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Accurate controlled deposition of silver nanoparticles on porous silicon by drifted ions in electrolytic solution
Current Applied Physics 19 (2019) 1024–1030
Contents lists available at ScienceDirect
Current Applied Physics journal homepage: www.elsevier.com/locate/cap
Accurate controlled deposition of silver nanoparticles on porous silicon by drifted ions in electrolytic solution
T
Mehdi Q. Zayera, Alwan M. Alwana, Ahmed S. Ahmedb, Amer B. Dheyabc,∗ a
Department of Applied Sciences, University of Technology, Baghdad, Iraq College of Nursing-basic Science Department, Misan University, Iraq c Ministry of Science and Technology, Baghdad, Iraq b
ARTICLE INFO
ABSTRACT
Keywords: PS Immersion plating Metallic nanostructures Drift motions
In this study, a low-cost, simple, single-step low-voltage operation and a well-controlled method for deposition of uniformed and unique size distributions of silver nanoparticles (AgNPs) on the porous silicon (PS) layer were achieved via controlling the drift velocity of electrons in an aqueous solution of AgNO3. The laser diode of 530 nm and 60 mW/cm2 laser wavelength and illumination power density was employed to prepare PS layer by a laser-assisted etching process. The PS layer was incorporated on the platinum disk cathode electrode, and a stainless steel plate as an anode was employed. Low applied operating voltage of about 3V DC at different drift currents of 10, 20, 30 and 40 mA for 2 min was applied to sustain the drift motion of Ag2+. Structural properties of AgNPs layer were examined via the field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) pattern. These measurements exposed that AgNPs were adjusted by controlling the drift current, and a uniform AgNPs with specific unique sizes were obtained. Grain size, specific surface area and nucleation sites of metallic AgNPs were intensely influenced by the drift current.
1. Introduction Preparation and characterization of AgNPs nanoparticles have attracted significant attention due to their important uses in optoelectronics, photo catalysis [1–4], chemical sensing [5] and biological labeling [6]. It is recognized that these uses are intensely reliant on the size distribution and form of the metal nanoparticles. PS layer performances as an efficient reducing means and can reduce metallic ions, as soon as dipped in there in an electrolytic solution (immersion-plating). Morphological features of the deposited metallic layers, specifically its density and the typical particle-size, are influenced by two essential aspects: a) the surface morphology of porous substrate, which is depended on the etching conditions [7–11] and b) the immersion conditions, essentially both of concentration of the metallic solution and the immersion time [12,13]. Many reports about the deposition of AgNPs) nanoparticles were targeted at producing metallic nanoparticle/porous silicon hetro structures active substrates for surface-enhanced Raman scattering (SERS) [14]. Lyla et al. [15], examined the influences of immersion times of as-prepared n-type PS in 1 mM aqueous solution AgNO3, to synthesize an approximately spherical AgNPs for efficient SERS active substrates. The size of the silver nanoparticles was
influenced by the immersion time: When the time in several seconds, AgNPs clusters of limited nanometers, while later increasing immersion time to 10 min min, the clusters were in the sizes range of 0.61–3.42 μm, AgNPs were obtained. Alaa et al. [16] immersed asprepared n-type PS substrates for 10 min in solutions of 1 mM–10 mM AgNO3 and found that the mostly feather-like Ag dendrites on the surface of PS have larger average sizes and a wider size-dispersion, up and around to ll nm. The controlling of the deposition of a metallic nanoparticle within a specific size remains a bigger task owing to two factors: a) random distribution of the dangling bonds Si-Hx groups over the porous surface. b) The reduction rate of the ions is greater than their diffusion rate, and consequently, they are frequently reduced randomly on the PS surface or close the pores’ openings. Fukami et al. [17] used an electrodeposition process for introducing metallic Pt, Au, and Pd inside the pores of macro-porous PS. They found that the supporting electrolyte and the pore morphology were important influences in the desired site of the deposition inside the pores. In this work, an accurately controlled deposition of AgNPs nanoparticles on porous silicon by drifted silvers ions in its electrolytic solution at a fixed concentration was described. Uniformly distributed
Corresponding author. E-mail addresses: [email protected] (M.Q. Zayer), [email protected] (A.M. Alwan), [email protected] (A.S. Ahmed), [email protected] (A.B. Dheyab). ∗
https://doi.org/10.1016/j.cap.2019.05.010 Received 25 December 2018; Received in revised form 20 April 2019; Accepted 18 May 2019 Available online 06 June 2019 1567-1739/ © 2019 Published by Elsevier B.V. on behalf of Korean Physical Society.
Current Applied Physics 19 (2019) 1024–1030
M.Q. Zayer, et al.
Fig. 1. The experimental set up of the (a) Etching process (b) controlled deposition cell.
AgNPs on PS in unique sizes over the porous layer were performed by controlling the electric current (electric field-assisted deposition). The role of the prompted metal ions drift motion on the uniformity of ions flux upon the PS surface and enhanced the uniformity of growth of formed nanoparticles into small size was characterized.
