Juree Hong

A highly sensitive hydrogen sensor with gas selectivity using a PMMA membrane-coated Pd nanoparticle/single-layer graphene hybrid.

A polymer membrane-coated palladium (Pd) nanoparticle (NP)/single-layer graphene (SLG) hybrid sensor was fabricated for highly sensitive hydrogen gas (H2) sensing with gas selectivity. Pd NPs were deposited on SLG via the galvanic displacement reaction between graphene-buffered copper (Cu) and Pd ion. During the galvanic displacement reaction, graphene was used as a buffer layer, which transports electrons from Cu for Pd to nucleate on the SLG surface. The deposited Pd NPs on the SLG surface were well-distributed with high uniformity and low defects. The Pd NP/SLG hybrid was then coated with polymer membrane layer for the selective filtration of H2. Because of the selective H2 filtration effect of the polymer membrane layer, the sensor had no responses to methane, carbon monoxide, or nitrogen dioxide gas. On the contrary, the PMMA/Pd NP/SLG hybrid sensor exhibited a good response to exposure to 2% H2: on average, 66.37% response within 1.81 min and recovery within 5.52 min. In addition, reliable and repeatable sensing behaviors were obtained when the sensor was exposed to different H2 concentrations ranging from 0.025 to 2%.

Graphene as an atomically thin barrier to Cu diffusion into Si

The evolution of copper-based interconnects requires the realization of an ultrathin diffusion barrier layer between the Cu interconnect and insulating layers. The present work reports the use of atomically thin layer graphene as a diffusion barrier to Cu metallization. The diffusion barrier performance is investigated by varying the grain size and thickness of the graphene layer; single-layer graphene of average grain size 2 ± 1 μm (denoted small-grain SLG), single-layer graphene of average grain size 10 ± 2 μm (denoted large-grain SLG), and multi-layer graphene (MLG) of thickness 5-10 nm. The thermal stability of these barriers is investigated after annealing Cu/small-grain SLG/Si, Cu/large-grain SLG/Si, and Cu/MLG/Si stacks at different temperatures ranging from 500 to 900 °C. X-ray diffraction, transmission electron microscopy, and time-of-flight secondary ion mass spectroscopy analyses confirm that the small-grain SLG barrier is stable after annealing up to 700 °C and that the large-grain SLG and MLG barriers are stable after annealing at 900 °C for 30 min under a mixed Ar and H2 gas atmosphere. The time-dependent dielectric breakdown (TDDB) test is used to evaluate graphene as a Cu diffusion barrier under real device operating conditions, revealing that both large-grain SLG and MLG have excellent barrier performance, while small-grain SLG fails quickly. Notably, the large-grain SLG acts as a better diffusion barrier than the thicker MLG in the TDDB test, indicating that the grain boundary density of a graphene diffusion barrier is more important than its thickness. The near-zero-thickness SLG serves as a promising Cu diffusion barrier for advanced metallization.

Gas-Driven Ultrafast Reversible Switching of Super-hydrophobic Adhesion on Palladium-Coated Silicon Nanowires

A gas-driven ultrafast adhesion switching of water droplets on palladium-coated Si nanowire arrays is demonstrated. By regulating the gas-ambient between the atmosphere and H2 , the super-hydrophobic adhesion is repeatedly switched between water-repellent and water-adhesive. The capability of modulating the super-hydrophobic adhesion on a super-hydrophobic surface with a non-contact mode could be applicable to novel functional lab-on-a-chip platforms.

Synthesis of Few-Layered Graphene Nanoballs with Copper Cores Using Solid Carbon Source

We report the fabrication of graphene-encapsulated nanoballs with copper nanoparticle (Cu NP) cores whose size range from 40 nm to 1 μm using a solid carbon source of poly(methyl methacrylate) (PMMA). The Cu NPs were prone to agglomerate during the annealing process at high temperatures of 800 to 900 °C when gas carbon source such as methane was used for the growth of graphene. On the contrary, the morphologies of the Cu NPs were unchanged during the growth of graphene at the same temperature range when PMMA coating was used. The solid source of PMMA was first converted to amorphous carbon layers through a pyrolysis process at the temperature regime of 400 °C, which prevented the Cu NPs from agglomeration, and they were converted to few-layered graphene (FLG) at the elevated temperatures. Raman and transmission electron microscope analyses confirmed the synthesis of FLG with thickness of approximately 3 nm directly on the surface of the Cu NPs. X-ray diffraction and X-ray photoelectron spectroscopy analyses, along with electrical resistance measurement according to temperature changes showed that the FLG-encapsulated Cu NPs were highly resistant to oxidation even after exposure to severe oxidation conditions.

