Immobilization Of Metal Nanoparticles Research Articles

Ag/Fe3O4 bifunctional nanocomposite for SERS detection of non-steroidal anti-inflammation drug diclofenac

In this work, a bifunctional nanocomposite based on silver and iron oxide nanoparticles (AgNPs/Fe3O4) was prepared and then used as SERS substrate (surface-enhanced Raman spectroscopy) for sensing diclofenac which is one of the most widely used non-steroid anti-inflammation drugs. AgNPs/Fe3O4 nanocomposite was synthesized by combining co-precipitation of iron oxide and in-situ reduction of silver nanoparticles. Morphology and structural studies revealed a conjugated structure in which silver nanoparticles (80 nm in diameter) were surrounded by iron oxide nanoparticles (18 nm in diameter). There is a slight blue-shift in position of plasmon peak from 405 nm for silver nanoparticles to 375 nm for AgNPs/Fe3O4 nanocomposite. Even the saturation magnetization (Ms) of the Ag/Fe3O4 nanocomposite only reached 28 emu.g-1 but still good enough for immobilizing nanocomposite structures onto the substrate. The use of AgNPs/Fe3O4 nanocomposite as SERS substrate for sensing application was demonstrated with using diclofenac as a model. The detection limit and enhancement factor of the SERS-based diclofenac sensor were found to be 10-12 M and 2.6×1010, respectively. Such kind of bifunctional nanocomposite will probably help us to avoid time-consuming process to immobilize metal nanoparticles onto the surface, and also allow us to regenerate the substrate for multiple uses.

In Situ Anchoring of Small-Sized Silver Nanoparticles on Porphyrinic Triazine-Based Frameworks for the Conversion of CO2 into α-Alkylidene Cyclic Carbonates with Outstanding Catalytic Activities under Ambient Conditions.

The preparation of catalytic hybrid materials by introducing highly dispersed metallic nanoparticles into porous organic polymers (POPs) may be an ideal and promising strategy for integrated CO2 capture and conversion. In terms of the carboxylative cyclization of propargyl alcohols with CO2, the anchoring of silver nanoparticles (AgNPs) on functional POPs to fabricate efficient heterogeneous catalysts is considered to be quite intriguing but remains challenging. In the contribution, well-dispersed AgNPs were successfully anchored onto the porphyrinic triazine-based frameworks by a simple "liquid impregnation and in situ reduction" strategy. The presence of N-rich dual active sites, porphyrin and triazine, which acted as the electron donor and acceptor, respectively, offered a huge opportunity for the nucleation and growth of metal nanoparticles. Significantly, the as-prepared catalyst Ag/TPP-CTF shows excellent catalytic activity (up to 99%) toward the carboxylative cyclization of propargyl alcohols with CO2 at room temperature, achieving record-breaking activities (TOF up to 615 h-1 at 1 bar and 3077 h-1 at 10 bar). Moreover, the catalyst can be easily recovered and reused at least 10 times with retention of high catalytic activity. The possible mechanism involves small-sized AgNP-mediated alkyne activation, which may promote highly efficient and green conversion of CO2. This work paves the way for immobilizing metal nanoparticles onto functional POPs by surface structure changes for enhanced CO2 catalysis.

Photothermally Triggered Nanoreactors with a Tunable Catalyst Location and Catalytic Activity.

Thermosensitive microgels based on poly(N-isopropylacrylamide) (PNIPAm) have been widely used to create nanoreactors with controlled catalytic activity through the immobilization of metal nanoparticles (NPs). However, traditional approaches with metal NPs located only in the polymer network rely on electric heating to initiate the reaction. In this study, we developed a photothermal-responsive yolk-shell nanoreactor with a tunable location of metal NPs. The catalytic performance of these nanoreactors can be controlled by both light irradiation and conventional heating, that is, electric heating. Interestingly, the location of the catalysts had a significant impact on the reduction kinetics of the nanoreactors; catalysts in the shell exhibited higher catalytic activity compared with those in the core, under conventional heating. When subjected to light irradiation, nanoreactors with catalysts loaded in the core demonstrated improved catalytic performance compared to direct heating, while nanoreactors with catalysts in the shell exhibited relatively similar activity. We attribute this enhancement in catalytic activity to the spatial distribution of the catalysts and the localized heating within the polydopamine cores of the nanoreactors. This research presents exciting prospects for the design of innovative smart nanoreactors and efficient photothermal-assisted catalysis.

