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Comparison between electrochemical and photoelectrochemical detection of dopamine based on titania-ceria-graphene quantum dots nanocomposite
, Article Biosensors and Bioelectronics ; Volume 151 , 2020 ; Bagherzadeh, M ; Nemati, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, titania-ceria-graphene quantum dot (TC-GQD) nanocomposite was synthesized by hydrothermal method for the first time. The prepared nanomaterials were characterized by XRD, FTIR dynamic light scattering (DLS), FESEM, HRTEM, and EDX spectroscopy along with elemental mapping. The synergistic effect of the nanocomposite components was studied by diffuse reflectance spectroscopy (DRS) and electrical conductivity meter. The results showed that band gap of TC-GQD nanocomposite was shifted to visible lights relative to its components (1.3 eV), and electrical conductivity of the sample was significant increased to 89.5 μS cm−1. After chemical and physical characterization, prepared new...
Development of multi-response optimization and quadratic calibration curve for determination of ten pesticides in complex sample matrices using QuEChERS dispersive liquid–liquid microextraction followed by gas chromatography
, Article Journal of Separation Science ; Volume 42, Issue 23 , 2019 , Pages 3553-3562 ; 16159306 (ISSN) ; Parastar, H ; Sharif University of Technology
Wiley-VCH Verlag
2019
Abstract
In this study, QuEChERS combined with dispersive liquid-liquid microextraction is developed for extraction of ten pesticides in complex sample matrices of water and milk. In this regard, effective factors of proposed extraction technique combined with gas chromatography with flame ionization detector were designed, modeled, and optimized using central composite design, multiple linear regression, and Nelder–Mead simplex optimization. Later, univariate calibration model for ten pesticides was developed in concentration range of 0.5–100 ng/mL. Surprisingly, quadratic calibration behavior was observed for some of the pesticides. In this regard, Mandel's test was used for evaluating linearity...
Novel microfluidic graphene oxide–protein amperometric biosensor for detecting sulfur compounds
, Article Biotechnology and Applied Biochemistry ; Volume 66, Issue 3 , 2019 , Pages 353-360 ; 08854513 (ISSN) ; Abdi, K ; Javadi, S ; Shehneh, M. Z ; Yazdian, F ; Omidi, M ; Rashedi, H ; Haghiralsadat, B. F ; Asayeshnaeini, O ; Sharif University of Technology
Wiley-Blackwell Publishing Ltd
2019
Abstract
Sulfur compounds are essential for many industries and organisms; however, they cause serious respiratory problems in human beings. Therefore, determination of sulfur concentration is of paramount importance. The research approach in the field of detecting contaminants has led to smaller systems that provide faster and more effective ways for diagnosis purposes. In this study, a novel portable amperometric graphene oxide–protein biosensor platform is investigated. The main characteristic of this structure is the implementation of a microfluidic configuration. With albumin metalloprotein as the biorecognition element, graphene oxide was synthesized and characterized by transmission electron...
MoS2 quantum-dots as a label-free fluorescent nanoprobe for the highly selective detection of methyl parathion pesticide
, Article Analytical Methods ; Volume 9, Issue 4 , 2017 , Pages 716-723 ; 17599660 (ISSN) ; Rashti, A ; Hormozi Nezhad, M. R ; Mahdavi, V ; Sharif University of Technology
Royal Society of Chemistry
2017
Abstract
A reliable, simple, and sensitive fluorescence method was developed for the determination of methyl parathion (MP) in rice using MoS2 quantum dots (QDs). Rapid hydrolysis of MP under alkaline conditions, and thus the formation of p-nitrophenol (p-NP) can be used for MP detection. The functional mechanism of the nanoprobe relies on p-nitrophenol-induced photoluminescence quenching of MoS2 QDs. The high probability of resonance energy transfer (RET) stems from the spectral overlap of MoS2 QD emission spectra and the absorption spectra of p-NP. The high value of the Stern-Volmer constant (KSV = 3.73 × 104 M-1) suggests the efficient quenching of MoS2 QDs by MP in the course of the ET process....
