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The present article reports the synthesis of hybrid structure along with non-precious cobalt-disulfide. A simple hydrothermal method was used to fabricate multi-faceted CoS2 introduced graphene aerogels. Studies on electrocatalytic activity showed that the presence of CoS2 facets along with graphene aerogel played a prominent role in the enhancement of proton reduction to hydrogen gas. The CoS2/graphene aerogel hybrid sample exhibits extremely low overpotential (160 mV vs. RHE), and high current density for HER in acidic solution. The activity enhancement can be attributed to increasing the active electrochemical surface area of graphene aerogel and faceted particles inside the 3D matrix of graphene. Furthermore, the CoS2/graphene hybrid retained its high activity even after 1000 cycles of cyclic voltammetry scans, signifying longer stability under acidic condition. The results suggest that CoS2/graphene aerogel hybrids show their potential application to hydrogen evolution reaction.

Given the increasing demand for multilayer ceramic capacitors (MLCCs) for miniaturization of electronic parts, a narrow nanoparticle size distribution is crucial to optimize MLCC performance and stability. We explored the sintering behavior of nickel powder with the goal of controlling particle size. A micro-sized nickel oxide powder was milled to uniform size (183.2 ± 53.8 nm) using a planetary ball mill; the size distribution was more uniform than that of a commercial powder (400.2 ± 183.4 nm). The sintering characteristics and capacitive features of the powders were analyzed after reduction in hydrogen. We found that the milled powder, with a narrow particle size distribution, exhibited delayed sintering rate, which paralleled the shrinkage of the of BaTiO3 layer. Discrete layers were thus obtained. Moreover, use of the milled powder reduced capacitance noise by 25% compared to that when other powders were employed; our milled powder contributed to the formation of stable electrodes.

Polyether sulfone (PES), which is a thermoplastic polymer, was added as a toughening agent to a bisphenol-A type epoxy resin to form a matrix of carbon-fiber-reinforced composites (CFRPs). For benchmarking, carboxyl-terminated butadiene acrylonitrile (CTBN), which is a rubber-based toughening agent, was added to the epoxy resin. The mechanical and thermal properties of the PES- and CTBN-toughened epoxy resins were compared. Dicyandiamide (DICY) was used as the hardening agent, whereas 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was used as the hardening accelerator. In addition, 4,4′-diamino diphenyl sulfone (DDS) was added to improve the dispersibility of PES in the epoxy resin. The CTBN-toughened epoxy resin exhibited improved impact strength and fracture toughness, but decreased tensile strength, tensile modulus, and glass transition temperature (Tg). The fracture toughness and Tg values of the PES-toughened epoxy resins increased with increasing amount of added PES. However, the tensile moduli and Tg values of the epoxy decreased upon addition of CTBN. The tensile and impact strengths of the specimen toughened with 10 phr PES increased by 14 % and 106 %, respectively, compared to those of the PES un-toughened epoxy resin. The ductility factor of the resin improved with increasing PES content. CTBN formed microvoids and CTBN particles within the epoxy matrix, which improved the fracture toughness of the resin, but deteriorated its tensile properties by stress concentration. In contrast, PES improved the properties of the epoxy resin. This was attributed to PES being well dispersed within the epoxy matrix, thereby absorbing the energy required for crack propagation. Hence, owing to their excellent mechanical properties, the PES-toughened epoxy resins were determined suitable for use as matrices for CFRPs.

Electrochromic devices (ECDs) using various polymer electrolyte membranes were evaluated in relation to their optical and electrochemical properties. It was found that the composition of polymer matrix markedly influence the transmittance change (ΔT) and stability of ECDs. The electrochromic (WO3) and ion storage (Antimony tin oxide; ATO) layers were fabricated using dry deposition method. Moreover, various types of polymer matrix were used as the electrolyte, i.e., Liquid; PVdF-HFP (UV-0); PEGDMA-PEGMA/PVdF-HFP blended (UV-30); and PEGDMA-PEGMA solid (UV-100) membranes. ECDs using UV-30 exhibited good cyclability, in which the ΔT of 35% was maintained over 200 cycles. Furthermore, as a result of electrochemical analysis, ECD using UV-30 showed charge density of 34.43 mC/cm2 with low charge transfer resistance of 237.7 Ω at the interface between the coloration layer and electrolyte. Therefore, the solid polymer matrix electrolyte (UV-30) improved the electrochromic performance including stability due to excellent ion dissociation and ion mobility in the electrolyte.

