Sharif Digital Repository

The development of cheaper electrocatalysts for fuel cells is an important research area. This work proposes a new, simpler and low-cost approach to develop nanostructured silver electrocatalysts by using natural cellulose as a template. Silver was deposited by reduction of Ag complexes on the surface of cellulose fibers, followed by heat removal of the template to create self-standing nanostructured silver fibers (NSSFs). X-Ray diffraction (XRD) showed fcc silver phase and X-Ray photoelectron spectroscopy (XPS) demonstrated that the surface was partially oxidized. The morphology of the fibers consisted of 50 nm nanoparticles as the building blocks, and they possessed a specific surface area... 

Laser assisted drug release from a synthesized plain polymer composed of poly (butyl methacrylate-co-acrylamide-co-methacrylic acid) [P(BMA-co-AAm-co-MAA)] and a metallo-polymer composed of silver nanoparticles (Ag NPs) grafted plain polymer (the nanocomposite) were studied to investigate their capability to serve as drug carriers. Positive temperature dependent swelling changes were observed for both carriers and their thermal sensitivity and thermal and optical switching properties were investigated in two buffered solutions. An acidic solution with pH = 1.2 to simulate stomach body condition and a neutral solution with pH = 7.4 to simulate intestine condition. Reversible phase transition... 

Herein, a novel quaternary Ag3PO4/BiPO4@MIL-88B(Fe)@g-C3N4 (AB@MIL-88B(Fe)@g-CN) nanocomposite with a core@shell structure is successfully fabricated in two simple steps. The prepared samples are characterized via various techniques. The photocatalytic activity of the prepared samples is evaluated by the degradation of navy Acid Blue 92 (AB92) dye as an organic pollutant under visible light irradiation. Highly enhanced photocatalytic efficiency is observed for the quaternary AB@MIL-88B(Fe)@g-CN nanocomposite compared to that for the other samples. The experimental results indicate that the photocatalytic activity enhancement is mainly attributed to the strong visible light absorption and... 

A composite coating containing silver, fluoride and hydroxyapatite (Ag-FHA) was developed on titanium substrate by sol-gel method. Triethylphosphite, hydrated calcium nitrate, ammonium fluoride and silver nitrate were used respectively, as P, Ca, F and Ag precursors with a Ca:P ratio 1.67 and concentration of silver was 0.3 wt%. Coatings were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and atomic absorption spectrometry (AAS). Potentiodynamic polarization measurements in simulated body fluid proved corrosion protection caused by both Ag-FHA coatings. Antibacterial activity of coatings against... 

A long-term antibacterial activity of implants without compromising their biocompatibility is highly desirable to minimize the biomaterial-associated infections. Although tantalum oxide nanotubes (Ta2O5 NTs) are promising coating materials for orthodontics and orthopedics applications, their insufficient antibacterial activity retains vulnerability to post-implantation infections. This study aimed to endow antibacterial characteristics to the Ta2O5 NTs-coated Ti6Al4V substrates by decoration of silver oxide nanoparticles (Ag2O NPs). The well-adherent Ta2O5 NTs were grown via anodization of a pure tantalum (Ta) layer coated by physical vapor deposition (PVD) on the Ti6Al4V substrates. The... 

The nanotubular arrays of titanium dioxide (TiO2 NTs) have recently received considerable interest for fabrication of dental and orthopedic implants. However, their antibacterial activity requires substantial improvement for the potential infections minimization, without compromise of their biocompatibility. In this work, TiO2 NTs were developed on Ti6Al4V substrates via anodization at a constant potential of 60 V for 60 min, followed by heat treatment at 500 °C for 90 min. Physical vapor deposition (PVD) was further employed to decorate silver oxide nanoparticles (Ag2O NPs) on the nanotubular edges. The results indicated that the highly-ordered TiO2 NTs with decorated Ag2O NPs could promote... 

