查看更多>>摘要：In this study, the nickel oxide (NiO_x) thin films were reactively sputtered at different working pressures in the oxide mode zone for application in flexible all-thin-film electrochromic devices (ATF-ECDs). The working pressure plays an important role on the various properties of the reactively sputtered NiO_x thin film including the deposition rate, grain structure (microstructure), morphology, chemical composition, optical properties and electrochemical properties. The flexible ATF-ECDs with ≥2 Pa NiO_x thin films perform high optical modulation and relatively fast response time during the electrochromic processes. The detailed electrochromic mechanism is discussed.
查看更多>>摘要：Toxic organic pollutants have a severe impact on the environment as well as the living organisms around the world. Surface-enhanced Raman spectroscopy (SERS) is considered to be one of the advanced sensing methods for the ultrasensitive detection of organic pollutants. Herein, a novel octahedral Ag_2SO_3 micro-crystal was synthesized using the silver-ammonia complex precipitation method for the detection of herbicide (4-chlorophenol) and synthetic dyes (sunset yellow and methylene blue dye). Ag_2SO_3 microcrystal exhibits superior sensitivity with an enhancement factor (EF) in the order of ~10~8. The large surface area with a rough octahedral morphology of Ag_2SO_3 favors the formation of abundant hotspots. The as-prepared Ag_2SO_3 also possesses excellent recyclability property via light irradiation attributed to the chemical enhancement mechanism. The capability of Ag_2SO_3 for the detection of 4-CP against interference in river water and honey was also investigated. It is assumed from the results that Ag_2SO_3 microcrystal is a promising substrate for reusable SERS applications.
查看更多>>摘要：Broad emission bands in semiconducting oxides due to native defects could readily be an efficient source of white light if they are adjusted properly. In this work, Zn_2GeO_4 nanoparticles of 10 and 16 nm sizes, obtained by a precipitation method, are presented as potential white light emitter. Temperature dependence measurements have been performed to discuss the Zn_2GeO_4 luminescence, which consist of emission bands in the ultraviolet, blue and green regions. The analysis of these results provided some clues about the interplay between defect-related centres and the surface states in nanocrystalline Zn_2GeO_4. Finally, a highly efficient cold-white emission at room temperature has been achieved from this nanomaterial.
查看更多>>摘要：Transition metal sulfides (TMSs) have been widely researched as promising electrode materials for super-capacitors because of their high theoretical capacitance and rich redox reactive sites. In this work, tremella-like core-shell Co_9S_8@NiCo_2S_4 heterogeneous nanosheets were directly grown on Nickel foamed (NF) through the hydrothermal+electrodeposition method to obtain a self-supporting electrode. Benefiting from its unique tremella-like structure, ultra-thin nanosheets, and the positive synergies between Co_9S_8 and NiCo_2S_4, the prepared Co_9S_8@NiCo_2S_4@NF electrode presents a high specific capacity of 513 C g~(-1) (specific capacitance -1026 F g~(-1)) at 1 A g~(-1) with superior rate capability (62.8% capacitance retention rate at 10 A g~(-1)). Furthermore, the fabricated Co_9S_8@NiCo_2S_4@NF//active carbon (AC) hybrid supercapacitor displays a high energy density of 30 Wh kg~(-1) at a power density of 731.8 W kg~(-1) and superior cycling stability. The results prove that the strategy of hydrothermal+electrodeposition is a very effective method for the preparation of energy storage and conversion materials with unique core-shell morphology.
查看更多>>摘要：From the XRD results, it is found that the studied La_(0.5)Ca_(0.2)Ag_(0.3)MnO_3 compound crystallizes in the or-thorhombic structure with Pnma space group. Electrical conductivity of La_(0.5)Ca_(0.2)Ag_(0.3)MnO_3 compound is investigated from 80 K to 480 K in the frequency range [40 Hz-6 × 10~5 Hz]. Several conduction models are used to identify the appropriate mechanisms governing the transport properties in the studied compound. The Overlapping-Large- Polaron Tunneling and the Correlated Barrier Hopping conduction processes are used to clarify the sub-linear dispersive regions in the DJPL/JPL frequency range. In these regions, the conductivity is examined according to double and single Jonscher power laws. At lower temperatures and for the second frequency range, the spectra reveal Superlinear Power-Law behavior. Beyond T = 280 K, this phenomenon is disappeared and replaced by Nearly Constant Loss behavior. At higher frequencies, the conductivity spectra exhibit a high frequency plateau. For the DC regime, the transport properties are governed by thermally activated Small Polaron Hopping conduction process at elevated temperatures. The Variable Range Hopping conduction mechanism is the dominant process in the intermediate temperature range. Thus, the cationic disorder plays a major role in the transport of charge carriers at low temperatures. Likewise, the investigated compound exhibits semi-conductor behavior over the explored temperature region. The deduced hopping energy is sensitive to the frequency parameter. At high frequencies, a signature of a metal-semiconductor transition is observed at 260 K. The magnetic investigation shows that the sample reveals a paramagnetic-ferromagnetic phase transition at 260 K.
查看更多>>摘要：A Li_(0.27)K_(0.72)Ni_(0.6)Co_(0.2)Mn_(0.2)O_2 (LKNCM) cathode for potassium-ion batteries (PIBs) was obtained from LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2 (NCM622) via ion exchange. In-situ X-ray diffraction and high-resolution transmission electron microscopy analyses showed the morphological and structural changes that occur during K~+-ion insertion. Particularly, the primary particles became porous, and the (003) interlayer distance expanded from 4.76 to 6.50 A, providing a potassiation/depotassiation framework. Inductively coupled plasma-optical emission spectroscopy revealed that 0.72 mol of K~+ ions were inserted into the Li-extracted NCM622 cathode per formula unit, indicating that the amounts of extracted Li~+ and inserted K~+ were similar. The developed LKNCM cathode exhibited a theoretical capacity of 160.79 mAh g~(-1) and an initial discharge capacity of 106.95 mAh g~(-1) with an average potential of 3.1 V vs. K/K~+. These results demonstrate that ion exchange enables layered NCM cathodes for lithium-ion batteries to be applied as cathodes for PIBs.
查看更多>>摘要：Luminescence thermometry (LT) is a remote technique of temperature monitoring, which shows immense potential and has become very popular among researchers in recent years. LT can be realized by several different measurement methods, but one of the most recently proposed and least studied relies on a single-band ratiometric (SBR) approach. In the SBR approach, the temperature readout is achieved from a single emission band being photoinduced by two different excitation conditions, i.e. ground (GSA) and excitated (ESA) state absorption. However, the intensity of emission resulting from ESA excitation is dependent on many factors such as host material properties, type and concentration of optically active dopant ions, surface effects, and others, so an in-depth understanding of photophysical processes is essential for the intentional development of novel highly sensitive luminescent thermometer operating on the SBR principle. In these studies, the impact of host and interionic interactions occurring through cross-relaxation on the thermometric properties of a single-band ratiometric thermometer based on nanosized NaYF_4 and NaGdF_4 fluorides doped with Eu~(3+) ions are investigated and discussed. The maximum relative temperature sensitivity was equal S_R= 16.9%/K at 163 K for the NaGdF_4:50%Eu~(3+) nanocrystals and was close to 1%/K over the entire higher temperature range analyzed.
查看更多>>摘要：The laser powder bed fusion (LPBF) was employed to process the ZK60 Mg alloy. The effect of heat treatment on the microstructure and hardness of LPBF ZK60 Mg alloy was investigated. The results showed that the grain boundary of LPBF ZK60 Mg alloy was composed of a network Mg_7Zn_3 phase. Three types of precipitated phases were distributed inside the grains: the type-I is Zn-rich precipitated phase with Zr-rich core, the type-II is Zn-rich precipitated phase without Zr, the type-Ill is Zr-rich particle. When the solution treatment was used, the Mg_7Zn_3 phase at the grain boundary melted and merged into the matrix. The precipitated phase in the grain mainly evolved into Zn-rich phase with Zn_2Zr core. Continue with the aging heat treatment, the rod-shaped pY-MgZn precipitated phase separated out from the a-Mg matrix. The length of the rod-shaped precipitated phase undergone double aging is longer and the quantity is more than that of the single aging. The rod-shaped β_1-MgZn precipitated phase significantly improved the mechanical properties of LPBF ZK60 Mg alloy. The average hardness increased from 0.88 ± 0.025 GPa to 1.01 ± 0.010 GPa and the ultimate tensile strength increased to 287 ± 4 MPa after the solution treatment plus double aging heat treatment.
查看更多>>摘要：The synergistic integration of compositional and structural advantages for anode material provides a feasible avenue toward high-performance lithium-ion batteries (LIBs). Here, a tailored Co/N-doped yolk-shell porous carbon skeleton is fabricated by graphitic carbon nanochambers and amorphous carbon to effectively enhance the electrochemical performances of LIBs. Benefitting from the exquisite composition and structure, the designed anode material delivers a desirable discharge capacity of 440.3 mA h g~(-1) after 2500 cycles at a current density of 4 A g~(-1) with the Coulombic efficiency of 99.5%. The assembled lithium full battery with LiFePO_4 cathode achieves 288 Wh kg~(-1) after 200 cycles. The present strategy expands the direction of advanced material preparations for long-lifespan battery applications.
查看更多>>摘要：There is an imperative need for a single photodetector that can be used to detect the entire electromagnetic spectrum from the ultraviolet (UV) to the near-infrared (NIR). Such a device can reduce the cost and surface area required for device integration. In addition to broadband photodetection, optical transparency must be considered as another critical parameter. Poor transparency or opacity renders their use a deprecated choice in transparent electronics. In this paper, a completely transparent, electrode-free n-n heterojunction (n-ZnO/n-V_2O_5) photodetector is developed for high responsivity and microsecond responses. This is the least-studied type of heterojunction. It is a Schottky junction and can provide rapid device performance due to its unipolar carrier transport. The wide bandgap of ZnO and the narrow bandgap of V_2O_5 make this heterojunction a transparent broadband photodetector. The n-ZnO/n-V_2O_5 photodetector offers > 50% optical transmittance in the Vis-NIR region, with remarkably high photoresponsivities of 18.86 A/W, 6.10 A/W, and 4.40 A/W in the UV, Vis, and NIR regions, respectively. The device also offers high detectivity, high external quantum efficiency, and fast rise and fall times of 230 and 340 us, respectively. Briefly, this work provides a path towards the development of transparent, electrode-free broadband photodetectors for next-generation transparent electronics.
NSTL
Elsevier