Synthesis of Hierarchical Silica/Titania Hollow Nanoparticles and Their Enhanced Electroresponsive Activity

Designing a highly near infrared-reflective black nanoparticles for autonomous driving based on the refractive index and principle

HYPOTHESIS

The development of highly NIR reflective black single-shell hollow nanoparticles (BSS-HNPs) can overcome the Light Detection and Ranging (LiDAR) sensor limitations of dark-tone materials. The crystalline phase of TiO2 and the refractive index can be controlled by calcination temperature. The formation of hollow structure and the refractive index is expected to simultaneously increase the light reflection and LiDAR detectability.

EXPERIMENTS

The BSS-HNPs are synthesized using the sol-gel method, calcination, NaBH4 reduction, and etching to form a hollow structure with true blackness. The computational bandgap calculation is conducted to determine the bandgap energy (Eg) of the white and black TiO2 with different crystalline structures. The blackness of the as-synthesized materials is determined by the Commission on Illumination (CIE) L*a*b* color system.

FINDINGS

The hydrophilic nature of BSS-HNPs enables the formulation of hydrophilic paints, allowing the mono-layer coating. With the synergistic effects of hollow structure and the refractive index, BSS-HNPs manifested superb NIR reflectance at LiDAR detection wavelengths. The high detectability, blackness, and hollow structure of BSS-HNPs can expand the variety of LiDAR-detectable dark-tone materials.

Vivid-Colored Electrorheological fluids with simultaneous enhancements in color clarity and Electro-Responsivity

HYPOTHESIS

Surface modification of dielectric materials changes the dipole-dipole interactions under electric fields, thereby controlling the electrorheological (ER) response. The introduction of metal oxides onto mica templates and further coating of dyes is expected to simultaneously improve the color clarity and ER performance.

EXPERIMENTS

Dye-coated TiO2 platelets on mica are synthesized for high-performance colorful ER fluids. A sol-gel method is utilized to grow TiO2 on mica to prepare precursor light-colored mica/TiO2 materials, which are coated with appropriate dyes to enhance the vividness as determined by the Commission Internationale de clairage L*a*b* color system. The color expression and color clarity improvement are explained via the light interference effect and the presence of chromophores.

FINDINGS

The uniform TiO2 layers can be obtained under low pH conditions with controlled nucleation kinetics. The addition of dyes to TiO2 increases the surface area and porosity of ER materials and introduces heteroatoms that act as positive factors. In practical ER applications, dye-coated TiO2-based ER fluids exhibit higher ER performances compared with the corresponding light-colored TiO2-based ER fluids. The vivid-colored ER fluids could provide an easy selection for a wide range of rheological systems requiring a specific magnitude of stress by confirming the color.

Synthesis of LiDAR-Detectable True Black Core/Shell Nanomaterial and Its Practical Use in LiDAR Applications

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.

Hollow TiO2 Nanoparticles Capped with Polarizability-Tunable Conducting Polymers for Improved Electrorheological Activity

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.

Enhanced response of titanium doped iron(ii) oxalate under electric field

Electrorheological (ER) fluid, containing polarized particles within an insulating liquid, represents a smart material, the mechanical properties of which can be altered mainly by an electric field.

Fabrication, functionalization and advanced applications of magnetic hollow materials in confined catalysis and environmental remediation

Magnetic hollow-structured functional hybrid materials with unique architectures and preeminent properties have always been an area of extensive research. They represent a subtle collaboration of hollow architecture, mesoporous nanostructure and magnetic character. Owing to the merits of a large void space, low density, high specific surface area, well-defined active sites and facile magnetic recovery, these materials present promising application projections in numerous fields, such as drug delivery, adsorption, storage, catalysis and many others. In this review, recent progress in the design, synthesis, functionalization and applications of magnetic hollow-meso/nanostructured materials are discussed. The first part of the review has been dedicated to the preparation and functionalization of the materials. The synthetic protocols have been broadly classified into template-assisted and template-free methods and major trends in their synthesis have been elaborated in detail. Furthermore, the benefits and drawbacks of each method are compared. The later part summarizes the application aspects of confined catalysis in organic transformations and environmental remediation such as degradation of organic pollutants, dyes and antibiotics and adsorption of heavy metal ions. Finally, an outlook of future directions in this research field is highlighted.

Raspberry-Like Mesoporous Zn1.07Ga2.34Si0.98O6.56:Cr0.01 Nanocarriers for Enhanced Near-Infrared Afterglow Imaging and Combined Cancer Chemotherapy

Near-infrared (NIR) persistent luminescence (PersL) nanoparticles based on trivalent chromium-doped gallates (ZGO) as nanocarriers show great potential for theranostics, owing to their autofluorescence-free background and deep tissue penetration. However, high drug loading capacity of ZGO nanocarriers remains a big challenge. Herein, raspberry-like mesoporous Zn_1.07Ga_2.34Si_0.98O_6.56:Cr_0.01 (designated as Si-ZGO) is first developed via a unique silica-assisted targeted etching strategy. The composition, morphology, NIR PersL capacities, and drug loading/releasing abilities of Si-ZGO have been explored. These results exhibit that Si-ZGO possess multiple inspiring characteristics including (i) spherical raspberry-like mesoporous morphology with a large cavity (total pore size ∼5.0 nm) and high specific surface area (∼80.653 m²·g^-1), promising excellent drug loading capacity (∼62 wt %); (ii) tunable sizes from 80 to 180 nm and improved aqueous-dispersibility, facilitating cellular uptake and permeation and retention (EPR) effect; (iii) new deep traps related to oxygen vacancies, achieving the brighter NIR PersL. These outstanding merits enable the further nanosystem (DOX-BSA@Si-ZGO) for proof-of-concept theranostics excellent chemotherapy effect, tumor-specific trackable ability, and pronounced NIR afterglow imaging in vivo. This work demonstrates the great potentials of Si-ZGO nanorasperries as a multifunctional theranostics platform, even more it hopefully could inspire other constructions of advanced functional materials.

Synthesis and Electroresponse Activity of Porous Polypyrrole/Silica-Titania Core/Shell Nanoparticles

Inverted conducting polymer/metal oxide core/shell structured pPPy/SiO₂-TiO₂ nanoparticles were prepared as electrorheological (ER) materials using sequential experimental methods. The core was synthesized via the low-temperature self-assembly of PPy and SiO₂ materials, and the outer TiO₂ shell was easily coated onto the core part using a sol-gel method and a titanium isopropoxide precursor. Sonication-mediated etching and redeposition were employed to etch out SiO₂ portions from the core part to blend with TiO₂ shells. Each step in nanoparticle synthesis involved morphological and physical changes to the surface area and porosity, with subsequent changes in the intrinsic properties of the materials. Specifically, the electrical conductivity and dielectric properties were successfully altered. The final pPPy/SiO₂-TiO₂ nanoparticle configuration was optimized for ER applications, offering low electrical conductivity, high dielectric properties, and increased dispersion stability. pPPy/SiO₂-TiO₂ nanoparticles exhibited 24.7- and 2.7-fold enhancements in ER performance compared to that of PPy-SiO₂ and PPy-SiO₂/TiO₂ precursor nanoparticles, respectively. The versatile method proposed in this study for the synthesis of inverted conducting polymer/metal oxide core/shell nanoparticles shows great potential for the development of custom-designed ER materials.