Exciton behavior is crucial to the exploitation of light-emitting conjugated polymer(LCPs)for optoelectronic devices.Singlet excitons are easily trapped by the intrinsically defect structures.Herein,we set a polyfluor...Exciton behavior is crucial to the exploitation of light-emitting conjugated polymer(LCPs)for optoelectronic devices.Singlet excitons are easily trapped by the intrinsically defect structures.Herein,we set a polyfluorenol(PPFOH)as an example to systematically investigate its photophysical behavior to check the role of defect structures in LCPs.According to time-resolved photoluminescence analysis,the feature emission peaks from individual chain of PPFOH in diluted DMF solution is effectively avoided the influence of fluorenone formation,but the residual green-band emission at 550nm is easily observed in the PL spectra of PPFOH dilute toluene solution obtained delay 1.5 ns,confirmed the formation of“vip”physical aggregation-induced defect structure.Remarkably,efficient and ultrafast energy transfer from individual chain to defect structure is observed in PPFOH films.Interestingly,the efficient energy transfer happened for the film obtained from DMF solution(200 ps)than those of toluene ones(600 ps).Meanwhile,compared to relatively stable green-band emission in PPFOH film from toluene solution,red-shifted emission peak(11 nm)of PPFOH film from DMF solutions exposed to saturated DNT vapor also confirmed their different aggregation-induced green-band emission.Therefore,this aggregation defect structures are influenced on the photophysical property of LCPs in solid states.展开更多
Although the Haber–Bosch process supports the growth of modern agriculture with abundant ammonia and fertilizer production,substantial energy consumption and enormous greenhouse emissions demand an alternative and su...Although the Haber–Bosch process supports the growth of modern agriculture with abundant ammonia and fertilizer production,substantial energy consumption and enormous greenhouse emissions demand an alternative and sustainable approach.Here,we report a novel approach that combines the nonphotosynthetic bacterium Shewanella oneidensis MR-1(S.oneidensis MR-1)with cadmium sulfide(CdS)nanoparticles(NPs)to enable the photosynthesis of ammonium(NH_(4)+)from nitrate(NO_(3)^(-))using photoexcited electrons as donors.The NO_(3)^(-)reduction efficiency reached almost 100%,with an NH_(4)^(+)production selectivity of over 90%.The maximum instantaneous quantum efficiency was 3.01%under light irradiation.The reverse metal-reducing(Mtr)pathway is responsible for the transfer of photoexcited electrons to intracellular compartments.Parallel reaction monitoring analysis illustrated that NO_(3)^(-)to NH_(4)^(+)was produced via the dissimilatory nitrate reduction to ammonium(DNRA)pathway in S.oneidensis MR-1.This study provides a facile strategy for light-driven ambient NH4+synthesis and solar-to-chemical conversion.展开更多
Small-sized Cd_(x) Zn_(1-x) S solid solution nanomaterial is an important candidate for efficient photocatalytic hydrogen evolution(PHE),but it still suffers from easy agglomeration,severe photo corrosion,and fast pho...Small-sized Cd_(x) Zn_(1-x) S solid solution nanomaterial is an important candidate for efficient photocatalytic hydrogen evolution(PHE),but it still suffers from easy agglomeration,severe photo corrosion,and fast photogenerated electron-hole recombination.To tackle these issues,herein,we propose a new strategy to modify Cd_(x) Zn_(1-x) S nanoreactors by the simultaneous utilization of ionic-liquid-assisted morphology engineering and MXene-incorporating method.That is,we designed and synthesized a novel hierarchi-cal Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) Schottky junction composite through the in-situ deposition of ultrathin Cd_(0.8) Zn_(0.2) S nanosheets on unique IL-modified Ti_(3) C_(2) MXenes by a one-pot solvothermal method for efficiently PHE.The unique construction strategy tailors the thickness of ultrathin Cd_(0.8) Zn_(0.2) S nanosheets and prevents them from stacking and agglomeration,and especially,optimizes their charge transfer pathways during the photocatalytic process.Compared with pristine Cd_(0.8) Zn_(0.2) S nanosheets,Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) has abun-dant photogenerated electrons available on the Ti_(3) C_(2) surface for proton reduction reaction,owing to the absence of deep-trapped electrons,suppression of electron-hole recombination in Cd_(0.8) Zn_(0.2) S and high-efficiency charge separation at the Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) Schottky junction interface.Moreover,the hy-drophilicity,electrical conductivity,visible-light absorption capacity,and surficial hydrogen desorption of Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) heterostructure are significantly improved.As a result,the heterostructure exhibits out-standing photocatalytic stability and super high apparent quantum efficiency,being rendered as one of the best noble-metal-free Cd-Zn-S-based photocatalysts.This work illustrates the mechanisms of mor-phology control and heterojunction construction in controlling the catalytic behavior of photocatalysts and highlights the great potential of the IL-assisted route in the synthesis of high-performance MXene-based heterostructures for photocatalytic hydrogen evolution.展开更多
