Novel g-C3N4/CoO nanocomposite application for photocatalytic H2 evolution were designed and fabricated for the first time in this work. The structure and morphology of g-C3N4/CoO were investigated by a wide range of characterization methods. The obtained g-C3N4/CoO composites exhibited more-efficient utilization of solar energy than pure g-C3N4 did, resulting in higher photocatalytic activity for H2 evolution. The optimum photoactivity in H2 evolution under visible-light irradiation for g-C3N4/CoO composites with a CoO mass content of 0.5 wt % (651.3 μmol h–1 g–1) was up to 3 times as high as that of pure g-C3N4 (220.16 μmol h–1 g–1). The remarkably increased photocatalytic performance of g-C3N4/CoO composites was mainly attributed to the synergistic effect of the junction or interface formed between g-C3N4 and CoO.Keywords: co-catalyst; g-C3N4/CoO nanocomposite; H2 evolution; heterostructure; photocatalyst; visible light;

Yellow-emitting BCNO phosphors, applied for white light-emitting-diodes (LEDs), were synthesized by a facile microwave heating route at lower temperature within short duration. The prepared BCNO phosphors exhibited amorphous form and tunable yellow emission in the range of 510–550 nm under the excitation of 450-nm blue light. The effects of carbon content on the photoluminescence properties for these BCNO phosphors and their application performances in white LEDs were investigated in detail. The demonstrated microwave synthesis route is promising in preparing low-cost phosphors, and the prepared BCNO phosphor may find potential application in blue-based white LEDs.

Ultrathin graphitic carbon nitride (g-C3N4) nanosheets were synthesized via thermal exfoliation of bulk urea-derived g-C3N4 under an argon atmosphere. As a visible-light responsive photocatalyst, this material exhibits a much superior photocatalytic activity in pollution degradation and H2 evolution than bulk g-C3N4, as a result of the extended region of visible light response and the enhanced surface area of ultrathin g-C3N4 nanosheets. These findings may provide a promising and facile approach to the design of high-performance photocatalysts.

In this work, Eu2+ doped CaAlSiN3 red-emitting nitride phosphors were synthesized for the first time from less-expensive and air-stable entire oxides raw materials, CaCO3, SiO2, Al2O3, and Eu2O3, through a common carbothermal reduction and nitridation (CTRN) method. The synthetic reaction processes involving in this CTRN route and the phase components, photoluminescent properties for the resultant CaAlSiN3:Eu2+ nitride phosphors were investigated in detail. The presented synthesis route using cost-effective entire oxides raw materials for preparation of CaAlSiN3:Eu2+ nitride phosphors shows promising prospect in promoting the application of CaAlSiN3:Eu2+ nitride phosphors in solid state lighting.

•AlN impurity was suppressed by deviating Al atoms from stoichiometry for CaAlSiN3:Eu2+ phosphor.•Suppression of AlN impurity could be realized by adding SrF2 flux for CaAlSiN3:Eu2+ phosphor.•Luminescence of CaAlSiN3:Eu2+ phosphor was enhanced through suppressing AlN impurity.Two strategies, deviation of stoichiometry and addition of flux, were employed in this work to suppress the emergence of AlN impurity in the synthesis of CaAlSiN3:Eu2+ phosphors under condition of atmospheric pressure. The influence of Al atoms deviation from ideal stoichiometry and SrF2 flux addition on the suppression of AlN impurity and their resultant photoluminescence properties are investigated for CaAlSiN3:Eu2+ phosphors. For a special Eu2+ doping concentration (0.02 mol), AlN impurity was suppressed effectively when Al element deviation is 0.2 mol (CaAl0.8SiN3) and the SrF2 flux addition is 7 wt% during preparation of CaAlSiN3:Eu2+ phosphors, respectively. The luminescent properties of CaAlSiN3:Eu2+ phosphors are found to be enhanced significantly owing to the suppression of AlN impurity. In addition, the suppression mechanisms of AlN impurity in atmospheric pressure-synthesized CaAlSiN3:Eu2+ phosphors are discussed. These results indicate the promising prospect for our proposed strategies in preparing high performance CaAlSiN3:Eu2+ phosphors under the condition of atmospheric pressure.