Study of black protective-decorative nanocomposite anodic coatings on the surface of AMg5 aluminum alloy

A widely used nanocomposite coating is a porous anodic alumina colored by particles of metals or their compounds deposited into the pores. The insertion of light-scattering nanosized particles into the pores changes the optical properties of the anodic oxide, whereas the immobilization of metal nanoparticles in pores ensures their corrosion resistance. We present the results of studying black protective and decorative coatings on the surface of AMg5 aluminum alloy. The surface morphology of the samples was analyzed using atomic force microscopy, and the electrophysical properties were monitored by electrochemical impedance spectroscopy (EIS). The growth kinetics of the anodic coating has been studied, and optimal conditions for the formation of a regularly porous oxide coating 10 – 12 μm thick with a regular pore diameter of 15 ± 5 nm on the alloy surface were determined. It is shown that subsequent electrochemical coloring for 15 min makes it possible to obtain a black color of the coatings due to the deposition of Cu and/or CuO nanoparticles into the pores. Simulation of electrical equivalent circuits makes it possible to separate and calculate the electrical parameters corresponding to different layers and elucidate their regular changes after coloring and hydrothermal treatment. The high corrosion resistance of electrochemically colored anodized alloy samples subjected to hydrothermal treatment has been revealed. The results obtained can be used in the application of protective and decorative anodic coatings for the manufacture, for example, of solar panels due to the high absorption and low reflectivity of black coatings.

Comparison of antibacterial properties between chitosan stabilized silver and zinc oxide nanoparticles immobilized on white silica beads

Most preparation of both silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) was relatively complicated. We proved a more straightforward method not only in the nanoparticle synthesis but also in their immobilization on the solid support. Since both the metal nanoparticles have antibacterial activities, comparing the efficacy and the preparation cost is still interesting to explore. TEM images show both colloidal chitosan stabilized-Ag NPs and ZnO NPs have dispersed and nano-size particles. The immobilized Ag NPs and ZnO NPs on white silica beads (SiG chi-Ag NPs and SiG chi-ZnO NPs) were successfully fabricated with appropriate techniques and suitable characteristics for antibacterial air filter materials. The colloidal and the immobilized metal NPs have high antibacterial properties against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria. The inhibition zone diameter of SiG chi-ZnO NPs and SiG chi-Ag NPs against S. aureus and E. coli were relatively similar but needed about ten times more weight zinc than silver to kill the bacteria at a similar inhibition zone size. Silver is ten times more expensive than zinc, but it is relatively simpler to prepare SiG chi-Ag NPs than to formulate SiG chi-ZnO NPs. The cytotoxicity of silver is more than ten times higher compared to zinc cytotoxicity. Therefore, it was reasonable to substitute silver with zinc nanoparticles for antibacterial air filter material.

Immobilizing Metal Nanoparticles on Hierarchically Porous Organic Cages with Size Control for Enhanced Catalysis

Incorporating metal nanoparticles (MNPs) into porous composites with controlled size and spatial distributions is beneficial for a broad range of applications, but it remains a synthetic challenge. Here, we present a method to immobilize a series of highly dispersed MNPs (Pd, Ir, Pt, Rh, and Ru) with controlled size (<2 nm) on hierarchically micro- and mesoporous organic cage supports. Specifically, the metal-ionic surfactant complexes serve as both metal precursors and mesopore-forming agents during self-assembly with a microporous imine cage CC3, resulting in a uniform distribution of metal precursors across the resultant supports. The functional heads on the ionic surfactants as binding sites, together with the nanoconfinement of pores, guide the nucleation and growth of MNPs and prevent their agglomeration after chemical reduction. Moreover, the as-synthesized Pd NPs exhibit remarkable activity and selectivity in the tandem reaction due to the advantages of ultrasmall particle size and improved mass diffusion facilitated by the hierarchical pores.

