Bifunctional nanocatalyst based on three-dimensional carbon nanotube-graphene hydrogel supported Pd nanoparticles: one-pot synthesis and its catalytic properties

Self-Standing Pd-Based Nanostructures for Electrocatalytic CO Oxidation: Do Nanocatalyst Shape and Electrolyte pH Matter?

Tailoring the shape of Pd nanocrystals is one of the main ways to enhance catalytic activity; however, the effect of shapes and electrolyte pH on carbon monoxide oxidation (CO_Oxid) is not highlighted enough. This article presents the controlled fabrication of Pd nanocrystals in different morphologies, including Pd nanosponge via the ice-cooling reduction of the Pd precursor using NaBH₄ solution and Pd nanocube via ascorbic acid reduction at 25 °C. Both Pd nanosponge and Pd nanocube are self-standing and have a high surface area, uniform distribution, and clean surface. The electrocatalytic CO oxidation activity and durability of the Pd nanocube were significantly superior to those of Pd nanosponge and commercial Pd/C in only acidic (H₂SO₄) medium and the best among the three media, due to the multiple adsorption active sites, uniform distribution, and high surface area of the nanocube structure. However, Pd nanosponge had enhanced CO_Oxid activity and stability in both alkaline (KOH) and neutral (NaHCO₃) electrolytes than Pd nanocube and Pd/C, attributable to its low Pd-Pd interatomic distance and cleaner surface. The self-standing Pd nanosponge and Pd nanocube were more active than Pd/C in all electrolytes. Mainly, the CO_Oxid current density of Pd nanocube in H₂SO₄ (5.92 mA/cm²) was nearly 3.6 times that in KOH (1.63 mA/cm²) and 10.3 times that in NaHCO₃ (0.578 mA/cm²), owing to the greater charge mobility and better electrolyte-electrode interaction, as evidenced by electrochemical impedance spectroscopy (EIS) analysis. Notably, this study confirmed that acidic electrolytes and Pd nanocube are highly preferred for promoting CO_Oxid and may open new avenues for precluding CO poisoning in alcohol-based fuel cells.

Unveiling the effect of shapes and electrolytes on the electrocatalytic ethanol oxidation activity of self-standing Pd nanostructures

Morphologically controlled Pd-based nanocrystals are the most efficient strategies for improving the electrocatalytic ethanol oxidation reaction (EOR) performance; however, their morphological-EOR activity relationship and effect of electrolytes at a wide pH range are still ambiguous. Here, we have synthesized porous self-standing Pd clustered nanospheres (Pd-CNSs) and Pd nanocubes (Pd-NCBs) for the EOR in acidic (H₂SO₄), alkaline (KOH), and neutral (NaHCO₃) electrolytes compared to commercial spherical-like Pd/C catalysts. The fabrication process comprises the ice-cooling reduction of Pd precursor by sodium borohydride (NaBH₄) and l-ascorbic acid to form Pd-CNSs and Pd-NCBs, respectively. The EOR activity of Pd-CNSs significantly outperformed those of Pd-NCBs, and Pd/C in all electrolytes, but the EOR activity was better in KOH than in H₂SO₄ and NaHCO₃. This is due to the 3D porous clustered nanospherical morphology that makes Pd active centers more accessible and maximizes their utilization during EOR. The EOR specific/mass activities of Pd-CNSs reached (8.51 mA/cm²/2.39 A/mg_Pd) in KOH, (2.98 mA/cm²/0.88 A/mg_Pd) in H₂SO₄, and (0.061 mA/cm²/0.0083 A/mg_Pd) in NaHCO₃, in addition to stability after 1000 cycles. This study affirms that porous 3D spherical Pd nanostructures are preferred for the EOR than those of 0D spherical-like and multi-dimensional cube-like nanostructures.

