A green strategy for fabrication of biobased reduced nanographene oxide (r-nGO) was developed. Cellulose derived nanographene oxide (nGO) type carbon nanodots were reduced by microwave assisted hydrothermal treatment with superheated water alone or in the presence of caffeic acid (CA), a green reducing agent. The carbon nanodots, r-nGO and r-nGO-CA, obtained through the two different reaction routes without or with the added reducing agent, were characterized by multiple analytical techniques including FTIR, XPS, Raman, XRD, TGA, TEM, AFM, UV−vis, and DLS to confirm and evaluate the efficiency of the reduction reactions. A significant decrease in oxygen content accompanied by increased number of sp 2 hybridized functional groups was confirmed in both cases. The synergistic effect of superheated water and reducing agent resulted in the highest C/O ratio and thermal stability, which also supported a more efficient reduction. Interesting optical properties were detected by fluorescence spectroscopy where nGO, r-nGO, and r-nGO-CA all displayed excitation dependent fluorescence behavior. r-nGO-CA and its precursor nGO were evaluated toward osteoblastic cells MG-63 and exhibited nontoxic behavior up to 200 μg mL −1 , which gives promise for utilization in biomedical applications.
Biodegradable polymers
complement recyclable materials in battling
plastic waste because some products are difficult to recycle and some
will end up in the environment either because of their application
or due to wear of the products. Natural biopolymers, such as cellulose,
are inherently biodegradable, but chemical modification typically
required for the obtainment of thermoplastic properties, solubility,
or other desired material properties can hinder or even prevent the
biodegradation process. This Review summarizes current knowledge on
the degradation of common cellulose derivatives in different laboratory,
natural, and man-made environments. Depending on the environment,
the degradation can be solely biodegradation or a combination of several
processes, such as chemical and enzymatic hydrolysis, photodegradation,
and oxidation. It is clear that the type of modification and especially
the degree of substitution are important factors controlling the degradation
process of cellulose derivatives in combination with the degradation
environment. The big variation of conditions in different environments
is also briefly considered as well as the importance of the proper
testing environment, characterization of the degradation process,
and confirmation of biodegradability. To ensure full sustainability
of the new cellulose derivatives under development, the expected end-of-life
scenario, whether material recycling or “biological”
recycling, should be included as an important design parameter.
Bioactive and reinforced poly(ε-caprolactone) (PCL) films were constructed by incorporation of cellulose derived reduced nanographene oxide (r-nGO) carbon nanodots. Two different microwave-assisted reduction routes in superheated water were utilized to obtain r-nGO and r-nGO-CA. For the latter, a green reducing agent caffeic acid (CA), was incorporated in the reduction process. The materials were extruded and compression molded to obtain proper dispersion of the carbon nanodots in the polymer matrix. FTIR results revealed favorable interactions between r-nGO-CA and PCL that improved the dispersion of r-nGO-CA. r-nGO, and r-nGO-CA endorsed PCL with several advantageous functionalities including improved storage modulus and creep resistance. The considerable increase in storage modulus demonstrated that the carbon nanodots had a significant reinforcing effect on PCL. The PCL films with r-nGO-CA were also evaluated for their osteobioactivity and cytocompatibility. Bioactivity was demonstrated by formation of hydroxyapatite (HA) minerals on the surface of r-nGO-CA loaded nanocomposites. At the same time, the good cytocompatibility of PCL was retained as illustrated by the good cell viability to MG63 osteoblast-like cells giving promise for bone tissue engineering applications.
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