Sharif Digital Repository

This thesis cantain two section. In the first section a novel extracting medium based on magnetic molecularly imprinted polymers (MIPs) nanoparticles was synthesized by chemical polymerization for micro-solid phase extraction. In this work, the modified chitosan magnetite nanoparticles (MNP-CS) was synthesized by co-precipitating Fe2+ and Fe3+ in the chitosan solution [1,2]. The characteristic properties of Fe3O4@MIPs nanoparticles were determined using Fourier transform infrared spectrometer. Extraction efficiency of the novel extracting medium was compared with MNP-CS sorbents for the determination of RhB in aqueous samples, via quantification by spectrofluorimetry. The obtained results... 

Depleting resources and heavy pollution of fossil fuels have drawn the world's attention to clean energy and the most ideal one is hydrogen. Water splitting is one of the most effective ways to produce hydrogen and due to slow kinetic rate different kind of catalysts (optical, electrochemical, etc.) are developed for this reaction. In this work a ZIF-67 and N-doped graphene quantum dots composite is developed and its electrocatalytic performance in oxygen evolution reaction is evaluated. The synthesized graphene quantum dots are between 2-4 nm and the incorporation of nitrogen atom in their structure was verified by FTIR analysis. The metal-organic framework which is produced in this work... 

Despite the excellent photovoltaic performance of perovskite solar cells (PSCs), the instability of PSCs under severe environment (e.g., humidity, intense light) limits further commercialization of such devices. Therefore, in recent years, many researches are conducted on utilizing Perovskite Quantum Dots (PQDs) to enhance performance of PSCs. Herein, CsPbI3 PQDs interfacial layer is incorporated in the perovskite/hole transport material (HTM) interface, on the purpose of increasing charge carrier mobility and preventing electron-hole recombination to increase performance of the PSCs. CsPbI3 PQDs is synthesized at 170℃ with oleic acid and oleylamine as organic ligands by hot-injection... 

In recent years, adjustable optical properties, simple and inexpensive synthesis, and excellent biocompatibility of carbon dots have attracted much attention. However, the widespread use of carbon dots in biomedical diagnostics, photoluminescence, and photocatalysis has been limited due to a lack of emission or excitation in the red or near-infrared region. Studies have shown that doping in carbon dots can affect the displacement and increase the light intensity. This study aims to use the engineering methods of optical properties of carbon points by doping heteroatoms and adjusting the surface state to synthesize biocompatible carbon dots with luminescence at long wavelengths with strong... 

In recent years, much attention has been focused on quantum dot films due to their high amount of surface area and their size-dependant band-gap tenability. However, high surface area results in increase in energy traps in case of insufficient surface passivation. In this research, PbS colloidal quantum dots were synthesized via hot injection route having the size of 3 nm approximately. Then cationic doping with Zn, Ca and Cd and ligand exchange of long oleic acid with short organic mercaptopionic acid were done. Excitonic peak of these dots and photoluminescence peak appeard in wavelengths of 930 and 1100 nm respectively. Optimum film thickness was also determined as 300 nm. Quantum dot... 

Over the past two decades, several studies have been investigated on synthesis and properties of semi-conductor quantum dots because of their applications in sensors, LEDs, detectors, solar cells, etc. One of challenging issues in synthesizing these nano-particles is their size distribution. In this study, Cadmium Selenide was synthesized by the method of colloidal synthesis. X-ray diffraction showed that the crystalline nano-particles have wurtzite structure. For obtaining a uniform size distribution, effect of various parameters such as molar ratio of components and reaction temperature on the growth kinetics of these particles, were studied. Results showed that molar ratio of Selenium to... 

Cancer is one of the most important problems that affects public health. If this disease is diagnosed quickly in the patient's body, it can be prevented and treated by determining the stage of the disease and establishing a treatment protocol. Magnetic resonance imaging (MRI) and fluorescence imaging (FI) are among the imaging methods. In order to increase the contrast of images, researchers have turned to the synthesis of materials under contrast agents, which improve diagnostic sensitivity. Synthesis of nanoparticles as multi-mode contrast agents can enhance imaging methods. In this research, the synthesis and characterization of the multifunctional Fe3O4-Mn3O4-LCysteine@g-C3N4 QDs system... 

