Search for: high-sensitivity
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    Optimization of a vanillin assay for determination of anthocyanins using D-optimal design

    , Article Analytical Methods ; Volume 4, Issue 3 , Feb , 2012 , Pages 824-829 ; 17599660 (ISSN) Khoshayand, M. R ; Roohi, T ; Moghaddam, G ; Khoshayand, F ; Shahbazikhah, P ; Oveisi, M. R ; Hajimahmoodi, M ; Sharif University of Technology
    The vanillin assay is a spectrophotometric method for anthocyanin determination that is simple, quick and inexpensive. The method is preferred because of its high sensitivity, specificity and simplicity; however, the results of this test are influenced by several factors. Hence, a D-optimal experimental design approach was investigated to simultaneously, without loss of information, optimize five factors that influence the vanillin assay: acid normality, vanillin concentration, temperature, time and acid type. Further optimization with a D-optimal design and response surface analysis (RSM) showed that a second-order polynomial model fit the experimental data appropriately. The optimum... 

    Polynomial segment model for radar target recognition using Gibbs sampling approach

    , Article IET Signal Processing ; Volume 11, Issue 3 , 2017 , Pages 285-294 ; 17519675 (ISSN) Hadavi, M ; Radmard, M ; Nayebi, M. M ; Sharif University of Technology
    Institution of Engineering and Technology  2017
    High resolution range profile (HRRP) is a widely noted tool in radar target recognition. However, its high sensitivity to the target's aspect angle makes it necessary to seek solutions for this problem. One alternative is to assume consecutive samples of HRRP identically and independently distributed in small frames of aspect angles, an assumption which is not true in reality. Based on this simplifying assumption, some models, such as the hidden Markov model, have been developed to characterise the sequential information contained in multi-aspect radar echoes. As a result, these models consider only the short dependency between consecutive samples. Considering such issues, in this study, the... 

    Fabrication of sensitive glutamate biosensor based on vertically aligned CNT nanoelectrode array and investigating the effect of CNTs density on the electrode performance

    , Article Analytical Chemistry ; Volume 84, Issue 14 , June , 2012 , Pages 5932-5938 ; 00032700 (ISSN) Gholizadeh, A ; Shahrokhian, S ; Iraji Zad, A ; Mohajerzadeh, S ; Vosoughi, M ; Darbari, S ; Koohsorkhi, J ; Mehran, M ; Sharif University of Technology
    In this report, the fabrication of vertically aligned carbon nanotube nanoelectrode array (VACNT-NEA) by photolithography method is presented. Electrochemical impedance spectroscopy as well as cyclic voltammetry was performed to characterize the arrays with respect to different diffusion regimes. The fabricated array illustrated sigmoidal cyclic voltammogram with steady state current dominated by radial diffusion. The fabricated VACNT-NEA and high density VACNTs were employed as electrochemical glutamate biosensors. Glutamate dehydrogenase is covalently attached to the tip of CNTs. The voltammetric biosensor, based on high density VACNTs, exhibits a sensitivity of 0.976 mA mM-1 cm-2 in the... 

    Mediator-less highly sensitive voltammetric detection of glutamate using glutamate dehydrogenase/vertically aligned CNTs grown on silicon substrate

    , Article Biosensors and Bioelectronics ; Volume 31, Issue 1 , 2012 , Pages 110-115 ; 09565663 (ISSN) Gholizadeh, A ; Shahrokhian, S ; Iraji zad, A ; Mohajerzadeh, S ; Vosoughi, M ; Darbari, S ; Sanaee, Z ; Sharif University of Technology
    A sensitive glutamate biosensor is prepared based on glutamate dehydrogenase/vertically aligned carbon nanotubes (GLDH, VACNTs). Vertically aligned carbon nanotubes were grown on a silicon substrate by direct current plasma enhanced chemical vapor deposition (DC-PECVD) method. The electrochemical behavior of the synthesized VACNTs was investigated by cyclic voltammetry and electrochemical impedance spectroscopic methods. Glutamate dehydrogenase covalently attached on tip of VACNTs. The electrochemical performance of the electrode for detection of glutamate was investigated by cyclic and differential pulse voltammetry. Differential pulse voltammetric determinations of glutamate are performed... 

