Catalytic Metal Nanoparticles Research Articles

Anthranilic Acid: A Versatile Monomer for the Design of Functional Conducting Polymer Composites

Polyaniline has been utilized in various applications, yet its widespread adoption has often been impeded by challenges. Composite systems have been proposed as a means of mitigating some of these limitations, and anthranilic acid (2-aminobenzoic acid) has emerged as a possible moderator for use in co-polymer systems. It offers improved solubility and retention of electroactivity in neutral and alkaline media, and, significantly, it can also bestow chemical functionality through its carboxylic acid substituent, which can greatly ease post-polymer modification. The benefits of using anthranilic acid (as a homopolymer or copolymer) have been demonstrated in applications including corrosion protection, memory devices, photovoltaics, and biosensors. Moreover, this polymer has been used as a versatile framework for the sequestration of metal ions for water treatment, and, critically, these same mechanisms serve as a facile route for the production of catalytic metallic nanoparticles. However, the widespread adoption of polyanthranilic acid has been limited, and the aim of the present narrative review is to revisit the early promise of anthranilic acid and assess its potential future use within modern smart materials. A critical evaluation of its properties is presented, and its versatility as both a monomer and a polymer across a spectrum of applications is highlighted.

Miniature physical sphere-in-contact models of heterogeneous catalysts and metal nanoparticles.

Physical molecular models have played a fundamental role in the understanding of chemical reactions on heterogeneous catalysts and on metal nanoparticles. To date, these physical models have been based on separate models of the metal nanoparticle (NP) or surface and of the substrate and the molecular structure of reactant and product adsorbates and their intermediates. In this paper, we try to provide a new miniature physical molecular model, the sphere-in-contact model of heterogeneous catalysts and metal nanoparticles that can build inexpensive, small and efficient molecular models that can be transported or shipped easily and that depict the chemical reaction as a whole, showing reactants, intermediates, products, the metal nanoparticle bound to the substrate which can give information about a reaction mechanism. These models reveal that there are certain rules with respect to the kind of sites you observe at the metal NP interface with the support by small movement of the nanoparticle. We have used in this study physical molecular models using the sphere-in-contact model. This is the first time such physical models are built for heterogeneous catalytic reactions and metal nanoparticles, and they are constructed out of spheres that fuse together when exposed to water.

(Invited) Hybrid Mixed-Metal-Oxide-Based Catalytic Systems for Efficient Electroreduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties. There has been growing interest in the electrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large over-potentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the electrochemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.We explore here the ability of polynuclear transition metal oxide based systems to function as cocatalysts and to stabilize and activate metal nanocenters. Here certain nanostructured metal oxides of zirconium, titanium, molybdenum or tungsten have been demonstrated to influence supported catalytic metal sites in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ru), thus affecting their chemisorptive and catalytic properties during CO2-reduction. Metal oxide (WO3, MoO3, TiO2) nanostructures can generate highly reactive –OH groups at electrocatalytic interface.Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Pd), thus affecting their chemisorptive properties. Metal oxide (ZrO2, WO3) nanospecies can generate –OH groups at electrocatalytic interface. Our electrocatalytic results with copper nanostructures over-coated with ZrO2 or WO3 nanostructures imply the systems’ improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as the lower tendency of copper sites to undergo poisoning.

Cationic Polymer Coating Increases the Catalytic Activity of Gold Nanoparticles toward Anionic Substrates.

Organic coatings on catalytic metal nanoparticles (NPs) typically hinder their activity due to the blocking of active sites. Therefore, considerable effort is made to remove organic ligands when preparing supported NP catalytic materials. Here, cationic polyelectrolyte coatings are shown to increase the catalytic activity of partially embedded gold nanoislands (Au NIs) toward transfer hydrogenation and oxidation reactions with anionic substrates compared to the activity of identical but uncoated Au NIs. Any potential steric hindrance caused by the coating is countered by a decrease in the activation energy of the reaction by half, resulting in overall enhancement. The direct comparison to identical but uncoated NPs isolates the role of the coating and provides conclusive evidence of enhancement. Our findings show that engineering the microenvironment of heterogeneous catalysts, creating hybrid materials that cooperatively interact with the reactants involved, is a viable and exciting path to improving their performance.