In this project, we have studied the geometric and electronic structures of CdS nano-particles. The bulk CdS is known to be a semiconductor with the experimental energy gap of 2.42eV which is more than twice the theoretical resuls based on LDA or GGA energy functionals used in the density functional theory. However the calculations based on Kohn-Sham formalism used in DFT (KS-DFT) predicts the geometric structure of bulk semiconductors fairly well. Therefore, we have employed the KS-DFT formalism for our CdS nano-particles and have used the Gaussian as well as SIESTA computer codes to predict the geometric structures of these nano-semiconductor-particles. For calculating their electronic... 

Levodopa [L-3, 4-dihydroxyphenylalanine, or L-DOPA] is an important neurotransmitter used for the treatment of neural disorders such as Parkinson’s disease. Abnormal L-Dopa concentrations in biological fluids can be used for evaluation of diseases such as Parkinson’s diseases. In the first part of this thesis, a rapid and sensitive method for levodopa detection was reported which is based on in situ formation of polylevodopa nanoparticles. The assay is very simple and low cost and uses only NaOH and HCl as reagents. Under alkaline conditions, levodopa is spontaneously oxidized to its quinone derivative and shows the fluorescence properties. The fluorescence signal of the oxidation product of... 

The electro-elastic fields of nano-sized piezoelectric structures are considered based on the non-classical continuum theory. Nowadays because of increasing the application of piezoelectric materials in nano technology and exclusive properties of this kind of materials, they can use as the ingredients of electromechanical systems. Therefore, the determination of induced electro-mechanical fields is important. In this study the constitutive equations based on non-classical continuum theory and general anisotropy for the elastic, piezoelectric and dielectric tensors are considered, and the electromechanical fields are determined using the micromechanical method. Furthermore, the size effects... 

Hydrogen peroxide (H2O2) is of great importance in numerous fields such as pharmaceuticals, mining, textile, environmental and food industry. Therefore, the development of low cost, on-site, and uncomplicated H2O2 sensors are of high interest. To date, colloidal quantum dots (QDs) have been used to detect H2O2 based on the quenching of fluorescence intensity in a single wavelength. However, intensity of fluorescent signal could be easily disturbed by various factors. To overcome these undesirable effects, here, a ratiometric sensor has been developed by adding a second fluorophore (as reference) to QDs. For this purpose TGA-capped CdTe QDs were prepared. To detect H2O2, the ratiometric... 

A new magnetic catalytic nanocomposite of Hal-MT-Cys-Ag/MNCD was fabricated and utilized for catalyzing reductive de-colorization of methyl orange and rhodamin B in aqueous media at room temperature. To prepare this material, Cl-functionalized halloysite nanoclay was successively reacted with melamine and 2,4,6-trichloro-1,3,5-triazine to furnish multi-nitrogen containing ligand on halloysite surface. Then, magnetic carbon dots were crafted through a facile method and decorated with Ag nanoparticles and cysteine to furnish Cys-Ag/MNCD species. The final nanocomposite was obtained via incorporation of this latter species onto functionalized halloysite. This was characterized through the XRD,... 

Today, the use of graphene quantum dots has been very much considered due to easy synthesis methods, strong fluorescence emission, and many sources of synthesis. In this study, the effect of changing capping agent of graphene quantum dots toward iron (Ⅲ), copper (Ⅱ) and mercury (Ⅱ) ions was studied. The linear range of response of the graphene quantum dots synthesized with ethylenediamine for mercury (Ⅱ) and iron (Ⅲ) ions was 10-70 µM, and this sensor also responded to Cu (Ⅱ) ions. Urea synthesized graphene quantum dots also responded to all three ions. The linear range of the response for mercury (Ⅱ) , iron (Ⅲ) and copper (Ⅱ) ions was 5-25, 10-70 and 120-120 μM respectively. The linear... 

