Up-conversion Luminescence Agent Research Articles

Preparation of (CaY)F 2 :Tm 3+ ,Yb 3+ deposited porous TiO 2 matrix with highly near‐infrared light photocatalytic activity

Porous titanium dioxide (TiO2) matrix deposited with upconversion luminescence agent (CaY)F2:Tm3+,Yb3+ was sol–gel prepared using polymethyl methacrylate (PMMA) microspheres as sacrificing template and tetrabutyl titanate as TiO2 precursors. The resulted photocatalysts were subsequently characterized by X-ray diffraction, scanning microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra (PL) etc. The photocatalytic activity and biocompatibility of TiO2/(CaY)F2:Tm3+,Yb3+ were evaluated by photocatalytic degradation of methyl orange (MO) and fibroblast cytotoxicity analysis, respectively. The results revealed that (CaY)F2:Tm3+,Yb3+ nanoparticles were well dispersed onto the pore walls of porous TiO2 matrix to generate a biocompatible composite. In addition, TiO2/(CaY)F2:Tm3+,Yb3+ was found to show excellent photocatalytic activity in both UV and infrared spectra, highlighted with the fact that (CaY)F2:Tm3+,Yb3+ nanocrystals can be excited to release UV light under near infrared light source, which can in consequence active TiO2. When the mass ratio of TiO2 to (CaY)F2:Tm3+,Yb3+ nanocrystals is 2:1, the best photocatalytic efficiency can be achieved with most of UV light released by (CaY)F2:Tm3+,Yb3+ absorbed by TiO2 to induce photo-oxidation. The outstanding photocatalytic performance along with its biocompatibility, makes TiO2/(CaY)F2:Tm3+,Yb3+ a promising candidate in environmental and biomedical applications.

Highly efficient visible-light driven photocatalytic hydrogen production over (MoSe2-RGO)/(Er3+:Y3Al5O12/ZnS)/RuO2 photocatalyst

The use of co-catalysts can observably enhance photocatalytic hydrogen production activity. In this work, a novel visible-light driven photocatalyst, (MoSe2-RGO)/(Er3+:Y3Al5O12/ZnS)/RuO2 nanocomposite, is prepared for the first time by loading Er3+:Y3Al5O12, MoSe2-RGO and RuO2 on the surface of ZnS nanoparticles. Er3+:Y3Al5O12 as an effective visible-to-ultraviolet up-conversion luminescence agent can provide the ultraviolet-light to activate wide band-gap ZnS. MoSe2-RGO and RuO2, acting as conduction band co-catalyst and valence band co-catalyst, respectively, can effectively separate the photo-generated carriers and supply more reactive sites. The activities of the photocatalysts were assessed via photocatalytic hydrogen production in Na2S and Na2SO3 aqueous solution under 300 W xenon lamp irradiation. In addition, the visible-light irradiation time and used times of the prepared samples as influence factors on the photocatalytic hydrogen production were also investigated. It was easily found that the prepared (MoSe2-RGO)/(Er3+:Y3Al5O12/ZnS)/RuO2 nanocomposite shows fairly high activity in photocatalytic hydrogen production, compared with single ZnS photocatalyst. It was mainly attributed to the excellent up-conversion luminescence property of Er3+:Y3Al5O12 and the efficient separation of photo-generated electrons and holes caused by MoSe2-RGO and RuO2. This research may pave an effective way for photocatalytic hydrogen production utilizing solar light.

Preparation of high proportion of Z-scheme Er3+:Y3Al5O12@Nb2O5/Pt/In2O3 composite for enhanced visible-light driven photocatalytic hydrogen production