We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the p...We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the photoexcited carrier dynamics, which can be attributed to the electron-spin and spin-lattice scattering processes influenced by the magnetic phase transition and modifications in magnetic anisotropy. The magnetization change can be revealed by the dynamics of coherent acoustic phonon. We also observe abrupt changes in the photoinduced spin dynamics near T^(*)and T^(†), which not only illustrate the spin-related scatterings closely related to the long-range magnetic order, but also reveal the D'yakonov–Perel and Elliott–Yafet mechanisms dominating at temperatures below and above T^(†), respectively. Our findings provide important insights into the nonequilibrium properties of the photoexcited(In,Fe)Sb.展开更多
Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of con...Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2) and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2) surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2) lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.展开更多
We detect a relaxation process of excited SQ02 dye in the chlorobenzene solution and an- chor SQ02 on Al2O3 and TiO2 film, so as to investigate the photophysical properties of pristine SQ02 in the monodisperse system,...We detect a relaxation process of excited SQ02 dye in the chlorobenzene solution and an- chor SQ02 on Al2O3 and TiO2 film, so as to investigate the photophysical properties of pristine SQ02 in the monodisperse system, aggregation state, and the corresponding inter- facial electron transfer process. The experimental data show that the lifetime of SQ02 in the monondisperse system is ～2.0 ns, but that of SQ02 anchored on the Al2O3 film could obviously decrease to ～21 ps. The time of electron transfer from excited SQ02 to TiO2 film is estimated to be ～2.6 ps and the yield of electron injection is estimated to be ～89.1%, which matches the incident photon to current efficiency of dye-sensitized solar cell based on SQ02. In addition, some dyes are found to pack on the other dyes anchored on the nanocrystal film, and their relaxation time could reach ～60 ps. They couldn＇t participate in the interfacial electron transfer, since they are far away from the TiO2 interface.展开更多
By using soft X-ray spectroscopy, we investigate the inner-shell excitation and relaxation processes in atomic and ionic neon targets. Resonant X-ray emission spectroscopy was applied to neutral neon atom in the regio...By using soft X-ray spectroscopy, we investigate the inner-shell excitation and relaxation processes in atomic and ionic neon targets. Resonant X-ray emission spectroscopy was applied to neutral neon atom in the regions of the [1s]np （n = 3, 4,…, ε） excited states and [1s2p]3pmp （m = 3,4） doubly excited states to obtain the spectroscopic information on the [2p]np and [2p^2]3prnp final electronic states, where square brackets indicate hole states. The energy levels of the [2p^2]3prnp （m = 3,4） electronic states were spectroscopically measured for the first time. As for the ionic neon target, on the other hand, the photoion yield spectroscopy was adopted to survey the 1s→ np （n = 2, 3） resonant excitation and subsequent Auger decay processes for Ne^＋ target-ions. The observed Ne^2＋ photoion yield spectrum is successflllly explained by the theoretical calculations based on the nmlticonfiguration Dirac-Fock method展开更多
As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potentia...As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].展开更多
The photochemical reaction of methylene blue (n-butyltriphenyl) borate, MBRBPh3 was examined. The ultrafast quenching rate and large negative value of Delta G indicated that the intra-ion pair ET plays an important ro...The photochemical reaction of methylene blue (n-butyltriphenyl) borate, MBRBPh3 was examined. The ultrafast quenching rate and large negative value of Delta G indicated that the intra-ion pair ET plays an important role in photoreaction of MBRBPh3. The sequent boron- carbon bond cleavage of butyltriphenylboranyl radical intermediate was found by GC-MS and photo-CIDNP studies.展开更多
