Sharif Digital Repository

A new and convenient format of single drop microextraction (SDME) was developed and applied for isolation of some selected aryloxyphenoxypropionate herbicides from aquatic media. In contrast to the conventional SDME procedure, in this set-up the extraction microdrop was positioned at the bottom of a conical vial in order to provide much higher stability for the organic extraction phase while a magnetic bar was used for stirring the aqueous solution. A simple magnet was used for positioning the bar on the top of the microdrop prior to stirring. The whole set-up led to the use of any volume of extraction solvent with unlimited stirring rates. Some important extraction parameters such as the... 

Due to the widespread use of pesticides and their harmful effects on humans and wildlife, monitoring their residual amounts in crops is critically essential but still challenging regarding the development of high-throughput approaches. Herein, a colorimetric sensor array has been proposed for discrimination and identification of triazole fungicides using monometallic and bimetallic silver and gold nanoparticles. Aggregation-induced behavior of AgNPs, AuNPs, and Au-AgNPs in the presence of four triazole fungicides produced a fingerprint response pattern for each analyte. Innovative changes to the metal composition of nanoparticles leads to the production of entirely distinct response patterns... 

An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of aryloxyphenoxypropionate herbicides from aquatic media. A microdrop of toluene was used as the extraction solvent. Some important extraction parameters such as type of solvent, solvent dropsize, stirring rate, ionic strength and extraction time were investigated and optimized. The microdrop volume of 1.5 μL, a sampling time of 25 min, and use of toluene were major parameters for achieving high enrichment factors. The linearity was studied by preconcentration of 4 mL of the water samples spiked with a standard solution of aryloxyphenoxypropionates at the concentration range of 0.15 to 30 ng... 

A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20×10-5 to... 

Intravitreal injection (IVI) is the most common treatment for eye posterior segment diseases such as endopthalmitis, retinitis, age-related macular degeneration, diabetic retinopathy, uveitis, and retinal detachment. Most of the drugs used to treat vitreoretinal diseases, have a narrow concentration range in which they are effective, and may be toxic at higher concentrations. Therefore, it is critical to know the drug distribution within the eye following intravitreal injection. Having knowledge of drug distribution, ophthalmologists can decide on drug injection frequency while minimizing damage to tissues. The goal of this study was to develop a computer model to predict intraocular... 

A nano-based sensor array has been developed for identification and discrimination of catecholamine neurotransmitters based on optical properties of their oxidation products under alkaline conditions. To produce distinct fluorescence response patterns for individual catecholamine, quenching of thioglycolic acid functionalized cadmium telluride (CdTe) quantum dots, by oxidation products, were employed along with the variation of fluorescence spectra of oxidation products. The spectral changes were analyzed with hierarchical cluster analysis (HCA) and principal component analysis (PCA) to identify catecholamine patterns. The proposed sensor could efficiently discriminate the individual... 

In this study, the morphological, rheological, and mechanical properties of PP/HDPE blend compatibilized with poly (propylene-g-maleic anhydride) were studied. Necessary blends were prepared using a counter current twin-screw extruder. The blend composition ranged from 10 to 50 wt% of dispersed phase (HDPE) and compatibilizer (MAPP) with two Concentration ranges 10, 20 wt% were used for PP/HDPE (80/20) blend with respect to the dispersed phase (HDPE). The results of morphological studies shows a droplet dispersion morphology in the composition to 50wt% HDPE content, which indicates that HDPE forms a dispersed phase and PP forms a continuous phase in these composition region. Addition of the... 

Detection of nitroaromatic explosives is of strong concern because of human health, public safety, environment, and military issues. In this study, we present a ratiometric sensor array for detection and discrimination of widely-used nitroaromatics (i.e., 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenol (TNP), and 2,4-dinitrotoluene (DNT)). In the design of sensor elements (SE) we employ blue emissive carbon dots (BCDs) in combination with yellow (SE-A) and red (SE-B) emissive cadmium telluride quantum dots (CdTe QDs). The fluorescence intensity of BCDs, YQDs, and RQDs is quenched by TNT, DNT, and TNP in various degrees. Both TNT and TNP cause the quenching and spectral shift of BCDs (TNT... 