Inkjet-printed patterns were formed on a paper substrate using anti-oxidant copper nano-ink for application to disposable electronic devices. To prevent substrate damage, the pattern was flash light sintered under ambient conditions using the multi-pulse technique. Pure copper nanoparticles were coated with 1-octanethiol for oxidation resistance using the dry-coating method. Mixing these with 1-octanol solvent at a concentration of 30 wt% produced the copper nano-ink. Photo paper was used as the substrate. The contact angle between the photo paper and copper nano-ink was 37.2&deg, and the optimal energy density for the multi-pulse flash light sintering technique was 15.6 J/cm2. Using this energy density, the optimal conditions were an on-time of 2 ms (duty cycle of 80%) for three pulses. The resistivity of the resulting pattern was 2.8 &times, 10&minus, 7 &Omega, ∙m. After bending 500 times to a radius of curvature of 30 mm, the relative resistance (&Delta, R/R0) of the multi-pulse flash light-sintered pattern hardly changed compared to that of the unbent pattern, while the single-pulse-sintered pattern showed dramatic increase by 8-fold compared to the unbent pattern. Therefore, the multi-pulse light sintering technique is a promising approach to produce an inkjet-printed pattern that can be applied to disposable electronic devices.

We introduce a method based on particle-printing technology to facilitate the fabrication of crack-free dual electrochromic devices (ECDs). A film prepared by blending Prussian blue (PB) with antimony tin oxide (ATO) powders had a dense structure free of surface cracks and was suitable as both anode and ion storage layers. We investigated the deposition conditions as a function of substrate temperature at room temperature, 80 °C, and 150 °C. The PB/ATO blending film formed at 150 °C had a uniform surface and high crystallinity; this was the optimal substrate temperature. At 150 °C, the as-fabricated dual ECD had an improved diffusion coefficient of 8.70 × 10−9 cm2/S due to the presence of the PB/ATO blending film. Moreover, there was over 4-fold improvement in the transmittance change at 800 nm compared with that of the WO3 film only with no anodic layer. The better ECD properties were attributed to improved ion mobility and ion storage capacity. Therefore, this blending film was successfully fabricated on the substrate without any cracks using facile particle printing technology to be served as both anodic and ion storage layer.

Tungsten oxide is an electrochromic material, from which thin films are conventionally fabricated via heat treatment. Here, we develop a flash light sintering method to reduce sintering time; sintering delivers instantaneous photon energy created via the photothermal effect. The electrochromic efficiency of device with a flash light-sintered electrode was 88.50 cm2/C, about 1.46-fold greater than that of the device with a heat-sintered electrode. The diffusion coefficients of the former device were 1.35- and 1.46-fold greater than those of the latter device during bleaching and coloring, respectively. Therefore, a new way of sintering electrode was studied to show that the device with flash light–sintered electrode demonstrate better electrochromic performance than the device with heat-sintered one by enabling amorphous phase formation.

Herein, a full spectrum-induced hybrid structure consisting of one-dimensional nickel titanate (NiTiO

The kinetically spraying method was used to fabricate an in situ copper- (Cu-) tin (Sn) intermetallic compound (IMC) film with its thickness of approximately 1 μm using a Cu-Sn mixed powder. Microsized Cu (~5 μm) and Sn (~10 μm) powders were mixed at its ratio of 45 : 55 wt.%, respectively, and then deposited onto a silicon substrate, forming an IMC layer. The actual composition of the deposited film was measured to be at a Cu : Sn ratio of 36 : 64 wt.% (in situ kinetically sprayed at 200°C). This kinetically sprayed process uses the energy source of collision and heat energy simultaneously, leading to the formation of an IMC phase. The IMC phase of Cu6Sn5 was formed successfully within 3 minutes of in situ deposition. Moreover, we obtained a Cu6Sn5 phase when the thin film was annealed in a furnace for 1 hour immediately after kinetically spraying at room temperature. However, an IMC phase was not formed in the thin film when kinetically sprayed at room temperature followed by heating on a hot plate for 3 minutes. It seems that the simultaneous supply of collision and heat energy is crucial to result in phase formation. Therefore, we have proven that the kinetically spraying process is capable of fabricating a super-thin layer of IMC film within a short time.

