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A randomly connected single-walled carbon nanotube (CNT) network film is suggested as an optically homogenous thin film to implement a tunable diffractive optical element with a subwavelength thickness. A Fresnel zone plate (FZP) as a thin-film lens is successfully realized by mask-free direct laser writing onto the CNT network film with a thickness of 450 nm. The fabricated FZP exhibits an intense three-dimensional focus having lateral and axial focal sizes of 0.95λ and 7.10λ, respectively, at the wavelength of 1550 nm. Furthermore, we show that the intensities at focal points of the first and second diffraction orders can be significantly modulated by 72% and 40% through ion-gel gating between +1.8 V and −1.8 V. These results may offer the potential for electro-optic tunability in multifocal diffraction flat optics and the like.

Skutterudite compounds have been studied as potential thermoelectric materials due to their high thermoelectric efficiency, which makes them attractive candidates for applications in thermoelectric power generation. In this study, the effects of double-filling on the thermoelectric properties of the CexYb0.2−xCo4Sb12 skutterudite material system were investigated through the process of melt spinning and spark plasma sintering (SPS). By replacing Yb with Ce, the carrier concentration was compensated for by the extra electron from Ce donors, leading to optimized electrical conductivity, Seebeck coefficient, and power factor of the CexYb0.2−xCo4Sb12 system. However, at high temperatures, the power factor showed a downturn due to bipolar conduction in the intrinsic conduction regime. The lattice thermal conductivity of the CexYb0.2−xCo4Sb12 skutterudite system was clearly suppressed in the range between 0.025 and 0.1 for Ce content, due to the introduction of the dual phonon scattering center from Ce and Yb fillers. The highest ZT value of 1.15 at 750 K was achieved for the Ce0.05Yb0.15Co4Sb12 sample. The thermoelectric properties could be further improved by controlling the secondary phase formation of CoSb2 in this double-filled skutterudite system.

A series of LEDs that have a green CdSe@ZnS quantum dot (QD) emitting layer (EML) in response to treatment with formic acid (FA), 1,3-benzenedithiol (BDT), and 1,2-ethanedithiol (EDT) were fabricated and investigated. The initial long-chained ligands of oleic acid-based CdSe@ZnS QD layers were partially replaced by short-chained and more conductive ligands of FA, BDT, and EDT that can offer to improve the performance of QD-LEDs (QLEDs). Comparison of the operation characteristics of QLEDs without and with various solution treatments revealed that the control of charge injection and recombination conditions in QD EMLs is the key step for the improvement of the efficiency of our devices. The best device performance was observed for EDT treatment with the maximum luminance and luminous efficiency of 3776 cd m−2 and 1.47 cd A−1, respectively, which are increased by 487% and 270% compared with those of the untreated QLED.

We investigated the variation of current density–voltage (J–V) characteristics of an organic solar cell (OSC) in the dark and at 9 different light intensities ranging from 0.01 to 1 sun of the AM1.5G spectrum. All three conventional parameters, short-circuit currents (Jsc), open-circuit voltage (Voc), and Fill factor (FF), representing OSC performance evolved systematically in response to light intensity increase. Unlike Jsc that showed quasi-linear monotonic increase, Voc and FF showed distinctive non-monotonic variations. To elucidate the origin of such variations, we performed extensive simulation studies including Shockley–Read–Hall (SRH) recombination losses. Simulation results were sensitive to defect densities, and simultaneous agreement to 10 measured J–V curves was possible only with the defect density of $$5 \times 10^{12} {\text{ cm}}^{ - 3}$$ 5 × 10 12 cm - 3 . Based on analyses of simulation results, we were able to separate current losses into SRH- and bimolecular-recombination components and, moreover, identify that the competition between SRH- and bimolecular-loss currents were responsible for the aforementioned variations in Jsc, Voc, and FF. In particular, we verified that apparent demarcation in Voc, and FF variations, which seemed to appear at different light intensities, originated from the same mechanism of dominance switching between recombination losses.

Oxide thermoelectric materials are considered promising for high-temperature thermoelectric applications in terms of low cost, temperature stability, reversible reaction, and so on. Oxide materials have been intensively studied to suppress the defects and electronic charge carriers for many electronic device applications, but the studies with a high concentration of defects are limited. It desires to improve thermoelectric performance by enhancing its charge transport and lowering its lattice thermal conductivity. For this purpose, here, we modified the stoichiometry of cation and anion vacancies in two different systems to regulate the carrier concentration and explored their thermoelectric properties. Both cation and anion vacancies act as a donor of charge carriers and act as phonon scattering centers, decoupling the electrical conductivity and thermal conductivity.

