Large Amount Of Oxygen Vacancies Research Articles

Flexible NO 2 gas sensors based on sheet-like hierarchical ZnO 1− x coatings deposited on polypropylene papers by suspension flame spraying

Abstract 2D sheet-like ZnO coatings composed of nanoparticles were deposited on flexible polypropylene papers equipped with gold electrodes in three steps. Firstly, sheet-like ZnO powder was synthesized by direct precipitation method. Then, the as-synthesized powders were dispersed in anhydrous ethanol to form feedstock suspension. At last, the feedstock suspension was injected into the acetylene-oxygen flame to deposit ZnO coatings. X-ray diffraction and field-emission microscopy results revealed that the coatings were hexagonal phase and porous hierarchical structure. With an increase in spray distance, the coatings exhibited a morphology with smaller particle size and sheet thickness. Photoluminescence and X-ray photoelectron spectra indicated that large amounts of oxygen vacancies were introduced into the coatings, and oxygen vacancy concentration increased with the spray distance. UV–vis spectra showed that the light absorption of the coatings was extended to visible light region, and wider absorption range was obtained when the spray distance was increased. The ZnO coatings exhibited good responses to sub-ppm level NO2 at room temperature under white LED light illumination, and the coating deposited with longer spray distance presented a better NO2 sensing performance.

A Convenient Route for Au@Ti–SiO2 Nanocatalyst Synthesis and Its Application for Room Temperature CO Oxidation

Small gold nanoparticles of size less than 5 nm encapsulated inside titanium modified silica shell have been reported. Here, a modified sol–gel method, which is a one-step process, produces Au@Ti–SiO2 nanocatalyst with a good control of titanium loading. With a titanium loading of 0.9 and 2.2 wt % in silica, unprecedented low temperature activity (full conversion) is observed for this catalyst for CO oxidation reaction compared to Au@SiO2 catalyst. A combination of optimum sized gold nanoparticles with a large amount of oxygen vacancies created due to Ti incorporation in silica matrix is considered to be the reason for this enhanced catalytic activity. The size of gold nanoparticles is maintained even after high temperature pretreatments, which show the benefit of encapsulation. The effect of the various pretreatments on the catalytic activity has also been reported.

Effect of Gd3+ and Al3+ on optical and dielectric properties of ZnO nanoparticle prepared by two-step hydrothermal method

Gd3+ and Al3+ co-doped ZnO nanoparticles were prepared by hydrothermal method. The effects of dopants on the microstructural, morphological, optical and dielectric properties of host ZnO system were investigated in the present report. The microstructural and morphological investigations of all the samples were carried out by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). To investigate the presence of various intrinsic defects inside the undoped and doped ZnO samples, the Raman spectroscopy and photoluminescence spectroscopy measurements were recorded. The dielectric spectroscopy was carried out as a function of frequency and temperature. The consequences of dielectric measurements suggest that the dielectric response of the 3% Gd3+ and Al3+ co-doped ZnO sample is significantly enhanced compared to that of undoped ZnO sample. The dielectric response enhances due to the presence of large amount of oxygen vacancies and grain boundaries in the nanostructure of the doped material. All the dielectric parameters confirm the presence of dielectric dispersion inside the doped ZnO samples. The values of dielectric constant as well as ac conductivities were found to decrease at higher concentration of Gd3+ and Al3+ in the doped ZnO sample and it occurs due to predominating acceptor effect of Al3+ at the interstitial site of ZnO nanostructure.

Effects of Y incorporation in TaON gate dielectric on electrical performance of GaAs metal–oxide–semiconductor capacitor

In this study, GaAs metal–oxide–semiconductor (MOS) capacitors using Y‐incorporated TaON as gate dielectric have been investigated. Experimental results show that the sample with a Y/(Y + Ta) atomic ratio of 27.6% exhibits the best device characteristics: high k value (22.9), low interfacestate density (9.0 × 1011 cm–2 eV–1), small flatband voltage (1.05 V), small frequency dispersion and low gate leakage current (1.3 × 10–5A/cm2 at Vfb + 1 V). These merits should be attributed to the complementary properties of Y2O3 and Ta2O5:Y can effectively passivate the large amount of oxygen vacancies in Ta2O5, while the positively‐charged oxygen vacancies in Ta2O5 are capable of neutralizing the effects of the negative oxide charges in Y2O3. This work demonstrates that an appropriate doping of Y content in TaON gate dielectric can effectively improve the electrical performance for GaAs MOS devices. Capacitance–voltage characteristic of the GaAs MOS capacitor with TaYON gate dielectric (Y content = 27.6%) proposed in this work with the cross sectional structure and dielectric surface morphology as insets.magnified imageCapacitance–voltage characteristic of the GaAs MOS capacitor with TaYON gate dielectric (Y content = 27.6%) proposed in this work with the cross sectional structure and dielectric surface morphology as insets.