Colorimetric detection of glutathione based on transverse overgrowth of high aspect ratio gold nanorods investigated by MCR-ALS
, Article RSC Advances ; Volume 5, Issue 101 , 2015 , Pages 82906-82915 ; 20462069 (ISSN) ; Shadabipour, P ; Hormozi-Nezhad, M. R ; Sharif University of Technology
Royal Society of Chemistry
2015
Abstract
In this paper, we present a simple platform for colorimetric detection of glutathione using gold nanorods (AR ∼ 6.5 ± 0.2) as a plasmonic sensor. The functional mechanism of the sensor is based on shifts of longitudinal plasmon resonance during selective transverse overgrowth induced by preferential binding of glutathione at the nanorod tips. Under the optimum conditions, a calibration curve showed two linear regimes at the range of 50 nM to 20 μM of glutathione with a detection limit as low as 40 nM. The nanosensor maintains relatively high selectivity for determination of glutathione in the presence of several other amino acids. However, cysteine at similar concentration levels strongly...
An ultrasensitive and selective turn-off fluorescent nanoprobe for the detection of copper ions
, Article Analytical Methods ; Volume 7, Issue 12 , 2015 , Pages 5067-5073 ; 17599660 (ISSN) ; Taghipour, M ; Sharif University of Technology
Royal Society of Chemistry
2015
Abstract
In this study, a novel approach for sensitive and extremely selective detection of copper ions has been developed based on fluorescence resonance energy transfer (FRET) between AuNPs as an acceptor and fluorescein isothiocyanate (FITC) as a donor. Initially, the fluorescence of the FITC molecule turns-off due to adsorption to the AuNPs surface. However, the fluorescence of the FITC-AuNPs system was switched to turn-on by adding d-Pencillamine (d-PC) to the solution mixtures as FITC molecules are released upon displacement by d-PC on the NPs surface. The higher affinity of d-PC toward the surface of AuNPs was further evidenced by controlling the fluorescence intensity enhancement of the...
A horizontally oriented setup for liquid-liquid-liquid microextraction of estrogens
, Article Analytical Methods ; Volume 5, Issue 22 , 2013 , Pages 6517-6522 ; 17599660 (ISSN) ; Maleki, H ; Es'Haghi, A ; Sharif University of Technology
2013
Abstract
A horizontally oriented liquid-liquid-liquid microextraction (HOLLLME) setup was developed and applied for the isolation of two major estrogens from aquatic media. In contrast to the conventional procedure, in this setup the extracting microdrop was suspended from a horizontally positioned needle in order to provide much higher stability to the extracting phase. The developed HOLLLME approach was applied to isolate two major selected estrogens from aquatic media followed by high performance liquid chromatography-ultraviolet (HPLC-UV) determination. Estrogens were, initially, extracted from water samples into hexane and subsequently, the back extraction stage was performed with 6 μL of sodium...
Using three different optical fiber designs to study humidity effect on the air refractive index
, Article Optics and Lasers in Engineering ; Volume 50, Issue 11 , November , 2012 , Pages 1495-1500 ; 01438166 (ISSN) ; Sharif University of Technology
2012
Abstract
Design and operation of three different optical designs based on the light intensity modulation for investigation of the humidity effects on the air index of refraction are described. The measurement variable is the transmitted power, which depends on the refractive index of the medium in the path of a fiber-to-fiber optical design. Three different probes (probe #1, #2, and #3) are tested in which probe #1 and probe #2 can also check the presence of water or any other transparent liquid in the gap between the two axial fibers. Performances of the new systems are tested as a refractive index monitoring mean and experimental results are given. The variations of the modulated powers as...
Spectrophotometric determination of glutathione and cysteine based on aggregation of colloidal gold nanoparticles
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 958-963 ; 10263098 (ISSN) ; Seyedhosseini, E ; Robatjazi, H ; Sharif University of Technology
2012
Abstract
We report herein the development of a highly sensitive colorimetric method for the determination of cysteine and glutathione, based on aggregation of the citrate capped gold nanoparticles (Au NPs). This was exploited from high affinity of low-molecular-weight aminothiols towards the Au NPs surface, which could induce displacement of the citrate shell by the thiolate shell of target molecules, resulting in aggregation of the NPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of aggregation, which can be affected by the ionic strength, pH and concentration of Au NPs, the plasmon band at around 521 nm decreases gradually, along with formation of a new red...
