Exploring the Size Effect of Graphene Oxide on Crystallization Kinetics and Barrier Properties of Poly(lactic acid)

Weathered coal-based carbon dots modified by organic amine for enhanced crystallinity and toughness of poly(lactic acid) film

Poly(lactic acid) (PLA) has its own limitations in terms of slow crystallization rate and low crystallinity during processing, resulting in poor toughness and thermal stability, which seriously restricts the practical application of PLA. Blending nanoparticles into the PLA matrix is an effective way to improve PLA crystallization. In this study, carbon dots (CDs) were prepared by green oxidation using weathered coal as carbon source and then surface-modified with dodecylamine (DDA) and octadecylamine (ODA). Modified CDs (MCDs)/PLA composite films were prepared using MCDs as filler to improve the crystallinity and toughness of PLA films. The results showed that the improvement effect of ODA-modified CDs (ODACDs) was better than that of DDA-modified CDs (DDACDs). The crystallinity of PLA composite film (0.05 wt% ODACDs) was increased from 7.20% (pure PLA film) to 35.44%, and its elongation at break was increased by 5.01 times compared with that of the pure PLA film. Moreover, thermogravimetric analysis suggested that the thermal stability of MCDs/PLA films was also improved. The results of simultaneous rheology and in-situ FTIR analysis as well as molecular dynamics simulations confirmed that MCDs had a strong interaction with PLA molecules, which promoted the crystallization of PLA film, thereby improving its toughness and thermal stability.

Sugarcane leave-derived cellulose nanocrystal/graphene oxide filter membrane for efficient removal of particulate matter

The goal of this study is to isolate cellulose nanocrystals (CNC) from sugarcane leaves (SCL) and fabricate filter membranes. Filter membranes consisting of the CNC and varying amount graphene oxide (GO) were fabricated using vacuum filtration technique. The α-cellulose content increased from 53.56 ± 0.49 % in untreated SCL to 78.44 ± 0.56 % and 84.99 ± 0.44 % in steam-exploded and bleached fibers, respectively. Atomic force microscopy (AFM) and transmission electron microscope (TEM) of CNC isolated from SCL indicated nanosized particles in the range of 7.3 nm and 150 nm for diameter and length, respectively. Morphologies of the fiber and CNC/GO membranes were determined by scanning electron microscopy (SEM) and crystallinity by X-ray diffraction (XRD) analysis of crystal lattice. The crystallinity index of CNC decreased with the addition of GO into the membranes. The CNC/GO-2 recorded the highest tensile index of 3.001 MPa. The removal efficiency increases with increasing GO content. The highest removal efficiency of 98.08 % was recorded for CNC/GO-2. CNC/GO-2 membrane reduced growth of Escherichia coli to 65 CFU compared to >300 CFU of control sample. SCL is a potential bioresource for isolation of cellulose nanocrystals and fabrication of high-efficiency filter membrane for particulate matter removal and inhibition of bacteria.

Graphene oxide classification and standardization

There is a need to classify and standardize graphene-related materials giving the growing use of this materials industrially. One of the most used and more difficult to classify is graphene oxide (GO). Inconsistent definitions of GO, closely relating it to graphene, are found in the literature and industrial brochures. Hence, although they have very different physicochemical properties and industrial applications, commonly used classifications of graphene and GO definitions are not substantial. Consequently, the lack of regulation and standardization create trust issues among sellers and buyers that impede industrial development and progress. With that in mind, this study offers a critical assessment of 34 commercially available GOs, characterized using a systematic and reliable protocol for accessing their quality. We establish correlations between GO physicochemical properties and its applications leading to rationale for its classification.