Charge-Transfer Dynamics Promoted by Hole Trap States in CdSe Quantum Dots–Ni2+ Photocatalytic System

2017 ◽  
Vol 121 (32) ◽  
pp. 17112-17120 ◽  
Author(s):  
Yun Ye ◽  
Xiuli Wang ◽  
Sheng Ye ◽  
Yuxing Xu ◽  
Zhaochi Feng ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Charge Transfer ◽  
Cdse Quantum Dots ◽  
Hole Trap ◽  
Trap States ◽  
Photocatalytic System ◽  
Charge Transfer Dynamics

scholarly journals Hydrophilic, Hole-Delocalizing Ligand Shell to Promote Charge Transfer from Colloidal CdSe Quantum Dots in Water

2017 ◽  
Vol 121 (28) ◽  
pp. 15160-15168 ◽  
Author(s):  
Jonathan R. Lee ◽  
Wei Li ◽  
Alexander J. Cowan ◽  
Frank Jäckel
Keyword(s):  
Quantum Dots ◽  
Charge Transfer ◽  
Cdse Quantum Dots ◽  
Ligand Shell

scholarly journals Coupled Charge Transfer Dynamics and Photoluminescence Quenching in Monolayer MoS2 Decorated with WS2 Quantum Dots

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Larionette P. L. Mawlong ◽  
Abhilasha Bora ◽  
P. K. Giri
Keyword(s):  
Quantum Dots ◽  
Charge Transfer ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Kelvin Probe ◽  
Photoluminescence Quenching ◽  
Force Microscopy ◽  
Level Model ◽  
Microscopy Analysis ◽  
Charge Transfer Dynamics

AbstractHerein, we have investigated the tunability of the photoluminescence (PL) of the monolayer MoS2 (1L-MoS2) by decorating it with WS2 quantum dots (WS2 QD). The direct bandgap 1L-MoS2 and WS2 QDs are grown by chemical vapor deposition and liquid exfoliation methods, respectively. The room temperature PL spectrum of bare 1L-MoS2 is systematically quenched with its decoration with WS2 QDs at different concentrations. A decrease in the work function of 1L-MoS2 with the decoration of WS2 QDs was established from the Kelvin probe force microscopy analysis. A detailed quantitative analysis using the four-energy level model involving coupled charge transfer was employed to explain the redshift and the systematic decrease in the intensity of the PL peak in 1L-MoS2/WS2 QD heterostructure. The modulation of the PL in the heterostructure is attributed to the increase in the formation of negative trions through the charge transfer from WS2 QD to the 1L-MoS2 and thus making the 1L-MoS2 heavily n-type doped, with increase in the electron density by ~1.5 × 1013 cm−2. This study establishes the contribution of defects in the coupled charge transfer dynamics in 1L-MoS2, and it lays out a convenient strategy to manipulate the optical and electrical properties of 1L-MoS2 for various optoelectronic applications.

Charge transfer dynamics between MPA capped CdTe quantum dots and methyl viologen

2017 ◽  
Vol 346 ◽  
pp. 382-389 ◽  
Author(s):  
Alessandro Iagatti ◽  
Luigi Tarpani ◽  
Eleonora Fiacchi ◽  
Laura Bussotti ◽  
Loredana Latterini ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Charge Transfer ◽  
Methyl Viologen ◽  
Cdte Quantum Dots ◽  
Charge Transfer Dynamics

scholarly journals Size-Dependent Non-FRET Photoluminescence Quenching in Nanocomposites Based on Semiconductor Quantum Dots CdSe/ZnS and Functionalized Porphyrin Ligands

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Eduard I. Zenkevich ◽  
Thomas Blaudeck ◽  
Alexander Milekhin ◽  
Christian von Borczyskowski
Keyword(s):  
Quantum Dots ◽  
Charge Transfer ◽  
Semiconductor Quantum Dots ◽  
Trap States ◽  
Quenching Rate ◽  
Time Resolved ◽  
Exciton Wave Function ◽  
Electron Hole Pair ◽  
Colloidal Semiconductor ◽  
Pl Quenching

We review recent experimental work to utilize the size dependence of the luminescence quenching of colloidal semiconductor quantum dots induced by functionalized porphyrin molecules attached to the surface to describe a photoluminescence (PL) quenching process which is different from usual models of charge transfer (CT) or Foerster resonant energy transfer (FRET). Steady-state and picosecond time-resolved measurements were carried out for nanocomposites based on colloidal CdSe/ZnS and CdSe quantum dots (QDs) of various sizes and surfacely attached tetra-mesopyridyl-substituted porphyrin molecules (“Quantum Dot-Porphyrin” nanocomposites), in toluene at 295 K. It was found that the major part of the observed strong quenching of QD PL in “QD-Porphyrin” nanocomposites can neither be assigned to FRET nor to photoinduced charge transfer between the QD and the chromophore. This PL quenching depends on QD size and shell and is stronger for smaller quantum dots: QD PL quenching rate constants scale inversely with the QD diameter. Based on the comparison of experimental data and quantum mechanical calculations, it has been concluded that QD PL quenching in “QD-Porphyrin” nanocomposites can be understood in terms of a tunneling of the electron (of the excited electron-hole pair) followed by a (self-) localization of the electron or formation of trap states. The major contribution to PL quenching is found to be proportional to the calculated quantum-confined exciton wave function at the QD surface. Our findings highlight that single functionalized molecules can be considered as one of the probes for the complex interface physics and dynamics of colloidal semiconductor QD.

Energetics at the Edge: Direct Optical Mapping of Bulk and Interfacial Electronic Structure in CdSe Quantum Dots using Broadband Electronic Sum Frequency Generation Microspectroscopy

2019 ◽  
Author(s):  
Brianna R. Watson ◽  
Benjamin Doughty ◽  
Tessa Calhoun
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Sum Frequency Generation ◽  
Cdse Quantum Dots ◽  
Trap States ◽  
Sum Frequency ◽  
Interfacial Electronic Structure ◽  
Wide Range ◽  
Frequency Generation ◽  
Gap States

Understanding and controlling the electronic structure of nanomaterials is the key to tailoring their use in a wide range of practical applications. Despite this need, many important electronic states are invisible to conventional optical measurements and are typically identified indirectly based on their inferred impact on luminescence properties. This is especially common and important in the study of nanomaterial surfaces and their associated defects. Surface trap states play a crucial role in photophysical processes yet remain remarkably poorly understood. Here we demonstrate for the first time that broadband electronic sum frequency generation (eSFG) microspectroscopy can directly map the optically bright and dark states of nanoparticles, including the elusive below gap states. This new approach is applied to model cadmium selenide (CdSe) quantum dots (QDs), where the energies of interfacial trap states have eluded direct optical characterization for decades. Our eSFG measurements show clear signatures of electronic transitions both above the band gap, which we assign to previously reported one- and two-photon transitions associated with the CdSe core, as well as broad spectral signatures below the bandgap that are attributed to interfacial trap states. In addition to the core states, this analysis reveals two distinct distributions of below gap states providing the first direct optical measurement of both shallow and deep trapping sites on this system. Finally, chemical modification of the surfaces via oxidation results in the relative increase in the signals originating from the interfacial trap states. Overall, our eSFG experiments provide an avenue to directly map the entirety of QD bulk and interfacial electronic structure, which is expected to open up opportunities to study how these materials are grown <i>in situ</i> and how surface states can be controlled to tune functionality.

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