Sharif Digital Repository

World population growth, depletion of fossil fuels resources depletion and increased air pollution resulting from their consumption, human society has had to replace fossil fuels with renewable sources. In this context, the production of hydrogen using solar energy is feasible candidate to replace fossil fuels, which can be produced by water splitting in a photoelectrochemical (PEC) cell using an appropriate photocatalyst. This clean production method has been attended by many researchers in recent years. The most common photocatalyst for the conversion of sunlight to hydrogen by splitting water is Titanium dioxide (TiO2). But high energy gap and fast electron-hole recombination rate in TiO2... 

Carboxamide ligands have been part of the growing research in the field of coordination chemistry of transition metal complexes. The solvent used in the classical method of synthesis of these compounds is pyridine, a solvent which is extremely toxic. In this project, we have developed a new method of synthesis using ionic liquids as the reaction media and have prepared Hqcq (1), Htp(2) under optimum conditions for Pd(II) and Pt(II) complexes of Hqcq and Co(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes of Htp with the formula:[Pd(qcq)(OAc)] (1a), [Pt(qcq)(Cl)] (1b), [Co(Htp)2(H2O)2].C2H5OH (2a), Co3O4 (2b), [Cu(tp)2(H2O)].CHCl3 (2c), CuO (2d), [Zn(tp)2(H2O)2] (2e), [Cd(tp)2(H2O)2].CH3OH... 

Octahedral crystals of Fe-Metal-organic frameworks like Fe-MIL-101, which is the most stable and active metal-organic frameworks; in combination with graphitic carbon nitride nanosheets could significantly enhance the photocatalytic activity of g-C3N4 for inorganic dye degradation under the irradiation of visible light application. This appropriate cocatalyst modifies the performance of semiconductor via suppressing the recombination of photo-induced carriers and since the synthesized composite prepared by in-situ procedure possesses close contact between each other, the migration of electrons in the photocatalytic reaction will be continued, so the degradation process via the active species... 

The main aim of present thesis is to synthesis and characterize of ferrite nanocomposites as a new generation phtocalyst and their application in degradation of various types of environmental pollutants in different irradiation time and dark conditions. Ferrites have been used anchored to carbon allotropes such as graphene oxide and carbon nanotubes, in order to improve their photocalytic activity as well as phase structure, textural and optical properties. Firstly, a new SnS2-BiFeO3/rGO nanocomposite has been prepared to increase the visible-light-responsive photodegradation of organic dyes such as cationic methylene blue (MB) and anionic methyl orange (MO). The obtained results showed... 

The Dye-sensitizers loading on TiO2 is decreasing the electron excitation energy and therefore improving the photocatalytic performance from the increasing the sensitivity under visible light irradiation.in this project CoPCTS , Mordant dye and N3(Ruthenium 535) used as dye-sensitizers. Also The addition of VIII group metals on TiO2 is improving the photocatalytic activity that increasing the photocatalytic reaction rate because of the intermediation role of them for moving the conduction band electrons to electron acceptors and increasing the pair electron-holes long-life that in this case Pt loading used as a VIII group metal. In this project Titanium Isopropoxide as a precursore and... 

In this thesis, photocatalytic oxidation as a potential method for the treatment of organic environmental contaminants is deeply investigated. While the photocatalytic degradation of various organic compounds under UV light irradiation has been widely investigated, visible-light-induced photocatalytic degradation of low-levels of the pollutants such as Dibenzothiophene (DBT) and 2-Nitrophenol (2-NP) are occasionally reported. In the present work, Lanthanide / Polyethylene glycol -modified TiO2 (La/PEG/TiO2) and Fe,Cu,S/TiO2 have been successfully synthesized by a sol–gel method. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission... 

Today, fossil fuels cause countless environmental pollutants, so replacing fossil fuels with clean energy sources is very important. Water splitting using light and a semiconductor is one of the new methods of producing oxygen and hydrogen, which due to its simplicity and cheapness, has attracted a lot of attention today. In this study, ZnMn2O4 photocatalyst nanoparticles were first loaded on a graphitic carbon nitride support in different ratios of ZnMn2O4 and carbon support by hydrothermal method. Then the photocatalysts were evaluated for evolution of oxygen and hydrogen photocatalysts through water splitting under visible light. In ZnMn2O4 / g-C3N4 (80:20) nanocomposite, the highest... 

The g-C3N4/Fe2O3 nanocomposite was produced by the combustion synthesis. The product was characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller study (BET), Ultraviolet-visible analysis (UV-vis) and photoluminescence measurement (PL). Effect of iron nitrate on stability and photocurrent density under simulated visible-light irradiation was determined. The highest photocurrent density obtained (4.25 μA/Cm2) was twelve times the pure g-C3N4. This improvement was due to a bandgap decrease, the specific surface area increase, reduction of the electron-hole recombination, and... 

The N-doped rGO/NiFe2O4@Ti-doped ZnO as a novel ternary nanocomposite with magnetic recyclable was obtained by a facile and low-cost hydrothermal method. The structure, morphology, and optical as well as magnetic properties of synthesized nanocomposite were analyzed using the X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), Raman spectroscopy, Emission scanning electron microscopy (FESEM) with Energy dispersive spectra, Transmission electron microscopy (TEM), UV-vis diffusive reflectance spectra, and Vibrating sample magnetometer (VSM). The photocatalytic activity was determined by the degradation of Methylene blue (MB) and Methylene orange (MO) dyes under visible light... 

