovskite halide, which is much higher than 7.39 % for the hole‐free device. The unencapsulated Cu(Cr,Ba)O2‐based PSC presents a remarkable stability in air in either 80 % humidity over 60 days or 80 °C conditions over 40 days or light illumination for 7 days. 相似文献
15.
Venugopal Bandi Dr. Mohamed E. El‐Khouly Dr. Kei Ohkubo Dr. Vladimir N. Nesterov Prof. Melvin E. Zandler Prof. Shunichi Fukuzumi Prof. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7221-7230
Donor–acceptor distance, orientation, and photoexcitation wavelength are key factors in governing the efficiency and mechanism of electron‐transfer reactions both in natural and synthetic systems. Although distance and orientation effects have been successfully demonstrated in simple donor–acceptor dyads, revealing excitation‐wavelength‐dependent photochemical properties demands multimodular, photosynthetic‐reaction‐center model compounds. Here, we successfully demonstrate donor– acceptor excitation‐wavelength‐dependent, ultrafast charge separation and charge recombination in newly synthesized, novel tetrads featuring bisferrocene, BF2‐chelated azadipyrromethene, and fullerene entities. The tetrads synthesized using multistep synthetic procedure revealed characteristic optical, redox, and photo reactivities of the individual components and featured “closely” and “distantly” positioned donor–acceptor systems. The near‐IR‐emitting BF2‐chelated azadipyrromethene acted as a photosensitizing electron acceptor along with fullerene, while the ferrocene entities acted as electron donors. Both tetrads revealed excitation‐wavelength‐dependent, photoinduced, electron‐transfer events as probed by femtosecond transient absorption spectroscopy. That is, formation of the Fc+–ADP–C60.? charge‐separated state upon C60 excitation, and Fc+–ADP.?–C60 formation upon ADP excitation is demonstrated. 相似文献
16.
Yufei Zhao Pengyun Chen Dr. Bingsen Zhang Prof. Dang Sheng Su Shitong Zhang Lei Tian Prof. Jun Lu Dr. Zhuoxin Li Prof. Xingzhong Cao Prof. Baoyi Wang Prof. Min Wei Prof. David G. Evans Prof. Xue Duan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):11949-11958
A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO6 units in an MTi‐layered double hydroxide matrix (M=Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H2‐production rate of 31.4 μmol h?1 as well as excellent recyclable performance. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) mapping and XPS measurement reveal that a high dispersion of TiO6 octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M2+‐O‐Ti network, rather different from the aggregation state of TiO6 in the inorganic layered material K2Ti4O9. Both transient absorption and photoluminescence spectra demonstrate that the electron–hole recombination process was significantly depressed in the Ti‐containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X‐ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO6 units was modified by the adjacent MO6 octahedron by means of covalent interactions, with a much decreased bandgap of 2.1 eV, which accounts for its superior water‐splitting behavior. Therefore, the dispersion strategy for TiO6 units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion. 相似文献
17.
Mechanistic Studies of TiO2 Photocatalysis and Fenton Degradation of Hydrophobic Aromatic Pollutants in Water 下载免费PDF全文
Dr. Yuanzheng Gong Dr. Chun Yang Prof. Hongwei Ji Prof. Chuncheng Chen Prof. Wanhong Ma Prof. Jincai Zhao 《化学:亚洲杂志》2016,11(24):3568-3574
HO–adduct radicals have been investigated and confirmed as the common initial intermediates in TiO2 photocatalysis and Fenton degradations of water‐insoluble aromatics. However, the evolution of HO–adduct radicals to phenols has not been completely clarified. When 4‐d‐toluene and p‐xylene were degraded by TiO2 photocatalysis and Fenton reactions, respectively, a portion of the 4‐deuterium or 4‐CH3 group (18–100 %) at the attacked ipso position shifted to the adjacent position of the ring in the formed phenols (NIH shift; NIH is short for the National Institutes of Health, to honor the place where this phenomenon was first discovered). The results, combined with the observation of a key dienyl cationic intermediate by in situ attenuated total reflectance FTIR spectroscopy, indicate that, for the evolution of HO–adduct radicals, a mixed mechanism of both the carbocation intermediate pathway and O2‐capturing pathway occurs in both aqueous TiO2 photocatalysis and aqueous Fenton reactions. 相似文献
18.
