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Mercury (Hg2+) as environmental pollutant is a widespread concern due to its cytotoxic effect in humans and animals and needs to be monitored through cost effective methods based on naked-eye detection. Herein, in this study, we extracted and isolated the limonin (LMN) via a facile procedure and then employed it as capping agent for the synthesis of silver nanoparticles (LMN-AgNPs) as a first report. LMN-AgNPs were characterized through Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS), Zeta Potential Analyzer (ZPA) and Fourier Transform Infrared (FTIR) spectroscopy. As-formed LMN-AgNPs were recognized as extremely selective and highly sensitive colorimetric sensor for Hg2+ with potential analytical application. The developed sensor showed an outstanding linear correlation with the concentration of Hg2+ in the range of 0.002 − 55 µM via a color change from deep yellow to transparent showing hypsochromic-hypochromic shift with the limit of detection (LOD) and the limit of quantification (LOQ) as low as 0.21 nM and 0.7 nM respectively. The sensor was further allied with smartphone for immediate and on-site quantification of Hg2+. The LOD and LOQ of 0.42 µM and 1.4 µM was true for smartphone based sensing in the range of 7.5–55 µM Hg2+. The detection of Hg2+ was not disrupted by the presence of other metals in either of mentioned cases. The practical applicability of the proposed Hg2+ sensor was tested using spectrophotometric and smartphone based approaches in human serum and urine as well as in tap water samples with acceptable ranges of recovery. As-developed sensor can work as a potential candidate for monitoring of Hg2+ pollution in diverse fields of studies. [ABSTRACT FROM AUTHOR]

MXenes are emerging rapidly as promising electrode materials for energy storage due to their high electronic conductivity and rich surface chemistry, but their potassium storage performance is unsatisfactory because of the large size of K+ and irreversible interfacial reaction. Here, a developed 3D foam‐like MXene scaffold (3D‐FMS) is constructed via an electrostatic neutralization of Ti3C2Tx with positive‐charged melamine followed with calcination, which offers massive surface‐active sites and facilitates fast K+ transfer for boosting the potassium‐ion storage capacity and dynamics. In addition, using KFSI‐based electrolyte, the formation of a robust solid electrolyte interface layer with more inorganic components on MXene anode is revealed for enhancing the Coulombic efficiency. Consequently, the 3D‐FMS with KFSI‐based electrolyte delivers enhanced potassium‐ion storage performance in terms of capacity (161.4 mAh g−1 at 30 mA g−1), rate capability (70 mAh g−1 at 2 A g−1), and cycling stability (80.5 mAh g−1 at 1 A g−1 after 2000 cycles). Moreover, the assembled 3D‐FMS//activated carbon potassium‐ion hybrid supercapacitor delivers a high energy density of 57 Wh kg−1 at a power density of 290 W kg−1. These excellent performances demonstrate the great superiority of 3D‐FMS in KFSI‐based electrolyte and may accelerate the development of MXene‐based materials for potassium storage systems. [ABSTRACT FROM AUTHOR]

Carbonaceous materials with closed pore structures have emerged as promising anodes for sodium-ion batteries. However, the rational design of closed pores and the investigation of their underlying sodium storage mechanisms face significant challenges. Herein, PVDF-derived pyrolytic carbon (PFC) with abundant open ultra-micropores and uniform pore size of 0.55 nm was chosen as the carbon matrix to construct a closed pore model to elucidate the sodium storage process in the closed pores. The transformation of ultra-micropores into closed pores was achieved with the assistance of polypropylene (PP), where the light aromatic compounds derived from PP can be deposited at the open pore entrance of the PFC during the pre-oxidation process, and subsequently pyrolyzed to a carbon layer in the carbonization stage, thus converting the open pores into closed pores. The obtained closed pore enriched carbon (PFCC@PP) showed a noticeable low-potential plateau region in the charge/discharge curve and an improved reversible capacity of 309.3 mA h g−1 with a high initial coulombic efficiency of 87.8%. When coupled with the O3-NaNi1/3Fe1/3Mn1/3O2 cathode, the assembled Na ion full cell realized a high energy density of 239.2 Wh kg−1 besides the remarkable rate capability. Additionally, theoretical calculations further validated the significant role of closed pores with optimal pore size in efficient Na ion storage. This work not only provides an interesting model for investigating closed-pore structures but also offers new insights into the rational design of carbon materials for advanced energy storage technology. [ABSTRACT FROM AUTHOR]

Potassium‐ion batteries (KIBs) have recently attracted considerable attention owing to their resource abundance, low cost and environmental friendliness. Graphite as a mature commercial anode material for lithium‐ion batteries, has been proved as a promising anode candidate for KIBs by reversible forming potassium‐graphite intercalation compounds. However, large volume expansion and sluggish K+ kinetics caused by the incompatibility between large radius of K+ and the small interlayer spacing of graphite, result in the poor cycle stability and rate performances, hindering its practical application. Extensive research efforts have focused on improving the potassium storage performance of graphite anodes. This review provides an overview of recent advances in addressing these challenges and optimizing the electrochemical performance of graphite anodes for KIBs. Various strategies to improve the electrochemical performance of graphite and graphitic carbon anodes, such as microcrystalline regulation, heteroatom doping, morphological adjustment, and coating modification, are discussed, while the critical issues and challenges associated with graphite anodes and the prospects for their advancement in KIBs are highlighted. The review offers valuable guidelines for rational structural design and promotes the commercial development of high‐performance graphite anode materials for KIBs. [ABSTRACT FROM AUTHOR]

Owing to unique physical and optical properties, fluorescent carbon dots (C-dots) are used in various biomedical applications. In this study, C-dots have been integrated as sensing agent on paper surface for colorimetric determination of clinically important analytes. Polyacrylamidebased C-dots coated C-dips showed visible color change from white to brown for iron (Fe2+, Fe3+) sample. Moreover, iron and copper (Cu2+) samples showed significant quenching of C-dots under UV. Images captured with/without UV were analyzed to study the relationship between different iron and copper concentrations and colorimetric intensity values. Color intensity and fluorescence showed a linear relationship with concentrations of iron and copper (Range: 1×10-4 to 1×10-2 M, Linearity: R² = 0.94). LOD from the paper sensor showed a sensitivity of 3.89×10-5 μM, 4.65×10-5 μM and 6.7×10-5 μM for Fe3+, Fe2+ and Cu2+ respectively, reflecting its reliability as low-cost sensing solution to analyze clinically relevant analytes as reported in current study. [ABSTRACT FROM AUTHOR]