Polyurethane-polypyrrole hybrid structural color films for dual-signal mechanics sensing

Flexible Inverse Opal Structural Color Films with High Strength and Harsh Environment Stability

Flexible photonic crystals (PCs) constructed by PCs and special polymers are very promising to achieve a combination of vivid structural colors, mechanical robustness, and environment stability. However, PCs that incorporate polymer binders are still susceptible to destruction and subsequent loss of structural color when subjected to significant external forces or harsh environments. Besides, because most of these polymers are highly flammable, crucial fire safety is difficult to be guaranteed in the application of these materials. In this study, we report a poly(m-phenyleneisophthalamide) inverse opal (PMIA IO) structural color film through a SiO2 PC template sacrificing method. Benefiting from the high rigid PMIA molecular structural configuration, the PMIA IO films are able to maintain their structural colors even in harsh conditions, such as large tensile stress, high and low temperatures, potent acids and bases, and ultraviolet radiation. More attractively, the PMIA IO films demonstrate excellent flame retardancy, with the limiting oxygen index (LOI) and flame retardant rating reaching 28 vol % and V0, respectively. We believe that the flexible structural color films with high strength, harsh environment stability, and flame retardancy, which are difficult for other structural color materials to possess simultaneously, have great potential for special applications in fire protection, national defense, aviation, marine, and aerospace fields.

Thermoresponsive Lamellar Hydrogels with Tunable Turbidity, Structural Color, and Anisotropic Swelling

We report a thermoresponsive anisotropic photonic hydrogel: poly(dodecyl glyceryl itaconate)/polyacrylamide-poly(N-isopropylacrylamide) hydrogel (PDGI/PAAm-PNIPAM hydrogel). Hydrogels with uniaxially aligned lamellar bilayers possess bright structural color and swelling anisotropy, while PNIPAM-based hydrogels exhibit distinct thermoresponsive properties around a lower critical solution temperature (LCST). Hybridization of thermoresponsive PNIPAM with the lamellar hydrogel can give the anisotropic photonic hydrogel various fascinating thermoresponsive properties, such as structural color/turbid transition, thermoresponsive structural color, and anisotropic deswelling/reswelling behavior by temperature stimuli. The temperature-induced changes in turbidity, structural color, and anisotropic swelling of the gel around the LCST can be tuned by controlling the incorporated PNIPAM density. PNIPAM can be regioselectively incorporated into the specific region of the lamellar hydrogels by photomasking during UV polymerization. The PDGI/PAAm-PNIPAM hydrogel can find diverse promising applications such as smart windows and smart displays.

Tunable Structural Coloration in Eccentric Water-in-Oil-in-Water Droplets

Structural colors show diverse advantages such as fade resistance, eco-friendliness, iridescence, and high saturation in comparison with chemical pigments. In this paper, we show tunable structural coloration in colorless water-in-oil-in-water double emulsion droplets via total internal reflection and interference at the microscale concave interfaces. Through experimental work and simulations, we demonstrate that the shell thickness and the eccentricity of the core-shell structures are key to the successful formation of iridescent structural colors. Only eccentric thin-shell water-in-oil-in-water droplets show structural colors. Importantly, structural colors based on water-oil interfaces are readily responsive to a variety of environmental stimuli, such as osmotic pressure, temperature, magnetic fields, and light composition. This work highlights an alternative structural coloration that expands the applications of droplet-based structural colors to aqueous systems.

Swarming Responsive Photonic Nanorobots for Motile-Targeting Microenvironmental Mapping and Mapping-Guided Photothermal Treatment

Micro/nanorobots can propel and navigate in many hard-to-reach biological environments, and thus may bring revolutionary changes to biomedical research and applications. However, current MNRs lack the capability to collectively perceive and report physicochemical changes in unknown microenvironments. Here we propose to develop swarming responsive photonic nanorobots that can map local physicochemical conditions on the fly and further guide localized photothermal treatment. The RPNRs consist of a photonic nanochain of periodically-assembled magnetic Fe3O4 nanoparticles encapsulated in a responsive hydrogel shell, and show multiple integrated functions, including energetic magnetically-driven swarming motions, bright stimuli-responsive structural colors, and photothermal conversion. Thus, they can actively navigate in complex environments utilizing their controllable swarming motions, then visualize unknown targets (e.g., tumor lesion) by collectively mapping out local abnormal physicochemical conditions (e.g., pH, temperature, or glucose concentration) via their responsive structural colors, and further guide external light irradiation to initiate localized photothermal treatment. This work facilitates the development of intelligent motile nanosensors and versatile multifunctional nanotheranostics for cancer and inflammatory diseases.

Quantitative analysis of phenanthrene in soil by fluorescence spectroscopy coupled with the CARS-PLS model

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants in soil and are teratogenic and carcinogenic. Therefore, rapid and accurate analysis of PAHs in soil can provide a theoretical basis and data support for soil contamination risk assessment. In this work, a fluorescence spectroscopy technique combined with partial least squares (PLS) was proposed for rapid quantitative analysis of phenanthrene (PHE) in soil. At first, the fluorescence spectra of 29 soil samples with different concentrations (0.3-10 mg g-1) of PHE were collected by RF-5301 PC fluorescence spectrophotometer. Secondly, the effects of different spectral preprocessing methods were investigated on the prediction performance of the PLS calibration model. And then, the influence of competitive adaptive reweighted sampling (CARS) wavelength points on the prediction performance of PLS calibration model was discussed. Finally, according to the selected wavelength points, a quantitative analytical model for PHE content in soil was constructed using the PLS calibration method. To further explore the predictive performance of the CARS-PLS calibration model, the predictive results were compared with those of the RAW spectrum-partial least squares calibration model (RAW-PLS) and the wavelet transform-standard normal variation (WT-SNV) calibration model. The CARS-PLS calibration model showed the optimal predictive performance and its coefficient of determination of cross-validation (R cv 2) and root mean square error of 10-fold cross-validation (RMSEcv) were 0.9957 and 18.98%, respectively. The coefficient of determination of prediction set (R p 2) and root mean square error of prediction set (RMSEp) were 0.9963 and 16.13%, respectively. Hence, the CARS algorithm based on fluorescence spectrum coupled with PLS can give a rapid and accurate quantitative analysis of the PHE content in soil.