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Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires
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Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires Yung-Hsiang Chang, Mao-Yuan Chiang, Jan-Hau Chang, Heh-Nan Lin n Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
art ic l e i nf o
a b s t r a c t
Article history: Received 27 August 2014 Accepted 24 September 2014
We report on the excellent photocatalytic activity of Cu2O nanoparticle (NP) modified ZnO nanowires (NWs) in the visible light range. The NP modification is realized by photoreduction and subsequent thermal annealing in vacuum. Transmission electron microscopy analysis confirms that the NPs are in the form of Cu2O. For the degradation of a 50 μM rhodamine B solution under the illumination of a halogen lamp, the zeroth-order kinetic constant of the NP modified NWs is around 0.22 μM min 1 and 8.8 times as high as that of as-grown NWs. The achieved performance compares well with reported results of visible light photocatalysis of NP modified ZnO NWs. Furthermore, a kinetic constant of 0.53 μM min 1 and a degradation efficiency of 97% in 2 h have been obtained by using sunlight illumination. & 2014 Published by Elsevier B.V.
Keywords: Semiconductors Nanocrystalline materials Zinc oxide nanowire Cuprous oxide nanoparticle Photocatalysis
1. Introduction
2. Experimental
The photocatalytic activity of ZnO nanowires (NWs) has been widely studied in recent years [1–6]. However, a major disadvantage is that the absorption band of ZnO is in the ultraviolet (UV) range and limits the utilization of the solar energy. One way to extend the photocatalytic activity towards the visible range is to dope ZnO NWs with metal ions and several possibilities, including Co [7], Cr [8], Cu [9], Mn [10], etc. have been reported in the literature. Another way is to create nanostructures on ZnO NWs with narrow band gap semiconductors such as CdS [11], ZnSe [12], V2O5 [13], CuO [14,15], Cu2O [16], etc. Among narrow band gap semiconductors, copper-based semiconductors are worthy of attention due to their advantages of low cost, abundance, non-toxicity, etc. Previous reports have shown that CuO NP modified ZnO NWs possess a good photocatalytic effect [14,15] and Cu2O NP modified ZnO NWs have a good antibacterial effect [16] in the visible range. However, photocatalytic results of Cu2O NP modified ZnO NWs are rare in the literature. In the present work, we report on the growth of Cu2O NP modified ZnO NWs. By degrading a 50 μM rhodamine B (RhB) solution under the illumination of a 100 W halogen lamp, it is found that the zeroth-order kinetic constant of NP modified ZnO NWs is 8.8 times as high as that of unmodified NWs. The NP modified NWs also perform well under sunlight illumination.
The ZnO NWs were first grown on Si substrates by thermal evaporation without catalysts [17,18]. For NP modification, a 1.5 1.5 cm2 NW sample was placed in a 1 mM CuSO4 solution and subjected to UV irradiation for 30 min. The sample was further annealed at 350 1C in a 10 3 Torr vacuum for 3 h. The photocatalytic activity was evaluated by degrading a 7.5 mL 50 μM ( 24 ppm) RhB solution under the illumination of a 100 W halogen lamp placed 20 cm away or direct sunlight. Details can be found in our previous reports [5,6].
n
Corresponding author. Tel.: þ 886 35736076; fax: þ 886 35722366. E-mail address: [email protected] (H.-N. Lin).
3. Result and discussion Two different batches of NWs with different diameters have been grown. The as-grown sample with NWs of a larger diameter will be called A-as grown. The sample after photoreduction will be called A-reduction and the one after further thermal annealing will be called A-annealing. Similarly, the samples with a smaller diameter will be called B-as grown, B-reduction, and B-annealing. The scanning electron microscopy (SEM) images of the two as-grown samples are shown in Fig. 1(a) and (b) and the insets reveal that the diameters are around 200 and 80 nm, respectively. The SEM images of A-reduction and B-reduction are shown in Fig. 1(c) and (d), respectively. As can be seen, both samples are covered with a thin layer of material after photoreduction and the NW surfaces are rough. Fig. 1(e) and (f) shows the SEM images of A-annealing and B-annealing, respectively. The NW surfaces in A-annealing become smooth, but the surfaces in B-annealing are still rough.
http://dx.doi.org/10.1016/j.matlet.2014.09.098 0167-577X/& 2014 Published by Elsevier B.V.
