Abstract
The prevalence of the antibiotic resistant bacteria remains a global issue. Cheap, sustainable and multifunctional antibacterial membranes are at the forefront of filtrating materials capable of treating multiple flow streams, such as water cleansing treatments. Carbon nanomaterials are particularly interesting objects shown to enhance antibacterial properties of composite materials. In this article, amino-functionalized, photoluminescent carbon nanodots (CNDs) were synthesized from chitosan by bottom-up approach via simple and green hydrothermal carbonization. A chemical model for the CNDs formation during hydrothermal treatment of chitosan is proposed. The use of urea as an additional nitrogen source leads to the consumption of hydroxyl groups of chitosan and higher nitrogen doping level as pyridinic and pyrrolic N-bonding configurations in the final carbonaceous composition. These functionalized carbon nanodots that consist of carbon core and various surface functional groups were used to modify the commercially available membranes in order to enhance their anti-biofouling properties and add possible functionalities, including fluorescent labelling. Incorporation of CNDs to membranes increased their hydrophilicity, surface charge without compromising membranes integrity, thereby increasing the factors affecting bacterial wall disruption. Membranes modified with CNDs effectively stopped the growth of two Gram-negative bacterial colonies: Klebsiella oxytoca (K. oxytoca) and Pseudomonas aeruginosa (P. aeruginosa).
Highlights
Various carbon-based starting materials, such as soot [1], carbohydrates [2,3,4,5], activated carbons [6,7], graphene oxide and graphite [8,9] have been reported in recent years as precursors to luminescent [10] carbon-based nanomaterials using straightforward oxidizing conditions at elevated temperatures
Based on the results obtained by the spectroscopic analysis (FTIR, and XPS), we propose a revised chemical reaction model for the formation of carbon nanodots (CNDs) in the presence of urea during hydrothermal carbonization of chitosan
Our work has shown that many of the properties of CNDs depend on their functionalization, including their optical and antibacterial properties
Summary
Various carbon-based starting materials, such as soot [1], carbohydrates [2,3,4,5], activated carbons [6,7], graphene oxide and graphite [8,9] have been reported in recent years as precursors to luminescent [10] carbon-based nanomaterials using straightforward oxidizing conditions at elevated temperatures. A broad family of carbon spherical nanomaterials includes, but is not limited to, graphene quantum dots (GQDs), described as a nanometer-scale graphene derivative where quantum confinement [19] and edge effects [20,21] introduce a band gap They have been reported to be comparable [16] to CDs and have similar dimensions, photoluminescence properties, surface characteristics, and were shown to be biologically applicable [22]. GQDs [24,25] and to CDs [26,27], all of which can have similar dimensions and structure but generally differ in their height profiles determined by atomic force microscopy (AFM) Due to these similarities as well as the initial synthesis precursors and conditions reported for the production of CDs [8,28,29] and GQDs [9,22,30], there is often no clear distinction between these nanomaterial classes, especially when comparing multilayer. The antimicrobial properties of CNDs were carried out on two bacterial families: K. oxytoca and P. aeruginosa
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