Sharif Digital Repository

In this work, carbon nanotubes (CNTs) were synthesized via arc discharge in an aqueous solution. The role of iron catalyst in CNTs formation was investigated utilizing arc discharge in iron salts solution (Fe2(SO4)3 and FeCl3). Thermogarvimetric (TG) analysis showed the presence of multi-layered structures including multi-walled carbon nanotubes (MWCNTs) and multi-shelled graphite particles when processing was performed in DI-water. In the presence of iron ions, single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were formed. The effect of iron ions (Fe3+) concentration on CNTs yield was investigated by Raman spectroscopy. The highest yield was obtained when... 

Simultaneous detection of pH and glucose levels in sweat is a promising tool for early skin disease detection and diabetes diagnosis. Hydrogels have attracted a lot of attention in the field of wearable biosensors due to sweat absorption capability, biocompatibility, and the ability to store enzymes and reagents in their cavities. In this research, we have presented an innovative wearable colorimetric biosensor based on polyvinyl alcohol (PVA) hydrogel, which can simultaneously measure pH level (in the range of 3-9) and glucose concentration (in the range of 0.025-0.5 mM) of sweat with the help of machine learning (ML). This wearable sensor consists of two main parts: sensors and a patch, in... 

Rotating machinery plays a significant role in various industries. One of the most important and influential parts in rotating machinery is rolling bearings, which play a vital role in the proper functioning of this equipment. Therefore, bearing failures can lead to unintended equipment downtime, financial losses, and reduced productivity. As a result, accurate diagnosis of bearing faults is crucial for improving the reliability and performance of industrial machinery. Despite significant advances in the field of condition monitoring and intelligent fault diagnosis, challenges such as the lack of labeled data and the impact of noise on the accuracy of fault diagnosis models remain major... 

Electrochemical sensing of glucose has received paramount attention in recent years, particularly, the non-enzymatic glucose sensing is one of the trends in the whole biosensing world. In this research, synthesis and evaluation of a hybrid structure of vertical oriented nickel nanorod-reduced graphene oxide sheets as a non-enzymatic glucose sensor were performed. The 3D array of nickel nanorods was synthesized by electrodeposition of nickel sulfate electrolyte in track-etched polycarbonate template with 100 nm pore size and 6-10 μm thickness. The electrodeposition performed in various conditions, and the best result was achieved by application of potential of 3 V for 60 minutes. The shiny... 

In the design of many drug delivery systems, the primary goal is to achieve controlled release at predetermined rates over a duration appropriate for the therapeutic application. Maintaining the drug concentration within the optimal therapeutic window reduces adverse side effects, lowers the required drug dose, optimizes drug utilization, and enhances patient compliance. An effective strategy for targeted drug delivery is the design of systems capable of providing the required amount of drug at the desired time and site in the body with controlled release. In this study, a silica-liposome hybrid carrier was designed and synthesized to achieve pH-responsive controlled release. Liposomes are... 

Development of active, durable, cost effective, and stable electrocatalysts are of urgent need for various industrial fields including renewable energy systems such as water splitting. State-of-the-art catalysts suffer from high cost, poor catalytic activity in alkaline medium due to sluggish kinetics. We used one-step electrochemical deposition technique to prepare NiFeCu layered double hydroxide and CoNiFeCu dendritic porous structure on Ni-foam and flexible three-dimensional graphene (3DG) networks, respectively. The fabricated 3D electrodes have a high surface area, high electrical conductivity, and multiple interfaces which along with the synergetic effect of transition metals provided... 

Graphene is a newly developed nanomaterial that has resived considerable attention in recent years. Graphene – based structures having remarkable properties, e.g. high specific surface area, ultrahigh electrical conductivity and good biocompability, are ideal choices for nanomedical applications such as biosensors and cell culture scaffolds. So, in this project 2D graphene and 3D graphene foam structures were synthesized by chemical vapor deposition (CVD) method and their electrical and biological properties were evaluated. First step of this project was to design and make a CVD system suitable for the synthesis of high quality graphene structures, i.e. single layer graphene and 3D graphene... 

Solution-processed quantum dots (QDs) have attracted significant attention for the low-cost fabrication of optoelectronic devices. Here, we synthesized PbS QDs via hot injection method and passivated the trap states by using short thiols and dopant elements for photovoltaic application. In order to study the effect of dopants on photovoltaic application, PbS QDs were doped by using three different cations: Cadmium, Calcium, and Zinc. The results showed that Cd dopant has a better improvement than Ca and Zn dopants in order to increase the efficiency of the PbS QDs solar cells. We achieved solar power conversion efficiencies of 5.81% using Cd therapy. Recently, hybrid nanocomposites... 

Density Functional Theory is one of the most robust Ab-intio methods for describing the structural and electronic properties of a wide range of materials. The ability to predict the material properties changes due to targeted material manipulation at the atomic scale has reduced the cost of many empirical experiments. It has improved the knowledge and understanding of the investigation and producing new materials and devices. Tow dimensional heterostructures are highly regarded due to their unique optoelectronic properties, potential application in nanoelectronic devices, energy storage devices, solid-state devices, and photovoltaic devices. In this study, the two-dimensional materials... 

