Yanxi Zhu

Hydrogel improved the response in the titania/graphene oxide one-dimensional photonic crystals.

Recently, one-dimensional photonic crystals (1DPCs) have attracted considerable interest because they exhibit a material-specific response profile to external stimuli. In our previous work, TiO2/GO 1DPCs, the stopbands of which can be made to span the whole visible range, were fabricated by spin-coating technique. The prepared 1DPCs have a double response to both dimethyl sulfoxide and alkali solution. However, the response is slow, insensitive, and irreversible. To improve the responsiveness of the 1DPCs, poly(ethylene glycol) (PEG)-cross-linked poly((methyl vinyl ether)-co-maleic acid) (PMVE-co-MA) hydrogels were embedded in those crystals. The results demonstrated that modified 1DPCs with different stopbands could be obtained by controlling the speed of the spin-coating technique. The prepared 1DPCs have better responsiveness to external solution pH.

Patterned one-dimensional photonic crystals with acidic/alkali vapor responsivity

A series of patterning responsive one-dimensional photonic crystals (1DPCs) were developed by using a photolithography technique to etch the template for acidic/alkali vapor sensing by the naked eye through a change in color.

Highly transparent and self-healing films based on the dynamic Schiff base linkage

Self-healing optically transparent coatings have attracted significant attention due to their high transparency and ability to heal damages at the same time. In this study, we report an optically transparent and self-healing film via a layer by layer assembly. This film is based on chitosan (CS) and poly(ethylene glycol) functionalized by dialdehyde groups (DF-PEG). The dynamic equilibrium of Schiff base linkage between the aldehyde groups on DF-PEG and amino groups on CS resulted in the self-healing property of the film. The CS/DF-PEG film can heal damages several times at the same location. Moreover, the Schiff base-bonded CS/DF-PEG films are highly transparent with a transmittance of up to 99.47%, and the transmittance of the film can remain at 99% after ten damage/healing processes. The combination of self-healing property and high transparency provides a new method for fabricating the optically transparent devices.

Self-healing polyelectrolyte multilayer composite film with microcapsules

Self-healing materials are gradually being developed because they can restore structural properties and maintain their function after being damaged. Here, branched poly(ethyleneimine) (bPEI), poly(acrylic acid) (PAA), and microcapsules were used to fabricate a functional (bPEI/PAA)*30-microcapsule composite PEM film based on a layer-by-layer (LbL) self-assembly technique. As a proof of concept, the model molecules hydrophilic rhodamine B (RB) and hydrophobic roxithromycin (ROX) were loaded in (bPEI/PAA)*30-microcapsule composite PEM films, and tests with these self-healing films showed them to be endowed with the desired functional properties and hence showed the microcapsules to constitute a promising functional carrier candidate. The results indicated that the microcapsules can be assembled successfully on polyelectrolyte multilayer (PEM) films, and the as-prepared (bPEI/PAA)*30-microcapsule composite PEM film can not only be tailored with desired properties but also show an excellent self-healing ability. Based on our study, we expect more functional molecules to be grafted onto self-healing PEM films using microcapsules and expect functional self-healing PEM composite films to have great potential applications in the future.

Aptamer-functionalized P(NIPAM-AA) hydrogel fabricated one-dimensional photonic crystals (1DPCs) for colorimetric sensing

As heavy metals cannot be biodegraded and are easily accumulated in food chain organisms and so enter the human body, a simple detection method becomes particularly important for human health. A robust means for the visual detection of highly toxic mercury ion (Hg2+) is developed with aptamer-functionalized one-dimensional photonic crystals (1DPCs). 1DPCs consisting of TiO2 and poly(N-isopropylacrylamide-acrylic acid), P(NIPAM-AA), were successfully fabricated by a spin-coating technique, whose stopbands span the total visible range. When the 1DPCs were exposed to mercury ion solution, the specific binding of cross-linked single-stranded aptamers and heavy metal ions in the hydrogel network caused the hydrogel to shrink. At the same time, there was a homologous blue shift in the Bragg diffraction peak position of the TiO2/P(NIPAM-AA) 1DPCs. The shift value could be used to estimate the number of target ions quantitatively. It was found that the 1DPCs apta-sensor could screen a wide concentration range of heavy metal ions with selectivity and sensitivity. It is expected that the technology may also be widely used in screening a wide range of metal ions in drugs, food, and the environment.

