High-purity indium vanadate (InVO₄) and graphitic carbon nitride (g-C₃N₄) were successfully synthesized and thoroughly characterized to investigate their optoelectronic properties and interfacial charge transfer behavior. X-ray diffraction (XRD) analysis confirmed the phase purity and crystallinity of the individual materials. UV–vis diffuse reflectance spectroscopy revealed direct band gaps of 2.48 eV for InVO₄ and 2.99 eV for g-C₃N₄, highlighting their suitability for visible-light-driven applications. X-ray photoelectron spectroscopy (XPS) provided detailed insight into the surface composition and valence band positions. Furthermore, Mott–Schottky measurements indicated that both materials exhibit n-type semiconducting behavior and allowed the determination of their conduction band edge potentials. The Fermi levels were estimated using valence band maximum (VBM) analysis, and the overall band alignment revealed a staggered (Type II) configuration at the interface.

To probe the charge carrier dynamics, steady-state photoluminescence (PL) spectroscopy was employed, specifically targeting the generation of hydroxyl (•OH) radicals under illumination. The enhanced production of these reactive oxygen species provided strong evidence for a direct Z-scheme charge transfer mechanism between InVO₄ and g-C₃N₄. This mechanism promotes effective charge separation and preserves strong redox potentials, making the heterostructure a promising candidate for photocatalytic applications such as pollutant degradation and hydrogen evolution. These findings offer valuable insights into band structure tuning and heterojunction design strategies.

In recent years, there has been increasing production of agro-industrial waste, resulting from the transformation of raw materials in the food industry, raising environmental, economic and nutritional concerns, but also becoming a strategic opportunity in the context of the circular bioeconomy (1,2). An example of these by-products is the wine industry, which produces high quantities of organic residues considered promising sources of valuable nutritional components, triggering various bioactive activities (3,4). This literature review aims to investigate the emerging role of bionanotechnology in altering these residues in the development of nanosystems. Several studies refer to the richness of grape extracts in polyphenols and flavonoids; however, these groups are characterized by their chemical instability and solubility, which lead to obstacles such as low permeability and bioavailability (5). For example, nanofibers loaded with grape seed extracts did not affect their morphology and still promoted a sustained release, favoring the antioxidant and regenerative activity of the extract (6,7). Another study nanoincorporated extracts into liposomal vesicles, demonstrating the ability to neutralize the basal production of reactive oxygen species (ROS) and showing that they were not cytotoxic to cells (8). Castangia et al. (2017) analyzed silver nanoparticles and an extract of grape pomace designed for skin protection, which were capable of inhibiting the proliferation of Staphylococcus aureus and Pseudomonas aeruginosa (9). Thus, the creation of nanosystems is a promising, natural and innovative technological solution for obtaining new sustainable food, pharmaceutical and cosmetic products, reducing the impacts caused by the wine industry and contributing to the improvement of the circular economy.