Effect of dexamethasone in combination with caudal analgesia on postoperative pain control in day-case paediatric orchiopexy

BACKGROUND Dexamethasone has a powerful anti-inflammatory action and has demonstrated reduced morbidity after surgery. The aim of this study was to examine the effects of a single i.v. dose of dexamethasone in combination with caudal block on postoperative analgesia in children. METHODS Seventy-seven children (aged 1-5 yr) undergoing day-case orchiopexy were included in this prospective, randomized, double-blinded study at a single university hospital. After inhalation induction of general anaesthesia, children received either dexamethasone 0.5 mg kg(-1) (maximum 10 mg) (n=39) or the same volume of saline (n=38) i.v. A caudal anaesthetic block was then performed using 1.5 ml kg(-1) of ropivacaine 0.15% in all patients. After surgery, rescue analgesic consumption, pain scores, and adverse effects were evaluated for 24 h. RESULTS Significantly, fewer patients in the dexamethasone group required fentanyl for rescue analgesia (7.9% vs 38.5%) in the post-anaesthetic care unit or acetaminophen (23.7% vs 64.1%) after discharge compared with the control group. The time to first administration of oral acetaminophen was significantly longer in the dexamethasone group (646 vs 430 min). Postoperative pain scores were lower in the dexamethasone group and the incidence of adverse effects was similar in both groups. CONCLUSIONS Intravenous dexamethasone 0.5 mg kg(-1) in combination with a caudal block augmented the intensity and duration of postoperative analgesia without adverse effects in children undergoing day-case paediatric orchiopexy. TRIAL REGISTRATION ClinicalTrials.gov. The number of registration: NCT01041378.

Comparison of intrathecal fentanyl and sufentanil in low-dose dilute bupivacaine spinal anaesthesia for transurethral prostatectomy

BACKGROUND The administration of low-dose bupivacaine can limit the distribution of spinal block to reduce adverse haemodynamic effects. Intrathecal opioids can enhance analgesia in combination with subtherapeutic doses of local anaesthetics. We aimed at comparing the efficacy of intrathecal fentanyl and sufentanil with low-dose diluted bupivacaine for transurethral prostatectomy (TURP) in elderly patients. METHODS Seventy patients undergoing TURP were randomly allocated into two groups. Group F (n=35) received fentanyl 25 microg+bupivacaine 0.5% (0.8 ml)+normal saline 0.3 ml and Group S (n=35) received sufentanil 5 microg+bupivacaine 0.5% (0.8 ml)+normal saline 0.7 ml--in total, bupivacaine 0.25% (1.6 ml) intrathecally. Onset and duration of the sensory block, the degree of the motor block, side-effects, and the perioperative analgesic requirements were assessed. RESULTS The median peak level of the sensory block was significantly higher in Group S than in Group F (P=0.049). Group S required fewer perioperative analgesics than Group F (P=0.008). The time to the first analgesic request was longer in Group S (P=0.025). There were no differences between the groups for the onset and recovery time of the sensory block, degree of the motor block, quality of anaesthesia, or adverse effects. CONCLUSIONS Low-dose diluted bupivacaine with fentanyl 25 microg or sufentanil 5 microg can provide adequate anaesthesia without haemodynamic instability for TURP in elderly patients. However, sufentanil was superior to fentanyl in the quality of the spinal block produced.

Textile-Based Electronic Components for Energy Applications: Principles, Problems, and Perspective

Textile-based electronic components have gained interest in the fields of science and technology. Recent developments in nanotechnology have enabled the integration of electronic components into textiles while retaining desirable characteristics such as flexibility, strength, and conductivity. Various materials were investigated in detail to obtain current conductive textile technology, and the integration of electronic components into these textiles shows great promise for common everyday applications. The harvest and storage of energy in textile electronics is a challenge that requires further attention in order to enable complete adoption of this technology in practical implementations. This review focuses on the various conductive textiles, their methods of preparation, and textile-based electronic components. We also focus on fabrication and the function of textile-based energy harvesting and storage devices, discuss their fundamental limitations, and suggest new areas of study.

Mutiscale substrates based on hydrogel-incorporated silicon nanowires for protein patterning and microarray-based immunoassays

Here, protein micropatterns were prepared on micropatterned nanostructures for potential applications in microarray-based multiplex bioassays with enhanced protein-loading capacity and detection sensitivity. Vertically-aligned silicon nanowires (SiNWs) that were about 8 μm in height and 150 nm in diameter were prepared using an etching process and were surface-modified with aminopropyltriethoxysilane (APTES) to allow them to covalently immobilize proteins. The SiNW substrate was then overlaid with a micropattern of poly(ethylene glycol) (PEG) hydrogel to create defined arrays of microwells consisting of APTES-modified SiNW on the bottom of the wells, with hydrogel on the walls of the wells. Due to the non-adhesiveness of PEG hydrogels toward proteins, proteins were selectively immobilized on the surface-modified SiNW regions to create protein micropatterns. The increase in surface area increased the protein loading capacity of the SiNWs by more than 10 times the capacity of a planar silicon substrate. Immunobinding assays between IgG and anti-IgG and between IgM and anti-IgM that were performed on micropatterned SiNWs emitted stronger fluorescent signals and showed higher sensitivity than assays performed on planar silicon substrates. Finally, microfluidic channels were successfully integrated into the micropatterned SiNWs to enable the simultaneous performance of multiple immunoassays on a single microarray platform.

Increased serum B cell-activating factor level in children with atopic dermatitis

Background.  B cell‐activating factor (BAFF) is a tumour necrosis factor superfamily member best known for its role in the survival and maturation of B cells. BAFF activity is seen in naïve and effector/memory T cells.

Spread of ropivacaine by a weight-based formula in a pediatric caudal block: a fluoroscopic examination

Background: Caudal block is the most common regional technique to provide post‐operative analgesia in pediatric infra‐umbilical surgery. This study was designed to define how many spinal segments would be covered by the weight‐based dosage of caudally administered 0.2% ropivacaine in children using the fluoroscopic method.