This manuscript reports the synthesis and piezoelectric properties of strontium titanate, SrTiO3-modified bismuth sodium titanate-barium titanate, 0.965Bi0.5Na0.5TiO3–0.035BaTiO3, (BNBT-xST, x = 0.00−0.30) ceramics produced by facile low temperature sol–gel and hydrothermal methods. Close inspection of the X-ray diffraction profile through Rietveld refinement indicates ST modification in BNBT leads to a phase transition from the dominant rhombohedral phase to a single tetragonal phase. This structural transition leads to enhancement of electromechanical and energy storage properties. A large dynamic piezoelectric coefficient (d*33 = 350 pC/V) was observed for BNBT-0.1ST sample. High energy storage density (Wrec = 0.37) and large energy storage efficiency (η = 75%) were observed at 75 °C for the BNBT-0.3ST sample. The energy storage response of the tunable ferrorelectric ceramics suggests their possible use for high-performance dielectric capacitor applications.

Vertical heterostructures of graphene and MoS2 are realized by successive growth of MoS2 and graphene, each by chemical vapor deposition. The MoS2 coverage on graphene is controlled by ozone treatment of graphene, which affects the absorption and aggregation of the nucleation promoter perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) for MoS2 seeds on the graphene surface. Mostly single or bilayer MoS2 flakes are grown on graphene with negligible defects even after the ozone treatment and the high-temperature growth process (up to 650 °C). Efficient charge transfer in the grown heterostructures is observed in the photoluminescence and photoresponses of devices based on the heterostructures.

In this work, we demonstrated a phonon-polariton in the terahertz (THz) frequency range, generated in a crystallized lead halide perovskite film coated on metamaterials. When the metamaterial resonance was in tune with the phonon resonance of the perovskite film, Rabi splitting occurred due to the strong coupling between the resonances. The Rabi splitting energy was about 1.1 meV, which is larger than the metamaterial and phonon resonance line widths; the interaction potential estimation confirmed that the strong coupling regime was reached successfully. We were able to tune the polaritonic branches by varying the metamaterial resonance, thereby obtaining the dispersion curve with a clear anticrossing behavior. Additionally, we performed

BiFeO3 with perovskite structure is a well-known material that has both ferroelectric and antiferromagnetic properties called multiferroics. However, leaky electrical properties and difficulty of controlling stoichiometry due to Bi volatility and difficulty of obtaining high relative density due to high dependency on the ceramic process are issues for BiFeO3 applications. In this work we investigated the sintering behavior of samples with different stoichiometries and sintering conditions. To understand the optimum sintering conditions, nonstoichiometric Bi1±xFeO3±δ ceramics and Ti-doped Bi1.03Fe1-4x/3TixO3 ceramics were synthesized by a conventional solid-state route. Dense single phase BiFeO3 ceramics were successfully fabricated using a two-step sintering and quenching process. The effects of Bi volatility on microstructure were determined by Bi-excess and Ti doping. Bi-excess increased grain size, and Ti doping increased sintering temperature and decreased grain size. It should be noted that Ti-doping suppressed Bi volatility and stabilized the BiFeO3 phase.