2.2. Deposition of AgNPs on PS surface Initially, the as-formed PS samples were washed with deionized water and immersed for 2 and 4 min in an electrolytic solution of AgNO3, of fixed concentrations of about 1 mM solution, to synthesize the references samples. Controlled deposition of AgNPs on the porous silicon surface was carried out in a home made cell, in which the asformed PS was fitted up on a plastic O-ring located within the cathode electrode, as shown in Fig. 1b. The physical distance between the uniform circular anode and the cathode was about 2 cm. The Ag+ was drifted by applying a low operating voltage of about 3V DC at different drift currents of 10, 20, 30 and 40 mA for 2 min to avoid the rising of the temperature during the controlled deposition process. Structural and morphological properties of as-formed PS and AgNPs on porous silicon layer were tested by X-ray diffraction (XRD-6000, Shimadzu), Field emission - Scanning electron microscope (FE-SEM, Tescan VEGA 3 SB) and Atomic Force Microscopy (AFM) technique in contact mode by 400 AFM system. Special Image-J software was employed to estimate the pore size and AgNPs distribution from the SEM image.
2. Experimental details 2.1. Formation of the PS layer Monocrystalline silicon wafers with (3–10 Ω cm) resistivity and (100) orientations were used to prepare the PS layer. The silicon wafer was divided into a number of fixed-size square pieces (1.5 cm × 1.5 cm). The wafer was cleaned after immersing it in a solution of hydrofluoric and ethanol by ratio 1/10 for about 10 min in an ultrasonic cleaning bath. The preparation process was carried out in a Teflon cell with Laser-Assisted etching process in an electrolyte containing 40%HF and 99.99% ethanol 1:1 by volume using a laser diode with 530 nm, 60 mw/cm2 laser wavelength and laser power density, respectively. To reduce the effects of the Gaussian distribution of the laser beam intensity and hence improves the homogeneity of the porous layer, a circular pine hole with an aperture having diameter of about 1/ 10 of the diameter of the Gaussian beam was used. A beam expander of expanding ratio of about 20 times was employed to increase the diameter from 0.5 cm to 5 cm. Fig. 1a shows the experimental set up of the etching process.
3. Results and discussion 3.1. Characterization of PS layer Fig. 2a illustrates the surface morphology of the PS layer. The FESEM image of PS shows that the PS surface consists of pores within a network of the macro pores-like structure. It's clear that the pores were
Fig. 2. FE-SEM image of the as-formed PS layer (a) surface morphology and (b) pores sizes distributions. 1025
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M.Q. Zayer, et al.
µ=
q
m
3kTm
(1)
And, the thermal motion th of ion occurs in all directions by a thermal velocity, as shown in following equation [18]. th
Fig. 3. 3D AFM image of the as-formed PS layer.
=
3kT m
(2)
Therefore, the immersion plating provides a huge and no controlled pathway for production of metallic nanoparticles. Some requirements were satisfied in an attempt to terminate these difficulties. Firstly, the prepared PS substrate contains a network of systematic, non-connected, and uniformly distribution and nearly has circular shapes, by controlling the illumination conditions in such way the inhomogeneity of etching rates due to the Gaussian distributed effects of the laser beam profile [12] was reduced. Secondly, the PS samples passed in the region of the uniform electric field and drifted Ag+ in its electrolytic solution. The adjustability of the drift current is one of the significant features forcontrolling the silver nano sizes distributions. Fig. 5 (a-d) displays the FE- SEM images of AgNPs nanoparticles deposited on the PS at different drift currents of 10, 20, 30 and 40 mA for 2 min. This figure reveals the different morphologies of AgNPs. The synthesized nanoparticles are highly uniform speed outside the walls of silicon and covered the overall porous surface with increasing the drift current due to the aggregation process among the individual nanoparticles. The statistical distribution of AgNPs sizes as a function of drift current is manifested in Fig. 6. From this figure, the distribution was various from 5 to 50 nm, and the peak of distribution was varied according to the drift current. The dependence of AgNPs sizes on the drift current is depicted in Fig. 7, where the AgNPs sizes increased with the drift current in a sem-linear relationship from the lower value of about 5 nm to a higher value of about 40 nm. This curve reflects a significant scientific point through controlling the metallic nanoparticles by adjusting the drift current. The total charges, which cross the plane of cross-section A in 1 s (current), I is given by
approximately systematic, non-connected, uniformly distributed and nearly have circular shapes. As shown in Fig. 2b, the pores size distribution was ranging from 0.1 μm to 2.1 μm and the average pore size is about 1.3 μm. Based on the gravimetric method [18], the porosity and the layer thickness were assessed about 87% and 6 μm, respectively. The 3D AFM micro image of the PS with the scanning area of (1000 nm*1000 nm) is given in Fig. 3, this images shows pyramids – similar form distributed arbitrarily above the wide-ranging PS surface, and the root mean square of the surface roughness, RMS of the PS is about 20 nm. 3.2. Characterization of AgNPs nanoparticles on the porous silicon surface The growth of AgNPs nanoparticles was varied according to the morphology of the dangling bonds groups) [16]. At the fixed surface morphology of as-formed PS layer, the variation in the deposition of PS layer due to its reliance on the density and location of growth sites (Si–Hx) time leads to modify the structural properties of the formed AgNPs nanoparticles. Fig. 4 displays the FE- SEM images of AgNPs nanoparticles deposited on the PS by uncontrolled immersion deposition without applying external voltage for 2 min in AgNO3 solutions. It is clear from this figure, in spite of the PS layer possesses a nearly uniform pore sizes distribution with a low value of surface roughness, the morphology of the deposited AgNPs over the surface for both deposition times has a non-uniform distribution. The silver regions tend to form continuous macro-regions over the surface similar to a coating process by increasing the growth rates of silver nanoparticles. The lowest value of the AgNPs size is higher than the macropore sizes, thus the amount of the AgNPs districts is predictable to develop outside the pore itself. These explanations are owing to the point that the AgNPs deposition process is governed by the Si–Hx dangling bonds groups [10,13]. As stated earlier, the deposition of a metallic nanoparticle within a specific size is more difficult owing to the random distribution of the dangling bonds Si-Hx groups over the porous surface, in addition to the uncontrolled mobility of the silver ions. The mobility of the ions µ in the electrolyte solution in terms of mean free path m , temperature T and effective mass m is given by Ref. [18].
