Controlled self-assembly into diverse stimuli-responsive microstructures: from microspheres to branched cylindrical micelles and vesicles

A series of amphiphilic PDMAEMA–SS–PCL chains with variable ratios of hydrophilic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) to hydrophobic poly(ε-caprolactone) (PCL) were prepared via ring-opening polymerization, in which the two different moieties were linked via a disulfide bond with reduction responsiveness. After cross-linking by the photodegradable o-nitrobenzyl linkage, the amphiphilic chains could self-assemble into microspheres, branched cylindrical micelles and vesicles, which were responsive to the reduction agent dl-dithiothreitol and UV light irradiation through different mechanisms.

A series of cross-linked amphiphilic PDMAEMA–SS–PCL were prepared, which could self-assemble into diverse microstructures with reduction and light responsiveness.     

Enhanced electrochemical performance of α-MoO3/graphene nanocomposites prepared by an in situ microwave irradiation technique for energy storage applications

Nanoparticles of α-molybdenum oxide (α-MoO₃) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method. The prepared α-MoO₃ and α-MoO₃/G nanocomposites are analysed by different characterization techniques to study their structural, morphological and optical properties. Transmission electron microscope images reveal the intercalation of three dimensional (3D) α-MoO₃ nanoparticles into 2D graphene sheets without any agglomeration. The electrochemical results exhibit improved performance for the α-MoO₃/G composite electrode compared to pristine α-MoO₃ owing to its structural superiority. The specific capacitance (C_s) values of the α-MoO₃/G composite and pristine α-MoO₃ are measured to be 483 and 142 F g⁻¹ respectively at a current density of 1 A g⁻¹. The α-MoO₃/G composite maintains a very strong cyclic performance after 5000 cycles. The capacitance retention of the composite electrode shows stable behavior without any degradation confirming its suitability as an enduring electrode material for high-performance supercapacitor applications.

Nanoparticles of α-molybdenum oxide (α-MoO₃) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method.     

Self-assembly of supra-amphiphiles building block fabricated by β-cyclodextrin and adamantane-based ionic liquid

A new adamantane-based ionic liquid, (11-(((-adamantane-1-carbonyl)oxy)undecyl)-1-methylimidazol-3-ium bromide (AD-C₁₁im), was synthesized from 1-adamantanecarboxylic acid and observed that it can aggregate into micelles in aqueous solution. A number of experiments were conducted to understand the self-assembly of supra-amphiphiles building block fabricated by β-cyclodextrin (β-CD) and adamantane-based ionic liquid at diverse molar ratios. Studies revealed that host–guest interaction between the adamantane group and β-CD occurred and AD-C₁₁im@1β-CD building block formed when same amount β-CD was added. Then the micelles aggregates formed by AD-C₁₁im only turned into spherical vesicles, which was confirmed by AFM, DLS and TEM. Besides, according to the results of AFM, it can be confirmed that the vesicles were monolayer structure. When double amount β-CD was added, both the adamantane group and the hydrophobic chain were encapsulated by β-CD and AD-C₁₁im@2β-CD building block formed. Thus the aggregations changed from vesicles to net-like nanofiber, which was observed by TEM. When the β-CD concentration increased to 40 mM, the formation of light blue hydrogel was observed during the self-assembling process of AD-C₁₁im@2β-CD building block.

The self-assembly of supra-amphiphiles building block fabricated by β-CD and AD-C₁₁im at diverse molar ratios was studied. The micelles of AD-C₁₁im turned into monolayer vesicles, net-like nanofibers and hydrogel at different β-CD/AD-C₁₁im system.     

