A Pd/SBA-15 composite: synthesis, characterization and protein biosensing

Preparation of highly dispersed Pd/SBA-15 catalysts for dodecahydro-N-ethylcarbazole dehydrogenation reaction by ion exchange-glow discharge

Dehydrogenation reactions are critical in hydrogen storage based on a liquid organic hydrogen carrier (LOHC) system. Speeding up the dehydrogenation rate and lowering the reaction temperature are the main focuses of LOHC dehydrogenation catalysts. In this paper, Pd/SBA-15 catalysts (Pd-IP/S15) were prepared by NaOH treatment of surface hydroxyl groups on SBA-15, the ion exchange of Na⁺ with Pd(NH₃)₄²⁺, and then reduction of Pd ions via glow discharge plasma. The dehydrogenation performance of dodecahydro-N-ethylcarbazole on the prepared catalysts is studied. The turnover frequency of Pd-IP/S15 is 13.94 min^-1 at 170°C, which is 10.25 times that of commercial Pd/C. It is ensured via the ion exchange method that Pd(NH₃)₄²⁺ could be precisely targeted at the Si-OH of SBA-15 to form Si-O-Pd(NH₃)₄²⁺, which effectively prevents the aggregation and uncontrollable growth of Pd nanoparticles (NPs) during the in situ reduction by plasma. Pd NPs with high dispersion are obtained on SBA-15, which enhances the catalytic activity of Pd-IP/S15. The coordination of Pd NPs with O of Si-OH on SBA-15 enabled Pd-IP/S15 to exhibit excellent catalytic stability. After 7 dehydrogenation cycles at 180°C, the dehydrogenation efficiency remained above 97%.

Heterogeneous catalysis with encapsulated haem and other synthetic porphyrins: Harnessing the power of porphyrins for oxidation reactions

Encapsulated metalloporphyrins have been widely studied for their use as efficient heterogeneous catalysts, inspired by the known catalytic activity of porphyrins in haemoproteins. The oxidation of organic substrates by haemoproteins is one of the well-known roles of these proteins, in which the haem (ferriprotoporphyrin IX = FePPIX) cofactor is the centre of reactivity. While these porphyrins are highly efficient catalysts in the protein environment, once removed, they quickly lose their reactivity. It is for this reason that they have garnered much interest in the field of heterogeneous catalysis of oxidation reactions. This review details current research in the field, focusing on the application of encapsulated haem, and other synthetic metalloporphyrins, applied to oxidation reactions.

Designing ordered mesoporous aluminosilicates under acidic conditions via an intrinsic hydrolysis method

A novel intrinsic hydrolysis method was employed for the synthesis of well-ordered mesoporous aluminosilicates, viz., H-AlSBA-15 and H-AlIITM-56, with trivalent aluminium, exclusively, in a tetrahedral framework structure.

An ionic liquid-mesoporous silica blend as a novel adsorbent for the adsorption and recovery of palladium ions, and its applications in continuous flow study and as an industrial catalyst

Aliquat-336@SBA-15 blend adsorbent effectively adsorbs Pd from a spent catalyst.

Nanostructured platinum in ordered mesoporous silica as novel efficient catalyst for propane total oxidation

Nanostructured platinum in ordered mesoporous silica SBA-15 and KIT-6 were synthesized. Pt particles with lower oxidation state were more homogeneously dispersed within the pores of KIT-6, making it an efficient catalyst for propane total oxidation.

Ionic liquid-derived nano-fibrillated mesoporous carbon based on solid-phase microextraction fiber for the analysis of volatile organic compounds from aqueous solutions

A nano-fibrillated mesoporous carbon solid phase microextraction fiber was successfully prepared and used for the extraction of volatile organic compounds.

Simple and direct synthesis of oxygenous carbon supported palladium nanoparticles with high catalytic activity

A concise synthesis of Pd nanoparticles encapsulated in a sponge-like carbonaceous support (Pd/C) was achieved by mixing a solution containing water, ethylene glycol and Pd(II) with diphosphorus pentoxide, leading to excellent catalytic performance of Pd/C towards the reduction of the model aromatic nitro compound.

