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Influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites prepared by hydrothermal process
Accepted Manuscript Influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites prepared by hydrothermal process Huang Jianfeng, Wang Dan, Yin Lixiong, Cao Liyun, Ouyang Haibo, Li Jiayin, Hao Wei PII: DOI: Reference:
S0925-8388(14)01286-9 http://dx.doi.org/10.1016/j.jallcom.2014.05.179 JALCOM 31368
To appear in: Received Date: Revised Date: Accepted Date:
20 January 2014 12 May 2014 24 May 2014
Please cite this article as: H. Jianfeng, W. Dan, Y. Lixiong, C. Liyun, O. Haibo, L. Jiayin, H. Wei, Influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites prepared by hydrothermal process, (2014), doi: http://dx.doi.org/10.1016/j.jallcom.2014.05.179
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites prepared by hydrothermal process Huang Jianfeng*, Wang Dan, Yin Lixiong, Cao Liyun, Ouyang Haibo, Li Jiayin, Hao Wei School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an, Shaanxi, 710021, China Abstract: Size–controlled samarium hydroxide (Sm(OH)3) nanocrystallites were prepared by a facile hydrothermal process using diethylenetriamine (DETA) as both alkaline and complexing agents. The phase composition, surface groups, morphologies, specific surface area and optical properties of the samples were characterized by X–ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, N2–sorption BET surface area and UV–vis diffuse reflectance spectroscopy. Results show that with the increase of DETA addition, the average length of the Sm(OH)3 nanorods was decreased. Sm(OH)3 nanorods prepared at 0.66 Vol% of DETA shows high photocatalytic activity to degrade Rhodamine B (RhB), which degradation efficiency reaches 90.3% under UV irradiation for 40 min. The big specific surface area of Sm(OH)3 nanorods are believed to greatly affect the final degradation efficiency of RhB in our research. Keywords: Samarium hydroxide; Nanostructured materials; Photocatalytic activity; Chemical synthesis.
*
Corresponding author: School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an
710021, China. E-mail addresses: [email protected] (Huang Jianfeng). Tel/fax: +86 29 86168802.
1. Introduction Lanthanide compounds were widely used as catalysts [1, 2], high–performance phosphors [3, 4], magnetic materials [5] and other functional materials as a result of their novel electronic [6], optical [7], and chemical properties [8] arising from their 4f electrons. Now, increasing interest in synthesis of lanthanide hydroxides, which are typical lanthanide functional materials, has been caught [9–11]. Many recent researches have demonstrated that hydrothermal process [12, 13] and homogeneous precipitation method [14, 15] were widely used to prepare lanthanide hydroxides, due to their facile, high efficiency and low cost. Up to now, the related literature reports about Sm(OH)3, which is one of the typical lanthanide hydroxide, mainly focus on the simple synthesis stage [12, 14, 16]. The properties of Sm(OH)3 still needs to be further investigated. Herein, we report the Sm(OH)3 nanocrystallites exhibiting high photocatalytic activity with controlled rod–like microstructure were synthesized by a facile and environmental hydrothermal process. In our previous research, the morphology–related photocatalytic activity of Sm(OH)3 nanocrystallites has been found [17]. To further research the affects of morphology on the photocatalytic activity of Sm(OH)3 nanocrystallites, diethylenetriamine (DETA) was proposed to use as both alkaline and complexing agents in this work. The influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites was particularly investigated. Rhodamine B (RhB) was used to test the photocatalytic efficiency of the prepared Sm(OH)3 nanocrystallites under UV
2
irradiation. The photocatalysis degradation reaction kinetics of RhB, which catalyzed by the as– prepared Sm(OH)3 nanocrystallites, was also researched in this paper. 2. Experimental 2.1. Preparation Sm(NO3)3 ·6H2O (Shanghai Diyang Chemical Industry Co. Ltd.) and DETA (Tianjin Kemiou Chemical Reagent Co. Ltd.) were of analytical reagent (A.R.) grade and used without further purification in our study. Distilled water was used in the whole experiment. First, 0.375 mmol Sm(NO3)3·6H2O was dissolved in 15 ml distilled water, then different volumes of DETA was added dropwise with magnetic stirring to form the precursor solution with 0.27, 0.40, 0.66 and 1.05 Vol% of DETA, respectively. The precursor solution was transferred to a 25 ml Teflon–lined stainless steel autoclave with the filling capacity of 60% and maintained in an oven at 160 °C for 24 h after stirring for 1 h. Afterwards, the products were centrifuged and washed with distilled water and dehydrated alcohol for several times, finally dried in the vacuum drying oven at 60 °C for 3 h. 2.2. Characterization The crystalline microstructures of the as–prepared powders were characterized by a powder X– ray diffraction (XRD, Rigaku D/max–2000) with Cu Kα radiation (λ=0.15406 nm). Fourier transform infrared spectra (FT–IR) were recorded using a VERTE70 FT–IR Spectrometer. The morphologies of the samples were observed by field emission scanning electron microscopy (FE–SEM, Hitachi S– 4800). The specific surface areas of the samples were measured by nitrogen adsorption method using
3
an American Quantachrome NOVA–2200E instrument and UV–vis diffuse reflectance spectra of the samples were measured by Shimadzu UV–2450 UV–vis spectrophotometer. 2.3. Photocatalytic activity test Photocatalytic activities of the prepared Sm(OH)3 nanocrystallites were evaluated by photocatalytic degradation of 5 mg·L–1 Rhodamine B (A.R. Sinopharm Chemical Reagent Co. Ltd.) aqueous solution. The photocatalytic activity test was carried out by employing a BL–GHX–V photocatalytic reactor (Xi’an, BILOBN, Co. Ltd.) with a 500 W mercury lamp as UV light source. The loading amount of catalysts was 1.0 g·L–1. Before illumination, the suspensions of Rhodamine B (RhB) with catalysts were magnetically stirred in the dark for 30 min, after dispersing in an ultrasonic bath for 5 min, to ensure the establishment of an adsorption–desorption equilibrium between Sm(OH)3 nanocrystallites and RhB. Then, the solution was exposed to a 500 W mercury lamp under magnetic stirring. By the irradiation time prolong, 6 ml of the solution was collected by centrifugation each 5 min. The concentrations of the remnant RhB in the collected solution were monitored by UV–vis spectroscopy (Unico UV–2600) at 553 nm [17]. In the process of photocatalytic reaction, the degradation efficiency of RhB was calculated by Eq. (1):
