Showing 12 results for Graphene
M. R Ostovari, R Safaiee, M.m Golshan,
Volume 6, Issue 1 (10-2012)
Abstract
In the present article we report the dynamical behavior of entanglement between π-electrons and photons in Graphene. It is shown that the degree of such entanglements depend on the orientation of π-electron momenta relative to the photonic polarization. Moreover, we show that as the detuning between the π-electron transition frequencies and that of the photons is increased, the degree of entanglement decreases.
Prof. Parviz Parvin, Zohreh Ghorannevis, Mohsen Mehrabi, Pooria Taghdiri, Zahra Mortazavi, Ali Reyhani,
Volume 9, Issue 1 (1-2015)
Abstract
In this paper, the magnetic properties of carbon based material, graphene is studied, which is generated by laser ablation in cryogenic media. Transmission electron microscopy (TEM) and alternating gradient force magnetometer (AGFM) are applied to investigate the graphene morphology and magnetic properties, respectively. The graphene synthesized by the laser ablation method exhibits diamagnetic behavior. However the magnetic transition from diamagnetic to paramagnetic effect is lucidly observed by functionalizing the graphene sample with silver atoms.
Reza Ghayoor, Alireza Keshavarz,
Volume 13, Issue 1 (1-2019)
Abstract
By developing the terahertz (THz) technology, in addition to generators and detectors of THz waves, the existence of some tools such as modulators and filters are needed. THz filters are important tools for various applications in the field of chemical and biological sensors. Linear and nonlinear optical properties of the graphene have attracted lots of attention. In fact graphene exhibits various nonlinear phenomena. Hence in this paper, by entering the graphene to the field of THz and using the graphene nonlinear properties with utilizing the transfer matrix method and transmission properties of a periodic structure containing graphene are investigated. A fairly straightforward computational method allows us to examine the effect of different structural parameters on the transmittance spectrum. Simulation results show that if the graphene nonlinear response in a periodic structure in the presence of a high-intensity THz field is considered, the proposed structure displays two bands of passes and stopping which can improve the design of the filters and controllers of THz waves.
Maryam Soltani, Alireza Keshavarz, Gholamreza Honarasa, Reza Ghayoor,
Volume 13, Issue 1 (1-2019)
Abstract
In a ring laser gyroscope, due to the rotation and the Sagnac effect, a phase difference between the two counter-propagating beams is generated. In this device, the higher phase difference between these two beams causes the better the interference pattern detection, and thus the sensitivity is increased. In this paper, the effect of inserting a dielectric-graphene photonic crystal inside a ring laser gyroscope on the interference pattern and the sensitivity of the device are studied and simulated using ABCD propagation matrix method. Results show that dielectric-graphene photonic crystal has a high transmission and therefore high efficiency in the wavelength of ring laser gyroscope. So it is a suitable choice to use in the ring laser gyroscope. Also, a comparison between ring laser gyroscope with and without dielectric-graphene photonic crystal shows that when the dielectric-graphene photonic crystal is in the system it is possible to build gyroscope with smaller lengths and high sensitivity.
Ahmadzia Sherzad, Hakimeh Zare, Zahra Shahedi, Fatemeh Ostovari, Yousef Fazaeli, Zeinab Pourghobadi,
Volume 14, Issue 2 (12-2020)
Abstract
Luminescent graphene oxide quantum dots (GOQDs) have attracted tremendous attention from scientists in chemistry, materials, biology, and physics science. They have specific properties such as low cytotoxicity, excellent electrochemical and optical properties, resistance to photo-bleaching, and good stability. In this study, GOQDs were synthesized using a simple and straightforward methodology. The synthesized GOQDs were characterized by Fourier Transform Infrared (FTIR) analyzer, ultraviolet–visible spectrophotometry (UV–VIS) absorption, Photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM) analyses. Then, optical properties of GOQDs such as absorption and luminescence with various pH values were investigated. GOQDs show absorption in the ultraviolet (UV) region and their position of photoluminescence peak is independent of pH value. The average size of QDs is less than 5 nm, as revealed by TEM. The GOQDs show green luminescence under UV irradiation (360 nm).
Morteza A. Sharif,
Volume 14, Issue 2 (12-2020)
Abstract
In this paper, an all optical graphene-based modulation approach is proposed induced by Modulation Instability (MI). The device structure is based on graphene sheets transferred on the both arms of a Mach-Zehnder interferometer to support amplified Surface Plasmon Polaritons (SPPs). Due to the nonlinear nature of MI to interfere in the modulation process, the proposed approach leads to an enhanced performance in comparison to the conventional Mach-Zehnder modulators; using a low power cw driving beam (~20 µW at λ=50 µm), a high speed modulation rate (~2 Tpps) and subsequently, a high depth (89%), wideband modulation (~81 GHz) can be resulted. Since the MI is a pre-state to the chaotic regime, the modulator can be also used for secure optical communication.
