Obtained Silica Nanoparticles Research Articles

Enhanced adsorption and non-linear optical properties of DNA-CTAB functionalized mesoporous silica nanoparticles and their influence on enhancement of photoluminescence of Rhodamine 6G dye

We report a novel template method for synthesizing silica nanoparticles that are mesoporous as well as biocompatible. The mesoporous silica nanoparticles were synthesized using the Stober process and peptization method. We have used surface-modified deoxyribonucleic acid (DNA) with cetyl trimethyl ammonium bromide as a capping agent. The obtained silica particles were analyzed using x-ray diffraction, UV–vis spectroscopy, the Brunauer–Emmet–Teller method, scanning electron microscopy, and the open aperture Z-scan technique. The characterization results indicated that the DNA polymer’s presence influenced the formation of the silica particles. The silica particles are mesoporous, nanosized, and good adsorbent and also show enhanced non-linear optical properties when compared with existing silica nanoparticles. The solubility of the silica nanoparticles was also verified in dimethyl sulfoxide (DMSO). We have verified that the enhanced mesoporous surface area and reduced porous size of the silica nanoparticles influenced the photoluminescence of Rhodamine 6G dye in DMSO. This can be applied to lower the lasing threshold of the gain medium in lasing applications. Hence, the obtained silica nanoparticles have a variety of applications such that they can be used as adsorbents of nanosized particles, which is applicable for drug delivery purposes, bioimaging, catalytic activities, doping surface for thin film making, biosensing applications, and improvement of material quality for solar devices. The non-linear optical property of the mesoporous silica nanoparticles can be used for optical limiting applications in photonic devices.

Characterization of Silica Nanoparticles and Nanocolloid Synthesized in Acidic and Alkaline Media

Nanosilica in known as one of the most widely used components in various industries. In the current study, silica nanoparticle/colloid were synthesized in acidic and alkaline media using sodium silicate as a precursor. The effect of synthesis parameters on the morphology of the obtained nanoparticles and the rheological properties of silica colloid were studied. Microscopic observations revealed that size and morphology of the obtained silica nanoparticles can be changed by varying the ammonia to ethanol ratio, as well as the concentration of sodium silicate solution. The results revealed that the particles size is raised by increasing the ethanol to ammonia ratio and increasing the sodium silicate concentration leads to irregular and larger particles. the particles In fact, at (EtOH/NH3 :1 and Na2SiO3/H2O:0.07) a stable colloidal silica containing silica nanoparticles with average diameter of 65nm could be achieved. Additionaly, gelation time (tgel) of nanocolloid was measured using time sweep at constant frequencies of 0.1, 0.3 and 0.5 Hz. Applying the gelation point relations, the relaxation power (Δ) and fractal dimension (df) were measured as 0.22 and 2.39, respectively, indicating that the current system follows a non-stoichiometric equilibrium. Furthermore, the Fourier transform infrared spectroscopy (FTIR) test confirmed the formation of silica chemical bonding and the purity of the washed silica particles was increased from 84.18% to 87.33%, measured via X-ray fluorescence spectroscopy (XRF)

Nanocarriers of Eu<sup>3+</sup> doped silica nanoparticles modified by APTES for luminescent monitoring of cloxacillin

<abstract> <p>Drug nanocarriers have been continuously improved to promote satisfactory release control. In this sense, luminescent materials have become an alternative option in clinical trials due to their ability to monitor drug delivery. Among the nanocarriers, silica stands out for structural stability, dispersibility, and surface reactivity. When using ceramic nanocarriers, one of the challenges is their interaction and selectivity capability for organic molecules, such as drugs. In order to overcome such adversity, superficial modifications can be carried out to enable a higher affinity for the desired drug. Thus, the present study aimed to obtain silica nanoparticles (NPs) doped with low concentrations of europium (III) superficially modified by (3-aminopropyl)triethoxysilane (APTES) to assess their interaction with the model drug cloxacillin benzathine. This drug was chosen because it is part of the ampicillin family and is commonly used in several treatments. Near-spherical and homogeneous silica NPs were obtained via sol-gel synthesis, with particle sizes of approximately 21 nm. It was possible to verify the fluorescence capacity of the silica NPs when doped with europium (III) in a mole percent that varied from 0.5 to 3.0%. A 10% volume percent of APTES caused the silica nanoparticles to increase the degree of hydrophobicity, with a shift in the contact angle from 8° to 51°. After surface modification by APTES, the silica nanocarrier (10 g·L<sup>-1</sup>) achieved a satisfactory degree of CLOX incorporation (25 g·L<sup>-1</sup>), increasing the adsorptive capacity to values above 50%. Therefore, silica NPs doped with europium (III) in a low percent of 0.5% (mole) modified by APTES showed promising results as an alternative option for trials and clinical studies of drug incorporation.</p> </abstract>

