scholarly journals Laser-induced reprecipitation of pyrene at 77 K and its dynamics as studied by spectroscopic techniques

2018 ◽  
Vol 17 (7) ◽  
pp. 910-916 ◽  
Author(s):  
Fuyuki Ito ◽  
Satoshi Miyadera ◽  
Hirohisa Matsuda ◽  
Yukihide Ishibashi ◽  
Syoji Ito ◽  
...  
Keyword(s):  
Laser Pulses ◽  
Spectroscopic Techniques ◽  
Glassy Solution

Reprecipitation of pyrene (Py) in the glassy solution of methylcyclohexane and isopentane at 77 K was observed by the repetitive irradiation of nanosecond (ns) laser pulses at 355 nm.

Preparation and Characterization of TiO2 Nanostructures for Catalytic CO2 Photoconversion

2011 ◽  
Vol 183 ◽  
pp. 89-94 ◽  
Author(s):  
Anna Iwulska ◽  
G. Sliwinski
Keyword(s):  
Active Surface ◽  
Laser Pulses ◽  
Point Of View ◽  
Deep Penetration ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray ◽  
Content Ratio ◽  
Photocatalytic Applications

The titanium dioxide target (99.7%) of 1 cm in dia was ablated in vacuum by laser pulses (6 ns) at 266 nm and at repetition rate of 10 Hz. During deposition the laser fluence between 1 and 3.5 J/cm2 and the O2 pressure from the range of 10-2 – 1 Pa were applied. The thin TiO2 films were deposited on glass substrate (1 × 1 cm2) heated up to 500 °C. The chemical composition of the film and samples produced by annealing were investigated by spectroscopic techniques (μ-Raman, EDX) and the structure, porosity and surface morphology were analysed by means of SEM and x-ray diffraction (XRD). The SEM inspection of the TiO2 thin film samples indicates that the obtained material is mostly crystalline. After annealing in O2 at 500 °C the structure characterized by the presence of both anatase and rutile phases is observed in the Raman spectra and confirmed by the XRD data. The phase content ratio depends on the O2 pressure applied. Results confirm that nanostructures produced in this way represent densely packed columns and promote deep penetration of guest particles such as CO2.The resulting large active surface is advantageous from the point of view of photocatalytic applications.

scholarly journals Micropatterning MoS2/Polyamide Electrospun Nanofibrous Membranes Using Femtosecond Laser Pulses

Photonics ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 3 ◽  
Author(s):  
Kelly T. Paula ◽  
Luiza A. Mercante ◽  
Rodrigo Schneider ◽  
Daniel S. Correa ◽  
Cleber R. Mendonca
Keyword(s):  
Laser Ablation ◽  
Composite Nanofibers ◽  
Electrospun Nanofibers ◽  
Scanning Speed ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Spectroscopic Techniques ◽  
Fs Laser ◽  
Nanofibrous Membranes ◽  
Scale Control

The capability of modifying and patterning the surface of polymer and composite materials is of high significance for various biomedical and electronics applications. For example, the use of femtosecond (fs) laser ablation for micropatterning electrospun nanofiber scaffolds can be successfully employed to fabricate complex polymeric biomedical devices, including scaffolds. Here we investigated fs-laser ablation as a flexible and convenient method for micropatterning polyamide (PA6) electrospun nanofibers that were modified with molybdenum disulfide (MoS2). We studied the influence of the laser pulse energy and scanning speed on the topography of electrospun composite nanofibers, as well as the irradiated areas via scanning electron microscopy and spectroscopic techniques. The results showed that using the optimal fs-laser parameters, micropores were formed on the electrospun nanofibrous membranes with size scale control, while the nature of the nanofibers was preserved. MoS2-modified PA6 nanofibrous membranes showed good photoluminescence properties, even after fs-laser microstructuring. The results presented here demonstrated potential application in optoelectronic devices. In addition, the application of this technique has a great deal of potential in the biomedical field, such as in tissue engineering.

PHOTOGENERATION OF HIGHLY ABSORBING TRANSIENT CHARGE STATES FROM MODEL DENDRITIC MACROMOLECULES BASED ON BIS-(DIPHENYLAMINO)DIPHENYLPOLYENE REPEAT UNITS

2000 ◽  
Vol 09 (04) ◽  
pp. 469-480 ◽  
Author(s):  
AMY HYFIELD ◽  
WENDI SONNENBERG ◽  
YANONG HAN ◽  
LEE H. SPANGLER ◽  
El HADJ ELANDALOUSSI ◽  
...  
Keyword(s):  
Cross Sections ◽  
Transient State ◽  
Laser Pulses ◽  
Photon Absorption ◽  
Spectroscopic Techniques ◽  
New Materials ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Repeat Units ◽  
Charge States

Bis-(diphenylamino)diphenylpolyenes form exceptionally stable, highly absorbing, bipolaronic charge states when oxidatively doped in solution, even at the stilbene level. These chromophores also display exceptionally large two-photon absorption cross-sections for ns laser pulses. 1,2-Bis-(diphenylamino)-E-stilbene moieties have now been incorporated into 3-arm and four-arm dendrimer structures as formal repeat units. These new G-0 model dendrimers also form exceptionally stable, highly-absorbing bipolaronic charge states when oxidized in solution. As such these new materials are attractive candidates for various photonic applications which depend on the fast photogeneration of highly absorbing transient states. In the current study we have demonstrated that such states can indeed be photogenerated from the model dendrimers in solution in the presence of efficient electron acceptors, such as C 60. In order to follow both the generation and decay of these excited state transient species, new spectroscopic techniques have been developed that have unique capabilities for examining transient state formation and subsequent dynamics.

