NANOSCALE
Year:2019 | Volume:6 | Issue:1 |Papers Count:7

In this work, at first thiolated graphene quantum dots (tio-GQDs) was synthesized. Characterization of the synthesized compound was carried out by the use of infrared spectroscopy. The obtained results confirmed that the tio-GQDs were successfully synthesized. The size of these quantum dots was investigated by TEM. On the base of achieved images, the average dimeters of nanoparticles were estimated about 50 nm. The oxidized GQDs were thiol functionalized with cysteamine. In the following the prepared nanoparticles were applied for the determination of trace amount of mercury. To this end, the fluorescent quenching process of tio-GQDs was investigated. Fluorescent quenching process was very fast that was an important advantage of this nanosensor. The limit of detection was obtained 0. 160 μ M and linear concentration rang 0. 5 µ M to 1 mM. Interference effects of other ions on mercury determination by thio-GQDs were studied in the presence of other species. The usage of tio-GQDs for determination of mercury is an easy, effective, fast, inexpensive, low toxicity and environmentally friendly method. Finally, the synthesized thiolated graphene quantum dots were applied for the determination of mercury in the real samples and selectivity with satisfactory results.

Cupric oxide (CuO) thin films were synthesized on commercial ITO substrate using thermal oxidation route, a Cu-layer deposited by PVD method were prepared in two cases: in absence and in presence of an adhesive oxide layer on the substrate. Samples were characterized by FESEM images, XRD and UV-Vis. spectra. We found sample without adhesive layer is grown in the form of nanograins with relatively slick surface, and the sample with adhesive layer is covered with porous grains containing small finegrains, about 30 nm or less. The XRD spectra of the samples indicate a polycrystalline structure in monoclinic phase with the main orientations of (111) and (1� 11). Among these samples, the sample with presence of an adhesive layer has a better physical conditions (i. e. bigger crystallite sizes, smaller band gap and higher optical absorbance). Finally, photoconductivity effect in metal-semiconductor-metal (MSM) structure was investigated using a red (620 nm) LED lamp. The results showed that sensitivity of the sample with adhesive layer is about 3 times bigger than one without adhesive layer, and also its variation vs. lamp electrical power is linear.

Escherichia coli (E. coli) is the most important species that causes dysentery. Present study was conducted to investigate the synergistic antimicrobial effects of Nano-selenium and lactobacillus on E. coli to suggest anti-diarrhea bio-drug. The antimicrobial effects of experimental treatments against E. coli were evaluated by disk diffusion and well diffusion methods as a measure of the growth inhibition zone. Moreover, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by microdilution method. The results of the well and disk diffusion methods showed that in both tests, the highest growth inhibition zone of the "Nano selenium-loaded lactobacillus" treatment on the standard strain of E. coli was 23/6 and 23/36 mm respectively. The results of MIC and MBC determination showed that in all experimental periods, "Nano selenium-loaded lactobacillus" and "Nano-selenium + lactobacillus" treatments with 590/7 and 615/38 μ g/ml for MIC and 955/32 and 1195/67 μ g/ml for MBC had the lowest amounts compared to other treatments (P<0. 05). The results of this experiment confirmed the anti-diarrhea ability of "Nano selenium-loaded lactobacillus" treatment. Therefore, provided that this test be repeated in future studies and ensured the accuracy of these results, manufacturing of bio-drug with this formulation may be advised for prevention or treatment of diarrheal disease.

Herein, the optical properties of CdS and Carbon quantum dots (QDs) for the first time under gamma irradiation was studied. The CdS QDs were synthesized by a rapid, facile and low cost microwave assisted method and carbon QDs extracted from orange juice by hydrothermal method. The CdS QDs were prepared just after a couple minute of microwave irradiation and the carbon QDs were synthesized after 150 min. in 120 C° in oven. The samples were exposure by gamma ray with source of Co-60 within 0-20 kGy. The results showed that gamma irradiation suppress the photoluminescence (PL) intensity of QDs. A linear relation between PL intensity and logarithmic dose of gamma was found for the matrixed CdS QDs deposited top of glass. The initial size of CdS QDs was indicated about 3. 4 nm by transmission electron microscopy (TEM). For water-soluble CdS QDs and powdered carbon QDs, PL intensity was decreased as dose of 20 kGy gamma irradiation. While the water-soluble carbon QDs were stable after gamma irradiation. These results shows that the luminescent nanostructure can be a new candidate for dosimetry.

