The influence exerted by addition of 3-(methacryloyloxy) propyltrimethoxysilane (MPTMOS) on the porosity and size of silica particles synthesized in a water-ethanol-ammonia-tetraethoxysilane (TEOS) ...mixture by the Stöber-Fink-Bohn method with the subsequent calcination in oxygen at 400 °C was studied. A set of particles was synthesized at the same relative amounts of the starting reagents and at the same temperature of the reaction mixture. It was shown that as the amount of MPTMOS in the TEOS + MPTMOS precursor is raised from 0 to 12.5 mol%, the final size of the resulting SiO2 particles decreases from ∼400 to ∼10 nm, which is presumably due to the increase in the number of nucleation centers by several orders of magnitude. It was found that the particles have micropores, which are presumably formed upon removal of methacryloyloxypropyl groups by calcination. As the MPTMOS:TEOS molar ratio is raised, the micropore volume and the apparent specific surface area of the particles first grow and reach values of 0.15 сm3 g−1 (350 m2 g−1), and then decrease to 0.05 сm3 g−1 (100 m2 g−1) because the particle size (∼10 nm) becomes comparable with the pore size (1–2 nm). Upon addition of one more porogen, cetyltrimethylammonium bromide (CTAB), to the reaction mixture, the micropore volume and the apparent specific surface area of the particles substantially increase to become 0.25 cm3 g−1 and 600 m2 g−1, correspondingly, and the particle size rises to 50 nm. Probably, mesopores formed upon oxidation of CTAB micelles and micropores are mutually connected and form a common network within the particles. The total pore volume and the specific surface area of the particles determined by BET reach values of 1.05 cm3 g−1 and 1200 m2 g−1, respectively.
Display omitted
•The Stöber method was used to synthesize microporous SiO2 particles from TEOS and MPTMOS.•On replacing 12.5 mol% TEOS with MPTMOS, the size of SiO2 particles becomes 40 times smaller.•The SiO2 particles have a specific surface area determined by BET of up to 1200 m2 g−1.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Submicrometer spherical micro-mesoporous SiO2 particles have been synthesized with a Brunauer–Emmett–Teller specific surface area of up to 1600 m2 g−1, comparable with that of nanoporous carbon ...materials. The particles are constituted by densely packed SiO2 channels, similarly to materials of the MCM-41 type. The particles have two pore subsystems: monodisperse cylindrical mesopores with controllably varied average diameter (2.5–3.5 nm) and micropores supposedly situated within the walls of the SiO2 channels and between their outer surfaces. The particles with combined micro-mesoporous structure are obtained by hydrolysis of a mixture of tetraethoxysilane (TEOS) and 3-(methacryloyloxy)propyltrimethoxysilane (MPTMOS) with molar ratio 5:1 in an alcoholic–aqueous–ammonia medium containing surfactant (cetyltrimethylammonium bromide + 1,3,5-trimethylbenzene). Negatively charged products of hydrolysis of silica precursors (TEOS and MPTMOS) are condensed near the positively charged amino groups situated on the surface of the cylindrical micelles of surfactant forming SiO2 layer containing hydrophilic methacryloyloxypropyl (MP) groups in the interior. Due to the Van der Waals forces, these micelles coated with a SiO2 layer are organized into surfactant–silica clusters forming identical spherical aggregates. Removing of surfactant micelles and MP groups leads to formation of mesopores and micropores consequently.
Display omitted
•Micro-mesoporous SiO2 particles are obtained by single-step soft-template synthesis.•Porous SiO2 particles have a Brunauer-Emmett-Teller specific surface area of up to 1600 m2 g−1.•Submicrometer porous SiO2 particles have a spherical shape and a narrow size distribution.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
An approach has been developed that allows the synthesis of submicron spherical silica particles with a controlled micro-mesoporous structure possessing a large specific surface area (up to 1300 m
g
...). Particle synthesis is carried out by the hydrolysis of a mixture of various organosilanes mostly associated either with CTAB or with each other. A change in the concentration of CTAB in the reaction mixture apparently leads to a change in the formation mechanism of nuclei for the silica particle growth, which allows for varying the diameter of the synthesized particles in the range from 40-450 nm. The effect of the composition of the silica precursor (3-(methacryloyloxy)propyltrimethoxysilane, (3-aminopropyl)triethoxysilane and tetraethoxysilane) on the formation process and porosity of the resulting particles is studied. It was shown that by simply varying the ratio of organosilanes in the composition of the precursor, one can control the pore diameter of the particles in a wide range from 0.6-15 nm. The large-pore (up to 15 nm) silica particles are used as a matrix for the spatial distribution of luminescent carbon dots. The incorporation of carbon dots into SiO
particles prevents their aggregation leading to emission quenching after drying, thus allowing us to obtain highly luminescent composite particles. LEDs based on the obtained composite material show bright visible luminescence with spectral characteristics similar to that of a commercial cold white LED.
