One-Step Synthesis of Transition Metal Dichalcogenide Quantum Dots Using Only Alcohol Solvents for Indoor-Light Photocatalytic Antibacterial Activity.

In this study, we report a one-step direct synthesis of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) quantum dots (QDs) through a solvothermal reaction using only alcohol solvents and efficient Escherichia coli (E. coli) decompositions as photocatalytic antibacterial agents under visible light irradiation. The solvothermal reaction gives the scission of molybdenum-sulfur (Mo-S) and tungsten-sulfur (W-S) bonding during the synthesis of MoS2 and WS2 QDs. Using only alcohol solvent does not require a residue purification process necessary for metal intercalation. As the number of the CH3 groups of alcohol solvents among ethyl, isopropyl, and tert(t)-butyl alcohols increases, the dispersibility of MoS2/WS2 increases. The CH3 groups of alcohols minimize the surface energy, leading to the effective exfoliation and disintegration of the bulk under heat and pressure. The bulky t-butyl alcohol with the highest number of methyl groups shows the highest exfoliation and yield. MoS2 QDs with a lateral size of about 2.5 nm and WS2 QDs of about 10 nm are prepared, exhibiting a strong blue luminescence under 365 nm ultraviolet (UV) light irradiation. Their heights are 0.68-3 and 0.72-5 nm, corresponding to a few layers of MoS2 and WS2, respectively. They offer a highly efficient performance in sterilizing E. coli as the visible-light-driven photocatalyst.

Analysis of Interface Phenomena for High-Performance Dual-Stacked Oxide Thin-Film Transistors via Equivalent Circuit Modeling.

Oxide thin-film transistors (TFTs) have attracted much attention because they can be applied to flexible and large-scaled switching devices. Especially, oxide semiconductors (OSs) have been developed as active layers of TFTs. Among them, indium-gallium-zinc oxide (IGZO) is actively used in the organic light-emitting diode display field. However, despite their superior off-state properties, IGZO TFTs are limited by low field-effect mobility, which critically affects display resolution and power consumption. Herein, we determine new working mechanisms in dual-stacked OS, and based on this, we develop a dual-stacked OS-based TFT with improved performance: high field-effect mobility (∼80 cm2/V·s), ideal threshold voltage near 0 V, high on-off current ratio (>109), and good stability at bias stress. Induced areas are formed at the interface by the band offset: band offset-induced area (BOIA) and BOIA-induced area (BIA). They connect the gate bias-induced area (GBIA) and electrode bias-induced area (EBIA), resulting in high current flow. Equivalent circuit modeling and the transmission line method are also introduced for more precise verification. By verifying current change with gate voltage in the single OS layer, the current flowing direction in the dual-stacked OS is calculated and estimated. This is powerful evidence to understand the conduction mechanism in a dual-stacked OS-based TFT, and it will provide new design rules for high-performance OS-based TFTs.

The effect of surface energy characterized functional groups of self-assembled monolayers for enhancing the electrical stability of oxide semiconductor thin film transistors.

The exact direction of the surface energy characterized functional groups of self-assembled monolayers (SAMs) is proposed for achieving enhanced electrical stability of indium gallium zinc oxide (IGZO) semiconductor thin film transistors (TFTs). The SAM treatment, particularly with the SAM functional group having lower surface energy, makes it difficult to adsorb oxygen molecules difficult onto IGZO. Such an effect greatly improves the positive bias stability (PBS) and clockwise hysteresis stability. For NH2 and CF3 functional groups, SAMs with surface energies of 49.4 mJ m-2 and 23.5 mJ m-2, respectively, improved the IGZO TFT PBS from 2.47 V to 0.32 V after the SAM treatment and the IGZO TFT clockwise hysteresis was also enhanced from 0.23 V to 0.11 V without any deterioration of TFT characteristics. Employing lower surface energy functional groups to the SAM, of the same head and body groups, passivates and protects the IGZO backchannel region from oxygen molecules in the atmosphere. Consequently, the enhanced electrical stability of IGZO TFTs can be achieved by the simple and economic SAM treatment.