Although the Z-scheme photocatalysts have high photocatalytic activity, it is difficult to obtain a high proportion of Z-scheme photocatalytic system. In this paper, it is reported for the first time that a high proportion of Z-scheme Er3+:Y3Al5O12@Nb2O5/Pt/In2O3 composite photocatalyst can be prepared by coating-demoulding (C-D) method. In this Z-scheme photocatalyst, Pt nanoparticles as conductive channels are fixed between Er3+:Y3Al5O12@Nb2O5 and In2O3. Er3+:Y3Al5O12 as up-conversion luminescence agent can provide enough ultraviolet-lights to activate wide band-gap Nb2O5. The as-prepared samples are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS), fourier transform infrared spectra (FT-IR), photoluminescence (PL) spectra and related electrochemical tests. Further, the effects of heat-treatment temperature, heat-treatment time and used times on the photocatalytic hydrogen production activity of C-D Z-scheme Er3+:Y3Al5O12@Nb2O5/Pt/In2O3 composite are studied in detail. The experimental results showed that the photocatalytic activity of C-D Z-scheme Er3+:Y3Al5O12@Nb2O5/Pt/In2O3 composite is the highest in photocatalytic hydrogen production when heat-treatment temperature and time are 500 °C and 1.0 h, respectively, and that the high photocatalytic activity can be maintained within four cycles. It can be confirmed that the C-D method can effectively combine different photocatalyst particles in predicted order, greatly enhancing the proportion of highly active Z-scheme photocatalyst particles.

Histone H2A-peptide-hybrided upconversion mesoporous silica nanoparticles for bortezomib/p53 delivery and apoptosis induction

The design and development of advanced gene/drug codelivery nanocarrier with good biocompatibility for cancer gene therapy is desirable. Herein, we reported a gene delivery nanoplatform to synergized bortezomib (BTZ) for cancer treatment with histone H2A-hybrided, upconversion luminescence (UCL)-guided mesoporous silica nanoparticles [UCNPs(BTZ)@mSiO2-H2A]. The functionalization of H2A on the surface of UCNPs(BTZ)@mSiO2 nanoparticles realized the improvement of biocompatibility and enhancement of gene encapsulation and transfection efficiency. More importantly, then UCNPs(BTZ)@mSiO2-H2A/p53 induced specific and efficient apoptotic cell death in p53-null cancer cells and restored the functional activity of tumor suppressor p53 by the success of co-delivery of BTZ/p53. Moreover, the transfection with UCNPs(BTZ)@mSiO2-H2A/p53 in p53-deficient non-small cell lung cancer cells changed the status of p53 and substantially enhanced the p53-mediated sensitivity of encapsulated BTZ inside the UCNPs(BTZ)@mSiO2/p53. Meanwhile, core-shell structured mesoporous silica nanoparticles UCNPs@mSiO2 as an UCL agent can detect the real-time interaction of nanoparticles with cells and uptake/penetration processes. The results here suggested that the as-developed UCNPs(BTZ)@mSiO2-H2A/p53 nanoplatform with coordinating biocompatibility, UCL image, and sustained release manner might be desirable gene/drug codelivery nanocarrier for clinical cancer therapy.

Er3+-doping induced formation of orthorhombic/monoclinic Bi5O7I heterostructure with enhanced visible-light photocatalytic activity for removal of contaminants

Bi5O7I is a member of the bismuth oxyiodides family with unique layered structures, generating an internal electrostatic field to promote the separation and transfer of photogenerated charge carriers. To further enhance its visible-light photocatalytic activity, various strategies, including creating the heterojunction, forming the defects, and engineering the bandgap and composition, have been applied. Another promising strategy is to construct a heterostructured photocatalyst. Here, we report a doping-induced formation of orthorhombic/monoclinic-Bi5O7I (o-Bi5O7I/m-Bi5O7I) heterostructure and its visible-light photocatalytic activity for organic dye degradation and NO removal. Under hydrothermal conditions, Bi5O7I is doped with Er3+, upconversion luminescence agent, in a varying content. The XRD results reveal that 3% Er3+ is decisive in commencing the phase transition from orthorhombic to monoclinic. Though an increasing content of Er3+ induces the phase transition, flower-like Bi5O7I microspheres assembled by nanosheets remains unchanged. An obvious redshift in the absorption edge and enhancement of visible-light absorption are observed for Bi5O7I samples doped with >3% Er3+ due to the orthorhombic-to-monoclinic phase transition. The photocatalytic activities of the samples were evaluated by the degradation of three different organic dyes (Rhodamine B, methyl orange and methylene blue) in aqueous solution under white LED light irradiation and the photooxidative removal of gaseous NO under simulated solar light irradiation. The 5% Er3+-doped Bi5O7I shows the highest photocatalytic activity for the photodegradation of Rhodamine B (91.3%), methyl orange (70.0%) and methylene blue (76.0%) and for the photooxidative removal of NO (54.0%) under visible light. A strong luminescence generating extra photons, the formation of an orthorhombic/monoclinic-Bi5O7I heterostructure promoting more effective charge separation, and the emergence of monoclinic-Bi5O7I absorbing more visible light are a collective mechanism leading to the enhancement of photocatalytic activity.

