STUDY ON PHOTOBLEACHING OF METHYLENE BLUE DOPED IN PMMA, PVA AND GELATIN USING PHOTOACOUSTIC TECHNIQUE

2003 ◽  
Vol 12 (01) ◽  
pp. 91-100 ◽  
Author(s):  
W. MAHMOOD MAT YUNUS ◽  
KOK SHENG CHAN ◽  
WAN MD. ZIN WAN YUNUS
Keyword(s):  
Methylene Blue ◽  
Raman Spectroscopy ◽  
Thermal Diffusivity ◽  
Laser Power ◽  
Solid Matrix ◽  
Beam Power ◽  
Poly Vinyl Alcohol ◽  
Photoacoustic Technique ◽  
Incident Laser ◽  
Incident Laser Power

The photobleaching of Methylene blue embedded in the solid matrix PMMA (poly(methylmethacrylate)), PVA (poly(vinyl alcohol)) and gelatin has been investigated using a photoacoustic technique. Photoacoustic signals were measured as a function of time, chopping frequency, and the beam power. Experimental results indicate that the photobleaching rate is proportional to the incident laser power (260–300 mW) and decreased with increasing the concentration of dopant molecules. Methylene blue embedded in PVA shows the highest photobleaching rate then followed by gelatin and PMMA. The increase of photobleaching rate in PVA is also noticed when the beam power is increased. The thermal diffusivity values obtained for bleached PMMA, PVA and gelatin are 1.46 × 10-3 cm2/s , 0.83 × 10-3, cm2/s and 1.10 × 10-3 cm2/s respectively. Spectrophotometer and Raman spectroscopy were used to confirm the photoacoustic results.

scholarly journals Size dependent efficiency of photophoretic swimmers

2015 ◽  
Vol 184 ◽  
pp. 381-391 ◽  
Author(s):  
Andreas P. Bregulla ◽  
Frank Cichos
Keyword(s):  
Particle Size ◽  
Laser Power ◽  
Symmetry Axis ◽  
Particle Surface ◽  
Finite Size ◽  
Optical Power ◽  
Surface Flow ◽  
Incident Laser ◽  
Size Dependent ◽  
Incident Laser Power

We investigate experimentally the efficiency of self-propelled photophoretic swimmers based on metal-coated polymer particles of different sizes. The metal hemisphere absorbs the incident laser power and converts its energy into heat, which dissipates into the environment. A phoretic surface flow arises from the temperature gradient along the particle surface and drives the particle parallel to its symmetry axis. Scaling the particle size from micro to nanometers, the efficiency of converting optical power into motion is expected to rise with the reciprocal size for ideal swimmers. However, due to the finite size of the metal cap, the efficiency of a real swimmer reveals a maximum depending sensitively on the details of the metal cap shape. We compare the experimental results to numerical simulations.

A Novel Multibranched Chromophore Containing Carbazole Moiety for Two-Photon Microfabrication

2012 ◽  
Vol 485 ◽  
pp. 566-569
Author(s):  
Zhi Yuan Hu ◽  
Fu Quan Guo ◽  
Hao Liang ◽  
Bin Guo
Keyword(s):  
Cross Section ◽  
Laser Power ◽  
Photon Absorption ◽  
Structural Motif ◽  
Incident Laser ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Incident Laser Power ◽  
Potential Applications ◽  
Pentaerythritol Triacrylate

A novel multibranched chromophore containing carbazole moiety，4, 4´, 4´´-tris(9-carbazyl-trans-styryl) triphenylamine (TCSTPA)，was synthesized and characterized by 1HNMR and elemental analysis. A larger two-photon absorption (TPA) cross section of the chromophore was obtained as high as 2350 GM compared to that of the traditional linear chromophore when pumped by a femtosecond laser at 800 nm. Microstructure based on TPA induced polymerization with a spatial resolution of submicron was fabricated under much lower incident laser power using TCSTPA as a TPA photoinitiator and a multifunctional resin of pentaerythritol triacrylate (PETA) as a polymerizable monomer. The result indicates potential applications of this kind of chromophores with multibranched structural motif in the fabrication of polymer and functional microdevices.

Laser Flash Raman Spectroscopy Method for Characterizing Thermal Diffusivity of Suspended and Supported 2D Nanomaterials

2016 ◽  
Author(s):  
Qin-Yi Li ◽  
Xing Zhang
Keyword(s):  
Thermal Conductivity ◽  
Raman Spectroscopy ◽  
Thermal Diffusivity ◽  
Laser Power ◽  
2D Materials ◽  
Laser Flash ◽  
Spectroscopy Method ◽  
Measured Temperature ◽  
Laser Absorption ◽  
2D Nanomaterials

2D nanomaterials have been attracting extensive research interests due to their superior properties and the accurate thermophysical characterization of 2D materials is very important for nanoscience and nanotechnology. Recently, a noncontact technique based on the temperature dependent Raman band shifts has been used to measure the thermal conductivity of 2D materials. However, the heat flux, i.e. the absorbed laser power, was either theoretically estimated or measured by a laser power meter with uncertainty, resulting in large errors in thermal conductivity determination. This paper presents a transient “laser flash Raman spectroscopy” method for measuring the thermal diffusivity of 2D nanomaterials in both the suspended and supported forms without knowing laser absorption. Square pulsed laser instead of continuous laser is used to heat the sample and the laser absorption can be eliminated by comparing the measured temperature rises for different laser heating time and laser spot radii. This method is sensitive for characterizing typical 2D materials and useful for nanoscale heat transfer research.

scholarly journals Photostability of Uranine via Crossed-Beam Thermal Lens Technique