Dr. Baoshun Liu Liping Wen Dr. Kazuya Nakata Prof. Dr. Xiujian Zhao Shanhu Liu Dr. Tsuyoshi Ochiai Dr. Taketoshi Murakami Prof. Dr. Akira Fujishima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12705-12711
The polymeric adsorption of methylene blue (MB) on a TiO2 surface is reported. The MB molecule on the TiO2 surface mainly exists as the H‐trimeric adsorption state, which results in the MB@TiO2 polymeric sol. The trimeric adsorption leads to a remarkable “blueshift” of visible‐light adsorption of MB. Electrostatic attraction is important for trimeric adsorption of MB on TiO2 surfaces. The trimer–monomer equilibrium is highly sensitive on temperature changes, showing an interesting reversible thermochromism. The MB@TiO2 polymeric sol can be photodegraded under UV illumination without destroying the equilibrium of trimer–monomer. Compared with anionic methyl orange, the TiO2 colloid hydrosol shows highly selective photocatalysis of MB and other cationic dyes, including crystal violet, methylene green, and victoria blue B. The MB@TiO2 polymeric sol is stable under visible‐light illumination because interfacial transfer of electrons does not exist between MB and TiO2. 相似文献
19.
Multistep Energy and Electron Transfer in a “V‐Configured” Supramolecular BODIPY–azaBODIPY–Fullerene Triad: Mimicry of Photosynthetic Antenna Reaction‐Center Events 下载免费PDF全文
Venugopal Bandi Fiona P. D'Souza Habtom B. Gobeze Prof. Dr. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2669-2679
A new photosynthetic antenna‐reaction‐center model compound composed of covalently linked BF2‐chelated dipyrromethene (BODIPY), BF2‐chelated azadipyrromethene (azaBODIPY), and fullerene (C60), in a “V‐configuration”, has been newly synthesized and characterized by using a multistep synthetic procedure. Optical absorbance and steady‐state fluorescence, computational, and electrochemical studies were systematically performed in nonpolar, toluene, and polar, benzonitrile, solvents to establish the molecular integrity of the triad and to construct an energy‐level diagram revealing different photochemical events. The geometry obtained by B3LYP/6‐31G* calculations revealed the anticipated V‐configuration of the BODIPY‐azaBODIPY‐C60 triad. The location of the frontier orbitals in the triad tracked the site of electron transfer determined from electrochemical studies. The different photochemical events originated from 1BODIPY* were realized from the energy‐level diagram. Accordingly, 1BODIPY* resulted in competitive ultrafast energy transfer to produce BODIPY–1azaBODIPY*–C60 and electron transfer to produce BODIPY . +–azaBODIPY–C60 . ? as major photochemical events. The charge‐separated state persisted for few nanoseconds prior populating 3C60*, which in turn revealed an unusual triplet–triplet energy transfer to produce 3azaBODIPY* prior returning to the ground state. These findings delineate the importance of multimodular systems in energy harvesting, and more importantly, their utility in building multifunction performing optoelectronic devices. 相似文献
20.
Kazuya Yamaguchi Dr. Takeshi Koike Jung Won Kim Yoshiyuki Ogasawara Noritaka Mizuno Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11480-11487
Supported ruthenium hydroxide catalysts (Ru(OH)x/support) were prepared with three different TiO2 supports (anatase TiO2 (TiO2(A), BET surface area: 316 m2 g?1), anatase TiO2 (TiO2(B), 73 m2 g?1), and rutile TiO2 (TiO2(C), 3.2 m2 g?1)), as well as an Al2O3 support (160 m2 g?1). Characterizations with X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and X‐ray absorption fine structure (XAFS) showed the presence of monomeric ruthenium(III) hydroxide and polymeric ruthenium(III) hydroxide species. Judging from the coordination numbers of the nearest‐neighbor Ru atoms and the intensities of the ESR signals, the amount of monomeric hydroxide species increased in the order of Ru(OH)x<Ru(OH)x/TiO2(C)<Ru(OH)x/Al2O3<Ru(OH)x/TiO2(B)<Ru(OH)x/TiO2(A). These supported ruthenium hydroxide catalysts, especially Ru(OH)x/TiO2(A), showed high catalytic activities and selectivities for liquid‐phase hydrogen‐transfer reactions, such as racemization of chiral secondary alcohols and the reduction of carbonyl compounds and allylic alcohols. The catalytic activities of Ru(OH)x/TiO2(A) for these hydrogen‐transfer reactions were at least one order of magnitude higher than those of previously reported heterogeneous catalysts, such as Ru(OH)x/Al2O3. These catalyses were truly heterogeneous, and the catalysts recovered after the reactions could be reused several times without loss of catalytic performance. The reaction rates monotonically increased with an increase in the amount of monomeric ruthenium hydroxide species, which suggests that the monomeric species are effective for these hydrogen‐transfer reactions. 相似文献