Yttrium and aluminum co-doped ZnO were successfully synthesized by the sol-gel method, showing high photocatalytic activity for hydrogen production (5.71 mmol h À1 g À1 ) in the water-lactic acid system under visible-light irradiation for the first time, exhibiting excellent stability and recyclability.As a kind of unique metal oxide, 1,2 because of its excellent optical and electrical properties, zinc oxide (ZnO) is a potential candidate for a variety of practical applications including semiconductors, eld-effect transistors, luminescence, solar cells, gas sensors, photodetectors, UV-blocking and other aspects. [3][4][5][6][7] Besides, ZnO has become a promising photocatalyst, owing to its lower cost, exible preparation method, non-toxicity, high photosensitivity, chemical and thermal stability. 8-12 Thus, more and more scientists are attracted to the intensive research on the photocatalytic H 2 production with ZnO recently. 13,14 While ZnO has a wide band gap of 3.2 eV and responds only to the UV part of the solar spectrum. 15,16 As a result, it is very desirable to enhance the photoactivity of ZnO and extend its light absorption capability into the visible region. 17,18 It is well known that semiconductor coupling, dye sensitization, and metal, non-metal or co-doping have been applied to develop visible light sensitive ZnO. 5,19,20 Among them, many reports on doping of ZnO with metals such as copper (Cu), 21 indium (In) 22 and lanthanum (La) 23 are available, resulting in the modication of their band gap, but there are relatively few using ZnO doped with aluminium (Al), 24 yttrium (Y) 25 or codoped ZnO. Noticeably, Al and Y have been found to be very efficient for visible light induced photocatalysis because they can decrease the energy band gap, promoting the surface segregation and the surface enrichment, and improving the photocatalytic performance. 25,26 Various methods such as the hydrothermal process, sol-gel method and co-precipitation method have been reported for the synthesis of undoped or doped ZnO nanoparticles (NPs). 27 In these approaches, sol-gel is the most effective and facile method to prepare the NPs. 23,28 However, to the best of our knowledge, Al and Y co-doped ZnO has never been synthesized by sol-gel and used for the eld of photocatalytic hydrogen production. Based on our previous research, 29-31 we report a modied sol-gel method to fabricate ZnO NPs embedded by Al and Y, driven by vacuum annealing (see Experimental details in the ESI †). The resulting ZnO NPs are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), UV-vis and photoluminescence (PL) spectroscopies. Futhermore, their photocatalytic activities are investigated under visible light irradiation.The purity and crystallinity of the as-synthesized samples were investigated by XRD, and the results are displayed in Fig. 1a and b. Fig. 1a shows the XRD patterns of aluminumdoped zinc oxide (AZO) NPs with different Y doping ratios. All diffraction peaks were in good agreemen...

Hexagonal BaAl 2 O 4 :Eu 2þ , Dy 3þ polynary complex nanotubes with long-lasting phosphorescence were obtained through a facile coprecipitation approach followed by a postcalcining reaction in a weak reducing atmosphere. In the case of low annealing temperature, anion vacancies and surface stress can induce lattice contraction due to poor crystallininty; moreover, Eu 2þ ions can occupy two different crystallographic Ba 2þ sites due to low symmetry, resulting in an appearance of double emission peaks. For the sample annealed at higher temperature, however, Eu 2þ ions only occupy substitutedly the Ba 2þ sites with lowest energy due to high crystallinity; moreover, as compared to the sample annealed at low temperature, its emission band redshifts as the results of both high crystal symmetry around Eu 2þ ions and large average optical path. Additionally, Eu 2þ and Dy 3þ ions substitute incompletely for Ba 2þ sites in nanostructures, leading to the decrease of effective electron trap densities and depths, and therefore tubular nanostructures show fast afterglow decay rate in comparison with the bulk counterpart.

SrAl2O4:Eu2+,Dy3+ long afterglow phosphors with one-dimensional nanostructures were synthesized by a hydrothermal method followed by post-annealing, and subsequently CdS was uniformly coated on their surfaces by a sol-gel approach. The nanocomposite system can significantly enhance the photocatalytic activity for the degradation of methyl orange and hexavalent chromium under ultraviolet and visible light irradiation. After the modification treatment with a 1 : 2 molar ratio of CdS to SrAl2O4:Eu2+,Dy3+ nanophosphors, the degradation rate of methyl orange can increase by 2.5 times and reach a maximum of 96.3% under visible light illumination for 30 min. The enhancement of photocatalytic activity originates from the improvement of light usage efficiency due to the hole migration from SrAl2O4:Eu2+,Dy3+ phosphors to the CdS semiconductor and the reutilization of SrAl2O4:Eu2+,Dy3+ luminescence.

No abstract