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Preparation of octahedral Cu2O nanoparticles by a green route
Author’s Accepted Manuscript Preparation of octahedral Cu2O nanoparticles by a green route Dehua Guo, Lixian Wang, Yingji Du, Zhuqiang Ma, Long Shen www.elsevier.com
PII: DOI: Reference:
S0167-577X(15)30410-9 http://dx.doi.org/10.1016/j.matlet.2015.08.055 MLBLUE19416
To appear in: Materials Letters Received date: 27 June 2015 Revised date: 30 July 2015 Accepted date: 10 August 2015 Cite this article as: Dehua Guo, Lixian Wang, Yingji Du, Zhuqiang Ma and Long Shen, Preparation of octahedral Cu2O nanoparticles by a green route, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2015.08.055 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 galley proof before it is published in its final citable 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.
Preparation of octahedral Cu2O nanoparticles by a green route Dehua Guo1, Lixian Wang1*, Yingji Du1, Zhuqiang Ma2, Long Shen2 1
School of Chemical and Environmental Engineering, Shanghai Institute of Technology,
100 Haiquan Road, Shanghai 201418, China 2
Rong Jian chemical plant, 269 Chuhua Road, shanghai 201400, China
E-mail address: [email protected] *Corresponding author School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418, China E-mail address: [email protected], TEL.: +86 02160877227 Abstract The fabrication of octahedral Cu2O was described by a green and simple chemical precipitation method in this study. All samples were characterized by X-ray powder diffractometer(XRD), scanning electron microscopy(SEM), Fourier transform infrared spectrometer(FTIR) and ultraviolet-visible spectrophotometer(UV-vis), respectively. The results show that products are composed of octahedral particles with an edge length of 200-300 nm, and narrow band gaps(2.26eV), which is blue shifted with respect to the bulk Cu2O value(2.17eV). Well-dispersed Cu2O with effectively absorbing visible light can be obtained through the route which is surfactant-free, cost effective, and suitable for large scale production. Key words: Octahedral Cu2O, Nanocrystalline materials, Semiconductors, X-ray techniques, Optical properties 1. Introduction
1
The synthesis, controlled inorganic materials with specific morphology and size, plays an important role in uncovering their shape-dependent properties and fully achieving their potential practical applications. As an important p-type semiconductor with a band gap value of 2.17 eV, Cu2O is a promising material in the field of solar energy conversion. besides, Cu2O is also used as catalyst for organic reactions, electrode for lithium ion battery, gas sensor and pholocatalyst for dye degradation[1-5]. In the past few years, numerous Cu2O products with well-controlled uniform morphologies
had
been
synthesized,
such
as
nanocubes[6],
nanotubes[7],
octahedrons[8], polyhedrons[9] and nanowires[10]. Some reports used copper salt as crude material, firstly to get cupric oxide, and then to prepare cuprous oxide by reduction. However, the extent of reduction was not easy to be controlled, and the productions always included cupric oxide or copper. In addition, the most exciting techniques to get spacial morphologies materials in the reports[11-13] had to rely on the proper selection of expensive surfactants or organic additives, such as polyvinyl pyrrolidone(PVP), cetylteimethylammonium bromide(CTAB) and methylpyridine. Therefore, it is necessary to exploit a facile route for the shape-controlled synthesis of Cu2O with specific morphology and size. Here, we successfully describe a novel shape-controlled synthesis route without any templates and surfactants for preparing cuprous oxide with octahedral morphology. 2. Experimental details 2.1. Preparation
2