Molecular dynamic simulation was performed to calculate the configurational entropy and the free energy for colloidal silver nanoparticles (Ag NPs) in 1-Ethyl-3-methylimidazolium Hexafluorophosphate [EMim][PF6] ionic liquid (IL). Furthermore, the density functional theory (DFT) was used to get the potential interaction between the metal surface and ion in IL. The effect of size and temperature on the configurational entropy and the free energy of colloidal Ag NPs were investigated. Then, it was compared with the gas phase. The Tsallis nonextensivity of entropy was investigated for different sizes of colloidal Ag NPs and it was shown that sub-extensivity of entropy occurs for colloidal Ag... 

We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc current the size of the nanoparticles increases. Optical absorption of silver nanoparticles after 3 weeks shows precipitation of them in a water medium. The effect of different surfactant and stabilizer concentrations such as cethyl trimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), sodium citrate, sodium dodecyl... 

Thermally stable cubic silver nanoparticles were grown by simply annealing a silver nano-thickness layer on a crystalline TiN buffer layer deposited on a Si(1 0 0) substrate. Formation of silver nanocubes was investigated by scanning electron microscopy, atomic force microscopy, x-ray diffractometry and UV-visible spectroscopy. The shapes of the silver nanoparticles were controlled by the thickness of the Ag layer. The silver nanocubes were self-ordered single crystals bounded mainly by {1 0 0} facets. It was found that a change in the shape of the nanoparticles from semi-spherical to cubic resulted in a substantial variation of their surface plasmon resonance absorption peak from 410 to 590... 

Silver nanoparticles (NPs) stored in pore-arrays (pa) SU-8 photoresist layer were utilized as an antibacterial nanocomposition against E. coli bacteria. The pa-SU-8 matrix was fabricated by an optical interference lithography method resulting in small pores with a diameter of ∼50 nm and a depth of ∼100 nm. The Ag NPs were deposited on the soft polymeric matrix at different drying temperatures of 50 and 90 °C. X-ray photoelectron spectroscopy showed that the deposited silver NPs were substantially in the metallic state, independent from the drying condition. However, the concentration of the immobilized Ag NPs on the film surface increased (by a factor of 2.5) at the higher drying... 

A novel modified carbon-paste electrode was employed for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) with good selectivity and high sensitivity. Silver nanoparticle and carbon nanotube modified carbon-paste electrode (Ag/CNT-CPE) displayed excellent electrochemical catalytic activities towards dopamine (DA) and ascorbic acid (AA). The oxidation overpotentials of DA and AA were decreased significantly compared with those obtained at the bare CPE. Differential pulse voltammetry was used for the simultaneous determination of DA and AA. The peak separation between DA and AA was 67 mV. The calibration curves for DA and AA were obtained in the range of 8.0 × 10-7-6.4 ×... 

The effect of an electric field on the antibacterial activity of columnar aligned silver nanorods was investigated. Silver nanorods with a polygonal cross section, a width of 20-60 nm and a length of 260-550 nm, were grown on a titanium interlayer by applying an electric field perpendicular to the surface of a Ag/Ti/Si(100) thin film during its heat treatment at 700 °C in an Ar+H2 environment. The optical absorption spectrum of the silver nanorods exhibited two peaks at wavelengths of 350 and 395 nm corresponding to the main surface plasmon resonance bands of the one-dimensional silver nanostructures. It was found that the silver nanorods with an fcc structure were bounded mainly by {100}... 

We study the quantum plasmonic features of gold and silver nanoparticles using TD-DFT+TB, a new density functional theory approach to the calculation of excited states, which combines a full DFT ground state with tight-binding approximations in the linear response calculation. In this framework, the optical properties of closed-shell Ag, Au and bimetallic Ag-Au nanoparticles with tetrahedral symmetry (with 20, 56, 120, and 165 atoms) and icosahedral structure (with 13, 55, and 147 atoms) were obtained and compared to full linear response time-dependent density functional theory (TD-DFT) as a reference and also to time-dependent density functional based tight binding (TD-DFTB) as a low-cost... 

