scholarly journals Spatial Dependence of the Dipolar Interaction between Quantum Dots and Organic Molecules Probed by Two-Color Sum-Frequency Generation Spectroscopy

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 294
Author(s):  
Thomas Noblet ◽  
Laurent Dreesen ◽  
Abderrahmane Tadjeddine ◽  
Christophe Humbert
Keyword(s):  
Quantum Dots ◽  
Spatial Dependence ◽  
Detection Threshold ◽  
Dipolar Interaction ◽  
Sum Frequency Generation ◽  
Attenuated Total Reflection ◽  
Sum Frequency ◽  
Non Linear ◽  
Frequency Generation ◽  
Linear Optical

Given the tunability of their optical properties over the UV–Visible–Near IR spectral range, ligand-capped quantum dots (QDs) are employed for the design of optical biosensors with low detection threshold. Thanks to non-linear optical spectroscopies, the absorption properties of QDs are indeed used to selectively enhance the local vibrational response of molecules located in their vicinity. Previous studies led to assume the existence of a vibroelectronic QD–molecule coupling based on dipolar interaction. However, no systematic study on the strength of this coupling has been performed to date. In order to address this issue, we use non-linear optical Two-Color Sum-Frequency Generation (2C-SFG) spectroscopy to probe thick QD layers deposited on calcium fluoride (CaF2) prisms previously functionalized by a self-assembled monolayer of phenyltriethoxysilane (PhTES) molecules. Here, 2C-SFG is performed in Attenuated Total Reflection (ATR) configuration. By comparing the molecular vibrational enhancement measured for QD–ligand coupling and QD–PhTES coupling, we show that the spatial dependence of the QD–molecule interactions (∼1/r3, with r the QD–molecule distance) is in agreement with the hypothesis of a dipole–dipole interaction.

scholarly journals Sum-Frequency Generation Spectroscopy of Plasmonic Nanomaterials: A Review

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 836 ◽  
Author(s):  
Christophe Humbert ◽  
Thomas Noblet ◽  
Laetitia Dalstein ◽  
Bertrand Busson ◽  
Grégory Barbillon
Keyword(s):  
Metallic Nanoparticles ◽  
Surface Enhanced Raman Spectroscopy ◽  
Research Field ◽  
Sum Frequency Generation ◽  
Localized Surface Plasmon ◽  
Linear Optics ◽  
Sum Frequency ◽  
Surface Probe ◽  
Non Linear ◽  
Frequency Generation

We report on the recent scientific research contribution of non-linear optics based on Sum-Frequency Generation (SFG) spectroscopy as a surface probe of the plasmonic properties of materials. In this review, we present a general introduction to the fundamentals of SFG spectroscopy, a well-established optical surface probe used in various domains of physical chemistry, when applied to plasmonic materials. The interest of using SFG spectroscopy as a complementary tool to surface-enhanced Raman spectroscopy in order to probe the surface chemistry of metallic nanoparticles is illustrated by taking advantage of the optical amplification induced by the coupling to the localized surface plasmon resonance. A short review of the first developments of SFG applications in nanomaterials is presented to span the previous emergent literature on the subject. Afterwards, the emphasis is put on the recent developments and applications of the technique over the five last years in order to illustrate that SFG spectroscopy coupled to plasmonic nanomaterials is now mature enough to be considered a promising research field of non-linear plasmonics.

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.

Toward industrial and fibered non-linear sum frequency generation devices

2021 ◽  
Author(s):  
Alexis Mehlman ◽  
David Holleville ◽  
Michel Lours ◽  
Sebastien Bize ◽  
Ouali Acef ◽  
...  
Keyword(s):  
Sum Frequency Generation ◽  
Sum Frequency ◽  
Non Linear ◽  
Frequency Generation

Terahertz emission in quantum dots by sum frequency generation

2016 ◽  
Vol 16 (7) ◽  
pp. 763-771
Author(s):  
M. Abdullah ◽  
Farah T. Mohammed Noori ◽  
Amin H. Al-Khursan
Keyword(s):  
Quantum Dots ◽  
Sum Frequency Generation ◽  
Terahertz Emission ◽  
Sum Frequency ◽  
Frequency Generation

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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