Hollow TiO₂ nanoparticles (HNPs) capped with conducting polymers, such as polythiophene (PT), polypyrrole (PPy), and polyaniline (PANI), have been studied to be used as polarizability-tunable electrorheological (ER) fluids. The hollow shape of TiO₂ nanoparticles, achieved by the removal of the SiO₂ template, offers colloidal dispersion stability in silicone oil owing to the high number density. Conducting polymer shells, introduced on the nanoparticle surface using vapor deposition polymerization method, improve the yield stress of the corresponding ER fluids in the order of PANI < PPy < PT. PT-HNPs exhibited the highest yield stress of ca. 94.2 Pa, which is 5.0-, 1.5-, and 9.6-times higher than that of PANI-, PPy-, and bare HNPs, respectively. The improved ER response upon tuning with polymer shells is attributed to the space charge contribution arising from the movement of the charge carriers trapped by the heterogeneous interface. The ER response of studied ER fluids is consistent with the corresponding polarizability results as indicated by the permittivity and electrophoretic mobility measurements. In conclusion, the synergistic effect of hollow nanostructures and conducting polymer capping effectively enhanced the ER performance.

Light detection and ranging (LiDAR) sensors utilize a near-infrared (NIR) laser with a wavelength of 905 nm. However, LiDAR sensors have weakness in detecting black or dark-tone materials with light-absorbing properties. In this study, SiO₂/black TiO₂ core/shell nanoparticles (SBT CSNs) were designed as LiDAR-detectable black materials. The SBT CSNs, with sizes of 140, 170, and 200 nm, were fabricated by a series of Stöber, TTIP sol-gel, and modified NaBH₄ reduction methods. These SBT CSNs are detectable by a LiDAR sensor and, owing to their core/shell structure with intrapores on the shell (ca. 2–6 nm), they can effectively function as both color and NIR-reflective materials. Moreover, the LiDAR-detectable SBT CSNs exhibited high NIR reflectance (28.2 R%) in a monolayer system and true blackness (L* < 20), along with ecofriendliness and hydrophilicity, making them highly suitable for use in autonomous vehicles.

Herein, the electrorheological (ER) performances of ER fluids were correlated with their colors to allow for the visual selection of the appropriate fluid for a specific application using naked eyes. A series of TiO₂-coated synthetic mica materials colored white, yellow, red, violet, blue, and green (referred to as color mica/TiO₂ materials) were fabricated via a facile sol–gel method. The colors were controlled by varying the thickness of the TiO₂ coating layer, as the coatings with different thicknesses exhibited different light interference effects. The synthesized color mica/TiO₂ materials were mixed with silicone oil to prepare colored ER fluids. The ER performances of the fluids decreased with increasing thickness of the TiO₂ layer in the order of white, yellow, red, violet, blue, and green materials. The ER performance of differently colored ER fluids was also affected by the electrical conductivity, dispersion stability, and concentrations of Na⁺ and Ca²⁺ ions. This pioneering study may provide a practical strategy for developing new ER fluid systems in future.

In this study, a flexible all-solid-state asymmetric supercapacitor (FASC) device has been successfully fabricated via full recycling of heated tobacco waste (HTW). Tobacco leaves and cellulose acetate tubes have been successfully carbonized (HTW-C) and mixed with metal oxides (MnO₂ and Fe₃O₄) to obtain highly active materials for supercapacitors. Moreover, poly(lactic acid) (PLA) filters have been successfully dissolved in an organic solvent and mixed with the as-prepared active materials using a simple paste mixing method. In addition, flexible MnO₂- and Fe₃O₄-mixed HTW-C/PLA electrodes (C-MnO₂/PLA and C-Fe₃O₄/PLA) have been successfully fabricated using the drop-casting method. The as-synthesized flexible C-MnO₂/PLA and C-Fe₃O₄/PLA electrodes have exhibited excellent electrical conductivity of 378 and 660 μS cm⁻¹, and high specific capacitance of 34.8 and 47.9 mF cm⁻² at 1 mA cm⁻², respectively. A practical FASC device (C-MnO₂/PLA//C-Fe₃O₄/PLA) has been assembled by employing the C-MnO₂/PLA as the positive electrode and C-Fe₃O₄/PLA as the negative electrode. The as-prepared FASC device showed a remarkable capacitance of 5.80 mF cm⁻² at 1 mA cm⁻². Additionally, the FASC device manifests stable electrochemical performance under harsh bending conditions, verifying the superb flexibility and sustainability of the device. To the best of our knowledge, this is the first study to report complete recycling of heated tobacco waste to prepare the practical FASC devices. With excellent electrochemical performance, the experiments described in this study successfully demonstrate the possibility of recycling new types of biomass in the future.