The effect of Surface energy characterized functional group of self-assembled monolayer for enhancing electrical stability of oxide semiconductor thin film transistor.

The exact direction, of the surface energy characterized functional group of self-assembled monolayer (SAM), is proposed for achieving the enhanced electrical stability of indium gallium zinc oxide (IGZO) semiconductor thin film transistor (TFT). The SAM treatment, particularly at the SAM functional group having lower surface energy, makes oxygen molecules difficult to be adsorbed onto IGZO. And such an effect much improves positive bias stability (PBS) and clockwise hysteresis stability to the same tendency. For NH2 and CF3 functional group SAMs with surface energies of 49.4 mJ/m2 and 23.5 mJ/m2, respectively, the IGZO TFT PBS was improved from 2.47 V to 0.32 V after the SAM treatment and the IGZO TFT clockwise hysteresis was also enhanced from 0.23 V to 0.11 V without any deterioration of TFT characteristics. Employing lower surface energy functional group to the SAM, of same head group and body group, does passivate and protect the IGZO backchannel region from oxygen molecules in the atmosphere. Consequently, the enhanced electrical stability of IGZO TFT can be achieved by the simple and economic SAM treatment.

Atmospheric-pressure plasma treatment toward high-quality solution-processed aluminum oxide gate dielectric films in thin-film transistors.

We present an atmospheric-pressure plasma (APP) treatment technique to improve the electrical performance of solution-processed dielectric films. This technique can successfully reduce leakage current and frequency dependence of solution-processed dielectric films. The APP treatment contributes to the conversion of metal hydroxide to metal oxide, and in the case of a solution-treated AlO x dielectric thin film, it effectively ascribes to the formation of high-quality AlO x dielectric thin films. The capacitance of the untreated AlO x dielectric thin film varies up to 9.9% with frequency change, but the capacitance of the APP treated AlO x dielectric thin film varies within 1.5%. When the solution-processed InO x thin-film transistors (TFTs) were fabricated using these dielectric films, the field-effect mobility of TFTs with the APP-treated AlO x dielectric film was increased significantly from 9.77 to 26.79 cm2 V-1 s-1 in comparison to that of TFTs with the untreated AlO x dielectric film. We also have confirmed that these results are similar to the properties of the sample prepared at high annealing temperature including electrical performance, conduction mechanism and chemical structure. The APP treatment technique provides a new opportunity to effectively improve the electrical performance of solution-processed dielectrics in the atmosphere at low temperature.

Solution-Grown Homojunction Oxide Thin-Film Transistors.

Growing attention has been given to low temperature, solution-processed metal oxide thin-film transistors because they can be applied in the emerging sector of flexible and large-scale electronics. However, major obstacles of solution-grown devices, such as their relatively low field-effect mobility and the difficulty of controlling carrier concentration, limit the further advancement of the electronics. Here, we overcome these constraints through a newly renovated structure, called a "homojunction", consisting of double-stacked semiconductors with same material. The homojunction oxide thin-film transistor has remarkable electrical performance with controllability, for example, tunable turn-on voltage (-80 V to -8 V) and high average field-effect mobility (∼50 cm2/V·s) are obtained via a low annealing temperature process (250 °C). Furthermore, notable achievements associated with stability, reliability, and uniformity are verified. These results are attributed to the unique phenomena of solution-grown thin films: the change of both chemical and physical properties of thin films. Our findings highlight that the thin films of high quality can be yielded through the solution process at low annealing temperatures, and thus solution-grown transistors hold great promise for widespread industrial applications.

Effective Atmospheric-Pressure Plasma Treatment toward High-Performance Solution-Processed Oxide Thin-Film Transistors.

