Substrate-dependent performance patterns in nanocoatings across interior materials

Nanostructured coatings are widely used to enhance surface durability while preserving visual appearance, yet it remains unclear whether performance is primarily governed by coating chemistry or by the underlying substrate. Here, we address this question through a structured scoping review (PRISMA-ScR) of 80 eligible empirical studies spanning seven material classes relevant to interior environments. Across 311 standardized observations, we find that substrate class emerged as the strongest observed association with simultaneous functional and optical performance. Non-porous substrates (e.g., glass, glazed ceramics) achieve dual performance targets in 67-82% of cases, compared to only 11-22% for highly porous materials (e.g., wood, textiles), revealing an approximately 4-fold performance gradient. This pattern is consistent with interfacial film formation mechanisms, including capillary depletion, hygroscopic stress, and surface heterogeneity. Exploratory study-level logistic regression (N = 80) supports this trend, with highly porous substrates showing substantially reduced odds of dual-axis success (odds ratio (OR) = 0.24; adjusted confidence interval (CI): 0.11-0.52). Coating chemistry, deposition conditions, and interfacial interactions further influence performance within these substrate-dependent trends: TiO₂-based systems enhance antimicrobial efficacy but incur greater optical degradation relative to SiO₂-based formulations. These findings support the interpretation of nanocoating performance as strongly influenced by substrate-dependent interfacial phenomena rather than a formulation-driven outcome alone. More broadly, they suggest that thin-film performance in complex environments is constrained by substrate-controlled transport and stress regimes, with implications for material selection and surface engineering beyond coating systems. As a synthesis based on proxy classification, these results are hypothesis-generating and highlight the need for controlled experiments directly testing substrate-controlled thin-film performance.