Fengxiang Chen

Highly Anti-UV Properties of Silk Fiber with Uniform and Conformal Nanoscale TiO2 Coatings via Atomic Layer Deposition

In this study, silk fiber was successfully modified via the application of a nanoscale titania coating using atomic layer deposition (ALD), with titanium tetraisopropoxide (TIP) and water as precursors at 100 °C. Scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscope, and field emission scanning electron microscope results demonstrated that uniform and conformal titania coatings were deposited onto the silk fiber. The thermal and mechanical properties of the TiO2 silk fiber were then investigated. The results showed that the thermal stability and mechanical properties of this material were superior to those of the uncoated substance. Furthermore, the titania ALD process provided the silk fiber with excellent protection against UV radiation. Specifically, the TiO2-coated silk fibers exhibited significant increases in UV absorbance, considerably less yellowing, and greatly enhanced mechanical properties compared with the uncoated silk fiber after UV exposure.

Atomic Layer Deposition of TiO2 for a High-Efficiency Hole-Blocking Layer in Hole-Conductor-Free Perovskite Solar Cells Processed in Ambient Air

In this study we design and construct high-efficiency, low-cost, highly stable, hole-conductor-free, solid-state perovskite solar cells, with TiO2 as the electron transport layer (ETL) and carbon as the hole collection layer, in ambient air. First, uniform, pinhole-free TiO2 films of various thicknesses were deposited on fluorine-doped tin oxide (FTO) electrodes by atomic layer deposition (ALD) technology. Based on these TiO2 films, a series of hole-conductor-free perovskite solar cells (PSCs) with carbon as the counter electrode were fabricated in ambient air, and the effect of thickness of TiO2 compact film on the device performance was investigated in detail. It was found that the performance of PSCs depends on the thickness of the compact layer due to the difference in surface roughness, transmittance, charge transport resistance, electron-hole recombination rate, and the charge lifetime. The best-performance devices based on optimized TiO2 compact film (by 2000 cycles ALD) can achieve power conversion efficiencies (PCEs) of as high as 7.82%. Furthermore, they can maintain over 96% of their initial PCE after 651 h (about 1 month) storage in ambient air, thus exhibiting excellent long-term stability.

Preparation and characterization of novel hydrophobic cellulose fabrics with polyvinylsilsesquioxane functional coatings

A series of novel hydrophobic cotton fabrics with polyvinylsilsesquioxane (PVS) polymer functional coatings were successfully prepared by solution immersion. The influence of the added amount of PVS polymer on the morphology, resistance to thermal and thermooxidative degradation, and hydrophobic properties of the treated cotton fabrics was studied by attenuated total reflection infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and water contact angle measurements, respectively. The experimental results show that the PVS polymer formed a protective film on the surface of the cotton fibers; the resistance to thermal and thermooxidative degradation, and the water-repellent properties of the novel cotton fabrics were also improved with increasing added amount of PVS polymer, compared with that of reference material. The enhancement in the thermal properties of the treated cotton fabrics can likely be attributed to synergistic carbonization between the PVS protective layer and the cellulose fibers during thermal degradation. Meanwhile, it was also found that, with increasing added amount of PVS polymer, the hydrophobicity of the treated cotton fabrics was greatly improved. The noticeable improvement in the hydrophobicity of the treated cotton fabrics is ascribed to the combination of low-surface-energy PVS film and the intrinsically rough surface of the woven cotton fabrics. This strategy for fabricating novel cellulose fabrics provides a guide for the development of high-performance functional cellulose fabrics with tunable properties in the textile industry.

Facile Fabrication of Multifunctional Hybrid Silk Fabrics with Controllable Surface Wettability and Laundering Durability.

To obtain a hydrophobic surface, TiO2 coatings are deposited on the surface of silk fabric using atomic layer deposition (ALD) to realize a hierarchical roughness structure. The surface morphology and topography, structure, and wettability properties of bare silk fabric and TiO2-coated silk fabrics thus prepared are evaluated using scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), scanning probe microscope (SPM), X-ray diffraction (XRD), static water contact angles (WCAs), and roll-off angles, respectively. The surfaces of the silk fabrics with the TiO2 coatings exhibit higher surface roughnesses compared with those of the bare silk fabric. Importantly, the hydrophobic and laundering durability properties of the TiO2-coated silk fabrics are largely improved by increasing the thickness of the ALD TiO2 coating. Meanwhile, the ALD process has a litter effect on the service performance of silk fabric. Overall, TiO2 coating using an ALD process is recognized as a promising approach to produce hydrophobic surfaces for elastic materials.

Adsorption of direct fast scarlet 4BS dye from aqueous solution onto natural superfine down particle

In this study, the agricultural solid waste, natural down fibers were produced into superfine down particle (NSDP), which was used as a low-cost adsorbent for the removal of direct fast scarlet 4BS (DFS-4BS) from aqueous solution. Scanning electron microscopy (SEM), N2 adsorption/desorption, and Fourier Transform infrared spectroscopy (FTIR) were used to characterize the adsorbent material, respectively. The effects of pH, adsorbent dose, initial dye concentration, temperature, and contact time on the adsorption capacity of DFS-4BS by NSDP were studied. The experimental adsorption data were well fitted by Langmuir adsorption isotherm and the maximum adsorption capacity of DFS-4BS by NSDP was found to be 120.34 mg/g at 45 °C, which was higher than other reported adsorbent. Overall, NSDP could be used as an effective and low-cost adsorbent to remove DFS-4BS from industrial wastewater.

