Intrinsically stretchable all-carbon-nanotube transistors with styrene–ethylene–butylene–styrene as gate dielectrics integrated by photolithography-based process

In recent years, stretchable electronics have attracted great attention because of their broad application prospects such as in the field of wearable electronics, skin-like electronics, medical transplantation and human–machine interaction. Intrinsically stretchable transistors have advantages in many aspects. However, integration of intrinsically stretchable layers to achieve stretchable transistors is still challenging. In this work, we combine the excellent electrical and mechanical properties of carbon nanotubes with excellent dielectric and mechanical properties of styrene–ethylene–butylene–styrene (SEBS) to realize intrinsically stretchable thin film transistors (TFTs). This is the first time that all the intrinsically stretchable components have been combined to realize multiple stretchable TFTs in a batch by photolithography-based process. In this process, a plasma resistant layer has been introduced to protect the SEBS dielectric from being damaged during the etching process so that the integration can be achieved. The highly stretchable transistors show a high carrier mobility of up to 10.45 cm² V⁻¹ s⁻¹. The mobility maintains 2.01 cm² V⁻¹ s⁻¹ even after the transistors are stretched by over 50% for more than 500 times. Moreover, the transistors have been scaled to channel length and width of 56 μm and 20 μm, respectively, which have a higher integration level. The stretchable transistors have light transmittance of up to 60% in the visible range. The proposed method provides an optional solution to large-scale integration for stretchable electronics.

In recent years, stretchable electronics have attracted great attention because of their broad application prospects such as in the field of wearable electronics, skin-like electronics, medical transplantation and human–machine interaction.     

Experimental and model research on chloride ion gas–solid distribution in the process of desulfurization wastewater evaporation

In this paper, research on chloride ion gas–solid distribution in the process of desulfurization wastewater evaporation was carried out. The factor analysis of temperature, pH, and concentrations of Cl^– Na⁺, Ca²⁺ and Mg²⁺ was explored by orthogonal experiments. Results show that the distribution coefficient increases with increasing temperature and Mg²⁺ concentration and decreasing pH, but decreases with increasing concentrations of Cl⁻, Ca²⁺ and Na⁺; The interaction and significance of each factor were compared and analyzed, and the order of influence significance on the chloride ion gas–solid distribution coefficient is listed as: temperature (0.781) > pH (0.611) > Cl⁻ concentration (0.366 ) > Mg²⁺ concentration (0.211) > Ca²⁺ concentration (0.079) > Na⁺ concentration (0.03). A chloride ion gas–solid phase distribution coefficient model ranging from 180 °C to 380 °C was built based on phase equilibrium theory and state equations. The study clarifies the gas phase transformation mechanism of chloride ions, and achieves the quantification and prediction of chloride ion volatilization under different environmental and water quality parameters; an important theoretical and practical reference for the application of high temperature flue gas evaporation technology is provided through the research.

In this paper, research on chloride ion gas–solid distribution in the process of desulfurization wastewater evaporation was carried out.     

Preparation and in vitro release kinetics of nitrendipine-loaded PLLA–PEG–PLLA microparticles by supercritical solution impregnation process

In this work, drug-loaded polymer microparticles were prepared by a supercritical solution impregnation (SSI) process with nitrendipine as the model drug and PLLA–PEG–PLLA as the drug carrier. The morphology, size, distribution and functional groups of the drug-loaded microparticles were characterized by scanning electron microscopy (SEM), laser particle size analyzer and fourier transform infrared analysis (FTIR). The effects of pressure, temperature and cosolvent concentration on the drug loading and release property of the microparticles prepared with and without cosolvent were investigated. The in vitro drug release kinetics of drug-loaded microparticles was studied with five models. The results indicated that the morphology of the drug-loaded polymer microparticles was not influenced by the SSI process. And the addition of ethanol cosolvent could significantly improve the drug loading of the microparticles. The most satisfied drug loading and the release properties of the microparticles were achieved under 55 °C, 13 MPa and cosolvent ethanol concentration of 3%. The drug could be released for more than 140 h. The analysis of the drug release kinetics showed that the experimental data fitted with Ritger–Peppas model were optimal. According to the release exponent value, the in vitro release process of the nitrendipine-loaded microparticles was controlled by Fickian diffusion, which can provides a theoretical basis for drug release of this type of experiment.

In this work, drug-loaded polymer microparticles were prepared by a supercritical solution impregnation (SSI) process with nitrendipine as the model drug and PLLA–PEG–PLLA as the drug carrier.     

Synthesis of biodiesel from waste cooking oil catalyzed by β-cyclodextrin modified Mg–Al–La composite oxide

In this study, Mg–Al–La composite oxide loaded with ionic liquid [Bmim]OH was used as a catalyst for the synthesis of fatty acid isobutyl ester (FAIBE) via transesterification between waste cooking oil and isobutanol. Mg–Al–La composite oxide was synthesized from the β-cyclodextrin (β-CD) intercalation modification of Mg–Al–La layered double hydroxides. The structure of the catalyst was characterized via XRD, BET and EDS. The results showed that the interlayer space of the catalyst was increased due to β-CD intercalation modification. The IL/CD–Mg–Al–La catalyst exhibited significant catalytic activity and regeneration performance in transesterification due to large interlayer space and strongly alkaline ionic liquid. The yield of FAIBE achieved was 98.3% under the optimum reaction condition and 95.2% after regeneration for six times. The viscosity–temperature curve of FAIBE was determined and the phase transition temperature was −1 °C. The pour point of FAIBE was only −10 °C, which exhibited excellent low temperature fluidity.

In this study, Mg–Al–La composite oxide loaded with ionic liquid [Bmim]OH was used as a catalyst for the synthesis of fatty acid isobutyl ester (FAIBE) via transesterification between waste cooking oil and isobutanol.     

