A vanillin-based copper(ii) metal complex with a DNA-mediated apoptotic activity

Vanillin (vanH) is the major component of vanilla and one of the most widely used flavoring agents. In this work the complex [Cu(phen)(van)₂] was prepared and characterized by structural (X-ray), spectroscopic (IR, UV-Vis, EPR) and electrochemical techniques. This compound showed an octahedral geometry with an unusual arrangement of the vanillin ligands, where the methoxy groups of the vanillinate ions are coordinated opposite to each other. The compound promoted DNA cleavage in the presence of glutathione (GSH) and H₂O₂. At 40 μmol L⁻¹ of complex with GSH (10 mmol L⁻¹), there is a complete cleavage of DNA to nicked form II, while only at 10 μmol L⁻¹ of this complex with H₂O₂ (1 mmol L⁻¹) an extensive cleavage leading to form III took place. Additionally, we have evidences of superoxide generation upon reaction with GSH. Therefore, DNA fragmentation occurs likely through an oxidative pathway. MTT assays indicated that the complex is highly cytotoxic against three distinct cell lines: B16–F10 (IC₅₀ = 3.39 ± 0.61 μmol L⁻¹), HUH-7 (IC₅₀ = 4.22 ± 0.31 μmol L⁻¹) and 786-0 (IC₅₀ = 10.38 ± 0.91 μmol L⁻¹). Flow cytometry studies conducted with 786-0 cell line indicated cell death might occur by apoptosis. Cell cycle progression evaluated at 5 and 10 μmol L⁻¹ resulted in a clear increase of 786-0 cells at G1 phase and depletion of G2/M, while higher doses showed an expressive increase of sub-G1 phase. Altogether, these results pointed out to a promising biological activity and potential as an anti-cancer agent.

Proposed catalytic cycle for ROS production in the vicinity of DNA after reduction of [Cu(phen)(van)₂] by glutathion.     

Application of pyrite and chalcopyrite as sensor electrode for amperometric detection and measurement of hydrogen peroxide

The sensing performance of solid-state amperometric sensors based on natural sulfide minerals, i.e., pyrite and chalcopyrite, has been characterized for the detection and measurement of hydrogen peroxide (H₂O₂) in aqueous medium. The sensors showed a wide linear relationship range between response current and the concentration of H₂O₂ from 1.0 × 10⁻⁵ mol L⁻¹ to 1.0 × 10⁻² mol L⁻¹ and 1.0 × 10⁻⁴ mol L⁻¹ to 3.0 × 10⁻² mol L⁻¹ for pyrite and chalcopyrite, respectively. The limit of detection (LOD) was as low as 8.6 × 10⁻⁶ mol L⁻¹ and 5.2 × 10⁻⁵ mol L⁻¹ (S/N = 3), respectively. The electrodes exhibited great sensitivity, repeatability and short response time (less than 5 s). The results show that pyrite and chalcopyrite can be used as a natural, low cost, reliable and sensitive sensor for hydrogen peroxide detection, creating a new and high value application for the sulfide minerals.

The sensing performance of solid-state amperometric sensors based on natural sulfide minerals, i.e., pyrite and chalcopyrite, has been characterized for the detection and measurement of hydrogen peroxide (H₂O₂) in aqueous medium.     

Aqueous supercapacitors based on carbonized silk electrodes

Graphitic nitrogen-doped hierarchical porous carbon nanosheets for supercapacitor application were derived from an easily obtained and green silk by simultaneous ZnCl₂ activation and FeCl₃ graphitization at different heating temperatures. By increasing the heating temperature from 700 to 850 °C, the degree of graphitization and BET surface area rose to their highest levels, while the nitrogen doping content was maintained at 2.24 wt%. Carbonized silk at 850 °C displays a nanosheet morphology and a considerable specific surface area (1285.31 m² g⁻¹), and it was fabricated into a supercapacitor as an electrode material, exhibiting superior electrochemical performance with a high specific capacitance of 178 F g⁻¹ at 0.5 A g⁻¹ and an excellent rate capability (81% capacitance retention ratio even at 20 A g⁻¹) in 1 mol L⁻¹ H₂SO₄ electrolyte. A symmetric supercapacitor using carbonized silk at 850 °C as the electrodes has an excellent specific energy of 14.33 W h kg⁻¹ at a power density of 251 W kg⁻¹ operated over a wide voltage range of 2.0 V in aqueous neutral Na₂SO₄ electrolyte.

