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In-situ synthesis of ZnO nanoparticles on bamboo pulp fabric
Materials Letters 97 (2013) 184–186
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
In-situ synthesis of ZnO nanoparticles on bamboo pulp fabric Guangyu Zhang a,n, Hideaki Morikawa a, Yuyue Chen b, Mikihiko Miura a a b
Faculty of Textile Science and Technology, Shinshu University 3-15-1, Tokida, Ueda, Nagano 386-8567, Japan College of Textile and Costume Engineering, Soochow University, Suzhou 215021, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 January 2013 Accepted 22 January 2013 Available online 30 January 2013
The research presents a novel strategy to synthesis ZnO nanoparticles on bamboo pulp fabric. Bamboo pulp fabric was treated with the zinc nitrate and Multi-amide compound (HSDA) mixing aqueous solution under hydrothermal condition by an impregnation method, and then we obtained the fabrics with deposited ZnO nanoparticles. The mechanism of the reaction process was investigated. The UV/ visible absorption spectrophotometry indicated that ZnO nanoparticles colloidal have been formed in mixing solution. The results of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques confirmed that ZnO nanoparticles have been fixed and well dispersed on bamboo pulp fabric. The resulting fabric coated with ZnO nanoparticles could be having UV protective and antibacterial properties. & 2013 Elsevier B.V. All rights reserved.
Keywords: ZnO nanoparticles Bamboo pulp fabric Synthesis
1. Introduction ZnO has been considered as promising semiconductors as it has wide band gap of 3.37 eV, large exciton energy of 60 meV. It is expected that the ZnO nanomaterial will be widely applied in nanolaser, solar battery, photo detectors, gas sensors, piezoelectric devices, etc. [1–3]. However, designing and modifying fabrics by ZnO nanoparticles for high protection against UV radiation, antibacterial, deodorant has attracted considerable interests in recent year. Recently, Li et al. reported that cotton fabric coating with ZnO nanoparticles could emit 82% more infrared than untreated cotton fabric [4]. Mao et al. treated cotton fabric with ZnO nanoparticles to enhance anti-UV property through hydrothermal method [5]. Li et al. reported that the cotton fabric have antibacterial performances when treated with ZnO nanoparticles [6]. Recently, hyperbranched polymers and dendrimers have been widely developed due to their special solution/melting properties and quasispherical branched architecture. Hyper branched polymers and their substitutes can be used as nanomaterials for host– guest encapsulation and the fabrication of organic–inorganic hybrids, even directly used as templates in inorganic nanoparticles [7,8]. In our previous study, an amino-terminated hyperbranched polymer (HBP-NH2) was synthesized. It was utilized to control the synthesis of Ag nanoparticles, also served as a binder to impart and fix the silver nanoparticles on the cotton fabric to provide antimicrobial properties [9]. In order to give the fabric
n
Corresponding author. Tel.: þ81 268215372. E-mail address: [email protected] (G. Zhang).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.01.096
multiple functions, this research use the Multi-amide compound (HSDA) to prepare ZnO nanoparticles and fix it on the fabric. A new cellulose-based material, Bamboo pulp fabric was chosen as the substrate for this research as it naturally smooth and round. In this process, HSDA served acts as a reactant and capture agent to fix the ZnO nanoparticles on bamboo pulp fabric.
2. Experimental Materisls: Bamboo pulp fabric chosen were purchased from Tanzhuzhuang bamboo fiber in Anji, Zhejiang, China, which was bleached and scoured, the density of the fabric is 138 g/m2 and a thickness of 0.29 mm. Multi-amide compound (HSDA) was prepared as described in our paper [9,10]. Zinc nitrate (Zn(NO3)2 6H2O) were purchased from Wako Chemical Reagent, Japan, as analytical reagents and employed without further purification. ZnO nanoparticles growth: An equimolar (0.01 M) aqueous solution of Zn(NO3)2 and 2 g/L HSDA were prepared in a beaker. Bamboo pulp fabric was immersed in the solution, the bath ratio is 1:50. The beaker was then sealed and held in the 80 1C water bath for 40 min with constant stirring. At the end of the process the fabric washed with deionized water several times to remove unfixed materials. The resulting bamboo pulp fabric was dried in drying oven at 100 1C for 2 min, 130 1C for 3 min. Bamboo pulp fabric characterize: Treated fabric was characterized and analyzed using SEM (Hitachi, Japan S4800), X-ray photoelectron spectroscopy (XPS, XSAM 800 electron spectrometer), and diffuse reflectance UV–Vis spectroscopy (Shimadzu, Japan UV-3010).
