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Novel Z-scheme-based BiVO4/CdS photocatalysts with efficient charge separation were prepared by simple in situ hydrothermal method. The compact structure of the CdS nanorod and BiVO4 nanosheet has formed a Z-scheme heterojunction. The as-prepared BiVO4/CdS composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, diffuse reflection spectroscopy, photoluminescence and photocurrent techniques. It was found that the BiVO4/CdS composites had the light-absorbing range and could efficiently degrade malachite green dye under visible-light irradiation. In this report, the result of the best degrading sample could achieve 92% in 30 min under visible light, respectively. BiVO4/CdS composites perform photocatalytic efficiently due to the Z-scheme. Furthermore, the Z-scheme-based BiVO4/CdS composites leaded to a major oxidation site at BiVO4, which successfully avoided photoetching of CdS during photocatalysis. Especially, the BiVO4/CdS system exhibits great photogenerated electron–hole pairs separation capabilities and high redox capabilities. This unique method of synthesizing Z-scheme-based BiVO4/CdS heterojunction has ability to reduce the cost and promote photocatalytic in visible-light range simultaneously.

BiOBr-reduced graphene oxide (RGO) composites were successfully synthesized via a simple hydrothermal method. Their morphology, structure and photocatalytic activity in the degradation of nitrobenzene were characterized by scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption, UV–vis absorption spectroscopy, photoluminescence spectra, electrochemical impedance spectra and total organic carbon, respectively. The results showed that the introduction of RGO could enhance the visible light photocatalytic activity of BiOBr. The BiOBr-RGO composite with 0.6 wt% RGO exhibited an optimal photocatalytic activity, and the maximum degradation rate of nitrobenzene was about 2.16 times that of pure BiOBr due to the increased light absorption and the reduced electron-hole pair recombination in BiOBr with the introduction of RGO.

A Z-scheme based BiOI/CdS heterojunction was synthesized by in-situ stirring and calcining method. Various characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, diffuse reflection spectroscopy (DRS), photoluminescence (PL) and photocurrent test were used to study the crystallographi structure, morphology and optical and electrical properties of the as-prepared samples. By constructing a Z-scheme heterojunction, the transfer of photogenerated carriers between BiOI and CdS is realized, thereby effectively improving the photocatalytic activity. Free radical capture experiments show that •O − 2 is the main active substance for photocatalytic dye degradation. The photocatalytic mechanism of the CdS/BiOI composites to form a Z-scheme heterojunction under visible-light is proposed. This work might provide novel conception for the design and construction of high-performance Z-scheme based photocatalysts.

In order to improve the catalytic efficiency of titanium dioxide (TiO2) under visible light, TiO2 nanoparticles was composed with the silver-covered carbon nanotubes (CA) to form CNTs-Ag-TiO2 (CAT) ternary structure via in situ reduction combined with sol-gel method. The composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. Using methylene blue (MB) as the model pollutant, photocatalytic activity of CAT was studied to investigate the influence of the composited amount of CA on the effect of photocatalysis. The results revealed that the photocatalytic activity of TiO2 under both visible light and UV light were improved by compositing with CA. When the mass ratio of CA is 15%, the degradation rare of methylene blue (MB) by CAT reached to 80.8% under visible light in 3 h, which is 16.5 times higher than that of TiO2. Accordingly, the degradation rate reached to 99.2% under UV light in 40 min, which is nearly twice as fast as that of TiO2.

Visible-light CdS/BiPO4 nanoparticles were prepared by a solvothermal method. The as-prepared CdS/BiPO4 nanoparticles were characterized by scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL). The CdS/BiPO4 nanoparticles exhibited better photocatalytic performance and higher stability of photodegradation of malachite green (MG). And the highest photodegradation rate of MG is up to 98 %. In addition, the mechanism of photocatalysis was demonstrated based on the radical-trapping experiments. The performance of CdS/BiPO4 nanoparticles in photocatalysis is mainly attributed to the carriers separation and electron migration from CdS to BiPO4 efficiently via intimate contact with the interface. The heterojunction formed by CdS/BiPO4 is helpful to inhibit the recombination of electrons and holes.This work puts forward a viewpoint for the design of CdS/BiPO4 nanoparticles in order to making use of solar energy more efficiently and providing some perspectives on the process of photo-generated carrier migration.