A novel photocatalyst, Y2SiO5:Pr3+,Li/Pt-NaNbxTa1−xO3, for highly efficient photocatalytic hydrogen evolution under visible-light irradiation

In this work, Y2SiO5:Pr3+,Li, as an excellent up-conversion luminescence agent from visible-light to ultraviolet-light, is synthesized by using sol-gel method. And then, a series of Y2SiO5:Pr3+,Li/NaNbxTa1−xO3 (x=0.00, 0.25 and 0.50) with different amounts of Y2SiO5:Pr3+,Li are prepared by using hydrothermal method. The prepared samples are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectroscopy and photoluminescence spectroscopy (PL). The activities of Y2SiO5:Pr3+,Li/Pt-NaNbxTa1−xO3 are investigated through photocatalytic hydrogen evolution in 10vol% methanol solution under visible-light irradiation. The influences of Nb content in NaNbxTa1−xO3, mass ratio of Y2SiO5:Pr3+,Li and NaNb0.5Ta0.5O3, visible-light irradiation time and reuse-times are examined on the visible-light photocatalytic hydrogen evolution. The experimental results showed that the prepared Y2SiO5:Pr3+,Li/Pt-NaNb0.5Ta0.5O3 with 0.4:1.0 mass ratio of Y2SiO5:Pr3+,Li and NaNb0.5Ta0.5O3 and 0.25wt% Pt loading displayed a highest evolved hydrogen activity under visible-light irradiation. This study may provide some significant references for large scale photocatalytic hydrogen evolution utilizing solar energy.

Three narrow band-gap semiconductors modified Z-scheme photocatalysts, Er3+:Y3Al5O12@NiGa2O4/(NiS, CoS2 or MoS2)/Bi2Sn2O7, for enhanced solar-light photocatalytic conversions of nitrite and sulfite

Three Z-scheme photocatalysts, Er3+:Y3Al5O12@NiGa2O4/NiS/Bi2Sn2O7, Er3+:Y3Al5O12@NiGa2O4/CoS2/Bi2Sn2O7 and Er3+:Y3Al5O12@NiGa2O4/MoS2/Bi2Sn2O7, are designed for synchronous conversions of nitrite and sulfite and fabricated by sol-hydrothermal and calcination methods. In these Z-scheme photocatalysts, three narrow band-gap semiconductors as “conductive ladder” are inserted between Er3+:Y3Al5O12@NiGa2O4 and Bi2Sn2O7 to accelerate the electron transfer from conduction band of Bi2Sn2O7 to valence band of NiGa2O4. Er3+:Y3Al5O12 as an up-conversion luminescence agent (from visible-light to ultraviolet-light) provides enough ultraviolet-light for satisfying the energy demand of wide band-gap NiGa2O4. The prepared photocatalysts are characterized by UV–vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) spectra and photoluminescence (PL) spectra. The photocatalytic activity of prepared photocatalysts is evaluated via conversions of nitrite and sulfite under simulated solar-light irradiation. The results show that the prepared Er3+:Y3Al5O12@NiGa2O4/NiS/Bi2Sn2O7, Er3+:Y3Al5O12@NiGa2O4/CoS2/Bi2Sn2O7 and Er3+:Y3Al5O12@NiGa2O4/MoS2/Bi2Sn2O7 composites exhibit the high and stable photocatalytic activity during the conversions of nitrite and sulfite. The highest conversion ratios (86.23% and 94.44%) for nitrite and sulfite can be obtained when the Er3+:Y3Al5O12@NiGa2O4/NiS/Bi2Sn2O7 is adopted as photocatalyst under simulated solar-light irradiation. Meanwhile, the effect of simulated solar-light irradiation time and corresponding reaction kinetics on photocatalytic conversions of nitrite and sulfite are also studied. Subsequently, the study of used times shows that the prepared Z-scheme photocatalysts can be effectively reused without an apparent inactivation on photocatalytic activity. These results demonstrate that the Er3+:Y3Al5O12@NiGa2O4/NiS/Bi2Sn2O7 is a potential Z-scheme photocatalyst to be used in actual conversions of nitrite and sulfite under solar-light irradiation.

