Carbon Dot-Modified Electrospun Cellulose Acetate Mats: Increased Susceptibility to Degradation under Soil Burial and UV Irradiation

Environmental pollution by release of nondegradable textile fibers and single-use fabrics, such as face masks, is a serious threat. Replacement of electrospun polypropylene fabrics with materials that have a better environmental degradation profile is therefore of interest. Here, a strategy is presented through carbon dot (CD) modification of cellulose acetate (CA) mats produced by a one-step electrospinning process. The mats were carefully characterized for their physicochemical properties and screened for any antioxidant or antibacterial properties before they were subjected to aging under UV irradiation or soil burial. Typically, the degree of substitution (DS) of CA needs to be under 2 for any significant biodegradation to take place. It was therefore of interest to notice that some deacetylation took place already during electrospinning as the initial DS of 2.2, as determined by nuclear magnetic resonance spectroscopy (NMR), decreased to 2.0 and 1.8 for CA and CD-modified CA (CA-CD), respectively. After 30 days of soil burial or 7 days of UV irradiation, the DS of CA-CD had further decreased to 1.1 and 0.9, while the corresponding values for plain CA were 1.5 and 1.8. CD modification thus significantly catalyzed the deacetylation process, helping to overcome the bottleneck of CA biodegradation. The degradation of the mats was supported by other physicochemical changes, such as decreased water contact angle and molecular weight values. It was further shown that degradation during soil burial was significantly faster for the electrospun mats compared to the corresponding CA and CA-CD films, which could be due to the combination of larger surface area and the deacetylation that took place during electrospinning, making the electrospun mats more susceptible to subsequent biodegradation. However, the catalyzing effect of CD was observed even for the film samples, leading to somewhat lower DS and higher mineralization as determined by CO2 release.