Nontoxic (CH3NH3)3Bi2I9 perovskite solar cells free of hole conductors with an alternative architectural design and a solution-processable approach

Methylammonium iodide bismuthate ((CH3NH3)3Bi2I9) (MBI) perovskite was introduced as a new lead-free and air-stable absorber for hole conductor-free perovskite solar cells. The two-step soaking-assisted sequential solution (2-S) method was adopted to fabricate MBI films for the first time. We compared the formation processes and final morphologies of the MBI films fabricated using the 1-S and 2-S methods on planar and mesoporous TiO2 layers, respectively. We also investigated the effects of the morphologies of MBI films and device architectural design on device performance. Results showed that the MBI films fabricated using the 2-S method achieved a superior coverage both on the compact TiO2 and mesoporous TiO2 layers. The mesoporous structure devices presented higher power conversion efficiencies than the planar structure devices. In addition, all devices exhibited excellent thermal and long-term stabilities. The presented architectural design and solution-processable approach could inspire further research and practical applications on lead-free organic–inorganic hybrid perovskite solar cells.

Facile and Effective Coloration of Dye-Inert Carbon Fiber Fabrics with Tunable Colors and Excellent Laundering Durability

Carbon fiber is a good candidate in various applications, including in the military, structural, sports equipment, energy storage, and infrastructure. Coloring of carbon fiber has been a big challenge for decades due to their high degrees of crystallization and insufficient chemical affinity to dyes. Here, multicolored carbon fiber fabrics are fabricated using a feasible and effective atomic layer deposition (ALD) technique. The vibrant and uniform structural colors originating from thin-film interference is simply regulated by controlling the thickness of conformal TiO2 coatings on the surface of black carbon fibers. Impressively, the colorful coatings show excellent laundering durability, which can endure 50 cycles of domestic launderings. Moreover, the mechanical properties only drop off slightly after coloring. Overall, these results open an alternative avenue for development of TiO2 nanostructured films with multifunctional features grown using ALD technologies. This technology is speculated to have potential applications in various fields such as color engineering and radiation-proof fabrics and will further guide material design for future innovations in functional optical and color-display devices. More importantly, this research demonstrates a route for the coloring of black carbon fiber-based materials with vibrant colors.

Exceptional wearability of multifunctional TiO2-coated hybrid silk fabric with controllable ultraviolet-protection properties

Ultraviolet (UV)-protective textiles have attracted significant attention because of their wide applicability. However, the anti-UV coatings of such textiles have an adverse effect on their wearing comfort, and other properties related to luster, softness and handle were also ignored. In this study, TiO2-coated silk fabric with controllable UV-protection properties was successfully fabricated via atomic layer deposition (ALD). The luster, bending properties, crease recovery, mechanical properties, air permeability and anti-UV properties of the TiO2-coated silk fabric were investigated. The results showed that the thickness, whiteness, bendability, tensile strength and anti-UV properties of the silk fabric increased progressively while its air permeability, wet crease recovery angle and dry crease recovery angle decreased with an increase in the thickness of the TiO2 coating. However, the coating did not have a negative effect on the usability of the fabric. Thus, the proposed ALD method is a promising one for modifying the surfaces of elastic textile materials in order to accord them with UV-protection properties.

Preparation of superfine down particles derived from down fiber wastes and their application as an efficient adsorbent toward acid brilliant scarlet 3R

Low-cost superfine down particles (SDP) were evaluated as an adsorbent for the removal of acid brilliant scarlet 3R (ABS-3R) dye from aqueous solutions. Scanning electron microscopy, particle size distribution, Brunauer–Emmett–Teller specific surface area, X-ray diffraction, Fourier transform infrared spectroscopy, and amino-acid analysis were used to characterize the structural characteristics of the adsorbent material. The effects of adsorption process parameters, including initial pH, adsorbent dose, initial dye concentration, adsorption time, and temperature, were systematically studied in batch adsorption experiments. Further, adsorption equilibrium data were modeled by Langmuir, Freundlich, and Dubinin–Radushkevich isotherms. The adsorption process followed the Langmuir isotherm model and the maximum adsorption capacity was 158.23 mg/g at 318 K. Kinetic studies at different temperatures showed that the pseudo-second-order kinetic model fitted well in correlation to the experimental results in comparison to the pseudo-first-order model. The activation energy of the adsorption process was 59.52 kJ/mol, using the Arrhenius equation, which indicated the chemisorption nature of ABS-3R adsorption onto SDP. Thermodynamic study showed that adsorption of ABS-3R was a spontaneous and endothermic process. In summary, SDP was found to be an efficient and eco-friendly adsorbent, which might be suitable for the removal of dyes from aqueous solutions.