Enhanced sunlight photocatalytic activity of porous TiO2 hierarchical nanosheets derived from petal template

Conformal Self-Assembly of Nanospheres for Light-Enhanced Airtightness Monitoring and Room-Temperature Gas Sensing

The fabrication of conformal nanostructures on microarchitectures is of great significance for diverse applications. Here a facile and universal method was developed for conformal self-assembly of nanospheres on various substrates including convex bumps and concave holes. Hydrophobic microarchitectures could be transferred into superhydrophilic ones using plasma treatment due to the formation of numerous hydroxyl groups. Because of superhydrophilicity, the nanosphere suspension spread on the microarchitectures quickly and conformal self-assembly of nanospheres can be realized. Besides, the feature size of the conformal nanospheres on the substrates could be further regulated by plasma treatment. After transferring two-dimensional tungsten disulfide sheets onto the conformal nanospheres, the periodic nanosphere array was demonstrated to be able to enhance the light harvesting of WS2. Based on this, a light-enhanced room-temperature gas sensor with a fast recovery speed (<35 s) and low detecting limit (500 ppb) was achieved. Moreover, the WS2-covered nanospheres on the microarchitectures were very sensitive to the changes in air pressure due to the formation of suspended sheets on the convex bumps and concave holes. A sensitive photoelectronic pressure sensor that was capable of detecting the airtightness of vacuum devices was developed using the WS2-decorated hierarchical architectures. This work provides a simple method for the fabrication of conformal nanospheres on arbitrary substrates, which is promising for three-dimensional microfabrication of multifunctional hierarchical microarchitectures for diverse applications, such as biomimetic compound eyes, smart wetting surfaces and photonic crystals.

Preparation and characterization of TiO2 based on wood templates

Titanium dioxide (TiO₂) was prepared from four natural wood spices that served as templates. The wood templates were impregnated by a titanium dioxide precursor and then underwent high-temperature calcination to obtain TiO₂ with a wood-like hierarchical porous structure. The microstructure of TiO₂ based on the wood template was characterized by scanning electron microscopy, X-ray diffraction and nitrogen adsorption–desorption tests. The formaldehyde adsorption and degradation properties of TiO₂ based on a wood template are discussed. The results showed that TiO₂ based on a wood template could effectively replicate the micro- and mesoscopic pore structure of wood, and the pore size distribution in the TiO₂ ranged from 1 to 100 nm. The TiO₂ that was prepared based on a wood template showed a certain adsorption effect on formaldehyde under visible light, and the photocatalytic degradation of a formaldehyde solution was achieved when irritated by ultraviolet light. In addition, the properties of the TiO₂ prepared by different tree species was also different. The TiO₂ prepared by larch and Chinese fir exhibited a large specific surface area, pore volume, and high degradation efficiency of formaldehyde solution. After 280 min of irradiation with an ultraviolet light source, the degradation rates of the formaldehyde solution were 19.91% and 18.85%.

Olive Leaves as Biotemplates for Enhanced Solar-Light Harvesting by a Titania-Based Solid

Olive leaves (by-product from olive oil production in olive mills) were used as biotemplates to synthesize a titania-based artificial olive leaf (AOL). Scanning electron microscopy (SEM) images of AOL showed the successful replication of trichomes and internal structure channels present in olive leaves. The BET surface area of AOL was 52 m²·g^-1. X-ray diffraction (XRD) and Raman spectra revealed that the resulting solid was in the predominantly-anatase crystalline form (7.5 nm average particle size). Moreover, the synthesis led to a red-shift in light absorption as compared to reference anatase (gap energies of 2.98 and 3.2 eV, respectively). The presence of surface defects (as evidenced by X-ray photoelectron spectroscopy, XPS, and electron paramagnetic resonance spectroscopy, EPR) and doping elements (e.g., 1% nitrogen, observed by elemental analysis and XPS) could account for that. AOL was preliminarily tested as a catalyst for hydrogen production through glycerol photoreforming and exhibited an activity 64% higher than reference material Evonik P25 under solar irradiation and 144% greater under ultraviolet radiation, (under voltage) UV.

Bio-mimicking TiO2 architectures for enhanced photocatalytic activity under UV and visible light

A multi-step chemical replication method using natural green leaves as templates can produce a porous, visible-light active TiO₂-based photocatalyst.

Synthesis of hierarchically porous structured CaCO3 and TiO2 replicas by sol-gel method using lotus root as template

Intensive attention has been put in mimicking the morphologies in nature owing to their uniqueness, complexity, and diversity. One of the effective approaches to mimic bio-morphologies is through biotemplating - the technique of using biological structures as template to reproduce intricate structure in other forms of materials. This work presents a facile sol-gel technique that can be widely used to convert various carbon-rich bio-structures into different materials. Lotus root, a biomorphic template with high porosity at varying length scales, was selected as the example to demonstrate this approach. The experiment was conducted by infiltrating precursors - titanium (IV) n-butoxide (TnBT) and acetic acid calcium solution - into the lotus root template under vacuum system, followed by calcination. After the treatment, the replicas were calcite CaCO3 and anatase TiO2. In both CaCO3 and TiO2 replicas, the intact structure of the template was preserved. In spite of the overall similarity of the CaCO3 and TiO2 lotus root replicas, some respective differences were found. TiO2 replica was covered with nanowire bundles of 100-200nm in diameter, formed by preferable crystallization of particles, while CaCO3 replica presented the gradient-distributed pores of 10-100μm, which greatly resembled the microstructure of lotus root template. In the BET result, TiO2 replica was mesoporous structure with pores centralizing in 3-4nm. On the other hand, CaCO3 replica had pores in a wider distribution ranging from micro to macro scale. In addition, the surface area was greatly enhanced in both cases. The synthesized materials with hierarchical biomorphic structures may have great potential for purification applications due to their large specific surface area, photocatalytic property, and high adsorption rate.

A versatile bio-inspired material platform for catalytic applications: micron-sized “buckyball-shaped” TiO2structures

A simple sol–gel synthesis method is presented for the production of micron-sized buckyball-like TiO₂architectures using naturally occurringLycopodium clavatum(LC) spores as biotemplates.

Hierarchical porous TiO2 templated from natural Artemia cyst shells for photocatalysis applications

A novel hierarchical porous TiO₂ is synthesized using a natural Artemia cyst shell as template, showing improved photocatalytic performance.