Showing 21 results for Nanoparticles
S. M Hamidi, M. M Tehranchi,
Volume 5, Issue 1 (1-2011)
Abstract
We report an experimental study on optical and magneto-optical properties of Cesubstituted yttrium iron garnet thin films incorporating gold nanoparticles. Au nanoparticles were formed by heating Au thin film on cubic quartz and garnet substrate in vacuum chamber and a Ce:YIG layer was deposited on them by the aid of Pulsed laser deposition method. A large enhancement of the longitudinal Kerr effect was obtained in sample with Au nanoparticles on quartz substrate and the effect of substrate material on improving optical and magneto-optical response of samples were investigated.
Mina Eslamifar, Nastaran Mansour,
Volume 6, Issue 1 (10-2012)
Abstract
In this work, thermo-optical properties of gold nanoparticle colloids are studied using continuous wave (CW) laser irradiation at 532 nm. The nanoparticle colloids are fabricated by 18 ns pulsed laser ablation of pure gold plate in the distilled water. The formation of the nanoparticles has been evidenced by optical absorption spectra and transmission electron microscopy. The nonlinear optical properties of gold nanoparticles colloids are investigated by closed Z-scan under irradiation of a low power CW laser. It will be shown that the thermal lens model is in excellent agreement with the experimental results of samples. The aperture-limitted optical limiters based on the nonlinear refraction of colloidal solution are presented. The tunability of limiting threshold of optical limiters can be accomplished by engineering of the experimental geometry.
Mohsen Dehbashi, Mousa Aliahmad,
Volume 6, Issue 2 (10-2012)
Abstract
Sn 0.986 Ni 0.014 O nanoparticles have been synthesized by a simple co-precipitation method. Nanoparticles crystallize in lower temperature (350°C) and shorter time (2h) respect to other methods. The sample characterized by various standard techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Atomic absorption spectroscopy (AAS) and UV–Vis spectroscopy. The X-ray diffraction reveals that sample is pure rutile-type tetragonal phase, the crystalline size Sn0.986Ni0.014O nanoparticles is 27 nm. UV-Vis spectroscopy is revealed the optical band gap to be 3.98 eV for Sn0.986Ni0.014O nanoparticles that is higher than the bulk value of SnO (2.5–3 eV).
Dr. Faegheh Hajizadeh, Dr. S.nader S. Reihani,
Volume 7, Issue 1 (6-2013)
Abstract
Thanks to their unique optical and electromagnetic properties, noble-metal nanoparticles are proven very useful in many scientific fields, from nanotechnology to biology, including detection of cancer cells. Irradiated gold nanoparticles, as a nano-smolder could be widely used in biomedical contexts such as tumor therapy. Laser destruction of a cancerous tissue depends on thermal and physical properties of the tissue, therefore temperature quantification of an irradiated metallic nanoparticle in different materials could be followed by interesting applications. In this research we quantify the temperature of irradiated gold nanoparticles in paraffin which is the most commonly used material for embedding of biological tissues in pathology. We have shown that the temperature increase rate for irradiated gold nanoparticles with diameters of 78 nm, 97 nm, and 149 nm are 1.31, 1.40, and 2.28 ◦C/mW, respectively. Considering that the conductivity of a biological tissue is an important parameter on temperature raise and destruction, these results could yield a valuable insight into the cancer therapy.
Mrs Marzieh Nadafan, Prof. Rasoul Malekfar, Mrs. Zahra Dehghani,
Volume 8, Issue 2 (7-2014)
Abstract
Polyurethane closed cell (PUCC)/SiO2 nanocomposites have been prepared by using in situ polymerization approach. The third-order optical nonlinearities of PUCC/SiO2 nanocomposites, dissolved in DMF are characterized by Z-scan technique at the measurement wavelength of 532 nm. The nonlinear refractive (NLR) indices and nonlinear absorption (NLA) coefficients of samples were calculated from closed and open aperture Z-scan in the order of 10-8 with negative sign and 10-5 , respectively. The origin of optical nonlinearity in this case may be attributed due to the presence of two photon absorption (TPA) effect. The synthesized samples were examined by optical microscopy, SEM imaging and Raman spectroscopy. All the results related to NLO properties, suggest that PUCC/SiO2 may be a promising candidate for the application to optical limiting in the visible region.