Aminated β-cyclodextrin-grafted Fe3O4-loaded gambogic acid magnetic nanoparticles: preparation,characterization, and biological evaluation

Based on aminated β-cyclodextrin (6-NH₂-β-CD)-grafted Fe₃O₄ and gambogic acid (GA) clathrate complexes, a nanoparticle delivery system was developed with the aim to achieve low irritation, strong targeting, and high bioavailability of a gambogic acid magnetic nanopreparation. 6-NH₂-β-CD grafted onto Fe₃O₄ MNPs was demonstrated by high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, zeta potential, and magnetic measurements. The average particle size of the Fe₃O₄@NH₂-β-CD MNPs was 147.4 ± 0.28 nm and the PDI was 0.072 ± 0.013. The encapsulation efficiency, drug loading, zeta potential, and magnetic saturation values of the Fe₃O₄@NH₂-β-CD MNPs were 85.71 ± 3.47%, 4.63 ± 0.04%, −29.3 ± 0.42 mV, and 46.68 emu g⁻¹, respectively. Compared with free GA, the in vitro release profile of GA from Fe₃O₄@NH₂-β-CD MNPs was characterized by two phases: an initial fast release and a delayed-release phase. The Fe₃O₄@NH₂-β-CD MNPs displayed continuously increased cytotoxicity against HL-60 and HepG2 cell lines in 24 h, whereas the carrier Fe₃O₄@NH₂-β-CD MNPs showed almost no cytotoxicity, indicating that the release of GA from the nanoparticles had a sustained profile and Fe₃O₄@NH₂-β-CD MNPs as a tumor tissue-targeted drug delivery system have great potential. Besides, blood vessel irritation tests suggested that the vascular irritation could be reduced by the use of Fe₃O₄@NH₂-β-CD MNPs encapsulation for GA. The t_1/2 and the AUC of the Fe₃O₄@NH₂-β-CD@GA MNPs were found to be higher than those for the GA solution by approximately 2.71-fold and 2.42-fold in a pharmacokinetic study, respectively. The better biocompatibility and the combined properties of specific targeting and complexation ability with hydrophobic drugs make the Fe₃O₄@NH₂-β-CD MNPs an exciting prospect for the targeted delivery of GA.

Based on aminated β-cyclodextrin (6-NH₂-β-CD)-grafted Fe₃O₄ and gambogic acid clathrate complexes, a nanoparticle delivery system was developed with the aim of achieving low irritation, strong targeting and high bioavailability of a gambogic acid magnetic nanopreparation.     

PHB/PCL fibrous membranes modified with SiO2@TiO2-based core@shell composite nanoparticles for hydrophobic and antibacterial applications

In order to prepare multifunctional fibrous membranes with hydrophobicity, antibacterial properties and UV resistance, we used silica and titanium dioxide for preparing SiO₂@TiO₂ nanoparticles (SiO₂@TiO₂ NPs) to create roughness on the fibrous membranes surfaces. The introduction of TiO₂ was used for improving UV resistance. N-Halamine precursor and silane precursor were introduced to modify SiO₂@TiO₂ NPs to synthesize SiO₂@TiO₂-based core@shell composite nanoparticles. The hydrophobic antibacterial fibrous membranes were prepared by a dip-pad process of electrospun biodegradable polyhydroxybutyrate/poly-ε-caprolactone (PHB/PCL) with the synthesized SiO₂@TiO₂-based core@shell composite nanoparticles. TEM, SEM and FT-IR were used to characterize the synthesized SiO₂@TiO₂-based core@shell composite nanoparticles and the hydrophobic antibacterial fibrous membranes. The fibrous membranes not only showed excellent hydrophobicity with an average water contact angle of 144° ± 1°, but also appreciable air permeability. The chlorinated fibrous membranes could inactivate all S. aureus and E. coli O157:H7 after 5 min and 60 min of contact, respectively. In addition, the chlorinated fibrous membranes exhibited outstanding cell compatibility with 102.1% of cell viability. Therefore, the prepared hydrophobic antibacterial degradable fibrous membranes may have great potential application for packaging materials.

Schematic illustration of the synthesis of SiO₂@TiO₂-based core@shell composite nanoparticles (top) and antibacterial hydrophobic behavior of fibrous membranes (bottom).     