G. Zhang et al. / Materials Letters 97 (2013) 184–186
185
Fig. 1. Schematic preparation of the ZnO nanoparticles coating on fabric.
Fig. 2. The UV–vis absorption spectra of HSDA and HSDA/ZnO nanoparticles.
3. Results and discussion Compared to the traditional approach Fig. 1 outlines our novel strategy for the solution scheme. HSDA is mildly alkaline, when in aqueous solution it will release OH-. In alkaline condition Zn2 þ may convert into Zn(OH)2 colloids. During the hydrothermal process Zn(OH)2 colloids dissolves into Zn(OH)42–, ZnO nucleates spontaneously from the solution of Zn(OH)42– to multi nuclei aggregates [11,12]. HSDA used as templates to entrap ZnO nanoparticles during the process, as it has interior cavities as well as inwardly and outwardly amino groups. As a cellulosic fiber, the bamboo pulp fabric surface is rich of hydroxyl groups. Amino groups can adsorb onto bamboo pulp fabric substance by hydrogen bonding. HSDA acts as a reagent agent and capture agent to deliver ZnO nanoparticles on the surface of bamboo pulp fabric. UV–vis spectrum was applied to characterize the formation of ZnO nanoparticles. Fig. 2 shows the UV spectra of HSDA and
Fig. 3. (a) SEM images of bamboo pulp fiber and (b) the treated bamboo pulp fiber.
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G. Zhang et al. / Materials Letters 97 (2013) 184–186
XPS analysis was performed to identify the presence of ZnO nanoparticles. Fig. 4(a) shows the XPS spectra of the bamboo pulp fabric treated with ZnO nanoparticles. It can be seen that besides the C 1s and O 1s peaks such peaks as Zn 2p, Zn LMN, Zn 3s, Zn 3p, Zn 3d emerged, indicating that the modified bamboo pulp fabric was mainly composed of zinc, oxygen and carbon. The binding energy of Zn 2p3/2 and Zn 2p1/2 (as seen in Fig. 4(b)) is determined at 1022.5 and 1045.4 eV and the peak separation between them is 22.9 eV. According to the research results of Wei et al. and Zhang et al., the Zn ions are mainly in form of ZnO [17,18].
4. Conclusion ZnO nanoparticles were growth on the surface of bamboo pulp fabric by in-situ method. The processes are environmentally friendly and versatile. In this process, HSDA served acts as a reactant and capture agent to fix the ZnO nanoparticles on bamboo pulp fabrics. All the result of UV–vis, SEM, XPS confirmed that the ZnO nanoparticles were synthesized and the ZnO nanoparticles were fixed and well dispersed on the bamboo pulp fabric.
Acknowledgment This research was supported by the Grants for Excellent Graduate Schools, MEXT, Japan and the National High Technology Research and Development Program of China (No. 2012AA030313). References
Fig. 4. (a) XPS spectrum of the bamboo pulp fabric and (b) XPS spectrum of Zn 2p.
HSDA/ZnO nanoparticles hybrid. The HSDA aqueous solution only has one characteristic peak at 298 nm. When the Zn(NO3)2 and RSD aqueous solution were mixed, a new characteristic absorption of ZnO particles appeared at 362 nm, this can confirms the formation of the ZnO nanoparticles [13,14]. To confirm the formation of ZnO nanoparticles on the surface of the bamboo pulp fiber, the samples were analyzed with scanning electron microscope. The surface morphology of bamboo pulp fiber and the ZnOtreated fiber can be seen in Fig. 3. In terms of surface roughness there is an obvious difference the two fibers. As shown in Fig. 3(a) the bamboo pulp fiber is made up of fibrils which is arranged along the length of the fiber basically, its morphology is straight stripes with a smooth, sleek shape. Fig. 3(b) reveals that nanograined ZnO nanoparticles were in-situ formed on the bamboo pulp fabric. Straumal et al. reported that the physical properties of ZnO nanoparticles depend on defects in amorphous intergranular regions, grain boundary character distribution and the presence of surfaces [15,16]. According to the grain boundaries and free surfaces as well as the inherent properties of ZnO nanoparticles, the fabric with deposited ZnO nanoparticles may possess UV protection, ferromagnetic and antibacterial properties [5,6,15].