In recent decades, desulfurization processes have become essential to decrease environmental pollution due to the emission of sulfur from fuels. In this study, in order to desulfurize liquid fuel, a model fuel (normal heptane) was investigated under visible light ) 350-watt sodium lamp(, using H2O2 as oxidant and methanol as a solvent in the presence of Cu-C-TiO2 nanostructure. C-TiO2 was synthesized by the hydrothermal method. In order to modify and improve the properties, we doped the copper metal by impregnation method with different loading of Cu. Experimental results exhibited the highest activity among samples attributed to 0.5% Cu-C-TiO2 Which caused 98.27% degradation of DBT after 2... 

LiFi is a bidirectional wireless optical networking technology that uses commercial LEDs for data transmission. In simpler terms, LiFi is considered a light-based WiFi that uses light instead of radio waves to transmit information. Using light to transmit data allows LiFi to deliver a couple of advantages, such as working in areas susceptible to electromagnetic, working across higher bandwidth while offering higher transmission speeds. Finally, the security of this technology is much more than other ways of communication since the light cannot penetrate through walls and doors, so other people who are not in the room could not access data.In this dissertation, a Li-Fi receiver that uses... 

Developing an efficient visible-light-driven photocatalyst is believed to be a practical solution for clean energy and environmental remediation. The present study aimed to broaden current knowledge of the graphitic carbon nitride (g-C3N4)-based plasmonic photocatalysts by decorating polydopamine-grafted g-C3N4 (PDA/g-C3N4) with silver nanoparticles (AgNPs). The ternary nanocomposite was prepared using a facile synthesis method, while XPS and electron microscopy measurements confirmed the homogenous dispersion of AgNPs on PDA/g-C3N4. It was revealed that AgNPs successfully reduced the recombination rate of photoinduced electron-hole charge carriers. The calculated bandgap energy was... 

Visible light communication (VLC) uses huge license-free spectral bandwidth of visible light for high-speed wireless communication. Since each VLC access point covers a small area, handovers of mobile users are inevitable. In order to deal with these handovers, developing fast and effective resource allocation algorithms is a challenge. this paper introduces the problem of mobility-aware optimization of resources in hybrid VLC and 5G radio access technologies networks using the T-step look-ahead policy and employing the notion of handover efficiency. It is shown that the handover efficiency can correlate the overall performance of the network with future actions based on the mobility of... 

In this dissertation, the optimization problem of visible light communication (VLC) access networks is discussed and investigated. Firstly, by examining the fundamental concepts in VLC systems, the channel capacity is analyzed, and the concept of capacity per unit cost is introduced to improve energy consumption. The appropriate relationship for channel capacity in optimization studies is also explored. In this regard, we reached a new distribution for transmitted signals, which, by reducing up to approximately 92% of the additional energy required for data communication, increases energy efficiency in visible light communication systems up to 98%, bringing the energy consumption of the... 

Textile dyes are a major category of organic pollutants and release of them in the environment causes serious problems. Among the most commonly used methods for colored wastewater, advanced oxidation processes, especially the photocatalytic process, are rapidly developing as a new and effective solution. However, there is still a need for high-level photocatalytic activity and improvement of this process to increase removal efficiency. In this study, we have tried to provide a higher performance for color removal using carbon nitride photocatalyst. Accordingly, two approaches have been proposed to improve the removal of rhodamine b, as one of the common dyes in the textile industries. The... 

Bismuth Vanadate (BiVO4) nanoparticles were prepared from two different precursors by precipitation method. The samples were characterized by Fourier transformed infrared (FT-IR), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and BET. The photocatalytic activities were examined by degradation of Acid Blue 92 under visible light. The results revealed that all the BiVO4 samples were in a monoclinic phase in nano range. The photocatalytic activity of BiVO4 depend on the calcination temperature and the concentration of photocatalyst. The photocatalytic activity increases with the amount of catalyst loading and decreases with increasing the... 

The photoreduction of CO2 to produce renewable solar fuel known as artificial photosynthesis attracted a lot of attention during the last two decades due to the global warming issue caused through increasing CO2 and shortage of fossil fuels resources. In this study, in order to enhance photocatalytic process of CO2 under visible light, TiO2-graphene and TiO2-copper nanocomposite utilized. A series of Cu/TiO2 photocatalysts were prepared with various Cu (2, 5 and 8 wt%) and a series of G/TiO2 photocatalysts with different graphene (G) content (5, 20 and 40 wt.%) were prepared and tested for the reduction of CO2. XRD, BET, DRS and TEM analyses employed to characterize the catalyst while the... 

Photocatalytic as well as photo-Fenton-like processes are promising and ideal technologies for using solar energy to regenerate energy as well as regenerate and revitalize the environment. In fact, photocatalytic processes are one of the most important chemical methods to reduce energy and environmental crises by converting endless solar energy into pure chemical potential. Photocatalytic processes and photocatalysts based on metal-organic frameworks (MOFs) have attracted special attention in recent years due to their excellent and unique properties such as adjustable structure and optical properties. In fact, metal-organic frameworks, as a group of newly emerged crystalline porous...