Degradation efficiency (%) = (1- Ct/C0) ×100%
(1)
Where C0 represents the initial concentration of RhB aqueous solution and Ct represents the concentration of RhB aqueous solution after different minutes of UV irradiation. 3. Results and discussion
4
3.1. Phase analysis (Fig.1. is supposed to be here.) Fig.1 shows the XRD patterns of the samples prepared at different volume percents of DETA. All the diffraction peaks of the samples shown in Fig.1 can be readily indexed to the pure typical hexagonal Sm(OH)3 (JCPDS No.83–2036). The well crystallized Sm(OH)3 nanocrystallites were obtained when the addition of DETA increased to 0.40 Vol%. The average crystallinity of Sm(OH)3 nanocrystallites prepared at 0.27, 0.40, 0.66 and 1.05 Vol% of DETA were calculated to be 42.35%, 53.22%, 60.42% and 61.80%, respectively, based on the XRD data. The average crystallinity of the as–prepared samples was increased with the volume percents of DETA increased from 0.40% to 1.05%. The adequate amount of DETA can not only hydrolyze to release enough OH– but also as complexing agents to control the growth rate of crystal nucleus, which is good to the crystallization process of Sm(OH)3 nanocrystallites. 3.2. FT–IR analysis (Fig.2. is supposed to be here.) The Sm(OH)3 nanocrystallites prepared at 0.66 and 1.05 Vol% of DETA were further supported by FT–IR spectra (Fig.2). In the FT–IR spectra, main strong absorption peaks were observed at ～ 3608 and 686 cm–1, which represent the broad stretching and bending vibrations of O–H and Sm–O–H bond, respectively [14]. Moreover, the weak absorption peaks located at 1510 and 1380 cm–1 were related to the stretching vibrations of NO3–, which may be due to the raw materials (Sm(NO3)3·6H2O).
5
Finally, the characterized absorption peaks (1250 ～1140, 1465, 1650～1600, 3400～3500 cm–1) attributed to DETA are not found in the FT–IR spectra, exhibiting that the prepared Sm(OH)3 nanocrystallites are without residual DETA encapsulated. 3.3. Morphology analysis (Fig.3. is supposed to be here.) The SEM images of the samples prepared at different volume percents of DETA are shown in Fig.3. It can be obviously observed that the morphologies of the as–prepared Sm(OH)3 nanocrystallites are rod–like with different sizes. The average length of the sample prepared at 0.27, 0.40, 0.66 and 1.05 Vol% of DETA is about 694, 340, 153 and 123 nm, respectively. This can be calculated from the histograms of the length distribution of Sm(OH)3 nanorods (Fig.4) according to Fig.3. With the increase of DETA addition, the average length of the nanorods was shortened obviously, which suggests increasing addition amount of DETA may be beneficial to increase the nucleation amount but inhibit the orientation grow of Sm(OH)3 nanocrystallites. (Fig.4. is supposed to be here.) The Sm(OH)3 nanocrystallites prepared at 0.27, 0.40 and 0.66 Vol% of DETA exhibits dispersed nanorods morphology. The average length of the sample prepared at 0.66 Vol% of DETA is 153 nm, which length distribution is uniform. When the addition amount of DETA increased to 1.05 Vol%, although the average length of the as–prepared sample was decreased to about 123 nm, the particles were agglomerated (Fig.3d) and the length distribution is nonuniform. The N2–sorbtion isotherm for
6
the samples prepared at different amounts of DETA is shown in Fig.5, which based on the method of BET specific surface area analysis. The specific surface area of the sample prepared at 0.27, 0.40, 0.66 and 1.05 Vol% is calculated to be 67.28, 71.84, 79.41 and 53.27 m2/g, respectively. Though the average length of the Sm(OH)3 nanorods prepared at 1.05 vol% of DETA is small (123 nm), the specific area of the sample is small, which is caused by the agglomeration morphology. These results show that the concentration of DETA plays a crucial role in the morphology control of the Sm(OH)3 nanocrystallites under the hydrothermal condition. (Fig.5. is supposed to be here.) DETA was used both as alkaline agent and complexing agent, which can not only hydrolyze to release OH– but also as ligand to form a Sm3+–DETA complex, due to its functional group of –NH2. The increase of volume percent of DETA will increase the concentrations of OH– would definitely weakened the coordination power between Sm3+ and DETA, therefore, the (NH2CH2CH2)2NH2+ ion in Sm3+–DETA would be gradually replaced by OH– and finally Sm(OH)3 nuclei appear. With the nucleation and their follow–up growth, Sm(OH)3 crystal nucleus tends to assembly to grow along a certain direction based on the relatively weak hydrogen–bond and van der Waals force interactions to reach rod–like morphology. The tendency to assemble to grow along a certain direction of Sm(OH)3 usually had been weakened to some extent when the concentration of DETA is high, in this case, Sm(OH)3 usually formed rod–like structure with lower aspect ratios. When there is too much redundant DETA in the reaction solution, the coordination effect and hydrogen–bond interactions
7
become stronger and lead to the Sm(OH)3 nanorod with small size, which also easy to get aggregation. The whole possible growth patterns of the nanorods prepared at different volume ratio of DETA are shown in Fig.6. (Fig.6. is supposed to be here.) 3.4. Optical and photocatalytical properties The UV–visible diffuse reflection spectra of the as–prepared Sm(OH)3 nanocrystallites are shown in Fig.7. The steep shape of the spectra indicates that the samples have good absorption property of deep ultraviolet. The samples prepared at 0.40 and 0.66 Vol% of DETA with the enhancing ultraviolet absorbing ability, which may be attributed to their smaller sizes. Nanosized rare earth compounds present great promise and opportunities for a new generation of catalysts [7]. Combine the good ultraviolet absorbing property and the unique 4f electrons structure of Sm(OH)3 nanocrystallites, the photocatalytic activity of Sm(OH)3 nanocrystallites was investigated in our research. (Fig.7. is supposed to be here.) The photocatalytic activity of the as–prepared hexagonal Sm(OH)3 nanocrystallites were evaluated by degradation of 5 mg·L–1 RhB aqueous solution under 500 W mercury lamp irradiation. The detailed results of the absorption spectra during the photocatalytic degradation process are shown in Fig.8a. As irradiation time prolong, the RhB absorption peak decreases in different extent without peak shifting, which suggests the degradation process follows an oxidation reaction, rather than a de– ethylation process of the RhB molecule [18]. The photocatalytic results of the Sm(OH)3
