Papers by Keyword: Ag Nanoparticles

Abstract: Urinary tract infection (UTI) is one of the most common types of infection caused by the growth of microorganisms in the human urinary tract. Nitrite, which results from nitrate degradation by microorganisms in disease, is an indicator in diagnosing UTIs. This research aims to determine the synthesis of Ag nanoparticles (AgNPs) using avocado leaf bioreductors (Persea americana Mill.) and carrageenan as a stabilizer that can be used for colorimetric detection of nitrites to minimize the use of dangerous and environmentally unfriendly inorganic materials. Characterization and analysis in this research used a UV-Vis spectrophotometer, FT-IR (Fourier Transform Infra-Red), PSA (Particle Size Analyzer), and SEM (Scanning Electron Microscopy). The AgNPs synthesis process was carried out by varying the bioreductant volume and carrageenan concentration. The optimum volume variation results were obtained at 1:1 with a maximum wavelength of 428 nm and an absorption 1.725. In addition, the optimum concentration of carrageenan was obtained at a concentration of 2.5% with a maximum wavelength of 404 nm and an absorbance of 2.582. The results obtained for AgNPs/carrageenan for colorimetric detection of nitrite showed a color change to purple with a LOD value of 0.2402 µM and LOQ of 0.8013 µM

Abstract: Photocatalysis properties enhanced by metal and organic polymer has been received more interest because of their ability to directly or indirectly degrade pollutants. The effect of PDA (polydopamine) and Ag nanoparticles on the different phases of ZnO to degrade organic dyes under visible and UV-vis light was investigated. ZnO@PDA, ZnO-Ag, and ZnO-Ag@PDA nanoparticles were synthesized. It’s shown that Ag particles with sizes of less than 20 nm were deposited evenly on the ZnO. There were a few changes in the structure of ZnO@PDA or ZnO-Ag @PDA. When the ZnO was coated by PDA, the photocatalytic activity could be enhanced. The photocatalytic activity under UV-vis and visible light of the ZnO@PDA were effectively improved. The degradation rate of ZnO-Ag@PDA was 97.9% under UV-vis light for 20 mins, which was 16.1% higher than that of ZnO. The photocatalytic activity of ZnO-Ag@PDA reached the maximum after polymerizing for 2 hours. The photocatalytic efficiency of ZnO-Ag@PDA-2h under UV-vis for 30 minutes can reach higher than 99.01%. The photocatalytic performance decreased rapidly with the increasing cycles. When the number of cycles was 5, the degradation rate was 65.84%. Afterward, the degradation rate changed small and became stable.

Abstract: Ag nanoparticles (NPs) have been successfully synthesized by the green synthesis method using Moringa oleifera (MO) extract with various incubation times (24 and 48 hours) as an active material for surface plasmon resonance (SPR) biosensor. Transmission electron microscopy analysis indicated the formation of spherical particles with an average crystal size of 29 nm. Selected area electron diffraction confirmed that Ag NPs is face-centered cubic (FCC) crystal structure. Fourier-transform infrared measurements show the band at 3330 cm^-1, 2067 cm^-1, 1634 cm^-1 for an incubation time of 24 hours and 3328 cm^-1, 2063 cm^-1, 1633 cm^-1 for an incubation time of 48 hours. The results prove the proteins and phenolics compound present in the MO extract responsible as reducing agents. The maximum absorption of the green-synthesized Ag NPs in the UV-Vis spectra shows the SPR band at 326 nm and 328 nm for an incubation time of 24 and 48 hours, respectively, and absorption intensity decrease with the increase of incubation time. The result shows the SPR angle shifted to the larger angle of incident light by using green-synthesized Ag NPs. However, the increased incubation time affects the angle shift to the lower angle of the SPR shift. The addition of the green-synthesized Ag NPs leads to enhance the sensitivity of the SPR biosensor.

Abstract: Smart packaging becomes more popular as it increases the safety of food consumption by monitoring a packaged food state and informing the customer about it, for example, by visual reaction of a special label on its surface. Nanomaterials can provide the needed functionality to such labels. Application of ink compositions containing silver nanoparticles on paper materials by screen printing is quite promising. A special ink composition was developed based on Ag nanoparticles that possess changeable photoluminescence properties in contact with compounds that indicate food decay. The possibility of application of this ink onto the surface of paper-based materials via screen printing was studied. The influence of ink layer thickness, characteristics of paper materials (degree of sizing, content of optical brighteners), and content of the fluorescent component in the ink composition on photoluminescence properties of printed labels for smart packaging was investigated. It was determined how to choose proper values of these technological parameters in order to obtain high luminescence intensity and predetermined luminescence color of printed labels using the developed nanophotonic inks. The results of the study allow industrial production of functional labels for smart packaging with nanophotonic elements with the needed optical (photoluminescence) characteristics, as well as for protecting packaging from counterfeiting.

