Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Modifying the Substrate-Dependent Pd/Fe2O3 Catalyst-Support Synergism with ZnO Atomic Layer Deposition

Low-loading Pd supported on Fe2O3 nanoparticles was synthesized. A common nanocatalyst system with previously reported synergistic enhancement of reactivity that is attributed to the electronic interactions between Pd and the Fe2O3 support. Fe2O3-selective precoalescence overcoating with ZnO atomic layer deposition (ALD), using Zn(CH2CH3)2 and H2O as precursors, dampens competitive hydrogenation reactivity at Fe2O3-based sites. The result is enhanced efficiency at the low-loading but high reactivity Pd sites. While this increases catalyst efficiency toward most aqueous redox reactions tested, it suppresses reactivity toward polyaromatic core substrates. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) show minimal electronic impacts for the ZnO overcoat on the Pd particles, implying a predominantly physical site blocking effect as the reason for the modified reactivity. This serves as a proof-of-concept of not only stabilizing supported nanocatalysts but also altering reactivity with ultrathin ALD overcoats. The results point to a facile ALD route for selective enhancement of reactivity for low-loading Pd-based supported nanocatalysts.

Dissolving microneedles for alopecia treatment

Alopecia is a treatable benign disease, however, approximately 15-30% of women and 50% of men suffer from alopecia, which greatly affects patient's self-esteem and quality of life. Currently, commercial products for alopecia treatment include topical minoxidil solution, oral finasteride tablets and oral baricitinib tablets. However, the barrier of stratum corneum, systemic adverse effects and poor cure rate limit the application of commercial products. Therefore, researchers investigated the mechanism of alopecia, and developed new drugs that could target lactate dehydrogenase-related pathways, remove excessive reactive oxygen in hair follicles, and reduce the escape of hair follicle stem cells, thus injecting new strength into the treatment of alopecia. Moreover, starting from improving drug stratum corneum penetration and reducing side effects, researchers have developed hair loss treatment strategies based on dissolved microneedles (MNs), such as drug powders/microparticles, nanoparticles, biomimetic cell membranes, phototherapy and magnetically responsive soluble microneedles, which show exciting alopecia treatment effects. However, there are still some challenges in the practical application of the current alopecia treatment strategy with soluble microneedles, and further studies are needed to accelerate its clinical translation.

Sustainable Bioengineering of Gold Structured Wide-Area Supported Catalysts for Hand-Recyclable Ultra-Efficient Heterogeneous Catalysis

Metal nanoparticles grafted within inert and porous wide-area supports are emerging as recyclable, sustainable catalysts for modern industry applications. Here, we bioengineered gold nanoparticle-based supported catalysts by utilizing the innate metal binding and reductive potential of eggshell as a sustainable strategy. Variable hand-recyclable wide-area three-dimensional catalysts between ∼80 ± 7 and 0.5 ± 0.1 cm² are generated simply by controlling the size of the support. The catalyst possessed high-temperature stability (300 °C) and compatibility toward polar and nonpolar solvents, electrolytes, acids, and bases facilitating ultra-efficient catalysis of accordingly suspended substrates. Validation was done by large-volume (2.8 liters) dye detoxification, gram-scale hydrogenation of nitroarene, and the synthesis of propargylamine. Moreover, persistent recyclability, monitoring of reaction kinetics, and product intermediates are possible due to physical retrievability and interchangeability of the catalyst. Finally, the bionature of the support permits ∼76.9 ± 8% recovery of noble gold simply by immersing in a royal solution. Our naturally created, low-cost, scalable, hand-recyclable, and resilient supported mega-catalyst dwarfs most challenges for large-scale metal-based heterogeneous catalysis.

Surface Charge-Directed Efficient and Selective Catalytic Activities of Porous M@UiO-66 Composites (M = Pt or Ag) for Reduction of Organic Pollutants

Precisely constructed porous composites containing catalytically active nanoparticles can stabilize unstable nanoparticles, thus improving catalytic activity and longevity while preventing agglomeration of active nanoparticles. Herein, we report the confined incorporation of highly active metal nanoparticles within a metal-organic framework support and efficient catalytic performances in the reduction of organic pollutants, such as methylene blue (MB) and 4-nitrophenol (4-NP). UiO-66-based porous composites (M@UiO-66, M = Pt or Ag) containing well-dispersed metal nanoparticles are constructed via the one-step thermal treatment of UiO-66 implanted with metal ions (UiO-66/Mⁿ⁺, Mⁿ⁺ = Pt²⁺ or Ag⁺). The comprehensive features of M@UiO-66s, such as well-dispersed nanocatalysts, well-developed pores, and characteristic surface charges, expedite not only efficient but also selective catalytic activities in the reduction of MB or 4-NP, along with impressive recyclability.

