Search

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.

Carbazole-based conjugated small molecule electrolytes (CSEs) containing different numbers of amine groups were synthesized and applied to bulk-heterojunction (BHJ) organic solar cells for the formation of a spontaneous self-assembled electron transporting layer (ETL). The active layer was spin-coated with a mixture solution containing the BHJ materials and a small amount of CSE, and a thin layer of CSE was formed underneath the active layer (CSE/BHJ bi-layer) via spontaneous phase separation, which is confirmed by the depth profile of the time of flight secondary ion mass spectroscopy (ToF-SIMS) spectrum. The amino groups in the CSEs form hydrogen-bonds with the surface of indium tin oxide (ITO), which acts as an ETL in BHJ solar cells. Moreover, the formed CSE layer is capable of changing the effective work function (WF) of ITO. An increasing number of amino groups in the CSEs (from Cz1N to Cz3N) provides more reduction of the effective WF of ITO, which results in a lower internal resistance and a higher power conversion efficiency (PCE). Furthermore, the enhanced hydrogen bonding between the amines and ITO with an increased number of amine groups has been studied by XPS. This result suggests that one-step processing provides a reduction of the manufacturing cost, which can provide an attractive design concept for ETL fabrication.

The chiral 1,2-diphenylethylenediamine derivative that is capable of spontaneous self-assembly was employed as an organogel template to produce a helical mesoporous silica nanotube containing gelators therein by following sol-gel polycondensation of TEOS. The synthesis enabled the successful introduction of the hydrocarbon of octyl silane (hydrophobic functional group) onto the outer surface of the silica nanotube while preserving the hydrophilic silanol (Si OH) group on internal surface of silica nanotube free from the gelators. This synthetic condition consists of a pre-stage of the introduction of a hydrophobic hydrocarbon functional group onto the outer surface of the silica nanotube selectively, and the post-stage washing of the gelators was presented together with a method analyzing the actions of organogels in the respective experimental processes.

Two liquid chromatographic chiral stationary phases based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid were applied to the resolution of the amide derivatives of cyclic α-amino acids including proline and pipecolic acid. Among the five amide derivatives of proline, aniline amide was resolved best on the first chiral stationary phase, which contains two N–H tethering amide groups, with the separation factor of 1.31 and the resolution of 2.60, and on the second chiral stationary phase, which contains two N–CH3 tethering amide groups, with the separation factor of 1.57 and the resolution of 5.50. Among the five amide derivatives of pipecolic acid, 2-naphthyl amide was resolved best on the first chiral stationary phase with the separation factor of 1.30 and the resolution of 1.75, but 1-naphthylmethyl amide was resolved best on the second chiral stationary phase with the separation factor of 1.30 and the resolution of 2.26. In general, the second chiral stationary phase was found to be better than the first chiral stationary phase in the resolution of the amide derivatives of cyclic α-amino acids. In this study, the second chiral stationary phase was first demonstrated to be useful for the resolution of secondary amino compounds.

A new chiral stationary phase (CSP) in which (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was linked to a silica gel surface through a long alkyl chain and which did not contain additional aminoundecyl groups was prepared. Generally, when enantiomers containing a primary amine group are optically resolved using a crown-ether-type CSP, a higher resolution is achieved if the surface of the CSP does not contain any residual amine. In this study, the chiral separation factor and resolution factor of a CSP with a long alkyl chain such as the aminoundecyl group were unusually low in the absence of the residual aminoundecyl groups. In this study, a chiral column was prepared by introducing a chiral selector having a long alkyl chain on the surface of silica gel to separate enantiomers of α-amino acids. Furthermore, it was confirmed that the residual-amine-containing CSP, which was easier to synthesize, facilitated more effective enantiomeric separation than the CSP without residual amines.

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.