8
nanocrystallites prepared at different volume percents of DETA are shown in Fig.8b. The adsorption test shows that the adsorption–desorption equilibrium between Sm(OH)3 nanocrystallites and RhB was achieved after the dark stirring for 30 min. The blank test demonstrates that the degradation of RhB is slow without photocatalysts. The photocatalytic results exhibit that the as–prepared Sm(OH)3 nanocrystallites in our research can mainly degrade RhB under 500 W mercury lamp in only 40 min, especially that prepared at 0.66 Vol% of DETA, which degradation efficiency reaches 90.3%. (Fig.8. is supposed to be here.) The better photocatalytic activity of the Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA is achieved with RhB degradation efficiency reaches 90.3%. Whereas, the degradation efficiency of the sample prepared at 0.27, 0.40 and 1.05 Vol% of DETA only reaches 71.3%, 85.4% and 48.7%. The high photocatalytic activity of the sample prepared at 0.66 Vol% of DETA may arise from the unique optical and chemical properties of lanthanide compounds [7, 8] and its 1D nanorod structure with big specific surface area and good ultraviolet absorbing ability. Because the dispersive small 1D rod–like nanostructure has a big influence on the optical and photocatalytic properties of the materials [23]. Furthermore, the photocatalytic reactions are typically surface–based processes, the photocatalytic efficiency is closely related to the specific surface area, morphology and microstructure of the materials [24]. In addition, comparing with the well known photocatalysts, such as TiO2 [19, 20] and ZnO [21, 22], Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA shows promising photocatalytic activity to degrade RhB under UV irradiation.
9
The degradation rate is another way to directly evaluate the photocatalytic activity of the as– prepared samples. The heterogeneous photocatalytic reaction between Sm(OH)3 nanocrystallites and RhB aqueous solution can be described by the pseudo–first–order kinetics, which is rationalized in terms of the Langmuir–Hinshelwood model (L–H) modified to accommodate reactions occurring at a solid–liquid interface [25, 26]. The photocatalytic activity of Sm(OH)3 nanocrystallites for degradation of RhB obeys the pseudo–first–order reaction kinetics and its expression is as follows:
dc / dt = − KcC
(2)
ln(C 0 / Ct ) = Kct
(3)
Where Kc is the rate constant of the pseudo–first–order reaction. A plot of ln(C0/Ct) versus the UV irradiation time for the RhB photodegradation, which catalyzed by Sm(OH)3 nanocrystallites, is shown in Fig.9. A near linear relation between ln(C0 /Ct) and the irradiation time have been observed, which explains the photodegradation of RhB by Sm(OH)3 nanocrystallites follows the pseudo–first– order kinetics. The calculated Kc, the corresponding first–order kinetic equation and the R2 values are summarized in Table1. (Fig.9. is supposed to be here.) Table 1 Parameter and linear kinetic equation of photocatalytic reaction of the samples prepared at different volume percents of DETA with different specific surface areas. DETA
(Vol%)
Special surface area 2
First–order kinetic equation
Kc
(m /g)
10
R2
0.27
67.28
0.02922
ln(C0 /Ct)=0.02922t + 0.10707
0.98831
0.40
71.84
0.04772
ln(C0 /Ct)=0.04772t + 0.04913
0.99688
0.66
79.41
0.05819
ln(C0/Ct )=0.05819t + 0.00669
0.97636
1.05
53.27
0.01397
ln(C0 /Ct)=0.01397t + 0.07010
0.98162
The high value of R2 (>0.95) demonstrates the pseudo–first–order kinetic equation fit the photocatalytic degradation of RhB perfectly. The higher the pseudo–first–order rate constant (Kc) suggests the more outstanding photocatalytic activity. The fast degradation rate to degrade RhB aqueous solution was obtained by Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA, which is almost double that prepared at 0.27 Vol% of DETA. The fast degradation rate may be due to the good ultraviolet absorbing ability and the big specific surface area of the sample. The good ultraviolet absorbing ability and big specific surface area of the Sm(OH)3 nanorods are believed to greatly affect the final degradation rate and degradation efficiency of RhB in our research. 4. Conclusion In summary, pure Sm(OH)3 nanorods with controllable size have been successfully prepared by a facile hydrothermal process. It is found that DETA significantly influences the structure and photocatalytic activity of the Sm(OH)3 nanorods. With the addition of DETA increased from 0.27 to 1.05 Vol%, the average size of the samples decreased from 694 to 123 nm. Better photocatalytic activity of the sample prepared at 0.66 Vol% of DETA with the degradation efficiency of RhB reaches 90.3% under UV irradiation for 40 min, which may originate from the dispersive small and uniform nanorods microstructure with the big specific area of the sample. Moreover, the as–prepared samples
11
show significant photocatalytic activity to decompose RhB, which suggests their potential application as photocatalytic materials in the future. Acknowledgments The authors are grateful to National Key Technology R&D Program (No. 2013BAF09B02), International Science and Technology Cooperation Project Funding of Shaanxi Province (No. 2011KW–11), Innovation Team Assistance Foundation of Shaanxi Province (2013KCT–06), Innovation Team Assistance Foundation of Shaanxi University of Science and Technology (No.TD09–05), and Graduate Innovation Fund of Shaanxi University of Science and Technology. References [1] T.N. Parac–Vogt, K. Deleersnyder, K. Binnemans, J. Alloys Compd. 374 (2004) 46–49. [2] T. N. Parac–Vogt, K. Binnemans, Tetrahedron Lett. 45 (2004) 3137–3139. [3] K. Park, M.H. Heo, K.Y. Kim, S.J. Dhoble, Y. Kim, J.Y. Kim, Powder Technol. 237 (2013) 102– 106. [4] M. Saif, J. Lumin. 135 (2013) 187–195. [5] R Sen, D.K. Hazra, S. Koner, M. Helliwell, M. Mukherjee, A. Bhattacharjee, Polyhedron 29 (2010) 3183–3191. [6] I. Djerdj, G. Garnweitner, D.S. Su, N. Markus, J Solid State Chem. 180 (2007) 2154–2165. [7] G.F. Wang, Q. Peng, Y.D. Li, Acc. Chem. Res. 44(2011) 322–332. [8] E. Van Der Kolk, P. Dorenbos, Chem. Mater. 18(2006) 3458–3462.