Synthesis of Ag nanoparticles by Celery leaves extract supported on magnetic biochar substrate, as a catalyst for the reduction reactions

Green synthesis of a noble metal such as Ag nanoparticles is an enormously developed research area. In this study, a biochar/Fe₃O₄–Ag magnetic nanocatalyst was produced via a green path by using Celery stalk as a carbon-based substrate and Celery leaf extract as reducing and stabilizing agents to construct Ag nanoparticles. The synthesized nanocatalyst was determined using various techniques, such as UV–Vis spectroscopy, FT-IR spectroscopy, XRD (X-ray diffraction), SEM/EDX spectroscopy (scanning electron microscopy/energy-dispersive X-ray), TEM (transmission electron microscopy), and VSM (vibrating sample magnetometer). To survey the catalytic action of the biochar/Fe₃O₄–Ag nanocatalyst, it was used in the reduction reaction of disparate nitroaromatics, aldehydes, and ketones. This catalyst has demonstrated good characteristics in terms of the amount, reusability, recoverability, activity, and structural integrity of the catalyst during the reaction. In addition, biochar/Fe₃O₄–Ag could be detached magnetically and recycled multiple times without significantly reducing its catalytic performance.

Porous aromatic frameworks with high Pd nanoparticles loading as efficient catalysts for the Suzuki coupling reaction

The development of efficient and recyclable heterogeneous Pd catalysts is an area of continuing attention due to their critical applications in organic synthesis and pharmaceutical production. In this study, two novel heterogeneous catalysts Pd@PAF-182 and Pd@PAF-183 were prepared by the immobilization/NaBH₄ reduction of PdCl₄^2- on hydrophilic cationic porous aromatic frameworks (PAF-182 and PAF-183), which were synthesized via a Yamamoto-type Ullmann coupling reaction from the corresponding aryl quaternary phosphonium salt monomer. Characterization by powder X-ray diffraction (PXRD), solid-state Cross-Polarization Magic-Angle-Spinning Nuclear Magnetic Resonance (CP/MAS NMR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) established the structures of the as-prepared catalysts. Inductively coupled plasma atomic emission spectrometry (ICP-AES) detection showed that the loading of Pd nanoparticles (Pd NPs) were 29.4 wt% for Pd@PAF-182 and 37.5 wt% for Pd@PAF-183, much higher than those of similar porous materials. Evaluation of the catalytic activity of the Pd@PAFs using Suzuki coupling as the model reaction demonstrated that as little as 0.12 mol% of Pd NPs could catalyze the Suzuki coupling with high efficiency, achieving yields up to 99% at 80 °C in 8 h. Recycling experiments also suggested that Pd@PAF-182 and Pd@PAF-183 maintained high catalytic activity with negligible leaching of Pd NPs after five cycles.

Nickel foam supported porous copper oxide catalysts with noble metal-like activity for aqueous phase reactions

Contiguous metal foams offer a multitude of advantages over conventional powders as supports for nanostructured heterogeneous catalysts; most critically a preformed 3-D porous framework ensuring full directional coverage of supported catalyst, and intrinsic ease of handling and recyclability. Nonetheless, metal foams remain comparatively underused in thermal catalysis compared to more conventional supports such as amorphous carbon, metal oxides, zeolites and more recently MOFs. Herein, we demonstrate a facile preparation of highly-reactive, robust, and easy to handle Ni foam-supported Cu-based metal catalysts. The highly sustainable synthesis requires no specialized equipment, no surfactants or additive redox reagents, uses water as solvent, and CuCl2(H2O)2 as precursor. The resulting material seeds as well-separated micro-crystalline Cu2(OH)3Cl evenly covering the Ni foam. Calcination above 400 °C transforms the Cu2(OH)3Cl to highly porous CuO. All materials display promising activity towards the reduction of 4-nitrophenol and methyl orange. Notably, our leading CuO-based material displays 4-nitrophenol reduction activity comparable with very reactive precious-metal based systems. Recyclability studies highlight the intrinsic ease of handling for the Ni foam support, and our results point to a very robust, highly recyclable catalyst system.