Copolyesters of ε-caprolactone and l-lactide catalyzed by a tetrabutylammonium phthalimide-N-oxyl organocatalyst

Aliphatic polyesters are biocompatible materials that can be used in biomedical applications. We report here the use of tetrabutylammonium phthalimide-N-oxyl catalyst (TBAPINO), as a thermally stable organocatalyst for the ring-opening polymerization (ROP) of cyclic esters under mild conditions. In the solution ROP of ε-caprolactone (ε-CL), quantitative conversion and M_n of ∼20 000 g mol⁻¹ are achieved in a wide temperature range from −15 to 60 °C. Under bulk condition, the conversion of ε-CL reaches over 85% at 120 °C within 2 h. The living ROP character of l-lactide (l-LA) catalyzed over TBAPINO is proved by multiple additions of monomer in the bulk polymerization. The catalyst shows comparable selectivity towards the ring-opening polymerization of l-LA and ε-CL. Their copolymerization over TBAPINO is carried out in one-pot bulk condition in terms of the reaction time, monomer feed ratio, and sequence of addition. The colorless poly(ε-caprolactone-co-lactide) (PCLA) is obtained with considerable conversion of both monomers with the M_n over 22 000 g mol⁻¹.

By utilizing tetrabutylammonium phthalimide-N-oxyl organocatalyst, copolymer PCLA with M_n over 20 000 g mol⁻¹ was synthesized by sequential ring-opening polymerization of ε-caprolactone and l-lactide under bulk conditions.     

Phosphorus pentoxide as a cost-effective,metal-free catalyst for ring opening polymerization of ε-caprolactone

The ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) using phosphorus pentoxide (P₂O₅) as a metal-free catalyst and isopropanol (iPrOH) as initiator resulted in the preparation of poly(ε-caprolactone) with narrow weight distribution. NMR spectroscopy analyses of the prepared PCL indicated the presence of the initiator residue at the end of the polymer chain, implying the occurrence of the ε-CL-catalysis ROP through a monomer activation mechanism. Kinetic experiments confirmed the controlled/living nature of ε-CL ring-opening catalyzed by phosphorus pentoxide. The commercial availability of phosphorus pentoxide and its easy-handling provide additional opportunities for polymer synthesis and nanocomposite manufacturing.

The ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) using phosphorus pentoxide (P₂O₅) as a metal-free catalyst and isopropanol (iPrOH) as initiator resulted in the preparation of poly(ε-caprolactone) with narrow weight distribution.     

Extraction and isolation of polyhydroxy triterpenoids from Rosa laevigata Michx. fruit with anti-acetylcholinesterase and neuroprotection properties

Rosa laevigata fruit, at present, is becoming increasingly popular as a functional foodstuff with several nutritional and medicinal properties. To explore the acetylcholinesterase (AChE) inhibitory activity of extracts from the Rosa laevigata Michx. fruit (RLMF), a simple and efficient enrichment purification technology based on microwave-assisted extraction (MAE) and multi vacuum extraction columns (VEC) was applied to screen and identify triterpenoids (TTs) in the RLMF extracts. The MAE conditions were optimized using the Box–Behnken design (BBD) with a quadratic regression model and the response surface method (RSM). The optimum conditions were as follows: ethanol concentration, 69%; extraction time, 12 min; ratio of liquid to raw material, 26 : 1 mL g⁻¹; and microwave power, 528 W. Under these conditions, the maximum content of triterpenoids reached 62.48 ± 0.25 mg g⁻¹, which was close to the predicted value of 62.69 mg g⁻¹. In addition, two pure polyhydroxy triterpenoids: 2α,3β,19α,23-tetrahydroxyurs-12-en-28-oic acid (1) and 2α,3β,19α,23-tetrahydroxyurs-12-en-28-oic acid-28-O-β-d-glucopyrannoside (2) were isolated and enriched to more than 500 mg by a multi VEC method. Furthermore, the quantities of compounds 1 and 2 from RLMF were 5.36 and 10.37 mg g⁻¹, respectively, as determined using HPLC. These compounds were further assessed for acetylcholinesterase inhibitory and neuroprotection properties. The results showed that 1 and 2 showed potent AChE inhibitory activities with IC₅₀ values of 29.22 and 45.47 μg mL⁻¹, respectively. At high concentration, compounds 1 and 2 produced a 92% and 89% inhibition on the target enzyme, which was consistent with docking results between AChE and each isolate. Moreover, both 1 and 2 exhibited potential neuroprotective activities against H₂O₂-induced SHSY5Y cell death.

