Comprehensive study on the Mn–ZnO/SiO2 nanocomposites: from the digital colorimetry to the visible-light photocatalysis

A series of manganese-doped ZnO/SiO 2 nanocomposites was studied to establish the structure-property relationships governing visible-light photocatalysis and to assess whether digital colorimetry, chemometrics and machine learning can provide rapid, nondestructive composition control for doped semiconductor/support systems, using the antiviral drug lopinavir as a model pollutant. The novelty lies in coupling machine learning, chemometrics-supported spectroscopy, and digital colorimetry with conventional characterization to enable rapid, nondestructive compositional quality control of this doped oxide/support system.Nanocomposites containing 3, 6, and 9 mmol of Mn–ZnO per gram of SiO 2 were prepared by a wet chemical route followed by thermal treatment at 600 °C. They were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy with AI-assisted image segmentation, nitrogen adsorption–desorption, atomic force microscopy, UV-visible spectroscopy and photoluminescence. Digital images were classified using convolutional neural network (Inception v3) embeddings combined with a support vector machine, and infrared spectra (FTIR and IR-ATR) were modeled by principal component analysis and NIPALS regression.Hexagonal wurtzite ZnO formed, with crystallite sizes of 27.7–31.0 nm. Changes in the Raman A 1 (LO) mode were consistent with defect-related lattice distortion, including contributions from oxygen vacancy- and zinc-interstitial-related states. The predominantly mesoporous solids exhibited specific surface areas of 110–160 m 2 g −1 and enhanced visible-light absorption with defect-mediated photoluminescence. The classification pipeline accurately discriminated the samples, and IR-ATR provided improved compositional predictions compared with conventional FTIR. The most active composite, 9-Mn–ZnO/SiO 2 , removed 96 % of lopinavir within 1 h under visible light ( k 1 = 0.0465 min −1 ), with • OH and O 2 −• implicated as the dominant reactive species and stable performance over four reuse cycles.This integrated approach provides mechanistic insight into structure-property relationships and practical, non-destructive quality-control tools for visible-light-active doped metal oxide/support photocatalysts.