Papers by Keyword: Mesoporous

Abstract: The use of mesoporous material as a carrier is increasingly gaining significant attention in recent years. The carrier often exists in the form of organic polymers, including chitosan and starch-g-poly (L-lactide), as well as inorganic substances, namely zeolites, sulfur, and silica. In this context, silica has the greatest abundance in nature and is extensively applied as a carrier medium due to its high selectivity, excellent regeneration ability, and environmental friendliness. However, this material shows some limitations, such as high surface tension and large inter-particle bonding forces, which can be addressed through modifications of the surface area and pore size by adding surfactants. The modifications will transform silica into a mesoporous structure, suitable for use as a slow-release carrier in various applications, including catalysts, sensors, adsorbents, chromatography, drug delivery systems, and intelligent corrosion inhibitors.

Abstract: Mesoporous SiO₂@TiO₂ (MP-SiO₂@TiO₂) core-shell particles were fabricated using mesoporous SiO₂ particles as a template in order to improve scattering performance and dye adsorption performance of the photoanode of dye-sensitized solar cells (DSSCs). They were used to make the scattering layer of the photoanode. Commercially available submicron TiO₂ particles G1 that have the same particle size as the fabricated SiO₂@TiO₂ particles were also used to make the scattering layer to compare the photoelectric properties of the DSSC. The DSSC with the photoanode without a scattering layer generated a conversion efficiency of 1.54 %. By introducing a scattering layer composed of MP-SiO₂@TiO₂ to the photoanode, the conversion efficiency was improved to 2.82 %. In addition, the DSSC with the scattering layer composed of MP-SiO₂@TiO₂ generated higher conversion efficiency than that of the DSSC with the scattering layer composed of G1 (2.35 %). From these results, MP-SiO₂@TiO₂ particles produced a high performance as scatterers in the photoanode of DSSCs.

Abstract: Biphasic calcium phosphate (BCP) is a bonegraft material which is a mixture of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA) and betatricalcium phosphate (Ca₃(PO₄)₂, β-TCP). The combination of HA and β-TCP provides faster osseointegration, compared to HA, into parent bone so it can accelerate the bone recovery process. The mesoporous structure of bone graft material is suitable for drug delivery purpose. In order to study the mesoporous structure of BCP, the BCPs were prepared by precipitation method using chitosan, aloe vera, and chitosan-aloe vera hybrid as templates. A solution containing Ca(NO₃)₂·4H₂O and template and a solution containing (NH₄)₂HPO₄ and NH₄HCO₃ were used as starting materials. All prepared samples were calcined at 900°C for 1 hour. The identification of phases and functional groups of obtained BCP powders were characterized by X-Ray Diffraction technique and Fourier Transform Infrared (FTIR) spectroscopy, repectively. The XRD patterns show typical peaks of both HA and β-TCP crystal phases. FTIR spectra confirm the presence of phosphate functional groups. Morphological analysis using Scanning Electron Microscope (SEM) observed the presence of regular porous structure, however, the mesoporous structure was not seen. Particle size distribution and pore size analysis were analyzed by Particle Size Analyzer and Brunauer–Emmett–Teller (BET) method, respectively.

Abstract: Reconstruction of bone defect due to a disease or a trauma can use autograft, allograft, xenograft or synthetic bonegraft as the bone substitute material. However, in particular cases, it is required a material that has a specific resorption characteristic, beside owning excellent bioactive properties, such as β-tricalcium phosphate (β-TCP). In this study, we report the synthesis of β-TCP particles with mesopores structure by using chitosan and aloe vera as templates. A solution of (NH₄)₂HPO₄ was added dropwise into solution of Ca(NO₃)₂·4H₂O and the template at 85°C for 2 hours, and subsequently aged for 3 hours. Then, the formed precipitate was washed and centrifuged repeatedly prior to drying at 80°C for 24 hours. Finally, the dried precipitate was calcined at 900°C for 1 hour to obtain β-TCP powder. Phase identification and mesopores structure were analyzed using X-ray diffraction (XRD), while the existence of functional groups was identified by Fourier-transform infrared (FTIR) spectroscopy. Microstructure and particle size distribution were characterized by scanning electron microscopy (SEM) and particle size analyzer (PSA), respectively. XRD analysis shows that β-TCP is dominant with the presence of small amount of impurities. Furthermore, low angle peak in XRD analysis indicates the formation of mesopores structure. From the SEM and PSA analysis, the morphology of both TCP-K and TCP-KA particles showed more large agglomerates and more heterogeneous particle size distribution due to the addition of the biopolymers in the synthesis of β-TCP.

Abstract: The drug loading capability and inherent cytotoxicity of mesoporous silica particles are two prime considerations for targeted drug delivery applications. In current study, uncoated mesoporous silica (UMS) carrier particles were synthesized by sol-gel emulsion approach. The morphology and structure of UMS was thoroughly characterized using atomic force microscope (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET). The scanning electron microscopy (SEM) and dynamic light scattering (DLS) measurements reveal that mono dispersed silica particles have an average size of 250 nm with narrow size distribution. The pore size was measured as 47nm. Concentration dependent biocompatibility of UMS was evaluated using MTT assay with Hep-2c cancer cell line and cell viability of ~65% at concentrations of 7.5 nM was observed. Finally, the drug loading capability of UMS carrier was studied using ibuprofen as a model drug.