I = n qvd A
vd =
I neA
(3) (4)
Where, q is the ion charge (coulomb), vd is the ion drift velocity (m/ sec), A is the conductor cross-section (cm2), and n is the number of free ions per unit volume of the conductor (ions density per m3). At the fixed electrolytic AgNO3, the number of ions per unit volume still constant, so the increasing of the drift current means more acceleration of drifted ions between the two electrodes and hence accelerates the metallic ions reduction process (growth rate). Fig. 8(a–d) evinces the Energy Dispersion Analysis (EDS) of AgNPs element deposited on the PS surface, which indicates the successful preparation of silver nanoparticles. The
Fig. 4. FE- SEM images of AgNPs on porous silicon by uncontrolled immersion deposition for (a) 2 min (b) 4 min in AgNO3 solutions.
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Fig. 5. The SEM images of AgNPs nanoparticles deposited on the PS at different drift current of a) 10 mA, b) 20 mA. C) 30 mA and d) 40 mA.
Fig. 6. The statistical distribution of AgNPs sizes at different drift currents of a) 10 mA, b) 20 mA. C) 30 mA and d) 40 mA.
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density of the formed AgNPs was increased with increasing the drifting current. Fig. 9(a–d) illustrates the XRD peaks of AgNPs at different drift currents. The diffraction peaks of the PS layer remain crystal-like in the plane (100) at (2θ) diffraction angle of about 32.9°. There are two reflections peaks at 38.2° and 44.4°. These two peaks were labeled according to the standards of diffraction card of the Joint Committee on Powder Diffraction Standards (JCPDS), at phase index as the (111) and (200) reflections of the face-centered cubic (FCC) silver nanoparticles. The specific surface area (S.S.A.) is unique of the figures of merit of the nanoparticles material, and it's recognized as [14]:
S. S. A. =
6000 Dp
(5)
Where, is the density of Ag for about 10.49 g/cm3, Table (1) tabulates the obtained results, comprising the experimental values of diffraction angles, Dp is nanoparticles size of AgNPs. The attendance of some larger nanoparticles is possibly owing to the tendency of AgNPs to agglomerate at the porous surface due to the existence of Si–Hx group (x = 1,2,3).
Fig. 7. The dependence of AgNPs sizes on the drift current.
Fig. 8. EDS spectra of AgNPs sizes at different drift currents of a) 10 mA, b) 20 mA. C) 30 mA and d) 40 mA. 1028
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Fig. 9. XRD Peaks of AgNPs sizes at different drift currents of a) 10 mA, b) 20 mA, C) 30 mA and d) 40 mA.
Table 1 Particle size and specific surface area of AgNPs. S.S.A of AgNPs (m2/gm)
Particle Size of AgNPs (nm)
FWHM (rad)
Etching different drift current (mA)
114.39 22.87 14.29 11.43
5 25 40 50
0.038 0.02 0.02 0.03
10 20 30 40
The reliance of S.S.A of AgNPs on the drift current is demonstrated in Fig. 10, where the S.S.A sizes were varied with drift currents. This figure reveals an important scientific fact through governing the S.S.A by adjusting the drift current. The Ag particles interact in many chemical processes, which often give the optimization of sensors quality and efficiency. The effect of Ag properties with porous silicon surface depends on the size, amount and distribution particle; for the purpose of sensor, sensitivity improves. The agglomeration mechanism of the Ag on the porous silicon is like the growth, which is related to the Drift Current process. This parameter
Fig. 10. The dependence of specific surface area on the drift current. 1029
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Fig. 11. The mechanism developing of AgNPs on the silicon surface. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
can become the basis for affectations understand of every process that used Ag particles with porous silicon. The deposition of large particles of Ag was achieved by the drift current control. The Ag particles increased clearly on the porous silicon surface by increasing the drift current. The schematic diagram of developing AgNPs on PS layer is shown in figure (11).
