Sharif Digital Repository

Tailoring the electronic properties of graphene is of fundamental interest regarding its application in electronic devices. One of the key strategies is chemical functionalization which modifies the p-electron system and thus can induce band gaps. However, in order to control the degree of functionalization it is crucial to know the exact amount of the chemisorbed species. We show with angle-resolved photoemission spectroscopy (ARPES) the formation of a band gap in graphene and estimate the hydrogen coverage from the scattering rate. Using X-ray photoemission spectroscopy (XPS) we identify the chemical environments in hydrogenated graphene and determine the total hydrogen to carbon... 

In order to improve its biological properties, graphene oxide can be modified with hydrophilic polymers. Therefore, in this study, the surface of graphene oxide was modified with polyethylene glycol and albumin by covalent methods. In the subsequent step, paclitaxel which is a hydrophobic anticancer drug was loaded onto the surface of the functionalized graphene by π-π interactions. The synthesis of the nanocarrier and its interaction with paclitaxel were evaluated by FT-IR, CD, TEM, UV, AFM, DLS and fluorescence experiments. Release of the loaded drug from albumin-graphene conjugate was investigated at pH 5.4, 6.8 and 7.4  

This work presents a procedure for functionalization of graphene sheets from edges by polyglycerol. Hyperbranched polyglycerol with a bi-dentate aromatic segment in its focal point was synthesized and used to sandwich graphene sheets from the cut-edges. Due to the hydrophobicity of the flat surface of the edge-functionalized graphenes and hydrophilicity of their edges, they changed their conformation from the extended- to the closed-state and formed nanocapsules in aqueous solutions. Spectroscopy and microscopy evaluations showed that the average size for nanocapsules is 300 nm. They were able to encapsulate hydrophobic molecules such as doxorubicin in aqueous solutions with a high loading... 

In the present work a novel multifunctional drug nanocarrier was prepared. Polyglycerol-. g-polycaprolactone was grafted on Mesoporous silica-coated magnetic graphene oxide. Doxorubicin, as anticancer drug, was loaded on this carrier. The in vitro drug release showed the controlled pH responsive behavior. At the endosomal pH (pH 5.5) the amount of drug release enhanced. This nanocarrier would have potential application in the tumor therapy owing to its biodegradability, controlled release and pH responsive behavior  

In this work, graphene oxide (GO) aqueous suspensions prepared by a chemical exfoliation method showed a fluorescence peak at ∼615 nm. Photoluminescence spectroscopy determined that functionalization of the GO sheets by 3-(2-Aminoethylamino) propyltrimethoxysilane molecules significantly quench the fluorescence property of the GO sheets. Fourier transform infrared spectroscopy confirmed proper functionalization of the GO sheets. Curcumin was applied as a fluorescent natural material with an emission peak at ∼550 nm wavelength for green fluorescent labeling of the functionalized-GO sheets. The curcumin-labeled functionalized-GO sheets showed an intense emission band fluorescent property with... 

The potential of carbon-based nanosheet membranes with functionalized pores is great as water treatment membranes. Using the molecular dynamic simulation technique, the dimethyl sulfoxide (DMSO) separation from the water/DMSO binary solution is investigated, and the functionalized graphene nanosheets are used as a membrane. This membrane was functionalized by –F (fluorine) and –H (hydrogen) functional groups. For the separation of DMSO, external hydrostatic pressures up to 100 MPa were applied to the considered systems. The separation mechanism was based on molecular size. Multiple analyses were done to study the capability of considered membranes for the separation of DMSO molecules from... 

In the present work, G-TiO2 and G-ODA-TiO2 hybrids were prepared by concurrent surface functionalization and reducing of graphene oxide (GO) using octadecylamine (ODA). The G-TiO2 and G-ODA-TiO2 powders were deposited on the copper surface by electrophoretic deposition (EPD) technique. The wettability of coatings revealed the preferable hydrophobic characteristic of G-ODA-TiO2 compared to G-TiO2 and bare copper with water contact angles of 130°, 101°, and 87°, respectively. The anti-corrosion performance of specimens in a 0.5 M H2SO4 solution was appraised by the potentiodynamic polarization (Tafel analysis), which clearly showed that G-TiO2 and G-ODA-TiO2 coatings can act as a great barrier... 

A straightforward three-stage method was applied to fabricate a super-hydrophobic mixed-matrix nanofiber membrane using the electrospinning method for desalination purpose. First, a hydrothermal technique was applied to synthesize a super-hydrophobic nano-sheet, called octadecylamine-reduced graphene oxide (ODA-rGO) with a water contact angle of 162°, which was then added to PVDF-HFP dope solution. After, 0.005 wt% LiCl was added to the dope solution to decrease the mean pore size by increasing solution conductivity. Moreover, some membranes were hot-pressed to improve liquid entry pressure (LEP). Eventually, a top-quality nanofiber membrane was synthesized using 0.1 wt% ODA-rGO and 0.005... 

A single-step green method for effective reduction and functionalization of graphene oxide (GO) by glucose was developed. Then, efficacy of the glucose-reduced GO sheets in photothermal therapy of LNCaP prostate cancer cells was investigated in vitro. The GO suspension reduced and functionalized by glucose in the presence of Fe catalyst showed a biocompatible property with an excellent near-infrared (NIR) photothermal therapy efficiency better than hydrazine-reduced GO, single-wall and multi-wall carbon nanotube suspensions which even showed some levels of toxicities. For complete destruction of the cancer cells at some time intervals of NIR irradiation (e.g., 0.5 and 12 min with a power... 

A specific structure of doped graphene with substituted silicon impurity is introduced and ab initio density-functional approach is applied for the energy band structure calculation of the proposed structure. Using the band structure calculation for different silicon sites in the host graphene, the effect of silicon concentration and unit cell geometry on the bandgap of the proposed structure is also investigated. Chemically, silicon-doped graphene results in an energy gap as large as 2eV according to density-functional theory calculations. As the authors will show, in contrast to previous bandgap engineering methods, such structure has significant advantages including wide gap tuning... 

According to current researches, graphene oxide (GO) membranes show promising desalination properties due to ease of synthesis, low production cost, and high efficiency. There are several experimental works to study ionic sieving properties of GO membranes. However, it is difficult to characterize atomistic mechanism of water permeation and ion rejection by experimental approaches. On the other hand, there exist a few reports in which the atomistic picture of water permeation across GO membranes is investigated by means of molecular dynamics (MD) simulation. In the present work, in addition to water desalination, the atomic scale mechanism of ion rejection is studied using large scale MD... 

In this research, a series of numerical simulations were conducted utilizing computational fluid dynamics (CFD) software in order to predict the heat transfer performance of queues nanofluids containing clove-treated graphene nanoplatelets (CGNPs) flowing in a horizontal stainless steel heated pipe. The GNPs were covalently functionalized with clove buds using free radical grafting reaction using an eco-friendly process. The advantage of this synthesis method was that it did not use hazardous acids, which are typically used in traditional treatment methods of carbon nanostructures. The thermo-physical properties of the aqueous nanofluids obtained experimentally were used as inputs for the... 

Convective heat transfer plays a significant role in numerous industrial cooling and heating applications. This method of heat transfer can be passively improved by reconfiguring flow passage, fluid thermophysical properties, or boundary conditions. The broader scope of nanotechnology introduced several studies of thermal engineering and heat transfer. Nano-fluids are one of such technology which can be thought of engineered colloidal fluids with nano-sized particles. In the present study, turbulent forced convection heat transfer to nanofluids in an axisymmetric abrupt expansion heat exchanger was investigated experimentally. During heat transfer investigation, the functionalized...