Dr. Esmaeil Shahriari, Dr. Mohammad Moradi, Dr. Mohsen Ghasemi Varnamkhasti,
Volume 9, Issue 2 (11-2015)
Abstract
In this research, Ag nanoparticles were prepared by using g-radiation at concentration of 5.18×10-3 M and irradiated at different doses. A green laser was employed as excited source for measuring nonlinear refractive index and absorption coefficient. The measurements were done by z-scan method for both, closed and open aperture at temperature room. We deduced that with growth of size of Ag nanoparticles, nonlinear refractive index increased while absorption coefficient of samples decreased
Hossein Mozaffari, Marzieh Akbari Jafarabadi, Mohammad Hossein Mahdieh,
Volume 11, Issue 2 (8-2017)
Abstract
In this paper, the dynamic behavior of laser induced optical breakdown in impure water was studied by using a pump- probe technique. The plasma was induced by a 1064 nm Nd:YAG laser pulse (with pulse duration ~10 ns) in distilled water with two types of impurities: (I) a solution (highly diluted salt water as a conductor) and (II) a colloidal (TiO2 in colloidal nanoparticle form as a dielectric); and finally the results were compared. The results show that, for both liquids, the probe beam transmission is reduced with pump laser intensity. Our results also show that, impurity size and type of conductivity can influence on plasma time evolution and transmissivity.
Hadi Zarei, Rasoul Malekfar,
Volume 12, Issue 1 (1-2018)
Abstract
In this paper, tetragonal chalcopyrite (CIGS) Cu(InxGa1-x)Se2 with x=0, 0.5, 0.8, 1 are synthesized by heating-up method. These nanoparticle structures differ in morphology and absorption properties due to the synthesis temperatures of 250, 255, 260, 265, 270 and 280 ºC, and gallium molar ratio over the total gallium and indium contents. These features are studied using scanning electron microscope, X-ray diffraction and absorption spectroscopy in visible, ultra-violet and near-infrared wavelengths. Results indicate that by increasing gallium content, absorption edge rises toward the visible light. Any modification in the absorption edge changes the band gap and as a result the energy gap and the absorption of cell increases considerably. Also in the heating-up method, increasing the reaction temperature improves nanoparticles crystallites. This leads the absorption improvement and higher cells efficiency. Produced nanoparticles are spherical shape with are varying the diameter around 30-80 nm.
Naemeh Aeineh, Nafiseh Sharifi, Abbas Behjat,
Volume 12, Issue 2 (12-2018)
Abstract
To investigate the plasmonic effect in perovskite solar cells, the effect of depositing Au@SiO2 nanoparticles on the top and the bottom of mesoporous TiO2 layers was studied. First, Au@SiO2 nanoparticles were synthesized. The particles were then deposited at the different interfaces of mesoporous TiO2 layers. Although the two structures show approximately similar optical absorption, only cells with Au@SiO2 nanoparticles deposited at the bottom of the mesoporous TiO2 layers demonstrated an improved photocurrent performance compared to the reference cells. This structure shows a short-circuit current density (JSC) of 20.7 mA/cm2 and open circuit voltage of 1081 mV. This enhancement may be attributed either to the interface surface engineering or plasmonic resonance of Au@SiO2 nanoparticles depends to the NPs size and position.