In recent years,photoinduced transition metal(TM)catalysis has garnered significant attention for advancing various asymmetric chemical transformations.Unlike traditional photocatalysis,photoexcited TM catalysis opera...In recent years,photoinduced transition metal(TM)catalysis has garnered significant attention for advancing various asymmetric chemical transformations.Unlike traditional photocatalysis,photoexcited TM catalysis operates through outer-sphere mechanisms,leveraging direct and strong substrate-metal interactions.The TM complex performs a dual role,both harvesting light and catalyzing chemical transformations,typically via single electron transfer pathways.This innovative approach establishes a multifunctional platform that facilitates the development of novel,particularly enantioselective,chemical transformations.Given that photoexcited TM asymmetric catalysis serves as an important complement to ground-state TM asymmetric catalysis,this review highlights recent advancements in photoexcited TM(Cu,Pd,Ir,Ti,etc.)asymmetric catalysis.展开更多
Crafting charge transfer channels at titanium dioxide(TiO_(2))based photoanodes remain a pressing bottleneck in solar-to-chemical conversion technology.Despite the tremendous attempts,TiO_(2)as the promising photoanod...Crafting charge transfer channels at titanium dioxide(TiO_(2))based photoanodes remain a pressing bottleneck in solar-to-chemical conversion technology.Despite the tremendous attempts,TiO_(2)as the promising photoanode material still suffers from sluggish charge transport kinetics.Herein,we propose an assembly strategy that involves the axial coordination grafting metalloporphyrin-based photosensitizer molecules(MP)onto the surface-modified TiO_(2)nanorods(NRs)photoanode,forming the composite MP/TiO_(2)NRs photoelectrode.As expected,the resulted unique MPB/TiO_(2)NRs photoelectrode displays significantly improved photocurrent density as compared to TiO_(2)NRs alone and MPA/TiO_(2)NRs photoelectrode.Scanning photoelectrochemical microscopy(SPECM)and intensity modulated photocurrent spectroscopy(IMPS)were employed to systematically evaluate the continuous photoinduced electron transfer(PET)dynamics for MP/TiO_(2)NRs photoelectrode.According to the data fitting,it is found that the photoelectron transfer rate(keff)constant for the MPB/TiO_(2)NRs is about 2.6 times higher than that for the pure TiO_(2)NRs under light irradiation.The high kinetic constant for the MPB/TiO_(2)NRs was ascribed to that the conjugated molecules MPB of D-A structure can effectively accelerate intramolecular electrons transfer as well as promote electrons taking part in the reduction reaction of I3to Iin the novel charge transfer channel.The results demonstrated in this study are expected to shed some light on investigating the mechanism in the charge transfer process of artificial photosynthesis and constructing efficient photoelectrodes.展开更多
Surface states are expected to play a key role in broadband terahertz(THz) emitters, where photoexcited carrier distributions are confined within about 1 μm of the surface. Optical pump and THz probe spectroscopy was...Surface states are expected to play a key role in broadband terahertz(THz) emitters, where photoexcited carrier distributions are confined within about 1 μm of the surface. Optical pump and THz probe spectroscopy was used to study the dynamics of nonequilibrium charge carriers in both textured and non-textured GaAs substrates.Our findings show that the textured surface acts as an antireflective layer, greatly boosting the infrared pump laser's coupling efficiency into the semi-insulating GaAs substrate. Additionally, texturing introduces a trapassisted recombination pathway, speeding up carrier relaxation and thus reducing Joule heating. Under the same pumping and bias field conditions, the coarse-textured GaAs photoconductive antenna shows nearly 7.85 times stronger THz emission amplitude than the non-textured device, along with improvement in signal-to-noise ratio.At a fixed bias field, higher pump power increases photogenerated carrier density, causing bias field screening and subsequent saturation of THz emission. At fixed pump power, when the bias field reaches ~2.5 kV/cm, both THz emission and photocurrent spectra show a clear kink, signaling intervalley scattering from the Γ valley to the L(X) valleys under high electric fields.展开更多
