Porous Multishell Hollow Cu2O Microspheres Experiment

Porous Multishell Hollow Cu2O Microspheres ExperimentPreparation of Porous MultishellHollow Cu2O Microspheres and their catalytic activity in photo humiliation of Rhodamine-BLingling Sun, Deyan Han*, Ruirui HaoGuohong Wang*AbstractIn this study, Porous Multishell Hollow Cu2O Microspheres were fabricated by One-Pot solvothermal method of papal bull(II) with glutamic acid under 160. The as-prep atomic number 18d monodisperse Cu2O hollow microspheres were characterized by Xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), fourier trans song infrared spectrum analysis (FTIR), photoluminescence (PL), and thermogravimetrydifferential thermal analysis (TGDTA). The organization of hydroxyl radicals (OH) on the surface of UVilluminated Cu2O is seed by photoluminescence using terqaephthalic acid as a probe molecule. The photocatalytic activity of monodisperse Cu2O hollow microspheres invite been tested by degradation of Rhodamine B (RhB) and PL spectral changes of terephthalic acid under UV easygoing. The results showed that the optimum add of glutamic acid is 0.05g and answer condemnation was 24h, respectively.IntroductionTransition metal oxides with different nanostructures have drawn much attention in recent years because of their fascinating applications in optoelectronics and expectant structureal flexibility combined with droll properties with potential applications.101719 So the transition metals oxides are an important class semiconductors. Among these transition metal oxides, Cuprous oxide ( Cu2O ) is a ptype semiconductor material with a narrow band gap (2 eV) and a large excition binding energy of 140 meV, it is non-toxic, inexpensive and abundand that widely use in photocatalysis, gas sensors, lithiumion batteries, electronics, solar energy conversion, magnetic storage, and so on. To date, different Cu2O nanostructures use capping agent or surface active agent have been discount, such as cetyltrimethy lammonium bromide (CTAB), polyvinylpyrrolid single (PVP) and sodium dodecyl sulfate (SDS) were widely used to synthesize Cu2O nanowires, Cu2O nanotubes, Cu2O nanothreads, Cu2O nanocubes, flowerlike Cu2O, urchin-like Cu2O, hollow Cu2O spheres. Hollow spheres have attracted great intimacy because of their special properties including low density, high surface area, good surface permeability and distinct optical properties. 15 Wangs group add of cetyltrimethylammonium bromide developed a facile room temperature dissolvent route for synthesis of doublewall Cu2O hollow spheres. Zeng et al. 9 reported the preparation of hollow Cu2O nanospheres from a reductive conversion of aggregate CuO nanocrystallites and the organizeation of CuO microspheres by a cardinaltiered organizing scheme. However, the poor conductivity limite Cu2O further application.In the inclose work, Porous Multishell Hollow Cu2O Microspheres have been synthesized using onepot solvothermal method of copper nitrate wi th glutamic acid under 160 after different hydrothermal time. Morphological, structural and optical properties and thermal behavior of the products have been place using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Xray diffraction (XRD), Fourier transformer infrared (FTIR) spectroscopy, UV-visibleNIR spectroscopy and thermogravimetrydifferential thermal analysis (TGDTA) and photoluminescence (PL). The other aim of present work is the investigation of the photocatalytic degradation of RhB under UVlight radiation at ambient temperature and using of Cu2O nanopowders synthesisd with different hydrothermal time. The porous Multishell Hollow Cu2O Microspheres exhibit a high photocatalytic activity due to the fact that Cu2O Microspheres have a high specific surface area and a larger band gap.Experimental2.1 synthetic thinking of Hollow Cu2O MicrospheresAnalytical grade copper nitrate (Cu(NO3)2 3H2O, purity 99.5%), L glutamic acid, and RhodamineB (C28H31ClN2 O3, purity 99.5%) were purchased from SigmaAldrich and were used without further purification. Deionized water was used for all synthesis and posttreatment processes. In a typical synthesis, 0.645 g Cu(NO3)2 3H2O and 0.05g glutamic acid were dissolved in 75 ml absolute ethanol stirred until Cu(NO3)2 3H2O was completely dissolved to form a navybiue solution. After filtered with the filter paper, the filtrate was then transferred into a stainless steel autoclave with a Teflon liner of 100 ml capacity and heated at 160 for different time. After cooling at room temperature, the product was centrifuged, washed with deionized water and absolute ethanol several(prenominal) times and dried in an oven at 60 for 12 h.2.2 CharacterizationXray diffraction (XRD) was used to identify product phases and cprresponding crystallite size. XRD patterns were obtained using a D8 Xray diffractometer (Bruker AXS, German) with