Bioinspired Photoelectronic Synergy Coating with Antifogging and Antibacterial Properties

Optically transparent glass with antifogging and antibacterial properties is in high demand for endoscopes, goggles, and medical display equipment. However, many of the previously reported coatings have limitations in terms of long-term antifogging and efficient antibacterial properties, environmental friendliness, and versatility. In this study, inspired by catfish and sphagnum moss, a novel photoelectronic synergy antifogging and antibacterial coating was prepared by cross-linking polyethylenimine-modified titanium dioxide (PEI-TiO2), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA). The as-prepared coating could remain fog-free under hot steam for more than 40 min. The experimental results indicate that the long-term antifogging properties are due to the water absorption and spreading characteristics. Moreover, the organic-inorganic hybrid of PEI and TiO2 was first applied to enhance the antibacterial performance. The Staphylococcus aureus and the Escherichia coli growth inhibition rates of the as-prepared coating reached 97 and 96% respectively. A photoelectronic synergy antifogging and antibacterial mechanism based on the positive electrical and photocatalytic properties of PEI-TiO2 was proposed. This investigation provides insight into designing multifunctional bioinspired surface materials to realize antifogging and antibacterial that can be applied to medicine and daily lives.

In Situ Photoactivated Antibacterial and Antioxidant Composite Materials to Promote Bone Repair

Trauma and tumor removal usually cause bone defects; in addition, the related postoperative infection also shall be carefully considered clinically. In this study, polylactic acid (PLLA) composite fibers containing Cerium oxide (CeO2) are first prepared by electrospinning technology. Then, the PLLA/CeO2@PDA/Ag composite materials are successfully prepared by reducing silver ion (Ag+) to nano-silver (AgNPs)  coating in situ and binding AgNPs to the materials surface by mussel structure liked polydopamine (PDA). In the materials, Ag+ can be slowly released in simulated body fluids. Based on the photothermal performance of AgNPs, the photothermal conversion efficiency of the materials is 21%, under NIR 808 nm illumination. The effective photothermal conversion can help materials fighting with E. coli and S. aureus in 3 h, with an antibacterial rate of 100%. Additionally, the sustained Ag+ release contributes to the antibacterial in long term. Meanwhile, the materials can mimic the bio-behavior of superoxide dismutase and catalase in decreasing the singlet oxygen level and removing the excess reactive oxygen species. Furthermore, the materials are beneficial for cell proliferation and osteogenic differentiation in vitro. In this study, a promising bone-regenerated material with high photothermal conversion efficiency and antibacterial and anti-oxidation properties, is successfully constructed.

Multi-Stimuli-Responsive Tadpole-like Polymer/Lipid Janus Microrobots for Advanced Smart Material Applications

Microrobots are of significant interest due to their smart transport capabilities, especially for precisely targeted delivery in dynamic environments (blood, cell membranes, tumor interstitial matrixes, blood-brain barrier, mucosa, and other body fluids). To perform a more complex micromanipulation in biological applications, it is highly desirable for microrobots to be stimulated with multiple stimuli rather than a single stimulus. Herein, the biodegradable and biocompatible smart micromotors with a Janus architecture consisting of PrecirolATO 5 and polycaprolactone compartments inspired by the anisotropic geometry of tadpoles and sperms are newly designed. These bioinspired micromotors combine the advantageous properties of polypyrrole nanoparticles (NPs), a high near-infrared light-absorbing agent with high photothermal conversion efficiency, and magnetic NPs, which respond to the magnetic field and exhibit multistimulus-responsive behavior. By combining both fields, we achieved an "on/off" propulsion mechanism that can enable us to overcome complex tasks and limitations in liquid environments and overcome the limitations encountered by single actuation applications. Moreover, the magnetic particles offer other functions such as removing organic pollutants via the Fenton reaction. Janus-structured motors provide a broad perspective not only for biosensing, optical detection, and on-chip separation applications but also for environmental water treatment due to the catalytic activities of multistimulus-responsive micromotors.

Vapor-Phase Synthesis of Molecularly Imprinted Polymers on Nanostructured Materials at Room-Temperature

Molecularly imprinted polymers (MIPs) have recently emerged as robust and versatile artificial receptors. MIP synthesis is carried out in liquid phase and optimized on planar surfaces. Application of MIPs to nanostructured materials is challenging due to diffusion-limited transport of monomers within the nanomaterial recesses, especially when the aspect ratio is >10. Here, the room temperature vapor-phase synthesis of MIPs in nanostructured materials is reported. The vapor phase synthesis leverages a >1000-fold increase in the diffusion coefficient of monomers in vapor phase, compared to liquid phase, to relax diffusion-limited transport and enable the controlled synthesis of MIPs also in nanostructures with high aspect ratio. As proof-of-concept application, pyrrole is used as the functional monomer thanks to its large exploitation in MIP preparation; nanostructured porous silicon oxide (PSiO2 ) is chosen to assess the vapor-phase deposition of PPy-based MIP in nanostructures with aspect ratio >100; human hemoglobin (HHb) is selected as the target molecule for the preparation of a MIP-based PSiO2 optical sensor. High sensitivity and selectivity, low detection limit, high stability and reusability are achieved in label-free optical detection of HHb, also in human plasma and artificial serum. The proposed vapor-phase synthesis of MIPs is immediately transferable to other nanomaterials, transducers, and proteins.

