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Synthesis of Ag-In-Zn-S alloyed nanorods and their biological application To cite this article: Xiaosheng Tang et al 2014 Nanotechnology 25 485702
View the article online for updates and enhancements.
- Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots Sirshendu Ghosh, Manas Saha, Vishal Dev Ashok et al. - Heterostructure of Au nanocluster tipping on a ZnS quantum rod: controlled synthesis and novel luminescence Yang Tian, Ligang Wang, Shanshan Yu et al. - Silver nanoparticles embedded mesoporous SiO2 nanosphere: an effective anticandidal agent against Candida albicans 077 M Qasim, Braj R Singh, A H Naqvi et al.
This content was downloaded from IP address 128.252.67.66 on 07/11/2017 at 09:43
Nanotechnology Nanotechnology 25 (2014) 485702 (6pp)
doi:10.1088/0957-4484/25/48/485702
Synthesis of Ag-In-Zn-S alloyed nanorods and their biological application Xiaosheng Tang1, Wei Wei1, Claudia Choon Chea Khng2, Zhigang Zang1, Ming Deng1, Tao Zhu1 and Junmin Xue2 1
Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, People’s Republic of China 2 Department of Materials Science & Engineering, Faculty of Engineering, National University of Singapore, Singapore E-mail: [email protected], [email protected] and [email protected] Received 5 September 2014, revised 27 September 2014 Accepted for publication 30 September 2014 Published 10 November 2014 Abstract
Monodisperse Ag-In-Zn-S (AIZS) nanorods with a length of 20 nm have been synthesized using a facile solution based route. These nanorods showed a wide range of fluorescence emissions from green to red, which was achieved by controlling the chemical composition. Moreover, the obtained AIZS nanorods showed high-quality photoluminescence, as well as attractive twophoton fluorescence properties, indicating their potential capability in biological tagging upon near-infrared excitation for deep tissue imaging. Furthermore, the AIZS nanorods presented in this report also show a promising perspective in applications such as solar cells and photocatalysts. S Online supplementary data available from stacks.iop.org/NANO/25/485702/mmedia Keywords: Ag-In-Zn-S nanorods, photoluminescence, cell labelling (Some figures may appear in colour only in the online journal) 1. Introduction
explored to improve the PL emission tunability and quantum yield [14–16]. The band gap of semiconductor nanoparticles can be adjusted by varying the chemical composition to make alloy as well as particle size, which is based on the quantum confinement effect [17–19]. In our previous research, the hot injection method was successfully used for synthesis of CuInS2-ZnS and AgInS2-ZnS alloy nanoparticles with bright and tunable PL, suggesting they are promising alternative materials to cadmium and lead-based semiconductor luminophore [20, 21]. Very recently, some groups reported that the PL emission could be tuned from the visible region to the near-infrared (NIR) region by adjusting the size and the composition of the nanoparticles [22]. Li et al prepared CuInS/ZnS core/shell nanocrystals with a spherical shape [23]. In addition, the shape and morphology of nanostructures were also reported to be able to influence the PL [17–19]. It has been claimed that nanorods and nanowires were observed to have different optical properties from those of nanoparticles [24, 25].
Over the last decade, colloidal semiconductor quantum dots (QDs) have been of great interest for both fundamental research and technical applications [1–3]. More recently, the synthesis of I-III-VI nanoparticles, such as CuInS2 and AgInS2, has attracted considerable attention because their main composition includes non-toxic elements, making them potential substitutes for the more commonly available nanoparticles that contain toxic and environmentally unfriendly heavy metal elements, such as Hg, Cd, and Pb [4–6]. The ternary I-III-VI2 semiconductor materials have been widely studied for a wide variety of applications, including biomedical imaging, color conversion, as well as photovoltaic solar cells, light emitting diodes, and photocatalytic H2 evolution under visible light irradiation [7–13]. The tunable photoluminescence (PL) color and high quantum yield are critical to the performance of the semiconductor nanoparticles in these applications. Therefore, strategies of adjusting band gap, fabricating heterodimer, and core/shell structure were 0957-4484/14/485702+06$33.00
1
© 2014 IOP Publishing Ltd Printed in the UK
Nanotechnology 25 (2014) 485702
X Tang et al
Therefore, tuning the composition, crystal phase, size, and shape of semiconductor nanoparticles remains an attractive research topic. Although significant progress has been made in the study of CuInZnS and AgInZnS, much of the work has been limited to spherical nanoparticles, with relatively little study on the other shapes and morphologies. For instance, Huang et al synthesized the quaternary AgInZn7S9 nanowires by Ag2S catalyzed growth, however; it only showed a red emission [26]. Ng et al fabricated new phase AgInSe2 nanorods by decomposing a single-source precursor [27]. Han et al developed alloyed (ZnS)x(CuInS2)1−x semiconductor nanorods with tuning band gap and photocatalytic properties, but the corresponding photoluminescence had not been studied [28]. Therefore, it is still a challenge to develop a simple method to synthesize a semiconductor of anisotropic shapes with tunable photoluminescence. To prepare a water-soluble fluorescent biological tag, graphene oxide (GO) was used to transfer the AIZS nanorods to an aqueous solution. GO, as a derivative of graphene that could be prepared from natural graphite, emerges as an attractive candidate for biomedical applications because of its chemical inertness, biocompatibility, and low toxicity [29– 31]. GO could be dispersed in water as there are many hydrophilic oxygenated functional groups such as epoxy, hydroxyl and carboxyl. These functional groups not only promote the water solubility, but also could modify the GO by other molecules via covalent or non-covalent bondings [32, 33]. Therefore, GO is extremely suitable for biomedical applications such as drug delivery and cell imaging [34–36]. Recently, there have been a few publications about GO-based nanocomposites, such as GO-CdTe and GO-CdS, using deposition or electrostatic assembly techniques [37–39]. However, quaternary Ag-In-Zn-S (AISZ) Cd-free alloyed nanorods have not been reported for biological applications. Herein, AIZS nanorods with tunable emissions from green to red were successfully achieved by a facile solution based route. Different emissions of AIZS nanorods were obtained by changing the composition of the precursors. The corresponding emission peaks from 520 to 680 nm of the resulting AIZS nanorods were adjusted by the amount of Zn. The AIZS nanorods showed higher quantum yield to that of the reported I-III-VI2 based nanocrystals, and the promising two-photon fluorescence properties indicate potential applications in biological tagging excited by near infrared. GO was successfully used for phase transfer of AIZS nanorods. Moreover, the biological cell labelling application of the AIZS nanorods has been demonstrated by the NIH/3T3 cells. In addition, the AIZS nanorods have widely potential applications such as solar cells and photocatalysts.
