Cycling-Induced Capacity Increase of Graphene Aerogel/ZnO Nanomembrane Composite Anode Fabricated by Atomic Layer Deposition

Abstract Zinc oxide (ZnO) nanomembranes/graphene aerogel (GAZ) composites were successfully fabricated via atomic layer deposition (ALD). The composition of GAZ composites can be controlled by changing the number of ALD cycles. Experimental results demonstrated that the anode made from GAZ composite with ZnO nanomembrane of 100 ALD cycles exhibited highest specific capacity and best rate performance. A capacity increase of more than 2 times during the first 500 cycles was observed, and a highest capacity of 1200 mAh g−1 at current density of 1000 mA g−1 was observed after 500 cycles. On the basis of detailed electrochemical investigations, we ascribe the remarkable cycling-induced capacity increase to the alloying process accompanied by the formation of a polymer layer resulting from kinetically activated electrolyte degradation at low voltage regions

Magnetic graphene quantum dots facilitate closed-tube one-step detection of SARS-CoV-2 with ultra-low field NMR relaxometry

The rapid and sensitive diagnosis of the highly contagious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the crucial issues at the outbreak of the ongoing global pandemic that has no valid cure. Here, we propose a SARS-CoV-2 antibody conjugated magnetic graphene quantum dots (GQDs)-based magnetic relaxation switch (MRSw) that specifically recognizes the SARS-CoV-2. The probe of MRSw can be directly mixed with the test sample in a fully sealed vial without sample pretreatment, which largely reduces the testers’ risk of infection during the operation. The closed-tube one-step strategy to detect SARS-CoV-2 is developed with homemade ultra-low field nuclear magnetic resonance (ULF NMR) relaxometry working at 118 μT. The magnetic GQDs-based probe shows ultra-high sensitivity in the detection of SARS-CoV-2 due to its high magnetic relaxivity, and the limit of detection is optimized to 248 Particles mL‒1. Meanwhile, the detection time in ULF NMR system is only 2 min, which can significantly improve the efficiency of detection. In short, the magnetic GQDs-based MRSw coupled with ULF NMR can realize a rapid, safe, and sensitive detection of SARS-CoV-2

Visualization 1: Making few-layer graphene photoluminescent by UV ozonation

Visualization 1 Originally published in Optical Materials Express on 01 November 2016 (ome-6-11-3527

Insights into the Oxidation Mechanism of sp²–sp³ Hybrid Carbon Materials: Preparation of a Water-Soluble 2D Porous Conductive Network and Detectable Molecule Separation

A thorough investigation of the oxidation mechanism of sp²–sp³ hybrid carbon materials is helpful for the morphological trimming of graphene. Here, porous graphene (PGN) was obtained via a free radical oxidation process. We further demonstrated the difference between traditional and free radical oxidation processes in sp²–sp³ hybrid carbon materials. The sp³ part of graphene oxide was oxidized first, and well-crystallized sp² domains were reserved, which is different from the oxidation mechanism in a traditional approach. The obtained PGN shows excellent performance in the design of PGN-based detectable molecule separation or other biomedical applications

Enhanced Crystallization from the Glassy State of Poly(l‑lactic acid) Confined in Anodic Alumina Oxide Nanopores

The crystallization behavior of poly­(l-lactic acid) (PLLA) infiltrated in anodic alumina oxide templates (AAO) was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). During heating from the glassy state, the crystallization of infiltrated PLLA was unexpectedly enhanced as compared with bulk PLLA. The cold crystallization temperature of infiltrated PLLA from the glassy state was much lower than that of bulk PLLA. The half-crystallization time (<i>t</i>_1/2) of infiltrated PLLA at 75 °C decreased with the diameter of AAO nanopores. The glass transition temperature of PLLA was not influenced by the geometrical confinement. The enhanced crystallization from the glassy state was explained by surface-induced nucleation of AAO walls on PLLA. Our results provide the first observation of enhanced cold crystallization of polymers in confined geometry

Electrochemical Fabrication of High Quality Graphene in Mixed Electrolyte for Ultrafast Electrothermal Heater

High quality graphene sheets have been considered as a promising candidate in several industrial applications due to their excellent electronic and thermal conductivity. However, the mass production of high quality graphene sheets from graphite bulk is still facing great challenges. Here we demonstrated a new approach to prepare high quality graphene by mixing a solution of oxalic acid and hydrogen peroxide as the electrolyte. The reaction did not involve the oxidation of graphite and thus exfoliated graphene possesses a uniform lateral size (2–6 μm, 78.1%), low oxygen content (2.41 at. %), few structure defects, and high conductivity of 26 692 S m^–1. The optimized mixed electrolyte is environmental friendly, cheap and safe, and most importantly it is easy to be removed through low temperature heating, which facilitates graphene purification. An electrothermal heater, made from highly concentrated graphene ink (8.5 mg mL^–1) on A4-size paper or polyester, exhibits excellent performance: a rapid rise of temperature (up to 75.2 °C) in a short time (30 s) under a low voltage of 10 V. The as-made graphene is considered as a promising material for future application of printable electronics and wearable devices