We fabricated 10 mm × 10 mm WO3 electrochromic devices (ECDs) using a nanoparticle deposition system (NPDS), which is a coating method that uses kinetic spray. NPDS has the advantage of mass production due to its relatively low pressure and low temperature working conditions but can result in porous surfaces, which has a negative effect on device durability. We developed an optical transmittance measurement and voltage control system that allows dynamic control. Transmittance was measured by Optical Power Meter, 2936-R Newport, while voltage was dynamically applied by NI9477, National Instrument. Current was measured by high resolution current, National Instrument. This system enables ECDs to be feedback controlled depending on the measured electronic properties. We then characterized the WO3 ECDs, focusing on the relationship between transmittance and current under well-known static operating conditions. Finally, we proposed a new algorithm to extend durability performance by adopting charge balance control and conducted an accelerated life test over 1,000,000 cycles. According to our results, the optical performance was maintained until the test ended, and there was a 45.4% difference in the maximum and minimum transmittance of the sample after the accelerated life test. Therefore, the charge balance control enhanced the lifetime of the ECDs by avoiding negative charge accumulation, verifying that the durability of ECDs could be enhanced by adopting dynamic control.

We have developed a facile method to fabricate Ag-doped SnO2 composite film prepared via one-step kinetic spraying process. We used supersonic/subsonic nozzles to accelerate powders to their maximum kinetic energies when bombarding the substrates; no post-treatment was required. Under optimized conditions, sensors fabricated from SnO2-based films with and without Ag nanoparticles (NPs) were smooth and about 7 µm in thickness. To improve CO-sensing performance, Ag NPs (to less than 1 wt%) were added to SnO2 films. The sensor response to CO of the film with 1 wt% Ag was up to 20-fold better than that of the Ag-free film, even a low CO concentration of 500 ppm. We thus confirmed that addition of a small amount of Ag NPs to a SnO2 film increased electron transport and improved catalysis of oxygen ionization on the film surface. Therefore, we have developed a facile method of Ag-doping in composite gas sensor and this crack-free composite gas sensor was found to be highly sensitive to CO gas.

Enthalpically driven dopant induced defects generated from the interaction of bulk titanium oxide and structure directed agents composed of charge separated ions have important consequences in dire...

This paper investigates how people perceive the same material differently according to sex and nationality and what types of materials they prefer. We surveyed the sense of and preference for materials through questionnaires. The survey used five specimens made of zirconia, alumina, aluminum alloy, titanium alloy, and polycarbonate, and was conducted in four cities: Seoul and Ansan (Korea), Atlanta (USA), and Arusha (Tanzania). The survey consisted of three tests (a tactile test, a visual with tactile test, and an acoustic test). Except for the visual with the tactile test, the tests were conducted without any visual information. Using a statistical method, it was found that people feel the same materials differently depending on their sex and nationality. Furthermore, evaluation items which are correlated with material preferences such as roughness, coldness, familiarity, stiffness and color brightness levels were found, with these results showing that the evaluation items related to the preferences differ depending on the person’s sex and nationality.

