Ultra large and single-layer graphene oxide sheets (up to millimeter in lateral size) are obtained by a modified Hummers’ method, where we replace the first aggressive oxidation process with a short sonication step in H2SO4 solutions. The lateral size of obtained GO sheets can be adjusted by the sonication period: it decreases with the increasing sonication time. The thin-film electrodes made from ultra large reduced GO sheets exhibit lower sheet resistance compared with those from small-size reduced GO sheets. Moreover, the transistor devices made from these single-layer GO sheets after 800 °C thermal reduction exhibit the effective hole mobility ranged between 4 and 12 cm2/(V s). Raman spectroscopic results suggest that the enhancement in mobility at a higher-mobility regime is well explained by the graphitization of GO rather than the removal of functional groups. The ratio between the 2D and G peak areas, I(2D)/I(G), is well correlated to the effective hole mobility values in reduced GO sheets.

Solution-based processes involving the chemical oxidation of graphite and reduction of the obtained graphene oxide (GO) sheets have attracted much attention for preparing graphene films for printed electronics and biosensors. However, the low electrical conductivity of reduced GO is still hindering the development of electronic applications. This article presents that GO sheets reduced by high-temperature alcohol vapors exhibit highly graphitic structures and excellent electrical conductivity. The sheet resistance of thin transparent films is lowered to ∼15 kΩ/◻ (>96% transparency). Field-effect transistors produced from these reduced GO sheets exhibit high effective field-effect hole mobility up to 210 cm(2)/V x s. Raman spectroscopic studies reveal that the conductivity enhancement in the low mobility regime is attributed to the removal of chemical functional groups and the formation of six-fold rings. In the high mobility regime, the growth of the graphitic domain size becomes dominant for enhancing its electrical conductivity. The excellent electrical conductivity of the reduced GO sheets promises potential electronic applications.

We synthesized centimeter-scale single-to few-layer graphene (FLG) films via chemical vapor deposition (CVD) on Ni foils. We demonstrates that the precipitation mechanism may not be the only important mechanism in the formation of graphene by CVD in Ni system, and that controlling the cooling rate in the CVD process may not be the appropriate way to control the thickness of graphene films. In addition, we are the first to demonstrate the transfer of centimeter-scale FLG from Ni foil to transparent flexible polyethylene terephthalate substrates via an efficient roll-to-roll process. Comparing to rigid substrates, synthesis of graphene on flexible Ni foil has necessity for the use of a roll-to-roll transfer process.

Telehealth has become an increasingly applied solution to delivering health care to rural and underserved areas by remote health care professionals. This study integrated social capital theory, social cognitive theory, and the technology acceptance model (TAM) to develop a comprehensive behavioral model for analyzing the relationships among social capital factors (social capital theory), technological factors (TAM), and system self-efficacy (social cognitive theory) in telehealth. The proposed framework was validated with 365 respondents from Nantou County, located in Central Taiwan. Structural equation modeling (SEM) was used to assess the causal relationships that were hypothesized in the proposed model. The finding indicates that elderly residents generally reported positive perceptions toward the telehealth system. Generally, the findings show that social capital factors (social trust, institutional trust, and social participation) significantly positively affect the technological factors (perceived ease of use and perceived usefulness respectively), which influenced usage intention. This study also confirmed that system self-efficacy was the salient antecedent of perceived ease of use. In addition, regarding the samples, the proposed model fitted considerably well. The proposed integrative psychosocial-technological model may serve as a theoretical basis for future research and can also offer empirical foresight to practitioners and researchers in the health departments of governments, hospitals, and rural communities.

The personal health record (PHR) is a system that enables borderless medical care services by combining technological innovation and human consideration. This study explored factors affecting the adoption of PHR from technical, medical, and social perspectives according to the Protection Motivation Theory (PMT) and Unified Theory of Acceptance and Use of Technology (UTAUT) model. A survey using a structured questionnaire was subsequently conducted, which produced the following results: (1) The PMT and UTAUT were effective at predicting PHR usage behaviors; (2) Perceived ease-of-use was the most decisive factor influencing the use of PHR, followed by self-efficacy and perceived usefulness; and (3) Behavioral intention for PHR was significantly and positively correlated with usage behavior. From the obtained results, this study recommends that health authorities and medical institutions promote self-efficacy in the use of PHR to improve the levels of behavioral intention and usage behavior among the people. Additionally, medical care institutions are recommended to promote health management and preventive healthcare concepts to help improve public acceptance of the PHR system as a means to self-manage their health. Finally, community centers, medical institutions, and health authorities are urged to work together to enhance public medical knowledge and pool resources for the PHR system, both of which are essential for improving the popularity of the PHR, public quality of life, and the effectiveness of health management.