The performance of a quartz crystal microbalance (QCM) used as a sensor/detector relies on the performance and quality of the film coated onto the quartz crystal sensor. This study focuses on the sensor coating preparation for the detection of glycine. Cellulose nanofibrils (CNFs), natural polymers, were coated on a quartz crystal (QC) surface by a spin-coating method. The prepared CNF-coated QC was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and water contact angle (WCA). The stable and fully covered QCs without further... 

A new method for simultaneous determination of dopamine (DA) and ascorbic acid (ASC) is proposed. The method is based on the reaction of dopamine and ascorbic acid with the oxidizing agent (silver nitrate) in the presence of PVP (as a stabilizer) and the formation of silver nanoparticles in a slightly basic medium. Spectrophotometry is used to monitor the changes of the surface plasmon resonance (SPR) band at a maximum wavelength of silver nanoparticles (440 nm) vs. time. Three-layered feed-forward artificial neural networks (ANN) trained by back propagation learning algorithm is used to model the relationship between absorbance and concentration to quantify analyte in mixtures under optimum... 

A nano-based sensor array has been developed for identification and discrimination of catecholamine neurotransmitters based on optical properties of their oxidation products under alkaline conditions. To produce distinct fluorescence response patterns for individual catecholamine, quenching of thioglycolic acid functionalized cadmium telluride (CdTe) quantum dots, by oxidation products, were employed along with the variation of fluorescence spectra of oxidation products. The spectral changes were analyzed with hierarchical cluster analysis (HCA) and principal component analysis (PCA) to identify catecholamine patterns. The proposed sensor could efficiently discriminate the individual... 

A highly sensitive and simple indirect spectrophotometric method has been developed for the determination of trace amounts of inorganic mercury (Hg2 +) in aqueous media. The method is based on the inhibitory effect of Hg2 + on the activity of horseradish peroxidase (HRP) in the oxidation of ascorbic acid by hydrogen peroxide followed by the reduction of Au3 + to Au-NPs by unreacted ascorbic acid and the measurement of the absorbance of localized surface plasmon resonance (LSPR) peak of gold nanoparticles (at 530 nm) which is directly proportional to the concentration of Hg2 +. Under the optimum conditions, the calibration curve was linear in the concentration range of 1-220 ng mL- 1. Limits... 

A label-free electrochemical biosensor was developed for the rapid detection of the matrix metalloproteinase 9 (MMP-9) biomarker on the basis of antibody immobilizing on the zinc oxide (ZnO) nanoparticle and ZnO nanorod electrodes. The charge transfer resistance (Rct) of the electrodes was used as the indicator for MMP-9 concentration, which was obtained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ZnO nanorod-based biosensor exhibited linear behavior in the MMP-9 concentration range of 1–1000 ng/ml, which is a wider range than the available concentration ranges for most of the conventional methods. The biosensor sensitivity was 32.5 μA/(decade × cm2)... 

A new unbreakable solid phase microextraction (SPME) fiber coating based on aniline-silica nanocomposite was electrodeposited on a stainless steel wire. The electropolymerization process was carried out at a constant deposition potential, applied to the corresponding aqueous electrolyte containing aniline and silica nanoparticles. The scanning electron microscopy (SEM) images showed the non-smooth and the porous surface structure of the prepared nanocomposite. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some environmentally important polycyclic aromatic hydrocarbons (PAHs), as model compounds, from aqueous samples.... 

A new type of composite material based on carbon nanotubes (CNTs) and sol-gel chemistry was prepared and used as sorbent for needle trap device (NTD). The synthesized composite was prepared in a way to disperse CNTs molecules in a sol-gel polymeric network. CNT/silica composites with different CNT doping levels were successfully prepared, and the extraction capability of each composite was evaluated. Effects of surfactant and the oxidation duration of CNTs on the extraction efficiency of synthesized composites were also investigated. The applicability of the synthesized sorbent was examined by developing a method based on needle trap extraction (NTE) and gas chromatography mass spectrometry...