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10 result(s) for "Tajabadi, Fariba"
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Chemically-stable flexible transparent electrode: gold-electrodeposited on embedded silver nanowires
Silver nanowires (AgNWs) with a low diameter, high aspect ratio, stable suspension, and easy synthesis have recently attracted the optoelectronic industry as a low-cost alternative to indium tin oxide transparent conductive films. However, silver nanowires are not chemically stable, and their conductivity diminishes over time due to reactions with atmospheric components. This is a bottleneck for their wide industrial applications. In this study, we aim to address this issue by synthesizing silver nanowires with an average diameter of approximately 65 nm and a length of approximately 13 µm. The prepared Ag nanowires are then applied to fabricate transparent, flexible, and chemically stable conductive films. The fabrication includes spraying of silver nanowires suspension on a glass substrate followed by Dr. blade coating of polystyrene (PS) solution and delamination of the PS-AgNWs film. The resulting film exhibits an optimum sheet resistance of 24 Ω/□ and transmittance of 84%. To further enhance the stability of the transparent conductive film, the facial and scalable double pulse electrodeposition method is used for coating of gold on the exposed surface of the AgNWs embedded in PS. The final transparent film with gold coating demonstrates a remarkable stability under harsh conditions including long exposure to UV light and nitric acid solution. After 100 min of UV/Ozone treatment, the increase in sheet resistance of the optimal PS-AgNW@Au sample is 15.6 times lower than the samples without gold coating. In addition, the change in sheet resistance after 2000 bending cycles in the optimal PS-AgNW@Au electrode is measured and it showed an increase of only 22% of its initial sheet resistance indicating its good flexibility. The proposed electrode performs an excellent chemical stability, good conductivity, transparency, and flexibility that makes it a potential candidate for various optoelectronic devices.
Effect of transparent substrate on properties of CuInSe2 thin films prepared by chemical spray pyrolysis
In this paper, the properties of CuInSe 2 (CISe) films deposited on three transparent substrates (FTO, FTO/NiO x , FTO/MoO 3 ) are studied. These substrates might be used for bifacial solar cells, in place of the conventional glass/Mo substrates. CISe layers are deposited by spray pyrolysis followed by a selenization process. For the same deposition conditions, the CISe layers on FTO show the largest grain size (~ 0.50 µm) and crystallinity, while FTO/MoO 3 substrates result in the smallest grains (~ 0.15 µm). The optical bandgap of the CISe films ranged from 1.35 eV for FTO substrate to 1.44 eV for FTO/MoO 3 substrate. All films show p-type conductivity, with the carrier densities of 1.6 × 10 17  cm −3 , 5.4 × 10 17  cm −3 , and 2.4 × 10 19  cm −3 for FTO, FTO/NiO x , and FTO/MoO 3 substrates, respectively. The CISe films also show different conduction, and valence levels, based on the substrate. In all cases, an ohmic behavior is observed between the CISe and substrate. The results demonstrate that CISe layer crystallinity, carrier concentration, mobility, and energy levels are strongly dependent on the chemical nature of the substrate. Bare FTO shows the most appropriate performance in terms of device requirements.
Investigation of precursors concentration in spray solution on the optoelectronic properties of CuInSe2 thin films deposited by spray pyrolysis method
Copper indium selenide CuInSe 2 (CISe) thin films were deposited by chemical spray pyrolysis (CSP) method of CuInS 2 (CIS) and subsequent selenization process. To study the effects of solution concentration, we prepared different precursors solution of CIS including different amount of indium salts from 0.025 to 0.100 M with In/Cu 1.25 and S/In 4. These results propose that solution concentration is critical for inflecting the morphological, optical, electrical, and electrochemical characteristics of solution-processed CISe films and device performance. The studied morphological properties of deposited samples were homogenous, crack-free with large grains in indium salt concentrations more than 0.075 M. The deposited film thickness depends on the spray precursor concentration and increases for higher concentration. In addition with increasing of indium precursor concentration from 0.025 to 0.100 M in spray solution, the optical bandgap of deposited film decreases from 1.40 to 1.35 eV. Also the films mobility and carrier density were notably influenced by any change in the solution concentration. Electrical and electrochemical properties showed a decrease in carrier density from ~ 10 20 to ~ 10 17  cm −3 and the increase in mobility of order ~ 10 –7 to ~ 10 –2 cm 2 /V s, respectively, for 0.025 M, 0.100 M CISe films. All films exhibited p-type conductivity owing to different concentrations. However, it seems that the concentration of the ideal solution is 0.100 molars.