Rosa laevigata fruit, at present, is becoming increasingly popular as a functional foodstuff with several nutritional and medicinal properties.     

Microwave hydrothermal synthesis of α-MnMoO4 nanorods for high electrochemical performance supercapacitors

Pristine α-MnMoO₄ nanorods were facilely prepared via co-precipitation (Cp) and microwave hydrothermal (MH) methods. X-ray diffraction (XRD) patterns showed pure monoclinic crystalline phase α-MnMoO₄ for the heat treated powder at 500 °C. Fourier Transform Infrared (FTIR) spectra showed that the chemical bond structure of α-MnMoO₄ corresponds to the strong vibrational modes of Mo–O–Mo, Mo–O and Mo O. Raman spectra showed the structural bonding and crystalline nature of α-MnMoO₄. Field Emission Scanning Electron Microscope (FE-SEM) images exposed the nanorod shape of the α-MnMoO₄ powder, with diameters of ∼200 nm and lengths of ∼1.6 μm. Electrochemical studies of the Cp- and MH-MnMoO₄ nanorods with 2 M NaOH as the electrolyte showed specific capacitances of 143 F g⁻¹ and 551 F g⁻¹, respectively, at a 1 A g⁻¹ constant discharge current density. Cyclic voltammetric (CV) studies of the MH-MnMoO₄ nanorods at various scan rates revealed the presence of redox pairs, suggesting a pseudocapacitive nature. The structural stability at different current densities demonstrated the high rate performances and good reversible capacity retention of the calcined MH-MnMoO₄ nanorods. A cycling life stability study of MH-MnMoO₄ demonstrated a good capacity retention of 89% of the initial specific capacitance at 5 A g⁻¹ after 1000 cycles.

Pristine α-MnMoO₄ nanorods were facilely prepared via co-precipitation (Cp) and microwave hydrothermal (MH) methods.     

MOF-derived (MoS2, γ-Fe2O3)/graphene Z-scheme photocatalysts with excellent activity for oxygen evolution under visible light irradiation

Constructing Z-scheme heterojunctions is considered as an effective strategy to obtain catalysts of high efficiency in electron–hole separation in photocatalysis. Unfortunately, suitable heterojunctions are difficult to fabricate because the direct interaction between two semiconductors may lead to unpredictable negative effects such as electron scattering or electron trapping due to the existence of defects which causes the formation of new substances. Furthermore, the van der Waals contact between two semiconductors also results in bad electron diffusion. In this work, a MOF-derived carbon material as a Z-scheme photocatalyst was synthesized via one-step thermal treatment of MoS₂ dots @Fe-MOF (MIL-101). Under visible light irradiation, the well-constructed Z-scheme (MoS₂, γ-Fe₂O₃)/graphene photocatalyst shows 2-fold photocatalytic oxygen evolution activity (4400 μmol g⁻¹ h⁻¹) compared to that of γ-Fe₂O₃/graphene (2053 μmol g⁻¹ h⁻¹). Based on ultraviolet photoelectron spectrometry (UPS), Mott–Schottky plot, photocurrent and photoluminescence spectroscopy (PL) results, the photo-induced electrons from the conduction band of γ-Fe₂O₃ could transport quickly to the valence band of MoS₂via highly conductive graphene as an electron transport channel, which could significantly enhance the electron–hole separation efficiency as well as photocatalytic performance.

