Sharif Digital Repository

Graphene quantum dots (GQDs) as a sort of carbon-based nanomaterials are applied in a multitude of exciting areas. They are effective fluorescent probe for many potential biological and medical applications. In comparison to conventional organic fluorescent probes (organic dyes), GQDs have substantial advantages, such as photostability, excellent solubility, low cytotoxicity and biocompatibility.
In this thesis, green fluorescent GQDs have been prepared via solvothermal method from graphite powder.Various analysis methods were utilized to characterization of the product. So, several experiments on GQDs in solution and in solid substrate at room temperature have been performed. The... 

Theranostic liposomes have recently found a broad range of applications in nanomedicine due to stability, the high solubility of biomacromolecules, bioavailability, efficacy, and low adverse effects. However, the limitations of liposomes concerning the short systemic circulation in the body, limited controllability of the release rate, and the inability of in vivo imaging remain challenging. Herein, the development of novel hybrid ultrasound-activated piezoelectric nanoparticles based on a hybrid liposome nanocarrier composed of poly(vinylidene fluoride‐trifluoroethylene), graphene quantum dots (GQDs), and Silibinin (a hydrophobic drug) is presented. The hybrid nanoparticles are an... 

Active packaging is a novel approach that can ensure food safety by removing undesirable compounds such as Oxygen, ethylene, moisture, and microbial contamination from fresh produce's environment and reducing product loss by extending shelf life. Current research on active food packaging materials focuses on using biopolymers such as carbohydrates, proteins, and lipids as alternatives to non-degradable petroleum-based packaging materials. Active nanomaterials are commonly used to impart functionality to packaging materials. However, the lack of functionality limits their industrial application.Therefore, the main objective of this work was to fabricate bioactive nanocomposite films by... 

Luminescent semiconductor nanocrystals otherwise known as quantum dots (QDs) have attracted intense interest over the past decade due to their unique properties and great potential in various applications. In this work we have studied the growth and luminescence properties of CdTe QDs and CdTe/CdS core-shell QDs and their application in hybrid organic/inorganic light-emitting diodes (LEDs) and fluorescent sensors. CdTe QDs were synthesized using a thermochemical method in aqueous phase. Central composite design (CCD) was applied to obtain the optimized conditions of the synthesis. The effects of four independent parameters including molar ratios of Cd to Te ions, TGA to Te ions, pH of the... 

In this research we focus on fabrication and characterization of Dye and Cadmium based Quantum Dot Sensitized Solar Cells (QDSCs) based on TiO2 nanostructures. TiO2 nanorods were synthesized with a simple chemical method. TiO2 nanorods, TiO2 nanorod/TiO2 and ZnO nanoparticle composite structures were integrated as photoanode in dye sensitized solar cells (DSSCs). Incorporation of TiO2 nanoparticles into the bare nanorods increased the efficiency more than 45%. Monitoring electron transport properties of the cells, pointed out the crucial role of electronic structure of composite film components on the performance of cells. Suitable morphology of TiO2 nanorods, led us to use them, to make a... 

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... 

In the current work, the two- and three-dimensional electro-elastic fields of periodically as well as arbitrarily distributed interacting quantum wires (QWRs) and interacting quantum dots (QDs) of arbitrary shapes within a piezoelectric matrix are studied analytically. The lattice mismatch between the QWR/QD and the barrier is accounted through prescribing an initial misfit strain field within the QWR/QD. The distinction between the electro-mechanical properties of the QWR/QD and those of the barrier is treated by introducing a novel electro-mechanical equivalent inclusion method in Fourier space (FEMEIM). Moreover, the theory can readily treat cases where the QWRs/QDs are multi-phase or... 

