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One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap
Materials Today: Proceedings xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap K. Kandasamy a, M. Venkatesh b, Y.A. Syed Khadar c, Paramasivan Rajasingh d,⇑ a
Department of Chemistry, K.S.R. College of Arts and Science for Women, Tiruchengode 637 215, Tamil Nadu, India Department of Physics, K.S. Rangasamy College of Arts and Science (Autonomous), Tiruchengode 637 215, Tamil Nadu, India c Department of Physics, K.S.R. College of Arts and Science for Women, Tiruchengode 637 215, Tamil Nadu, India d Department of Chemistry, Chikkanna Government Arts College, Tiruppur 641 602, Tamil Nadu, India b
a r t i c l e
i n f o
Article history: Received 24 April 2019 Received in revised form 28 May 2019 Accepted 2 June 2019 Available online xxxx Keywords: Opuntia ficus-indica CdS Quantum dots Green synthesis High-resolution transmission electron microscopy
a b s t r a c t A simple and novel one-pot synthesis of CdS, quantum dots from naturally available fruit sap Opuntia ficus-indica was performed. We have investigated a green route for the synthesis of CdS QDs using eco-friendly and naturally renewable Opuntia ficus-indica fruit sap as green template. Synthesized CdS QDs were determined by Fourier transform infrared spectroscopy, UV–visible (323 nm), X-ray diffraction (cubic structure), X-ray fluorescence, Dynamic light scattering (d50 = 9.56 nm), High resolution transmission electron microscopy (Spherical shaped). Overall the present work describes the green synthesis of CdS nanoparticles from Opuntia ficus-indica fruit sap with extrinsic crystallite size control in the quantum confinement range. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
1. Introduction Biosynthesis of low-dimensional semiconductor quantum dots (QDs) (<10 nm) have unique properties such as optical sensing, photo-degradation and bio-sensing compared to their high dimensional (>10 nm) nanoparticles (NPs). Synthesis of cadmium sulphide (CdS) QDs is one of the major challenges through green synthesis method [1]. The preparations of CdS QDs have been carried out using several methods such as microwave heating [2], hot injection [3], colloidal synthesis [4], plasma synthesis [5] and ultrasonic irradiation [6]. Generally, the chemical synthesis methods are complicated due to their cost, slow rate of reaction, low yield, risky and human health hazard concerns [7]. In the recent years, natural plant and agriculture waste extract are used as reducing, stabilizing and capping agents for the synthesis of QDs because of better biocompatible, environmental friendly and cost effective nature [8,9]. Especially, fruits sap contains remarkable organic capping agents like cellulose, carbohydrates, proteins, pectin, vitamins and minerals [10]. Opuntia ficus-indica (O. ficus-indica) fruits are rich source of flavonoids, terpenoids, steroids and carotenes [11]. These molecules have major functional groups such as amine (proteins), carboxylic acid (pectin) ⇑ Corresponding author. E-mail address: [email protected] (P. Rajasingh).
and hydroxyl group (cellulose) [12]. These functional groups are believed to play a major role in bio-reduction reaction and they readily bond with inorganic materials. For example, recently 3–5 nm scaled CdS QDs synthesis was reported using tea-leaf extract which plays a key role in size reducing and as capping agent [13]. O. ficusindica sap contains 80–90% of water, 10–20% of macronutrients and organic capping molecules like vitamins (12–81 mg) and antioxidants (10–60 mg) [14]. These chemical compositions of O. ficus-indica fruits sap play a main role in the synthesis of CdS QDs. This work highlights the synthesis of lower dimensional semiconductor CdS QDs via biocompatible materials. The present novel research work reports an one-pot simple approach for the synthesis of CdS QDs using a O. ficus-indica fruit sap. We have made an attempt to synthesis CdS QDs using eco-friendly and naturally renewable source such as O. ficus-indica fruit sap as green template. The effect of sap concentration on the particle size, morphology, crystalline behavior, elements distribution of the as-synthesized CdS QDs has been reported.