54 Background: We aimed to retrospectively analyze the efficacy and toxicity of capecitabine, as a salvage treatment, in metastatic colorectal cancer (mCRC) that progressed after prior standard 5FU included chemotherapies. Methods: From January 1, 2008, to December 31, 2017, patients with mCRC, age ≥ 18, who received capecitabine as third- or fourth-line treatment at five different centers in South Korea, were included. All had disease progression on prior palliative chemotherapies including 5FU, oxaliplatin, and/or irinotecan. Results: A total of 131 patients were analyzed with a median age of 62 (range, 35-87). Almost all patients were exposed to prior 5FU (100%), irinotecan (100%), and oxaliplatin (98.5%). Patients were treated with cetuximab (26.7%), or bevacizumab (45.8%) before capecitabine. The median and mean duration from the last 5FU exposure to capecitabine start were 21 and 67.3 days, respectively (range, 5-1322). The objective response rate (ORR) of capecitabine was 3.6%, and the disease control rate was 30.4%. The median progression free survival (mPFS) and median overall survival (mOS) was 2.77 (95% CI, 2.495-3.045) and 9.60 months (95% CI, 7.625-11.575), respectively. There was a significant difference in efficacy according to the duration from the last 5FU exposure to the time of starting capecitabine. Compared to patients who started capecitabine earlier than 67 days after the last 5-FU administration, those who started capecitabine later than that time showed higher ORR (11.1% vs 1.2%; p-value = 0.043), mPFS (4.430 (95% CI, 2.274-6.586) vs 2.570 months (95% CI, 2.326-2.814); p-value = 0.011), and mOS (14.070 (95% CI, 5.627-22.513) vs 9.500 months (95% CI, 7.370-11.630, p-value = 0.021) (Table). 68.7% patients experienced any grade of adverse events, but only 4.6% complained grade 3 or higher. There was no treatment related death. Conclusions: Capecitabine showed modest antitumor activity with good tolerability in mCRC patients whose disease progressed after oxaliplatin and/or irinotecan. It could be considered as an alternative treatment option for mCRC patients, especially for those who have longer treatment free interval after 5FU based chemotherapies. [Table: see text]

In the present work, lead-free piezoelectric ceramics 0.65Bi1.05Fe1−xTixO3-0.35BaTi1−yNbyO3, where x = y = 0, 0.01, 0.015, 0.02, and 0.025, abbreviated as BFT-BTNb, were successfully synthesized by a solid-state reaction method and an air quenching method. The effects of B-Site donor modifications (Nb5+ and Ti4+) on the crystal structure, the morphology and the electrical properties of the 0.65BF-0.35BT ceramics were studied. X-ray diffraction patterns showed the formation of a pure perovskite structure, without any secondary phases. Scanning electron microscope (SEM) micrographs revealed that the average grain size of the BF-BT ceramics decreased with the addition of B-Site donors. Improvements in the ferroelectric properties (P-E loops) and the electric field-induced strain properties (S-E loops) were obtained at the optimum composition of the BFT-BTN ceramics. In addition, the dynamic piezoelectric coefficient (d33*) was enhanced from 265 pm/V for (BFT-BTNb-0) to 360 pm/V for (BFT-BTNb-1) with high working temperature, Tm = 320 °C.

Large-scale growth of mostly monolayer molybdenum disulfide (MoS2) on quartz, sapphire, SiO2/Si, and waveguide substrates is demonstrated by chemical vapor deposition with the same growth parameters. Centimeter-scale areas with large flakes and films of MoS2 on all the growth substrates are observed. The atomic force microscopy and Raman measurements indicate the synthesized MoS2 is monolayer with high quality and uniformity. The MoS2 field effect transistors based on the as-grown MoS2 exhibit carrier mobility of 1–2 cm2V−1s−1 and On/Off ratio of ~104 while showing large photoresponse. Our results provide a simple approach to realize MoS2 on various substrates for electronics and optoelectronics applications.

The thermal stability of the dielectric behavior and the crystal structure, surface morphology, polarization, and piezoelectric properties of lead-free BiGaO3 (BG)-modified 0.65Bi1.05FeO3–0.35BaTiO3 (abbreviated as BF–BT–xBG with 0 ≤ x ≤ 0.03) ceramics were investigated. XRD analysis of BF–BT–xBG dielectric ceramics revealed no remarkable change in the crystal structure within the studied composition range. Around the critical composition (BF–BT–0.02BG), the piezoelectric constant (d33) and electromechanical coupling factor (kp) reached maximum values of ⁓205 pC/N and 34.5%, respectively. The BF–BT–BG dielectric system also exhibited a thermally-stable er (801–902, at 30 °C – 500 °C), high Tmax (395 °C – 416 °C), colossal ermax (46,363–76,303), and ermid (2241 ± 15%–3678 ± 15%, with tanδ ≤ 0.08) across a wide temperature range of 198 °C–332 °C. This improvement in the dielectric properties and high Tmax of the optimum specimen can be attributed to the BiGaO3-modification and quenching process, which made the system viable for applications that require high-temperature dielectric stability.

