scholarly journals Temperature dependence of acoustic vibrations of CdSe and CdSe–CdS core–shell nanocrystals measured by low-frequency Raman spectroscopy

2016 ◽  
Vol 18 (41) ◽  
pp. 28797-28801 ◽  
Author(s):  
A. Jolene Mork ◽  
Elizabeth M. Y. Lee ◽  
William A. Tisdale
Keyword(s):  
Raman Spectroscopy ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Low Frequency ◽  
Inhomogeneous Broadening ◽  
Core Shell ◽  
Acoustic Vibrations ◽  
Frequency Shifts ◽  
Higher Harmonic ◽  
Large Frequency

Low-temperature Raman spectroscopy reveals inhomogeneous broadening, surprisingly large frequency shifts, and the origin of higher harmonic peaks in core–shell nanocrystals.

scholarly journals Fundamental Investigations into Single Molecule Surface Enhanced Raman Spectroscopy

2021 ◽  
Author(s):  
◽  
Camille G. Artur
Keyword(s):  
Raman Spectroscopy ◽  
Temperature Dependence ◽  
Single Molecule ◽  
Nile Blue ◽  
Surface Enhanced Raman Spectroscopy ◽  
Inhomogeneous Broadening ◽  
Single Molecule Detection ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Homogeneous Broadening

<p>After the first claim of single molecule (SM) detection by surface enhanced Raman spectroscopy (SERS) was published in 1997 and years of debate and maturing, SM-SERS can now be considered as an established subfield of SERS. Besides the obvious promising advances in analytical spectroscopy that SM-SERS enables, some more fundamental studies are now also accessible. The main focus of this thesis is to understand certain aspects and tackle some outstanding issues in SM-SERS, both in methods and applications. In the first part of this thesis, we focus on the application of SM-SERS to the study of the homogeneous broadening of molecular vibrations. We show that the homogeneous linewidth of the dye Nile blue as measured on single molecule SERS spectra is much smaller than the inhomogeneous broadening obtained from the average signal. Individual molecules having the central Raman frequency occurring at slightly different positions is therefore the main cause of the inhomogeneous broadening in this system. Furthermore, we show that the homogeneous broadening of the mode of single molecules exhibits a strong temperature dependence from 80K to 300 K. This is suggestive of the vibrational energy exchange model which explicitly relates the temperature dependence of the linewidth of a vibrational mode to its interaction with other modes of the molecule or its environment. The average signal does not show this temperature dependence, this property is indeed washed out by ensemble averaging and its unravelling is made possible by SM-SERS. This study is the first example of direct measurement and study of the homogeneous broadening of a Raman peak. In the second part of this work, we focus on a particular method to prove single molecule sensitivity and demonstrate the single molecule detection of the iconic C₆₀ by SM-SERS using its peculiar spectral properties regarding isotopic substitution. A change in one unit mass in one of the carbon atoms is readily observed as a detectable frequency shift in the Ag(2) mode on the Raman spectrum of one C₆₀. This remarkable result is a direct consequence of the high symmetry of the molecule and is only accessible experimentally by measuring individual molecules. We perform SM-SERS detection of a isotopically enriched C₆₀ and show how the distribution of frequencies for the Ag(2) mode reflects the isotopic spread of the sample. Density Functional Theory (DFT) calculations support the experimental results. This provides the first ever evidence of single molecule detection of C₆₀ via SERS. Finally, we focus on the photostability of dyes excited resonantly in SERS conditions. Photobleaching of the molecule is an issue when doing SERS (and SM-SERS) at resonance. Nile blue is deposited on a highly ordered gold nanolithographic substrate and the time dependence of the SERS signal is monitored. Using a simple two-level system model to describe the mechanisms of photobleaching and express the photobleaching rate, we analyse the SERS intensity decay at different powers. This study is the first to be dedicated to the photobleaching decay rates of molecules on metallic surfaces and to highlight that the decay dynamics contains rates spanning four orders of magnitude. This work can potentially reveal information on the distribution of SERS enhancement factors on the surface.</p>

scholarly journals Fundamental Investigations into Single Molecule Surface Enhanced Raman Spectroscopy

2021 ◽  
Author(s):  
◽  
Camille G. Artur
Keyword(s):  
Raman Spectroscopy ◽  
Temperature Dependence ◽  
Single Molecule ◽  
Nile Blue ◽  
Surface Enhanced Raman Spectroscopy ◽  
Inhomogeneous Broadening ◽  
Single Molecule Detection ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Homogeneous Broadening