[5] [6] [7]
4. Conclusion
[8]
In this paper, the simple and efficient approach of controlling the deposition process of AgNPs on Porous Silicon was achieved by govering the drift current in Electrolytic Solution. Well controlling the AgNPs sizes led to form uniform AgNPs with specific unique. Grain size and specific surface area of AgNPs were intensely influenced by the drift current. Additional works in the application of these new AgNPs structures will expose a novel prospect in the field of nanoplasmonics.
[9] [10] [11] [12]
Acknowledgments
[13]
The author would like to thank the Department of Applied Sciences University of Technology, Nanotechnology and Advanced Materials Research Center - University of Technology, the financial support is also acknowledged.
[14] [15]
References [16]
[1] M.A. Lieberman, A.J. Lichtenberg, Principles of Plasma Discharges and Materials Processing, John Wiley, New York, 1994. [2] P. Buffat, J.P. Borel, Size effect on the melting temperature of gold particles, Phys. Rev. 13 (1976) 2287. [3] Q.L. Feng, J. Wu, G.Q. Chen, F.Z. Cui, T.N. Kim, J.O. Kim, A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus, J. Biomed. Mater. Res. 52 (4) (2000) 662–668. [4] Mohamed A. Etman, Parametric study of silver nanoparticles production using
[17]
[18]
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submerged arc-discharge technique in de-ionized water, Nanosci. Nanotechnol. 3 (3) (2013) 56–61. Alwan M. Alwan, Rasha B. Rashid, Amer B. Dheyab, Morphological and Electrical Properties of Gold Nanoparticles/macroPorous Silicon for CO2 Gas 59 (2018), pp. 57–66 No.1A. Carolyn Richmonds, R. Mohan Sankaran, Plasma-liquid electrochemistry: rapid synthesis of colloidal metal nanoparticles by microplasma reduction of aqueous cations" Appl, Phys. Lett. 93 (2008) 131501. Ali Akbar Ashkarran, A novel method for synthesis of colloidal silver nanoparticles by arc discharge in liquid, Curr. Appl. Phys. 10 (2010) 1442–1447. Amer B. Dheyab, Alwan M. Alwan, Mehdi Q. Zayer, Optimizing of gold nanoparticles on porous silicon morphologies for a sensitive carbon monoxide gas sensor device, Plasmonics (2018), https://doi.org/10.1007/s11468-018-0828-x. Der-Chi Tien, Liang-Chia Chen, Nguyen Van Thai, Sana Ashraf, Study of Ag and Au nanoparticles synthesized by arc discharge in DeionizedWater, J. Nanomater. (2010) 9. Article ID 634757. Alwan M. Alwan, Ruaa A. Abbas, Amer B. Dheyab, Study the characteristic of planer and sandwich PSi gas sensor (comparative study), Silicon 10 (2018) 2527–2534. Wail H. Ali, Amer B. Dheyab, Alwan M. Alwan, Optimization and synthesis of gold nanoparticles on N-type porous silicon substrates as highly-gas sensitive, Int. J. Mech. Eng. Technol. 9 (9) (2018) 1393–1401 September. A.M. Alwan, A.B. Dheyab, Room temperature CO2 gas sensors of AuNPs/mesoPSi hybrid structures, Appl. Nanosci. (2017) 7–335. A.M. Alwan, A.B. Dheyab, A.J. Allaa, Study of the influence of incorporation of gold nanoparticles on the modified porous silicon sensor for petroleum gas detection, Eng. Technol. J. 35 (8) (2017) 811–815 Part A. Alwan M. Alwan, Intisar A. Naseef, Amer B. Dheyab, Well controlling of plasmonic features of gold nanoparticles on macro porous silicon substrate by HF acid concentration, Plasmonics (2018), https://doi.org/10.1007/s11468-018-0720-8. Duaa A. Hashim, Layla A. Walia, Alwan M. Alwan, Amer B. Dheyab, Excellent fabrication of Pd-Ag NPs/PSi photocatalyst based on bimetallic nanoparticles for improving methylene blue Photocatalytic degradation, Optik Int. J. Light Electron. Optic. 179 (2019) 708–717. J.H. Adawyia, M.A. Alwan, A.J. Allaa, Optimizing of porous silicon morphology for synthesis of silver nanoparticles, Microporous Mesoporous Mater. 227 (2016) 152–160. A. Munoz-Noval, K. Fukami, A. Koyama, D. Gallach, Accelerated growth from amorphous clusters to metallic nanoparticles observed in electrochemical deposition of platinum within nanopores of porous silicon, Electrochem. Commun. 71 (2016) 9–12. S.M. Sze, Kwok K. Ng, Physics of Semiconductor Devices, third ed., A JOHN WILEY & SONS, INC., PUBLICATION, Hoboken, New Jersey, 2007.
