Sharif Digital Repository

A new method for fluorescent microscopy has been proposed. Proposed method uses indirect excitation of fluorophores with nanometer localized illuminating source. Localized source is created at corners of gold nanotriangles which are deposited on glass substrate. Actually the combination of gold nanotriangle (deposited on glass) acts as active substrate (where species will be placed) for our proposed method. The structure will be scanned with a focused beam of laser (or combination of beams). Due to electric field enhancement in corners and edges of nanotringle (because of surface plasmons), third order nonlinear effect will be enhanced accordingly. Enhancement in third order nonlinearity... 

Iron oxide nanoparticles, γ-Fe2O3NP, were deposited onto the surface of multi-walled carbon nanotubes and CNT/γ-Fe2O3NP hybrid nanomaterials were obtained. Then linear-dendritic ABA type block copolymers consisting of polyethylene glycol as B block and poly(citric acid) as A block, PCA-PEG-PCA, were synthesized and cisplatin (cis-diamminedichloroplatinum (CDDP) - a platinum-based chemotherapy drug) was conjugated with their carboxyl functional groups and CDDP/PCA-PEG-PCA anticancer prodrugs were prepared. Noncovalent interactions between CDDP/PCA-PEG-PCA anticancer prodrugs and CNT/γ-Fe2O3NP hybrid nanomaterials led to CDDP/PCA-PEG-PCA/CNT/γ-Fe2O3NP drug delivery systems. There are several... 

A novel approach for phototherapy is proposed. The proposed method is based on cell apoptosis according to halting activation of cancer cell membrane receptor by exposure to UV light pulses without any side effect. In the proposed method, gold nanoparticles are directed to cancerous cells by conjugating their surface with specific ligands. UV light is created locally adjacent to cells around the gold nanoparticles. UV light is generated due to nonlinear interaction of visible light with gold nanoparticles because of enhancement in third order nonlinear effects. For example, by using 780 nm laser, 260 nm UV will be generated around the nanoparticle because of third harmonic generation... 

The efficient structure for optical fiber based surface Plasmon resonance sensor has been investigated. The sensor structure is based on removing the cladding of a multimode optical fiber and replacing it with thin film of gold. The incident light inside the fiber will excite surface plasmons which will be resulted in the absorption in specific wavelengths. The absorption behavior is dependent on the dielectric constants at the vicinity of the metallic thin film. Based on the amount of removed cladding and deposition regions on the core structure of the fiber, different configurations can be considered. Based on the computational analysis, we have studied performance of sensor for three... 

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... 

Multi electrode arrays (MEA) have been exploited in different electrophysiological applications. In neurological applications, MEAs are the vital interfaces between neurons and the electronic circuits with dual role; transmitting electric signal to the neurons and converting neural activity to the electric signal. Since the performance of the electrodes has a direct effect on the quality of the recorded neuronal signal, as well as the stimulation, the true choice of electrode material for MEA is crucial. Gold is one of the best candidates for fabrication of MEAs due to its high electrical conductivity, biocompatibility and good chemical stability. However, noble metals such as gold do not... 

Multielectrode array (MEA) structures are the vital parts in the interface between neural structures and external electronic circuits, both in excitation and detection. As a transducer, the performance of electrodes has direct effect on the quality of the recorded neural signal, as well as induced charge density during the stimulation in neural prosthesis. The size and geometry of the electrode structure have distinct effect on the performance of electrodes accordingly. In this paper, the effect of size and geometry of the electrodes has been investigated in their performance and the impedimetric features of the fabricated electrodes with different structures have been studied. Based on the... 

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... 

Light scattering design in dye and quantum dot sensitized solar cells is one of the main concerns in enhancing their light harvesting efficiency, and also in improving their power conversion efficiency. Herein, we present a theoretical analysis to calculate the dependence of the light scattering efficiency in dye solar cells that have employed scattering agents with various sizes and morphologies incorporated in nanostructured photoanodes with different designs. Various isotropic and anisotropic nanostructures, including filled and hollow spheres, spherical voids, nanowires and hollow fibres in a size range of 100 nm to 900 nm, have been considered as scattering centres. The scattering... 

Three-dimensional TiO2 nanostructures take advantages of large surface area and superior light-harvesting efficiency, as well as appropriate charge carrier transport and separation features. Here in this research, we report for the first time on measurement of density of localized trap states in three-dimensional TiO2 nanostructures with various morphologies. Bare 1-dimensional TiO2 nanofibers have been synthesized via two different methods: electrospinning and hydrothermal processes. The surface of TiO2 nanofibrous has been modified with nanoparticles and nanobranches thorough second hydrothermal process. Various morphologies of nanostructured TiO2 have been fabricated including... 

Catecholamine neurotransmitters, specifically, dopamine (DA), epinephrine (EP), and norepinephrine (NE), are known as substantial indicators of various neurological diseases. Developing rapid detection methods capable of simultaneously screening their concentrations is highly desired for early clinical diagnosis of such diseases. To this aim, we have designed an optical sensor array using three fluorescent dyes with distinct emission bands and have monitored variations in their emission profiles upon the addition of DA, EP, and NE in the presence of gold ions. Because of the different reducing power of catecholamines, differently sized gold nanoparticles (GNPs) with different levels of... 

