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Oxyapatite[Ca2Nd8(SiO4)6O2] glass-ceramics have been suggested as wasteforms for the immobilisation of rare-earth radioactive nuclides because of their high waste-loading capability and good chemical durability. In particular, a partitioning effect is predicted to contribute to an enhancement of corrosion resistance in glass-ceramics compared with that of conjugate glasses of the same composition. Because rare-earths are inherently insoluble nuclides, detection of changes in corrosion behavior between glass-ceramics and conjugate glasses under normal conditions is not easy. In this study, therefore, we revealed the partitioning effect by exposing glass-ceramics and glasses to solution of pH 2, 7 and 10 at 90 °C for 20 d. In addition, we proposed the corrosion mechanism for oxyapatite glass-ceramics under various corrosion conditions. Especially, the glassy phase dissolved first, followed by the oxyapatite phase during pH 7 corrosion.

Transparent conductive oxide (TCO) thin films are cornerstones in many optoelectronic applications including displays, photovoltaics and touchscreens. In these devices, thin films with simultaneous high optical transparency and electrical conductivity are needed. Ideally, heat generated during normal device operation must ideally be compensated for to achieve optimum functionality. One possible way to address the thermal management problem is adding thermoelectric (TE) properties to TCO films. However, improving TE properties while maintaining optimal electrical conductivity and optical transparency is challenging: thermal and electrical transport properties are deeply intertwined. Here, we demonstrate an approach allowing for independent optimization of optical transparency, electrical conductivity and thermal conductivity. An embedded nanopattern structure is filled with indium tin oxide (ITO) and sandwiched between two ITO layers. The resulting triplelayered structure exhibits reduced thermal conductivity and excellent electrical conductivity. This is made possible by electron channels in the embedded ITO nanopattern that electrically connect top and bottom layers, while at the same time limiting phonon-mediated heat conduction. The filling fraction and thickness of the nanopattern are adjusted to improve optical transmission, achieving transparency higher than bare ITO film. The result is a transparent TCO triple layer film with simultaneous high TCO and thermoelectric figures of merit.

We report an optimized multi-step chemical vapor deposition process for growing MoS2 thin films. This process enables large-area processing, film patterning simply by using shadow masks, and precise control of the final thickness by changing the initial thickness of the first step of MoO3 film deposition. The structural characterization of the MoS2 films is performed with transmission electron microscopy and X-ray diffraction as a function of film thickness. MoS2 film with a thickness of 3 nm possesses a highly crystalline structure with a spacing of 0.62 nm. The crystallinity and orientation of the films are degraded with increased film thickness. Careful analysis by time-of-flight secondary ion mass spectroscopy reveals that a film with a thickness of 9 nm is not completely sulfurized, and unreacted MoO3 is left at the bottom of the film. These fundamental analyses coincide with the thickness dependence of thin-film transistor (TFT) performance. A TFT with the optimal film thickness of 3 nm achieves high performance, namely a carrier mobility of 0.57 cm2 V−1 s−1 and an on/off ratio of ~ 102.

Transparent glass of xEu2O3-(100-x)TeO2 binary system is obtained by using the melt-quenching method and especially studied for x = 5 in xEu2O3-(100-x)TeO2 composition. Optical properties such as transmission, excitation, and emission spectra of Eu2O3-TeO2 glass-ceramics are studied and carefully compared for the samples heated at different temperatures. The one step heat-treatment affects the crystallinities as well as phase formation and yields cubic [Eu2Te6O15], orthorhombic [TeO2], and tetragonal [TeO2] phases depending on the heat treating temperature. Glass-ceramics of Eu3+-doped tetragonal [TeO2] shows stronger emission intensity at wavelength of 613 nm with an excitation wavelength of 394 nm compared with that from cubic [Eu2Te6O15] or Eu3+-doped orthorhombic [TeO2]. Enhancement of emission intensity in Eu3+-doped tetragonal [TeO2] is related to the local environment of Eu3+ ions substituted in tetragonal TeO2 lattice.