CoFe-Layered Double Hydroxide Coupled with Pd Particles for Electrocatalytic Ethanol Oxidation

Electrocatalytic efficiency and stability have emerged as critical issues in the ethanol oxidation reaction (EOR) of direct ethanol fuel cells. In this paper, Pd/Co₁Fe₃-LDH/NF as an electrocatalyst for EOR was prepared by a two-step synthetic strategy. Metal-oxygen bonds formed between Pd nanoparticles and Co₁Fe₃-LDH/NF guaranteed structural stability and adequate surface-active site exposure. More importantly, the charge transfer of the formed Pd-O-Co(Fe) bridge could effectively modulate the electrical structure of hybrids, improving the facilitated absorption of OH^- radicals and oxidation of CO_ads. Benefiting from the interfacial interaction, exposed active sites, and structural stability, the observed specific activity for Pd/Co₁Fe₃-LDH/NF (17.46 mA cm^-2) was 97 and 73 times higher than those of commercial Pd/C (20%) (0.18 mA cm^-2) and Pt/C (20%) (0.24 mA cm^-2), respectively. Besides, the j_f/j_r ratio representing the resistance to catalyst poisoning was 1.92 in the Pd/Co₁Fe₃-LDH/NF catalytic system. These results provide insights into optimizing the electronic interaction between metals and the support of electrocatalysts for EOR.

Integrated Papertronic Techniques: Highly Customizable Resistor, Supercapacitor, and Transistor Circuitry on a Single Sheet of Paper

Humanity's excessive production of material waste poses a critical environmental threat, and the problem is only escalating, especially in the past few decades with the rapid development of powerful electronic tools and persistent consumer desire to upgrade to the newest available technology. The poor disposability of electronics is especially an issue for the newly arising field of single-use devices and sensors, which are often used to evaluate human health and monitor environmental conditions, and for other novel applications. Though impressive in terms of function and convenience, usage of conventional electronic components in these applications would inflict an immense surge in waste and result in higher costs. This work's primary objective is to develop a cost-effective, eco-friendly, all-paper, device for single-use applications that can be easily and safely disposed of through incineration or biodegradation. All electronic components are paper-based and integrated on paper-based printed circuit boards (PCBs), innovatively providing a realistic and practical solution for green electronic platforms. In particular, a methodology is discussed for simultaneously achieving very tunable resistors (20 Ω to 285 kΩ), supercapacitors (∼3.29 mF), and electrolyte-gated field-effect transistors on and within the thickness of a single sheet of paper. Each electronic component is completely integrated into functionalized paper regions and exhibits favorable electrical activity, adjustability, flexibility, and disposability. A simple amplifier circuit is successfully demonstrated within a small area and within the thickness of a single sheet of paper, displaying component versatility and the capability for their fabrication processes to be performed in parallel for efficient and rapid development.

Ultralow detection limit and ultrafast response/recovery of the H2 gas sensor based on Pd-doped rGO/ZnO-SnO2 from hydrothermal synthesis

Hydrogen (H2) sensors are of great significance in hydrogen energy development and hydrogen safety monitoring. However, achieving fast and effective detection of low concentrations of hydrogen is a key problem to be solved in hydrogen sensing. In this work, we combined the excellent gas sensing properties of tin(IV) oxide (SnO2) and zinc oxide (ZnO) with the outstanding electrical properties of reduced graphene oxide (rGO) and prepared palladium (Pd)-doped rGO/ZnO-SnO2 nanocomposites by a hydrothermal method. The crystal structure, structural morphology, and elemental composition of the material were characterized by FE-SEM, TEM, XRD, XPS, Raman spectroscopy, and N2 adsorption-desorption. The results showed that the Pd-doped ZnO-SnO2 composites were successfully synthesized and uniformly coated on the surface of the rGO. The hydrogen gas sensing performance of the sensor prepared in this work was investigated, and the results showed that, compared with the pure Pd-doped ZnO-SnO2 sensor, the Pd-doped rGO/ZnO-SnO2 sensor modified with 3 wt% rGO had better hydrogen (H2)-sensing response of 9.4-100 ppm H2 at 380 °C. In addition, this sensor had extremely low time parameters (the response time and recovery time for 100 ppm H2 at 380 °C were 4 s and 8 s, respectively) and an extremely low detection limit (50 ppb). Moreover, the sensor exhibited outstanding repeatability and restoration. According to the analysis of the sensing mechanism of this nanocomposite, the enhanced sensing performance of the Pd-doped rGO/ZnO-SnO2 sensor is mainly due to the heterostructure of rGO, ZnO, and SnO2, the excellent electrical and physical properties of rGO and the synergy between rGO and Pd.