A novel Z-scheme sonocatalyst system, Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4, and application in sonocatalytic degradation of sulfanilamide

A novel Z-scheme coated composite, Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4, was designed for sonocatalytic degradation of sulfanilamide and fabricated by sol-hydrothermal and calcination methods. The prepared sample was characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), UV–vis diffuse reflectance spectra (DRS), fourier transform infrared (FT-IR) spectra, Raman spectra and photoluminescence (PL) spectra. In Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4, Ni(Fe0.05Ga0.95)2O4 and BiVO4 form a Z-scheme sonocatalytic system, Er3+:Y3Al5O12 as an up-conversion luminescence agent (from visible-light to ultraviolet-light) provides the ultraviolet-light for satisfying the energy demand of wide band-gap Ni(Fe0.05Ga0.95)2O4 and Au nanoparticles as co-catalyst forms more active sites to enrich electrons. Also, Au nanoparticles as conductive channels promotes the electrons (e−) from conduction band of BiVO4 to transfer to valence band of Ni(Fe0.05Ga0.95)2O4. Due to the characteristics of valence state diversity, the Fe3+ and V5+ constitute a redox reaction recombination system, which can also push electrons (e−) on conduction band of BiVO4 to quickly transfer to valence band of Ni(Fe0.05Ga0.95)2O4. The sonocatalytic activity of Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4 nanocomposite was detected through degradation of sulfanilamide under ultrasonic irradiation. A high sonocatalytic degradation ratio (95.64%) of sulfanilamide can be obtained when the conditions of 10.00 mg/L sulfanilamide, 1.00 g/L Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4, 300 min ultrasonic irradiation and 100 mL total volume were adopted. Some factors such as ultrasonic irradiation time and cycle number on the sonocatalytic degradation efficiency are also investigated by using TOC and UV–vis spectroscopy. Subsequently, the effects of hydroxyl radicals (OH) and hole scavengers were investigated to elaborate the mechanism. The researches show that the prepared Z-scheme Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4 coated composite displayed an excellent sonocatalytic activity in degradation of sulfanilamide under ultrasonic irradiation.

Preparation of Y2SiO5:Pr3+,Li and Na2NbxTa2−xO6/(Au/RGO) composites and investigation into visible-light driven photocatalytic hydrogen production

A three-component photocatalytic system is constructed by using Na2NbxTa2−xO6 as the main catalyst, Y2SiO5:Pr3+,Li as the up-conversion luminescence agent and Au/RGO as the co-catalyst.

Highly efficient near-infrared light photocatalytic hydrogen evolution over MoS2 supported Ta2O5 combined with an up-conversion luminescence agent (β-Tm3+,Yb3+:NaYF4/MoS2–Ta2O5 nanocomposite)

The photocatalytic hydrogen evolution activity of Ta2O5 can be greatly enhanced by adding up-conversion luminescence agent (β-Tm3+,Yb3+:NaYF4) and co-catalyst (MoS2).

Highly efficient visible-light driven photocatalytic hydrogen production from a novel Z-scheme Er3+:YAlO3/Ta2O5-V5+||Fe3+-TiO2/Au coated composite

In this work, the preparation of a novel Z-scheme photocatalyst, Er3+:YAlO3/Ta2O5-V5+||Fe3+-TiO2/Au coated composite, for visible-light photocatalytic hydrogen production is reported for the first time. In this photocatalyst, Au nanoparticles as conduction band co-catalyst provide more active sites to enrich electrons. Ta2O5-V5+||Fe3+-TiO2 as composite redox cycle system thoroughly separates the photo-generated electrons and holes. In addition, Er3+:YAlO3 as up-conversion luminescence agent (from visible-light to ultraviolet-light) provides enough ultraviolet-light for satisfying the energy demand of wide band-gap semiconductors (TiO2 and Ta2O5). The photocatalytic hydrogen production can be achieved from methanol as sacrificial agent (electron donor) under visible-light irradiation. The main influence factors such as initial solution pH and molar ratio of TiO2 and Ta2O5 on visible-light photocatalytic hydrogen production activity of Er3+:YAlO3/Ta2O5-V5+||Fe3+-TiO2/Au coated composite are discussed in detail. The results show that the Er3+:YAlO3/Ta2O5-V5+||Fe3+-TiO2/Au coated composite with 1.0:0.5 M ratio of TiO2 and Ta2O5 in methanol aqueous solution at pH = 6.50 displays the highest photocatalytic hydrogen production activity. Furthermore, a high level of photocatalytic activity can be still maintained within three cycles under the same conditions. It implies that the prepared Z-scheme Er3+:YAlO3/Ta2O5-V5+||Fe3+-TiO2/Au coated composite may be a promising photocatalyst utilizing solar energy for hydrogen production.