In the first part of this research, we reported a liquid sensor array for detection and classification of biological thiols, based on aggregation of gold nanoparticles (AuNPs) with different coatings as sensor elements. Thiol mediated aggregation of AuNPs was visualized via UV–vis spectra. The spectral changes, as a consequence of aggregation of AuNPs, made a unique pattern of spectra for each analyte and allowed for the selective detection and discrimination of the biological molecules. HCA and PCA analysis demonstrated the discrimination of various thiols of different concentrations (i.e. 10–800 mmol L-1 for cysteine, 200–700 mmol L-1 for both glutathione and glutathione disulfide).... 

In recent years, studies in luminescent carbon dots are overgrowing, the prominent features of carbon quantum dots include cheap and straightforward synthesis, excellent biocompatibility, and adjustable optical properties. However, the widespread use of carbon dots in biomedical diagnostics, photoluminescence, and photocatalysis has been limited due to a lack of emission and excitation in the red or near-infrared region.. However, the widespread use of carbon dots in biomedical diagnostics, photoluminescence, and photocatalysis has been limited due to a lack of emission and excitation in the red or near-infrared region. This research tried to produce carbon dots with redshift in emission... 

In the first part of this research, we have developed a simple and effective ratiometric fluorescence sensor for selective detection of dopamine (DA) in alkaline media by simply mixing thioglycolic acid (TGA) functionalized orange fluorescent cadmium telluride (CdTe) quantum dots (QDs) with amino-functionalized blue fluorescent carbon nanodots (CDs). Under a single excitation wavelength of 365 nm, the sensor exhibits dual-emissions centered at 445 and 603 nm. The fluorescence of CdTe QDs is selectively quenched by DA, whereas the fluorescence of CDs is insensitive to the analyte. In the presence of different amounts of DA, the variations in the dual emission intensity ratios exhibit a... 

One of the Advanced Oxidation Process (AOP) is Photocatalyst method. Structure of this method is according to three foundation: 1. Catalyst, 2. Source of energy, 3. Wastewater. Progress of human activity around variety of fields such as pharmaceutical, plastic industry, and medical science has produced some micro pollutants such as Bisphenol A (BPA) that has aroused the public concerns in recent years. The half-life of this components in water, air and soil is too long, so typical methods such as biological method, activated sludge and carbon adsorption are inefficient in removing BPA. This work describes a visible light responsive Carbon Quantum Dots(CQDs) embedded on TiO_2 nanoparticles... 

Coupling of optical and mechanical degrees of freedom through radiation pressure was, first, observed in the experiments for detection of gravitational waves. Recent experimental advances have granted reality to the long-hankered-after coupling between microscopic and macroscopic systems. In the first step, this thesis will review different aspects of cavity Optomechanics, such as: cooling, side-band formation and dynamics of an Optomechanical cavity. Then we will go further and study the Optomechanical dynamics of a cavity in the presence of an atom. To do so, we will analyze the entanglement, created between the center of mass motion of the atom and the mirror and will probe into its... 

In this M.Sc. thesis the behavior patterns of the cavity quantum electrodynamics of complex systems are analyzed, such systems are quantum optic multi-partite systems and consist of an arbitrary number of quantum dots in interaction with arbitrary number of cavity modes.
First, the coefficients matrix of the ket sate of the system was measured, in order to achieve it; the general time-dependent state of the most general possible system was specified. Its related Hamiltonian was written, and finally the Schrodinger equation was measured in different coupling regimes. It was done in Schrodinger picture without any approximation.Second, the presence probabilities of the quantum dots of any... 

In this research, a facile, two-step synthesis was reported for 34-LCysteine- nanocomposites. The first step comprises the preparation of LCysteine functionalized magnetic nanoparticles (MNPs) core-shell structures via co-precipitation method. In the second step, graphene quantum dots (GQDs), which were synthesized by citric acid carbonization, added to the functionalized MNPs and finally refluxed at the appropriate time and temperature. LCysteine as a biocompatible, natural amino acid were used to link MNPs with GQDs. This nanocomposite was characterized by various techniques. XRD and FT-IR were used to investigate the formation of MNPs and LCysteine existence on the MNPs surface. XPS...