Orange-red emitting (Sr 0.883- x Ba 0.1 Lu 0.0.17 Eu x ) 3 (Si 0.95 Al 0.05 )O 5 phosphors were synthesized by conventional solid-state reaction. The effect of NH 4 F flux on structural and luminescent properties of phosphors was investigated. Results suggested that the optimal content of NH 4 F flux was 3 wt.% and the optimal doping concentration of Eu 2+ was x =0.023 mol. The phosphors showed intense absorption in near-ultraviolet to blue region and exhibited orange-red emissions. The thermal stability of synthesized (Sr 0.86 Ba 0.1 Lu 0.017 Eu 0.023 ) 3 (Si 0.95 Al 0.05 )O 5 phosphor were examined and compared with commercial YAG:Ce 3+ yellow phosphors. Combining an InGaN blue 460 nm chip and a white-emitting (Sr 0.86 Ba 0.1 Lu 0.017 Eu 0.023 ) 3 (Si 0.95 Al 0.05 )O 5 phosphor produced a white- light LED, demonstrating CIE chromaticity coordinates of (0.314, 0.329) and a color temperature of 5595 K. All results showed that this phosphor is a promising candidate as orange-red emitting phosphor for white light emitting diode (w-LED) application.

Highly photoluminescent carbon nanoparticles with a quantum yield of 37.40% were directly synthesized by a simple hydrothermal treatment of oatmeal in pure water without using any surface passivation and oxidizing agents. Due to the bright fluorescence, high photo-stability, low toxicity and good biocompatibility, the as-prepared carbon nanoparticles are demonstrated to be excellent probes in bio-imaging.

Red phosphors of Li-doped CaTiO 3 :Eu 3+ that enhance photoluminescence have been synthesized by a solid-state method, and their structure and morphology were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The luminescence property was measured using photoluminescence excitation (PLE) and photoluminescence (PL) spectra, respectively. The effect of sintered temperature and Eu 3+ and Li + concentration in as-prepared series phosphors was studied. Results indicate that the optimal luminescence properties of CaTiO 3 :Eu 3+ (CTE) phosphors are typically obtained at 1300 °C with 12 mol% of Eu 3+ concentration, and the emission intensity can be greatly enhanced by the incorporation of Li + into the CTE phosphors, attributing that Li not only compensates positive charge defect by replacement of Ca 2+ with Eu 3+ , but also plays a role of flux, which could enhance the crystallinity of the phosphors. The intensity of the optimal Li-doped CaTiO 3 :Eu 3+ phosphor (CLTE) is 2.3 times of that of CTE. PL spectrum showed that CLTE phosphor was efficiently excited by near-ultraviolet light at wavelength around 398 nm and emitted intensive red light with a peak around 616 nm corresponding to the 5 D 0 → 7 F 2 transition of Eu 3+ . Furthermore, this phosphor has very good thermal stability and high color purity, implying the potential to be a promising red phosphor in white light emitting diodes.

We present for the first time the synthesis of Eu(3+)-doped β-phase sodium gadolinium fluoride (NaGdF4:Eu) nanocrystals (NCs) using a hydrothermal method and the application of down conversion (DC) NaGdF4:Eu NCs to efficient dye-sensitized solar cells (DSSCs). The as-prepared NaGdF4:Eu(3+) NCs were characterized by X-ray diffraction, photoluminescence spectrometry, and scanning and transmission electron microscopy. DC layers consisting of poly(methyl methacrylate) (PMMA) doped with luminescent NaGdF4:Eu(3+) were prepared and attached onto the back of a prefabricated TiO2 anode to form a more efficient DSSC, compared with a device based on a pure TiO2 electrode. The influences of both doped and undoped NaGdF4 NC layers on the photovoltaic devices were compared and evaluated by the measurement of the device's incident-photon-to-current efficiency (IPCE). An obvious increase in IPCE was observed when the DC layer was added in the device. As the down-converted photons can be reabsorbed within DSSCs to generate photocurrent, the DSSC with a 100 nm thick NaGdF4:Eu(3+) DC-PMMA layer improved photoelectric conversion efficiency by 4.5% relative to the uncoated solar cell. The experiments conclude that NaGdF4:Eu(3+) nanocrystals mainly act as luminescent DC centers and light scatterers in the ultraviolet and visible domains, respectively, for enhancing the spectral response of the device in the measured spectral regime.

