Anomalous Raman Scattering In Few Monolayer MoTe2

MRS Advances ◽  
2017 ◽  
Vol 2 (29) ◽  
pp. 1539-1544 ◽  
Author(s):  
Katarzyna Gołasa ◽  
Magdalena Grzeszczyk ◽  
Maciej R. Molas ◽  
Małgorzata Zinkiewicz ◽  
Karol Nogajewski ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Room Temperature ◽  
Effect Of Temperature ◽  
Destructive Interference ◽  
Scattering Spectrum ◽  
Out Of Plane ◽  
Light Excitation ◽  
Phase Out ◽  
Plane Mode ◽  
Intensity Evolution

ABSTRACTThe effect of temperature (5K to 300K) on the Raman scattering due to A1g/A1’ modes associated with the out-of-plane vibrations in bilayer (2L) and trilayer (3L) MoTe2 is investigated. The temperature evolution of the modes critically depends on the flake thickness. The A1g mode intensity in 2L MoTe2 observed with λ=632.8 nm light excitation decreases with decreasing temperature down to 220K and the mode vanishes from the Stokes scattering spectrum in the temperature range between 160K and 220K. The peak recovers at lower temperatures and at T=5K it becomes three times more intense that at room temperature. Similar non-monotonic intensity evolution is observed for the A1’ mode in 3L MoTe2 in which tellurium atoms in all three layers vibrate in-phase. On the contrary, the intensity of the other out-of-plane Raman-active mode in which vibrations of tellurium atoms in the central layer of 3L MoTe2 are shifted by 180° with respect to vibrations in outer layers, only weakly depends on temperature.The observed quenching of the out-of-plane modes in the Raman scattering in thin MoTe2 layers is related to the destructive interference of the resonant- and the non-resonant contributions to the Raman scattering. The resonance with the M point of the Brillouin zone in few-layers of MoTe2 is considered. Effects related to the resonant quenching of the in-phase out-of-plane mode are discussed.

scholarly journals Resonant quenching of Raman scattering due to out-of-plane A1g/A′1 modes in few-layer MoTe2

Nanophotonics ◽  
2017 ◽  
Vol 6 (6) ◽  
pp. 1281-1288 ◽  
Author(s):  
Katarzyna Gołasa ◽  
Magda Grzeszczyk ◽  
Maciej R. Molas ◽  
Małgorzata Zinkiewicz ◽  
Łukasz Bala ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Scattering Amplitude ◽  
Destructive Interference ◽  
Phonon Modes ◽  
Temperature Dependent ◽  
Scattering Spectrum ◽  
Out Of Plane ◽  
Light Excitation ◽  
Scattering Study ◽  
Plane Mode

AbstractTemperature-dependent (5 K–300 K) Raman scattering study of A1g/A′1 phonon modes in mono-layer (1L), bilayer (2L), trilayer (3L), and tetralayer (4L) MoTe2 is reported. The temperature evolution of the modes’ intensity critically depends on the flake thickness. In particular with λ=632.8-nm light excitation, a strongly non-monotonic dependence of the A1g mode intensity is observed in 2L MoTe2. The intensity decreases with decreasing temperature down to 220 K, and the A1g mode almost completely vanishes from the Stokes scattering spectrum in the temperature range between 160 K and 220 K. The peak recovers at lower temperatures, and at T=5 K, it becomes three times more intense that at room temperature. Similar non-monotonic intensity evolution is observed for the out-of-plane mode in 3L MoTe2 in which tellurium atoms in all three layers vibrate in-phase. The intensity of the other out-of-plane Raman-active mode (with vibrations of tellurium atoms in the central layer shifted by 180° with respect to the vibrations in outer layers) only weakly depends on temperature. The observed quenching of the Raman scattering in 2L and 3L MoTe2 is attributed to a destructive interference between the resonant and non-resonant contributions to the Raman scattering amplitude. The observed “antiresonance” is related to the electronic excitation at the M point of the Brillouin zone in few-layer MoTe2.

Effect of Temperature on ADP-Induced Platelet Aggregation

1973 ◽  
Vol 29 (01) ◽  
pp. 183-189
Author(s):  
C. A Praga ◽  
E. M Pogliani
Keyword(s):  
Platelet Aggregation ◽  
Incubation Period ◽  
Room Temperature ◽  
Important Variable ◽  
Practical Significance ◽  
Effect Of Temperature ◽  
Induce Platelet Aggregation ◽  
Cuvette Holder ◽  
Exact Temperature

SummaryTemperature represents a very important variable in ADP-induced platelet aggregation.When low doses of ADP ( < 1 (μM) are used to induce platelet aggregation, the length of the incubation period of PRP in the cuvette holder of the aggregometer, thermostatted at 37° C, is very critical. Samples of the same PRP previously kept at room temperature, were incubated for increasing periods of time in the cuvette of the aggregometer before adding ADP, and a significant decrease of aggregation, proportional to the length of incubation, was observed. Stirring of the PRP during the incubation period made these changes more evident.To measure the exact temperature of the PRP during incubation in the aggre- gometer, a thermocouple device was used. While the temperature of the cuvette holder was stable at 37° C, the PRP temperature itself increased exponentially, taking about ten minutes from the beginning of the incubation to reach the value of 37° C. The above results have a practical significance in the reproducibility of the platelet aggregation test in vitro and acquire particular value when the effect of inhibitors of ADP induced platelet aggregation is studied.Experiments carried out with three anti-aggregating agents (acetyl salicyclic acid, dipyridamole and metergoline) have shown that the incubation conditions which influence both the effect of the drugs on platelets and the ADP breakdown in plasma must be strictly controlled.