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
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Y.-H. Chang et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Fig. 1. SEM images of (a), (b) NWs in A-as grown and B-as grown, respectively, (c), (d) NWs after photoreduction in A-reduction and B-reduction, respectively, and (e), (f) NWs after further annealing in A-annealing and B-annealing, respectively. The insets are enlarged NW images.
From transmission electron microscopy (TEM) analysis, small Cu2O NPs are created on the NW surfaces after photoreduction (see SI-1). Fig. 2 (a) is a TEM image of an NP modified NW in A-annealing. In comparison with SI-1, the NPs become larger after thermal annealing. Fig. 2(b) and (c) shows enlarged images of an NP and the NW surface. Fig. 2(d) is the Fourier transform pattern of the NP and the (111) interplanar spacing is determined to be 0.247 nm. This value is in agreement with the (111) interplanar distance of 0.2465 nm for Cu2O (JCPDS card no. 05-0667), but disagrees with the
value of 0.2330 nm for CuO (JCPDS card no. 05-0661). Similarly, the pattern in Fig. 2(e) also confirms that the surface layer is ZnO. The composition of Cu2O is also verified by a simple test. On putting an annealed sample in a KMnO3 solution, the purple color of the solution changes to light purple due to oxidation of Cu þ to Cu þ þ (see SI-2). Additionally, it is worth mentioning that the annealing process may induce Cu doping in the NWs [9] and subsequent grain boundary modification [19]. Both effects influence the properties of ZnO NWs and probably lead to better photocatalytic performance.
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Y.-H. Chang et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 2. TEM images of (a) a Cu2O NP modified NW in A-annealing, (b) the NP, and (c) the surface layer. (d), (e) Fourier transform patterns of, respectively (b) and (c).
Fig. 3 shows the PL spectra of all NW samples. The PL spectra of the two as-grown samples exhibit strong UV emission with a peak at around 386 nm and blue–green sideband emission. The UV peak of A-as grown is much broader than that of B-as grown, which is mainly due to the difference in size and morphology of the NWs [20]. After photoreduction and thermal annealing the PL intensities decrease apparently, especially for the thin NWs. The decrease is mainly due to absorption of Cu2O NPs since the band gap ( 2.1 eV) corresponds to a wavelength of around 590 nm. The greater drops in the PL intensities of the thin NW samples in Fig. 3(b) can also be reasonably attributed to the large portion of the NPs on thin NWs than on thick ones. The ratios of the RhB concentration as a function of irradiation time C t to the initial concentration C 0 are plotted in Fig. 4(a) and (b) for the thick and the thin NWs, respectively. As can be seen in Fig. 4(a), the performance of A-reduction is much better than
that of A-as grown and the performance of A-annealing is even better. This observation should hold also for the thin NW samples although the result for B-reduction is not available. For the photodegradation kinetics, it is known from our previous works that a zeroth-order kinetics is suitable [5,6] and the results in Fig. 4 follow a linear relationship. The zeroth-order kinetics equation is simplyC t ¼ C 0 k0 t, where t is the time and k0 the zeroth-order constant [4–6]. The zeroth-order constants in Fig. 4 are obtained by least squares linear fitting and they are 0.025 (A-as grown), 0.12 (A-reduction), 0.22 (A-annealing), 0.031 (B-as grown), and 0.23 (B-annealing) μM min 1. The kinetic constants of A-reduction and A-annealing are 4.8 and 8.8 times as high as that of A-as grown, respectively. The present results can be compared with visible light photocatalytic results of ZnO NWs modified by others types of NPs [11–15].
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
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Y.-H. Chang et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 3. PL spectra of (a) the thick and (b) the thin NW samples.
