Preparation and characterization of SnO2 doped TiO2 nanoparticles: Effect of phase changes on the photocatalytic and catalytic activity

The SnO2/TiO2 nanoparticles have been successfully synthesized via the surfactant-assisted sol-gel method. The results showed that the anatase to rutile phase transformation and the crystallite size increased with increasing the calcination temperature.

Journal of Science: Advanced Materials and Devices (2019) 400e412 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Preparation and characterization of SnO2 doped TiO2 nanoparticles: Effect of phase changes on the photocatalytic and catalytic activity Shawky M Hassan a, *, Awad I Ahmed a, Mohammed A Mannaa b, ** a b Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt Chemistry Department, Faculty of Science, Amran University, Sa'dah, Yemen a r t i c l e i n f o a b s t r a c t Article history: Received 28 February 2019 Received in revised form 17 June 2019 Accepted 23 June 2019 Available online 28 June 2019 The effects of phase changes on the photocatalytic and catalytic activities of SnO2/TiO2 nanoparticles prepared via a surfactant-assisted sol-gel method were investigated The as-prepared SnO2/TiO2 was calcined at 400 , 500 , 600 , and 700  C The prepared samples were studied by XRD, TEM, SEM, FTIR, BET, UV-vis diffuse reflection spectroscopy (DRS) and Photoluminescence (PL) spectra The results showed that the crystallite size and anatase-to-rutile phase transformation increased greatly with increasing the calcination temperature The transformation of anatase to rutile phase was found to be between 400 and 600  C, and then the anatase completely transformed to rutile phase at 700  C Also, the specific surface area and pore volume decreased, whereas the mean pore size increased with increasing the calcination temperature The effect of calcination temperature on the catalytic activity of the samples was tested by different applications: photodegradation of Methylene Blue (MB), Rhodamine B (RhB) dyes and phenol and synthesis of xanthene (14-phenyl-14H-dibenzo [a,j]xanthene) The mineralization of MB and RhB has been confirmed by chemical oxygen demand (COD) measurements The SnO2/TiO2 nanoparticles calcined at 500  C are found to exhibit the highest photocatalytic and catalytic activities © 2019 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: SnO2/TiO2 nanoparticle Calcination temperature Photodegradation Xanthene Methylene blue Rhodamine B Phenol Introduction Metal oxides play an important role in heterogeneous catalysis as solid catalysts in the industry and many synthetic conversions [1,2] In recent years, metal oxide semiconductors were used as photocatalysts for environmental protection from pollutants that resulted from industrial waste products such as dyes, organic and inorganic pollutants which caused considerable problems to microorganisms, aquatic environments, and human beings [3e11] Photodegradation method is one of the most popular methods in wastewater treatment due to its effectiveness, operational simplicity, and low cost [12e18] Among various oxides semiconductors photocatalysts, TiO2 has considerable attention due to its special optoelectronic properties, physicochemical stability and nontoxicity [19e23] TiO2 has a wide bandgap (3.2 eV) and the fast * Corresponding author ** Corresponding author E-mail addresses: smhassan@mans.edu.eg (S.M Hassan), mnnaam@yahoo.com (M.A Mannaa) Peer review under responsibility of Vietnam National University, Hanoi recombination of the photogenerated charge carriers (electron/ hole, e/h, pairs) still hinders the application of this technique [24,25] The photocatalytic activity of TiO2 can be improved by morphological modifications [26] and chemical modifications [27], or a combination of morphological and chemical modifications [28] Different methods have been developed for enhancing the efficiency of the TiO2 powders The most popular method depends on doping TiO2 with metal and nonmetal elements [29,30], semiconductor coupling [31], dye sensitization [32] … etc Coupling TiO2 with other semiconductors can enhance the photoactivity of TiO2 due to the reducing of the recombination rate of e/h pairs [31,33e35] Coupling SnO2 and TiO2 is one of the effective methods to lower e/h pair's recombination [3], which increases the quantum efficiency and enhances the photocatalytic activity Hence, coupling TiO2 with SnO2 can reduce e/h pairs recombination rate which increases the photocatalytic activity of TiO2 [36] In addition, the calcination temperature can affect the structure, morphology, crystal phase, the crystal size of the TiO2 doped SnO2 which in turn affects the photoactivity, and catalytic activity of the SnO2/TiO2 nanoparticle [37e39] However, few studies have been carried out on the effects of calcination temperatures on structural, photocatalytic, biological and catalytic properties of SnO2/TiO2 https://doi.org/10.1016/j.jsamd.2019.06.004 2468-2179/© 2019 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 nanoparticles Sato et al and Zhang et al showed that calcination of samples leads to release of lattice