Two-step Synthesis Route Research Articles

Wet chemical synthesis of self-standing single-crystalline copper telluride Cu7Te4 nanorods: Characterizations and mechanism

Single crystalline Cu7Te4 nanorods were obtained from a two-step synthesis route. The first step is the electrochemical deposition of self-standing tellurium nanorods on Pt-coated glass electrode in an ionic liquid electrolyte acting as a structuring solvent. Afterwards, soft chemical transformation in Cu7Te4 is performed by immersing the Te-covered electrode in a Cu(II) solution in presence of ascorbic acid acting as reducer at room temperature and atmospheric pressure. Tellurium seems to undergo a reaction of disproportionation induced by the simultaneous presence of Cu(II) and Cu(I) into Te(IV) and Cu7Te4, which is supported by thermodynamic considerations. The copper telluride nanorods were analyzed by XRD, SEM-EDX, HRTEM-FFT/SAED, EELS and XPS that allowed to set the required parameters in terms of molar ratio of precursors in the bath to induce the targeted chemical reaction. The analyses highlight the obtention of single crystalline Cu7Te4 with a homogeneous chemical composition along the nanorods. A detailed analysis of the microstructure shows the presence of stacking local defects, leading to curved nanostructures.

The effect of cation size on structure and properties of Ba-based tetragonal tungsten bronzes Ba4M2Nb10O30 (M = Na, K or Rb) and Ba4M2Nb8Ti2O30 (M = Ca or Sr).

The second largest family of oxide ferroelectrics, after perovskites, are the tetragonal tungsten bronzes (TTB) with the general formula A24A12C4B12B28O30. Cation disorder in TTBs is known to occur if the size difference between cations is small, but the impact of cation disorder on structure and properties has not yet been extensively addressed. In this study we investigate the effect of the size of the M cation, including cation disorder, on the crystal structure and dielectric properties in the two series Ba4M2Nb10O30 (BMN, A = Na, K and Rb) and Ba4M2Nb8Ti2O30 (BMNT, M = Ca, Sr). Dense and phase pure ceramics in the two series were prepared by a two-step solid state synthesis route. The crystal structures of the materials were characterized by powder X-ray diffraction combined with Rietveld refinement. A close to linear relation between the in-plane lattice parameter (a) and the size of the M-cation were observed. Ba4M2Nb8Ti2O30 was shown to possess cation disorder on the A-sites in line with previous work on Ba4M2Nb10O30. Thermodynamic calculations from density functional theory also indicated a drive for cation disorder in the three BMN compositions. Non-ambient temperature X-ray diffraction revealed contraction of the in-plane (a) and expansion of the out-of-plane (c) lattice parameters at the ferroelectric phase transition for Ba4M2Nb10O30. The ferroelectric transition temperature acquired by dielectric spectroscopy showed a systematically increasing TC with decreasing size of the M-cation within both compositional series studied. The compositional dependence of TC is discussed with respect to the size of the M-cation, cation disorder and the tetragonality, as well as the Ti-content. The relaxor to ferroelectric properties observed by polarization-electric field hysteresis loops are discussed in relation to the relative size of cations on the on A1 and A2 sites and the Ti-content.

Ammonia synthesis via chromium-based nitrogen carrier looping

Redox nitrogen fixation-nitride hydrolysis looping provides a promising pathway for ammonia synthesis; however, high N fixation temperature and low N3−lattice supplement efficiency limit its further development and application. In this regard, a two-step chemical looping ammonia synthesis route, chromium-based nitrogen carrier enabled low-temperature N fixation and nitrogen carrier hydrolysis, is proposed to intensify ammonia generation. In the N fixation step, the effects of carbon species on the carbothermal reduction performance are investigated. Results reveal that decreasing the graphitization degree of the carbon species can effectively reduce the nitrogen activation temperature from 1054 °C to 948 °C. Meanwhile, the C/Cr2O3 ratio required is correlated with the amount of oxygen in carbon species, and the appropriate active carbon/biochar-to-Cr ratios are 4.00 and 3.25, respectively. In the ammonia synthesis step, the nitrogen carrier hydrolysis rate is mainly limited by the diffusion of reactive species. The ammonia formation rate reaches 0.127 mmol·h−1·g−1 nitrogen carrier at 1100 °C. XRD retrieve refinement results reveal that the utilization of the lattice nitrogen decreases with the increase in the ammonia releasing temperature. This study provides new implications for advanced nitrogen carrier exploitation, which will substantially promote the development of chemical looping ammonia synthesis technologies with lowered energy consumption.