An aqueous symmetrical supercapacitor was achieved by assembling SC-850 electrodes, which possess a specific energy of 14.33 W h kg⁻¹ at a power density of 251 W kg⁻¹ operated over the wide voltage range of 2.0 V in aqueous neutral Na₂SO₄ electrolyte.     

α-Glucosidase inhibitors from Chinese bayberry (Morella rubra Sieb. et Zucc.) fruit: molecular docking and interaction mechanism of flavonols with different B-ring hydroxylations

Inhibition of α-glucosidase alleviates postprandial high glycemic levels in diabetic or prediabetic population. In Chinese bayberry fruit, myricetin, quercetin and kaempferol are main flavonols, which differ only in their hydroxylation on the B-ring. Kaempferol (4′-OH) showed high IC₅₀ (65.36 ± 0.27 μmol L⁻¹) against α-glucosidase, while quercetin (3′,4′-OH) exhibited stronger inhibition (46.91 ± 0.54 μmol L⁻¹) and myricetin (3′,4′,5′-OH) possessed the strongest inhibitory activity (33.20 ± 0.43 μmol L⁻¹). Molecular docking analysis illustrated that these flavonols could insert to the active cavity of α-glucosidase. Adjacent hydroxyl groups at B-ring of myricetin and quercetin positively contributed to form hydrogen bonds that were important to the stability of flavonol–enzyme complex, while kaempferol had no adjacent hydroxyl groups. Such observation was further validated by molecular dynamics simulations, and in good consistency with in vitro kinetic analysis and fluorescence spectroscopy analysis. Among three flavonols tested, myricetin possessed the strongest inhibition effects on α-glucosidase with the lowest dissociation constant (K_i = 15.56 μmol L⁻¹) of myricetin-α-glucosidase, largest fluorescence quenching constant (K_sv) of (14.26 ± 0.03) × 10⁴ L mol⁻¹ and highest binding constant (K_a) of (1.38 ± 0.03) × 10⁵ L mol⁻¹ at 298 K with the enzyme. Bio-Layer Interferometry (BLI) and circular dichroism (CD) analysis further confirmed that myricetin had high affinity to α-glucosidase and induced conformational changes of enzyme. Therefore, myricetin, quercetin and kaempferol are all excellent dietary α-glucosidase inhibitors and their inhibitory activities are enhanced by increasing number of hydroxyl groups on B-ring.

Inhibition of α-glucosidase alleviates postprandial high glycemic levels in diabetic or prediabetic population.     

A novel bio-electro-Fenton system with dual application for the catalytic degradation of tetracycline antibiotic in wastewater and bioelectricity generation

In this new insight, the potential application of the eco-friendly Bio-Electro-Fenton (BEF) system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source. To shed light on this issue, catalytic degradation of tetracycline was directly accrued via in situ generated hydroxyl free radicals from Fenton''s reaction in the cathode chamber. Simultaneously, the in situ electricity generation as renewable bioenergy was carried out through microbial activities. The effects of operating parameters, such as electrical circuit conditions (in the absence and presence of external resistor load), substrate concentration (1000, 2000, 5000, and 10 000 mg L⁻¹), catholyte pH (3, 5, and 7), and FeSO₄ concentration (2, 5, and 10 mg L⁻¹) were investigated in detail. The obtained results indicated that the tetracycline degradation was up to 99.04 ± 0.91% after 24 h under the optimal conditions (short-circuit, pH 3, FeSO₄ concentration of 5 mg L⁻¹, and substrate concentration of 2000 mg L⁻¹). Also, the maximum removal efficiency of anodic COD (85.71 ± 1.81%) was achieved by increasing the substrate concentration up to 2000 mg L⁻¹. However, the removal efficiencies decreased to 78.29 ± 2.68% with increasing substrate concentration up to 10 000 mg L⁻¹. Meanwhile, the obtained maximum voltage, current density, and power density were 322 mV, 1195 mA m⁻², and 141.60 mW m⁻², respectively, at the substrate concentration of 10 000 mg L⁻¹. Present results suggested that the BEF system could be employed as an energy-saving and promising technology for antibiotic-containing wastewater treatment and simultaneous sustainable bioelectricity generation.

