Interfacial assembly of mussel-inspired polydopamine@Ag core-shell nanoparticles as highly recyclable catalyst for nitroaromatic pesticides degradation

With the abundant use of pesticides in agriculture and grassland farming, water contamination unavoidably occurs due to the leaching of pesticide residues into environment. Now, most of the research on degradation of nitroaromatic pesticides residues has focused on nano catalysis-based method, however, effective post-reaction separation and recycling of the tiny nanocatalysts is also a significant technological challenge to be addressed. Herein, we report a simple and versatile strategy for the construction of efficient and recyclable catalysts of polydopamine (PDA)@Ag/polystyrene (PS) films for degradation of pesticides based on multi-purpose PDA microspheres inspired by mussel adhesion. The PDA not only functioned as a scaffold, a reductant as well as a stabilizer for the formation and dispersions of Ag NPs in situ, but also served as an adhesive layer between the nanocatalysts and the substrate. The obtained PDA@Ag/PS films were evaluated for the first time against the catalytic degradation of pendimethalin. Most importantly, the recovery of catalysts can be easily realized by simply pulling out PS substrate from the reaction mixture and the catalytic activity of the nanofilms was found to be equally efficient for seven catalytic cycles. Considering their excellent catalytic activity and recyclability in the degradation of nitroaromatic pesticides, the PDA@Ag/PS films have great potential applications in the fields of environment protection, soil contamination remediation, and sewage treatment. Also, by virtue of the remarkable reducing and stabilizing ability and adhesive versatility of PDA, this approach can be extended to the deposition of various metals and semiconducting NPs, which can be stably anchored on a diverse range of solid substrates regardless of physiochemical and morphology.

Highly Efficient and Environmentally Stable Flexible Color Converters Based on Confined CH3NH3PbBr3 Nanocrystals

In this work, we demonstrate a synthetic route to attain methylammonium lead bromide (CH₃NH₃PbBr₃) perovskite nanocrystals (nc-MAPbBr₃, 1.5 nm < size < 3 nm) and provide them with functionality as highly efficient flexible, transparent, environmentally stable, and adaptable color-converting films. We use nanoparticle metal oxide (MOx) thin films as porous scaffolds of controlled nanopores size distribution to synthesize nc-MAPbBr₃ through the infiltration of perovskite liquid precursors. We find that the control over the reaction volume imposed by the nanoporous scaffold gives rise to a strict control of the nanocrystal size, which allows us to observe well-defined quantum confinement effects on the photo-emission, being the luminescence maximum tunable with precision between λ = 530 nm (green) and λ = 490 nm (blue). This hybrid nc-MAPbBr₃/MOx structure presents high mechanical stability and permits subsequent infiltration with an elastomer to achieve a self-standing flexible film, which not only maintains the photo-emission efficiency of the nc-MAPbBr₃ unaltered but also prevents their environmental degradation. Applications as adaptable color-converting layers for light-emitting devices are envisaged and demonstrated.

One Dimensional Photonic Crystals Using Ultrahigh Refractive Index Chalcogenide Hybrid Inorganic/Organic Polymers

We report on the fabrication of wholly polymeric one-dimensional (1-D) photonic crystals (i.e., Bragg reflectors, Bragg mirrors) via solution processing for use in the near (NIR) and the short wave (SWIR) infrared spectrum (1-2 μm) with very high reflectance (R ∼ 90-97%). Facile fabrication of these highly reflective films was enabled by direct access to solution processable, ultrahigh refractive index polymers, termed, Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs). The high refractive index (n) of CHIPs materials (n = 1.75-2.10) allowed for the production of narrow band IR Bragg reflectors with high refractive index contrast (Δn ∼ 0.5) when fabricated with low n polymers, such as cellulose acetate (n = 1.47). This is the highest refractive index contrast (Δn ∼ 0.5) demonstrated for an all-polymeric Bragg mirror which directly enabled high reflectivity from films with 22 layers or less. Facile access to modular, thin, highly reflective films from inexpensive CHIPs materials offers a new route to IR Bragg reflectors and other reflective coatings with potential applications for IR photonics, commercial sensing, and LIDAR applications.