Comparative assessment of 9-bromo noscapine ionic liquid and noscapine: Synthesis, in-vitro studies plus computational & biophysical evaluation with human hemoglobin

Noscapine is a proficient anticancer drug active against wide variety of tumors including lung cancer. Over time, several noscapine analogues have been assessed to maximize the efficiency of the drug, amongst which 9-bromo noscapine remains one of the most potent analogues till date. In the present work, we have synthesized 9-bromo noscapine ionic liquid [9-Br-Nos]IBr2, an active pharmaceutical ingredient based ionic liquid (API-IL) to address the existing issues of solubility and targeted drug delivery in the parent alkaloid as well as the synthesized analogues. We have devised a novel two-step synthesis route (first-ever ionic to ionic bromination) to obtain the desired [9-Br-Nos]IBr2 which is advantageous to its organic analogue in terms of increased solubility, lesser reaction time and better yield. Furthermore, we have compared 9-bromo noscapine ionic liquid with noscapine based on its binding interaction with human hemoglobin (Hb) studied via computational along with spectroscopic studies, and bioactivity against non-small cell lung cancer. We inferred formation of a complex between [9-Br-Nos]IBr2 and Hb in the stoichiometric ratio of 1:1, similar to noscapine. At 298 K, [9-Br-Nos]IBr2-Hb binding was found to exhibit Kb and ∆G of 36,307 M−1 and -11.5 KJmol−1, respectively, as compared to 159 M−1 and -12.5 KJmol−1 during Noscapine-Hb binding. This indicates a more stronger and viable interaction between [9-Br-Nos]IBr2 and Hb than the parent compound. From computational studies, the observed higher stability of [9-Br-Nos]I and better binding affinity with Hb with a binding energy of −91.75 kcalmol−1 supported the experimental observations. In the same light, novel [9-Br-Nos]IBr2 was found to exhibit an IC50 = 95.02 ± 6.32 μM compared to IC50 = 128.82 ± 2.87 μM for noscapine on A549 (non-small lung cancer) cell line at 48 h. Also, the desired ionic liquid proved to be more cytotoxic inducing a mortality rate of 87 % relative to 66 % evoked by noscapine at concentrations of 200 μM after 72 h.

A one-pot synthesis of high-density biofuels through bifunctional mesoporous zeolite-encapsulated Pd catalysts

Developing a powerful bifunctional catalyst for tandem reactions is essential to the future carbon neutrality by reducing the energy consumption in chemical industries. Herein, mesoporous zeolite-encapsulated palladium (Pd) nanoparticles (Pd@meso-ZSM-5) synthesized via emulsification-demulsification followed by a dry-gel transformation method were demonstrated to have a remarkable catalytic performance for a one-pot multiple tandem reaction of cyclic ketones (cyclopentanone, cyclohexanone) to bicyclic alkanes (bicyclopentane, bicyclohexane). Compared with supported catalysts (Pd/meso-ZSM-5) and microporous zeolite-encapsulated catalysts (Pd@ZSM-5) with a primary product of monocyclic alkane (cyclopentane, cyclohexane), Pd@meso-ZSM-5 shows much higher catalytic efficiency for the bicyclic alkanes synthesis, which was previously unattainable in the conventional two-step synthesis route. Controlled experiments and detailed characterizations show that mesoporosity provides sufficient space for the generation and diffusion of large molecular intermediates, and the intimate acid-Pd interface promotes the conversion of intermediates. This work proposes a design strategy for a mesoporous zeolite-encapsulated metal catalyst, which efficiently provides cooperative acid-hydrogenation catalysis.

Controlled Growth Cu2S Nanoarrays with High-Performance Photothermal Properties.