In this new insight, the potential application of the Bio-Electro-Fenton system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source.     

Fabrication of an (α-Mn2O3:Co)-decorated CNT highly sensitive screen printed electrode for the optimization and electrochemical determination of cyclobenzaprine hydrochloride using response surface methodology

A new chemically optimized screen-printed electrode modified with a cobalt-doped α-Mn₂O₃ nanostructure on carbon nanotube paste (α-Mn₂O₃:Co@CNTs) has been constructed for the recognition of cyclobenzaprine hydrochloride. The prepared paste is based on the incorporation of oxide ion conductors, such as the α-Mn₂O₃ nanostructure with cobalt and ion pairs (tetraphenyl borate coupled with the drug), as electroactive species in the screen-printed electrode to increase the sensor surface area and decrease electrical resistance. The central composite design is a useful methodology for the estimation and modeling of the exact optimum parameters specifically designed for this process. This is a good way to graphically clarify the relationship between various experimental variables and the slope response. The proposed sensor, α-Mn₂O₃:Co@CNTs, possesses very good sensitivity and the ability to recognize the drug over the concentration range of 1 × 10⁻⁶ to 1 × 10⁻² mol L⁻¹ at 25 ± °C with a detection limit of 2.84 × 10⁻⁷ mol L⁻¹. It exhibits a reproducible potential and stable linear response for six months at a Nernstian slope of 58.96 ± 0.76 mV per decade. The proposed electrode approach has been successfully applied in the direct determination of the drug in its pure and dosage forms.

A new chemically optimized screen-printed electrode modified with a cobalt-doped α-Mn₂O₃ nanostructure on carbon nanotube paste (α-Mn₂O₃:Co@CNTs) has been constructed for the recognition of cyclobenzaprine hydrochloride.     

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.     

Molecular dynamics simulations of Y(iii) coordination and hydration properties

Y mainly exists in ionic rare-earth resources. During rare-earth carbonate precipitation, rare-earth ion loss in the precipitated rare-earth mother liquor often occurs due to CO₃²⁻ coordination and Y(iii) hydration. Microscopic information on the coordination and hydration of CO₃²⁻ and H₂O to Y(iii) has not yet been elucidated. Therefore, in this study, the macroscopic dissolution of Y(iii) in different aqueous solutions of Na₂CO₃ was studied. The radial distribution function and coordination number of Y(iii) by CO₃²⁻ and H₂O were systematically analyzed using molecular dynamics (MD) simulations to obtain the complex ion form of Y(iii) in carbonate solutions. Density functional theory (DFT) was used to geometrically optimize and calculate the UV spectrum of Y(iii) complex ions. This spectrum was then analyzed and compared with experimentally determined ultraviolet-visible spectra to verify the reliability of the MD simulation results. Results showed that Y(iii) in aqueous solution exists in the form of [Y·3H₂O]³⁺ and that CO₃²⁻ is present in the bidentate coordination form. In 0–0.8 mol L⁻¹ CO₃²⁻ solutions, Y(iii) was mainly present as the 5-coordinated complex [YCO₃·3H₂O]⁺. When the concentration of CO₃²⁻ was increased to 1.2 mol L⁻¹, [YCO₃·3H₂O]⁺ was converted into a 6-coordinated complex [Y(CO₃)₂·2H₂O]⁻. Further increases in CO₃²⁻ concentration promoted Y(iii) dissolution in solution in the form of complex ions. These findings can be used to explain the problem of incomplete precipitation of rare earths in carbonate solutions.

Based on MD results, DFT was used to geometrically optimize and calculate the UV spectrum of Y(iii) complex ions. Data validation was further performed using UV-vis experiments to reveal Y(iii) coordination and hydration properties.     