Pt-modified BiVO4 nanosheets for enhanced acetone sensing

Two-dimensional (2D) BiVO4 nanosheets (NSs), featuring distinctive chemical properties and dangling-bond-rich surfaces, are promising for developing high-performance gas sensors. However, the previously reported 2D BiVO4 NSs-based devices suffer from a low responsivity and poor selectivity. Here, catalytic metal (Pt) nanoparticles (NPs) are functionalized on the surface of BiVO4 NSs to improve the sensing ability. Comparative investigations verify the significant enhancement in acetone sensing after Pt modification. The Pt NPs-loaded BiVO4 exhibits a response of 12.5–100 ppm acetone, which is 3.2 times higher than that of pure BiVO4 sensor. Besides, the Pt-BiVO4 sensor possesses better selectivity and lower detection limit. From both the experimental results and density functional theory (DFT) calculation, the effects of Pt modification are elucidated as a synergy of chemical and electronic sensitization. The loading of Pt benefits the thickening of electron depletion layer, and accumulating and activating the acetone molecules, which accelerate the reaction between acetone and chemisorbed oxygen species, resulting in enhanced sensing performance. This work gives deep insights into the effects of noble metal modification on metal oxide-based sensing material and could serve as a guideline for further designing novel high-performance sensing materials.

Chitosan hydrogel anchored phthalocyanine supported metal nanoparticles: Bifunctional catalysts for pollutants reduction and hydrogen production

Metal nanoparticles possess high catalytic activity in various organic transformation reactions. A catalyst must be recovered and re-used effectively and economically to lower the overall reaction cost. The recovery of a catalyst remains a challenge due to their extreme small size. In this research work, catalytic metal nanoparticles were synthesized on Zn-phthalocyanine (ZnPc) and chitosan hydrogel (CH) composite which acts as catalyst support. The ZnPc-CH support facilitate the easy recovery of the loaded metal nanoparticles. Metal nanoparticles (M0) based on Cu0, Ag0, Ni0, Co0 and Fe0 were decorated inside and on ZnPc-CH hydrogel surface. The developed M0@ZnPc-CH were utilized for the enhanced selective reduction of toxins and hydrogen production by methanolysis and hydrolysis of NaBH4. Effective catalytic reduction and hydrogen generation was successfully achieved with Co0@ZnPc-CH and ZnPc-CH. Under optimized conditions, Co0@ZnPc-CH showed complete reduction of 4-nitrophenol (4-NP) in 8.0 min with the fast 4-NP reduction kinetics (K = 0.611 min−1). Among the developed catalysts, ZnPc-CH showed fast H2 generation with high H2 generation rate (HGR = 4100 mLg−1min−1) under optimized conditions. Metal leaching from Co0@ZnPc-CH was negligible during recycling of the catalyst, suggesting that it could be implemented to 4-NP treatment from real water samples. Similarly, ZnPc-CH could produce same quantity of H2 throughout 4 continuous cycles of durability testing without any deactivation and leaching and ZnPc-CH showed high stability, indicating the effectiveness of the catalyst to be applied for H2 production on large scale.

Nanozyme-catalysed CRISPR assay for preamplification-free detection of non-coding RNAs.

CRISPR-based diagnostics enable specific sensing of DNA and RNA biomarkers associated with human diseases. This is achieved through the binding of guide RNAs to a complementary sequence that activates Cas enzymes to cleave reporter molecules. Currently, most CRISPR-based diagnostics rely on target preamplification to reach sufficient sensitivity for clinical applications. This limits quantification capability and adds complexity to the reaction chemistry. Here we show the combination of a CRISPR-Cas-based reaction with a nanozyme-linked immunosorbent assay, which allows for the quantitative and colorimetric readout of Cas13-mediated RNA detection through catalytic metallic nanoparticles at room temperature (CrisprZyme). We demonstrate that CrisprZyme is easily adaptable to a lateral-flow-based readout and different Cas enzymes and enables the sensing of non-coding RNAs including microRNAs, long non-coding RNAs and circular RNAs. We utilize this platform to identify patients with acute myocardial infarction and to monitor cellular differentiation in vitro and in tissue biopsies from prostate cancer patients. We anticipate that CrisprZyme will serve as a universally applicable signal catalyst for CRISPR-based diagnostics, which will expand the spectrum of targets for preamplification-free, quantitative detection.

Evaporation-Induced Self-Assembly of Metal Oxide Inverse Opals: From Synthesis to Applications.

