Search results for "mesoporous material"

Mesocrystalline anatase nanoparticles synthesized using a simple hydrothermal approach with enhanced light harvesting for gas-phase reaction

2018

Mesocrystalline TiO2 nanoparticles were synthesized using a hydrothermal approach. A simple two-step procedure at low temperature (<140 °C) allowed the nucleation of primary particles sized 2–4 nm and their subsequent assembly as almost spherical aggregates sized ≈20 nm. X-ray powder diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) studies, and HRTEM studies confirmed anatase as the unique TiO2 crystalline phase. The mesocrystalline structure of the anatase aggregates was clearly evidenced by HRTEM and SAED results. The mesocrystalline nanopowders exhibit a mesoporous structure with a surface area and pore volume of 63.5 m2 g−1 and 0.22 cm3 g−1, respectively. Ultraviolet …

2018

We report a novel multi-step method for the preparation of ordered mesoporous titania scaffolds and show an illustrative example of their application to solar cells. The method is based on (monolayer) colloidal nanosphere lithography that makes use of polystyrene nanoparticles organised at a water–air interface and subsequently transferred onto a solid substrate. A titania precursor solution (titanium(IV) isopropoxide in ethanol) is then drop-cast onto the monolayer and left to “incubate” overnight. Surprisingly, instead of the expected inverse monolayer-structure, a subsequent calcination step of the precursor yields an ordered monolayer of hollow titania nanospheres with a wall thickness …

Borate-driven gatelike scaffolding using mesoporous materials functionalised with saccharides.

2009

We report the development of an MCM-41 mesoporous support that is functionalised with saccharides at the pore outlets and contains the dye [Ru(bipy)(3)](2+) in the pores (solid S1; bipy = 2,2'-bipyridyl). For this hybrid system, the inhibition of mass transport of the dye from the pore voids to the bulk solution in the presence of borate is demonstrated in water at neutral pH. The formation of the corresponding boroester derivative is related to the selective reaction of borate with the appended saccharides. This control is selective and only anion borate, among several anions and cations, can act as a molecular tap and inhibit the delivery of the entrapped guest. Additionally, the S1-borat…

Spectroelectrochemistry of cytochrome c and azurin immobilized in nanoporous antimony-doped tin oxide

2011

Stable immobilization of two redox proteins, cytochrome c and azurin, in a thin film of highly mesoporous antimony-doped tin oxide is demonstrated via UV-vis spectroscopic and electrochemical investigation.

Mesoporous aluminum phosphite

2009

Abstract High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S+I− surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acid…

Mesoporous iron phosphate/phosphonate hybrid materials

2014

Abstract Relatively high surface area pure mesoporous iron-phosphorus oxide-based derivatives have been synthesized through an S + I − surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from iron atrane complexes and phosphoric and phosphonic acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from iron phosphate up to hybrids involving approximately 30% of organophosphorus entities (phosphonates or diphosphonates). X-ray powder diffraction, transmission elect…

Tailored syntheses of nanostructured silicas: Control of particle morphology, particle size and pore size

1998

Ordered mesoporous silicas with spherical morphology and average particle size in the range between 100 nm and 2 μm were synthesised according to two novel routes. Both synthesis routes used tetraethoxysilane, water, alcohol and aqueous ammonia for producing spherical silica beads. The porosity was created by adding two different kinds of pore structure directing agents to the starting solution: one was an n-alkyltrialkoxysilane which was covalently bonded to the silica framework, the other was an n-alkylamine which acted as a nonionic template. After calcination and post treatment the resulting particles showed a specific surface area up to 1000 m2 g-1, a specific pore volume of up to 0.8 …

Generalised syntheses of ordered mesoporous oxides: the atrane route

2000

Abstract A new simple and versatile technique to obtain mesoporous oxides is presented. While implying surfactant-assisted formation of mesostructured intermediates, the original chemical contribution of this approach lies in the use of atrane complexes as precursors. Without prejudice to their inherent unstability in aqueous solution, the atranes show a marked inertness towards hydrolysis. Bringing kinetic factors into play, it becomes possible to control the processes involved in the formation of the surfactant–inorganic phase composite micelles, which constitute the elemental building blocks of the mesostructures. Independent of the starting compositional complexity, both the mesostructu…

Expanding the atrane route: Generalized surfactant-free synthesis of mesoporous nanoparticulated xerogels

2008

Abstract A diversity of silica-based and non-silica nanoparticulated mesoporous xerogels have been synthesized from aqueous solution using a surfactant-free strategy, and starting from molecular atrane complexes as precursors. This approach constitutes an extension of the “atrane route” previously described for the surfactant-assisted synthesis of mesoporous materials, and allows us to unify the multiplicity of protocols described for the preparation of conventional xerogels. In fact, we have used exactly the same preparative conditions for obtaining all the compositions reported here. The xerogels synthesized in this way include pure silica (UVM-11), aluminosilicates and titanosilicates (M…

Novel pathways for the preparation of mesoporous MCM-41 materials: control of porosity and morphology

1999

Two novel synthesis routes for the preparation of mesoporous MCM-41 materials are introduced. Both methods use tetra-n-alkoxysilanes such as tetraethoxysilane (TEOS) or tetra-n-propoxysilane (TPS) as a silica source which are added to an aqueous solution of a cationic surfactant in the presence of ammonia as catalyst. In this study, n-alkyltrimethylammonium bromides and n-alkylpyridinium chlorides were employed as templates. The addition of an alcohol (e.g. ethanol or isopropanol) leads to a homogeneous system which allows the formation of spherical MCM-41 particles. The main advantages of these methods are short reaction times, excellent reproducibility and easy preparation of large batche…