Frequency of Interruptions to Sitting Time: Benefits for Postprandial Metabolism in Type 2 Diabetes

OBJECTIVETo determine whether interrupting sitting with brief bouts of simple resistance activities (SRAs) at different frequencies improves postprandial glucose, insulin, and triglycerides in adults with medication-controlled type 2 diabetes (T2D).RESEARCH DESIGN AND METHODSParticipants (n = 23, 10 of whom were female, with mean ± SD age 62 ± 8 years and BMI 32.7 ± 3.5 kg · m⁻²) completed a three-armed randomized crossover trial (6- to 14-day washout): sitting uninterrupted for 7 h (SIT), sitting with 3-min SRAs (half squats, calf raises, gluteal contractions, and knee raises) every 30 min (SRA3), and sitting with 6-min SRAs every 60 min (SRA6). Net incremental areas under the curve (iAUC_net) for glucose, insulin, and triglycerides were compared between conditions.RESULTSGlucose and insulin 7-h iAUC_net were attenuated significantly during SRA6 (glucose 17.0 mmol · h · L⁻¹, 95% CI 12.5, 21.4; insulin 1,229 pmol · h · L⁻¹, 95% CI 982, 1,538) in comparison with SIT (glucose 21.4 mmol · h · L⁻¹, 95% CI 16.9, 25.8; insulin 1,411 pmol · h · L⁻¹, 95% CI 1,128, 1,767; P < 0.05) and in comparison with SRA3 (for glucose only) (22.1 mmol · h · L⁻¹, 95% CI 17.7, 26.6; P = 0.01) No significant differences in glucose or insulin iAUC_net were observed in comparison of SRA3 and SIT. There was no statistically significant effect of condition on triglyceride iAUC_net.CONCLUSIONSIn adults with medication-controlled T2D, interrupting prolonged sitting with 6-min SRAs every 60 min reduced postprandial glucose and insulin responses. Other frequencies of interruptions and potential longer-term benefits require examination to clarify clinical relevance.     

Graphitic carbon nitride and APTES modified advanced electrochemical biosensor for detection of 17β-estradiol in spiked food samples

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples. The biosensing system is based on graphitic carbon nitride (g-C₃N₄) and a conductive polymer 3-aminopropyltriethoxysilane (APTES). The proposed biosensor shows the ability to detect E2 in attomolar levels within a wide linear logarithm concentration range of 1 × 10⁻⁶ to 1 × 10⁻¹⁸ mol L⁻¹ with a limit of detection (LOD) of 9.9 × 10⁻¹⁹ mol L⁻¹. The selectivity of the developed biosensor was confirmed by conducting the DPV of similarly structured hormones and naturally occurring substances. The proposed biosensor is highly stable and applicable to detect E2 in the presence of spiked food and environmental samples with satisfactory recoveries ranging from 95.1 to 104.8%. So, the designed electrochemical biosensor might be an effective alternative tool for the detection of E2 and other endogenous substances to attain food safety.

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples.     

New Tb3+–simvastatin optical biosensor for sensitive determination of folic acid,progesterone, testosterone and vitamin D3 in biological fluids

An innovative, simple and cost effective Tb³⁺–simvastatin photo probe was designed and used as a core for a spectrofluorometric approach to sensitively determine four vital biological compounds in different matrices. A Tb³⁺–simvastatin complex displays a characteristic electrical band with λ_em at 545 nm with significant luminescence intensity, which is quenched in the presence of folic acid, progesterone, testosterone and vitamin D₃ at four variant sets of pH: 5.0, 6.2, 7.5 and 9.0, respectively. The conditions were optimized and the best solvent for operation was found to be acetonitrile at λ_ex at 340 nm. Folic acid was successfully estimated in tablet dosage form, urine and serum in the concentration range of 2.49 × 10⁻⁹ to 1.28 × 10⁻⁶ mol L⁻¹. Progesterone, testosterone and vitamin D₃ were also assessed in serum samples using the same optimal conditions within concentration ranges of 5 × 10⁻⁹ to 1.9 × 10⁻⁶, 5 × 10⁻⁹ to 2.8 × 10⁻⁶ and 5 × 10⁻⁹ to 4.2 × 10⁻⁶ mol L⁻¹, respectively. The proposed luminescence method was validated in accordance with ICH guidelines and found to be accurate, precise, and specific and free from any interference at the working pH for each analyte. The cost effectiveness and applicability of the method make it a good choice for routine analysis of the four compounds and early diagnosis of chronic diseases associated with abnormalities in their physiological levels.