A polypyrrole-mediated photothermal biosensor with a temperature and pressure dual readout for the detection of protein biomarkers

A novel photothermal biosensor with a temperature and pressure dual readout was developed for CRP detection. The in situ synthesized polypyrrole exhibits photothermal effect under NIR light to increase temperature and pressure for portable readout.

Photonic Multilayer Structure Induced High Near-Infrared (NIR) Blockage as Energy-Saving Window

Energy-saving window that selectively blocks near-infrared (NIR) is a promising technology to save energy consumption. However, it is hard to achieve both high transmittance in visible light and high reflectance in NIR for the energy-saving windows. Here, a TiO₂ /Ag/TiO₂ /SiO₂ /TiO₂ multilayer is demonstrated on a glass substrate to selectively block NIR while maintaining high transmittance to visible light. The thickness of a TiO₂ /Ag/TiO₂ structure is first design and optimized; the metal layer reflects NIR and the dielectric layers increase transmittance of visible light with zero reflection condition. To further enhance NIR-blocking capability, a TiO₂ back reflector is implemented with a SiO₂ spacer to TiO₂ /Ag/TiO₂ structure. The back reflector can induce additional Fresnel reflection without sacrificing transmittance to visible light. The optimal TiO₂ (32 nm)/Ag (22 nm)/TiO₂ (30 nm)/SiO₂ (100 nm)/TiO₂ (110 nm)/glass shows solar energy rejection 89.2% (reflection 86.5%, absorption 2.7%) in NIR, visible transmittance 69.9% and high long-wave (3 ≤ λ ≤ 20 µm) reflectance > 95%. This proposed visible-transparent, near-infrared-reflecting multilayer film can be applied to the windows of buildings and automobiles to reduce the energy consumption.

Carbon Nanomaterials Embedded in Conductive Polymers: A State of the Art

Carbon nanomaterials are at the forefront of the newest technologies of the third millennium, and together with conductive polymers, represent a vast area of indispensable knowledge for developing the devices of tomorrow. This review focusses on the most recent advances in the field of conductive nanotechnology, which combines the properties of carbon nanomaterials with conjugated polymers. Hybrid materials resulting from the embedding of carbon nanotubes, carbon dots and graphene derivatives are taken into consideration and fully explored, with discussion of the most recent literature. An introduction into the three most widely used conductive polymers and a final section about the most recent biological results obtained using carbon nanotube hybrids will complete this overview of these innovative and beyond belief materials.

Photothermal-Irradiated Polyethyleneimine-Polypyrrole Nanopigment Film-Coated Polyethylene Fabrics for Infrared-Inspired with Pathogenic Evaluation

Influenza, pneumonia, and pathogenic infection of the respiratory system are boosted in cold environments. Low temperatures also result in vasoconstriction, restraint of blood flow, and decreased oxygen to the heart, and the risk of a heart attack would increase accordingly. The present face mask fabric fails to preserve its air-filtering function as its electrostatic function vanishes once exposed to water. Therefore, its filtering efficacy would be decreased meaningfully, making it nearly impracticable to reuse the disposable face masks. The urgent requirement for photothermal fabrics is also rising. Nanobased polyethyleneimine-polypyrrole nanopigments (NPP NPs) have been developed and have strong near-infrared spectrum absorption and exceptional photothermal convertible performance. Herein, the mask fabric used PE-fiber-constructed membrane (PEFM) was coated by the binding affinity of the cationic polyethyleneimine component of NPP NPs forming NPP NPs-PEFM. To the best of our knowledge, no study has investigated NPP NP-coated mask fabric to perform infrared red (solar or body) photothermal conversion efficacy to provide biocompatible warming, remotely photothermally captured antipathogen, and antivasoconstriction in vivo. This pioneering study showed that the developed NPP NPs-PEFM could be washable, reusable, breathable, biocompatible, and photothermal conversable for active eradication of pathogenic bacteria. Further, it possesses warming preservation and antivasoconstriction.

A low-cost paper-based flexible energy storage device using a conducting polymer nanocomposite

Herein, a simple approach is demonstrated for the fabrication of a paper-based flexible symmetrical supercapacitor as an energy saving device with composite functional materials of nickel nanoparticles (Ni NPs) and polypyrrole (PPy).