Effects of Annealing Temperatures on the Structural and Dielectric Properties of ZnO Nanoparticles

ZnO nanoparticles with hexagonal wurtzite structure were synthesized by using microwave irradiation. The effects of annealing temperatures on the structural, surface morphology and dielectric properties of annealed ZnO nanoparticles were investigated by XRD, FTIR spectra, and dielectric measurements. The XRD reveals the presence of hexagonal wurtzite structure of ZnO average grain size 25.7–36.4 nm. The spectra obtained from FTIR containing two intense absorption bands are attributed to bending and stretching vibrations absorption of Zn–O bond for all annealed ZnO nanoparticles. Dielectric properties of annealed ZnO nanoparticles at different temperatures were studied with respect to frequency. The dielectric measurements reveal that the dielectric response of ZnO nanoparticles is significantly enhanced, especially in the low-frequency range. In conclusion, both the rotation direction polarization and space charge polarization due to a large amount of oxygen vacancies and nano-size effects are responsible for the enhancement of the dielectric properties of ZnO nanoparticles.

Oxygen-deficient Zn2Ti3O8−x nanoparticle as anode material for lithium ion batteries

Zn2Ti3O8−x nanoparticles containing oxygen vacancies were prepared with nanotube titanium acid as the titanium source via molten salt method in air atmosphere in order to improve the electronic conductivity of zinc titanate as the anode of lithium-ion batteries. The effect of oxygen vacancies on the structure and electrochemical properties of the as-prepared Zn2Ti3O8−x nanoparticles as the electrode material of lithium ion batteries was studied with Zn2Ti3O8 prepared from commercial P25-TiO2 as a control. Findings indicate that the as-prepared Zn2Ti3O8−x nanoparticles contain a large amount of oxygen vacancies and Ti3+ in the bulk phase, and they exhibit markedly improved electrochemical properties than Zn2Ti3O8 without oxygen vacancy. Namely, the electrode made of the as-prepared Zn2Ti3O8−x nanoparticles exhibits a high capacity of 246, 222, 181, 156, 127 and 88 mA h/g at a current density of 0.1, 0.2, 0.5, 1, 2 and 5 A/g, and it does not undergo obvious capacity fading after 450 cycle of charge/discharge at a current density of 0.1 A/g, showing great potential as the anode material for high-rate and long-life lithium-ion batteries. This is because the oxygen vacancies and Ti3+ in the bulk phase can significantly enhance the electronic conductivity of the electrode material.

Oxygen-Deficient Zirconia (ZrO2-x): A New Material for Solar Light Absorption.

Here, we present oxygen-deficient black ZrO2−x as a new material for sunlight absorption with a low band gap around ~1.5 eV, via a controlled magnesiothermic reduction in 5% H2/Ar from white ZrO2, a wide bandgap(~5 eV) semiconductor, usually not considered for solar light absorption. It shows for the first time a dramatic increase in solar light absorbance and significant activity for solar light-induced H2 production from methanol-water with excellent stability up to 30 days while white ZrO2 fails. Generation of large amounts of oxygen vacancies or surface defects clearly visualized by the HR-TEM and HR-SEM images is the main reason for the drastic alteration of the optical properties through the formation of new energy states near valence band and conduction band towards Fermi level in black ZrO2−x as indicated by XPS and DFT calculations of black ZrO2−x. Current reduction method using Mg and H2 is mild, but highly efficient to produce solar light-assisted photocatalytically active black ZrO2−x.