An innovative, simple and cost effective Tb³⁺–simvastatin photo probe was designed and used as a core for a spectrofluorometric approach to sensitively determine four vital biological compounds in different matrices.     

Disodium citrate-assisted hydrothermal synthesis of V2O5 nanowires for high performance supercapacitors

Orthorhombic vanadium pentoxide (V₂O₅) nanowires with uniform morphology were successfully fabricated via a facile hydrothermal process. The effect of disodium citrate dosage on the crystallinity, morphology and electrochemical properties of the products was analyzed. Experimental results indicate that orthorhombic V₂O₅ nanowires with high crystallinity and diameter of about 20 nm can be obtained at 180 °C for 24 h when the dosage of disodium citrate is 0.236 g. Furthermore, the prepared V₂O₅ nanowires demonstrate a high specific capacitance of 528.2 F g⁻¹ at 0.5 A g⁻¹ and capacitance retention of 85% after 1000 galvanostatic charge/discharge cycles at 1 A g⁻¹ when used as supercapacitors electrode in 0.5 M K₂SO₄.

Orthorhombic vanadium pentoxide (V₂O₅) nanowires with uniform morphology were successfully fabricated via a facile hydrothermal process.     

Catalytic activation of peroxymonosulfate with manganese cobaltite nanoparticles for the degradation of organic dyes

In this work, we report the facile hydrothermal synthesis of manganese cobaltite nanoparticles (MnCo₂O_4.5 NPs) which can efficiently activate peroxymonosulfate (PMS) for the generation of sulfate free radicals (SO₄˙⁻) and degradation of organic dyes. The synthesized MnCo₂O_4.5 NPs have a polyhedral morphology with cubic spinel structure, homogeneously distributed Mn, Co, and O elements, and an average size less than 50 nm. As demonstrated, MnCo₂O_4.5 NPs showed the highest catalytic activity among all tested catalysts (MnO₂, CoO) and outperformed other spinel-based catalysts for Methylene Blue (MB) degradation. The MB degradation efficiency reached 100% after 25 min of reaction under initial conditions of 500 mg L⁻¹ Oxone, 20 mg L⁻¹ MnCo₂O_4.5, 20 mg L⁻¹ MB, unadjusted pH, and T = 25 °C. MnCo₂O_4.5 NPs showed a great catalytic activity in a wide pH range (3.5–11), catalyst dose (10–60 mg L⁻¹), Oxone concentration (300–1500 mg L⁻¹), MB concentration (5–40 mg L⁻¹), and temperature (25–55 °C). HCO₃⁻, CO₃²⁻ and particularly Cl⁻ coexisting anions were found to inhibit the catalytic activity of MnCo₂O_4.5 NPs. Radical quenching experiments revealed that sulfate radicals are primarily responsible for MB degradation. A reaction sequence for the catalytic activation of PMS was proposed. The as-prepared MnCo₂O_4.5 NPs could be reused for at least three consecutive cycles with small deterioration in their performance due to low metal leaching. This study suggests a facile route for synthesizing MnCo₂O_4.5 NPs with high catalytic activity for PMS activation and efficient degradation of organic dyes.

Catalytic degradation of organic dyes via manganese cobaltite nanoparticles-activated peroxymonosulfate.     

