فصلنامه دنیای نانو
پیاپی 68 (پاییز 1401)

The study of printed electronics is one of the important elements in the development of industrial productions. To achieve this, in the present study, a) an electrode based on conductive graphene ink was printed using a screen printing process, b) an air-curing condition was applied to graphene ink, and c) enzyme stabilization (using 3D graphene) and the electrochemical performance of the printed biosensor were investigated. This method of producing scalable biosensors has significant characteristics such as high sensitivity769.9 𝜇A.mM-1.cm-2 , and its linear range of 0.2 to 16 mM is suitable for human blood sugar monitoring in a short response time during a day. The results signified high selectivity against interfering species such as ascorbic acid and lactose, and high repeatability and reproducibility with low relative standard deviation values of 1.04% and 1.5%, respectively, for the device. No considerable reduction in the printed electrochemical biosensor (PEB) performance was observed after bending cycles of up to 100, indicating the high flexibility of the biosensor. The PEB presented a great potential to be used as a personalized health monitoring device in complex biological fluids.

Molecular dynamics (MD) simulation is a well-known subject in the field of bioinformatics. MD simulations study the complexity of biological processes in the aqueous dynamic environment similar to the cellular world at the nanoscale. Over the last five decades since the first molecular dynamics simulations were performed on a protein, the biological understanding of the mechanism of molecular processes has been transformed from several perspectives by these simulations. In this review article, the most important molecular dynamics simulation studies on the biological systems are discussed. While reviewing the most important studies, the focus would be on the three main breakthroughs in this field. These Three turning points include: protein folding, the role of the cell membrane in the function of the cell receptors and the effect of water molecules in MD simulations. Finally, the means of determining the simulation time and the number of atoms in the system are discussed.

Various solvents are used in different industrial processes such as the pharmaceutical industry, and these solvents enter the environment as industrial effluents. Two major goals can be achieved, if it is possible to separate the mixture of solvents used in industrial processes. Firstly, the entry of these organic solvents into the environment is prevented, and secondly, these solvents can be reused and prevented from being discarded. Based on this, in this research, two organic solvents including methanol and ethanol have been considered and the separation of their mixture has been investigated. Two-dimensional graphene oxide nanostructured membrane has been used to separate this mixture and the molecular dynamics simulation method has been used. The results showed that by forming a lamellar structure of graphene oxide membrane (with proper distance between the layers), a membrane with good selectivity relative to methanol molecules was obtained. This type of lamellar membrane can also be used to separate other mixed solvents.

X-ray diffraction pattern (XRD), Transmission electron microscope (TEM), Raman spectroscopy and Fourier transform infrared (FTIR) are used to characterize the structure of graphene oxide nanosheets. The results show the presence of thin graphene oxide layers, which have a suitable crystal structure with a peak of about 10 degrees and a ratio of ID/IG about 0.99. Also, by employing Kramers-Kronig (KK) relations and obtaining their refractive index, extinction coefficient and dielectric function via FTIR spectroscopy, the optical phonon modes, the transverse optical phonon (TO) and the longitudinal optical phonon (LO), of this material have been calculated. Then, the nonlinear optical (NLO) properties were obtained through the single-beam Z-scan method using a continuous wave (CW) Nd:YAG laser with a wavelength of 532 nm. The Z-scan results show that graphene oxide nanosheets have the phenomena of self-focusing and two photon absorption (TPA). In addition, a suitable figure of merit (FOM) was obtained for these nanosheets.

The aim of this research is the fabrication of nanosensor based on the metal oxide semiconductor tungsten trioxide with the ability to detect acetone gas from exhalation. The structural characteristics of the prepared samples were examined by scanning electron microscope and X-ray diffraction. The characterization of synthesized and porous spherical nanostructure were performed by DLS, BET and BJH analyses. The obtained powders were coated on an inter-digitated electrode by deposition method and the electrical resistivity was measured exposed to acetone and some volatile gases. In order to evaluate the sensore selectivity of the sensors, their sensitivity to several samples of volatile organic gases was also examined by increasing the temperature of the sensor to 200°C and 300°C. The obtained results showed that using of tungsten trioxide porous nanostructures in concentrations less than 5 ppm, with very promising linear performance, offers a sensor sensitivity of 44/44 %/ppm. Quantitative evaluations proved that the sensor selectivity of this nanostructure is excellent to acetone at the concentration of 1.8 ppm as the threshold concentration of type 1 diabetes biomarker in the presence of several disturbing organic gases. The response of the sensor in certain concentrations of acetone has been superior to other references. The fabricated sensor with a response time of 18 seconds reacts faster, which is improved by about 21% compared to the best sample presented.

The aim of this study was to investigate the effect of carbon nanocomposites based on carbon nanotubes on the structure of flock powder (polyester). Modified flock was prepared in the presence and absence of CTAB. Investigations showed that the geometric shape of the flock and the length of the flock fibers were investigated by the flock device of this spec, and the particle size of the flock should be optimally between 0.4-0.7 mm. The results showed that after modification with nanocomposite materials, the flock structure was not damaged and their size is between 0.5, 0.4 and..... After modifying the flock fibers, the nanocomposite particles were evenly distributed on the flock fibers and did not cause any damage to the original structure of the sample. The structure and appearance of the flock did not change before and after modification with nanocomposites. The outer diameter of carbon nanotubes decreases due to functionalization, which can be due to the removal of amorphous (amorphous) carbon from carbon nanotubes due to oxidation.

In this research work, for the first time, gold and silver nanoparticles were successfully synthesized using exopolysaccharide extracted from the culture medium of porphyridium purpureum microalgae and then their antibacterial activity was evaluated. In this method, in addition to reducing the metal ions of gold and silver, exopolysaccharide also play a role in stabilizing the nanoparticles synthesized in aqueous solution. UV-Vis spectroscopy method was used to confirm the formation of synthesized nanoparticles. Also, transmission electron microscopy (TEM) was used to determine the size and morphology of the gold and silver nanoparticles synthesized using microalgae exopolysaccharide. Finally, the antibacterial activity of nanoparticles synthesized using exopolysaccharide derived from microalgae was evaluated on two types of gram-positive bacteria (E. Faecalis) and gram-negative bacteria (E. coli). For this purpose, disk diffusion test was used, as a result of which it was found that these stabilized nanoparticles have significant antibacterial activity. Exopolysaccharide-stabilized silver nanoparticles also show better antibacterial activity than exopolysaccharide-stabilized gold nanoparticles.