Contents lists available at ScienceDirect
Current Applied Physics journal homepage: www.elsevier.com/locate/cap
Accurate controlled deposition of silver nanoparticles on porous silicon by drifted ions in electrolytic solution
T
Mehdi Q. Zayera, Alwan M. Alwana, Ahmed S. Ahmedb, Amer B. Dheyabc,∗ a
Department of Applied Sciences, University of Technology, Baghdad, Iraq College of Nursing-basic Science Department, Misan University, Iraq c Ministry of Science and Technology, Baghdad, Iraq b
ARTICLE INFO
ABSTRACT
Keywords: PS Immersion plating Metallic nanostructures Drift motions
In this study, a low-cost, simple, single-step low-voltage operation and a well-controlled method for deposition of uniformed and unique size distributions of silver nanoparticles (AgNPs) on the porous silicon (PS) layer were achieved via controlling the drift velocity of electrons in an aqueous solution of AgNO3. The laser diode of 530 nm and 60 mW/cm2 laser wavelength and illumination power density was employed to prepare PS layer by a laser-assisted etching process. The PS layer was incorporated on the platinum disk cathode electrode, and a stainless steel plate as an anode was employed. Low applied operating voltage of about 3V DC at different drift currents of 10, 20, 30 and 40 mA for 2 min was applied to sustain the drift motion of Ag2+. Structural properties of AgNPs layer were examined via the field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) pattern. These measurements exposed that AgNPs were adjusted by controlling the drift current, and a uniform AgNPs with specific unique sizes were obtained. Grain size, specific surface area and nucleation sites of metallic AgNPs were intensely influenced by the drift current.
1. Introduction Preparation and characterization of AgNPs nanoparticles have attracted significant attention due to their important uses in optoelectronics, photo catalysis [1–4], chemical sensing [5] and biological labeling [6]. It is recognized that these uses are intensely reliant on the size distribution and form of the metal nanoparticles. PS layer performances as an efficient reducing means and can reduce metallic ions, as soon as dipped in there in an electrolytic solution (immersion-plating). Morphological features of the deposited metallic layers, specifically its density and the typical particle-size, are influenced by two essential aspects: a) the surface morphology of porous substrate, which is depended on the etching conditions [7–11] and b) the immersion conditions, essentially both of concentration of the metallic solution and the immersion time [12,13]. Many reports about the deposition of AgNPs) nanoparticles were targeted at producing metallic nanoparticle/porous silicon hetro structures active substrates for surface-enhanced Raman scattering (SERS) [14]. Lyla et al. [15], examined the influences of immersion times of as-prepared n-type PS in 1 mM aqueous solution AgNO3, to synthesize an approximately spherical AgNPs for efficient SERS active substrates. The size of the silver nanoparticles was
influenced by the immersion time: When the time in several seconds, AgNPs clusters of limited nanometers, while later increasing immersion time to 10 min min, the clusters were in the sizes range of 0.61–3.42 μm, AgNPs were obtained. Alaa et al. [16] immersed asprepared n-type PS substrates for 10 min in solutions of 1 mM–10 mM AgNO3 and found that the mostly feather-like Ag dendrites on the surface of PS have larger average sizes and a wider size-dispersion, up and around to ll nm. The controlling of the deposition of a metallic nanoparticle within a specific size remains a bigger task owing to two factors: a) random distribution of the dangling bonds Si-Hx groups over the porous surface. b) The reduction rate of the ions is greater than their diffusion rate, and consequently, they are frequently reduced randomly on the PS surface or close the pores’ openings. Fukami et al. [17] used an electrodeposition process for introducing metallic Pt, Au, and Pd inside the pores of macro-porous PS. They found that the supporting electrolyte and the pore morphology were important influences in the desired site of the deposition inside the pores. In this work, an accurately controlled deposition of AgNPs nanoparticles on porous silicon by drifted silvers ions in its electrolytic solution at a fixed concentration was described. Uniformly distributed
Corresponding author. E-mail addresses: [email protected] (M.Q. Zayer), [email protected] (A.M. Alwan), [email protected] (A.S. Ahmed), [email protected] (A.B. Dheyab). ∗
https://doi.org/10.1016/j.cap.2019.05.010 Received 25 December 2018; Received in revised form 20 April 2019; Accepted 18 May 2019 Available online 06 June 2019 1567-1739/ © 2019 Published by Elsevier B.V. on behalf of Korean Physical Society.
Current Applied Physics 19 (2019) 1024–1030
M.Q. Zayer, et al.
Fig. 1. The experimental set up of the (a) Etching process (b) controlled deposition cell.
AgNPs on PS in unique sizes over the porous layer were performed by controlling the electric current (electric field-assisted deposition). The role of the prompted metal ions drift motion on the uniformity of ions flux upon the PS surface and enhanced the uniformity of growth of formed nanoparticles into small size was characterized.
