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Showing 4 results for Nanostructures

Mrs. Hajar Ghanbari, Dr. Rasoul Sarraf-Mamoory, Prof. Jamshid Sabbagh Zadeh, Mr. Ali Chehrghani, Dr. Rasoul Malekfar,
Volume 7, Issue 2 (8-2013)
Abstract

In this study, Highly Oriented Pyrolytic Graphite was ablated in various polar and nonpolar solvents by Q-switched neodymium: yttrium-aluminum-garnet laser (wavelength=1064 nm, frequency=2 kHz, pulse duration=240 ns). Then, the products were examined using Scanning Electron Microscopy and UV-Vis spectroscopy. The images showed that different carbon structures such as cauliflower-like structures in benzene, spiral integrated forms in toluene, organic integrated networks in hexane, and nanoparticles in ethanol were formed. In n-methyl-2-pyrrolidone (NMP), sheets and bulk deformed structures were seen. Also, in Dimethylacetamide, particles in different stages of growth could be detected. The nonlinear optical absorption (NLA) behaviors of the products were investigated by exposing them to a 532 nm nanosecond laser using the Z-scan technique. The saturated NLA coefficient, obtained from structures of NMP and hexane-based synthesized samples, are 1.1×10-8 and 2.4×10-8 cm W-1, respectively. The saturable absorption responses of these samples were switched to the reverse saturable absorption responses in the other synthesis mediums. The maximum nonlinear absorption coefficient of 10.2×10-8 cm W 1 was measured for spiral integrated superstructures, produced in the toluene medium.
Vahid Eskandari, Nafiseh Sharifi,
Volume 14, Issue 1 (1-2020)
Abstract

In this study, silver nanoparticles were chemically synthesized and deposited on glass substrates using a reducing agent of sucrose, at 50°C. Different characterizations including atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy were obtained to study silvery substrates. Then, the silvery substrates were used as the SERS substrates to detect vibrational modes of phenylalanine amino acid up to the concentration of 10-7 M. The importance of phenylalanine amino acid detection is due to the early diagnosis of phenylketonuria in neonates. Therefore, the blood plasma of a healthy neonate and a neonate with phenylketonuria disease were adsorbed on the SERS substrates. They enhance the intensity of molecular vibration peaks of phenylalanine amino acid of two kinds of blood plasmas. The intensities of molecular vibrations of unhealthy plasma are stronger than healthy plasma due to the higher concentrations of phenylalanine amino acid, which is the sign of Phenylketonuria disease.

 
Mr Saeed Ranjbar, Dr. Abbas Azarian,
Volume 15, Issue 2 (7-2021)
Abstract

In this article, the optical properties of silver cubic-shape nanostructures (SCNs) were analyzed by employing the discrete dipole approximation (DDA) in aqueous media. The absorption, dispersion and extinction cross-sections of these nanostructures were calculated based on the wavelength change of the incident light in the visible and near infrared region. Moreover, the height change, wavelength and full width at half maximum (FWHM) of extinction cross-section peaks (from plasmon resonances) based on the size of nanoparticles and the environment dielectric constant were surveyed. The results showed that only two peak modes, named dipole peak and quadrupole peak, exist in this spectrum, such as spherical particles.
Sahar Sohrabi, Hedieh Pazokian, Mohsen Montazerolghaem,
Volume 17, Issue 2 (6-2023)
Abstract

Laser pulse overlapping (LPO) is an important factor affect the behavior of the laser treated surfaces. For laser surface treatment especially at high fluences, the laser beam must be focused to reach the desired fluence. Then laser beam or sample scanning in 2 directions is done to treat a surface area. In this paper, effect of the distance between laser treated lines (scanned in x direction) on the surface properties including morphological changes and wettability modifications of 304 stainless steel is investigated. The results show that the morphology and chemistry of the surface are influenced effectively by changing the overlap between laser treated line on the surface. Then, it should be considered as an important parameter in laser modification of a large surface with focused laser beam.

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