جستجوی مقالات مرتبط با کلیدواژه "نانوذرات نقره" در نشریات گروه "شیمی"

In recent decades, silver nanoparticles have gained significant attention from researchers due to their antibacterial properties. Silver nanoparticles can be effective in combating bacterial infections by disrupting the bacterial cell walls and interfering with their biological processes. There are various methods for synthesis of silver nanoparticles, which have advantages and disadvantages. In recent years, green synthesis of silver nanoparticles has been increasingly studied due to its reduced harmful environmental effect, safety, and other benefits. The current research was carried out with the aim of introducing the most appropriate green synthesis method for the preparation of silver nanoparticles with antibacterial properties. The results show that the antibacterial activity of silver nanoparticles synthesized with microorganisms is greater than silver nanoparticles synthesized with plant extracts. Furthermore, studies show that the antibacterial properties of silver nanoparticles depend on the physical and chemical characteristics of the bacterial cell wall. In this regard, the antibacterial effect of silver nanoparticles on Gram-negative bacteria is grater than on Gram-positive bacteria.

In this study, silver nanoparticles (Ag-NPs) as catalysts in the photocatalytic degradation reaction of Sunset Yellow FCF (SYF) azo dye in aqueous solution were investigated. Ag-NPs were prepared by using walnut (Juglans regia L.) leaf extract. The synthesis of Ag-NPs has been done using green chemistry, which is an environmentally friendly, low-cost, fast, and safe method. Extraction was done with a facile method, as well as the synthesis of Ag-NPs in a short period and with high efficiency. The Ag-NPs were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDS), X-Ray Diffraction (XRD), and Fourier Transform InfraRed (FT-IR) spectroscopy. Optimum conditions for dye degradation were determined using Taguchi experimental design method with (L9(34)) orthogonal array. Analysis of the response of each experiment was based Signal to Noise (S/NL) ratio calculated. The effects of operational parameters such as catalyst amount, pH, irradiation time, and temperature in three levels for each factor were studied. The Taguchi results showed that catalyst amount= 20 mg/l (level 2), pH= 4 (level 1), irradiation time = 45 min. (level 3) and temperature= 30 °C (level 3) was the optimum conditions for this process. The most influence of each factor on the process was determined using the Analysis of Variance (ANOVA) method. The most significant factor in this process was pH. The interaction between pH×catalyst amount was the most influencing interaction. The analysis of primary ANOVA showed that percent (p(%)) parameters were: catalyst amount (12.002%), pH (46.298%), irradiation time (35.311%), and temperature (6.383%). The contribution of factors in this process was found to be in the following order: catalyst amount (0.142), pH (0.431), irradiation time (0.397), and temperature (0.18). A pseudo-first-order kinetic reaction with rate constant k=0.0721 min−1 was observed for dye photocatalytic degradation.

Plasma printing techniques are being developed as a modern approach for depositing different functional materials. In this work, a nonthermal plasma jet working in atmospheric pressure was employed to print silver nanoparticles on flexible polyester fabric substrates. Atomized droplets of silver nitrate solution were exposed to plasma reducing them to silver nanoparticles, which were printed on the substrates in a controlled condition. X-ray diffraction results confirmed the deposition of face-center cubic nanoparticles on the substrates. Field-enhanced electron scanning microscopy images demonstrated that these nanoparticles have an almost spherical shape. Surface-enhanced Raman scattering (SERS) responses of the coated substrates were investigated using a Raman marker of Rhodamine B. SERS performance for coated fabrics printed in various precursor concentrations and printing durations was investigated. The best performance corresponded to the fabric printed with a precursor of 24mM concentration and a printing time of 5min. Finally, Ag-printed fabrics were used to detect sulfite remainders of SO2-treated raisins showing promising potential in trace analysis.

Many researchers have reported the synthesis of metal nanoparticles by plant extracts and their potential applications. Cherry tree leaf extract is one of the effective materials in the synthesis of AgNPs, which is confirmed by the results of FTIR analysis. Did AgNPs according to the design of the experiment carried out by the Mixture Design method by mixing three regenerating substances (cherry tree leaves 0-3 ml), basic salt substance (1 mM solution of AgNO3 5-9 ml) and stabilizing agent (AloeVera gel) (0-1 ml) was synthesized by green method. After the optimization, the results showed that the amounts of 2.51, 5.79 and 0.69 mL respectively for reducing agent, basic solution and stabilizing agent were the most suitable mode of synthesis of nanoparticles, and in this mode, the highest concentration of 16.88 ppm, the lowest average particle size of 36 nm, the most appropriate PDI of 0.43 and the highest zeta potential of 25 mV will be obtained. The properties of synthesized AgNPs were evaluated in optimal conditions and the results of UV-Vis and DLS analyzes confirmed the obtained results with slight differences. AgNPs showed good antioxidant properties of 28.45% and antibacterial properties against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Antifungal properties were also found to be 65.55%.

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.