Electrochemical determinations of 6-mercaptopurine on the surface of a carbon nanotube-paste electrode modified with a cobalt salophen complex
, Article Journal of Solid State Electrochemistry ; Volume 16, Issue 4 , April , 2012 , Pages 1643-1650 ; 14328488 (ISSN) ; Ghorbani Bidkorbeh, F ; Mohammadi, A ; Dinarvand, R ; Sharif University of Technology
2012
Abstract
A mixture of multi-walled carbon nanotube/graphite paste electrode modified with a salophen complex of cobalt was prepared and was applied for the study of the electrochemical behavior of 6-mercaptopurine (MP) using cyclic and differential pulse voltammetry (DPV). An excellent electrocatalytic activity toward the oxidation of MP was achieved, which led to a considerable lowering in the anodic overpotential and remarkable increase in the response sensitivity in comparison with unmodified electrode. Utilizing DPV method, a linear dynamic range of 1-100 μM with detection limit of 0.1 μM was obtained in phosphate buffer of pH 3.0. The electrochemical detection system was very stable, and the...
Novel polyamide-based nanofibers prepared by electrospinning technique for headspace solid-phase microextraction of phenol and chlorophenols from environmental samples
, Article Analytica Chimica Acta ; Volume 716 , 2012 , Pages 34-39 ; 00032670 (ISSN) ; Aghakhani, A ; Baghernejad, M ; Akbarinejad, A ; Sharif University of Technology
2012
Abstract
A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100-200nm for polyamide nanofibers with a homogeneous and porous surface...
Polyaniline-nylon-6 electrospun nanofibers for headspace adsorptive microextraction
, Article Analytica Chimica Acta ; Volume 713 , 2012 , Pages 63-69 ; 00032670 (ISSN) ; Aghakhani, A ; Sharif University of Technology
2012
Abstract
A headspace adsorptive microextraction technique was developed using a novel polyaniline-nylon-6 (PANI-N6) nanofiber sheet, fabricated by electrospinning. The homogeneity and the porosity of the prepared PANI-N6 sheet were studied using the scanning electron microscopy (SEM) and nanofibers diameters were found to be around 200nm. The novel nanofiber sheet was examined as an extracting medium to isolate some selected chlorobenzenes (CBs), as model compounds, from aquatic media. The extracted analytes were desorbed using μL-amounts of solvent and eventually an aliquot of extractant was injected into gas chromatography-mass spectrometry (GC-MS). Various parameters affecting the extraction and...
Investigation of humidity effect on the air refractive index using an optical fiber design
, Article Journal of Applied Sciences ; Volume 11, Issue 16 , 2011 , Pages 3022-3027 ; 18125654 (ISSN) ; Golnabi, H ; Sharif University of Technology
2011
Abstract
In this study operation of an optical design based on the intensity modulation for the refractive index change has been described. The reported instrument measures the transmitted output power depending up on the medium refractive index in the light path of a fiber-to-fiber design. A liquid cell is located between the fibers in the light path and power variations for different cold and hot water levels in the cell are measured. By using a reference humidity meter the calibration curve representing the relative humidity (%RH) as a function of the transmitted output power is obtained. For the hot water with the final temperature of T = 32.7°C the output power range of 255.0 -313.OnW is...
Synthesis and characterisation of nanosized TiO2-ZrO2 binary system prepared by an aqueous sol-gel process: Physical and sensing properties
, Article Sensors and Actuators, B: Chemical ; Volume 155, Issue 2 , July , 2011 , Pages 568-576 ; 09254005 (ISSN) ; Fray, D. J ; Sharif University of Technology
2011
Abstract
Nanostructured TiO2-ZrO2 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route. Titanium (IV) isopropoxide and zirconium (IV) acetate hydrate were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy revealed that the powder were crystallised at the low temperature of 500 °C, containing anatase-TiO 2 and tetragonal-ZrO2 phases. Furthermore, it was found that ZrO2 retarded the anatase-to-rutile transformation up to 900 °C. The activation energies for crystallite growth of TiO2 and ZrO2 components in...
Novel nanofiber coatings prepared by electrospinning technique for headspace solid-phase microextraction of chlorobenzenes from environmental samples
, Article Analytical Methods ; Volume 3, Issue 6 , Apr , 2011 , Pages 1284-1289 ; 17599660 (ISSN) ; Aghakhani, A ; Sharif University of Technology
2011
Abstract
Novel unbreakable solid phase microextraction (SPME) fiber coatings were fabricated by electrospinning method in which the polymeric solution was converted to nanofibers using high voltages. Four different polymers, polyurethane (PU), polycarbonate (PC), polyamide (PA) and polyvinyl chloride (PVC) were prepared as the fiber coatings on thin stainless steel wires. The extraction efficiencies of new coatings were investigated by headspace solid-phase microextraction (HS-SPME) of some environmentally important chlorobenzenes from aqueous samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Among them, PU showed a prominent efficiency. Effects of coating time and polymer...
