Sharif Digital Repository

Background: Glucose sensors have been extensively researched in patent studies and manufactured a tool for clinical diabetes diagnosis. Although some kinds of electrochemical enzymatic glucose sensors have been commercially successful, there is still room for improvement, in selectivity and reliability of these sensors. Because of the intrinsic disadvantages of enzymes, such as high fabrication cost and poor stability, non-enzymatic glucose sensors have recently been promoted as next generation diagnostic tool due to their relatively low cost, high stability, prompt response, and accuracy. Objective: In this research, a novel free standing and binder free non-enzymatic electrochemical sensor... 

The pharmaceutical industry is facing enormous challenges due to high drug attribution rates. For the past decades, novel methods have been developed for safety and efficacy testing, as well as for improving early development stages. In vitro screening methods for drug-receptor binding are considered to be good alternatives for decreasing costs in the identification of drug candidates. However, these methods require lengthy and troublesome labeling steps. Biosensors hold great promise due to the fact that label-free detection schemes can be designed in an easy and low-cost manner. In this paper, for the first time in the literature, we aimed to compare the potential of label-free optical and... 

Sol composition and ripening conditions are two important parameters in silica fiber production through the conventional sol-gel process. In the current study, silica nanofibers were successfully obtained via the electrospinning technique, and sol-gel formation occurred during this process. Based on previous reports, with the aim of increasing the selectivity, we used the molecular imprinted methodology to produce a selective medium via sol-gel electrospinning. In this process, sol-gel was formed during electrospinning and then, the backbone polymer was removed by heating. To obtain a thin layer of silica nanofibers, the influencing parameters such as backbone polymer types, imprinting time... 

Hydrogen storage capacities of raw, oxidized, purified and Fe-doped multi-walled carbon nanotubes (MWCNTs) were studied by electrochemical method. Based on transmission electron microscopy and Raman spectroscopic data, thermal oxidation removed defective graphite shells at the outer walls of MWCNTs. The analysis results indicated that the acid treatment dissolved most of the catalysts and opened some tips of the MWCNTs. Thermal gravimetric analysis and differential scanning calorimetry results illustrated that by oxidation and purification of MWCNTs, the weight loss peak shifts toward a higher temperature. N2 adsorption isotherms of the purified and oxidized MWCNTs showed an increase in N2... 

So-called negative capacitance seems to remain an obscure feature in the analysis of the frequency-dependent impedance of perovskite solar cells. It belongs to one of the puzzling peculiarities arising from the mixed ionic-electronic conductivity of this class of semiconductor. Here we show that apparently high capacitances in general (positive and negative) are not related to any capacitive feature in the sense of a corresponding charge accumulation. Instead, they are a natural consequence of slow transients mainly in forward current of the diode upon ion displacement when changing voltage. The transient current leads to a positive or negative ‘capacitance’ dependent on the sign of its... 

The present study investigates the diversification and dynamic behavior of a multi-population microfluidic microbial fuel cell (MFC) as a biosensor. The cost effective microfluidic MFC coupled to a comprehensive model, presents a novel platform for monitoring chemical and biological phenomena. The importance of competition among different microbial groups, hierarchical biochemical processes, bacterial chemotaxis and different mechanisms of electron transfer were significant considerations in the present model. The validation of the model using experimental data from a microfluidic MFC shows an appropriate match with the hierarchal biodegradation processes of a complex substrate as well as... 

Herein, we present a novel, simple, and ultrasensitive electrochemical DNA (E-DNA) sensor based on hollow carbon spheres (HCS) decorated with polyaniline (PANI). A thiolated 21-mer oligonucleotide, characteristic of HBV DNA, is immobilized via electrodeposited gold nanoparticles on HCS-PANI. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) are used to characterize the electrochemical properties of the prepared nanocomposite. Scanning electron microscopy is employed to investigate the morphological texture of the fabricated modifier. An enhanced intrinsic signal of PANI is probed to evaluate the biosensing ability of the prepared... 

Wire-shaped micro-supercapacitors attracted extensive attentions in next-generation portable and wearable electronics, due to advantages of miniature size, lightweight and flexibility. Herein, NiMoO 4 nanorods supported on Ni film coated Cu wire are successfully fabricated thorough direct deposition of Ni film onto Cu wire as the conductive substrate, followed by growth of the NiMoO 4 nanorods on Ni film coated Cu wire substrate by means a hydrothermal annealing process. The prepared 3D, porous electrode demonstrates extremely high areal specific capacitance of 12.03F cm −2 at the current density of 4 mA cm −2 and retained capacitance of 8.23 F cm −2 at a much higher current density of 80... 

A chemiresistive sensor is described for the lung cancer biomarker hexanal. A composite consisting of molecularly imprinted polymer nanoparticles and multiwalled carbon nanotubes was used in the sensor that is typically operated at a voltage of 4 V and is capable of selectively sensing gaseous hexanal at room temperature. It works in the 10 to 200 ppm concentration range and has a 10 ppm detection limit (at S/N = 3). The sensor signal recovers to a value close to its starting value without the need for heating even after exposure to relatively high levels of hexanal  

An impedimetric human papilloma virus (HPV) DNA biosensor based on gold nanotubes (AuNTs) in label free detection was materialized. The AuNTs decorated nanoporous polycarbonate (AuNTs-PC) template as biosensor electrode was fabricated by electrodeposition method. The single strand DNA (ss-DNA) probe was covalently immobilized onto the AuNTs-PC electrode. The hybridization of target sequences with the ss-DNA probe was observed by the electrochemical impedance spectroscopy (EIS). The biosensor showed high selectivity and could differentiate between the complementary, mismatch and non-complementary DNA sequences. The EIS measurements were matched to Randle's equivalent circuit. The... 