ConspectusInverse opals (IOs) are highly interconnected three-dimensional macroporous structures with applications in a variety of disciplines from optics to catalysis. For instance, when the pore size is on the scale of the wavelength of visible light, IOs exhibit structural color due to diffraction and interference of light rather than due to absorption by pigments, making these structures valuable as nonfading paints and colorants. When IO pores are in an ordered arrangement, the IO is a 3D photonic crystal, a structure with a plethora of interesting optical properties that can be used in a multitude of applications, from sensors to lasers. IOs also have interesting fluidic properties that arise from the re-entrant geometry of the pores, making them excellent candidates for colorimetric sensors based on fluid surface tension. Metal oxide IOs, in particular, can also be photo- and thermally catalytically active due to the catalytic activity of the background matrix material or of functional nanoparticles embedded within the structure.Evaporation-induced self-assembly of sacrificial particles has been developed as a scalable method for forming IOs. The pore size and shape, surface chemistry, matrix material, and the macroscopic shape of the IO, as well as the inclusion of functional components, can be designed through the choice of deposition conditions such as temperature and humidity, types and concentrations of components in the self-assembly mixture, and the postassembly processing. These parameters allow researchers to tune the optical, mechanical, and thermal transport properties of IOs for optimum functionality.In this Account, we focus on experimental and theoretical studies to understand the self-assembly process and properties of metal oxide IOs without (bare) and with (hybrid) plasmonic or catalytic metal nanoparticles incorporated. Several synthetic approaches are first presented, together with a discussion of the various forces involved in the assembly process. The visualization of the deposition front with time-lapse microscopy is then discussed together with analytical theory and numerical simulations to determine the conditions needed for the deposition of a continuous IO film. Subsequently, we present high-resolution scanning electron microscopy (SEM) of assembled colloids over large areas, which provides a detailed view of the evolution of the assembly process, showing that the organization of the colloids is initially dictated by the meniscus of the evaporating suspension on the substrate, but that gradually all grains rotate to occupy the thermodynamically most favorable orientation. High-resolution 3D transmission electron microscopy (TEM) is then presented together with analysis of the wetting of the templating colloids by the matrix precursor to provide a detailed picture of the embedding of metallic nanoparticles at the pore–matrix interface. Finally, the resulting properties and applications in optics, wetting, and catalysis are discussed, concluding with an outlook on the future of self-assembled metal-oxide-based IOs.

Enzyme-free sandwich-type electrochemical immunosensor based on high catalytic binary PdCu mesoporous metal nanoparticles and conductive black phosphorous nanosheets for ultrasensitive detection of pro-SFTPB in non-small cell lung cancer

Pro-surfactant protein B (pro-SFTPB) has been proven to be a powerful biomarker for the early diagnosis of non-small-cell lung cancer (NSCLC). In this study, a novel enzyme-free electrochemical immunosensor is developed for the ultrasensitive detection of pro-SFTPB using binary PdCu mesoporous metal nanoparticles (MMNs) and few-layer black phosphorous (BP nanosheets). Concretely, PdCu MMNs, as novel essential signal labels, were successfully synthesized, offering excellent outstanding peroxidase-like catalytic activity toward hydrogen peroxide (H2O2). Meanwhile, the combination of BP nanosheets with biocompatible gold nanoparticles (AuNPs) served as the substrate on the electrode. With the aid of binary PdCu MMNs nanozymes and BP nanosheets, the enzyme-free electrochemical immunosensor revealed ultrasensitivity detection of pro-SFTPB ranging from 10 pg/mL to 100 ng/mL with an ultralow limit of detection of 5.3 pg/mL. In addition, the immunosensor enables accurate detection of pro-SFTPB in serum samples. Altogether, the developed electrochemical immunosensor provides an enzyme-free platform for pro-SFTPB detection, providing a new method for the early diagnosis of NSCLC.

Catalytic activity of Co–Ag nanoalloys to dissociate molecular hydrogen. New insights on the chemical environment

