فصلنامه نانو مقیاس
سال هفتم شماره 4 (پیاپی 28، زمستان 1399)

Confinement of light at nanoscale dimensions in plasmonic structures has many advantages including enhanced light-matter interactions. This enhancement can be well utilized in resonantly coupled atomic-plasmonic systems. In such coupled resonant systems, broad plasmonic resonance in contrast to narrow atomic resonance gives rise to reflection atomic spectroscopy with high resolution. In this paper, the reflection from thin gold layer in the vicinity of the rubidium vapor in Kretschmann configuration was modeled and the modification of hyperfine structure of the atomic spectral lines were studied. By selecting the angle of incidence of light we could change the frequency of resonance of surface plasmon-polariton mode from the central frequency of atomic resonance lines, so the EIT and Fano resonance phenomena have been observed.

Dyes colors are one of the most important organic pollutants in the industry which cause a lot of environmental problems. Therefore, the determination and removal of dyes from aqueous effluents is one of the most significant environmental importance. The aim of the present study was to investigate the potential of applicability of COFe2O4 nanoparticles loaded on activated carbon (AC) (CA-COFe2O4) for the removal and adsorption of Chrysoidine in water samples. In this research, nanocomposite (CA-COFe2O4) was prepared. Then, the properties of sorbent (nanocomposite) are characterized by Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscope (SEM) techniques. In this study, nanoparticles are dispersed in aqueous media by ultrasonic were to facilitate the dispersion of the sorbent. The CA-COFe2O4containing the extracted dyes was separated from the sample aqueous by centrifuge. The residual Chrysoidine G concentrations were determined by UV-Vis spectroscopy. The factors affecting such as pH, ultrasonic time, adsorbent mass and initial Chrysoidine G concentration on the Chrysoidine G removal of CA-COFe2O4 was investigated. The experimental results also showed that the adsorption followed with pseudo second-order kinetics model, and the adsorption behavior was accordance with the Freundlich isotherm model. Also, the adsorption capacity of 28.57 mg/g was achieved by CA-COFe2O4.

The quality of the perovskite film as an absorbing layer has a key role on photovoltaic performance of perovskite solar cells. One of the essential ways to control the perovskite crystal layer quality and morphology, is application of the suitable deposition method. In this work, we have used four optimised methods (i.e. S1: two step immersion, S2: one step with antisolvent, S3: one step without antisolvent and S4: vapor- assisted solution process) of fabricating perovskite absorbing layer of solar cells. The study of fabricated solar cells revealed that the S4 method leads to the dense and pin-hole-free and fully coverage layers of perovskite which present the best performance (PCE: 8.82%, J SC 13.70 mA/cm 2 , V OC 1 V and FF: 0.63). However, in commercialization and economical point of view, S3 method is suggested.

In this research, iron oxide nanoparticles were synthesized by co-precipitation method. Then by solving the nanoparticles in toluene and reducing the solubility of them by acetone as anti-solvent, different sizes of nanoparticles were selected and separated. After selection and separation, the band structure of the nanoparticles was studied by photoluminescence spectroscopy (PL). X-ray diffraction was used for phase and structure determination of nanoparticles and dynamic light scattering (DLS) and transition electron microscopy (TEM) were used for size determination. The results confirmed the possibility of selection and separation of iron oxide nanoparticles of three nanometers (3nm) and also photoluminescence spectroscopy results showed a red-shift by reducing the size of the iron oxide nanoparticles.

In this study, iron-doped tin oxide semiconductor nanoparticles with an iron to tin mole ratio of 0, 1, 2 and 3% synthesized by microwave method. The crystal structure, surface morphology, chemical bonds, and optical properties of the samples were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), infrared fourier transform spectroscopy (FTIR), and UV–Vis spectroscopy. Elements analysis was performed by EDAX. The X-ray diffraction results showed that the samples were polycrystalline, and have the preferred peaks of plates (110), (101), (200), (211), (220), (002), (310), (112), and (301) SnO2 phase with rutile rectangular structure. Increasing the iron impurity density from zero to three percent causes the reducing average size of nanocrystals from 23.53 to 11.03 nm, reducing grain size from 37 to 28 nm, and increasing unit cell volume from 70.61 to 71.40  and the optical band gap from 3.3 to 4.2 eV. The results of FTIR analysis confirm the SnO2 bond in the samples. Investigation of the sensing properties of ethanol gas by the samples showed that the response time of the sensors is in the range of 15.75 to 38.85 s. The sensor made with nanoparticles with a concentration of 1% iron exhibited optimum sensing conditions.

Single-walled carbon nanotubes, as one of the most well-known categories of carbon nanomaterials, have various applications in different fields of science and industry, including photovoltaic applications such as solar cells and additives to increase the strength of composites. In some applications of these nanotubes, it is required to have these compounds in the solution phase. Therefore, choosing the right solvent for dispersing these compounds is very important. In this study, using the quantitative structure-property relationship (QSPR) method, the structure-property of the model is presented. Based on the results, a multiple linear model was obtained including 5 descriptors. The correlation coefficient in the training set, cross-validation and test set were 0.84, 0.91 and 0.92, respectively which indicate the efficiency of model. The possible interactions of the carbon nanotubes -solvent obtained from the proposed structure-dispersion model can be used to select the appropriate solvents for the solution (dispersion) of single-walled carbon nanotubes.