0.1 mM AgNO3 (Ag precursor), and 5 mM (1.2 mL) 1dodecanethiol (DDT) was mixed with 4 mL of ODE, 0.2 mM (45.7 mg) oleic acid, and 0.1 mL (46.25 mg) of TOP in a 100 mL three-necked bottle flask. Oleic acid and DDT served as capping ligands, where DDT was used to control the relative activity of the precursors. The mixture was heated to an intermediate temperature under a nitrogen atmosphere and was magnetically stirred until a homogenous clear solution was observed. Two injection solutions of Zn and S precursors were prepared: 0.6 mM sulfur powder in 100 μl oleylamine and 0.6 mM zinc stearate in 100 μl oleylamine and 400 μl ODE at 120 °C. At the intermediate temperature, both Zn and S precursors were injected dropwise into the reaction solution. Then the temperature increased to 210 °C and kept reaction for 2 h. The obtained nanorods were first washed using absolute ethanol and toluene to remove unreacted precursors, and the washing process was repeated three times. The purified nanorods were then dispersed in toluene or chloroform for storage. 2.2. Phase transfer by GO
2. Experimental section
Phase transfer from toluene to water was performed according to Peng’s method of emulsion without an emulsion stabilizer and solvent evaporation to prepare water-soluble biocompatible AIZS nanocrystals for biomedical applications [40]. The amount and overall hydrodynamic size of hosted AIZS nanocrystals were controlled by the ratio of nanocrystals to GO and duration of sonication during emulsion, respectively, where an increase in sonication time reduced hydrodynamic sizes. First, nanosized GO sheets synthesized via modified Hummer’s method [41] were grafted with oleylamine to transfer GO to a non-polar organic solvent. This was achieved by mixing dried GO flakes, oleylamine, and CHCl3. The resultant solution mixture (GO-g-OAM) was sonicated by ultrasonic homogenizer for 30 min to form a dark brown solution. Next, an equal volume of ethanol was added to GOg-OAM and the resultant mixture was centrifuged at 10 000 rpm for 10 min to precipitate GO-g-OAM. CHCl3 was added and the resultant solution sonicated in an ultrasonic bath for 20 min and stored in an enclosed glass vial at room temperature without further purification. Second, AIZS nanocrystals in CHCl3 were added to GO-g-OAM in CHCl3, mixed, and sonicated for 5 min in an ultrasonic bath to form a homogenous mixture. Subsequently, distilled water was added to the resultant mixture for emulsification under the ultrasonic homogenizer. Next, the light brown emulsion was placed in a beaker that had been heated to 60–70 °C, where CHCl3 was allowed to evaporate for at least 30 min under magnetic stirring at constant temperature. Lastly, the resultant dark brown transparent aqueous solution was centrifuged at 10 000 rpm for 10 min to eliminate large impurities and kept in enclosed glass vials at room temperature.
2.1. Preparation of AIZS nanorods
2.3. Characterization
AIZS nanorods were prepared via a facile one-pot thermal decomposition in which 0.1 mM In(Ac)3 (In precursor),
Powder x-ray diffraction (XRD) was performed on a D8 Advance Bruker-AXS (GmbH, Karlsruhe, Germany), using 2
Nanotechnology 25 (2014) 485702
X Tang et al
Cu Kα (1.5405 Å) (40 kV, 200 mA) x-ray source. The powder samples were prepared by drying the purified product at room temperature on a glass slip. Photoluminescence (PL) spectra were measured using a LS 55 Perkin–Elmer luminescence spectrometer. UV–visible absorption spectra were recorded by a Varian Cary 5000 UV−vis−NIR spectrophotometer. Transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM) images, and energy dispersive spectroscopy (EDS) were performed using Philips CM300 FEGTEM operating at 300 kV. A line scan for single and multiple nanoparticles was performed using FEI Titan Scanning/TEM (80–300 kV) operated at 200 kV in STEM mode. Samples characterized in TEM were prepared by dispersing the samples in toluene and depositing a drop of dispersed samples onto a carbon-coated copper grid. Subsequently, the solvent was evaporated in air at room temperature. Thus, chemical compositions, morphology, size, and optical behavior of the nanocrystals were obtained.