The Role of Mixed Reaction Promoters in Polyol Synthesis of High Aspect Ratio Ag Nanowires for Transparent Conducting Electrodes
In recent years, thin silver nanowires (Ag NWs) with diameters smaller than 150 nm have been synthesized by implementation of NaCl or FeCl3 as reaction promoters and high molecular weight polyvinylpyrrolidone (PVP) as the capping agent. However, the yield of Ag NWs still remains low, mostly due to the insufficient aspect ratio (AR) of the synthesized nanostructures and the production of Ag nanoparticles, which is an undesirable by product. This study proposes a modified technique to alleviate the problem by using a mixture of FeCl3/CuCl2 as the reaction promoter and two different types of PVP with molecular weight of 360 k and 40 k as the capping agents. The appropriate mixtures of FeCl3/CuCl2 (molar ratio of 1.48:1.45) and PVP 360 k/40 k (molar ratio of 2:1) allow for the rapid synthesis of NWs with diameter of about 110 nm and length of up to 50 μm. It is revealed that the ARs of the synthesized NWs are much greater. The NWs are then used for the fabrication of transparent conductive films (TCFs). The obtained TCF prepared by a scalable, in-house, and cost-efficient spray apparatus possesses a transmittance of 91%, sheet resistance of 10 Ω/sq, and optical haze value of 6.6%. In fact, the AR of the NWs is increased as much as 1135%, and further the figure␣of merit of the TCFs is improved by as much as 2785%.
Optimum Thermal Concentration of Solar Thermoelectric Generators (STEG) in Realistic Meteorological Condition
Global warming and air pollution concerns make renewable energies inevitable. Thermoelectric (TE) generators—solid-state devices which can convert thermal energy into electricity—are one of the candidates to capture the energy of the sun’s rays. Impact of high thermal on flat panel Solar Thermoelectric Generator (STEG) performance is known. In this research, a method to optimize thermal concentration in realistic terrestrial condition is introduced. To this end, a Simulink model of the STEG was developed, and module performance curves are determined. According to the results, Thermal concentration in realistic condition is more than double, compared to standard condition. The efficiency of the STEG was 4.5%, 6.8%, and 7.7% when the module figure of merit (ZT) was set to 0.8, 1.2, and 1.5, respectively, in locations with a higher ratio of diffused radiation (e.g., Aalborg and Denmark). These values corresponded to 70%, 106%, and 121% of the electrical power produced by parabolic troughs under the same meteorological condition. Furthermore, the possibility of controlling the ratio of heat and electricity in the cogeneration system is possible by controlling the heating flow or electric current. Heating flow can be controlled by the electrical current in STEG over 17 percent of its value in optimum condition.
Highly sensitive electrochemical sensor based on carbon paste electrode modified with graphene nanoribbon–CoFe2O4@NiO and ionic liquid for azithromycin antibiotic monitoring in biological and pharmaceutical samples
In this report, Azithromycin (Azi) antibiotic was measured by carbon paste electrode (CPE) improved by graphene nanoribbon–CoFe2O4@NiO nanocomposite and 1-hexyl-3 methylimidazolium hexafluorophosphate (HMIM PF6) as an ionic liquid binder. The electrochemical behavior of Azi on the graphene nanoribbon–CoFe2O4@NiO/HMIM PF6/CPE is investigated by voltammetric methods, and the results showed that the modifiers improve the conductivity and electrochemical activity of the CPE. According to obtained data, the electrochemical behavior of Azi is related to pH. under optimum conditions, the sensor has linear ranges from 10 µM to 2 mM with a LOD of 0.66 µM. The effect of scan rate and chronoamperometry were studied, which showed that the Azi electro-oxidation is diffusion controlled with the diffusion coefficient of 9.22 × 10–6 cm2/s. The reproducibility (3.15%), repeatability (2.5%), selectivity, and stability (for 30 days) tests were investigated, which results were acceptable. The actual sample analysis confirmed that the proposed sensor is an appropriate electrochemical tool for Azi determination in urine and Azi capsule.
Stable dye-sensitized solar cells based on a gel electrolyte with ethyl cellulose as the gelator
A simple gelating process is developed for the conventional acetonitrile-based electrolyte of dye solar cells, based on ethyl cellulose as the gelator. The electrolyte becomes quasi-solid-state upon addition of an ethanolic solution of ethyl cellulose to the conventional acetonitrile-based liquid electrolyte. The photovoltaic conversion efficiency with the new gel electrolyte is only slightly lower than with the liquid electrolyte, e.g., 6.5 % for liquid electrolyte versus 5.9 % for gel electrolyte with 5.8 wt% added ethyl cellulose. Electrolyte gelation has small effect on the ionic diffusion coefficient of iodide, and the devices are remarkably stable for at least 550 h under irradiation at 55 °C.
Effect of transparent substrate on properties of CuInSe 2 thin films prepared by chemical spray pyrolysis
In this paper, the properties of CuInSe (CISe) films deposited on three transparent substrates (FTO, FTO/NiO , FTO/MoO ) are studied. These substrates might be used for bifacial solar cells, in place of the conventional glass/Mo substrates. CISe layers are deposited by spray pyrolysis followed by a selenization process. For the same deposition conditions, the CISe layers on FTO show the largest grain size (~ 0.50 µm) and crystallinity, while FTO/MoO substrates result in the smallest grains (~ 0.15 µm). The optical bandgap of the CISe films ranged from 1.35 eV for FTO substrate to 1.44 eV for FTO/MoO substrate. All films show p-type conductivity, with the carrier densities of 1.6 × 10  cm , 5.4 × 10  cm , and 2.4 × 10  cm for FTO, FTO/NiO , and FTO/MoO substrates, respectively. The CISe films also show different conduction, and valence levels, based on the substrate. In all cases, an ohmic behavior is observed between the CISe and substrate. The results demonstrate that CISe layer crystallinity, carrier concentration, mobility, and energy levels are strongly dependent on the chemical nature of the substrate. Bare FTO shows the most appropriate performance in terms of device requirements.