Due to its high discharge capacity, low cost, and good safety, LiNi0.5Co0.2Mn0.3O2 (NCM 523) is regarded as a promising cathode material for the next-generation of lithium-ion batteries. However, poor cycling stability and rate capability are the main disadvantages of the NCM 523 cathode material. In this work, SiO2 single layer-coated and reduced graphene oxide (outer)/SiO2 (inner) double layer-coated NCM 523 have been prepared by a facile wet chemical method. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy results confirm that NCM 523... 

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... 

In this study, the different parts of carthamus tinctorius plant, including petal (SPE), leaf (SLE), and shoot (SSE), have been extracted. Adsorption of the extracts on mild steel in 3.5 wt. % NaCl solution was evaluated employing electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and electrochemical noise measurements (EN). The field-emission scanning electron microscopy (FE-SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were employed to appraise the morphology of the samples surface subjected to the test solutions. According to the EIS results, the maximum adsorption efficiency belonged to the solution containing 1 g L−1 of... 

Growing demands for clean and renewable energy technologies have sparked broad research on the development of highly efficient and stable non-noble metal electrocatalysts for oxygen evolution reaction (OER). In this regard, in the present work a three-dimensional Fe2TiO5/nitrogen-doped graphene (denoted as 3D FTO/NG) hybrid electrocatalyst was synthesized via a facile in-situ process using a hydrothermal method. Structural characterization of the prepared nanocomposite is performed by various techniques e.g. field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) analysis, Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS),... 

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)... 

In this study, for the first time, we reported a fast and facile three-step in situ strategy for direct controllable growth of the Co3(BTC)2 MOFs thin films on the GCE, through the rapid conversion of the electrodeposited Co(OH)2 nano-flakes on rGO/GCE, to crystalline rectangular bar-shape structures of MOFs. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and elemental mapping analysis used to the structural and morphological characterization of the well-synthesized MOFs. The as-prepared Co3(BTC)2 MOFs were used to construct a non-enzymatic sensing platform for determining the glucose... 

Artificial neural networks were used to predict the oxidation peaks potentials of 7 monosaccharides under linear sweep voltammetry regime. Two sets of descriptors, one based on molecular properties calculated through DFT and another based on simple geometric distributions of hydroxyl groups and asymmetric carbon atoms along molecular chains, were employed to introduce the molecules to networks. Relatively, simple networks of (3,3,1) and (3,3,3,1) structures with the number of epochs not exceeding 15 through training process were capable of correctly predicting the peaks positions with R values in the range of 0.97-0.99. © 2008 Elsevier Ltd. All rights reserved  

Solid-phase microextraction (SPME) coupled to gas chromatography (GC) was applied to the extraction of phenol and some of its volatile derivatives in water samples. The SPME fiber consisted of a thin layer of polyaniline, which was electrochemically coated on a fine Pt wire. The stability of the coating was such that it could be used at temperatures as high as 325 °C, without any deterioration. The effects of various parameters affecting the extraction efficiency were studied, simultaneously. From these, optimization of the extraction temperature, extraction time, coating thickness, sample pH, salt concentration and desorption time was carried out by means of a (26-2) fractional factorial... 

Herein, MIL-101(Fe), CoFe2O4, novel binary (MIL-101(Fe)/CoFe2O4, MIL-101(Fe)/GO and CoFe2O4/GO), and ternary (MIL-101(Fe)/CoFe2O4/(3%)GO and MIL-101(Fe)/CoFe2O4/(7%)GO) magnetic composites based upon the MIL-101(Fe) were synthesized. The XRD, FESEM, TEM, EDX, BET-BJH, FTIR, VSM, DRS, PL, EIS and other electrochemical analyses were applied to characterize samples. The MIL/CoFe2O4/(3%)GO demonstrated the best performance compared to other samples for visible light photocatalytic and photo-Fenton-like degradation of Direct Red 23 (DtR-23), Reactive Red 198 (ReR-198) dyes as well as Tetracycline Hydrochloride (TC-H) antibiotic. Degradation of dyes using the ternary composite after 70 min of... 

Coronaviruses are a group of envelop viruses which lead to diseases in birds and mammals as well as human. Seven coronaviruses have been discovered in humans that can cause mild to lethal respiratory tract infections. HCoV-229E, HCoV-OC43, HCoV-NL63, and HCoV-HKU1 are the low-risk members of this family and the reason for some common colds. Besides, SARS-CoV, MERS-CoV, and newly identified SARS-CoV-2, which is also known as 2019-nCoV, are the more dangerous viruses. Due to the rapid spread of this novel coronavirus and its related disease, COVID-19, a reliable, simple, fast, and low-cost detection method is necessary for patient diagnosis and tracking worldwide. Human coronaviruses detection...