The controlled growth of Cu2S nanoarrays was constructed by a facile two-step impregnation synthesis route. The as-synthesized Cu2S/CuO@Cu samples were precisely characterized in terms of surface morphology, phase, composition, and oxidation states. At the laser irradiation of 808 nm, Cu2S/CuO@Cu heated up to 106 °C from room temperature in 120 s, resulting in an excellent photothermal conversion performance. The Cu2S/CuO@Cu exhibited excellent cycling performance-sustaining the photothermal performance during five heating-cooling cycles. The finite difference time domain (FDTD) simulation of optical absorption and electric field distributions assured the accuracy and reliability of the developed experimental conditions for acquiring the best photothermal performance of Cu2S/CuO@Cu.

Synthesis and Visible Light Catalytic Performance of BiOI/Carbon Nanofibers Heterojunction

Semiconductor materials as photocatalysts hold great prospects for renewable energy substitutes and environmental protection. Nanostructured BiOX (X=Cl, Br, I) with favorable features of a unique layered crystal structure and suitable band gaps has been demonstrated to be a promising photocatalytic material. In this paper, a two-step synthesis route combining an electrospinning technique and SILAR reaction has been accepted as a straightforward protocol for the exploitation of BiOI/carbon nanofibers’ (CNFs) hierarchical heterostructures. As expected, the BiOI/CNFs presented a much higher degradation rate of methyl orange than that of the pure BiOI under visible light. The degradation rate of methyl orange reaches 85% within 210 min. The enhanced photocatalytic activity could be attributed to the fact that conductive CNFs as substrate could effectively improve the separation and transformation of photogenerated charges. Moreover, the fabricated BiOI/CNFs after five cycles could be easily recycled without a decrease in photocatalytic activity due to their ultra-long one-dimensional nano-structural property.

Synergistic effect stemming from vertically anchored seamless 2D MoSe2 nanosheets on 1D NiTiO3 nanofibers toward CO2 photoreduction

Herein, nickel titanate nanofiber/molybdenum diselenide nanosheet (NiTiO3 NF/MoSe2) heterostructures were prepared and their photocatalytic CO2 photoreduction performance was assessed. The heterostructures were synthesized via a facile two-step synthesis route combining an electrospinning technique followed by a solvothermal method. The MoSe2 nanosheets were vertically anchored to the surface of NiTiO3 NF, thereby increasing the number of exposed active edges that are pivotal to photocatalytic performance. By tuning the loading of MoSe2 in the heterostructure, the optimal condition was obtained for the fabrication of the NiTiO3 NF/MoSe2 heterojunctions. The as-prepared heterojunctions exhibited higher photocatalytic activity than pure NiTiO3 NF and MoSe2 for the photocatalytic reduction of CO2 under ultraviolet-visible light irradiation. Among the several hybrid samples, the optimal sample displayed a 6.6- and 7.7-fold enhanced production of CO (386 µmol g–1) compared with that of pure NiTiO3 NF (58 µmol g–1) and pure MoSe2 (50 µmol g–1), respectively, with overall CO2 selectivity of 86%. This enhanced photocatalytic activity was attributed to synergy created by tailored loading of MoSe2 nanosheets onto the 1D NiTiO3 NF. This hierarchical growth of MoSe2 over NiTiO3 NF provided more exposed edge sites, enhanced light absorption over the entire spectrum, and improved separation of photogenerated electrons and holes at the NiTiO3 NF/MoSe2 heterojunction interface. Such NiTiO3 NF/MoSe2 heterojunctions with broad spectral photocatalytic performance have potential applications in water splitting and water treatment.

