Sharif Digital Repository

Nanoparticles (NPs) are increasingly being used in different branches of science and in industrial applications; however, their rapid detection and characterization at low concentration levels have remained a challenge; more specifically, there is no single technique that can characterize the physicochemical properties of NPs (e.g. composition and size). In this work we have developed a colorimetric sensor array for defining the physicochemical properties of NPs in aqueous solution with ultra-low concentrations (e.g. 10-7g ml-1 for gold NPs). Various NPs were readily identified using a standard chemometric approach (i.e. hierarchical clustering analysis), with no misclassifications over 400... 

A magneto-photothermal therapy for cancer (in vitro photothermal therapy of prostate cancer cells and in vivo photothermal therapy of human glioblastoma tumors in the presence of an external magnetic field) was developed using superparamagnetic zinc ferrite spinel (ZnFe2O4)-reduced graphene oxide (rGO) nanostructures (with various graphene contents). In vitro application of a low concentration (10 μg mL-1) of the ZnFe 2O4-rGO (20 wt%) nanostructures under a short time period (∼1 min) of near-infrared (NIR) irradiation (with a laser power of 7.5 W cm-2) resulted in an excellent destruction of the prostate cancer cells, in the presence of a magnetic field (∼1 Tesla) used for localizing the... 

The diffusion and deposition of TiO2 nanoparticles in EOR application was investigated in this paper. TEM image of nanoparticles showed that the particles are elongated with average long and short axis sizes of 54 and 15 nm. Water flooding tests showed that the recovery factor can be improved from 49% to 80% using TiO2 nanoparticles. Viscosity and interfacial tension measurements showed that by using TiO2 nanoparticles the viscosity of injected fluid and interfacial tension do not change significantly and can not explain the change in recovery factor. Contact angle measurements showed that nanoparticles deposition changed the wettability of the rock surface from oil-wet to water-wet. SEM... 

Development of a model for optimal power generation from the thermal oxidation of a low concentration coal bed mine has been considered as the main objective of this investigation. The model has been applied to identify the optimal thermodynamic characteristics of the power generation system through using a mixture with 1.6% methane concentration in a recuperative lean-burn gas turbine and coupling a gas engine to the system for more power generation from the remaining coal bed methane. The implementation of the model based on the real site condition would lead to the generation of 6.97 MW electricity in Tabas coal mine of Iran. © 2016 Taylor & Francis  

In this study, ethanol gas sensing of PVP fiber membranes based on Quartz Crystal Microbalance (QCM) was investigated. The fibers were deposited on the QCM's electrodes by electrospinning the viscous blend solutions of PVP. The effects of PVP concentration on morphology of the fibers and their permeability when exposed to ethanol were investigated. Membranes which were prepared using low concentration solutions, contained beads and high packing fibers and showed low permeability. Increase of the PVP concentration to 12 wt% resulted in continuous fine fibers with good permeability. Furthermore, higher PVP concentrations were found to decrease ethanol permeability due to larger fiber radius... 

Graphene oxide (GO) sheets with a low concentration (∼1 wt%) were deposited on surface of hydrothermally synthesized ZnO nanorod films. The deposited films were heat treated at 450 °C in order to achieve suitable GO/ZnO hybrid thin films for photocatalytic purposes. The photocatalytic activity of the nanocomposite films was investigated based on degradation of methylene blue (MB) dye which is a typical pollutant model. The GO/ZnO hybrid thin films could degrade higher MB (∼90%) than the bare ZnO nanorods (which showed only ∼75% degradation) after 450 min UV irradiation. A further significant improvement (resulting in a nearly complete degradation of MB) was achieved by exposing the GO/ZnO... 

Surface chemistry of as-received nanodiamond (ND) was first tailored by dry thermal oxidation to obtain carboxylated ND (ND-COOH) and by wet chemistry to obtain ethylenediamine-functionalized ND (ND-EDA). Then, the surface-functionalized ND particles were dispersed in polyamide 6 (PA6) using the melt-mixing method. Transmission optical and scanning electron microscopies indicated a fine dispersion at low nanodiamond concentrations, e.g. 0.25 wt%, particularly with ND-EDA. Differential scanning calorimetry revealed that ND-EDA favoured the α-phase crystal and enhanced the degree of crystallinity of PA6. Experimental data indicated that ND-EDA had considerably improved tensile properties at... 