ZnS films were deposited by pulsed laser deposition （PLD） on porous silicon （PS） substrates formed by electrochemical anodization of p-type （100） silicon wafer. The photoluminescence （PL） spectra of ZnS/PS com...ZnS films were deposited by pulsed laser deposition （PLD） on porous silicon （PS） substrates formed by electrochemical anodization of p-type （100） silicon wafer. The photoluminescence （PL） spectra of ZnS/PS composites were measured at room temperature. Under different excitation wavelengths, the relative integrated intensities of the red light emission from PS layers and the blue-green emission from ZnS films had different values. After samples were annealed in vacuum at different temperatures （200, 300, and 400 ~C） for 30 min respectively, a new green emission located at around 550 nm appeared in the PL spectra of all ZnS/PS samples, and all of the ZnS/PS composites had a broad PL band （450 - 700 nm） in the visible region, exhibiting intensively white light emission.展开更多
The luminescence dynamics of a polypyridyl ruthenium II [Ru（phen）2（ip）]2＋ and 5,10,15,20- tetraphenylporphyrin （H2TPP） dyad have been measured by using time-resolved fluorescence spectroscopy. The transient lum...The luminescence dynamics of a polypyridyl ruthenium II [Ru（phen）2（ip）]2＋ and 5,10,15,20- tetraphenylporphyrin （H2TPP） dyad have been measured by using time-resolved fluorescence spectroscopy. The transient luminescent spectra of the dyad show an ultrafast energy transfer within 300 ps after pho- toexcitation of the [Ru（phen）2（ip）]2＋ at 453 am. However, no energy transfer has been observed as the excitation wavelength is 400 nm, corresponding to the absorption peak of H2TPP. The origin of the energy transfer from [Ru（phen）2（ip）]2＋ to H2TPP has been analyzed according to the FSrster energy-transfer theory.展开更多
Understanding the ultrafast carrier dynamics and the mechanism of two-dimensional(2D)transition metal dichalcogenides(TMDs)is key to their applications in the field of optoelectronic devices.In this work,a single puls...Understanding the ultrafast carrier dynamics and the mechanism of two-dimensional(2D)transition metal dichalcogenides(TMDs)is key to their applications in the field of optoelectronic devices.In this work,a single pulse pump probe method is introduced to detect the layer-dependent ultrafast carrier dynamics of monolayer and few-layer WS_(2) excited by a femtosecond pulse.Results show that the ultrafast carrier dynamics of the layered WS_(2) films can be divided into three stages:the fast photoexcitation phase with the characteristic time of 2–4 ps,the fast decay phase with the characteristic time of 4–20 ps,and the slow decay phase lasting several hundred picoseconds.Moreover,the layer dependency of the characteristic time of each stage has been observed,and the corresponding mechanism of free carrier dynamics has been discussed.It has been observed as well that the monolayer WS_(2) exhibits a unique rising time of carriers after photoexcitation.The proposed method can be expected to be an effective approach for studying the dynamics of the photoexcited carriers in 2D TMDs.Our results provide a comprehensive understanding of the photoexcited carrier dynamics of layered WS_(2),which is essential for its application in optoelectronics and photovoltaic devices.展开更多
Herein,we report an unprecedented molecular editing strategy for cycloketones that involves the precise translocation and removal of single oxygen atom enabled by dual photoexcited palladium and photoredox catalysis.I...Herein,we report an unprecedented molecular editing strategy for cycloketones that involves the precise translocation and removal of single oxygen atom enabled by dual photoexcited palladium and photoredox catalysis.In contrast to conventional ketone molecular editing strategies,which often rely on the loss of pre-functionalized groups or the addition of additional acylating agents,this approach facilitates the efficient recycling of pre-functionalized moieties.This is accomplished through a photoexcited palladium catalyzed N–O bond cleavage of cycloketone oxime esters,generating cyanoalkyl radicals and a palladium carboxylate complex.The subsequent photoredox-catalyzed deoxygenation,mediated by phosphoranyl radicals,then leads to the coupling of cyanoalkyl radicals,ultimately yielding the desired products.This molecular editing strategy features good atom economy due to precise skeletal modifications,broad compatibility with various functional groups,and significant potential for late-stage functionalization of pharmaceutical derivatives.展开更多
基金the National Natural Science Foundation of China(Nos.22105099,61874053)Natural Science Foundation of Jiangsu Province(No.BK20200700)the open research fund from Anhui Province Key Laboratory of Optoelectronic Materials Science and Technology(No.OMST202101).