Studying the behavior of piezoelectric materials containing self-assembled quantum wires and quantum dots is of great interest. This work is devoted to analytical and exact determination of the electro-elastic fields associated to quantum wires and quantum dots in piezoelectric mediums. The present work accounts for: (1) different shapes and orientations of quantum wires and quantum dots, (2) different types of anisotropy, and (3) high concentrations of quantum wires and quantum dots, that is, the corresponding interaction is considered properly. The presented solution is valid for general anisotropy and different shapes of quantum wires and quantum dots. In this work, periodic and... 

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... 

The biocompatibility and chemical stability of boron nitride nanomaterials surpass those of carbon nanomaterials. In addition, boron nitride nanomaterials share the same structure as graphene materials, making them a suitable replacement for graphene in biological applications. In this study, SKOV3 cancer cells were actively targeted using amine-functionalized boron nitride quantum dots that were covalently modified by CD133 antibody. Under the condition that they are not conjugated with antibody, these nanoparticles were also incorporated into the microfluidic device designed to image MCF7 cancer cells. These nanoparticles were produced via solvothermal synthesis in an organic solvent... 

In tissue engineering and nerve cell treatments, biocompatible and conductive substrates are needed to stimulate nerve cells. In this project, we fabricated a composite of polyaniline and gelatin along with metal-organic frameworks and graphene quantum dots, which perform this repair process for us. For this purpose, we used polyaniline. Due to its conductivity, this polymer stimulates the nervous tissue and in this way, it can perform the repair work. By conducting UV-Vis and FTIR tests, it was observed that the synthesis of aniline polymer has been achieved successfully. SEM analysis showed that the polymer chains were well formed. The other part of the composite used is MOF (metal-organic... 

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... 

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... 

In this work, encapsulating cesium-based perovskite quantum dots (PQDs) in zeolitic imidazolate framework-8 (ZIF-8) was investigated in order to enhance their environmental, water and thermal stabilities. It was shown that physical mixing of pre-synthesized PQDs and nanocrystalline ZIF-8 (structure-I) does not have any influence on stability enhancement. In second structure, nanocrystals of perovskite were crystalized in ZIF-8 pores. These nanostructures kept 50% of their initial photoluminescence after 24 hours maintenance in water. In third structure, both perovskite nanoparticles and ZIF-8 structures were crystalized simultaneously which resulted in more efficient encapsulation and kept... 

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 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 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... 

In the last years, perovskite QDs have emerged as the novel candidate due to their unique optical properties such as high-absorption coefficient, long-range charge transport, low exciton-binding energy, and etc. Nonetheless, poor stability of perovskite in ambient conditions made researchers to consider this issue. Recently, amoung various types of organic-inorganic perovskites, Formamidinium lead iodide has attracted tremendous attention due to its near IR absorption wavelength in addition to the higher stability compared to MAPbI3. In this work, FAPbI3 perovskite stability improvement was investigated by several methods under different conditions. In the first step, FAPbI3 QDs colloidal... 

Graphene based photodetectors which are modified with quantum dots, are the new generation of detectors. In these supplies an integration of graphene’s unique characteristics like high conductivity and mobility and the high light absorption of quantum dots, are used.In this research graphene by chemical vapor deposition in centimetric large scales, tungsten disulfide quantum dots, boron nitride and graphene quantum dots and 2D tungsten disulfide have been synthesized. In the next step each of them were characterized to modify the quality of used layers in heterostructure.Based on the characteristic tests, quantum dots aspect ratios were 1 to 5 nanometers. Also tungsten disulfide was obtained... 

The use of magnetic compounds for drug delivery and magnetic imaging has been studied in many studies. The easy use of magnetic particles makes them widespread. By applying a magnetic field, the particles reach the desired position and return to the original state by cutting off the field. The use of these magnetic materials in the nanoscale also adds other benefits, including: convenient and rapid transfer of nanoparticles, rapid repulsion of the kidneys, reducing the risk of overdose, etc. In recent years, the use of quantum dots for the diagnosis and treatment of tumors has attracted much attention. The use of hybrid quantum dots and magnetic nanoparticles can incorporate the desired...