Point defect or doping in Strontium titanium oxide (STO) largely determines the thermoelectric (TE) properties. So far, insufficient knowledge exists on the impact of double Schottky barrier on the TE performance. Herein, we report a drastic effect of double Schottky barrier on the TE performance in undoped STO. It demonstrates that incorporation of Reduced Graphene Oxide (RGO) into undoped STO weakens the double Schottky barrier and thereby results in a simultaneous increase in both carrier concentration and mobility of undoped STO. The enhanced mobility exhibits single crystal-like behavior. This increase in the carrier concentration and mobility boosts the electrical conductivity and power factor of undoped STO, which is attributed to the reduction of the double Schottky barrier height and/or the band alignment of STO and RGO that allow the charge transfer through the interface at grain boundaries. Furthermore, this STO/RGO interface also enhances the phonon scattering, which results in low thermal conductivity. This strategy significantly increases the ratio of σ/κ, resulting in an enhancement in ZT as compared with pure undoped STO. This study opens a new window to optimize the TE properties of many candidate materials.

We present the study of structural, morphological, dielectric, transport and ferroelectric properties of (1-x)BFO–xPTO solid solutions, with 0.3 ≤ x ≤ 0.6, prepared via non-conventional synthesis methods. These methods include Sol-gel and Single-step solid state method. Structural analysis revealed presence of mixed phases i.e. monoclinic (CC) and tetragonal (P4mm) phases, for all compositions showing a Morphotropic Phase Boundary. For the compositions with higher concentration of PTO, an increase in tetragonal phase fraction has been observed. Quantitative analysis showed, in general, higher value of c/a (i.e. tetragonality) for all samples as compared to the bulk PTO. The morphological analysis shows small grain size irrespective of synthesis method and composition. The low temperature frequency dependent tangent loss shows dielectric relaxation with small magnitude of dielectric constant indicating absence of extrinsic contributions. High temperature dielectric anomaly is observed around 400–500 K corresponding to magnetic phase transformation of BFO at Neel temperature which suggest the presence of magneto-electric coupling in specific compositions. Sol-gel prepared composite appeared to be more resistive than the Single-step synthesized composite and shows Arrhenius type dependence of high temperature ac conductivity. Ferroelectricity was observed in all ceramic samples which sustained high applied electric field up to 190 kV/cm. Finally, a correlation between polarization, tetragonal phase fraction and c/a ratio, has been drawn and discussed. It is concluded that c/a ratio (i.e. tetragonality) is more important parameter which can be tuned to achieve enhanced ferroelectric response as compared to the tetragonal phase fraction in (1-x)BFO–xPTO solid solutions.

We report a facile and efficient way to enhance and modulate thermoelectric performance by incorporating chemically synthesized Cu2Te nanoparticles on p-type Bi0.5Sb1.5Te3 matrix. By varying the amount of Cu2Te nanoparticles, the temperature of maximum thermoelectric performance shifted systematically from room temperature to 425 K. The highest figure-of-merit value, 1.1, was achieved at 377 K by incorporating 0.1 wt% Cu2Te nanoparticles in Bi0.5Sb1.5Te3 matrix, which is due to enhancement in power factor and reduction in lattice thermal conductivity. The results demonstrate that Cu2Te incorporation could be an effective strategy for Bi-Te based thermoelectric power generation.

Binary solid solution of gallium (Ga3+)-modified 0.65Bi1.05FeO3–0.35BaTiO3 (BFGO–BTO with 0–2 mol% Ga3+ content) ceramics were synthesized by a solid-state reaction method, followed by wate...

Controlling oxygen vacancy in undoped SrTiO3 was used to realize the phonon-glass electron-crystal (PGEC) concept. The undoped SrTiO3 samples were synthesized through solid-state-reaction method in air and then reduced through annealing under low oxygen partial pressure conditions. We show that decreasing the oxygen partial pressure (Po2) results in increase of the electrical conductivity, and the oxygen vacancies act as phonon scattering centers, which lead to decrease in the lattice thermal conductivity. Both the enhanced electrical conductivity (σ) and reduced thermal conductivity (κ) were achieved simultaneously through oxygen vacancy in undoped SrTiO3. This significantly increases the ratio of σ/κ that results in an enormously enhanced ZT value of about 13 times larger as compared with the samples reduced under relatively high Po2. Density-functional theory calculations also reveal that oxygen vacancies in SrTiO3 reduce the band-gap, and consequently increase the electrical conductivity.

