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.
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.
Due
to large energy requirements of the traditional gas separation
processes, novel and less energy-intensive technologies, such as adsorption-
and membrane-based ones, are anticipated to play major role in future
industrial separations. Thus, finding new means for economical fabrication
of materials related to these processes is of significant importance
to facilitate their implementation in large-scale operations. In this
work, we synthesized high-quality activated porous carbons (AC) and
carbon nanotube (CNT) membranes using asphaltene, an abundant waste
of the petroleum industry. The resulting materials were tested for
CO2 separation in adsorption and membrane modes. Among
the various porous carbons produced, AC from raw asphaltene reached
a CO2 sorption capacity of 7.56 mmol/g at 4 bar and 25
°C with a relatively low heat of adsorption (up to 23 kJ/mol)
implying low energy requirement for regeneration. The versatility
of the asphaltene precursors in the formation of carbon nanomaterials
was also demonstrated by growing, for the first time, CNT membranes
via template-based, catalyst-free carbonization of asphaltene inside
the pores of anodized alumina. The resulting CNT membranes attained
a promising separation performance with permeability ratios exceeding
the respective Knudsen values for H2/CO2, N2/CO2, N2/CH4, and H2/CH4 gas pairs.
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