Development of simple yet precise sensing platforms for rapid determination of biological species and drugs is of paramount importance, not only for analysis of pharmaceutical formulations during the production stage, but also in clinical practices and medical diagnosis. In the present research, we report on the electrochemical determination of atorvastatin (ATOR) by using silver nanowires/gold-modified glassy carbon electrode (Ag NWs/Au/GCE). The modified electrode was constructed through a two-step procedure in which narrow silver nanowires synthesized via a polyol method are drop casted on a pre-modified GCE with electrodeposited gold particles. The results of XRD analysis indicated the... 

In this study, we investigate the use of catalytic copper-silver-palladium substrates for the growth of multiwalled carbon nanotubes via the thermal chemical vapor deposition. These layers are comprised of nanocrystals of Cu2O, CuO, Ag, Pd, Cu, and PdO and were grown using a DC magnetron sputtering method. Scanning electron microscopy characterizations confirmed the significant growth of carbon nanotubes on the catalytic layer. A comparison of the growth of nanotubes indicated that the thickness of the catalytic layers has a significant impact on the quality and the diameter of the carbon nanotubes. Two major peaks were seen in the Raman spectrum. The formation of graphite multiwalled... 

Apatite-coated Ag/AgBr/TiO2 was prepared by deposition of Ag as novel metal to generate electron-hole pairs by extending the excitation wavelength to the visible-light region, AgBr, and hydroxy apatite as photosensitive material and adsorption bioceramic, respectively. The energy dispersive X-ray spectrometry clearly showed the presence of Ti, Ag, Ca, and P elements on the surface of catalyst. The bactericidal experiments in dark media indicated that only the novel catalyst shows inhibiting growth of bacteria in this case. A transmission electron microscopy image illustrated that catalyst nanoparticles adhere to the outer membrane of the cell and act as an inhibitor to the nourishment of... 

In the bone tissue engineering field (BTE), it is of significant importance to develop bioactive multifunctional scaffolds with enhanced osteoconductivity, osteoinductivity, and antibacterial properties required for lost bone tissue regeneration. In this work, a bioactive glass-ceramic scaffold was manufactured via a novel polymer-derived ceramics (PDC) manufacturing method. To gain antibacterial properties, the silver ions were incorporated in controlled amount along with other precursors in the PDC processing stage. Microstructural and structural properties of the fabricated silicate-phosphate glass-ceramic scaffold were evaluated by scanning electron microscopy (SEM) equipped with energy... 

Several pieces of research have been done on transition metal nanoparticles and their nanocomplexes as research on their physical and chemical properties and their relationship to biological features are of great importance. Among all their biological properties, the antibacterial and antimicrobial are especially important due to their high use for human needs. In this article, we will discuss the different synthesis and modification methods of silver (Ag) and gold (Au) nanoparticles and their physicochemical properties. We will also review some state-of-art studies and find the best relationship between the nanoparticles’ physicochemical properties and potential antimicrobial activity. The... 

The potential of hydrogen (pH) is a basic and critical parameter representing the function of numerous chemicals/biomolecules. Due to the widespread applications of pH in diverse fields, the development of rapid and simple yet reliable probes for the determination of pH has attracted significant interest. In this paper, by using AuNRs, silver ions, and ascorbic acid as colorimetric pH sensor, a multicolorimetric nanosensor is described for pH measurement. The reduction of silver ions by ascorbic acid which is strongly influenced by pH, results in silver nanoshell deposition on the surface of AuNRs. Consequently, the formation of Au@Ag core-shell NRs causes a series of blue shifts in the... 

In the current study, two series of antimicrobial dressings conjugated with silver sulfadiazine (SSD) and silver nanoparticles (AgNPs) were developed and evaluated for chronic wound healing. Highly porous polycaprolactone (PCL)/polyvinyl alcohol (PVA) nanofibers were loaded with different concentrations of SSD or AgNPs and compared comprehensively in vitro and in vivo. SSD and AgNPs indicated a strong and equal antimicrobial activity against S. aureus. However, SSD had more toxicity against fibroblast cells over one week in vitro culture. An in vivo model of wound healing on male Wistar rats was developed with a full thickness wound. All the wound dressings indicated enough flexibility and...