Monodispersed Mesoporous Silica Spheres Research Articles

Formation of GaN Nanorods in Monodisperse Spherical Mesoporous Silica Particles

Gallium-nitride nanorods with a diameter of 15–40 nm and length of 50–150 nm are synthesized in monodisperse spherical mesoporous silica particles (MSMSPs) by high-temperature annealing of the Ga2O3 precursor in ammonia. The template material (a-SiO2) is selectively removed by etching the composite MSMSP/GaN particles with HF to give individual GaN nanorods. It is shown that the size of the GaN nanorods substantially exceeds the pore size of the MSMSPs (diameter ~3 nm, length ~10 nm). A possible mechanism by which GaN nanorods are formed is proposed. Redistribution of the material within the composite MSMSP/GaN particles possibly occurs via the surface diffusion of gaseous molecules within mesopores and via the diffusion of Ga and N atoms in a-SiO2.

Люминесцентные плазмонные структуры из наночастиц золота и углеродных наноточек в мезопористых частицах кремнезема

The composite plasmonic structures consisting of gold nanoparticles and carbon nanodots within monodisperse spherical mesoporous silica particles were synthesized. A threefold increase of visible photoluminescence intensity of carbon nanodots in these structures was demonstrated compared to structures without gold nanoparticles

Формирование наностержней GaN в монодисперсных сферических мезопористых частицах кремнезема

Gallium nitride nanorods with a 15- 40 nm diameter and a 50-150 nm length have been synthesized in monodisperse spherical mesoporous silica particles (MSMSP) by high-temperature annealing the Ga2O3 precursor in ammonia. The template material (a-SiO2) was selectively removed by etching the composite MSMSP/GaN particles in HF. The individual GaN nanorods were thus obtained. It is shown, that the size of GaN nanorods was much higher than the pore size of MSMSP (diameter ~3 nm, length ~10 nm). The possible mechanism of formation of GaN nanorods was proposed. Redistribution of material inside the composite particles MSMSP/GaN possibly occurred by surface diffusion of gaseous molecules in mesopores and by diffusion of Ga and N atoms in a-SiO2.

Pore size control of monodisperse silica particles by dual template sol–gel method

Sub 2-μm monodisperse mesoporous silica spheres (MMSS) were synthesized using a mixed template system in a MeOH/H2O solution. 1-Dodecylamine (DDA) and polymeric type Jeffamine surfactants, including D2000, D4000, and T5000, were employed as templates. These mixed template syntheses realized to gain MMSS materials with good spherical shape and uniform particle size. When the MeOH/H2O (v/v) ratio was controlled between 2.5:1 and 3.0:1, mesoporous silica spheres of 2.10–2.35 μm with excellent dispersibility can be obtained. Depending on the surfactant chain length of Jeffamine, hydrothermal aging pH (4–9), time (12–24 h), and temperature (80–140 °C), MMSS with large-pore sizes (up to 14.3 nm), surface areas (153–791 m2/g), and pore volumes (0.47–1.28 cm3/g) can be synthesized.

Evaluating the internal structure of monodispersed mesoporous silica spheres by small-angle X-ray scattering

Although the spherical morphology and mesoporous structure of monodispersed mesoporous silica spheres (MMSS) have been extensively investigated by scanning electron microscopy and transmission electron microscopy, the statistical distribution of mesopores from the surface to the center of a particle, average density of the spheres, and volume fraction of silica have not been investigated. Herein, small-angle X-ray scattering (SAXS) was performed on aqueous dispersions of MMSS with diverse sphere diameter, mesopore radius, and nanoparticle inclusion. The SAXS spectra fitted by a spherical model showed that the mesopores were homogeneously distributed in each particle. The mass density of the MMSS was obtained from the zero scattering intensity, and the volume fraction of silica was calculated considering the absorbed water in the pores. While the sphere diameter and mesopore radius had little influence, nanoparticle inclusion induced an increase in the volume fraction of silica.