Influence of Cl− ions on anodic polarization behaviour of API X80 steel in high potential/current density conditions in Na2SO4 solution

Pipeline steel has considerable risk of corrosion in the high voltage direct current interference cases. Thus, under high potential/current density conditions, the anodic polarization behaviour of X80 steel in Na₂SO₄ solution and the influence of Cl⁻ ions were investigated using reversed potentiodynamic polarization, the current interrupt method, galvanostatic polarization, scanning electron microscopy, and X-ray photoelectron spectroscopy. In the Na₂SO₄ solution free of Cl⁻ ions, steel was passivated above 0.120 A cm⁻² and the potential increased from −0.32 V to 1.43 V. The passive film was composed of Fe₃O₄, γ-Fe₂O₃, and FeOOH. The addition of Cl⁻ ions observably influenced the passivation by attacking the passivate film. Low concentration of Cl⁻ ions (<5 mg L⁻¹ NaCl) could set higher demands of current density to achieve passivation and increase the requirement of potential to maintain passivation. A high concentration of Cl⁻ ions (>5 mg L⁻¹ NaCl) completely prevented passivation, showing strong corrosiveness. Thus, the X80 steel was corroded even under high-current-density conditions. The corrosion products were mainly composed of Fe₃O₄, α-Fe₂O₃, and FeOOH.

X80 steel gets passivated in high potential/current density conditions in Na₂SO₄ solution. Low concentration of Cl⁻ ions weakens the passivation. High concentration of Cl⁻ ions totally prevents the passivation.     

Thermodynamics of the double sulfates Na2M2+(SO4)2·nH2O (M = Mg,Mn, Co,Ni, Cu,Zn, n = 2 or 4) of the blödite–kröhnkite family

The double sulfates with the general formula Na₂M²⁺(SO₄)₂·nH₂O (M = Mg, Mn, Co, Ni, Cu, Zn, n = 2 or 4) are being considered as materials for electrodes in sodium-based batteries or as precursors for such materials. These sulfates belong structurally to the blödite (n = 4) and kröhnkite (n = 2) family and the M cations considered in this work were Mg, Mn, Co, Ni, Cu, Zn. Using a combination of calorimetric methods, we have measured enthalpies of formation and entropies of these phases, calculated their Gibbs free energies (Δ_fG°) of formation and evaluated their stability with respect to Na₂SO₄, simple sulfates MSO₄·xH₂O, and liquid water, if appropriate. The Δ_fG° values (all data in kJ mol⁻¹) are: Na₂Ni(SO₄)₂·4H₂O: −3032.4 ± 1.9, Na₂Mg(SO₄)₂·4H₂O: −3432.3 ± 1.7, Na₂Co(SO₄)₂·4H₂O: −3034.4 ± 1.9, Na₂Zn(SO₄)₂·4H₂O: −3132.6 ± 1.9, Na₂Mn(SO₄)₂·2H₂O: −2727.3 ± 1.8. The data allow the stability of these phases to be assessed with respect to Na₂SO₄, MSO₄·mH₂O and H₂O(l). Na₂Ni(SO₄)₂·4H₂O is stable with respect to Na₂SO₄, NiSO₄ and H₂O(l) by a significant amount of ≈50 kJ mol⁻¹ whereas Na₂Mn(SO₄)₂·2H₂O is stable with respect to Na₂SO₄, MnSO₄ and H₂O(l) only by ≈25 kJ mol⁻¹. The values for the other blödite–kröhnkite phases lie in between. When considering the stability with respect to higher hydrates, the stability margin decreases; for example, Na₂Ni(SO₄)₂·4H₂O is still stable with respect to Na₂SO₄, NiSO₄·4H₂O and H₂O(l), but only by ≈20 kJ mol⁻¹. Among the phases studied and chemical reactions considered, the Na–Ni phase is the most stable one, and the Na–Mn, Na–Co, and Na–Cu phases show lower stability.

The double sulfates with the general formula Na₂M²⁺(SO₄)₂·nH₂O (M = Mg, Mn, Co, Ni, Cu, Zn, n = 2 or 4) are being considered as materials for electrodes in sodium-based batteries or as precursors for such materials.     

