Sharif Digital Repository

Graphene oxide nanowalls with extremely sharp edges and preferred vertical orientation were deposited on a graphite electrode by using electrophoretic deposition in an Mg 2+-GO electrolyte. Using differential pulse voltammetry (DPV), reduced graphene nanowalls (RGNWs) were applied for the first time, in developing an ultra-high-resolution electrochemical biosensor for detection of the four bases of DNA (G, A, T, and C) by monitoring the oxidation signals of the individual nucleotide bases. The extremely enhanced electrochemical reactivity of the four free bases of DNA, single-stranded DNA, and double-stranded DNA (dsDNA) at the surface of the RGNW electrode was compared to electrochemical... 

Mg2+-charged spongy graphene electrodes (SGEs) were fabricated by using electrophoretic deposition of chemically exfoliated graphene oxide sheets on graphite rods. The SGEs were able to present two distinguishable signals (originated from electrochemical oxidation of guanine) in differential pulse voltammetry (DPV) of leukemia and normal blood cells, in contrast to glassy carbon electrodes giving only one overlapped peak. Hence, the SGEs were applied in fast (60 min) and ultra sensitive detection of leukemia (single abnormal cells in ∼109 normal cells) in a blood serum. The sensitivity obtained by the SGEs was three orders of magnitude better than that of the best available and current... 

Graphene oxide nanoplatelets (GONPs) with extremely sharp edges (lateral dimensions ∼20-200 nm and thicknesses <2 nm) were applied in extraction of the overexpressed guanine synthesized in the cytoplasm of leukemia cells. The blood serums containing the extracted guanine were used in differential pulse voltammetry (DPV) with reduced graphene oxide nanowall (rGONW) electrodes to develop fast and ultra-sensitive electrochemical detection of leukemia cells at leukemia fractions (LFs) of ∼10-11 (as the lower detection limit). The stability of the DPV signals obtained by oxidation of the extracted guanine on the rGONWs was studied after 20 cycles. Without the guanine extraction, the DPV peaks... 

In this work, graphene oxide (GO) aqueous suspensions prepared by a chemical exfoliation method showed a fluorescence peak at ∼615 nm. Photoluminescence spectroscopy determined that functionalization of the GO sheets by 3-(2-Aminoethylamino) propyltrimethoxysilane molecules significantly quench the fluorescence property of the GO sheets. Fourier transform infrared spectroscopy confirmed proper functionalization of the GO sheets. Curcumin was applied as a fluorescent natural material with an emission peak at ∼550 nm wavelength for green fluorescent labeling of the functionalized-GO sheets. The curcumin-labeled functionalized-GO sheets showed an intense emission band fluorescent property with... 

Graphene oxide foam (GOF) layers with thicknesses of ∼15-50 μm and density of ∼10 graphene oxide (GO) sheets/μm were fabricated by precipitation of chemically exfoliated GO sheets in an aqueous suspension at ∼80 °C under UV irradiation. Then, rolled GOFs with desirable scales were developed as electrically conductive 3D-scaffolds and applied in directional growth of neural fibers, through differentiation of human neural stem cells (hNSCs) into neurons under an electrical stimulation. X-ray photoelectron spectroscopy indicated that the UV irradiation resulted in partial deoxygenation of the layers. Scanning electron microscopy and Raman spectroscopy confirmed the presence of multilayer GO... 

Graphene nanoplatelets with lateral dimensions of ∼50-200 nm and thicknesses <2 nm were utilized for the extraction of nucleic acids (NAs) from eukaryotic and prokaryotic cells. The graphene nanoplatelets (both chemically exfoliated graphene oxide nanoplatelets and hydrazine-reduced graphene oxide nanoplatelets) successfully extracted plasmid DNA (pDNA) from Escherichia coli bacteria, comparable to a conventional phenol-chloroform (PC) method. Furthermore, it was found that the yield of graphene nanoplatelets in genomic DNA (gDNA) and RNA extractions from embryonic stem cells (ESCs) was also comparable to the yield of the conventional methods. The effects of the graphene nanoplatelets on... 

In the last two decades, quantum dots nanomaterials have garnered a great deal of scientific interest because of their unique properties. Quantum dots (QDs) are inorganic fluorescent nanocrystals in the size range between 1 and 20 nm. Due to their structural properties, they possess distinctive properties and behave in different way from crystals in macro scale, in many branches of human life. Cadmium telluride quantum dots (CdTe QDs) were labeled with 68Ga radio nuclide for fast in vivo targeting and coincidence imaging of tumors. Using instant paper chromatography, the physicochemical properties of the Cadmium telluride quantum dots labeled with 68Ga NPs (68Ga@ CdTe QDs) were found high... 

Graphene oxide-polyvinyl chloride composite was prepared using tetrahydrofuran solvent-assisted dispersion of characterized nano flakes of graphene oxide in polymer matrix. Electrical percolation threshold of GO/PVC nanocomposite was determined via a finite element simulation method with a 2D model and compared with experimental results. A conductive cell with two silver coated walls was designed and fabricated for exploring dosimetric properties of the composite. Some characteristics of the new nanocomposite such as linearity of dose response, repeatability, sensitivity and angular dependence are investigated. According to 2D proposed method, obtained data associated to electrical... 