The aim of this study was to develop a cheap, selective, sensitive and practical method for detecting melamine in raw milk samples. Tris-dithiocarbamate was prepared by the reaction of 2-amino-2-hydroxy-propane-1,3-diol (tris base), as a cheap and available base, with carbon disulfide. Due to the presence of the dithiocarbamate together with the hydroxyl functional groups, there is a strong tendency to interact with melamine. Electron donor-electron acceptor interaction between melamine and tris-dithiocarbamate on the surface of silver nanoparticles leads to the aggregation of silver nanoparticles, which causes the absorption wavelength of nanoparticles to shift to higher wavelengths and the color of the solution changes from bright yellow to red. This color change has been recorded and measured using ultraviolet-visible (UV-Vis) spectroscopy. This method can be used to quickly measure the small amount of melamine in pasteurized milk samples. The detection limit of the method is 0.7 µM, and the sensor is completely selective towards melamine. The linear range of the method is 2 µM -12 µM, which is competitive with many similar methods reported.

In this paper, a direct deposition method was used to print graphene oxide/silver (GO/Ag) nanocomposites from silver nitrate and graphene oxide suspension with reduction using a non-thermal plasma jet. Aerosol droplets of the solution were reduced to GO/Ag nanocomposite in the plasma and deposited on the substrate. The hybrid materials were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy and Raman spectroscopy. The XRD results showed that the face centered cubic phase of Ag nanoparticles were developed in crystalline planes. The FESEM images confirmed that graphene oxide surfaces were decorated by Ag nanoparticles. The EDS analysis demonstrated that Ag was introduced on GO surface successfully via the plasma jet. GO exhibited distinctive Raman scattering for its D and G band, which were at 1355cm-1 and 1590cm-1, respectively, but they were weak for sensitive quantification purpose. By deposition silver nanoparticles on the surface of graphene oxide Both D and G bands of GO get enhanced.

Amyloid aggregations are the major biomarkers of various chronic diseases. Currently, one of the most common tests for in-vitro quantification of amyloid fibrillation kinetics is Thioflavin T assay, which is based on the flurescence emission of Thioflavin T. Inspite of its helpfulness, still has some drawbacks, and hence, introducing other tests to confirm its results is indispensible. Herein, we used Z-scan method to find the nonlinear refractive indices of silver nano particles at various concentrations. According to the results, silver nano particles altered the order of the aggregations from 10-10 to 10-9 such way that the magnitude of the nonlinear refractive indices and the florescence intensities increased and decreased, respectively with increment in the concentrations. Having the maximum diminution in the fluorescence intensity and the and the largest magnitude of nonlinear refractive index, 0.24 μg/ml was recorded as the optimal concentration. Therefore, the results of Thioflavin T and Z-scan, aligned perfectly with each other in a way that the more the concentrations of the silver nano particles were, the more the magnitude of the nonlinear refractive indices, and the more decrement in the fluorescence intensities, and thus, silver nano particles can wipe out the aggregations, which is quantitatively measurable.

The nano silver particles has been attractive the large number of researchers. These properties are due to the very high volume ratio of these particles. Although there are different methods have been offered for the synthesis of nano particles of silver but the chemical recovery method because of the simplicity and ability to control and particle's size is the most common methods to product nano particles. In this research the effect of silver disinfection in water has been investigated. The silver particles are produced with using silver nitrate and sodium citrate and then the polyamide is coated on the polymer and used as absorbent filter. Morphology was determined by absorbing the surface and the shape and size of nano particles with an electron microscope and also it the same about the present of silver in the polymer after coating with an X-ray diffraction device (EDAX). The nutrient agar is used for investigate of the effect of nano silver disinfection in water pollution (Escherichia coli) from the general culture medium and also the effects of changing of power hydrogen (pH) temperatures and duration of contact required for disinfection water studied.

A novel kind of AgNPs-MWCNTs/TiO2 nanotubes/Ti electrocatalyst for the electrocatalytic oxidation of glycerol was fabricated via electrodeposition of Ag nanoparticles and functionalized multi walled carbon nanotubes on previously formed TiO2 nanotubes/Ti electrode. The morphology studies showed that AgNPs-MWCNTs nanocomposites have dendritic structures, where Ag nanoparticles are uniformly dispersed on the surface of MWCNTs. Electrochemical investigation exhibited that the AgNPs-MWCNTs/TiO2NTs/Ti show much higher peak current density and lower charge transfer resistance towards the glycerol oxidation than AgNPs/TiO2NTs/Ti electrode, indicating good electrocatalytic performance and kinetic reversibility of the AgNPs-MWCNTs/TiO2NTs/Ti electrocatalysts. The improved electrocatalytic activity of modified electrode is originated from the synergetic effect of AgNPs-MWCNTs, the unique nanostructure and large surface area which can provide more active sites to catalyze the glycerol oxidation.