Atomically dispersed and oxygen deficient CuO clusters as an extremely efficient heterogeneous catalyst

Preparation of high-density and atomically-dispersed clusters is of great importance yet remains a formidable challenge, which precludes rational design of high-performance, ultrasmall heterogeneous catalysts for alleviating the energy and environmental crises. In this study, we demonstrated an appealing non-equilibrium growth model to give sub-2 nm CuO clusters not from the growth of nuclei but from the top-down growth of metastable bulk crystals. These CuO clusters have high density and intriguingly uniform orientation, and are atomically scattered on an inactive ultrathin AlOOH substrate, which has been driven by the lattice matching between the CuO clusters and the utlrathin AlOOH substrate. The catalytic activity of CuO clusters, with the hydrogenation of 4-nitrophenol as a model reaction, proved to be extremely efficient and showed a rate constant of 130.0 s^-1 g^-1, outperforming the commercial Pd/C catalysts and reported state-of-the-art noble-metal catalysts (1.89-117.2 s^-1 g^-1). These clusters have abundant interfacial oxygen vacancies (OVs) whose concentration can be regulated, and the OVs are found to be essential, according to density functional theory (DFT) calculations, in reducing the energy barrier of catalytic reduction and significantly boosting the catalytic reaction. These findings could add to the library of crystals downsized to the atomic level and demonstrate how engineering point defects on the sub-nanometer materials help design high-efficient catalysts.

Foliar Application with Iron Oxide Nanomaterials Stimulate Nitrogen Fixation, Yield, and Nutritional Quality of Soybean

Sustainable strategies for the management of iron deficiency in agriculture are warranted because of the low use efficiency of commercial iron fertilizer, which confounds global food security and induces negative environmental consequences. The impact of foliar application of differently sized γ-Fe2O3 nanomaterials (NMs, 4-15, 8-30, and 40-215 nm) on the growth and physiology of soybean seedlings was investigated at different concentrations (10-100 mg/L). Importantly, the beneficial effects on soybean were size- and concentration-dependent. Foliar application with the smallest size γ-Fe2O3 NMs (S-Fe2O3 NMs, 4-15 nm, 30 mg/L) yielded the greatest growth promotion, significantly increasing the shoot and nodule biomass by 55.4 and 99.0%, respectively, which is 2.0- and 2.6-fold greater than the commercially available iron fertilizer (EDTA-Fe) with equivalent molar Fe. In addition, S-Fe2O3 NMs significantly enhanced soybean nitrogen fixation by 13.2% beyond that of EDTA-Fe. Mechanistically, transcriptomic and metabolomic analyses revealed that (1) S-Fe2O3 NMs increased carbon assimilation in nodules to supply more energy for nitrogen fixation; (2) S-Fe2O3 NMs activated the antioxidative system in nodules, with subsequent elimination of excess reactive oxygen species; (3) S-Fe2O3 NMs up-regulated the synthesis of cytokinin and down-regulated ethylene and jasmonic acid content in nodules, promoting nodule development and delaying nodule senescence. S-Fe2O3 NMs also improved 13.7% of the soybean yield and promoted the nutritional quality (e.g., free amino acid content) of the seeds as compared with EDTA-Fe with an equivalent Fe dose. Our findings demonstrate the significant potential of γ-Fe2O3 NMs as a high-efficiency and sustainable crop fertilizer strategy.

Construction of polymer brush-decorated amphiphilic Janus graphene oxide nanosheets via a Pickering emulsion template for catalytic applications

2D amphiphilic Janus GO nanocatalysts were prepared using Pickering emulsions and grafted polymer brushes, with excellent performance in homogeneous and interfacial catalysis.

Plasmonic MoO2 embedded MoNi4 nanosheets prepared by NiMoO4 transformation for visible-light-enhanced 4-nitrophenol reduction

Plasmonic hybrid catalysts have attracted great interest for the reduction of nitrobenzene waste to valuable aminobenzene, because they can use renewable solar energy to accelerate the catalytic reaction. However, the economical synthesis of non-precious plasmonic hybrid catalysts remains a big challenge. Herein we report the synthesis of plasmonic MoO₂-embedded MoNi₄ nanosheets (MoNi₄-MoO₂) by thermal annealing of NiMoO₄ at 600 °C under a hydrogen atmosphere. The MoNi₄-MoO₂ hybrid catalysts retain strong plasmon absorption from MoO₂ and demonstrate good catalytic activity from MoNi₄ for 4-nitrophenol reduction in the dark. Under visible light irradiation, the excitation of MoO₂ plasmon promotes the catalytic reaction further due to hot electron-induced increase of catalytic activity of MoNi₄. In addition, the hybrid catalysts are relatively stable even under illumination reaction conditions.