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[9] J.S. Xie, Q.S. Wu, D. Zhang, Y.P. Ding, Cryst. Growth Des.9 (2009) 3889–3897. [10] Y.P. Fang, A.W. Xu, L.P. You, R.Q. Song, J.C. Yu, H. X. Zhang, Q. Li, H.Q. Liu, Adv. Funct. Mater. 12 (2003) 955–960. [11] Q.Y. Mu, Y.D. Wang, J. Alloys Compd. 509 (2011) 396–401. [12] N. Zhang, R. Yi, L.B. Zhou, G.H. Gao, R.G. Shi, G. Z. Qiu, L.X. He, Mater. Chem. Phys. 114 (2009) 160–167. [13] N. Zhang, X.H. Liu, R. Yi, R.R. Shi, G.H. Gao, G.Z Qiu, J.Phys. Chem. C 112 (2008) 17788– 17795. [14] Q.Y. Mu, Y.D. Wang, J. Alloys Compd. 509 (2011) 2060–2065. [15] J.X. Zhu, Z. Gui, Y.Y. Ding, Mater. Lett. 62 (2008) 2373–2376. [16] L.W. Qian, Y.C. Gui, S. Guo, Q. Gong, X.F. Qian, J. Phys. Chem. Solids. 70 (2009) 688–693. [17] D. Wang, J.F. Huang, L.X. Yin, L.Y. Cao, H.B. Ouyang, J.Y. Li, W. Hao, Mater. Lett. 116(2014) 393–395. [18] T.X. Wu, G.M. Liu, J.C. Zhao, J. Phys. Chem. B102 (1998) 5845–5851. [19] Z.L. He, W. X. Que, Y.C. He, Mater. Lett. 94(2013) 136–139. [20] M.M. Rashad, E.M. Elsayed, M.S. Al–Kotb, A.E. Shalan, J. Alloys Compd. 581 (2013) 71–78. [21] Q.P Luo, X.Y. Yu, B.X. Lei, H.Y. Chen, D.B. Kuang, C.Y. Su, J. Phys. Chem. C. 116 (2012) 8111–8117. [22] Y.C. Lu, L.L. Wang, D.J. Wang, T.F. Xie, L.P. Chen, Mater. Chem. Phys. 129 (2011) 281–287.
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[23] X.Y. Li, J. Wang, J.H. Yang, J.H. Lang, S.Q. Lü, M.B. Wei, X.W. Meng, C.L. Kon, X.F. Lei, J. Alloys Compd. 580 (2013) 205–210. [24] H. Tong, S.X. Ouyang, Y.P. Bi, N. Umezawa, O. Mitsutake, Adv. Mater. 24 (2012) 229–251. [25] D. Li, J.F. Huang, L.Y. Cao, J.Y. Li, H.B. Ouyang, C.Y. Yao, Ceram. Int. l40 (2014) 2647–2653. [26] L.L. Liu, J.F. Huang, L.Y. Cao, J.P. Wu, J. Fei, H.B. Ouyang, C.Y. Yao, Ceram. Int. l40 (2013) 3165–3171.
Figure captions
Fig.1. XRD patterns of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA. Fig.2. FT–IR spectra of the Sm(OH)3 nanocrystallites prepared at 0.66 Vol% and 1.05 Vol% of DETA. Fig.3. SEM images of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%. Fig.4. Histograms of the length distribution of Sm(OH)3 nanorods prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%. Fig.5. Nitrogen adsorption–desorption isotherm of Sm(OH)3 nanorods prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%. Fig.6. The schematic diagram of the possible growth pattern of the 1D Sm(OH)3 nanorods prepared at different volume ratio of DETA. Fig.7. UV–vis diffuses reflectance spectra of the Sm(OH)3 nanocrystallites prepared at different
14
volume percents of DETA. Fig.8. (a) UV–vis absorption spectra changes of RhB obtained by using the Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA as catalyst (b) Photocatalytic results of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA. Fig.9. Relationship between ln(C0 /Ct) and UV irradiation time of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%.
15
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
H NH+ H 2N
NH
NH 2
H
H
NH 2
crystallize
3+
+
Sm
NH +
NH2
N H2
assembly
growth crystallize
assembly
t an d un TA d e r DE
replace by OH nuclation
N H2
Sm(NO3)3 hydrolysis H2O DETA coordination
Figure 7
Figure 8
Figure 9
Table 1 Parameter and linear kinetic equation of photocatalytic reaction of the samples prepared at different volume percents of DETA with different specific surface areas. DETA
(Vol%)
Special surface area
(m2/g)
Kc
First–order kinetic equation
R2
0.27
67.28
0.02922
ln(C0 /Ct)=0.02922t + 0.10707
0.98831
0.40
71.84
0.04772
ln(C0 /Ct)=0.04772t + 0.04913
0.99688
0.66
79.41
0.05819
ln(C0/Ct)=0.05819t + 0.00669
0.97636
1.05
53.27
0.01397
ln(C0 /Ct)=0.01397t + 0.07010
0.98162
DETA was proposed to use as an alkaline agent to prepare Sm(OH)3 nanocrystallites. Size–controlled Sm(OH)3 nanorods were achieved by adjusting the addition of DETA. Size–related photocatalytic activity of Sm(OH)3 nanocrystallites was shown.
The photocatalysis degradation reaction kinetics of RhB was researched.
