ABSTRACT
Chemical vapor deposition (CVD) has emerged as the most promising technique towards manufacturing of large area, high quality graphene. Characterization, understanding, and controlling of various structural defects in CVD-grown graphene are essential to realize its true potential for real-world applications. We report a new method for in situ chemical probing of vacancy defects in CVD-grown graphene at room temperature. Our approach is based on a solid-gas phase reaction that occurs selectively in graphene vacancy defect regions such as holes and cracks. Our new probing technique has a unique combination of the following advantages: (1) no exposure to liquids; (2) non-damaging in situ probing; (3) high selectivity, sensitivity, and reliability towards vacancy defects; (4) simplicity and scalability. By focusing on hexagonal graphene domains, we have made the following findings: (1) the nucleation centers of graphene domains are favorable locations of hole defects. (2) The lengthy electron-beam irradiation at very low energy (3.5 keV) could etch the graphene. (3) Graphene cracks often kink at the angle of primarily 150° or 120°. (4) There exist complex graphene cracks such as cracks with clock-hands patterns, and cracks with snowflake-like branched structures. (5) There exist discontinuous cracks in some graphene domains, where hole defects are oriented along a straight or curved line. Such discontinuous cracks may arise from the ductile fracture of graphene. In addition, we have shown that our method is also applicable to chemical probing of vacancy defects such as holes, continuous and discontinuous cracks in CVD-grown monolayer polycrystalline graphene films on copper. Our study also suggests that the copper grain and copper grain boundary play significant roles in formation and distribution of graphene vacancy defects.
ABSTRACT
INTRODUCTION: The potential value of serum levels of intercellular adhesion molecule-1 (ICAM-1) in the staging and pathological nature of bladder cancer was investigated in this study. MATERIALS AND METHODS: A total of 90 patients (mean age 64.5 +/- 7.1) having transitional cell carcinoma of the bladder and 30 control patients (mean age 64.0 +/- 5.5) were enrolled in the study. The serum samples of the patients were obtained on the day before surgery, at the same hour of the day. RESULTS: The preoperative sICAM-1 levels were found to be 46.2 +/- 14.7 and 28.0 +/- 7.8 ng/ml in the tumor group and the control group respectively, which is significantly higher (p = 0.00). The ICAM-1 levels were not different in the invasive tumor group (36 patients) and the superficial tumor group (54 patients; 47.3 +/- 13.8 ng/ml in the invasive group and 45.5 +/- 15.3 ng/ml in the superficial tumor group; p = 0.520). The serum levels of sICAM-1 were significantly higher in grade III tumors than grade I and II tumors (62.0 +/- 8.7, 38.4 +/- 11.9 and 42.2 +/- 8.2 ng/ml respectively; p = 0.000). The mean serum sICAM-1 levels in tumors >3 cm and <3 cm were found to be 52.6 +/- 15.8 and 40.7 +/- 11.0 ng/ml respectively which is statistically significant (p = 0.000). CONCLUSIONS: In this study, serum ICAM-1 levels were found to be related to tumor presence, grade and size. Larger series are needed for the thorough understanding of the role of ICAM-1 in bladder cancer.