The Half-Heusler (Hf0.5Zr0.5)1-xTixNiSn0.998Sb0.002 (x = 0, 0.1, 0.3, 0.5 and 0.7) compounds were prepared by vacuum induction melting method combined with annealing, mechanical grinding and spark plasma sintering (SPS) process. For the sintered bodies, the phase and the temperature dependent thermoelectric properties were characterized. The pure phases of Half-Heusler (HH) structure were successfully obtained by subsequent SPS at 1273 K for 1 h under vacuum. With Ti substitution the lattice parameter decreased systematically and carrier concentration increased showing n-type semiconducting behavior, and the thermal conductivity decreased due to reduction of lattice thermal conduction. As a result, it was obtained the figure of merit ZT∼0.92 at 837 K at x = 0.3.

Lead-free piezoelectric ceramics, (Bi0.70Ba0.35)(Fe0.65Ti0.35)O3 (BBFT), were fabricated via a solid-state reaction method and then treated using different heat-treatment processes (furnace cooling, air quenching (AQ), and water quenching). In all these ceramics, the X-ray diffraction analysis revealed morphotropic phase boundaries between the rhombohedral and tetragonal phases. Changes in the average grain size, relative density, and electrical properties in the BBFT–AQ composition were observed. For the optimum BBFT–AQ ceramic, significantly enhanced dynamic (d33* ~ 340 pm/V) and static (d33 ~ 165 pC/N) piezoelectric coefficients were obtained. Moreover, the d33* increased to 40% (d33* ~ 475 pm/V) with increasing temperature from 25 °C to 75 °C upon the application of a 4.0 kV/mm electric field. The related defect states were established by the variation in the transition of Fe3+ to Fe2+ and OV or $$V_{O}^{ \bullet \bullet }$$ concentration observed using X-ray photoelectron spectroscopy analysis. These factors are directly related to the electromechanical response enhancement in the BBFT piezoceramics. This study provides a paradigm for a deeper analysis of particular scientific heat-treatment mechanisms and the enhancement of functional properties in BBFT ceramics.

We report a five-fold luminance increase of green-light-emitting CdSe@ZnS quantum-dot LEDs (QLEDs) in response to treatment with a 2-ethoxyethanol solution of cesium carbonate (Cs

Metal-insulator-semiconductor (MIS) structures have been widely used in Si-based solar water-splitting photoelectrodes to protect the Si layer from corrosion. Typically, there is a tradeoff between efficiency and stability when optimizing insulator thickness. Moreover, lithographic patterning is often required for fabricating MIS photoelectrodes. In this study, we demonstrate improved Si-based MIS photoanodes with thick insulating layers fabricated using thin-film reactions to create localized conduction paths through the insulator and electrodeposition to form metal catalyst islands. These fabrication approaches are low-cost and highly scalable, and yielded MIS photoanodes with low onset potential, high saturation current density, and excellent stability. By combining this approach with a p+n-Si buried junction, further improved oxygen evolution reaction (OER) performance was achieved with an onset potential of 0.7 V versus RHE and saturation current density of 32 mA/cm2. Moreover, in stability testing in 1M KOH aqueous solution, a constant photocurrent density of ~ 22 mA/cm2 was maintained at 1.3 V versus RHE for 7 days.

Metal-insulator-semiconductor (MIS) structures are widely used in Si-based solar water-splitting photoelectrodes to protect the Si layer from corrosion. Typically, there is a tradeoff between efficiency and stability when optimizing insulator thickness. Moreover, lithographic patterning is often required for fabricating MIS photoelectrodes. In this study, we demonstrate improved Si-based MIS photoanodes with thick insulating layers fabricated using thin-film reactions to create localized conduction paths through the insulator and electrodeposition to form metal catalyst islands. These fabrication approaches are low-cost and highly scalable, and yield MIS photoanodes with low onset potential, high saturation current density, and excellent stability. By combining this approach with a p+n-Si buried junction, further improved oxygen evolution reaction (OER) performance is achieved with an onset potential of 0.7 V versus reversible hydrogen electrode (RHE) and saturation current density of 32 mA/cm2 under simulated AM1.5G illumination. Moreover, in stability testing in 1 M KOH aqueous solution, a constant photocurrent density of ~22 mA/cm2 is maintained at 1.3 V versus RHE for 7 days., Authors demonstrate Si-based MIS photoanodes using Al thin-film reactions to create localized conduction paths through the insulator and Ni electrodeposition to form metal catalyst islands. These approaches yielded low onset potential, high saturation current density, and excellent stability.