In this work, a plasma treatment is employed to modify the surface properties of g-C3N4 photocatalyst to enhance its photocatalytic performance. A suite of characterization methods are used to investigate the influence of plasma treatment on the surface properties, such as morphology, hydrophilicity and chemical bonding states. The comparative photocatalytic performance of pristine g-C3N4 and the plasma-treated g-C3N4 (PT-g-C3N4) for the degradation of Rhodamine B (RhB) are demonstrated. The degradation efficiency under visible light irradiation for PT-g-C3N4 is >2.0 times as high as that of pristine g-C3N4. The remarkably enhanced photocatalytic performance for pollution degradation results from the optimization of the surface properties induced by plasma treatment. These findings may provide a promising and facile approach to design high-performance photocatalysts.Download high-res image (249KB)Download full-size image

•Z-scheme heterostructure g-C3N4/PSi photocatalysts were constructed by loading PSi.•The constructed Z-scheme g-C3N4/PSi exhibit enhanced photocatalytic H2 evolution activity.•The synergistic effect between g-C3N4 and PSi is responsible for the enhanced activity.In this work, Z-scheme heterostructure were constructed over the visible light response g-C3N4 photocatalysts by loading Porous silicon (PSi) to enhance the photocatalytic H2 evolution performance. The synthesized Z-scheme g-C3N4/PSi composites with a PSi loading content of 2.50 wt% achieves the highest photocatalytic H2 evolution rate at 870.4 µmol h−1 g−1, which is about 2 times as high as the pure g-C3N4 with H2 evolution rate of 427.2 µmol h−1 g−1. Various techniques including XRD, SEM, TEM, FTIR, XPS, UPS, PL and electrochemical method were employed to demonstrate the successful construction of g-C3N4/PSi composites and to investigate the origin of the enhanced potocatalytic activity. The formed heterostructure between g-C3N4 nanosheets and PSi were verified to be the dominant reason for the enhancement of photocatalytic activity, resulting from the separation promotion of photogenerated charge carriers in a direct Z-scheme mechanism. This study presented a promising Z-scheme g-C3N4/PSi photocatalysts with promising H2 evolution performance, which might drive the progress of solar energy conversion technologies.Z-scheme heterostructure g-C3N4/PSi photocatalysts were constructed successfully by loading PSi particles on g-C3N4 nanosheets to enhance photocatalytic H2 evolution performance, resulting form improved separation rate of photogenerated charge carries associated with the construction of heterostructure at the interface.Download high-res image (94KB)Download full-size image

In this work, we demonstrate damage-free removal of residual carbon in a dielectric barrier discharge (DBD) plasma for carbothermal-synthesized materials, such as CaAlSiN3:Eu2+ phosphors, SnSb alloy anode materials, and TiN ceramic powders. The efficiency of residual carbon removal and the damaging effects of the plasma for treated materials are investigated in detail, with carbothermal-synthesized CaAlSiN3:Eu2+ phosphors being used as an example. Results show that the residual carbon in carbothermal-synthesized CaAlSiN3:Eu2+ phosphors could be removed effectively within a DBD plasma generator, resulting in the significant improvement of luminescent properties. The damage-free character of this DBD plasma decarburization process to phosphors is revealed, showing amazing superiority over the traditional high-temperature decarburization route. These results offer an attractive strategy for the removal of residual carbon for various carbothermal-synthesized materials with finely controlled compositions.

A red-emitting Eu2+ activated CaAlSiN3 phosphor was successfully prepared via an atmospheric pressure solid-state reaction method with the aid of variable fluxes, namely SrF2, NH4F, BaF2, NaF, AlF3, CaF2 and NH4Cl. The experimental results showed that the addition of SrF2 flux effectively reduced the formation temperature of CaAlSiN3: Eu2+ about 100 °C, improved the morphology of CaAlSiN3: Eu2+ and suppressed the appearance of AlN impurity phase, suggesting that SrF2 flux modifies the formation mechanism of CaAlSiN3: Eu2+. The phosphor of the CaAlSiN3:Eu2+ produced with 4 wt% SrF2 flux had an enhanced emission intensity, which was a result of the high crystallinity, the absence of AlN secondary phases, and the clean surfaces of the particles in the final product.