Mr Mohammad Javad Haji Najafi, Ms Seyedeh Bita Saadatmand, Dr. Vahid Ahmadi, Prof. Seyedeh Mehri Hamidi,
Volume 15, Issue 1 (1-2021)
Abstract
Two-dimensional nanomaterials have attracted increasing attention for enhancing surface plasmon resonance (SPR) biosensors application. In this work, we use the graphene layer to improve the sensitivity of the SPR biosensors based on the conventional Kretschmann configuration. We employ Tungsten disulfide (WS2) and Molybdenum disulfide (MoS2) Two-dimensional materials as an interlayer to enhance the sensitivity of Au/Graphene biosensor in angle interrogation method. The transfer matrix method (TMM) is used to analyze the characteristics of the device. Results show that using WS2 in Au/Graphene structure increases sensitivity by about 12.64%, which is higher than MoS2. Combining graphene based SPR and ellipsometry as a highly sensitive, label-free, real-time, and versatile method can be used to measure a very small concentration of biomolecules, which leads to 170-fold enhancement compared to angle interrogation method and improves the detection accuracy and quality factor.
Dr. Morteza Janfaza, Dr. Hamed Moradi, Mr. Morteza Maleki,
Volume 15, Issue 2 (7-2021)
Abstract
Graphene and molybdenum disulfide (MoS2), as two of the most attractive two-dimensional (2D) materials, are used to improve the temperature and strain sensing responses of the few-mode fibers (FMFs). The temperature and strain effects are detected based on distributed optical fiber sensors equations, where the Brillouin scattering (BS) is investigated for the FMF tapered region. For this purpose, the 2D materials were assumed as cover layers on the tapered FMF to enhance its sensitivity. Graphene and MoS2 are used as the cover layer on the FMF cladding at a distance of 10 μm from the core, and the impact of the number of material layers is investigated. By increasing the graphene layers, the temperature and strain sensitivities increase (3% and 16%, respectively) due to the rise of the inter-modal interference of the FMF. Moreover, the increasing of the MoS2 layer number improves the temperature sensitivity by 28% but shows a lower impact on strain sensitivity (about 13%). The advantage of MoS2 with respect to graphene originates from the imaginary part of the refractive index of graphene (assumed with chemical potential of 0.4 eV at the working wavelength of 1550 nm), which leads to a lower effective index of the tapered region, hence lower sensitivities. This sensitivity enhancement can improve the performance of the BS-based sensors for local detection of the parameters under-investigation in multi-parameter sensors.
Shima Haghgooyan, Fatemeh Ostovari, Hakimeh Zare, Zahra Shahedi,
Volume 16, Issue 1 (1-2022)
Abstract
ta charset="UTF-8" >Silk fibroin (SF) is a natural material that has received special attention due to its excellent mechanical and electrical properties. Nowadays, it is tried to improve the properties of SF by adding other nanomaterials such as graphene oxide (GO). Here, we extracted SF from silk cocoon and studied its properties in pure state and in the combination with graphene oxide (SF/GO). The results have shown that the presence of graphene oxide in the structure of fibroin increases the random winding formation of SF. The measurements show that the water content has a great effect on the properties of SF and SF/GO films. The contact angle (less than 70) indicates the hydrophilic property of these films. In addition, in times greater than 50 seconds, the contact angles drop to 27° and 5° for SF and SF/GO respectively. Also, the surface resistance of the completely dried SF/GO film increases from 50 kW/sq to 220 kW/sq for 42% wt water content.
Nasrin Vahedi. G, Asghar Asgari, Gholamreza Dehghan,
Volume 16, Issue 2 (7-2022)
Abstract
Efforts to understand genetic diseases and mutations in biological systems are the most important driver of research development in medical and biomolecular sciences. Rapid, sensitive, accurate, and cost-effective biomolecule analysis is particularly important in diagnosis and treatment. The discovery of graphene as a new nanomaterial with a carbon structure with a single atom thickness due to its unique electronic, mechanical, thermal, and optical properties has opened a new topic in research in various biomedical sciences and the production of biosensors for biomolecule analysis. In this research, a biosensor based on a graphene field-effect transistor (GFET) is used to detect DNA with optimal accuracy and sensitivity, which can be a basis for making DNA detection tools. In the studied structure, using non-equilibrium Green function equations and Poisson equation, we study the electron transfer in graphene field-effect transistors. Then, by examining the interaction between nucleotide bases (C, G, A, T) and O6-carboxymethylguanine related to the colorectal cancer DNA sequence to detection of mutation will be identified by GFET, and their binding energy determined.
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.
Maryam Bahreini, Zahra Sabzevari,
Volume 18, Issue 1 (10-2024)
Abstract
Due to the unique properties of graphene, since its discovery, many applications in different fields from chemical sensors to transistors have been proposed for it. One of the most important applications of graphene is in the enhancement of Raman spectroscopy, which has recently attracted the attention of scientists. This article investigates its potential as a substrate for Raman enhancement called graphene-enhanced Raman spectroscopy (GERS). We use rhodamine 6G (R6G) and crystal violet (CV) to illustrate the effect of graphene oxide on Raman enhancement. It was shown that Raman peaks of rhodamine 6G and crystal violet solutions deposited by solution soaking on the graphene-based substrate have significantly increased compared to those deposited on the bare glass substrate. Using a Raman spectrometer, The Raman spectra of these materials were taken and their graphs were compared. It is shown that this method can enhance the Raman signals of molecules of rhodamine 6G and crystal violet.