Eu2+ and Mn2+ co-doped SrSi2O2N2 phosphors were firstly synthesized via a simple sol–gel method using low-cost SrCO3, Eu2O3, Mn(CH3COO)2 ⋅ 4H2O, α-Si3N4 and C8H20O4Si (TEOS) as the starting materials. Their luminescence properties, quantum yield, and thermal stability were investigated in comparison with the single Eu2+ doped samples. The green emission intensity of Eu2+ ions is greatly enhanced by introducing Mn2+ ions into SrSi2O2N2:Eu2+ due to the coexcitation and energy transfer between Mn2+ and Eu2+. The energy transfer probability from Mn2+ to Eu2+ depends strongly on the Mn2+ concentration, which is maximized at 2.0 mol%. Mn2+. Simultaneously, quantum efficiency and thermal stability in SrSi2O2N2:0.03Eu2+, 0.02Mn2+ is dramatically improved. All these excellent optical properties indicate that SrSi2O2N2:Eu2+, Mn2+ synthesized in the present work is a promising green-emitting phosphor for white-light emitting diodes with near-UV LED chips.

Bi2O3 was successfully synthesized via microwave-assisted reaction of Bi2O3 precursor in aqueous solution using a microwave system. Their morphologies, structures and photocatalytic performances in the degradation of methylene blue (MB) were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence spectroscopy and UV-vis absorption spectroscopy, respectively. The results show that Bi2O3 synthesized at pH value of 7 exhibits an optimal photocatalytic performance with the MB degradation rate of 76% at 240 min under visible light irradiation due to its higher visible light absorption and comparatively low electron-hole pair recombination.

A reddish-orange-emitting SnO2:Eu3+ phosphor for field emission displays (FEDs) was successfully synthesized via a homogeneous precipitation route using urea as a precipitant. The influences of the dopant concentration of Eu3+ and calcination temperature on optical properties were investigated. The low-voltage field emission properties of the FED device prepared using the synthesized SnO2:Eu3+ phosphors were reported. Under the UV light, SnO2:Eu3+ phosphors display the strong orange–red emission peaked at 587, 591, and 597 nm due to the 5D0→7F1 magnetic dipole transition of Eu3+. The phosphor doped with 1.0 mol% Eu3+ possesses the highest photoluminescent (PL) intensity. Under the low-voltage excitation of 300 V, the fabricated FED device exhibits the bright orange–red emission, high-voltage brightness saturation, and high color purity, which has a potential application in low-voltage full color FEDs.

This paper reports the spectral variation of Sr3SiO5: Ce3+, Li+ phosphor. It was synthesized by the conventional solid state method. The effects of calcining temperature and codoption of Mg2+ and Ba2+ on phase composition, structure, photoluminescence and thermal stability were firstly investigated in detail. Under the near-UV excitation of 415 nm, Sr3SiO5: Ce3+, Li+ emits a bright greenish-yellow color centered at 532nm, which originates from 5d to 4f (2F7/2 and 2F5/2) transition of Ce3+. The PL spectra show the different emission color variation with substituting Sr2+ cations with smaller Mg2+ or larger Ba2+, which makes it be applied as a color-tunable phosphor for LED based on near-UV chip/phosphor technology. Simultaneously, the thermal stability of (Sr,Ba)3SiO5: Ce3+, Li+ phosphor is improved markedly.

This article reports a low-cost yellow-emitting Y3Al5-xBxO12-xNx:Ce3+ phosphor with an enhanced luminescent intensity and excellent thermal stability for white light-emitting diodes (LEDs). It was synthesized by a simple gas-pressure sintering (GPS) process. The effect of B3+–N3− incorporation on the optical properties of Y3Al5O12:Ce3+ phosphor was investigated. The addition of appropriate amounts of boron nitride (BN) leads to a marked increase in photoluminescent intensity and a slight shift of its emission spectra toward the blue region, which is assigned to the improved crystallinity and increased particle size. Especially, the prepared oxynitride phosphor does not exhibit any thermal quenching under high temperature, and the emission intensity at 250°C even increases up to 175% of that measured at 20°C. Finally, the white LED flat lamp with luminous efficiency as high as 101 lm/W, color rendering index of 72, and correlated color temperature of about 6600 K is successfully realized by using YAG:Ce3+ phosphor doped with 0.5 molar ratio BN, which is acceptable and promising for general indoor illuminations to replace fluorescent or incandescent lamps.