Monodisperse carbon nanodots (MCNDs) having an identical composition, structure, shape and size possess identical chemical and physical properties, making them highly promising for various technical ...and medical applications. Herein, we report a facile and effective route to obtain monodisperse carbon nanodots 3.5 ± 0.9 nm in size by thermal decomposition of organosilane within the pores of monodisperse mesoporous silica particles with subsequent removal of the silica template. Structural studies demonstrated that the MCNDs we synthesized consist of ∼7-10 defective graphene layers that are misoriented with respect to each other and contain various oxygen-containing functional groups. It was demonstrated that, owing to their identical size and chemical composition, the MCNDs are formed via coagulation primary aggregates ∼10-30 nm in size, which are, in turn, combined into secondary porous spherical aggregates ∼100-200 nm in diameter. The processes of coagulation of MCNDs and peptization of their hierarchical aggregates are fully reversible and can be controlled by varying the MCND concentration or the pH value of the hydrosols. Submicrometer spherical aggregates of MCNDs are not disintegrated as the hydrosol is dried. The thus obtained porous spherical aggregates of MCNDs are promising for drug delivery as a self-disassembling container for medicinal preparations.
Luminescent composites based on entirely non-toxic, environmentally friendly compounds are in high demand for a variety of applications in photonics and optoelectronics. Carbon dots are a recently ...developed kind of luminescent nanomaterial that is eco-friendly, biocompatible, easy-to-obtain, and inexpensive, with a stable and widely tunable emission. Herein, we introduce luminescent composites based on carbon dots of different chemical compositions and with different functional groups at the surface which were embedded in a nanoporous silicate glass. The structure and optical properties of these composites were comprehensively examined using electron microscopy, Fourier transform infrared transmission, UV-Vis absorption, and steady-state and time-resolved photoluminescence. It is shown that the silicate matrix efficiently preserved, and even enhanced the emission of different kinds of carbon dots tested. The photoluminescence quantum yield of the fabricated nanocomposite materials reached 35–40%, which is comparable to or even exceeds the values for carbon dots in solution.
Spherical micro-mesoporous silicon (mSi) particles were fabricated by thermal decomposition of monosilane (SiH4) within the mesopores of monodisperse silica particles (MSP) and subsequent etching out ...of the template material. The thermal destruction of SiH4 occurs within the whole pore volume uniformly because in the thermal chemical vapor deposition method we developed, the limiting stage of the process in which MSP pores are filled with silicon is the reaction in which monosilane is decomposed, rather than its diffusion within template mesopores. The porosity of the mSi particles synthesized can be varied without changes in the shape and outer diameter of the particles by varying the parameters of the technological process of silane decomposition. The particles have large Brunauer-Emmett-Teller specific surface area (250–350 m2 g−1) and pore volume (0.3–0.5 cm3 g−1). For the first time the obtained submicron spherical porous silicon particles are monodisperse with a size scatter not exceeding 10%, which provides the identity of their hydrodynamic and adsorption properties so important for biomedical applications. We introduced the cytostatic drug doxorubicin (DOX) into mSi pores by the physical adsorption method. It was shown that DOX is desorbed from the mSi pores and penetrates into K-562 cancer cells, with local DOX concentration maxima observed in the intracellular space. The cytotoxicity of the mSi and mSi/DOX particles was studied, and the inhibition capacities of the cancer-cell proliferation by doxorubicin adsorbed by mSi particles and a DOX solution were compared in vitro. It was shown that the half-maximal inhibitory concentration (IC50) is four times lower under the action of DOX-loaded mSi particles as compared with free doxorubicin.