oxygen from TiO2 which enhances the photocatalytic activity [40,41] The present study aims to study the effect of phase changes on the photocatalytic and catalytic properties of the SnO2/TiO2 nanoparticles The catalytic activity of SnO2/TiO2 nanoparticles was investigated by photodegradation of MB, RhB and phenol as well as the synthesis of 14-phenyl-14H-dibenzo [a,j] xanthene Experimental 2.1 Preparation of SnO2/TiO2 nanoparticles A conventional sol-gel method was employed to prepare SnO2/ TiO2 nanoparticles from titanium (IV) isopropoxide (Aldrich, 97%) as a Ti-precursor and SnCl4.xH2O as a Sn-precursor CTAB was used as template and ethanol as solvent The synthetic procedure was carried out as follows [19,42]: g of CTAB was dissolved in 50 ml of ethanol and stirred for 30 min; then 11.7 ml of titanium (IV) isopropoxide was added under continuously stirred conditions 0.70 g of SnCl4.xH2O was dissolved in ethanol and added to the mixture under vigorous stirring for h with 1:9 mol% ratio of SnO2:TiO2 Then, ml of ammonia (32%) was added dropwise to the mixture The mixture was left in air for 24 h to complete the reaction After that, the gel was filtrated and washed with de-ionized water several times until the ammonia and all chloride ions were removed (chloride ions tested by silver nitrate solution) and then dried in an oven at 100  C for 24 h Finally, the powder was calcined at 400 , 500 , 600 and 700  C for h 2.2 Characterization XRD patterns were conducted on a Philips PW 1830 diffractometer with Cu Ka radiation operated at 40 kV (2q range of 10e80 ) and the crystallite size (D) was calculated from the Scherrer equation [36] Transmission electron microscopy (TEM) was performed using a JEOL 2000FX operated at 120 kV The SEM micrographs were obtained using SEM: JEOL JSM-5800LV Surface 401 area measurements were conducted on a Quantachrome Autosorb 3B using nitrogen as the adsorbent The surface area was calculated using the BrunauereEmmetteTeller (BET) equation from the adsorption branch The pore size distribution was calculated by analyzing the adsorption branch of the nitrogen sorption isotherm using BarreteJoynereHalenda (BJH) method Fourier transform infrared (FTIR) spectra were performed using Shimadzu FTIR The spectra were recorded in the range of 400e4000 cmÀ1 using the KBr disk technique The UV-vis diffuse reflectance spectra (DRS) of the samples were examined by a PerkinElmer Lambda 950 instrument to estimate the bandgap energy of the prepared photocatalysts Photoluminescence (PL) spectra were measured on an FP6500 fluorescence spectrophotometer with the excitation wavelength of 315 nm 2.3 Catalytic activity measurements 2.3.1 Photocatalytic activity evaluation The photocatalytic activity of the SnO2/TiO2 nanoparticles was measured by the photodegradation of MB, RhB and phenol solutions under UV-vis irradiation The examination of the photocatalytic reactions was occurred using a cooling-water-cycle system keeping the reaction temperature constant The source of light was Halogen lamp (400 W) which fixed at a distance of 30 cm from the reactor The mixture of 0.05 g of the catalyst was dispersed in 50 ml of dye (10 mg LÀ1) The reaction was initially stirred for 30 in the dark to achieve the adsorption-desorption equilibrium of dye on the surface of the catalyst After that, ml of the solution was taken at fixed intervals; centrifuged and ml of the supernatant was diluted in a 10 ml flask for analysis on a Shimadzu, MPC-2200 UV-vis spectrophotometer at lmax 666 nm for MB and 554 nm for RhB and 276 nm for phenol The photocatalytic degradation rate (D %) has been calculated according to the following formula [43]:  D% ¼ Co À Ct Co   100 Fig XRD patterns of SnO2/TiO2 nanoparticles calcined at (a) 400 (b) 500 (c) 600 and (d) 700  C 402 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 where Co and Ct are the concentration of dye solution at initial and after irradiation time (t) Also, for exploring the reactive species might produce in the photocatalytic reaction, we used different scavengers including Na2EDTA, isopropanol (IPA), carbon tetrachloride (CCl4), and benzoquinone (BQ) as scavengers of Hỵ, $OH, ee and $OĂ , respectively, at concentration of mM [44] The COD was determined using HACH DR2800 photometer The mineralization (%COD) of MB and RhB solutions after photodegradation were calculated from the equation:  %COD ¼ CODInitial À CODFinal CODInitial 2.3.2 Synthesis of 14-phenyl-14H-dibenzo [a,j] xanthene The reaction was carried out using a mixture of the benzaldehyde (1 mmol) and b-naphthol (2 mmol) with 0.10 g of the activated catalyst (at 120  C for h) in an oil bath at 125  C under stirring for the appropriate time The reaction completion was examined by TLC The catalyst was separated from the product by simple filtration where the solid product was dissolved in chloroform Chloroform was evaporated and the product was recrystallized using aqueous ethanol (15%) for two times [45,46] The product was identified by m.p and FTIR spectra The %yield of xanthene was calculated as follows:  100 Yield wt%ị ẳ Obtained weight of product  100 Theoretical