Xuexue Li

Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production

Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g−1 at 1.25 A g−1) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 μmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 μmol h−1.

Cu superstructures fabricated using tree leaves and Cu–MnO2 superstructures for high performance supercapacitors

Copper (Cu) superstructures have been originally synthesized by using natural sapless leaves. A novel hybrid nanoarchitecture, Cu–MnO2 composite, is prepared through facile coating of a thin MnO2 nanofilm onto the highly electronically conductive Cu superstructures. Benefiting from their unique structures, as electrode materials of supercapacitors the composite superstructures have a high specific capacity of 1024 F g−1 at 1.5 A g−1 and good capacity retention of around 96% after 2000 electrochemical cycles.

Porous Mn3[Co(CN)6]2·nH2O nanocubes as a rapid organic dyes adsorption material

Porous Mn3[Co(CN)6]2·nH2O nanocubes were successfully synthesized by a surfactant-assisted (PVP) process through a simple precipitation method at room temperature. X-Ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were employed for the morphology and structure characterization. The fine-detailed information about porous structures of the samples has also been studied using the Brunauer–Emmet–Teller (BET) isotherm. Most importantly, the prepared porous structured Mn3[Co(CN)6]2·nH2O showed excellent adsorption capacity and rapid adsorption rate for dyes in aqueous solution, such as methyl violet, neutral red, methyl orange and especially for methylene blue. The effects of contact time, initial concentration and initial pH were also investigated. The maximum adsorption capacity of methylene blue was as high as 489.9 mg g−1 and 96.5% of the dye was removed within initial 5 min of contact time. Due to the simple synthetic method, fast adsorption rate and its high adsorption capacity, the synthesized Mn3[Co(CN)6]2·nH2O porous nanocubes could be used as an effective adsorbent for removing dye pollutants from waste water.

Floral fragrances of Hemerocallis L. (daylily) evaluated by headspace solid-phase microextraction with gas chromatography-mass spectrometry

ABSTRACT Traditional breeding objectives focusing on flower type and colour have resulted in the lack of floral fragrances in modern daylilies. Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to determine the contributions of floral volatiles to floral fragrances in 46 daylilies (seven species, one variety, and 38 cultivars). Thirty-seven floral volatiles were identified, including 30 terpenoids, five benzenoids, and two nitrogenous compounds. Sensory evaluation and HS-SPME-GC-MS revealed that variations in the relative emission rates and proportions of (E)-β-ocimene and linalool were mainly responsible for different fragrance patterns in Hemerocallis. The studied daylilies were grouped to six fragrance patterns: (1) intense herbaceous and pungent scent, having the highest (E)-β-ocimene emission level; (2) intense flowery and pungent scent, having medium (E)-β-ocimene and low linalool emission levels; (3) medium flowery and sweet scent, having very low (E)-β-ocimene and the highest linalool emission levels; (4) low flowery and fresh scent, having low (E)-β-ocimene and no linalool emission levels; (5) very low herbaceous and fresh scent, having very low (E)-β-ocimene and linalool emission levels; and (6) no scent, having trace amounts of floral volatiles.

High pressure phase transitions and depressurization amorphization of Bi2Fe4O9

High pressure structural behavior of Bi2Fe4O9 has been studied by in situ angular-dispersive X-ray diffraction (ADXD) measurements up to 51.3 GPa. Two phase transitions have been observed at 7.6 and 22.6 GPa, respectively. A second high pressure structure (HP2) involving the tripling of lattice parameter c has been identified. An unusual amorphization occurs after releasing pressure. The high pressure phase transitions can be understood in terms of the increase in the coordination number of Fe3+ ion. The depressurization amorphization results from the appearance of the metastable HP2 and its collapse after releasing pressure. The results extend our understanding of pressure-induced amorphization.

Photosynthesis of Hosta under light and controlled-release nitrogen fertilizer

The interactive effects of light intensity and controlled-release nitrogen fertilizer (CRNF) supply on growth, gas exchange, and chlorophyll (Chl) fluorescence parameters of two species of potted Hosta seedlings, original species of the genus Hosta in China, were studied. N4 (4 g of CRNF per pot), N8 (8 g of CRNF per pot), and sometimes N12 (12 g of CRNF per pot), significantly increased total dry weights, net photosynthetic rate (PN), stomatal conductance (gs), transpiration rate (E), the maximum quantum yield of PSII photochemistry (Fv/Fm), the maximum ratio of quantum yields of photochemical and concurrent nonphotochemical processes in PSII (Fv/F0), actual efficiency of photochemical energy conversion in PSII under light (ΦPSII), and photochemical quenching coefficient (qP), but significantly decreased internal CO2 concentration (Ci) and nonphotochemical Chl fluorescence quenching (NPQ) compared to control plants at different growth stages of the two Hosta species in two levels of light intensities (50% of natural light (L50) and 70% of natural light (L70)). Based on the available data, we concluded that the increments in total dry weights of Hosta clausa var. ensata and Hosta ventricosa by appropriate amount of CRNF supply treatments under L50 and/or L70 light conditions are directly related to the increments in the PN, which may be due to both stomatal and nonstomatal improvements for a longer growing time. Furthermore, there was an interaction between light intensity and CRNF supply treatments on growth and photosynthetic characteristics of the two Hosta species. The adaptability of Hosta plants with obvious stoloniferous rootstock to stronger light was higher than that of Hosta plants without obvious stoloniferous rootstock.