CuK1 radiation ( = 1.5406 ). The accelerating voltage, emission current, and sc anning speed were 40 kV, 49 mA and 0.02/s, respectively. Scanning electron microscopy (SEM) was performed with a S3400 SEM (Rili, Japan) at an accelerating voltage of 15 kV. Transmission electron microscopy (TEM) analysis was conducted using a Tecnai G20 microscope at an accelerating voltage of 200 kV. The Fourier transform infrared spectra (FTIR) of the samples were recorded on a Nicolet Forier 5700 spectrometer in the range of 400-4000 cm-1 using conventional KBr pellets. Photoluminescence (PL) spectra of the samples were measured at room temperature with a Hiachi FL4500 fluorescence spectrophotometer, with an provocation wavelength of 315 nm, the scanning speed is 1200 nm/min, and a PMT voltage of 700 V. The width of the excitation slit and emission slit was 5 nm. For thermal analysis, 10 mg of the dried Cu2O powders was used in TGDTA thermal analyzer (Pyris Diamond TG/DTA) at a heating rate of 10C/min from 20 to 800 C in an inert gas atmosphere.2.3 Photocatalytic performancePho tocatalytic activity of the Hollow Cu2O Microspheres was evaluated by the degradation RhB aqueous solution under a 15 W ultraviolet lamp at room temperature (ca. 20 ). In each experiment, 0.04 mg of the prepared powders were sprinkle in 30 ml of RhB aqueous solution with a concentrstion of 1.010-5 M in a rectangle cell (52W 155L 30H mm), and the solution was placed in the dark for 30min forwards illumination to ensure the establishment of an adsorption-desorption equilibrium between the photocatalyst powders and RhB. Then the solution was irradiated with a 30 mW/cm2 UV light (=365 nm), and during irradiation about 3 ml of the suspension was taken from the mixture at regular intervals (20 min) and centrifuged to separate the photocatalyst particles. To determine the degree of degradation the supernatants was analyzed by a UVvis spectrophotometer (U3010) to measure the submerging of RhB which exhibits characteristic preoccupancy at 554 nm 112.4 Analysis of hydroxyl radical (OH)Th e formation rates of hydroxyl radicals (OH) on the surface of the UVilluminated Cu2O were performed by a photoluminescence (PL) method using terephthalic acid as a probe molecule method as follows. 0.04 g of Cu2O powder sample was dispersed in a 30 ml of 5 10-4 M terephthalic acid aqueous solution with a concentration of 2 10-3 M NaOH in a peach tree with a diameter of about 9.0 cm. The experiment was carried out under UV irradiation using a 15 W ultraviolet lamp (25 cm higher up the dishes). The average light intensity striking on the surface of the answer solution was about 30 mW cm-2, as measured by a UV radiometer with the peak intensity of 365 nm. PL spectra of generated luminescent 2hydroxyterephtalic acid (TAOH) were measured on a Hiachi FL4500 fluorescence spectrophotometer. After UV irradiation for every 15 min, the reaction solution was ltrated to measure the increase of the PL intensity at 390 nm of TAOH excited by 315 nm light.Results and Discussion3.1 XRD analysisT he crystalline structures of the as-prepared samples were examined by Xray diffraction. Fig. 1 shows the XRD patterns of the asprepared samples synthesized with different fares of glutamic acid. The results illustrate that with increase glutamic acid from 0.02, 0.03, 0.04 0.05 to 0.06 g all the samples appear the sphere Cu2OJCPDS No, 011142. For the samples prepared with the amount of glutamic acid below 0.05 g, the talk terms product copper hydroxynitrate is dominant, but there is a amount of sphere Cu2O found in it. The peak at 2 = 12.8 corresponds to the (011) plane diffraction of the copper hydroxynitrate JCPDS No, 03-0061, with the amount of glutamic acid increase the diffraction peak of copper hydroxynitrate become weaker to disappears and the sphere Cu2O peaks intensities steadily become stronger, implying that glutamic acid acted as a reducing agent in the reaction process.To investigate the growth process of porous multishell hollow Cu2O microspheres, time-dependent exper iments were studied by hydrothermal reaction. Fig. 2 shows that the products obtained at 160 with 0.05 g glutamic acid for 2 h are 5m hollow microspheres were heartycrystallize but still the intermediate product copper hydroxynitrate. With increase reaction time to 24 h, the intermediate product copper hydroxynitrate complete transformed into cubic symmetry Cu2O, no obvious diffraction peaks of impurities were observed, indicating the high purity of the synthesized products. Also the intense and sharp diffraction peaks indicate that well crystallized Cu2O nanocrystalss can be obtained under reaction time is 24 h. But further prolongation of reaction time to 48 h resulted in the intensities of the diffraction pesks of Cu2O are not increase significantly. It can be founded that with increase in reaction time the intensity of diffraction peaks increased, indicating the improvement in the crystallinity. 