weight of product Table Structural and catalytic properties and %yield for SnO2/TiO2 nanoparticles calcined at different temperatures Temperature (oC) D (nm) Eg (eV) SBET (m2/g) Vp (cm3/g) DP (nm) %Xanthene 400 500 600 700 6.9 9.2 18.4 23.5 3.07 2.95 2.94 2.91 33.5 29.6 25.7 19.7 0.13 0.11 0.09 0.07 9.3 10.6 16.2 25.3 89.12 93.50 78.58 68.62 Fig TEM and HRTEM images of SnO2/TiO2 nanoparticles calcined at (a, b) 500 and (c, d) 700  C S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 403 Results and discussion 3.2 TEM analysis 3.1 XRD analysis The morphology and particles size of SnO2/TiO2 calcined at different temperatures were analyzed by TEM and HRTEM Fig shows that the average particle size increased with increasing the calcination temperature This resulted due to fuse the particles together and forming larger agglomerates [51] Both samples showed an almost spherical shape with different average particle sizes HRTEM images exhibit lattice fringes with interplanar spacing 0.34 nm and 0.32 nm which corresponding to (101) anatase and (110) rutile planes, respectively [43] With increasing the calcination temperature to 700  C, only 0.32 interplanar spaces appeared This confirms the transformation of anatase to rutile with increasing calcination temperature These results showed that the rutile phase is more stable at high calcination temperatures compared with the anatase phase XRD patterns of the SnO2/TiO2 nanoparticles calcined at different temperature are shown in Fig It can be seen that all the samples were composed of anatase (2q ¼ 25.28 ) and rutile (2q ¼ 27.5 ) phases [47,48] The intensity of the peaks that attributed to the anatase phase decreased with increasing the calcination temperature, while the rutile phase increased and became more preferential, indicating the improvement of rutile phase crystallization At 400  C, the transformation of anatase to rutile phase is small and increased with increasing the temperature to 600  C and at 700  C the anatase peak disappeared These results indicate that the rutile phase is more stable at the high calcination temperatures The peaks associated with the corresponding SnO2 are not detected in the XRD patterns for samples calcined at 400 and 500  C, which indicate that SnO2 is well dispersed on the TiO2 surface At 700  C, new peaks appeared at 2Ɵ ¼ 26.7, 32.32 and 33.9 which indicating the aggregation of SnO2 crystals on TiO2 surface [49] The crystallite size of SnO2/TiO2 nanoparticles was calculated and listed in Table It is clearly shown, with increasing the calcination temperature, the crystallite size increased gradually This because of increasing the particles aggregation accelerate the growth of crystallite sizes [43] According to the kinetics studies, the transformation from anatase-to-rutile phase needs high activation energy to overcome both strain energy for the oxygen ions and break the TieO bonds as the titanium ions redistribute [50] 3.3 SEM analysis Fig illustrates the surface morphology of SnO2/TiO2 nanoparticles calcined at different temperatures The images show that the increasing in the calcination temperature was accompanied by increases in the protrusion and aggregation of SnO2 on the surface of TiO2 due to the densification of the TiO2 morphology [52] Also, the average size of aggregated particles increased with increasing the calcination temperature The increase in the particle size resulted due to the primary crystallite size of anatase and rutile increases during the heat treatment and another reason is due to the increasing aggregation of particles at high calcination temperature [6] Fig SEM images of SnO2/TiO2 nanoparticles calcined at (a) 400 , (b) 500 and (c) 700  C 404 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 3.4 Surface areas and pore size distribution Fig 4a shows nitrogen adsorption-desorption isotherms of SnO2/TiO2 calcined at 400 , 500 , 600 , and 700  C The samples exhibited typical type IV adsorption isotherms, indicating the characteristics of mesoporous materials [39] With increasing the calcination temperature from 400 to 700  C, the specific surface area and pore volume decrease, whereas the mean pore size increases (Table 1) Moreover, with increasing the calcination temperature, the hysteresis loops shift to higher relative pressure range and the areas of the hysteresis loops decrease indicating that some pores collapse during the calcination [41] This indicated that the average pore size increased and the volume of pore decreased with increasing calcination temperature The pore size distribution was calculated from the desorption branch of the isotherm and presented in Fig 4b It can be seen that the calcination temperature influenced the pore size distribution of the SnO2/TiO2 nanoparticles With increasing the calcination temperature, the BJH pore size distribution of samples exhibited a systematic shift toward larger mesopores which can be associated with the severe collapse of the initial porous structure occurred for the calcination temperature increases Fig N2 adsorption-desorption isotherms (a) and pore size distribution curves (b) of