The effects of probiotic supplementation on metabolic status in type 2 diabetic patients with coronary heart disease
Background This study was conducted to evaluate the effects of probiotic supplementation on metabolic profiles in diabetic patients with coronary heart disease (CHD). Methods This randomized, double-blind, placebo-controlled trial was performed among 60 diabetic patients with CHD, aged 40–85 years at a cardiology clinic in Kashan, Iran, from October 2017 through January 2018. Patients were randomly divided into two groups to take either probiotic supplements (n = 30) or placebo (n = 30) for 12 weeks. Fasting blood samples were taken at the beginning of the study and after the 12-week intervention to determine related markers. Results After 12-week intervention, probiotic supplementation significantly decreased fasting plasma glucose (β − 20.02 mg/dL; 95% CI − 33.86, − 6.17; P  = 0.005), insulin (β − 2.09 µIU/mL; 95% CI − 3.77, − 0.41; P  = 0.01), insulin resistance (β − 0.50; 95% CI − 0.96, − 0.03; P  = 0.03) and total-/HDL-cholesterol ratio (β − 0.27; 95% CI − 0.52, − 0.03; P  = 0.02), and significantly increased insulin sensitivity (β 0.008; 95% CI 0.001, 0.01; P  = 0.02) and HDL-cholesterol levels (β 2.52 mg/dL; 95% CI 0.04, 5.00; P  = 0.04) compared with the placebo. Moreover, probiotic supplementation led to a significant reduction in serum high sensitivity C-reactive protein (β − 0.88 mg/L; 95% CI − 1.39, − 0.38; P  = 0.001), and a significant elevation in total antioxidant capacity (β 108.44 mmol/L; 95% CI 47.61, 169.27; P  = 0.001) and total glutathione levels (β 45.15 µmol/L; 95% CI 5.82, 84.47; P  = 0.02) compared with the placebo. Probiotic supplementation did not affect other metabolic profiles. Conclusions Overall, we found that probiotic supplementation for 12 weeks had beneficial effects on glycemic control, HDL-cholesterol, total-/HDL-cholesterol ratio, biomarkers of inflammation and oxidative stress in diabetic patients with CHD. Trial registration Clinical trial registration number http://www.irct.ir : IRCT2017082733941N5
The Effects of Synbiotic Supplementation on Carotid Intima-Media Thickness, Biomarkers of Inflammation, and Oxidative Stress in People with Overweight, Diabetes, and Coronary Heart Disease: a Randomized, Double-Blind, Placebo-Controlled Trial
Synbiotics are known to exert multiple beneficial effects, including anti-inflammatory and antioxidant actions. The aim of this study was to evaluate the effects of synbiotic supplementation on carotid intima-media thickness (CIMT), biomarkers of inflammation, and oxidative stress in people with overweight, diabetes, and coronary heart disease (CHD). This randomized, double-blind, placebo-controlled trial was conducted and involved 60 people with overweight, diabetes, and CHD, aged 50–85 years old. Participants were randomly allocated into two groups to take either synbiotic supplements containing three probiotic bacteria spices Lactobacillus acidophilus strain T16 (IBRC-M10785), Lactobacillus casei strain T2 (IBRC-M10783), and Bifidobacterium bifidum strain T1 (IBRC-M10771) (2 × 10 9  CFU/g each) plus 800 mg inulin or placebo ( n  = 30 each group) for 12 weeks. Fasting blood samples were taken at baseline and after the 12-week intervention period to determine metabolic variables. After the 12-week intervention, compared with the placebo, synbiotic supplementation significantly reduced serum high-sensitivity C-reactive protein (hs-CRP) (− 3101.7 ± 5109.1 vs. − 6.2 ± 3163.6 ng/mL, P  = 0.02), plasma malondialdehyde (MDA) (− 0.6 ± 1.0 vs. − 0.1 ± 0.3 μmol/L, P  = 0.01), and significantly increased nitric oxide (NO) levels (+ 7.8 ± 10.3 vs. − 3.6 ± 6.9 μmol/L, P  < 0.001). We did not observe any significant changes of synbiotic supplementation on other biomarkers of oxidative stress and CIMT levels. Overall, synbiotic supplementation for 12 weeks among people with overweight, diabetes, and CHD had beneficial effects on serum hs-CRP, plasma NO, and MDA levels; however, it did not have any effect on other biomarkers of oxidative stress and CIMT levels.