Metal Nanocluster-Metal Organic Framework-Polymer Hybrid Nanomaterials for Improved Hydrogen Detection.

The development of hydrogen sensors is of paramount importance for timely leak detection and remains a crucial unmet need. Palladium-based materials, well known as hydrogen sensors, still suffer from poisoning and deactivation. Here, a hybrid hydrogen sensor consisting of a Pd nanocluster (NC) film, a metal-organic framework (MOF), and a polymer, are proposed. The polymer coating, as a protection layer, endows the sensor with excellent H2 selectivity and CO-poisoning resistance. The MOF serves as an interface layer between the Pd NC film and the polymer layer, which alters the nature of the interaction with hydrogen and leads to significant sensing performance improvements, owing to the interfacial electronic coupling between Pd NCs and the MOF. The strategy overcomes the shortcomings of retarded response speed and degraded sensitivity induced by the polymer coating of a Pd NC film-polymer hybrid system. This is the first exhibition of a hydrogen-sensing enhancement mechanism achieved by engineering the electronic coupling between Pd and a MOF. The work establishes a deep understanding of the hydrogen-sensing enhancement mechanism at the nanoscale and provides a feasible strategy to engineer next-generation gas-sensing nanodevices with superior sensing figures of merit via hybrid material systems.

Preparation and characterization of gelatin/chitosan/3-phenylacetic acid food-packaging nanofiber antibacterial films by electrospinning.

In this study, antibacterial nanofiber films were prepared by electrospinning gelatin, chitosan, and 3-phenyllactic acid (PLA). The addition of PLA improved the microstructures of the nanofibers, and the nanofiber films (GCP-1 and GCP-2) had uniform and continuous structures with a diameter range of 40--70 nm when the PLA concentrations in the polymers were 1% and 2%. Under acidic conditions, chitosan and PLA interacted and formed hydrogen bonds, which decreased the crystallinity of the nanofiber films. The GCP-2 nanofiber film had the best thermal stability, water stability, and water vapor permeability. Compared with the control GCP-0 film, the four nanofiber films with PLA (GCP-1, GCP-2, GCP-3, and GCP-4) had more effective antibacterial effects, and GCP-2 film reduced approximately 4 log CFU/mL of Salmonella enterica Enteritidis and Staphylococcus aureus in 30 min. Results suggested that the GCP-2 nanofiber film mat can be used as an active food packaging.

Preparation and antibacterial properties of ε-polylysine-containing gelatin/chitosan nanofiber films.

An effective antibacterial nanofiber film was prepared through the incorporation of ε-polylysine (ε-PL) into gelatin/chitosan-based polymers. All nanofiber films had uniformly disordered fibrous structure with good diameter distribution. The weight ratio of the gelatin/chitosan/ε-PL (G/C/P) influenced the solution property and nanofiber morphology. The addition of ε-PL can decrease the viscosity and increase the conductivity of solutions, which lead to a decrease in the diameter of nanofibers. The three polymers of gelatin, chitosan, and ε-PL were interacted by hydrogen bonding, and the crystallinity of nanofiber films was decreased by the electrospinning process. The addition of ε-PL can enhance the thermal stability, and decrease the water vapor permeability and oxygen permeability of the films, and ε-PL did not easily release from the nanofiber films. The G/C/P (6:1:0.125) nanofiber film was more effective to control six foodborne pathogens than the G/C nanofiber films by destroying the bacterial cell membranes. The result indicated that the gelatin/chitosan/ε-PL nanofiber films can be used as a food-packaging material to reduce the risk of foodborne pathogens.