Self-healing polyelectrolyte multilayered coating for anticorrosion on carbon paper

Ideally, if the corrosion resistance coating on carbon paper (CP) can be endowed with the self-healing property, the service life and the reliability of the carbon paper will be greatly increased as the gas diffusion layer. In this paper, different cycles of s branched poly (ethyleneimine) (bPEI) and poly (acrylic acid) (PAA) were modified on the surface of the carbon paper via layer-by-layer (LbL) self-assembly technology. The prepared polyelectrolyte multilayered coatings can not only protect the carbon fiber from corrosion, but also take advantages of the surrounding water to quickly repair themselves after damaged. The effects of the assembly cycles on morphology, resistance, air permeability and the contact angle of carbon papers were investigated, then the differences of the carbon papers in electrolysis process were explored. The results reveal that all the prepared coatings can protect carbon papers from corrosion, while when the assembly cycles was 10, the coatings are most efficient.

Humidity responsive self-healing based on intermolecular hydrogen bonding and metal–ligand coordination

Here, we report the fabrication of a self-healing, colorful polyelectrolyte multilayer (PEM) composite film with humidity responsive properties, based on intermolecular hydrogen bonding and metal–ligand coordination. The synthetic strategy involves the fabrication of multilayer chitosan (CS)/polyacrylic acid (PAA) film with a layer-by-layer (LbL) self-assembly technique, followed by immersing the resulting CS/PAA PEM film in a cobalt chloride solution. According to the theory calculation and experimental results, cobalt chloride annealing treatment plays a critical role in rebuilding the reversible interactions that facilitate the PEM film to heal the mechanical damages and endow the PEM film with the property of reversibly changing its color in different conditions of humidity. Such a metal induced, humidity responsive, self-healing PEM film may broaden the application of the self-healing materials.

Graphene oxide hydrogel improved sensitivity in one-dimensional photonic crystals for detection of beta-glucan

Hydrogels are environment sensitive and they were introduced to 1DPhCs to improve the sensitivity in our previous research. In this paper, a new method was developed for quantitative determination of beta-glucan in oats by introducing graphene oxide (GO) hydrogels in one-dimensional photonic crystals (1DPhCs) with a polyaniline (PANI) defect layer. GO hydrogels were synthesized via a one-step hydrothermal method, characterized with scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), and then they were employed as a component to fabricate 1DPhCs using a spin-coating method. Synthesized 1DPhCs combined with Congo red dye were in use for the quantification of beta-glucan. Reflection spectra demonstrated that a linear relationship existed between the photonic band gap and the beta-glucan concentration within 1–10 mg mL−1. The detection limit for beta-glucan is 0.18 mg mL−1 with a sensitivity of 7.53 nm mL mg−1.

Anti-Oxidative and Antibacterial Self-Healing Edible Polyelectrolyte Multilayer Film in Fresh-Cut Fruits.

The consumption of fresh-cut fruits is limited because of the oxidation browning and pathogenic bacterias growth on the fruit surface. Besides, crack of the fresh-keeping film may shorten the preservation time of fruit. In this work, polyelectrolyte multilayer (PEM) film was fabricated by layer-by-layer (LBL) electrostatic deposition method. The film was made by carboxy methylcellulose sodium (CMC) and chitosan (CS). The as-prepared PEM film had good anti-oxidative and antibacterial capability. It inhibited the growth of Gram-negative bacteria and the antibacterial rate was more than 95%. The stratified structure and linear increase of the absorbance in the film verified a linear increase of film thickness. The slight scratched film could self-heal rapidly after the stimulation of water whatever the layer number was. Moreover, the film could heal cracks whose width was far bigger than the thickness. The application of PEM film on fresh-cut apples showed that PEM film had good browning, weight loss and metabolic activity inhibition ability. These results showed that the PEM film is a good candidate as edible film in fresh-cut fruits applications.

Beta-glucan quantification by fluorescence analysis using photonic crystals

One-dimensional photonic crystal (1DPhC) was fabricated using a spin-coating method to be utilized as a Bragg reflection mirror. Gold was deposited on 1DPhC films by thermal evaporation under a vacuum. The beta-glucan–fluorochrome complex, whose emission wavelength was largely consistent with the photonic stopband of the 1DPhC, spin coated on the surface of 1DPhC with Au. The fluorescence of beta-glucan–fluorochrome complex deposited on 1DPhCs with Au was obviously enhanced in comparison with that on glass. There was 10-fold fluorescence enhancement. In this study, 1DPhCs with Au were used for the quantitative determination of beta-glucan. Fluorescence spectra demonstrated that a linear relationship existed between the fluorescence intensity and the beta-glucan concentration within 1–6 μg mL−1. The detection limit for beta-glucan is 0.083 μg mL−1 with a sensitivity of 19.53 mL μg−1.