Conjugated small molecular electrolytes (CSMEs), based on carbazole, containing different number of N and F atoms, were synthesized and introduced as the electron transport layer (ETL) for the fabrication of the polymer solar cells. Active-layer materials of bulk heterojunction and synthesized CSMEs were mixed as one solution which was coated on ZnO/ITO in one go to provide the spontaneous phase separation of the active-layer and ETL, which is identified by ToF-SIMS, for the generation of enhanced device performance. Caused by the interaction of the amino groups with ZnO, assisted by the fluorine atoms of the CSMEs, the spontaneous formation of the ETL layer was achieved for the enhancement of the efficiency of the device. The efficiency of polymer solar cells was improved as increasing the number of F atoms (from CzN1 to CzN1F4 and from CzN4 to CzN4F4). It was caused by the introduced F atom which could be led to the n-doping effect. The polymer solar cells utilizing one solution of CzN1F4 and PTB7-Th:PC71BM showed the highest power conversion efficiency (PCE) of 8.93%, with VOC of 0.78 V, Jsc of 16.09 mA/cm2 and FF of 0.72.

A Fe-TiO2 photocatalyst was manufactured using temperature regulated chemical vapour deposition and subsequent annealing at 750 °C. Photocatalytic removal of acetaldehyde and toluene over Fe-TiO2 under visible light were studied at various humid conditions (0, 30, and 60 relative humidity %, RH%). The total oxidation of the two volatile organic compounds (VOCs) on the Fe-TiO2 surface can be facilitated by water vapours although the apparent removal of the VOCs reduced with increasing humidity due to the competitive adsorption between water and VOCs. Besides, the decomposition pathways of two VOCs on the Fe-TiO2 surface can be varied by humidity levels. The total oxidation of acetaldehyde was gradually enhanced with increasing humidity. Whereas the total oxidation of toluene was maximized at moderate RH condition (30 RH%) and further increase in humidity (60 RH%) inhibited the total oxidation. We also demonstrated two possible regeneration methods for efficient recovery of the photocatalytic activity of spent Fe-TiO2 for real air purifying applications.

Fe-oxide particles were deposited on commercial Pt/Al2O3 in a highly dispersed manner via simple temperature regulated-chemical vapor deposition. We found that the catalytic activity of Pt/Al2O3 toward CO oxidation at room temperature can be enhanced by deposition of Fe-oxide on Pt/Al2O3. Particularly, as Fe-loading decreased from ∼10 to 0.34 wt%, catalytic activity toward CO oxidation gradually increased. Results of various analyses of catalysts attributed this Fe-oxide-induced enhancement effect to the boundary sites of Pt-Fe on Fe-Pt/Al2O3. It is worth noting that the enhanced catalytic activity of Pt/Al2O3 upon Fe-oxide loading was observed even in the presence of water vapor (40% of the relative humidity). In addition, Fe-oxide-loaded Pt/Al2O3 showed high thermal stability, and the catalytic activity at room temperature was retained after repeated exposure to high temperatures. Our results show the potential of Fe-oxide-loaded Pt/Al2O3 prepared by tr-CVD as a catalyst for low-temperature CO oxidation in practical applications.

A new chiral stationary phase (CSP) based on macrocyclic amide receptor was prepared starting from (1R,2R)-1,2-diphenylethylenediamine. The new CSP was successfully applied to the resolution of various N-(substituted benzoyl)-α-amino amides with reasonably good separation factors and resolutions (α = 1.75 ~ 2.97 and RS = 2.89 ~ 6.82 for 16 analytes). The new CSP was also applied to the resolution of 3-substituted 1,4-benzodiazepin-2-ones and some diuretic chiral drugs including bendroflumethiazide and methylchlothiazide and metolazone. The resolution results for 3-substituted 1,4-benzodiazepin-2-ones and some diuretic chiral drugs were also reasonably good.

A new wide band gap polymer, P(BDTT–BTBDPPD), consisting of electron rich 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTT) and electron deficient bithiophene-incorporated bis(pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione) (BTBDPPD) derivative was prepared to improve the photovoltaic performances of a reported polymer, P(BDTT–TBDPPD), containing BDTT and thiophene-incorporated bis(pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione) (TBDPPD) derivative. Polymer P(BDTT–BTBDPPD) exhibited maximum absorption at 478 nm and the calculated optical band gap was 2.10 eV. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of P(BDTT–BTBDPPD) were estimated to be −5.44 eV and −3.34 eV. The hole mobility of P(BDTT–BTBDPPD) was 3.22 × 10−4 cm2 V−1 s−1. The polymer solar cells (PSCs) prepared using P(BDTT–BTBDPPD) : PC70BM (1 : 2 wt%) + 3 vol% DIO blend offered a maximum power conversion efficiency (PCE) of 4.62% with an open-circuit voltage (Voc) of 0.90 V, a short-circuit current (Jsc) of 7.99 mA cm−2, and a fill factor (FF) of 64%. This study suggests that the replacement of the thiophene spacer unit located between the pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione units of bis(pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione) derivative with a bithiophene unit did not considerably alter the energy levels and charge transport properties of the resulting polymer. However, the overall photovoltaic performance was improved due mainly to the enhanced morphology of the photoactive layer.

