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Shape-controlled silver NPs for shape-dependent biological activities
, Article Micro and Nano Letters ; Volume 12, Issue 9 , 2017 , Pages 647-651 ; 17500443 (ISSN) ; Yazdanpanah, A ; Abrishamkar, A ; Moztarzadeh, F ; Ramedani, A ; Pouraghaie, S ; Shirinzadeh, H ; Samadikuchaksaraei, A ; Chauhan, N. P. S ; Hopkinson, L ; Sefat, F ; Mozafari, M ; Sharif University of Technology
Abstract
The most important issue during synthesis of nanoparticles (NPs) is to avoid particle agglomeration and adhesion. There have been several attempts to use special substances such as organic surfactants, polymers and stable ligands for this purpose. In this study, silver NPs were synthesised with and without gelatin macromolecules, as a green natural biopolymer, which resulted in NPs with varying shapes and sizes. The effect of morphological characteristics on the antibacterial and antifungal properties of the synthesised NPs were studied, by comparing Gram-negative (Escherichia coli) versus Gram-positive (Staphylococcus aureus) bacteria as well as fungi (Candida albicans) by calculation of...
Hydrothermal synthesis of ZnO nanorod arrays for photocatalytic inactivation of bacteria
, Article Journal of Physics D: Applied Physics ; Volume 42, Issue 22 , 2009 ; 00223727 (ISSN) ; Mehrabian, M ; Mirabbaszadeh, K ; Azimirad, R ; Sharif University of Technology
2009
Abstract
Arrays of ZnO nanorods were synthesized on ZnO seed layer/glass substrates by a hydrothermal method at a low temperature of 70 °C. The effect of pH > 7 of the hydrated zinc nitrate-NaOH precursor on the morphology and topography (e.g. size, surface area and roughness), the optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and antibacterial activity of the grown ZnO nanostructure and nanorod coatings were investigated. For pH = 11.33 of the precursor (NaOH concentration of 0.10M), a fast growth of ZnO nanorods on the seed layer (length of ∼1 νm in 1.5 h) was observed. The fast growth of the ZnO nanorods resulted in a significant reduction in the optical...
Photocatalytic property of Fe2O3 nanograin chains coated by TiO2 nanolayer in visible light irradiation
, Article Applied Catalysis A: General ; Volume 369, Issue 1-2 , 2009 , Pages 77-82 ; 0926860X (ISSN) ; Azimirad, R ; Sharif University of Technology
2009
Abstract
The visible light photocatalytic activity of α-Fe2O3 nanograin chains coated by anatase TiO2 nanolayer, as a photocatalyst thin film for inactivation of Escherichia coli bacteria, was investigated for the solutions containing 106 colony forming units per milliliter of the bacteria, without and with H2O2 (60 μM). Thin films of the α-Fe2O3 nanograins with the grain size of 40-280 nm were grown on glass substrates by post-annealing of the thermal evaporated Fe3O4 thin films at 400 °C in air. The TiO2 layer with thickness of about 20 nm was coated on the nanograins by dipping the Fe2O3 thin films in a prepared TiO2 sol and re-annealing them at 400 °C in air. The antibacterial activity of the...
Synthesis of titania/carbon nanotube heterojunction arrays for photoinactivation of E. coli in visible light irradiation
, Article Carbon ; Volume 47, Issue 14 , 2009 , Pages 3280-3287 ; 00086223 (ISSN) ; Abdolahad, M ; Abdi, Y ; Mohajerzadeh, S ; Sharif University of Technology
2009
Abstract
TiO2/multi-wall carbon nanotube (MWNT) heterojunction arrays were synthesized and immobilized on Si(0 0 1) substrate as photocatalysts for inactivation of Escherichia coli bacteria. The vertically aligned MWNT arrays were grown on ∼5 nm Ni thin film deposited on the Si by using plasma enhanced chemical vapor deposition at 650 °C. Then, the MWNTs were coated by TiO2 using dip-coating sol-gel method. Post annealing of the TiO2/MWNTs at 400 °C resulted in crystallization of the TiO2 coating and formation of Ti-C and Ti-O-C carbonaceous bonds at the heterojunction. The visible light-induced photoinactivation of the bacteria increased from MWNTs to TiO2 to TiO2/MWNTs, in which the bacteria could...