All the chemicals were analytical grade reagents. In a typical synthesis, 1.0 g CuCl powder was dissolved in 100 ml of 6 M NaCl solution to form transparent solution. The transparent solution and 20.0 ml of Na3PO4 (0.6 M)solution were added simultaneously into a beaker with 100 ml distilled water, and the precipitate with bright yellow color would be obtained immediately. The yellow color solution was stirred at 60 ℃ for 20 min, then to be cooled to room temperature. Finally, the precipitate was separated from the solution by filtration, then to be washed with distilled water and absolute ethanol, respectively. The final product could be obtained after drying the precipitate at 90 ℃ for 3 h. 2.2. Characterization The obtained malachite samples were confirmed by powder X-ray diffraction (XR D, D/Max 2400, Rigaku, by a diffractometer equipped with a Cu Kα radiation source λ= 1.5418 Å) in the 2θ angles ranging from 10° to 80°. The morphologies of as-synthesized malachite samples were characterized by using a scanning electron microscope (SEM, S-3400N) with 15 kV of accelerated voltages. FT-IR spectra were recorded on a Fourier transmission infrared spectrometry (FT-IR, NEXUS) at wavenumbers 400-4000 cm-1. The UV-vis transmission spectra were determined with a spectrophotometer(U-3900). 3. Results and discussion The preparation of Cu+ complex is according to Eqs. (1): CuCl
+ Cl-
→
[CuCl2]- ↔
The preparation of OH-
Cu+
+
2Cl-
(1)
is according to Eqs. (2)
3
PO43- + H2O → HPO42- +
OH- (2)
The synthesis mechanism of Cu2O is described by Eqs. (3) and (4) : Cu+
+ OH- → CuOH
2CuOH
→ Cu2O + H2O (heating)
(3) (4)
In this work, Na3PO4 was introduced as a precipitator to provide OH-. It is well known that, CuCl is undissolved in deionized water. Therefore, CuCl should be made into copper complex so as to be dissolved in NaCl solution. When copper complex solution was mixed with sodium phosphate solution, the copper complex solution slowly released Cu+, Na3PO4 solution was slowly hydrolyzed OH-, Cu+ and OH- reacted CuOH. CuOH under high temperature is not stable, which will resolve into Cu2O. In order to get micro-nano-sized particles, the reaction rate must be controlled in low range. Since CuOH and Cu2O are solid, the production rate of Cu2O was determined by Eqs. (3) in which the reaction rate was controlled by the concentration of Cu+ and OH-. When the concentration of Cu+ was fixed, the generation rate of Cu2O would be controlled by the concentration of OH-. In present work, control experiments were performed by replacing Na3PO4 with NaOH or Na2CO3, which prepared amorphous, larger particle size sample. Therefore, the key to preparation of octahedral
10
20
30
40
50
60
(311)
(110)
(220)
(200)
Intensity
(111)
Cu2O nanocrystals is Na3PO4.
70
80
2θ(degree)
Fig. 1. XRD pattern of the sample.
4
Fig. 1 shows XRD pattern of the sample in the typical synthesis. The XRD spectrum shows five characteristic peaks at 2θ values of 29.5°, 36.4°, 42.3°, 61.4° and 73.5°, which correspond to the crystal planes of (110), (111), (200), (220) and (311), respectively. All diffraction peaks can be indexed to the octahedral phase of cuprous oxide crystal(JCPDS. NO. 05-0667). Furthermore, peaks due to impurities of Cu(0), CuO, and Cu(OH)2 are not detected from the XRD pattern, which indicates that pure cuprous oxide can be obtained under current synthetic conditions.
Fig. 2. Low-magnification and high-resolution SEM images of the sample (a, b) The morphology of as-prepared Cu2O is observed by SEM as shown in Fig. 2a. It is obvious that the sample is consisted of well-dispersed octahedral particles with an edge length of 200-300 nm. The high-resolution image of a typical bulk is shown in Fig. 2b, it can be seen that the sample shows octahedral morphology, which is the same as the low-magnification SEM result. Some small particles can be found in Fig.2 except for the octahedral particles. According to infrared spectra analysis about Fig.3., it’s probably the copper salt impurity, which cannot be washed away by routine way. The method to get more pure product needs to be studied further. 100
80
1626.72
3440.05
60 50 40 4000
Na3PO4·12H2O Cu2O bulk Cu2O
3500
3000
2500
2000
1500
1000
622.34
630.03
70
1040.18
Transmittance(%)
90
500
Wavenumber(cm-1)
5
Fig.3. FT-IR spectra of Na3PO4·12H2O , as-prepared Cu2O sample and bulk Cu2O. For pure Na3PO4·12H2O FT-IR spectrum in Fig.3, the peak at 1040 cm-1 can be attributed to the P-O group. For Cu2O sample FT-IR spectrum in Fig.3, the weaker peak also appears at 1040 cm-1, which may be the absorption peak of copper salt impurity. Moreover, a new characteristic peak appears at 630 cm-1. [14] reports that Cu2O has only one IR active mode at 620 cm-1, such as the spectrum of bulk Cu2O in Fig.3. However, for nanoscale particles, the absorption bands of FT-IR spectrum shift to higher wave-number[15]. According to the analysis above, the peak at 630 cm-1 shown in Fig. 3 may belong to the Cu-O vibration of Cu2O crystals. The broad band at 3440 cm-1 corresponds to the stretching vibration of the hydroxyls while that of 1626 cm-1 should be generated by bending vibration, which originates from the surface absorbed water. 1.5
40
a
bulk Cu2O
b
as-perpared Cu2O sample
20
(eV)2
1.0
h
Absorbance
30
0.5
10 bulk Cu2O
Eg=2.17eV
as-prepared Cu2O sample
300
400
500
600
Wavelength(nm)
700
800
Eg=2.24eV
0 2
3
h(eV)
4
5
Fig. 4. (a) UV–vis absorption spectra and (b) the corresponding plots of (αhν)2 vs. hv curve of as-prepared Cu2O sample and bulk Cu2O. The UV-vis absorption spectra of the as-prepared Cu2O sample and bulk Cu2O are shown in Fig.4(a). It shows that absorption peaks of two samples appear around 430 nm and 570 nm, respectively. Therefore, The UV-vis absorption spectrum of as-prepared Cu2O shows blue shift effect comparing to bulk Cu2O’s. According to [16], the UV-vis absorption would be greatly affected by the morphology and crystallinity of Cu2O crystals. So the morphology and crystallinity of as-prepared Cu2O crystals, which have
6
single-crystalline octahedral structure, may relate to the above-mentioned blue shift. In addition, the blue shift may be also attributed to the particle size of product, which is less than 300nm. Because the material has dimensional effect. According to the equation (5) the band gaps energy of the as-prepared samples could be estimated[17]. (αhν)2=K(hν-Eg)
(5)
where α is the absorption coefficient, K is a proportionality constant, and Eg is the band-gap energy. As is shown in Fig.4b, the band gap (Eg) of this sample is about 2.24eV which is slightly greater than that of bulk Cu2O(2.17eV). 4. Conclusion Cuprous oxide has been successfully prepared by a simple approach. The prepared Cu2O product has octahedral structure and narrow band gap, which could effectively absorb visible light and might have potential applications in photocatalyst. Furthermore, the preparation of Cu2O does not require the assistance of organic compounds or surfactants, thus the prepared method can be considered as facile and green synthesis route, which is suitable for large scale production. References [1] Lin YK, Chiang YJ, Hsu YJ. Sensors and Actuators B 2014;204 : 190–6. [2]
Qi WJ, Huang CZ, Chen LQ. Talanta 2010;80:1400-5.
[3] Zhou LJ, Zou YC, Zhao J, Wang PP, Feng LL, Sun LW, et al. Sensors and Actuators B 2013;188:533–9. [4] Min SX, Wang F, Jin ZL, Xu J. Superlattices and Microstructures 2014;74:294–307.
7
[5] Wang LD, Zhao WX, Wang GH, Zhou H, Geng C, Wu CQ, et al. Solar Energy Materials & Solar Cells 2014;130:387-92. [6] Susman MD, Feldman Y, Vaskevich A, Rubinstein I. Acs Nano 2014;8:162-74. [7] Aref AA, Xiong LB, Yan NN, Abdulkarem AM, Yu Y. Materials Chemistry and Physics 2011;127:433-9. [8] Andrea P, Rosaria B, Mirko P, Mauro P, Sergio M, Luca DT, et al. ACS Appl. Mater. Interfaces 2013;5:2745-51. [9] Leng M, Liu MZ, Zhang YB, Wang ZQ, Yu C, Yang XG, et al. J. AM. CHEM. SOC 2010;132:17084-7. [10] Hua Q, Chen K, Chang SJ, Ma YS, Huang WX. J. Phys. Chem. C 2011;115:20618-27. [11] Li Q, Xu P, Zhang B, Tsai HH, Zheng SJ, Wu G, Wang HL. J. Phys. Chem. C 2013;117:13872-8. [12] Qi WJ, Huang CZ, Chen LQ. Talanta 2010;80:1400-5. [13] Pal J, Ganguly M, Mondal C. J.Phys.Chem.C 2013;117:24640-53. [14] Li BJ, Li YY, Zhao YB, Sun L. Journal of Physics and Chemistry of Solids 2013;74:1842-7. [15]Basu M, Sinha AK, Pradhan M, Sarkar S, Pal A, Mondal C, et al. J. Phys. Chem. C 2012;116:25741-7. [16] Xu YY, Jiao XL, Chen DR. J. Phys. Chem. C 2008;112:16769–73. [17] Zhang DF, Zhang H, Shang Y, Guo L, Crystal Growt h & Design 2011;11:3748–53.
8
Highlights 1 A novel green method was introduced to fabricate Cu2O nanocrystals. 2 Octahedral Cu2O crystals were fabricated without any surfactants. 3 XRD and FT-IR indicate that Cu2O is almost pure phase. 4 The as-prepared Cu2O exhibits good optical properties.
9
PII: DOI: Reference:
S0167-577X(15)30410-9 http://dx.doi.org/10.1016/j.matlet.2015.08.055 MLBLUE19416
To appear in: Materials Letters Received date: 27 June 2015 Revised date: 30 July 2015 Accepted date: 10 August 2015 Cite this article as: Dehua Guo, Lixian Wang, Yingji Du, Zhuqiang Ma and Long Shen, Preparation of octahedral Cu2O nanoparticles by a green route, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2015.08.055 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 galley proof before it is published in its final citable 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.
Preparation of octahedral Cu2O nanoparticles by a green route Dehua Guo1, Lixian Wang1*, Yingji Du1, Zhuqiang Ma2, Long Shen2 1
School of Chemical and Environmental Engineering, Shanghai Institute of Technology,
100 Haiquan Road, Shanghai 201418, China 2
Rong Jian chemical plant, 269 Chuhua Road, shanghai 201400, China
E-mail address: [email protected] *Corresponding author School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418, China E-mail address: [email protected], TEL.: +86 02160877227 Abstract The fabrication of octahedral Cu2O was described by a green and simple chemical precipitation method in this study. All samples were characterized by X-ray powder diffractometer(XRD), scanning electron microscopy(SEM), Fourier transform infrared spectrometer(FTIR) and ultraviolet-visible spectrophotometer(UV-vis), respectively. The results show that products are composed of octahedral particles with an edge length of 200-300 nm, and narrow band gaps(2.26eV), which is blue shifted with respect to the bulk Cu2O value(2.17eV). Well-dispersed Cu2O with effectively absorbing visible light can be obtained through the route which is surfactant-free, cost effective, and suitable for large scale production. Key words: Octahedral Cu2O, Nanocrystalline materials, Semiconductors, X-ray techniques, Optical properties 1. Introduction
1
The synthesis, controlled inorganic materials with specific morphology and size, plays an important role in uncovering their shape-dependent properties and fully achieving their potential practical applications. As an important p-type semiconductor with a band gap value of 2.17 eV, Cu2O is a promising material in the field of solar energy conversion. besides, Cu2O is also used as catalyst for organic reactions, electrode for lithium ion battery, gas sensor and pholocatalyst for dye degradation[1-5]. In the past few years, numerous Cu2O products with well-controlled uniform morphologies
had
been
synthesized,
such
as
nanocubes[6],
nanotubes[7],
octahedrons[8], polyhedrons[9] and nanowires[10]. Some reports used copper salt as crude material, firstly to get cupric oxide, and then to prepare cuprous oxide by reduction. However, the extent of reduction was not easy to be controlled, and the productions always included cupric oxide or copper. In addition, the most exciting techniques to get spacial morphologies materials in the reports[11-13] had to rely on the proper selection of expensive surfactants or organic additives, such as polyvinyl pyrrolidone(PVP), cetylteimethylammonium bromide(CTAB) and methylpyridine. Therefore, it is necessary to exploit a facile route for the shape-controlled synthesis of Cu2O with specific morphology and size. Here, we successfully describe a novel shape-controlled synthesis route without any templates and surfactants for preparing cuprous oxide with octahedral morphology. 2. Experimental details 2.1. Preparation
2
All the chemicals were analytical grade reagents. In a typical synthesis, 1.0 g CuCl powder was dissolved in 100 ml of 6 M NaCl solution to form transparent solution. The transparent solution and 20.0 ml of Na3PO4 (0.6 M)solution were added simultaneously into a beaker with 100 ml distilled water, and the precipitate with bright yellow color would be obtained immediately. The yellow color solution was stirred at 60 ℃ for 20 min, then to be cooled to room temperature. Finally, the precipitate was separated from the solution by filtration, then to be washed with distilled water and absolute ethanol, respectively. The final product could be obtained after drying the precipitate at 90 ℃ for 3 h. 2.2. Characterization The obtained malachite samples were confirmed by powder X-ray diffraction (XR D, D/Max 2400, Rigaku, by a diffractometer equipped with a Cu Kα radiation source λ= 1.5418 Å) in the 2θ angles ranging from 10° to 80°. The morphologies of as-synthesized malachite samples were characterized by using a scanning electron microscope (SEM, S-3400N) with 15 kV of accelerated voltages. FT-IR spectra were recorded on a Fourier transmission infrared spectrometry (FT-IR, NEXUS) at wavenumbers 400-4000 cm-1. The UV-vis transmission spectra were determined with a spectrophotometer(U-3900). 3. Results and discussion The preparation of Cu+ complex is according to Eqs. (1): CuCl
+ Cl-
→
[CuCl2]- ↔
The preparation of OH-
Cu+
+
2Cl-
(1)
is according to Eqs. (2)
3
PO43- + H2O → HPO42- +
OH- (2)
The synthesis mechanism of Cu2O is described by Eqs. (3) and (4) : Cu+
+ OH- → CuOH
2CuOH
→ Cu2O + H2O (heating)
(3) (4)
In this work, Na3PO4 was introduced as a precipitator to provide OH-. It is well known that, CuCl is undissolved in deionized water. Therefore, CuCl should be made into copper complex so as to be dissolved in NaCl solution. When copper complex solution was mixed with sodium phosphate solution, the copper complex solution slowly released Cu+, Na3PO4 solution was slowly hydrolyzed OH-, Cu+ and OH- reacted CuOH. CuOH under high temperature is not stable, which will resolve into Cu2O. In order to get micro-nano-sized particles, the reaction rate must be controlled in low range. Since CuOH and Cu2O are solid, the production rate of Cu2O was determined by Eqs. (3) in which the reaction rate was controlled by the concentration of Cu+ and OH-. When the concentration of Cu+ was fixed, the generation rate of Cu2O would be controlled by the concentration of OH-. In present work, control experiments were performed by replacing Na3PO4 with NaOH or Na2CO3, which prepared amorphous, larger particle size sample. Therefore, the key to preparation of octahedral
10
20
30
40
50
60
(311)
(110)
(220)
(200)
Intensity
(111)
Cu2O nanocrystals is Na3PO4.
70
80
2θ(degree)
Fig. 1. XRD pattern of the sample.
4
Fig. 1 shows XRD pattern of the sample in the typical synthesis. The XRD spectrum shows five characteristic peaks at 2θ values of 29.5°, 36.4°, 42.3°, 61.4° and 73.5°, which correspond to the crystal planes of (110), (111), (200), (220) and (311), respectively. All diffraction peaks can be indexed to the octahedral phase of cuprous oxide crystal(JCPDS. NO. 05-0667). Furthermore, peaks due to impurities of Cu(0), CuO, and Cu(OH)2 are not detected from the XRD pattern, which indicates that pure cuprous oxide can be obtained under current synthetic conditions.
Fig. 2. Low-magnification and high-resolution SEM images of the sample (a, b) The morphology of as-prepared Cu2O is observed by SEM as shown in Fig. 2a. It is obvious that the sample is consisted of well-dispersed octahedral particles with an edge length of 200-300 nm. The high-resolution image of a typical bulk is shown in Fig. 2b, it can be seen that the sample shows octahedral morphology, which is the same as the low-magnification SEM result. Some small particles can be found in Fig.2 except for the octahedral particles. According to infrared spectra analysis about Fig.3., it’s probably the copper salt impurity, which cannot be washed away by routine way. The method to get more pure product needs to be studied further. 100
80
1626.72
3440.05
60 50 40 4000
Na3PO4·12H2O Cu2O bulk Cu2O
3500
3000
2500
2000
1500
1000
622.34
630.03
70
1040.18
Transmittance(%)
90
500
Wavenumber(cm-1)
5
Fig.3. FT-IR spectra of Na3PO4·12H2O , as-prepared Cu2O sample and bulk Cu2O. For pure Na3PO4·12H2O FT-IR spectrum in Fig.3, the peak at 1040 cm-1 can be attributed to the P-O group. For Cu2O sample FT-IR spectrum in Fig.3, the weaker peak also appears at 1040 cm-1, which may be the absorption peak of copper salt impurity. Moreover, a new characteristic peak appears at 630 cm-1. [14] reports that Cu2O has only one IR active mode at 620 cm-1, such as the spectrum of bulk Cu2O in Fig.3. However, for nanoscale particles, the absorption bands of FT-IR spectrum shift to higher wave-number[15]. According to the analysis above, the peak at 630 cm-1 shown in Fig. 3 may belong to the Cu-O vibration of Cu2O crystals. The broad band at 3440 cm-1 corresponds to the stretching vibration of the hydroxyls while that of 1626 cm-1 should be generated by bending vibration, which originates from the surface absorbed water. 1.5
40
a
bulk Cu2O
b
as-perpared Cu2O sample
20
(eV)2
1.0
h
Absorbance
30
0.5
10 bulk Cu2O
Eg=2.17eV
as-prepared Cu2O sample
300
400
500
600
Wavelength(nm)
700
800
Eg=2.24eV
0 2
3
h(eV)
4
5
Fig. 4. (a) UV–vis absorption spectra and (b) the corresponding plots of (αhν)2 vs. hv curve of as-prepared Cu2O sample and bulk Cu2O. The UV-vis absorption spectra of the as-prepared Cu2O sample and bulk Cu2O are shown in Fig.4(a). It shows that absorption peaks of two samples appear around 430 nm and 570 nm, respectively. Therefore, The UV-vis absorption spectrum of as-prepared Cu2O shows blue shift effect comparing to bulk Cu2O’s. According to [16], the UV-vis absorption would be greatly affected by the morphology and crystallinity of Cu2O crystals. So the morphology and crystallinity of as-prepared Cu2O crystals, which have
6
single-crystalline octahedral structure, may relate to the above-mentioned blue shift. In addition, the blue shift may be also attributed to the particle size of product, which is less than 300nm. Because the material has dimensional effect. According to the equation (5) the band gaps energy of the as-prepared samples could be estimated[17]. (αhν)2=K(hν-Eg)
(5)
where α is the absorption coefficient, K is a proportionality constant, and Eg is the band-gap energy. As is shown in Fig.4b, the band gap (Eg) of this sample is about 2.24eV which is slightly greater than that of bulk Cu2O(2.17eV). 4. Conclusion Cuprous oxide has been successfully prepared by a simple approach. The prepared Cu2O product has octahedral structure and narrow band gap, which could effectively absorb visible light and might have potential applications in photocatalyst. Furthermore, the preparation of Cu2O does not require the assistance of organic compounds or surfactants, thus the prepared method can be considered as facile and green synthesis route, which is suitable for large scale production. References [1] Lin YK, Chiang YJ, Hsu YJ. Sensors and Actuators B 2014;204 : 190–6. [2]
Qi WJ, Huang CZ, Chen LQ. Talanta 2010;80:1400-5.
[3] Zhou LJ, Zou YC, Zhao J, Wang PP, Feng LL, Sun LW, et al. Sensors and Actuators B 2013;188:533–9. [4] Min SX, Wang F, Jin ZL, Xu J. Superlattices and Microstructures 2014;74:294–307.
7
[5] Wang LD, Zhao WX, Wang GH, Zhou H, Geng C, Wu CQ, et al. Solar Energy Materials & Solar Cells 2014;130:387-92. [6] Susman MD, Feldman Y, Vaskevich A, Rubinstein I. Acs Nano 2014;8:162-74. [7] Aref AA, Xiong LB, Yan NN, Abdulkarem AM, Yu Y. Materials Chemistry and Physics 2011;127:433-9. [8] Andrea P, Rosaria B, Mirko P, Mauro P, Sergio M, Luca DT, et al. ACS Appl. Mater. Interfaces 2013;5:2745-51. [9] Leng M, Liu MZ, Zhang YB, Wang ZQ, Yu C, Yang XG, et al. J. AM. CHEM. SOC 2010;132:17084-7. [10] Hua Q, Chen K, Chang SJ, Ma YS, Huang WX. J. Phys. Chem. C 2011;115:20618-27. [11] Li Q, Xu P, Zhang B, Tsai HH, Zheng SJ, Wu G, Wang HL. J. Phys. Chem. C 2013;117:13872-8. [12] Qi WJ, Huang CZ, Chen LQ. Talanta 2010;80:1400-5. [13] Pal J, Ganguly M, Mondal C. J.Phys.Chem.C 2013;117:24640-53. [14] Li BJ, Li YY, Zhao YB, Sun L. Journal of Physics and Chemistry of Solids 2013;74:1842-7. [15]Basu M, Sinha AK, Pradhan M, Sarkar S, Pal A, Mondal C, et al. J. Phys. Chem. C 2012;116:25741-7. [16] Xu YY, Jiao XL, Chen DR. J. Phys. Chem. C 2008;112:16769–73. [17] Zhang DF, Zhang H, Shang Y, Guo L, Crystal Growt h & Design 2011;11:3748–53.
8
Highlights 1 A novel green method was introduced to fabricate Cu2O nanocrystals. 2 Octahedral Cu2O crystals were fabricated without any surfactants. 3 XRD and FT-IR indicate that Cu2O is almost pure phase. 4 The as-prepared Cu2O exhibits good optical properties.
9