2.2. Deposition of AgNPs on PS surface Initially, the as-formed PS samples were washed with deionized water and immersed for 2 and 4 min in an electrolytic solution of AgNO3, of fixed concentrations of about 1 mM solution, to synthesize the references samples. Controlled deposition of AgNPs on the porous silicon surface was carried out in a home made cell, in which the asformed PS was fitted up on a plastic O-ring located within the cathode electrode, as shown in Fig. 1b. The physical distance between the uniform circular anode and the cathode was about 2 cm. The Ag+ was drifted by applying a low operating voltage of about 3V DC at different drift currents of 10, 20, 30 and 40 mA for 2 min to avoid the rising of the temperature during the controlled deposition process. Structural and morphological properties of as-formed PS and AgNPs on porous silicon layer were tested by X-ray diffraction (XRD-6000, Shimadzu), Field emission - Scanning electron microscope (FE-SEM, Tescan VEGA 3 SB) and Atomic Force Microscopy (AFM) technique in contact mode by 400 AFM system. Special Image-J software was employed to estimate the pore size and AgNPs distribution from the SEM image.
2. Experimental details 2.1. Formation of the PS layer Monocrystalline silicon wafers with (3–10 Ω cm) resistivity and (100) orientations were used to prepare the PS layer. The silicon wafer was divided into a number of fixed-size square pieces (1.5 cm × 1.5 cm). The wafer was cleaned after immersing it in a solution of hydrofluoric and ethanol by ratio 1/10 for about 10 min in an ultrasonic cleaning bath. The preparation process was carried out in a Teflon cell with Laser-Assisted etching process in an electrolyte containing 40%HF and 99.99% ethanol 1:1 by volume using a laser diode with 530 nm, 60 mw/cm2 laser wavelength and laser power density, respectively. To reduce the effects of the Gaussian distribution of the laser beam intensity and hence improves the homogeneity of the porous layer, a circular pine hole with an aperture having diameter of about 1/ 10 of the diameter of the Gaussian beam was used. A beam expander of expanding ratio of about 20 times was employed to increase the diameter from 0.5 cm to 5 cm. Fig. 1a shows the experimental set up of the etching process.
3. Results and discussion 3.1. Characterization of PS layer Fig. 2a illustrates the surface morphology of the PS layer. The FESEM image of PS shows that the PS surface consists of pores within a network of the macro pores-like structure. It's clear that the pores were
Fig. 2. FE-SEM image of the as-formed PS layer (a) surface morphology and (b) pores sizes distributions. 1025
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µ=
q
m
3kTm
(1)
And, the thermal motion th of ion occurs in all directions by a thermal velocity, as shown in following equation [18]. th
Fig. 3. 3D AFM image of the as-formed PS layer.
=
3kT m
(2)
Therefore, the immersion plating provides a huge and no controlled pathway for production of metallic nanoparticles. Some requirements were satisfied in an attempt to terminate these difficulties. Firstly, the prepared PS substrate contains a network of systematic, non-connected, and uniformly distribution and nearly has circular shapes, by controlling the illumination conditions in such way the inhomogeneity of etching rates due to the Gaussian distributed effects of the laser beam profile [12] was reduced. Secondly, the PS samples passed in the region of the uniform electric field and drifted Ag+ in its electrolytic solution. The adjustability of the drift current is one of the significant features forcontrolling the silver nano sizes distributions. Fig. 5 (a-d) displays the FE- SEM images of AgNPs nanoparticles deposited on the PS at different drift currents of 10, 20, 30 and 40 mA for 2 min. This figure reveals the different morphologies of AgNPs. The synthesized nanoparticles are highly uniform speed outside the walls of silicon and covered the overall porous surface with increasing the drift current due to the aggregation process among the individual nanoparticles. The statistical distribution of AgNPs sizes as a function of drift current is manifested in Fig. 6. From this figure, the distribution was various from 5 to 50 nm, and the peak of distribution was varied according to the drift current. The dependence of AgNPs sizes on the drift current is depicted in Fig. 7, where the AgNPs sizes increased with the drift current in a sem-linear relationship from the lower value of about 5 nm to a higher value of about 40 nm. This curve reflects a significant scientific point through controlling the metallic nanoparticles by adjusting the drift current. The total charges, which cross the plane of cross-section A in 1 s (current), I is given by
approximately systematic, non-connected, uniformly distributed and nearly have circular shapes. As shown in Fig. 2b, the pores size distribution was ranging from 0.1 μm to 2.1 μm and the average pore size is about 1.3 μm. Based on the gravimetric method [18], the porosity and the layer thickness were assessed about 87% and 6 μm, respectively. The 3D AFM micro image of the PS with the scanning area of (1000 nm*1000 nm) is given in Fig. 3, this images shows pyramids – similar form distributed arbitrarily above the wide-ranging PS surface, and the root mean square of the surface roughness, RMS of the PS is about 20 nm. 3.2. Characterization of AgNPs nanoparticles on the porous silicon surface The growth of AgNPs nanoparticles was varied according to the morphology of the dangling bonds groups) [16]. At the fixed surface morphology of as-formed PS layer, the variation in the deposition of PS layer due to its reliance on the density and location of growth sites (Si–Hx) time leads to modify the structural properties of the formed AgNPs nanoparticles. Fig. 4 displays the FE- SEM images of AgNPs nanoparticles deposited on the PS by uncontrolled immersion deposition without applying external voltage for 2 min in AgNO3 solutions. It is clear from this figure, in spite of the PS layer possesses a nearly uniform pore sizes distribution with a low value of surface roughness, the morphology of the deposited AgNPs over the surface for both deposition times has a non-uniform distribution. The silver regions tend to form continuous macro-regions over the surface similar to a coating process by increasing the growth rates of silver nanoparticles. The lowest value of the AgNPs size is higher than the macropore sizes, thus the amount of the AgNPs districts is predictable to develop outside the pore itself. These explanations are owing to the point that the AgNPs deposition process is governed by the Si–Hx dangling bonds groups [10,13]. As stated earlier, the deposition of a metallic nanoparticle within a specific size is more difficult owing to the random distribution of the dangling bonds Si-Hx groups over the porous surface, in addition to the uncontrolled mobility of the silver ions. The mobility of the ions µ in the electrolyte solution in terms of mean free path m , temperature T and effective mass m is given by Ref. [18].