The nano-particle deposition system (NPDS) is an environmentally friendly, room temperature, dry particle deposition technique to impart thin films of metal or ceramic particles onto different substrates without any additional chemicals. In this work, graphite and WO3 powders with different graphite contents (0–30 wt%) were successfully deposited on a polypropylene substrate by an NPDS without generating any thermal damage of the substrate. The graphite particles can easily be fragmented into small few-layer graphene nano-flakes along with WO3 utilizing the high kinetic energy during NPDS. With field emission scanning electron microscopy, fragmentation of particles due to the high impact velocity of the powders during deposition was observed. X-ray diffraction showed the absence of any graphite peak in the composite thin film. Finally, the existence of few-layer graphene in the fabricated thin film was confirmed by Raman spectroscopy. To evaluate the photocatalytic activity of the fabricated thin films, degradation of methylene blue dye under illumination of light for 2 h was observed. Degradation of the dye was evaluated using absorbance values measured by UV/Vis spectroscopy before and after the test. The results showed that the photocatalytic performance was significantly enhanced when the WO3 contained added graphite and suggested that 15 wt% of graphite was the optimal level in the composite thin film. The photocatalytic reaction followed pseudo-first-order kinetics. Repeatability determines the feasibility of thin films in using real applications. Here, all the thin films showed good stability up to five cycles. The few-layer graphene/WO3 composite thin films were easily prepared for the photocatalytic application using NPDS.

One-dimensional nickel titanate nanofibers (NiTiO3 NFs) were synthesized and loaded with acetic acid-treated exfoliated and sintered sheets of graphitic carbon nitride (AAs-gC3N4) to fabricate a unique heterogeneous structure. This novel fabrication method for porous AAs-gC3N4 sheets using acetic acid-treated exfoliation followed by sintering provided gC3N4 with a surface area manifold larger than that of bulk gC3N4, with an abundance of catalytically active sites. Hybrid photocatalysts were synthesized through a two-step process. Firstly, NiTiO3 NFs (360 nm in diameter) were made by electrospinning, and these NiTiO3 NFs were sensitized with exfoliated gC3N4 sheets via a sonication process. Varying the weight ratio of NiTiO3 fibers to porous AAs-gC3N4 established that NiTiO3 NFs containing 40 wt% of porous AAs-gC3N4 exhibited optimal activity, i.e., removal of methylene blue and H2 evolution. After 60 min exposure to visible light irradiation, 97% of the methylene blue molecules were removed by the hybrid photocatalyst, compared with 82%, 72%, and 76% by pristine AAs-gC3N4, NiTiO3 NFs, and bulk gC3N4, respectively. The optimal structure also displayed excellent H2 evolution performance. The H2 evolution rate in the optimal sample (152 μmol g−1) was 2.2, 3.2 and 3-fold higher than that in pure AAs-gC3N4 (69 μmol g−1), NiTiO3 NFs (47 μmol g−1) and bulk gC3N4 (50 μmol g−1), respectively. This clearly shows that the holey AAs-gC3N4 nanosheets interacted synergistically with the NiTiO3 NFs. This extended the lifetime of photogenerated charge carriers and resulted in superior photocatalytic activity compared with pristine NiTiO3 NFs and bulk gC3N4. The higher Brunauer-Emmett-Teller surface area and the presence of many catalytically active sites also enhanced the photocatalytic performance of the hybrid sample. Moreover, through photoluminescence and photocurrent response analysis, a significant decrease in the recombination losses of the hybrid photocatalysts was also confirmed. Thus, this is a novel strategy to fabricate highly efficient photocatalysts with precisely tunable operating windows and enhanced charge separation.

Inkjet-printed patterns and droplets were formed by the inkjet printing method on a Standard Clean-1 (SC-1)-treated substrate using anti-oxidized copper nano-ink. The hydrophobicity of the substrate increased after the SC-1 treatment. Copper nanoparticles were coated with 1-octanethiol vapors via a dry coating method to produce anti-oxidized nanoparticles, which were dispersed in a solvent to form a nano-ink. Droplets of the 1-octanethiol-coated copper nano-ink at 50 wt% concentration had a uniform morphology when printed on the SC-1-treated glass substrate. The minimum printed pattern line width was 55 μm on the SC-1-treated glass and had a resistivity of 1.73 × 10−7 Ω m. This resistivity was 4.3-times lower than that of the untreated substrate. Moreover, the pattern printed using the nano-ink made with 1-octanethiol-coated copper nanoparticles showed good adhesion and provided approximately 2.1-times lower resistivity. The dispersion of the nanoparticles within the droplet was more hydrophobic and formed uniform inkjet-printed patterns that had lower resistivity compared with those made with the uncoated nanoparticle-containing ink.

