The growth of epitaxial graphene on SiC and its metal intercalation: a review.

High-quality epitaxial graphene (EG) on SiC is crucial to high-performance electronic devices due to the good compatibility with Si-based semiconductor technology. Metal intercalation has been considered as a basic technology to modify EG on SiC. In the past ten years, there have been extensive research activities on the structural evolution during EG fabrication, characterization of the atomic structure and electronic states of EG, optimization of the fabrication process, as well as modification of EG by metal intercalation. In this perspective, the developments and breakthroughs in recent years are summarized and future expectations are discussed. A good understanding of the growth mechanism of EG and subsequent metal intercalation effects is fundamentally important.

Self-efficacy and well-being in the association between caregiver burden and sleep quality among caregivers of elderly patients having multiple chronic conditions in rural China: a serial multiple mediation analysis.

BACKGROUND: Caregivers of elderly patients with multiple chronic conditions have heavy caregiver burden and poor sleep quality, which has an important impact on both caregivers and patients. This study aimed to examine among rural caregivers of elderly patients who have multiple chronic conditions in China, whether self-efficacy and well-being mediate the link between caregiver burden and sleep quality. METHODS: The study recruited 325 caregivers of elderly patients having multiple chronic conditions in rural China. Several measures including the Caregiver Burden Inventory (CBI), Athens Insomnia Scale (AIS), General Self-Efficacy Scale (GSES) and Index of Well-Being (IWB) were utilized to collect data. Structural equation modeling was employed to study the relationships among caregiver burden, sleep quality, self-efficacy, as well as well-being. RESULTS: Significant correlations were found between the measured variables (each p < 0.01). Self-efficacy and well-being acted as mediators in the link between caregiver burden and sleep quality, accounting for 10.94% and 15.63% of the total effect, respectively. In addition, self-efficacy and well-being had a serial multiple mediating effect in the association between caregiver burden and sleep quality, with this mediating pathway, explaining 9.93% of the total effect. CONCLUSIONS: Caregivers of elderly patients having multiple chronic conditions in rural China experienced poor sleep quality due to the caregiver burden. Self-efficacy and well-being had serial mediating roles on the relationship between caregiver burden and sleep quality. Effective interventions should be developed to improve self-efficacy and well-being of caregivers, reduce their caregiver burden and, eventually, improve their sleep quality.

Chicken cecal microbiota reduces abdominal fat deposition by regulating fat metabolism.

Cecal microbiota plays an essential role in chicken health. However, its contribution to fat metabolism, particularly in abdominal fat deposition, which is a severe problem in the poultry industry, is still unclear. Here, chickens at 1, 4, and 12 months of age with significantly (p < 0.05) higher and lower abdominal fat deposition were selected to elucidate fat metabolism. A significantly (p < 0.05) higher mRNA expression of fat anabolism genes (ACSL1, FADS1, CYP2C45, ACC, and FAS), a significantly (p < 0.05) lower mRNA expression of fat catabolism genes (CPT-1 and PPARα) and fat transport gene APOAI in liver/abdominal fat of high abdominal fat deposition chickens indicated that an unbalanced fat metabolism leads to excessive abdominal fat deposition. Parabacteroides, Parasutterella, Oscillibacter, and Anaerofustis were found significantly (p < 0.05) higher in high abdominal fat deposition chickens, while Sphaerochaeta was higher in low abdominal fat deposition chickens. Further, Spearman correlation analysis indicated that the relative abundance of cecal Parabacteroides, Parasutterella, Oscillibacter, and Anaerofustis was positively correlated with abdominal fat deposition, yet cecal Sphaerochaeta was negatively correlated with fat deposition. Interestingly, transferring fecal microbiota from adult chickens with low abdominal fat deposition into one-day-old chicks significantly (p < 0.05) decreased Parabacteroides and fat anabolism genes, while markedly increased Sphaerochaeta (p < 0.05) and fat catabolism genes (p < 0.05). Our findings might help to assess the potential mechanism of cecal microbiota regulating fat deposition in chicken production.

Multifunctional CaF2: Yb3+, Ho3+, Gd3+ Nanocrystals: Insight into Crystal Growth and Properties of Upconversion Luminescence, Magnetic, and Temperature Sensing Properties.