Direct Z-scheme composite of CdS and oxygen-defected CdWO4: An efficient visible-light-driven photocatalyst for hydrogen evolution

Direct Z-scheme photocatalyst, which enables efficient charge separation and retains high redox ability, is promising material for visible-light-driven hydrogen evolution. Here we developed a one-step solvothermal method to fabricate direct Z-scheme CdS/CdWO4 composite via treating W18O49 with CH3CSNH2 and Cd(CH3COO)2. By controlling the dosage of Cd(CH3COO)2, CdS nanoparticles decorated CdWO4 nanowires (CS-2) is synthesized. UV–vis DRS and XPS spectra demonstrate that the CdWO4 possesses a large amount of oxygen vacancies, which help to form ohmic contact and broaden light absorption. Compared with CdS, CS-2 Exhibits 18 times higher visible-light H2 evolution activity using lactic acid as sacrificial agent and shows 7.8-fold higher photocurrent density. Moreover, photoelectrochemical test manifests the efficient separation of the photo-induced charge carriers. Radical-trapping experiments along with in-situ Pt photodeposition further prove that the charge transfer and separation follows Z-scheme mechanism. This work highlights the critical role of defects in the formation of direct Z-scheme composite.

Effects of High-Pressure Hydrogen Annealing (HPHA) on Reliability Characteristics of RRAM.

Reliability characteristics (retention and endurance) of RRAM are critical for its practical realization and need to be improved. In this work, we confirmed the trade-off between retention and endurance by using various top electrode thickness conditions. The trade-off between retention and endurance characteristics was mainly due to the different amount of oxygen in scavenging layer (Ta) and the amount of oxygen vacancy in switching layer (HfO2). The amount of the oxygen in scavenging layer (Ta) and the amount of the oxygen vacancy in switching layer (HfO2) will be increased with the increase of Ta thickness. Therefore, the thicker Ta cells have worse retention because the large amount of oxygen in scavenging layer (Ta) can diffuse back into switching layer (HfO2) and recombine with oxygen vacancies in the filament. However, it has longer endurance because the large amount of oxygen vacancy in switching layer (HfO2) can be a source of the filament. Hence, there exists a trade-off relation between retention and endurance under the various Ta thickness conditions. To improve both retention and endurance characteristics, we proposed a new method by using high-pressure hydrogen annealing (HPHA). The thin Ta cells have longer retention and worse endurance because it has small amount of both oxygen in scavenging layer (Ta) and oxygen vacancy in switching layer (HfO2). Therefore, to generate more oxygen vacancies in switching layer (HfO2) maintaining small amount of oxygen in scavenging layer (Ta), we treated the samples by HPHA before Ta deposition. Finally, we obtained both improved retention and endurance characteristics in HfO2 based RRAM devices after high-pressure hydrogen annealing treatment.

High Efficiency CeCu Composite Oxide Catalysts Improved via Preparation Methods for Propyl Acetate Catalytic Combustion in Air

Abstract A famous hard-template method (HT), coprecipitation method (PC), and complex method (CA) were used to prepare CeCu composite oxide catalysts. The prepared catalysts were characterized via XRD, BET, Raman, XPS, FI–IR, and O2–TPD, and their catalytic activity and stability were evaluated for the propyl acetate catalytic combustion. The results showed that the CeCu oxide solid solution and oxygen vacancies were formed in the prepared CeCu oxide catalysts, even for CeCu–PC and CeCu–CA having a specific amount of isolated crystalline or amorphous CuO species. Comparing with the CeCu–PC and CeCu–CA of low porosity, CeCu–HT developed a mesoporous structure with a much larger specific surface area through a negative replica on the structure of KIT-6, and in it, CuO was completely dissolved in the CeO2 lattice to form more CeCu oxide solid solution and a large amount of oxygen vacancies. As a result, the CeCu–HT catalyst has more surface-adsorbed oxygen species, more –OH group which can also change into surface-adsorbed oxygen species at relatively high temperatures, higher oxygen desorption ability, and higher oxygen mobility than CeCu–PC and CeCu–CA. The CeCu–HT catalyst shows high and stable propyl acetate catalytic combustion performance at 190 °C. The propyl acetate catalytic combustion activity on the prepared CeCu oxide catalysts can be ranked as: CeCu–HT > CeCu–PC > CeCu–CA, which follows the orders of CeCu oxide solid solution content, surface-active oxygen content, and oxygen desorption and mobility of the CeCu composite oxide catalysts.

