Carbon Dot-Triggered Photocatalytic Degradation of Cellulose Acetate

Abstract

Chemical modification of biopolymers, before use in thermoplastic applications, can reduce the susceptibility to open environment degradation. We demonstrate carbon dots (CDs) as green photocatalytic triggers that can render the common cellulose derivative, cellulose acetate (CA), degradable under open environment relevant conditions. CD-modified cellulose acetate (CA + CD) films were subjected to UV-A irradiation in air and simulated sea water, and the degradation process was mapped by multiple spectroscopic, chromatographic, and microscopy techniques. The addition of CDs effectively catalyzed the deacetylation reaction, the bottleneck preventing biodegradation of CA. The photocatalytically activated degradation process led to significant weight loss, release of small molecules, and regeneration of cellulose fibers. The weight loss of CA + CD after 30 days of UV-A irradiation in air or simulated sea water was 53 and 43%, respectively, while the corresponding values for plain CA films were 12 and 4%. At the same time the weight average molar mass of CA + CD decreased from 62,000 to 11,000 g/mol and 15,000 g/mol during UV-A irradiation in air and simulated sea water, respectively, and the degree of substitution (DS) decreased from 2.2 to 1.6 both in air and in water. The aging in water alone did not affect the weight average molar mass, but the DS was decreased to 1.9. Control experiments confirmed the generation of hydrogen peroxide when aqueous CD dispersion was subjected to UV-A irradiation, indicating a free radical mechanism. These results are promising for the development of products, such as mulching films, with photocatalytically triggered environmental degradation processes.

Investigation of the influence of crosslinking activation methods on the physicochemical and Cu(II) adsorption characteristics of cellulose hydrogels

“…TGA profiles of the WBH and MWH are depicted in Fig. 4c, revealing two mass loss events in the temperature range of 30-600 • C. A sharp weight loss of 57.1% and 55.6% for WBH and MWH, respectively, between 250 and 400 • C corresponds to the thermal degradation of crosslinked cellulose chains, which is in good agreement with previous reports [48,49]. The DTG curves (inset) indicate that both the hydrogel samples exhibit similar maximum decomposition temperature (T max ) at about 330 • C, suggesting that the crosslinking activation method either by WB heating or MW irradiation does not considerably affect the physical structure and the thermal stability of the resulting hydrogels.…”

Degradation of Cellulose Acetate in Simulated Aqueous Environments: One‐Year Study

“…CA with DS 2.2 as determined by NMR spectroscopy, [ 21 ] ammonium chloride, synthetic sea salt, magnesium sulfate 7‐hydrate, potassium nitrate, potassium phosphate, acetic acid, and trifluoroacetic acid were obtained from Sigma–Aldrich. Sodium chloride, sodium hydroxide (NaOH) pellets, acetone, and dimethyl sulfoxide (DMSO) were of technical grade and purchased from VWR.…”

“…[7] In the previous work, we evaluated the catalytic effect of carbon dots on the degradation of CA under simulated sunlight (UV-A irradiation). [21] Here, we present a long-term study on the effect of different aqueous environments simulating or accelerating the potential degradation of CA in natural water systems, such as lakes or oceans. The physicochemical changes caused by the aging in different aqueous environments during 1 year were carefully monitored by multiple spectroscopic, chromatographic, and thermal analysis tools.…”

Degradation of Cellulose Derivatives in Laboratory, Man-Made, and Natural Environments

“…In accordance, the addition of H 2 O 2 to the artificial seawater led to rapid degradation of CA on UVA irradiation, leading to a similar effect as the addition of CDs. 71 In another study, polyphosphate incapsulated TiO 2 photocatalyst was incorporated into CA films with the aim of inducing degradation if the material would end up in seawater. This seawater activated catalyst only led to collapse of the CA films when exposed to seawater and UV irradiation.…”

“…(b) Images of the aged samples showing basically unaffected films with the exception of CD modified and UVA irradiated samples that had totally fragmented in agreement with the large weight loss. Reprinted from ref ( 71 ). Copyright 2021 American Chemical Society (No changes were made to the copyrighted material).…”