文摘Exciton behavior is crucial to the exploitation of light-emitting conjugated polymer(LCPs)for optoelectronic devices.Singlet excitons are easily trapped by the intrinsically defect structures.Herein,we set a polyfluorenol(PPFOH)as an example to systematically investigate its photophysical behavior to check the role of defect structures in LCPs.According to time-resolved photoluminescence analysis,the feature emission peaks from individual chain of PPFOH in diluted DMF solution is effectively avoided the influence of fluorenone formation,but the residual green-band emission at 550nm is easily observed in the PL spectra of PPFOH dilute toluene solution obtained delay 1.5 ns,confirmed the formation of“vip”physical aggregation-induced defect structure.Remarkably,efficient and ultrafast energy transfer from individual chain to defect structure is observed in PPFOH films.Interestingly,the efficient energy transfer happened for the film obtained from DMF solution(200 ps)than those of toluene ones(600 ps).Meanwhile,compared to relatively stable green-band emission in PPFOH film from toluene solution,red-shifted emission peak(11 nm)of PPFOH film from DMF solutions exposed to saturated DNT vapor also confirmed their different aggregation-induced green-band emission.Therefore,this aggregation defect structures are influenced on the photophysical property of LCPs in solid states.
基金supported by the National Key Research and Development Project(2019YFA0705804).
文摘Although the Haber–Bosch process supports the growth of modern agriculture with abundant ammonia and fertilizer production,substantial energy consumption and enormous greenhouse emissions demand an alternative and sustainable approach.Here,we report a novel approach that combines the nonphotosynthetic bacterium Shewanella oneidensis MR-1(S.oneidensis MR-1)with cadmium sulfide(CdS)nanoparticles(NPs)to enable the photosynthesis of ammonium(NH_(4)+)from nitrate(NO_(3)^(-))using photoexcited electrons as donors.The NO_(3)^(-)reduction efficiency reached almost 100%,with an NH_(4)^(+)production selectivity of over 90%.The maximum instantaneous quantum efficiency was 3.01%under light irradiation.The reverse metal-reducing(Mtr)pathway is responsible for the transfer of photoexcited electrons to intracellular compartments.Parallel reaction monitoring analysis illustrated that NO_(3)^(-)to NH_(4)^(+)was produced via the dissimilatory nitrate reduction to ammonium(DNRA)pathway in S.oneidensis MR-1.This study provides a facile strategy for light-driven ambient NH4+synthesis and solar-to-chemical conversion.
基金financial supports pro-vided by the National Natural Science Foundation of China(No.21905279)the Natural Science Foundation of Fujian Province(No.2020J05086).
文摘Small-sized Cd_(x) Zn_(1-x) S solid solution nanomaterial is an important candidate for efficient photocatalytic hydrogen evolution(PHE),but it still suffers from easy agglomeration,severe photo corrosion,and fast photogenerated electron-hole recombination.To tackle these issues,herein,we propose a new strategy to modify Cd_(x) Zn_(1-x) S nanoreactors by the simultaneous utilization of ionic-liquid-assisted morphology engineering and MXene-incorporating method.That is,we designed and synthesized a novel hierarchi-cal Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) Schottky junction composite through the in-situ deposition of ultrathin Cd_(0.8) Zn_(0.2) S nanosheets on unique IL-modified Ti_(3) C_(2) MXenes by a one-pot solvothermal method for efficiently PHE.The unique construction strategy tailors the thickness of ultrathin Cd_(0.8) Zn_(0.2) S nanosheets and prevents them from stacking and agglomeration,and especially,optimizes their charge transfer pathways during the photocatalytic process.Compared with pristine Cd_(0.8) Zn_(0.2) S nanosheets,Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) has abun-dant photogenerated electrons available on the Ti_(3) C_(2) surface for proton reduction reaction,owing to the absence of deep-trapped electrons,suppression of electron-hole recombination in Cd_(0.8) Zn_(0.2) S and high-efficiency charge separation at the Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) Schottky junction interface.Moreover,the hy-drophilicity,electrical conductivity,visible-light absorption capacity,and surficial hydrogen desorption of Cd_(0.8) Zn_(0.2) S/Ti_(3) C_(2) heterostructure are significantly improved.As a result,the heterostructure exhibits out-standing photocatalytic stability and super high apparent quantum efficiency,being rendered as one of the best noble-metal-free Cd-Zn-S-based photocatalysts.This work illustrates the mechanisms of mor-phology control and heterojunction construction in controlling the catalytic behavior of photocatalysts and highlights the great potential of the IL-assisted route in the synthesis of high-performance MXene-based heterostructures for photocatalytic hydrogen evolution.