SnO2/TiO2 calcined at different temperatures S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 3.5 FTIR measurements Fig illustrates the FTIR spectra of SnO2/TiO2 nanoparticles calcined at 400 , 500 , 600 , and 700  C The spectra display broadband centered at 3410 cmÀ1 which assigned to the stretching vibration of eOH and/or physically adsorbed water on the SnO2/ TiO2 surface [22,53] Another band appeared at 1625 cmÀ1 is related to the bending vibration of hydroxyl groups on the surface of the oxides [22,54] No bands correspond to the organic template, 405 CTAB, indicating that the calcination treatment at 400  C is sufficient to remove the template The broadband in the region below 800 cmÀ1 is associated with the stretching mode of vibrations of bridged SneOeSn, TieOeTi and TieOeSn bonds of titanium and tin oxides [3,53] The small bands that notice at 1350 and 1030 cmÀ1 assigned to the hetero TieOeSn bond [42] At 700  C, the intensity of the bands at 1625 cmÀ1 decreased This is due to the release of hydroxyl groups on the surface of SnO2/TiO2 nanoparticles when calcined at 700  C [55] Fig FTIR spectra of the SnO2/TiO2 nanoparticles calcined at (a) 400 (b) 500 (c) 600 (d) 700  C Fig UVevis spectra of the SnO2/TiO2 nanoparticles calcined at different temperatures 406 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 3.6 UVevis diffuse reflectance UVevis spectra of the SnO2/TiO2 nanoparticles calcined at 400 , 500 , 600 , and 700  C are shown in Fig All samples show a strong absorption below 450 nm due to the interband electronic transitions [6,43] It's reported that the coupling of TiO2 with SnO2 can improve the photocatalytic activity This may be due to created additional energy levels by Sn ions in the bandgap of TiO2 [56,57], which facilitates the transition of electrons from VB to the CB The small absorption edges in the visible region are mainly caused by Fig The PL spectra of SnO2/TiO2 calcined at different temperatures Fig Effect of calcination temperature of SnO2/TiO2 nanoparticles on the photodegradation of (a) MB, (b) RhB and (c) phenol S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 oxygen vacancies [58,59] The bandgap energy (Eg) can be estimated according to the relation [60,61]: ahv ¼ Aðhv À Eg Án where a is the absorbance coefficient, h is the Planck constant, v is the wavenumber, A is a constant and Eg is the bandgap energy in which n ¼ 1/2 for direct bandgap materials and n ¼ for indirect bandgap [62] The bandgap energy values of SnO2/TiO2 nanoparticles calcined at 400 , 500 , 600 , and 700  C were estimated from the plot of (ahn)2 versus photon energy in electron volts (Fig inset) The obtained Eg are shown in Table The results show the Eg became narrower with increasing the calcination temperature This may due to two reasons: the first, as the calcination temperature increased, the crystallite 407 size increased and led to a decrease in the bandgap energy, and the second reason, due to the phase transformation increased with increasing the calcination temperature where the bandgap of the rutile phase is smaller than that of anatase phase [6,37,41,43] 3.7 Photoluminescence spectra Photoluminescence spectra of the SnO2/TiO2 calcined at different temperature were conducted in the wavelength range of 350e600 nm As presented in Fig 7, the shape of the PL spectra for all samples were similar The PL signals at about 385 and 405 nm were ascribed to the band-band PL emission which was generated by the incident light with energy approximately equal to that of the band gaps of the anatase and the rutile phases of TiO2, respectively [6,37] The PL emission peaks at about 470 nm are possibly Fig Photodegradation of (a) MB and (b) RhB over SnO2/TiO2 calcined at 500  C in the absence and presence of different scavengers under similar reaction conditions Scheme Postulated mechanism of electron transfer in SnO2/TiO2 nanoparticles 408 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 attributed to defect states in the band gaps resulting from oxygen vacancies at different depths [20] Moreover, the PL intensity decreased with the increasing calcination temperature from 400 to 500  C and then enhanced sharply at 600 and 700  C The weak PL intensity of SnO2/TiO2 calcined at 500  C suggested a low recombination efficiency of the photoinduced e/h pairs and consequently a longer lifetime of the photoinduced electrons [37] Increasing PL intensity of the SnO2/TiO2 with increasing the calcination temperature could be ascribed to the excessive rutile phase and the destruction of the surface microstructure [63] 3.8 Catalytic activity measurements 3.8.1 Photocatalytic measurements Fig shows the photodegradation of aqueous solutions of MB, RhB and phenol over SnO2/TiO2 nanoparticles calcined at 400 , Table Correlation coefficients and rate constants for MB and RhB photodegradation Calcination temperature  400 500 600 700 MB RhB K1 R2 K1 R2 0.02863 0.03871 0.02347 0.01951 0.99090 0.98749 0.98832 0.99784 0.02529 0.03033 0.01837 0.01392 0.98893 0.99290 0.98555 0.99226 500 , 600 , and 700  C The photocatalytic activity of the SnO2/TiO2 increases with