Reversible filtration redox of methylene blue in dimethylsulfoxide by manganese oxide loaded carbonaceous nanofibrous membrane through Fenton-like oxidation

The reversible redox of methylene blue in organic solvents was highly attractive, yet was rarely reported. In this study, we realized the continuous filtration redox of methylene blue (MB) in dimethylsulfoxide (DMSO) through Fenton-like oxidization by using MnO₂ loaded carbonaceous nanofibrous membrane (cPAN-MnO₂). The carbonaceous nanofibrous membrane (cPAN) was fabricated through electrospun of polyacrylonitrile and subsequent carbonization. The obtained cPAN nanofibrous membrane showed excellent stability in polar DMSO. MnO₂ can be readily coated on cPAN nanofibers through an in situ redox reaction between cPAN and potassium permanganate. The fabricated cPAN-MnO₂ membrane exhibited instantaneous reduction property towards MB in DMSO during a gravity-driven continuous filtration process. Interestingly, MB reduction was initiated by a typical Fenton-like oxidization, where hydroxyl radicals were firstly generated from hydrogen peroxide catalyzed by MnO₂ in DMSO. Then hydroxyl radicals attacked DMSO to further produce methyl radicals, which resulted in the reduction of MB. In addition, MB reduction process in DMSO was reversible. Our study provides a novel strategy for continuous redox of MB in polar organic solvent and might give new ideas for MB applications.

A Novel Carbon Support: Few-Layered Graphdiyne-Decorated Carbon Nanotubes Capture Metal Clusters as Effective Metal-Supported Catalysts

Carbon-supported metal nanocatalysts have received substantial attention for heterogeneous catalysis in industry. Hunting for suitable and impactful carbon supports that have strong interactions with metal nanocatalyst is a matter of great urgency. Herein, a well-designed graphdiyne layer decorated on the carbon nanotubes sidewalls (CNT@GDY) serves as a novel carbon support. This unique hybrid structure effectively traps platinum and palladium atomic clusters (Pt/Pd-ACs) with dimensions of 0.65 nm and 1.05 nm uniformly and firmly, forming novel carbon-supported metal nanocatalysts (Pt(Pd)-ACs/CNT @ GDY) for efficient hydrogen generation and aromatic nitroreduction, respectively. The Pt-ACs/CNT@GDY can deliver an HER current density of 10 mA cm^-2 with a small overpotential of 23 mV in 0.5 M H₂ SO₄ , showing a greatly enhanced mass activity, intrinsic activity than the commercial Pt/C catalyst. The Pd-ACs/CNT@GDY also exhibits excellent catalytic activity and a high turnover frequency of 38.0 min^-1 for aromatic nitroreduction. The carbon support turns out to possess excellent conductivity, abundant and uniform reactive sites, low redox potential, more negative surface and large specific surface area as well as a strong interaction with ACs, as anticipated in ideal supports, which can be applied in other metal-supported catalysts.

Promotion effects of halloysite nanotubes on catalytic activity of Co3O4 nanoparticles toward reduction of 4-nitrophenol and organic dyes

Nanosized clay minerals have been widely used as efficient supports to immobilize catalyst nanoparticles. However, clay support-induced interactions and their influences on the catalyst structure and performance currently have not been fully understood. Here, Co₃O₄ nanoparticles supported on halloysite nanotubes (HNTs) were synthesized by a facile deposition-precipitation approach followed by thermal treatment. A series of characterization methods were employed for the Co₃O₄/HNTs hybrid nanostructure to identify its crystal phase, chemical composition, morphology, specific surface area, surface chemical states, and redox property. Characterization results showed that HNTs not only impacted the particle size of Co₃O₄ nanoparticles, but also modified surface chemical surface states of the later, which ultimately promoted the effective catalytic reduction of 4-nitrophenol (4-NP) and azo dyes with sodium borohydride. The interaction between HNTs and Co₃O₄ nanoparticles was found to shorten the induction period of the 4-NP reduction. Meanwhile, the Co₃O₄/HNTs catalyst for the 4-NP reduction achieved an apparent rate constant of 0.265 min^-1 and an activity parameter of 1.63 × 10⁴ min^-1 g^-1 as well as a turnover frequency of 4.37 min^-1. In addition, Co₃O₄/HNTs showed an improvement in reduction efficiency of the azo dyes when compared to bare Co₃O₄ nanoparticles.