Highly uniform, self-supported PbTiO3 nanotube arrays are fabricated on a transparent conducting glass by an all solution-based, hard-templating procedure. A new concept of site-isolation has been realized by Pt-sol infiltration only in the internal core of deposited nanotube arrays and thus physically separating electron and hole reaction sites on inside and external surface of the nanotubes, respectively. The effective charge separation by the site-isolated Pt-nanodot deposited PbTiO3 nanotube photoanode leads to greatly enhanced photocurrent generation and H2 evolution efficiencies relative to those of the particulate-type photoanode or PbTiO3 nanotube without Pt infiltration in photoelectrochemical water splitting under visible light. The physical site isolation through nano-engineering of the material fabrication is expected to offer an effective strategy for preparation of high-efficiency photoelectrochemical devices.

A new approach based on differential pulse voltammetry (DPV) was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) using a modified glassy carbon electrode (GCE). The sensor was constructed by a simple “one-step” technique, wherein de-bundled single-walled carbon nanotubes (SWCNTs) were drop-cast onto the GCE. Without de-bundling, the SWCNTs were poorly dispersed in aqueous solution and were ineffective for the one-step procedure. De-bundling of the SWCNTs was achieved using a small amount (0.1 wt%) of the synthesized polymer dispersant, sulfonated poly(ether sulfone) (SPES); the de-bundled SWCNTs had a high aspect ratio (length = 2.5 ± 1.0 μm; height = 2 ± 1 nm, as determined using transmission electron microscopy and atomic force microscopy). The de-bundled SWCNTs also led to enhanced electrocatalytic activity and selectivity of the modified sensor for the simultaneous determination of AA, DA, and UA in DPV measurements: the peak-to-peak separation values were 221, 119, and 340 mV (vs. Ag/AgCl) for DA–AA, UA–DA, and AA–UA, respectively. The dynamic linear ranges for AA, DA, and UA were 0.2–1.6 mM, 5.0–50 μM, and 5.0–60 μM, and the detection limits were 10.6 μM, 15 nM, and 113 nM (S/N = 3), respectively. The analytical performance of the developed sensor was demonstrated in the determination of AA and DA in commercial pharmaceutical samples (vitamin C tablets and DA injection). The characteristics of the modified sensor make it promising for the individual or simultaneous determination of AA, DA, and UA.

A new disposable amperometric biosensor for sarcosine (Sar, a biomarker for prostate cancer) was designed based on screen-printed carbon electrodes, Prussian blue, polymer dispersed reduced graphene oxide (P-rGO) nanosheets, and sarcosine oxidase (SOx). Poly(sodium 4-styrenesulfonate-r-LAHEMA) denoted as PSSL was newly synthesized as dispersant for rGO. The P-rGO was utilized for SOx immobilization, the sulfonate and disulfide functionalities in PSSL enable physical adsorption of SOx and its bioactivity and stability properties were improved. The biosensor was optimized by various enzyme concentration, applied potential, and operating pH. Under the optimized conditions, the biosensor exhibited maximum current responses within 5 s at an applied potential of −0.1 V vs. integrated Ag/AgCl reference electrode. The biosensor had a dynamic linear range of 10–400 μM, with a sensitivity of 9.04 μA mM−1 cm−2 and a low detection limit of 0.66 μM (S/N = 3). Additionally, the biosensor possesses strong anti-interference capability, high reproducibility, and storage stability over 3 weeks. Furthermore, its clinical applicability was tested in urine samples from both prostate cancer patients and healthy control, and the analytical recoveries were satisfactory. Therefore, this biosensor has significant potential in the rapid and non-invasive point-of-care testing for prostate cancer diagnosis.