Photonic structuring improves the colour purity of rare-earth nanophosphors

Nanophosphor integration in an optical cavity allows unprecedented control over both the chromaticity and the directionality of the emitted light, without modifying the chemical composition of the emitters or compromising their efficiency. Our approach opens a route towards the development of nanoscale photonics based solid state lighting.

Nanophotonic-Engineered Photothermal Harnessing for Waste Heat Management and Pyroelectric Generation

At present, there are various limitations to harvesting ambient waste heat which include the lack of economically viable material and innovative design features that can efficiently recover low grade heat for useful energy conversion. In this work, a thermal nanophotonic-pyroelectric (TNPh-pyro) scheme consisting of a metamaterial multilayer and pyroelectric material, which performs synergistic waste heat rejection and photothermal heat-to-electricity conversion, is presented. Unlike any other pyroelectric configuration, this conceptual design deviates from the conventional by deliberately employing back-reflecting NIR to enable waste heat reutilization/recuperation to enhance pyroelectric generation, avoiding excessive solar heat uptake and also retaining high visual transparency of the device. Passive solar reflective cooling up to 4.1 °C is demonstrated. Meanwhile, the photothermal pyroelectric performance capitalizing on the back-reflecting effect shows an open circuit voltage (V_oc) and short circuit current (I_sc) enhancement of 152 and 146%, respectively. In addition, the designed photoactive component (TiO₂/Cu) within the metamaterial multilayer provides the TNPh-pyro system with an effective air pollutant photodegradation functionality. Finally, proof-of-concept for concurrent photothermal management and enhanced solar pyroelectric generation under a real outdoor environment is demonstrated.

Catechol-based layer-by-layer assembly of composite coatings: a versatile platform to hierarchical nano-materials

Inspired by the marine mussel's ability to adhere to surfaces underwater, an aqueous catechol-based dip coating platform was developed. Using a catechol-functionalized polyacrylamide binder in combination with inorganic nanoparticles enables the facile fabrication of robust composite coatings via a layer-by-layer process. This modular assembly of well-defined building blocks provides a versatile alternative to electrostatic driven approaches with layer thickness and refractive indices being readily tunable. The platform nature of this approach enables the fabrication of hierarchically ordered nano-materials such as Bragg stacks.

Mesoporous TiO₂ Bragg stack templated by graft copolymer for dye-sensitized solar cells

Organized mesoporous TiO₂ Bragg stacks (om-TiO₂ BS) consisting of alternating high and low refractive index organized mesoporous TiO₂ (om-TiO₂) films were prepared to enhance dye loading, light harvesting, electron transport, and electrolyte pore-infiltration in dye-sensitized solar cells (DSSCs). The om-TiO₂ films were synthesized via a sol-gel reaction using amphiphilic graft copolymers consisting of poly(vinyl chloride) backbones and poly(oxyethylene methacrylate) side chains, i.e., PVC-g-POEM as templates. To generate high and low index films, the refractive index of om-TiO₂ film was tuned by controlling the grafting ratio of PVC-g-POEM via atomic transfer radical polymerization (ATRP). A polymerized ionic liquid (PIL)-based DSSC fabricated with a 1.2-μm-thick om-TiO₂ BS-based photoanode exhibited an efficiency of 4.3%, which is much higher than that of conventional DSSCs with a nanocrystalline TiO₂ layer (nc-TiO₂ layer) (1.7%). A PIL-based DSSC with a heterostructured photoanode consisting of 400-nm-thick organized mesoporous TiO₂ interfacial (om-TiO₂ IF) layer, 7-μm-thick nc-TiO₂, and 1.2-μm-thick om-TiO₂ BS as the bottom, middle and top layers, respectively, exhibited an excellent efficiency of 7.5%, which is much higher than that of nanocrystaline TiO₂ photoanode (3.5%).

Modulation of polymer refractive indices with diamond nanoparticles for metal-free multilayer film mirrors

Modulation of the refractive index of a polymer was achieved by combining it with diamond nanoparticles (NDs). The increase in the refractive index was controlled by the amount of NDs added, according to the Lorentz-Lorenz equation. The refractive index of poly(vinyl alcohol) (PVA), which was used as the base polymer, increased from 1.52 to 1.88. A multilayer film consisting of alternating layers of ND-PVA composite and poly(methyl methacrylate) exhibited ca. 80% reflectance with 10 bilayers.