Sharif Digital Repository

Dye sensitized solar cells (DSCs) are among the 3rd generation solar cells which their mechanism of light absorption is similar to chlorophyll in green leafs and is based on photo-excitation of dyes. The electron-hole pairs of photo-excited dye separate at the interface of mesoporous semiconductor-dye-electrolyte. One of the approaches to increase the light path length and therefore the light harvesting efficiency in DSC is the addition of light scatterers inside the mesoporous semiconductor (photoanode).In this research, nanoparticulated hollow TiO2 fibers are introduced as novel light scatterers in DSCs with simultaneous light scattering, light trapping and high surface area. Light... 

Polymers not just because of their increasing applications in industry but according to their fundamental role in biological mechanisms, has been a topic of interest among different scientific groups. Chemical structure, acroscopic properties and dynamical behavior of these macromolecules are studied in different ways. An important sub-group of polymers are those which according to their chemical properties, after dissolving, release some ions in water and become charged and called polyelectrolytes. A polyelectrolyte with vital importance in our life is DNA which encodes the genetic instructions used in the development and functioning of all known living organisms. One of the main goals in... 

Polymer translocation through the nanopores is one of the fundamental macromolecular processes in life. Some examples are , mRNA translocation through nuclear pores, injection of DNA from a virus head into a host cell, protein translocation across biological membranes through membrane channels. Also some applications are suggested for the process, e.g. DNA sequencing by probing the signals during the translocation, drug delivery and/or gene therapy. During the translocation the polymer should pass entropic barrier of the pore and it can be facilitated by changing the chemical potential, application of eclectic field, flow field, or chemical concentrations. In electrically driven... 

In recent years, advances have been made in the field of miniaturization of the devices (in order to increase their efficiency, lessen the materials needed for the constructions and experiments, reduce costs and energy usage) resulting in the dramatic increase of surface to volume ratio in these devices. This progress has led to the dominance of surface forces which can be used to control very important interface phenomena having a special application such as electrokinetic. Using today’s manufacturing technology; it is possible to construct micro-nanochannels made from different materials such as silicon, glass, quartz, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) whose... 

Conical nanochannels have desirable electrokinetic properties due to asymmetry,including ionic current rectification and ion selectivity. The present study numerically addressed the effect of slip length on the ionic current rectification and ion selectivity in conical-shaped electrolyte-loaded nanochannels with and without a coated polyelectrolyte layer. The electrolyte was considered a salted incompressible Newtonian fluid. The polyelectrolyte layer was also modeled as a rigid and charged porous solid saturated with a salted Newtonian fluid. The electrolyte-polyelectrolyte layer interface was modeled as a surface, considering ion partitioning with distinct physical properties across the... 

Polyelectrolyte complexes based on polysaccharides have attracted the attention of researchers due to their potential for use in advanced industries. One of the most widely used cationic polysaccharides is chitosan. However, chitosan alone limits applications for smart and sustainable drug delivery due to uncontrolled degradation. For this reason, combining chitosan with another polyelectrolyte and forming a polyelectrolyte complex due to electrostatic interaction has been proposed as a solution. In the first phase of this dissertation, the effects of mixing ratio and concentration of Chitosan and Quince seed gum (QSG) on the physical and rheological properties of chitosan-QSG...