Introducing a new approach to preparing bionanocomposite sponges based on poly(glycerol sebacate urethane) (PGSU) with great interconnectivity and high hydrophilicity properties for application in tissue engineering

In this study, a three-dimensional porous structure of poly(glycerol sebacate urethane) (PGSU) comprising nano-clay and polyacrylic acid (PAAc) was synthesized through a two-step synthesis route. Particulate leaching technique by introducing spun sugar as porogen was also performed as a fabrication method. It was hypothesized that the introduction of spun sugar with its filamentous shape would create interrelated pores required for cell adhesion and proliferation. Polarity, stiffness, and swelling capacity of PGSU would be enhanced by eco-friendly in-situ polymerization of PAAc and the contribution of biocompatible nanoclay. After characterizing the synthesis of PGSU-based scaffolds, viscoelastic behavior, hydrophilicity, and biocompatibility of scaffolds were evaluated. Doubling of swelling capacity in dry state and decrement of water contact angle (WCA) approved the effect of polar carboxyl groups of PAAc in the improvement of polarity and hydrophilicity of PGSU. DMTA results in dry and wet states demonstrated that increasing the concentration of nanoclay and the presence of PAAc chains led to the increase in the storage modulus while the elastic behavior at body temperature was preserved. Eventually, the feasibility of the porous structure of PGSU-based scaffolds in tissue engineering became clear by in vitro biocompatibility test and significant cell adhesion in plasma-treated PGSU/PAAC/nanoclay. Accordingly, introducing clay nanoparticles and in-situ polymerization of acrylic acid, together with porous structure, make PGSU a suitable substrate for cellular interactions.

A highly stable CuO-derived adsorbent with dual Cu(I) sites for selective CO adsorption

Cu(I)-based adsorbents with high stability and adsorption capacity enable effective carbon monoxide separation. Starting from CuO nanoparticles, we synthesized a CO adsorbent with Cu2O and CuCl on the surface by a two-step synthesis route. The first step was a fast thermal reduction under 5 vol% flow of H2 at 673 K. CuCl was then introduced by a room temperature liquid-phase reaction between surface metallic copper and CuCl2. X-ray diffraction was used to investigate the stability of the dual-active site adsorbent under atmospheric air. Compared to single Cu(I) site counterparts, the dual-active site adsorbent has a superior adsorption capacity and selectivity for CO, making itself a promising candidate for CO-CO2 mixture separation. Site energy distribution was used to describe the heterogeneity of the adsorbent surface based on equilibrium adsorption isotherm models. Each synthesis step resulted in the formation of sites at both high and low ends of the site energy spectrum. Adsorption kinetics of CO and CO2 to the adsorbent was also investigated by fitting kinetics results to various adsorption kinetic models. We found that adventitious metallic copper reaction with air forms new active Cu2O sites. Further reaction with ambient air formed a protective layer of copper oxide and carbonate on the surface. These surface moieties enhanced adsorbent stability under atmospheric air for up to 10 days while retaining the adsorption capacity once activated. The oxygen-resistant layer can be easily removed by heating under a vacuum. This study provides a path for the design and synthesis of Cu(I)-based adsorbents with high CO adsorption capacity and stability.

Improvement of the saturation magnetization of PEG coated superparamagnetic iron oxide nanoparticles

Polyethylene glycol (PEG) coated iron oxide nanoparticles are of interest because of their distinctive properties and potential applications such as magnetic resonance imaging, magnetic hyperthermia and drug delivery. In this study, PEG coated iron oxide nanoparticles were obtained by a two-step synthesis route including coprecipitation and coating. Different amounts of PEG6000 were used for coating and the effect of PEG amount on the structural and magnetic properties of the nanoparticles was investigated. Crystal structure, surface coating and particle size of the nanoparticles were characterized by X-ray diffraction technique, Fourier transform infrared spectroscopy and transmission electron microscopy. The particle size of iron oxide nanoparticles remained almost constant (7–8 nm) with the increase of PEG amount. It was determined from thermogravimetric analysis that the coating percentage of the nanoparticles steadily increased from 2.6 to 6.9 % with the increase of PEG amount from 5 to 15 g. Magnetic properties of the nanoparticles were studied by vibrating sample magnetometer and all samples were found to be superparamagnetic. PEG coated iron oxide nanoparticles showed higher saturation magnetization, Ms values than the uncoated iron oxide nanoparticles. Also, Ms of the coated nanoparticles increased with the increase of PEG coating and reached a value of 62.4 emu/g showing an increase of 19 % over uncoated iron oxide nanoparticles while maintaining the superparamagnetic behavior. This remarkable rise in the Ms of PEG coated iron oxide nanoparticles may improve the control and delivery of the nanoparticles for potential applications.

