Multicolor Emitting Carbon Dot-Reinforced PVA Composites as Edible Food Packaging Films and Coatings with Antimicrobial and UV-Blocking Properties

Abstract

Active food packaging has become attractive because of the possibility to provide a longer shelf-life by loading functional agents into the packages to maintain the quality of food products. Herein, photoluminescent and transparent polyvinyl alcohol (PVA)-based composites embedding multicolor fluorescent carbon dots (CD/PVA) were prepared by the solvent casting method. The prepared CDs emit a strong and stable fluorescence in solution while the CD/PVA composite films were transparent, flexible, and showed UV-blocking activity with a strong fluorescence emission. Blue color-emitting CDs showed the highest UV blockage at UVA (87.04%), UVB (87.04%), and UVC (92.22%) regions while PVA alone absorbed only less than 25% of the light in all UV regions. UV blockage capacity was shown to be decreased by half, in line with the emission color shift from blue to red. Thermal properties of the PVA film were improved by the addition of CDs to the polymer, and in vitro cell viability tests showed that none of the CDs were cytotoxic against the human lung fibroblast healthy cell line (MRC-F cells) when integrated into the PVA. The antimicrobial activity of CD/PVA nanofilms was qualitatively determined. The prepared films exhibited good antimicrobial activity against both Gram-positive and Gram-negative bacteria with mild antioxidant and metal chelating activity, and significant inhibition of biofilm formation with a strong link with emitted color and the concentration of the composites. Green- and red-emitting CD/PVA with the highest antimicrobial activity were then analyzed and compared with the plane PVA employing their effect on the shelf-life of strawberries as a model for perishable foods. Fresh strawberries dip coated with CD/PVA and PVA were monitored over time, and virtual evaluations showed that CDs/PVA film coating resulted in reduced weight and moisture loss and significantly inhibited the fungal growth and spoiling for over 6 days at RT and 12 days at fridge conditions maintaining the visual appearance and natural color of the fruit. The findings in this work indicated the potential of reported CD as non-cytotoxic, UV-blocking antimicrobial additives for the development of edible coatings and packages for their use in the food industry, as well as pharmaceutical and healthcare applications.

Prospective Nanomaterials for Food Packaging and Safety

“…The application of CDs /PVA film as active packaging is capable of notably increasing the shelf life of various foods such as jujube, banana, and fried meatballs. Flexible, transparent, and photoluminescent CDs reinforced PVA based nanocomposite films show UV-blocking, mild antioxidant, and good antimicrobial activity against both gram-positive and gram-negative bacteria [35]. This CDs/PVA films significantly extend the shelf-life of strawberries as a model for perishable food products (Fig.…”

Flexible Photothermal Membrane Based on PVA/Carbon Dot Hydrogel Films for High-Performance Interfacial Solar Evaporation

“…The presence of amine functional groups on the surface of CDs was characterized by the presence of C–NH–C bonds, proved by the vibrations at 1175 cm –1 . Furthermore, the peak at approximately 1340 cm –1 was identified as the sp 3 C–H band, while the peak at 760 cm –1 was attributed to the aromatic sp 2 C–H (CH 2 ) band . For the spectrum of PVA, several characteristic peaks could be identified, such as a broad absorption peak at 3000–3500 cm –1 due to stretching vibration of O–H, a peak at 2990 cm –1 attributed to the stretching vibration of C–H alkyl functional groups of PVA, a peak at 1418 cm –1 corresponded to CH/CH 2 deformation vibration, and a prominent peak at 1087 cm –1 attributed to the stretching of hydroxyl C–O. ,,, The intense peak at 1700 cm –1 owing to the stretching band CO of the ester is caused by esterification of PVA and citric acid (CA), confirming the formation of a cross-linking reaction .…”

The coupling of blue emitting carbon dots with Eu3+/Tb3+ co-doped luminescent glasses for utilization in white light emitting diodes

“…S1b, ESI †). 40 The prepared BCD-polyvinylpyrrolidone (BCD/PVP) solutions, having excellent water solubility and stability, are then coated on luminescent glass surfaces using the spin-coating method to control the thickness and uniformity of the films (see Fig. S1c, ESI †).…”