We have introduced a new fabrication process for a CO gas sensor using a kinetically sprayed Cu thin layer, followed by oxidation at 250 °C. The resulting 200 nm-thick CuO thin layer exhibited semi-transparent optical properties. The as-fabricated CO gas sensor was tested under two conditions with varying CO gas concentration ranging from 1000 to 5000 ppm and operating temperatures of 200, 250, and 300 °C: (1) a reaction time of 600 s and a recovery reaction time in an air atmosphere of 1800 s; and (2) a gas reaction time of 1200 s and a recovery time of 7200 s. As a result, the sensor response showed its improvement under a high operating temperature of 300 °C with a reaction time of 600 s and a recovery time of 1800 s regardless of the CO gas concentration. In contrast, the response of the CuO gas sensor showed its maximum value of 0.209 at a lower temperature of 200 °C, due to a sufficient recovery time of 7200 s. Therefore, we have proved that a kinetically sprayed CuO thin layer can be operated with varying CO gas concentration, as well as varying the temperature and time, to be useful as a gas sensor.

Herein, we newly design a ternary structure of 1-dimensional hollow g-C3N4 nanofibers (HGCNF) decorated with molybdenum disulfide (MoS2) and sulfur/nitrogen-doped graphene (SNG) via a one-pot hydrothermal treatment at relatively low temperature. The firstly presented HGCNF are fabricated using electrospinning followed by the thermal sintering method. After that, MoS2 is grown onto HGCNF, while SNG covered the structures during the hydrothermal method. We observed the morphological structures, chemical composition and optical absorbance of this ternary HGCNF/SNG/MoS2 structure. Of the as-prepared catalysts, HGCNF/SNG/MoS2 exhibited a good possibility to produce hydrogen as an electrocatalyst. Furthermore, we evaluated its stability performance using chronoamperometry for 48 hours, as well as by 3000 cycles of cyclic voltammetry. From the double-layer capacitance measurement, HGCNF/SNG/MoS2 proved itself as an electrocatalyst due to the higher value of electrocatalytically active sites to be 6.97 × 10−3 F cm−2 than that of only HGCNF (0.18 × 10−5 F cm−2) and the binary structure of HGCNF/MoS2 (2.54 × 10−3 F cm−2). We believe that our novel 1-dimensional ternary HGCNF/SNG/MoS2 structure has expedited the electron pathways by reducing the resistance at interfaces among HGCNF, SNG and MoS2, to be potentially useful for the hydrogen evolution reaction.

A unique decomposition pathway of urea involving gas evolution was exploited as a way to introduce voids and mesopores into one-dimensional carbon nanofibers. While the conventional carbonization of electrospun polyacrylonitrile (PAN) nanofibers produces microporous and solid carbon nanofibers, adding a simple step involving a urea coating over PAN prior to the carbonization drastically changes the porous structure of the resulting carbon nanofibers. Besides its role as a porogen for the creation of voids and mesopores, urea serves as an additional nitrogen source for the carbon nanofibers, and as a consequence, heavily nitrogen-doped carbon fibers are produced. Compared with conventional carbon nanofibers derived from the pyrolysis of electrospun PAN, hollow carbon nanofibers are superior in lithium-ion battery applications because of their larger specific surface area, higher nitrogen doping, and voids combined with mesopores that are beneficial for lithium-ion (de-)intercalation. Due to its versatility and simplicity, this urea-assisted template-less synthesis strategy paves a new way for the production of various porous carbon nanostructures.