Preparation of new visible-light driven nanocomposite photocatalysts, X/NaTaO3/Er3+:YAlO3 (X = Ag, Au and Pt), for photocatalytic conversion of Cr(VI)

Abstract In order to expand the light response range of wide band-gap semiconductor photocatalyst (NaTaO3) for effective photocatalytic conversion of Cr(VI), an up-conversion luminescence agent (Er3+:YAlO3) is combined with NaTaO3 and a visible-light driven photocatalyst, NaTaO3/Er3+:YAlO3, is prepared. Moreover, several conduction band co-catalysts (Ag, Au and Pt) are deposited the surface of NaTaO3/Er3+:YAlO3, respectively, to facilitate the transfer rate of photo-generated electrons. X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) analyses are employed to confirm the morphology, microstructure and composition of the prepared photocatalysts. In addition, UV–vis diffuse reflectance spectra are determined to explore the visible-light absorption properties of Er3+:YAlO3, NaTaO3, NaTaO3/Er3+:YAlO3 and X/NaTaO3/Er3+:YAlO3 (X = Ag, Au and Pt). Photoluminescence (PL) spectra are used to estimate the recombination rate of electron–hole pairs. The effects of irradiation time, photosource kind, solution acidity and used times on the photocatalytic capabilities of NaTaO3/Er3+:YAlO3 and X/NaTaO3/Er3+:YAlO3 (X = Ag, Au and Pt) are investigated in detail. The results show that the uses of up-conversion luminescence agent (Er3+:YAlO3) and co-catalysts (Ag, Au and Pt) can promote NaTaO3 to utilize visible-light to carry out the photocatalytic conversion of Cr(VI). Particularly, the prepared Au/NaTaO3/Er3+:YAlO3 nanocomposite with 1.0 wt% Au and 0.3:1.0 molar ratio of Er3+:YAlO3 and NaTaO3 shows the highest photocatalytic activity in conversion of Cr(VI).

A novel Z-scheme Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-reduced graphene oxide photocatalyst with superior photocatalytic hydrogen evolution activity

Here, a high effective visible-ultraviolet up-conversion luminescence agent (Er3+:YAlO3) was synthesized and the Er3+:YAlO3/Ta2O5 composite was prepared by sol-gel method. The MoSe2-reduced graphene oxide (MoSe2-RGO) hybrid as co-catalyst was prepared by hydrothermal method. Afterwards, a new Z-scheme photocatalyst, Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO, was successfully assembled by hydrothermal methods for visible-light photocatalytic hydrogen evolution. The Er3+:YAlO3, MoSe2-RGO, Er3+:YAlO3/Ta2O5, CaIn2S4/MoSe2-RGO, Er3+:YAlO3/Ta2O5/MoSe2-RGO and Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO were all characterized by X-ray diffractometer (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy dispersive spectrometer (EDS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The UV–vis absorption spectra and photoluminescence (PL) spectra of Er3+:YAlO3 were also measured. The photocatalytic hydrogen production activity of Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO was examined under visible-light irradiation. In addition, the reused times of Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO for photocatalytic hydrogen production were investigated. The results showed that the Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO photocatalyst in aqueous methanol solution displayed the highest photocatalytic hydrogen production activity under visible-light irradiation and after five-times photocatalytic hydrogen experiment the photocatalytic activity of Er3+:YAlO3/Ta2O5-CaIn2S4/MoSe2-RGO is basicly stable in the process of splitting methanol aqueous solutions.

