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Crystallization and Structural Linkages of COFs
Published in Atsushi Nagai, Covalent Organic Frameworks, 2019
Nowadays, Schiff base chemistry or dynamic imine chemistry is profusely utilized for the synthesis of COFs. Imine is a functional group or chemical compound containing a carbon-nitrogen double bond and is typically prepared by the condensation of primary amines and aldehydes and less commonly ketones (Eq. 2.5). In terms of mechanism, such reactions proceed via nucleophilic addition, giving a hemiaminal –C(OH)(NHR)– intermediate, followed by the elimination of water to give the imine (–N=C–) compound. The equilibrium in this reaction usually favors the carbonyl compound and amine, so azeotropic distillation or use of a dehydrating agent, such as molecular sieves or magnesium sulfate, is required to push the reaction in favor of imine formation. In recent years, several reagents, such as tris(2,2,2-trifluoroethyl)borate, pyrrolidine, acetic acid, and titanium ethoxide, have been shown to catalyze imine formation. Especially, according to synthesis of COFs, aqueous acetic acid as a catalyst is most useful.
Sol−Gel Processing
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
If titanium ethoxide is introduced into the solution with vigorous stirring, heterocondensation occurs: (RO)3Si−OH+RO−Ti(OR)3→fast(RO)3Si−O−Ti(OR)3+ROH
Synthesis Methods
Published in Ranjeet Kumar Sahu, Somashekhar S. Hiremath, Corona Discharge Micromachining for the Synthesis of Nanoparticles, 2019
Ranjeet Kumar Sahu, Somashekhar S. Hiremath
In the aerosol synthesis method, a liquid precursor (e.g. titanium ethoxide; titanium isopropoxide; titanium tetrachloride; tri-isobutylaluminium) is mistified to make a liquid aerosol (dispersion of uniform droplets of liquid in a gas) and this liquid aerosol solidifies through evaporation of solvent resulting in the synthesis of nanoparticles. Aerosols can be relatively easily produced by sonication or spinning. This method is simple and cheap, but its disadvantages include aggregation, inhomogeneous morphology, and the occurrence of broad distribution of particles. This method is used for synthesizing metal and metal oxide nanoparticles (Cao, 2004; Kalpowitz et al., 2010).
PEGylated TiO2 nanoparticles mediated inhibition of cell migration via integrin beta 1
Published in Science and Technology of Advanced Materials, 2018
Qingqing Sun, Koki Kanehira, Akiyoshi Taniguchi
TiO2-PEG NPs were prepared as previously described [31]. In brief, 0.1 M titanium ethoxide in ethanol was mixed with 50% (v/v) acetonitrile and hydrolyzed for 60 min at room temperature. Ammonium hydroxide was then added to form a hydrolysis solution. The final concentrations of ammonium hydroxide ranged from 0.01 to 0.1% (w/v) and were dependent on the desired particle size. The hydrolysis solution was subsequently heated under reflux. The generated spherical TiO2 particles were then collected and finally adjusted to 20% (w/v) with methanol. Finally, a PEG co-polymer was coated on the surface of the spherical TiO2 NPs as described previously [32]. The morphology of NPs is displayed in Figure S1 (supplemental information). Besides that, the polydispersity index (PDI) of NPs was detected after dilution and stock in the cell culture medium for 24 h as follows: 0.1 (100 nm), 0.1 (200 nm), and 0.3 (300 nm).