Magnetron sputtered Au-decorated vanadium oxides composite thin films for methane-sensing properties at room temperature

Room temperature methane (CH4) gas sensing properties of Au-decorated vanadium oxide (VOx) nanostructured films have been prepared by dc-magnetron sputtering of V metal, followed by rapid thermal annealing (RTA) in O2 atmosphere from 470 °C to 500 °C on the sapphire substrate. The structural properties of the Au/VOx films were measured by X-ray diffraction (XRD) and vanadium oxide phases were found and identified as VOx. The films showed a cracking and porous morphology structure, measured by field emission scanning electron microscope (FESEM). The CH4-sensing properties of the sensor based on Au/VOx composite films were carried out in the temperatures span ranging from room temperature (∼25 °C) to 100 °C. The films sensors achieved their maximum response values toward CH4 at room temperature (RT) and the optimal concentration at the concentration of 1500 ppm. At RT, the sensor exhibited higher gas response, good repeatability and excellent selectivity characteristics toward CH4 gas due to its high specific surface area, special structure, and large amounts of oxygen vacancies. Obtained results revealed that the Au/VOx films sensors showed a broad commercial applications prospect to detect CH4 in the field of RT.

Defective TiO2 with oxygen vacancy and nanocluster modification for efficient visible light environment remediation

Defective TiO2 with oxygen vacancy and Cu(II) nanocluster modification has been prepared by reducing in hydrogen atmosphere followed with an impregnation process. The obtained TiO2 samples with optimum oxygen vacancy did not show visible light enhancement. However, the photocatalytic performances of TiO2 samples with larger amount of oxygen vacancies were sharply decreased, even they exhibited much enhanced visible light absorptions. After the modification of Cu(II) nanoclusters, the reduction TiO2 with optimum oxygen vacancy presented much enhanced visible light photocatalytic performance for organic decomposition both in water and air, compared with unreduced TiO2 and other reduced TiO2 samples. Thus, this work provides a facile and efficient route to enhance the photocatalytic performance of TiO2 for practical applications.

Suppression of Carbon Deposition on Ni Films by Redox Treatment of Ceria Substrates

For solid oxide fuel cells (SOFCs), ceria is very attractive material used as electrolyte or Ni-cermet. It possesses the fast oxygen transport due to its high concentration of oxygen vacancy under reducing atmosphere. In addition, it was reported that this oxygen vacancy defects can be rapidly formed and eliminated even at room temperature giving it a high oxygen storage capacity. However, it was not expected that the redox ceria can recovery completely after re-oxidized. Since it was reported that ceria can suppress the carbon deposition on Ni surface using Ni-cermet or Ni film supported on ceria, therefore, we want to clear whether or not this redox behavior play an positive role to suppress the carbon deposition on Ni film. In this work, we prepared Ni film with micrometer size on an as sintered Gd doped ceria (GDC) and GDC with redox treatment. We can reproduce the suppression of carbon deposition on Ni film using GDC with redox treatment as the substrate. However, this behavior disappears when as sintered GDC is used as the substrate. It seems that the GDC substrate after a single redox processing helps to suppress the carbon deposition on Ni film. Here, it is considered that large amount of oxygen vacancy and high concentration of electron in GDC after redox treatment play an important role to suppress the carbon deposition on Ni film for Ni/GDC.

Structural properties of alumina supported Ce–Mn solid solutions and their markedly enhanced catalytic activity for CO oxidation