Poor optical absorbance and charge recombination are the major drawbacks of polymeric graphitic carbon nitride (g-C3N4)-based photocatalysts. In this paper, we show for the first time a single-step in situ technique to control the porosity of two-dimensional g-C3N4 sheets and exfoliate them by introducing ascorbic acid (AA) molecules. The AA simultaneously acts as the carbon (C) source and deposits amorphous C onto g-C3N4 sheets. Nanosized pores are also introduced into the g-C3N4 sheets, leading to a large number of active sites. The as-prepared C-doped porous g-C3N4 nanosheets demonstrate a high visible light-photocatalytic H2 production activity of 793 μmol g−1 with the optimum structure, which is almost 25 times higher than the value obtained with bulk g-C3N4 (31 μmol g−1). This exceptional photocatalytic performance arises from the C-doped conjugated system and porous nanosheets. The enhanced photocatalytic H2 evolution was attributed to the effective separation and transport of charge carriers by the deposition of C onto the nanosheets and an increased number of active sites resulting from the nanopores created inside the g-C3N4 sheets. Moreover, molecular dynamics (MD) simulations confirm that the interaction between AA and melamine molecules at elevated temperatures results in the formation of C-doped porous and exfoliated g-C3N4 structures. Therefore, the present approach is very promising for application to the design of new and efficient photocatalysts for photocatalytic H2 evolution under visible irradiation.

With the growth of the automobile, machinery, and aerospace industries, demand for high-performance surface coatings having multifunctional characteristics for use in mechanical parts is increasing. In this study, ternary/quaternary Mo–Cu–Cr–(N) nanocomposite coatings were deposited at different N2 gas flow rates using direct current magnetron sputtering from a multicomponent single-alloy target. The use of a single-alloy target simplifies the deposition process and improves the coating uniformity. The influence of the nitrogen content was investigated regarding the microstructural, mechanical, and tribological properties, and corrosion resistance of these coatings. The Mo–Cu–Cr–N coating containing 30.5 at.% nitrogen showed a nanocomposite structure comprising transition metal nitride phases (Mo–N/Cr–N) having high mechanical properties and corrosion resistance, while retaining the excellent tribological properties of ternary Mo–Cu–N coatings.

In this study, a cupric oxide (CuO) flexible humidity sensor was fabricated using a kinetic spray process. After deposition of a 200-nm-thick Cu film, the as-deposited Cu layer was annealed at 250 °C, a relatively low temperature, in air conditions to create a CuO layer. N-type CuO (carrier concentration: −23.08 × 1014 cm−3) formed after reacting with oxygen during the annealing process in air via oxygen vacancy formation. The semi-transparent properties of the CuO film were characterized by measuring visible light transmittance. Stable sensing signals of 0.16–0.18 were obtained after the 1000th bending test. Scanning electron microscopy was used to examine the surface morphology of the CuO layer after the bending test; despite the presence of a few microcracks, delamination was not observed. Thus, a CuO-based humidity sensor was successfully fabricated through simple particle spray deposition and low-temperature annealing processes; the sensor maintained its performance under repeated bending stress (up to 1000 cycles).

A self-powered electrochromic device was fabricated on an indium tin oxide-polyethylene naphthalate flexible substrate using a dyesensitized solar cell (DSSC) as a self-harvesting source; the electrochromic device was naturally bleached and operated under outdoor light conditions. The color of the organic electrochromic polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, was shifted from pale blue to deep blue with an antimony tin oxide film as a charge-balanced material. Electrochromic performance was enhanced by secondary doping using dimethyl sulfoxide. As a result, the device showed stable switching behavior with a high transmittance change difference of 40% at its specific wavelength of 630 nm for 6 hrs. To improve the efficiency of the solar cell, 1.0 wt.% of Ag NWs in the photoanode was applied to the TiO2 photoanode. It resulted in an efficiency of 3.3%, leading to an operating voltage of 0.7 V under xenon lamp conditions. As a result, we built a standalone self-harvesting electrochromic system with the performance of transmittance switching of 29% at 630 nm, by connecting with two solar cells in a device. Thus, a self-harvesting and flexible device was fabricated to operate automatically under the irradiated/dark conditions.

