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272 result(s) for "mesoporous film"
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Harnessing Work Function Modulation for Hydrogen Evolution Catalysis in Mesoporous Bimetallic Pt‐M Alloys: The Role of Mesopores in Work Function Optimization
Work function (WF) influences electron transport and intermediates adsorption, enabling charge balance and catalytic optimization for the hydrogen evolution reaction (HER). However, the understanding of the role of mesopores and the relationship between composition and WF in pristine Pt‐based alloys remains lacking. Herein, various mesoporous binary Pt‐M alloy films (m‐Pt‐M, M = Pd, Rh, and Ru) with uniform pores and elemental distributions are synthesized, providing an experimental platform to investigate this relationship. It has been demonstrated that the WFs of m‐Pt‐M catalysts are strongly influenced by their compositions and mesoporous structures, thereby impacting HER activities. Among them, m‐Pt‐Ru with tailored WF lowers the thermodynamic energy barrier and accelerates the kinetic processes of HER. The mass activity of m‐Pt‐Ru in alkaline media is 17.8× and 5.1× higher, compared to Pt black and m‐Pt, respectively. This work not only provides a simple method for the fabrication of well‐defined binary metallic alloy films but also offers experimental insights into the rational design of highly efficient electrocatalysts with tunable WFs. This study presents mesoporous binary Pt‐M alloy films (m‐Pt‐M, M = Pd, Rh, and Ru) with uniform porosity and tailored work functions (WFs) as an experimental study platform. The WFs of the m‐Pt‐M films exhibit a volcano‐type relationship with their HER performance. Among them, the m‐Pt‐Ru demonstrates superior activity, requiring only 16 mV overpotential to reach 10 mA cm−2 in alkaline media.
Facile synthesis of aluminum oxyhydroxide-PVA films and its adsorptive evaluation for the removal of methylene blue dye from water: kinetics, optimization studies and mechanism
Aluminum oxyhydroxide-polyvinyl alcohol films were synthesized by the sol–gel method with varying metal-polymer ratios. The results of the characterization confirmed the formation of aluminum oxyhydroxide and the incorporation of metal into the polymer. The adsorption isotherms of the film exhibited type IV isotherms indicating the mesoporous nature with a non-uniform pore size distribution. The optical profilometric studies confirmed the surface roughness of the film. The adsorptive nature of the film was tested for the removal of methylene blue dye from the aqueous solution. Optimization studies were conducted to investigate the effect of various parameters on the adsorption process. The adsorption isotherms of methylene blue fit with the Langmuir isotherm model and follow a pseudo-second-order equation. A suitable reaction mechanism was proposed, which confirms the adsorptive nature of the film is due to the electrostatic attraction. The synergetic effect of the metal-polymer blend, surface roughness and pore size of the film, which ranges from 0.01 to 0.025 nm, enhances the adsorption of methylene blue. The comparison of results obtained in the current study with earlier reports confirms that the aluminum oxyhydroxide-polyvinyl alcohol films can be considered an eco-friendly, cost-effective adsorbent for removing methylene blue.
Low-Temperature Synthesis of Micro–Mesoporous TiO2–SiO2 Composite Film Containing Fe–N Co-Doped Anatase Nanocrystals for Photocatalytic NO Removal
A simple low-temperature (< 100 °C) hot-water treatment was used to synthesize Fe–N co-doped anatase nanocrystals which were uniformly dispersed in micro–mesoporous SiO 2 host film for the first time. The Fe–N co-doped TiO 2 –SiO 2 (FNTS) film exhibited stable photocatalytic activities. A NO removal efficiency of 56.1% was achieved under simulated solar light irradiation without any obvious inactivation in 30 min. The transient photocurrent response of FNTS film is approximately six times higher than that of non-doped TiO 2 –SiO 2 film, indicating the superior charge separation of photo-generated electron–hole pairs. Electron spin resonance analysis showed that the ·OH and ·O 2 − radicals were key species to remove NO. Combined with quantitative reaction intermediates, the possible photocatalytic degradation mechanism of NO over FNTS film was proposed. In addition, the FNTS thin films exhibited intrinsic super-hydrophilicity and durable self-cleaning property even after 6 months of storage in the dark. This work provides a facile method to load the catalyst on thermal labile substrates, such as soda–lime glass and organic polymer for more practical applications. Graphic Abstract A simple low-temperature (< 100 °C) hot-water treatment was used to synthesize micro–mesoporous TiO 2 –SiO 2 composite film, which shows good self-cleaning ability and superior photodegradation activity for NO removal under solar light.