Recent developments in hydrogels containing copper and palladium for the catalytic reduction/degradation of organic pollutants

The elimination of toxic and hazardous contaminants from different environmental media has become a global challenge, causing researchers to focus on the treatment of pollutants. Accordingly, the elimination of inorganic and organic pollutants using sustainable, effective, and low-cost heterogeneous catalysts is considered as one of the most essential routes for this aim. Thus, many efforts have been devoted to the synthesis of novel compounds and improving their catalytic performance. Recently, palladium- and copper-based hydrogels have been used as catalysts for reduction, degradation, and decomposition reactions because they have significant features such as high mechanical strength, thermal stability, and high surface area. Herein, we summarize the progress achieved in this field, including the various methods for the synthesis of copper- and palladium-based hydrogel catalysts and their applications for environmental remediation. Moreover, palladium- and copper-based hydrogel catalysts, which have certain advantages, including high catalytic ability, reusability, easy work-up, and simple synthesis, are proposed as a new group of effective catalysts.

The elimination of toxic and hazardous contaminants from different environmental media has become a global challenge, causing researchers to focus on the treatment of pollutants.

Highly efficient catalytic hydrogenation of nitrophenols by sewage sludge derived biochar

Finding a low cost and effective alternative to noble metal based catalyst has long been concerned in wastewater treatment and organic transformation. This work developed a highly efficient sewage sludge-based catalyst via a simple one-step pyrolysis method, and for the first time, applied it in the catalytic reduction of nitrophenols. Due to the higher content of graphitic nitrogen, abundant defect sites and low electron transfer resistance, sewage sludge derived biochar obtained at 800 °C (SSBC-800) exhibits the best catalytic performance, with the reaction rate of 0.48 min^-1 and turnover frequency for 4-nitrophenol calculated to be 1.25 × 10^-4 mmol•mg^-1 min^-1, which is comparable to or even superior than some reported noble metal-based catalyst. Moreover, SSBC-800 showed good recyclability of 90% 4-nitrophenol removal within 8 min after 4 runs, and maintained high catalytic activity in reduction of other substituent nitrophenols, such as 2-nitrophenol (0.54 min^-1), 3-nitrophenol (0.61 min^-1) and 2,4-dinitrophenol (0.18 min^-1), and in real water samples, indicating its practical applicability. The electron paramagnetic resonance spectra and electrochemical characterization demonstrate that SSBC-800 accelerates the dissociation of BH₄^- to form active hydrogen, which is the main species responsible for 4-nitrophenol reduction, while electron transfer reaction involving the surface bound hydride derived from the intimate contact between BH₄^- and SSBC-800 plays an important role in this process. This research not only provides a novel valorization pathway for sewage sludge, but also sheds new light on further designing of carbon-based catalyst for nitrophenol reduction.

Synthesis of bimetallic nanoparticles loaded on to PNIPAM hybrid microgel and their catalytic activity

This study was designed to preparecarboxyl-functionalized poly (N-isopropylacrylamide) PNIPAM microgels having excellent catalytic properties.Recently, researchers are trying to fabricate cost effective and efficient hybrid catalytic materials for the synthesis of nitrogenous compounds along with enhanced optical properties. For the same motive, synthesis of carboxyl-functionalized PNIPAM microgels was performed by using polymerization of soap-free emulsion of N-isopropyl acrylamide, which is NIPAM along with acrylic acid (AA). The thiol group was introduced through the imide bond mediated by carbodiimide, between carboxyl-functionalized microgels through carboxyl group and aminoethanethiol (AET). Copper, Palladium and Cu/Pd nanoparticles were incorporated successfully into thiol-functionalized PNIPAM microgels through metals thiol linkage. The synthesized microgels and hybrid encompassing metallic nanoparticles were characterized in detail by using Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron (XPS) and Fourier transformed infrared spectroscopy for structural interpretation. The thermal properties of the pure and hybrid microgels were inspected by TG analysis. The prepared nanocomposites PNIPAM-Cu, PNIPAM-Pd and PNIPAM-Cu/Pd exhibited decent catalytic properties for the degradation of 4-Nitrophenol and methylene blue, but the bimetallic Cu/Pd have remarkable catalytic properties. The catalytic reaction followed pseudo-first-order reaction with rate constants 0.223 min-1, 0.173 min-1 for 4-Nitrophenol and methylene blue in that order. In this study,we were able to establish that Cu/Pd hybrid is an efficient catalyst for 4-Nitrophenol and methylene blue as compared to its atomic analogue.

