A multimetallic nanozyme enhanced colorimetric biosensor for Salmonella detection on finger-actuated microfluidic chip.

Salmonella screening is essential to avoid food poisoning. A simple, fast and sensitive colorimetric biosensor was elaborately developed for Salmonella detection on a microfluidic chip through limiting air chambers for precise air control, switching rotary valves for accurate fluid selection, a convergence-and-divergence passive micromixer and an extrusion-and-suction active micromixer for efficient fluid mixing, and immune gold@platinum palladium nanocatalysts for effective signal amplification. The mixture of bacteria, immune magnetic nanobeads and nanocatalysts was first rapidly mixed to form nanobead-bacteria-nanocatalyst conjugates and magnetically separated for enrichment. After washing with water, the conjugates were used to catalyze colorless substrate and blue product was finally analyzed using ImageJ for quantifying bacterial concentration. The finger-actuated microfluidic chip enabled designated control of designated fluids in designated places towards designated directions by simple press-release operations on designated air chambers without any external power. Under optimal conditions, this sensor could detect Salmonella at 45 CFU/mL in 25 min.

3D-Continuous Nanoporous Covalent Framework Membrane Nanoreactors with Quantitatively Loaded Ultrafine Pd Nanocatalysts.

The confinement effect of catalytic nanoreactors containing metal catalysts within nanometer-sized volumes has attracted significant attention for their potential to enhance reaction rate and selectivity. Nevertheless, unregulated catalyst loading, aggregation, leaching, and limited reusability remain obstacles to achieving an efficient nanoreactor. A robust and durable catalytic membrane nanoreactor prepared by incorporating palladium nanocatalysts within a 3D-continuous nanoporous covalent framework membrane is presented. The reduction of palladium precursor occurs on the pore surface within 3D nanochannels, producing ultrafine palladium nanoparticles (Pd NPs) with their number density adjustable by varying metal precursor concentrations. The precise catalyst loading enables controlling the catalytic activity of the reactor while preventing excess metal usage. The facile preparation of Pd NP-loaded free-standing membrane materials allows hydrodechlorination in both batch and continuous flow modes. In batch mode, the catalytic activity is proportional to the loaded Pd amount and membrane area, while the membrane retains its activity upon repeated use. In continuous mode, the conversion remains above 95% for over 100 h, with the reactant solution passing through a single 50 µm-thick Pd-loaded membrane. The efficient nanoporous film-type catalytic nanoreactor may find applications in catalytic reactions for small chemical devices as well as in conventional chemistry and processes.

Self-Metallized Whole Cell Vaccines Prepared by Microfluidics for Bioorthogonally Catalyzed Antitumor Immunotherapy.

Tumor whole cell, carrying a complete set of tumor-associated antigens and tumor-specific antigens, has shown great potential in the construction of tumor vaccines but is hindered by the complex engineering means and limited efficacy to cause immunity. Herein, we provided a strategy for the self-mineralization of autologous tumor cells with palladium ions in microfluidic droplets, which endowed the engineered cells with both immune and catalytic functions, to establish a bioorthogonally catalytic tumor whole-cell vaccine. This vaccine showed strong inhibition both in the occurrence and recurrence of tumor by invoking the immediate antitumor immunity and building a long-term immunity.

Nano-sized and microporous palladium catalyst supported on modified chitosan/cigarette butt composite for treatment of environmental contaminants.

This study reports a versatile process for the fabrication of a microporous heterogeneous palladium nanocatalyst on a novel spherical, biodegradable, and chemically/physically resistant catalyst support consisting of chitosan (CS) and cigarette waste-derived activated carbon (CAC). The physicochemical properties of the microporous Pd-CS-CAC nanocatalyst developed were successfully determined by FTIR, XRD, FE-SEM, TEM, BET, and EDS techniques. TEM studies showed that the average particle size of the synthesized Pd NPs was about 30 nm. The catalytic prowess of microporous Pd-CS-CAC was evaluated in the reduction/decolorization of various nitroarenes (2-nitroaniline (2-NA), 4-nitroaniline (4-NA), 4-nitrophenol (4-NP), and 4-nitro-o-phenylenediamine (4-NPD)) and organic dyes (methyl red (MR), methyl orange (MO), methylene blue (MB), congo red (CR), and rhodamine B (RhB)) in an aqueous medium in the presence of NaBH4 as the reducing agent at room temperature. The catalytic activities were studied by UV-Vis absorption spectroscopy of the supernatant at regular time intervals. The short reaction times, mild reaction conditions, high efficiency (100% conversion), easy separation, and excellent chemical stability of the catalyst due to its heterogeneity and reusability are the advantages of this method. The results of the tests showed that reduction/decolorization reactions were successfully carried out within 10-140 s due to the good catalytic ability of Pd-CS-CAC. Moreover, Pd-CS-CAC was reused for 5 consecutive times with no loss of the initial shape, size, and morphology, confirming that it was a sustainable and robust nanocatalyst.