Vertically aligned core–shell PbTiO3@TiO2 heterojunction nanotube arrays are fabricated on F:SnO2 (FTO) glass substrate via a unique three-step process: an electron beam vapor deposition of Ti thin film on FTO, anodic oxidation of the Ti film to TiO2 nanotubes, and finally formation of PbTiO3 perovskite layer at the inner wall of the TiO2 nanotubes. The PbTiO3@TiO2 nanotube array exhibits dramatically improved photoactivity relative to TiO2 nanotubes or PbTiO3/TiO2 composite powders in photoelectrochemical water splitting and photocatalytic isopropyl alcohol decomposition under visible light irradiation (>420 nm). In the core–shell heterojunction electrodes, PbTiO3 serves as a visible light responsive inorganic photosensitizer with its small band gap and forms a heterojunction with TiO2 for effective charge separation.

Leaching behaviors and mechanisms of commercialized glass wasteforms to sequester low-level solid-wastes were investigated: SG glass for resin waste and DG-2 glass for dry active waste. After ANS 16.1 leaching test, leachabilities of the nuclides, Co, Cs, and Sr, were all lager than 14, which met the requirement of the US-Nuclear Regulatory Commission. Holes of diameters 5–10 μm remained on the surface of the SG and crevices of lengths 10–50 μm were observed on the surface of the DG-2. We analyzed elemental compositions of the SG and the DG-2 with depths. For the SG, Si, Al, Ca, and Mg were accumulated and Na was depleted up to nearly 1.5 μm compared to an internal glass. For the DG-2, concentrations of B, Na, Al, Ca and Sr started to decrease from 2.5 μm even though other minor elements are still remained their concentrations. We suggested leaching mechanisms: alkali elements including H would diffuse through the holes on the SG, while most of the elements including Si and Al would diffuse through the crevices on the DG-2.

A long-life electrochemical sensor for the continuous analysis of heavy metal ions (Zn(II), Cd(II), Pb(II), Cu(II), and Hg(II)) was developed using the graphene oxide (GO) anchored-functionalized polyterthiophene (poly[3′-(2-aminopyrimidyl)-2,2′:5′,2′′-terthiophene], polyPATT) composite. The PATT monomer was synthesized and polymerized with GO to form the composite using a potential cycling method, followed by Nafion coating. The modified sensor surface was characterized employing electrochemical and surface analysis methods. Experimental variables affecting the analytical performance were optimized. Interference effects of other metal ions having similar redox potentials were also investigated. The performance of chronocoulometry (CC) without predeposition was compared with the results of square wave anodic stripping voltammetry (SWASV) with predeposition. The dynamic range of CC for the target ions were between 1 ppb and 10 ppm, respectively with the detection limits between 0.05 (±0.05) and 0.20 (±0.15) ppb for the CC method without predeposition, and between 0.08 (±0.05) and 0.30 (±0.12) ppb for the SWASV with 300 sec of deposition time (n=3). The reliability of the method was evaluated by continuously analysing environmental water samples using a single sensor probe in a flow system for 93 days.

Recently, industrial wastewater is being discharged in large quantities due to the development of industry and this wastewater contains a various heavy metal ion. Exposure to high levels of trace metal ions [Cd (II), Pb (II), Cu (II)] causes a variety of health and environmental problems. These toxic species accumulated in the human body through the water source have a low rate of clearance. [1,2] To minimize the exposure of humans to these contaminants through effective water quality monitoring, anode stripping voltammetry (ASV) method was used. ASV method has wide linear dynamic range, low detection limit (ppb), multi-element analysis capability and the simplicity of the instrumentation, which is relatively inexpensive and small in size, requires low levels of electrical power and is sufficiently portable to permit its use in the field. So, ASV has been used successfully for the determination of heavy metals in water. The sensitivity of differential pulse anode stripping voltammetry (DPASV) is higher than other classical voltammetry, because of its enhanced faradaic current and decreased non-faradaic charging current. [2] In generally, Ir, Au, Ag and Hg electrodes have been used for stripping analysis of trace metals, but the Ir, Au, Ag electrodes have low sensitivity, Hg electrode have toxicity and volatility. [2] To solve this drawbacks, we fabricate a Boron-doped diamond (BDD) electrodes. BDD electrodes are candidate for use in the detection of a trace heavy metal ions, because these show good electrical conductivity, low background current, and non-toxicity. In this study, BDD electrodes on Si substrate deposited by hot filament chemical vapour deposition (HFCVD) and applied to DPASV measurement. Through the optimization of the deposition condition of BDD electrodes and measurement condition of DPASV, we increased the detection sensitivity of heavy metal ions. The BDD electrode with the optimum boron doping concentration by controlling the boron doping concentration from 100 to 10000 ppm in the deposition process optimization step has excellent durability and selectivity of heavy metal ions. As a result of electrochemical measurement, BDD electrode with 8000 ppm B was displayed high sensitive response and wide potential window range of -1.7 V to 1.6 V with the detection limit of 0.001 mg/L to 0.01 mg/L ±5 % about heavy metal ions [Cd (II), Pb (II), Cu (II)]. [1] M.O. Park et al, Electroanalysis. 2017, 29, pp. 514 – 520 [2] J. –H. Yoon et al, Bull. Korean Chem. Soc. 2010, Vol. 31, No. 1 This study was supported by the Korea Environmental Industry & Technology Institute[grant number 20190027400012] and R&D Center for Green Patrol Technologies through R&D for Global Top Environmental Technologies [grant number 20180018400013] funded by the Ministry of Environment, Republic of Korea (MOE), Figure 1