基金supported by the National Key R&D Program of China (Grant No. 2024YFA1408502)the National Natural Science Foundation of China (Grant Nos. 92365102, 62027807, 12474107, and 12174383)+1 种基金the Chinese Academy of Sciences project for Yong Scientists in Basic Research (Grant No. YSBR-030)the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2024A1515011600)。
文摘We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the photoexcited carrier dynamics, which can be attributed to the electron-spin and spin-lattice scattering processes influenced by the magnetic phase transition and modifications in magnetic anisotropy. The magnetization change can be revealed by the dynamics of coherent acoustic phonon. We also observe abrupt changes in the photoinduced spin dynamics near T^(*)and T^(†), which not only illustrate the spin-related scatterings closely related to the long-range magnetic order, but also reveal the D'yakonov–Perel and Elliott–Yafet mechanisms dominating at temperatures below and above T^(†), respectively. Our findings provide important insights into the nonequilibrium properties of the photoexcited(In,Fe)Sb.
文摘Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2) and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2) surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2) lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.
文摘We detect a relaxation process of excited SQ02 dye in the chlorobenzene solution and an- chor SQ02 on Al2O3 and TiO2 film, so as to investigate the photophysical properties of pristine SQ02 in the monodisperse system, aggregation state, and the corresponding inter- facial electron transfer process. The experimental data show that the lifetime of SQ02 in the monondisperse system is ～2.0 ns, but that of SQ02 anchored on the Al2O3 film could obviously decrease to ～21 ps. The time of electron transfer from excited SQ02 to TiO2 film is estimated to be ～2.6 ps and the yield of electron injection is estimated to be ～89.1%, which matches the incident photon to current efficiency of dye-sensitized solar cell based on SQ02. In addition, some dyes are found to pack on the other dyes anchored on the nanocrystal film, and their relaxation time could reach ～60 ps. They couldn＇t participate in the interfacial electron transfer, since they are far away from the TiO2 interface.
文摘By using soft X-ray spectroscopy, we investigate the inner-shell excitation and relaxation processes in atomic and ionic neon targets. Resonant X-ray emission spectroscopy was applied to neutral neon atom in the regions of the [1s]np （n = 3, 4,…, ε） excited states and [1s2p]3pmp （m = 3,4） doubly excited states to obtain the spectroscopic information on the [2p]np and [2p^2]3prnp final electronic states, where square brackets indicate hole states. The energy levels of the [2p^2]3prnp （m = 3,4） electronic states were spectroscopically measured for the first time. As for the ionic neon target, on the other hand, the photoion yield spectroscopy was adopted to survey the 1s→ np （n = 2, 3） resonant excitation and subsequent Auger decay processes for Ne^＋ target-ions. The observed Ne^2＋ photoion yield spectrum is successflllly explained by the theoretical calculations based on the nmlticonfiguration Dirac-Fock method
基金supported by the National Key R&D Program of China (2018YFE0208500)the Japan Science and Technology Agency (JST) Mirai program (JPMJMI17EA)。
文摘As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].
文摘The photochemical reaction of methylene blue (n-butyltriphenyl) borate, MBRBPh3 was examined. The ultrafast quenching rate and large negative value of Delta G indicated that the intra-ion pair ET plays an important role in photoreaction of MBRBPh3. The sequent boron- carbon bond cleavage of butyltriphenylboranyl radical intermediate was found by GC-MS and photo-CIDNP studies.