    Voltammetric studies of sumatriptan on the surface of pyrolytic graphite electrode modified with multi-walled carbon nanotubes decorated with silver nanoparticles

    , Article Talanta ; Volume 80, Issue 1 , 2009 , Pages 31-38 ; 00399140 (ISSN) Ghalkhani, M ; Shahrokhian, S ; Ghorbani Bidkorbeh, F ; Sharif University of Technology
    Multi-walled carbon nanotube decorated with silver nanoparticles (AgNPs-MWCNT) is used as an effective strategy for modification of the surface of pyrolytic graphite electrode (PGE). This modification procedure improved colloidal dispersion of the decorated MWCNTs in water, affording uniform and stable thin films for altering the surface properties of the working electrode. Robust electrode for sensing applications is obtained in a simple solvent evaporation process. The electrochemical behavior of sumatriptan (Sum) at the bare PGE and AgNPs-MWCNT modified PGE is investigated. The results indicate that the AgNPs-MWCNT modified PGE significantly enhanced the oxidation peak current of Sum. A... 

    Multi sensing grasper for minimally invasive surgery

    , Article IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM, 3 July 2011 through 7 July 2011, Budapest ; July , 2011 , Pages 344-349 ; 9781457708381 (ISBN) Fattahi, S. J ; Zabihollah, A ; Adldoost, H ; Sharif University of Technology
    In the present work, a multi sensing grasper has been developed for minimally invasive surgery with embedded ZnO piezoelectric and Fiber Bragg Grating sensors. In this model, a sensing patch equipped with three FBG sensors to sense the temperature in rage of 800 n.m and two separated FBG in range of 1550 m.m to detect the displacement in x and y directions. ZnO piezoelectric is highly sensitive to time and provides a good resistance to temperature. Therefore, this sensor is used for measuring the rate of strain and creep coefficient. A finite element approach based on the viscous material theory and plane displacement theory of anisotropic materials has been utilized to obtain the compliance... 

    In situ solid-phase microextraction and post on-fiber derivatization combined with gas chromatography-mass spectrometry for determination of phenol in occupational air

    , Article Analytica Chimica Acta ; Volume 742 , 2012 , Pages 17-21 ; 00032670 (ISSN) Es haghi, A ; Baghernejad, M ; Bagheri, H ; Sharif University of Technology
    Elsevier  2012
    A method based on solid-phase microextraction (SPME) followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) for determination of phenol in air was developed. Three different types of SPME fibers, polar and non-polar poly(dimethylsiloxane) (PDMS) and polyethylene glycol (PEG) were synthesized using sol-gel technology and their feasibility to the sampling of phenol were investigated. Different derivatization reagents for post on-fiber derivatization of phenol were studied. Important parameters influencing the extraction and derivatization process such as type of fiber coating, type and volume of derivatizing reagent, derivatization time and temperature,... 

    The decoration of TiO2/reduced graphene oxide by Pd and Pt nanoparticles for hydrogen gas sensing

    , Article International Journal of Hydrogen Energy ; Volume 37, Issue 20 , 2012 , Pages 15423-15432 ; 03603199 (ISSN) Esfandiar, A ; Ghasemi, S ; Irajizad, A ; Akhavan, O ; Gholami, M. R ; Sharif University of Technology
    Elsevier  2012
    Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol-gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti-C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time... 