The heterojunction between MoS₂ and γ-Fe₂O₃ was constructed via linking by in situ formed graphene, which resulted in a good photocatalyst for the oxygen evolution reaction, showing O₂ evolution activity of 4400 μmol g⁻¹ h⁻¹.     

Preparation of α-Fe2O3/rGO composites toward supercapacitor applications

Reduced graphene oxide (rGO) integrated with iron oxide nanoparticles (α-Fe₂O₃/rGO) composites with different morphologies were successfully obtained through the in situ synthesis and mechanical agitation methods. It was found that the α-Fe₂O₃ was densely and freely dispersed on the rGO layer. By comparing electrochemical properties, the sheet-like α-Fe₂O₃/rGO composites demonstrate excellent electrochemical performance: the highest specific capacitance, and excellent cycling stability and rate capacity. The specific capacitance is 970 F g⁻¹ at a current density of 1 A g⁻¹ and the capacitance retention is 75% after 2000 cycles with the current density reaching 5 A g⁻¹. It is mainly due to the synergistic effect between the α-Fe₂O₃ and rGO, and the high conductivity of the rGO offers a fast channel for the movement of electrons.

Preparation of α-Fe₂O₃/rGO composites for supercapacitor application using in situ synthesis and a mechanical agitation method.     

Optical and dielectric properties of NaCoPO4 in the three phases α, β and γ

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns. These compounds are crystallized in the orthorhombic, hexagonal and monoclinic system, in Pnma, P6₅ and P2₁/n space groups, respectively. The optical properties were measured by means of the UV-vis absorption spectrometry in order to deduce the absorption coefficient α and optical band gap E_g. The calculated values of the indirect band gaps (E_gi) for three samples were estimated at 4.71 eV, 4.63 eV and 3.8 for compounds α, β and γ, respectively. The Tauc model was used to determine the optical gap energy of the synthesized compounds. Then, the results of the dielectric proprieties measured by varying the frequency are described.

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns.     

Sucrose-templated interconnected meso/macro-porous 2D symmetric graphitic carbon networks as supports for α-Fe2O3 towards improved supercapacitive behavior

In this study, ultrahigh electrochemical performance for interconnected meso/macro-porous 2D C@α-Fe₂O₃ synthesized via sucrose-assisted microwave combustion is demonstrated. Hematite (α-Fe₂O₃) synthesized via the same approach gave an encouraging electrochemical performance close to its theoretical value, justifying its consideration as a potential supercapacitor electrode material; nonetheless, its specific capacitance was still low. The pore size distribution as well as the specific surface of bare α-Fe₂O₃ improved from 145 m² g⁻¹ to 297.3 m² g⁻¹ after it was coated with sucrose, which was endowed with ordered symmetric single-layer graphene (2D graphene). Accordingly, the optimized hematite material (2D C@α-Fe₂O₃) showed a specific capacitance of 1876.7 F g⁻¹ at a current density of 1 A g⁻¹ and capacity retention of 95.9% after 4000 cycles. Moreover, the material exhibited an ultrahigh energy density of 93.8 W h kg⁻¹ at a power density of 150 W kg⁻¹. The synergistic effect created by carbon-coating α-Fe₂O₃ resulted in modest electrochemical performance owing to extremely low charge transfer resistance at the electrode–electrolyte interface with many active sites for ionic reactions and efficient diffusion process. This 2D C@α-Fe₂O₃ electrode material has the capacity to develop into a cost-effective and stable electrode for future high-energy-capacity supercapacitors.

In this study, ultrahigh electrochemical performance for interconnected meso/macro-porous 2D C@α-Fe₂O₃ synthesized via sucrose-assisted microwave combustion is demonstrated.     

