Ramandeep Kaur

The rising environmental concerns surrounding plastic pollution and the depletion of fossil resources have accelerated interest in biodegradable and sustainable alternatives such as biopolymers. This chapter explores the valorization of fruit waste as a renewable and low-cost substrate for biopolymer production, presenting a sustainable solution to both plastic- and agro-waste challenges. Key biopolymers derived from fruit waste—such as starch, cellulose, pectin, polylactic acid (PLA) and polyhydroxyalkanoates (PHAs)—are discussed in terms of their market trends, commercial applications, extraction methodologies, physicochemical properties and industrial relevance. A comprehensive comparison of conventional and advanced green extraction technologies is provided, highlighting innovations such as enzymatic, microwave and ultrasonic-assisted techniques. Furthermore, the chapter evaluates the structural attributes, thermal behavior and functional properties of the extracted polymers, linking them to their potential applications in food packaging, pharmaceuticals and agriculture. The chapter underscores the future potential of fruit waste-derived biopolymers in driving the circular bio-economy, offering a pathway toward sustainable materials and zero-waste strategies.

Carbon-based quantum dots and their nanocomposites have sparked immense interest for researchers as sensors due to their attractive physico-chemical properties caused by edge effects and quantum confinement. In this review article, we have discussed the synthesis and application of nanocomposites of graphene quantum dots (GQDs) and carbon quantum dots (CQDs). Different synthetic strategies for CQDs, GQDs, and their nanocomposites, are categorized as top-down and bottom-up approaches which include laser ablation, arc-discharge, chemical oxidation, ultrasonication, oxidative cleavage, microwave synthesis, thermal decomposition, solvothermal or hydrothermal method, stepwise organic synthesis, carbonization from small molecules or polymers, and impregnation. A comparison of methodologies is presented. The environmental application of nanocomposites of CQDs/GQDs and pristine quantum dots as sensors are presented in detail. Their applications envisage important domains dealing with the sensing of pollutant molecules. Recent advances and future perspective in the use of CQDs, GQDs, and their nanocomposites as sensors are also explored.