Phosgene-free synthesis of N-methyl-N′,N′-diphenylurea

Akardite II (AK-II, N-methyl-N′,N′-diphenylurea) is a well-known stabilizer for nitrocellulose (NC) propellants as it scavenges NOx. Currently, AK-II is produced using phosgene, a highly toxic gas. An alternative, two-step synthesis route is presented here that does not rely on phosgene. First, symmetrical organic carbonates (R2CO3, with R ​= ​Me, Et, or Ph) and diphenylamine react to form their corresponding carbamates in good yields for R ​= ​Me and Et (80% and 57%) and low yield for R ​= ​Ph (9%), catalyzed by 3-methyl-1-butylimidazolium chloride ([BMIM]Cl). The carbamate species are suggested to be formed in an equilibrium reaction. Evaporation of the alcohol side products pushes the equilibrium to the carbamate product. The second step converts the diphenyl carbamates into the targeted compound by treatment with (mono)methylamine (MMA), with reversed yield trend (4% for R ​= ​Me and Et, 81% for R ​= ​Ph). For the alkyl carbamates, the formation of AK-II appears to run in parallel with an MMA-alkylation reaction, which severely lowers the product yield. Overall, the synthesis of AK-II via the carbamate route is feasible, yet the carbonate side groups should be chosen carefully to obtain a high overall yield.

Template-free formation of oriented oxide nanowalls via topotactic-like pseudomorphic transformation: [110]-MgO(111) nanowall arrays

The template-free formation of oriented MgO nanowall arrays is successfully achieved by a two-step synthesis route of (i) electrodeposition of vertically aligned hydroxide and (ii) its topotactic-like pseudomorphic transformation to oxide.

Tailoring growth of MOF199 on hierarchical surface of bamboo and its antibacterial property

Bamboo, as a fast-grown forest resource, can be functionalized by metal–organic frameworks (MOFs) with various potential applications. However, the stability of MOFs immobilized on bamboo surface remains to be improved. In this work, MOF199, as known as HKUST-1, was in situ anchoring on moso bamboo via regulating pretreatment of bamboo and a green two-step synthesis route. The two-step synthesis route was completed under room temperature and both precursor solutions can be reused. The results indicated that, with the collaboration of delignification and carboxymethylation pretreatment of bamboo, a dense and well-dispersed MOF coating was successfully synthesized, the adhesion between MOF199 and bamboo surface was also improved. Besides, the quantity and size of MOF199 on bamboo can be tailored by tunning the carboxyl groups of pretreated bamboo and the concentration of copper nitrate solution. More importantly, results show that the formation of carboxyl-copper (II) complex served as nucleation sites for the growth of MOF199 crystals, which was essential to prepare uniform MOF layers. The growth of MOF199 endowed bamboo with good antibacterial activity against Escherichia coli. This method provides a facile and practical strategy for designing MOF coated woody materials.

Preparation of TiO2–based hollow microspheres by spray drying and their use as novel active pigments for photocatalytic coatings

The use of TiO2 nanoparticles in organic-based photocatalytic coatings imposes several challenges: poor activity under visible light, binder photo-degradation, need for UV activation and toxicity concerns. Here we present a scalable two-step synthesis route to prepare TiO2-based hollow microspheres (HoS) as alternative photocatalyst to commercial TiO2 nanoparticles. The hollow microspheres of TiO2 or WO3-doped TiO2 (3 mol% WO3) are synthesized via template-assisted spray-drying followed by calcination. The structure and composition of the powders are characterized and their photocatalytic performance is assessed using methylene blue photo-degradation under UV irradiation as model reaction. XRD analysis reveals the presence of anatase and TiO2(B) phases, indicating the heterostructured nature of the samples. The results of the dye photo-degradation tests confirm the photocatalytic functionality of the TiO2-based HoS. Moreover, the introduction of WO3 (TiO2/WO3 HoS) leads to an enhancement of the performance, approaching that of commercial (Aeroxide P25, ~21 nm) nanoparticles. The most active TiO2/WO3 HoS are incorporated into an acrylic formulation and the resulting coatings tested towards pollutant abatement under UV light. A coating containing P25 nanoparticles undergoes an activation process where binder degradation leads to increased TiO2 exposure and a rise in catalytic activity but possibly at the expense of coating stability. By contrast TiO2/WO3 HoS-acrylic coatings exhibit catalytic activity similar to the initial activity of P25 containing coatings, but does not cause the same partial binder photo-degradation.