One-step synthesis of SiO2 α−Fe2O3 / Fe3O4 composite nanoparticles with magnetic properties from rice husks

This paper presents different methodologies for the preparation of Fe2O3@SiO2 nanoparticles (composites) and their characterization. The composite nanoparticles were prepared directly from rice husks. Two methodologies were used, (i) impregnation with an ionic iron solution of rice husks followed with a thermal treatment and (ii) impregnation of the pre-calcinated and lixiviated rice husks. In both methods, a low density, homogenous and highly porous SiO2 nanoparticles with a mean diameter of 20 nm and loaded with different types of iron oxide are generated. The synthetized products were systematically characterized by SEM, AFM, DLS, FT-IR, Mössbauer and VSM. The results show that two different composites were obtained, one mostly composed by α-Fe2O3@SiO2 and a second one mostly composed by γ-Fe2O3@SiO2. Mössbauer and VMS spectra show that iron oxide nanoparticles are formed in the pores of the SiO2 nanoparticles and the first method promote production of composites with magnetic properties. These results highlight a new one-step methodology to obtain silica nanoparticles loaded with iron oxides and with high magnetic properties.

Facile Synthesis Silica Nanoparticles from Indonesia Silica Sand and their Physico-Chemical Properties

Silica nanoparticles are a very promising functional material when purified from silica sand for wide application. In addition, a low cost and easy method to obtain the material will be increasing the value of silica sand. To synthesize of nanoparticles using an easily scalable, cheap and simple method, we suggest a sodium silicate solution as a precursor that silica sand was diluted on the NaOH. After that, the sodium silicate solution under various alcohols (methanol and ethanol) in the acid medium was conducted by sol gel method to obtain silica nanoparticles. The synthesized of silica nanoparticles was observed to the non-agglomerate, homogeneous and spherical shape with an average size about 200 nm. We also noted the existence of NaNO3 by side product of reaction on the system, which may be the amorphous silica unidentified on the XRD results.

Silica Nanoparticles: Preparation, Characterization and Applications in Biomedicine

A rapid and effective methodology has been developed in order to obtain silica nanoparticles which are broadly characterized by various techniques including electron microscopy, differential scanning calorimetry, ultraviolet and infrared spectroscopy, determining their charge via electrophoretic mobility, and zeta potential measurements. The ability of nanoparticles to incorporate distinct active ingredients, 5-fluoruracil and two UV protectors (Neo Heliopan BB and Eusolex 232), has been studied in order to verify (among other parameters) the effectiveness of their encapsulation and the most appropriate conditions for carrying out this process. The obtained nanoparticles were found to have an ideal size for administration via different means and a zeta potential that indicated their good stability.

Natural Rubber Reinforced with Silica Nanoparticles Extracted from Jasmine and Riceberry Rice Husk Ashes

Silica nanoparticles were synthesized by rice husk ash (RHA) produced from jasmine rice husk and riceberry rice husk via sol-gel method for the use as reinforcing fillers in natural rubber (NR). The obtained silica nanoparticles are spherical in shape and the particle sizes were observed to be in the 10-20 nm range with uniformly size distribution. The surface of silica nanoparticles was treated with a silane coupling agent confirmed by FTIR. The treated silica nanoparticles were then incorporated into NR and vulcanized with electron beam irradiation. The rubber nanocomposites with silica nanoparticles, produced from jasmine rice husk and riceberry rice husk, resulted in higher mechanical properties (tensile strength and modulus) than neat rubber vulcanizate. The modified rubber vulcanizates revealed rougher surface with tear lines as compared to the neat rubber vulcanizates, indicating the improved strength. Interestingly, the rubber nanocomposites with silica nanoparticles from jasmine rice husk showed higher tensile strength and modulus than silica nanoparticles produced from riceberry rice husk. The micrographs indicated better dispersion of NR composites with jasmine rice husk which leads to a strong interaction between silica nanoparticles and rubber matrix, thereby improving the strength.