2. Experimental section Cadmium sulfate (CdSO4, HiMedia and 99% purity) and sodium sulfide (Na2S, Molychem and 98% purity) were purchased.
https://doi.org/10.1016/j.matpr.2019.06.003 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
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K. Kandasamy et al. / Materials Today: Proceedings xxx (xxxx) xxx
Deionized (DI) water used throughout the experiment was obtained from ultra-pure water purification system followed by KMnO4 distillation method. 2.1. Preparation of O. ficus-indica fruit sap The O. ficus-indica fruits were obtained from local village area (Tiruchengode, Namakkal) in India. First, fruits were washed with DI water, peel was removed and then the sap was collected from O. ficus-indica fruits. Later the sap was filtered through Whatman qualitative filter paper (Grade number 1) and this freshly prepared extract was used for synthesis. 2.2. One-pot green synthesis of QDs To synthesize the CdS QDs in a single step, 100 mL of O. ficusindica fruit extract was stirred for 30 min. Then freshly prepared 0.5 M of CdCl2H2O solution was added into it and further 0.5 M of Na2SH2O was added drop by drop until it attains orangeyellow color which indicates the formation of CdS. The above mixture was stimulated using magnetic stirrer for 24 h at room temperature. The obtained orange-yellow coloured CdS nanoparticle was centrifuged, washed with DI water for five times and then dried at 110 °C for 4 h. 3. Analytical techniques The crystalline properties of CdS sample powder were characterised by XRD using CuKa as a radiation source (k = 15406 Å) which is generated at 40 keV and 40 mA. The samples were scanned in the 2h range from 10 to 80°. X-ray fluorescence (XRF) is used to identify the nano powder employing qualitative and quantitative elemental analysis and composition of the products. To confirm the presence of organic compounds from the O. ficusindica fruit sap on CdS, the FT-IR spectra was recorded at room temperature from the range of 4000 to 400 cm 1 where, 100 mg of potassium bromide (KBr) was used as a reference to discover the presence of functional groups. The ultraviolet (UV)-visible absorption spectra of CdS QDs was measured using Cary 5000 UV–VIS Spectrophotometer. The absorption spectra of the samples were recorded in standard 10 nm quartz cuvettes. The particle size analyses were carried out using Sympa NANOPHOX Dynamic Light Scattering (DLS) and measured with the sub micrometer particle size analyzer. The particle size of the samples measured in the range of 1–100 nm at the scattering angle of 90°. The HR-TEM was operated at 200 kV to obtain TEM images. To prepare TEM sample, the CdS QDs were ultrasonically dispersed in acetone and then a drop of the CdS QD solution was introduced onto a copper-carbon TEM grid. Then, the resulting TEM grid was dried in the air.
Fig. 1. FT-IR Spectrum of O. ficus-indica CdS QDs.
aromatic CAH bending vibration. The medium band at 1069 cm 1 shows the CAO stretching vibration of primary alcohol and also CAN stretching vibration of amine groups. A weak peak observed at 624 cm 1 indicates the formation of CdS QDs [15,16]. 4.2. Ultra violet visible absorption spectroscopy (UV–Visible) Fig. 2 shows the absorption spectrum taken for O. ficus-indica CdS QDs to identify the characteristic energy absorption edge. We could observe that the absorption band of CdS QDs was shifted to short wavelength. The ‘‘blue shift” shows that there is decrease in size and formation of QDs. The CdS QDs formed indicate the presence of low-dimensional semiconductor property [17,18]. The absorption spectrum maximum for CdS QDs is at 323 nm which corresponds to band gap energy of 3.8 eV and the observed biomineralized Cds QDs are within the well-known quantum confined size range for CdS [19,20]. 4.3. Structural studies (XRD) Fig. 3 shows the XRD pattern of the as-synthesized CdS QDs and confirms the crystalline nature. The XRD peaks found at 2h values of 26.8°, 44.1° and 52.2° attributes to (1 1 1), (2 2 0) and (3 1 1) diffraction planes of cubic structure CdS QDs which is corresponding to the JCPDS file number 10-0454 [16,21]. The broad peaks
4. Result and discussion 4.1. Vibrational spectroscopy (FT-IR) The FT-IR spectrum of the CdS QDs is shown in the Fig. 1 which gives the information about the functional groups involved in the reduction of cadmium ions and detects some possible biomolecules that are capped on CdS QD. The FT-IR spectrum shows wavenumber peaks at (cm 1) 3417, 2917, 1597, 1402, 1069, 624. The broad band at 3417 cm 1 corresponds to the polymeric OH stretching vibration and a weak peak at 2917 cm 1 shows CAH asymmetric stretching vibration. The FT-IR spectrum of CdS QDs shows absorption band due to asymmetric C@O stretching vibration at 1597 cm 1. The peak is observed at 1402 cm 1 indicating
Fig. 2. Absorption Spectrum of O. ficus-indica CdS QDs.
Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
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K. Kandasamy et al. / Materials Today: Proceedings xxx (xxxx) xxx Table 2 XRF analysis confirming the co-existence of Cd and S in the QDs. Analyst
Result
Line
Cd S K
80.210% 18.882% 0.908%
Cd Ka S Ka K Ka
Fig. 3. Powder XRD pattern of O. ficus-indica CdS QDs.
indicate that the particles were obtained in the nature of small crystalline sizes and also no impurity peak was observed. The mean crystallite sizes (D) of the CdS QDs (3–5 nm) was calculated using Debye Scherrer’s formula. The inter-planar spacing value dhkl was 3.32 Å and dislocation density value is 1.20 which is shown in Table 1 [8]. The result indicates that O. ficus-indica fruits sap acts as a stabilizing and capping agent. 4.4. X-ray fluorescence (XRF) XRF elemental analysis was done for the synthesized CdS QDs to confirm the independent quantitative measurements of nanoparticles distributed. Concentration distribution of the CdS QDs sample is shown in Table 2. The results of XRF analysis showed 80.210% of Cd and 18.882% of S. The above result shows that the prepared NPs consist of CdS QDs [22]. 4.5. Dynamic light scattering (DLS) The DLS analysis was done in order to determine the particle size distribution of the synthesized CdS QDs (Fig. 4). The result obtained from the DLS analysis showed the average particle size of CdS QDs was 9.56 nm [23]. (It is supported by HRTEM analysis). 4.6. High-resolution transmission electron microscopy (HRTEM) HRTEM image of O. ficus-indica CdS QDs is shown in Fig. 5 which confirms the shape and size of the CdS QDs and matches with that of the XRD results [24]. HRTEM clearly shows the spherical shaped CdS QDs and their average diameter range from 3 to 5 nm [25] and the result confirms the formation of quantum dots (<10 nm) [26]. This represents that the resultant CdS QDs are suitable to (1 1 1) cubic crystalline structure of CdS [13]. The comparison of XRD
Fig. 4. Representative DLS spectrum of O. ficus-indica CdS QDs.
results with HRTEM confirms similarities in the particle size and hence the formation of CdS QDs. In addition, the DLS results are also in agreement with these observations. 5. Conclusion One-pot green synthesis of CdS QDs was successfully achieved using O. ficus-indica fruit sap. The organic moieties such as carbohydrate, flavonoids, terpenoids, steroids, carotenes and proteins present in the O. ficus-indica fruit sap play a key role as stabilizing and capping agent and form highly homogeneous CdS spherical nanoparticle with an average size range of 3–5 nm. The XRD and XRF spectra support the formation of crystalline QDs. The capping of biomolecules onto CdS QDs from O. ficus-indica fruit sap was confirmed by FTIR. The spherical shaped particles were confirmed by HRTEM analysis. From the studies it is clear that O. ficus-indica fruit sap can be efficiently used as a stabilizing and capping agent for synthesis of CdS QDs using our green protocol. The obtained result suggests that O. ficus-indica fruit sap could be considered for synthesizing CdS semiconductor quantum dots. The synthesized O. ficus-indica fruit sap mediated CdS QDs are promising low dimensional biomedical tools used for a wide range of biomedical applications such as antibacterial, bioimaging, catalysis and therapeutic.
Table 1 XRD peak list of CdS QDs. 2h of intense peak (deg)
Height [cts]
FWHM[b]
d-spacing [Å]
hkl
Average crystallite size (nm)
Average Dislocation Density
26.6802 43.9936 52.5651
265.58 162.71 123.32
0.4920 1.1808 0.7872
3.34129 2.05827 1.74106
111 220 311
3–5
1.20
Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
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Fig. 5. HRTEM image of O. ficus-indica CdS QDs.
Acknowledgements This work was supported by Science and Engineering Research Board (SERB-DST). Project Order No. SB/EMEQ-265/2013. Author P. R sincerely thanks SERB-DST for the financial support provided.