The optical polarization properties of virus-infected cells have been measured, analyzed, and compared with the uninfected cells. In this regard, Vero and HeLa cells have been used as the host for Herpes simplex viruses (HSV). By using polarization microscopy imaging technique, the Mueller matrix images of infected and uninfected cells have been recorded. Through image processing and further analysis, the polarization properties of host cells are compared with their infected ones. For quantitative analysis, the multispectral Mueller matrix transformation (MMT) parameters (A and b) are calculated to identify the microstructural differentiations between uninfected and infected cells by HSV.... 

The authors describe an impedimetric method for the quantitation of the DNA of the human papilloma virus (HPV) type 16. A glassy carbon electrode (GCE) was modified with gold nanosheets and is shown to be superior to a common gold disk electrode. A single-stranded 25mer oligonucleotide (ssDNA) acting as the probe DNA was immobilized via its thiolated 5′ end on both electrodes. After hybridization with target (analyte) DNA, electrochemical impedance spectra were acquired in the presence of hexacyanoferrate as a redox marker. The sensor can distinguish between complementary, non-complementary and single base pair mismatches of HPV ssDNA. At a 1 mM hexacyanoferrate concentration, the biosensors... 

Investigation of non-covalent interaction of hydrophobic surfaces with the protein G (PrG) is necessary due to their frequent utilization in immunosensors and ELISA. It has been confirmed that surfaces, including carbonous-nanostructures (CNS) could orient proteins for a better activation. Herein, PrG interaction with single-walled carbon nanotube (SWCNT) and graphene (Gra) nanostructures was studied by employing experimental and MD simulation techniques. It is confirmed that the PrG could adequately interact with both SWCNT and Gra and therefore fine dispersion for them was achieved in the media. Results indicated that even though SWCNT was loaded with more content of PrG in comparison with... 

Background: Study of nanostructure-protein interaction for development of various types of nano-devices is very essential. Among carbon nanostructures, carbon nanotube (CNT) provides a suitable platform for functionalization by proteins. Previous studies have confirmed that the CNT induces changes in the protein structure. Methods: Molecular dynamics (MD) simulation study was employed to illustrate the changes occurring in the protein G (PGB) in the presence of a CNT. In order to predict the PGB surface patches for the CNT, Autodock tools were utilized. Results: Docking results indicate the presence of two different surface patches with diverse amino acids: the dominant polar residues in the... 

Effect of sandblasting of the copper electrode structures before deposition of gold thin film for micro electrical impedance tomography (EIT) system has been studied experimentally. The comparison has been performed on the unmodified copper electrodes and the sandblasted electrodes before deposition of gold layer, using structural analysis while their performance in EIT system has been measured and analyzed. The results of scanning electron microscopy and atomic force microscopy show that the sandblasting of the electrodes results in the deposition of gold film with smaller grain size and uniformly, comparing to the unmodified structure. The measurement of impedance shows that the... 

Catecholamine neurotransmitters, generally including dopamine (DA), epinephrine (EP) and norepinephrine (NE) are known as substantial indicators of various neurological diseases. Simultaneous detection of these compounds and their metabolites is highly recommended in early clinical diagnosis. To this aim, in the present contribution, a high performance colorimetric sensor array has been proposed for the detection and discrimination of catecholamines based on their reducing ability to deposit silver on the surface of gold nanorods (AuNRs). The amassed silver nanoshell led to a blue shift in the longitudinal localized surface plasmon resonance (LSPR) peak of AuNRs, creating a unique pattern... 

A novel electrode structure is introduced for micro-electrical impedance tomography. The composite electrode structure is made up of gold nanoparticles (AuNPs) and carbon nanotube (CNT) which are deposited on the surface. The nanostructure-based composition of electrodes improved the effective surface area, increased the double-layer capacitance of electrodes, and enhanced the electron transfer on the electrode–analyte interface. The proposed electrodes exhibit lower frequency-dependent electrical properties in impedance measurement. © 2020, Springer Science+Business Media, LLC, part of Springer Nature  

Third order nonlinear effects and its enhancement in gold nanostructures has been numerically studied. Analysis method is based on computationally solving nonlinear Maxwell's equations, considering dispersion behavior of permittivity described by Drude model and third order nonlinear susceptibility. Simulation is done by method of nonlinear finite difference time domain method, in which nonlinear equations of electric field are solved by Newton-Raphshon method. As the main outcomes of third order nonlinear susceptibility, four wave mixing and third harmonic generation terms are produced around gold nanostructures. Results of analysis on different geometries and structures show that third... 

Considering electronic skin applications, a pressure sensor based on periodic structure of graphene oxide-reduced graphene oxide (GO-rGO) has been designed and fabricated based on a low cost direct laser writing technique by utilizing the laser diode of DVD drive's pickup head. The optimization of sensor structure has been performed using computational modelling through Finite Element Method (FEM) in the COMSOL environment. The optimized structure is fabricated based on the deposition of thin layer of GO on the surface of Kapton and the pattering is performed by laser irradiation. The fabricated sensor structure has been characterized structurally and functionally. The results show that the...