Silica nanoparticle with a single His-tag for addressable functionalization, reversible assembly, and recycling

For many biomedical and catalytic applications, such as encapsulation of proteins/enzymes in nanoparticles (NPs), it is preferable to have well-dispersed small NPs that are stable in solution and behave quasi-homogeneously. However, conventional liquid phase methods for small-NP synthesis and functionalization usually face great difficulties in separation/purification and recycling. In addition, controlling the orientation of proteins inside NPs is also a crucial issue to maximize the activity of the encapsulated proteins. Herein, we report a solid phase method to solve these problems. Using His-tagged proteins as cores, well-dispersed core-shell silica NPs are facilely synthesized and functionalized in a column. The core His-tagged proteins are kept bound on the surface of the resin beads in the column during the entire process, making the separation/purification of NPs and their precursors during the multiple-step process as simple as a few-minutes procedure of draining and washing the column. Each obtained silica NP has an adjustable eccentric core-shell structure with only one His-tag sticking out of the particle. This single His-tag on the surface of each NP not only makes it easy for addressable and stoichiometric functionalization of the NP but also provides an easy way to reversibly assemble NPs into dimers or be oriented on the surface of large particles. Notably, this solid phase approach also provides a versatile means to control the orientation of proteins inside NPs, and the His-tag makes it easy to recycle those well-dispersed small NPs.

Silica nanoparticles produced by DC arc plasma from a solid raw materials

Plasma synthesis of SiO2 nanoparticles in experimental atmospheric pressure plasma reactor on the basis of DC arc plasma generator was presented in this paper. Solid high-silica raw materials such as diatomite from Kamyshlovskoye deposit in Russia, quartzite from Chupinskoye deposit in Russia and milled window glass were used. The obtained nanoparticles were characterized based on their morphology, chemical composition and size distribution. Scanning electron microscopy, laser diffractometry, nitrogen absorption (Brunauer–Emmett–Teller method), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy were used to characterize the synthesized products. The obtained silica nanoparticles are agglomerated, have spherical shape and primary diameters between 10-300 nm. All samples of synthesized nanopowders were compared with commercial nanopowders.

Nanosilica extraction from processed agricultural residue using green technology

Rice Husk Ash is a major voluminous and bulky by-product of rice-milling industries and its disposal is a major environmental concern. Considering this, a green technology was applied to obtain silica nano particles from Rice husk ash using sol-gel method. The solution of sodium silicate was prepared through hydrothermal activation of Rice husk ash instead of commercially available expensive and sometimes toxic raw materials. Further, the commercial production of silica requires high temperature up to 1300 °C, which makes the process energy and cost intensive. Structure, composition, morphology and size of synthesized silica powder were studied using by various techniques. X-ray Diffractometry analysis revealed broad peak of silica at diffraction angle of 22˚confirming its amorphous and non-crystalline nature. Fourier transform infrared spectroscopy results indicated the presence of silica oxygen bonding (- SiOSi) at 796 cm−1 and SiOH bonds (300-3500 cm−1). Scanning electron microscopy revealed the surface morphology of spheroid particles with little agglomeration and transmission electron microscopy gave a detailed view of internal morphology of particles interlinked with each other and of varying size in range of 10–30 nm. EDX analysis revealed presence of silicon and oxygen elements together comprising 99% by weight. Hence, proposed environmental-friendly method yielded nearly ultra-pure (98.9%) amorphous nano silica particles at lower temperature, which can be utilized in various industrial applications such as for the preparation of solar cells, nano medicine, cosmetics and filler in plastics and rubber.

Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T1-weighted MR imaging capability

The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40–55nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5T with the use of both NMR analyzer and whole body NMR scanner. Longitudinal relaxivities of the obtained silica nanoparticles reveal significant dependence on the confinement mode, changing from 4.1 to 49.6mM−1s−1 at 0.47T when the localization of Gd(III) complexes changes from core to superficial zones of the silica spheres. The results highlight predominant contribution of the complexes located close to silica/water interface to the relaxivity of the nanoparticles. Low effect of blood proteins on the relaxivity in the aqueous colloids of the nanoparticles was exemplified by serum bovine albumin. T1- weighted MRI data indicate that the nanoparticles provide strong positive contrast at 1.5T, which along with low cytotoxicity effect make a good basis for their application as contrast agents.