Rapid Immobilization of Silver Nanoparticles via Amino-quinone Coatings Enables Surface-Enhanced Raman Scattering Detection.

Immobilization of metal nanoparticles (NPs) on flexible substrates for surface-enhanced Raman scattering (SERS) has received great attention. Anchoring NPs on substrates generally involves the process of surface modification, thanks to its simple, universal, and nondestructive features. 2-Hydroxy-1,4-naphthoquinone (HNQ), a plant-derived compound used to dye hairs and nails, may interact with polyamine or metal ions to form a surface coating. Here, we report the formation of amino-quinone coatings via the co-deposition of HNQ and polyethyleneimine, which provides a functionalized platform to rapidly immobilize Ag NPs on substrates such as a poly(dimethylsiloxane) (PDMS) film to fabricate Ag-PDMS substrates for SERS detection. The detection concentrations are down to 10-8 M for rhodamine 6G. This work expands the system of surface co-deposition and further provides a facile route to prepare a highly efficient SERS substrate.

Covalent Organic Frameworks for Electrochemical Sensors: Recent Research and Future Prospects

Background: In recent years, electrochemical sensors are widely preferred because of their high sensitivity, rapid response, low cost and easy miniaturization. Covalent organic frameworks (COFs), a porous crystalline polymer formed by organic units connected by covalent bonds, have been widely used in gas adsorption and separation, drug transportation, energy storage, photoelectric catalysis, electrochemistry and other aspects due to their large specific surface, excellent stability, high inherent porosity, good crystallinity as well as structural and functional controllability. The topological structure of COFs can be designed in advance, the structural units and linkage are diversified, and the structure is easy to be functionalized, which are all beneficial to their application in electrochemical sensors. Methods: The types, synthesis methods, properties of covalent organic frameworks and some examples of using covalent organic frameworks in electrochemical sensors are reviewed. Results: Due to their characteristics of a large specific surface, high porosity, orderly channel and periodically arranged π electron cloud, COFs are often used to immobilize metal nanoparticles, aptamers or other materials to achieve the purpose of building electrochemical sensors with high sensitivity and good stability. Since the structure of COFs can be predicted, different organic units can build COFs with different structures and properties. Therefore, organic units with certain functional groups can be selected to build COFs with certain properties and used directly for electrochemical sensors. Conclusion: COFs have a good application prospect in electrochemical sensors.

Development of a Simultaneous Process of Surface Modification and Pd Nanoparticle Immobilization of a Polymer Substrate Using Radiation.

Pd nanoparticles were immobilized on an acrylonitrile–butadiene–styrene copolymer (ABS) substrate using ionizing radiation. The samples were prepared by irradiating plastic zipper packs containing ABS substrates and a Pd(NO3)2 aqueous solution with a high-energy electron beam (4.8 MeV). Pd nanoparticles immobilized on the ABS substrate surfaces were observed using scanning electron microscopy (SEM). The chemical state of Pd was found to be coordinated to a carbonyl group or a metallic state by X-ray photoelectron spectroscopy (XPS) measurements. The peel strength of the Cu film on the Pd/ABS samples was 0.7 N/mm or higher. This result shows that the prepared Pd/ABS samples have high adhesion strength, despite not undergoing treatments such as etching with chromic acid. This method is expected to immobilize metal nanoparticles, not only on plastic plates but also on various other materials.

A general strategy to immobilize metal nanoparticles on MXene composite fabrics for enhanced sensing performance and endowed multifunctionality

A general strategy was developed to enhance the sensing performance of MNWF composites and realize multifunctional applications by introducing metal NPs.

Highly dispersed Ni nanocatalysts supported by MOFs derived hierarchical N-doped porous carbon for hydrogenation of dicyclopentadiene

N-doped carbon possesses the advantages of electronic modification and immobilization of metal nanoparticles. Hence, N-doped carbon-based metal catalysts have received extensive attention. This study prepared uniformly dispersed Ni nanoparticles (24.0 wt%) on porous N-doped carbon, which was fabricated via the high temperature pyrolysis of nitrogen-rich ZnNi MOFs with 1H-1,2,3-triazole as the ligand. The 1H-1,2,3-triazole as a high energy ligand could volatilize violently to form a N-doped macroporous carbon-based structure. Zn acted as a fence and prevented the accumulation of Ni during the pyrolysis of ZnNi MOFs. The synergistic effect from the abundant porous structure together with uniformly dispersed Ni nanoparticles proves the excellent catalytic activity toward the hydrogenation of dicyclopentadiene, showing 100% DCPD conversion and >99% THDCPD selectivity.