This paper reports a low-cost yellow-orange emitting Y 3 Al 5− x Si x O 12− x N x :Ce 3+ phosphor with excellent color rendering for warm white LEDs. It was synthesized by a simple gas pressure sintering (GPS). The effect of Si 4+ N 3− incorporation on the optical properties of Y 3 Al 5 O 12 :Ce 3+ phosphor was investigated. The addition of Si 3 N 4 leads to an obvious shift of its emission spectra toward the red region and an increase of FWHM accompanying a significant decrease of photoluminescent intensity, which is assigned to incorporation of N 3− in Ce 3+ nearest neighbor coordination. Adding nanosized amorphous Si 3 N 4 or flux can greatly improve the emission intensity of Y 2.925 Ce 0.075 Al 5− x Si x O 12− x N x phosphor. Finally, the white LED flat lamp with a CRI as high as 83, luminous efficiency of 65 lm/W, and CCT of about 3700 K is successfully realized by using a single oxynitride phosphor combined with a blue LED chip, which is acceptable for general indoor illuminations to replace fluorescent or incandescent lamps.

Ce3+,Li+-codoped Ca-α-Sialon phosphors with the formula [Ca(1−2x)CexLix]m/2Si12−(m+n)Alm+nOnN16−n (0≤x≤0.25, 0.5≤m≤3.5, and 0.16≤n≤2.0) have been synthesized by gas pressure sintering (GPS). The effects of the activator concentration and the overall composition of host lattice on the phase evolution, morphology, and optical properties were investigated. The single-phase Ca-α-Sialon:Ce3+,Li+ can be synthesized at x

A low-cost ZnAl 2 O 4 :Mn 2+ green nanophosphor for field emission display (FED) was successfully synthesized by the coprecipitation method and a two-step firing, firstly calcining at 1200 °C for 2 h in air and then annealing at 900 °C for 3 h in flowing NH 3 gas. The effects of the preparation process and the Mn 2+ concentration on optical properties of ZnAl 2 O 4 :Mn 2+ were investigated. The phase composition, particle morphology, photoluminescence (PL) spectra of the ZnAl 2 O 4 :Mn 2+ phosphor as well as low-voltage field emission properties of the FED device prepared by using the synthesized ZnAl 2 O 4 :Mn 2+ phosphor were examined. Similar to ZnGa 2 O 4 :Mn 2+ , Mn 2+ -doped ZnAl 2 O 4 showed two green emission bands centered at 508 and 517 nm, respectively, which originate from 4 T 1 ( 4 G)→ 6 A 1 ( 6 S) transitions of Mn 2+ on T d and O h sites. The PL intensity reached the maximum at 0.5 at.% Mn 2+ . Under the low-voltage excitation, the FED device exhibited bright green emission, high voltage brightness saturation, and high color purity.

Dispersed and spherical Y2O3:Eu3+ red phosphor particles were prepared by the urea homogeneous precipitation method. In2O3 nanoparticles were successfully coated on the surface of the phosphor. Phase compositions, morphologies, photoluminescence (PL) spectra, and cathodoluminescence (CL) properties of Y2O3:Eu3+ phosphors before and after In2O3 coating were examined. It was found that CL properties such as luminous efficiency, lifetime, and stability of In2O3-coated phosphor screen were improved significantly, even though its PL intensity decreased compared with that of the uncoated sample. The reason is attributed to the increase of the electrical conductivity and the decrease of the charge accumulating effect. The present results prove that Y2O3:Eu3+ phosphor coated with an appropriate amount of In2O3 is more suitable to the requirement for low-voltage field-emission displays.

Photoluminescence, photoabsorption, and X-ray photoelectron spectroscopic study revealed that an optical transition of porous silicon from red-shift to blue-shift, and Si -2p binding energy transition from low to high at a critical anodization temperature, 343 K. Possible origin for the reverse variations happening at temperature below and above the critical temperature is discussed.

Cu , Al , and Ti films of ~ 10 nm thickness were deposited on porous silicon (PS) at room temperature using Filtered Cathodic Vacuum Arc system and annealed at 800°C for 10 min in vacuum. The PS layers were obtained by anodization of Si wafer. X-ray photoelectron spectroscopy, photoluminescence (PL), photo-absorption (PA), and X-ray diffraction studies revealed that before annealing just Cu -deposited sample exhibited PL blueshift, PA redshift, and Si -2p level shift due to the Cu diffusion at the surface of PS. While after annealing, Cu - and Ti -deposited samples exhibited obvious PA redshift and Si -2p level shift, which arise from the crystal field variation due to the formation of Cu / Ti silicides at the surface as well as the conduction electronic transportation.