The electrical stability and reliability of molybdenum disulfide (MoS2) thin film transistors (TFTs) were investigated by associating thickness-dependent structural defects with degradation mechanism. Patterned MoS2 films with different thicknesses were fabricated for use as transistor channels via the modified multi-step chemical vapor deposition method. X-ray photoelectron spectroscopic (XPS) analyses revealed that highly layered and stoichiometric MoS2 films of up to ∼3 nm thickness were formed around the surface, whereas Mo metal bonds were dominant around the bottom of the films (9 nm). Variations in transistor properties of the thus prepared MoS2 films were examined by applying positive and negative bias stress (PBS and NBS, respectively). The experimental data indicated that MoS2 TFTs with 3-nm-thick films exhibited stable behavior under both PBS and NBS conditions, whereas those with 9-nm-thick films exhibited clear shifts in electrical performance ( △ V t h △ μ s a t s ). These results, together with XPS analyses, revealed that the instability of the MoS2 TFTs under PBS is dominated by sulfur interstitials, whereas their instability under NBS is caused by oxygen vacancies and metallic Mo defects. Additional details about the correlation between the atomic structural defects, which are generated due to insufficient sulfurization of thick films, and the electrical instability of the MoS2 TFTs were discussed.

In this study, GO-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates with various amounts of GO by using an electrochemical deposition. We investigated the effects of the GO content on the morphological, structural, optical, and photoelectrochemical (PEC) properties of the GO-Cu2O composite film and on its XPS spectrum. The highest XRD (111) peak intensity was obtained for the 10-wt% sample, which had an optical energy band gap of 2.15 eV. However, the highest photocurrent density was -4.74 mA/cm2 for the 1-wt% sample, which had an optical energy band gap of 1.94 eV. The photocurrent density for the 1-wt% sample was approximately 1.75 times greater than that for the 0-wt% sample. From the XPS measurements, we observed that the oxygen concentration for the sample with 1-wt% GO was higher than it was for the 0-wt% GO, which may have improved the photocurrent density of the sample with 1-wt% GO.

In this work, graphene oxide–cuprous oxide (GO–Cu 2 O) composite films were grown on fluorine-doped tin oxide substrates by electrochemical deposition. We investigated the effects of the annealing temperature on the morphological, structural, optical and photoelectrochemical (PEC) properties of GO–Cu 2 O composite films. As a result, our work shows that while GO–Cu 2 O composite films exhibit the highest XRD (111) peak intensity at 300 °C sample, the highest photocurrent density value obtained was −4.75 mA/cm 2 at 200 °C sample (using 0.17 V versus a reversible hydrogen electrode (RHE)). In addition, a reduction reaction at 300 °C sample was observed using XPS analysis from the shift in the O1s peak in addition to a weaker O1s peak intensity.

