Search results for "surface properties"
showing 10 items of 421 documents
Neural cell pattern formation on glass and oxidized silicon surfaces modified with poly(N-isopropylacrylamide)
1996
Control over the adsorption of proteins and over the adsorption and spatial orientation of mammalian cells onto surfaces has been achieved by modification of glass and other silicon oxide substrates with poly(N-isopropylacrylamide) (PNIPAM). The functionalization of the substrates was achieved either by a polymer-analogous reaction of aminosilanes with reactive N-(isopropylacrylamide) (NIPAM)-copolymers and by copolymerization of NIPAM with surface-bound methacrylsilane. The obtained coatings were characterized by FT-1R, ellipsometry, and surface plasmon resonance measurements. The adsorption of two proteins-fibrinogen and ribonuclease A-on these surfaces was studied in situ by real time su…
Tuning size and thermal hysteresis in bistable spin crossover nanoparticles.
2010
Nanoparticles of iron(II) triazole salts have been prepared from water-organic microemulsions. The mean size of the nanoparticles can be tuned down to 6 nm in diameter, with a narrow size distribution. A sharp spin transition from the low spin (LS) to the high spin (HS) state is observed above room temperature, with a 30-40-K-wide thermal hysteresis. The same preparation can yield second generation nanoparticles containing molecular alloys by mixing triazole with triazole derivatives, or from metallic mixtures of iron(II) and zinc(II). In these nanoparticles of 10-15 nm, the spin transition "moves" towards lower temperatures, reaching a 316 K limit for the cooling down transition and mainta…
Surface AFM microscopy of unworn and worn samples of silicone hydrogel contact lenses
2008
Abstract: Purpose. To evaluate the qualitative and quantitative topographic changes in the surface of worn contact lenses (CLs) of different materials using atomic force microscopy (AFM). Methods. The topography of five different CL materials was evaluated withAFM over a surface of 25 lm2 according to previously published experimental setup. Average roughness (Ra) and root mean square (Rms) values were obtained for unworn and worn samples. Results. The Ra value increased for balafilcon A (11.62–13.68 nm for unworn and worn samples, respectively), lotrafilcon A (3.67–15.01 nm for unworn and worn samples, respectively), lotrafilcon B (4.08–8.42 nm for unworn and worn samples, respectively), g…
Plasmonic Focusing Reduces Ensemble Linewidth of Silver-Coated Gold Nanorods
2008
Silver coating gold nanorods reduces the ensemble plasmon line width by changing the relation connecting particle shape and plasmon resonance wavelength. This change, we term "plasmonic focusing", leads to less variation of resonance wavelengths for the same particle size distribution. We also find smaller single particle linewidth comparing resonances at the same wavelength but show that this does not contribute to the ensemble linewidth narrowing.
Identifying yeasts using surface enhanced Raman spectroscopy
2019
Made available in DSpace on 2019-10-06T15:40:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-07-05 Tekes Academy of Finland Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The molecular fingerprints of yeasts Saccharomyces cerevisiae, Dekkera bruxellensis, and Wickerhamomyces anomalus (former name Pichia anomala) have been examined using surface-enhanced Raman spectroscopy (SERS) and helium ion microscopy (HIM). The SERS spectra obtained from cell cultures (lysate and non-treated cells) distinguish between these very closely related fungal species. Highly SERS active silver nano-particles suitable for detecting complex biomolecules were fabricated using a simple synt…
Laser-Ablation-Induced Synthesis of SiO2-Capped Noble Metal Nanoparticles in a Single Step
2010
Here we describe a simple, powerful technique based on the laser ablation of a target immersed in a water solution of a metal salt. With this method, nanoparticles of different metals and alloys can be processed very quickly. Both the target and the salt solution can be chosen to produce metal nanoparticles of different sizes, surface-oxidized nanoparticles (silica-silver, for example), or even more complex structures to be defined by the researcher on one or more steps because the technique combines the advantages of both physical and chemical methods. We have applied this technique to the fabrication of inert silica-metal (silver, gold, and silver-gold) nanoparticles with a strong surface…
Switchable Bactericidal Effects from Novel Silica-Coated Silver Nanoparticles Mediated by Light Irradiation
2011
Here we report on the triggering of antibacterial activity by a new type of silver nanoparticle coated with porous silica, Ag@silica, irradiated at their surface plasmon resonant frequency. The nanoparticles are able to bind readily to the surface of bacterial cells, although this does not affect bacterial growth since the silica shell largely attenuates the intrinsic toxicity of silver. However, upon simultaneous exposure to light corresponding to the absorption band of the nanoparticles, bacterial death is enhanced selectively on the irradiated zone. Because of the low power density used for the treatments, we discard thermal effects as the cause of cell killing. Instead, we propose that …
Nuclear Magnetic Resonance for Cultural Heritage
2007
Abstract Nuclear magnetic resonance (NMR) portable devices are now being used for nondestructive in situ analysis of water content, pore space structure and protective treatment performance in porous media in the field of cultural heritage. It is a standard procedure to invert T 1 and T 2 relaxation data of fully water-saturated samples to get “pore size” distributions, but the use of T 2 requires great caution. It is well known that dephasing effects due to water molecule diffusion in a magnetic field gradient can affect transverse relaxation data, even if the smallest experimentally available half echo time τ is used in Carr–Purcell–Meiboom–Gill experiments. When a portable single-sided N…
Porous titania surfaces on titanium with hierarchical macro- and mesoporosities for enhancing cell adhesion, proliferation and mineralization
2014
Titanium received a macroporous titania surface layer by anodization, which contains open pores with average pore diameter around 5 μm. An additional mesoporous titania top layer following the contour of the macropores, of 100-200 nm thickness and with a pore diameter of 10nm, was formed by using the evaporation-induced self-assembly (EISA) method with titanium (IV) tetraethoxide as the precursor. A coherent laminar titania surface layer was thus obtained, creating a hierarchical macro- and mesoporous surface that was characterized by high-resolution electron microscopy. The interfacial bonding between the surface layers and the titanium matrix was characterized by the scratch test that con…
A Mesoporous 3D Hybrid Material with Dual Functionality for Hg2+Detection and Adsorption
2008
Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission…