Key Engineering Materials Vol. 861

Abstract: The rectangular-structured resin with one of its triangular long-period fiber grating surface is designed and printed out by using a high resolution 3D printer, so called long-period fiber grating (LPFG) resin. This LPFG resin is directly pressed on the bare single-mode fiber by a digital force meter to filter out partial band of light inside the fiber. The grating period is expanded by tilting the resin from the initial fiber axis. The optical filter is observed as resonant wavelengths from the broadband wavelength. The results show that the resonant wavelength shift is a linear function of the grating period with the coefficient of determination over 0.99. The proposed scheme has a great potential to be employed as a sensor such as a selective optical filter and a buried intrusion sensor.

Abstract: The clarification of the degree of ionic dissociation occurring in liquid-electrolyte systems such as those used in current lithium-ion batteries is important from both, fundamental and application points of views. In the present study, based on the bond strength–coordination number fluctuation (BSCNF) model proposed by the authors, we consider the relation between the ionic diffusion and dissociation in room-temperature ionic liquids. Specifically, we show firstly, that the molar conductivity Λ is well correlated with the degree of molecular cooperativity N_B defined by the BSCNF model. This correlation enables to connect the cooperativity with the degree of ionic dissociation in ionic liquids. Through the comparison between the ionic diffusion coefficients and the molar conductivity, we discuss on a possible relation between these quantities.

Abstract: In this research, CuO powder was prepared by low temperature hydrothermal method. Copper (II) nitrate trihydrate (Cu (NO₃)₂.3H₂O) and sodium hydroxide (NaOH) were used as the starting precursors. The final pH value of the mixed solution was adjusted to 9 by 4M NaOH and treated at 100 oC and 200 oC for 4 and 6 h. The black fine powder was obtained after dried at 80 oC for 4 h. The phase was characterized by X-ray diffraction (XRD). A single phase of monoclinic structure of CuO powder prepared by low temperature hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination step. The morphology and particle size were investigated by scanning electron microscopy (SEM). The morphology was flower-like in shape and the average particle size in range of 0.3×0.7 μm. The element composition was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.95 keV) and oxygen (Kα = 0.53 keV). The functional group was indentified by fourier transform spectrophotometry (FTIR). The wavenumber at 433-531 cm^-1 was corresponded to vibration of Cu-O stretching.

Abstract: Olivine-type LiFePO₄ is widely considered as a cathode for lithium-ion batteries owing to its environmental friendliness and low-cost, yet its applicability in the pristine state is limited due to poor electronic and ionic conductivity. To investigate the conductivity enhancement of LiFePO₄, first-principles method under the GGA+U framework is implemented to study effects of doping with Ti⁴⁺ at Fe²⁺ sites under the lithium-deficient environment. LiFePO₄ crystal and electronic structures as well as conductivity are investigated. Ti doping creates the impurity states at the acceptor level, which are normally degenerate states, but split into multiple states by the crystal field splitting. Doping under the lithium-deficient environment induces small hole polarons localizing at the Fe atoms and creates defect states located in the intermediate band. Both phenomena combine to facilitate charge carrier hopping. The climbing-image nudge elastic band (cNEB) calculation shows that Li hopping can be promoted by doping with high Ti concentration. This co-doping mechanism therefore can enhance both the electronic and ionic conductivities, which can be beneficial benchmark for cathode-material synthesis in the future.

Abstract: Mn₃O₄ nanosheets were deposited electrochemically on graphene modified carbon cloth (G–CC). The graphene layer improved significantly the hydrophilic property of carbon cloth and its compatibility with active materials, as a result, lower resistance and better structural stability were obtained for Mn₃O₄/G–CC compared with those for the electrode based on neat carbon cloth. Furthermore, the Mn₃O₄/G–CC possessed a capacitance of 1335 mF cm^–2 at a current density of 2 mA cm⁻², and a capacitance retention of up to 88 % after 2000 cycles at 10 mA cm^–2. It is believed that manganese oxide was anchored strongly on graphene layer through C–O–metal bonds, and the graphene layer on the surface of the CC could serve as elastic buffering layers to release the strain within manganese oxide, resulting the remarkable improvements in electrochemical performance. These excellent characteristics make this kind of the composites promising candidates as high performance electrodes for supercapacitor.