Green synthesis of platinum nanoclusters using lentinan for sensitively colorimetric detection of glucose

The sensitive colorimetric detection of glucose using nanomaterials has been attracting considerable attention. To improve the detection sensitivity, highly stable lentinan stabilized platinum nanoclusters (Pt-LNT NCs) were prepared, in which lentinan was employed as a mild reductant and stabilizer. The size of platinum nanoclusters (Pt NCs) was only 1.20 ± 0.29 nm. Pt-LNT NCs catalyzed the oxidation of substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂) to produce a blue oxidation product with absorption peak at 652 nm, indicating their peroxidase-like properties. Their enzymatic kinetics followed typical Michaelis-Menten theory. In addition, fluorescence experiments confirmed their ability to efficiently catalyze the decomposition of H₂O₂ to generate •OH, which resulted in the peroxidase-like mechanism of Pt-LNT NCs. Moreover, a colorimetric method for highly selective and sensitive detection of glucose was established by using Pt-LNT NCs and glucose oxidase. The linear range of glucose detection was 5-1000 μM and the detection limit was 1.79 μM. Finally, this method was further used for detection of glucose in human serum and human urine. The established colorimetric method may promote the development of biological detection and environmental chemistry in the future.

Highly effective catalytic reduction of nitrobenzene compounds with gold nanoparticle-immobilized hydroxyapatite nanowire-sintered porous ceramic beads

A catalytic ceramic bead with micron-sized and interconnected porous channels, adjustable porosity, high catalytic activity, and long-term stability is prepared.

Transdermal Composite Microneedle Composed of Mesoporous Iron Oxide Nanoraspberry and PVA for Androgenetic Alopecia Treatment

The transdermal delivery of therapeutic agents amplifying a local concentration of active molecules have received considerable attention in wide biomedical applications, especially in vaccine development and medical beauty. Unlike oral or subcutaneous injections, this approach can not only avoid the loss of efficacy of oral drugs due to the liver's first-pass effect but also reduce the risk of infection by subcutaneous injection. In this study, a magneto-responsive transdermal composite microneedle (MNs) with a mesoporous iron oxide nanoraspberry (MIO), that can improve the drug delivery efficiency, was fabricated by using a 3D printing-molding method. With loading of Minoxidil (Mx, a medication commonly used to slow the progression of hair loss and speed the process of hair regrowth), MNs can break the barrier of the stratum corneum through the puncture ability, and control the delivery dose for treating androgenetic alopecia (AGA). By 3D printing process, the sizes and morphologies of MNs is able to be, easily, architected. The MIOs were embedded into the tip of MNs which can deliver Mx as well as generate mild heating for hair growth, which is potentially attributed by the expansion of hair follicle and drug penetration. Compared to the mice without any treatments, the hair density of mice exhibited an 800% improvement after being treated by MNs with MF at 10-days post-treatment.

Graphene oxide nanocomposite magnetic microbeads for the remediation of positively charged aromatic compounds

Integrating graphene as an inorganic nanostructure within a hydrogel matrix enables the creation of a unique hybrid composite combining the peculiar chemical and physical properties of graphene with the high porosity and stability of hydrogels as for example agarose gel. As a consequence, the resulting material forms a double-network system providing advantages deriving from both the components. In this study, we present the synthesis of novel magnetic porous agarose-based graphene oxide microbeads for the adsorption and separation of positively charged aromatic molecules. The hydrogel-based graphene oxide beads revealed an ultrafast adsorption kinetics for positively charged aromatic dyes. We tested this material for the purification of fluorescent-tagged biomolecules. In addition, reduced graphene oxide microbeads were decorated with palladium nanoparticles, showing a high catalytic activity towards the reduction of dyes by sodium borohydride. Our results show that magnetic agarose based graphene microbeads with enhanced physical-chemical properties can be used for several biochemical applications.

Shape Control of Monodispersed Sub-5 nm Pd Tetrahedrons and Laciniate Pd Nanourchins by Maneuvering the Dispersed State of Additives for Boosting ORR Performance

It is a great challenge to simultaneously control the size, morphology, and facets of monodispersed Pd nanocrystals under a sub-5 nm regime. Meanwhile, quantitative understanding of the thermodynamic and kinetic parameters to maneuver the shape evolution of nanocrystals in a one-pot system still deserves investigation. Herein, a systematic study of the density functional theory (DFT)-calculated adsorption energy, thermodynamic factors, and reduction kinetics on Pd growth patterns is reported by combining theory and experiments, with a focus on the dispersed state of additives. As pure models, monodispersed Pd tetrahedrons enclosed by (111) facets with a narrow size distribution of 4.9 ± 1 nm and a high purity approaching 98% can be obtained when using 1,1'-binaphthalene (C₂₀ H₁₄ ) +2NH₃ as additives. Specifically, laciniate Pd nanourchins (Pd LUs) can evolve via anisotropic growth when replacing additive with dose-consistent 1,1'-binaphthyl-2,2'-diamine (C₂₀ H₁₆ N₂ , two NH₂ binding in C₂₀ H₁₄ ). Catalytic investigations show that the sub-5 nm Pd tetrahedrons exhibit higher activity in both the oxygen reduction (E_onset = 1.025 V, E_1/2 = 0.864 V) and formic acid oxidation reaction with respect to the Pd LUs and Pd black, which represents a great step for the development of well-defined Pd nanocrystals with size in the sub-5 nm regime as non-Pt electrocatalysts.