Fly ash supported Pd-Ag bimetallic nanoparticles exhibiting a synergistic catalytic effect for the reduction of nitrophenol

Coal fly ash (FA) supported Pd-Ag bimetallic nanoparticles (FA-Pd-Ag) were prepared by reducing Pd(II) and Ag(I) salts together onto the dispersed solid support in aqueous medium. Electron microscope analysis (FE-SEM, HRTEM) in combination with elemental mapping (EDS) suggests that the nanoparticles are well dispersed on fly ash with an average diameter of 6-8 nm. The powder XRD analysis indicates that alloying of the interface occurs between Pd and Ag nanoparticles in FA-Pd-Ag, while XPS reveals that charge transfer takes place between the Pd and Ag moieties that come into contact with each other. The FA-Pd-Ag in aqueous NaBH4 solution exhibits an efficient catalytic reduction of 4-nitrophenol into 4-aminophenol and follows pseudo-first-order reaction kinetics (kPd-Ag = 0.7176 min-1). The higher rate constant for FA-Pd-Ag compared to that for their monometallic analogues (FA-Pd (kPd = 0.5449 min-1)) and (FA-Ag (kAg = 0.5572 min-1)) as well as their physical mixture ((FA-Pd + FA-Ag) (kPd+Ag = 0.4075 min-1)) suggests the synergistic catalytic effect of the bimetallic system. Moreover, the present bimetallic nanocatalyst exhibits the highest normalized rate constant (KPd-Ag ≈ 51 100 min-1 mmol-1) compared to the reported bimetallic Pd-Ag nanocatalysts.

Fabrication of CS/GA/RGO/Pd composite hydrogels for highly efficient catalytic reduction of organic pollutants

In this study, natural polymer material chitosan (CS) and graphene oxide (GO) with large specific surface area were used to prepare a new CS/RGO-based composite hydrogel by using glutaraldehyde (GA) as cross-linking agent. In addition, a CS/GA/RGO/Pd composite hydrogel was prepared by loading palladium nanoparticles (Pd NPs). The morphologies and microstructures of the prepared hydrogels were characterized by SEM, TEM, XRD, TG, and BET. The catalytic performance of the CS/GA/RGO/Pd composite hydrogel was analyzed, and the experimental results showed that the CS/GA/RGO/Pd composite hydrogel had good catalytic performance for degradation of p-nitrophenol (4-NP) and o-nitroaniline (2-NA). Therefore, this study has potential application prospect in wastewater treatment and provides new information for composite hydrogel design.

New functional CS/GA/RGO/Pd composite hydrogels are prepared via a self-assembly process, demonstrating potential applications in catalysis as well as composite materials.

Transformation from 3D Boron Organic Polymers to 1D Nanorod Arrays: Loading Highly Dispersed Nanometal for Green Catalysis

The increasing global demands for eco-friendly and low-cost catalysts have propelled the advent of nanosized non-noble-metal catalysts to replace traditional noble metals. In this work, ultrafine NiO nanoparticles were prepared rapidly in situ by the strategy of transforming three-dimensional (3D) metal boron organic polymers (BOPs@Ni²⁺) to one-dimensional (1D) boron organic polymers (BOPs@Ni) nanorod arrays at room temperature. The 3D BOPs@Ni²⁺ can be quickly obtained by the interaction of 4,4'-bipyridine with Ni²⁺ and dodecaborate (B₁₂H₁₂^2-) in an aqueous solution. When Ni²⁺ is converted into NiO in situ, 1D BOPs@Ni nanostructure transformation from the 3D BOPs@Ni²⁺ framework was achieved due to the B-H···π interaction between B₁₂H₁₂^2- and 4,4'-bipyridine. Furthermore, BOPs@Ni exhibits high catalytic activity and rapid kinetics in the conversion of 4-nitrophenol to 4-aminophenol, and the high stability of 1D nanorod arrays guarantees the catalytic activity of BOP@Ni to barely change under recycling for at least 10 times. BOPs@Ni also exhibits good catalytic performance and high selectivity characteristics in the catalytic reduction of a series of nitrobenzene derivatives. This strategy of using BOPs@Ni²⁺ for loading self-supporting nanometal not only exhibits a highly efficient catalytic hydrogenation of nitrobenzene and its derivative but also provides an effective technical route for designing self-supported nanometal materials.