A gyrotron is used as a microwave power source in an electron-cyclotron-resonance (ECR) ion source system. In order to test the gyrotron, which operates at a frequency of 28 GHz in the continuous-wave (CW) mode, the Korea Basic Science Institute (KBSI) developed a water load that absorbed up to 10 kW of power. The water load consists of an aluminum jacket, a quartz window, and a waveguide. A distilled water flow of 13 L/min, sealed with the quartz window, is used as the absorbent. At 28 GHz, the S11 parameter and the voltage standing-wave ratio (VSWR) of the water load design were calculated to be less than −30 dB and 1.05, respectively. In practical experiments, the increase in the water’s temperature was approximately 10 °C at the highest power.

The Korea Basic Science Institute has developed a heavy ion accelerator for fast neutron radiography [1] . To meet the requirements for fast neutron generation, we have developed an accelerator system that consists of an electron cyclotron resonance ion source (ECR-IS), low-energy beam transport (LEBT) system, radio-frequency quadrupole (RFQ), medium-energy beam transport system, and drift tube linac. In this paper, we present the development of the LEBT system as a part of the heavy ion accelerator system, which operates from the ECR-IS to the RFQ entrance.

A Cu(II)-Poly(terthiophene carboxylic acid) (pTTC)/Nafion modified glassy carbon electrode has been used for the chiral recognition and discrimination of d- and l-prolines by the catalytic oxygen reduction pro- cess and the shape of crystals formed on the electrode surface. The cyclic voltammetry with the modified elec- trode in the presence of oxygen recognized d- and l-form of prolines by exhibiting a difference in the peak poten- tial and the peak current of the oxygen reduction. The effect of pH and proline concentration on the peak cur- rent and the peak potential of oxygen have been studied. The SEM studies on the nature of crystals formed on a proline-Cu(II)pTTC complex. The oxidation state of the copper species present at the electrode surface was characterized by ESCA.

A recent study on nanoporous carbon based materials (J. Am. Chem. Soc. 2012, 134, 2864) showed that the presence of abundant graphitized sp(2) carbon species in the frameworks led to higher affinity for aromatic hydrocarbons than their aliphatic analogues. Herein, improved understanding of the sensitive and selective detection of aromatic substances by using mesoporous carbon (MPC)-based materials, combined with a quartz crystal microbalance (QCM) sensor system, was obtained. MPCs were synthesized by direct carbonization of mesoporous polymers prepared from resol through a soft templating approach with Pluronic F127. The carbon-based frameworks can be graphitized through the addition of a cobalt source to the precursor solution, according to the catalytic activity of the cobalt nanoparticles formed during the carbonization process. From the Raman data, the degree of the graphitization was clearly increased by increasing the cobalt content and elevating the carbonization temperature. From a QCM study, it was proved that the highly graphitized MPCs exhibited a higher affinity for aromatic hydrocarbons than their aliphatic analogues. By increasing the degree of graphitization in the carbon-based pore walls, the MPCs showed both larger adsorption uptake and faster sensor response towards toxic benzene and toluene vapors.

Nanoporous layer of Ni-dealloyed AuNi composited with a functionalized conductive polymer (poly[3′-(2-aminopyrimidyl)-2,2′:5′,2′′-terthiophene] (pPAT)) was electrochemically synthesized, characterized, and applied for a Cr(VI) sensor. At first, we examined the voltammetric response of different kinds of Au alloys (AuCu, AuCo, and AuNi) for the Cr(VI) reduction reaction, where porous AuNi alloy reveals the best performance to the catalytic reduction. Hence, the final sensor was prepared through composition of AuNi and pPAT followed by Ni dealloying, which enhances the catalytic performance through increasing the electrochemical active area by about 12.6 times. The sensor revealed a well-behavioural catalytic Cr(VI) reduction at around +0.5 V. The surface analysis and electrochemical characterization were performed for each sensor layer to elucidate morphology and surface composition. Experimental parameters affecting the Cr(VI) analysis were optimized and the interference effects were also investigated. The dynamic range of square wave voltammetry was between 1.0 ppb and 10.0 ppm Cr(VI) with the detection limit of 0.25 ± 0.05 ppb (n = 3). The reliability of proposed sensor was evaluated by analysing real water samples and standard reference material.

