Ziwei Zhao,Haoyun Dou,Xuanpan Xu,Rongjie Zhe,Qingye Zhao,Lingxia Zheng,Xinjun Bao,Ting Zhu,Hong-En Wang
Rational design of effective cathode host materials is an effective way to solve the problems of serious shuttle and slow conversion of polysulfides in lithium-sulfur batteries (LSBs). However, the redox reaction of sulfur differs from conventional “Rocking chair” type batteries and involves a cumbersome phase transition process, so a single-component catalyst cannot consistently and steadily enhance the reaction rate throughout the redox process. In this work, a hybrid composed of magnetopyrite Fe 1−x S catalyst-modified with N/S-doped porous carbon spheres (Fe 1−x S@NSC) is proposed as a novel sulfur host to synergistically promote the adsorption and redox catalysis conversion of polysulfides. In this hybrid, the NSC skeleton provides excellent electrical conductivity and abundant adsorption sites for the physical immobilization of polysulfides; the magnetopyrite Fe 1−x S nanoparticles promote the fast conversion reaction from Li 2 S 2 to Li 2 S, affording strong adsorption and catalytic conversion. The optimal LSB with Fe 1−x S@NSC manifests a high initial capacity of 971 mAh g −1 at 0.2 C (1 C = 1675 mAh g −1 ) and a retention rate of up to 75 % after 100 cycles. This work can provide a new approach for rationalizing the novel transition metal sulfide/porous carbon-based composite hosts with efficient lithium polysulfides (LiPSs) adsorption and catalytic conversion in high-performance lithium-sulfur batteries.
N/S-doped carbon dots/gold nanoparticles/Ag + (N/S-CDs/AuNPs/Ag + ) as a dual-mode nanoprobe was constructed to detect ascorbic acid (AA). Compared with simple carbon dots, N/S-CDs exhibited superior fluorescence properties, which could play a more important role in building a sensitive homogenous FRET fluorescence detection platform. Moreover, AuNPs/Ag + was reduced to core-shell Au@AgNPs by AA in an alkaline environment, which could induce the localized surface plasmon resonance (LSPR) and led to the change of UV absorption peak position from 520 nm to 426 nm with the color changing from pink to bright yellow. Due to the fluorescence “turn on-off” and LSPR, the N/S-CDs/AuNPs/Ag + nanoprobe is inspected for the sensitive dual-mode detection of AA. The linear detection ranges are from 0.5 to 100 μM for colorimetric mode and 0.5–90 μM for fluorescence method. Their LODs are 0.17 and 0.10 μM, respectively. Furthermore, this proposed nanoprobe showed high sensitivity and accuracy for AA detection in real orange juice, displaying great possibility in food testing.
Yao Fan,Lu Shen,Yaqi Liu,Ying Hu,Wanjun Long,Haiyan Fu,Yuanbin She
A ratiometric fluorescent probe based on N/S doped carbon dots (N/S-CQDs) and mercaptoacetic acid capped CdTe quantum dots (TGA-CdTe QDs) with sensitized and self-calibration functions was constructed to sensitively detect multiple tetracycline antibiotics (TCs). N/S-CQDs could attach stably to TGA-CdTe QDs and form a new composite ratiometric fluorescent probe that had a more than tenfold increase in sensitivity to TCs compared with each single QD. The probe could detect four common TCs as the color of the probe changed from bright red to dark red, and the limit of detection (LOD) was 1.47 × 10 −2 –1.78 × 10 −2 mg/L. Practical applications of the probe in food and urine were also verified with recovery rates of 95.21%-104.97%. Due to the abundant spectral fingerprints provided by both QDs, this novel probe could accurately recognize not only different single TCs but also mixed TC samples even in actual samples combined with chemometrics.
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