<p>After the first claim of single molecule (SM) detection by surface enhanced Raman spectroscopy (SERS) was published in 1997 and years of debate and maturing, SM-SERS can now be considered as an established subfield of SERS. Besides the obvious promising advances in analytical spectroscopy that SM-SERS enables, some more fundamental studies are now also accessible. The main focus of this thesis is to understand certain aspects and tackle some outstanding issues in SM-SERS, both in methods and applications. In the first part of this thesis, we focus on the application of SM-SERS to the study of the homogeneous broadening of molecular vibrations. We show that the homogeneous linewidth of the dye Nile blue as measured on single molecule SERS spectra is much smaller than the inhomogeneous broadening obtained from the average signal. Individual molecules having the central Raman frequency occurring at slightly different positions is therefore the main cause of the inhomogeneous broadening in this system. Furthermore, we show that the homogeneous broadening of the mode of single molecules exhibits a strong temperature dependence from 80K to 300 K. This is suggestive of the vibrational energy exchange model which explicitly relates the temperature dependence of the linewidth of a vibrational mode to its interaction with other modes of the molecule or its environment. The average signal does not show this temperature dependence, this property is indeed washed out by ensemble averaging and its unravelling is made possible by SM-SERS. This study is the first example of direct measurement and study of the homogeneous broadening of a Raman peak. In the second part of this work, we focus on a particular method to prove single molecule sensitivity and demonstrate the single molecule detection of the iconic C₆₀ by SM-SERS using its peculiar spectral properties regarding isotopic substitution. A change in one unit mass in one of the carbon atoms is readily observed as a detectable frequency shift in the Ag(2) mode on the Raman spectrum of one C₆₀. This remarkable result is a direct consequence of the high symmetry of the molecule and is only accessible experimentally by measuring individual molecules. We perform SM-SERS detection of a isotopically enriched C₆₀ and show how the distribution of frequencies for the Ag(2) mode reflects the isotopic spread of the sample. Density Functional Theory (DFT) calculations support the experimental results. This provides the first ever evidence of single molecule detection of C₆₀ via SERS. Finally, we focus on the photostability of dyes excited resonantly in SERS conditions. Photobleaching of the molecule is an issue when doing SERS (and SM-SERS) at resonance. Nile blue is deposited on a highly ordered gold nanolithographic substrate and the time dependence of the SERS signal is monitored. Using a simple two-level system model to describe the mechanisms of photobleaching and express the photobleaching rate, we analyse the SERS intensity decay at different powers. This study is the first to be dedicated to the photobleaching decay rates of molecules on metallic surfaces and to highlight that the decay dynamics contains rates spanning four orders of magnitude. This work can potentially reveal information on the distribution of SERS enhancement factors on the surface.</p>

Raman Spectroscopy of the Kaolinite Hydroxyls at 77 K

1998 ◽  
Vol 52 (10) ◽  
pp. 1277-1282 ◽  
Author(s):  
Ursula Johansson ◽  
Ray L. Frost ◽  
Willis Forsling ◽  
J. Theo Kloprogge
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Low Temperature ◽  
Liquid Nitrogen Temperature ◽  
Hydroxyl Groups ◽  
Frequency Shifts ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Inner Surface ◽  
Raman Microprobe

Raman spectroscopy of two types of kaolinites has been obtained at liquid nitrogen temperature (77 K) with the use of a Raman microprobe and a thermal stage. The Raman spectrum is characterized by the combination of the frequencies of the inner hydroxyl and the inner surface hydroxyl groups. The inner hydroxyl frequency is reduced, and the outer hydroxyl frequencies move to higher frequencies upon cooling to 77 K. The inner hydroxyl frequency shifts from 3620 cm−1 at 298 K to 3615 cm−1 at 77 K. The two in-phase inner surface hydroxyl frequencies move from 3684 and 3689 cm−1 at 298 K to 3690 and 3699 cm−1 at 77 K. The two out-of-phase vibrations shift from 3650 and 3668 cm−1 to 3656 and 3675 cm−1. The bandwidth of the inner hydroxyl frequency decreases from 3.7 to 2.1 cm−1 at 77 K. The bandwidth of the inner surface hydroxyl frequency ( v1) increases upon cooling from 17.4 to 19.2 cm−1. It is proposed that the increased resolution at low temperature enabled an additional inner surface hydroxyl frequency to be observed.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

The Microscopic Structure Of Shallow Donors In Silicon Carbide

1996 ◽  
Vol 442 ◽  
Author(s):  
J.-M. Spaeth ◽  
S. Greulich-Weber ◽  
M. März ◽  
E. N. Kalabukhova ◽  
S. N. Lukin
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Double Resonance ◽  
Epr Spectra ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
Temperature Spectra ◽  
Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

Raman spectroscopy study of acetonitrile at low temperature

2021 ◽  
Vol 246 ◽  
pp. 119065
Author(s):  
Shuo Zhang ◽  
Hongsheng Jia ◽  
Mingxing Song ◽  
He Shen ◽  
Li Dongfei ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Low Temperature ◽  
Spectroscopy Study

scholarly journals Bimetallic Core–Shell Nanoparticles of Gold and Silver via Bioinspired Polydopamine Layer as Surface-Enhanced Raman Spectroscopy (SERS) Platform

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 688 ◽  
Author(s):  
Asli Yilmaz ◽  
Mehmet Yilmaz
Keyword(s):  
Raman Spectroscopy ◽  
Low Cost ◽  
Silver Ions ◽  
Surface Enhanced Raman Spectroscopy ◽  
Core Shell ◽  
Silver Deposition ◽  
Shell Nanoparticles ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Core Shell Nanoparticles

Despite numerous attempts to fabricate the core–shell nanoparticles, novel, simple, and low-cost approaches are still required to produce these efficient nanosystems. In this study, we propose the synthesis of bimetallic core–shell nanoparticles of gold (AuNP) and silver (AgNP) nanostructures via a bioinspired polydopamine (PDOP) layer and their employment as a surface-enhanced Raman spectroscopy (SERS) platform. Herein, the PDOP layer was used as an interface between nanostructures as well as stabilizing and reducing agents for the deposition of silver ions onto the AuNPs. UV-vis absorption spectra and electron microscope images confirmed the deposition of the silver ions and the formation of core–shell nanoparticles. SERS activity tests indicated that both the PDOP thickness and silver deposition time are the dominant parameters that determine the SERS performances of the proposed core–shell system. In comparison to bare AuNPs, more than three times higher SERS signal intensity was obtained with an enhancement factor of 3.5 × 105.

The low temperature dependence of magnetization of as-deposited Fe-Hf-C-N nanocrystalline thin films

1999 ◽  
Vol 12 (5-8) ◽  
pp. 1097-1102 ◽  
Author(s):  
K.S. Kirn ◽  
Y.H. Seong ◽  
S.C. Yu ◽  
S.H. Han ◽  
H.J. Kim
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Nanocrystalline Thin Films
Sign in / Sign up

Export Citation Format

Share Document