S0925-8388(14)01286-9 http://dx.doi.org/10.1016/j.jallcom.2014.05.179 JALCOM 31368
To appear in: Received Date: Revised Date: Accepted Date:
20 January 2014 12 May 2014 24 May 2014
Please cite this article as: H. Jianfeng, W. Dan, Y. Lixiong, C. Liyun, O. Haibo, L. Jiayin, H. Wei, Influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites prepared by hydrothermal process, (2014), doi: http://dx.doi.org/10.1016/j.jallcom.2014.05.179
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites prepared by hydrothermal process Huang Jianfeng*, Wang Dan, Yin Lixiong, Cao Liyun, Ouyang Haibo, Li Jiayin, Hao Wei School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an, Shaanxi, 710021, China Abstract: Size–controlled samarium hydroxide (Sm(OH)3) nanocrystallites were prepared by a facile hydrothermal process using diethylenetriamine (DETA) as both alkaline and complexing agents. The phase composition, surface groups, morphologies, specific surface area and optical properties of the samples were characterized by X–ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, N2–sorption BET surface area and UV–vis diffuse reflectance spectroscopy. Results show that with the increase of DETA addition, the average length of the Sm(OH)3 nanorods was decreased. Sm(OH)3 nanorods prepared at 0.66 Vol% of DETA shows high photocatalytic activity to degrade Rhodamine B (RhB), which degradation efficiency reaches 90.3% under UV irradiation for 40 min. The big specific surface area of Sm(OH)3 nanorods are believed to greatly affect the final degradation efficiency of RhB in our research. Keywords: Samarium hydroxide; Nanostructured materials; Photocatalytic activity; Chemical synthesis.
*
Corresponding author: School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an
710021, China. E-mail addresses: [email protected] (Huang Jianfeng). Tel/fax: +86 29 86168802.
1. Introduction Lanthanide compounds were widely used as catalysts [1, 2], high–performance phosphors [3, 4], magnetic materials [5] and other functional materials as a result of their novel electronic [6], optical [7], and chemical properties [8] arising from their 4f electrons. Now, increasing interest in synthesis of lanthanide hydroxides, which are typical lanthanide functional materials, has been caught [9–11]. Many recent researches have demonstrated that hydrothermal process [12, 13] and homogeneous precipitation method [14, 15] were widely used to prepare lanthanide hydroxides, due to their facile, high efficiency and low cost. Up to now, the related literature reports about Sm(OH)3, which is one of the typical lanthanide hydroxide, mainly focus on the simple synthesis stage [12, 14, 16]. The properties of Sm(OH)3 still needs to be further investigated. Herein, we report the Sm(OH)3 nanocrystallites exhibiting high photocatalytic activity with controlled rod–like microstructure were synthesized by a facile and environmental hydrothermal process. In our previous research, the morphology–related photocatalytic activity of Sm(OH)3 nanocrystallites has been found [17]. To further research the affects of morphology on the photocatalytic activity of Sm(OH)3 nanocrystallites, diethylenetriamine (DETA) was proposed to use as both alkaline and complexing agents in this work. The influence of DETA on the structure and photocatalytic activity of Sm(OH)3 nanocrystallites was particularly investigated. Rhodamine B (RhB) was used to test the photocatalytic efficiency of the prepared Sm(OH)3 nanocrystallites under UV
2
irradiation. The photocatalysis degradation reaction kinetics of RhB, which catalyzed by the as– prepared Sm(OH)3 nanocrystallites, was also researched in this paper. 2. Experimental 2.1. Preparation Sm(NO3)3 ·6H2O (Shanghai Diyang Chemical Industry Co. Ltd.) and DETA (Tianjin Kemiou Chemical Reagent Co. Ltd.) were of analytical reagent (A.R.) grade and used without further purification in our study. Distilled water was used in the whole experiment. First, 0.375 mmol Sm(NO3)3·6H2O was dissolved in 15 ml distilled water, then different volumes of DETA was added dropwise with magnetic stirring to form the precursor solution with 0.27, 0.40, 0.66 and 1.05 Vol% of DETA, respectively. The precursor solution was transferred to a 25 ml Teflon–lined stainless steel autoclave with the filling capacity of 60% and maintained in an oven at 160 °C for 24 h after stirring for 1 h. Afterwards, the products were centrifuged and washed with distilled water and dehydrated alcohol for several times, finally dried in the vacuum drying oven at 60 °C for 3 h. 2.2. Characterization The crystalline microstructures of the as–prepared powders were characterized by a powder X– ray diffraction (XRD, Rigaku D/max–2000) with Cu Kα radiation (λ=0.15406 nm). Fourier transform infrared spectra (FT–IR) were recorded using a VERTE70 FT–IR Spectrometer. The morphologies of the samples were observed by field emission scanning electron microscopy (FE–SEM, Hitachi S– 4800). The specific surface areas of the samples were measured by nitrogen adsorption method using
3
an American Quantachrome NOVA–2200E instrument and UV–vis diffuse reflectance spectra of the samples were measured by Shimadzu UV–2450 UV–vis spectrophotometer. 2.3. Photocatalytic activity test Photocatalytic activities of the prepared Sm(OH)3 nanocrystallites were evaluated by photocatalytic degradation of 5 mg·L–1 Rhodamine B (A.R. Sinopharm Chemical Reagent Co. Ltd.) aqueous solution. The photocatalytic activity test was carried out by employing a BL–GHX–V photocatalytic reactor (Xi’an, BILOBN, Co. Ltd.) with a 500 W mercury lamp as UV light source. The loading amount of catalysts was 1.0 g·L–1. Before illumination, the suspensions of Rhodamine B (RhB) with catalysts were magnetically stirred in the dark for 30 min, after dispersing in an ultrasonic bath for 5 min, to ensure the establishment of an adsorption–desorption equilibrium between Sm(OH)3 nanocrystallites and RhB. Then, the solution was exposed to a 500 W mercury lamp under magnetic stirring. By the irradiation time prolong, 6 ml of the solution was collected by centrifugation each 5 min. The concentrations of the remnant RhB in the collected solution were monitored by UV–vis spectroscopy (Unico UV–2600) at 553 nm [17]. In the process of photocatalytic reaction, the degradation efficiency of RhB was calculated by Eq. (1):