Band-gap shrinked NiO@Co3O4 nanotubes as high-performance supercapacitor electrodes

Novel band-gap shrinked NiO@Co3O4 nanotube arrays on Ni foam have been fabricated via a two-step synthesis route. Hexagonal NiO nanotube arrays are obtained by electrodeposition of Ni nanoparticles onto ZnO nanoprisms followed by selective dissolution of ZnO. The inside and outside surfaces of the NiO nanotubes are homogeneously covered with Co3O4 nanosheets via hydrothermal treatment, which enlarges the surface area and accelerates electron transferring. Benefiting from the hierarchically hollow structure and the synergistic effects, the obtained NiO@Co3O4 nanotube arrays deliver a superior specific capacitance of 1769.2 F/g at 1 A/g and outstanding cycling stability (87.5% capacitance retention after 10,000 cycles at 20 A/g). Density functional theory calculations reveal that the disappearance of the band-gap of the NiO@Co3O4 composite is one intrinsic reason that the conductivity and the capacitive charge storage performance are enhanced significantly. The as-prepared NiO@Co3O4 nanotube arrays are highly promising electrodes for high-performance supercapacitors.

Synthesis and Formation Mechanism of Colloidal Janus-Type Cu2-xS/CuInS2 Heteronanorods via Seeded Injection.

Colloidal heteronanocrystals allow for the synergistic combination of properties of different materials. For example, spatial separation of the photogenerated electron and hole can be achieved by coupling different semiconductors with suitable band offsets in one single nanocrystal, which is beneficial for improving the efficiency of photocatalysts and photovoltaic devices. From this perspective, axially segmented semiconductor heteronanorods with a type-II band alignment are particularly attractive since they ensure the accessibility of both photogenerated charge carriers. Here, a two-step synthesis route to Cu2–xS/CuInS2 Janus-type heteronanorods is presented. The heteronanorods are formed by injection of a solution of preformed Cu2–xS seed nanocrystals in 1-dodecanethiol into a solution of indium oleate in oleic acid at 240 °C. By varying the reaction time, Janus-type heteronanocrystals with different sizes, shapes, and compositions are obtained. A mechanism for the formation of the heteronanocrystals is proposed. The first step of this mechanism consists of a thiolate-mediated topotactic, partial Cu+ for In3+ cation exchange that converts one of the facets of the seed nanocrystals into CuInS2. This is followed by homoepitaxial anisotropic growth of wurtzite CuInS2. The Cu2–xS seed nanocrystals also act as sacrificial Cu+ sources, and therefore, single composition CuInS2 nanorods are eventually obtained if the reaction is allowed to proceed to completion. The two-stage seeded growth method developed in this work contributes to the rational synthesis of Cu2–xS/CuInS2 heteronanocrystals with targeted architectures by allowing one to exploit the size and faceting of premade Cu2–xS seed nanocrystals to direct the growth of the CuInS2 segment.

Multi-walled carbon nanotubes and chromium ferrites nanoparticles nanohybrids as anode materials for lithium-ion batteries