Simultaneously synthesis and encapsulation of metallic nanoparticles using linear-dendritic block copolymers of poly (ethylene glycol)-poly (citric acid)
, Article Key Engineering Materials, 8 July 2010 through 9 July 2010 ; Volume 478 , July , 2011 , Pages 7-12 ; 10139826 (ISSN) ; 9783037851357 (ISBN) ; Vossoughi, M ; Adeli, M ; Sharif University of Technology
2011
Abstract
Linear-dendritic triblock copolymers of linear poly(ethylene glycol) and hyperbranched poly(citric acid) (PCA-PEG-PCA) were used as the reducing and capping agents to encapsulate gold and silver nanoparticles (AuNPs and AgNPs). PCA-PEG-PCA copolymers in four different molecular weights were synthesized using 2, 5, 10 and 20 citric acid/PEG molar ratios and were called A 1, A 2, A 3 and A 4, respectively. Nanoparticles were encapsulated simultaneously during the preparation process. AuNPs were simply synthesized and encapsulated by addition a boiling aqueous solution of HAuCl 4 to aqueous solutions of A 1, A 2, A 3 and A 4. In the case of silver, an aqueous solution of AgNO 3 was reduced...
A sensitive colorimetric detection of ascorbic acid in pharmaceutical products based on formation of anisotropic silver nanoparticles
, Article Scientia Iranica ; Volume 17, Issue 2 F , 2010 , Pages 148-153 ; 10263098 (ISSN) ; Karimi, M. A ; Shahheydari, F ; Sharif University of Technology
2010
Abstract
A sensitive colorimetric method for the detection of ascorbic acid was proposed in this research based on the reduction of silver ions by ascorbic acid in the presence of citrate-stabilized silver seeds, additional trisodium citrate and a polymer such as polyvinylpyrrolidone. The color of the stable sol is controlled by varying the concentration of trisodium citrate (TSC), polyvinylpyrrolidone, silver nitrate and silver seeds. The reduction of Ag + to triangle silver nanoparticles (Ag-NPs) by ascorbic acid in the presence of trisodium citrate (TSC) and silver seeds produced two very intense surface plasmon resonance peaks of Ag-NPs. The plasmon absorbance of Ag-NPs allows the quantitative...
Nanostructured TiO2-CeO2 mixed oxides by an aqueous sol-gel process: Effect of Ce:Ti molar ratio on physical and sensing properties
, Article Sensors and Actuators, B: Chemical ; Volume 150, Issue 2 , 2010 , Pages 631-640 ; 09254005 (ISSN) ; Fray, D. J ; Sharif University of Technology
2010
Abstract
Nanostructured TiO2-CeO2 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route. Titanium (IV) isopropoxide and cerium chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. The effect of Ce:Ti molar ratio was studied on the crystallisation behaviour of the products. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders crystallised at the low temperature of 500 °C, containing anatase-TiO2, rutile-TiO2 and cubic-CeO2 phases, as well as Ti 8O15, Ti3O5 and Ce 11O20 depending on annealing temperature and Ce:Ti molar...
Simultaneous voltammetric determination of ascorbic acid, acetaminophen and isoniazid using thionine immobilized multi-walled carbon nanotube modified carbon paste electrode
, Article Electrochimica Acta ; Volume 55, Issue 3 , 2010 , Pages 666-672 ; 00134686 (ISSN) ; Asadian, E ; Sharif University of Technology
2010
Abstract
A carbon paste electrode (CPE) modified with thionine immobilized on multi-walled carbon nanotube (MWCNT), was prepared for simultaneous determination of ascorbic acid (AA) and acetaminophen (AC) in the presence of isoniazid (INZ). The electrochemical response characteristics of the modified electrode toward AA, AC and INZ were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic role for the electro-oxidation of AA and AC, leading to a remarkable peak resolution (∼303 mV) for two compounds. On the other hand, the presence of INZ, which is considered as important drug interference for AC, does not affect the voltammetric responses...
An interior needle electropolymerized pyrrole-based coating for headspace solid-phase dynamic extraction
, Article Analytica Chimica Acta ; Volume 634, Issue 2 , 2009 , Pages 209-214 ; 00032670 (ISSN) ; Babanezhad, E ; Khalilian, F ; Sharif University of Technology
2009
Abstract
A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography-mass spectrometry (GC-MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the...