from XRD patterns [20]. The corresponding FFT further confirmed the hexagonal crystal structure of the nanorods. Figure 2(a) shows high angle annular dark-field scanning TEM (HAADF-STEM) image of AIZS nanorods. It could be observed that the element is homogeneous distribution in the AIZS nanorods. In a particular nanorod, starting from the bright spot 1 to 5 (figure 2(a)), Zn composition exhibits a nearly similar ratio along the longitudinal axis of the rod (figure 2(b)). In addition, the AIZS nanorod also exhibits uniform composition of Ag, In, and S, without any gradient (figure 2(b)). Hence, this suggests the presence of Zn diffusion from one end of the nanorod to form a uniformly Zndoped AgInS2 nanorod. The presence of Zn ions in AIZS nanorods of different emission wavelengths was further determined by energy-dispersive x-ray elemental analysis (figure S1). The increasing amount of Zn present in the nanocrystals relative to the composition of Ag, In, and Zn indicates that the blue shift in emission wavelengths was due to an increase in the amount of Zn diffused and doped into the nanocrystal. The optical behaviors of the AIZS nanorods were then characterized. In the absorption spectra shown in figure 3(a), the absorption onsets of the nanocrystals were blue shifted with increasing the ratio of Zn. Figure 3(b) presented the PL properties of the synthesized nanocrystals under excitation of UV (365 nm). The emission wavelengths were 630, 580, 550, and 510 nm for the samples prepared at 120, 150, 180, and 210 °C, respectively, which also suggested a blue shift in emission with increasing Zn mole fraction. The corresponding digital photo shown in figure 3(b) also displayed the strong emissions of the nanocrystals in toluene, and their corresponding photoluminescence quantum yields were 36, 38, 43, and 35% (figure S2). Herein, the photodecomposition of rhodamine 6G (R6G) was chosen as a model reaction to examine the catalytic properties of SiO2/Ag hybrid microspheres. The characterized peak located at 526 nm for the R6G solution measured by a UV–vis spectrophotometer was used to determine its reduction efficiency at given time interval. Figures 4(a) and (b) show that nearly 100% of R6G had been photodegraded within 5 min, indicating the as-prepared SiO2/Ag hybrid microspheres with excellent catalytic performance toward the R6G solution. The upconversion fluorescence test under excitation of 800 nm laser was applied to all AIZS nanorods with different emissions, and the corresponding spectra were displayed in figure 4(a). From figure 4(a), it could be observed that the various visible emissions could be achieved for these samples (figure 4(a)). Moreover, the emission peaks excited by 800 nm matched well with their respective counterparts under UV excitation (figure 3(b)). Furthermore, the upconversion fluorescence emission peaks were located at 635, 581, 556, and 511 nm, which have very slight red shift compared to the PL emission peaks. The corresponding TEM images and SAED pattern of the as-prepared AIZS nanorods with yellow, orange, and green emissions are shown in the supporting information (figures S3–S5). The AIZS nanorods with yellow emission were chose for testing the power dependence property of the as-prepared AIZS nanorods, which was
3. Results and discussion The crystal structures of the synthesized AIZS of varying emission wavelengths were characterized by XRD (figure 1(a)). The nanocrystals exhibited three broad peaks at 2θ = 27.6°, 47.8°, and 56.7°, which were assignable to diffraction of the (002), (110), and (112) planes, respectively, of hexagonal AgInZn2S4 crystal structure (JCPDF 25-0383) [20]. As nucleation reaction temperature decreased, the respective nanocrystal exhibited a peak present between the corresponding peaks of bulk cubic ZnS and chalcopyrite AgInS2, where angle increase and peak shift toward ZnS was observed with decreasing temperature. The reason is the ion radii of Ag+ (1.14 Å) and In3+ (0.76 Å) are larger than that of Zn2+ (0.74 Å) [42–44]. Thus, the as-synthesized AIZS were not a mixture of ZnS and AgInS2 phases but a ZnS-AgInS2 solid solution where an increase in ZnS present accompanied an increase in Zn2+ precursor content, as reported in bulk materials [16, 20, 21]. The morphology of the AIZS samples was measured by TEM technique. From the TEM image of figure 1(b), it can be seen that high-quality AIZS nanorods were obtained. The AIZS nanorods possessed a narrow size distribution, with an average length of 20 nm (figure 1(b) inset). Figure 1(c) shows the HRTEM image of part of the AIZS nanorods. The lattice of the single AIZS nanorod could be clearly observed, which indicated the high quality crystalline of AIZS nanorods structure. Additionally, the corresponding selected area electron diffraction (SAED) displayed the diffraction rings of (002), (110), and (201) indices of hexagonal crystal structure. Figure 1(d) showed the HRTEM image of a typical AIZS nanorods and its FFT. The lattice fringes of the nanorods were clearly observed, of which two lattice indices of hexagonal crystal structure. As shown in figure 2(d), the distance between two adjacent planes in the labeled image is measured to be 0.29 nm, corresponding to (101) planes of hexagonal structure, which is also consistent with the results obtained 3
Nanotechnology 25 (2014) 485702
X Tang et al
Figure 1. (a) XRD pattern of the AIZS nanorods with different emissions. (b) TEM images of the as-obtained AIZS nanorods with red
emission. Inset: corresponding length distribution of the sample. (c) Magnified TEM image of AIZS nanorods with red emission. Inset is the SAED patterns of the sample. (d) HRTEM of a single AIZS nanorod. Inset: corresponding fast Fourier transform (FFT) image.
Figure 2. (a) HAADF-STEM of AIZS nanorods. (b) Line profile of Ag, In, Zn, and S dispersion in AIZS nanorods.
displayed in figure 4(b). Using the relation of I ∼ PowerK, the value of K was around 2.05 (figure 4(c)). Therefore, it could concluded that the upconversion fluorescence mechanism in the sample was two-photon excitation in nature . To demonstrate their potential applications in bio-tagging, the as-prepared AIZS nanorods with yellow and red
emissions were transferred to water solution via GO. The photoluminescence of the AIZS nanorods after phase transferred was characterized in figure S6. The PL spectra of the AIZS-GO nanorods displayed nearly the same as the AIZS nanorods dispersed in toluene, and the emission photograph of AIZS-GO dispersed in water, which is the 4
Nanotechnology 25 (2014) 485702
X Tang et al
Figure 3. (a) The absorption spectra, (b) PL spectra of the AIZS nanorods with different emissions, and (inset) the corresponding digital
photographs of the AIZS nanorods dispersed in toluene under excitation of 365 nm.
Figure 4. (a) Upconversion spectra of the AIZS nanorods with different emissions. The measurements were under excitation of an 800 nm laser. The inset is the digital photograph of the samples in toluene under excitation of 800 nm. (b) Two-photon emission of the AIZS nanorods with various input powers. (c) Quadratic dependence of integrated fluorescence intensity with the input power of laser.