[1] Park WI, Yi GC, Kim JW, Park SM. Schottky nanocontacts on ZnO nanorod arrays. Appl Phys Lett 2003;82:4358–60. [2] Liu ZF, Jin ZG, Li W, Qiu JJ. Preparation of ZnO porous thin films by sol–gel method using PEG template. Mater Lett 2005;59:3620–5. [3] Hara Y, Brownson JRS, Anderson MA. Fabrication of thin-films composed of ZnO nanorods using electrophoretic deposition. Int J Appl Ceram Technol 2012;9:115–23. [4] Li Y, Wu DX, Hu JY, Wang SX. Novel infrared radiation properties of cotton fabric coated with nano Zn/ZnO particles. Colloids Surf. A 2007;300:140–4. [5] Mao ZP, Shi QP, Zhang LP, Cao HT. The formation and UV-blocking property of needle-shaped ZnO nanorod on cotton fabric. Thin Solid Films 2009;517:2681–6. [6] Li Q, Chen SL, Jiang WC. Durability of nano ZnO antibacterial cotton fabric to sweat. J Appl Polym Sci 2007;103:412–6. [7] Taniguchi Y, Shirai K, Saitoh H, Yamauchi T, Tsubokawa N. Postgrafting of vinyl polymers onto hyperbranched poly(amidoamine)-grafted nano-sized silica surface. Polymer 2005;46:2541–7. [8] Sun YY, Wang D, Gao JG, Zheng Z, Zhang QJ. Synthesis of silver (nano)particle under hyperbranched poly(amido amine)s. J Appl Polym Sci 2007;103:3701–5. [9] Zhang F, Wu XX, Chen YY, Lin H. Application of silver nanoparticles to cotton fabric as an antibacterial textile finish. Fiber Polym 2009;10:496–501. [10] Wu XX, Chen YY, He HT. Synthesis of the hyperbranched Polymers-RSD compound and its application in dyeability modification of cotton. Adv Mater Res 2011;175:750–4. [11] Duan JX, Huang XT, Wang E. PEG-assisted synthesis of ZnO nanotubes. Mater Lett 2006;60:1918–21. [12] Hu X, Masuda Y, Ohji T, Kato K. Low-temperature fabrication of ZnO nanoarray films by forced hydrolysis of anhydrous zinc acetate layer. J Cryst Growth 2009;311:597–600. [13] Herna´ndez A, Maya L, Sa´nchez-Mora E, Sa´nchez EM. Sol–gel synthesis, characterization and photocatalytic activity of mixed oxide ZnO–Fe2O3. J Sol–Gel Sci Technol 2007;42:71–8. [14] Prasad V, D’Souza C, Yadav D, Shaikh AJ, Vigneshwaran N. Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction. Spectrochim Acta 2006;65:173–8. [15] Straumal B, Mazilkin A, Protasova S, Myatiev A, Straumal P, Goering E, et al. Influence of texture on the ferromagnetic properties of nanograined ZnO films. Phys Status Solidi B 2011;248:1581–6. [16] Straumal B, Mazilkin A, Protasova S, Myatiev A, Straumal PB, Goering E, et al. Amorphous grain boundary layers in the ferromagnetic nanograined ZnO films. Thin Solid Films 2011;520:1192–4. [17] Zhang WJ, Zhu SL, Li Y, Wang FH. Photocatalytic Zn-doped TiO2 films prepared by DC reactive magnetron sputtering. Vacuum 2007;82:328–35. [18] Wei HY, Wu SY, Wu LL, Hu XC. Preparation and photoluminescence of surface N-doped ZnO nanocrystal. Mater Lett 2005;59:271–5.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
In-situ synthesis of ZnO nanoparticles on bamboo pulp fabric Guangyu Zhang a,n, Hideaki Morikawa a, Yuyue Chen b, Mikihiko Miura a a b
Faculty of Textile Science and Technology, Shinshu University 3-15-1, Tokida, Ueda, Nagano 386-8567, Japan College of Textile and Costume Engineering, Soochow University, Suzhou 215021, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 January 2013 Accepted 22 January 2013 Available online 30 January 2013
The research presents a novel strategy to synthesis ZnO nanoparticles on bamboo pulp fabric. Bamboo pulp fabric was treated with the zinc nitrate and Multi-amide compound (HSDA) mixing aqueous solution under hydrothermal condition by an impregnation method, and then we obtained the fabrics with deposited ZnO nanoparticles. The mechanism of the reaction process was investigated. The UV/ visible absorption spectrophotometry indicated that ZnO nanoparticles colloidal have been formed in mixing solution. The results of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques confirmed that ZnO nanoparticles have been fixed and well dispersed on bamboo pulp fabric. The resulting fabric coated with ZnO nanoparticles could be having UV protective and antibacterial properties. & 2013 Elsevier B.V. All rights reserved.
