On the Synergetic Catalytic Effect in Heterogeneous Nanocomposite Catalysts

Sustainable hybrid photocatalysts: titania immobilized on carbon materials derived from renewable and biodegradable resources

This review comprises the preparation, properties and heterogeneous photocatalytic applications of TiO2 immobilized on carbon materials derived from earth-abundant, renewable and biodegradable agricultural residues and sea food waste resources. The overview provides key scientific insights into widely used TiO2 supported on carbonaceous materials emanating from biopolymeric materials such as lignin, cellulose, cellulose acetate, bacterial cellulose, bamboo, wood, starch, chitosan and agricultural residues (biochar, charcoal, activated carbon and their magnetic forms, coal fly ash) or seafood wastes namely eggshell, clamshell and fish scales; materials that serve as a support/template for TiO2. Heightened awareness and future inspirational developments for the valorisation of various forms of carbonaceous functional materials is the main objective. This appraisal abridges various strategies available to upgrade renewable carbon-based feedstock via the generation of sustainable TiO2/carbon functional materials and provides remarks on their future prospects. Hopefully, this will stimulate the development of efficient and novel composite photocatalysts and engender the necessary knowledge base for further advancements in greener photocatalytic technologies.

Graphitic Carbon Nitride Sensitized with CdS Quantum Dots for Visible-Light-Driven Photoelectrochemical Aptasensing of Tetracycline

Graphitic carbon nitride (g-C₃N₄) is a new type of metal-free semiconducting material with promising applications in photocatalytic and photoelectrochemical (PEC) devices. In the present work, g-C₃N₄ coupled with CdS quantum dots (QDs) was synthesized and served as highly efficient photoactive species in a PEC sensor. The surface morphological analysis showed that CdS QDs with a size of ca. 4 nm were grafted on the surface of g-C₃N₄ with closely contacted interfaces. The UV-visible diffuse reflection spectra (DRS) indicated that the absorption of g-C₃N₄ in the visible region was enhanced by CdS QDs. As a result, g-C₃N₄-CdS nanocomposites demonstrated higher PEC activity as compared with either pristine g-C₃N₄ or CdS QDs. When g-C₃N₄-CdS nanocomposites were utilized as transducer and tetracycline (TET)-binding aptamer was immobilized as biorecognition element, a visible light-driven PEC aptasensing platform for TET determination was readily fabricated. The sensor showed a linear PEC response to TET in the concentration range from 10 to 250 nM with a detection limit (3S/N) of 5.3 nM. Thus, g-C₃N₄ sensitized with CdS QDs was successfully demonstrated as useful photoactive nanomaterials for developing a highly sensitive and selective PEC aptasensor.

Ordered Mesoporous Polymers for Biomass Conversions and Cross-Coupling Reactions

Amino group-functionalized, ordered mesoporous polymers (OMP-NH2 ) were prepared using a solvent-free synthesis by grinding mixtures of solid raw precursors (aminophenol, terephthaldehyde), using block copolymer templates, and curing at 140-180 °C. OMP-NH2 was functionalized with acidic sites and incorporated with palladium, giving multifunctional solid catalysts with large Brunauer-Emmett-Teller (BET) surface areas, abundant and ordered mesopores, good thermal stabilities, controllable concentrations, and good dispersion of active centers. The resultant solid catalysts showed excellent catalytic activities and good reusability in biomass conversions and cross-coupling reactions-much superior to those of various reported solid catalysts such as Amberlyst 15, SBA-15-SO3 H, and Pd/C and comparable to those of homogeneous catalysts such as heteropoly acid, HCl, and palladium acetate. A facile green approach was developed for the synthesis of ordered mesoporous polymeric solid catalysts with excellent activities for conversion of low-cost feedstocks into useful chemicals and clean biofuels.

Low Pt-Loaded Mesoporous Sodium Germanate as a High-Performance Electrocatalyst for the Oxygen Reduction Reaction

Although Pt/C catalysts show relatively high activities for the oxygen reduction reaction (ORR) and great potential for use in polymer electrolyte membrane fuel cells, the large amount of Pt required and the poor stability of Pt/C-based catalysts remain big challenges. Herein, mesoporous Na4 Ge9 O20 micro-crystals have been successfully synthesized to serve as a new kind of electrocatalyst support owing to its special structural characteristics and high structural stability. After loading a low amount of Pt (5 wt %) nanoparticles of 2-5 nm in diameter, the obtained mesoporous Pt/Na4 Ge9 O20 composite shows not only high electrocatalytic activity for ORR in both acidic and alkaline electrolyte media, which are comparable to those of conventional 20 wt % Pt/C, but also remarkably enhanced Pt mass-specified ORR current density and durability. Synergetic catalytic effects between loaded Pt and the support for the ORR activity has been proposed.

