In this study, carbon quantum dots (CQDs), which were synthesized from arabica coffee ground-derived activated carbon, have been successfully employed as a fluorescence sensor to detect Fe³⁺ ions. CQDs were fabricated using microwave heating for 5-10 min, which emitted vibrant blue light at 455 nm when exposed to excitation at 365 nm. Dynamic light scattering (DLS) analysis revealed that the average size of CQDs was 10.12 nm with a quantum yield of 6.01%. Fluorescence detection was developed for sensing Fe³⁺, Pb²⁺, and Cr³⁺ ions. The addition of the three metal ions resulted in a decrease in the fluorescence (FL) intensity of the CQDs, with the addition of Fe³⁺ ions demonstrating a more significant decrease in FL compared to the addition of both Cr³⁺ and Pb²⁺ ions. The results indicated that the CQDs synthesized from activated carbon of arabica coffee waste performed as a selective fluorescent detector for Fe³⁺ ions, with a detection limit of 0.27 μM.

Seaweed bio-composite films with different proportion of Lemang and Semantan bamboo microcrystalline cellulose (MCC) were fabricated via solvent casting. The seaweed/MCC composite films were flexible, transparent, and slightly yellow. The MCC particles further enhanced mechanical properties and opacity of films. The thermal stability of seaweed films was moderately improved upon addition of bamboo MCC particles. Bamboo MCC was found to be comparable to commercial MCC in reducing the water vapor permeability (WVP), water solubility (WS), and moisture absorption capacity (MSC) of seaweed films. The tensile strength (TS) of seaweed films was increased by 20 to 23% with addition of up to 5% MCC particles. In addition, bamboo MCC efficiently reduced the WVP of seaweed films comparable to commercial MCC particles. The WS of seaweed films was decreased by 10 to 19% with addition of 1% MCC particles loading. Lemang bamboo MCC (SB-MCC) was remarkably reduced the moisture absorption capacity (MAC) of films up to 25% with inclusion of only 1% MCC. Morphological analysis via Scanning Electron Microscopy (SEM) confirmed that there was homogeneous dispersion of MCC particles in the films. MCC particles improved the mechanical, thermal, and optical properties of seaweed films making them more suitable for food packaging applications.

This study aimed to compare the performance of fabricated microbially induced precipitated calcium carbonate– (MB–CaCO₃) based red seaweed (Kappaphycus alvarezii) bio-polymer film and commercial calcium carbonate– (C–CaCO₃) based red seaweed bio-film with the conventional biodegradable mulch film. To the best of our knowledge, there has been limited research on the application of commercial CaCO₃ (C–CaCO₃) and microbially induced CaCO₃ (MB–CaCO₃) as fillers for the preparation of films from seaweed bio-polymer and comparison with biodegradable commercial plasticulture packaging. The results revealed that the mechanical, contact angle, and biodegradability properties of the polymer composite films incorporated with C–CaCO₃ and MB–CaCO₃ fillers were comparable or even superior than the conventional biodegradable mulch film. The seaweed polymer film incorporated with MB–CaCO₃ showed the highest contact angle of 100.94°, whereas conventional biodegradable mulch film showed a contact angle of 90.25°. The enhanced contact angle of MB–CaCO₃ resulted in high barrier properties, which is highly desired in the current scenario for plasticulture packaging application. The water vapor permeability of MB–CaCO₃ based seaweed films was low (2.05 ± 1.06 g·m/m²·s·Pa) when compared to conventional mulch film (2.68 ± 0.35 g·m/m²·s·Pa), which makes the fabricated film an ideal candidate for plasticulture application. The highest tensile strength (TS) was achieved by seaweed-based film filled with commercial CaCO₃ (84.92% higher than conventional mulch film). SEM images of the fractured surfaces of the fabricated films revealed the strong interaction between seaweed and fillers. Furthermore, composite films incorporated with MB–CaCO₃ promote brighter film, better water barrier, hydrophobicity, and biodegradability compared to C–CaCO₃ based seaweed polymer film and conventional mulch film. From this demonstrated work, it can be concluded that the fabricated MB–CaCO₃ based seaweed biopolymer film will be a promising candidate for plasticulture and agricultural application.