Nonlinear spectroscopy in the near-field: time resolved spectroscopy and subwavelength resolution non-invasive imaging

Nanophotonics ◽  
2014 ◽  
Vol 3 (1-2) ◽  
pp. 61-73 ◽  
Author(s):  
Mahesh Namboodiri ◽  
Tahirzeb Khan ◽  
Khadga Karki ◽  
Mehdi Mohammad Kazemi ◽  
Sidhant Bom ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Near Field ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Nonlinear Spectroscopy ◽  
Spectroscopic Techniques ◽  
Time Resolved ◽  
Spatially Resolved ◽  
First Results ◽  
Wavelength Resolution

AbstractThe combination of near-field microscopy along with nonlinear optical spectroscopic techniques is presented here. The scanning near-field imaging technique can be integrated with nonlinear spectroscopic techniques to improve spatial and axial resolution of the images. Additionally, ultrafast dynamics can be probed down to nano-scale dimension. The review shows some examples for this combination, which resulted in an exciton map and vibrational contrast images with sub-wavelength resolution. Results of two-color femtosecond time-resolved pump-probe experiments using scanning near-field optical microscopy (SNOM) on thin films of the organic semiconductor 3,4,9,10 Perylenetetracarboxylic dianhydride (PTCDA) are presented. While nonlinear Raman techniques have been used to obtain highly resolved images in combination with near-field microscopy, the use of femtosecond laser pulses in electronic resonance still constitutes a big challenge. Here, we present our first results on coherent anti-Stokes Raman scattering (fs-CARS) with femtosecond laser pulses detected in the near-field using SNOM. We demonstrate that highly spatially resolved images can be obtained from poly(3-hexylthiophene) (P3HT) nano-structures where the fs-CARS process was in resonance with the P3HT absorption and with characteristic P3HT vibrational modes without destruction of the samples. Sub-diffraction limited lateral resolution is achieved. Especially the height resolution clearly surpasses that obtained with standard microCARS. These results will be the basis for future investigations of mode-selective dynamics in the near-field.

X-ray Raman scattering: a building block for nonlinear spectroscopy

2019 ◽  
Vol 377 (2145) ◽  
pp. 20170471 ◽  
Author(s):  
Nina Rohringer
Keyword(s):  
Raman Scattering ◽  
Laser Pulses ◽  
Nonlinear Spectroscopy ◽  
Atomic Gases ◽  
Successful Implementation ◽  
Spectroscopic Techniques ◽  
X Rays ◽  
X Ray ◽  
First Results ◽  
Electronic Motion

Ultraintense X-ray free-electron laser pulses of attosecond duration can enable new nonlinear X-ray spectroscopic techniques to observe coherent electronic motion. The simplest nonlinear X-ray spectroscopic concept is based on stimulated electronic X-ray Raman scattering. We present a snapshot of recent experimental achievements, paving the way towards the goal of realizing nonlinear X-ray spectroscopy. In particular, we review the first proof-of-principle experiments, demonstrating stimulated X-ray emission and scattering in atomic gases in the soft X-ray regime and first results of stimulated hard X-ray emission spectroscopy on transition metal complexes. We critically asses the challenges that have to be overcome for future successful implementation of nonlinear coherent X-ray Raman spectroscopy. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

Differential polarization imaging of sickled cells

1988 ◽  
Vol 46 ◽  
pp. 62-63
Author(s):  
Marcos F. Maestre
Keyword(s):  
Optical Properties ◽  
Theoretical Approach ◽  
Polarized Light ◽  
Polarization Microscopy ◽  
Spectroscopic Techniques ◽  
Polarization Imaging ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Microscopic Scale ◽  
Chiral Structures

Recently we have developed a form of polarization microscopy that forms images using optical properties that have previously been limited to macroscopic samples. This has given us a new window into the distribution of structure on a microscopic scale. We have coined the name differential polarization microscopy to identify the images obtained that are due to certain polarization dependent effects. Differential polarization microscopy has its origins in various spectroscopic techniques that have been used to study longer range structures in solution as well as solids. The differential scattering of circularly polarized light has been shown to be dependent on the long range chiral order, both theoretically and experimentally. The same theoretical approach was used to show that images due to differential scattering of circularly polarized light will give images dependent on chiral structures. With large helices (greater than the wavelength of light) the pitch and radius of the helix could be measured directly from these images.

Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

1988 ◽  
Vol 46 ◽  
pp. 880-881
Author(s):  
Bradley L. Thiel ◽  
Chan Han R. P. ◽  
Kurosky L. C. Hutter ◽  
I. A. Aksay ◽  
Mehmet Sarikaya
Keyword(s):  
Grain Boundary ◽  
Cuprous Oxide ◽  
Room Temperature ◽  
Boundary Phase ◽  
Spectroscopic Techniques ◽  
Transition Width ◽  
Practical Applications ◽  
Thin Foils ◽  
Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

Causal heat transport induced by zeptosecond laser pulses

2002 ◽  
Vol 12 (3) ◽  
pp. 201-206 ◽  
Author(s):  
Janina Marciak-Kozłowska ◽  
Mirosław Kozłowski
Keyword(s):  
Heat Transport ◽  
Laser Pulses

Transient collisional excitation X-ray laser generation with picoseconds laser pulses

2001 ◽  
Vol 11 (PR2) ◽  
pp. Pr2-39-Pr2-42 ◽  
Author(s):  
M. Kado ◽  
T. Kawachi ◽  
N. Hasegawa ◽  
M. Tanaka ◽  
K. Sukegawa ◽  
...  
Keyword(s):  
Laser Pulses ◽  
Laser Generation ◽  
Collisional Excitation ◽  
X Ray
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