Oxygen release from metal oxide for repeated hydrogen regeneration by proton irradiation with polyvinylpyrrolidone

In this study, we investigated the reduction of a 3D microporous NiO_x structure, used as a metal oxide catalyst, by proton irradiation with polyvinylpyrrolidone (PVP) for hydrogen regeneration. In general, the reduction process for hydrogen regeneration requires high temperatures (1000–4000 °C) to release saturated oxygen from the metal oxide catalyst. Proton irradiation with PVP could regenerate abundant oxygen vacancies by releasing the oxygen attached to NiO_x at room temperature. The 3D microporous NiO_x structure provided the maximum hydrogen generation rate of ∼4.2 μmol min⁻¹ g⁻¹ with the total amount of generated hydrogen being ∼460 μmol g⁻¹ even in the repetitive thermochemical cycle; these results are similar to the initial hydrogen generation data. Therefore, continuous regeneration of hydrogen from the oxygen-reduced 3D microporous NiO_x structure was possible. It is expected that the high thermal energy, which is the major problem associated with hydrogen regeneration through the conventional heat treatment method, would be resolved in future using such a method.

The reduction of a 3D microporous NiO_x structure, used as a metal oxide catalyst, was performed by proton irradiation with polyvinylpyrrolidone (PVP) for hydrogen regeneration.     

Tunable surface wettability and pH-responsive 2D structures from amphiphilic and amphoteric protein microfibrils

Two dimensional films and paper-like structures (60–170 μm thick) have been facilely fabricated by casting ethanolic dispersions of amphiphilic and amphoteric protein microfibrils (ca. 1.3 μm width; 53 μm length) under controlled temperatures and moisture levels. Surface hydrophilicity or hydrophobicity can be easily tuned by the abillity of the highly responsive microfibers to self-organize at the interface to mimic the hydrophilicity or hydrophobicity of cast substrates. For instance, surfaces cast on hydrophobic polystyrene or Teflon were moderately hydrophobic with water contact angles (WCAs) of 54°–71° while those on hydrophilic glass or exposed to air were hydrophilic (WCAs: 5°–10°). Thin film dried in the presence of moisture (60% RH) at 65 °C had the highest crystallinity (CrI: 56%) and β structure (64%), including 48% β-sheet form, and exhibited moisture-responsive T_g, pH-responsive planar swelling, and excellent wet resiliency in extremely acidic (pH = 0) to basic (pH = 10) conditions. The pH-dependent release of highly water-soluble cationic methylene blue bound to protein microfibril (SPMF) films attests to their amphoterism and demonstrates the applicability of such 2D structures for pH-dependent controlled release of other cationic and anionic species. Such versatility of amphiphilic and amphoteric protein microfibrils can be engineered into 2D structures with tunable surface hydrophilicity and hydrophobicity, moisture- and pH-responsive behaviors and controlled release capabilities.

2D structures from amphiphilic and amphoteric protein microfibrils with tunable surface amphiphilicity, pH-responsive controlled release of cationic and anionic species.     

Al-doped α-MnO2 coated by lignin for high-performance rechargeable aqueous zinc-ion batteries

Zn/MnO₂ batteries, one of the most widely studied rechargeable aqueous zinc-ion batteries, suffer from poor cyclability because the structure of MnO₂ is labile with cycling. Herein, the structural stability of α-MnO₂ is enhanced by simultaneous Al³⁺ doping and lignin coating during the formation of α-MnO₂ crystals in a hydrothermal process. Al³⁺ enters the [MnO₆] octahedron accompanied by producing oxygen vacancies, and lignin further stabilizes the doped Al³⁺via strong interaction in the prepared material, Al-doped α-MnO₂ coated by lignin (L + Al@α-MnO₂). Meanwhile, the conductivity of L + Al@α-MnO₂ improves due to Al³⁺ doping, and the surface area of L + Al@α-MnO₂ increases because of the production of nanorod structures after Al³⁺ doping and lignin coating. Compared with the reference α-MnO₂ cathode, the L + Al@α-MnO₂ cathode achieves superior performance with durably high reversible capacity (∼180 mA h g⁻¹ at 1.5 A g⁻¹) and good cycle stability. In addition, ex situ X-ray diffraction characterization of the cathode at different voltages in the first cycle is employed to study the related mechanism on improving battery performance. This study may provide ideas of designing advanced cathode materials for other aqueous metal-ion batteries.