Experimental Assessment of the Structural Parameters of Highly Porous Silica: Probe Microscopy Data

The morphology of monodisperse spherical mesoporous silica particles with a regular pore structure is studied with atomic force microscopy. The size of nanotubes is found: the internal diameter is 2.6 nm, the external diameter is 4.8 nm, and the wall thickness is 1.1 nm. A method for assessing the strength parameters of highly porous materials is proposed. The calculated Young’s modulus of a nanotube along its axis is 91.7 GPa.

Synthesis of high-quality carbon nanotubes by using monodisperse spherical mesoporous silica encapsulating iron oxide nanoparticles

Well-graphitized carbon nanotubes (CNTs) were grown by using monodisperse spherical mesoporous silica encapsulating single iron oxide (Fe3O4) nanoparticles (MSEINPs) as catalytic templates by chemical vapor deposition (CVD) and using acetylene as carbon source. The catalytic templates were synthesized by a sol-gel method. The MSEINPs exhibited better activity and selectivity in CNT synthesis than bare Fe3O4 catalysts. The synthesized multiwall carbon nanotubes (MWCNTs) were analyzed by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy. The carbon deposits are rich in MWCNTs, as confirmed by FESEM and TGA. The wall thickness of the MWCNTs is controlled primarily by the size of the spherical mesoporous silica layer encapsulating the Fe3O4 NPs, while the inner diameter of the CNTs is determined by the size of the Fe3O4 NPs at the center of the MSEINPs. The average diameter of the MWCNTs increased significantly with increases in the growth temperature and acetylene flow rate. The analytical results show that the CNTs prepared on MSEINPs are well graphitized with a narrow size distribution in thickness, and straight and longer tubes are obtained without major defects as compared to the CNTs grown on bare Fe3O4 NPs.

Investigation of Toxic Effect and Penetration into Cells of Monodisperse Spherical Composite Particles Based on Mesoporous Silica

Сomposite particles based on monodisperse spherical mesoporous silica particles (MSMSPs) are synthesized by noncovalent binding of organic active components (propidium iodide fluorescent dye and Radakchlorin photosensitizer) from aqueous solutions. Hybrid particles with a core–shell structure are synthesized, which are MSMSPs filled with Fe3O4 and coated with mesoporous silica, the internal surface of which is modified by Fluorescein isothiocyanate (FITC) fluorescence dye by means of chemisorption. The toxicity and penetration of the obtained particles into the cells of the HeLa and K-562 cell lines were studied. The effective photodynamic action of MSMSPs containing Radachlorin in mesopores is demonstrated, which indicates the promise of using the synthesized composite particles for medical purposes.

Template Synthesis of Monodisperse Spherical Nanocomposite SiO2/GaN:Eu3+ Particles

A nanocomposite in the form of monodisperse spherical mesoporous silica particles (mSiO2) filled with GaN:Eu3+ is synthesized by the template method. The method is based on the capillary impregnation of pores of mSiO2 particles with a melt of crystal hydrates of gallium and europium (0.22 wt %) nitrates, followed by thermal decomposition and ammonia treatment. It is shown that nanocomposite particles contain hexagonal GaN:Eu3+, are of spherical shape, monodisperse and do not coalesce with each other. The photoluminescence spectra of the mSiO2/GaN:Eu3+ particles show a group of lines characteristic of intracenter transitions in Eu3+.

Матричный синтез монодисперсных сферических нанокомпозитных частиц SiO-=SUB=-2-=/SUB=-/GaN:Eu-=SUP=-3+-=/SUP=-

AbstractA nanocomposite in the form of monodisperse spherical mesoporous silica particles (mSiO_2) filled with GaN:Eu^3+ is synthesized by the template method. The method is based on the capillary impregnation of pores of mSiO_2 particles with a melt of crystal hydrates of gallium and europium (0.22 wt %) nitrates, followed by thermal decomposition and ammonia treatment. It is shown that nanocomposite particles contain hexagonal GaN:Eu^3+, are of spherical shape, monodisperse and do not coalesce with each other. The photoluminescence spectra of the mSiO_2/GaN:Eu^3+ particles show a group of lines characteristic of intracenter transitions in Eu^3+.