A controllable asymmetrical/symmetrical coating strategy for architectural mesoporous organosilica nanostructures

We describe a facile and controllable asymmetrical/symmetrical coating strategy for the preparation of various novel periodic mesoporous organosilica (PMO) nanostructures, including Au&PMO Janus, Au@PMO yolk-shell and Au@PMO/mSiO2 yolk-double shell nanoparticles, by using Au@SiO2 nanoparticles as seeds. During this process, ammonia first functions as a basic catalyst facilitating the hydrolyzation and condensation of the organosilica precursor, and additionally as an etching agent selectively in situ dissolving the SiO2 shells of Au@SiO2 nanoparticles to form these unique nanostructures. All these three types of nanoparticles have high surface areas, large pore volumes and tailorable cavity structures. Both the Au&PMO and Au@PMO nanoparticles exhibit excellent catalytic activity for the decomposition of H2O2 and the reduction of 4-nitrophenol. Based on these unique structural merits and organic-inorganic hybrid components, the fabricated Janus and hollow PMO nanoparticles show much improved hemocompatibility, which could be further applied in nano-biomedicines without the need for surface modification.

Manganese Oxide Nanorod-Decorated Mesoporous ZSM-5 Composite as a Precious-Metal-Free Electrode Catalyst for Oxygen Reduction

A precious-metal-free cathode catalyst, MnO2 nanorod-decorated mesoporous ZSM-5 zeolite nanocomposite (MnO2 / m-ZSM-5), has been successfully synthesized by a hydrothermal and electrostatic interaction approach for efficient electrochemical catalysis of the oxygen reduction reaction (ORR). The active MnOOH species, that is, Mn(4+) /Mn(3+) redox couple and Brønsted acid sites on the mesoporous ZSM-5 matrix facilitate an approximately 4 e(-) process for the catalysis of the ORR comparable to commercial 20 wt % Pt/C. Stable electrocatalytic activity with 90 % current retention after 5000 cycles, and more importantly, excellent methanol tolerance is observed. Synergetic catalytic effects between the MnO2 nanorods and the mesoporous ZSM-5 matrix are proposed to account for the high electrochemical catalytic performance.

Chemistry of Mesoporous Organosilica in Nanotechnology: Molecularly Organic-Inorganic Hybridization into Frameworks

Organic-inorganic hybrid materials aiming to combine the individual advantages of organic and inorganic components while overcoming their intrinsic drawbacks have shown great potential for future applications in broad fields. In particular, the integration of functional organic fragments into the framework of mesoporous silica to fabricate mesoporous organosilica materials has attracted great attention in the scientific community for decades. The development of such mesoporous organosilica materials has shifted from bulk materials to nanosized mesoporous organosilica nanoparticles (designated as MONs, in comparison with traditional mesoporous silica nanoparticles (MSNs)) and corresponding applications in nanoscience and nanotechnology. In this comprehensive review, the state-of-art progress of this important hybrid nanomaterial family is summarized, focusing on the structure/composition-performance relationship of MONs of well-defined morphology, nanostructure, and nanoparticulate dimension. The synthetic strategies and the corresponding mechanisms for the design and construction of MONs with varied morphologies, compositions, nanostructures, and functionalities are overviewed initially. Then, the following part specifically concentrates on their broad spectrum of applications in nanotechnology, mainly in nanomedicine, nanocatalysis, and nanofabrication. Finally, some critical issues, presenting challenges and the future development of MONs regarding the rational synthesis and applications in nanotechnology are summarized and discussed. It is highly expected that such a unique molecularly organic-inorganic nanohybrid family will find practical applications in nanotechnology, and promote the advances of this discipline regarding hybrid chemistry and materials.

Synthesis of perovskite-based nanocomposites for deNOx catalytic activity

Three different types of perovskite-based nanocomposites were synthesized by calcination of the same gel mixtures (molar ratio for La:Sr:Co 0.4:0.6:1.0) under different reaction conditions (unconventional method: calcination at 1000 °C and 800 °C under vacuum; and conventional method: calcination in air at 1000 °C). The obtained products were studied by multianalytic techniques including powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). NOx reduction using propene (C3H6) as a reductant in the presence of oxygen was studied using temperature-programmed surface reaction (TPSR). The analyzed results showed that multiphase products were found by the unconventional method (in the absence of oxygen), whereas the conventional method (in the presence of oxygen) yielded single-phase perovskites. The multiphase nanocomposite products prepared under vacuum at 1000 °C exhibited higher catalytic activity and higher N2 yield compared with the samples obtained under vacuum at lower temperature (800 °C) and the single-phase perovskites.

