Mesoporous Titania Silica Research Articles

CuFeS2 supported on dendritic mesoporous silica-titania for persulfate-assisted degradation of sulfamethoxazole under visible light

Sulfamethoxazole (SMX) is a prevalent sulfonamide antibiotic found in the environment, and it has a variety of detrimental effects on environmental sustainability and water safety. Recently, the combination of photocatalysis and sulfate radical-based advanced oxidation processes (SR-AOPs) has attracted a lot of interest as a viable technique for degradation of refractory pollutants. In this study, a visible light active CuFeS2 supported on dendritic mesoporous silica-titania (CuFeS2-DMST) photocatalyst was synthesized to improve the ability of TiO2 to activate persulfate (PS) by introducing CuFeS2 (Fe2+/Fe3+, Cu+/Cu2+ redox cycles). The CuFeS2-DMST/PS/Vis system demonstrated superior SMX degradation efficiency (88.9%, 0.0146 min−1) than TiO2 because of reduced e-/h+ recombination, excellent charge separation and mobility, and a greater surface area than TiO2. Furthermore, after four consecutive photocatalytic cycles, the system demonstrated moderate stability. From chemical quenching tests, O2●-, h+, 1O2, SO4●- and ●OH were found to be the main reactive oxidizing species. The formed intermediates during the degradation process were identified, and degradation mechanisms were proposed. This study proposes a viable technique for activating PS using a low-cost, stable, and high-surface-area TiO2-based photocatalyst, and this concept can be applied to design photocatalysts for water treatment.

Characteristics of Synaptic Function of Mesoporous Silica-Titania and Mesoporous Titania Lateral Electrode Devices.

In this paper, we have fabricated non-volatile memory resistive switching (RS) devices and analyzed analog memristive characteristics using lateral electrodes with mesoporous silica-titania (meso-ST) and mesoporous titania (meso-T) layers. For the planar-type device having two parallel electrodes, current-voltage (I-V) curves and pulse-driven current changes could reveal successful long-term potentiation (LTP) along with long-term depression (LTD), respectively, by the RS active mesoporous two layers for 20~100 μm length. Through mechanism characterization using chemical analysis, non-filamental memristive behavior unlike the conventional metal electroforming was identified. Additionally, high performance of the synaptic operations could be also accomplished such that a high current of 10-6 Amp level could occur despite a wide electrode spacing and short pulse spike biases under ambient condition with moderate humidity (RH 30~50%). Moreover, it was confirmed that rectifying characteristics were observed during the I-V measurement, which was a representative feature of dual functionality of selection diode and the analog RS device for both meso-ST and meso-T devices. The memristive and synaptic functions along with the rectification property could facilitate a chance of potential implementation of the meso-ST and meso-T devices to neuromorphic electronics platform.

A Comparative Study of PMETAC-Modified Mesoporous Silica and Titania Thin Films for Molecular Transport Manipulation.

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both mesoporous silica and mesoporous titania thin films. Pores were proven to be filled using ellipsometry and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Furthermore, the employed method leads to a polymer overlayer, whose thickness could be discriminated using a double-layer ellipsometry model. Cyclic voltammetry experiments reveal that the transport of electrochemically active probes is affected by the PMETAC presence, both due to the polymer overlayer and the confined charge of the pore-tethered PMETAC. A more detailed study demonstrates that ion permeability depends on the combined role of the inorganic scaffolds' (titania and silica) surface chemistry and the steric and charge exclusion properties of the polyelectrolyte. Interestingly, highly charged negative walls with positively charged polymers may resemble zwitterionic polymer behavior in confined environments.

