Interface engineering and charge dynamics in NiO/Carbon quantum dot nanocomposites: from rational design to practical environmental remediation

Nickel oxide (NiO)/carbon quantum dot (CQD) nanocomposites have attracted increasing attention as visible-light-responsive platforms for environmental remediation, yet their reported performance remains difficult to interpret without a clear understanding of interfacial charge-transfer processes. This review analyzes how interface engineering regulates charge dynamics, redox activity, and functional performance in NiO/CQD systems, with emphasis on moving from material synthesis toward mechanism-guided design. We examine synthetic strategies that govern interfacial coupling, defect populations, and CQD dispersion, and discuss how these parameters influence band alignment, carrier separation, recombination pathways, and surface reaction kinetics under visible-light irradiation. Reported applications in pollutant photodegradation, adsorption-assisted removal, and electrochemical sensing are evaluated not only in terms of activity enhancement but also with respect to mechanistic consistency and practical relevance. Particular attention is given to persistent challenges, including ambiguous interpretation of optical/electrochemical signatures, insufficient testing in realistic water matrices, and limited insight into durability and scale-up. By integrating structure–property relationships with application-level constraints, this review outlines key design principles for developing interface-stable, scalable, and practically relevant NiO/CQD nanocomposites for next-generation environmental treatment technologies.

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