This work presents the synthesis and characterization of alumina supported ceria–manganese solid solutions (Ce–Mn/Al), which were prepared by a deposition coprecipitation method followed by calcination at different temperatures from 773 to 1073K. The physicochemical properties of the synthesized samples were deeply investigated by various characterization techniques, namely, XRD, ICP-OES, BET surface area, TEM-HRTEM, Raman, XPS, and H2-TPR. The catalytic activity was evaluated for CO oxidation. BET surface area measurements revealed that synthesized samples exhibit reasonably high specific surface area. XRD and Raman results confirmed that the present Ce–Mn/Al samples are single-phase solid solutions with good structural homogeneity and high thermal stability up to 1073K. TEM analyses showed that the particle sizes of Ce–Mn/Al samples are in the range of ∼5–14nm. XPS analysis revealed that Ce is in the form of Ce4+ and Ce3+, and Mn existed in the form of Mn4+, Mn3+, and Mn2+ on the surface of the samples. The solid solution particles in the nanosize form are well distributed over the support surface. As a result of solid solution formation and high dispersion over the support, the Ce–Mn/Al samples exhibited better redox behaviour. The CO oxidation results revealed that the Ce–Mn/Al samples show an excellent CO oxidation performance compared with alumina supported undoped CeO2 (Ce/Al) and MnOx (Mn/Al) samples. Among various samples, the Ce–Mn/Al calcined at 773K showed outstanding CO activity with T50=∼340K. The enhanced catalytic activity was mainly attributed to high surface area, large amount of oxygen vacancies, and excellent redox behaviour. The metal–support interaction also seems to play a decisive role in their high catalytic activity by stabilizing the Ce–Mn–O dispersion.

Room temperature NO2-sensing properties of porous silicon/tungsten oxide nanorods composite

One-dimensional single crystalline WO3 nanorods have been successfully synthesized onto the porous silicon substrates by a seed-induced hydrothermal method. The controlled morphology of porous silicon/tungsten oxide nanorods composite was obtained by using oxalic acid as an organic inducer. The reaction was carried out at 180°C for 2h. The influence of oxalic acid (pH value) on the morphology of porous silicon/tungsten oxide nanorods composite was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The NO2-sensing properties of the sensor based on porous silicon/tungsten oxide nanorods composite were investigated at different temperatures ranging from room temperature (∼25°C) to 300°C. At room temperature, the sensor behaved as a typical p-type semiconductor and exhibited high gas response, good repeatability and excellent selectivity characteristics toward NO2 gas due to its high specific surface area, special structure, and large amounts of oxygen vacancies.

Mesostructured Cu–Mn–Ce–O composites with homogeneous bulk composition for chlorobenzene removal: Catalytic performance and microactivation course

Cu–Mn–Ce–O composites with enhanced surface area and developed mesoporosity were synthesized using a homogeneous coprecipitation (hcp) method, and were tested in the catalytic destruction of chlorobenzene (CB). X-ray diffraction (XRD), N2 adsorption/desorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (H2-TPR), temperature programmed desorption of CB/O2 (CB/O2-TPD), and diffuse reflectance ultraviolet visible spectroscopy (DRUV-Vis) were used to characterize the structure and textural properties of catalysts. Mn and Cu enter CeO2 matrix with a fluorite-like structure, and produce large amounts of oxygen vacancies. Addition of manganese promotes the formation of reduced copper phase, and the presence of large numbers of high valence Mn4+ ions strongly enhances the redox couple of Cu+–Cu2+ in the composites. Both the synthesis protocol and metal doping amount significantly affect the catalyst reducibility, surface state and oxygen density. Cu0.15Mn0.15Ce0.85Ox synthesized via the hcp method exhibits the highest catalytic activity with 90% of chlorobenzene destructed at 255 °C (CO2 selectivity > 99.5%). Enriched surface oxygen, excellent active oxygen mobility and CB adsorption ability guarantee the superior activity and stability of Cu–Mn–Ce–O composite catalysts. Nucleophilic and electrophilic substitutions happen in sequence during chlorobenzene destruction, and the adsorbed Cl can be finally removed in the form of Cl2 via the Deacon reaction. Furthermore, the incorporation of CuO and MnOx phases can inhibit the formation of organic byproducts, such as phenolates, maleates, and o-benzoquinone-type species, especially at elevated reaction temperatures.