Reflective Paint Consisting of Mesoporous Silica Aerogel and Titania Nanoparticles for Thermal Management

Thermal insulation paint material is an energy-critical coating component for thermal management in energy-efficient buildings, vehicles, electronics, and data centers. Long-standing pursuits for the paint coating materials are high thermal insulation and light reflectance, mechanical durability, and wear resistance. Here we describe an aqueous-based hierarchical coating nanocomposite composed of mesoporous silica aerogel and titania nanoparticle pigment paint which exhibits a low thermal conductivity of 0.029 W/m K, a high visible reflectance of 90%, and a mechanical Young’s modulus of ∼4.86 MPa with a high abrasion resistance. The hierarchical and hydrophobic nanocomposite coatings show robust thermal cycling and thermal resistance, resulting in an equivalent cooling power of 928 W/m2. The design and manufacturing principle reported here could extend to a variety of insulation coating materials to achieve energy efficiency and sustainability.

Examining the Role of Atomic Scale Heterogeneity on the Thermal Conductivity of Transparent, Thermally Insulating, Mesoporous Silica–Titania Thin Films

This paper examines the effect of compositional heterogeneity on the thermal conductivity of transparent, mesoporous silica–titania composites that contain either 10 or 20 mol % titania. The relative hydrolysis rates of the silica and titania precursors were modified to control their compositional heterogeneity, while the ratio of polymer to inorganic precursors (silica + titania) was varied to control the porosity of the films. All films were optically transparent at thicknesses up to 1 μm with transmittance above 90% and haze below 5% at visible wavelengths. It was found that the heterogeneity of the titania species in the 10 mol % titania samples could be easily tailored from highly dispersed titania to a composition with heterogeneous silica-rich and titania-rich domains. By contrast, samples with 20 mol % titania always showed a heterogeneous titania distribution. The results show that mesoporous films with more homogeneously distributed titania had a lower thermal conductivity at all porosities, likely due to increases in propagon and diffuson scattering as a result of the increased number density of titania heteroatom scattering centers. These results increase our understanding of heat carrier propagation in amorphous materials and add to the design rules for creating amorphous, optically clear, low thermal conductivity materials.

Facile synthesis of mesoporous Pt-doped, titania-silica nanocomposites as highly photoactive under visible light

Mesoporous titania-silica (MTO) and mesoporous Pt-doped titania-silica (Pt@MTO) nanocomposites were synthesized by a facile synthesis procedure, and then, the nanocomposites were analyzed through a diverse range of techniques. XRD peaks and HRTEM images showed that the anatase phase of MTO and platinum was doped on the surface of the morphology of MTO as dots with an average size of 6nm. Pt metallic nanoparticles were present in samples highly dispersed into mesoporous MTO. The varying portion of doping with Pt in the samples has a positive impact on the surface characteristics of nanocomposites. In addition, the increased ratio of Pt metallic nanoparticles in the samples reduced the band gap energies to 2.12eV for 2.0% Pt@MTO and reduced the intensity of the emission spectrum by shifting the emission spectrum to a higher wavelength. The photocatalytic activity was measured by the degradation of ciprofloxacin (CIP) in the suspension. The 1.5% Pt@MTO photocatalyst fully photodegraded CIP after 60min of irradiation. That performance exhibited excellent stability and recyclability.

Cavitation-Inducible Mesoporous Silica-Titania Nanoparticles for Cancer Sonotheranostics.

Sonodynamic therapy has received increasing attention for cancer treatments as an alternative to photodynamic therapy. However, its clinical applications have been limited by the lack of a sonosensitizer that is capable of producing sufficient amounts of reactive oxygen species (ROS) in response to ultrasound (US) exposure. Herein, PEGylated mesoporous silica-titania nanoparticles (P-MSTNs) are prepared and used as US-responsive nanocarriers for cancer sonotheranostics. Perfluorohexane (PFH), which is chosen as the gas precursor, is physically encapsulated into P-MSTNs using the oil-in-water emulsion method. Owing to the vaporization of the gas precursor, PFH@P-MSTNs (137 nm in diameter) exhibit a strong photoacoustic signal in vivo for at least 6 h. Compared to P-MSTNs, PFH@P-MSTNs generate significantly higher amounts of ROS due to the nanobubble-induced cavitation in the presence of US. When systemically administered to tumor-bearing mice, PFH@P-MSTNs effectively accumulate in the tumor site due to the passive targeting mechanism. Consequently, PFH@P-MSTNs show much higher antitumor efficacy than P-MSTNs due to the enhanced cavitation-mediated ROS generation in response to US exposure. It is considered that PFH@P-MSTNs may hold significant potential for cancer sonotheranostics.