Improved sensitivity via layered-double-hydroxide-uniformity-dependent chemiluminescence

In the last two decades nanoparticles have been widely applied to enhance chemiluminescence (CL). The morphology of nanoparticles has an important influence on nanoparticle-amplified CL. However, studies of nanoparticle-amplified CL focus mainly on the size and shape effects, and no attempt has been made to explore the influence of uniformity in nanoparticle-amplified CL processes. In this study we have investigated nanoparticle uniformity in the luminol-H₂O₂ CL system using layered double hydroxides (LDHs) as a model material. The results demonstrated that the uniformity of LDHs played a key role in CL amplification. A possible mechanism is that LDHs with high uniformity possess abundant catalytic active sites, which results in high CL intensity. Meanwhile, the sensitivity for H₂O₂ detection was increased by one order of magnitude (1.0 nM). Moreover, the uniform-LDH-amplified luminol CL could be applied to selective detection of glucose in human plasma samples. Furthermore, such a uniformity-dependent CL enhancement effect could adapted to other redox CL systems-for example, the peroxynitrous acid (ONOOH) CL system.

Self-Assembly Fabrication of Coaxial Te@poly(3,4-ethylenedioxythiophene) Nanocables and Their Conversion to Pd@poly(3,4-ethylenedioxythiophene) Nanocables with a High Peroxidase-like Activity

Here, we report a simple one-step procedure to fabricate coaxial Te@poly(3,4-ethylenedioxythiophene) (PEDOT) nanocables via a self-assembly redox polymerization between 3,4-ethylenedioxythiophene monomer and the oxidant of sodium tellurite without the assistance of any templates and surfactants. The as-synthesized Te@PEDOT coaxial nanocables have diameters of center cores in the range of 5-10 nm, and the size of the outer shell from several nanometers to 15 nm. More interestingly, the as-prepared Te@PEDOT nanocables can be converted to Pd@PEDOT nanocables via a galvanic replacement reaction. The center core of the Pd nanowire exhibits a high crystallinity. The application of the synthesized Pd@PEDOT nanocables as peroxidase-like catalysts for the colorimetric detection of H2O2 is reported. The synergistic effect between the Pd nanowire and electrically conducting PEDOT enhances the catalytic activity toward the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. A detection limit toward H2O2 is as low as 4.83 μM, and a linear range from 10 to 100 μM has been achieved. This work offers a potential versatile route for the fabrication of cable-like nanocomposites with conducting polymers and other active components, which display great promise in applications such as catalysis, nanoelectronic devices, and energy storage and conversion.

Size effects of alkylimidazolium cations on the interfacial properties and CO2 uptake capacity in layered organic–inorganic imidazolium–TiO2 hybrids

Interfacial properties of layered TiO₂–ILs hybrids could be tuned by the alkyl chain length in imidazolium cations, which can in turn affect the performance of CO₂ uptake.

Facile construction of CuFe2O4/g-C3N4 photocatalyst for enhanced visible-light hydrogen evolution

A new type of CuFe₂O₄/g-C₃N₄ composite for photocatalytic H₂ production by water splitting under visible light has been prepared by a facile one-pot calcination approach using urea and a CuFe₂O₄ gel as precursors.

Activated nanostructured bimetallic catalysts for C–C coupling reactions: recent progress

This minireview highlights the recent progress made in the last decade towards the development of activated bimetallic alloy nanoparticle catalysts for C–C coupling reactions, including asymmetric C–C bond coupling reactions.

Synthesis of Au@UiO-66(NH2) structures by small molecule-assisted nucleation for plasmon-enhanced photocatalytic activity

Au@UiO-66(NH₂) core/shell heterostructures were synthesized via an acetic acid/carbon dioxide-assisted solution-encapsulation process. Excited electrons, produced by photo-adsorption of UiO-66(NH₂) and plasmonic sensitization with Au NPs, at the LUMO level with a localized electronic state were transferred to O₂ for the enhancement of photocatalytic activity of alcohol oxidation.

Improving the NOx decomposition and storage activity through co-incorporating ammonium and copper ions into Mg/Al hydrotalcites

We report a 40% and 70% improvement of NO_x decomposition and storage rate based on synthetic Mg/Al/Cu/NH₄⁺ hydrotalcites (HT), compared with Mg/Al/NH₃ and Mg/Al/Cu HTs. TGA and DTG show that ammonium has been released from HT below 160 °C.

Large-pore mesoporous Ca–Si-based bioceramics with high in vitro bioactivity and protein adsorption capability for bone tissue regeneration

A new type of large pore mesoporous Ca–Si-based bioceramics demonstrates high in vitro bioactivity and protein adsorption capability.