Adsorption of molecular hydrogen on the surface of catalytic metal nanoparticles and its dissociation in atomic hydrogen are processes of interest in many chemical technologies. As in other chemical reactions, alloying can improve the efficiency of the catalysts. By focusing on Co6, Co5Ag, Co3Ag3 and CoAg5, we explore the effect of changing the relative concentration of the two components in small ComAgn clusters, a peculiar nanoalloy because Co and Ag do not form bulk solid alloys. Molecular hydrogen adsorbs preferentially on the Co atoms, and the binding is mainly due to the electrical polarization of the charges of adsorbate and host. The preference for Co sites and the trend in the strength of the H2-cluster binding are explained by the combination of two effects characterizing the host environment. One of these is geometric, arising from the degree of exposure of the host atom: the lower the atomic coordination of the host atom, the stronger its bonding with H2. The second effect, newly identified, reveals the importance of the chemical nature of the host atom environment: host Co atoms having both Co and Ag neighbors maintain their capacity to bind hydrogen more intact than those with only Co neighbors. The alloy nanoclusters catalyze the dissociation of adsorbed H2 by building up quite small activation barriers. After dissociation, the H atoms occupy bridge positions between Co atoms (between Co and Ag in CoAg5). H2 adsorption and dissociation may trigger structural transformations of the cluster. The work shows that the adsorption and dissociation properties of H2 can be tuned by varying the relative composition of the two atomic species in the nanoalloy.

Enhancement of Activity of Copper Sites Toward Electroreduction of Carbon Dioxide through Hierarchical Deposition of Metal Oxide Cocatalysts

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties. There has been growing interest in the electrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large over-potentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the electrochemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.We explore here the ability of polynuclear transition metal oxide based systems to function as cocatalysts and to stabilize and activate metal nanocenters. Here certain nanostructured metal oxides of zirconium, titanium, molybdenum or tungsten have been demonstrated to influence supported catalytic metal sites in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ru), thus affecting their chemisorptive and catalytic properties during CO2-reduction. Metal oxide (WO3, MoO3, TiO2) nanostructures can generate highly reactive –OH groups at electrocatalytic interface.Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Pd), thus affecting their chemisorptive properties. Metal oxide (ZrO2, WO3) nanospecies can generate –OH groups at electrocatalytic interface. Our electrocatalytic results with copper nanostructures over-coated with ZrO2 or WO3 nanostructures imply the systems’ improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as the lower tendency of copper sites to undergo poisoning.

Enhancement of Activity of Copper Sites Toward Electroreduction of Carbon Dioxide through Hierarchical Deposition of Metal Oxide Cocatalysts

There has been growing interest in preparation of the advanced catalytic systems that efficiently utilize nanosized materials with well-defined composition, structure, thickness and desirable electrocatalytic properties. The ability of polynuclear inorganic metal oxo systems to support, stabilize and functionalize catalytic metal nanostructures is explored here. Certain nanostructured metal oxides, including oxides of zirconium and tungsten, have been demonstrated to influence catalytic metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu), thus affecting their chemisorptive and catalytic properties. Metal oxide (ZrO2, WO3) nanospecies can generate –OH groups at electrocatalytic interface. Our electrocatalytic results with copper nanostructures over-coated with ZrO2 or WO3 nanostructures imply the systems’ improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as the lower tendency of copper sites to undergo poisoning

Highly Active and Stable a-Site Deficient La0.4Sr0.4Ti0.94Ni0.06O3-δ SOFC Anode Material with in-Situ Exsolved of Ni Nanoparticles

La-doped strontium titanates with a perovskite structure are promising candidates of the anode materials for solid oxide fuel cells (SOFCs) owing to their good chemical compatibility with other components and superior redox-stability. Among these La-doped SrTiO3 (LST), A-site deficient LST materials have attracted much interest due to their improved electrochemical characteristics. Recently, exsolution in A-site deficient LST has been intensively studied, because catalytic active and durable metal nanoparticles can be exsolved on the LST surface. In this study, we developed the A-site deficient Ni-doped La0.4Sr0.4TiO3 (LSTN)-Ce0.9Gd0.1O1.95 (GDC) composite anodes, and investigate their electrochemical performance and redox stability on La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte-based SOFCs. The maximum power density(MPD) of LSTN44-GDC anode based cell was 0.698 mW cm-2 at 900℃ in wet H2 fuel (3% H2O). Also, during redox cyclic tests combined with long-term stability test, The LSTN44-GDC cell maintained its performance without any degradation. All these results demonstrate that the A-site deficient LSTN-GDC is a promising material for an efficient and stable SOFC anode.