Farshad Farhadnia, Ali Rostami, Samiey Matloub,
Volume 13, Issue 1 (1-2019)
Abstract
In this article, the effect of plasmonic properties of metal nanoparticles with different shapes, and moreover, their plasmonic-photonic interaction, on solar cell performance were investigated and simulated. Because of low conversion efficiency and then high cost of solar cells, it is difficult to commercialize and replace them with conventional energy resources. But in recent years, the plasmonic solar cell has been very popular. In this study, it is shown that the enhancement of near-field electromagnetic waves severely affects the generation rate, which handles the carrier’s generation in the solar cell equations and causes alteration of the photocurrent. This means that by manipulating the plasmonic properties of nanoparticles (shape and density) and their interaction with photons in solar cell structure, distribution of electromagnetic fields will be altered. Hence, the optical power related to the poynting vector is changed. So, with the aim of improving the solar cell some important parameters such as alteration of nanoparticle shape and their inter-distance were investigated. Finally, a comparison between traditional solar cells and our improved structure was undertaken.
Bahareh Morovvati , Rasoul Malekfar,
Volume 13, Issue 2 (12-2019)
Abstract
The active substrates in surface enhanced Raman scattering (SERS) spectroscopy were prepared through self-assembly of nanoparticles on functionalized glasses. Colloidal silver nanoparticles (Ag NPs) were prepared chemically in two different sizes by reduction of AgNO3 using trisodium citrate and sodium borohydride. Gold–silver core–shell nanoparticles were also prepared to compare between the optical behaviors of their silver shell and Ag NPs. Absorption spectra of nanoparticles were measured by ultraviolet–visible (UV–Vis.) spectroscopy, and their approximate sizes were determined by dynamic light scattering (DLS). The core–shell nanoparticles were approximately the same size as the largest Ag NPs (35 nm) and had the same maximum absorption wavelength. The potential of these substrates for detection applications was investigated with 1 M and 0.1 mM solutions of Raman-active molecule of crystal violet (CV) dye. The Raman enhancement signal was recorded for 0.1 mM solution with 532 nm laser wavelength, and the obtained spectra enhancement factor (EF) was calculated. EF values indicated that although the silver and gold–silver core–shell nanoparticles had the same surface plasmon resonance, the substrate with smaller Ag NPs had the highest enhancement factor compared to other substrates, which was 9.5´103, and the core–shell substrate even had a slightly lower enhancement factor in compare with the large Ag NPs.
Foozieh Sohrabi, Seyedeh Mehri Hamidi,
Volume 13, Issue 2 (12-2019)
Abstract
Compared to the long history of plasmonic gratings, there are only a few studies regarding the bandgap in the propagation of plasmonic surface waves. Considering the previous studies on interpretation of plasmonic bandgap formation, we discuss this phenomenon using the effect of both surface plasmon polariton (SPP) and localized surface plasmon (LSP) for our fabricated one-dimensional metallic-polymeric grating. This structure is composed of metallic grating on the surface of PDMS with different concentration of embedded gold nanoparticles. By sweeping the incident angles, we have seen that the SPP, LSP and their coupling cause two gaps in reflection regime which are originated from SPP supported by thin film gold film and LSP supported by gold nanoparticles. The first gap is attributed to the patterned metallic film because it vanishes by increasing the nanoparticles which may destroy the pattern while the second gap can be formed by embedded nanoparticles because it becomes more considerable by raising the incubation time. Therefore, the drowning time of patterned samples (e.g. 24h, 48h, and 72h) in HAuCl4 plays the key role in adjustability of plasmonic bandgap. Notably, the interaction between SPP and LSP can be the origin of the shift in gap center from 300 to 550. To best of over knowledge, this study is the first study on the plasmonic band gap as a function of both SPP and LSP.
Saeideh Ebrahimiasl, Ali Noori, Azmi Zakria,
Volume 13, Issue 2 (12-2019)
Abstract
Since Amaranth (AM) is one of the dye compounds which is harmful to human’s life its removal from industrial waste water would reduce their environmental impact and health effect. Copper nanoparticle (CuNP) is a simple and eco-friendly material which can be used to remove this pollutant. In this paper, copper nanoparticles were synthesized, for removal of AM dye. The experiments were designed by response surface methodology with a modified cubic model to predict the variables. To investigate variables and interaction between them analysis of variance was used with high F-value (1.44), low P-value (<0.0409), non-significant lack of fit, the determination coefficient of 0.898 and the adequate precision of 7.25. Experimental and predicted values of the response illustrated a good correlation. The optimum parameters catalyst amount (0.14 w/w%), initial concentration (7.38 mg/l), reaction time (47.75 s) and pH (2.83) for the highest removal percentage of (96.10%) was attained.