In this work, tunable luminescence of dicalcium silicate doped with Eu2+ ions is demonstrated based on crystal engineering. Five types of dicalcium silicate polymorphs (γ-, β-, αL′-, αH′-, α-Ca2SiO4) are synthesized by incorporating a crystal-phase stabilizer (CPS), in order to afford variable accommodation frameworks for the Eu2+ activator. Tunable luminescence is observed as the polymorph transforms from one crystal form into another. In addition, the luminescence of Eu2+ in peculiar crystal-phase Ca2SiO4 hosts is further customized by crystal-site engineering, which regulates the coordination environment of Eu2+ in multiple types of Ca2+ sites. The luminescence properties of our Eu2+-doped dicalcium silicate polymorphs show promising prospects for LED lighting applications.

In this work, tunable emission from green to red and the inverse tuning from red to green in α′L-(Ca, Sr)2SiO4:Eu2+ phosphors were demonstrated magically by varying the incorporation content of Eu2+ and Sr2+ ions, respectively. The tunable emission properties and the tuning mechanism of red-shift resulting from the Eu2+ content as well as that of blue-shift induced by the Sr2+ content were investigated in detail. As a result of fine-controlling the incorporation content of Eu2+, the emission peak red-shifts from 541 nm to 640 nm. On the other hand, the emission peak inversely blue-shifts from 640 nm to 546 nm through fine-adjusting the incorporation content of Sr2+. The excellent tuning characteristics for α′L-(Ca, Sr)2SiO4:Eu2+ phosphors presented in this work exhibited their various application prospects in solid-state lighting combining with a blue chip or a near-UV chip.

●Tunable emission for Calcium-phosphate phosphors was induced by phase evolution.●Red emission shifted into blue as luminescent host evolved from TTCP to α-TCP.●Phase evolution and the resultant color-tunable emission were investigated in detail.In this paper, color-tunable emission of Eu2+ doped Calcium-phosphate based phosphors resulted from the phase evolution of luminescent host was demonstrated. Red emission peaked at 675 nm was tuned to blue emission peaked at 480 nm as the Calcium-phosphate luminescent host evolved from Ca4(PO4)2O (TTCP) to α-Ca3(PO4)2 (α-TCP) by increasing calcination temperature from 1400 °C to 1500 °C. The phase transformation and the resultant color-tunable emission as well as the dependence of emission on phase composition for Calcium-phosphate based phosphors were investigated in detail. The results presented a promising approach to tailor the luminescent properties for phosphors materials by means of phase evolution of hosts.Color-tunable emission of Eu2+ ion in Calcium-phosphate phosphors was demonstrated as luminescent host evolved from Ca4(PO4)2O (TTCP) to α-Ca3(PO4)2 (α-TCP) by controlling calcination temperature.

Morphology control of cage-like (Ba, Sr)3MgSi2O8: Eu, Mn luminous sphere in micrometer size with a simultaneous 660 nm/430 nm-featured band emission was investigated via microwave (MW) firing procedure. A firing temperature range associated with distinct reaction of xerogel particles was determined by thermal analysis, at which the pure host phase of (Ba, Sr)3MgSi2O8 was formed and the release of decomposed gas from the precipitated nitrates played a key role in controlling the multi-scale structured morphology. As-prepared Ba1.14Sr1.7MgSi2O8:0.06Eu2+,0.1Mn2+ samples featured in a band emission simultaneously emitting at both 660 and 430 nm under 350 nm light excitation by MW procedure with an enhancement emission compared to the sample by solid state procedure. The results suggested that MW firing procedure affected assembling cage-like particle in meso-, nano- and submicro- meters to achieve photoluminescence (PL) enhancement of the simultaneous red/blue emission.A proposed morphology evolution regime in ‘one-droplet-one particle’ model for microsized Ba1.14Sr1.7MgSi2O8:0.06Eu2+,0.1Mn2+ phosphor in spray-MW firing procedure

White-light emission is realized through assembling a blue-emitting amorphous phase on a yellow-emitting Ca-SiAlON: Eu2+ phosphor particle in the form of a coating. The variation of the yellowish–white–blue color is traced with the control of a blue-emitting coating formed via in situ penetration of silicon oxide into a Ca-SiAlON network.