Chemiresistive acetylene sensor fabricated from Ga-doped ZnO nanofibers functionalized with Pt catalysts

Herein, we demonstrate a sensitization strategy via solid-solution doping and catalytic metal nanoparticles (NPs) onto porous metal oxide nanofibers (NFs) for superior acetylene (C2H2) sensing capabilities. The introduction of dopants and catalysts not only increases the inherent reactivity of metal oxides, but also induces the spillover of C2H2 onto metal oxides, significantly improving the sensing properties. We elucidate that the high porosity of the metal oxide NFs, prepared by electrospinning and utilizing saponin as a sacrificial template, is the key to achieving high gas permeability and numerous active sites. Consequently, Ga-doped ZnO porous NFs functionalized with Pt catalysts exhibited the highest C2H2 sensing responses among the current state-of-the-art C2H2 sensors (Ra/Rg = 26.2 at 400 °C) with a fast response time (10.2 s), at a particularly low concentration of 5 ppm. Moreover, these NFs showed excellent selectivity against the interfering gas (H2, C7H8, CO, CH4, C8H10, CH3COCH3, HCHO and C2H5OH) and outstanding stability up to 20 sensing cycles to 0.4 ppm of C2H2. These results provide an efficient strategy to tailor composites of metal oxide nanostructures, dopants, and catalysts for highly sensitive gas sensors.

Adsorption of transition metal clusters on Boron-graphdiyne

Layered carbon materials can be useful as supports for catalytic metallic nanoparticles in different applications. Also, doping porous carbons with metal atoms and nanoparticles enhances the hydrogen storage capacity of those materials. We have investigated the adsorption of transition metal atoms and small clusters on boron graphdiyne (BGDY) using density functional theory. This layered material contains uniformly distributed large hexagonal holes that can host the metal clusters. Single V, Co and Pd atoms sit at the hexagon corners, near the B atoms. Their binding energies are large enough to make the systems suitable for single-atom catalysis but atomic diffusion cannot be overlooked. Formation of dimers of those three elements near the hexagon corners is preferred over decoration by two separated atoms. The octahedral structure of the free hexamers is preserved on adsorption of V6 and Co6, but it changes in Pd6. The adsorption sites of the three hexamers are different. The adsorption energies of single atoms, dimers and hexamers on BGDY are substantially larger than those on pristine graphene, and similar to those on graphdiyne, but the larger holes existing in BGDY make this system better tuned for some applications.

Metal nano-drills directionally regulate pore structure in carbon

The exact control of pore structure in carbon is desirable for offering a leap forward in a wide range of industrial applications, but the intractable hurdle relating to the anisotropic etching of carbon remains. Here, metal nano-drills are developed by which controllable pore size and adjustable hole depth can be rationally designed in both SP2- and SP2-SP3 hybridized carbon. A new catalytic drilling behavior is demonstrated, whereby the catalytic metal nanoparticles (Ru, Ni, Au, Pt, etc.) as drilling forces, accompanied by chemical etching, thermodynamically catalyze the decomposition of the surface barrier layer (K2CO3) and dynamically accelerate the anisotropic carbon etching rates. Subsequently, metal nano-drills open the enclosed internal spaces of activation carbonized microtubes (RCMT). Benefiting from the drilling structure featured by outer-inter connecting, RCMT exhibits 2.5 times higher Li2O2 accommodation capacity as the lithium-oxygen battery cathode and 2.8 times higher specific capacitance as the electric double-layer supercapacitor electrode than the carbonized microtube without the drilling process.

(Invited) Hybrid Mixed-Metal-Oxide-Based Catalytic Systems for Efficient Electroreduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties. There has been growing interest in the electrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large over-potentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the electrochemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and derivatize metal and carbon nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, molybdenum or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ru), thus affecting their chemisorptive and catalytic properties. Metal oxide (WO3, MoO3, TiO2) nanospecies can generate –OH groups at electrocatalytic interface.Our electrocatalytic results with copper-substituted polytungstates (or polyoxometallate-network-stabilized copper oxo assemblies)and with copper nanostructures over-coated with WO3 or MoO3 nanostructures imply improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as lower tendency of copper sites to undergo poisoning. We believe that the partially reduced WO3 or MoO3 are capable of sorption of hydrogen, or shifting the proton discharge toward more negative potentials, rather than inducing hydrogen evolution.