A transparent conductive electrode (TCE) using the mxiture of graphite and silver nanowires (AgNWs) powder was fabricated with a nanoparticle deposition system (NPDS), a facile dry deposition approach using a graphite-AgNW powder mixture. The deposited film formed a composite structure with few-layered graphene, single layered graphene sheets, and AgNWs forming a fused junction under optimal heat treatment at 80 °C. The sheet resistance of the deposited film was measured to be 24–28 Ω/□, in accordance with values measured for commercial TCEs. Transmittance of 58–67% was measured for the deposited sample, which was lower than the 20–30% measured for conventional TCEs, due to scattering of incident light by few-layered graphene and AgNWs within the deposited film. An electrochromic (EC) cell with fabricated TCE performed well, showing a transmittance change of 15% at its wavelength of 630 nm. CV measurements were conducted for 500 cycles to confirm the stability of the EC device and TCE, and no performance degradation was observed for the device after 500 cycles, which represents good cyclic stability. Therefore, a TCE using graphite and AgNWs was successfully fabricated using the facile NPDS process, which represents a new fabrication process for TCEs based on graphene and AgNWs.

Coupling of graphitic carbon nitride (GCN) with electrospun carbon nanofibers (CNFs) enhanced the photoelectrochemical (PEC) performance of a pristine GCN photoanode. Polyacrylonitrile (PAN) was electrospun to form fibers that were then carbonized to form one-dimensional (1D) CNFs, which were then used to fabricate the GCN structure. The optimum GCN/CNFs hybrid structure was obtained by controlling the amount of GCN precursors (urea/thiourea). The surface morphology of the hybrid structure revealed the coating of GCN on the CNFs. Additionally, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction confirmed the phases of the GCN/CNFs hybrids. PEC results showed a higher photocurrent of 3 μA for the hybrid compared with that of 1 μA for the pristine GCN. The high photocurrent for the hybrid structures indicated the formation of heterojunctions that resulted from a lower recombination rate of charge carriers. Moreover, UTh0.075 (0.075 g of urea and 0.075 g of thiourea) hybrid sample showed the highest performance of hydrogen generation with its numerical value of 437 μmol/g, compared to those of UTh0.1(0.1 g of urea and 0.1 g of thiourea) and UTh0.05 (0.05 g of urea and 0.05 g of thiourea) composite samples. This higher hydrogen production could be explained again with successful formation of heterojunctions between GCN and CNFs. Overall, we report a new approach for obtaining 1D hybrid structures, having better PEC performance than that of pristine GCN. These hybrids could potentially be used in energy-related devices.

Electrochromic cells were fabricated via a nanoparticle deposition system (NPDS) using different particle sizes of monoclinic tungsten oxide (WO3). Mixtures of micro- and nano-sized WO3 powders in the ratios of WO3 (micro):WO3 (nano) = 9:1, 5 : 5 and 1 : 9 vol%, were used in this study. NPDS, which was used to fabricate the electrochromic layer, is a low-cost process that can cover a large deposition area and provides a highly porous film. This method can replace sol-gel and sputtering methods, which are expensive and have environmental issues. The WO3 electrochromic layers displayed different surface structures that could adsorb Li+ ions. The transmittance change, cyclic switching speed and coloration efficiency (CE) results demonstrated that the electrochromic cell made with the mixed WO3 (micro):WO3 (nano) powders had better performance than that of the electrochromic cell made with separate micro-sized single powders. Various analyses showed that the WO3 mixed powders contained larger sites for Li+ ion adsorption compared with the single-sized powder because of a structure consisting of a compact layer of micro-WO3 with a porous layer of nano-WO3. Consequently, a cell composed of mixed-particle electrochromic layer showed higher transmittance change, CE and electrochromic performance than a cell made with a micro-sized single powder.

Copper nanoparticles were protected against oxidation by coating with 1-octanethiol. The copper nano-ink was synthesized by dispersing the coated copper powder in 1-octanol solvent at a concentration of 18 wt%. Inkjet patterns printed on a flexible polyimide film and subjected to flash-light sintering displayed excellent anti-oxidation behavior over 2 months. The optimal light-sintering condition was 24.7 J/cm2 of energy density from a 5-ms pulse, which resulted in a resistivity of 2.4 × 10−7 Ω∙m. After bending more than 1000 times, the resistivity of the light-sintered pattern was 1.45-times higher than that of the unbent pattern. The light-sintered pattern printed with the anti-oxidative copper nano-ink shows great promise for flexible device applications.