Construction of a thermo-responsive copolymer-stabilized Fe3O4@CD@PdNP hybrid and its application in catalytic reduction

A thermo-responsive copolymer stabilized Fe₃O₄@CDs@PdNP hybrid was fabricated as a nanocatalyst for catalytic reduction reaction with excellent recyclability and controllable thermo-responsive catalytic property.

Facile and green synthesis of palladium nanoparticles loaded into cyclodextrin nanofibers and their catalytic application in nitroarene hydrogenation

Facile and green synthesis of Pd nanoparticles using cyclodextrin and their electrospinning into polymer-free nanofibers were reported.

Controllable synthesis of mussel-inspired catechol-formaldehyde resin microspheres and their silver-based nanohybrids for catalytic and antibacterial applications

Size-controlled CFR microspheres and their silver-based nanohybrids were constructed and the nanohybrids display high catalytic reduction activity and antibacterial properties.

Ruthenium nanoparticles supported on nitrogen-doped porous carbon as a highly efficient catalyst for hydrogen evolution from ammonia borane

The two-dimensional magnetic NC-Fe materials were prepared and modified with Ru nanoparticles to form Ru/NC-Fe nanocatalyst with excellent catalytic activity for hydrogen evolution from ammonia borane.

Mussel-Inspired Catechol-Formaldehyde Resin-Coated Fe3O4 Core-Shell Magnetic Nanospheres: An Effective Catalyst Support for Highly Active Palladium Nanoparticles

Magnetic Fe₃O₄@catechol-formaldehyde resin (CFR) core-shell nanospheres were fabricated via a controllable hydrothermal method. The shell thickness of Fe₃O₄@CFR nanospheres can be effectively regulated in the range of 10-170 nm via adjusting reaction parameters. In particular, catechol groups on the surface of nanospheres also play a significant role in mussel-inspired chemistry to further combine with graphene oxide (GO) to wrap the Fe₃O₄@CFR spheres. The obtained Fe₃O₄@CFR and Fe₃O₄@CFR@GO nanospheres can be used as the effective catalyst supports of small Pd nanoparticles (PdNPs, <10 nm) formed via an in situ synthesis route. The as-fabricated nanohybrid catalysts of Fe₃O₄@CFR@PdNPs and Fe₃O₄@CFR@GO@PdNPs with excellent dispersibility and stability are reusable after magnetic separation from catalytic systems. In particular, a super active performance was demonstrated for the catalytic reduction of methylene blue dye with highest turnover frequency (5260 min^-1) yet reported in the literature using a very low dosage of the Fe₃O₄@CFR@GO@PdNP catalyst. In addition, the Fe₃O₄@CFR@GO@PdNP catalyst also exhibits a highly catalytic efficiency for the Suzuki coupling reaction using pure water as a green solvent at room temperature.

A dual-sensitive mesoporous silica nanoparticle based drug carrier for cancer synergetic therapy

A multifunctional envelope-type mesoporous silica nanoparticle (MSN) was delicately designed for subcellular co-delivery of drug and therapeutic peptide to tumor cells. Firstly, a kind of cell apoptosis peptide (KLAKLAK)₂ (KLA) was anchored on surface of MSN via disulfide bond to obtain MSN-SS-KLA. Subsequently, anticancer drug doxorubicin hydrochloride (DOX) was loaded into the pores of MSN-SS-KLA. Then, the drug loaded MSN-SS-KLA (DOX@MSN-SS-KLA) was further coated with bovine serum albumin (BSA) to obtain a biological media stable MSN based drug delivery system (DDS), DOX@MSN-SS-KLA/BSA, for cancer synergetic therapy. The results show that stability of the DOX@MSN-SS-KLA/BSA is much better than that of DOX@MSN-SS-KLA and it could keep well dispersed in serum for more than 24 h. After accumulating at tumor site by EPR effect, the DOX@MSN-SS-KLA/BSA could be effectively phagocytosed by HeLa cells and release apoptotic peptide KLA as well as DOX simultaneously responding to reductive stimulus inside the cells. In vitro cell experiment results show that the DOX@MSN-SS-KLA/BSA complex exhibits much better inhibition on HeLa cells compared with pure DOX, indicating that co-delivery of KLA and DOX is expected to achieve synergetic therapy of cancer.