Advances in Matrix-Supported Palladium Nanocatalysts for Water Treatment.

Advanced catalysts are crucial for a wide range of chemical, pharmaceutical, energy, and environmental applications. They can reduce energy barriers and increase reaction rates for desirable transformations, making many critical large-scale processes feasible, eco-friendly, energy-efficient, and affordable. Advances in nanotechnology have ushered in a new era for heterogeneous catalysis. Nanoscale catalytic materials are known to surpass their conventional macro-sized counterparts in performance and precision, owing it to their ultra-high surface activities and unique size-dependent quantum properties. In water treatment, nanocatalysts can offer significant promise for novel and ecofriendly pollutant degradation technologies that can be tailored for customer-specific needs. In particular, nano-palladium catalysts have shown promise in degrading larger molecules, making them attractive for mitigating emerging contaminants. However, the applicability of nanomaterials, including nanocatalysts, in practical deployable and ecofriendly devices, is severely limited due to their easy proliferation into the service environment, which raises concerns of toxicity, material retrieval, reusability, and related cost and safety issues. To overcome this limitation, matrix-supported hybrid nanostructures, where nanocatalysts are integrated with other solids for stability and durability, can be employed. The interaction between the support and nanocatalysts becomes important in these materials and needs to be well investigated to better understand their physical, chemical, and catalytic behavior. This review paper presents an overview of recent studies on matrix-supported Pd-nanocatalysts and highlights some of the novel emerging concepts. The focus is on suitable approaches to integrate nanocatalysts in water treatment applications to mitigate emerging contaminants including halogenated molecules. The state-of-the-art supports for palladium nanocatalysts that can be deployed in water treatment systems are reviewed. In addition, research opportunities are emphasized to design robust, reusable, and ecofriendly nanocatalyst architecture.

Flexible reusable hierarchical hybrid catalyst for rapid and complete degradation of triclosan in water.

A flexible, durable, and reusable nanocatalyst system was fabricated by anchoring palladium nanoparticles on carbon nanotube (CNT) carpets covalently attached to carbon cloth. These hierarchical hybrid materials were tested for catalytic degradation of triclosan (TCS), an emerging contaminant. Materials were characterized using scanning & transmission electron microscopy techniques (SEM and TEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). The reaction kinetics was studied using HPLC and reaction pathways proposed based on LC-MS/GC-MS analyses. In the presence of hydrogen, complete step-wise chlorine removal was seen until complete dechlorination was accomplished. The pseudo-first-order rate constant was measured to be orders of magnitude higher than earlier reported values. Moreover, the same material was usable for multiple cycles in flowing water. This study demonstrates that robustness and reusability of larger structural materials can be combined with the ultra-high surface activity of nanocatalysts to provide practical and eco-friendly solutions for water sustainability.

Size-Dependent Catalytic Activity of Palladium Nanoparticles Fabricated in Porous Organic Polymers for Alkene Hydrogenation at Room Temperature.

Ultrafine palladium nanoparticles (Pd NPs) with 8 and 3 nm sizes were effectively fabricated in triazine functionalized porous organic polymer (POP) TRIA that was developed by nonaqueous polymerization of 2,4,6-triallyoxy-1,3,5-triazine. The Pd NPs encapsulated POP (Pd-POP) was fully characterized using several techniques. Further studies revealed an excellent capability of Pd-POP for catalytic transfer hydrogenation of alkenes at room temperature with superior catalytic performance and high selectivity of desired products. Highly flammable H2 gas balloon at high pressure and temperature used in conventional hydrogenation reactions was not needed in the present synthetic system. Catalytic activity is strongly dependent on the size of encapsulated Pd NPs in the POP. The Pd-POP catalyst with Pd NPs of 8 nm in diameter exhibited higher catalytic activity for alkene hydrogenation as compared with the Pd-POP catalyst encapsulating 3 nm Pd NPs. Computational studies were undertaken to gain insights into different catalytic activities of these two Pd-POP catalysts. High reusability and stability as well as no Pd leaching of these Pd-POP catalysts make them highly applicable for hydrogenation reactions at room temperature.