The treatment of real dyeing wastewater by the electro-Fenton process using drinking water treatment sludge as a catalyst

This study aims to evaluate the performance of the electro-Fenton process (EFP) using drinking water treatment sludge (DWTS) for the treatment of dyeing wastewater. Effects of operating parameters including pH, electrode distance, applied voltage, operation temperature and time on the electro-Fenton-oxidation of dyeing wastewater were investigated. The decolorization and COD degradation efficiencies of 97.8% and 89.8%, respectively, were achieved indicating almost complete mineralization of organic pollutants after 90 minutes of reaction at pH 4.0, dosage of DWTS of 2.0 g, applied voltage of 20.0 V, electrode distance of 3.0 cm and ambient temperature. The morphology of the sludge and presence of Fe(OH)₃ after Fenton-oxidation were investigated to understand the mechanisms involved. The degradation of COD in EFP was found to fit well the pseudo-first-order kinetic model. The thermodynamic constants of the Fenton oxidation process were also determined and showed that the Fenton-oxidation process was spontaneous and endothermic. This study provides an efficient and low-cost method for the degradation of non-biodegradable pollutants in dyeing wastewater to solve waste using waste.

This study aims to evaluate the performance of the electro-Fenton process (EFP) using drinking water treatment sludge (DWTS) for the treatment of dyeing wastewater.     

Beneficial use of ultrasound irradiation in synthesis of beta–clinoptilolite composite used in heavy oil upgrading process

A novel beta–clinoptilolite composite was prepared from beta zeolite and alkaline treated clinoptilolite by employing conventional and sonicated mixing procedures. Parent and prepared catalysts were characterized by XRD, FE-SEM, N₂ adsorption–desorption and NH₃-TPD analyses. Prepared composite of beta zeolite and treated clinoptilolite exhibited improved structural properties especially upon sonicated mixing procedure. Employing ultrasound irradiation notably improved beta distribution in the composite and increased mesoporous volume and specific surface area from 0.245 cm³ g⁻¹ and 171.3 m² g⁻¹ in conventionally mixed composite to 0.353 cm³ g⁻¹ and 232.9 m² g⁻¹ in sonicated sample. Catalytic performance of prepared composite was evaluated in heavy oil upgrading process in a continuous fixed bed apparatus. Liquid product was specified by conducting SIMDIS-GC and GC/MS analyses. Spent catalysts were characterized by TGA, FTIR and XRD. Beta–clinoptilolite composite containing only 30 wt% of beta zeolite, exhibited similar performance to beta zeolite catalyst by resulting 75.3% viscosity reduction while producing lower amount of coke. Amount of light hydrocarbons produced over beta–clinoptilolite composite was 33.51 wt% while beta zeolite catalyst produced 35.58 wt% light hydrocarbons in upgrading process. Ultrasound irradiated composite showed more stable structure in catalytic cracking procedure compared to conventionally mixed composite. After 5 h time on stream, relative crystallinity of clinoptilolite phase in the conventionally mixed composite was reduced by 34.5% while sonicated sample remarkably preserved its structure during the reaction and only 1% reduction occurred for this sample.

Beta–clinoptilolite composite synthesized in the presence of ultrasound irradiation exhibited high stability in heavy oil upgrading process while producing equal amount of light fuels and lower amount of coke compared to beta zeolite catalyst.     

Concentration–composition-isotherm for the ammonia absorption process of zirconium phosphate

The ammonia absorption process of zirconium phosphate has been studied using the concentration-composition-isotherm (CCI), X-ray diffraction and thermogravimetry-mass spectrometry (TG-MS). It was clarified that the equilibrium plateau concentration appeared due to two phase coexistence.

Ammonia absorption process of zirconium phosphate has been studied by concentration–composition-isotherm, X-ray diffraction and thermogravimetry-mass spectrometry. The equilibrium plateau concentration appeared due to two phase coexistence.