Disposable gold nanoparticle functionalized and bare screen-printed electrodes for potentiometric determination of trazodone hydrochloride in pure form and pharmaceutical preparations

In the present study, screen-printed electrodes unmodified and chemically modified with gold nanoparticles were used as sensitive electrochemical sensors for the determination of trazodone hydrochloride. The sensors were based on the use of a tetraphenylborate ion association complex as an electroactive material in screen-printed electrodes with dioctyl phthalate (DOP) as a solvent mediator modified with gold nanoparticles which improve the electrode conductivity and enhance the surface area. The sensors displayed a stable response for 5, 6 and 7 months with a reproducible potential and linear response over the concentration range 1 × 10⁻⁵–1 × 10⁻² mol L⁻¹ at 25 ± 1 °C with Nernstian slopes of 57.50 ± 0.66, 58.30 ± 0.45 and 59.05 ± 0.58 mV per decade and detection limits of 7.9 × 10⁻⁶, 7.6 × 10⁻⁶ and 6.8 × 10⁻⁶ mol L⁻¹ for sensor 1, 2 and 3 respectively. The analytical performance of the screen printed electrodes in terms of selectivity coefficients for trazodone hydrochloride relative to the number of potentially interfering substances was investigated. The proposed method has been applied successfully for the analysis of the drug in its pure and dosage forms and there is no interference from any common pharmaceutical additives.

In the present study, screen-printed electrodes unmodified and chemically modified with gold nanoparticles were used as sensitive electrochemical sensors for the determination of trazodone hydrochloride.     

A low-temperature hydrothermal synthesis of submicron spherical BaF2

The sub-micron spherical barium fluoride (BaF₂) was successfully synthesized via a low-temperature hydrothermal method using ethylenediamine tetraacetic acid disodium salt (EDTA-2Na) as the chelating agent. The effect of pH, the molar ratio of EDTA to Ba²⁺, barium hydroxide octahydrate (Ba(OH)₂·8H₂O) concentration, hydrofluoric acid (HF) concentration, hydrothermal temperature and time, on the formation of spherical BaF₂ were investigated. The formation mechanism of spherical BaF₂ has been proposed based on the experimental results. The results show that the spherical BaF₂, with an average size of 346.9 nm, is formed by the self-assembly of nanocubes. The optimized synthesis conditions are: pH = 14, EDTA-2Na : Ba²⁺ = 1 : 1, Ba(OH)₂ concentration is 0.1 mol L⁻¹, HF concentration is 2.0 mol L⁻¹, hydrothermal temperature is 80 °C and hydrothermal time is 2.0 h. The self-assembly mechanism of the spherical secondary structure was revealed from the perspective of crystal nucleation and growth, and the important role of EDTA in the spherical BaF₂ formation is explained.

BaF₂ submicron spherical particles, formed by the self-assembly of nanocubes, were prepared by a low-temperature hydrothermal method with the aid of EDTA-2Na.     

Hydrothermal synthesis of a novel nanolayered tin phosphate for removing Cr(iii)

In this work, an outstanding nanolayered tin phosphate with 15.0 Å interlayer spacing, Sn (HPO₄)₂·3H₂O (SnP–H⁺), has been synthesized by conventional hydrothermal method and first used in the adsorptive removal of Cr(iii) from aqueous solution. A number of factors such as contact time, initial concentration of Cr(iii), temperature, pH, and ionic strength on adsorption were investigated by batch tests. Moreover, the isothermal adsorption characteristics and kinetic model of Cr(iii) onto SnP–H⁺ were studied. The results showed that the adsorption of Cr(iii) by SnP–H⁺ was in accordance with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model. The adsorption capacity of Cr(iii) onto SnP–H⁺ at temperature 40.0 °C and pH 3.0 could reach 81.1 mg g⁻¹. And the distribution coefficient K_d was 23.0 g L⁻¹. Overall, experiments certified that SnP–H⁺ was an excellent adsorbent that can effectively remove Cr(iii) from aqueous solution.

In this work, an outstanding nanolayered tin phosphate with 15.0 Å interlayer spacing, Sn (HPO₄)₂·3H₂O (SnP–H⁺), has been synthesized by conventional hydrothermal method and first used in the adsorptive removal of Cr(iii) from aqueous solution.     