Mesoporous Titania-Silica nanocomposite as an effective material for the degradation of Bisphenol A under visible light

A simple and very effective method is proposed for the removal of Bisphenol A (BPA) under visible light using mesoporous TiO2-SiO2 nanocomposite. The material was characterized using FTIR, XRD, DRS, XPS, FESEM, HRTEM, and BET techniques. The photo degradation efficiency of TiO2-SiO2 compared with bare TiO2. The effect of calcination temperature on the photo-degradation of the materials is also studied. The radical intermediates formed during the degradation of BPA were followed with different radical scavengers. The solution after reaction is subjected to TOC (Total Organic Carbon content) and LCMS analysis to determine the mineralization rate and degradation products exist in the solution. Kinetic studies were revealed that the degradation process follow pseudo first order kinetics.

Thermally stable Au decorated silica-titania mesoporous nanocomposite for pH sensing evaluation

Herein, doping/decoration of gold nanoparticles (AuNPs) within mesoporous silica-titania nanocomposite is achieved via a facile and co-assembly sol-gel method. Polyethylene glycol is used as a co-structure-directing-agent. For sensing analysis, a mixture of organic dyes i.e., bromophenol blue, phenol red, and cresol red is encapsulated in the AuST nanocomposite matrix. FESEM/EDX analysis shows a crack-free surface, porous network and uniform distribution of Au, Ti, Si, along with dye species. FTIR and XRD suggested the heterogeneous chemical bonding and crystallite size 24 nm after encapsulation. AuST nanocomposite shows thermally stable behavior after 450 °C even after co-dyes encapsulation. High surface area 322 ± 2.5 m2/g, pore diameter 30.2 Å, and pore volume 0.24 cm3/g, average surface roughness 10 nm, and refractive index 1.29 is advantageous for good sensing response at pH 1–12. The sensitivity is measured as 10 counts/pH at 441 nm. Moreover, good reversible response, fast response time 2.1 sec in acidic media, and 0.9 sec in basic media is observed.

Preparation of mesoporous anatase titania with large secondary mesopores and extraordinarily high photocatalytic performances

A mesoporous titania (SN2) with three-dimensional (3D) large secondary mesopores (6.2 nm) highly connecting the mesochannels was prepared employing the method of first synthesizing an ordered 2D hexagonal mesoporous titania-silica nanocomposite (SN1) via “synchronous-assembly” of inorganic precursors with surfactant molecules, then “extracting silica”. Our tactic adopts a large amount of silica, a high crystallization temperature and mild silica extraction. The 3D interconnectivities of the resultant mesochannels are quite high, but the mesostructures are retained intact. Titania is fully anatase crystalline with uniform nanocrystals size (11.2 nm) and a high specific surface area (∼ 174 m2 g−1). This strategy is gentle, simple and easily reproducible. SN2 presents extremely-high photocatalytic degradation activities to anionic azo dyes like acid red 1 and reactive brilliant red X3B, which reach 55.9 and 51.1 times that of commercial P25 photocatalyst, even up to 87.0 and 84.7 times that of SN1, respectively; and far higher than that of the contrast sample (CS) possessing 3D small secondary mesopores (2.7 nm). Additionally, SN2 also displays a very high activity to microcystin-LR, which is much higher than that of P25 and CS, respectively. Our results clearly indicate that the large secondary mesopores play a key role in the great increases of activities. Moreover, our photocatalyst is considerably stable and reusable. Such results have hitherto not been seen in the literature. Furthermore, this method would pave the way for the rational design and preparation of ordered mesoporous other metal-oxides with large secondary mesopores and unexpected performances.