In situ fabrication of layered double hydroxide film immobilizing gold nanoparticles in capillary microreactor for efficient catalytic carbonylation of glycerol

• Layered double hydroxides crystallite were in situ fabricated on inner wall of capillary. • Thickness and morphology of LDH film on inner-wall of capillary was finely controlled. • Au NPs were immobilized on layered double hydroxides film. • Au/LDH film showed good catalytic activity in carbonylation of glycerol with urea. • The productivity of glycerol carbonate reached 3.78 g•h −1 •g −1 on Au/LDH catalytic film. Microreactor is capable of intensifying catalytic reaction processes. The fabricating of catalytic film inside microchannels for catalytic reaction remains a challenge. Here we report a facile method for in situ fabrication of layered double hydroxide (LDH) film immobilizing gold nanoparticles in capillary microreactor. Through adjusting the reaction condition of in situ hydrothermal crystallization process and flow deposition process inside microchannel, film thickness, film morphology and Au loading of Au/LDH coating can be finely controlled. Such Au/LDH film inside microchannel exhibited good performance in catalytic carbonylation of glycerol with urea. The yield of glycerol carbonate reached 31.9% at flow rate of 10 µl/min, residence time of 6.62 min and reaction temperature of 413 K under atmospheric pressure. The maximum productivity of 3.78 g∙h −1 ⋅g −1 was obtained at flow rate of 40 µl/min and residence time of 1.65 min under same reaction temperature and pressure. Continuously running the microreactor for 30 h proved the high stability of this catalytic film inside microchannels. This approach could be extended to fabricate other diatomic and triatomic metal LDH films immobilizing metal nanoparticles inside microchannels for heterogeneous catalysis.

Stable Mesoscale Nonwovens of Electrospun Polyacrylonitrile and Interpenetrating Supramolecular 1,3,5-Benzenetrisamide Fibers as Efficient Carriers for Gold Nanoparticles.

The immobilization of metal nanoparticles without agglomeration and leaching within composite nonwovens is often challenging and of great importance, for example, for catalytic applications. In this study, we prepared composite nonwovens based on electrospun polyacrylonitrile (PAN) short fibers and supramolecular terpyridine-functionalized benzene-1,3,5-tricarboxamide (BTA1) nanofibers by a sheet-forming wet-laid process. The formation of an interpenetrating and entangled network of supramolecular BTA1 nanofibers and PAN short fibers results in mechanically stable mesoscale nonwovens. Because of the peripheral terpyridine substituents of the BTA1, nonaggregated gold nanoparticles (AuNPs) could be immobilized efficiently in the composite nonwovens. The functionality of the resulting AuNPs-loaded composite nonwovens was verified by catalytic reduction of 4-nitrophenol to 4-aminophenol as a standard model reaction. The AuNPs-loaded PAN/BTA1 composite nonwovens showed high catalytic activity, reusability, and excellent stability.

Engineering the Electronic Interaction between Metals and Carbon Supports for Oxygen/Hydrogen Electrocatalysis

Carbon materials-supported metal catalysts are of great significance to the renewable energy conversion. More than a support to immobilize metal nanoparticles and improve atomic usage, the carbon materials can also impact the catalysis performance in a way of engineering the electronic structure of active metal components. The modulation of such an electronic metal–support interaction (EMSI) for designing efficient catalysts has been a hotspot in recent years. Benefiting from the development of advanced characterization techniques and theoretical simulations, one can shed light on the key points regarding EMSI and construct the relationship between EMSI and catalysis performance. In this Review, we summarize the recent work concerning the electronic interaction between carbon supports and metals, and discuss the underlying factors, including the nature of metal, metal morphology, metal particle size, carbon structure, heteroatom doping, carbon coating, and interfacial binding. The relationship between EMSI and the catalytic performance, by taking hydrogen/oxygen electrocatalysis for examples, is highlighted. These summaries would deepen the understanding of EMSI and favor the progress of carbon-supported metal catalysts.