Sub-10 nm Ag Nanoparticles/Graphene Oxide: Controllable Synthesis, Size-Dependent and Extremely Ultrahigh Catalytic Activity

While tremendous advancements in Ag nanoparticle (AgNP)-based materials have been made, the development of a facile protocol for preparing sub-10 nm AgNPs with controllable size and ultrahigh performance remains a formidable challenge. It is shown that AgNPs/graphene oxide (AgNPs/GO) bearing 2.5, 4.3, and 6.2 nm AgNPs (2.5-AgNPs/GO, 4.3-AgNPs/GO, and 6.2-AgNPs/GO, respectively) could be fabricated via light-induced synthesis. Their catalytic activity toward 4-nitrophenol (4-NP) reduction, which is a "gold standard" for evaluating the performance of noble metal-based catalysts, is studied. When normalized by mole and area, the activity exhibits an order of 4.3-AgNPs/GO > 6.2-AgNPs/GO > 2.5-AgNPs/GO and 6.2-AgNPs/GO > 4.3-AgNPs/GO > 2.5-AgNPs/GO, respectively. This trend is a result of GO-induced electron concentration reduction with decreasing AgNP size. Significantly, under similar conditions, the activity of 4.3-AgNPs/GO is substantially superior to that of numerous state-of-the-art noble metal-based catalysts. The ultrafine size of the AgNPs and their surface accommodation on the unobstructed 2D GO scaffolds without capping reagents/covers, which make the abundantly exposed catalytically active sites highly accessible to substrate molecules, play an important role in their extremely ultrahigh performance. This work paves a new avenue for high-performance AgNP-based materials, and by taking 4-NP reduction as a proof-of-concept, provides new scientific insights into the rational design of surface-based advanced materials.

Nanotoxicity of different sizes of graphene (G) and graphene oxide (GO) in vitro and in vivo

Graphene family nanomaterials (GFNs) have attracted significant attention due to their unique characteristics and applications in the fields of biomedicine and nanotechnology. However, previous studies highlighted the in vitro and in vivo toxicity of GFNs with size and oxidation state differences are still elusive. Therefore, we prepared graphene (G) and graphene oxide (GO) of three different sizes (S-small, M-medium, and L-large), and characterized them using multiple surface-sensitive analytical techniques. In vitro assays using HEK 293T cells revealed that the small and large sizes of G and GO significantly reduced the cell viability and increased DNA damage, accompanying with activated reactive oxygen species (ROS) generation and induced various expressions of associated critical genetic markers. Moreover, the bacterial assays highlighted that G and GO caused strong acute toxicity on Tox2 bacteria. Effects of G were higher than GO and showed size dependent effect: L > M > S, while the medium size of GO induced mild genetic toxicity on RecA bacteria. In vivo assays revealed that exposure to G and GO caused the developmental toxicity, induced ROS generation, and activated related pathways (specifically GO) in zebrafish. Taken together, G showed stronger ability to decrease the survival rate and induce the acute toxicity, while GO showed obvious toxicity in terms of DNA damages, ROS generation, and abnormal gene expressions. Our findings highlighted that G and GO differentially induced toxicity based on their varying physical characteristics, especially sizes and oxidation state, and exposure concentrations and sensitivity of the employed in vitro and in vivo models. In short, this study provided deep insights on the negative effects of GFNs exposure.

Ultra-small and recyclable zero-valent iron nanoclusters for rapid and highly efficient catalytic reduction of p-nitrophenol in water

The synthesis of nanoscale zero-valent iron (NZVI) nanoclusters with dimensions ranging from 20 to 100 nm for the control of environmental pollutants has received substantial attention. However, due to the strong van der Waals and magnetic attraction forces of ZVI, synthesizing ZVI nanoclusters with a subnanometre size while retaining their surface activity and avoiding aggregation is challenging. Moreover, NZVI particles can be oxidized easily after the removal of contaminants even in anoxic environments, which makes the recovery and recycling of the particles very difficult. Here, for the first time, ultra-small zero-valent iron (ZVI) nanoclusters are successfully prepared in a micelle assisted method under mild conditions, and can be recycled simply. It is found that by encapsulating Fe3+ within the micelles, controlling the release of sulfur ions (S2-) from thiourea and forming the FeS nanoparticles as intermediates, the ZVI nanoclusters are produced with a precisely controlled size (<1 nm). A large number of zero-valent iron nanoclusters were assembled into quasi-spherical assemblages (with around 5 nm size), in which most of the nanoclusters exist discretely because of being coated by entangled hydrocarbon chains of the surfactant. The ZVI nanoclusters (with a diameter of <1 nm) exhibit excellent dispersibility and accessibility in solution, presenting significantly enhanced catalytic activity in the removal of p-nitrophenol from water. The as-prepared ZVI nanoclusters possess excellent stability and durability with the aid of NaBH4. Their catalytic activity/reusability can be comparable to those of the commonly used noble metal catalysts.

