Direct Coating Pen Ink Carbon on a Carbonized Melamine Sponge as a Flexible Free-Standing Electrode

One stone for four birds: A "chemical blowing" strategy to synthesis wood-derived carbon monoliths for high-mass loading capacitive energy storage in low temperature

Biomass-derived carbon materials are promising electrode materials for capacitive energy storage. Herein, inspired by the hierarchical structure of natural wood, carbon monoliths built up by interconnected porous carbon nanosheets with enriched vertical channels were obtained via zinc nitrate (Zn(NO3)2)-assisted synthesis and served as thick electrodes for capacitive energy storage. Zn(NO3)2 is proved to function as expansion agent, activator, dopant, and precursor of the template. The dense and micron-scale thickness walls of wood were expanded by Zn(NO3)2 into porous and interconnected nanosheets. The pore volume and specific surface area were increased by more than 430 %. The initial specific capacitance and rate performance of the optimized carbon monolith was approximately three times that of the pristine dense carbon framework. The assembled symmetric supercapacitor possessed a high initial specific capacitance of 4564 mF cm-2 (0-1.7 V) at -40 °C. Impressively, the robust device could be cycled more than 100,000 times with little capacitance attenuation. The assembled zinc-ion hybrid capacitor (0.2-2 V) delivered a large specific capacitance of 4500 mF cm-2 at -40 °C, approximately 74 % of its specific capacitance at 25 °C. Our research paves a new avenue to design thick carbon electrodes with high capacitive performance by multifunctional Zn(NO3)2 for low-temperature applications.

High Rate Performance Supercapacitors Based on N, O Co-Doped Hierarchical Porous Carbon Foams Synthesized via Chemical Blowing and Dual Templates

N, O Co-Doped porous carbon materials are promising electrode materials for supercapacitors. However, it is still a challenge to prepare high capacitance performance N, O Co-Doped porous carbon materials with balanced pore structure. In this work, a simple chemical blowing method was developed to produce hierarchal porous carbon materials with Zn(NO3)2·6H2O and Fe(NO3)3·9H2O as the foaming agents and precursors of dual templates. Soybean protein isolate served as a self-doping carbon source. The amount of Fe(NO3)3·9H2O influenced the microstructure, element content and capacitance performance of the obtained porous carbon materials. The optimized sample CZnFe-5 with the addition of 5% Fe(NO3)3·9H2O displayed the best capacitance performance. The specific capacitance reached 271 F g-1 at 0.2 A g-1 and retained 133 F g-1 at 100 A g-1. The CZnFe-5//CZnFe-5 symmetric supercapacitors delivered a maximum energy density of 16.83 Wh kg-1 and good stability with capacitance retention of 86.33% after 40,000 cycles tests at 50 A g-1. The symmetric supercapacitors exhibited potential applications in lighting LED bulbs with a voltage of 3 V. This work provides a new strategy for the synthesis of hierarchical porous carbon materials for supercapacitors from low-cost biomass products.

Application of silanized melamine sponges in matrix purification for rapid multi-residue analysis of veterinary drugs in eggs by UPLC-MS/MS

Fast and convenient matrix purification is an important prerequisite for high-throughput analysis of drug multiresidues in food. In this study, a silanized melamine sponge was prepared and first applied in the rapid determination of multiclass veterinary drugs in eggs by ultrahigh-performance liquid chromatography-tandem mass spectrometry. Within five seconds, fast, convenient and efficient matrix separation could be achieved through simple soaking and squeezing. Compared to other matrix adsorbents, the developed material demonstrated equivalent or better purification performance. Good validation results were obtained in terms of drug recoveries (61.5%~97.0%, relative standard deviation (RSD) ≤ 10.8%), and linearities (R² ≥ 0.999), as well as low limits of quantitation (0.3 ~ 10.9 μg·kg^-1) and detection (0.1 ~ 3.8 μg·kg^-1). By analyzing 52 egg samples, high concentrations of ofloxacin, trimethoprim, metronidazole, and dimetridazole were found at 542.9, 121.2, 66.1 and 58.0 μg·kg^-1, respectively. The silanized melamine sponge has shown its great potential for rapid analysis of multiclass residues in food safety.

Development of a modified quick, easy, cheap, effective, rugged, and safe method based on melamine sponge for multi-residue analysis of veterinary drugs in milks by ultra-performance liquid chromatography tandem mass spectrometry

The purpose of this study was to develop a modified QuEChERS method based on melamine sponge for rapid determination of multi-class veterinary drugs in milks by UPLC-MS/MS. Through simple infiltration and extrusion, fast and convenient matrix purification could be achieved within several seconds, and there was no need of extra phase separation operations. Good linearity with correlation coefficient (R²) ≥0.999 was obtained for all drugs in the range of 2~500 µg·kg^-1. The obtained matrix effects were within ±20% for all monitored drugs. The recoveries of all monitored drugs ranged from 60.7% to 116.0% at three spiked levels (50, 100, and 200 µg·kg^-1), with relative standard deviations less than 7.4%. Comparatively low LODs and LOQs were obtained in the ranges of 0.1~3.8 µg·kg^-1 and 0.2~6.3 µg·kg^-1, respectively. Compared with conventional purification adsorbents, melamine sponge yielded an equal or higher purification performance with matrix removal rate as high as 52.5% and acceptable recoveries in range of 60%-120% for all monitored drugs. The satisfactory results have demonstrated the good potential of melamine sponge in matrix purification for rapid determination of multiclass residues in food safety.