Keywords: ZnO nanoparticles Bamboo pulp fabric Synthesis
1. Introduction ZnO has been considered as promising semiconductors as it has wide band gap of 3.37 eV, large exciton energy of 60 meV. It is expected that the ZnO nanomaterial will be widely applied in nanolaser, solar battery, photo detectors, gas sensors, piezoelectric devices, etc. [1–3]. However, designing and modifying fabrics by ZnO nanoparticles for high protection against UV radiation, antibacterial, deodorant has attracted considerable interests in recent year. Recently, Li et al. reported that cotton fabric coating with ZnO nanoparticles could emit 82% more infrared than untreated cotton fabric [4]. Mao et al. treated cotton fabric with ZnO nanoparticles to enhance anti-UV property through hydrothermal method [5]. Li et al. reported that the cotton fabric have antibacterial performances when treated with ZnO nanoparticles [6]. Recently, hyperbranched polymers and dendrimers have been widely developed due to their special solution/melting properties and quasispherical branched architecture. Hyper branched polymers and their substitutes can be used as nanomaterials for host– guest encapsulation and the fabrication of organic–inorganic hybrids, even directly used as templates in inorganic nanoparticles [7,8]. In our previous study, an amino-terminated hyperbranched polymer (HBP-NH2) was synthesized. It was utilized to control the synthesis of Ag nanoparticles, also served as a binder to impart and fix the silver nanoparticles on the cotton fabric to provide antimicrobial properties [9]. In order to give the fabric
n
Corresponding author. Tel.: þ81 268215372. E-mail address: [email protected] (G. Zhang).
0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.01.096
multiple functions, this research use the Multi-amide compound (HSDA) to prepare ZnO nanoparticles and fix it on the fabric. A new cellulose-based material, Bamboo pulp fabric was chosen as the substrate for this research as it naturally smooth and round. In this process, HSDA served acts as a reactant and capture agent to fix the ZnO nanoparticles on bamboo pulp fabric.
2. Experimental Materisls: Bamboo pulp fabric chosen were purchased from Tanzhuzhuang bamboo fiber in Anji, Zhejiang, China, which was bleached and scoured, the density of the fabric is 138 g/m2 and a thickness of 0.29 mm. Multi-amide compound (HSDA) was prepared as described in our paper [9,10]. Zinc nitrate (Zn(NO3)2 6H2O) were purchased from Wako Chemical Reagent, Japan, as analytical reagents and employed without further purification. ZnO nanoparticles growth: An equimolar (0.01 M) aqueous solution of Zn(NO3)2 and 2 g/L HSDA were prepared in a beaker. Bamboo pulp fabric was immersed in the solution, the bath ratio is 1:50. The beaker was then sealed and held in the 80 1C water bath for 40 min with constant stirring. At the end of the process the fabric washed with deionized water several times to remove unfixed materials. The resulting bamboo pulp fabric was dried in drying oven at 100 1C for 2 min, 130 1C for 3 min. Bamboo pulp fabric characterize: Treated fabric was characterized and analyzed using SEM (Hitachi, Japan S4800), X-ray photoelectron spectroscopy (XPS, XSAM 800 electron spectrometer), and diffuse reflectance UV–Vis spectroscopy (Shimadzu, Japan UV-3010).
