Investigation of the Electronic Structure of CdS Nanoparticles with Sum Frequency Generation and Photoluminescence Spectroscopy

Wang, Jingjing; Wu, Xuejiao; He, Yuhan; Guo, Weinong; Zhang, Qinghong; Wang, Ye; Wang, Zhaohui

doi:10.1021/acs.jpcc.9b09750

Cited by 12 publications

(6 citation statements)

References 42 publications

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“…Next, photoluminescence (PL) was used to check the charge separation of the two heterojunction electrodes. − PL mapping (Figure a,b) showed that the PL intensity on CdS/TiO 2 -S is sharply lower than that on CdS/TiO 2 -S, clearly indicating the low radiative recombination in CdS/TiO 2 -S. Significant PL quenching for CdS/TiO 2 -S would originate from the efficient charge separation and transfer with the help of polaron states at the heterojunction interface. Steady-state PL spectra (Figure c) showed, under 488 nm excitation, a broad PL peak from 550 to 800 nm centered at 700 nm and an 830 nm-centered PL peak, which were assigned to the surface-defect-states (S or Cd vacancies) emission of CdS. − The TiO 2 nanotube cannot be excited at this excitation wavelength, implying that the PL processes in the two heterojunction electrodes inherently resulted from the radiative recombination of CdS. The CdS/TiO 2 and CdS/TiO 2 -S follow the same PL process with the lower PL intensity in CdS/TiO 2 -S, suggesting that the PL quenching is expected via the new nonradiative pathways created by surface polaron states on TiO 2 nanotubes.…”

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confidence: 96%

Polaron States as a Massive Electron-Transfer Pathway at Heterojunction Interface

Zhu

Yang

Liu

et al. 2020

J. Phys. Chem. Lett.

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For heterojunction semiconductor photoelectrodes, efficient charge separation is localized in the junction-induced electric field region and charge transfer follows a band-to-band charge-transfer pathway. Here, we found that polaron states at the heterojunction interface have a function of storing and transferring electrons. As a successful demonstration, we verified that the polaron states (Ti3+OH) on TiO2 are not passivated when used to create a CdS/TiO2 heterojunction and function as an efficient pathway for massively capturing, storing, and transferring the electrons from conduction bands of both TiO2 and CdS, thus effectively enhancing the charge separation efficiency of the heterojunction photoanode. The electron throughput of polaron states remains a positive correlation with polaron state density. Interfacial electron transfer through the TiO2 surface polaron states has great potential application in the development of high-performance heterojunction devices based on TiO2.

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confidence: 96%

Polaron States as a Massive Electron-Transfer Pathway at Heterojunction Interface

Zhu

Yang

Liu

et al. 2020

J. Phys. Chem. Lett.

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“…In addition to band-edge emission, a red-shifted and broad emission is commonly observed in CdS and CdSe NRs, and it has been assigned to radiative emission involving trapped carriers. , The broad nature of trap emission has been attributed to two causes in CdS and CdSe QDs: heterogeneous trap energies and/or strong coupling of trapped carriers with phonons. − Trap state PL can be seen in Figure with a maximum around 650 nm. The intensity of the trap emission is very dependent on the surface passivation of the NR.…”

Section: Steady State Optical Properties Of Cd-chalcogenide Nrs and N...mentioning

confidence: 99%

Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods

et al. 2023

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The cylindrical quasi-one-dimensional shape of colloidal semiconductor nanorods (NRs) gives them unique electronic structure and optical properties. In addition to the band gap tunability common to nanocrystals, NRs have polarized light absorption and emission and high molar absorptivities. NR-shaped heterostructures feature control of electron and hole locations as well as light emission energy and efficiency. We comprehensively review the electronic structure and optical properties of Cd-chalcogenide NRs and NR heterostructures (e.g., CdSe/CdS dot-in-rods, CdSe/ZnS rod-in-rods), which have been widely investigated over the last two decades due in part to promising optoelectronic applications. We start by describing methods for synthesizing these colloidal NRs. We then detail the electronic structure of single-component and heterostructure NRs and follow with a discussion of light absorption and emission in these materials. Next, we describe the excited state dynamics of these NRs, including carrier cooling, carrier and exciton migration, radiative and nonradiative recombination, multiexciton generation and dynamics, and processes that involve trapped carriers. Finally, we describe charge transfer from photoexcited NRs and connect the dynamics of these processes with light-driven chemistry. We end with an outlook that highlights some of the outstanding questions about the excited state properties of Cd-chalcogenide NRs.