For example an efficiency improvement of 35% for photodegradation of 10 μM RhB (71% degradation efficiency for original NWs to 96% for NP modified NWs in 9 h) is reported in Ref. [12], whereas the present improvement is 7.3 times (9% for A-as grown to 75% for A-annealing [Fig. 4(a)] in 3 h). Additionally, the photocatalysis of A-annealing has been tested under direct sunlight (no focusing) illumination. A kinetic constant of 0.53 μM min 1 and a degradation efficiency of 97% in 2 h have been obtained (see SI-3).
4. Conclusions In this study, excellent photocatalytic activity of Cu2O NP modified ZnO NWs in the visible light range is reported. The NP modification is realized by photoreduction and subsequent vacuum thermal annealing. The NPs are in the form of Cu2O as is verified by TEM analysis. For the degradation of a 50 μM RhB solution under the illumination of a 100 W halogen lamp, the zeroth-order kinetic constant of the NP modified NWs is 0.22 μM min 1 and 8.8 times as high as that of asgrown NWs. The present performance compares well with reported results of visible light photocatalysis of NP modified ZnO NWs. Furthermore a kinetic constant of 0.53 μM min 1 and a degradation efficiency of 97% in 2 h have been obtained by using direct sunlight illumination, showing a good potential for solar photocatalysis.
Acknowledgment This work was supported by the Ministry of Science and Technology, Taiwan, under Grant no. 102-2112-M-007-004.
Fig. 4. (a), (b) Concentration ratios as a function of irradiation time due to photocatalysis of the NW samples. The zeroth-order constants are obtained by least squares linear fitting.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.09.098 References [1] Kuo TJ, Lin CN, Kuo CL, Huang MH. Chem Mater 2007;19:5143–7. [2] Wang G, Chen D, Zhang H, Zhang JZ, Li JH. J Phys Chem C 2008;112:8850–5. [3] Bae J, Han JB, Zhang XM, Wei M, Duan X, Zhang Y, et al. J Phys Chem C 2009;113:10379–83. [4] Liu Y, Kang ZH, Chen ZH, Shafiq I, Zapien JA, Bello I, et al. Cryst Growth Des 2009;9:3222–7. [5] Chang JH, Lin HN. J Nanomater 2014;2014:426457. [6] Chang JH, Lin HN. Mater Lett 2014;132:134–7. [7] Qiu X, Li G, Sun X, Li L, Fu X. Nanotechnology 2008;19:215703. [8] Wu C, Shen L, Zhang YC, Huang Q. Mater Lett 2011;65:1794–6. [9] Wu C, Shen L, Yu H, Zhang YC, Huang Q. Mater Lett 2012;74:236–8. [10] Lu Y, Lin Y, Xie T, Shi S, Fan H, Wang D, et al. Nanoscale 2012;4:6393–400. [11] Nayak J, Sahu SN, Kasuya J, Nozaki S. Appl Surf Sci 2008;254:7215–8. [12] Chen W, Zhang N, Zhang MY, Zhang XT, Gao H, Wen J. Cryst Eng Comm 2014;16:1201–6. [13] Zou CW, Rao YF, Alyamani A, Chu W, Chen MJ, Patterson DA, et al. Langmuir 2010;26:11615–20. [14] Jung S, Yong K. Chem Commun 2011;47:2643–5. [15] Wei A, Xiong L, Sun L, Liu YJ, Li WW. Chin Phys Lett 2013;30:046202. [16] Wang Y, She G, Xu H, Liu Y, Mu L, Shi W, et al. Mater Lett 2012;67:110–2. [17] Ho ST, Chen KC, Chen HA, Lin HY, Cheng CY, Lin HN, et al. Chem Mater 2007;19:4083–6. [18] Ho ST, Wang CY, Liu HL, Lin HN. Chem Phys Lett 2008;463:141–4. [19] Straumal BB, Protasova SG, Mazilkin AA, Tietze T, Goering E, Schütz G, et al. Beilstein J Nanotechnol 2013;4:361–9. [20] He H, Yang Q, Liu C, Sun L, Ye Z. J Phys Chem C 2011;115:58–64.
