Coffee Grounds to Multifunctional Quantum Dots: Extreme Nanoenhancers of Polymer Biocomposites

Abstract

Central to the design and execution of nanocomposite strategies is the invention of polymer-affinitive and multifunctional nanoreinforcements amenable to economically viable processing. Here, a microwave-assisted approach enabled gram-scale fabrication of polymer-affinitive luminescent quantum dots (QDs) from spent coffee grounds. The ultrasmall dimensions (approaching 20 nm), coupled with richness of diverse oxygen functional groups, conferred the zero-dimensional QDs with proper exfoliation and uniform dispersion in poly(l-lactic acid) (PLLA) matrix. The unique optical properties of QDs were inherited by PLLA nanocomposites, giving intensive luminescence and high visible transparency, as well as nearly 100% UV-blocking ratio in the full-UV region at only 0.5 wt % QDs. The strong anchoring of PLLA chains at the nanoscale surfaces of QDs facilitated PLLA crystallization, which was accompanied by substantial improvements in thermomechanical and tensile properties. With 1 wt % QDs, for example, the storage modulus at 100 °C and tensile strength increased over 2500 and 69% compared to those of pure PLLA (4 and 57.3 MPa), respectively. The QD-enabled energy-dissipating and flexibility-imparting mechanisms upon tensile deformation, including the generation of numerous shear bands, crazing, and nanofibrillation, gave an unusual combination of elasticity and extensibility for PLLA nanocomposites. This paves the way to biowaste-derived nanodots with high affinity to polymer for elegant implementation of distinct light management and extreme nanoreinforcements in an ecofriendly manner.

Manufacturing and compatibilization of PLA/PBAT binary blends by cottonseed oil-based derivatives

“…[7][8][9][10]. With the increasing development of nanotechnology, many research works have been focused of using nanostructures to improve the properties of PLA-based materials [11][12][13] and interactions. Typical PLA materials are characterized by low toughness and this is one of the main drawbacks in a massive use of this biopolyester.…”

Spider Silk Inspired Robust and Photoluminescent Soybean‐Protein‐Based Materials

“…In SPI/ESO10/GQD0.6 spectra, amide I and amide II moved from 1645 and 1548 cm −1 to 1653 and 1553 cm −1 , indicating that GQD had reacted by hydrogen bond with SPI/ESO. [ 30,31 ]…”

“…In SPI/ESO10/GQD0.6 spectra, amide I and amide II moved from 1645 and 1548 cm −1 to 1653 and 1553 cm −1 , indicating that GQD had reacted by hydrogen bond with SPI/ESO. [30,31] The crystal structure of SPI-based films was analyzed by XRD as shown in Figure 4b. The diffraction peaks of SPI at 2𝜃 = 9.44°a nd 19.64°were 𝛼-helix structure and 𝛽-fold structure, respectively, which were the typical secondary conformations of SPI.…”

Valorization of Spent Coffee Grounds as Precursors for Biopolymers and Composite Production

“…A composite with 1 wt.% of QD showed good UV shielding and important transmission to the visible light, coupled with significantly improved mechanical properties, compared to the neat PLA, i.e., 69% and 67% increases in the tensile strength and the elastic modulus, respectively. The authors also propose the use of this material as a high-performance nanocomposite for applications involving transparency and UV protection [ 137 ]. Another interesting work reported good results by using PP and lignin as a compatibilizer for PLA/SCG composites.…”