Volatile Organic Compounds Sensing Using Optical Fibre Long Period Grating with Mesoporous Nano-Scale Coating
A long period grating (LPG) modified with a mesoporous film infused with a calixarene as a functional compound was employed for the detection of individual volatile organic compounds (VOCs) and their mixtures. The mesoporous film consisted of an inorganic part, SiO2 nanoparticles (NPs), along with an organic moiety of poly(allylamine hydrochloride) polycation PAH, which was finally infused with the functional compound, p-sulphanato calix[4]arene (CA[4]) or p-sulphanato calix[8]arene (CA[8]). The LPG sensor was designed to operate at the phase matching turning point to provide the highest sensitivity. The sensing mechanism is based on the measurement of the refractive index (RI) change induced by a complex of the VOCs with calixarene. The LPG, modified with a coating of 5 cycles of (SiO2 NPs/PAH) and infused with CA[4] or CA[8], was exposed to chloroform, benzene, toluene and acetone vapours. The British Standards test of the VOCs emissions from material (BS EN ISO 16000-9:2006) was used to test the LPG sensor performance.
Facile Synthesis and Characterization of TiO2/SnS Nanocomposites by Eco-Friendly Methods
The acid etching mechanism of FTO film using zinc powders has been explored, and sulfuric and hydrochloric acid solutions of different concentrations were tested as etching agents. Compact and mesoporous films of titanium dioxide were prepared by spin-coating and doctor blade techniques on FTO glass. Tin sulfide films were formed through a successive ionic layer adsorption and reaction (SILAR) process using different numbers of deposition cycles, and TiO2/SnS nanocomposites were synthesized. The thin films and the prepared composites were characterized using X-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses. In this study, the principal characteristics of deposited tin sulfide films on two different types of TiO2 films are shown.
Sensitive Electrochemical Detection of Carcinoembryonic Antigen Based on Biofunctionalized Nanochannel Modified Carbonaceous Electrode
The convenient construction of carbon-based electrochemical immunosensors with high performance is highly desirable for the efficient detection of tumor biomarkers. In this work, an electrochemical immunosensor was fabricated by integrating a biofunctionalized mesoporous silica nanochannel film with a carbon-based electrode, which can enable the sensitive determination of carcinoembryonic antigen (CEA) in serum. The commonly used carbonaceous electrode, glassy carbon electrode (GCE), was employed as the supporting electrode and was pre-treated through electrochemical polarization to achieve the stable binding of a vertically ordered mesoporous silica film with amino groups (NH2-VMSF) without the use of any adhesive layer. To fabricate the immunorecognition interface, antibodies were covalently immobilized after the amino groups on the outer surface of NH2-VMSF was derivatized to aldehyde groups. The presence of amino sites within the high-density nanochannels of NH2-VMSF can facilitate the migration of negatively charged redox probes (Fe(CN)63-/4-) to the supporting electrode through electrostatic adsorption, leading to the generation of electrochemical signals. In the presence of CEA, the formation of immunocomplexes on the recognitive interface can reduce the electrochemical signal of Fe(CN)63-/4- on the supporting electrode. Based on this principle, the sensitive electrochemical detection of CEA was achieved. CEA can be determined to range from 0.01 ng mL−1 to 100 ng mL−1 with a limit of detection of 6.3 pg mL−1. The fabricated immunosensor exhibited high selectivity, and the detection of CEA in fetal bovine serum was achieved.
N-Doped Graphene Quantum Dots Confined within Silica Nanochannels for Enhanced Electrochemical Detection of Doxorubicin
Herein, we describe a fast and highly sensitive electrochemical sensor for doxorubicin (DOX) detection based on the indium tin oxide (ITO) modified with a binary material consisting of vertically-ordered mesoporous silica films (VMSFs) and N-doped graphene quantum dots (NGQDs). VMSFs, with high permeability and efficient molecular transport capacity, is attached to the ITO electrode via a rapid and controllable electrochemical method, which can serve as a solid template for the confinement of numerous NGQDs through facile electrophoresis. By virtue of the excellent charge transfer capacity, π-π and electrostatic preconcentration effects of NGQDs, as well as the electrostatic enrichment ability of VMSF, the presented NGQDs@VMSF/ITO shows amplified electrochemical signal towards DOX with a positive charge, resulting in good analytical performance in terms of a wide linear range (5 nM~0.1 μM and 0.1~1 μM), high sensitivity (30.4 μA μM−1), and a low limit of detection (0.5 nM). Moreover, due to the molecular sieving property of VMSF, the developed NGQDs@VMSF/ITO sensor has good selectivity and works well in human serum and urine samples, with recoveries of 97.0~109%, thus providing a simple and reliable method for the direct electrochemical analysis of DOX without complex sample pretreatment procedures.