SiAlON-based crystal–glass composite phosphors with tunable yellow-green-blue emission are exploited. Substitution of Al–N by Si–O in a SiAlON lattice and the introduction of a Si–Al–O–N glass phase are induced by melting corrosion as SiAlON polycrystal powders were heat-treated with nano-SiO2 additive. The melting corrosion process involving liquid penetration, solid dissolution, liquid transportation is discussed and assigned to the origin of morphology transformation. The substitution extent and the glass content are identified to increase with the addition of nano-SiO2 additive. The resultant tunable photoluminescence of Eu2+ in the SiAlON lattice and Si–Al–O–N glass matrix and the microstructure evolution are detailed, respectively. The emission color of the SiAlON-based crystal–glass composite phosphors is traced continuously from yellow to green then to blue with the combination of changeable emissions of Eu2+ originated from the SiAlON phase and glass phase. This artful SiAlON-based crystal–glass composite phosphor shows flexible color-adjustable capability with the control of SiO2 melting corrosion, indicating the potential applications in lighting and display fields.

SiAlON-based crystal–glass composite phosphors with tunable yellow-green-blue emission are exploited. Substitution of Al–N by Si–O in a SiAlON lattice and the introduction of a Si–Al–O–N glass phase are induced by melting corrosion as SiAlON polycrystal powders were heat-treated with nano-SiO2 additive. The melting corrosion process involving liquid penetration, solid dissolution, liquid transportation is discussed and assigned to the origin of morphology transformation. The substitution extent and the glass content are identified to increase with the addition of nano-SiO2 additive. The resultant tunable photoluminescence of Eu2+ in the SiAlON lattice and Si–Al–O–N glass matrix and the microstructure evolution are detailed, respectively. The emission color of the SiAlON-based crystal–glass composite phosphors is traced continuously from yellow to green then to blue with the combination of changeable emissions of Eu2+ originated from the SiAlON phase and glass phase. This artful SiAlON-based crystal–glass composite phosphor shows flexible color-adjustable capability with the control of SiO2 melting corrosion, indicating the potential applications in lighting and display fields.

In this work, tunable emission from green to red and the inverse tuning from red to green in α′L-(Ca, Sr)2SiO4:Eu2+ phosphors were demonstrated magically by varying the incorporation content of Eu2+ and Sr2+ ions, respectively. The tunable emission properties and the tuning mechanism of red-shift resulting from the Eu2+ content as well as that of blue-shift induced by the Sr2+ content were investigated in detail. As a result of fine-controlling the incorporation content of Eu2+, the emission peak red-shifts from 541 nm to 640 nm. On the other hand, the emission peak inversely blue-shifts from 640 nm to 546 nm through fine-adjusting the incorporation content of Sr2+. The excellent tuning characteristics for α′L-(Ca, Sr)2SiO4:Eu2+ phosphors presented in this work exhibited their various application prospects in solid-state lighting combining with a blue chip or a near-UV chip.

In this work, tunable luminescence of dicalcium silicate doped with Eu2+ ions is demonstrated based on crystal engineering. Five types of dicalcium silicate polymorphs (γ-, β-, αL′-, αH′-, α-Ca2SiO4) are synthesized by incorporating a crystal-phase stabilizer (CPS), in order to afford variable accommodation frameworks for the Eu2+ activator. Tunable luminescence is observed as the polymorph transforms from one crystal form into another. In addition, the luminescence of Eu2+ in peculiar crystal-phase Ca2SiO4 hosts is further customized by crystal-site engineering, which regulates the coordination environment of Eu2+ in multiple types of Ca2+ sites. The luminescence properties of our Eu2+-doped dicalcium silicate polymorphs show promising prospects for LED lighting applications.

White-light emission is realized through assembling a blue-emitting amorphous phase on a yellow-emitting Ca-SiAlON: Eu2+ phosphor particle in the form of a coating. The variation of the yellowish–white–blue color is traced with the control of a blue-emitting coating formed via in situ penetration of silicon oxide into a Ca-SiAlON network.