WO3 electrochromic (EC) and ATO ion storage films were fabricated by a kinetic spray technique at various substrate heating temperatures. The optimal heating condition for WO3 deposition was 80oC, which provided a total transmittance change of 31%. Furthermore, the total transmittance change (at 800 nm) of the WO3 EC cell fabricated with the ATO ion storage layer deposited at 150°C was 42%, which was caused a comparably large shift in the transmittance. The charge/discharge density of the EC cell with the ATO ion storage layer deposited at 150°C was 11.12-11.37 mC cm-2. Finally, the cyclic transmittance of 40% was maintained for 1 h. The uniform and densely packed microstructure that resulted from the heated substrate had good inter-grain and particles connections that provided sufficient absorption sites for ions. Therefore, it was established that microstructural control of the EC and ion storage layers are crucial to improving EC performance.

The electrochromic (EC) performance of a WO3 film fabricated using a kinetic spray technique (nanoparticle deposition system, NPDS) was examined as a function of the particle size and phase of the WO3 particles. The total transmittance change of the deposited WO3 film containing crystalline nano-sized WO3 particles was 56% at 800 nm, which resulted in a large shift in its transmission spectrum after coloring. Moreover, the charge density of the EC film using crystalline nano-sized WO3 particles was 22.06 mC cm−2, which was 2.8 times higher than that of the film composed of crystalline micro-sized WO3 particles (7.97 mC cm−2). Using crystalline nano-sized WO3 particles greatly increased the surface area, increased the number of absorption sites for Li ions inside the film, and thereby improved the charge density and transmittance. The transmittance change of the EC films using dual-phased nano-sized WO3 particles was 64% (at 800 nm), which was still higher than that with crystalline nano-sized WO3 particles. The amorphous phase in the dual-phase nano-sized WO3 film provided good diffusion of Li ions; it had a high diffusion coefficient of 1.53 × 10−12 cm2 s−1 that derived from its loosely packed atomic structure. The amorphous region in a heterostructured WO3 film was effective for the fast diffusion of Li ions, while the crystalline nano-sized region in such a film provided a large surface area for an increased number of absorption sites for Li ions. This resulted in a dramatic improvement of the EC performance.

Antimony-doped tin oxide (ATO), titanium dioxide (TiO 2 ) and ATO/TiO 2 mixtures (30:70, 50:50, 70:30 vol%) powders were deposited using a nanoparticle deposition system (NPDS). X-ray diffraction (XRD) data and field-emission scanning electron microscope (FE-SEM) images confirmed that the phases and morphologies of the deposited ATO and TiO 2 were similar to those of their pristine structures. Photoelectrochemical (PEC) measurements showed the highest photocurrent of 1.5 mA for the 50:50 vol% ATO/TiO 2 film, which compared with 1.2 mA for the other (30:70 and 70:30 vol% ATO/TiO 2 ) hybrid samples, and 0.35 and 0.04 mA for pure TiO 2 and ATO, respectively. Methylene blue (MB) dye was degraded in the presence of the 50:50 vol% ATO/TiO 2 film, which had the best photocatalytic activity after 7 h of ultraviolet (UV) irradiation. The kinetic rate constant of this film was 0.15 h −1 , which was double that of the TiO 2 film (0.06 h −1 ). The photoluminescence intensity of the 50:50 vol% ATO/TiO 2 film was low over a wide range of wavelengths, which indicated that its recombination rate was less than that of the ATO and TiO 2 films. Finally, the recycle results demonstrated that the 50:50 vol% ATO/TiO 2 film was stable to photodegradation for up to six cycles. These heterojunction films containing ATO and TiO 2 thus had better photocatalytic properties than the pure TiO 2 and ATO films due to the reduction in recombination. Our facile method of preparing heterojunction films by a dry deposition method provided films with good photocatalytic properties.