Polythiolactone-Decorated Silica Particles: A Versatile Approach for Surface Functionalization, Catalysis and Encapsulation.

The surface chemistry of colloidal silica has tremendous effects on its properties and applications. Commonly the design of silica particles is based on their de novo synthesis followed by surface functionalization leading to tailormade properties for a specific purpose. Here, the design of robust “precursor” polymer‐decorated silica nano‐ and microparticles is demonstrated, which allows for easy post‐modification by polymer embedded thiolactone chemistry. To obtain this organic‐inorganic hybrid material, silica particles (SiO2P) were functionalized via surface‐initiated atom transfer radical polymerization (SI‐ATRP) with poly(2‐hydroxyethyl acrylate) (PHEA)‐poly(thiolactone acrylamide (PThlAm) co‐polymer brushes. Exploiting the versatility of thiolactone post‐modification, a system was developed that could be used in three exemplary applications: 1) the straightforward molecular post‐functionalization to tune the surface polarity, and therefore the dispersibility in various solvents; 2) the immobilization of metal nanoparticles into the polymer brushes via the in situ formation of free thiols that preserved catalytic activity in a model reaction; 3) the formation of redox‐responsive, permeable polymer capsules by crosslinking the thiolactone moieties with cystamine dihydrochloride (CDH) followed by dissolution of the silica core.

Rationally designed SERS AgNPs/GO/g-CN nanohybrids to detect methylene blue and Hg2+ ions in aqueous solution

The newly developed AgNPs/GO/g-CN nanohybrids by combining silver nanoparticles, graphene oxide and carbon nitride (g-CN) in the present study has emerged as a much sensitive one to detect methylene blue (MB) and Hg2+ ions. Its multiple charge transfer from 2D sheets to AgNPs and then to MB is verified beyond the doubts with analytical techniques and it is the cause for an enhanced SERS intensity. A very low concentration of 10−12 M with enhancement factor of 4.25 × 108, 6.15 × 108, 6.11 × 108 and 6.59 × 108 for the peaks at 450, 502, 1400 and 1624 cm−1, respectively for MB could be detected by this SERS substrate. The ideas implemented in this study could also be applicable to other 2D sheets and metal nanoparticles. The essential criterion is the 2D sheets should have delocalized electronic cloud and capable of bonding to each other and facilitate immobilizing metal nanoparticles on their surface. The analyte MB bonding to the metal nanoparticles of the SERS substrate could be used as a and Raman tag to study selective SERS sensing of Hg2+ ions at very low concentration of 0.01986 ppm. Thus the present SERS substrate is expected to be a promising candidate for the determination of waste water contaminants.

Hierarchically porous CoP@CNR nanorod derived from metal-organic frameworks as noble-metal-free catalyst for dehydrogenization of ammonia-borane

The development of effective and inexpensive catalysts for hydrogen release from hydrogen-storage compounds such as ammonia-borane (AB) is crucial in academic and industrial fields for the reduction of greenhouse gas emissions. Herein, we report a facile method to fabricate well-dispersed CoP nanoparticles (NPs) with an average particle size of 4.3 nm. The CoP NPs were encapsulated in carbonaceous nanorods (CoP@CNR) using metal-organic frameworks (MOFs) as a sacrificial precursor. The CoP@CNR catalysts were characterized, and their catalytic performance for the dehydrogenization of AB at 25 °C in an alkaline solution was determined. CoP@CNR (400) with a hierarchically meso-microporous structure (micropore area = 73.6 m2 g-1 and micropore volume = 0.19 cm3 g-1) and a specific surface area of 88.4 m2 g-1 was synthesized during the phosphorization process. The hierarchically porous structure was instrumental in immobilizing metal NPs and accelerating mass diffusion. Moreover, the incorporation of P into Co NPs modified the electronic structure of the latter and accelerated the dehydrogenization of AB. This resulted in a hydrogen release rate of 10,014 mL/(min·g), which was 13 times higher than that of the pure Co nanocatalyst. In addition, we reported the kinetic studies for AB hydrolysis catalyzed by CoP@CNR (400) in terms of the temperature effect, isotope effect, catalyst concentration, AB concentration, and NaOH concentration.

