SBA-15 Nanoporous Silica Research Articles

Effective transport of aggregated hypericin encapsulated in SBA-15 nanoporous silica particles for photodynamic therapy of cancer cells

Photodynamic therapy (PDT) represents an interesting modality for the elimination of damaged biomaterials and cells. This treatment takes advantage of the photosensitizing properties of molecules that are active only when irradiated with light. In the present work, a dual property of hypericin, a hydrophobic molecule with high performance in photodiagnostics and photodynamic therapy, was exploited. The non-fluorescent and photodynamically inactive form of hypericin aggregates was loaded into the nanopores of SBA-15 silica particles. The synthesized particles were characterized by infrared spectroscopy, thermogravimetry, differential thermal analysis, small-angle X-ray scattering and transmission electron microscopy. Hypericin aggregates were confirmed by absorption spectra typical of aggregated hypericin and by its short fluorescence lifetime. Release of hypericin from the particles was observed toward serum proteins, mimicking physiological conditions. Temperature- and time-dependent uptake of hypericin by cancer cells showed gradual release of hypericin from the particles and active cellular transport by endocytosis. A closer examination of SBA-15-hypericin uptake by fluorescence lifetime imaging showed that aggregated hypericin molecules, characterized by a short fluorescence lifetime (∼4 ns), were still present in the SBA-15 particles upon uptake by cells. However, monomerization of hypericin in cancer cells was observed by extending the hypericin fluorescence lifetime by ∼8 ns, preferentially in lipid compartments and the plasma membrane. This suggests a promising prognosis for delayed biological activity of the entire cargo, which was confirmed by effective PDT in vitro. In summary, this work presents an approach for safe, inactive delivery of hypericin that is activated at the target site in cells and tissues.

Immobilization of (l)-valine and (l)-valinol on SBA-15 nanoporous silica and their application as chiral heterogeneous ligands in the Cu-catalyzed asymmetric allylic oxidation of alkenes

Chiral heterogeneous ligands AL*-i-Pr-SBA-15 and AA*-i-Pr-SBA-15 were synthesized and then used in Cu-catalyzed asymmetric allylic oxidation of alkenes. Allylic esters with moderate enantiomeric excess and good yields were obtained.

Size and distribution of the iron oxide nanoparticles in SBA-15 nanoporous silica via SANS study

Structural characteristics of nanocomposite series consisting of iron oxide nanoparticles (NPs) embedded in the regular pores of amorphous silica matrix (SBA-15) were investigated by means of small angle neutron scattering (SANS). By virtue of unique neutron properties, insight into the inner structure and matter organization of this kind of systems was facilitated for the first time. Based on rigorous experimental support, fundamental model describing the neutron scattering intensity distribution was proposed by assuming general composite structural features. Model application to SANS data confirmed the presence of iron oxide NPs in the body of examined matrices, providing additional information on their shape, concentration and size distribution. Scattering superposition principle employed in the model conception allows for tailoring its fundamental characteristics, and renders it a potent and versatile tool for a wide range of applications.

Efficient removal of cadmium(II) with SBA-15 nanoporous silica: studies on equilibrium, isotherm, kinetics and thermodynamics

Nanomesoporous silica SBA-15 was prepared by hydrothermal method. The samples were characterized by powder X-ray diffraction and scanning electron microscopy. The fibrous particles with a diameter of 333 ± 10 nm were obtained. Nanoporous mesoporous SBA-15 was used as an adsorbent to adsorb Cd2+ in water body. The effects of conditions such as acidity were studied, and the optimized adsorption conditions were obtained. The results showed that when the pH value was 5.0, the temperature was 25 ± 1 °C and the adsorption time was 40 min, the nanomesoporous SBA-15 had the best adsorption effect for Cd2+ and the adsorption rate was reached 73.28% and the adsorption capacity was 9.84 mg/g. Study found that the adsorption is the quasi-second-order kinetic model, which belongs to the Freundlich adsorption type. The results of adsorption thermodynamics showed that when the temperature is 25–55 °C, the adsorption is spontaneous exothermic reaction, ∆G0 < 0, the adsorption enthalpy change ΔH0 = − 54.732 kJ/mol, the adsorption entropy change ∆S0 = − 129.343 J/(mol K). The effects of nitric acid and hydrochloric acid on desorption were investigated, respectively. The results showed that the desorption effect of 0.1 mol/L nitric acid as desorbent was better than that of hydrochloric acid. At desorption for 10 h, the desorption rate was the highest, reaching 65.56%.

A Novel Fluorescent Chemosensor Assembled with 2,6-Bis(2-Benzimidazolyl)Pyridine-Functionalized Nanoporous Silica-Type SBA-15 for Recognition of Hg2+ Ion in Aqueous Media

A novel fluorescent sensor for the recognition of Hg2+ in aqueous media was developed by assembly of 2,6-bis(2-benzimidazolyl) pyridine to SBA-15 nanoporous silica. The synthesized materials were characterized by techniques such as XRD, FT-IR, N2 adsorption–desorption, and TGA. Investigation of fluorescence properties of prepared material revealed emission spectra having maxima at 396 nm following excitation at 353 nm. It was found that the fluorescence intensity of the SBA-15 functionalized material remarkably quenched in the presence of Hg2+ ions in the pH range of 6–8, showing high selectively toward mercury ion among the more common tested cations. The fluorescence titration studies confirmed the linear relation between the concentration of Hg2+ ion and the fluorescence intensity quenching, and the lowest detection limit was calculated as 2.6 × 10−6 M.