Core–shell structured magnetic mesoporous silica-titania: A novel, powerful and recoverable nanocatalyst

In this research, a novel core–shell nanostructured magnetic Ti-silica (Mag@MCM-41/TiO2) is synthesized, characterized and its catalytic application is investigated in the production of 1-(α-aminoalkyl)-2-naphthols. The Mag@MCM-41/TiO2 was prepared via surfactant directed hydrolysis and co-condensation of tetramethoxysilane (TMOS) around Mag@SiO2 NPs followed by treatment with tetrabutylorthotitanate (Ti(OtBu)4). The Mag@MCM-41/TiO2 catalyst was characterized using VSM, FTIR, EDX, SEM, TEM and PXRD. The Mag@MCM-41/TiO2 was applied as an efficient catalyst in the synthesis of 1-(α-aminoalkyl)-2-naphthols under ultrasonic conditions at 50 °C. This nanocatalyst was recovered and reused for several times under applied conditions.

Analog Memristive Characteristics of Mesoporous Silica-Titania Nanocomposite Device Concurrent with Selection Diode Property.

A threshold resistive switching (RS) device concurrently demonstrating analog memristive property with mesoporous silica-titania (m-ST) nanocomposites is introduced in this study. The nanostructured m-ST layer in an Al/m-ST/Pt device was constructed by facile soft templating of evaporation-induced self-assembly (EISA) method to demonstrate nonlinear threshold RS behaviors accompanying with discrete synaptic characteristics along with adaptive motions. The EISA layer was composed of well-ordered mesopores (∼10 nm), where paths of electrical currents could be controllably guided and sequentially activated by repeated voltage sweeps. The combinational memristive behavior accompanying the shift of threshold voltage (Vth) could implicate concurrent performances of threshold RS and selection diode devices. In addition, synaptic functionalities of long-term potentiation and depression were characterized by variations of pulse timing width (7-100 ms). Physical and chemical features of the m-ST were analyzed with Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and optical microscopy to investigate the unique origin of dual operation modes of the device. The m-ST synaptic device could have potential for further development of a hybrid selection diode having both a low sneaky current loss and memristive characteristics accomplishing low level of cross-talk between RS devices.

CO Preferential Photo-Oxidation in Excess of Hydrogen in Dark and Simulated Solar Light Irradiation over AuCu-Based Catalysts on SBA-15 Mesoporous Silica-Titania.

In this work, SBA-15 silica and silica-titania have been used as supports for photocatalysts based on AuCu alloy (Au:Cu = 1) to be used in the preferential oxidation of CO (CO-PROX) in excess of hydrogen at room temperature and atmospheric pressure both in the dark and under simulated solar light irradiation. To study their textural, structural, chemical and optical properties, the samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), adsorption-desorption of N2 at −196 °C, 13C and 29Si solid state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance ultraviolet-visible (DRUV-vis) spectroscopy. Titanium was present mainly in the form of titania aggregates, but also as small particles interacting with the SBA support. In both catalysts, the metal alloy nanoparticles displayed an average size of 4 nm as demonstrated by TEM measurements. AuCu/Ti-SBA turned out to be photoactive and selective in the photo-CO-PROX reaction showing the highest activity, with conversion and selectivity towards CO2 of 80%, due both to the presence of titania incorporated in SBA-15 and to the synergistic effect of Cu when alloyed with Au.

Au and AuCu Nanoparticles Supported on SBA-15 Ordered Mesoporous Titania-Silica as Catalysts for Methylene Blue Photodegradation.