The upconversion (UC) emission intensity of Ln3+-doped CaF2 nanomaterials is not ideal, which limits their application in some advanced scientific fields. Hence, it is extremely imperative to enhance the emission intensity of UC nanocrystals. In this work, an ionic-liquid-assisted hydrothermal method based on an ethylene glycol (EG) and ionic liquid (IL) two-phase system was used to synthesize CaF2 doped with Yb3+ and Ho3+. The influence of the amount of IL and the reaction time as well as the concentration of Gd3+ doping on morphology and size was studied in detail, and the growth mechanism was proposed. Green UC luminescence materials were obtained through co-doping Yb3+ and Ho3+ ions. Furthermore, the luminescence of UC was increased monotonically with the introduction of Gd3+ ions. The effect mechanism of Gd3+ doping on the UC luminescence was put forward, which might provide a new method for the promotion of UC luminescence. In addition, the temperature sensing of CaF2: Yb3+/Ho3+/Gd3+ was investigated, which demonstrated that the phosphor has a potential application prospect in thermal sensing. Meanwhile, CaF2: Yb3+/Ho3+/Gd3+ also exhibited a paramagnetic property at room temperature. Therefore, these multifunctional nanocrystals may have prospective applications in optical bioimaging, magnetic resonance imaging, and temperature sensing.

A universal CRISPR/Cas12a nucleic acid sensing platform based on proximity extension and transcription-unleashed self-supply crRNA.

The extraordinary genome-editing tool CRISPR/Cas12a has also been utilized as a powerful sensing technology owing to its highly-specificity and isothermal signal amplification. Nevertheless, the widespread application of Cas12a-based sensing methods in nucleic acid detection is limited by the targeting range and high undesired background. Herein, we established a universal Cas12a-based nucleic acid sensing strategy by using proximity extension and transcription-unleashed self-suppling of crRNA. The target was recognized and bound to a pair of adjacent probes, and then triggered the proximity-induced primer extension and transcription amplification to produce numerous crRNAs. The amplified abundant crRNAs assembled with Cas12a and dsDNA activators containing PAM to form a ternary complex, which trans-cleaved ssDNA-FQ reporters continuously to generate a strong fluorescent signal. Thus, the cascade enzymatic amplification was performed and subsequently applied for detecting target DNA down to 41.7 amol with a low nonspecific background. The application of this strategy in RNA detection has also been demonstrated, and it is expected to provide a universal and sensitive sensing platform for molecular diagnosis applications.

Nanostructured Bi Grown on Epitaxial Graphene/SiC.

Controllable growth of metal nanostructures on epitaxial graphene (EG) is particularly interesting and important for the applications in electric devices. Bi nanostructures on EG/SiC are fabricated through thermal decomposition of SiC and subsequent low-flux evaporation of Bi. The orientation, atomic structure, and thickness-dependent electronic states of Bi are investigated by scanning tunneling microscopy/spectroscopy. It is found that metallic Bi nanoflakes and nanorods prefer to grow on the SiC buffer layer region with higher diffusion barrier, but Bi nanoribbons are formed on regularly ordered EG. Although the thicker Bi nanoribbons of 11 monolayers on EG are still metallic, the thinner ones become semiconducting owing to the interfacial effect. This indicates that the electronic states and physical properties of Bi are substrate-dependent. The results are helpful for the design of Bi- and graphene-based electronic and spintronic devices.

Thickness dependent Raman spectra and interfacial interaction between Ag and epitaxial graphene on 6H-SiC(0001).

Graphene as the thinnest material has an extremely large specific surface area, and thus the physical properties of graphene based devices should be sensitively dependent on the contacted metals. Moreover, the interfacial interaction between graphene and metals is complicated and it is difficult to probe. In this paper, epitaxial graphene is prepared by thermal decomposition of 6H-SiC(0001), and then Ag is deposited on it. It is found that the morphology and distribution of Ag particles on graphene domains are independent of the graphene thickness. The Ag particles induce the surface enhanced Raman scattering (SERS) effect and the doping effect in epitaxial graphene. The enhancement factor of SERS as well as the splitting of the G band and the shift of the 2D band decreases with increasing graphene thickness, which can be ascribed to the weakened interaction between Ag and EG. This is confirmed by the charge transfer between the Ag atom and epitaxial graphene on 6H-SiC predicted by first-principles calculations. The results are helpful to the design and development of graphene-based composites and devices.