Immobilization of metalloporphyrin on functionalized SBA-15 nanoporous silica

SBA-15 nanoporous silica was prepared by cooperation assembly of tetraethylorthosilicate precursor in the presence of poly (ethylene glycol)–block- poly (propylene glycol)–block- poly (ethylene glycol) copolymer surfactant and functionalized with (3-aminopropyl) triethoxysilane (APTES) via sol-gel reaction to obtain APTES-SBA-15. Tetra-(p-chlorophenyl) porphyrin (TClPP) was synthesized using modified Alder- Longo method. Zinc was inserted into the TClPP using zinc acetate as a metal source The existance of zinc in porphyrin was confirmed by the appearance of Soret band and Q band in UV- vis spectra. ZnTClPP was also characterized using FTIR and NMR spectroscopy SBA-15 was modified with APTES to immobilize the metalloporphyrin on SBA-15 surface. The product (NH-SBA-15 ZnP) can be used as a heterogenous catalyst in various reactions. The formation of this material was confirmed by FTIR spectroscopy, XRD and BET adsorption.

SAXS, FESEM AND BET STUDIES OF MESOPOROUS CATALYST SBA-15CONTAINING ZINC PORPHYRIN FOR EPOXIDATION OF LIMONENE

SBA-15 nanoporous silica was prepared by cooperative self-assembly of tetraethylorthosilicate precursor in the presence of poly(ethylene glycol)–block–poly(propylene glycol)–block–poly(ethylene glycol) copolymer surfactant and functionalized with (3-aminopropyl) triethoxysilane (APTES) via sol-gel reaction to obtain NH2-SBA-15. The metalloporphyrin, [meso-tetrakis-(p-chlorophenyl)porphyrinato]Zn(II) (ZnTClPP) was synthesized from the reaction of meso-tetrakis-(p-chlorophenyl) porphyrin (H2TClPP) using zinc acetate dihydrate as a metal source and then immobilized on SBA-15 surface. The material, NH2-SBA-15-ZnP was characterized by SAXS, FESEM and BET studies and showed a similar pattern as SBA-15 indicating that the mesoporous hexagonal structure of SBA-15 was still retained. Then, the material was applied to catalyze the epoxidation of limonene, using H2O2 / ammonium acetate at various temperatures and conditions. All the products formed from the epoxidation reaction were analyzed using GC-FID and GC-MS.

Application of a New Functionalized Nanoporous Silica for Simultaneous Trace Separation and Determination of Cd(II), Cu(II), Ni(II), and Pb(II) in Food and Agricultural Products

A novel sorbent for simultaneous separation of cadmium, copper, nickel, and lead was prepared by functionalizing SBA-15 nanoporous silica with dithizone. A solid-phase extraction method using the above sorbent was developed to separate and preconcentrate trace amounts of cadmium, copper, nickel, and lead ions from food and agricultural products by flame atomic absorption spectrometry measurements. The optimum experimental conditions such as pH; flow rates; type, concentration, and volume of the eluent; breakthrough volume; and effect of coexisting ions on the separation and determination of these heavy metals were evaluated. The extraction efficiencies for the mentioned heavy metals were greater than 97 %, and the limits of detection were 0.09, 0.16, 0.21, and 0.45 μg L−1 for cadmium, copper, nickel, and lead, respectively. The preconcentration factor for simultaneous analysis of the four heavy metals was found to be 100 approximately. The relative standard deviations of the method were <5 % for 10 separate column experiments for the determination of 5.0 μg of cadmium, copper, nickel, and lead ions. The adsorption capacity of the dithizone-SBA-15 was 189 mg g−1 for cadmium, 102 mg g−1 for copper, 91 mg g−1 for nickel, and 208 mg g−1 for lead.

A novel method for the simple and simultaneous preconcentration of Pb2+, Cu2+ and Zn2+ ions with aid of diethylenetriamine functionalized SBA-15 nanoporous silica compound

A rapid method for the extraction and monitoring of nanogram level of Pb2+, Cu2+ and Zn2+ ions using uniform silanized mesopor (SBA-15) functionalized with diethylenetriamine groups and flame atomic absorption spectrometry (FAAS) is presented. The preconcentration factor of the method is 100 and detection limit of the technique is 5.5 ng mL−1 and 1.4 ng mL−1 and 0.1 ng mL−1 for Pb2+, Cu2+ and Zn2+ respectively. The time and the optimum amount of the sorbent, pH and minimum amount of acid for stripping of ions from functionalized SBA-15 were tested. The maximum capacity the functionalized SBA-15 was found to be 183.0 (±1.9) µg, 156.0 (±1.5) µg and 80.0 (±1.6) µg of Pb2+, Cu2+ and Zn2+/mg functionalized SBA-15, respectively.