Preparation of sponge carrier supported photocatalyst by self-assembly technique for phenol photodegradation in visible light

The up-conversion luminescence agent Er3+:YAlO3 could up-convert visible light to ultraviolet light which could then be absorbed by the synthesized photocatalyst that contained TiO2. Accordingly, we successfully prepared the visible light responsive photocatalyst Er3+:YAlO3/TiO2 hybrid composites by the sol-gel technique and hydrothermal treatment at different temperatures in the range of 90–170°C. Subsequently, a novel self-assembly technique was used to coat a thin and even layer of Er3+:YAlO3/TiO2 hybrid composites on the sponge-type carriers. The prepared composites were characterized by various techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra and Fluorescence spectra. The phenol (50mgL−1) was used as the model pollutant to compare the degradation by the Er3+:YAlO3/TiO2-coated carriers with four different coating ratios (10, 20, 30 and 40gL−1). The corresponded phenol removal efficiencies were 90.2%, 97.6%, 78.4% and 58.0% in 8h, respectively, which were much higher than that for the pristine sponge (26.5%) under visible light irradiation. On the basis of these experimental results, a possible photocatalytic mechanism over the sponge carrier supported photocatalyst was suggested to explain the phenol photodegradation.

Photocatalytic degradation of organic dyes by Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar irradiation

In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.

Enhanced visible-light photocatalytic hydrogen evolution activity of Er3+:Y3Al5O12/PdS–ZnS by conduction band co-catalysts (MoO2, MoS2 and MoSe2)

Several conduction band co-catalysts (CBCOs), MoO2, MoS2 and MoSe2, were prepared to improve the visible-light photocatalytic hydrogen evolution activity of Er3+:Y3Al5O12/PdS–ZnS from water splitting, in which the PdS is a valence band co-catalyst (VBCO) used to facilitate the photo-generated hole transfer and the Er3+:Y3Al5O12 is an up-conversion luminescence agent from visible light to ultraviolet light used to provide the ultraviolet light satisfying the energy demands of wide band-gap ZnS photocatalyst. XRD, SEM, TEM and EDX analyses were employed to confirm the morphology, microstructure and composition of the prepared photocatalysts. UV–vis absorption and PL spectra were also determined to explore luminescence effect of the Er3+:Y3Al5O12. The visible-light photocatalytic hydrogen evolution activity of the prepared photocatalysts was evaluated by using Na2S and Na2SO3 as sacrificial reagents in aqueous solution under visible light irradiation. The influential factors such as contents of CBCOs (MoO2, MoS2 and MoSe2) and visible-light irradiation time on visible-light photocatalytic hydrogen evolution of Er3+:Y3Al5O12/PdS–ZnS–MoX2 (X = O, S and Se) were investigated in detail. Particularly, Er3+:Y3Al5O12/PdS–ZnS–MoSe2 with 0.30 wt% MoSe2 shows the highest photocatalytic hydrogen evolution activity.

Solar degradation of contaminants in water: TiO2 solar photocatalysis assisted by up-conversion luminescent materials

Solar energy, along with other renewable resources, could potentially solve environmental problems, as demonstrated by recent developments in the use of solar energy, such as solar photocatalysis. Solar photocatalytic technology has been demonstrated to be effective for treating groundwater, drinking water, wastewater and air and soil pollution. In this study, a solar photocatalytic application for wastewater decontamination is presented. Luminescent material has been evaluated as up-conversion material for enhancing the photocatalytic activity. Wastewater decontamination by heterogeneous photocatalysis has been developed in a slurry photo-reactor, using TiO2 as a photocatalyst. The photoactivity of TiO2 under several sun irradiation conditions was investigated. The up-conversion luminescence agent ZBLAN, a rare-earth (Yb-Er-Tm) co-doped fluoride glass (ZrF4– BaF2–LaF3–AlF3–NaF), was incorporated to enhance the solar-driven activity of TiO2 because this material could transform the unused near-infrared sunlight tail into UV–vis radiation available for photoreaction activation. The use of ZBLAN has demonstrated an improvement over ordinary titanium dioxide photocatalytic activity under sunlight irradiation for the photocatalytic degradation of pollutants in wastewater. Our results demonstrating the contribution of up-conversion luminescence to the improved photoactivity of titanium dioxide suggest that it can be used to develop new technologies for treating wastewater using solar light.