Degradation efficiency (%) = (1- Ct/C0) ×100%
(1)
Where C0 represents the initial concentration of RhB aqueous solution and Ct represents the concentration of RhB aqueous solution after different minutes of UV irradiation. 3. Results and discussion
4
3.1. Phase analysis (Fig.1. is supposed to be here.) Fig.1 shows the XRD patterns of the samples prepared at different volume percents of DETA. All the diffraction peaks of the samples shown in Fig.1 can be readily indexed to the pure typical hexagonal Sm(OH)3 (JCPDS No.83–2036). The well crystallized Sm(OH)3 nanocrystallites were obtained when the addition of DETA increased to 0.40 Vol%. The average crystallinity of Sm(OH)3 nanocrystallites prepared at 0.27, 0.40, 0.66 and 1.05 Vol% of DETA were calculated to be 42.35%, 53.22%, 60.42% and 61.80%, respectively, based on the XRD data. The average crystallinity of the as–prepared samples was increased with the volume percents of DETA increased from 0.40% to 1.05%. The adequate amount of DETA can not only hydrolyze to release enough OH– but also as complexing agents to control the growth rate of crystal nucleus, which is good to the crystallization process of Sm(OH)3 nanocrystallites. 3.2. FT–IR analysis (Fig.2. is supposed to be here.) The Sm(OH)3 nanocrystallites prepared at 0.66 and 1.05 Vol% of DETA were further supported by FT–IR spectra (Fig.2). In the FT–IR spectra, main strong absorption peaks were observed at ～ 3608 and 686 cm–1, which represent the broad stretching and bending vibrations of O–H and Sm–O–H bond, respectively [14]. Moreover, the weak absorption peaks located at 1510 and 1380 cm–1 were related to the stretching vibrations of NO3–, which may be due to the raw materials (Sm(NO3)3·6H2O).
5
Finally, the characterized absorption peaks (1250 ～1140, 1465, 1650～1600, 3400～3500 cm–1) attributed to DETA are not found in the FT–IR spectra, exhibiting that the prepared Sm(OH)3 nanocrystallites are without residual DETA encapsulated. 3.3. Morphology analysis (Fig.3. is supposed to be here.) The SEM images of the samples prepared at different volume percents of DETA are shown in Fig.3. It can be obviously observed that the morphologies of the as–prepared Sm(OH)3 nanocrystallites are rod–like with different sizes. The average length of the sample prepared at 0.27, 0.40, 0.66 and 1.05 Vol% of DETA is about 694, 340, 153 and 123 nm, respectively. This can be calculated from the histograms of the length distribution of Sm(OH)3 nanorods (Fig.4) according to Fig.3. With the increase of DETA addition, the average length of the nanorods was shortened obviously, which suggests increasing addition amount of DETA may be beneficial to increase the nucleation amount but inhibit the orientation grow of Sm(OH)3 nanocrystallites. (Fig.4. is supposed to be here.) The Sm(OH)3 nanocrystallites prepared at 0.27, 0.40 and 0.66 Vol% of DETA exhibits dispersed nanorods morphology. The average length of the sample prepared at 0.66 Vol% of DETA is 153 nm, which length distribution is uniform. When the addition amount of DETA increased to 1.05 Vol%, although the average length of the as–prepared sample was decreased to about 123 nm, the particles were agglomerated (Fig.3d) and the length distribution is nonuniform. The N2–sorbtion isotherm for
6
the samples prepared at different amounts of DETA is shown in Fig.5, which based on the method of BET specific surface area analysis. The specific surface area of the sample prepared at 0.27, 0.40, 0.66 and 1.05 Vol% is calculated to be 67.28, 71.84, 79.41 and 53.27 m2/g, respectively. Though the average length of the Sm(OH)3 nanorods prepared at 1.05 vol% of DETA is small (123 nm), the specific area of the sample is small, which is caused by the agglomeration morphology. These results show that the concentration of DETA plays a crucial role in the morphology control of the Sm(OH)3 nanocrystallites under the hydrothermal condition. (Fig.5. is supposed to be here.) DETA was used both as alkaline agent and complexing agent, which can not only hydrolyze to release OH– but also as ligand to form a Sm3+–DETA complex, due to its functional group of –NH2. The increase of volume percent of DETA will increase the concentrations of OH– would definitely weakened the coordination power between Sm3+ and DETA, therefore, the (NH2CH2CH2)2NH2+ ion in Sm3+–DETA would be gradually replaced by OH– and finally Sm(OH)3 nuclei appear. With the nucleation and their follow–up growth, Sm(OH)3 crystal nucleus tends to assembly to grow along a certain direction based on the relatively weak hydrogen–bond and van der Waals force interactions to reach rod–like morphology. The tendency to assemble to grow along a certain direction of Sm(OH)3 usually had been weakened to some extent when the concentration of DETA is high, in this case, Sm(OH)3 usually formed rod–like structure with lower aspect ratios. When there is too much redundant DETA in the reaction solution, the coordination effect and hydrogen–bond interactions
7
become stronger and lead to the Sm(OH)3 nanorod with small size, which also easy to get aggregation. The whole possible growth patterns of the nanorods prepared at different volume ratio of DETA are shown in Fig.6. (Fig.6. is supposed to be here.) 3.4. Optical and photocatalytical properties The UV–visible diffuse reflection spectra of the as–prepared Sm(OH)3 nanocrystallites are shown in Fig.7. The steep shape of the spectra indicates that the samples have good absorption property of deep ultraviolet. The samples prepared at 0.40 and 0.66 Vol% of DETA with the enhancing ultraviolet absorbing ability, which may be attributed to their smaller sizes. Nanosized rare earth compounds present great promise and opportunities for a new generation of catalysts [7]. Combine the good ultraviolet absorbing property and the unique 4f electrons structure of Sm(OH)3 nanocrystallites, the photocatalytic activity of Sm(OH)3 nanocrystallites was investigated in our research. (Fig.7. is supposed to be here.) The photocatalytic activity of the as–prepared hexagonal Sm(OH)3 nanocrystallites were evaluated by degradation of 5 mg·L–1 RhB aqueous solution under 500 W mercury lamp irradiation. The detailed results of the absorption spectra during the photocatalytic degradation process are shown in Fig.8a. As irradiation time prolong, the RhB absorption peak decreases in different extent without peak shifting, which suggests the degradation process follows an oxidation reaction, rather than a de– ethylation process of the RhB molecule [18]. The photocatalytic results of the Sm(OH)3