Immobilization and characterization of Fe(0) catalyst on NaOH-treated coal fly ash for catalytic reduction of p-nitrophenol

In this study, coal fly ash (CFA), i.e., an industrial waste product created in large quantities by thermoelectric power plants, was treated with sodium hydroxide to afford a novel Fe (0) catalyst supported on alkaline-treated CFA. The NaOH-treated CFA (NCFA) exhibited a morphological change from slick spheres to pointed, leaf-like spheres, which was accompanied by a noticeable increase in specific surface area from 1.2 to 7.5 m²/g. Sequential addition of an Fe(III) precursor and NaBH₄ solution to a suspension of NCFA resulted in the formation of Fe (0) particles on the surface of NCFA (Fe/NCFA). The catalytic activity of Fe/NCFA toward the reduction of p-nitrophenol (p-NP) was examined; among the Fe/NCFAs synthesized from different NCFAs (1, 3, and 7 M NaOH), the Fe/3 M NCFA sample displayed the highest activity owing to the highest Fe content on its surface, without leaching any toxic heavy metals. In addition, the effects of NaBH₄ concentration, Fe loading, and catalyst dosage on the catalytic reduction of p-NP by Fe/NCFA were comprehensively investigated. Finally, the recyclability and stability of Fe/NCFA were examined, demonstrating the complete reduction of p-NP over four continuous recycling cycles. The present results demonstrate the marked potential of CFA as a component in reactive catalysts for the removal of environmental pollutants from wastewater.

Fabrication and catalytic properties of ordered cyclopalladated diimine monolayer : investigation on catalytic mechanism

"Channel-like" self-assembled monolayers having aliphatic and aromatic diimines (denoted as Si@1DIS, Si@2DIS and Si@3DIS) immobilized on substrates and their palladacycle monolayers (Si@1DIS-Pd, Si@2DIS-Pd and Si@3DIS-Pd) were prepared and characterized. Their catalytic performances were investigated using the Suzuki coupling reaction as a model. Si@3DIS-Pd showed the highest catalytic activity in water without ligands, and better recyclability than that of Si@2DIS-Pd and Si@1DIS-Pd. The reason was the carbon in the aliphatic diimine of Si@2DIS-Pd and Si@1DIS-Pd was easily hydrolyzed because of the active hydrogen of α-C, resulting in poor recyclability. Control of the amount of catalyst could be achieved by modulating the diameter of the channel-like structure, which also affected the catalytic activity. The catalytic process and mechanism were investigated systematically and proposed based on the experimental results obtained by the water contact angle, ultraviolet spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry and atomic force spectroscopy. Changes in the morphology of monolayer surfaces during the catalytic process with or without stirring presented a clear process from order to disorder, and indicated that the reaction was a heterogeneous catalytic process occurring on the surface of the catalyst monolayer.

Pt incorporated mesoporous carbon spheres: controllable structure with enhanced catalytic activity and stability

We report a simple synthesis process to prepare well-dispersed Pt nanoparticles incorporated in mesoporous carbon spheres. By manipulating the relative ratio of Pt precursor and resorcinol-formaldehyde resin (RF), Pt/carbon composites with different morphologies and Pt content were achieved. The as-prepared Pt/C composite materials show higher catalytic activity and reusability for the reduction of 4-nitrophenol (4-NP) than the Pt deposited commercial activated carbon (Pt/AC), which can be ascribed to the high dispersion of Pt nanoparticles in the carbon spheres.

We report a simple synthesis process to prepare well-dispersed Pt nanoparticles incorporated in mesoporous carbon spheres.

Catalytically Active Bacterial Nanocellulose-Based Ultrafiltration Membrane

Large quantities of highly toxic organic dyes in industrial wastewater is a persistent challenge in wastewater treatment processes. Here, for highly efficient wastewater treatment, a novel membrane based on bacterial nanocellulose (BNC) loaded with graphene oxide (GO) and palladium (Pd) nanoparticles is demonstrated. This Pd/GO/BNC membrane is realized through the in situ incorporation of GO flakes into BNC matrix during its growth followed by the in situ formation of palladium nanoparticles. The Pd/GO/BNC membrane exhibits highly efficient methylene orange (MO) degradation during filtration (up to 99.3% over a wide range of MO concentrations, pH, and multiple cycles of reuse). Multiple contaminants (a cocktail of 4-nitrophenol, methylene blue, and rhodamine 6G) can also be effectively treated by Pd/GO/BNC membrane simultaneously during filtration. Furthermore, the Pd/GO/BNC membrane demonstrates stable flux (33.1 L m^-2 h^-1 ) under 58 psi over long duration. The novel and robust membrane demonstrated here is highly scalable and holds a great promise for wastewater treatment.