8 The diffraction peaks becomes narrower as the reaction time increased, indicati ng the increase in the crystallite size.3.2 FTIR Studies.Fig. 4 showed the FTIR spectra of the Cu2O samples synthesized with additi0on of different amount of glutamic acid in the region of 4004000 cm-1, which are relate to IR-active fundamental vibrations of Cu2O itself and vibrations associated with surface adsorbates. The intense vibrational bands at 3000-3600 cm-1 were attributed to OH stretching vibrations and at 1635 cm-1 corresponded to HOH bending vibration all of surface adsorbed H2O. 30 The bands at 3000-3600 cm-1 was split into two components centered at 3184 and 3403 cm-1, corresponding to chemically adsorbed water complexes and physically adsorbed H2O, respectively . Besides, the IR band 1346 cm-1 and 1652 cm-1 are assigned to the surface monodentate carbonate-like (CO3) and bicarbonate species (HCO3) vibrational modes that because of adsorbed carbonic acid gas from the atmosphere.A metal oxide generally gives absorption bands below 1000 cm-1 that arises from stretching vibration mode of MO bond. So the IR-active fundamental vibrations of Cu2O nanocrystals appear in 4001000 cm-1, the band at 456 cm-1 and 633 cm-1 are attributed to the stretching vibrations of Cu1+O bond confirm the formation of Cu2O phase.3.3 SEM and TEM images.3.4 Mechanism for the formation of porous multishell hollow Cu2O microspheresThe formation of porous multishell hollow Cu2O microspheres can be explained by a self-transformation process of the metastable aggregated particles accompanied by the Ostwald ripening 1131.Similar mechanisms have been involved in the preparation of Cu2O, TiO2 and CdMoO4 hollow spheres 31. The formation of mechanism of porous multishell hollow Cu2O microspheres in this work is proposed as illustrated as illustrated in Fig. During the Ostwald ripening process in nine to reduce the higher surface energy, the crystallites at the central relocate themselves to the shell that formed the hollow structures. 14 Initially in the synthesis process, under the 160 hydrothermalconditions the coherent distribution of Cu2+ ions combine with glutamic acid to form Cu2(OH)3NO3 as intermediate hollow microspheretemplate. The aggregated spherical particles have many voids in the surface, the reducing angent quickly though the channels in the intermediate hollow microspheretemplate precipitate product in the inbred surface of the shell form double shells. Also the internal microsphere sueface is loosely with many voids that not used up intermediate would grow third shells on the inner double shells and so on. At last form porous multishell hollow Cu2O microspheres. With the solvothermal time increase, glutamic acid contributed to the morphological evolution on the microstructure transformation and acted as a reducing agent the copper () reduced to copper (), last cuprous oxide precipitated out because it have a low solubility in ethanol.3.5 Photocatalytic Activity.The photocatalytic activities of the asprepared porous multishell hollow Cu2O mi crospheres were ecaluated by photocatalytic degradation of RhB dyestuff in aqueous solution under UVlight irradiation at room temperature. The RhB characteristic absorption at 554 nm was chosen to admonisher the amount of RhB left during photocatalytic degradation process. Fig. 6 shows the UVvis absorption spectrum of the RhB aqueous solution in the presence of (0.04 g) porous multishell hollow Cu2O microspheres under UVlight irradiation. For comparison, the photocatalytic activities of the Cu2O nanoparticles synthesized were all evaluated under the same conditions. It is observed that with time extended the absorption peaks of RhB diminish gradually, indicating the photocatalytic degradation of RhB. During the whole process there is no new absorption peak appear indicates the complete photodegradation of RhB. It can be seen that the samples of use 0.05g glutamic acid at solvothermally hard-boiled time increased from 2h to 48h, the degradation rate increase from 8.43% to 35.78%. A mong them solvothermally treated 24h show the best performance, which show a 55.3% decrease of RhB after 40 min UV irradiation. Based on the above experimental results, this is not impress because of the Cu2O band gap is 2.17 eV and it can be excited by photons with wavelengths below 349 nm (our light source is 365 nm UV light). P2499 Also the unique porous multishell hollow structure which can be considered as an ideal transport way for reactant and product molecules moving in or out of the photocatalyst, devising the chemical reactions occurring more quickly and easily. According to the present study nanoparticles size and crystalline nature play an important role in influence the photocatalytic activity.