Efficient photocatalytic hydrogen evolution from methanol/water splitting over Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12/MoS2–NaTaO3 nanocomposite particles under infrared–visible light irradiation

In this paper, two efficient up-conversion luminescence agents, Tm3+,Yb3+:NaYF4 (from infrared light to ultravoilet light) and Er3+:Y3Al5O12 (from visible light to ultravoilet light), were synthesized by hydrothermal and sol–gel methods, respectively. And then, a novel photocatalyst, Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12/MoS2–NaTaO3 nanocomposite particles, were successfully prepared by hydrothermal and calcination methods for infrared–visible light photocatalytic hydrogen evolution. For comparison and confirmation, Tm3+,Yb3+:NaYF4, Er3+:Y3Al5O12, MoS2–NaTaO3, Tm3+,Yb3+:NaYF4/MoS2–NaTaO3, Er3+:Y3Al5O12/MoS2–NaTaO3, and Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12/MoS2–NaTaO3 were all characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The photocatalytic activity of Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12/MoS2–NaTaO3 nanocomposite particles was examined through photocatalytic hydrogen evolution from methanol splitting under infrared–visible light irradiation. The influence factors such as mass ratio of Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12 and NaTaO3, calcination temperature, solution acidity (pH) and used time on the infrared–visible light photocatalytic hydrogen evolution activity of Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12/MoS2–NaTaO3 nanocomposite particles were studied. Particularly, the prepared Tm3+,Yb3+:NaYF4–Er3+:Y3Al5O12/MoS2–NaTaO3 nanocomposite particles with the mass ratio of 0.3:1.0 heat-treated at 500°C for 120min in pH=6.0 solution with 10.0wt % methanol displayed a high infrared–visible light photocatalytic activity in hydrogen production from water solution.

The effect of different co-catalysts (CuO, MoS2 and Pt) on hydrogen production of Er3+:YAlO3/NaTaO3 by visible-light-induced methanol splitting

In this work, a high effective up-conversion luminescence agent (from infrared and visible light to ultraviolet light), Er3+:YAlO3, was synthesized by sol–gel method. And then, the CuO, MoS2 and Pt were adopted as co-catalysts and the NaTaO3 was used as bulk catalyst, and then the three corresponding visible-light photocatalysts, Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3, were successfully prepared by hydrothermal and direct mixing methods, respectively. Er3+:YAlO3, NaTaO3, Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3 were all characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The visible-light photocatalytic activities of Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3 were examined through photocatalytic hydrogen evolution from methanol aqueous solution under visible-light irradiation. The influence factors such as the contents of co-catalysts (CuO, MoS2 and Pt), heat-treated temperature and initial pH value on the visible-light photocatalytic hydrogen evolution activity of Er3+:YAlO3/CuO–NaTaO3, Er3+:YAlO3/MoS2–NaTaO3 and Er3+:YAlO3/Pt–NaTaO3 were studied. The results showed that the Er3+:YAlO3/MoS2–NaTaO3 with 0.2 wt% MoS2 in solution (pH = 6.0) with 5.0 wt% methanol displayed the highest visible light photocatalytic hydrogen production activity.

Preparation of Er3+:YAlO3/Fe- and Co-doped TiO2–ZnO coated composites and their visible-light photocatalytic activity in degradation of some organic dyes

In this paper, an up-conversion luminescence agent (Er3+:YAlO3), which can effectively transform the visible light in solar light into ultraviolet light, was prepared. Then, for a visible-light photocatalytic degradation reaction, the prepared Er3+:YAlO3 was coated by Co- and Fe-doped TiO2–ZnO films thorough sol–gel process, respectively, and the Er3+:YAlO3/Fe- and Co-doped TiO2–ZnO coated composites were obtained. The crystal forms, particle sizes, chemical compositions, and weight change process of the Er3+:YAlO3/Fe- and Co-doped TiO2–ZnO coated composites were analyzed by using XRD, TEM, SEM, EDX, and TG–DTA instruments. The photocatalytic activities of the Er3+:YAlO3/Fe- and Co-doped TiO2–ZnO coated composites were evaluated through the degradation of azo fuchsine under visible light irradiation. It indicated that the visible light photocatalytic reduction ratio of Fe- and Co-doped TiO2–ZnO composites were 47.8 and 67.9 %, while after adding 15 wt% Er3+:YAlO3, the reduction ratio reached 93.5 and 95.5 %, respectively. In addition, the photocatalytic effect of Er3+:YAlO3/Co-doped TiO2–ZnO is better than that of Er3+:YAlO3/Fe-doped TiO2–ZnO.