A Durable and High-Voltage Mn-Graphite Dual-Ion Battery Using Mn-Based Hybrid Electrolytes.

Rechargeable Mn-metal batteries (MMBs) can attract considerable attention because Mn has the intrinsic merits including high energy density (976 mAh g-1 ), high air stability, and low toxicity. However, the application of Mn in rechargeable batteries is limited by the lack of proper cathodes for reversible Mn2+ intercalation/de-intercalation, thus leading to low working voltage (<1.8 V) and poor cycling stability (≤200 cycles). Herein, a high-voltage and durable MMB with graphite as the cathode is successfully constructed using a LiPF6 -Mn(TFSI)2 hybrid electrolyte, which shows a high discharge voltage of 2.34 V and long-term stability of up to 1000 cycles. Mn(TFSI)2 can reduce the plating/stripping overpotential of Mn ions, while LiPF6 can efficiently improve the conductivity of the electrolyte. Electrochemical in-situ characterization implies the dual-anions intercalation/de-intercalation at the cathode and Mn2+ plating/stripping reaction at the anode. Theoretical calculations unveil the top site of graphite is the energetically favorable for anions intercalation and TFSI- shows the low migration barrier. This work paves an avenue for designing high-performance rechargeable MMBs towards electricity storage.

J-Aggregates of zinc tetraphenylporphyrin: a new pathway to excellent electrochemiluminescence emitters.

Low-potential electrochemiluminescence (ECL) luminophores with excellent ECL behavior have attracted considerable interest in biological analysis. Herein, we explored the ECL behavior of ZnTPP with different aggregates for the first time. In this work, we used the mixed solvent method to prepare the H- and J-aggregates of zinc tetraphenylporphyrin (ZnTPP). This resulted in a completely disparate morphology, such as nanoparticles and rod-aggregates, which were observed by recording atomic force microscopy (AFM) images. Characteristic changes in the optical properties and electrochemical properties of ZnTPP appeared when it underwent H- and J-aggregation. Significantly, the measured ECL behavior varied for the same ZnTPP molecules when they were in the form of H- and J-aggregates; and the ECL intensity of the J-aggregates was more than ten times that of the H-aggregates due to a narrower band gap and the formation advantages in J-aggregates. The narrower band gap of J-aggregates not only facilitates the electron-hole pair recombination, but also facilitates the electron injection into the J-aggregates. The formation advantage of the J-aggregates is likely to contribute to the strong ECL intensity of the J-aggregates. Maybe the big number of ZnTPP molecules in a J-aggregate unit increases the opportunity of generating excited states and light from excited state radiation. The ECL property could be regulated with the different aggregation of ZnTPP, which led to a decline of ECL cathode potential in the J-aggregates (191 mV) compared with the H-aggregates. This work provides an effective and novel strategy for developing ECL emitters with low potential and high ECL emission intensity via adjusting aggregation motifs.

Investigation into the Oxygen-Involved Electrochemiluminescence of Porphyrins and Its Regulation by Peripheral Substituents/Central Metals.

We provide evidence of oxygen-involved electrochemiluminescence (ECL) of metal-free porphyrins and metalloporphyrins first. O2•- and OH•, which are oxygen intermediates, are indispensable for the formation of excited porphyrins, which has been proven by trapping free radical strategies. The wide differences regarding emission location and mechanism between metal-free porphyrins [including meso-tetra(4-methoxyphenyl)porphine (H2TMPP), meso-tetraphenylporphyrin (H2TPP), and meso-tetra(4-carboxyphenyl)porphine (H2TCPP)] and metalloporphyrins (MTPP) depend on whether protons are present in the center of the porphin ring. Besides, the oxygen-involved ECL of porphyrins can be controlled regularly by peripheral substituents with different polarities. Because of the stretched molecular structure and the decrease in electron density around the protons located at porphin ring, electron-withdrawing groups are more conducive to protons being attacked by O2•-, as well as the enhancement of porphyrins ECL. The ECL efficiency [ΦECL, which is normalized with respect to Ru(bpy)3(PF6)2 (taking ΦECL of Ru(bpy)3(PF6)2 = 1)] is gradually improved from H2TMPP (ΦECL = 0.16), to H2TPP (ΦECL = 2.20), to H2TCPP (ΦECL = 3.83); the ΦECL = 4.21 of Zn(II)TPP is significantly higher than those of other MTPPs [e.g., Co(II)TPP and Cu(II)TPP]. A deeper understanding regarding the improvement of porphyrins ECL efficiency and new application toward porphyrins-related devices can be achieved from this work.

Biomimetic Interfacial Electron-Induced Electrochemiluminesence.

We provide here, for the first time, a new interfacial electron-induced electrochemiluminescence (IEIECL) system, realizing bionic construction of bioluminescence (BL) by exploiting electrochemiluminescence (ECL) and ITIES (the interface between two immiscible electrolyte solutions). Significantly, the superiority of the IEIECL system is embodied with the solution of the two bottlenecks encountered in the conventional ECL innovation: that are (a) the applications of hydrophobic luminophores in more commonly used aqueous solution are inhibited tremendously due to the poor inherent solubility and the instability of radicals and (b) the analytes, insoluble in water, are hard to be discovered in an aqueous system because of too little content. More productive IEIECL radiation, analogous to BL, originates from the triplet excited state porphyrin in comparison to the homogeneous ECL. The mechanism of IEIECL, as well as the interaction mechanism between IEIECL and charge transfer (comprising electron transfer (ET), ion transfer (IT), and facilitated ion transfer (FIT)) at the ITIES, are explored in detail. Finally, we emphasize the actual application potential of the IEIECL system with the detection of cytochrome c (Cyt c); it is a key biomolecule in the electron transport chain in the process of biological oxidation and is also an intermediate species in apoptosis. Potentially, the IEIECL system permits ones to explore the lifetime and diffusion path of free radicals, as well as imparting a possibility for the construction of a bionic sensor.

Bimodal Electrochemiluminescence of G-CNQDs in the Presence of Double Coreactants for Ascorbic Acid Detection.

How to improve the accuracy of target detection substance in low-content and complex of real sample, which is still a major challenge in the analysis field. There is no doubt that the internal standard method is the best choice in the analysis methods. The internal standard method of ECL strategy can furnish more accurate detection results in the changeable complex environment, and it can dispel the primary vaguest interference in the system through the self-calibration of two emission spectra. Herein, we effectually explored a strong and stable bimodal ECL system based on graphitic carbon nitride quantum dots (g-CNQDs) as single luminophore in the presence of double coreactants potassium persulfate (K2S2O8) and tetrabutylammonium bromide (TBAB) under the optimized conditions. ECL-1 at 2.82 V and ECL-2 at 1.73 V were observed when the potential was scanned between -3 and 3 V at the scan rate of 0.2 V·s-1. The ECL-1 was responding to the analyte, that is, ascorbic acid (AA) and the ECL-2 was not for a certain concentration of AA; hence, the developed bimodal ECL system was used as internal standard method for quantitative AA in human serum due to the different sensitivity of the double-peak ECL signals to the target analytes. The linear relationships were obtained based on the ln I (ECL-1/ECL-2) against the concentration of AA in the concentration range of 3.5 to 330 nM, with a detection limit of 110 pM (S/N = 3).