I = n qvd A
vd =
I neA
(3) (4)
Where, q is the ion charge (coulomb), vd is the ion drift velocity (m/ sec), A is the conductor cross-section (cm2), and n is the number of free ions per unit volume of the conductor (ions density per m3). At the fixed electrolytic AgNO3, the number of ions per unit volume still constant, so the increasing of the drift current means more acceleration of drifted ions between the two electrodes and hence accelerates the metallic ions reduction process (growth rate). Fig. 8(a–d) evinces the Energy Dispersion Analysis (EDS) of AgNPs element deposited on the PS surface, which indicates the successful preparation of silver nanoparticles. The
Fig. 4. FE- SEM images of AgNPs on porous silicon by uncontrolled immersion deposition for (a) 2 min (b) 4 min in AgNO3 solutions.
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Fig. 5. The SEM images of AgNPs nanoparticles deposited on the PS at different drift current of a) 10 mA, b) 20 mA. C) 30 mA and d) 40 mA.
Fig. 6. The statistical distribution of AgNPs sizes at different drift currents of a) 10 mA, b) 20 mA. C) 30 mA and d) 40 mA.
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density of the formed AgNPs was increased with increasing the drifting current. Fig. 9(a–d) illustrates the XRD peaks of AgNPs at different drift currents. The diffraction peaks of the PS layer remain crystal-like in the plane (100) at (2θ) diffraction angle of about 32.9°. There are two reflections peaks at 38.2° and 44.4°. These two peaks were labeled according to the standards of diffraction card of the Joint Committee on Powder Diffraction Standards (JCPDS), at phase index as the (111) and (200) reflections of the face-centered cubic (FCC) silver nanoparticles. The specific surface area (S.S.A.) is unique of the figures of merit of the nanoparticles material, and it's recognized as [14]:
S. S. A. =
6000 Dp
(5)
Where, is the density of Ag for about 10.49 g/cm3, Table (1) tabulates the obtained results, comprising the experimental values of diffraction angles, Dp is nanoparticles size of AgNPs. The attendance of some larger nanoparticles is possibly owing to the tendency of AgNPs to agglomerate at the porous surface due to the existence of Si–Hx group (x = 1,2,3).
Fig. 7. The dependence of AgNPs sizes on the drift current.
Fig. 8. EDS spectra of AgNPs sizes at different drift currents of a) 10 mA, b) 20 mA. C) 30 mA and d) 40 mA. 1028
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Fig. 9. XRD Peaks of AgNPs sizes at different drift currents of a) 10 mA, b) 20 mA, C) 30 mA and d) 40 mA.
Table 1 Particle size and specific surface area of AgNPs. S.S.A of AgNPs (m2/gm)
Particle Size of AgNPs (nm)
FWHM (rad)
Etching different drift current (mA)
114.39 22.87 14.29 11.43
5 25 40 50
0.038 0.02 0.02 0.03
10 20 30 40
The reliance of S.S.A of AgNPs on the drift current is demonstrated in Fig. 10, where the S.S.A sizes were varied with drift currents. This figure reveals an important scientific fact through governing the S.S.A by adjusting the drift current. The Ag particles interact in many chemical processes, which often give the optimization of sensors quality and efficiency. The effect of Ag properties with porous silicon surface depends on the size, amount and distribution particle; for the purpose of sensor, sensitivity improves. The agglomeration mechanism of the Ag on the porous silicon is like the growth, which is related to the Drift Current process. This parameter
Fig. 10. The dependence of specific surface area on the drift current. 1029
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Fig. 11. The mechanism developing of AgNPs on the silicon surface. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
can become the basis for affectations understand of every process that used Ag particles with porous silicon. The deposition of large particles of Ag was achieved by the drift current control. The Ag particles increased clearly on the porous silicon surface by increasing the drift current. The schematic diagram of developing AgNPs on PS layer is shown in figure (11).