increasing the calcination temperature to reach a maximum at 500  C and then decreases with the further increase in the calcination temperature These results indicate that at 500  C the interaction between mixed phases is the strongest which makes the sample more active than that calcined at 400  C and above 500  C Also at 500  C, the samples show good crystallization Fig 10 % COD removal and photodegradation of MB and RhB dyes vs time 5 400 C 500 C 600 C 700 C 4 ( b) ln (Co/Ct) ln (Co/Ct) 400 C 500 C 600 C 700 C ( a) 2 1 0 20 40 Time( min) 60 80 100 20 40 60 80 100 Time( min) Fig 11 The pseudo-first-order kinetics of degradation of (a) MB and (b) RhB over SnO2/TiO2 nanoparticles at different calcination temperatures S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 409 Fig 12 Effect of calcination temperature on the %xathene for SnO2/TiO2 nanoparticles small amounts of colorless intermediates that not degraded The significant COD removal values confirm the mineralization of MB and RhB The kinetic study of the photocatalytic degradation of MB and RhB was investigated for SnO2/TiO2 nanoparticles calcined at 400 , 500 , 600 , and 700  C by LangmuireHinshelwood kinetic model This model belongs to the first-order kinetics according to the following formula [67]: and low surface defects, which in turn enhanced the photocatalytic activity [6,64] Also, the samples that calcined blew 500  C show weak photocatalytic activity than that calcined at 500  C due to low crystallization of anatase phase [31] As the temperature increases above 500  C, the photoactivity decreases due to the increases in phase transformation [65] Increasing the amount of rutile phase compared to that of the anatase phase led to decrease the photodegradation of MB, RhB, and phenol because the photocatalytic activity of rutile phase is lower than that of the anatase phase [36,66] Fig shows the effects of the addition of radicals scavengers on the photodegradation of MB and RhB over SnO2/TiO2 calcined at 500  C The results showed slightly retardation of MB and RhB degradation after additions of Na2EDTA and BQ indicating small effects of Hỵ and $OĂ species in the photodegrading of MB and RhB, while the additions of CCl4 and IPA were accompanied with remarkably decrease in the photodegradation of MB and RhB indicating that ee and $OH played the main role in the degradation process Scheme illustrates the suggested photodegradation mechanism of MB, RhB and phenol over SnO2/TiO2 Fig 10 shows the %COD removal of MB and RhB solutions after photodegradation for 180 of irradiation The results illustrate that the SnO2/TiO2 that calcined at 500  C showed the highest photodegradation and %COD removal values of MB and RhB, indicating that the calcination at 500  C is the appropriate temperature The difference in the values of both photodegradation of MB and RhB and %COD refers to the presence of  In Co Ct  ¼ kt where Co and Ct are concentrations of dye at initial and after irradiation time t (min) and k is the rate constant of dyes photodegradation Fig 11a, b show the kinetic curves of photodegradation of MB and RhB over SnO2/TiO2 nanoparticles, respectively The rate constants (k) and the correlation coefficients (R2) were calculated and listed in Table The linear relationship between ln (Co/C) and t indicates that the degradation of MB and RhB obey the pseudo-first-order reaction The value of k increases with increasing the calcination temperature to reach a maximum at 500  C and then decreases as the calcination temperature increases 3.8.2 Synthesis of 14-phenyl-14H-dibenzo [a,j] xanthene O OH H + SnO2/TiO2 O 410 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 100 % Xanthene 80 60 40 20 fresh run1 run2 run3 run4 Reuse Fig 13 Effect of reuse of SnO2/TiO2 nanoparticles calcined at 500  C on the % yield of xanthene Effect of calcination temperature of SnO2/TiO2 nanoparticles on the formation of xanthene is shown in Fig 12 and Table The results illustrate that the % yield increased with increasing the calcination temperature to 500  C and then decreased as the calcination temperature increased The calcination at 500  C is the optimum temperature of SnO2/TiO2 nanoparticles where the catalyst showed the highest catalytic activity Compared with other results obtained over other catalysts as sulfamic acid/Cr-MIL-101 [68], modified SBA-15, MCM-41 [69], ZnO [70] and NbCl4 [71] indicate that the SnO2/TiO2 acted as an efficacious catalyst The reusability of SnO2/TiO2 nanoparticles calcined at 500  C was checked using the recovered catalyst The catalyst was recovered by dissolving the product in chloroform and separated by simple filtration, washed with chloroform and dried at 100  C for h The results showed that no significant loss in the catalytic activity of the SnO2/TiO2 nanoparticles with increasing the number of reuse times of the catalyst as shown in Fig 13 Conclusion The SnO2/TiO2 nanoparticles have been successfully synthesized via the surfactant-assisted sol-gel method The results showed that the anatase to rutile phase transformation and the crystallite size increased with increasing the calcination