Monodisperse core–shell particles composed of magnetite and dye-functionalized mesoporous silica

Hybrid particles with a core–shell structure have been obtained in the form of monodisperse spherical mesoporous silica particles filled with magnetite and covered with a mesoporous silica shell functionalized with a luminescent dye. The particles have a small root-mean-square size deviation (at most 10%), possess a specific surface area and specific pore volume of up to 250 m2/g and 0.15 cm3/g, respectively, and exhibit visible luminescence peaked at a wavelength of 530 nm. The particles can be used in diagnostics of cancerous diseases, serving simultaneously for therapeutic (magnetic hyperthermia and targeted drug delivery) and diagnostic (contrast agent for magnetic-resonance tomography and luminescent marker) purposes.

Ni-functionalized submicron mesoporous silica particles as a sorbent for metal affinity chromatography

In this research, a novel IMAC sorbent with high specificity for chlorine-containing compounds was developed. Ni-functionalized monodisperse spherical mesoporous silica particles of 500±25nm diameter were synthesized and their metal affinity properties were studied with the use of diclofenac as the model substance. The particles were aggregatively stable in the pH range of 3–12. The sorbent demonstrated a high adsorption capacity (0.60±0.06μg of DCF per 1mg of the sorbent) and high adsorption/desorption rate (20 and 5min was enough for the sorbent saturation and desorption of DCF, correspondingly). A mixture of eluents with addition of PFOS providing the almost complete recovery (98%) of diclofenac was first proposed. The monodispersity and the high sedimentation and aggregative stability of the particles provide the formation of a stable hydrosol even under ultrasound treatment which makes the mSiO2/Ni particles suitable for batch chromatography.

Preparation of sub-2 μm large-pore monodispersed mesoporous silica spheres using mixed templates and application in HPLC

Sub-2 μm large-pore monodispersed mesoporous silica spheres (MMSS) were synthesized by using mixed non-ionic surfactants of dodecylamine (DDA) and dodecylamine polyoxyethylene ether (AC1210) as templates through an alkali-catalyzed silica sol–gel technique combined with the template method. Methanol-H2O volume ratio on morphology was researched in detail. In addition, by using hydrothermal treatment, the average pore size of MMSS could be enlarged to 11 nm from 4.4 nm. The mesoporous silica particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser particle size analyzer, X-ray diffraction, N2 physisorption technique. The synthesized sub-2 μm monodispersed mesoporous silica microspheres were successfully functionalized by dimethyloctadecylchlorosilane and used as a packing material in high performance liquid chromatography (HPLC).

In situ green synthesis of fluorescent monodispersed mesoporous silica spheres/poly(p-phenylenevinylene) composites

A facile one-pot synthesis for the composite materials fabricated from conjugated polymer, poly(p-phenylenevinylene) (PPV), and monodispersed mesoporous silica spheres (MMSS) is demonstrated. Composite materials having superior photoluminescence properties are easily obtained using ethylene glycol as a reaction solvent in which PPV monomers are effectively exchanged with cationic surfactants in MMSS and subsequently polymerized in the solution. The method can prevent serious reduction of photoluminescence properties which occurs inevitably during thermal treatment (200°C) to polymerize PPV. In our method, the temperature of 100°C is enough to obtain the fully polymerized PPV, which is confirmed in Fourier transform infrared (FT-IR) spectrum. Reaction mechanism is verified through direct observation of its distinguishable color changes in the reaction solution and the measurement of surface electrical potential (ζ-potential). The obtained results strongly support that PPV chains are impregnated within mesopores in isolated condition, leading to high fluorescence quantum yield (nearly 80%). Compared to the conventional route, this method reduces multistep synthesis to one-step and eliminates high temperature and high vacuum process, leading to the facile eco-friendly procedure.