In this work, we report on the fabrication, morphology, and electrical and optical characterization of sandwich devices of bromo indium phthalocyanine thin film nanostructures in aluminum electrodes using electron beam evaporation in a high vacuum which are promising for sensing applications. We investigate the influence of both parameters of temperature and frequency on the conduction mechanism to determine the transport process of the charge carriers. Result demonstrates that the capacitance and the loss factor decrease with increasing the frequency and increase for high temperatures. The behavior of the capacitance and loss factor fits well with the model of Goswami and Goswami and the results imply the domination of the hopping theory. In addition, analysis of absorption spectrum indicates that the optical band gap energy is 3eV. Furthermore, morphological analysis demonstrates that all films have a smooth surface with homogeneous small crystal grains with a nanoscale size order of 40 ± 10nm. Thus, temperature and frequency dependent experiments of optical and electrical parameters of the bromo indium phthalocyanine thin film nanostructures show their potential to be employed for developing a multifunction sensor.

In this paper, Fe3O4 magnetic nanoparticles were synthesized by a co-precipitation method at room temperature with and without magnetic field during the synthesizing process. Their magnetic properties were measured by vibrating sample magnetometer (VSM) instrument. VSM was used for studding the paramagnetic properties of the nanoparticles and the effect of the magnetic field on the magnetic properties of nanoparticles. The results showed that the sample synthesized in the presence of magnetic field has the saturation magnetization value as about 42 emu/gr. The saturation magnetization value for the synthesized sample in the absence of magnetic field is about 64 emu/gr. The X-ray diffraction (XRD) pattern revealed the low crystallinity for the synthesized nanoparticles in the presence of magnetic field in comparison with synthesized nanoparticles in the absence of magnetic field. The Fourier-transform infrared (FTIR) spectroscopy confirmed the chemical bond formation of the magnetic nanoparticles. The scanning electron microscopy (SEM) images showed the morphology of the nanoparticles. The reduction of saturation magnetization value and the crystallinity of nanoparticles can be related to the magnetic dipole orientation by the magnetic field during the synthesizing.

In this paper, graphene oxide was synthesized using the Hummer’ s method. Then, an efficient method for the synthesis of Reduced Graphene Oxide/Magnetite (RGO/Fe3O4) nanocomposite is presented. The properties of RGO/Fe3O4 nanocomposite were investigated using FT-IR, XRD, VSM and SEM. The SEM images show that magnetite nanoparticles were appropriately placed on graphene sheet. Distribution of Fe3O4 nanoparticles on the graphene sheets was properly established. The average size of 22 ± 5 nm for Fe3O4 nanoparticles, which have been put on graphene substrates, was measured using SEM images. The VSM results demonstrate that there is no apparent change in the properties of magnetite nanoparticles in RGO/Fe3O4 nanocomposite. Therefore, this nanocomposite could be appropriate for magnetic applications. A cyclic voltammetric analysis was performed to investigate the electron transfer kinetics in nanocomposite. Distribution of Fe3O4 NPs on the graphene layers increased the efficiency and sensitivity of the electrochemical sensor, causing the RGO/Fe3O4 nanocomposite to have considerably higher electrochemical catalytic properties. A modified GCE was also fabricated based on RGO/Fe3O4 nanocomposite to investigate the electrocatalytic oxidation of K3[Fe(CN)6] using cyclic voltammetry detection. In cyclic voltammetry studies, oxidation current enhancement was observed when magnetite nanoparticles loaded on graphene substrates, which could make RGO/Fe3O4 nanocomposite as an efficient electrochemical sensor.