Apparent lattice expansion in ordered nanoporous silica during capillary condensation of fluids

Ordered nanoporous silica materials containing cylindrical pores on a two-dimensional hexagonal lattice are known to deform upon adsorption and condensation of fluids. These sorption strains can be measured byin situsmall-angle X-ray scattering by analysing the shift of the Bragg peaks from the ordered pore lattice. Besides the real lattice deformation due to the interaction of the solid pore walls with the fluid, a hitherto unexplained apparent lattice expansion is found experimentally in SBA-15 nanoporous silica in a narrow pressure region for three different fluids (pentane, perfluoropentane and water). It is shown that the Bragg peak shift in this region results partly from a subtle contrast effect. The pore form factor changes during capillary condensation owing to the sequential filling of pores according to their diameter. Together with the structure factor from a lattice of finite size, this leads to an effective shift of the Bragg peaks, resulting in the measured apparent lattice strain. Two simple models are presented, which aim to quantitatively describe these apparent strains. The first model employs cylindrical pores with a size distribution on a two-dimensional hexagonal lattice. Filling of pores is achieved by changing the contrast between the pores of a certain size with respect to the surrounding matrix, and the peak shift is calculated from the power spectrum of this lattice. The second model derives analytical expressions for the peak shifts as a function of pore filling fraction by using a Taylor expansion of the pore form factor and a uniform pore size distribution. Both models are able to reproduce the experimental results satisfactorily, providing the possibility to separate these apparent lattice strains from real pore wall deformation in nanoporous materials.

Simultaneous separation and determination of trace amounts of Cd(II) and Cu(II) in environmental samples using novel diphenylcarbazide modified nanoporous silica

A novel sorbent for simultaneous separation of cadmium and copper was prepared by functionalizing SBA-15 nanoporous silica with diphenylcarbazide. A solid-phase extraction method using the above sorbent has been developed to separate and concentrate trace amount of cadmium and copper ions from environmental samples by flame atomic absorption spectrophotometry measurements. The optimum experimental conditions such as pH, flow rates, type and the smallest amount of eluent for elution of cadmium and copper ions, break through volume and effect of coexisting ions on the separation and determination of cadmium and copper ions were evaluated. The extraction efficiency for cadmium and copper ions were greater than 98% and limit of detection (LOD) was 0.15 and 0.45ngmL−1 for cadmium and copper, respectively. The preconcentration factor was 294 and 291 for cadmium and copper, respectively, and the relative standard deviation (RSD) of the method was <4% for 10 separate column experiments for the determination of 5.0μg cadmium and copper ions. The adsorption capacity of the nanoporous silica was 198mgg−1 for cadmium and 105mgg−1 for copper on functionalized SBA-15 nanoporous silica. Validation of the outlined method was performed by analyzing certified reference materials (Soil (NCS DC 73323) and ore polymetallic gold Zidarovo-PMZrZ (206 BG 326)). The practical applicability of the developed sorbent was examined using real samples such as sea water, fish and sediment samples.

Novel Magnetite-Silica Nanocomposite (Fe&lt;SUB&gt;3&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt;-SBA-15) Particles for DNA Binding and Gene Delivery Aided by a Magnet Array

Novel magnetite-silica nanocomposite particles were prepared using SBA-15 nanoporous silica as template. Magnetite nanoparticles were impregnated into the nanopore array of the silica template through thermal decomposition of iron(III) acetylacetonate, Fe(AcAc)3 at 200 degrees C. These composite particles were characterized using TEM, XRD and SQUID magnetometry. The TEM images showed that the size of composite particles was around 500 nm and the particles retained the nanoporous array of SBA-15. The formation of magnetite nanoparticles was confirmed by the powder XRD study. These composite particles also exhibited ferrimagnetic properties. By coating with short chain polyethyleneimine (PEI), these particles are capable of binding DNA molecules for gene delivery and transfection. With an external magnetic field, the transfection efficiency was shown to have an increase of around 15%. The results indicated that these composite nanoparticles may be further developed as a new tool for nanomagnetic gene transfection.

Synthesis, structure and adsorption properties of nanoporous SBA-15 materials with framework and surface functionalities

Highly ordered SBA-15 nanoporous silica containing ethylene, phenylene bridges or/and amine, thiol, vinyl and phenyl surface groups were synthesized by using amphiphilic block copolymer as the structure-directing agent. The XRD data shows high degree of the order of the final structures. Obtained materials have well-developed porous structure—values of specific surface area are in the range 700–1050 m2/g and the sizes of cylindrical mesopores are in the range 6.5–9.5 nm. It was determined that size of the mesopores strongly depends even on small amounts of co-monomers co-condensing with TEOS. A new technique to introduce some amount of pendant amine groups by co-condensation of proper monomers has been proposed. Tetragonal structure was obtained when small amount of vinyl groups was introduced to the system. A new approach of determining pore size based only on the XRD measurements was compared with KJS method, confirming full usefulness of the former for calculation of the size of mesopores in SBA-15 materials.