8
nanocrystallites prepared at different volume percents of DETA are shown in Fig.8b. The adsorption test shows that the adsorption–desorption equilibrium between Sm(OH)3 nanocrystallites and RhB was achieved after the dark stirring for 30 min. The blank test demonstrates that the degradation of RhB is slow without photocatalysts. The photocatalytic results exhibit that the as–prepared Sm(OH)3 nanocrystallites in our research can mainly degrade RhB under 500 W mercury lamp in only 40 min, especially that prepared at 0.66 Vol% of DETA, which degradation efficiency reaches 90.3%. (Fig.8. is supposed to be here.) The better photocatalytic activity of the Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA is achieved with RhB degradation efficiency reaches 90.3%. Whereas, the degradation efficiency of the sample prepared at 0.27, 0.40 and 1.05 Vol% of DETA only reaches 71.3%, 85.4% and 48.7%. The high photocatalytic activity of the sample prepared at 0.66 Vol% of DETA may arise from the unique optical and chemical properties of lanthanide compounds [7, 8] and its 1D nanorod structure with big specific surface area and good ultraviolet absorbing ability. Because the dispersive small 1D rod–like nanostructure has a big influence on the optical and photocatalytic properties of the materials [23]. Furthermore, the photocatalytic reactions are typically surface–based processes, the photocatalytic efficiency is closely related to the specific surface area, morphology and microstructure of the materials [24]. In addition, comparing with the well known photocatalysts, such as TiO2 [19, 20] and ZnO [21, 22], Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA shows promising photocatalytic activity to degrade RhB under UV irradiation.
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The degradation rate is another way to directly evaluate the photocatalytic activity of the as– prepared samples. The heterogeneous photocatalytic reaction between Sm(OH)3 nanocrystallites and RhB aqueous solution can be described by the pseudo–first–order kinetics, which is rationalized in terms of the Langmuir–Hinshelwood model (L–H) modified to accommodate reactions occurring at a solid–liquid interface [25, 26]. The photocatalytic activity of Sm(OH)3 nanocrystallites for degradation of RhB obeys the pseudo–first–order reaction kinetics and its expression is as follows:
dc / dt = − KcC
(2)
ln(C 0 / Ct ) = Kct
(3)
Where Kc is the rate constant of the pseudo–first–order reaction. A plot of ln(C0/Ct) versus the UV irradiation time for the RhB photodegradation, which catalyzed by Sm(OH)3 nanocrystallites, is shown in Fig.9. A near linear relation between ln(C0 /Ct) and the irradiation time have been observed, which explains the photodegradation of RhB by Sm(OH)3 nanocrystallites follows the pseudo–first– order kinetics. The calculated Kc, the corresponding first–order kinetic equation and the R2 values are summarized in Table1. (Fig.9. is supposed to be here.) Table 1 Parameter and linear kinetic equation of photocatalytic reaction of the samples prepared at different volume percents of DETA with different specific surface areas. DETA
(Vol%)
Special surface area 2
First–order kinetic equation
Kc
(m /g)
10
R2
0.27
67.28
0.02922
ln(C0 /Ct)=0.02922t + 0.10707
0.98831
0.40
71.84
0.04772
ln(C0 /Ct)=0.04772t + 0.04913
0.99688
0.66
79.41
0.05819
ln(C0/Ct )=0.05819t + 0.00669
0.97636
1.05
53.27
0.01397
ln(C0 /Ct)=0.01397t + 0.07010
0.98162
The high value of R2 (>0.95) demonstrates the pseudo–first–order kinetic equation fit the photocatalytic degradation of RhB perfectly. The higher the pseudo–first–order rate constant (Kc) suggests the more outstanding photocatalytic activity. The fast degradation rate to degrade RhB aqueous solution was obtained by Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA, which is almost double that prepared at 0.27 Vol% of DETA. The fast degradation rate may be due to the good ultraviolet absorbing ability and the big specific surface area of the sample. The good ultraviolet absorbing ability and big specific surface area of the Sm(OH)3 nanorods are believed to greatly affect the final degradation rate and degradation efficiency of RhB in our research. 4. Conclusion In summary, pure Sm(OH)3 nanorods with controllable size have been successfully prepared by a facile hydrothermal process. It is found that DETA significantly influences the structure and photocatalytic activity of the Sm(OH)3 nanorods. With the addition of DETA increased from 0.27 to 1.05 Vol%, the average size of the samples decreased from 694 to 123 nm. Better photocatalytic activity of the sample prepared at 0.66 Vol% of DETA with the degradation efficiency of RhB reaches 90.3% under UV irradiation for 40 min, which may originate from the dispersive small and uniform nanorods microstructure with the big specific area of the sample. Moreover, the as–prepared samples
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show significant photocatalytic activity to decompose RhB, which suggests their potential application as photocatalytic materials in the future. Acknowledgments The authors are grateful to National Key Technology R&D Program (No. 2013BAF09B02), International Science and Technology Cooperation Project Funding of Shaanxi Province (No. 2011KW–11), Innovation Team Assistance Foundation of Shaanxi Province (2013KCT–06), Innovation Team Assistance Foundation of Shaanxi University of Science and Technology (No.TD09–05), and Graduate Innovation Fund of Shaanxi University of Science and Technology. References [1] T.N. Parac–Vogt, K. Deleersnyder, K. Binnemans, J. Alloys Compd. 374 (2004) 46–49. [2] T. N. Parac–Vogt, K. Binnemans, Tetrahedron Lett. 45 (2004) 3137–3139. [3] K. Park, M.H. Heo, K.Y. Kim, S.J. Dhoble, Y. Kim, J.Y. Kim, Powder Technol. 237 (2013) 102– 106. [4] M. Saif, J. Lumin. 135 (2013) 187–195. [5] R Sen, D.K. Hazra, S. Koner, M. Helliwell, M. Mukherjee, A. Bhattacharjee, Polyhedron 29 (2010) 3183–3191. [6] I. Djerdj, G. Garnweitner, D.S. Su, N. Markus, J Solid State Chem. 180 (2007) 2154–2165. [7] G.F. Wang, Q. Peng, Y.D. Li, Acc. Chem. Res. 44(2011) 322–332. [8] E. Van Der Kolk, P. Dorenbos, Chem. Mater. 18(2006) 3458–3462.