2007 ◽  
Vol 2007 ◽  
pp. 1-5
Author(s):  
M. Zein El-Din ◽  
K. Elsayed ◽  
S. M. Al-Sherbini ◽  
M. A. Harith
Keyword(s):  
Thermal Lens ◽  
Laser Power ◽  
Modulation Frequency ◽  
Wavelength Modulation ◽  
Incident Laser ◽  
Diagnostic Aid ◽  
Sample Concentration ◽  
Incident Laser Power ◽  
Experimental Parameters ◽  
Photochemical Quantum Yield

Uranine is a diagnostic aid in ophthalmology and is used as an immunohistological stain. A photostability study on this important compound using a crossed-beam thermal lens (TL) technique was carried out. The study is based on the photodegradation (PD) behavior and rate regarding some experimental parameters such as the incident laser power, wavelength, modulation frequency, and sample concentration. The effects of such parameters on the TL signal and PD rate are discussed in details. It has been found that the PD rate is proportional to the power of the pumping laser and the concentration of the sample within the investigated range. However, the modulation frequency is found not to influence the PD rate. The photochemical quantum yield has been measured using potassium ferrioxalate actinometry and it was found to be very low.

Effect of incident laser power and incorporating polariton effects in GaN microrods

2019 ◽  
Vol 209 ◽  
pp. 328-332
Author(s):  
Poulami Ghosh ◽  
Dapeng Yu ◽  
Mingyuan Huang
Keyword(s):  
Laser Power ◽  
Incident Laser ◽  
Incident Laser Power

scholarly journals Plasmon-driven surface catalytic reaction of 4-ethynylaniline in a liquid environment

RSC Advances ◽  
2018 ◽  
Vol 8 (37) ◽  
pp. 20499-20504
Author(s):  
Yu Liu ◽  
Caiqing Ma ◽  
Yanqiu Yang ◽  
Yuanchun Zhao ◽  
Shiwei Wu ◽  
...  
Keyword(s):  
Exposure Time ◽  
Catalytic Reaction ◽  
Laser Power ◽  
Incident Laser ◽  
Interesting Phenomenon ◽  
Liquid Environment ◽  
Incident Laser Power ◽  
Raman Intensities

The mechanism of Ag NP induced dimerization of PEAN was investigated by using SERS spectra. A very interesting phenomenon was discovered, that is where the relative Raman intensities of b2 modes increased either with increasing incident laser power or exposure time.

scholarly journals Investigation of thermostability of Mo6S3I6 nanowires using Raman spectroscopy

2009 ◽  
Vol 63 (3) ◽  
pp. 217-220
Author(s):  
Jelena Todorovic ◽  
Dejan Djokic ◽  
Zorana Dohcevic-Mitrovic ◽  
Dragan Mihailovic ◽  
Zoran Popovic
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Room Temperature ◽  
Group Analysis ◽  
Temperature Treatment ◽  
Incident Laser ◽  
Chevrel Phase ◽  
Incident Laser Power ◽  
Raman Modes ◽  
Good Agreement

The thermostability (phase stability) of Mo6S3I6 nanowires was investigated by Raman spectroscopy, varying the incident laser power (1-9 mW) or by gradual heating of the sample from room temperature to 600?C. We have noticed 18 Raman modes in the room temperature Raman spectra, which is in good agreement with the factor group analysis prediction for P1 space group. We confirmed that the vibrations of Mo6S8 clusters dominate in vibrational properties of the Mo6S3I6 nanostructure, since nanowires Raman spectra are similar to Chevrel phase Raman spectra. During the temperature treatment, it was established that in the temperature range between 300 and 400?C a new Raman mode appeares. This mode can be ascribed to molybdenum oxide (MoO3). With further temperature increase, the intensity of this mode increases, drawing a conclusion that at temperature above 300?C the phase separation takes place in this system followed by a formation of oxide layer.

scholarly journals Demonstration of temperature-plateau superheated liquid by photothermal conversion of plasmonic titanium nitride nanostructures

Nanoscale ◽  
2018 ◽  
Vol 10 (39) ◽  
pp. 18451-18456 ◽  
Author(s):  
Satoshi Ishii ◽  
Ryosuke Kamakura ◽  
Hiroyuki Sakamoto ◽  
Thang D. Dao ◽  
Satish L. Shinde ◽  
...  
Keyword(s):  
Titanium Nitride ◽  
Laser Power ◽  
Superheated Liquid ◽  
Liquid Temperature ◽  
Incident Laser ◽  
Photothermal Conversion ◽  
Incident Laser Power ◽  
Conductive Substrate ◽  
Temperature Plateau

When photothermally superheated liquid is on a high thermal conductive substrate, the liquid temperature stays constant for a certain range of incident laser power before bubbles are formed.

Self-Focusing of Laser Light and Stimulated Scattering Processes in Transparent and Absorbing Liquids: 1. Self-Focusing

1970 ◽  
Vol 25 (12) ◽  
pp. 1868-1879 ◽  
Author(s):  
M. Maier ◽  
O. Rahn ◽  
G. Wendl
Keyword(s):  
Laser Power ◽  
Laser Light ◽  
Beam Diameter ◽  
Incident Laser ◽  
Stimulated Scattering ◽  
Light Pulses ◽  
Incident Laser Power ◽  
Self Focusing ◽  
Stimulated Brillouin ◽  
Good Agreement

Abstract The spatial and temporal development of self-focusing of light pulses is investigated. The beam diameter in CS2 and molten para-di-chlorobenzene decreases with increasing incident laser power to small values in good agreement with theory. The strong influence of beam divergence, non-linearity of refractive index, and absorption on self-focusing action is found to agree well with numerical calculations. It is shown that both backward stimulated Brillouin and Raman scattering terminate the self-focusing process.

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