Figure 5. (a) Image of NIH/3T3 cells labeled with the heterodimers with yellow and (b) red emission under UV.
same as the figure 3 inset. The in vitro cellular imaging was also performed on the NIH/3T3 cells (figure 5). The AIZSGO nanorods with yellow (figure 5(a)) and red (figure 5(b)) emissions were chosen as the labeling application. The yellow
and red emissions were clearly observed from the cells. These results suggested that the obtained AIZS nanorods had promising cell labeling applications under either UV or NIR excitations. 5
Nanotechnology 25 (2014) 485702
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4. Conclusions
[13] Aldakov D, Lefrancois A and Reiss P 2013 J. Mater. Chem. C 1 3756 [14] Chung W, Jung H, Lee C and Kim S 2014 J. Mater. Chem. C 2 4227 [15] Ke J, Li X, Zhao Q, Shi Y and Chen G 2014 Nanoscale 6 3403 [16] Tang X, Yu K, Xu Q, Choo E, Goh G and Xue J 2011 J. Mater. Chem. 21 11239 [17] Wang Y A, Zhang X, Bao N, Lin B and Gupta A 2011 J. Am. Chem. Soc. 133 11072 [18] Peng X G, Manna L, Yang W D, Wickham J, Scher E, Kadavanich A and Alivisatos A P 2000 Nature 404 59 [19] Wang J, Gudiksen M S, Duan X, Cui Y and Lieber C M 2001 Science 293 1455 [20] Tang X, Ho W and Xue J 2012 J. Phys. Chem. C 116 9769 [21] Tang X, Cheng W and Choo E 2011 J. Xue. Chem. Commun. 47 5217 [22] Wang Y, Zhang X, Bao N, Lin B and Gupta A 2011 J. Am. Chem. Soc. 133 11072 [23] Li L, Daou T, Texier I, Chi T, Liem N and Reiss P 2009 Chem. Mater. 21 2422 [24] Howes P, Rana S and Stevens M 2014 Chem. Soc. Rev. 43 3835 [25] Motla N E, Smith A F, DeSantisa C J and Skrabalak S E 2014 Chem. Soc. Rev. 43 3823 [26] Zou C, Li M, Zhang L, Yang Y, Li Q, Chen X, Xu X and Huang S 2011 Cryst. Eng. Comm. 13 3515 [27] Ng M, Boothroyd C and Vittal J 2006 J. Am. Chem. Soc. 128 7118 [28] Ye C, Regulacio M, Lim S, Xu Q and Han M 2012 Chem. Eur. J. 18 11258 [29] Paredes J I, Villar-Rodil S, Mart′ınez-Alonso A and Tasc′on J M D 2008 Langmuir 24 10560 [30] Bao H Q, Pan Y Z, Ping Y, Sahoo N G, Wu T F, Li L, Li J and Gan L H 2011 Small 7 1569 [31] Zhang L M, Xia J G, Zhao Q H, Liu L W and Zhang Z J 2010 Small 6 537 [32] Bai H, Xu Y X, Zhao L, Li C and Shi G Q 2009 Chem. Commun. 2009 1667 [33] Yang X Y, Zhang X Y, Liu Z F, Ma Y F, Huang Y and Chen Y S 2008 J. Phys. Chem. C 112 17554 [34] Liu Z, Robinson J T, Sun X M and Dai H J 2008 J. Am. Chem. Soc. 130 10876 [35] Sun X M, Liu Z, Welsher K, Robinson J T, Goodwin A, Zaric S and Dai H J 2008 Nano Res. 1 203 [36] Zhang C L, Yuan Y X, Zhang S M, Wang Y H and Liu Z H 2011 Angew. Chem., Int. Ed. 50 6851 [37] Zhao X M, Zhou S W, Jiang L P, Hou W H, Shen Q M and Zhu J J 2012 Chem. Eur. J. 18 4974 [38] Chen M L, Liu J W, Hu B, Chen M L and Wang J H 2011 Analyst 136 4277 [39] Guo Y et al 2008 Adv. Funct. Mater. 18 2489 [40] Peng E, Choo E, Chandrasekharan P, Yang C T, Ding J and Xue J 2012 Small 23 3620 [41] Hummers W and Offeman R 1958 J. Am. Chem. Soc. 80 1339 [42] Park J and Kim S 2011 J. Mater. Chem. 21 3745 [43] Shannon R D 1976 Acta Crystallogr. Sect. A: Cryst. Phys. Diffr. Theor. Gen. Crystallogr. 32 751 [44] Dai P C, Shen X N, Lin Z J, Feng Z Y, Xu H and Zhan J H 2010 Chem. Commun. 46 5749
In conclusion, we have successfully demonstrated a facile solution based route to synthesize AIZS nanorods containing less toxic elements. In this method, different ratios of AIZS nanorods were achieved by changing the composition of the precursor, and the emission colors of the resulting AIZS nanorods are tunable from green to red by adjusting the chemical composition. The line profile of the single AIZS nanorod indicated the diffusing mechanism of the silver ions. Moreover, the obtained AIZS nanorods showed attractive two-photon fluorescence properties and higher quantum yield compared to that of the reported I-III-VI2 based nanocrystals, indicating their potential capability in biological tagging upon NIR excitation for deep tissue imaging. The biological cell labeling application of the AIZS nanorods has been demonstrated by the NIH/3T3 cells. In addition, the AIZS nanorods have attractive potentials in a wide variety of applications including QD-based solar cells and photocatalysts.
Acknowledgments This work is supported by initial funding of the Hundred Young Talents Plan at Chongqing University 0210001104430.