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
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Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires Yung-Hsiang Chang, Mao-Yuan Chiang, Jan-Hau Chang, Heh-Nan Lin n Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
art ic l e i nf o
a b s t r a c t
Article history: Received 27 August 2014 Accepted 24 September 2014
We report on the excellent photocatalytic activity of Cu2O nanoparticle (NP) modified ZnO nanowires (NWs) in the visible light range. The NP modification is realized by photoreduction and subsequent thermal annealing in vacuum. Transmission electron microscopy analysis confirms that the NPs are in the form of Cu2O. For the degradation of a 50 μM rhodamine B solution under the illumination of a halogen lamp, the zeroth-order kinetic constant of the NP modified NWs is around 0.22 μM min 1 and 8.8 times as high as that of as-grown NWs. The achieved performance compares well with reported results of visible light photocatalysis of NP modified ZnO NWs. Furthermore, a kinetic constant of 0.53 μM min 1 and a degradation efficiency of 97% in 2 h have been obtained by using sunlight illumination. & 2014 Published by Elsevier B.V.
Keywords: Semiconductors Nanocrystalline materials Zinc oxide nanowire Cuprous oxide nanoparticle Photocatalysis
1. Introduction
2. Experimental
The photocatalytic activity of ZnO nanowires (NWs) has been widely studied in recent years [1–6]. However, a major disadvantage is that the absorption band of ZnO is in the ultraviolet (UV) range and limits the utilization of the solar energy. One way to extend the photocatalytic activity towards the visible range is to dope ZnO NWs with metal ions and several possibilities, including Co [7], Cr [8], Cu [9], Mn [10], etc. have been reported in the literature. Another way is to create nanostructures on ZnO NWs with narrow band gap semiconductors such as CdS [11], ZnSe [12], V2O5 [13], CuO [14,15], Cu2O [16], etc. Among narrow band gap semiconductors, copper-based semiconductors are worthy of attention due to their advantages of low cost, abundance, non-toxicity, etc. Previous reports have shown that CuO NP modified ZnO NWs possess a good photocatalytic effect [14,15] and Cu2O NP modified ZnO NWs have a good antibacterial effect [16] in the visible range. However, photocatalytic results of Cu2O NP modified ZnO NWs are rare in the literature. In the present work, we report on the growth of Cu2O NP modified ZnO NWs. By degrading a 50 μM rhodamine B (RhB) solution under the illumination of a 100 W halogen lamp, it is found that the zeroth-order kinetic constant of NP modified ZnO NWs is 8.8 times as high as that of unmodified NWs. The NP modified NWs also perform well under sunlight illumination.
The ZnO NWs were first grown on Si substrates by thermal evaporation without catalysts [17,18]. For NP modification, a 1.5 1.5 cm2 NW sample was placed in a 1 mM CuSO4 solution and subjected to UV irradiation for 30 min. The sample was further annealed at 350 1C in a 10 3 Torr vacuum for 3 h. The photocatalytic activity was evaluated by degrading a 7.5 mL 50 μM ( 24 ppm) RhB solution under the illumination of a 100 W halogen lamp placed 20 cm away or direct sunlight. Details can be found in our previous reports [5,6].
n
Corresponding author. Tel.: þ 886 35736076; fax: þ 886 35722366. E-mail address: [email protected] (H.-N. Lin).
3. Result and discussion Two different batches of NWs with different diameters have been grown. The as-grown sample with NWs of a larger diameter will be called A-as grown. The sample after photoreduction will be called A-reduction and the one after further thermal annealing will be called A-annealing. Similarly, the samples with a smaller diameter will be called B-as grown, B-reduction, and B-annealing. The scanning electron microscopy (SEM) images of the two as-grown samples are shown in Fig. 1(a) and (b) and the insets reveal that the diameters are around 200 and 80 nm, respectively. The SEM images of A-reduction and B-reduction are shown in Fig. 1(c) and (d), respectively. As can be seen, both samples are covered with a thin layer of material after photoreduction and the NW surfaces are rough. Fig. 1(e) and (f) shows the SEM images of A-annealing and B-annealing, respectively. The NW surfaces in A-annealing become smooth, but the surfaces in B-annealing are still rough.
http://dx.doi.org/10.1016/j.matlet.2014.09.098 0167-577X/& 2014 Published by Elsevier B.V.
