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

On-signal amplification of silver nanosol RRS/SERS aptamer detection of ultratrace urea by polystyrene nanosphere catalyst

The catalytic amplification signal of polystyrene nanosphere (PN) is used to conveniently fabricate the resonance Rayleigh scattering (RRS)/surface-enhanced Raman scattering (SERS) dual-mode method to sensitively and selectively detect urea in food. PN has strong catalysis of the slow nanoreaction of citrate-Ag(I) to produce yellow silver nanoparticles (AgNP), which exhibit strong RRS effect and SERS effect with molecular probes. When aptamer (Apt) is present, the Apt is adsorbed on the PN surface, the catalysis is weakened, the AgNP is reduced, and the SERS/RRS signal is weakened. After adding urea to exhibit specific Aptamer reaction, the Apt is desorbed from the PN surface and the catalysis is restored. As urea increase, the desorbed PNs increase to produce more AgNPs indicator to increase SERS/RRS signal. The increase value △I of SERS/RRS is linearly to urea concentration. Therefore, a sensitive and selective SERS/RRS dual-mode method for urea is established based on aptamers-regulated the catalysis of PNs. This method is applied to the detection of urea in milk with satisfactory results. The relative standard deviation is 3.9-6.8% and the recovery rate is 94.5-102%.

Studies on Hydrophobic Silica/Silicone Rubber Composite Microspheres with Dual-Size Microstructures

In this study, a series of microsphere composites were prepared by the hydrosilylation of nanospherical SiO₂ and silicon rubber microspheres. The influence of different host-guest size ratios on the wettability of the SiO₂/silicone rubber composite microspheres was explored. The structures and performance of the composite microspheres were investigated using scanning electron microscopy and contact angle testing. The results showed that the prepared SiO₂/silicone rubber composite microspheres had a raspberry-like structure and exhibited a rose petal effect. When the SiO₂ content was 30%, the water contact angle of the SiO₂/silicone rubber composite microspheres reached a maximum, and 30% was used as the optimal ratio for compounding SiO₂ having different particle diameters with silicone rubber microspheres. Wettability calculations and analyses were performed for the surface with the composite microspheres. The results indicated that the structure with dual-size roughness could significantly improve surface hydrophobicity. As the ratio of the host-guest size increased, the contact angle of the water phase also increased. However, the surface structures of the composite microspheres were not uniform because of the surface chemical composition and the uncontrollable distribution of the small spheres on the surface of the large spheres during compounding. As a result, water droplets appeared in the Cassie-impregnated state on the composite microsphere particle coating, resulting in the phenomenon of high hydrophobicity and high adhesion.

Magnetic polymer bowl for enhanced catalytic activity and recyclability

This work introduces the fabrication of a magnetic polymer bowl for enhanced catalytic activity and recyclability, which involves the synthesis of silica-coated Fe3O4 magnetic clusters, seeded dispersion polymerization using the magnetic clusters, and transformation into a bowl-like structure via a phase separation route. The additional treatment with tannic acid (TA) on the bowls allows the in situ formation of silver nanoparticles (AgNPs) on their surfaces. The openness and larger surface area of the bowls, as compared with those of other structured particles, such as spheres and flowers, enable a considerably higher immobilization of AgNPs, thus leading to an excellent catalytic reduction for 4-nitrophenol (4-NP), methylene blue (MB), and rhodamine B. Furthermore, the strong magnetic response originating from the magnetic clusters inside the bowls endows a good magnetic recovery and an excellent reusability for the repeated reduction of the organic dyes without loss of catalytic activity.

Sonication-Assisted Synthesis of Bimetallic Hg/Pd Alloy Nanoparticles for Catalytic Reduction of Nitrophenol and its Derivatives

In this article, we report a facile approach for the synthesis of an inexpensive catalyst of bimetallic Hg/Pd alloys comprising nanoparticles with various structures using a unique ultrasonic reaction that is conducted without the use of any reducing agent. The nanoparticles of Hg/Pd alloys (HgPd and Hg₂Pd₅) were achieved for the first time by sonicating an aqueous solution of Palladium (II) nitrate with metallic liquid mercury, as evidenced by XRD. EDS further confirmed the presence of Pd and Hg elements in the alloy. The surface morphology and structure of the nanoparticles have been systematically investigated by HRSEM, HRTEM and SAED pattern. In order to explore the catalytic activity of the as-synthesized nanoalloys, the catalytic reduction of 4-nitrophenol and a few other nitrophenol derivatives were investigated. Excellent catalytic activity was obtained for Hg/Pd (1:1) alloy, and the rate constant for the reduction of 4-NP with Hg/Pd at room temperature was found to be 58.4 × 10^-3 s^-1, which is possibly the highest ever reported. The catalyst exhibited superior stability and reusability when compared with those reported in the literature for other catalysts based on noble metals.

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.

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.