Two-step synthesis route was opted for the preparation of multi-walled carbon nanotubes (MWCNTs) and chromium ferrites (CrFe2O4) nanoparticles nanohybrids. In the first step, CrFe2O4 nanoparticles were prepared through co-precipitation route, while in second step an ultra-sonication assisted route was chosen for dispersion of these nanoparticles on the surface of MWCNTs. A polar solvent toluene was used for the dispersion of these nanoparticles and MWCNTs to obtain the final product (MWCNTs)x/CrFe2O4; x = 0–20 wt% nanohybrids. X-rays diffraction (XRD) confirmed the corresponding crystal structures of MWCNTs and (MWCNTs)x/CrFe2O4 nanohybrids. It was evident from scanning electron microscopy (SEM) that CrFe2O4 nanoparticles were evenly distributed on the surface of MWCNTs. The morphology of (MWCNTs)x/CrFe2O4 nanohybrids confined the pulverization of active material that ensured electron-ion transport efficiency during lithiation and de-lithiation. Consequently, these nanohybrids exhibited prime cyclic performance at different values of current densities. These (MWCNTs)x/CrFe2O4 nanohybrids revealed better Li+ storage properties with high Coulombic efficiency ‘Ce’, better cyclic stability, improved reversible specific discharge capacity after 100 cycles and enhanced rate capability. Thus, current study offered a low-cost and facile synthesis route to prepare these nanohybrids as anode materials for lithium-ion batteries.

Two-step synthesis of niobium doped Na\u2013Ca\u2013(Mg)\u2013P\u2013Si\u2013O glasses

Niobium doped biosolubility glasses in the Na–Ca–(Mg)–P–Si–O system were prepared by using an untypical two-step synthesis route. The parent glass was melted in air atmosphere at 1350 °C followed by re-melting the glass in Nb crucible with the addition of metallic Mg/Ca powder in the nitrogen atmosphere. The second melting step was carried out at 1450–1650 °C, using an induction furnace. The topography and structure of the obtained glasses were characterized by confocal microscopy, X-ray powder diffraction and infrared spectroscopic techniques. The chemical compositions were examined by energy-dispersive X-ray spectroscopy (EDS). The glasses were found to be of grayish color, X-ray amorphous and having network connectivity between ~ 2.5 and 2.7. The network connectivity of re-melted glasses was lower than the one of the parent glass. The glass structure consists of a highly disrupted silicate network of predominantly Q2 groups as well as isolated orthophosphate tetrahedra. The parent glass contains nanocrystallites consisted of apatitic PO43− groups. The re-melted glasses contain non-apatitic or amorphous calcium phosphates. The obtained glass transition temperatures range from 530 to 568 °C and exhibit higher values for glassed doped with Ca metal. These glasses have improved thermal stability as compared to reference bioglasses. The biosolubility test in phosphate buffered saline solution (PBS) confirms that the glasses have biosolubility properties and HAp formation on the surfaces was observed.

Three-dimensional porous reduced graphene oxide/PEDOT:PSS aerogel: Facile preparation and high performance for supercapacitor electrodes

Graphene derivatives have great potential in the field of energy storage, because of their high specific surface area, great electrical conductivity, and stable electrochemical properties. For the graphene-based electrodes with a three-dimensional (3D) porous structure, the interlayer stacking of the graphene sheets largely limits their capacitive performance, and thus hinders their wide applications. In this work, we successfully developed a lightweight, freestanding and 3D porous reduced graphene oxide (rGO)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) composite aerogel by incorporating the conducting polymer PEDOT:PSS into interconnected rGO networks through a facile, low-cost and all-water-processable two-step synthesis route. PEDOT:PSS covering on the rGO sheets was found to not only prevent the stacking of rGO sheets, but also greatly improve the ion accessibility and mechanical stability of this highly porous spongy meshwork. Due to the synergistic effect of rGO and PEDOT:PSS, the aerogel electrodes delivered a high gravimetric specific capacitance (471 F g−1 at 0.2 A g−1), an excellent rate capability, and a remarkable capacitance retention (98.71% over 20,000 cycles at 20 A g−1). Furthermore, the aerogel-based symmetric supercapacitor exhibited a wide potential window (0–1.4 V) and an excellent energy storage performance. A high energy density of 48.18 Wh kg−1 with the power density of 1.4 kW kg−1 at 0.5 A g−1, or an energy density of 32.67 Wh kg−1 corresponding to the great power density of 14,000 W kg−1 at 5 A g−1 was achieved. These results demonstrate the great potential of the rGO/PEDOT:PSS aerogel as an excellent electrode material for energy storage applications.