In this report, a combination of in-situ chemical synthesis and electrolysis methods was applied for the preparation of zinc oxide/graphene quasi core-shell nanoparticles. Pure zinc oxide was also prepared using the same method at different temperatures. The degree of 100 ◦C was selected for synthesizing of ZnO-GO quasi core-shell (zinc oxide as a core and few layer of graphene oxide as a shell). The particle size was 15±2 nm in all samples. In both processes, oxygen was the main reason for the connection between the core and the shell. Unlike chemical process that has all kind of functions in electrolysis process, one kind of function was produced and confirmed by FTIR. XRD patterns also... 

An isopropanol supercritical reducing environment was prepared by fabricating a high temperature, high pressure autoclave, in order to make a hybridized structure of zinc oxide and graphene oxide, entitled as ZnO-G. In this novel structure, the oxygen acts as bridging element between zinc and carbon, that connects a wide band gap semiconductor to a narrow banded one. The hybridization mechanism is studied by FTIR analysis, and morphology is shown by FE-SEM. The micrographs obtained from the thin film show a stacked pile of ZnO-G disks, like a button, dispersed on a crack free layer. In addition, the crystallographic structure was revealed by comparing low angle X-ray diffraction patterns to... 

We demonstrated efficient direct electron transfer from the enzyme glucose oxidase to vertically aligned gold nanorods with a diameter of ~160 nm and a length of ~2 μm that are covalently linkage to a 3-dimensional network of reduced graphene oxide nanosheets. The assembly can be prepared by a 2-step electrochemical procedure. This hybrid structure holds the enzyme in a favorable position while retaining its functionality that ultimately provides enhanced performance for enzymatic sensing of glucose without utilizing mediators. The nanorod assembly was applied to the voltammetric detection of glucose. Figures of merit include an electrochemical sensitivity of 12 µA⋅mM-1⋅cm-2 (obtained from... 

In recent years, quantum dots specially NIR QDs like lead sulfide have attracted a lot of attentions in various bioapplications such as bioimaging, stem cell tracking, etc. However, these materials are generally synthesized by using organic lagands like oleic acid which is not appropriate for bioapplications. Moreover, the cytotoxicity of these materials have severely restricted their applications. In this research, lead sulfide quantum dots were synthesized via a hot injection route. The nanocrystals had an average size of 3 nm passivated with oleic acid ligands and graphene nanosheets. Excitonic and photoluminescence peaks were observed in wavelengths of 950 and 1100 nm, respectively.... 

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... 

Graphene is a single-atomic two-dimensional crystal that has considerable properties due to its unique structure and physics with applications in different fields. Due to its atomic thin thickness, substrates have a considerable effect on the electrical properties of Graphene. As these effects are determinative of the general behavior of systems, one should consider this effect in the design and fabrication of a device. Moreover, the conventional fabrication methods for Graphene-based electronic devices restrict the possibility of the device fabrication on a wide range of substrates, specially flexible and biocompatible substrates.In this work, the LPCVD Graphene growth process has been... 

Chitosan (CS) is a natural polysaccharide, which is widely used for various biomedical applications due to its excellent properties such as biocompatibility, biodegradability, bioadhesivity, and bactericidal capacity. Nevertheless, the poor mechanical strength and the loss of structural integrity limit the applications of chitosan. Graphene oxide (GO) has been recognized as an ideal filler for reinforcement of a polymer matrix and its excellent water solubility makes it as a promising candidate for biopolymers. In this work, biocompatible chitosan-graphene oxide nanocomposites were synthesized. First, graphene oxide was prepared using modified Hummer’s method from graphite powder. Solvent... 

Drug-eluting bone implant coatings is a new era that has gained a lot of attention in recent years. In this matter, drug is loaded in the coating and local and targeted release of the drug results in preventing the side effects of implantation and increasing the healing process of the patient. The aim of this project was to synthesis the antibiotic eluting chitosan-based composite using electrophoretic deposition for bone implant coating. By using electrophoretic deposition chitosan and chitosan-bioglass composite coatings were synthesized. Then the probability of loading of drug into coating by using electrophoretic deposition was evaluated and by using this process chitosan and... 

Chronic wounds are among the serious injuries which have called the attention of scientists to invest in an effort to fabricate temporary skin grafts and wound dressing materials. One of the widely acceptable solutions to this obstacle is to design a bioactive scaffold capable of regenerating tissue as well as delivering active agents to the site specific area. To this end, natural biopolymers are considered as suitable candidates to be employed in regenerative medicine due to their excellent biocompatibility. In addition, nanoparticles possess special properties such as the ability in sequestering the drug release which make them promising candidates in the fabrication of the... 

In recent years, temporary skin grafts based on natural biopolymers modified with carbon nanostructures has received considerable for wound healing applications. In this study, Nanofibrous structures that mimic the native extracellular matrix and promote cell adhesion have attracted considerable interest for biomedical applications. Chitosan-polyvinylpyrrolidone (CS/PVP) films containing graphene oxide (GO) nanosheets (~1 nm thickness and micrometer length) were prepared by solvent casting methods. Experimental results showed that PVP concentration had a critical role on the water vapor permeability, transparency, hydrophilicity and thermal stability of the nanocomposite films. Antibacterial... 

Implant-associated infections are one of the most serious complications in orthopaedic and trauma surgery as it may result in poor functional outcome, implant failure, chronic osteomyelitis or even death. Great concerns have been taken to reduce implant-associated infections through progressing in operating standards, minimizing the possibility of contamination during surgery, reducing the establishment of infection by perioperative antibiotic prophylaxis, and confining of pathogenic strains by patient isolation. In spite of these preventions, the percentage of postoperative infections is still rising. Composite coatings with bone-bioactivity and drug-eluting capacity are considered as...