temperature The anatase to rutile phase transformation increased with increasing the calcination temperature and the anatase phase disappeared at 700  C The optimum calcination temperature of the SnO2/TiO2 catalyst is 500  C At this temperature, the % yield of xanthene was 93.5% whereas the photodegradation percentage of MB and RhB dyes was 100% and 90% for phenol after h Increasing the calcination temperature over 500  C led to a sharp decrease in the catalytic activity The presence of anatase and rutile phases together showed a higher activity compared with anatase or rutile alone These results show that the catalytic activities and physicochemical properties of the SnO2/TiO2 nanoparticles strongly depend on the calcination temperature References [1] S.M Hassan, M.A Mannaa, A.A Ibrahim, Nano-sized mesoporous phosphated tin oxide as an efficient solid acid catalyst, RSC Adv (2019) 810e818 [2] M.B Gawande, R.K Pandey, R.V Jayaram, Role of mixed metal oxides in catalysis sciencedversatile applications in organic synthesis, Catal Sci Technol (2012) 1113 [3] S.E Hosseini Yeganeh, M Kazazi, B Koozegar Kaleji, S.H Kazemi, B Hosseinzadeh, Electrophoretic deposition of Sn-doped TiO2 nanoparticles and its optical and photocatalytic properties, J Mater Sci Mater Electron 29 (2018) 10841e10852 [4] S.M El-Dafrawy, M Farag, S.M Hassan, Photodegradation of organic compounds using chromium oxide-doped nano-sulfated zirconia, Res Chem Intermed 43 (2017) 6343e6365 [5] M.A Mannaa, S.M Hassan, A.I Ahmed, Synthesis and bioactivities of H3 PW12 O40/SnO2 -TiO2 nanocomposite, Int J Mod Chem 10 (2018) 69e79 [6] M Zhou, J Yu, S Liu, P Zhai, L Jiang, Effects of calcination temperatures on photocatalytic activity of SnO2/TiO2 composite films prepared by an EPD method, J Hazard Mater 154 (2008) 1141e1148 [7] L Zhang, Y Li, Q Zhang, H Wang, Well-dispersed Pt nanocrystals on the heterostructured TiO2/SnO2 nanofibers and the enhanced photocatalytic properties, Appl Surf Sci 319 (2014) 21e28 [8] S Asuha, X.G Zhou, S Zhao, Adsorption of methyl orange and Cr(VI) on mesoporous TiO2 prepared by hydrothermal method, J Hazard Mater 181 (2010) 204e210 [9] P Kongsong, L Sikong, S Niyomwas, V Rachpech, Photocatalytic antibacterial performance of glass fibers thin film coated with N-doped SnO2/TiO2, Sci World J 2014 (2014) [10] Z Pei, Z Kaiqiang, D Yu, B Bo, G Weisheng, S Yourui, Adsorption of organic dyes by TiO2 @Yeast-carbon composite microspheres and their in situ regeneration evaluation, J Nanomater 2015 (2015) [11] S.M Hassan, A.A Ibrahim, S.A El-Hakam, M.A Mannaa, Surface acidity and catalytic activity of phosphomolybdic acid/SnO2 catalysts, Int J Mod Chem (2013) 104e116 n, M Ostwald, G Berndes, G Lakshmi, [12] L Axelsson, M Franze N.H Ravindranath, Perspective: jatropha cultivation in southern India: assessing farmers' experiences, Biofuels Bioprod Biorefining (2012) 246e256 [13] L Sikong, J Damchan, K Kooptarnond, S Niyomwas, Effect of doped SiO2 and calcinations temperature on phase transformation of TiO2 photocatalyst prepared by sol-gel method, Songklanakarin J Sci Technol 30 (2008) 385e391 [14] K.H Bourne, F.R Cannings, R.C Pitkethly, The structure and properties of acid sites in a mixed-oxide system I Synthesis and infrared characterization, J Phys Chem 74 (1970) 2197 [15] S.-T Ong, P.-S Keng, W.-N Lee, S.-T Ha, Y.-T Hung, Dye waste treatment, Water (2011) 157e176 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 [16] H ullah, I Khan, Z.H Yamani, A Qurashi, Sonochemical-driven ultrafast facile synthesis of SnO2 nanoparticles: growth mechanism structural electrical and hydrogen gas sensing properties, Ultrason Sonochem 34 (2017) 484e490 [17] V Vimonses, S Lei, B Jin, C.W.K Chow, C Saint, Kinetic study and equilibrium isotherm analysis of Congo Red adsorption by clay materials, Chem Eng J 148 (2009) 354e364 [18] L.C Chen, F.R Tsai, S.H Fang, Y.C Ho, Properties of sol-gel SnO2/TiO2 electrodes and their photoelectrocatalytic activities under UV and visible light illumination, Electrochim Acta 54 (2009) 1304e1311 [19] S.M Hassan, M.A Mannaa, Photocatalytic degradation of brilliant green dye by SnO2/TiO2 nanocatalysts, Int J Nano Mater Sci (2016) 9e19 [20] X Wan, R Ma, S Tie, S Lan, Effects of calcination temperatures and additives on the photodegradation of methylene blue by tin dioxide nanocrystals, Mater Sci Semicond Process 27 (2014) 748e757 [21] N Wetchakun, B Incessungvorn, K Wetchakun, S Phanichphant, Influence of calcination temperature on anatase to rutile phase transformation in TiO2 nanoparticles synthesized by the modified solegel method, Mater Lett 82 (2012) 195e198 [22] G Yang, Z Jiang, H Shi, T Xiao, Z Yan, Preparation of highly visible-light active N-doped TiO2 photocatalyst, J Mater Chem 20 (2010) 5301 [23] G Yang, T Xiao, J Sloan, G Li, Z Yan, Lowerature synthesis of visible-light active fluorine/sulfur co-doped mesoporous TiO2 microspheres, Chem Eur J 17 (2011) 1096e1100 [24] C Li, W Yang, Q Li, TiO2-based photocatalysts prepared by oxidation of TiN nanoparticles and their photocatalytic activities under visible light illumination, J Mater Sci Technol 34 (2018) 