Reinforcement of polydimethylsiloxane (PDMS) was investigated using untreated nanodiamond (uND) and silane functionalized ND (sND) at various degrees of silanization. Scanning electron microscopy revealed an improved dispersion of ND in PDMS by silanization. The incorporation of uND and sNDs enhanced tensile strength up to 45% and 70%, respectively; however, greater improvement was observed for sNDs at very low concentrations, e.g. 0.2 wt%. The much improvement in crosslinking density, analyzed by Flory-Rehner model and Mooney-Rivlin plot, and interfacial interaction, characterized by Kraus and Cunneen-Russell plots, was also observed for sNDs. Interestingly, it was found that the extent of... 

Poly (vinyl alcohol) and nano-diamond, PVA/ND, hydrogels were prepared and assessed as prosthetic material suitable for replacement of the nucleus pulposus. The hydrogels were prepared by gamma irradiation at various doses (15 kGy, 25 kGy, 35 kGy, 45 kGy) and at various ND concentrations ranging from 0.25 wt.% to 3 wt.%. Extent of gelation, equilibrium water content, and viscoelastic properties of swelled hydrogels at definite water contents were measured and examined as a function of ND concentration as well as gamma dose. According to viscoelastic measurements, the strength of hydrogels increased considerably over that of pure PVA at a low concentration of ND. By increasing irradiation... 

In this research, inorganic copper thiocyanate (CuSCN) hole transport layer (HTL) was applied in conventional structure of perovskite solar cells (PSCs). Besides, mixed halides perovskite (Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3) was utilized as the light absorbing layer and deposited on FTO/compact TiO2 substrates through a one-step coating method in ambient condition. The mentioned perovskite is more stable against high temperature, high irradiation and humidity compared to commonly applied MAPbI3 perovskite. Nevertheless, the CuSCN could not be well dissolved in usual dipropyl sulfide solution and should be deposited for several times to achieve suitable thickness, this could reduce the... 

Concentration procedures have always been implemented when trace analysis of compounds in real matrices is contemplated. A variety of concentration strategies have been reported aiming at decreasing the limits of detection (LODs). The optical concentration of the substance in solution is one of the novel concepts for the enhancement of the analytical sensitivity. In this study, the optical concentration has been measured by the trapping of gold nanoparticles ((Formula presented.) nm) dispersed in water at low-concentrations at the focal volume of the laser beam. The influence of factors such as the time of gold nanoparticle trapping, the size of the nanoparticles, the intensity of the laser... 

Over the last two decades, mathematical modeling has become a popular tool in study of blood coagulation. This paper describes the coagulation pathway and presents a mathematical model for the generation of blood clot in human vasculature. Parameters of interest in this study include procoagulants and anticoagulants whose activity may be enhanced by various activator enzymes. The process of human blood clotting involves a complex interaction between these parameters and continuous time and state processes. In this work, we propose to model these highly inter-relational processes by a set of nonlinear chemical rate equations. We have modeled this process as a dynamical system, as chemical... 

Single-layer reduced graphene oxide nanoribbons (rGONRs) were obtained through an oxidative unzipping of multi-walled carbon nanotubes and a subsequent deoxygenation by hydrazine and bovine serum albumin. Human mesenchymal stem cells (hMSCs) were isolated from umbilical cord blood and used for checking the concentration- and time-dependent cyto- and geno-toxic effects of the rGONRs and reduced graphene oxide sheets (rGOSs). The cell viability assay indicated significant cytotoxic effects of 10 μg/mL rGONRs after 1 h exposure time, while the rGOSs exhibited the same cytotoxicity at concentration of 100 μg/mL after 96 h. The oxidative stress was found as the main mechanism involved in the... 