G. Zhang et al. / Materials Letters 97 (2013) 184–186
185
Fig. 1. Schematic preparation of the ZnO nanoparticles coating on fabric.
Fig. 2. The UV–vis absorption spectra of HSDA and HSDA/ZnO nanoparticles.
3. Results and discussion Compared to the traditional approach Fig. 1 outlines our novel strategy for the solution scheme. HSDA is mildly alkaline, when in aqueous solution it will release OH-. In alkaline condition Zn2 þ may convert into Zn(OH)2 colloids. During the hydrothermal process Zn(OH)2 colloids dissolves into Zn(OH)42–, ZnO nucleates spontaneously from the solution of Zn(OH)42– to multi nuclei aggregates [11,12]. HSDA used as templates to entrap ZnO nanoparticles during the process, as it has interior cavities as well as inwardly and outwardly amino groups. As a cellulosic fiber, the bamboo pulp fabric surface is rich of hydroxyl groups. Amino groups can adsorb onto bamboo pulp fabric substance by hydrogen bonding. HSDA acts as a reagent agent and capture agent to deliver ZnO nanoparticles on the surface of bamboo pulp fabric. UV–vis spectrum was applied to characterize the formation of ZnO nanoparticles. Fig. 2 shows the UV spectra of HSDA and
Fig. 3. (a) SEM images of bamboo pulp fiber and (b) the treated bamboo pulp fiber.
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G. Zhang et al. / Materials Letters 97 (2013) 184–186
XPS analysis was performed to identify the presence of ZnO nanoparticles. Fig. 4(a) shows the XPS spectra of the bamboo pulp fabric treated with ZnO nanoparticles. It can be seen that besides the C 1s and O 1s peaks such peaks as Zn 2p, Zn LMN, Zn 3s, Zn 3p, Zn 3d emerged, indicating that the modified bamboo pulp fabric was mainly composed of zinc, oxygen and carbon. The binding energy of Zn 2p3/2 and Zn 2p1/2 (as seen in Fig. 4(b)) is determined at 1022.5 and 1045.4 eV and the peak separation between them is 22.9 eV. According to the research results of Wei et al. and Zhang et al., the Zn ions are mainly in form of ZnO [17,18].
4. Conclusion ZnO nanoparticles were growth on the surface of bamboo pulp fabric by in-situ method. The processes are environmentally friendly and versatile. In this process, HSDA served acts as a reactant and capture agent to fix the ZnO nanoparticles on bamboo pulp fabrics. All the result of UV–vis, SEM, XPS confirmed that the ZnO nanoparticles were synthesized and the ZnO nanoparticles were fixed and well dispersed on the bamboo pulp fabric.
Acknowledgment This research was supported by the Grants for Excellent Graduate Schools, MEXT, Japan and the National High Technology Research and Development Program of China (No. 2012AA030313). References
Fig. 4. (a) XPS spectrum of the bamboo pulp fabric and (b) XPS spectrum of Zn 2p.
HSDA/ZnO nanoparticles hybrid. The HSDA aqueous solution only has one characteristic peak at 298 nm. When the Zn(NO3)2 and RSD aqueous solution were mixed, a new characteristic absorption of ZnO particles appeared at 362 nm, this can confirms the formation of the ZnO nanoparticles [13,14]. To confirm the formation of ZnO nanoparticles on the surface of the bamboo pulp fiber, the samples were analyzed with scanning electron microscope. The surface morphology of bamboo pulp fiber and the ZnOtreated fiber can be seen in Fig. 3. In terms of surface roughness there is an obvious difference the two fibers. As shown in Fig. 3(a) the bamboo pulp fiber is made up of fibrils which is arranged along the length of the fiber basically, its morphology is straight stripes with a smooth, sleek shape. Fig. 3(b) reveals that nanograined ZnO nanoparticles were in-situ formed on the bamboo pulp fabric. Straumal et al. reported that the physical properties of ZnO nanoparticles depend on defects in amorphous intergranular regions, grain boundary character distribution and the presence of surfaces [15,16]. According to the grain boundaries and free surfaces as well as the inherent properties of ZnO nanoparticles, the fabric with deposited ZnO nanoparticles may possess UV protection, ferromagnetic and antibacterial properties [5,6,15].