Three-dimensional composite of Co3O4 nanoparticles and nitrogen-doped reduced graphene oxide for lignin model compound oxidation

3D composite of Co₃O₄ nanoparticles and N-doped reduced graphene oxide can effectively catalyze the oxidation of lignin model compounds.

Simple surface-assisted formation of palladium nanoparticles on polystyrene microspheres and their application in catalysis

Herein we develop a facile and green method for assembling palladium nanoparticles on polystyrene microsphere with excellent catalytic performance.

Label-free electrochemical immunosensor for ultrasensitive detection of neuron-specific enolase based on enzyme-free catalytic amplification

Enzyme-free catalytic amplification is of great significance for sensitive label-free electrochemical immunosensors. In this study, an enzyme-free catalytic amplification based label-free amperometric immunosensor was developed for sensitive detection of neuron-specific enolase (NSE) by use of a AuPd nanoparticle-multiwalled carbon nanotube (AuPd-MWCNT) composite, ferrocenecarboxaldehyde (Fc-CHO), and chitosan hybrid hydrogel. The intrinsic virtues of chitosan not only resulted in bioactivity of the attached antibodies and made the other component of the immunosensor easier to fix on the electrode, but also imparted abundant binding sites to the hydrogel to condense Fc-CHO to achieve the initial signal amplification. Fc-CHO, which served as an electroactive species to generate a redox response, also exhibits excellent electrocatalytic activity toward H₂O₂. AuPd-MWCNT composite, with enhanced peroxidase-like catalytic activity, could catalyze H₂O₂ to accelerate electron transfer. When H₂O₂ was present in the detection solution, synergetic catalysis of Fc-CHO and AuPd-MWCNT composite toward H₂O₂ was achieved, thus realizing enzyme-free signal amplification. On the basis of this enzyme-free signal amplification, the electrochemical immunosensing platform provided a wide linear range from 1 pg mL^-1 to 100 ng mL^-1, a low detection limit of 0.483 pg mL^-1, and high sensitivity of 7.22 μA (log₁₀ C _NSE)^-1. Moreover, the immunosensor showed enormous potential in clinical application. Graphical abstract An enzyme-free catalytic amplification based label-free amperometric immunosensor was developed for sensitive detection of neuron-specific enolase (NSE) by use of a AuPd nanoparticle-multiwalled carbon nanotube (MWCNT) composite, ferrocenecarboxaldehyde (Fc-CHO), and chitosan (CS) hybrid hydrogel. BSA bovine serum albumin, GA glutaraldehyde, SWV square wave voltammetry.

Graphene hydrogel supported palladium nanoparticles as an efficient and reusable heterogeneous catalysts in the transfer hydrogenation of nitroarenes using ammonia borane as a hydrogen source

Addressed herein is a facile one-pot synthesis of graphene hydrogel (GHJ) supported Pd nanoparticles (NPs), namely Pd-GHJ nanocomposites, via a novel method that comprises the combination of hydrothermal treatment and polyol reduction protocols in water. The structure Pd-GHJ nanocomposites were characterized by TEM, HR-TEM, XRD, XPS, Raman spectroscopy and BET surface area analysis. Then, Pd-GHJ nanocomposites were used as a heterogeneous catalysts in the tandem dehydrogenation of ammonia borane and hydrogenation of nitroarenes (Ar–NO2) to anilines (Ar–NH2) in the water/methanol mixture at room temperature. A variety of Ar–NO2 derivatives (total 9 examples) were successfully converted to the corresponding Ar–NH2 by the help of Pd-GHJ nanocomposites catalyzed tandem reactions with the conversion yields reaching up to 99% in only 20 min reaction time. Moreover, Pd-GHJ nanocomposites were demonstrated to be the reusable catalysts in the tandem reactions by preserving their initial catalytic performance after five consecutive catalytic cycles. It is believed that the presented synthesis protocol for the Pd-GHJ nanocomposites and the catalytic tandem hydrogenation reactions will make a significant contribution to the catalysis and synthetic organic chemistry fields.