Ionic association analysis of LiTDI,LiFSI and LiPF6 in EC/DMC for better Li-ion battery performances

New lithium salts such as lithium bis(fluorosulfonyl)imide (LiFSI) and lithium 4,5-dicyano-2-(trifluoromethyl)imidazole-1-ide (LiTDI) are now challenging lithium hexafluorophosphate (LiPF₆), the most used electrolyte salt in commercial Li-ion batteries. Thus it is now important to establish a comparison of these electrolyte components in a standard solvent mixture of ethylene carbonate and dimethyl carbonate (EC/DMC: 50/50 wt%). With this aim, transport properties, such as the ionic conductivity, viscosity and ⁷Li self-diffusion coefficient have been deeply investigated. Moreover, as these properties are directly linked to the nature of the interionic interactions and ion solvation, a better understanding of the structural properties of electrolytes can be obtained. The Li salt concentration has been varied over the range of 0.1 mol L⁻¹ to 2 mol L⁻¹ at 25 °C and the working temperature from 20 °C to 80 °C at the fixed concentration of 1 mol L⁻¹. Experimental results were used to investigate the temperature dependence of the salt ion-pair (IP) dissociation coefficient (α_D) with the help of the Walden rule and the Nernst–Einstein equation. The lithium cation effective solute radius (r_Li) has been determined using the Jones–Dole–Kaminsky equation coupled to the Einstein relation for the viscosity of hard spheres in solution and the Stokes–Einstein equation. From the variations of α_D and r_Li with the temperature, it is inferred that in EC/DMC LiFSI forms solvent-shared ion-pairs (SIP) and that, LiTDI and LiPF₆ are likely to form solvent separated ion-pairs (S₂IP) or a mixture of SIP and S₂IP. From the temperature dependence of α_D, thermodynamic parameters such as the standard Gibbs free energy, enthalpy and entropy for the ion-pair formation are obtained. Besides being in agreement with the information provided by the variations of α_D and r_Li, it is concluded that the ion-pair formation process is exergonic and endothermic for the three salts in EC/DMC.

Insight is given on the type of ion-pairs that could be formed in EC/DMC by Li-salts LiTDI, LiFSI and LiPF₆.     

Annealing temperature effects on photoelectrochemical performance of bismuth vanadate thin film photoelectrodes

The effects of annealing treatment between 400 °C and 540 °C on crystallization behavior, grain size, electrochemical (EC) and photoelectrochemical (PEC) oxygen evolution reaction (OER) performances of bismuth vanadate (BiVO₄) thin films are investigated in this work. The results show that higher temperature leads to larger grain size, improved crystallinity, and better crystal orientation for the BiVO₄ thin film electrodes. Under air-mass 1.5 global (AM 1.5) solar light illumination, the BiVO₄ thin film prepared at a higher annealing temperature (500–540 °C) shows better PEC OER performance. Also, the OER photocurrent density increased from 0.25 mA cm⁻² to 1.27 mA cm⁻² and that of the oxidation of sulfite, a hole scavenger, increased from 1.39 to 2.53 mA cm⁻² for the samples prepared from 400 °C to 540 °C. Open-circuit photovoltage decay (OCPVD) measurement indicates that BiVO₄ samples prepared at the higher annealing temperature have less charge recombination and longer electron lifetime. However, the BiVO₄ samples prepared at lower annealing temperature have better EC performance in the absence of light illumination and more electrochemically active surface sites, which are negatively related to electrochemical double-layer capacitance (C_dl). C_dl was 0.0074 mF cm⁻² at 400 °C and it decreased to 0.0006 mF cm⁻² at 540 °C. The OER and sulfide oxidation are carefully compared and these show that the efficiency of charge transport in the bulk (η_bulk) and on the surface (η_surface) of the BiVO₄ thin film electrode are improved with the increase in the annealing temperature. The mechanism behind the light-condition-dependent role of the annealing treatment is also discussed.

The effects of annealing treatment on crystallization behavior, grain size, electrochemical (EC) and photoelectrochemical (PEC) oxygen evolution reaction (OER) performances of bismuth vanadate (BiVO₄) thin films are investigated in this work.