Al³⁺ doping combined with lignin coating improves the structural stability and electrochemical performance of the modified α-MnO₂, L + Al@α-MnO₂.     

Enhancing oxygen and hydrogen evolution activities of perovskite oxide LaCoO3via effective doping of platinum

In this study, a series of perovskite oxides LaCo_1−xPt_xO_3−δ (x = 0, 0.02, 0.04, 0.06, and 0.08) were prepared by the citric acid–ethylenediaminetetraacetic acid (CA–EDTA) complexing sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Then, the samples were investigated as OER and HER bifunctional electrocatalysts in alkaline media. Compared with other catalysts, LaCo_0.94Pt_0.06O_3−δ had good stability and presented more activity at a lower overpotential of 454 mV (at 10 mA cm⁻²), a lower Tafel slope value of 86 mV dec⁻¹ and a higher mass activity of 44.4 A g⁻¹ for OER; it displayed a lower overpotential of 294 mV (at −10 mA cm⁻²), a lower Tafel slope value of 148 mV dec⁻¹ and a higher mass activity of −34.5 A g⁻¹ for HER. The improved performance might depend on a larger ECSA, faster charge transfer rate and higher ratio of the highly oxidative oxygen species (O₂²⁻/O⁻). Furthermore, the e_g orbital filling of Co approaching 1.2 in the B site might play a leading role.

Among the perovskite LaCo_1−xPt_xO_3−δ catalysts, LaCo_0.94Pt_0.06O_3−δ proved best for catalyzing OER/HER, with η = 454/294 mV, which might be attributed to LCP6 having the e_g orbital filling of Co closest to 1.2.     

Novel azobenzene-based amphiphilic copolymers: synthesis,self-assembly behavior and multiple-stimuli-responsive properties

A series of novel azobenzene-based amphiphilic random copolymers P(POSSMA-co-AZOMA-co-DMAEMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A light and reduction dual-responsive azo group, pH-responsive tertiary amine group and super hydrophobic POSS moiety were incorporated into the polymer chain to generate multi-stimuli-responsiveness. Self-assembly of these amphiphilic copolymers led to the formation of spherical micelles in aqueous solution. The light, pH and reduction responsive properties of the micelles were investigated systematically by DLS, TEM, UV-vis, FTIR and NMR. The azo groups can undergo trans–cis isomerization under UV light irradiation, thus causing a diameter change of the micelles. Owing to the large proportion of tertiary amine groups in amphiphiles, these micelles showed sensitive pH-response behavior. The hydrophobic azo pendant in the polymer chain completely reduced to a more hydrophilic substituted aniline in a reductive environment, resulting in the increase of overall hydrophilicity of amphiphiles and the disassembly of polymeric micelles. Owing to these multi-stimuli–responses, the polymeric micelles showed rapid and efficient release properties of hydrophobic molecules in response to pH and reductive stimuli.

Polymeric micelles encapsulating and releasing hydrophobic guest molecules.     