This research reports the preparation and examination of Cadmium Telluride (CdTe) Quantum Dots and doping CdTe QDs with Europium (Eu), Gadolinium (Gd), and Manganese (Mn) prepared in aqueous solution using TGA as a capping agent. Magnetic QDs (MQDs) are important agents for fluorescence (FL) /magnetic resonance (MR) dual-modal imaging due to their excellent optical and magnetic properties. Herein, the chemical bonds, structural, fluorescence, and magnetized properties of CdTe QDs and effect of Mn, Eu, and Gd ions doping on their properties were examined by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTM), Energy-dispersive X-ray spectroscopy (EDX),... 

Two-dimensional (2D) transition metal dichalcogenides are promising candidates of photodetectors where they are commonly grown parallel to the substrate due to their 2D characteristics in micrometer scales from exfoliation of bulk crystals or through high temperature chemical vapor deposition (CVD) methods. In this study, semi-hexagonal vertical nanosheets of SnS2 layered have been fabricated on FTO substrate without using Sn source through CVD method at relatively low temperature (500 °C). Due to exceptional band alignment of triple cation lead perovskite (TCLP) with semi-hexagonal SnS2 nanosheets, an improved photodetector has been fabricated. This type of photodetectors fabricated through... 

Graphene oxide (GO) sheets functionalized by aminopropylsilyl groups (8.0 wt.%) were labeled by 198,199Au nanoparticle radioisotopes (obtained through reduction of HAuCl4 in sodium citrate solution followed by thermal neutron irradiation) for fast in vivo targeting and SPECT imaging (high purity germanium-spectrometry) of tumors. Using instant thin layer chromatography method, the physicochemical properties of the amino-functionalized GO sheets labeled by 198,199Au NPs (198,199Au@AF-GO) were found to be highly stable enough in organic phases, e.g. a human serum, to be reliably used in bioapplications. In vivo biodistribution of the 198,199Au@AF-GO composite was investigated in rats bearing... 

Concentration-dependent cyto and genotoxicities of graphene oxide (GO) and reduced GO (rGO) sheets on spermatozoa were studied. rGO sheets with various surface chemical states were achieved using hydrazine (N2H 4) hydrothermal (HT) reactions and green tea polyphenols (GTPs). Although 0.1 μg mL-1 graphene could not change sperm viability and kinetic parameters, <40% and 20% of spermatozoa were viable and progressively motile, after 2 h incubation with 400 μg mL-1 GO or rGO, respectively. All the graphene nanomaterials induced concentration- dependent reductions of adenosine triphosphate and NAD+/NADH produced by spermatozoa for motility and metabolic activity. While GO, N 2H4-rGO, and HT-rGO... 

Superparamagnetic iron oxide (SPIO) nanomaterials are widely used as magnetic resonance imaging (MRI) contrast agents (CAs). These CAs significantly shorten transverse relaxation time (T2) and so decrease the intensity of the T2-weighted MRI (negative contrast imaging). However, the partial-volume effect is known to be one of the problems in negative contrast MRI. In this work, SPIO nanoparticles were modified by dextran and graphene oxide (GO) nanosheets to achieve a positive contrast MRI with high intensity. This modification resulted in shortening the longitudinal relaxation time (T1) of the SPIO nanoparticles (in addition to the T2 shortening).... 

Multi-component nanocomposite thin films (composed of cellulose nanofiber (CNF), alginate, bioglass nanoparticles (BG NPs) and gentamicin) were prepared by using cathodic electrophoretic deposition (EPD) under different isostatic pressures of 10−2 mbar (LP), atmospheric (AP), and 5 bar (HP). According to thermal gravity analysis, larger amounts of CNF and alginate could be deposited on the surface at the AP condition in comparison with the LP and HP conditions. On the other hand, higher amounts of the BG NPs could be deposited at the LP condition as compared to the other conditions. The drug (gentamicin) loading/releasing of the samples prepared at the HP condition was found to be higher... 

In this paper, a bottom-up hydrothermal route is reported for the synthesis of oxygen and nitrogen co-decorated carbon quantum dots (CQDs) using ammonium hydrogen citrate (AHC) as a single precursor. DLS data approved the formation of 4.0 nm (average size) CQDs. XRD pattern shows the interlayer spacing (002) of 3.5 Å for CQDs, which is exactly the same as that of crystalline graphite. XPS and FTIR spectra verified the formation of oxygen and nitrogen functional groups on the CQDs surface. Co-decorated carboxyl, hydroxyl and amine groups on the CQDs surfaces make them as promising polyelectrolyte for gene delivery. Toxicity assay showed a survival rate of 70% under different incubation times... 

In the present work, the effect of graphene oxide (GO) nanosheets on the antibacterial activity of CuO nanowire arrays under visible light irradiation is shown. A combined thermal oxidation/electrophoretic deposition technique was employed to prepare three-dimensional networks of graphene oxide nanosheets hybridized with vertically aligned CuO nanowires. With the help of standard antibacterial assays and X-ray photoelectron spectroscopy, it is shown that the light-activated antibacterial response of the hybrid material against gram-negative Escherichia coli is significantly improved as the oxide functional groups of the GO nanosheets are reduced. In order to explore the physicochemical... 

A temperature-induced degenerate p-type graphene nanopore/reduced graphene oxide (GNP/rGO) heterojunction-based nanodevice was prepared and studied for the first time, showing a robust negative differential resistance (NDR) feature. In this regard, cellulose-based perforated graphene foams (PGFs), containing numerous nanopores (with an average size of ∼2 nm surrounded by nearly six-layer rGO walls) were synthesized using bagasse as a green starting material. The PGFs with an essential p-type semiconducting property showed a band gap energy of ∼1.8 eV. The observed two-terminal NDR peak could present stable and reversible features at high temperatures of 586-592 K. It was demonstrated that...