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Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap K. Kandasamy a, M. Venkatesh b, Y.A. Syed Khadar c, Paramasivan Rajasingh d,⇑ a
Department of Chemistry, K.S.R. College of Arts and Science for Women, Tiruchengode 637 215, Tamil Nadu, India Department of Physics, K.S. Rangasamy College of Arts and Science (Autonomous), Tiruchengode 637 215, Tamil Nadu, India c Department of Physics, K.S.R. College of Arts and Science for Women, Tiruchengode 637 215, Tamil Nadu, India d Department of Chemistry, Chikkanna Government Arts College, Tiruppur 641 602, Tamil Nadu, India b
a r t i c l e
i n f o
Article history: Received 24 April 2019 Received in revised form 28 May 2019 Accepted 2 June 2019 Available online xxxx Keywords: Opuntia ficus-indica CdS Quantum dots Green synthesis High-resolution transmission electron microscopy
a b s t r a c t A simple and novel one-pot synthesis of CdS, quantum dots from naturally available fruit sap Opuntia ficus-indica was performed. We have investigated a green route for the synthesis of CdS QDs using eco-friendly and naturally renewable Opuntia ficus-indica fruit sap as green template. Synthesized CdS QDs were determined by Fourier transform infrared spectroscopy, UV–visible (323 nm), X-ray diffraction (cubic structure), X-ray fluorescence, Dynamic light scattering (d50 = 9.56 nm), High resolution transmission electron microscopy (Spherical shaped). Overall the present work describes the green synthesis of CdS nanoparticles from Opuntia ficus-indica fruit sap with extrinsic crystallite size control in the quantum confinement range. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
1. Introduction Biosynthesis of low-dimensional semiconductor quantum dots (QDs) (<10 nm) have unique properties such as optical sensing, photo-degradation and bio-sensing compared to their high dimensional (>10 nm) nanoparticles (NPs). Synthesis of cadmium sulphide (CdS) QDs is one of the major challenges through green synthesis method [1]. The preparations of CdS QDs have been carried out using several methods such as microwave heating [2], hot injection [3], colloidal synthesis [4], plasma synthesis [5] and ultrasonic irradiation [6]. Generally, the chemical synthesis methods are complicated due to their cost, slow rate of reaction, low yield, risky and human health hazard concerns [7]. In the recent years, natural plant and agriculture waste extract are used as reducing, stabilizing and capping agents for the synthesis of QDs because of better biocompatible, environmental friendly and cost effective nature [8,9]. Especially, fruits sap contains remarkable organic capping agents like cellulose, carbohydrates, proteins, pectin, vitamins and minerals [10]. Opuntia ficus-indica (O. ficus-indica) fruits are rich source of flavonoids, terpenoids, steroids and carotenes [11]. These molecules have major functional groups such as amine (proteins), carboxylic acid (pectin) ⇑ Corresponding author. E-mail address: [email protected] (P. Rajasingh).
and hydroxyl group (cellulose) [12]. These functional groups are believed to play a major role in bio-reduction reaction and they readily bond with inorganic materials. For example, recently 3–5 nm scaled CdS QDs synthesis was reported using tea-leaf extract which plays a key role in size reducing and as capping agent [13]. O. ficusindica sap contains 80–90% of water, 10–20% of macronutrients and organic capping molecules like vitamins (12–81 mg) and antioxidants (10–60 mg) [14]. These chemical compositions of O. ficus-indica fruits sap play a main role in the synthesis of CdS QDs. This work highlights the synthesis of lower dimensional semiconductor CdS QDs via biocompatible materials. The present novel research work reports an one-pot simple approach for the synthesis of CdS QDs using a O. ficus-indica fruit sap. We have made an attempt to synthesis CdS QDs using eco-friendly and naturally renewable source such as O. ficus-indica fruit sap as green template. The effect of sap concentration on the particle size, morphology, crystalline behavior, elements distribution of the as-synthesized CdS QDs has been reported.
2. Experimental section Cadmium sulfate (CdSO4, HiMedia and 99% purity) and sodium sulfide (Na2S, Molychem and 98% purity) were purchased.
https://doi.org/10.1016/j.matpr.2019.06.003 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Materials and Modeling.
Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
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Deionized (DI) water used throughout the experiment was obtained from ultra-pure water purification system followed by KMnO4 distillation method. 2.1. Preparation of O. ficus-indica fruit sap The O. ficus-indica fruits were obtained from local village area (Tiruchengode, Namakkal) in India. First, fruits were washed with DI water, peel was removed and then the sap was collected from O. ficus-indica fruits. Later the sap was filtered through Whatman qualitative filter paper (Grade number 1) and this freshly prepared extract was used for synthesis. 2.2. One-pot green synthesis of QDs To synthesize the CdS QDs in a single step, 100 mL of O. ficusindica fruit extract was stirred for 30 min. Then freshly prepared 0.5 M of CdCl2H2O solution was added into it and further 0.5 M of Na2SH2O was added drop by drop until it attains orangeyellow color which indicates the formation of CdS. The above mixture was stimulated using magnetic stirrer for 24 h at room temperature. The obtained orange-yellow coloured CdS nanoparticle was centrifuged, washed with DI water for five times and then dried at 110 °C for 4 h. 3. Analytical techniques The crystalline properties of CdS sample powder were characterised by XRD using CuKa as a radiation source (k = 15406 Å) which is generated at 40 keV and 40 mA. The samples were scanned in the 2h range from 10 to 80°. X-ray fluorescence (XRF) is used to identify the nano powder employing qualitative and quantitative elemental analysis and composition of the products. To confirm the presence of organic compounds from the O. ficusindica fruit sap on CdS, the FT-IR spectra was recorded at room temperature from the range of 4000 to 400 cm 1 where, 100 mg of potassium bromide (KBr) was used as a reference to discover the presence of functional groups. The ultraviolet (UV)-visible absorption spectra of CdS QDs was measured using Cary 5000 UV–VIS Spectrophotometer. The absorption spectra of the samples were recorded in standard 10 nm quartz cuvettes. The particle size analyses were carried out using Sympa NANOPHOX Dynamic Light Scattering (DLS) and measured with the sub micrometer particle size analyzer. The particle size of the samples measured in the range of 1–100 nm at the scattering angle of 90°. The HR-TEM was operated at 200 kV to obtain TEM images. To prepare TEM sample, the CdS QDs were ultrasonically dispersed in acetone and then a drop of the CdS QD solution was introduced onto a copper-carbon TEM grid. Then, the resulting TEM grid was dried in the air.
Fig. 1. FT-IR Spectrum of O. ficus-indica CdS QDs.
aromatic CAH bending vibration. The medium band at 1069 cm 1 shows the CAO stretching vibration of primary alcohol and also CAN stretching vibration of amine groups. A weak peak observed at 624 cm 1 indicates the formation of CdS QDs [15,16]. 4.2. Ultra violet visible absorption spectroscopy (UV–Visible) Fig. 2 shows the absorption spectrum taken for O. ficus-indica CdS QDs to identify the characteristic energy absorption edge. We could observe that the absorption band of CdS QDs was shifted to short wavelength. The ‘‘blue shift” shows that there is decrease in size and formation of QDs. The CdS QDs formed indicate the presence of low-dimensional semiconductor property [17,18]. The absorption spectrum maximum for CdS QDs is at 323 nm which corresponds to band gap energy of 3.8 eV and the observed biomineralized Cds QDs are within the well-known quantum confined size range for CdS [19,20]. 4.3. Structural studies (XRD) Fig. 3 shows the XRD pattern of the as-synthesized CdS QDs and confirms the crystalline nature. The XRD peaks found at 2h values of 26.8°, 44.1° and 52.2° attributes to (1 1 1), (2 2 0) and (3 1 1) diffraction planes of cubic structure CdS QDs which is corresponding to the JCPDS file number 10-0454 [16,21]. The broad peaks
4. Result and discussion 4.1. Vibrational spectroscopy (FT-IR) The FT-IR spectrum of the CdS QDs is shown in the Fig. 1 which gives the information about the functional groups involved in the reduction of cadmium ions and detects some possible biomolecules that are capped on CdS QD. The FT-IR spectrum shows wavenumber peaks at (cm 1) 3417, 2917, 1597, 1402, 1069, 624. The broad band at 3417 cm 1 corresponds to the polymeric OH stretching vibration and a weak peak at 2917 cm 1 shows CAH asymmetric stretching vibration. The FT-IR spectrum of CdS QDs shows absorption band due to asymmetric C@O stretching vibration at 1597 cm 1. The peak is observed at 1402 cm 1 indicating
Fig. 2. Absorption Spectrum of O. ficus-indica CdS QDs.
Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
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K. Kandasamy et al. / Materials Today: Proceedings xxx (xxxx) xxx Table 2 XRF analysis confirming the co-existence of Cd and S in the QDs. Analyst
Result
Line
Cd S K
80.210% 18.882% 0.908%
Cd Ka S Ka K Ka
Fig. 3. Powder XRD pattern of O. ficus-indica CdS QDs.
indicate that the particles were obtained in the nature of small crystalline sizes and also no impurity peak was observed. The mean crystallite sizes (D) of the CdS QDs (3–5 nm) was calculated using Debye Scherrer’s formula. The inter-planar spacing value dhkl was 3.32 Å and dislocation density value is 1.20 which is shown in Table 1 [8]. The result indicates that O. ficus-indica fruits sap acts as a stabilizing and capping agent. 4.4. X-ray fluorescence (XRF) XRF elemental analysis was done for the synthesized CdS QDs to confirm the independent quantitative measurements of nanoparticles distributed. Concentration distribution of the CdS QDs sample is shown in Table 2. The results of XRF analysis showed 80.210% of Cd and 18.882% of S. The above result shows that the prepared NPs consist of CdS QDs [22]. 4.5. Dynamic light scattering (DLS) The DLS analysis was done in order to determine the particle size distribution of the synthesized CdS QDs (Fig. 4). The result obtained from the DLS analysis showed the average particle size of CdS QDs was 9.56 nm [23]. (It is supported by HRTEM analysis). 4.6. High-resolution transmission electron microscopy (HRTEM) HRTEM image of O. ficus-indica CdS QDs is shown in Fig. 5 which confirms the shape and size of the CdS QDs and matches with that of the XRD results [24]. HRTEM clearly shows the spherical shaped CdS QDs and their average diameter range from 3 to 5 nm [25] and the result confirms the formation of quantum dots (<10 nm) [26]. This represents that the resultant CdS QDs are suitable to (1 1 1) cubic crystalline structure of CdS [13]. The comparison of XRD
Fig. 4. Representative DLS spectrum of O. ficus-indica CdS QDs.
results with HRTEM confirms similarities in the particle size and hence the formation of CdS QDs. In addition, the DLS results are also in agreement with these observations. 5. Conclusion One-pot green synthesis of CdS QDs was successfully achieved using O. ficus-indica fruit sap. The organic moieties such as carbohydrate, flavonoids, terpenoids, steroids, carotenes and proteins present in the O. ficus-indica fruit sap play a key role as stabilizing and capping agent and form highly homogeneous CdS spherical nanoparticle with an average size range of 3–5 nm. The XRD and XRF spectra support the formation of crystalline QDs. The capping of biomolecules onto CdS QDs from O. ficus-indica fruit sap was confirmed by FTIR. The spherical shaped particles were confirmed by HRTEM analysis. From the studies it is clear that O. ficus-indica fruit sap can be efficiently used as a stabilizing and capping agent for synthesis of CdS QDs using our green protocol. The obtained result suggests that O. ficus-indica fruit sap could be considered for synthesizing CdS semiconductor quantum dots. The synthesized O. ficus-indica fruit sap mediated CdS QDs are promising low dimensional biomedical tools used for a wide range of biomedical applications such as antibacterial, bioimaging, catalysis and therapeutic.
Table 1 XRD peak list of CdS QDs. 2h of intense peak (deg)
Height [cts]
FWHM[b]
d-spacing [Å]
hkl
Average crystallite size (nm)
Average Dislocation Density
26.6802 43.9936 52.5651
265.58 162.71 123.32
0.4920 1.1808 0.7872
3.34129 2.05827 1.74106
111 220 311
3–5
1.20
Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003
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Fig. 5. HRTEM image of O. ficus-indica CdS QDs.
Acknowledgements This work was supported by Science and Engineering Research Board (SERB-DST). Project Order No. SB/EMEQ-265/2013. Author P. R sincerely thanks SERB-DST for the financial support provided.
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Please cite this article as: K. Kandasamy, M. Venkatesh, Y. A. Syed Khadar et al., One-pot green synthesis of CdS quantum dots using Opuntia ficus-indica fruit sap, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.003