Display omitted
•Monodisperse micro-mesoporous Si particles are obtained by hard-template synthesis.•Silicon is synthesized within mesoporous silica particles by thermal decomposition of SiH4.•The template material is removed by treatment of SiO2/Si particles with HF.•The IC50 value of doxorubicin-loaded mSi particles is four times lower than the IC50 of free doxorubicin.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Carbon dots (CDs) with an emission in the near infrared spectral region are attractive due to their promising applications in bio-related areas, while their fabrication still remains a challenging ...task. Herein, we developed a template-assisted method using porous silica microspheres for the formation of CDs with optical transitions in the near infrared. Two organic dyes, Rhodamine 6G and IR1061 with emission in the yellow and near infrared spectral regions, respectively, were used as precursors for CDs. Correlation of morphology and chemical composition with optical properties of obtained CDs revealed the origin of their emission, which is related to the CDs' core optical transitions and dye-derivatives within CDs. By varying annealing temperature, different kinds of optical centers as derivatives of organic dyes are formed in the microsphere's pores. The template-assisted method allows us to synthesize CDs with an emission peaked at 1085 nm and photoluminescence quantum yield of 0.2%, which is the highest value reported so far for CDs emitting at wavelengths longer than 1050 nm.
•Immobilization of Ni2+ ions at the inner surface of monodisperse spherical mesoporous SiO2 particles.•Monodisperse spherical mesoporous SiO2/Ni particles of 500±25nm diameter as metal affinity ...sorbents.•Diclofenac extraction by IMAC technique.•Addition of PFOS to IMAC eluents improves the recovery degree of diclofenac (up to 98%).•The obtained thermodynamics analysis data indicate the chemical nature of the DCF interaction with the surface of the sorbent.
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.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The approach is developed to obtain submicron spherical particles of amorphous silica with interconnected micropores. The particles were synthesized via hydrolysis of organosilanes, i.e. ...tetraethoxysilane (TEOS) and (3-methacryloyloxy) propyltrimethoxysilane (MPTMOS) in a presence of quat surfactants. It was shown that the replacement of a part of TEOS with MPTMOS in the reaction mixture led to formation of particles containing only micropores instead of mesopores. At comparable amounts of MPTMOS and quat for both Cquat > CMC and Cquat < CMC the particle growth mechanism changed from aggregative to that of the layer-by-layer type. Presumably, various associates are formed in the reaction mixture from quat surfactant and MPTMOS molecules by the van der Waals and Coulomb interactions. The associates are built into the silica framework formed as a result of hydrolysis of organosilanes. After the organics are removed, a branched system of interconnected micropores 0.5 - 2 nm in size is formed within the particles at place of the associates. The synthesized microporous particles have a specific surface area of up to ~ 1000 m2 g−1 and pore volume of up to 0.5 cm3 g−1. The adsorption of transition-metal ions (Co2+, Ni2+) by the synthesized microporous particles was studied. It was shown that the adsorption capacity of microporous particles is twice that of particles with mesopores.
Display omitted
•Fully microporous spherical SiO2 particles with SSA of up to ~1000 m2 g−1 are synthesized.•A mechanism of the particles growth from organosilane and quat molecules is proposed.•Interconnected micropores are formed at comparable amounts of MPTMOS and quat.•The adsorption capacity of microporous particles is twice that of mesoporous particles.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•Co-SiO2 composites are obtained using silica spheres with different SSA 10-1600m2/g.•SiO2 morphology determines CO3O4 particle size, distribution and Co electronic state.•Activity in ...CO oxidation and CO–PROX correlates with ratios of Co/Si and Co3+/Co2+.•Co-decorated synthetic opal with a specific surface area of 10m2/g is the most active.
Porous (0.6–30 nm) and non-porous spherical silica nanoparticles are synthesized. These silicas with different morphologies are decorated with cobalt (2.9 wt%) using Co(NO3)2·6H2O as precursor. Co-SiO2 particles are studied by N2 sorption, TEM, XRD, XPS, FTIR and TPR-H2 methods. Specific surface area (SSA) of the prepared materials is 10–1200 m2/g. The main crystalline phase is identified as Co3O4. The activity of Co-SiO2 composites in the CO oxidation and preferential oxidation of CO (PROX) in a H2-rich gas mixture improves with increasing atomic ratios of Co/Si and Co3+/Co2+ on the silica surface. Catalysts with the large mesopores containing mainly Co2+ are the least active. Co-SiO2 composites based on synthetic opal grown by sedimentation of non-porous silica particles with the lowest SSA demonstrate the highest catalytic activity. The CO conversion reaches 100% at 150 °C in the absence of hydrogen, while in PROX the 90% conversion of CO is achieved at 170 °C. The large Co3O4 aggregates between non-porous spherical silica particles of opal are the most active and stable during CO-PROX reaction. The lower interaction of Co3O4 nanoparticles with this support promotes the stabilization of the oxidized state Co3+ and provides a higher yield of CO2 in CO-PROX reaction.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