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“…It is worth mentioning that static interactions of electronic and nucleic motions at interfaces and surfaces were demonstrated more over decades ago. − Such a technique is frequency-domain doubly resonant sum frequency generation (DR-SFG), which is generated by mixing a visible beam and an IR beam. The IR beam is varied to be resonant with a vibrational transition of the ground state of molecules, while the visible beam is tuned and used to upconvert the vibrational free induction decay to be resonant with electronic transitions. − Recently, a femtosecond broadband IR was introduced to mix with a tunable picosecond beam to be doubly resonant with multiple vibrational transitions and electronic transitions simultaneously. − Although the DR-SFG has provided coupling of electronic and vibrational degrees of freedom, studies of dynamic vibronic coupling at interfaces and surfaces are lacking.…”

Section: Introductionmentioning

confidence: 99%

Development of Two-Dimensional Electronic-Vibrational Sum Frequency Generation (2D-EVSFG) for Vibronic and Solvent Couplings of Molecules at Interfaces and Surfaces

et al. 2023

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Many photoinduced excited states’ relaxation processes and chemical reactions occur at interfaces and surfaces, including charge transfer, energy transfer, proton transfer, proton-coupled electron transfer, configurational dynamics, conical intersections, etc. Of them, interactions of electronic and vibrational motions, namely, vibronic couplings, are the main determining factors for the relaxation processes or reaction pathways. However, time-resolved electronic-vibrational spectroscopy for interfaces and surfaces is lacking. Here we develop interface/surface-specific two-dimensional electronic-vibrational sum frequency generation spectroscopy (2D-EVSFG) for time-dependent vibronic coupling of excited states at interfaces and surfaces. We further demonstrate the fourth-order technique by investigating vibronic coupling, solvent correlation, and time evolution of the coupling for photoexcited interface-active molecules, crystal violet (CV), at the air/water interface as an example. The two vibronic absorption peaks for CV molecules at the interface from the 2D-EVSFG experiments were found to be more prominent than their counterparts in bulk from 2D-EV. Quantitative analysis of the vibronic peaks in 2D-EVSFG suggested that a non-Condon process participates in the photoexcitation of CV at the interface. We further reveal vibrational solvent coupling for the zeroth level on the electronic state with respect to that on the ground state, which is directly related to the magnitude of its change in solvent reorganization energy. The change in the solvent reorganization energy at the interface is much smaller than that in bulk methanol. Time-dependent center line slopes (CLSs) of 2D-EVSFG also showed that kinetic behaviors of CV at the air/water interface are significantly different from those in bulk methanol. Our ultrafast 2D-EVSFG experiments not only offer vibrational information on both excited states and the ground state as compared with the traditional doubly resonant sum frequency generation and electronic-vibrational coupling but also provide vibronic coupling, dynamical solvent effects, and time evolution of vibronic coupling at interfaces.

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Investigation of the Electronic Structure of CdS Nanoparticles with Sum Frequency Generation and Photoluminescence Spectroscopy

Cited by 12 publications

References 42 publications

Polaron States as a Massive Electron-Transfer Pathway at Heterojunction Interface

Polaron States as a Massive Electron-Transfer Pathway at Heterojunction Interface

Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods

Development of Two-Dimensional Electronic-Vibrational Sum Frequency Generation (2D-EVSFG) for Vibronic and Solvent Couplings of Molecules at Interfaces and Surfaces

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