Mesoporous Silica Supported Au and AuCu Nanoparticles for Surface Plasmon Driven Glycerol Oxidation

Herein, we report for the first time the visible-light-assisted rate enhancement for glycerol oxidation using direct plasmonic photocatalysis. Au nanoparticles were loaded on various mesoporous SiO2 supports, and the catalytic performance was investigated with and without visible-light illumination. Monodispersed mesoporous silica spheres loaded with Au nanoparticles demonstrated a superior photoassisted catalytic rate enhancement compared to Au loaded ordered mesoporous silica (SBA-15, KIT-6, and MCM-41). The enhancement is attributed to the particle size of the Au nanoparticles and better light interaction resulting from the small SiO2 domains. Au loaded monodispersed mesoporous silica spheres exhibit a constant and remarkably small particle diameter of 2 nm at Au loadings of up to 15 wt % as a result of the support’s small domain size and efficient pore confinement. The performance of the Au catalyst could be further improved by preparing bimetallic AuCu nanoparticles. Synergistic effects between Au an...

Activator-free luminescent nanocontainers for theranostics of cancerous growths

Single-stage synthesis has been used to obtain submicrometer monodisperse spherical mesoporous silica particles exhibiting bright wide-band luminescence in the visible spectral range. The particles have a specific surface area of 550 m2/g, pore volume of 0.36 cm3/g, and average pore diameter of 0.3 nm. The synthesis technology provides formation of an active inner surface (surface of mesopores), which will enable binding and retention of medicinal preparations upon their introduction into the particles. The particles are promising for application in theranostics of cancerous growths as nanocontainers simultaneously serving as biomarkers.

Hollow Metal-Incorporated Monodispersed Mesoporous Silica Spheres.

Expansion of mesopores and concomitant incorporation of metal species into mesoporous silica particles was achieved through the hydrothermal treatment of monodispersed mesoporous silica spheres in an aqueous metal salt solution. Mesopore size was increased to 24 nm from 2.2 nm while retaining monodispersed spherical shape. Surprisingly, hollow spheres were produced when Mg salt was used. Incorporation of metal species led to drastic improvement in adsorption performance. The amount of Rhodamine B adsorbed was increased by 27 times.

Synthesis of Mesoporous Silica Microspheres by PICA and Pseudomorphic Transformation Using Silica Fume as Silica Source

Monodisperse mesoporous silica microspheres (MSM-SF) were successfully prepared through PICA and pseudomorphic transformation using silica fume as original silica source. The structure and morphology of spheres were quantitatively investigated by Zata potential and particle size analyzer, N2 sorption isotherms, XRD, SEM and TEM. The results showed that the monodisperse spherical mesoporous silica microspheres (MSM-SF) exhibited uniform spherical morphology, worm-like mesoporous, large BET surface area of 559.9m2/g; its BJH average pore size diameter and total pore volume are 3.3nm and 0.12cm3/g, respectively. This preparation method provides a new synthetic strategy to control the particle morphology and structure simultaneously, meanwhile this method can also significantly reduce the cost of synthesis of mesoporous silica microspheres.

Damping of coherent acoustic vibrations by nanosized pores in colloidal hypersonic crystals

We investigated the damping of the coherent acoustic vibrations in the presence of the nanosized pores in colloidal hypersonic crystals. The colloidal crystal samples are comprised of close-packed silica or monodisperse mesoporous silica spheres, where the mesoporous silica sphere contains radially aligned uniform nanosized pores. The decay of the acoustic vibrations was monitored by using ultrafast pump-probe spectroscopy. Two types of coherent acoustic modes are observed, the propagating bulk mode and the localized surface mode. Our studies show that porous structure could have different effects on different modes of vibrations. While the bulk mode is heavily damped due to the scattering from the nanosized pores, the surface mode is much less influenced.

Hypersonic properties of monodisperse spherical mesoporous silica particles

We use the picosecond acoustic pump-probe technique to study the elastic properties of monodisperse mesoporous silica spheres filled with nickel and deposited in the form of opal-like films on silica substrates. The picosecond pump-probe optical transmission signal shows harmonic oscillations corresponding to the lower energy radial Lamb mode in the vibrational spectrum of the spheres. These oscillations, with a frequency of several gigahertz last for several nanoseconds in the spheres with diameter 1050 nm, showing high homogeneity of the sphere parameters. By analysis of the oscillation spectrum of films with different sphere diameters and nickel content we obtain the elastic moduli of the mesoporous silica spheres.