Liu Xiangyi,Zheng Qianye,Jia Deqi,Wang Wenwen,Zhao Hong,Tao Xiansen,Sha Jingquan
To explore novel nanozymes as colorimetric biosensors with highly activities, the ternary MIL-101(Fe)@P 2 W 18 @SWNT nanocomposite was successfully fabricated based on the optimal matching principle, namely, Wells–Dawson-type polyoxometalates (POMs, H 6 P 2 W 18 O 62 abbreviated as P 2 W 18 ) were encapsulated in a custom MIL-101(Fe) cavity, and single-walled carbon nanotubes (SWNT) was then fixed. The peroxidase-like activities of MIL-101(Fe)@P 2 W 18 @SWNT nanocomposite were evaluated by detecting hydrogen peroxide (H 2 O 2 ) and glucose (GLC). Compared with the MIL-101(Fe), P 2 W 18 and SWNT, the MIL-101(Fe)@P 2 W 18 @SWNT exhibits better peroxidase-like properties and stability due to the nature of all components and their optimal synergy. Based on the excellent catalytic activity of MIL-101(Fe)@P 2 W 18 @SWNT , two colorimetric biosensors for detecting H 2 O 2 and GLC with linear ranges of 0–80 μM (H 2 O 2 ) and 0–150 μM (GLC) were constructed, and the low detection limit of 0.3 μM for H 2 O 2 and 0.2 μM for GLC are superior to the most reported nanozymes. The work opens a promising route in constructing heterogeneous MOFs and POMs-based nanozymes for biosensing application.
All-in-one electrochromic devices (ECDs) have potential applications in wearable stretchable electronics. However, ECDs today are inflexible, slow to respond and at risk of electrolyte leakage. We have prepared a novel electrochromic hydrogel by introducing polyoxometalates [P 2 W 18 O 62 ] 6− (P 2 W 18 ) into polyacrylamide (PAAm) via ionic and covalent cross-linking. Negatively charged P 2 W 18 have ionic conductive properties, thus the hydrogel is able to undergo electrochromic behavior without the addition of electrolytes. PAAm/P 2 W 18 hydrogel has good flexibility and tensile properties , high transparency and a simple preparation process. The PAAm/P 2 W 18 hydrogel is reversibly switchable between colorless and dark blue over a voltage range from 0 V to −2.8 V. The ECDs had a large transmittance contrast (53.7 %), fast response time (coloring/bleaching times of 6.9 s and 5.6 s) and satisfactory coloring efficiency (125.5 cm 2 /C). PAAm/P 2 W 18 hydrogel has good open-circuit memory properties which maintains coloring state after 7 days of power off. The sandwich-structured (ITO/hydrogel/ITO) electrochromic device based on this hydrogel is simple to manufacture, low in cost and fast in response, which have potential applications in the fields of smart windows, energy-saving displays, and anti-glare mirrors.
In this study, a novel electrochromic hydrogel AG/P(AAm-AAc)/P 2 W 18 was prepared by loading polyoxometalate K 6 P 2 W 18 ·10H 2 O (P 2 W 18 ) into a double-network hydrogel formed with agar (AG) and copolymer of polyacrylamide (PAAm) and polyacrylic acid (PAAc). The mechanical properties of hydrogels can be tuned by adjusting the proportion of PAAc in the copolymer P(AAm-AAc). Electrochromic hydrogel shows the best mechanical properties when the proportion of PAAc is 10 % (AG/P(AAm-AAc)-10/P 2 W 18 ), and the maximum elongation at break and the fracture stress are about 2.0 and 2.5 times higher than that of pure PAAm. P 2 W 18 gives good electrochromic properties to the hydrogels without the addition of electrolytes. Under the external voltage, the electrochromic hydrogel changes from colorless to blue with the optical contrast up to 65.54 % at 700 nm. The electrochromic device based on this hydrogel is simple in structure, easy to manufacture and highly stretchable, which has good application potential in the field of wearable electronics.
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