Abstract: Herein, Ag-anatase photocatalysts were synthesized though chemical reduction method under room temperature by using PVP and NaBH₄ as stabilizer and strong reducing agent, respectively. The prepared photocatalysts were characterized by the following technique: XRD, SEM, HR-TEM, EDX, and UV-Vis-NIR. The photocatalytic performance of 0.05 g of photocatalysts were performed under UV irradiation within 1 h by using 10 mg/L of rhodamine B as the representative of organic pollutant. The results demonstrated that the optimum Ag loading contents were 2 %wt (2-ST) which can degrade rhodamine B up to 98.54%. Therefore, the photocatalytic performance of bare anatase could be enhanced by deposited Ag nanoparticles. Further, this prepared Ag-anatase could be suitable for environmental application.

Abstract: In the present study, an application of Ag nanoparticles (AgNPs) in order to obtain Surface-enhanced Raman spectroscopy (SERS) of disperse dyes on single cotton fiber is presented. In detail, we prepared colloid Ag by use of citrate reduction method. Add one drop of the colloid on single colored fiber and then Raman spectra recorded with excitation wavelength at 785 nm were carried out on a Renishaw Raman spectrometer coupled to a 20x object lens. Cotton fibers dyed by disperse red 17 (DR17) and disperse blue 35 (DB35) are characterized and analyzed. This method was found out to be an effectively way to identify both DR17 and DB35 on single cotton fibers. Furthermore, SERS expands methods for identification disperse dyes on fibers, and provide a good method for verify colored cotton fibers.

Abstract: The present study involves preparation of Ag nanoparticles (Ag NPs) deposited on non-woven fabrics by a two-step method including the chemical precipitation of Ag₂O nanoparticles on the fabrics followed by in situ reducing of the precursor into Ag NPs by different reductive processes including chemical reduction, photo-reduction and dielectric barrier discharge (DBD) cold plasma treatment. The morphology as well as the antibacterial efficiency of the Ag NPs deposited on non-woven fabrics are also evaluated. The Ag NPs-modified fabrics prepared by DBD plasma treatment exhibit significant antibacterial properties against both Escherichia coli and Staphylococcus aureus, and accordingly have potential applications in the healthcare and medicine fields.

Abstract: In this work, tungsten oxide (WO₃) nanofibers were synthesized using electrospinning technique. Direct current electrophoretic deposition (DC-EPD) was conducted to deposit the nanofibers onto fluorine-doped tin oxide (FTO) electrodes. The photoelectrochemical performance of WO₃ nanostructured electrodes was investigated and compared between the samples containing pristine WO₃ and Ag/WO₃ composite nanofibers. An up-to-6-fold enhancement in photoconversion efficiency (PCE) was obtained from Ag/WO₃ composite nanofiber photoanode.

Abstract: We report the structural, bioactivity and antibacterial effect of silver nanoparticle embedded calcium borosilicate ceramics obtained by a simple sol-gel route and post annealing approach. The structural properties were studied by means of powder X-ray diffraction (XRD), UV-visible, Fourier transform infrared (FTIR) and transmission electron microscopy (TEM). The glass-ceramic nature of the sample was confirmed by XRD and FTIR. TEM and UV spectrum reveal the Ag nanoparticle embedment on amorphous matrix. The hydroxyapatite layer formation is investigated by in-vitro approach using Dulbecco’s Modified Eagle’s Medium. The antibacterial effects were tested with different bacteria using an agar well diffusion method. Samples show good antibacterial effect without compromising the formation of hydroxyapatite.

Abstract: In this research, we focused on silver (Ag) nanoparticles that exhibit various colors on the basis of their localized surface plasmon resonance (LSPR). The effects of step-voltage parameters on the coloration of the Ag deposition-based electrochromic device were investigated. Further, we report the use of reduced graphene oxide (RGO)/biaxially oriented polypropylene (BOPP) as the transparent conductive electrode. RGO was synthesized directly from graphite under a microwave heating system. BOPP film was coated with RGO by drop-casting method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), electrical resistance measurements and cyclic voltammetry (CV). The SEM and TEM images exist as typical wrinkled structure, folded region, transparent, indicating these layers are exfoliated to a very large extent. Our results primarily indicate that the novel BOPP/RGO/Ag/RGO/BOPP configuration presents an easy and expeditious way of preparing the voltage-tunable multicolor electrochromic device. The electrochromic device can be switched from the transparent state to the black state and yellow state.