Improving the Photocatalytic Activity of Mesoporous Titania Films through the Formation of WS2/TiO2 Nano-Heterostructures
Heterostructures formed by anatase nanotitania and bidimensional semiconducting materials are expected to become the next-generation photocatalytic materials with an extended operating range and higher performances. The capability of fabricating optically transparent photocatalytic thin films is also a highly demanded technological issue, and increasing the performances of such devices would significantly impact several applications, from self-cleaning surfaces to photovoltaic systems. To improve the performances of such devices, WS2/TiO2 heterostructures obtained by incorporating two-dimensional transition metal dichalcogenides layers into titania mesoporous ordered thin films have been fabricated. The self-assembly process has been carefully controlled to avoid disruption of the order during film fabrication. WS2 nanosheets of different sizes have been exfoliated by sonication and incorporated in the mesoporous films via one-pot processing. The WS2 nanosheets result as well-dispersed within the titania anatase mesoporous film that retains a mesoporous ordered structure. An enhanced photocatalytic response due to an interparticle electron transfer effect has been observed. The structural characterization of the heterostructure has revealed a tight interplay between the matrix and nanosheets rather than a simple additive co-catalyst effect.
Carbon Nitride Nanosheets as an Adhesive Layer for Stable Growth of Vertically-Ordered Mesoporous Silica Film on a Glassy Carbon Electrode and Their Application for CA15-3 Immunosensor
Vertically ordered mesoporous silica films (VMSF) are a class of porous materials composed of ultrasmall pores and ultrathin perpendicular nanochannels, which are attractive in the areas of electroanalytical sensors and molecular separation. However, VMSF easily falls off from the carbonaceous electrodes and thereby impacts their broad applications. Herein, carbon nitride nanosheets (CNNS) were served as an adhesive layer for stable growth of VMSF on the glassy carbon electrode (GCE). CNNS bearing plentiful oxygen-containing groups can covalently bind with silanol groups of VMSF, effectively promoting the stability of VMSF on the GCE surface. Benefiting from numerous open nanopores of VMSF, modification of VMSF’s external surface with carbohydrate antigen 15-3 (CA15-3)-specific antibody allows the target-controlled transport of electrochemical probes through the internal silica nanochannels, yielding sensitive quantitative detection of CA15-3 with a broad detection range of 1 mU/mL to 1000 U/mL and a low limit of detection of 0.47 mU/mL. Furthermore, the proposed VMSF/CNNS/GCE immunosensor is capable of highly selective and accurate determination of CA15-3 in spiked serum samples, which offers a simple and effective electrochemical strategy for detection of various practical biomarkers in complicated biological specimens.
Dual-Mode Sensing Platform for Cancer Antigen 15-3 Determination Based on a Silica Nanochannel Array Using Electrochemiluminescence and Electrochemistry
An electrochemiluminescence-electrochemistry (ECL-EC) dual-mode sensing platform based on a vertically-ordered mesoporous silica films (VMSF) modified electrode was designed here for the sensitive and selective determination of cancer antigen 15-3 (CA 15-3), a specific biomarker of breast cancer. VMSF was assembled through a rapid electrochemically assisted self-assembly (EASA) method and plays a crucial role in signal amplification via a strong electrostatic interaction with the positively charged bifunctional probe Ru(bpy)32+. To construct the biorecognition interface, epoxy functional silane was linked to the surface of VMSF for further covalent immobilization of the antibody. As a benefit from the specific combination of antigen and antibody, a non-conductive immunocomplex layer was formed in the presence of CA 15-3, leading to the hinderance of the mass and electron transfer of the probes. Based on this strategy, the dual-mode determination of CA 15-3 ranging from 0.1 mU/mL to 100 mU/mL with a LOD of 9 μU/mL for ECL mode, and 10 mU/mL to 200 U/mL with a LOD of 5.4 mU/mL for EC mode, was achieved. The proposed immunosensor was successfully employed for the detection of CA 15-3 in human serum without tedious pretreatment.