Sustainable Fabrication of Graphene Oxide Cathodes from Graphite of Failed Commercial Li-Ion Batteries for High-Performance Aqueous Zn-Ion Batteries.

The need for revamping spent graphite (SG) from battery waste of commercial lithium-ion batteries and employing it as a source for the synthesis of graphene oxide (GO) is focused. Thus, this work emphasizes the study of GO sheets, synthesized via modified Hummer's method from spent graphite (SG-GO) as cathodes for an aqueous zinc ion battery (AZIB) system, for the first time in literature. For comparison, graphene oxide is also synthesized using commercial graphite powder, its structural and morphological properties are analyzed with SG-GO. The coin cell AZIB device is fabricated for both the GOs and the electrochemical performances revealed that SG-GO portrayed an enhanced charge capacity of 270 mAh g-1 at 0.1 A g-1 in 3 m ZnSO4 in comparison to GO which delivered ≈198 mAh g-1 at the same current density of 0.1 A g-1. The long-run cycling analysis of SG-GO elucidated the capacity retention of 77.3% at 1 A g-1 even after 1000 cycles. Moreover, the performance of SG-GO is inspected in different electrolyte systems and the suitable electrolyte underwent concentration variation studies to figure out the capability of the system in storing Zn2+ ions which is found to be more in 3 M ZnSO4 electrolyte.

Improved photoluminescence stability and defect passivation in SbBr3 post-treated CsPbBr3 quantum dots under ambient conditions.

Inorganic cesium lead halide perovskites have evoked wide popularity because of their excellent optoelectronic properties, high photoluminescence (PL) quantum yield (PLQY), and narrowband emission. Here, cesium lead bromide (CsPbBr3 ) quantum dots (QDs) were synthesized via the ligand-assisted re-precipitation method. Post-synthesis treatment of CsPbBr3 QDs using antimony tribromide improved the PL stability and optoelectronic properties of the QDs. In addition, the PLQY of the post-treated sample was enhanced to 91% via post-treatment, and the luminescence observed was maintained for 8 days. The post-synthesis treatment ensured defect passivation and improved the stability of CsPbBr3 perovskite QDs. High-resolution transmission electron microscopy revealed the presence of more ordered, uniform-sized CsPbBr3 QDs after post-synthesis treatment, and the uniformity of the sample improved as the day passed. The formation of a mixed crystal phase was observed from X-ray diffraction in both as-synthesized, as well as post-treated QDs samples with the possibility of a polycrystalline nature in the post-treated CsPbBr3 QDs as per the selected area electron diffraction pattern. The X-ray photoelectron spectroscopy spectra confirmed the presence of antimony and the possibility of defect passivation in the post-treated samples. These QDs can act as potential candidates in various optoelectronic applications such as photodetectors and light-emitting diodes due to their high PLQY and longer lifetime.

Solvent Evaporation Induced Large-Scale Synthesis of Cs4PbBr6 and CsPbBr3 Microcrystals: Optical Properties and Backlight Application for LEDs.

The contemporary work focuses on embossing the emissive nature of lead halide perovskite materials, specifically Cs4PbBr6 microcrystal powder prepared via single step bulk recrystallization method followed by the solvent evaporation route from gram to kilogram scale. The X-ray diffraction pattern confirms the formation of phase pure Cs4PbBr6 with a goodness of fit value of 1.51 calculated from Rietveld refinement and the fluorophore powder manifesting an intrinsic band gap of 3.76 eV. The experimental yield of 99.4% indicates the absence of any unreacted precursors. The fabricated flexible, free-standing Cs4PbBr6@PMMA film encompassed better moisture stability without undergoing phase transitions for 400 days. The temperature-dependent photoluminescence spectra denote that 51% of the intensity was retained when cooled back to room temperature after heating it till 180 °C. Moisture studies at two extreme humidity conditions also reveal the appreciable stability of the fluorophore film against moisture. The stability studies with respect to UV irradiation substantiate that the film retained its stability even after exposing it continuously to UV radiation for seven days. The outstanding optical properties of these microcrystals, owing to the higher exciton binding energy, make them a promising candidate as excellent fluorophores for color conversion, backlight, and light-emitting applications. The Cs4PbBr6@PMMA film was employed as the top cover of a commercial blue LED, producing a robust green emission which revealed its possible application as a phosphor material.