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
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Y.-H. Chang et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Fig. 1. SEM images of (a), (b) NWs in A-as grown and B-as grown, respectively, (c), (d) NWs after photoreduction in A-reduction and B-reduction, respectively, and (e), (f) NWs after further annealing in A-annealing and B-annealing, respectively. The insets are enlarged NW images.
From transmission electron microscopy (TEM) analysis, small Cu2O NPs are created on the NW surfaces after photoreduction (see SI-1). Fig. 2 (a) is a TEM image of an NP modified NW in A-annealing. In comparison with SI-1, the NPs become larger after thermal annealing. Fig. 2(b) and (c) shows enlarged images of an NP and the NW surface. Fig. 2(d) is the Fourier transform pattern of the NP and the (111) interplanar spacing is determined to be 0.247 nm. This value is in agreement with the (111) interplanar distance of 0.2465 nm for Cu2O (JCPDS card no. 05-0667), but disagrees with the
value of 0.2330 nm for CuO (JCPDS card no. 05-0661). Similarly, the pattern in Fig. 2(e) also confirms that the surface layer is ZnO. The composition of Cu2O is also verified by a simple test. On putting an annealed sample in a KMnO3 solution, the purple color of the solution changes to light purple due to oxidation of Cu þ to Cu þ þ (see SI-2). Additionally, it is worth mentioning that the annealing process may induce Cu doping in the NWs [9] and subsequent grain boundary modification [19]. Both effects influence the properties of ZnO NWs and probably lead to better photocatalytic performance.
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Y.-H. Chang et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 2. TEM images of (a) a Cu2O NP modified NW in A-annealing, (b) the NP, and (c) the surface layer. (d), (e) Fourier transform patterns of, respectively (b) and (c).
Fig. 3 shows the PL spectra of all NW samples. The PL spectra of the two as-grown samples exhibit strong UV emission with a peak at around 386 nm and blue–green sideband emission. The UV peak of A-as grown is much broader than that of B-as grown, which is mainly due to the difference in size and morphology of the NWs [20]. After photoreduction and thermal annealing the PL intensities decrease apparently, especially for the thin NWs. The decrease is mainly due to absorption of Cu2O NPs since the band gap ( 2.1 eV) corresponds to a wavelength of around 590 nm. The greater drops in the PL intensities of the thin NW samples in Fig. 3(b) can also be reasonably attributed to the large portion of the NPs on thin NWs than on thick ones. The ratios of the RhB concentration as a function of irradiation time C t to the initial concentration C 0 are plotted in Fig. 4(a) and (b) for the thick and the thin NWs, respectively. As can be seen in Fig. 4(a), the performance of A-reduction is much better than
that of A-as grown and the performance of A-annealing is even better. This observation should hold also for the thin NW samples although the result for B-reduction is not available. For the photodegradation kinetics, it is known from our previous works that a zeroth-order kinetics is suitable [5,6] and the results in Fig. 4 follow a linear relationship. The zeroth-order kinetics equation is simplyC t ¼ C 0 k0 t, where t is the time and k0 the zeroth-order constant [4–6]. The zeroth-order constants in Fig. 4 are obtained by least squares linear fitting and they are 0.025 (A-as grown), 0.12 (A-reduction), 0.22 (A-annealing), 0.031 (B-as grown), and 0.23 (B-annealing) μM min 1. The kinetic constants of A-reduction and A-annealing are 4.8 and 8.8 times as high as that of A-as grown, respectively. The present results can be compared with visible light photocatalytic results of ZnO NWs modified by others types of NPs [11–15].
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132
Y.-H. Chang et al. / Materials Letters ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 3. PL spectra of (a) the thick and (b) the thin NW samples.
For example an efficiency improvement of 35% for photodegradation of 10 μM RhB (71% degradation efficiency for original NWs to 96% for NP modified NWs in 9 h) is reported in Ref. [12], whereas the present improvement is 7.3 times (9% for A-as grown to 75% for A-annealing [Fig. 4(a)] in 3 h). Additionally, the photocatalysis of A-annealing has been tested under direct sunlight (no focusing) illumination. A kinetic constant of 0.53 μM min 1 and a degradation efficiency of 97% in 2 h have been obtained (see SI-3).