The photocatalytic degradation of methylene blue (MB) dye has been performed under UV irradiation in aqueous suspension, employing photocatalysts based on Au (1.5 wt %) and AuCu (Au/Cu = 1, 2.0 wt %), and supported on SBA-15-ordered mesoporous silica, with and without titania (Si/Ti = 3), in order to evaluate the versatility of this mesoporous support in this type of reaction of great impact from the environmental point of view. Samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption at −196 °C, and X-ray photoelectron spectroscopy (XPS), so as to study their structural, optical, and chemical properties. All the prepared catalysts were found to be active in the test reaction. The bimetallic AuCu-based catalysts attained very high MB degradation values, in particular AuCu/SBA-15 titania-silica sample reached 100% of dye oxidation after the monitored reaction period (120 min).

Effect of the Composition of Mesoporous Titania–Silica Oxide Photocatalysts on Their Activity During the Destruction of Methylene Blue in Aqueous Solutions

Mesoporous titania–silica oxide materials of various compositions with high crystallinity and predominantly in the anatase modification were produced by hydrolysis and subsequent heat treatment of a mixture of titanium tetrachloride and oligodimethylsiloxane (ODMS) containing terminal Si–Cl groups. The synthesized samples were tested as photocatalysts in the destruction of methylene blue dye in aqueous solutions. The highest activity, significantly exceeding the activity of commercial TiO2, the highest specific surface area, and porosity was exhibited by the photocatalyst prepared from 33 wt.% ODMS. The photocatalysts are active not only under the action of UV but also of visible light. This may be due to the effect of carbon doping of TiO2 during ODMS decomposition, which increases the light absorption and improves the separation of the photogenerated charges.

Hollow mesoporous architecture: A high performance Bi-functional photoelectrocatalyst for overall water splitting

The metal/metal oxide and halide nanocomposites are emerging and effective photo/electrocatalyst to replace very expensive materials. These are remarkably preferred for efficient hydrogen production in energy conversion and storage technologies. Regardless of recent progress, their activity and durability are still far from adequate, due to less visible light effectiveness, wide band gape and high overpotential and low current density. Herein we successfully coupled a novel visible light accessible photo/electrocatalyst, silver-silver bromide doped hollow mesoporous silica-titania (Ag-AgBr/HMST). The syntheses of these composites were carried out using a facile one-pot micro-emulsification method at controlled calcination temperature. The results of the physicochemical characterization indicates that the composite obtained at optimal calcination temperature (550 °C), has exceptional morphology, high surface area, and uniformly distributed particles. These features exhibits the illustrious visible light induced photo/electrocatalytic behavior for overall water splitting. The hollow silica-titania provides incredible quality conducting channel, to get better mass loading and boost the charge transportation. While well-built connection of Ag, AgBr with titania, provides well active sites that accomplish obvious photo/electrocatalytic performance with OER current density of 10 mAcm−2 at 280 mV and HER current density of 65 mAcm−2 at −173 mV. This is almost equal to RuO2 and Pt/C that are very expensive catalyst for water oxidation. Therefore, the present work establishes the first example of hollow mesoporous photo/electrocatalyst for OER and HER water splitting. The outstanding durability prop up the use of mesoporous material for renewable energy application.

Dendritic mesoporous silica–titania nanospheres with enhanced photocatalytic activities

Dendritic mesoporous silica–titania nanospheres (DMSTN) show remarkable performance as a photocatalyst and an adsorbent for photochromic methylene green (MG) dye.

Synthesis of Mesoporous Titania–Silica Monolith Composites — A Comprehensive Study on their Photocatalytic Degradation of Acid Blue 113 Dye Under UV Light