Synthesis of silica nanoparticles from sodium silicate under alkaline conditions

Compared to the synthesis of silica nanoparticles from tetraethyl orthosilicate, its synthesis from sodium silicate solution (SSS) in alkaline medium is less investigated. Herein, we present a study for the synthesis of non-agglomerated silica nanoparticles from SSS under alkaline conditions. SSS was diluted with water and slowly added in the mixture of ethanol and ammonia to form a sol which was aged and centrifuged to obtain silica nanoparticles. Effect of different ratios of ethanol and ammonia in the mixture on the size of silica nanoparticles was studied, and these nanoparticles were characterized using scanning electron microscopy, Fourier transformation infrared spectroscopy and X-ray diffraction techniques. It was found that the produced silica nanoparticles were spherical in shape, non-agglomerated in nature and their size could be tailored with the change in the ratio of ammonia and ethanol.

Influence of Surfactants on the Physical Properties of Silica Nanoparticles Synthesis via Sol-Gel Method

Silica nanoparticles (n-SiO2) have been synthesized using hydrolysis of Tetraethyl orthosilicate (TEOS) as starting material and ethanol as solvent by sol-gel method. The effect of different surfactants such as non-ionic surfactants sorbitan tristearate (Span 65) and sorbitan trioleate (Span 85) and anionic surfactants Sodium dodecyl sulfate (SDS) and emulsifier T-80 (Tween-80) on morphology and size of the particles was investigated. The role of these surfactants in controlling the size and properties of silica nanoparticles has been discussed. The particles size of silica nanoparticles is controlled also using Ammonia as base catalyst. Silica nanoparticles with average particles size 18 nm have been synthesized with span 65. Various analytical methods, i.e., scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV- visible absorption spectroscopy and X-ray diffraction (XRD) were used to comprehensively characterize the obtained silica nanoparticles. The synthesized Si NPs has been used for adsorption of uranium from aqueous waste solution and the best conditions were achieved at pH 4.0. The adsorption isotherms were described by means of Langmuir and Freundlich isotherm models. The maximum sorption capacity of the prepared Si NPs and experimental results showed this to be 20.6 mg.g-1.

Comparative Study on Isolation and Characterization of Amorphous Silica Nanoparticles From Different Grades of Rice Hulls

Synthesis of silica nanoparticles from three varieties of rice hulls, namely Ponni, IR-20, and CO-36, collected from five districts of Tamil Nadu, India, has been reported. Silica nanoparticles were synthesized using facile thermal decomposition method at 750°C in a muffle furnace for 3 h under controlled oxygen atmosphere. The result of an X-ray diffraction study showed that the obtained silica nanoparticles were in amorphous phase. The scanning electron microscopy and transmission electron microscopy methods were used to examine the morphology and microstructure of silica particles. The chemical and elemental compositions of the obtained silica nanoparticles were characterized by Fourier transform infrared and energy-dispersive X-ray spectroscopy, respectively.

In situ Surface Functionalization of Hydrophilic Silica Nanoparticles via Flame Spray Process

Hydrophobic silica nanoparticles grafted with a high amount of organic molecules were successfully prepared by an in situ functionalization method in flame spray pyrolysis (FSP) process. Hydrophilic SiO2 nanoparticles were converted into hydrophobic ones by silylation between 3-methacryloxypropyltrimethoxyl silane (MPS) and silica's surface hydroxyl groups. The freshly formed silica nanoparticles in flame were continuously functionalized by a fine spray of 3-methacryloxypropyltrimethoxyl silane (MPS) solution at a preferred temperature. The functionalization extent, morphology structure and size of silica nanoparticles were characterized by transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectronic spectroscopy (XPS). The influence of concentration, pH value and pre-activation of organic silane solution on the surface grafting density was investigated in detail. The obtained silica nanoparticles had a higher MPS functional content of 15.0 wt% (an average density of 2.7 MPS molecule/nm2) than that of the silica modified by wet chemistry route, showing an excellent, stable hydrophobic property. The results have demonstrated that the in situ FSP functionalization process is a simple, effective and promising route for the scalable preparation of advanced, hydrophobic nanomaterials.

