Nanostructured Lipid Carriers
SLNs produced by high-pressure homogenization at elevated temperature hot homogenization technique are formed during the cooling process of the hot o w emulsion as mentioned above. To summarize occurring disadvantages, the immediate formation of a perfect crystal or formation during the long-term storage can cause drug expulsion. To avoid this, a less ordered lipid matrix with many imperfections is desirable for better accommodation of the drug, especially to avoid drug expulsion during...
Reduction of Protein Adsorption
Albumin is a model protein commonly used to study the protein-resistance properties of surfaces 53 . A 15fold reduction of albumin adsorption was found with PEG-coated PEG-PLA nanospheres compared to PLA ones 54 . Similar albumin-rejecting abilities were observed in the case of PLGA nanospheres surface modified by adsorption of PEG-PLA diblock copolymers 55 . Fibrinogen was used as a model blood protein to test the efficacy of the PEG coating on PEG-PACA nanospheres 49 . After freeze-fracture,...
Strengthening Mechanisms
The hardening mechanism of nanocomposites should be more complicated 165, 385, 386 than that in coarse-grained polycrystalline materials. The hardness of nanocomposites is most precisely approximated by the Hall-Petch equation, but currently there is no agreement on the strengthening mechanism of nanocomposites. A few strengthening models of nanostructured materials at nanoscale thicknesses of the bilayer repeat period below the Hall-Petch breakdown were proposed Orowan mechanism 344, 387-393 ,...
Optical Absorption
Another way to probe the electronic properties of SWNTs is through their optical absorption spectra. This technique is based on the well known phenomenon of light absorption Figure 14. Resonant Raman spectra in the tangential mode G mode obtained using three different laser excitation energies, for SWNT samples produced by CO disproportionation at 950 C. Reprinted with permission from 88 , J. E. Herrera et al., J. Nanotech., in press. American Scientific Publishers. by a chromophore group...
SolGel and Spray Pyrolysis
Chemical deposition has been widely used to prepare oxide films, such as ferroelectrics and semiconductor films 37 , since it is a fast and cost-efficient preparation method. In nebulized spray pyrolysis, a solution containing the organic derivatives of the relevant metals in a suitable solvent is nebulized by making use of a CMR transducer. The nebulized spray is slowly deposited on a solid substrate at a relatively low temperature, with sufficient control of the rate deposition to yield the...
Using NonAlkoxide Precursor
Alkoxides are usually very costly. However, this problem can be overcome by using the cheap, commercially available non-alkoxide precursors, namely SnCl4, without further purification or modification. Following procedures are generally followed to prepare pure and modified SnO2 thin films by means of sol-gel technique utilizing non-alkoxide precursors. In the first method 5, 13, 14 , tin tetrachloride SnCl4 is first dissolved in propanol or any other alcohol forming a solution of tin compounds...
SYNTHESIS OF NANOCRYSTALLINE SnO2 VIA SOLGEL
Two sol-gel synthesis routes or precursors are generally used for producing SnO2 thin films first is the hydrolysis of tin alkoxide 8, 34, 74, 75 and the second is the hydrolysis of tin IV chloride 5, 6, 9-19, 21-26, 29, 30, 33, 37, 76 . SnO2 thin films can also be prepared from an aqueous SnO2 sol, which is synthesized via tin IV chloride hydrothermal treatment 16 . Semiconductor SnO2 gas sensor can be fabricated into three types of devices i sintered block 12, 16, 19 , ii thick film 27, 28 ,...
Info Tia
Figure 12. Resistance as a function of temperature for Co100-xPdx alloys. Reprinted with permission from 55 , M. L. Rao and S. Sundar Manoharan private communication . crystalline magnetic anisotropies define an energy scale that controls the magnetic irreversibility. Introducing this energy scale yields a self-consistent explanation of the experimental data. Cao and co-workers 63 showed the method for the preparation of pure amorphous Fe2O3 powder with a particle size of 25 nm. Pure amorphous...
CHARACTERIZATION OF SOLGEL COATED SnO2 THIN FILMS
Typical SEM micrograph of nanocrystaUine SnO2 thin film coated on a Pyrex glass substrate is shown in Figure 4 77 . The SnO2 thin film appears to be relatively smooth. At some locations, few cracks are observed on the film surface, which are characteristic features of the sol-gel dip-coated thin films. Typical broad-scan XPS spectrum, within the B.E. range of 0-1100 eV, obtained for the nanocrystalline SnO2 thin film dip-coated on the Pyrex glass substrate is shown in Figure 5a 77 , which...
SolGel SpinCoating Process
Spin-coating is used for many applications where relatively flat substrates or objects are coated with a thin layer of material. In spin-coating, Figure 1, the material, in the form of a stable sol, to be made into coating is deposited onto the substrate surface and spun off to leave a uniform layer. There are four key stages in the sol-gel spin-coating process, Figure 2 3 1 Stage 1 This step involves the deposition of the sol onto the substrate surface, Figure 2. This can be done using a...
Advantages of SolGel Process
Sol-gel technique, as a method for synthesizing thin- or thick-film gas sensor, offers several advantages 1, 2 i The sol-gel technique is simpler and cheaper than others, ii it allows an easy coating of large and complex shaped substrates if the angles are not too sharp , iii the process is inexpensive with respect to the initial investment of the production plant and the running cost, iv it produces no perturbations of devices in the case of deposition on top, v it offers easy control of film...
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Figure 4. Scheme for the process of highly concentrated nanoparticle dispersions. For explanations, see text. cle dispersions above 30 are not liquid anymore. They are creamy, gel paste-like with a further increase of lipid concentration, and are more or less solid at approximately 80 . For the production of NLCs by high-pressure homog-enization, any type of high-pressure homogenizer can be used which allows temperature control, which means keeping the preemulsion above the melting point of the...
HallPetch Strengthening Mechanism
The experimental Hall-Petch relationship applied to hardness shows that the hardness of microcrystalline materials increases with a decrease in the average diameter of the grains 328-332 where d is the average diameter of the grains, H is the hardness, H0 is the hardness of the monocrystal when d x gt , and kH is the Hall-Petch intensity constant. Extrapolation of the Hall-Petch relationship to nanostruc-tured materials should show a much higher hardness than that of coarse-grained materials...
Opsonins and Dysopsonins
Immediately after intravenous administration, the nano-particles encounter hundreds of different plasma proteins. A protein layer begins to form within seconds at the nano-particles' surface after contact with blood. The adsorption of plasma proteins that are capable to interact with receptors on the MPS cells, thus promoting the particle uptake by these cells, is called opsonization. The complement is considered to be one of the main opsonins involved in the uptake of intravenously...
Disadvantages of SolGel Process
The sol-gel process has a few limitations, too. The real application of this synthesis route for the serial devices needs efforts in R amp D. Much work and time are needed in optimizing the stability of the sol, the durability, and the reproducibility of the results for the production of sensor devices. Moreover, the alkoxide precursors are generally costlier. In spite of these disadvantages, the sol-gel process has been proven to be a highly applicable and industrially viable process for...