Mohammad Javad Azarm, Alireza Keshavarz, Gholamreza Honarasa,
Volume 15, Issue 1 (1-2021)
Abstract
The absorption cross-section of gold and silver nanoparticles has been demonstrated in confined wavelength spectra based on Mie's theory. For this purpose, the numerical study performed with COMSOL for defined particle size to clarify absorption spectra and final results have been compared with experimental data to express the absorption peak occurs in higher wavelength for large particle size which is in around 530 nanometers for gold and 400 nanometer for silver particles. These results show that particle size affects directly on absorption spectra of metallic nanoparticles.
Parisa Khajegi, Majid Rashidi-Huyeh,
Volume 15, Issue 1 (1-2021)
Abstract
Nobel metal nanoparticles (NPs) are widely used in various applications including optical and biological sensors, biomedicine, photocatalysts, electronics, and photovoltaic cells. The optical properties of gold NPs are surveyed in this paper under the Localized Surface Plasmon Resonance (LSPR) effect, which increases the light absorption and scattering at the LSPR wavelength. This LSPR frequency depends on various factors, including the shape and size of the particles as well as incident electromagnetic polarization. Here, the optical response of gold NPs with different shapes and sizes are investigated using the finite element method (FEM). The results show that the bandwidth, amplitude, and LSPR wavelength depend on the shape and dimensions of the NPs as well as the polarization of the incident light. The LSPR wavelength changes from 500 to 650 nm for different shapes of the gold NPs including sphere, octahedral, cube, ellipsoid, triangle, and with identical volume. To study the NP size effect on the optical properties, the absorption and scattering cross-sections (CSs) are also investigated for different sizes of NPs. The results show a redshift in the LSPR wavelength by increasing the NP size.
Hanie Yazdanfar , Seyedeh Mehri Hamidi, Neda Roostaei, Younes Mazhdi, Asieh Soheilian,
Volume 16, Issue 1 (1-2022)
Abstract
ta charset="UTF-8" >Color vision deficiency (CVD) is a disorder in which patients cannot distinguish specific colors. In the last few decades, the researchers have attempted to find a solution to cure this deficiency, despite valuable attempts by scientists, a promising and effective remedy has not been attained yet. As curing of CVD with the tinted or dyed glasses and lenses in colorblind patients is not satisfying, in this work, we have studied a novel and simple method using plasmonic gold nanoparticles in the contact lenses to improve CVD based on surface plasmon resonance of gold nanoparticles in the visible spectral range. In this technique, the dispersion of gold particles into the contact lens and transforming them to plasmonic gold nanoparticles provides a color filter that can be applied in the correction of the red-green type of colorblindness.The modified lens blocks a narrow band centered at 560nm, the wavelength that vision spectra of CVD patients overlap at those ones.
Bita Azemoodeh Afshar, Akbar Jafari, Rahim Naderali, Mir Maqsood Golzan,
Volume 16, Issue 2 (7-2022)
Abstract
In this study, we investigated the production of silver nanoparticles by pulsed Nd: YAG laser ablation with λ=532nm in distilled water. The sodium citrate used to control the size of nanoparticles (Nps). The sample containing Ag NPs was characterized by linear absorption spectroscopy (UV-Visible spectroscopy) and transmission electron microscopy (TEM observation). The behavior of nonlinear optical properties of silver nanoparticles was studied using the Z-Scan method at two optimum numbers of the laser pulses and four optimum laser energy densities. In the Z-Scan method, the nonlinear thermal properties of Ag NPs were investigated under exposure to nanosecond laser pulse at λ=532nm. They were gained by fitting theoretical and experimental data. The values of the nonlinear refractive index (n2) and the nonlinear absorption coefficient (β ) were compared concerning to two optimum numbers and four optimum energy densities. The results of the nonlinear refractive index showed a negative value for each sample, this means that samples act as a divergent lens, and the thermal self-defocusing effect can be the main factor of nonlinear behavior. Following the comparison of two quantities, n2 and β , we found that the nonlinear refractive index increased when the number of laser pulses light increased. In addition, the nonlinear absorption coefficient decreased when the number of laser pulses light increased. As a result, the application of these Ag NPs for optical switching devices was investigated, which demonstrated that the large Ag NPs are applicable tools for optical switching devices.
