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Graphene (GE)-based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this article, we present a general approach for the preparation of GE/poly(vinyl alcohol) (PVA) nanocomposites. The basic strategy involved the preparation of graphite oxide from graphite, complete exfoliation of graphite oxide into graphene oxide sheets, followed by reduction to GE nanosheets, and finally, the preparation of the GE/PVA nanocomposites by a simple solution-mixing method. The synthesized products were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, and differential scanning calorimetry analysis.The GE nanosheets were well dispersed in the PVA matrix, and the restacking of the GE sheets was effectively prevented. Because of the strong interfacial interaction between PVA and GE, which mainly resulted from the hydrogenbond interaction, together with the improvement in the PVA crystallinity, the mechanical properties and thermal stability of the nanocomposites were obviously improved. The tensile strength was increased from 23 MPa for PVA to 49.5 MPa for the nanocomposite with a 3.25 wt % GE loading.

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Background This study aimed to evaluate the clinical performance of low serum calcium and phosphorus in discriminative diagnosis of the severity of patients with coronavirus disease 2019 (COVID‐19). We conducted a single‐center hospital‐based study and consecutively recruited 122 suspected and 104 confirmed patients with COVID‐19 during January 24 to April 25, 2020. Clinical risk factors of COVID‐19 were identified. The discriminative power of low calcium and phosphorus regarding the disease severity was evaluated. Low calcium and low phosphorus are more prevalent in severe or critical COVID‐19 patients than moderate COVID‐19 patients (odds ratio [OR], 15.07; 95% confidence interval [CI], 1.59–143.18 for calcium; OR, 6.90; 95% CI, 2.43–19.64 for phosphorus). The specificity in detecting the severe or critical patients among COVID‐19 patients reached 98.5% (95% CI, 92.0%–99.7%) and 84.8% (95% CI, 74.3%–91.6%) by low calcium and low phosphorus, respectively, albeit with suboptimal sensitivity. Calcium and phosphorus combined with lymphocyte count could obtain the best discriminative performance for the severe COVID‐19 patients (area under the curve [AUC] = 0.80), and combined with oxygenation index was promising (AUC = 0.71). Similar discriminative performances of low calcium and low phosphorus were found between suspected and confirmed COVID‐19 patient. Low calcium and low phosphorus could indicate the severity of COVID‐19 patients, and may be utilized as promising clinical biomarkers for discriminative diagnosis.