Bactericidal effects of Ag nanoparticles immobilized on surface of SiO2 thin film with high concentration
, Article Current Applied Physics ; Volume 9, Issue 6 , 2009 , Pages 1381-1385 ; 15671739 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2009
Abstract
Bactericidal activity of high concentration Ag nanoparticles immobilized on surface of an aqueous sol-gel silica thin film was investigated against Escherichia coli and Staphylococcus aureus bacteria. Size of the surface nanoparticles was estimated in the range of 35-80 nm by using atomic force microscopy. Due to accumulation of the silver nanoparticles at near the surface (at depth of 6 nm and about 40 times greater than the silver concentration in the sol), the synthesized Ag-SiO2 thin film (with area of 10 mm2) presented strong antibacterial activities against E. coli and S. aureus bacteria with relative rate of reduction of the viable bacteria of 1.05 and 0.73 h-1 for initial...
Storage of Ag nanoparticles in pore-arrays of SU-8 matrix for antibacterial applications
, Article Journal of Physics D: Applied Physics ; Volume 42, Issue 13 , 2009 ; 00223727 (ISSN) ; Abdolahad, M ; Asadi, R ; Sharif University of Technology
2009
Abstract
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...
Lasting antibacterial activities of Ag-TiO2/Ag/a-TiO2 nanocomposite thin film photocatalysts under solar light irradiation
, Article Journal of Colloid and Interface Science ; Volume 336, Issue 1 , 2009 , Pages 117-124 ; 00219797 (ISSN) ; Sharif University of Technology
2009
Abstract
Photodegradation of Escherichia coli bacteria in presence of Ag-TiO2/Ag/a-TiO2 nanocomposite film with an effective storage of silver nanoparticles was investigated in the visible and the solar light irradiations. The nanocomposite film was synthesized by sol-gel deposition of 30 nm Ag-TiO2 layer on ∼200 nm anatase(a-)TiO2 film previously doped by silver nanoparticles. Both Ag/a-TiO2 and Ag-TiO2/Ag/a-TiO2 films were transparent with a SPR absorption band at 412 nm. Depth profile X-ray photoelectron spectroscopy showed metallic silver nanoparticles with diameter of 30 nm and fcc crystalline structure were self-accumulated on the film surface at depth of 5 nm of the TiO2 layer and also at the...
Capping antibacterial Ag nanorods aligned on Ti interlayer by mesoporous TiO2 layer
, Article Surface and Coatings Technology ; Volume 203, Issue 20-21 , 2009 , Pages 3123-3128 ; 02578972 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2009
Abstract
In this work, aligned and compact Ag nanorods capped by sol-gel mesoporous TiO2 layer were grown on Ti/Si(100) in order to be applied in antibacterial applications. The Ag nanorods with a high effective surface were grown by applying an electric field perpendicular to the surface of the Ag/Ti/Si thin film while it was being heat-treated at 700 °C in an Ar + H2 ambient. The grown silver nanorods had widths and lengths of 20-50 and 250-500 nm with an abundance in {100} facet, respectively. The TiO2 cap layer also had the specific surface area, the total pore volume and the pore diameter of 474 m2/g, 0.49 cm3/g and 8.0 nm, respectively. Antibacterial activities of the TiO2-capped Ag nanorods...
Enhancement of antibacterial properties of Ag nanorods by electric field
, Article Science and Technology of Advanced Materials ; Volume 10, Issue 1 , 2009 ; 14686996 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2009
Abstract
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}...
The performances of the chi-square test and complexity measures for signal recognition in biological sequences
, Article Journal of Theoretical Biology ; Volume 251, Issue 2 , 2008 , Pages 380-387 ; 00225193 (ISSN) ; Kargar, M ; Sheari, A ; Poormohammadi, H ; Sadeghi, M ; Pezeshk, H ; Eslahchi, C ; Sharif University of Technology
2008
Abstract
With large amounts of experimental data, modern molecular biology needs appropriate methods to deal with biological sequences. In this work, we apply a statistical method (Pearson's chi-square test) to recognize the signals appear in the whole genome of the Escherichia coli. To show the effectiveness of the method, we compare the Pearson's chi-square test with linguistic complexity on the complete genome of E. coli. The results suggest that Pearson's chi-square test is an efficient method for distinguishing genes (coding regions) form pseudogenes (noncoding regions). On the other hand, the performance of the linguistic complexity is much lower than the chi-square test method. We also use the...
Apatite-coated Ag/AgBr/TiO2 visible-light photocatalyst for destruction of bacteria
, Article Journal of the American Chemical Society ; Volume 129, Issue 31 , 2007 , Pages 9552-9553 ; 00027863 (ISSN) ; Rahimnejad, S ; Haghighi, S ; Gholami, M. R ; Sharif University of Technology
2007
Abstract
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...