Solution-processed oxide semiconductors (OSs) have attracted much attention because they can simply, quickly, and cheaply produce transparent channels on flexible substrates. However, despite such advantages, in the fabrication process of OS thin-film transistors (TFTs) using the solution process, it is a fatal problem that there are hardly any ways to simply and effectively control important TFT parameters, including the turn-on voltage ( Von) and on/off current ratio. For the practical application of solution-processed OS TFT, approaches to simply and effectively control the parameters are urgently required. Here, we newly propose an atmospheric-pressure plasma (APP) treatment that can simply and effectively control the electrical properties in solution-processed InO x TFTs. Through exposure of APP, we successfully realized the changes in important TFT parameters of solution-processed InO x TFT, Von from -11.4 to -1.9 V and the on/off current ratio from ∼103 to ∼106, which still keep up the high field-effect mobility (>20 cm2 V-1 s-1). On the basis of various analyses such as X-ray-based analysis and UV-visible spectroscopy, we identified that the APP treatment can effectively control oxygen vacancy and carrier concentration in solution-processed OS.

Comparison of long-term oncological outcomes of appendiceal cancer and colon cancer: A multicenter retrospective study.

BACKGROUND: There has been no comparative study of the long-term oncological outcomes of appendiceal cancer and colon cancer. We hypothesized that the oncological outcome is worse in appendiceal cancer because perforation is more frequent than in colon cancer. METHODS: Patients with stage I-III were selected from 5046 patients with appendiceal or colon cancer, between September 2001 and June 2010. The 5-year disease-free survival (DFS) was the primary endpoint. Multivariate analyses with Cox proportional hazards model for DFS and logistic regression model for perforation were conducted. A matching model was used to compensate for the heterogeneity between groups. RESULTS: The perforation rate was 44.7% in appendiceal cancer (n = 47), but 1.1% in colon cancer (n = 2828) (p = 0.001). The 5-year DFS rate was lower in appendiceal cancer than in colon cancer (57.9% vs. 85.2%, p = 0.001; matching model, 54.2% vs. 78.4%, p = 0.038), with a higher rate of peritoneal seeding (25.5% vs. 2.5%, p = 0.001; matching model, 24.0% vs. 4.0%, p = 0.007). Multivariate Cox regression showed that appendiceal cancer was an independent prognostic factor for poor DFS (hazard ratio = 2.602, 95% confidence interval = 1.26-5.35, p = 0.009), and logistic regression confirmed that appendiceal cancer was the risk factor associated with perforation (odds ratio = 66.265, 95% confidence interval = 28.21-155.61, p = 0.001). CONCLUSIONS: This study suggested that the long-term oncological outcomes are worse for appendiceal cancer than for colon cancer, attributed to higher perforation rate in appendiceal cancer.

Acid-free and oxone oxidant-assisted solvothermal synthesis of graphene quantum dots using various natural carbon materials as resources.

To prepare carbon-based fluorescent materials such as graphene quantum dots (GQDs), new and effective methods are needed to convert one-dimensional (1D) or two-dimensional (2D) carbon materials to 0D GQDs. Here, we report a novel acid-free and oxone oxidant-assisted solvothermal synthesis of GQDs using various natural carbon resources including graphite (G), multiwall carbon nanotubes (M), carbon fibers (CF), and charcoal (C). This acid-free method, not requiring the neutralization process of strong acids, exhibits a simple and eco-friendly purification process and also represents a recycling production process, together with mass production and high yield. Newly synthesized GQDs exhibited a strong blue photoluminescence (PL) under 365 nm UV light illumination. The PL emission peaks of all the recycled GQDs did not change.

Mass production of graphene quantum dots by one-pot synthesis directly from graphite in high yield.

One of the most efficient and straightforward methods for production of graphene quantum dots (GQDs) could be their direct preparation from graphite powder by one-pot synthesis using high-powered microwave irradiation. It is believed that in this way, graphite can be multiply broken by repeated redox reactions, which leads to a high yield and mass production.