Fe-oxide/Al2O3 catalysts were fabricated by depositing Fe-oxide nanoparticles with a lateral size less than ~2 nm in a highly dispersed manner within mesoporous Al2O3 using temperature-regulated chemical vapor deposition (TRCVD). The Fe-oxide/Al2O3 catalysts were post-annealed at either 450 °C (for 2 h) or 750 °C (for 2 or 8 h) and were used to catalyze NO reduction by CO. Catalytic activity was significantly enhanced with increased annealing temperature and time. Secondary ion mass spectrometry using Bi3+ as the primary ion shows an increase in the FeAlO+ signal from the interfaces between Fe-oxide and Al2O3 with increasing annealing temperature and time, suggesting that the enhanced interaction between Al2O3 and Fe-oxide is responsible for the increased catalytic activity. It is shown that TRCVD with a proper post-annealing step is a competitive tool for preparation of heterogeneous catalysts with highly dispersed catalyst nanostructures within mesoporous substrates that contain rich oxide/oxide interfaces and allow enhanced catalytic activity.

With the increasing adoption of organic light-emitting diodes (OLEDs), analytical methods and tools for their inspection are becoming an important part of the field. In this study, we analyzed four organic materials for OLEDs by using time-of-flight secondary ion mass spectrometry (ToF-SIMS) with 20 keV Ar cluster ion beam projectiles. The fragmentation ratio was plotted as a function of the size of the Ar cluster ions. We reconfirmed that a larger Ar cluster ion beam, which has lower energy per atom, is more effective for detecting secondary molecular ion signals. However, the fragmentation ratio of 4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC) showed a different tendency. The reason for this difference was investigated and validated by scanning the cluster ion size and comparing it with other mass spectrometric results. This study demonstrates the potential of ToF-SIMS in combination with a cluster ion beam to verify defects in OLEDs that might occur in the manufacturing process.

A new chiral stationary phase (CSP) based on macrocyclic amide receptor was prepared starting from (1R,2R)-1,2-diphenylethylenediamine. The new CSP was successfully applied to the resolution of various N-(substituted benzoyl)-α-amino amides with reasonably good separation factors and resolutions (α = 1.75 ~ 2.97 and RS = 2.89 ~ 6.82 for 16 analytes). The new CSP was also applied to the resolution of 3-substituted 1,4-benzodiazepin-2-ones and some diuretic chiral drugs including bendroflumethiazide and methylchlothiazide and metolazone. The resolution results for 3-substituted 1,4-benzodiazepin-2-ones and some diuretic chiral drugs were also reasonably good.

Two new diastereomeric chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as a chiral tethering group and a Π-basic chiral unit such as (R)-1-(1-naphthyl)ethylamine (CSP 1) or (S)-1-(1-naphthyl)ethylamine (CSP 2) were prepared. The two CSPs were applied to the enantiomeric separation of N-(3,5-dinitrobenzoyl)-1-phenylalkylamines and N-(3,5-dinitrobenzoyl)-α-amino acid derivatives using 20% isopropyl alcohol in hexane as a normal mobile phase. To elucidate the effect of the two chiral units on the chiral recognition, the chiral recognition abilities of the two CSPs were compared with each other and with that of a CSP (CSP 3) based on (R)-1-(1-naphthyl)ethylamine. From the chromatographic chiral recognition results, (R)-1-(1-naphthyl)ethylamine and (+)−(18-crown-6)-2,3,11,12-tetracarboxylic acid constituting CSP 1 were concluded to show a cooperative (“matched”) effect on the chiral recognition while (S)-1-(1-naphthyl)ethylamine and (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid constituting CSP 2 were concluded to show an uncooperative (“mismatched”) effect on the chiral recognition. From these results, it was concluded that (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid can be successfully used as a chiral tethering group for the preparation of new CSPs.