Controlling hydrophobicity of silica nanocapsules prepared from organosilanes (original) (raw)
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Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011
ABSTRACT In this study, surface functionalized silica nanoparticles were prepared through a continuous two-step sol–gel process. After the TEOS-derived silica particles were synthesized, silane compounds were added during the second sol–gel process without any filtration or purification processes. The introductions of the organic chains to their surfaces were measured using 13C solid-state NMR. The effects of the hydrophilicity of the organo-chains on the silica particles were evaluated and analyzed by water contact angle and water wettability tests. The differences of surface charge in the dispersion state were analyzed by measuring the zeta-potential and the variations in the charge were measured as a function of pH.Graphical abstractHighlights► Surface modified silica particles were prepared through a continuous sol–gel process. ► The organic chains were introduced on the surface of the silica particles. ► The introduction effects of organic chains were the variations of surface properties. ► The hydrophilicity of silica particles was changed by the organic chains. ► The pH dependency of the surface charge was changed by the organic chains.
Versatile Preparation of Silica Nanocapsules for Biomedical Applications
Particle & Particle Systems Characterization, 2020
Multifunctional nanocarriers integrating the properties of bioimaging, targeting, and stimuli-responsive release of guest molecules allow a spatiotemporal controlled delivery and tracking of therapeutics, which is the prime prerequisite for in vivo Core-shell nanocapsules are receiving increasing interest for drug delivery applications. Silica nanocapsules have been the focus of intensive studies due to their biocompatibility, versatile silica chemistry, and tunable porosity. However, a versatile one-step preparation of silica nanocapsules with well-defined core-shell structure, tunable size, flexible interior loading, and tailored shell composition, permeability, and surface functionalization for site-specific drug release and therapeutic tracking remains a challenge. Herein, an interfacially confined sol-gel process in miniemulsion for the one-step versatile preparation of functional silica nanocapsules is developed. Uniform nanocapsules with diameters from 60 to 400 nm are obtained and a large variety of hydrophobic liquids are encapsulated in the core. When solvents with low boiling point are loaded, subsequent solvent evaporation converts the initially hydrophobic cavity into an aqueous environment. Stimuli-responsive permeability of nanocapsules is programmed by introducing disulfide or tetrasulfide bonds in the shell. Selective and sustained release of dexamethasone in response to glutathione tripeptide for over 10 d is achieved. Fluorescence labeling of the silica shell and magnetic loading in the internal cavity enable therapeutic tracking of nanocapsules by fluorescence and electron microscopies. Thus, silica nanocapsules represent a promising theranostic nanoplatform for targeted drug delivery applications.
Composite Silica Particles Using a Mixture of Organosilane Monomers
Journal of Sol-Gel Science and Technology, 2004
Composite silica particles were synthesized by a two-step (acid-base) process in an aqueous solution with a mixture of organoalkoxysilane monomers. The two-step process separates the hydrolysis and condensation procedures to easily control condensation rate. In this study, the silane monomers used were phenyltrimethoxysilane (PTMS), vinyltrimethoxysilane (VTMS), methyltrimethoxysilane (MTMS), and tetraethyl-orthosilicate (TEOS). The physical properties of the resultant composite particles were investigated with the change in the molar ratio of monomers. The size of the particles increased with increasing the molar ratio of R a Si(OR) 3 /R b Si(OR) 3 or R a Si(OR) 3 /TEOS (R a : phenyl; R b : vinyl, methyl).
Preparation of the hydrophilic/hydrophobic silica particles
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2002
Silicas of high dispersion degree were obtained. The process included formation of silica particles and their aggregation. Glycerin solution was used in precipitation process, resulting in a partial blocking of the silica surface hydroxyl groups (silanol groups) and, thus, in a decreased hydrophilicity of silica. Studies on the surface modification of silicas using silane coupling agents are described. The best modifiers were selected, which induced a change of the silica surface from the hydrophilic to the hydrophobic one. Basic physicochemical analyses of the obtained silicas were performed. Near infrared spectroscopy (NIR) was used to determine the degree of condensation of silica surface silanol groups. The degree of hydrophobization of silica surface was determined by a calorimetric method. Moreover, zeta potential, size distribution of primary particles, aggregates and agglomerates structures were determined by ZetaPlus instrument using electrophorectic (ELS) and dynamic (DLS) light scattering techniques.
Advances in Experimental Medicine and Biology, 2021
Silica consists of one silicon atom and two oxygen atoms (SiO 2) and is commonly used in various aspects of daily life. For example, it has been used as glass, insulator, and so on. Nowadays, silica is used as core reagents for fabricating and encapsulating nanoparticles (NPs). In this chapter, the usage of silica in nanotechnology is described. Synthesis and surface modification of silica nanoparticles (SiNPs), including via the Stöber method, reverse microemulsion method, and modified sol-gel method, are illustrated. Then, various NPs with silica encapsulation are explained. At last, the biological applications of those mentioned NPs are described.
HYDROLYSIS OF SILICA SOURCES: APS AND DTSACl IN MICROENCAPSULATION PROCESSES
Physicochem. Probl …, 2012
The process of formation of silica shells around emulsion droplets was investigated. The 1 H-NMR spectroscopy was applied to follow the silica shell formation around emulsion droplets by hydrolysis and condensation of selected silanes in the emulsion system. (3-aminopropyl) triethoxysilane (APS) and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DTSACl) were used as silica sources in microencapsulation process. The NMR analysis revealed strong dependence of the hydrolysis reaction rate on pH. Obtained information allowed selecting the optimal conditions for the formation of the capsules with silica shells. The obtained capsules' suspensions were stable for several weeks.
Effect of the Synthesis Methods on Hydrophobic Properties of Modified Silicas
Adsorption Science & Technology, 2015
Composites based on fumed silica with surface hydrophobic groups were synthesized by chemical substitution of silanol groups' proton for trimethylsilyl (TMS) groups, adsorption of poly(dimethylsiloxane) (PDMS) and combined chemical-adsorption methods. Microcalorimetry measurements and values of the wetting contact angle with water (Θ) were obtained to investigate the hydrophobic properties of prepared materials. The hydrophilicity indexes (K h) were determined from the relationship of heat of immersion in water Q w to non-polar decane Q d. The Θ and Q w demonstrated changes with increase of modification degree (d m) for composites containing a monolayer of PDMS. All samples with excess of PDMS had high Θ (>110°) and relatively low Q w and K h. Composites modified with TMS groups demonstrated hydrophobic properties in accordance with K h at d m 0.7, whereas Θ > 90° is observed only for those samples with d m = 1.0. The different methods of synthesis may be applied based on the morphological characteristics and hydrophobicity of the samples.
Synthesis and characterization of silica microcapsules using a sustainable solvent system template
Materials Research Bulletin, 2011
In this paper is described the synthesis of silica microspheres of low dimensionality, that is, with diameters ranging from ca. 200 to 450 nm. The structure and essential features of these materials have been studied by electron microscopy and analysis of isotherms of physical adsorption and, in contrast of the previously established, the presence of a mesoporous structure within the silica spheres has been unambiguously demonstrated. r