Polycrystalline silicon carbide ( P-SiC ) films containing SiC nanoparticles and Er were prepared by r.f. reactive magnetron co-sputtering technique with SiC and Er targets on low-temperature silicon (111) and silicon dioxide substrates with the mixed gas of pure argon, methane, and hydrogen. Surface morphology and photoluminescence (PL) properties of them were measured by field-emission scanning electron microscope and Raman spectroscopy. The peak position, intensity, and the full width at half maximum (FWHM) of PL spectra were relevant with Er doping levels and deposition conditions.

Eu2+ and Mn2+ co-doped SrSi2O2N2 phosphors are prepared via a sol-gel method using HNO3 solutions of SrCO3 and Eu2O3, EtOH solutions of Mn(OAc)2 and Si(O-Et)4 (TEOS), and α-Si3N4 and citric acid at 80 °C followed by drying the resulting gel (200 °C, 4 h) and calcination under reducing atmosphere (1400 °C, 6 h, 5% H2/N2).

Mn(2+) doped-AlN red phosphors were prepared by the solid-state reaction method. X-ray diffraction, SEM-EDS, photoluminescence and cathodoluminescence were utilized to characterize the prepared phosphor. Under UV light or electron beam excitation, the AlN:Mn(2+) phosphors exhibit a strong red emission centered at 600 nm, which is ascribed to the characteristic (4)T1((4)G)-(6)A1((6)S) transition of Mn(2+). Energy level diagrams were constructed to discuss the photoluminescence and cathodoluminescence processes of the AlN:1% Mn(2+) phosphor. The oxygen-related defects in AlN have great influence on the photoluminescence and cathodoluminescence properties of the AlN:1% Mn(2+) phosphor. The dependence of brightness on accelerating voltage or electric current, the decay behavior of CL intensity under the electron bombardment, and the stability of CIE chromaticity coordinates were investigated in detail. The results indicate that the AlN:Mn(2+) phosphor exhibits a higher brightness, higher color purity, and lower saturation compared to the red Y2O3:Eu(3+) phosphor, which gives the AlN:Mn(2+) phosphor great potential as a red phosphor for full color FEDs.

Bi2O3/F–TiO2 composites were successfully synthesized via an aqueous precipitation method. Their morphologies, structures and photocatalytic performance in the degradation of methyl orange (MO) were characterized by scanning electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy and photoluminescence spectroscopy. The results show that the Bi2O3/F–TiO2 composites exhibit enhanced photocatalytic performance in the degradation of MO with a maximum degradation rate of 95% under visible light irradiation for 180 min, which is mainly ascribed to the increase in light adsorption and the reduction in electron–hole pair recombination in Bi2O3 with the introduction of F–TiO2.

An Eu 2+ -activated BaSi 7 N 10 cyan phosphor for UV-pumping white light-emitting diodes (LEDs) was successfully synthesized by direct gas reduction and nitridation of the homogeneous oxide precursor of a BaO-SiO 2 -Eu 2 O 3 system in flowing NH 3 and CH 4 mixture gas. The phase purity, morphology, chemical composition, and luminescence properties were investigated. The effect of activator concentration on the optical properties of Eu 2+ in BaSi 7 N 10 was discussed. The synthesized powders have a nearly pure BaSi 7 N 10 phase and consist of microsized particles. Eu 2+ -doped BaSi 7 N 10 phosphors absorb strongly in the UV part of the electromagnetic spectrum and exhibit an intense cyan emission band centered at 482-500 nm, which agrees with earlier papers. The optical properties depend greatly on the Eu 2+ concentration. Under an UV excitation, BaSi 7 N 10 :Eu 2+ phosphors doped with a 20 atom % activator give the best luminescent properties, such as high emission intensity, high quantum efficiency, and very low thermal quenching, which suggests that Eu 2+ -doped BaSi 7 N 10 can be a good green-blue phosphor for UV-pumping white LEDs.

Although the size- and shape-induced blueshift in the photoluminescence and photoabsorption of nanostructured ZnO has been extensively investigated, the underlying mechanism remains yet unclear. Here we show that theoretical reproduction of the observed trends clarifies that the blueshift originates from the Hamiltonian perturbation due to the broken-bond-induced local strain and quantum trapping and electron-phonon coupling in the surface skin up to two atomic layers in depth while bonds in the core interior retain their bulk nature. The extent of the blue shift depends on the tunable fraction of undercoordinated atoms in the surface skin. Therefore, the quantum confinement effect is indeed more “superficial” than first thought [H. Winn, OE Mag. 8, 10 (2005)].