[5] [6] [7]
4. Conclusion
[8]
In this paper, the simple and efficient approach of controlling the deposition process of AgNPs on Porous Silicon was achieved by govering the drift current in Electrolytic Solution. Well controlling the AgNPs sizes led to form uniform AgNPs with specific unique. Grain size and specific surface area of AgNPs were intensely influenced by the drift current. Additional works in the application of these new AgNPs structures will expose a novel prospect in the field of nanoplasmonics.
[9] [10] [11] [12]
Acknowledgments
[13]
The author would like to thank the Department of Applied Sciences University of Technology, Nanotechnology and Advanced Materials Research Center - University of Technology, the financial support is also acknowledged.
[14] [15]
References [16]
[1] M.A. Lieberman, A.J. Lichtenberg, Principles of Plasma Discharges and Materials Processing, John Wiley, New York, 1994. [2] P. Buffat, J.P. Borel, Size effect on the melting temperature of gold particles, Phys. Rev. 13 (1976) 2287. [3] Q.L. Feng, J. Wu, G.Q. Chen, F.Z. Cui, T.N. Kim, J.O. Kim, A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus, J. Biomed. Mater. Res. 52 (4) (2000) 662–668. [4] Mohamed A. Etman, Parametric study of silver nanoparticles production using
[17]
[18]
1030
submerged arc-discharge technique in de-ionized water, Nanosci. Nanotechnol. 3 (3) (2013) 56–61. Alwan M. Alwan, Rasha B. Rashid, Amer B. Dheyab, Morphological and Electrical Properties of Gold Nanoparticles/macroPorous Silicon for CO2 Gas 59 (2018), pp. 57–66 No.1A. Carolyn Richmonds, R. Mohan Sankaran, Plasma-liquid electrochemistry: rapid synthesis of colloidal metal nanoparticles by microplasma reduction of aqueous cations" Appl, Phys. Lett. 93 (2008) 131501. Ali Akbar Ashkarran, A novel method for synthesis of colloidal silver nanoparticles by arc discharge in liquid, Curr. Appl. Phys. 10 (2010) 1442–1447. Amer B. Dheyab, Alwan M. Alwan, Mehdi Q. Zayer, Optimizing of gold nanoparticles on porous silicon morphologies for a sensitive carbon monoxide gas sensor device, Plasmonics (2018), https://doi.org/10.1007/s11468-018-0828-x. Der-Chi Tien, Liang-Chia Chen, Nguyen Van Thai, Sana Ashraf, Study of Ag and Au nanoparticles synthesized by arc discharge in DeionizedWater, J. Nanomater. (2010) 9. Article ID 634757. Alwan M. Alwan, Ruaa A. Abbas, Amer B. Dheyab, Study the characteristic of planer and sandwich PSi gas sensor (comparative study), Silicon 10 (2018) 2527–2534. Wail H. Ali, Amer B. Dheyab, Alwan M. Alwan, Optimization and synthesis of gold nanoparticles on N-type porous silicon substrates as highly-gas sensitive, Int. J. Mech. Eng. Technol. 9 (9) (2018) 1393–1401 September. A.M. Alwan, A.B. Dheyab, Room temperature CO2 gas sensors of AuNPs/mesoPSi hybrid structures, Appl. Nanosci. (2017) 7–335. A.M. Alwan, A.B. Dheyab, A.J. Allaa, Study of the influence of incorporation of gold nanoparticles on the modified porous silicon sensor for petroleum gas detection, Eng. Technol. J. 35 (8) (2017) 811–815 Part A. Alwan M. Alwan, Intisar A. Naseef, Amer B. Dheyab, Well controlling of plasmonic features of gold nanoparticles on macro porous silicon substrate by HF acid concentration, Plasmonics (2018), https://doi.org/10.1007/s11468-018-0720-8. Duaa A. Hashim, Layla A. Walia, Alwan M. Alwan, Amer B. Dheyab, Excellent fabrication of Pd-Ag NPs/PSi photocatalyst based on bimetallic nanoparticles for improving methylene blue Photocatalytic degradation, Optik Int. J. Light Electron. Optic. 179 (2019) 708–717. J.H. Adawyia, M.A. Alwan, A.J. Allaa, Optimizing of porous silicon morphology for synthesis of silver nanoparticles, Microporous Mesoporous Mater. 227 (2016) 152–160. A. Munoz-Noval, K. Fukami, A. Koyama, D. Gallach, Accelerated growth from amorphous clusters to metallic nanoparticles observed in electrochemical deposition of platinum within nanopores of porous silicon, Electrochem. Commun. 71 (2016) 9–12. S.M. Sze, Kwok K. Ng, Physics of Semiconductor Devices, third ed., A JOHN WILEY & SONS, INC., PUBLICATION, Hoboken, New Jersey, 2007.