Biological synthesis of nanoparticles (NPs) has attracted recent attention of many researchers due to higher biocompatibility and eco-friendly properties compared to other methods. Possess the coating of biomolecules on the surface of these NPs makes them proper for application in different fields such as biomedical and pharmaceutical sciences and also textile and cosmetic industries. In this research, the biosynthesis of Ag NPs using Trifolium resupinatum and Trigonella foenum-graecum secreted extract during seed germination stage under cold treatment and its bactericidal properties has been reported for the first time. UV-vis spectrophotometry, XRD, FESEM and DLS were used to confirm the Ag NPs formation and characterization. FTIR results revealed the functional groups of the extracts responsible for the process and Disc diffusion method was used for antibacterial properties of the biosynthesized Ag NPs. The results showed that the cold treatment produced multidimensional Ag NPs with smaller size and higher antibacterial activities. The Ag NPs biosynthesized using cold treated seed extracts of T. resupinatum revealed the smallest size (9.25 nm) and the most antibacterial properties with a zone of inhibition about 10.83 nm.

Today, nanoparticles include a wide range of particles with unique properties. Due to their small size and unique properties, these particles can be used in various sciences. Nanoscale biological compounds have unique physical-chemical properties that are In recent years, recently, the efficacy of antimicrobial nanoparticles, especially silver nanoparticles and their antimicrobial activity, has been the focus of researchers and researches have been conducted. In this study, recent advances and research results of researchers in the use of antibacterial and antiseptic properties of silver nanoparticles, silver and silver composites have been reviewed.The search was done on SID and Google Scholar sites. We did not have a time limit for the search, and all the articles that met the entry criteria were included in the study until March 2018. Among the articles found, some of the articles with the conditions including the complete article have antibacterial and anti-infective properties. 10 articles were evaluated. All the articles have anti-bacterial and anti-infective properties of Silver nanoparticles, silver and silver composites have been in different levels.

In this work, the effect of alkali and alkaline earth cations on modified silver nanoparticles AgNPs was investigated. The nanoparticles were used as a simple and low-cost colorimetric sensor for detecting alkaline earth metal cation. The determination process was based on the surface plasmon resonance properties of AgNPs. Interaction of AgNPs with alkaline earth metal cations in the presence of cysteine molecules induced a red shift in the surface plasmon resonance SPR maximum of AgNPs, as a result of nanoparticles aggregation. Consequently, yellow color of AgNPs solution was changed to pink. The examined cations were consisted of Mg2 , Ca2 and Ba2 . The calibration curve was obtained for each cation. Limit of detection, linear range and sensitivity of each cation was obtained and compared. The best detection limit and sensitivity were observed for Ba2 ions. Thus, this method was applied to the determination of barium ions in aqueous samples. In order to eliminate the interferences due to the presence of other cations, all measurements were carried out at pH 7 and in the presence of appropriate amounts of EDTA as masking agent.

Today, the use of medicinal plants has been considered by the researchers due to the reduction of side effects. Syrian rue has long been used to disinfect. The aim of this study was to investigate the effect of silver nanoparticles on the antimicrobial activity of Syrian rue against E. coli. First, silver nanoparticles were prepared by a new green method and then used to produce silver nanoparticles/Syrian rue extract composite. Antibacterial process was performed using diffusion method on Mullerinton medium. Due to the lack of growth around the discs, which shows the antagonistic effects of silver nanoparticles and the extract of Syrian rue, the antimicrobial activity of the nanocomposite is higher than that of each of the silver nanoparticles and Syrian rue plant separately.

An efficient, simple and green procedure has been developed for the synthesis of tetrahydrobenzo[b]pyran deravitives via the condensation one-pot and three-component of aldehydes, malononitrile and 5,5-dimethyl-1,3-cyclohexandione or 1,3-cyclohexandione in present heterogeneous catalysts silica-supported antimony(III)chloride (SbCl3/SiO2) and nano catalyst CdO under condition reflux in Ethanol. The advantages this method can be presented to the use of catalysts cheap, accessible, simple separation products, improve the efficiency of products, the use of solvents that are relatively less environmental pollution, an easy way to recyclability and reused catalyst. Also, in present work, (2A-3C-4P-5O-TBP) was used as a platform for dispersion and immobilization of AgNPs on the glassy carbon electrode. The functional groups at (2A-3C-4P-5O-TBP) have effective interaction with silver ions and cause to electrochemical immobilization of AgNPs on the electrode surface. The surface of electrode was investigated by scanning electron microscopy (SEM) and the results showed good distribution of AgNPs on the electrode surface modified with (2A-3C-4P-5O-TBP).

In this research, biosynthesis of Ag nanoparticle investigated using Urtica extract. Different parameter such as temperature, pH, time and concentration of Ag salt optimize for this goal. Synthesized nanoparticle characterized by Uv-vis, XRD and TEM methods. Results show Ag nanoparticle synthesized in the size of 10 nm. In continuous, Ag nanoparticle was used for preparation of modified carbon paste electrode. And its effect investigated on electron exchange system for K4[Fe(CN6)] as a standard system. The obtained result shows that synthesized nanoparticle can be improved electrical conductivity of electron exchange in electrochemical systems.