Synthesis of Novel Bio-based Urea-Urethane Aerogels In-Situ Impregnated with Catalytic Metallic Nanoparticles for the Removal of Methylene Blue and Congo Red from Wastewater

To combat environmental pollution resulting from discharge of hazardous contaminants into water streams, novel porous biocompatible urea-urethane aerogels in situ impregnated with catalytic metallic nanoparticles were synthesized. FTIR confirmed the formation of highly structured 2D-bifurcated hydrogen bonding network among neighboring urea groups creating aerogels that are strong enough to withstand the pressures of supercritical drying. In-situ impregnation with the catalytic metallic nanoparticles ensured that the systems are efficient in adsorbing, degrading and removing a variety of hazardous contaminants from polluted water. BET measurements indicated an almost reversible Type II isotherm and confirmed the macroporosity of the samples with surface area of around 6 m2 g−1. And swelling capvity of up to 700% The equilibrium uptake capacity of each contaminant increased with increasing the initial concentration due to the increasing driving force and has reached more than 90%. Thermodynamics interpretation indicated exothermic spontaneous processes for all systems with R2 values around 0.9. Almost all adsorption processes followed a Langmuirian type behavior. Kinetics profile revealed that the adsorption is best fitted by pseudo-second order model with an intra-particle diffusion model suggesting that both pore diffusion and contaminant uptake by the aerogels play pivotal role in controlling the kinetics of the adsorption process.

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

Encapsulation of metal-organic frameworks (MOFs) with a shell of mesoporous silica can boost overall performance of MOFs, offering versatility for synthetic architecture of integrated nanocatalysts with reactor-like features. Recently, Yu et al. report a green approach to make yolk-shell nanoreactors.

High Performance UV-LED Activated Sensor Development By Modulating the Morphology and Composition

Metal Oxide Semiconductor (MOS) gas sensors have been studied for monitoring indoor/outdoor air pollutants. A drawback of conventional chemical-resistive gas sensing is the high operating temperature (up to 500°C) that is required for surface reactions. The high temperature operation, however, causes drift problems and makes sensors unsafe for environments containing flammable gases.Ultraviolet light-emitting diode (UV-LED) is a new technological field that has recently seen rapid improvements and novel possible applications. These include the development of UV-LED based gas sensors. UV photons emitted from UV-LED could activate sensors to allow detection of chemicals at ambient temperature. UV irradiation can also improve the sensor performance in harsh environments, where SO2 or NOx gases are present, through desorbing surface contaminants. The state-of-the-art ultraviolet light emitting diode (UV-LED) that emit radiation at a power of a few milli-watts is a promising UV source for this application.UV-activated sensors have a variety of advantages, compared to the traditional chemi-resistive metal oxide semiconductor (MOS) sensors, such as higher stability, lower preparation time, and the ability to safely detect flammable gases. The advances in ultra-violet light emitting diode (UV-LED) technology and its utilization in the gas sensing industry may offer a breakthrough in UV-based sensors, providing several important progresses such as broader application, smaller size, and higher efficiency of the developed sensors.Among the various metal oxides that have been studied for gas sensing applications, ZnO nano-materials have shown promisebecause of high electron conductivity features. ZnO has strong luminescent properties, broad UV absorption, and high stability. Thephoto-activity of ZnO can be improved by synthesizing one-dimensional (1D) nanostructuresand by functionalizing with catalytic metal nanoparticles. This combination lowers the requiredactivationenergy and reduces the recombination rate of photo-generated charge carriers.We will present the fabrication of a sensitive 1D nanostructure ZnO gas sensor decorated with Pt nanoparticles to detect low concentrations of toxic gases at room temperature under UV-LED irradiation (Figure 1). ZnO nanoparticles and nanowires decorated with platinum nanoparticles in different loading concentrations were prepared to detect low concentrations of NO2 under UV-LED irradiation. Solution precipitation, self-assembly crystallization, and photo-deposition techniques were used to synthesize the sensing material. The synthesized sensors at different stages of development were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analyses.To obtain a certain visual evidence of Pt nanoparticleson the surface of ZnO nanowires, High-resolution transmission electron microscopy (HRTEM) and STEM imaging were employed. The presence of Pt nanoparticles was further confirmed through high-angle annular dark-field (HAADF) STEM analysis.Although the sensing response of the pristine ZnO nanoparticles was relatively high (0.4) for NO2 detection, the sensing response improved significantly using ZnO nanowires in the identical photo-activation settings. The decoration ofthe surface of the ZnO nanowires with Pt nanoparticles further enhanced the sensing performance, whereas the 0.1wt% Pt-decorated ZnO nanowire sensor exhibited a response of more than one order of magnitude higher (1.5) than the response generated by the ZnO nanoparticles. This improved performance is attributed to the role of Pt active sites in promoting NO2 adsorption on the ZnO nanowires’ surface as well as enhancing the layer electron utilization.We will present the results and discuss how UV-LED has the potential to significantly impact sensor development and portable gas monitoring systems by enabling novel sensor design concepts. Figure 1