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[9] J.S. Xie, Q.S. Wu, D. Zhang, Y.P. Ding, Cryst. Growth Des.9 (2009) 3889–3897. [10] Y.P. Fang, A.W. Xu, L.P. You, R.Q. Song, J.C. Yu, H. X. Zhang, Q. Li, H.Q. Liu, Adv. Funct. Mater. 12 (2003) 955–960. [11] Q.Y. Mu, Y.D. Wang, J. Alloys Compd. 509 (2011) 396–401. [12] N. Zhang, R. Yi, L.B. Zhou, G.H. Gao, R.G. Shi, G. Z. Qiu, L.X. He, Mater. Chem. Phys. 114 (2009) 160–167. [13] N. Zhang, X.H. Liu, R. Yi, R.R. Shi, G.H. Gao, G.Z Qiu, J.Phys. Chem. C 112 (2008) 17788– 17795. [14] Q.Y. Mu, Y.D. Wang, J. Alloys Compd. 509 (2011) 2060–2065. [15] J.X. Zhu, Z. Gui, Y.Y. Ding, Mater. Lett. 62 (2008) 2373–2376. [16] L.W. Qian, Y.C. Gui, S. Guo, Q. Gong, X.F. Qian, J. Phys. Chem. Solids. 70 (2009) 688–693. [17] D. Wang, J.F. Huang, L.X. Yin, L.Y. Cao, H.B. Ouyang, J.Y. Li, W. Hao, Mater. Lett. 116(2014) 393–395. [18] T.X. Wu, G.M. Liu, J.C. Zhao, J. Phys. Chem. B102 (1998) 5845–5851. [19] Z.L. He, W. X. Que, Y.C. He, Mater. Lett. 94(2013) 136–139. [20] M.M. Rashad, E.M. Elsayed, M.S. Al–Kotb, A.E. Shalan, J. Alloys Compd. 581 (2013) 71–78. [21] Q.P Luo, X.Y. Yu, B.X. Lei, H.Y. Chen, D.B. Kuang, C.Y. Su, J. Phys. Chem. C. 116 (2012) 8111–8117. [22] Y.C. Lu, L.L. Wang, D.J. Wang, T.F. Xie, L.P. Chen, Mater. Chem. Phys. 129 (2011) 281–287.
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[23] X.Y. Li, J. Wang, J.H. Yang, J.H. Lang, S.Q. Lü, M.B. Wei, X.W. Meng, C.L. Kon, X.F. Lei, J. Alloys Compd. 580 (2013) 205–210. [24] H. Tong, S.X. Ouyang, Y.P. Bi, N. Umezawa, O. Mitsutake, Adv. Mater. 24 (2012) 229–251. [25] D. Li, J.F. Huang, L.Y. Cao, J.Y. Li, H.B. Ouyang, C.Y. Yao, Ceram. Int. l40 (2014) 2647–2653. [26] L.L. Liu, J.F. Huang, L.Y. Cao, J.P. Wu, J. Fei, H.B. Ouyang, C.Y. Yao, Ceram. Int. l40 (2013) 3165–3171.
Figure captions
Fig.1. XRD patterns of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA. Fig.2. FT–IR spectra of the Sm(OH)3 nanocrystallites prepared at 0.66 Vol% and 1.05 Vol% of DETA. Fig.3. SEM images of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%. Fig.4. Histograms of the length distribution of Sm(OH)3 nanorods prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%. Fig.5. Nitrogen adsorption–desorption isotherm of Sm(OH)3 nanorods prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%. Fig.6. The schematic diagram of the possible growth pattern of the 1D Sm(OH)3 nanorods prepared at different volume ratio of DETA. Fig.7. UV–vis diffuses reflectance spectra of the Sm(OH)3 nanocrystallites prepared at different
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volume percents of DETA. Fig.8. (a) UV–vis absorption spectra changes of RhB obtained by using the Sm(OH)3 nanocrystallites prepared at 0.66 Vol% of DETA as catalyst (b) Photocatalytic results of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA. Fig.9. Relationship between ln(C0 /Ct) and UV irradiation time of the Sm(OH)3 nanocrystallites prepared at different volume percents of DETA (a) 0.27 Vol% (b) 0.40 Vol% (c) 0.66 Vol% (d) 1.05 Vol%.
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Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
H NH+ H 2N
NH
NH 2
H
H
NH 2
crystallize
3+
+
Sm
NH +
NH2
N H2
assembly
growth crystallize
assembly
t an d un TA d e r DE
replace by OH nuclation
N H2
Sm(NO3)3 hydrolysis H2O DETA coordination
Figure 7
Figure 8
Figure 9
Table 1 Parameter and linear kinetic equation of photocatalytic reaction of the samples prepared at different volume percents of DETA with different specific surface areas. DETA
(Vol%)
Special surface area
(m2/g)
Kc
First–order kinetic equation
R2
0.27
67.28
0.02922
ln(C0 /Ct)=0.02922t + 0.10707
0.98831
0.40
71.84
0.04772
ln(C0 /Ct)=0.04772t + 0.04913
0.99688
0.66
79.41
0.05819
ln(C0/Ct)=0.05819t + 0.00669
0.97636
1.05
53.27
0.01397
ln(C0 /Ct)=0.01397t + 0.07010
0.98162
DETA was proposed to use as an alkaline agent to prepare Sm(OH)3 nanocrystallites. Size–controlled Sm(OH)3 nanorods were achieved by adjusting the addition of DETA. Size–related photocatalytic activity of Sm(OH)3 nanocrystallites was shown.
The photocatalysis degradation reaction kinetics of RhB was researched.