Plasmonic Au-Loaded Hierarchical Hollow Porous TiO2 Spheres: Synergistic Catalysts for Nitroaromatic Reduction

Plasmonic Au nanoparticle (NP)-loaded hierarchical hollow porous TiO₂ spheres are designed and synthesized with the purpose of enhancing the overall catalytic activity by introducing the Au plasmonic effect into the system, where Au NPs themselves are catalytically active. The constructed nanohybrid exhibits both high activity in 4-nitrophenol reduction, compared to all of the previously reported Au-based catalysts, and high selectivity. The synergy of the inherent catalytic property of Au NPs and the plasmonic effect (mainly via hot electron transfer) under irradiation is confirmed by a series of control experiments. The specifically designed, porous hollow structure also greatly contributes to the good catalytic activity because it provides a large surface area, facilitates reactant adsorption, and hinders charge recombination. In addition, theoretical calculations reveal that such a structure also leads to an increase in light absorption of about 21% in the range of 400-800 nm with respect to a uniform water-TiO₂ background featuring the same filling factor. This work provides insight into the rational design of plasmon-enhanced catalysts that will show their versatility in various electro-/photocatalysis.

Mussel-inspired construction of thermo-responsive double-hydrophilic diblock copolymers-decorated reduced graphene oxide as effective catalyst supports for highly dispersed superfine Pd nanoparticles

Well-dispersed ultrafine palladium nanoparticles supported by reduced graphene oxide functionalized with catechol-terminated thermo-responsive block copolymer (PdNPs@BPrGO) were successfully constructed for highly efficient heterogeneous catalytic reduction. We first synthesized a novel temperature-responsive episulfide-containing double-hydrophilic diblock copolymer, poly(poly(ethylene glycol) methyl ether methacrylate-co-2,3-epithiopropyl methacrylate)-block-poly(N-isopropylacrylamide) (P(PEGMA-co-ETMA)-b-PNIPAM), through a reversible addition-fragmentation chain transfer (RAFT) polymerization utilizing a chain-transfer agent with a catechol unit as the end group. The obtained block copolymers can be facilely anchored to the surface of GO via mussel-inspired chemistry. The PdNPs were loaded on GO decorated with block copolymer brushes (BPrGO) as a support via the in situ reduction of palladium precursors with the episulfide ligands of the block copolymer as a stabilizer. The resulting PdNPs@BPrGO nanohybrid catalyst had good water dispersibility and stability. Furthermore, a low dosage of PdNPs@BPrGO catalyst exhibited excellent catalytic performance in the reduction of methylene blue and nitrophenols. The performance was attributed to the ability of PdNPs@BPrGO to facilitate the diffusion of reactants compared to PdNPs@GO without polymer modification. PdNPs@BPrGO also possessed an interesting temperature-responsive catalytic property due to the reversible "coil-to-globule" phase transition behaviour of PNIPAM blocks onto the surface of catalyst. The PdNPs@BPrGO catalyst was successfully recovered and reused five times without any detectible loss in catalytic activity, demonstrating its great potential in a wide range of industrial catalytic applications.

Facile Fabrication of Highly Active Magnetic Aminoclay Supported Palladium Nanoparticles for the Room Temperature Catalytic Reduction of Nitrophenol and Nitroanilines

Magnetically recyclable nanocatalysts with excellent performance are urgent need in heterogeneous catalysis, due to their magnetic nature, which allows for convenient and efficient separation with the help of an external magnetic field. In this research, we developed a simple and rapid method to fabricate a magnetic aminoclay (AC) based an AC@Fe₃O₄@Pd nanocatalyst by depositing palladium nanoparticles (Pd NPs) on the surface of the magnetic aminoclay nanocomposite. The microstructure and the magnetic properties of as-prepared AC@Fe₃O₄@Pd were tested using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM) analyses. The resultant AC@Fe₃O₄@Pd nanocatalyst with the magnetic Fe-based inner shell, catalytically activate the outer noble metal shell, which when combined with ultrafine Pd NPs, synergistically enhanced the catalytic activity and recyclability in organocatalysis. As the aminoclay displayed good water dispersibility, the nanocatalyst indicated satisfactory catalytic performance in the reaction of reducing nitrophenol and nitroanilines to the corresponding aminobenzene derivatives. Meanwhile, the AC@Fe₃O₄@Pd nanocatalyst exhibited excellent reusability, while still maintaining good activity after several catalytic cycles.