References [1] Colvin V L, Schlamp M C and Alivisatos A P 1994 Nature 370 354 [2] Tessler N, Medvedev V, Kazes M, Kan S and Banin U 2002 Science 295 1506 [3] Coe S, Woo W K, Bawendi M G and Bulovic V 2002 Nature 420 800 [4] Xie R, Rutherford M and Peng X 2009 J. Am. Chem. Soc. 131 5691 [5] Zhong H, Zhou Y, Ye M, He Y, Ye J, He C, Yang C and Li Y 2008 Chem. Mater. 20 6434 [6] Zhong H, Bai Z and Zou B 2012 J. Phys. Chem. Lett. 3 3167 [7] Yi L, Liu Y, Yang N, Tang Z, Zhao H, Ma G, Su Z and Wang D 2013 Energy Environ. Sci. 6 835 [8] Zhang J, Xie R and Yang W 2011 Chem. Mater. 23 3357 [9] Kolny-Olesiak J and Weller H 2013 ACS Appl. Mater. Interfaces 5 12221 [10] Li X, Chen G, Wang Q, Wang X, Zhou A and Shen Z 2010 Adv. Funct. Mater. 20 3390 [11] Shen H, Yuan H, Wu F, Ba X, Zhou C, Wang H, Lu T, Qin Z, Ma L and Li L 2012 J. Mater. Chem. 22 18623 [12] Yang X, Tang Y, Tan S T, Bosman M, Dong Z, Leck K S, Ji Y, Demir H V and Sun X W 2013 Small 9 2689
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Related content
PAPER
Synthesis of Ag-In-Zn-S alloyed nanorods and their biological application To cite this article: Xiaosheng Tang et al 2014 Nanotechnology 25 485702
View the article online for updates and enhancements.
- Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots Sirshendu Ghosh, Manas Saha, Vishal Dev Ashok et al. - Heterostructure of Au nanocluster tipping on a ZnS quantum rod: controlled synthesis and novel luminescence Yang Tian, Ligang Wang, Shanshan Yu et al. - Silver nanoparticles embedded mesoporous SiO2 nanosphere: an effective anticandidal agent against Candida albicans 077 M Qasim, Braj R Singh, A H Naqvi et al.
This content was downloaded from IP address 128.252.67.66 on 07/11/2017 at 09:43
Nanotechnology Nanotechnology 25 (2014) 485702 (6pp)
doi:10.1088/0957-4484/25/48/485702
Synthesis of Ag-In-Zn-S alloyed nanorods and their biological application Xiaosheng Tang1, Wei Wei1, Claudia Choon Chea Khng2, Zhigang Zang1, Ming Deng1, Tao Zhu1 and Junmin Xue2 1
Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, People’s Republic of China 2 Department of Materials Science & Engineering, Faculty of Engineering, National University of Singapore, Singapore E-mail: [email protected], [email protected] and [email protected] Received 5 September 2014, revised 27 September 2014 Accepted for publication 30 September 2014 Published 10 November 2014 Abstract
Monodisperse Ag-In-Zn-S (AIZS) nanorods with a length of 20 nm have been synthesized using a facile solution based route. These nanorods showed a wide range of fluorescence emissions from green to red, which was achieved by controlling the chemical composition. Moreover, the obtained AIZS nanorods showed high-quality photoluminescence, as well as attractive twophoton fluorescence properties, indicating their potential capability in biological tagging upon near-infrared excitation for deep tissue imaging. Furthermore, the AIZS nanorods presented in this report also show a promising perspective in applications such as solar cells and photocatalysts. S Online supplementary data available from stacks.iop.org/NANO/25/485702/mmedia Keywords: Ag-In-Zn-S nanorods, photoluminescence, cell labelling (Some figures may appear in colour only in the online journal) 1. Introduction
explored to improve the PL emission tunability and quantum yield [14–16]. The band gap of semiconductor nanoparticles can be adjusted by varying the chemical composition to make alloy as well as particle size, which is based on the quantum confinement effect [17–19]. In our previous research, the hot injection method was successfully used for synthesis of CuInS2-ZnS and AgInS2-ZnS alloy nanoparticles with bright and tunable PL, suggesting they are promising alternative materials to cadmium and lead-based semiconductor luminophore [20, 21]. Very recently, some groups reported that the PL emission could be tuned from the visible region to the near-infrared (NIR) region by adjusting the size and the composition of the nanoparticles [22]. Li et al prepared CuInS/ZnS core/shell nanocrystals with a spherical shape [23]. In addition, the shape and morphology of nanostructures were also reported to be able to influence the PL [17–19]. It has been claimed that nanorods and nanowires were observed to have different optical properties from those of nanoparticles [24, 25].
Over the last decade, colloidal semiconductor quantum dots (QDs) have been of great interest for both fundamental research and technical applications [1–3]. More recently, the synthesis of I-III-VI nanoparticles, such as CuInS2 and AgInS2, has attracted considerable attention because their main composition includes non-toxic elements, making them potential substitutes for the more commonly available nanoparticles that contain toxic and environmentally unfriendly heavy metal elements, such as Hg, Cd, and Pb [4–6]. The ternary I-III-VI2 semiconductor materials have been widely studied for a wide variety of applications, including biomedical imaging, color conversion, as well as photovoltaic solar cells, light emitting diodes, and photocatalytic H2 evolution under visible light irradiation [7–13]. The tunable photoluminescence (PL) color and high quantum yield are critical to the performance of the semiconductor nanoparticles in these applications. Therefore, strategies of adjusting band gap, fabricating heterodimer, and core/shell structure were 0957-4484/14/485702+06$33.00
1
© 2014 IOP Publishing Ltd Printed in the UK
Nanotechnology 25 (2014) 485702
X Tang et al
Therefore, tuning the composition, crystal phase, size, and shape of semiconductor nanoparticles remains an attractive research topic. Although significant progress has been made in the study of CuInZnS and AgInZnS, much of the work has been limited to spherical nanoparticles, with relatively little study on the other shapes and morphologies. For instance, Huang et al synthesized the quaternary AgInZn7S9 nanowires by Ag2S catalyzed growth, however; it only showed a red emission [26]. Ng et al fabricated new phase AgInSe2 nanorods by decomposing a single-source precursor [27]. Han et al developed alloyed (ZnS)x(CuInS2)1−x semiconductor nanorods with tuning band gap and photocatalytic properties, but the corresponding photoluminescence had not been studied [28]. Therefore, it is still a challenge to develop a simple method to synthesize a semiconductor of anisotropic shapes with tunable photoluminescence. To prepare a water-soluble fluorescent biological tag, graphene oxide (GO) was used to transfer the AIZS nanorods to an aqueous solution. GO, as a derivative of graphene that could be prepared from natural graphite, emerges as an attractive candidate for biomedical applications because of its chemical inertness, biocompatibility, and low toxicity [29– 31]. GO could be dispersed in water as there are many hydrophilic oxygenated functional groups such as epoxy, hydroxyl and carboxyl. These functional groups not only promote the water solubility, but also could modify the GO by other molecules via covalent or non-covalent bondings [32, 33]. Therefore, GO is extremely suitable for biomedical applications such as drug delivery and cell imaging [34–36]. Recently, there have been a few publications about GO-based nanocomposites, such as GO-CdTe and GO-CdS, using deposition or electrostatic assembly techniques [37–39]. However, quaternary Ag-In-Zn-S (AISZ) Cd-free alloyed nanorods have not been reported for biological applications. Herein, AIZS nanorods with tunable emissions from green to red were successfully achieved by a facile solution based route. Different emissions of AIZS nanorods were obtained by changing the composition of the precursors. The corresponding emission peaks from 520 to 680 nm of the resulting AIZS nanorods were adjusted by the amount of Zn. The AIZS nanorods showed higher quantum yield to that of the reported I-III-VI2 based nanocrystals, and the promising two-photon fluorescence properties indicate potential applications in biological tagging excited by near infrared. GO was successfully used for phase transfer of AIZS nanorods. Moreover, the biological cell labelling application of the AIZS nanorods has been demonstrated by the NIH/3T3 cells. In addition, the AIZS nanorods have widely potential applications such as solar cells and photocatalysts.