Synthesis and characterization of "hairy urchin"-like polyaniline by using β-cyclodextrin as a template

A novel synthesis of "hairy urchin"-shaped polyaniline (PAni) and its surface coverage with nanospikes was achieved from a simple microemulsion polymerization technique in the presence of β-cyclodextrin (β-CD). The rodlike micelle phase was characterized, and the key factors affecting the formation of PAni nanostructures were systematically examined. Ferric chloride (FeCl(3)) has played a role as a structural directing agent to fabricate the polymer as hairy urchin-like structure/nanorods via a cooperative interaction between FeCl(3) and DoTAC in an aqueous medium. Host-guest inclusion complex of β-cyclodextrin with aniline was used as a monomer. It has been revealed that the formation of the supramolecular complexes of polyaniline with β-CD due to host-guest interaction is indispensable for the fabrication of these unique PAni nanostructures, and a suitable β-CD to aniline molar ratio is essential to their exclusive formation. Different varieties of PAni nanostructures such as hairy urchin, branched particles consisting of rodlike branches, and regular rodlike particles were obtained in the presence of FeCl(3). Also, in the absence of FeCl(3), a predominant product of regular spherical particles and wirelike aggregation exhibiting faceted surfaces were obtained. The structures of polyaniline hairy urchin-like nanorods were analyzed using transmission electron microscopy (TEM). The synthesized polymer was characterized by Fourier-transform infrared spectroscopy and X-ray diffraction technique. Additionally, the relationship between the morphology and the conductivity of the PAni nanostructures was investigated as well.

Twenty second synthesis of Pd nanourchins with high electrochemical activity through an electrochemical route

A rapid, templateless, surfactantless, electrochemical route is reported to synthesize uniform and clean Pd nanoparticles (∼350 nm in diameter) with a substructure of sharp nanospikes (∼95 nm in length). The effects of electrodeposition potential, PdCl(2) concentration, and supporting electrolyte were explored for the formation of the Pd nanourchins. The systematic studies revealed that the concentration of Pd(II) greatly affects the density of the nanospikes on the Pd nanourchins in this short-time synthesis. The substructure of the nanospikes on the nanourchins was examined to be a single-crystal quadrangular pyramid. Further investigation of the Pd nanourchins by cyclic voltammetry (CV) showed their high electrochemical activity toward formic acid oxidation.

The use of nanoparticles in electroanalysis: an updated review

The use of nanoparticles in electroanalysis is an area of research which is continually expanding. A wealth of research is available discussing the synthesis, characterization and application of nanoparticles. The unique properties of nanoparticulate materials (e.g. enhanced mass transport, high surface area, improved signal-to-noise ratio) can often be advantageous in electroanalytical techniques. The aim of this paper is to provide an updated overview of the work in this field. In this review we have concentrated on the advances with regards to silver, gold, platinum, palladium, ruthenium, copper and nickel. The synthesis, characterization and practical application of these materials are discussed. We have also identified the conditions under which each metal is likely to be stable, which is likely to be a useful tool for those practising in the field. Furthermore, we have provided a theoretical overview of advances in the theoretical modelling and simulation of nanoparticle behaviour.

Cerium phosphate nanotubes: synthesis, characterization and biosensing

Cerium phosphate (CeP) nanotubes have been synthesized and confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The 1D nanomaterial has a monoclinic crystal structure with a mean width of 15-20 nm and a length up to several micrometers. The nanotubes have been employed as electrode substrates for immobilization and direct electrochemistry of heme proteins/enzymes with myoglobin (Mb) as a model. The electrochemical characteristics of the Mb-CeP/GC electrode were studied by voltammetry. After being immobilized on the nanotubes, Mb can keep its natural structure and undergo effective direct electron transfer reaction with a pair of well-defined redox peaks at -(367 +/- 3) mV (pH 7.5). The apparent electron transfer rate constant is (9.1 +/- 1.4) s(-1). The electrode displays good features in the electrocatalytic reduction of H(2)O(2), and thus can be used as a biosensor for detecting the substrate with a low detection limit (0.5 +/- 0.05 microM), a wide linear range (0.01-2 mM), high sensitivity (14.4 +/- 1.2 microA mM(-1)), as well as good stability and reproducibility. CeP nanotubes can become a simple and effective biosensing platform for the integration of heme proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.

Mesoporous Silicate Materials in Sensing

Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through cocondensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.