Transcription of G-quartet supramolecular aggregates into hierarchical mesoporous silica nanotubes

Hierarchical porous silica nanotubes or porous silica hollow spheres were prepared employing a low concentration of G-quartet supramolecular aggregates as a template.

Promotional role of La addition in the NO oxidation performance of a SmMn2O5 mullite catalyst

A series of La_xSm_1−xMn₂O_δ (x = 0, 0.1, 0.3, 0.5) catalysts were synthesized through a co-precipitation method. The catalytic activity for NO oxidation was enhanced with La substitution, and the maximum activity was achieved at x = 0.3.

Synthesis of MoS2 nanosheet supported Z-scheme TiO2/g-C3N4 photocatalysts for the enhanced photocatalytic degradation of organic water pollutants

MoS₂ nanosheets loaded with Z-scheme TiO₂/g-C₃N₄ photocatalysts were prepared using a wetness impregnation method.

A colloidoscope of colloid-based porous materials and their uses

Colloids assemble into a variety of bioinspired structures for applications including optics, wetting, sensing, catalysis, and electrodes.

Degradation of 4-chlorophenol in a Fenton-like system using Au–Fe3O4magnetic nanocomposites as the heterogeneous catalyst at near neutral conditions

The proposed mechanism for the generation of ˙OH and degradation of 4-CP in the Au–Fe₃O₄/H₂O₂system.

Evolution of iron species for promoting the catalytic performance of FeZSM-5 in phenol oxidation

Facile modification of FeZSM-5 utilizing an organic directing agent (ODA) for iron species evolution toward better Fenton activity was developed.

Synthesis of bifunctional reduced graphene oxide/CuS/Au composite nanosheets for in situ monitoring of a peroxidase-like catalytic reaction by surface-enhanced Raman spectroscopy

In this work, we have demonstrated the synthesis of bifunctional reduced graphene oxide/CuS/Au composite nanosheets for in situ monitoring of peroxidase-like catalytic reaction by surface-enhanced Raman spectroscopy.

Pd(0)@UiO-68-AP: chelation-directed bifunctional heterogeneous catalyst for stepwise organic transformations

A bifunctional heterogeneous catalyst Pd(0)@UiO-68-AP based on a chelation-directed post-synthetic approach is reported.

Two new energetic coordination compounds based on tetrazole-1-acetic acid: syntheses, crystal structures and their synergistic catalytic effect for the thermal decomposition of ammonium perchlorate

The DSC curves of the AP thermal decomposition in the absence and presence of compounds 1, 2 or their mixtures.

Solubility product difference-guided synthesis of Co3O4–CeO2 core–shell catalysts for CO oxidation

Co₃O₄–CeO₂ core–shell catalysts are successfully fabricated by an ion exchange procedure between Co(CO₃)_0.35Cl_0.2(OH)_1.1 nanorods and Ce³⁺ aqueous solution, followed by a calcination step.

Enhancement of the photocatalytic activity of a TiO2/carbon aerogel based on a hydrophilic secondary pore structure

The surface/interface synergy effect plays a positive role on the spatial separation and utilization of electrons and holes in photocatalytic process, which suggests a potential strategy for designing high efficiency photocatalysts.

LaCoO3 perovskite in Pt/LaCoO3/K/Al2O3 for the improvement of NOx storage and reduction performances

A series of x wt% Pt/LaCoO₃/K/Al₂O₃ (x = 0, 0.3 and 1.0) were synthesized for NOx storage and reduction. 0.3 wt% Pt/LaCoO₃/K/Al₂O₃ shows higher NOx storage capacities, stronger SO₂ tolerance and better regenerability than 1.0 wt% Pt/K/Al₂O₃.

Nanoparticles-in-concavities as efficient nanocatalysts for carbon dioxide reforming of methane to hydrogen and syngas

The ceria concavity-loaded Ni nanoparticle catalysts can lead to more active sites and promote CO₂ dissociative activation and CO desorption, thus enhancing significantly the catalytic performances for methane dry reforming with CO₂.

Porous palladium coated conducting polymer nanoparticles for ultrasensitive hydrogen sensors

Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and in the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen leak detection and surveillance sensor systems are needed; additionally, the ability to maintain uniformity through repetitive hydrogen sensing is becoming increasingly important. In this report, we detail the fabrication of porous palladium coated conducting polymer (3-carboxylate polypyrrole) nanoparticles (Pd@CPPys) to detect hydrogen gas. The Pd@CPPys are produced by means of facile alkyl functionalization and chemical reduction of a pristine 3-carboxylate polypyrrole nanoparticle-contained palladium precursor (PdCl(2)) solution. The resulting Pd@CPPy-based sensor electrode exhibits ultrahigh sensitivity (0.1 ppm) and stability toward hydrogen gas at room temperature due to the palladium sensing layer.