Abstract: Magnetite nanoparticles have been successfully prepared by hydrothermal method from FeCl₃ as starting material. The properties and morphology of the products with different synthesis time and FeCl₃ concentration were investigated. Firstly, the FeCl₃ with concentration of 0.05 – 0.15 M and 0.10 M sodium citrate as well as 0.15 M were mixed with distilled water containing 0.1 g polyethylene glycol. Subsequenly, the solution was transferred into a Teflon-lined autoclave and it heated into an oven at 210°C for 12 hours. The black precipitate that formed was separated by a bar magnet, then washed with water and ethanol, and dried at 60°C overnight. The magnetite formation begun at 3.5 hours synthesis time with crystal diameter in range of 9.4-30 nm. The crystallinity and crystal size of magnetite increased with reaction time and concentration of FeCl₃. The magnetite nanoparticles had a mesoporous structure and bigger pores at higher concentration. The saturation magnetization (Ms) of magnetite was in the range of 59 – 81 Emu/g with coercivity value was near to zero showing that magnetite nanoparticle had superparamagnetic properties.

Abstract: A nanosized magnesium substituted beta-tricalcium phosphate (Mg:β-TCP) was synthesized by an aqueous precipitation method, at room temperature, in one single step. In the present study, the novel and stable Mg:β-TCP resulted in a crystalline and spherical nanoparticles (diameter of approximately 20 nm) with mesoporous structures and a high specific surface area (about 574 m²/g). These special characteristics make this novel crystalline mesoporous Mg: β-TCP nanoparticles ideal candidates for drug delivery system and a promising non-viral vector for gene therapy.

Abstract: The hollow mesoporous SiO₂/dense SiO₂/Fe₃O₄ composite particles with different pore sizes were prepared by a multistep coating technique. TEOS as a silicon source, and P123 were combinated with co-surfactant CTAB as template to coat mesoporous on the dense SiO₂/Fe₃O₄ composite particles. The influence of the pore diameter in the composite particles on the laccase immobilization amount in the composite particles and the catalytic efficiency of 2,4-dichlorophenol on hollow composite particles were researched in detail. When the pore diameter of the hollow composite particles was 4.30 nm, the laccase immobilization amount reached the maximum (234 mg/g). The pH was within 3 ~ 8 range, and the activity of immobilized laccase was obviously higher than that of free laccase molecule. And the relative activity of immobilized lactase was highest when pH was 4. When the temperature was within 303K ~ 353K, the immobilized laccase had higher relative activity than free laccase and the activity of immobilized laccase still remained 28%. The removal rate of 2,4-dichlorophenol of immobilized laccase in the composite particles was about 80%.

Abstract: In the fabrication of perovskite solar cells, the perovskite layer is typically deposited onto the TiO₂ semiconductor layer. The TiO₂ layer serves as an electron transport material (ETM). In order to form the perovskite layer firmly and evenly, a structured mesoporous (MS) TiO₂ surface is required. A porous layer could also make the electrons move more quickly through the pores to reach the contact. However, the electron-hole recombination and electron trapping in the dead end pore are still occurred. One of the solutions to overcome this problem is to add a thin compact layer (CL)-TiO₂ under MS-TiO₂ layer. The CL-TiO₂ is expected as to prevent recombination and attract electrons trapped in the MS-TiO₂ layer. In this paper, we report the addition of a thin compact layer (CL)-TiO₂ under MS-TiO₂ layer in the fabrication of perovskite solar cells based on methyl ammonium lead iodide (CH₃NH₃PbI₃). The compact layer TiO₂ was grown under mesoporous TiO₂ layer by dip-coating in TiCl₄ solution. The time of the dip coating was varied to obtain an optimum efficiency improvement. The structure of the device is glass/FTO/CL-TiO₂/MS-TiO₂/ CH₃NH₃PbI₃/Spiro-OMeTAD/Ag/FTO/glass. It was concluded that the addition of CL-TiO₂ can improve the perovskite solar cells power conversion efficiencies. The best efficiency was obtained from the 15 minutes dip-coating, which corresponded to the thinnest CL-TiO₂ out of all samples. The electrical characterization performed under irradiation with an intensity of 50 mW/cm² at 25 °C generated an open circuit voltage of 0.28 V, a short circuit current density of 0.25 mA/cm² and a power conversion efficiency of 0.60 %.

Abstract: Ceramic membranes have received significant attention from both academia and industry, as they show the great potential in several important applications such as H₂ separation, recovery of CO₂ from natural gas and reduction of green-house gas emission from flue gas. The aim of the present study was to evaluate the effect of peptizing agent concentration on morphology of unsupported alumina membranes that are suitable for gas separation. The unsupported alumina membranes were prepared by the sol-gel method using aluminum-tri-sec-butoxide as a precursor and acetic acid as a peptizing agent. The particle size distributions of produced boehmite sols, as measured by dynamic light scattering technique, range from 10 to 600 nm. The increase in the concentration of acetic acid results in formation of particles of smaller median diameter. The pore volume and size distribution of unsupported alumina membranes were characterized by the Brunauer–Emmett–Teller (BET) method of adsorption of nitrogen gas. The pore size distributions of membranes were rather narrow in the range of 3 to 6 nm. The average diameter and volume of pores increase and the surface area decreases while the concentration of acetic acid increased.