Microbial transformation of mestanolone by Macrophomina phaseolina and Cunninghamella blakesleeana and anticancer activities of the transformed products

The microbial transformation of anabolic androgenic steroid mestanolone (1) with Macrophomina phaseolina and Cunninghamella blakesleeana has afforded seven metabolites. The structures of these metabolites were characterized as 17β-hydroxy-17α-methyl-5α-androsta-1-ene-3,11-dione (2), 14α,17β-dihydroxy-17α-methyl-5α-androstan-3,11-dione (3), 17β-hydroxy-17α-methyl-5α-androstan-1,14-diene-3,11-dione (4), 17β-hydroxy-17α-methyl-5α-androstan-3,11-dione (5), 11β,17β-dihydroxy-17α-methyl-5α-androstan-1-ene-3-one (6), 9α,11β,17β-trihydroxy-17α-methyl-5α-androstan-3-one (7), and 1β,11α,17β-trihydroxy-17α-methyl-5α-androstan-3-one (8). All the metabolites, except 5 and 6, were identified as new compounds. Substrate 1 (IC₅₀ = 27.6 ± 1.1 μM), and its metabolites 2 (IC₅₀ = 19.2 ± 2.9 μM) and 6 (IC₅₀ = 12.8 ± 0.6 μM) exhibited moderate cytotoxicity against the HeLa cancer cell line (human cervical carcinoma). All metabolites were noncytotoxic to 3T3 (mouse fibroblast) and H460 (human lung carcinoma) cell lines. The metabolites were also evaluated for immunomodulatory activity, and all were found to be inactive.

The microbial transformation of anabolic androgenic steroid mestanolone (1) with Macrophomina phaseolina and Cunninghamella blakesleeana has afforded seven metabolites. Some of them have exhibited moderate cytotoxicity against HeLa cancer cell line.     

Silver cluster doped graphyne (GY) with outstanding non-linear optical properties

This research study addresses the computational simulations of optical and nonlinear optical (NLO) characteristics of silver (Ag) cluster doped graphyne (GY) complexes. By precisely following DFT and TD-DFT hypothetical computations, in-depth characterization of GY@Ag_center, GY@Ag_side, GY@2Ag_{perpendicular}, GY@2Ag_above, and GY@3Ag_center is accomplished using CAM-B3LYP/LANL2DZ while the CAM-B3LYP/mixed basis set is used for study of 2GY@Ag_center, 2GY@Ag_side, 2GY@2Ag_{perpendicular}, 2GY@2Ag_above, and 2GY@3Ag_center. The effects of various graphyne surface based complexes on hyperpolarizabilities, frontier molecular orbitals (FMOs), density of states (DOS), absorption maximum (λ_max), binding energy (E_b), dipole moment (μ), electron density distribution map (EDDM), transition density matrix (TDM), electrostatic potential (ESP), vertical ionization energy (E_VI) and electrical conductivity (σ) have been investigated. Infrared (IR), non-covalent interaction (NCI) analysis accompanied by isosurface are performed to study the vibrational frequencies and type of interaction. Doping strategies in all complexes impressively reformed charge transfer characteristics such as narrowing band gap (E_g) in the range of 2.58–4.73 eV and enhanced λ_max lying in the range of 368–536 nm as compared to pure GY with 5.78 eV E_g and 265 nm λ_max for (GY@Ag_center–GY@3Ag_center). In the case of (2GY@Ag_center–2GY@3Ag_center), when compared to 2GY with 5.58 eV E_g and 275 nm absorption, maximum doping techniques have more effectively modified λ_max in the region of 400–548 nm and E_g, which is in the order of 2.55–4.62 eV. GY@3Ag_center and 2GY@3Ag_center reflected a noteworthy increment in linear polarizability α_O (436.90 au) and (586 au) and the first hyperpolarizability β_O (5048.77 au) and (17 270 au) because of their lowest excitation energy (ΔE) when studied in comparison with GY (α_O = 281.54 and β_O = 0.21 au) and 2GY surface (α_O = 416 and β_O = 0.06 au). Focusing on harmony between the tiny Ag clusters and graphyne surface as well as their influences on NLO properties, graphyne doping using its two-unit cells (2GY) is found to be expedient for the development of future nanoscale devices.

This research study addresses the computational simulations of optical and nonlinear optical (NLO) characteristics of silver (Ag) cluster doped graphyne complexes.