Utilizing Carbonaceous Materials Derived from [BMIM][TCM] Ionic Liquid Precursor: Dual Role as Catalysts for Oxygen Reduction Reaction and Adsorbents for Aromatics and CO2.

This work presents the synthesis of N-doped nanoporous carbon materials using the Ionic Liquid (IL) 1-butyl-3-methylimidazolium tricyanomethanide [BMIM][TCM] as a fluidic carbon precursor, employing two carbonization pathways: templated precursor and pyrolysis/activation. Operando monitoring of mass loss during pyrolytic and activation treatments provides insights into chemical processes, including IL decomposition, polycondensation reactions and pore formation. Comparatively low mass reduction rates were observed at all stages. Heat treatments indicated stable pore size and increasing volume/surface area over time. The resulting N-doped carbon structures were evaluated as electrocatalysts for the oxygen reduction reaction (ORR) and adsorbents for gases and organic vapors. Materials from the templated precursor pathway exhibited high electrocatalytic performance in ORR, analyzed using Rotating Ring-Disk electrode (RRDE). Enhanced adsorption of m-xylene was attributed to wide micropores, while satisfactory CO2 adsorption efficiency was linked to specific morphological features and a relatively high content of N-sites within the C-networks. This research contributes valuable insights into the synthesis and applications of N-doped nanoporous carbon materials, highlighting their potential in electrocatalysis and adsorption processes.

Adsorption of Hydrogen Sulfide on Activated Carbon Materials Derived from the Solid Fibrous Digestate.

The goal of this work is to develop a sustainable value chain of carbonaceous adsorbents that can be produced from the solid fibrous digestate (SFD) of biogas plants and further applied in integrated desulfurization-upgrading (CO2/CH4 separation) processes of biogas to yield high-purity biomethane. For this purpose, physical and chemical activation of the SFD-derived BC was optimized to afford micro-mesoporous activated carbons (ACs) of high BET surface area (590-2300 m2g-1) and enhanced pore volume (0.57-1.0 cm3g-1). Gas breakthrough experiments from fixed bed columns of the obtained ACs, using real biogas mixture as feedstock, unveiled that the physical and chemical activation led to different types of ACs, which were sufficient for biogas upgrade and biogas desulfurization, respectively. Performing breakthrough experiments at three temperatures close to ambient, it was possible to define the optimum conditions for enhanced H2S/CO2 separation. It was also concluded that the H2S adsorption capacity was significantly affected by the restriction to gas diffusion. Hence, the best performance was obtained at 50 °C, and the maximum observed in the H2S adsorption capacity vs. the temperature was attributed to the counterbalance between adsorption and diffusion processes.

Ion-Based Metal/Graphene Antibacterial Agents Comprising Mono-Ionic and Bi-Ionic Silver and Copper Species.

Design of novel and more efficient antibacterial agents is a continuous and dynamic process due to the appearance of new pathogenic strains and inherent resistance development to existing antimicrobial treatments. Metallic nanoparticles (NPs) are highly investigated, yet the role of released ions is crucial in the antibacterial activity of the NP-based systems. We developed herein ion-based, metal/graphene hybrid structures comprising surface-bound Ag and Cu mono-ionic and Ag/Cu bi-ionic species on functionalized graphene, without involvement of NPs. The antibacterial performance of the resulting systems was evaluated against Escherichia coli cells using a series of parametrization experiments of varying metal ion types and concentrations and compared with that of the respective NP-based systems. It was found that the bi-ionic Ag/Cu-graphene materials exhibited superior performance compared to that of the mono-ionic analogues owing to the synergistic action of the combination of the two different metal ions on the surface and the enhancing role of the graphene support, whereas all ion-based systems performed superiorly compared to their NP-based counterparts of the same metal type and concentration. In addition, the materials exhibited sustained action, as their activity was maintained after reuse in repeated cycles employing fresh bacteria in each cycle. The systems developed herein may open new prospects toward the development of novel, efficient, and tunable antibacterial agents by properly supporting and configuring metals in ionic form.

Ag and Cu Monometallic and Ag/Cu Bimetallic Nanoparticle-Graphene Composites with Enhanced Antibacterial Performance.

Increased proliferation of antimicrobial resistance and new strains of bacterial pathogens severely impact current health, environmental, and technological developments, demanding design of novel, highly efficient antibacterial agents. Ag, Cu monometallic and Ag/Cu bimetallic nanoparticles (NPs) were in situ grown on the surface of graphene, which was produced by chemical vapor deposition using ferrocene as precursor and further functionalized to introduce oxygen-containing surface groups. The antibacterial performance of the resulting hybrids was evaluated against Escherichia coli cells and compared through a series of parametrization experiments of varying metal type and concentration. It was found that both Ag- and Cu-based monometallic graphene composites significantly suppress bacterial growth, yet the Ag-based ones exhibit higher activity compared to that of their Cu-based counterparts. Compared with well-dispersed colloidal Ag NPs of the same metal concentration, Ag- and Cu-based graphene hybrids display weaker antibacterial activity. However, the bimetallic Ag/CuNP-graphene hybrids exhibit superior performance compared to that of all other materials tested, i.e., both the monometallic graphene structures as well as the colloidal NPs, achieving complete bacterial growth inhibition at all metal concentrations tested. This striking performance is attributed to the synergistic action of the combination of the two different metals that coexist on the surface as well as the enhancing role of the graphene support.

Magnetic carbon nanotubes with particle-free surfaces and high drug loading capacity.

Open-ended, multi-wall carbon nanotubes (CNTs) with magnetic nanoparticles encapsulated within their graphitic walls (magCNTs) were fabricated by a combined action of templated growth and a ferrofluid catalyst/carbon precursor, and tested as drug hosts. The hybrid nanotubes are stable under extreme pH conditions due to particle protection provided by the graphitic shell. The magCNTs are promising for high capacity drug loading given that the magnetic functionalization did not block any of the active sites available for drug attachment, either from the CNT internal void or on the internal and external surfaces. This is in contrast to typical approaches of loading CNTs with particles that proceed through surface attachment or capillary filling of the tube interior. Additionally, the CNTs exhibit enhanced hydrophilic character, as shown by water adsorption measurements, which make them suitable for biological applications. The morphological and structural characteristics of the hybrid CNTs are evaluated in conjunction to their magnetic properties and ability for drug loading (diaminophenothiazine). The fact that the magnetic functionality is provided from 'inside the walls' can allow for multimode functionalization of the graphitic surfaces and makes the magCNTs promising for targeted therapeutic applications.