[1] Park WI, Yi GC, Kim JW, Park SM. Schottky nanocontacts on ZnO nanorod arrays. Appl Phys Lett 2003;82:4358–60. [2] Liu ZF, Jin ZG, Li W, Qiu JJ. Preparation of ZnO porous thin films by sol–gel method using PEG template. Mater Lett 2005;59:3620–5. [3] Hara Y, Brownson JRS, Anderson MA. Fabrication of thin-films composed of ZnO nanorods using electrophoretic deposition. Int J Appl Ceram Technol 2012;9:115–23. [4] Li Y, Wu DX, Hu JY, Wang SX. Novel infrared radiation properties of cotton fabric coated with nano Zn/ZnO particles. Colloids Surf. A 2007;300:140–4. [5] Mao ZP, Shi QP, Zhang LP, Cao HT. The formation and UV-blocking property of needle-shaped ZnO nanorod on cotton fabric. Thin Solid Films 2009;517:2681–6. [6] Li Q, Chen SL, Jiang WC. Durability of nano ZnO antibacterial cotton fabric to sweat. J Appl Polym Sci 2007;103:412–6. [7] Taniguchi Y, Shirai K, Saitoh H, Yamauchi T, Tsubokawa N. Postgrafting of vinyl polymers onto hyperbranched poly(amidoamine)-grafted nano-sized silica surface. Polymer 2005;46:2541–7. [8] Sun YY, Wang D, Gao JG, Zheng Z, Zhang QJ. Synthesis of silver (nano)particle under hyperbranched poly(amido amine)s. J Appl Polym Sci 2007;103:3701–5. [9] Zhang F, Wu XX, Chen YY, Lin H. Application of silver nanoparticles to cotton fabric as an antibacterial textile finish. Fiber Polym 2009;10:496–501. [10] Wu XX, Chen YY, He HT. Synthesis of the hyperbranched Polymers-RSD compound and its application in dyeability modification of cotton. Adv Mater Res 2011;175:750–4. [11] Duan JX, Huang XT, Wang E. PEG-assisted synthesis of ZnO nanotubes. Mater Lett 2006;60:1918–21. [12] Hu X, Masuda Y, Ohji T, Kato K. Low-temperature fabrication of ZnO nanoarray films by forced hydrolysis of anhydrous zinc acetate layer. J Cryst Growth 2009;311:597–600. [13] Herna´ndez A, Maya L, Sa´nchez-Mora E, Sa´nchez EM. Sol–gel synthesis, characterization and photocatalytic activity of mixed oxide ZnO–Fe2O3. J Sol–Gel Sci Technol 2007;42:71–8. [14] Prasad V, D’Souza C, Yadav D, Shaikh AJ, Vigneshwaran N. Spectroscopic characterization of zinc oxide nanorods synthesized by solid-state reaction. Spectrochim Acta 2006;65:173–8. [15] Straumal B, Mazilkin A, Protasova S, Myatiev A, Straumal P, Goering E, et al. Influence of texture on the ferromagnetic properties of nanograined ZnO films. Phys Status Solidi B 2011;248:1581–6. [16] Straumal B, Mazilkin A, Protasova S, Myatiev A, Straumal PB, Goering E, et al. Amorphous grain boundary layers in the ferromagnetic nanograined ZnO films. Thin Solid Films 2011;520:1192–4. [17] Zhang WJ, Zhu SL, Li Y, Wang FH. Photocatalytic Zn-doped TiO2 films prepared by DC reactive magnetron sputtering. Vacuum 2007;82:328–35. [18] Wei HY, Wu SY, Wu LL, Hu XC. Preparation and photoluminescence of surface N-doped ZnO nanocrystal. Mater Lett 2005;59:271–5.