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We have developed a new low-fluorine solution consisting of non-fluorine (F-free) barium and copper salts, and fluorine-containing yttrium trifluoroacetate. Using this new low-fluorine solution, the BaCO3 phase was avoided in the pyrolyzed precursor films. Instead, CuO, Y and Ba fluorides (YF3 and BaF2) were formed in the precursor films pyrolyzed at 450 °C, which was the same as when an All-TFA solution (prepared using Y, Ba, Cu trifluoroacetates as precursors) or other fluorine-reduced solutions were used. This new kind of low-fluorine solution has only 23% of the fluorine content in an All-TFA solution, and the fluorine content was lower than any other fluorine-reduced solution. Thus, rapid production of YBa2Cu3O7−x (YBCO) films can be easily realized. Using a heating rate of 10 °C min−1 in the pyrolysis process, a high critical current density (Jc) of 5 MA cm−2 (at 77 K, 0 T) was obtained in YBCO films fabricated on LaAlO3 (LAO) single crystal substrates from the new starting solution.

Abstract:In this paper, chitosan (CS)/graphene oxide (GO) composite films were prepared, and the effect of γ-ray irradiation on the properties of composite films was investigated. The irradiation crosslinking reaction occurred in composite films with the existence of acetic acid, and the properties changed upon the various irradiation dose. The swelling degree of the composite film with 0 wt % GO decreased with the increasing of the irradiation dose, but the swelling degree of which with GO increased instead. The thermal stability increased with the increasing of the irradiation dose, but the effect of the irradiation on the thermal stability weakened as the increasing of the content of GO, due to the enhanced irradiation resistance performance. The tensile strength increased firstly and decreased subsequently with the increasing of the irradiation dose and the content of GO. Composite films showed the enhanced antibacterial activity against Bacillus subtilis, compared to Escherichia coli and Staphylococcus aureus. The antibacterial activity weakened with the increasing of the content of GO. The antibacterial activity was relatively stronger when the irradiation dose was 20 KGy. In addition, the structural, crystal, and morphological properties of composite films were characterized by FT-IR, XRD, and SEM. It is worth noting that the GO was pre-functionalized via KH560 for the better compatibility with CS matrix.

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Bi5FeTi3O15 (BFTO) and BFTO/CuO films were deposited by a sol-gel technique, which exhibited macroscopic ferroelectric properties. It was found that the BFTO/CuO films showed a short circuit photocurrent density (Jsc) enhanced by nearly 10 times and power conversion efficiency increased by 13-fold compared to those of the BFTO film. The significant increase in the photovoltaic (PV) response may be attributed to the p-n junction internal electric field acting as the driving force of photogenerated carriers. Furthermore, both BFTO and BFTO/CuO films indicated a switchable PV response in both polarities. The open circuit voltage (Voc) and Jsc for BFTO and BFTO/CuO were observed to be −0.59 V and +43.88 μA/cm2 and −0.23 V and +123.16 μA/cm2, respectively, after upward poling, whereas after downward poling, +0.11 V and −6.26 μA/cm2 and +0.17 V and −83.21 μA/cm2 for BFTO and BFTO/CuO were observed, respectively. The switchable PV responses were explained by the ferroelectric depolarization field, whose direction could be altered with the variation in the applied poling field. This work provides an efficient approach to developing ferroelectric film based PV devices with low cost.

BackgroundThe COVID-19 pandemic has made many countries adopt restrictive measures like home quarantine. Children were required to study at home, which made parents worried about the rapid myopic progression of their children. To compare myopia progression during the COVID-19 pandemic home quarantine with the time before it and risk factors of myopia progression, we conducted this study.MethodsWe searched PubMed, Embase, the Cochrane Library, and Web of Science to find literature from December 2019 to March 2022 related to COVID-19 pandemic home quarantine and children's myopia progression. Outcomes of myopia progression included axial length and spherical equivalent refraction. Factors of digital screen device time and outdoor activity time were analyzed.ResultsTen studies were included in this meta-analysis. Compared to the same period before the COVID-19 pandemic, spherical equivalent refraction decreased (OR = −0.27; 95% CI = [−0.33, −0.21]; Z = 8.42; P < 0.00001). However, the subgroup analysis showed that there were no significant differences in spherical equivalent refraction between the two groups in higher-grade school-aged children (grades 4 and above, 11 to 18 years old) (OR = 0.01; 95% CI = [−0.05, 0.07]; Z =0.4; P = 0.69). The outcome of axial length showed no significant difference (OR = 0.06; 95% CI = [−0.31, 0.44]; Z = 0.34; P = 0.74). As for risk factors, the forest plots showed that digital screen device time (OR = 4.56; 95% CI = [4.45, 4.66]; Z = 85.57; P < 0.00001) and outdoor activity time (OR = −1.82; 95% CI = [−2.87, −0.76]; Z = 3.37; P = 0.0008) were risk factors of myopia progression.ConclusionCompared with the time before the COVID-19 pandemic, myopia progression in children during COVID-19 pandemic home quarantine was accelerated, especially in younger children. Increased digital screen device and decreased outdoor activity times were risk factors. When home quarantine eases, more time on outdoor activities and less time on digital screen devices are needed for children.Systematic Review Registrationhttps://www.crd.york.ac.uk/prospero/logout.php.

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