0.1 mM AgNO3 (Ag precursor), and 5 mM (1.2 mL) 1dodecanethiol (DDT) was mixed with 4 mL of ODE, 0.2 mM (45.7 mg) oleic acid, and 0.1 mL (46.25 mg) of TOP in a 100 mL three-necked bottle flask. Oleic acid and DDT served as capping ligands, where DDT was used to control the relative activity of the precursors. The mixture was heated to an intermediate temperature under a nitrogen atmosphere and was magnetically stirred until a homogenous clear solution was observed. Two injection solutions of Zn and S precursors were prepared: 0.6 mM sulfur powder in 100 μl oleylamine and 0.6 mM zinc stearate in 100 μl oleylamine and 400 μl ODE at 120 °C. At the intermediate temperature, both Zn and S precursors were injected dropwise into the reaction solution. Then the temperature increased to 210 °C and kept reaction for 2 h. The obtained nanorods were first washed using absolute ethanol and toluene to remove unreacted precursors, and the washing process was repeated three times. The purified nanorods were then dispersed in toluene or chloroform for storage. 2.2. Phase transfer by GO
2. Experimental section
Phase transfer from toluene to water was performed according to Peng’s method of emulsion without an emulsion stabilizer and solvent evaporation to prepare water-soluble biocompatible AIZS nanocrystals for biomedical applications [40]. The amount and overall hydrodynamic size of hosted AIZS nanocrystals were controlled by the ratio of nanocrystals to GO and duration of sonication during emulsion, respectively, where an increase in sonication time reduced hydrodynamic sizes. First, nanosized GO sheets synthesized via modified Hummer’s method [41] were grafted with oleylamine to transfer GO to a non-polar organic solvent. This was achieved by mixing dried GO flakes, oleylamine, and CHCl3. The resultant solution mixture (GO-g-OAM) was sonicated by ultrasonic homogenizer for 30 min to form a dark brown solution. Next, an equal volume of ethanol was added to GOg-OAM and the resultant mixture was centrifuged at 10 000 rpm for 10 min to precipitate GO-g-OAM. CHCl3 was added and the resultant solution sonicated in an ultrasonic bath for 20 min and stored in an enclosed glass vial at room temperature without further purification. Second, AIZS nanocrystals in CHCl3 were added to GO-g-OAM in CHCl3, mixed, and sonicated for 5 min in an ultrasonic bath to form a homogenous mixture. Subsequently, distilled water was added to the resultant mixture for emulsification under the ultrasonic homogenizer. Next, the light brown emulsion was placed in a beaker that had been heated to 60–70 °C, where CHCl3 was allowed to evaporate for at least 30 min under magnetic stirring at constant temperature. Lastly, the resultant dark brown transparent aqueous solution was centrifuged at 10 000 rpm for 10 min to eliminate large impurities and kept in enclosed glass vials at room temperature.
2.1. Preparation of AIZS nanorods
2.3. Characterization
AIZS nanorods were prepared via a facile one-pot thermal decomposition in which 0.1 mM In(Ac)3 (In precursor),
Powder x-ray diffraction (XRD) was performed on a D8 Advance Bruker-AXS (GmbH, Karlsruhe, Germany), using 2
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Cu Kα (1.5405 Å) (40 kV, 200 mA) x-ray source. The powder samples were prepared by drying the purified product at room temperature on a glass slip. Photoluminescence (PL) spectra were measured using a LS 55 Perkin–Elmer luminescence spectrometer. UV–visible absorption spectra were recorded by a Varian Cary 5000 UV−vis−NIR spectrophotometer. Transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM) images, and energy dispersive spectroscopy (EDS) were performed using Philips CM300 FEGTEM operating at 300 kV. A line scan for single and multiple nanoparticles was performed using FEI Titan Scanning/TEM (80–300 kV) operated at 200 kV in STEM mode. Samples characterized in TEM were prepared by dispersing the samples in toluene and depositing a drop of dispersed samples onto a carbon-coated copper grid. Subsequently, the solvent was evaporated in air at room temperature. Thus, chemical compositions, morphology, size, and optical behavior of the nanocrystals were obtained.