scholarly journals Green Biosynthesis of Silver Nanoparticles Using Leaf Extract of Carissa carandas L. and Their Antioxidant and Antimicrobial Activity against Human Pathogenic Bacteria

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 299
Author(s):  
Reetika Singh ◽  
Christophe Hano ◽  
Gopal Nath ◽  
Bechan Sharma
Keyword(s):  
Silver Nanoparticles ◽  
Pathogenic Bacteria ◽  
Leaf Extract ◽  
Room Temperature ◽  
Xrd Analysis ◽  
Antibacterial Activities ◽  
Effect Of Temperature ◽  
Human Pathogenic Bacteria ◽  
Carissa Carandas ◽  
Antioxidant And Antimicrobial Activity

Carissa carandas L. is traditionally used as antibacterial medicine and accumulates many antioxidant phytochemicals. Here, we expand this traditional usage with the green biosynthesis of silver nanoparticles (AgNPs) achieved using a Carissa carandas L. leaf extract as a reducing and capping agent. The green synthesis of AgNPs reaction was carried out using 1mM silver nitrate and leaf extract. The effect of temperature on the synthesis of AgNPs was examined using room temperature (25 °C) and 60 °C. The silver nanoparticles were formed in one hour by stirring at room temperature. In this case, a yellowish brown colour was developed. The successful formation of silver nanoparticles was confirmed by UV–Vis, Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) analysis. The characteristic peaks of the UV-vis spectrum and XRD confirmed the synthesis of AgNPs. The biosynthesised AgNPs showed potential antioxidant activity through DPPH assay. These AgNPs also exhibited potential antibacterial activity against human pathogenic bacteria. The results were compared with the antioxidant and antibacterial activities of the plant extract, and clearly suggest that the green biosynthesized AgNPs can constitute an effective antioxidant and antibacterial agent.

scholarly journals Consecutive Vibrational Redistribution and Predissociation Processes in s-Tetrazine–Argon Van Der Waals Complexes

1983 ◽  
Vol 2 (3-4) ◽  
pp. 125-135 ◽  
Author(s):  
J. J. F. Ramaekers ◽  
L. B. Krijnen ◽  
H. J. Lips ◽  
J. Langelaar ◽  
R. P. H. Rettschnick
Keyword(s):  
Decay Time ◽  
Van Der Waals ◽  
Stagnation Pressure ◽  
Van Der Waals Complexes ◽  
Supersonic Expansion ◽  
Vibrational Predissociation ◽  
Out Of Plane ◽  
Spectrally Resolved ◽  
Plane Mode

s-Tetrazine argon complexes T−Arn (n = 1, 2) are formed in a supersonic expansion of argon seeded with s-tetrazine. The expansion was conducted through a nozzle of 50 or 100 μm with an argon stagnation pressure between 1 and 1.5 bar. From spectrally resolved measurements it is clear that vibrational redistribution processes as well as vibrational predissociation processes take place after SVL excitation within the complex.From rise and decay time experiments it can be concluded, that after excitation of the 6a1 complex level, the above mentioned processes are consecutive and not parallel. It appears that the out of plane mode 16a couples with the Van der Waals stretching mode. The predissociation rate of the 16a2 complex is observed to be 2.3 × 109 s−1.

ROOM TEMPERATURE PHOTOLUMINESCENCE OF POLYCRYSTALLINE SIC PREPARED FROM CARBON-SATURATED SI MELT

2002 ◽  
Vol 16 (06n07) ◽  
pp. 1047-1051
Author(s):  
JIANPING MA ◽  
ZHIMING CHEN ◽  
GANG LU ◽  
MINGBIN YU ◽  
LIANMAO HANG ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Uv Light ◽  
X Ray Diffraction ◽  
X Ray ◽  
Room Temperature Photoluminescence ◽  
Composition And Structure ◽  
Light Excitation ◽  
Scanning Electron

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline SiC samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650°C. Composition and structure of the samples have been confirmed by means of X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. PL measurements with 325 nm UV light excitation revealed that the room temperature PL spectrum of the samples consists of 3 luminescent bands, the peak energies of which are 2.38 eV, 2.77 eV and 3.06 eV, respectively. The 2.38 eV band is much stronger than the others. It is suggested that some extrinsic PL mechanisms associated with defect or interface states would be responsible to the intensive PL observed at room temperature.

Rotational Temperature Measurement in Multicomponent Gases Using Raman Scattering Spectroscopy

1976 ◽  
Vol 30 (2) ◽  
pp. 179-183 ◽  
Author(s):  
R. S. Hickman ◽  
A. E. Kassem ◽  
L. H. Liang
Keyword(s):  
Temperature Field ◽  
Raman Scattering ◽  
Temperature Measurement ◽  
Cross Section ◽  
Room Temperature ◽  
Rotational Temperature ◽  
Raman Scattering Spectroscopy ◽  
Scattering Experiment ◽  
Cross Section Area ◽  
Section Area

The rotational temperature at pressures near 1 atm and at room temperature has been successfully measured using spectra obtained in an intracavity Raman scattering experiment. The accuracy of the method is sufficient to allow local temperature measurement of multicomponent gases with no disturbance in the temperature field. The advantage of the method lies in the fact that it does not require knowledge of the relative scattering cross-section area of the component gases.

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