Abstract: Dye-sensitized solar cells have better development prospects than silicon cells, and their main structural composition of nanoporous semiconductor films is particularly important. It is the tin dioxide film, and the effect of preparing tin oxide film on dye-sensitized solar cells under different conditions is studied. In this paper, the SnO₂ powder was prepared by hydrothermal method, and the experiment was studied by controlled variable method. The properties of the obtained tin dioxide powder were characterized by SEM and three-dimensional ultra-depth microscope and XRD. The XRD diffraction peak is shown as tetragonal phase rutile type SnO₂, With the increase of the concentration of tin tetrachloride solution, the coarser the particle size of the tin oxide crystal in the film, the more complicated the surface morphology, so that the specific surface area of the film is larger. At 0.1 mol/L, the surface of the film is a porous structure in the form of a loose sheet is presented. After analyzing the surface microstructure and flatness of the tin dioxide film, it can be concluded that the effect of salt concentration on the specific surface area of the film is extremely large. When the salt concentration is higher or lower, the obtained two the surface of the tin oxide film is relatively flat and has poor performance. When the salt concentration is 0.1mol/L, the surface of the obtained film has a large undulation and a large specific surface area, and the ability to adsorb the dye molecules can be predicted to be the greatest, and the photoelectric conversion efficiency is optimal in the photocatalytic process.

Abstract: Electron transport layer (ETL) plays an important role in improving the performance and stability of perovskite solar cells (PSCs). SnO₂ is a good semiconductor material with high electromigration and wide band gap. TiO₂ has the advantages of superior position of conducting band (CB), long electronic life and low preparation cost, so SnO₂ and TiO₂ are often used in ETL of PSCs. In this paper, the preparation progress of SnO₂, TiO₂ and SnO₂/TiO₂ composite ETL is reviewed.

Abstract: Sorangium cellulosum can product many secondary metabolites that is unique structural and makes these microorganisms highly attractive for drug development, especially epothilone, on cancer cells a cytotoxic macrolide which is naturally produced by Soxhlet cellulose that have the action of microtubule stabilization, is a promising anticancer drug. In this research, the factors affecting the regeneration and preparation of the protoplast of Sorangium cellulosum were discussed, those were regeneration media, enzymes and osmotic stabilizers. This study provide the distruction for improving the production of epothilone through genome shuffling, mutation, fusion and transformation.

Abstract: Highly active Al-based Ag dendrites SERS plasmonic substrates have been rapidly synthesized by the one-step galvanic displacement reaction without the use of any surfactants and templates. The as-prepared SERS substrates were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. XRD measurements confirmed the metallic nature of the formed Ag dendrites. None of the organic additives were used in the synthesis process, which ensures the substrates surfaces are completely clean and avoiding the introduction of organic contaminants. The innovative rough bionic substrates yield a final silver dendritic structure that offers large specific surface area and high-density hotspots. Using malachite green as a model target, the Al-based Ag dendrites SERS substrates exhibited acceptable reproducibility (relative standard deviation of 23.8%) and high enhancement capacities (pushed the detection limit down to 10 pM). Importantly, these Ag dendrites could potentially be employed as highly active and cost effective flexible SERS sensors for label-free ultrasensitive detection of biomolecules.

Abstract: Selenols (R-SeH) are similar to thiols , both of them are important reducing substance. Selenocysteine (Sec) and hydrogen selenide (H₂Se) are two important selenols. They play a key role in cancer research and disease treatment. Recently, fluorescent probes and nanoprobes for detecting selenols have been developed rapidly because that fluorescent methods can be applied for biological imaging of cells or in vivo. Therefore, it is very important to the detect selenols. In this paper, we summarized the fluorescent probes for detecting the selenols in recent years.