    Resonant light scattering toward optical fiber humidity sensors

    , Article Photonic Sensors ; Volume 9, Issue 1 , 2019 , Pages 60-68 ; 16749251 (ISSN) Dehghani Sanij, M ; Bahrampour, A ; Bahrampour, A. R ; Sharif University of Technology
    Springer Verlag  2019
    The deposition of tetrakis (4-sulonatophenyl) porphyrin (TPPS) thin film on optical fibers presents many possibilities for sensing applications. The J-form aggregation with a narrow and sharp spectral feature at about 490 nm and its sensitivity to humidity have been discussed; a fast change of wavelength occurs according with variation in the humidity level. The reproducibility and high sensitivity of TPPS-coated fibers, along with the capabilities of optical fibers, suggest the device as a good candidate for humidity sensing in harsh environments. © 2018, The Author(s)  

    Investigation of conductivity effects on capacitance measurements of water liquids using a cylindrical capacitive sensor

    , Article Journal of Applied Sciences ; Volume 10, Issue 4 , 2010 , Pages 261-268 ; 18125654 (ISSN) Behzadi, G ; Golnabi, H ; Sharif University of Technology
    In this study by using a Cylindrical Capacitive Sensor (CCS), the Electrical Conductivity (EC), effects on the capacitance measurements of the water liquids was investigated. Theoretical values of the capacitance measurements of water liquids with the cylindrical length in the range 0.5-5 cm are calculated. Our obtained results indicate that measured capacitance value by CCS depends on the liquid capacitance and reactance capacitance. Liquid capacitance value of the distilled water for permittivity of 80 is about 33.5 pF and reactance capacitance value is about 0.290 μF, when the cylindrical length value is about 1.6 cm. The reactance capacitance for the mineral, tap and dilute salt water... 

    Electrodeposition of long gold nanotubes in polycarbonate templates as highly sensitive 3D nanoelectrode ensembles

    , Article Electrochimica Acta ; Volume 75 , 2012 , Pages 157-163 ; 00134686 (ISSN) Bahari Mollamahalle, Y ; Ghorbani, M ; Dolati, A ; Sharif University of Technology
    Elsevier  2012
    Electrodeposition of long and well-defined gold nanotubes in polycarbonate (PC) templates is still a major concern due to pore blockage problems. In the present study, we introduce a novel method for electrodeposition of long gold nanotubes within the pores of PC templates for the first time. In order to deposit gold atoms onto the pore walls preferentially, pore walls were functionalized with a coupling agent. Short and thin Ni nanotubes were then electrodeposited at the bottom of the pores. Gold nanotubes were subsequently electrodeposited at constant potentials and low solution concentrations. The morphology of nanotubes was characterized by electron microscopy and their formation... 

    Finite element martensite ratio derivation of NiTi via measurable criteria of strain rate

    , Article Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems 2009, SMASIS2009, 21 September 2009 through 23 September 2009, Oxnard, CA ; Volume 1 , 2009 , Pages 641-647 ; 9780791848968 (ISBN) Amini, A ; Mehdigholi, H ; Elahinia, M ; Sharif University of Technology
    The shape memory alloys (SMAs) and smart composites have a large use in high and low level industry, while a lot of research is being done in this field. The existence of smart composite structures is because of the advance mechanical benefits of the above materials. This work refers to dynamic and quasi static nonlinear explanation of these materials. After mathematical model consideration on the rate of strain, a model which is about martensite ratio of NiTi has been presented. This work has been done because of the high sensitivity of these materials to strain rate and use of visual and measurable engineering criteria to access other variables. As the martensite ratio is not engineering... 

    Copper oxide nanoflakes as highly sensitive and fast response self-sterilizing biosensors

    , Article Journal of Materials Chemistry ; Volume 21, Issue 34 , Jul , 2011 , Pages 12935-12940 ; 09599428 (ISSN) Akhavan, O ; Ghaderi, E ; Sharif University of Technology
    Vertical copper oxide nanoflakes were synthesized on a Cu foil through oxidation in alkaline conditions. X-ray photoelectron spectroscopy showed that after exposing the nanoflakes to an Escherichia coli bacterial suspension, the outermost surface of the nanoflakes was chemically reduced through the glycolysis process of the bacteria. Current-voltage (I-V) characteristics of the nanoflakes (measured perpendicular to surface of the Cu foil by using conductive atomic force microscopy) indicated that electrical resistivity of the nanoflakes increased about one order of magnitude after exposure to the bacterial suspension. The nanoflakes reduced by the bacterial suspension could also be...