from XRD patterns [20]. The corresponding FFT further confirmed the hexagonal crystal structure of the nanorods. Figure 2(a) shows high angle annular dark-field scanning TEM (HAADF-STEM) image of AIZS nanorods. It could be observed that the element is homogeneous distribution in the AIZS nanorods. In a particular nanorod, starting from the bright spot 1 to 5 (figure 2(a)), Zn composition exhibits a nearly similar ratio along the longitudinal axis of the rod (figure 2(b)). In addition, the AIZS nanorod also exhibits uniform composition of Ag, In, and S, without any gradient (figure 2(b)). Hence, this suggests the presence of Zn diffusion from one end of the nanorod to form a uniformly Zndoped AgInS2 nanorod. The presence of Zn ions in AIZS nanorods of different emission wavelengths was further determined by energy-dispersive x-ray elemental analysis (figure S1). The increasing amount of Zn present in the nanocrystals relative to the composition of Ag, In, and Zn indicates that the blue shift in emission wavelengths was due to an increase in the amount of Zn diffused and doped into the nanocrystal. The optical behaviors of the AIZS nanorods were then characterized. In the absorption spectra shown in figure 3(a), the absorption onsets of the nanocrystals were blue shifted with increasing the ratio of Zn. Figure 3(b) presented the PL properties of the synthesized nanocrystals under excitation of UV (365 nm). The emission wavelengths were 630, 580, 550, and 510 nm for the samples prepared at 120, 150, 180, and 210 °C, respectively, which also suggested a blue shift in emission with increasing Zn mole fraction. The corresponding digital photo shown in figure 3(b) also displayed the strong emissions of the nanocrystals in toluene, and their corresponding photoluminescence quantum yields were 36, 38, 43, and 35% (figure S2). Herein, the photodecomposition of rhodamine 6G (R6G) was chosen as a model reaction to examine the catalytic properties of SiO2/Ag hybrid microspheres. The characterized peak located at 526 nm for the R6G solution measured by a UV–vis spectrophotometer was used to determine its reduction efficiency at given time interval. Figures 4(a) and (b) show that nearly 100% of R6G had been photodegraded within 5 min, indicating the as-prepared SiO2/Ag hybrid microspheres with excellent catalytic performance toward the R6G solution. The upconversion fluorescence test under excitation of 800 nm laser was applied to all AIZS nanorods with different emissions, and the corresponding spectra were displayed in figure 4(a). From figure 4(a), it could be observed that the various visible emissions could be achieved for these samples (figure 4(a)). Moreover, the emission peaks excited by 800 nm matched well with their respective counterparts under UV excitation (figure 3(b)). Furthermore, the upconversion fluorescence emission peaks were located at 635, 581, 556, and 511 nm, which have very slight red shift compared to the PL emission peaks. The corresponding TEM images and SAED pattern of the as-prepared AIZS nanorods with yellow, orange, and green emissions are shown in the supporting information (figures S3–S5). The AIZS nanorods with yellow emission were chose for testing the power dependence property of the as-prepared AIZS nanorods, which was
3. Results and discussion The crystal structures of the synthesized AIZS of varying emission wavelengths were characterized by XRD (figure 1(a)). The nanocrystals exhibited three broad peaks at 2θ = 27.6°, 47.8°, and 56.7°, which were assignable to diffraction of the (002), (110), and (112) planes, respectively, of hexagonal AgInZn2S4 crystal structure (JCPDF 25-0383) [20]. As nucleation reaction temperature decreased, the respective nanocrystal exhibited a peak present between the corresponding peaks of bulk cubic ZnS and chalcopyrite AgInS2, where angle increase and peak shift toward ZnS was observed with decreasing temperature. The reason is the ion radii of Ag+ (1.14 Å) and In3+ (0.76 Å) are larger than that of Zn2+ (0.74 Å) [42–44]. Thus, the as-synthesized AIZS were not a mixture of ZnS and AgInS2 phases but a ZnS-AgInS2 solid solution where an increase in ZnS present accompanied an increase in Zn2+ precursor content, as reported in bulk materials [16, 20, 21]. The morphology of the AIZS samples was measured by TEM technique. From the TEM image of figure 1(b), it can be seen that high-quality AIZS nanorods were obtained. The AIZS nanorods possessed a narrow size distribution, with an average length of 20 nm (figure 1(b) inset). Figure 1(c) shows the HRTEM image of part of the AIZS nanorods. The lattice of the single AIZS nanorod could be clearly observed, which indicated the high quality crystalline of AIZS nanorods structure. Additionally, the corresponding selected area electron diffraction (SAED) displayed the diffraction rings of (002), (110), and (201) indices of hexagonal crystal structure. Figure 1(d) showed the HRTEM image of a typical AIZS nanorods and its FFT. The lattice fringes of the nanorods were clearly observed, of which two lattice indices of hexagonal crystal structure. As shown in figure 2(d), the distance between two adjacent planes in the labeled image is measured to be 0.29 nm, corresponding to (101) planes of hexagonal structure, which is also consistent with the results obtained 3
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Figure 1. (a) XRD pattern of the AIZS nanorods with different emissions. (b) TEM images of the as-obtained AIZS nanorods with red
emission. Inset: corresponding length distribution of the sample. (c) Magnified TEM image of AIZS nanorods with red emission. Inset is the SAED patterns of the sample. (d) HRTEM of a single AIZS nanorod. Inset: corresponding fast Fourier transform (FFT) image.
Figure 2. (a) HAADF-STEM of AIZS nanorods. (b) Line profile of Ag, In, Zn, and S dispersion in AIZS nanorods.
displayed in figure 4(b). Using the relation of I ∼ PowerK, the value of K was around 2.05 (figure 4(c)). Therefore, it could concluded that the upconversion fluorescence mechanism in the sample was two-photon excitation in nature . To demonstrate their potential applications in bio-tagging, the as-prepared AIZS nanorods with yellow and red
emissions were transferred to water solution via GO. The photoluminescence of the AIZS nanorods after phase transferred was characterized in figure S6. The PL spectra of the AIZS-GO nanorods displayed nearly the same as the AIZS nanorods dispersed in toluene, and the emission photograph of AIZS-GO dispersed in water, which is the 4
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Figure 3. (a) The absorption spectra, (b) PL spectra of the AIZS nanorods with different emissions, and (inset) the corresponding digital
photographs of the AIZS nanorods dispersed in toluene under excitation of 365 nm.