Preparation and Characterization of Nano Silica from Equisetum arvenses

With the progress of nanotechnology and increase in demand, several silica processing industries have started producing silica nanoparticles. As a result, the search for new sources capable of producing this material has been attracting the interest of many researchers. With this background, a study was carried out to obtain silica nano particles from the Equisetum arvenses, a plant that possesses one of the highest amounts of silicon. This paper presents the preparation of nano silica particles with different combinations of acid washing and calcination at varying temperatures between 773 K and 873 K. The nanoparticles produced were characterized for nitrogen adsorption, morphology using transmission electron microscope and structural analysis by X-ray fluorescence and diffraction. It was found that nanoparticles produced by two cycles of acid washing and calcination at 773 K gave the best results, producing a material with white color, the highest specific surface area of about 330 m²/g with diameter of about 8 nm, and 93.5% of amorphous silica. The nanoparticles obtained can be potential industrial raw material for many applications.

Highly Mesoporous Silica Nanoparticles for Potential Drug Delivery Applications

There is an increasing interest in the use of silica nanoparticles (NPs) for bioapplications. Highly mesoporous fluorescein dye-doped silica NPs that can carry a drug payload have been successfully synthesized through a facile microemulsion process. The morphology of the as-prepared silica NPs were characterized by scanning electron microscope and transmission electron microscope, whereas their optical properties were studied by photoluminescence spectroscopy. The results revealed that these silica NPs exhibit excellent properties, including large pore volume, a narrow size distribution and strong fluorescent properties. The synthesized silica NPs showed a good biocompatibility and a low cytotoxicity when incubated in a murine fibroblast L-929 cell line. The obtained silica NPs were further used as drug delivery carriers to investigate the in vitro drug release properties using doxorubicin (DOX) as a representative drug model. It was shown that synthesized silica NPs well sustained drug release properties, suggesting their potential applications for drug delivery.

Selective removal of heavy metal ions from aqueous solutions with surface functionalized silica nanoparticles by different functional groups

The industrial silica fume pretreated by nitric acid at 80 °C was re-used in this work. Then, the obtained silica nanoparticles were surface functionalized by silane coupling agents, such as (3-Mercaptopropyl) triethoxysilane (MPTES) and (3-Amincpropyl) trithoxysilane (APTES). Some further modifications were studied by chloroaceetyl choride and 1,8-Diaminoaphalene for amino modified silica. The surface functionalized silica nanoparticles were characterized by Fourier transform infrared (FI-IR) and X-ray photoelectron spectroscopy (XPS). The prepared adsorbent of surface functionalized silica nanoparticles with differential function groups were investigated in the selective adsorption about Pb2+, Cu2+, Hg2+, Cd2+ and Zn2+ ions in aqueous solutions. The results show that the (3-Mercaptopropyl) triethoxysilane functionalized silica nanoparticles (SiO2-MPTES) play an important role in the selective adsorption of Cu2+ and Hg2+, the (3-Amincpropyl) trithoxysilane (APTES) functionalized silica nanoparticles (SiO2-APTES) exhibited maximum removal efficiency towards Pb2+ and Hg2+, the 1,8-Diaminoaphalene functionalized silica nanoparticles was excellent for removal of Hg2+ at room temperature, respectively.

Nucleation of Silica Nanoparticles Measured in Situ during Controlled Supersaturation Increase. Restructuring toward a Monodisperse Nonspherical Shape

The first stages of the nucleation and growth of silica nanoparticles are followed in situ using both SAXS and Raman spectroscopy. Coupling these two techniques allows the determination of the fractions of soluble and solid silica as a function of the reaction time. SAXS also enables demonstrating that major modifications of the structure occur after the initial precipitation period, inducing an increase of the precipitate density. These structural modifications have important implications in the initial nucleation growth stages, which have never been introduced either in classical models or in more recent kinetic nucleation theories. Such restructuration stages could contribute to explain the monodispersity of the obtained silica nanoparticles that is not predicted by classical models.

Recent Patents on the Synthesis and Application of Silica Nanoparticles for Drug Delivery

Drug delivery systems are designed to improve therapy efficacy as well as patient compliance. This could be accomplished by specifically targeting a medication intact to its active site, therefore reducing side-effects and enabling high local drug concentrations. Silica nanoparticles have gained ground in the biomedical field for their biocompatibility and biodegradability, being themselves inert and stable, thus enabling a variety of formulation designs for application in the pharmaceutical industry. This paper is a review of the recent patents on the applications of silica nanoparticles for drug delivery and their preparation. The review will focus on the different techniques available to obtain silica nanoparticles with variable morphology and their drug targeting applications, providing an overview of silica particles synthesis described in the literature.