Blue luminescent carbon dots (CDs) with a high photoluminescence (PL) quantum yield (48.3 ± 5.3%) were prepared by the one-pot hydrothermal reaction of citric acid with poly(ethylenimine) (PEI). The CDs display bright PL, narrow emission spectra, pH-dependent PL intensity, high photostability, and up-converted luminescence. The CDs exhibit a quenching of both down- and up-conversion PL in the presence of morin and thus serve as useful probes for morin detection. Both down- and up-conversion measurements allow the quantification of concentrations from 0 to 300 μmol/L with a detection limit of 0.6 μmol/L, and this dual-mode detection increases the reliability of the measurement. The proposed method of determination is simple, sensitive, and cost-effective, with potential applications in clinical and biochemical assays.

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The optical properties of Cs0.33WO3 were analyzed based on experimental results reported in the literature. Its potential for use as a transparent energy-saving filter was evaluated using theoretical optical results. The results showed that Cs0.33WO3 exhibits excellent near-infrared radiation reflectance/absorption and high transmissivity of visible light, so it is ideal for use as a solar radiative filter for windows. In addition, Cs0.33WO3 provides perfect solar radiation shielding, suggesting that this material could be applied for compacted filters and nanoparticle-dispersed coatings. Two types of Cs0.33WO3 filters exhibited more than 80% transmissivity of visible light and excellent solar radiation shielding performance. This research work indicates that the doping of the Cs ion into hex-WO3 induces a persistent n-type electronic conductivity with metal-like characteristics and dramatically enhances near-infrared radiation absorption while maintaining excellent visible light transparency.

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