Figure 4. (a) Upconversion spectra of the AIZS nanorods with different emissions. The measurements were under excitation of an 800 nm laser. The inset is the digital photograph of the samples in toluene under excitation of 800 nm. (b) Two-photon emission of the AIZS nanorods with various input powers. (c) Quadratic dependence of integrated fluorescence intensity with the input power of laser.
Figure 5. (a) Image of NIH/3T3 cells labeled with the heterodimers with yellow and (b) red emission under UV.
same as the figure 3 inset. The in vitro cellular imaging was also performed on the NIH/3T3 cells (figure 5). The AIZSGO nanorods with yellow (figure 5(a)) and red (figure 5(b)) emissions were chosen as the labeling application. The yellow
and red emissions were clearly observed from the cells. These results suggested that the obtained AIZS nanorods had promising cell labeling applications under either UV or NIR excitations. 5
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4. Conclusions
[13] Aldakov D, Lefrancois A and Reiss P 2013 J. Mater. Chem. C 1 3756 [14] Chung W, Jung H, Lee C and Kim S 2014 J. Mater. Chem. C 2 4227 [15] Ke J, Li X, Zhao Q, Shi Y and Chen G 2014 Nanoscale 6 3403 [16] Tang X, Yu K, Xu Q, Choo E, Goh G and Xue J 2011 J. Mater. Chem. 21 11239 [17] Wang Y A, Zhang X, Bao N, Lin B and Gupta A 2011 J. Am. Chem. Soc. 133 11072 [18] Peng X G, Manna L, Yang W D, Wickham J, Scher E, Kadavanich A and Alivisatos A P 2000 Nature 404 59 [19] Wang J, Gudiksen M S, Duan X, Cui Y and Lieber C M 2001 Science 293 1455 [20] Tang X, Ho W and Xue J 2012 J. Phys. Chem. C 116 9769 [21] Tang X, Cheng W and Choo E 2011 J. Xue. Chem. Commun. 47 5217 [22] Wang Y, Zhang X, Bao N, Lin B and Gupta A 2011 J. Am. Chem. Soc. 133 11072 [23] Li L, Daou T, Texier I, Chi T, Liem N and Reiss P 2009 Chem. Mater. 21 2422 [24] Howes P, Rana S and Stevens M 2014 Chem. Soc. Rev. 43 3835 [25] Motla N E, Smith A F, DeSantisa C J and Skrabalak S E 2014 Chem. Soc. Rev. 43 3823 [26] Zou C, Li M, Zhang L, Yang Y, Li Q, Chen X, Xu X and Huang S 2011 Cryst. Eng. Comm. 13 3515 [27] Ng M, Boothroyd C and Vittal J 2006 J. Am. Chem. Soc. 128 7118 [28] Ye C, Regulacio M, Lim S, Xu Q and Han M 2012 Chem. Eur. J. 18 11258 [29] Paredes J I, Villar-Rodil S, Mart′ınez-Alonso A and Tasc′on J M D 2008 Langmuir 24 10560 [30] Bao H Q, Pan Y Z, Ping Y, Sahoo N G, Wu T F, Li L, Li J and Gan L H 2011 Small 7 1569 [31] Zhang L M, Xia J G, Zhao Q H, Liu L W and Zhang Z J 2010 Small 6 537 [32] Bai H, Xu Y X, Zhao L, Li C and Shi G Q 2009 Chem. Commun. 2009 1667 [33] Yang X Y, Zhang X Y, Liu Z F, Ma Y F, Huang Y and Chen Y S 2008 J. Phys. Chem. C 112 17554 [34] Liu Z, Robinson J T, Sun X M and Dai H J 2008 J. Am. Chem. Soc. 130 10876 [35] Sun X M, Liu Z, Welsher K, Robinson J T, Goodwin A, Zaric S and Dai H J 2008 Nano Res. 1 203 [36] Zhang C L, Yuan Y X, Zhang S M, Wang Y H and Liu Z H 2011 Angew. Chem., Int. Ed. 50 6851 [37] Zhao X M, Zhou S W, Jiang L P, Hou W H, Shen Q M and Zhu J J 2012 Chem. Eur. J. 18 4974 [38] Chen M L, Liu J W, Hu B, Chen M L and Wang J H 2011 Analyst 136 4277 [39] Guo Y et al 2008 Adv. Funct. Mater. 18 2489 [40] Peng E, Choo E, Chandrasekharan P, Yang C T, Ding J and Xue J 2012 Small 23 3620 [41] Hummers W and Offeman R 1958 J. Am. Chem. Soc. 80 1339 [42] Park J and Kim S 2011 J. Mater. Chem. 21 3745 [43] Shannon R D 1976 Acta Crystallogr. Sect. A: Cryst. Phys. Diffr. Theor. Gen. Crystallogr. 32 751 [44] Dai P C, Shen X N, Lin Z J, Feng Z Y, Xu H and Zhan J H 2010 Chem. Commun. 46 5749
In conclusion, we have successfully demonstrated a facile solution based route to synthesize AIZS nanorods containing less toxic elements. In this method, different ratios of AIZS nanorods were achieved by changing the composition of the precursor, and the emission colors of the resulting AIZS nanorods are tunable from green to red by adjusting the chemical composition. The line profile of the single AIZS nanorod indicated the diffusing mechanism of the silver ions. Moreover, the obtained AIZS nanorods showed attractive two-photon fluorescence properties and higher quantum yield compared to that of the reported I-III-VI2 based nanocrystals, indicating their potential capability in biological tagging upon NIR excitation for deep tissue imaging. The biological cell labeling application of the AIZS nanorods has been demonstrated by the NIH/3T3 cells. In addition, the AIZS nanorods have attractive potentials in a wide variety of applications including QD-based solar cells and photocatalysts.
Acknowledgments This work is supported by initial funding of the Hundred Young Talents Plan at Chongqing University 0210001104430.
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