Controllable Preparation of Hierarchical ZnO Nanocages and its Oxygen Vacancy through the Nanoscale Kirkendall Process

The synthesis of ZnO with tailorable shapes and point defects is important for its potential applications. Here, a facile approach is demonstrated to prepare ZnO nanocages with controllable porous shell structures though sintering a Zn-based cyanide-bridged coordination polymer under different temperatures. The transformation of ZnCP microspheres into ZnO nanocages is based on two types of nanoscale Kirkendall effect, which are related to low temperature solid–solid interfacial oxidation and high temperature solid–gas interfacial reaction, respectively. At low temperature (around 300 °C) and before the ZnCP decomposition, the novel “hierarchical ZnO bigger nanocages embedded with smaller nanocages with 10 nm nanocrystals” can be generated. By contrast, when coming to the total decomposition of ZnCP at 800 °C, ZnO nanocages with significantly increased sizes and large cavities are generated, and large amounts of oxygen vacancies (VO) are created at the same time, leading to the dramatic increased luminescence intensities of the UV peak due to VO at 540 nm. Thus, the luminescence intensities versus defect concentration in the prepared ZnO nanocages can also be controlled by tuning the sintering temperatures.

Fabrication and Characterization of Fe-Doped In2O3 Dilute Magnetic Semiconducting Nanowires**Supported by the National Basic Research Program of China under Grant Nos 2014CB921101, 2014CB921103 and 2013CB922103, the National Natural Science Foundation of China under Grant Nos 11274003, 61176088 and 61274102, the Program for the New Century Excellent Talents in University under Grant No NCET-11-0240, the PAPD Project, and the Fundamental Research

Fe-doped In2O3 dilute magnetic semiconducting nanowires are fabricated on Au-deposited Si substrates by the chemical vapor deposition technique. It is confirmed by energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy that Fe has been successfully doped into lattices of In2O3 nanowires. The EDS measurements reveal a large amount of oxygen vacancies existing in the Fe-doped In2O3 nanowires. The Fe dopant exists as a mixture of Fe2+ and Fe3+, as revealed by the XPS. The origin of room-temperature ferromagnetism in Fe-doped In2O3 nanowires is explained by the bound magnetic polaron model.

Effectively enhance catalytic performance by adjusting pH during the synthesis of active components over FeVO4/TiO2–WO3–SiO2 monolith catalysts

The effect of pH during co-precipitation on the structural and physicochemical properties of a FeVO4/TiO2–WO3–SiO2 catalyst was investigated by using XRD, SEM, HR-TEM, BET, TPD, TPR and XPS. The as-prepared catalysts were tested in an NH3-SCR reaction within a wide temperature range of 175–500°C. When the active component FeVO4 was synthesized at pH=4.5, the corresponding catalyst (FeVO4-4.5-C) showed the best catalytic activities with high resistance to H2O and SO2 poisoning under a gas hourly space velocity of 30,000h−1. It could even reach over 90% NOx conversions in a wide temperature range of 246–476°C with relatively high N2 selectivity in the presence of 10% H2O. Taking the structure performances into consideration, the FeVO4/TiO2–WO3–SiO2 may be defined as a kind of structure-sensitive catalyst. For such FeVO4-4.5-C, the SEM and TEM results showed that it displayed relatively uniform particles and crystal morphologies with the smallest average particle sizes. The NH3-TPD patterns showed that it had the largest amount of acid sites. The H2-TPR and XPS results indicated that the remarkably improved redox performance and deep surface-enrichment of FeVO4 played a key role in its enhanced catalytic performance. The surface-enrichment and the particle sizes effect induced, synergistically, a larger amount of oxygen vacancies. All of the above-mentioned account for the excellent catalytic performance. Summarizing these characterization results, it can be concluded that the pH values adopted during the synthesis can greatly affect the nano-structures and morphologies, which play a dominant role in the catalytic activity.

Scalable in situ growth of SnO2 nanoparticle chains on SiC ultrathin fibers via a facile sol–gel-flame method

SnO2 nanoparticle chains (SNPCs) were controllably in situ grown on the electrospun SiC ultrathin fibers (SUFs) by a scalable sol–gel-flame method to form a flexible mat. While bulk SnO2 was obtained by relatively slow pyrolysis in conventional horizontal tube furnace. The effect of process parameters on the microstructure and morphology of SNPCs/SUFs mats was discussed. I–V characteristics of the SNPCs/SUFs mats revealed a nonlinear curve, indicating the formation of Schottky-type junctions. The composite fibers mats also exhibited broad and strong emission bands between 400 and 650nm. This may be attributed to the existence of a large amount of oxygen vacancies and defects in SNPCs caused by the fast pyrolysis process. Such composite fibers mats may have great potentials in high-temperature gas sensors, light-emitting diodes and lithium-ion storages, etc.