基金supported by the National Natural Science Foundation of China(22371119)。
文摘In recent years,photoinduced transition metal(TM)catalysis has garnered significant attention for advancing various asymmetric chemical transformations.Unlike traditional photocatalysis,photoexcited TM catalysis operates through outer-sphere mechanisms,leveraging direct and strong substrate-metal interactions.The TM complex performs a dual role,both harvesting light and catalyzing chemical transformations,typically via single electron transfer pathways.This innovative approach establishes a multifunctional platform that facilitates the development of novel,particularly enantioselective,chemical transformations.Given that photoexcited TM asymmetric catalysis serves as an important complement to ground-state TM asymmetric catalysis,this review highlights recent advancements in photoexcited TM(Cu,Pd,Ir,Ti,etc.)asymmetric catalysis.
基金We are thankful to the National Natural Science Foundation of China(22174110 and 22127803)the Industrial Support Plan of Gansu Provincial Department of Education(2021cyzc-01)the Special Fund Project for Guiding Local Scientific and Technological Development by the Central Government(2020-2060503-17).
文摘Crafting charge transfer channels at titanium dioxide(TiO_(2))based photoanodes remain a pressing bottleneck in solar-to-chemical conversion technology.Despite the tremendous attempts,TiO_(2)as the promising photoanode material still suffers from sluggish charge transport kinetics.Herein,we propose an assembly strategy that involves the axial coordination grafting metalloporphyrin-based photosensitizer molecules(MP)onto the surface-modified TiO_(2)nanorods(NRs)photoanode,forming the composite MP/TiO_(2)NRs photoelectrode.As expected,the resulted unique MPB/TiO_(2)NRs photoelectrode displays significantly improved photocurrent density as compared to TiO_(2)NRs alone and MPA/TiO_(2)NRs photoelectrode.Scanning photoelectrochemical microscopy(SPECM)and intensity modulated photocurrent spectroscopy(IMPS)were employed to systematically evaluate the continuous photoinduced electron transfer(PET)dynamics for MP/TiO_(2)NRs photoelectrode.According to the data fitting,it is found that the photoelectron transfer rate(keff)constant for the MPB/TiO_(2)NRs is about 2.6 times higher than that for the pure TiO_(2)NRs under light irradiation.The high kinetic constant for the MPB/TiO_(2)NRs was ascribed to that the conjugated molecules MPB of D-A structure can effectively accelerate intramolecular electrons transfer as well as promote electrons taking part in the reduction reaction of I3to Iin the novel charge transfer channel.The results demonstrated in this study are expected to shed some light on investigating the mechanism in the charge transfer process of artificial photosynthesis and constructing efficient photoelectrodes.
基金supported by the National Key Research and Development Program of China (Grant No.2023YFF0719200)the National Natural Science Foundation of China (Grant Nos.62322115,U24A20226,62588201,62435010,and 62335012)+2 种基金the 111 Project (Grant No.D18014)the Key project supported by Science and Technology Commission Shanghai Municipality (Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality (Grant Nos.22JC1400200 and 21S31907400)。
文摘Surface states are expected to play a key role in broadband terahertz(THz) emitters, where photoexcited carrier distributions are confined within about 1 μm of the surface. Optical pump and THz probe spectroscopy was used to study the dynamics of nonequilibrium charge carriers in both textured and non-textured GaAs substrates.Our findings show that the textured surface acts as an antireflective layer, greatly boosting the infrared pump laser's coupling efficiency into the semi-insulating GaAs substrate. Additionally, texturing introduces a trapassisted recombination pathway, speeding up carrier relaxation and thus reducing Joule heating. Under the same pumping and bias field conditions, the coarse-textured GaAs photoconductive antenna shows nearly 7.85 times stronger THz emission amplitude than the non-textured device, along with improvement in signal-to-noise ratio.At a fixed bias field, higher pump power increases photogenerated carrier density, causing bias field screening and subsequent saturation of THz emission. At fixed pump power, when the bias field reaches ~2.5 kV/cm, both THz emission and photocurrent spectra show a clear kink, signaling intervalley scattering from the Γ valley to the L(X) valleys under high electric fields.