The alcoholic suspensions of titania nano-particles were prepared using the methanol, ethanol, isopropanol and butanol as the solvents as well as triethanolamine (TEA) as an dispersant. The colloidal stability of suspensions, both in the absence as well as presence of TEA, was studied by measuring the zeta potential, sedimentation, pH and electrical conductivity of suspensions, dispersant adsorption and particles size distribution. Results showed that in the absence of TEA, the stability of the suspensions increases with the molecular size of alcohol (from methanol to butanol), while the zeta potential decreases. It was also observed that with the addition of TEA up to the optimum dosage (4... 

The authors carried out the study to prepare chitosan N-isopropylacrylamide hydrogel via heating and radiation processes. Properties investigation of prepared samples revealed that radiation prepared samples show higher yield and swelling ratios in comparison with the heating prepared ones. Effects of hydrogel addition to drilling mud on its important rheological properties such as apparent viscosity, plastic viscosity, and stress-strain behavior are measured. The rheological properties of hydrogel were compared with cellulosemethylcarboxyl and resins that are widely used in drilling fluid. The results demonstrate that whereas linear polymer effects on mud properties are more significant in... 

Molecular self-assembly of cadmium selenide quantum dots-end-capped polyrotaxane hybrid nanostructures (PRCdSe QDs) was led to a new type of core-shell hybrid nanomaterials consisting of cadmium selenide quantum dot (CdSe QDs) core and polyrotaxane shell (PR@QDs). Structure of PR@QDs was characterized using various techniques. It has been observed that the size of PR@QDs was between 20-25 nm in which diameter of core and thickness of shell were between 15-20 and 2-3 nm, respectively. Short-term in vitro cytotoxicity tests, using MTT (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, were conducted on mouse tissue connective fibroblast adhesive cell line (L929) in order to... 

Graphene thin films with very low concentration of oxygen-containing functional groups were produced by reduction of graphene oxide nanosheets (prepared by using a chemical exfoliation) in a reducing environment and using two different heat treatment procedures (called one and two-step heat treatment procedures). The effects of heat treatment procedure and temperature on thickness variation of graphene platelets and also on reduction of the oxygen-containing functional groups of the graphene oxide nanosheets were studied by atomic force microscopy and X-ray photoelectron spectroscopy. While formation of the thin films composed of single-layer graphene nanosheets with minimum thickness of... 

The influence of the addition of the nonionic surfactants C12DMPO, C14DMPO, C10OH, and C10EO5 at concentrations between 10-5 and 10-1 mmol/L to solutions of β-casein (BCS) and β-lactoglobulin (BLG) at a fixed concentration of 10-5 mmol/L on the dilational surface rheology is studied. A maximum in the viscoelasticity modulus |E| occurs at very low surfactant concentrations (10-4 to 10-3 mmol/L) for mixtures of BCS with C12DMPO and C14DMPO and for mixtures of BLG with C10EO5, while for mixture of BCS with C10EO5 the value of |E| only slightly increased. The |E| values... 

Solvent extraction of rare earths from nitrate leach liquor of apatite using mixtures of tributyl phosphate (TBP) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) was studied. The effects of nitrate and hydrogen ion concentration of the aqueous phase as well as the composition and concentration of extractants in the organic phase on the extraction behavior of lanthanum, cerium, neodymium, and yttrium were investigated. The distribution ratio of REEs increases by increasing the nitrate concentration in aqueous phase and concentration of extractants in organic phase, but the hydrogen ion concentration in aqueous phase has a decreasing effect. Yttrium as a heavy rare earth is more sensitive to... 

The formation of water drops as a Newtonian fluid and formation of a shear-thinning non-Newtonian fluid, Carboxyl Methyl Cellulose (CMC) from a capillary into different bulk fluids are experimentally investigated. A high speed camera is used to visualize the images of the drops and an image-processing code employed to determine the drop properties from each image. It was found that the properties of the water drops when they are drooped into the liquids bulk fluids such as toluene and n-hexane are almost the same while they differed substantially when they were drooped into the air bulk fluid. It is shown that during the formation of water drop in all three kinds of bulk fluids, the drop...