Cell-Laden Electroconductive Hydrogel Simulating Nerve Matrix To Deliver Electrical Cues and Promote Neurogenesis

Natural nerve tissue is composed of nerve bundles with multiple aligned assembles, and matrix electroconductivity is beneficial to the transmission of intercellular electrical signals, or effectively deliver external electrical cues to cells. Herein, aiming at the biomimetic design of the extracellular matrix for neurons, we first synthesized electroconductive polypyrrole (PPy) nanoparticles with modified hydrophilicity to improve their uniformity in collagen hydrogel. Next, cell-laden collagen-PPy hybrid hydrogel microfibers with highly oriented microstructures were fabricated via a microfluidic chip. The hydrogel microfibers formed a biomimetic three-dimensional microenvironment for neurons, resulting from the native cell adhesion domains, oriented fibrous structures, and conductivity. The oriented fibrous microstructures enhanced neuron-like cells aligning with fibers' axon; the matrix conductivity improved cell extension and upregulated neural-related gene expression; moreover, external electrical stimulation further promoted the neuronal functional expression. This mechanism was attributed to the electroconductive matrix and its delivered electrical stimulation to cells synergistically upregulated the expression of an L-type voltage-gated calcium channel, resulting in an increase in the intracellular calcium level, which in turn promoted neurogenesis. This approach has potential in constructing the biomimetic microenvironment for neurogenesis.

Synthesis of Solution-Stable PEDOT-Coated Sulfonated Polystyrene Copolymer PEDOT:P(SS-co-St) Particles for All-Organic NIR-Shielding Films

We prepared poly(3,4-ethylenedioxythiophene) (PEDOT)-coated sulfonated polystyrene copolymer particles as efficient heat-shielding agents, which showed strong near-infrared (NIR) absorption, with high solid contents and good solution stability. The poly(styrene sulfonate-co-styrene) (P(SS-co-St)) copolymers were successfully synthesized via radical solution polymerization, and PEDOT-coated P(SS-co-St) (PEDOT:P(SS-co-St)) was synthesized via Fe+-catalyzed oxidative polymerization. PEDOT:P(SS-co-St) was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopies. The particle size and morphology of PEDOT:P(SS-co-St) were examined using transmission electron microscopy, dynamic light scattering, and zeta potential measurements. The maximum NIR-shielding efficiency of the film was 92.0% with 40% transmittance. The high solution stability of PEDOT:P(SS-co-St) make it an ideal candidate for heat-insulating materials that find application in semi-transparent heat-insulator-coated windows.

Interactive effects of solar UV radiation and climate change on material damage

Solar UV radiation adversely affects the properties of organic materials used in construction, such as plastics and wood.

Facile synthesis of P(EDOT/Ani) : PSS with enhanced heat shielding efficiency via two-stage shot growth

Poly(3,4-ethylenedioxythiophene/aniline) : poly(styrene sulfonate), P(EDOT/Ani) : PSS, with enhanced absorption of near infrared light, was prepared by oxidative polymerization. We demonstrated that a two-stage shot growth process optimizes the absorption of the polymer in the near infrared region via a controlled monomer addition time. In other words, the optical properties of the polymer complex were improved by controlling the time intervals of aniline monomer addition. P(EDOT/Ani) : PSS was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The shielding efficiency of the P(EDOT/Ani) : PSS films was calculated by using data from ultraviolet, visible, and near infrared (UV-vis-NIR) spectroscopy. The introduction of polyaniline to PEDOT increased the absorption in the near infrared area. In comparison with PEDOT : PSS film, the total shielding efficiency of the P(EDOT/Ani) : PSS film increased to 65.8% from 54.6% at 60% transmittance. The maximum NIR shielding efficiency (SE_NIR) of the film is 92.7% and the transmittance is 46.5%. Also, large-scale P(EDOT/Ani) : PSS film was fabricated using roll-to-roll slot-die equipment and a heat shielding test of the film was conducted by measuring the temperature variation, in order to prove the enhanced heat shielding effect. P(EDOT/Ani) : PSS prepared by a two-stage shot growth system showed excellent potential as a heat shielding material.

Poly(3,4-ethylenedioxythiophene/aniline) : poly(styrene sulfonate), P(EDOT/Ani) : PSS, with enhanced absorption of near infrared light, was prepared by oxidative polymerization.

Gradual modification of ITO particle's crystal structure and optical properties by pulsed UV laser irradiation in a free liquid jet

Indium tin oxide (ITO) particle coatings are known for high transparency in the visible, good conductive properties and near-infrared absorption. These properties depend on ITO particle's stoichiometric composition, defects and size. Here we present a method to gradually change ITO particle's optical properties by a simple and controlled laser irradiation process. The defined irradiation process and controlled energy dose input allows one to engineer the absorption and transmission of coatings made from these particles. We investigate the role of the surrounding solvent, influence of laser fluence and the specific energy dose targeting modification of the ITO particle's morphology and chemistry by stepwise laser irradiation in a free liquid jet. TEM, SEM, EDX, XPS, XRD and Raman are used to elucidate the structural, morphological and chemical changes of the laser-induced ITO particles. On the basis of these results the observed modification of the optical properties is tentatively attributed to chemical changes, e.g. laser-induced defects or partial reduction.