Finding easy-to-operate strategy to obtain anode material with well-designed structure and excellent electrochemical performance is necessary to promote the development of the future potassium-ion batteries (PIBs). In this work, we synthesized reduced graphene oxide doping flower-like Fe 7 S 8 nanosheets electrode materials using one-step hydrothermal strategy. The rGO@Fe 7 S 8 composite is composed of homogeneous Fe 7 S 8 and reduced graphene oxide thin nanosheets. This unique structure not only promotes the penetration of electrolyte and increases the conductive of the pure Fe 7 S 8 electrode materials, but also relieves the volume expansion of K + during charge/discharge process. When applied this interesting anode electrode for PIBs, the rGO@Fe 7 S 8 exhibits excellent electrochemical performance. It delivers a high reversible specific capacity of 445 mAh g −1 at 50 mA g −1 , excellent rate performance (284 mAh g −1 at 500 mA g −1 and 237 mAh g −1 at 1000 mA g −1 ), and a high cycling stability at 100 mA g −1 (maintained 355 mAh g −1 after 300 cycles).
Shangying Qin,Li Huang,Chuang Wen,Zhongwei Lin,Yilin Wang,Xin Shu
By using Fe 7 S 8 nanosheets (NSs) as catalyst, O -phenylenediamine (OPD) as chromogenic substrate, H 2 O 2 as oxidant, and ascorbic acid (AA) as regulator, a dual ratio colorimetric and fluorescence sensing system for determining AA was constructed. The inherent peroxidase like activity of Fe 7 S 8 NSs enables it to catalyze the oxidation of OPD in the existence of H 2 O 2 , resulting in the formation of yellow-colored 2, 3-diaminophenazine (DAP) with a characteristic absorption peak at 450 nm and a fluorescence emission peak at 560 nm. However, the presence of AA could suppress the oxidation of OPD and induce the generation of quinoxaline derivative (QXD) 3-(dihydroxyethyl) furo [3,4-b] quinoxaline-1-one with absorption and fluorescence emission peaks located at 345 and 435 nm, respectively. Thus, employing the absorption of QXD at 345 nm and emission at 435 nm as the reporting signals, and the absorption of DAP at 450 nm and emission at 560 nm as the reference signals, a ratio colorimetric ( A 345 / A 450 ) and ratio fluorescence ( F 435 / F 560 ) dual signal detection method for AA was developed. Under the optimized conditions, the value of A 345 / A 450 was found to be linear with AA concentration in the ranges of 1.0–40 μM and 40–100 μM, and the value of F 435 / F 560 was strongly correlated with AA concentration in the ranges of 1.0–30 μM and 30–100 μM. When applied for the assay of AA in human serum samples, an acceptable recovery ranging from 93.1 to 106.6 % was obtained, confirming the potential of the sensing system in practical applications.
Shu Zhu,Shangying Qin,Chonghui Wei,Li Cen,Luyun Xiong,Xingyu Luo,Yilin Wang
Background Organophosphorus pesticides (OPs) play important roles in the natural environment, agricultural fields, and biological prevention. The development of OPs detection has gradually become an effective strategy to avoid the dangers of pesticides abuse and solve the severe environmental and health problems in humans. Although conventional assays for OPs analysis such as the bulky instrument required analytical methods have been well-developed, it still remains the limitation of inconvenient, inefficient and lab-dependence analysis in real samples. Hence, there is an urgent demand to develop efficient detection methods for OPs analysis in real scenarios. Results Here, by virtue of the highly efficient catalytic performance in Fe 7 S 8 nanoflakes (Fe 7 S 8 NFs), we propose an OPs detection method that rationally integrated Fe 7 S 8 NFs into the acetylcholine (ACh) triggered enzymatic cascade reaction (ATECR) for proceeding better detection performances. In this method, OPs serve as the enzyme inhibitors for inhibiting ATECR among ACh, acetylcholinesterase (AChE), and choline oxidase (CHO), then reduce the generation of H 2 O 2 to suppress the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) that catalyzed by Fe 7 S 8 NFs. Benefiting from the integration of Fe 7 S 8 NFs and ATECR, it enables a sensitive detection for OPs ( e.g. dimethoate). The proposed method has presented good linear ranges of OPs detection ranging from 0.1 to 10 μg mL −1 . Compared to the other methods, the comparable limits of detection (LOD) of OPs are as low as 0.05 μg mL −1 . Significance Furthermore, the proposed method has also achieved a favorable visual detection performance of revealing OPs analysis in real samples. The visual signals of OPs can be transformed into RGB values and gathered by using smartphones, indicating the great potential in simple, sensitive, instrument-free and on-site analysis of pesticide residues in environmental monitoring and biosecurity research.
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