Reza Pourahmad, Sheila Shahidi, Amirhossein Sari, Mohammadreza Hantezadeh,
Volume 17, Issue 1 (1-2023)
Abstract
In this research, an attempt is made to approach a specific type of carbon, such as graphene or carbon nanotubes by using pulsed laser ablation technique in deionized water environment with changing the laser factors such as wavelength and fluence. Nd:YAG laser with two wavelengths of 1064 and 532 nm and three fluence of 0.8, 1 and 1.2 J/cm2 were selected that number of pulses was 5000 with a frequency of 10 Hz to be irradiated on the graphite target at about 10 minutes. The medium was distilled water. Graphite was located in the 40 ml of distilled water.
The effects of wavelength and fluence of the laser have been experimentally investigated on types of carbon characteristics with different analysis such as Raman scattering spectrum, FE-SEM images, UV–Vis-NIR spectrum and X-ray diffraction (XRD). By using the mentioned analysis, the type of synthesized nano carbon is studied.
This study evaluates the effects of the pulse energy and laser wavelength on properties of synthesized carbon nanoparticle in laser ablation method in medium of distilled water.
Mohammad Moradi, Forouzan Habibi, Asieh Rafiee,
Volume 17, Issue 2 (6-2023)
Abstract
In this study, copper cobalt ferrite nanoparticles were synthesized by chemical formula Co1-xCuxFe2O4 and (x=0, 0.2, 0.4, 0.6, 0.8, 1) by co-precipitation method. The X-ray diffraction pattern of the samples confirmed the single-phase spinel structure of the fabricated nanoparticles and the average size of the crystals was calculated from the entire width of the diffraction peak with the highest intensity and Scherrer relationship. Using transmission electron microscope images, the nanoparticle size was about 10 nm. The magnetic properties of copper cobalt ferrite nanoparticles were measured by AGFM and it was seen that with increasing substitution of copper Cations instead of cobalt Cations in the samples, the amount of induction decreased and the saturation magnetization first increased and then decreased. In order to investigate the Faraday effect on copper cobalt ferrite nanoparticles, the transmittance values were measured using a laboratory experiment and their graphs were plotted in terms of the applied magnetic field, all of which were in agreement with the theory. In addition, transmittance was investigated for two angular positions of the analyzer at -45˚ and +45˚ in different fields.
Neda Roostaei, Seyedeh Mehri Hamidi,
Volume 17, Issue 2 (6-2023)
Abstract
Color vision deficiency (CVD), or color blindness, is a prevalent ocular disorder that hinders the recognition of different colors, affecting many people worldwide (8−10% of males and 0.4−0.5% of females). Recently, there has been a significant focus on plasmonic nanostructures as an alternative to chemical dyes for managing color blindness due to their remarkable characteristics and the tunability of plasmonic resonances. In this work, the plasmonic glasses based on silver nanoparticles with a TiO2 thin layer coating were fabricated using the sputtering technique and proposed for blue-yellow (tritanopia) CVD management. The proposed plasmonic glasses based on silver nanoparticles are more selective than commercial Enchroma glasses because of the tunability of plasmonic properties of silver nanoparticles by controlling their morphology, which provides insights for applications of color vision deficiency improvement. Also, the antibacterial activity of the proposed plasmonic glasses based on silver nanoparticles was investigated against E. coli and S. aureus bacteria, which have exhibited effective antibacterial properties. The results indicate that the silver nanoparticle-based glasses not only aid in tritanopia management but also offer potential for antibacterial applications such as implant coatings.