Nanoparticle packing within block copolymer micelles prepared by the interfacial instability method

The interfacial instability method has emerged as a viable approach for encapsulating high concentrations of nanoparticles (NPs) within morphologically diverse micelles. In this method, transient interfacial instabilities at the surface of an emulsion droplet guide self-assembly of block co-polymers and NP encapsulants. Although used by many groups, there are no systematic investigations exploring the relationship between NP properties and micelle morphology. Here, the effect of quantum dot (QD) and superparamagnetic iron oxide NP (SPION) concentration on the shape, size, and surface deformation of initially spherical poly(styrene-b-ethylene oxide) (PS-b-PEO) micelles was examined. Multi-NP encapsulation and uniform dispersion within micelles was obtained even at low NP concentrations. Increasing NP concentration initially resulted in larger numbers of elongated micelles and cylinders with tightly-controlled diameters smaller than those of spherical micelles. Beyond a critical NP concentration, micelle formation was suppressed; the dominant morphology became densely-loaded NP structures that were coated with polymer and exhibited increased polydispersity. Transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) revealed that NPs in densely-loaded structures can be well-ordered, with packing volume fractions of up to 24%. These effects were enhanced in magnetic composites, possibly by dipole interactions. Mechanisms governing phase transitions triggered by NP loading in the interfacial instability process were proposed. The current study helps establish and elucidate the active role played by NPs in directing block copolymer assembly in the interfacial instability process, and provides important guiding principles for the use of this approach in generating NP-loaded block copolymer composites.

Continuous generation of hydroxyl radicals for highly efficient elimination of chlorophenols and phenols catalyzed by heterogeneous Fenton-like catalysts yolk/shell Pd@Fe3O4@metal organic frameworks

Core/shell Fe₃O₄-decorated Pd nanoparticles (NPs) hybrids (Pd@Fe₃O₄) are prepared through a "green", and one-pot chemical process. The Pd@Fe₃O₄ hybrids consisted of faceted quasi-spherical Pd nanoparticles (NPs) cores (∼20 nm) surrounded by close-packed Fe₃O₄ NPs (∼7 nm). To improve the stability and avoid aggregation of Pd@Fe₃O₄ hybrids in water, hollow Fe-metal organic frameworks (Fe-MOFs) were applied to enwrap Pd@Fe₃O₄ to obtain yolk/shell structured composites. Sub-10 nm Fe₃O₄ and Pd NPs close to each other were distributed evenly in the MOFs shell of Pd@Fe₃O₄@MOFs. The yolk/shell Pd@Fe₃O₄@MOFs can catalyze the oxidative degradation of chlorophenols and phenols by hydroxyl radicals (OH) decomposed from H₂O₂. With low molar ratio of H₂O₂/pollutants, the pollutants are degraded and mineralized efficiently and rapidly. The outstanding catalytic efficiency of Pd@Fe₃O₄@MOFs is contributed by the fast and continuous generation of OH radicals in Pd@Fe₃O₄@MOFs suspension which is detected with the electron spin resonance spin-trap technique and a continuous-flow chemiluminescence system. Lack of consumption of hydroperoxyl radicals/superoxide radicals (HO₂/O₂^-) in the Pd@Fe₃O₄@MOFs-H₂O₂ system might suggest that the production of OH radicals results from the electron transferring from Pd to Fe₃O₄ component both in the inner Pd@Fe₃O₄ and MOF shell, which facilitates fast Fe(III)/Fe(II) redox cycle.

Synthesis of Supported Bimetal Catalysts using Galvanic Deposition Method

Supported bimetallic catalysts have been studied because of their enhanced catalytic properties due to metal-metal interactions compared with monometallic catalysts. We focused on galvanic deposition (GD) as a bimetallization method, which achieves well-defined metal-metal interfaces by exchanging heterogeneous metals with different ionisation tendencies. We have developed Ni@Ag/SiO₂ catalysts for CO oxidation, Co@Ru/Al₂ O₃ catalysts for automotive three-way reactions and Pd-Co/Al₂ O₃ catalysts for methane combustion by using the GD method. In all cases, the catalysts prepared by the GD method showed higher catalytic activity than the corresponding monometallic and bimetallic catalysts prepared by the conventional co-impregnation method. The GD method provides contact between noble and base metals to improve the electronic state, surface structure and reducibility of noble metals.

Low-cost palladium decorated on m-aminophenol-formaldehyde-derived porous carbon spheres for the enhanced catalytic reduction of organic dyes

A novel method for the synthesis of recyclable Pd@PCS catalyst was applied for the reduction of CV, EY, and SY.