The world is shifting toward a society that reaches zero CO₂ emissions due to environmental issues.^1,2 Ammonia is a CO₂ free fuel and easily liquefied by compression at 1 MPa and 298 K, and has a high gravimetric hydrogen density of 17.8 wt% and a highest volumetric hydrogen density that is above 1.5 times that of liquid hydrogen.³ Ammonia is also a burnable substance. Therefore, ammonia has advantages as a hydrogen and energy carrier for renewable energy. Unfortunately, ammonia is a deleterious substance. As the demand for ammonia increases, it is necessary to ensure safety. A large amount of water is used as an ammonia absorbent when leakage of ammonia occurs by accidents because of large solubility in water.^4–6 However, ammonia water has the higher ammonia equilibrium vapour concentration.⁷ Many solid-state ammonia storage materials such as metal halides, complex hydrides, proto-based materials and porous materials have been studied to decrease the vapour concentration of ammonia.⁴Recently we have focused on zirconium phosphate to suppress the release of ammonia vapour concentration because of stable in air and water. The large ammonia absorption capacity 10.2 wt% and low ammonia vapour concentration below 2 ppm have been reported.⁴ The low vapour concentration follows from acid–base reaction. X-ray diffraction indicated that zirconium phosphate undergoes a structural change by ammonia absorption.^8,9 The large capacity of zirconium phosphate will be based on the structural phase transition by ammonia absorption. In general, ammonia pressure–composition-isotherm (PCI) has been used to characterize the phase transition behaviour by ammonia absorption.⁴ However, this phase transition cannot be observed by ammonia PCI measurement for zirconium phosphate because the practical lower detection limit of the measuring system is 1 Pa (10 ppm).¹⁰ The ammonia vapour concentration and the ammonia concentration in the water solution have similar values.⁴In this study, ammonia absorption process of zirconium phosphate was investigated by using ammonia concentration–composition-isotherm (CCI), X-ray diffraction (XRD) and thermogravimetry-mass spectrometry (TG-MS).We used zirconium phosphate (ZrP) with layer structure (α-zirconium phosphate, CZP-100 manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., Japan). Montmorillonite also has a layer structure. Unfortunately, the silicate layers of montmorillonite are dispersed in water and wasn''t used as a reference. Therefore, insoluble proton-exchanged zeolite (HSZ-331HSA, silica/alumina ratio: 6 mol mol⁻¹, specific surface area: 600 m² g⁻¹, particle size: 2–3 μm, manufactured by TOSOH Co., Ltd., Japan) was used as a reference. Those samples were used as received without further purification. The proton exchange capacities for ZrP and the zeolite are 6.6 mmol g⁻¹ and 2.0 mmol g⁻¹, respectively. The dilute ammonia water [200 (0.02 wt%) to 3000 ppm (0.3 wt%)] was prepared using the 10 wt% solution supplied from KENEI Pharmaceutical Co., Ltd. with ion-exchanged water.The following experiment was performed to evaluate the ammonia storage capacity. ZrP was added to the ammonia water having various concentrations at about 298 K. The NH₃ concentration and the potential of hydrogen (pH) were measured using ammonia meter (Orion Star A324 and Orion 9512 manufactured by Thermo Scientific Orion) and pH meter (CyberScan pH310 manufactured by EUTECH Ins.). Lower detection limit of the ammonia meter is 0.01 ppm.Here, ammonia has two kinds of forms which are NH₃ and NH₄⁺ in ammonia water. NH₃ concentration ([NH₃]) was measured by the ammonia meter. Then, NH₄⁺ concentration ([NH₄⁺]) was calculated using the following equation:¹¹1where K_b is the base dissociation constant (K_b = 1.8 × 10⁻⁵ M, at 298 K)¹² and pH is the potential of hydrogen. Then, we calculated the ammonia storage capacity (C_st) asC_st = ([NH₃]_af + [NH₄⁺]_af − [NH₃]_be + [NH₄⁺]_be) × L2where [NH₃]_be and [NH₃]_af are NH₃ concentration before and after ZrP is added, [NH₄⁺]_be and [NH₄⁺]_af are NH₄⁺ concentration before and after ZrP is added and L is the volume of ammonia water. Fig. 1(a) shows the ammonia CCI of ZrP. The ammonia equilibrium concentration is lower than 0.01 ppm below the ammonia storage capacity about 3 mmol g⁻¹ (1 mol NH₃ per mol ZrP).Open in a separate windowFig. 1Ammonia CCI in water at about 298 K. (a) ZrP, (b) proton-exchanged zeolite.ZrP has the ammonia equilibrium plateau concentration of ca. 1 ppm in the range from 4–6 mmol g⁻¹ (1 to 2 mol NH₃ per mol ZrP), so we found that two phases coexist in this plateau region. The increase in the equilibrium concentration of ammonia from 3–4 mmol g⁻¹ will be based on the appearance of Zr(NH₄PO₄)₂·H₂O phase. Subsequently, the ammonia equilibrium concentration drastically increases when ZrP is absorbed ammonia above 6 mmol g⁻¹ (2 mol NH₃ per mol ZrP). This capacity corresponds to the proton exchange capacity of ZrP (6.6 mmol g⁻¹). It is suggested that ammonia is bonded to the proton site of ZrP and form ammonium ion below 6 mmol g⁻¹ (2 mol NH₃ per mol ZrP). Ammonia equilibrium concentration increases above 6 mmol g⁻¹, since the proton site is absent.According to ammonia CCI, we can interpret that two kinds of ammonia absorption sites exist in zirconium phosphate, which is shown in the formula,Zr(HPO₄)₂·H₂O + NH₃ ⇌ Zr(NH₄PO₄)(HPO₄)·H₂O3Zr(NH₄PO₄)(HPO₄)·H₂O + NH₃ ⇌ Zr(NH₄PO₄)₂·H₂O4 Fig. 1(b) shows ammonia CCI of the zeolite as a reference. Ammonia equilibrium concentration is lower than 0.01 ppm below the ammonia storage capacity of 0.7 mmol g⁻¹. The ammonia concentration increases with the storage capacity above this value. When ammonia is adsorbed up to the proton exchange capacity (2 mmol g⁻¹), the ammonia concentration becomes about 500 ppm. The plateau concentration is not observed for the zeolite. This may be due to the fact that the zeolite has a porous structure and structural phase change does not occur by ammonia adsorption. Ammonia can be absorbed in ZrP by the structure change, because ZrP has interlayer spacing and interlayer proton for ammonia movement and the reaction.It has been reported that the Zr(HPO₄)₂·H₂O and Zr(NH₄PO₄)₂·H₂O has two-dimensional crystals.^8,9 Zr(HPO₄)₂·H₂O and Zr(NH₄PO₄)₂·H₂O have the interlayer distance of 0.76 nm ⁸ and 0.96 nm,⁹ respectively.XRD measurement was made in order to characterize the structures of the ZrP before and after ammonia absorption. XRD patterns were recorded on a Bragg–Brentano diffractometer (Rigaku RINT-2500V manufactured by Rigaku Co.) and CuKα at tube current of 200 mA and tube potential of 40 kV. All samples were evacuated at room temperature for 20 hours to remove water from the surface of ZrP before XRD measurements. Each sample was pressed at a constant load on a glass holder before XRD measurement. Fig. 2(a–c) show XRD patterns of ZrP, ZrP absorbed ammonia, Zr(HPO₄)₂·H₂O (JCPDS 00-019-1489) and Zr(NH₄PO₄)₂·H₂O (JCPDS 01-071-1633) of the International Center for Diffraction Data (ICDD). Two peaks are observed for ZrP absorbed ammonia at 1.4 and 1.8 mol NH₃ per mol ZrP as shown in Fig. 2(b). The peak around 2θ of 9.4° is the same as (002) diffraction of Zr(NH₄PO₄)₂·H₂O having an interlayer distance of 0.96 nm. Bragg peaks of the ZrP absorbed ammonia (1.4, 1.8 and 2.0 mol NH₃ per mol ZrP) scattered to wide angle at 2θ of 13–40° include all diffraction peaks of Zr(NH₄PO₄)₂·H₂O (see Fig. 2(c)). We confirmed the presence of Zr(NH₄PO₄)₂·H₂O in the ZrP absorbed ammonia. The interplanar spacing calculated by the broad peaks around 2θ of 11.6° at 1.4 and 1.8 mol NH₃ per mol ZrP is similar to the interlayer distance 0.76 nm of ZrP in Fig. 2(a). However, according to Fig. 1(a) in the range from 4–6 mmol g⁻¹ (1 to 2 mol NH₃ per mol ZrP) and eqn (4), the broad peak around 2θ of 11.6° can be explained by the presence of Zr(NH₄PO₄)(HPO₄)·H₂O having smaller crystallites and defects.¹³ The wide angle XRD patterns of the ZrP absorbed ammonia (1.4 mol NH₃ per mol ZrP) show new shoulder at 2θ of 24.5° which are absent in ZrP and Zr(NH₄PO₄)₂·H₂O (Fig. 2(c)). This new shoulder may come from the structure of Zr(NH₄PO₄)(HPO₄)·H₂O. One possible explanation is that two phases observed by ammonia CCI are Zr(NH₄PO₄)(HPO₄)·H₂O and Zr(NH₄PO₄)₂·H₂O in the range from 1 to 2 mol NH₃ per mol ZrP.Open in a separate windowFig. 2XRD patterns of ZrP, ZrP absorbed ammonia, Zr(HPO₄)₂·H₂O (JCPDS 00-019-1489) and Zr(NH₄PO₄)₂·H₂O (JCPDS01-071-1633), (a) small angle XRD patterns at 2θ of 8–13° (ammonia storage capacity: 0.2, 0.6 mol NH₃ per mol ZrP), (b) small angle XRD patterns at 2θ of 8–13°(ammonia storage capacity: 1.4, 1.8 and 2.0 mol NH₃ per mol ZrP), (c) wide angle XRD patterns at 2θ of 13–40°(ammonia storage capacity: 0–2.0 mol NH₃ per mol ZrP). Fig. 2(a) shows the small angle XRD patterns of ZrP and ZrP absorbed ammonia at 0.2 and 0.6 mol NH₃ per mol ZrP. Only one peak is observed for ZrP absorbed ammonia. XRD patterns of ZrP and ZrP absorbed NH₃ are similar except for the XRD peaks at 2θ of 24.5° and 33.3° of the ZrP absorbed ammonia (0.6 mol NH₃ per mol ZrP). The new peaks suggest the presence of Zr(NH₄PO₄)(HPO₄)·H₂O. These results can be understood by the coexistence of ZrP and Zr(NH₄PO₄)(HPO₄)·H₂O in the range from 0 to 1 mol NH₃ per mol ZrP.Schematic representation of the two crystal phases in the ammonia equilibrium plateau concentration is shown in Fig. 3. The ratio of these two phases will be changed depending on the ammonia storage capacity from 1 to 2 mol NH₃ per mol ZrP.Open in a separate windowFig. 3Schematic representation of two-phase co-existence in zirconium phosphate absorbed ammonia (NH₃/ZrP: 1–2 mol mol⁻¹).TG-MS measurement was carried out in order to obtain the desorbed gas, desorption temperature, and the weight loss of ZrP absorbed ammonia. TG-MS spectra were recorded on a TG (Rigaku plus RS-8200 manufactured by Rigaku Co.) and MS (M-QA200TS manufactured by Anelva Co.) in a flowing Ar gas (300 cm³ min⁻¹) with a heating rate of 5 K min⁻¹. All samples were evacuated at room temperature for 20 hours to remove water from the surface of ZrP before TG-MS measurements. Fig. 4(a) and (b) show the temperature dependences of mass spectra with m/z 16 and 18 for Zr(NH₄PO₄)₂·H₂O and Zr(HPO₄)₂·H₂O. Here, the signal of m/z 18 indicates a mainly water (H₂O) and the signal of m/z 16 indicates an ammonia (NH₂⁺). It is noted that m/z 16 is defined as ammonia rather than m/z 17 due to the water fragment ion effect on m/z 17. The peaks of m/z 16 for Zr(NH₄PO₄)₂·H₂O are observed around 390 K, 440 K and 610 K. It is indicated that Zr(NH₄PO₄)₂·H₂O desorbs ammonia around these temperatures. Then, the peak area of ammonia based on m/z 16 from 350 to 460 K is the same as the peak area of ammonia from 550 to 650 K. The peak area corresponds to the amount of ammonia desorption. Thus, Zr(NH₄PO₄)₂·H₂O is suggested to release 1 mol of ammonia from 350 to 460 K and 1 mol of ammonia from 550 to 650 K. The water desorption peaks of m/z 18 for Zr(NH₄PO₄)₂·H₂O and Zr(HPO₄)₂·H₂O are observed around 390 K and 410 K, respectively. The peak shift toward lower temperature of Zr(NH₄PO₄)₂·H₂O may be based on the interaction between water and ammonia.Open in a separate windowFig. 4MS spectra of (a) Zr(NH₄PO₄)₂·H₂O and (b) Zr(HPO₄)₂·H₂O. Blue, purple and red lines are m/z 18, 17 and 16 curves. TG spectra of (c) Zr(NH₄PO₄)₂·H₂O and (d) Zr(HPO₄)₂·H₂O. Fig. 4(c) and (d) show the TG curves of Zr(NH₄PO₄)₂·H₂O and Zr(HPO₄)₂·H₂O. In Fig. 3(c), two main weight losses are observed in this process. The weight loss of Zr(NH₄PO₄)₂·H₂O from 330 to 460 K is 10.5 wt% and the weight loss from 550 to 650 K is 5.1 wt%. These weight losses come from the desorption of ammonia and water. In Fig. 3(d), the weight loss of Zr(HPO₄)₂·H₂O is 6.0 wt% from 330 to 460 K. Thus, Zr(NH₄PO₄)₂·H₂O desorbs 1 mol water and 1 mol ammonia from 330 to 460 K, and desorbs 1 mol ammonia from 550 to 650 K by TG-MS measurement. Therefore, two kinds of ammonia absorption sites can exist in Zr(NH₄PO₄)₂·H₂O, as shown in the formula,Zr(NH₄PO₄)₂·H₂O → Zr(NH₄PO₄)(HPO₄) + H₂O + NH₃5Zr(NH₄PO₄)(HPO₄) → Zr(HPO₄)₂ + NH₃6We have demonstrated that the structural phase transition was observed using ammonia concentration–composition-isotherm (CCI) measurement for the first time. The structural phase transition was confirmed by the X-ray diffraction (XRD). In addition two kinds of ammonia absorption sites were observed by TG-MS. Therefore, CCI is a useful method for investigating structural phase transition as well as PCI.     

Effect of heat treatment on corrosion behavior of Mg–5Gd–3Y–0.5Zr alloy

The effects of different heat treatment processes on the microstructure and corrosion behavior of Mg–5Gd–3Y–0.5Zr (GW53K) magnesium alloy were studied by means of microanalysis, weight loss test and electrochemical test. The results show that appropriate heat treatment can improve the corrosion resistance of the alloy. Among the tested alloys, the T6-12 h alloy has the best corrosion resistance, which is mainly attributed to the morphology and distribution of the Mg-RE phase. The corrosion rate of the T4 alloy is similar to that of the T6-12 h alloy. The corrosion resistance of the T4 alloy may be reduced under long-term corrosion due to the existence of surface corrosion microcracks.

The effects of different heat treatment processes on the microstructure and corrosion behavior of Mg–5Gd–3Y–0.5Zr (GW53K) magnesium alloy were studied by means of microanalysis, weight loss test and electrochemical test.     

Study of the discharge/charge process of lithium–sulfur batteries by electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy (EIS) was used to study the initial discharge/charge process in a sulfur cathode with different potentials. In the second discharge region (2.00–1.70 V), where soluble polysulfides are reduced to Li₂S, the EIS spectra exhibit three semicircles/arcs as the frequency decreased. An appropriate equivalent circuit is proposed to fit the experimental EIS data. Based on detailed analysis of the change in kinetic parameters obtained from simulating the experimental EIS data as functions of potential, the high-frequency, middle-frequency and low-frequency semicircles/arcs can be attributed to the Schottky contact reflecting the electronic properties of materials, the charge transfer step and the formation of Li₂S respectively. The inclined line arises from the diffusion process in the detectable potentials and frequency range. Several important electrochemical reactions also have been verified by cyclic voltammetry curves.

Schematic model for the electrochemical reaction mechanism of a sulfur electrode in the discharge process.     

Novel hydrophobic catalysts to promote hydration at the water–oil interface

The limitation of the cyclohexene hydration reaction is that it is a three-phase immiscible reaction. We have described a strategy to overcome this interfacial mass transfer limitation by grafting an organosilane surfactant ((octyl)-trimethoxysilane (OTS)) onto the HZSM-5 zeolite surface. The characterization of the OTS-HZSM-5 zeolite was performed by FTIR, CA, BET, TPD, pyridine-IR, XPS, TGA and XRD techniques. The functionalization of the HZSM-5 zeolite could increase hydrophobicity without significantly reducing the density of acid sites. As a result, the OTS-HZSM-5 zeolite had high catalytic activity (20.87% conversion) compared with HZSM-5 (4.15% conversion) at 130 °C after 4 h. The high catalytic activity makes it a promising candidate for other acid-catalyzed two-phase reactions.

The limitation of the cyclohexene hydration reaction is that it is a three-phase immiscible reaction.     

Microstructure–mechanical properties of Ag0/Au0 doped K–Mg–Al–Si–O–F glass-ceramics

In understanding the catalytic efficacy of silver (Ag⁰) and gold (Au⁰) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ system is studied. The thermal parameters viz., glass transition temperature (T_g) and crystallization temperature (T_c) were extensively changed by varying NPs (in situ or ex situ). Tc was found to be increased (T_c = 870–875 °C) by 90–110 °C when ex situ NPs were present in the glass system. Under controlled heat-treatment at 950 ± 10 °C, the glasses were converted into glass-ceramics with the predominant presence of crystalline phase (XRD) fluorophlogopite mica, [KMg₃(AlSi₃O₁₀)F₂]. Along with the secondary phase enstatite (MgSiO₃), the presence of Ag and Au particles (FCC system) were identified by XRD. A microstructure containing spherical crystallite precipitates (∼50–400 nm) has been observed through FESEM in in situ doped GCs. An ex situ Ag doped GC matrix composed of rock-like and plate-like crystallites mostly of size 1–3 μm ensured its superior machinability. Vicker''s and Knoop microhardness of in situ doped GCs were estimated within the range 4.45–4.61 GPa which is reduced to 4.21–4.34 GPa in the ex situ Ag system. Machinability of GCs was found to be in the order, ex situ Ag > ex situ Au ∼ in situ Ag > in situ Au. Thus, the ex situ Ag/Au doped SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ GC has potential for use as a machinable glass-ceramic.

In understanding the catalytic efficacy of silver (Ag⁰) and gold (Au⁰) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ system is studied.     

Temperature-triggered reversible breakdown of polymer-stabilized olive–silicone oil Janus emulsions

A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol% oleoyl side chains. Completely engulfed emulsion droplets remained stable at room temperature and could be destabilized on demand upon heating to the transition temperature of the polymeric stabilizer. Time-dependent light micrographs demonstrate the temperature-induced breakdown of the Janus droplets, which opens new aspects of application, for instance in biocatalysis.

A one-step moderate energy vibrational emulsification method was successfully employed to produce thermo-responsive olive/silicone-based Janus emulsions stabilized by poly(N,N-diethylacrylamide) carrying 0.7 mol% oleoyl side chains.     

Operating envelope of Haber–Bosch process design for power-to-ammonia

The power-to-ammonia concept allows for the production of ammonia, one of the most produced inorganic chemicals, from air, water and (renewable) electricity. However, power-to-ammonia requires flexible operation for use with a directly intermittent renewable energy supply. In this paper, we systematically analyse the operating envelope for steady-state operation of the three bed autothermic Haber–Bosch reactor system for power-to-ammonia by pseudo-homogeneous model. Operational flexibilities of process variables, hydrogen intake and ammonia production flexibilities are analysed, along with maximum and minimum possible changes in recycle load and recycle to feed ratio for the following process variables: reactor pressure, inert gas percentage in synthesis loop, NH₃ concentration, H₂-to-N₂ ratio, total flow rate and feed temperature. Among the six process variables, inert gas fraction and H₂-to-N₂ ratio provided very high flexibilities, ca. 255% operational flexibility for Ar, up to 51 to 67% flexibility in hydrogen intake, and up to 73% reduction and 24% enhancement in ammonia production. However, a decrease in ammonia production by H₂-to-N₂ ratio significantly increases recycle load. Besides inert gas fraction and H₂-to-N₂ ratio, the total mass feed flow rate is also significant for minimum hydrogen intake and ammonia production.

The Haber–Bosch process is viable for power-to-ammonia, as it can be operated for a wide range of the operating envelope while maintaining the process variables'' operational, hydrogen feed intake and ammonia production flexibilities.     

Instant in situ formation of a polymer film at the water–oil interface

The water–oil interface is an environment that is often found in many contexts of the natural sciences and technological arenas. This interface has always been considered a special environment as it is rich in different phenomena, thus stimulating numerous studies aimed at understanding the abundance of physico-chemical problems that occur there. The intense research activity and the intriguing results that emerged from these investigations have inspired scientists to consider the water–oil interface even as a suitable setting for bottom-up nanofabrication processes, such as molecular self-assembly, or fabrication of nanofilms or nano-devices. On the other hand, biphasic liquid separation is a key enabling technology in many applications, including water treatment for environmental problems. Here we show for the first time an instant nanofabrication strategy of a thin film of biopolymer at the water–oil interface. The polymer film is fabricated in situ, simply by injecting a drop of polymer solution at the interface. Furthermore, we demonstrate that with an appropriate multiple drop delivery it is also possible to quickly produce a large area film (up to 150 cm²). The film inherently separates the two liquids, thus forming a separation layer between them and remains stable at the interface for a long time. Furthermore, we demonstrate the fabrication with different oils, thus suggesting potential exploitation in different fields (e.g. food, pollution, biotechnology). We believe that the new strategy fabrication could inspire different uses and promote applications among the many scenarios already explored or to be studied in the future at this special interface environment.

A completely new method for easy and quick formation of a thin polymer film at the special setting of a stratified oil/water interface. Morphological SEM and quantitative full-field characterization have been reported using digital holography.     

Enhancement of Fe–N–C carbon catalyst activity for the oxygen reduction reaction: effective increment of active sites by a short and repeated heating process

Controlling the formation of Fe–N–C catalytic sites is crucial to activate the oxygen reduction reaction (ORR) for realization of non-precious electrocatalysts in proton exchange membrane fuel cells (PEMFCs). We present a quantitative study on the effect of a newly obtained thermal history on the formation of Fe–N–C catalytic sites. A short and repeated heating process is employed as the new thermal history, where short heating (1 min) followed by quenching is applied to a sample with arbitrary repetition. Through electrochemical quantitative analysis, it is found that the new process effectively increases the Fe–N–C mass-based site density (MSD) to almost twice that achieved using a conventional continuous heating process, while the turn-over frequency (TOF) is independent of the process. Elemental analysis shows that the new process effectively suppresses the thermal desorption of Fe and N atoms during the initial formation stage and consequently contributes to an increase in the Fe–N–C site density. The resultant catalytic activity (gravimetric kinetic current density (0.8 V vs. RHE)) is 1.8 times higher than that achieved with the continuous heating process. The results indicate that fine control of the thermal history can effectively increase the catalytic activity and provide guidelines for further activation of non-precious ORR electrocatalysts for PEMFCs.

Controlling the formation of Fe–N–C catalytic sites is crucial to activate the oxygen reduction reaction (ORR) for realization of non-precious electrocatalysts in proton exchange membrane fuel cells (PEMFCs).     

Modulation of spatiotemporal dynamics in the bromate–sulfite–ferrocyanide reaction system by visible light

We have carried out the first systematic study of the effects of visible light on the homogenous dynamics in the bromate–sulfite–ferrocyanide (BSF) reaction. Under flow conditions, the reaction system displayed photoinduction and photoinhibition behavior, and the oscillatory period decreased with the increase of light intensity, which is due to the fact that light irradiation mainly enhanced the negative process and affected the positive feedback. The light effect on positive and negative feedback is studied by analyzing the period length of pH increasing and decreasing in detail. With the increase of light intensity, the period length of pH increasing decreases monotonically, while the period length of pH decreasing changes nonmonotonically. These results suggest that light could be used as a powerful tool to control homogenous dynamics. Results obtained from numerical simulations are in good agreement with experimental data.

The BSF reaction system displayed photoinduction and photoinhibition behavior under flow conditions. The oscillatory period decreased as the light irradiation mainly enhanced the negative process and affected the positive feedback.     

Assembly of iron oxide nanosheets at the air–water interface by leucine–histidine peptides

The fabrication of inorganic nanomaterials is important for a wide range of disciplines. While many purely inorganic synthetic routes have enabled a manifold of nanostructures under well-controlled conditions, organisms have the ability to synthesize structures under ambient conditions. For example, magnetotactic bacteria, can synthesize tiny ‘compass needles’ of magnetite (Fe₃O₄). Here, we demonstrate the bio-inspired synthesis of extended, self-supporting, nanometer-thin sheets of iron oxide at the water–air interface through self-assembly using small histidine-rich peptides.

The fabrication of inorganic nanomaterials is important for a wide range of disciplines.

Since the discovery of magnetotactic bacteria, researchers have been fascinated by the ability of these specialized organisms to orient within the Earth''s magnetic field.¹ To be able to react to magnetic fields, magnetotactic bacteria use specialized compartments, called magnetosomes, to produce the iron oxide magnetite (Fe₃O₄). Magnetosomes have a typical size of 30–120 nm and establish a permanent magnetic moment along a fixed axis within the bacteria.^2,3 The magnetization is used to navigate and orient within the terrestrial magnetic field to find favorable living conditions.⁴ It has been shown that the size and morphology of magnetic particles used are tightly genetically controlled and vary for different species.^5,6 The biomimetic synthesis of magnetic nanomaterials has been of substantial interest in the past years. Potential applications include biotechnology,⁷ medicine⁸ and data storage.⁹ While the biomimetic preparation of magnetic particles and surface patterns using proteins derived from magnetotactic bacteria has been reported before,^10–12 the biomimetic production of extended 2D magnetic materials using proteins has not been shown. At the same time, 2D nanomaterials have received much attention as ultrathin, high fidelity materials with new properties.¹³ Such 2D structures hold great promise as a material that can be self-assembled using effective, low-cost, bottom-up fabrication methods and then tuned chemically to the application.¹⁴ 2D materials can often be synthesized from simple building blocks and are very flexible in terms of surface morphology, porosity, chemical functionality, electronic and magnetic properties. It has been shown that functional 2D inorganic materials can be templated by organic precursor structures at interfaces.¹⁵ In nature, proteins act as the surface “engineers” and steer the growth of minerals at interfaces.¹⁶ 2D materials based on silica, calcium carbonate, and calcium oxalate have been assembled previously by biomimetic peptides at interfaces.^17–19 In this study, we describe the preparation of magnetic 2D materials using peptides mimicking the precipitation of magnetite within magnetosomes.The processes leading to the production of magnetite is complex and not entirely understood. Faivre et al. have suggested the involvement of bi- and trivalent iron ions taken up from sediments and that magnetite is then synthesized via templated ferrihydrite precursors.³ Proton pumps maintain the basic pH required for magnetite formation within the magnetosomes. In analogy to biomineralization of bone, teeth, and shells, the crystal phase and structure of the iron oxide generated have been hypothesized to be controlled by specialized proteins within the magnetosome.^10,12 Sone et al. have shown that, within these proteins, histidine sites play an important role because of their ability to chelate Fe²⁺-ions.⁶The rationale of this study has been to mimic the precipitation mechanism used by bacteria with a peptide that can precipitate iron oxide 2D sheets and also can effectively bind the air–water interface. We chose a synthetic peptide with the amino acid sequence Ac-LHHLLHLLHHLLHL (short: LHα14, see Fig. 1A), which contains only histidine (H) and leucine (L). In analogy with leucine–lysine (LK) peptides designed by deGrado and Lear,²⁰ the leucine side chains are intended to bind to the air–water interface, while histidines are expected to be exposed to the water phase and available for interactions with iron ions. The hydrophobic periodicity of 3.5 should favor an α-helical secondary structure at an interface and provide a stable platform for interfacial assembly.²¹ The peptide design allows a maximum number of histidines to be exposed to the solution phase, while the leucine are intended to stabilize the peptide at the water surface.Open in a separate windowFig. 1(A) Front and side view of the LHα14 peptide after energy minimization in bulk water using the software package PEP-FOLD. The sequence is designed to induce a helical fold with hydrophobic leucines for binding to the air–water interface on one side and iron-chelating histidines on the other sides. (B) Schematic of the film formation process. (C) SFG spectra collected with ssp and sps polarization for LHα14 at the solution-air interface before and after the iron precipitation is triggered by increasing the solution pH.We used SFG spectroscopy and surface tension measurements to follow the surface assembly (schematic in Fig. 1B and S1^†): first, LHα14 is injected into a Teflon trough with the iron chloride solution at neutral pH. The surface tension increased to 19.1 ± 0.8 mN m⁻¹ (measured of 3000 s after stabilization of the film assembly) upon peptide injection, indicating full monolayer coverage of the water surface. The structure of the LHα14 monolayer was determined using sum-frequency generation (SFG) spectroscopy in the amide I region.²² SFG can probe the secondary structure and orientation of peptides and proteins at liquid surfaces. As second-order nonlinear spectroscopy, SFG is intrinsically surface-specific due to selection rules: SFG is only allowed where inversion symmetry is broken, which is typically the case within an interfacial layer between two bulk isotropic media, such as water and air.²³ Amide I SFG spectra of LHα14 at the FeCl solution surface collected with ssp (s-polarized SFG, s-polarized visible, p-polarized infrared) and sps polarization, are shown in Fig. 1C. Both ssp and sps SFG spectra show a pronounced amide I band centered near 1644 cm⁻¹, which can be assigned to α-helical structure in D₂O.²⁴Following surface adsorption, the subphase was diluted by a factor of eight to reduce the bulk peptide concentration and avoid precipitation in the volume. Subsequently, the pH is increased using ammonia vapor to trigger the precipitation of iron oxide by protonating the histidine sites. SFG spectra recorded in this state (Fig. 1C) show a reduction of the signal level but the resonance position remains unchanged at basic pH. This implies that the secondary structure of LHα14 remains unchanged.The interaction of protonated LHα14 with iron ions leads to the precipitation of sheets of iron oxide which can be lifted off the solution surface with transmission electron microscopy (TEM) grids (Fig. 2A). A TEM image of a film transferred from the air–water is shown in Fig. 2A. The sheet covers the openings within the TEM grid and is stable on a length scale of tens of micrometers. Control samples, where iron oxide was precipitated without LHα14, resulted in fragmented and unstable films, as can be seen in the SEM image of a film deposited onto a silicon wafer surface in Fig. 2B. Clearly, the peptides are key to stabilize the iron oxide layer. Higher-resolution SEM images in Fig. 2C and D show the LHα14-precipitated films have a sponge-like porous structure consisting of ∼15 nm particles interconnected by wire-like protrusions. Atomic force microscopy (AFM) showed the particles are approximately 20 nm high, leading to the conclusion the particles are roughly spherical (see Fig. 3). The films have a thickness of 22.2 ± 4.3 nm according to AFM line scans across edges of the film.Open in a separate windowFig. 2(A) TEM image of LHα14-templated iron oxide nanosheets spanning the holes of a TEM grid. (B) SEM image of iron oxide film precipitated without peptides and deposited onto a silicon wafer. (C and D) SEM images of LHα14-precipated sheets. (E) TEM image of freestanding nanosheets. The higher resolution TEM in (F) shows crystalline domains. (G) Electron diffraction pattern of the nanosheets.Open in a separate windowFig. 3Atomic force microscopy image of LHα14 precipitated iron oxide nanosheets. (Left) Nanosheet at the edge of a defect to measure the height profile going from the substrate to the iron oxide sheet. The height difference is 22.2 ± 4.3 nm. (Right) Higher magnification image at the position marked in the left panel. The height profile shows an average particle height of 20 nm.High-resolution TEM images of an edge in the film are displayed in Fig. 2E. It can be clearly seen that the films are freestanding nanosheets and stable without substrate support. The sheets consist of amorphous areas without crystalline structure and crystalline domains of an approximate size of the particles (Fig. 2F). The respective electron diffraction pattern (Fig. 2G) shows the diffraction rings related to the polycrystalline structures. The average intensities as a function of the diffraction angle are plotted along with reference peak positions for ferrihydrite (red) and magnetite (cyan).²⁵ The ferrihydrite diffraction peaks are generally in good agreement with the experimental peak positions. Some diffraction peaks are not fully resolved within the resolution of the experiment and appear as shoulders (e.g. the peak near 27 nm⁻¹). This is likely also the reason the first two ferrihydrite peaks are not visible in the experimental data. Several peak positions and their relative intensities match the typical magnetite diffraction peaks near 24, 37, 39 and 42 nm⁻¹. The data show that the nanosheets contain both magnetite and its precursor ferrihydrite.X-ray photoelectron spectroscopy (XPS) shows that the sheets contain significant amounts of iron and oxygen as well as the expected nitrogen and carbon from the peptides in the film (

Solute displacement in the aqueous phase of water–NaCl–organic ternary mixtures relevant to solvent-driven water treatment

Twelve water miscible organic solvents (MOS): acetone, tetrahydrofuran, isopropanol, acetonitrile, dimethyl sulfoxide, 1,4-dioxane, dimethylacetamide, N-methyl-2-pyrrolidone, trifluoroethanol, isopropylamine, dimethylformamide, and dimethyl ether (DME) were used to produce ternary mixtures of water–NaCl–MOS relevant to MOS-driven fractional precipitation. The aqueous-phase composition of the ternary mixture at liquid–liquid equilibrium and liquid–solid endpoint was established through quantitative nuclear magnetic resonance and mass balance. The results highlight the importance of considering the hydrated concentrations of salts and suggest that at high salt concentrations and low MOS concentration, the salt concentration is governed by competition between the salt ions and MOS molecules. Under these conditions a LS phase boundary is established, over which one mole of salt is replaced by one mole of MOS (solute displacement). At higher MOS concentrations, MOS with higher water affinity deviate from the one-to-one solute exchange but maintain a LS boundary with a homogenous liquid phase, while MOS with lower water affinity form a liquid–liquid phase boundary. DME is found to function effectively as an MOS for fractional precipitation, precipitating 97.7% of the CaSO₄ from a saturated solution, a challenging scalant. DME-driven water softening recycles the DME within the system improving the atom-efficiency over existing seawater desalination pretreatments by avoiding chemical consumption.

Water–NaCl–organic ternary mixtures evaluated with hydrates salt concentrations to reveal general phenomenon of the one-for-one molar displacement of NaCl by organic solutes as well as implications on solvent driven water treatments.