969e975 [25] H Shi, M Zhou, D Song, X Pan, J Fu, J Zhou, S Ma, T Wang, Highly porous SnO2/TiO2 electrospun nanofibers with high photocatalytic activities, Ceram Int 40 (2014) 10383e10393 [26] J Chen, X Nie, H Shi, G Li, T An, Synthesis of TiO2 hollow sphere multimer photocatalyst by etching titanium plate and its application to the photocatalytic decomposition of gaseous styrene, Chem Eng J 228 (2013) 834e842 [27] S Bagwasi, B Tian, J Zhang, M Nasir, Synthesis, characterization and application of bismuth and boron Co-doped TiO2: a visible light active photocatalyst, Chem Eng J 217 (2013) 108e118 [28] M Li, S Zhang, L Lv, M Wang, W Zhang, B Pan, A thermally stable mesoporous ZrO2-CeO2-TiO2 visible light photocatalyst, Chem Eng J 229 (2013) 118e125 [29] V Rodríguez-Gonz alez, S.O Alfaro, L.M Torres-Martínez, S.H Cho, S.W Lee, Silver-TiO2 nanocomposites: synthesis and harmful algae bloom UV-photoelimination, Appl Catal B Environ 98 (2010) 229e234 [30] L Kong, G Duan, G Zuo, W Cai, Z Cheng, Rattle-type Au@TiO2 hollow microspheres with multiple nanocores and porous shells and their structurally enhanced catalysis, Mater Chem Phys 123 (2010) 421e426 [31] S Wang, L Zhao, J Ran, Z Shu, G Dai, P Zhai, Effects of calcination temperatures on photocatalytic activity of ordered titanate nanoribbon/SnO2 films fabricated during an EPD process, Int J Photoenergy 2012 (2012) 1e7 [32] Y Gai, J Li, S.S Li, J.B Xia, S.H Wei, Design of narrow-gap TiO2: a passivated codoping approach for enhanced photoelectrochemical activity, Phys Rev Lett 102 (2009) 23e26 n, M.C Hidalgo, J.A Navío, Photocatalytic behaviour of sulphated TiO2 [33] G Colo for phenol degradation, Appl Catal B Environ 45 (2003) 39e50 [34] H Kim, J Kim, W Kim, W Choi, Enhanced Photocatalytic and Photoelectrochemical Activity in the Ternary Hybrid of CdS/TiO2/WO3 through the Cascadal Electron Transfer, 2011, pp 9797e9805 [35] D.R Baker, P.V Kamat, Photosensitization of TiO2 nanostructures with CdS quantum dots: particulate versus tubular support architectures, Adv Funct Mater 19 (2009) 805e811 [36] M Huang, S Yu, B Li, D Lihui, F Zhang, M Fan, L Wang, J Yu, C Deng, Influence of preparation methods on the structure and catalytic performance of SnO2-doped TiO2photocatalysts, Ceram Int 40 (2014) 13305e13312 [37] D Li, X Cheng, X Yu, Z Xing, Preparation and characterization of TiO2 based nanosheets for photocatalytic degradation of acetylsalicylic acid: influence of calcination temperature, Chem Eng J 279 (2015) 994e1003 [38] A Simpraditpan, T Wirunmongkol, S Pavasupree, W Pecharapa, Effect of calcination temperature on structural and photocatalyst properties of nanofibers prepared from low-cost natural ilmenite mineral by simple hydrothermal method, Mater Res Bull 48 (2013) 3211e3217 [39] R Jiang, H.Y Zhu, H.H Chen, J Yao, Y.Q Fu, Z.Y Zhang, Y.M Xu, Effect of calcination temperature on physical parameters and photocatalytic activity of mesoporous titania spheres using chitosan/poly(vinyl alcohol) hydrogel beads as a template, Appl Surf Sci 319 (2014) 189e196 [40] M Zhang, Q Wang, C Chen, L Zang, W Ma, J Zhao, Oxygen atom transfer in the photocatalytic oxidation of alcohols by tio2: oxygen isotope studies, Angew Chem Int Ed 48 (2009) 6081e6084 [41] G Wang, L Xu, J Zhang, T Yin, D Han, Enhanced photocatalytic activity of TiO2 powders (P25) via calcination treatment, Int J Photoenergy 2012 (2012) [42] S.M Hassan, A.I Ahmed, M.A Mannaa, Structural, photocatalytic, biological and catalytic properties of SnO2/TiO2 nanoparticles, Ceram Int 44 (2018) 6201e6211 [43] S.M Hassan, A.I Ahmed, M.A Mannaa, Surface acidity, catalytic and photocatalytic activities of new type H3PW12O40/Sn-TiO2 nanoparticles, Colloids Surfaces A Physicochem Eng Asp 577 (2019) 147e157 [44] M.M Mohamed, W.A Bayoumy, T.Y Mansour El-Ashkar, M.E Goher, M.H Abdo, Graphene oxide dispersed in N-TiO2 nanoplatelets and their implication in [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] 411 wastewater remediation under visible light illumination: photoelectrocatalytic and photocatalytic properties, J Environ Chem Eng (2019) 102884 H.R Shaterian, M Honarmand, A.R Oveisi, Multicomponent synthesis of 3,5diaryl-2,6-dicyanoanilines under thermal solvent-free conditions, Monatshefte Für Chemie Chem Mon 141 (2010) 557e560 B Rajitha, B Sunil Kumar, Y Thirupathi Reddy, P Narsimha Reddy, N Sreenivasulu, Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14H-dibenzo[a.j]xanthenes under conventional heating and microwave irradiation, Tetrahedron Lett 46 (2005) 8691e8693 A Omri, S.D Lambert, J Geens, F Bennour, M Benzina, Synthesis, surface characterization and Photocatalytic activity of TiO2supported on Almond shell activated carbon, J Mater Sci Technol 30 (2014) 894e902 Y Chen, A Li, Q Li, X Hou, L.N Wang, Z.H Huang, Facile fabrication of three-dimensional interconnected nanoporous N-TiO2 for efficient photoelectrochemical water splitting, J Mater Sci Technol 34 (2018) 955e960 J Zhao, W Wang, Y Liu, J Ma, X Li, Y Du, G Lu, Ordered mesoporous Pd/SnO2 synthesized by a nanocasting route for high hydrogen sensing performance, Sensor Actuator B Chem 160 (2011) 604e608 J.F Porter, Y.G Li, C.K Chan, Effect of calcination on the microstructural characteristics and photoreactivity of Degussa P-25 TiO2, J Mater Sci 34 (1999) 1523e1531 S.