The present work deals with the synthesis of bi-continuous macro and mesoporous crack-free titania–silica monoliths, with well-defined structural dimensions and high surface area. The work also highlights their potential photocatalytic environmental applications. The highly ordered titania–silica monoliths are synthesized through direct surface template method using organic precursors of silica and titania in the presence of surface directing agents such as pluronic P123 and PEG, under acetic acid medium. The monoliths are synthesized with different Ti/Si ratios to obtain monolithic designs that exhibit better photocatalytic activity for dye degradation. The titania–silica monoliths are characterized using XRD, SEM, EDAX, FT-IR, TG–DTA and BET analysis. The photocatalytic activity of the synthesized monoliths is tested on the photodegradation of a textile dye (acid blue 113). It is observed that the monolith with 7:3 ratio of Ti/Si showed significant photocatalysis behavior in the presence of UV light. The influence of various physico-chemical properties such as, solution pH, photocatalyst dosage, light intensity, dye concentration, effect of oxidants, etc. are analyzed and optimized using a customized photoreactor set-up. Under optimized conditions, the monoliths exhibited superior degradation kinetics, with the dye dissipation complete within 10[Formula: see text]min of photolysis. The mesoporous catalysts are recoverable and reusable up to four cycles of repeated usage.

Mesoporous SiO2–TiO2 nanocomposite for pH sensing

Thermally stable mesoporous silica–titania nanocomposite matrix was obtained via sol–gel method. The samples prior and after heat treatment were characterized by analytical instrumental techniques like Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDX), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), surface area, porosity measurements and UV–Vis Spectroscopy. The FE-SEM and AFM micrographs suggest that the indicator molecules are homogeneously diffused into matrix pores of the silica–titania network. The matrix exhibits regular morphology with large pores without any cracks. Energy Dispersive X-ray Spectroscopy (EDX) analysis verified the stoichiometric formation of encapsulated silica–titania nanocomposite matrix whereas calculated average crystallite size 3.82nm was obtained by XRD. N2 adsorption isotherms explain the mesoporous nature of the silica–titania nanocomposite matrix with high surface area value of 401m2/g with a pore size of 3.3nm and pore volume of 0.33cm3/g. UV–vis spectroscopic determinations revealed that the prepared nanomatrix shows good sensitivity between pH range of 3–5 for acidic medium within 6.9s and pH 12 for basic medium within 1.03s; it is indicative that pH sensor is more responsive toward strong basis. It can be deduced that the sensing species are probably better encapsulated in the matrix and show faster response time. The fabricated pH sensor was found to have a six months age stability and high reproducibility in terms of absorption and color stability with response time. A reversible response over a range of pH values between 3 and 12 were obtained. The encapsulated pH indicator silica–titania nanocomposite matrix after 2h heating at 150°C shows a great potential to be used as pH sensor with good material stability, reproducibility/repeatability, reversibility, fast response and long life time behavior.

Esterification of oleic acid by heteropolyacid/TiO2SiO2 catalysts synthesized from less expensive precursors

AbstractA series of 12‐tungstophosphoric acid [HPW, H3PW12O40 (HPW)] catalysts supported on mesoporous titania–silica composite (TSC) were prepared by impregnation method. Primarily, TSC with mesostructure was successfully prepared by a modified sol–gel process using a less expensive silica precursor (sodium silicate) and titanium oxychloride as a titania source. In order to develop catalysts with various properties, the HPW loading over mesoporous TSC was controlled between 5 and 50 wt%. The surface morphology and structural properties of the prepared catalysts were characterized using N2 gas physisorption analysis, Fourier transform infrared spectroscopy, X‐ray diffraction, ultraviolet spectroscopy, transmission electron microscopy, and scanning electron microscopy analysis. The X‐ray diffraction and ultraviolet spectroscopy results were useful in determining the HPW dispersion on the support material. The catalytic activities of the samples were tested in liquid phase esterification of oleic acid with methanol. The results suggested that HPW dispersion on the support material was essential for the stability and performance of the catalysts during the esterification reaction. Even though the activity of the synthesized catalysts increased with increasing HPW loading, the homogeneity decreased in the samples with higher HPW content (30–50 wt%). The 20%HPW/TSC sample was found to be an active and catalytically stable catalyst, which was successfully regenerated and recycled for three consecutive runs. Copyright © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.