In the current work, reduced graphene oxide/Nano star platinum (rGO/Pt(NS)) nanocomposite is introduced as a novel hole transporting layer (HTL) to replace PEDOT:PSS in polymer solar cells (PSCs). The rGO/Pt(NS) nanocomposite was synthesized by in situ crystallization method, while formic acid and ethylene glycol vapor was used as the  reducing agent. Physical, chemical and electrochemical properties of the rGO/Pt(ns) nanocomposite was evaluated using different characterization techniques including FT-IR, XRD, TEM, EIS, CV and J-V tests. The rGO/Pt(NS) nanocomposite, appeared to have a desirable electrical conductivity  as a hole transporting material. Moreover, the prepared nanocomposite provided charge transfer resistance of 138Ω which was considerably lower than that obtained for PEDOT:PSS (208Ω). Also, by calculating the fermi level of rGO/Pt(NS) composite, it was found that the fermi level of rGO/Pt(ns) composite was in a more suitable place than the PEDOT:PSS. The photovoltaic performance of the rGO/Pt(NS) – based HTL PSCs was compared with those of the PEDOT:PSS – based HTL devices as standard PSCs. Results revealed that the rGO/Pt(NS) based PSCs can provide higher (about 13%) short circuit current (Jsc) and higher (18 %) power conversion efficiency (PCE).

Zeolite Y, MIL-53, and zeolite – MOF nanocomposite were synthesized. Synthesized samples were evaluated using X-ray diffraction, scanning electron microscopy, energy dispersive X-Ray spectroscopy and transmission electron microscopy. The XRD profiles of the zeolite Y /MIL-53 nanoporous coordination polymer nanocomposite depicted diffraction peaks that had been ascribed to individual MIL-53 MOF and zeolite Y. Based on the transmission electron microscopy result of the nanocomposite, it was determined that the compound was synthesized with a core-shell structure. TEM image of the consisted of two regions. One dark region related to Zeolite Y with a diameter of about 500 nm and light part with an average diameter of 60 nm that related to the MIL-53 shell. The EDX spectra of the core@shell sample show that the nanocomposite contained O, C, Al, Na, and Si elements. In this research, disk diffusion method and MIC were used to evaluate the antibacterial activity of prepared samples on gram-negative (E. coli and Pseudomonas aeruginosa) and gram-positive (S. aureus) compared to standard commercial antibiotic disks. Nanocomposite exhibited antibacterial activity with minimal inhibitory concentration of 55 µg/mL against E. coli, Pseudomonas aeruginosa and S. aureus.

The absorbent layer of the heart is a solar cell that plays an important role in its function. In recent years, Cu (In, Ga) Se2 has been highly regarded as an absorbent layer in chalcogenide solar cells. In this research, a cheap, fast and commercially available spray pyrolysis method has been used to make CISe layers. Then, the effect of soaking time of samples in sodium-containing solution on the electrical, optical, structural and morphological properties of the sprayed layers was investigated and the optimal amount of sodium in the structure was introduced. Analyzes performed to evaluate these features include X-ray diffraction pattern (XRD), field emission electron microscopy (FESEM) with elemental analysis (EDS), transmittance spectroscopy (UV-Vis), electrochemical analysis of Mott-Schottky and current-voltage curve measurements in the dark ambient. The results show that the change of soaking time in the solution and consequently the amount of sodium in the structure affects the crystallinity and morphological properties of the layers. The layers resulting from the soaking time of 15 minutes are finer than 5 and 10 minutes and are also porous in the cross-sectional area images. While the best crystallinity and maximum porosity of the mobility (~10-1cm2 / V.s) were obtained for a sample with a soaking time of 10 minutes. Sodium diffusion in the structure changed from ~1019cm-3 to ~1017cm-3. However, the energy levels of the band structure do not change significantly as the soaking time changes. On the other hand, by changing the soaking time of the direct band gap from 1.38 to 1.41 eV has changed. So that the expansion of the band gap with a value of 1.41 eV is visible for the optimal amount of sodium with a soaking time of 10 minutes. In general, according to the results of this study, the CISe:Na layer can be used in various optoelectronic structures by using the optimized amounts of sodium in the structure of the solar cell.

Ag/ZnO magnetic photocatalyst based on Bentonite (Ag/Fe3O4/ZnO/Bentonite) was synthesized by green method and investigated by various techniques: XRD, FT-IR, -EDAXSEM and VSM. To synthesize this nanocomposite, first Zno nanoparticles were synthesized on bentonite substrate by green method in the presence of vulgare extract and then Fe3O4 and Ag nanoparticles were prepared on ZnO/Bentonite. The prepared nanocomposite showed high photocatalytic properties for the decomposition of methylene blue (MB) and Eriochrome Black T (EBT) in the presence of sunlight, and the decomposition kinetics of MB and EBT followed the Langmuir-Hinslowwood model. On the other hand, the decomposition of colors and weight loss of the nanocomposite was very low after five tests, indicating that the synthesized magnetic nanocomposite has a high stability and is easily recoverable.

In this study, carbon was extracted using flaxseed plant waste and activated carbon was obtained by potassium hydroxide. Magnetic Fe 3 O 4 nanoparticles were loaded by in situ method onto activated carbon. Magnetic activated carbon (MGAC) was used to remove the antibiotic Cefixime. The results show that magnetically activated carbon is formed in nanoscale and has a specific surface area of 11.23 m 2 g -1 , which is a desirable and acceptable. Optimization of the important factors in the adsorption of cefixime on magnetic activated carbon was performed by Design Expert 7 software. First, a pre-design was performed using Taguchi method, which showed that the two factors of initial adsorption concentration and contact time had little effect on the adsorption percent, which was omitted. Then, using Box-Beckman method, the effect of three effective factors of pH, adsorbent dose (minimum possible value) and temperature were investigated. Their optimal values were 2, 0.02 g and 85 °C, respectively, which by considering these optimal values, absorption percent of the drug by the adsorbent is equal to 95.33%.