Hierarchical self-entangled carbon nanotube tube networks

Three-dimensional (3D) assemblies based on carbon nanomaterials still lag behind their individual one-dimensional building blocks in terms of mechanical and electrical properties. Here we demonstrate a simple strategy for the fabrication of an open porous 3D self-organized double-hierarchical carbon nanotube tube structure with properties advantageous to those existing so far. Even though no additional crosslinking exists between the individual nanotubes, a high reinforcement effect in compression and tensile characteristics is achieved by the formation of self-entangled carbon nanotube (CNT) networks in all three dimensions, employing the CNTs in their high tensile properties. Additionally, the tubular structure causes a self-enhancing effect in conductivity when employed in a 3D stretchable conductor, together with a high conductivity at low CNT concentrations. This strategy allows for an easy combination of different kinds of low-dimensional nanomaterials in a tube-shaped 3D structure, enabling the fabrication of multifunctional inorganic-carbon-polymer hybrid 3D materials.

Low-dimensional nanomaterials are crucial conducting components of stretchable electronics, but their mechanical reinforcement remains challenging. Here, the authors infiltrate carbon nanotubes into a porous ceramic network to produce a 3D nanofelted self-entangled assembly with high conductivity and mechanical stability.

In Situ Growth of Clean Pd Nanoparticles on Polystyrene Microspheres Assisted by Functional Reduced Graphene Oxide and Their Excellent Catalytic Properties

Herein an in situ growth of clean palladium nanoparticles (Pd NPs) on functional reduced graphene oxide (RGO)-coated polystyrene (PS) microspheres is achieved by a simple two-step process. On the basis of the hydrophobic interaction and π-electron interaction, the PS/RGO composite particles are first prepared by the reduction of graphene oxide in the presence of PS microspheres. Second, without using any additional reducing agent or stabilizer, the clean Pd NPs grow in situ on the surface of PS/RGO composite particles in water through a spontaneous redox reaction between Pd²⁺ and RGO. Significantly, owing to the stabilizer-free surface of Pd NPs and the synergistic effect of RGO and Pd NPs, the resultant PS/RGO@Pd composite particles feature pronounced catalytic activity toward the reduction of p-nitrophenol and Suzuki coupling reactions. Moreover, the catalyst particles can be easily recovered by centrifugation because of the large size of support microspheres and recycled consecutively.

Metallic cobalt nanoparticles imbedded into ordered mesoporous carbon: A non-precious metal catalyst with excellent hydrogenation performance

Ordered mesoporous carbon (OMC)-metal composites have attracted great attention owing to their combination of high surface area, controlled pore size distribution and physicochemical properties of metals. Herein, we report the cobalt nanoparticles/ordered mesoporous carbon (CoNPs@OMC) composite prepared by a one-step carbonization/reduction process assisted by a hydrothermal pre-reaction. The CoNPs@OMC composite presents a high specific surface area of 544m²g^-1, and the CoNPs are uniformly imbedded or confined in the ordered mesoporous carbon matrix. When used as a non-precious metal-containing catalyst for hydrogenation reduction of p-nitrophenol and nitrobenzene, it demonstrates high efficiency and good cycling stability. Furthermore, the CoNPs@OMC composite can be directly used to catalyze the Fischer-Tropsch synthesis for the high-pressure CO hydrogenation, and presents a good catalytic selectivity for C₅⁺ hydrocarbons. The excellent catalytic performance of the CoNPs@OMC composite can be ascribed to synergistic effect between the high specific surface area, mesoporous structure and well-imbedded CoNPs in the carbon matrix.

Dendritic unzipped carbon nanofibers enable uniform loading of surfactant-free Pd nanoparticles for the electroanalysis of small biomolecules

Illustration of the mechanisms of SCNF and preparation of Pd/GNF composites and Pd/GNF sensors for the simultaneous determination of small biomolecules.

One-pot fabrication of ferric ferrocyanide functionalized graphene hydrogel for cesium removal in aqueous solution

A novel ferric ferrocyanide functionalized graphene hydrogel was fabricated and was used for cesium removal in aqueous solution.

Recyclable palladium–graphene nanocomposite catalysts containing ionic polymers: efficient Suzuki coupling reactions

Palladium nanoparticles on ionic polymer-doped graphene (Pd–IPG) nanocomposite catalysts exhibited efficient catalytic performance in Suzuki coupling reactions.