Fe and Ni nanoparticles-loaded zeolites as effective catalysts for catalytic reduction of organic pollutants

Three zeolites with different structures (mazzit, faujasite and MFI) were prepared by hydrothermal way, and then were used to stabilize the Fe and Ni nanoparticles using ion exchange followed by treatment with a solution of NaBH4 as reducing agent. The designed nanocatalysts were used in the catalytic reduction of methylene blue dye (MB) and 4-nitrophenol (4-NP) in a simple and binary system under NaBH4 solution to determine their effectiveness in wastewater treatment. The obtained samples were characterized by XRD, XPS, nitrogen sorption at 77 K, XRF, FTIR, UV–vis, SEM and TEM. The obtained results revealed that the structure of the zeolites was well retained after immobilization of metal nanoparticles (NPs), but their textural properties were slightly reduced. The XPS results clearly show that the zero charge nanoparticles were well obtained using NaBH4 solution. As confirmed by TEM the nanoparticles were well dispersed in the surface of the zeolites their sizes were around 3–13 nm for the zeolites modified by Fe NPs and 2–6 nm for those modified by Ni NPs. The catalyst Ni–Y exhibited excellent catalytic activity towards the reduction of MB dye and 4-NP in binary and simple system due to its large surface area containing well dispersed Ni nanoparticles. The rate constant in a simple system was 0.02 s−1 and 0.005 s−1 for 4-NP and MB dye respectively, while in the binary system was 0.002 s−1 and 0.014 s−1. The catalyst Ni–Y was used in five consecutive experiments without important loss of activity, confirming its stability.

Synthesis and Immobilization of Metal Nanoparticles Using Photoactive Polymer‐Decorated Zeolite L Crystals and Their Application in Catalysis

AbstractA facile route to generate Au and Pd nanoparticles (NPs) on zeolite L crystals decorated with photoactive polymer brushes is described. The polymers used in this approach serve a dual role: Upon irradiation with UV light, they release highly reducing ketyl radicals in a Norrish‐Type‐I reaction. These radicals serve as one electron donors to reduce metal salts to the corresponding metal NPs. At the same time the polymer shell stabilizes the in situ generated metal NPs. It is shown that the zeolite‐polymer‐NP composites can be used as recyclable catalysts for the oxidation of benzylic alcohols to aldehydes and the stereoselective semihydrogenation of alkynes to Z‐alkenes. The polymer shell in these hybrid catalysts protects the NPs from aggregation and also alters their catalytic properties.magnified image

Tetraalkylammonium Functionalized Hydrochars as Efficient Supports for Palladium Nanocatalysts

AbstractWith the aim of preparing bio‐sourced supports with enhanced properties in catalysis, we devised an original strategy allowing the immobilization of metal nanoparticles. Thus, size‐controlled hydrochars with a high degree of hydroxyl functionalities, from both neat sucrose or modified with acrylic acid (10 wt.%), were derivatized with ether linkers containing ammonium groups. These non‐porous carbon‐based materials were used as suitable supports for the immobilization of palladium nanoparticles. The catalytic materials were synthesized by reduction of Pd(OAc)2 to Pd(0) under H2 atmosphere in the presence of the corresponding hydrochar, and fully characterized by standard methods. Among the different hydrochar‐supported palladium materials, those functionalized with tetraalkylammonium groups afforded heterogeneous catalysts, exhibiting high activity in hydrogenations of different types of substrates (alkynes, alkenes, and carbonyl and nitro derivatives). The most efficient catalyst was recycled up to ten runs without loss of catalytic behavior, in agreement with the unchanged composite materials after catalysis (Transmission Electron Microscopy (TEM) analyses) and the lack of metal leaching in the extracted organic products (no palladium detected by Inductively Coupled Plasma‐Atomic Emission Spectrometry (ICP‐AES)); these systems exhibited enhanced recyclability properties as compared to commercial Pd/C catalyst.