In order to accelerate ions, a radio-frequency quadrupole (RFQ) linear accelerator is being developed at the Korea Basic Science Institute (KBSI). The KBSI RFQ is designed to accelerate 1-pmA of lithium trivalent ions (A/Q = 7/3) by using a four-vane structure. We chose 88-MHz for the RF operating frequency. The energy of the beam injected into the RFQ is 12 keV/u whereas the energy of the downstream output beam is 300 keV/u. The beam dynamics inside RFQ linear accelerator was studied using the PARMTEQM code. The length of the RFQ was approximately 2 m with a transmission rate of 97.4% for lithium trivalent ions. For the structural design, a 2-dimensional geometry structure was studied using the SUPERFISH code near the resonance frequency of the quadrupole and the dipole modes. The 3-dimensional field distributions inside the RFQ cavity were investigated using CST Microwave Studio. The RFQ’s conceptual design and preliminary results for this model are reported.

A non-enzymatic potentiometric glucose sensor for the determination of glucose in the micomolar level in saliva was developed based on a molecularly imprinted polymer (MIP) binding on a conducting polymer layer. A MIP containing acrylamide, and aminophenyl boronic acid, as a host molecule to glucose, was immobilized on benzoic acid-functionalized poly(terthiophene) (pTBA) by the amide bond formation onto a gold nanoparticles deposited-screen printed carbon electrode (pTBA/AuNPs/SPCE). Aromatic boronic acid was incorporated into the MIP layer to stably capture glucose and create a potentiometric signal through the changed pKa value of polymer film by the formation of boronate anion-glucose complex with generation of H+ ions by the cis-diol reaction. Reversible binding and extraction of glucose on the sensor surface was observed using a quartz crystal microbalance. Each layer of the sensor probe was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The potentiometric response at the optimized conditions exhibited a wide linear dynamic range of 3.2×10-7 to 1.0×10-3M, with a detection limit of 1.9 (±0.15)×10-7M. The sensor probe revealed an excellent selectivity and sensitivity for glucose compared to other saccharides. In addition, the reliability of the proposed glucose sensor was evaluated in physiological fluid samples of saliva and finger prick blood.

The 28 GHz superconducting electron cyclotron resonance (ECR) ion source has been developed to produce a high current heavy ion for the linear accelerator at KBSI (Korea Basic Science Institute). The objective of this study is to generate fast neutrons with a proton target via a p(Li,n)Be reaction. The design and fabrication of the essential components of the ECR ion source, which include a superconducting magnet with a liquid helium re-condensed cryostat and a 10 kW high-power microwave, were completed. The waveguide components were connected with a plasma chamber including a gas supply system. The plasma chamber was inserted into the warm bore of the superconducting magnet. A high voltage system was also installed for the ion beam extraction. After the installation of the ECR ion source, we reported the results for ECR plasma ignition at ECRIS 2014 in Russia. Following plasma ignition, we successfully extracted multi-charged ions and obtained the first results in terms of ion beam spectra from various species. This was verified by a beam diagnostic system for a low energy beam transport system. In this article, we present the first results and report on the current status of the KBSI accelerator project.

The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm(2). The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

The Korea Basic Science Institute (KBSI) has been developing a heavy ion accelerator system to accelerate high current, multi-charge state ions produced by a 28 GHz superconducting electron cyclotron ion source. A beam analyzing system as a part of the low energy beam transport apparatus was developed to select charged particles with desirable charge states from the ion beams. The desired species of ion, which is generated and extracted from the ECR ion source including various ion particles, can be selected by 90° dipole electromagnet. Due to the non-symmetrical structure in the coil as well as the non-linear permeability of the yoke material coil, a three dimensional analysis was carried out to confirm the design parameters. In this paper, we present the experimental results obtained as result of an analysis of KBSI accelerator. The effectiveness of beam selection was confirmed during the test of the analyzing system by injecting an ion beam from an ECR ion source.