基金the Natural Science Foundation of Shandong Province under Grant No.Y2002A09.
文摘ZnS films were deposited by pulsed laser deposition （PLD） on porous silicon （PS） substrates formed by electrochemical anodization of p-type （100） silicon wafer. The photoluminescence （PL） spectra of ZnS/PS composites were measured at room temperature. Under different excitation wavelengths, the relative integrated intensities of the red light emission from PS layers and the blue-green emission from ZnS films had different values. After samples were annealed in vacuum at different temperatures （200, 300, and 400 ~C） for 30 min respectively, a new green emission located at around 550 nm appeared in the PL spectra of all ZnS/PS samples, and all of the ZnS/PS composites had a broad PL band （450 - 700 nm） in the visible region, exhibiting intensively white light emission.
基金supported by the National Natural Science Foundation of China (Nos. 60478013, 20571089,90608012)the Natural Science Foundation of Guangdong Province of China (No. 05101819)the National "973" Program of China (No. 2007CB815306)
文摘The luminescence dynamics of a polypyridyl ruthenium II [Ru（phen）2（ip）]2＋ and 5,10,15,20- tetraphenylporphyrin （H2TPP） dyad have been measured by using time-resolved fluorescence spectroscopy. The transient luminescent spectra of the dyad show an ultrafast energy transfer within 300 ps after pho- toexcitation of the [Ru（phen）2（ip）]2＋ at 453 am. However, no energy transfer has been observed as the excitation wavelength is 400 nm, corresponding to the absorption peak of H2TPP. The origin of the energy transfer from [Ru（phen）2（ip）]2＋ to H2TPP has been analyzed according to the FSrster energy-transfer theory.
基金supported by the National Natural Science Foundation of China (Nos. 51975232 and 51727809)the Experiment Center for Advanced Manufacturing and Technology in the School of Mechanical Science & Engineering of HUST for the technical support.
文摘Understanding the ultrafast carrier dynamics and the mechanism of two-dimensional(2D)transition metal dichalcogenides(TMDs)is key to their applications in the field of optoelectronic devices.In this work,a single pulse pump probe method is introduced to detect the layer-dependent ultrafast carrier dynamics of monolayer and few-layer WS_(2) excited by a femtosecond pulse.Results show that the ultrafast carrier dynamics of the layered WS_(2) films can be divided into three stages:the fast photoexcitation phase with the characteristic time of 2–4 ps,the fast decay phase with the characteristic time of 4–20 ps,and the slow decay phase lasting several hundred picoseconds.Moreover,the layer dependency of the characteristic time of each stage has been observed,and the corresponding mechanism of free carrier dynamics has been discussed.It has been observed as well that the monolayer WS_(2) exhibits a unique rising time of carriers after photoexcitation.The proposed method can be expected to be an effective approach for studying the dynamics of the photoexcited carriers in 2D TMDs.Our results provide a comprehensive understanding of the photoexcited carrier dynamics of layered WS_(2),which is essential for its application in optoelectronics and photovoltaic devices.
基金support from the National Natural Science Foundation of China(22171233)the Science and Technology Department of Sichuan Province(2023NSFSC1086)the Science and Technology Project of Luzhou City(2024RCX207)。
文摘Herein,we report an unprecedented molecular editing strategy for cycloketones that involves the precise translocation and removal of single oxygen atom enabled by dual photoexcited palladium and photoredox catalysis.In contrast to conventional ketone molecular editing strategies,which often rely on the loss of pre-functionalized groups or the addition of additional acylating agents,this approach facilitates the efficient recycling of pre-functionalized moieties.This is accomplished through a photoexcited palladium catalyzed N–O bond cleavage of cycloketone oxime esters,generating cyanoalkyl radicals and a palladium carboxylate complex.The subsequent photoredox-catalyzed deoxygenation,mediated by phosphoranyl radicals,then leads to the coupling of cyanoalkyl radicals,ultimately yielding the desired products.This molecular editing strategy features good atom economy due to precise skeletal modifications,broad compatibility with various functional groups,and significant potential for late-stage functionalization of pharmaceutical derivatives.