-L Chen, A.-J Wang, C Dai, J.B Benziger, X.-C Liu, The effect of photonic band gap on the photo-catalytic activity of nc-TiO2/SnO2 photonic crystal composite membranes, Chem Eng J 249 (2014) 48e53 R Nirmala, H.Y Kim, R Navamathavan, C Yi, J.J Won, K Jeon, A Yousef, R Afeesh, M El-Newehy, Photocatalytic activities of electrospun tin oxide doped titanium dioxide nanofibers, Ceram Int 38 (2012) 4533e4540 Q Wang, Y Fang, H Meng, W Wu, G Chu, H Zou, D Cheng, J Chen, Enhanced simulated sunlight induced photocatalytic activity by pomegranate-like S doped SnO2 @TiO2 spheres, Colloids Surfaces A Physicochem Eng Asp 482 (2015) 529e535 D Shaposhnik, R Pavelko, E Llobet, F Gispert-Guirado, X Vilanova, Hydrogen sensors on the basis of SnO2-TiO2 systems, Sensor Actuator B Chem 174 (2012) 527e534 H Roh, I Eum, D Jeong, B.E Yi, J Na, C.H Ko, The effect of calcination temperature on the performance of Ni/MgOeAl2O3 catalysts for decarboxylation of oleic acid, Catal Today 164 (2011) 457e460 N.P Tangale, P.S Niphadkar, V Samuel, S.S Deshpande, P.N Joshi, S.V Awate, Synthesis of Sn-containing anatase (TiO2) by sol-gel method and their performance in catalytic water splitting under visible light as a function of tin content, Mater Lett 171 (2016) 50e54 K Lalitha, G Sadanandam, V.D Kumari, M Subrahmanyam, B Sreedhar, N.Y Hebalkar, Highly stabilized and finely dispersed Cu2O/TiO2 : a promising visible sensitive photocatalyst for continuous production of hydrogen from glycerol:water mixtures, J Phys Chem C 114 (2010) 22181e22189 A.A Lisachenko, V.N Kuznetsov, M.N Zakharov, R.V Mikhailov, The interaction of O2 , NO, and N2O with surface defects of dispersed titanium dioxide, Kinet Catal 45 (2004) 189e197 n, M.C Hidalgo, G Munuera, I Ferino, M.G Cutrufello, J.A Navío, G Colo Structural and surface approach to the enhanced photocatalytic activity of sulfated TiO2 photocatalyst, Appl Catal B Environ 63 (2006) 45e59 S Sarkar, N.S Das, K.K Chattopadhyay, Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering, Solid State Sci 33 (2014) 58e66 G Zhao, L Liu, J Li, Q Liu, Efficient removal of dye MB: through the combined action of adsorption and photodegradation from NiFe2O4/Ag3PO4, J Alloy Comp 664 (2016) 169e174 Y.Y Wang, Y Zhang, F Yu, C Jin, X Liu, J Ma, Y.Y Wang, Y Huang, J Wang, Correlation investigation on the visible-light-driven photocatalytic activity and coordination structure of rutile Sn-Fe-TiO2 nanocrystallites for methylene blue degradation, Catal Today 258 (2015) 112e119 Q Chen, H Liu, Y Xin, X Cheng, Electrochimica Acta TiO2 nanobelts e effect of calcination temperature on optical , photoelectrochemical and photocatalytic properties, Electrochim Acta 111 (2013) 284e291 H.S Zhuang, H.L Xia, T Zhang, D.C Xiao, Synthesis , characterization , and visible-light photocatalytic activity of Fe2 O3/SnO2 nanocomposites, Mater Sci 26 (2008) 517e526 J Cai, W Xin, G Liu, D Lin, D Zhu, Effect of calcination temperature on structural properties and photocatalytic activity of Mn-C-codoped TiO2, Mater Res 19 (2015) 401e407 R Zhang, H Wu, D Lin, W Pan, Preparation of necklace-structured TiO2/SnO2 hybrid nanofibers and their photocatalytic activity, J Am Ceram Soc 92 (2009) 2463e2466 P Kongsong, L Sikong, S Niyomwas, V Rachpech, Photocatalytic degradation of glyphosate in water by N-doped SnO2/TiO2 thin-film-coated glass fibers, Photochem Photobiol 90 (2014) 1243e1250 S.A El-Hakam, S.E Samra, S.M El-Dafrawy, A.A Ibrahim, R.S Salama, A.I Ahmed, Synthesis of sulfamic acid supported on Cr-MIL-101 as a heterogeneous acid catalyst and efficient adsorbent for methyl orange dye, RSC Adv (2018) 20517e20533 J Mondal, M Nandi, A Modak, A Bhaumik, Functionalized mesoporous materials as efficient organocatalysts for the syntheses of xanthenes, J Mol Catal A Chem 363e364 (2012) 254e264 412 S.M Hassan et al / Journal of Science: Advanced Materials and Devices (2019) 400e412 [70] G.B Dharma Rao, M.P Kaushik, A.K Halve, An efficient synthesis of naphtha [1,2-e]oxazinone and 14-substituted-14H- dibenzo[a,j]xanthene derivatives promoted by zinc oxide nanoparticle under thermal and solvent-free conditions, Tetrahedron Lett 53 (2012) 2741e2744 [71] A De Andrade Bartolomeu, M.L De Menezes, L.C Da Silva Filho, Efficient onepot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives promoted by niobium pentachloride, Chem Pap 68 (2014) 1593e1600  ... enhances the photocatalytic activity [40,41] The present study aims to study the effect of phase changes on the photocatalytic and catalytic properties of the SnO2/ TiO2 nanoparticles The catalytic activity. .. 2.3.1 Photocatalytic activity evaluation The photocatalytic activity of the SnO2/ TiO2 nanoparticles was measured by the photodegradation of MB, RhB and phenol solutions under UV-vis irradiation The. .. reuse of SnO2/ TiO2 nanoparticles calcined at 500  C on the % yield of xanthene Effect of calcination temperature of SnO2/ TiO2 nanoparticles on the formation of xanthene is shown in Fig 12 and