4. Conclusions In this study, excellent photocatalytic activity of Cu2O NP modified ZnO NWs in the visible light range is reported. The NP modification is realized by photoreduction and subsequent vacuum thermal annealing. The NPs are in the form of Cu2O as is verified by TEM analysis. For the degradation of a 50 μM RhB solution under the illumination of a 100 W halogen lamp, the zeroth-order kinetic constant of the NP modified NWs is 0.22 μM min 1 and 8.8 times as high as that of asgrown NWs. The present performance compares well with reported results of visible light photocatalysis of NP modified ZnO NWs. Furthermore a kinetic constant of 0.53 μM min 1 and a degradation efficiency of 97% in 2 h have been obtained by using direct sunlight illumination, showing a good potential for solar photocatalysis.
Acknowledgment This work was supported by the Ministry of Science and Technology, Taiwan, under Grant no. 102-2112-M-007-004.
Fig. 4. (a), (b) Concentration ratios as a function of irradiation time due to photocatalysis of the NW samples. The zeroth-order constants are obtained by least squares linear fitting.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.09.098 References [1] Kuo TJ, Lin CN, Kuo CL, Huang MH. Chem Mater 2007;19:5143–7. [2] Wang G, Chen D, Zhang H, Zhang JZ, Li JH. J Phys Chem C 2008;112:8850–5. [3] Bae J, Han JB, Zhang XM, Wei M, Duan X, Zhang Y, et al. J Phys Chem C 2009;113:10379–83. [4] Liu Y, Kang ZH, Chen ZH, Shafiq I, Zapien JA, Bello I, et al. Cryst Growth Des 2009;9:3222–7. [5] Chang JH, Lin HN. J Nanomater 2014;2014:426457. [6] Chang JH, Lin HN. Mater Lett 2014;132:134–7. [7] Qiu X, Li G, Sun X, Li L, Fu X. Nanotechnology 2008;19:215703. [8] Wu C, Shen L, Zhang YC, Huang Q. Mater Lett 2011;65:1794–6. [9] Wu C, Shen L, Yu H, Zhang YC, Huang Q. Mater Lett 2012;74:236–8. [10] Lu Y, Lin Y, Xie T, Shi S, Fan H, Wang D, et al. Nanoscale 2012;4:6393–400. [11] Nayak J, Sahu SN, Kasuya J, Nozaki S. Appl Surf Sci 2008;254:7215–8. [12] Chen W, Zhang N, Zhang MY, Zhang XT, Gao H, Wen J. Cryst Eng Comm 2014;16:1201–6. [13] Zou CW, Rao YF, Alyamani A, Chu W, Chen MJ, Patterson DA, et al. Langmuir 2010;26:11615–20. [14] Jung S, Yong K. Chem Commun 2011;47:2643–5. [15] Wei A, Xiong L, Sun L, Liu YJ, Li WW. Chin Phys Lett 2013;30:046202. [16] Wang Y, She G, Xu H, Liu Y, Mu L, Shi W, et al. Mater Lett 2012;67:110–2. [17] Ho ST, Chen KC, Chen HA, Lin HY, Cheng CY, Lin HN, et al. Chem Mater 2007;19:4083–6. [18] Ho ST, Wang CY, Liu HL, Lin HN. Chem Phys Lett 2008;463:141–4. [19] Straumal BB, Protasova SG, Mazilkin AA, Tietze T, Goering E, Schütz G, et al. Beilstein J Nanotechnol 2013;4:361–9. [20] He H, Yang Q, Liu C, Sun L, Ye Z. J Phys Chem C 2011;115:58–64.
Please cite this article as: Chang Y-H, et al. Enhanced visible light photocatalysis of cuprous oxide nanoparticle modified zinc oxide nanowires. Mater Lett (2014), http://dx.doi.org/10.1016/j.matlet.2014.09.098i
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