CHEMICAL DEPOSITION OF LEAD SULFIDE NANOPARTICLES FROM AQUEOUS SOLUTION

​ABSTRACT

In this paper, optimal parameters based on the formation of PbS nanostructures are given and structural properties are studied.The obtained results were studied under scanning electron microscope, raman spectroscopy was performed. The spectrum of elemental analysis of the PbS nanostructure by energy dispersion analysis is presented, from which it is proved that the stoichiometric ratio of PbS is fulfilled, there are no foreign chemical elements and the percentage of the Pb atom is 57.13%, and the percentage of the S atom is 42.87%. Examination of the PbS nanostructure under a scanning electron microscope (SEM) showed that the surface of the structure is rough and their shape is approximately the same size. It was proved that the crystals in the PbS nanostructure have the same size. Raman scattering on PbS nanostructures was also studied using a Raman spectrometer.

Keywords: PbS nanostructure; reagent; chemical reaction; stable structure; optimal parameters.

Introduction

Lead sulfide (PbS) is a widely studied p-type semiconductor because it can be used in various fields by changing its optical and electrical properties. For example, since the value of the forbidden area (0.41 ev) is equal, and the value of the exciton bor on radius (18 nm) is equal, infrared sensors have been successfully developed and manufactured, and in solar energy, lead sulfide (PbS) is used for the manufacture of photovoltaic cells [1]. In addition, PbS nanoparticles are used to convert solar energy into chemical energy. It is established that the value of the limiting voltage of thin-film transistors based on PbS is approximately from ≈ 7.8 V to 1.0 V [2]. It was found that PbS film-based gas sensors are sensitive to NO₂ and NH₃ compounds at room temperature. In accordance with the special electronic properties of the PbS compound in the optoelectronic system, in particular, in infrared photodetectors, optical switches, photoelectronics, electroluminescence, hotoluminescence, displays, as well as in thermoelectronic devices, as important materials, there are few concrete studies of the PbS compound to date [3-4].These studies will be the starting point for future research, since the PbS nanocrystal occupies a special place in optoelectronics as the main nanomaterial of a semiconductor. According to the research, during the experiments it was found that the structural, optical and electronic properties of the PbS compound change with the transition from the macrometer to the nanoscale [5].  As established by research, the properties of the PbS film directly depend on the synthesis method and landing parameters. Currently, PbS nanostructure can be formed by various methods, such as pyrolysis by spraying, ion layer reaction and deposition in a chemical bath. These methods use different temperature values[6-7] . The chemical bath deposition method is the preferred method for obtaining inexpensive and high-quality homogeneous films. The PbS nanostructure was grown at room temperature based on the reaction of  Pb₂+ S₂ ions in a liquid solution available in this method. This is a reaction that does not require energy expenditure [8]. For this reason, this effective and inexpensive method based on growing PbS nanofilm was used during the experiment [9].

The experiment and the results obtained

Nanostructures of lead sulfide (PbS) were prepared by chemical bath deposition on purified  on a silicon substrate. First: lead nitrate 25 ml, 0.18 M (1.4 g), sodium hydroxide 65 ml of 0.38 m (1.48g) solutions were mixed in a 150 ml glass for 80 minutes. Sometimes 40 ml of 0.11 M (0.360 g) thiourea was added to this solution. As parameters T =room temperature t = 80 minutes. 

Figure 1. The reaction of growing a PbS nanostructures on a silicon surface

The reaction mixture of metal chalcogenides, including in the chemical precipitation of sulfides, is an aqueous solution of one or more metal salts of  Me+, sulfidating (a source of sulfur) and complexing. In the latter process, silicon substrate cleaned by ultrasound .  Finally, the resulting nanostructures were washed and dried with deionized water.

Figure 2. Investigation of the morphology and elemental analysis of PbS nanostructures, using a scanning electron microscope

As can be seen from Figure 2  images of the PbS nanostructures are shown with a scanning electron microscope. It is clear that the surface of the thin film is rough, that is, it consists of crystallites, and their shape is approximately the same size as a cube. Fig.2  the spectrum of elemental analysis obtained by the method of energy dispersion analysis of a PbS thin film is given, from which it can be seen that the stoichiometric ratio of  PbS is performed and shows that there are no foreign chemical elements, and the intensity of our  P  and S atoms at an energy value of  2.5ev is high.

Figure 5. Raman spectroscopy of nanostructures PbS

From this figure 5 it is clearly seen that the peaks are the peaks of Pb and S atoms. In this research paper, it is established that the resulting nanostructures consists of these two compounds.  The classic way to check whether this study is a Raman spectrum is to change the excitation wavelength and react differently to the change in the excitation wavelength.This study shows that the resulting nanostructure consists of these two compounds in pure form.  Here, the wavelength of the exciting light was 632.8 nm, and the power was 0.05 mW. The Raman displacement of a semiconductor corresponds to an optical phonon. To study the crystal structure of PbS, the raman scattering process was considered in the range of 100-1000 cm^-1. The process was carried out at room temperature and constant pressure. The peak of 140 cm^-1 corresponds to the transverse one, and the peak of 195-463 cm^-1 corresponds to the longitudinal optical phonon of the first and second order. Peaks in the range of 140-463 cm^-1 correspond to combinational oscillatory modes. As can be seen from the figure, the raman scattering spectra of nanocrystals are located in the arls of peaks 93 - 463 cm^-1. Thus, a study of raman scattering on PbS nanostructures was carried out.

Conclusion

During the study  PbS nanostructures were formed using the CBD method. The spectrum of elemental analysis obtained by the method of energy dispersion analysis of the PbS nanostructures are presented, from which it is proved that the stoichiometric ratio of  PbS is fulfilled and there are no extraneous chemical elements. The study of the PbS nanostructures using SEM showed that the surface of the nanostructures are rough, that is, it consists of crystals, and their shapes are approximately the same size. It was also found that the nanostructures formed using Raman spectra are pure and consist of lead and sulfur atoms. During the study, the optimal parameters of  growing  PbS nanostructures were identified, it was shown that it is cheap and effective.  The obtained results served as a starting point for new research, since the  PbS  nanocrystals  occupy a special place in optoelectronics as the main nanomaterial of a semiconductor.

References:

1. Mustafa Mohammed K. A.   Studying the structural, morphological, optical, and electrical properties of CdS/PbS thin films for photovoltaic applications.
2. Yesica B.  Castillo-S´anchez, A.  Luis Gonz´alez * Сhemically deposited pbs thin films by reaction media with glycine for use in photovoltaics/ https://doi.org/10.1016/j.mssp.2020.105405
3. Azab A. A. ,  Ward , . M. Mahmoud1 ,  Structural and dielectric properties of prepared PbS and PbTe nanomaterials/ Received 20 July 2018, revised manuscript received 15 September 2018 ©2018 Chinese Institute of  Electronics
4. Sergey  Zimin P. , Kolesnikov N.    ,  Amirov I.  ,  Naumov V.  , Egor Gorlachev S., Variation of surface nanostructures on (100) pbs single crystals during argon plasma treatment
5. Cao Y., "Lead Sulfide Nanocrystals as a Promising Photovoltaic Material: A Review." Advanced Materials, vol. 25, no. 46, 2013, pp. 6505-6516.
6. Mamiyev  Z. , Narmina O.,  Balayeva  PbS nanostructures: A review of recent advances/ Received 16 September 2022, Revised 11 December 2022, Accepted 26 December 2022, Available online 2 January 2023, Version of Record 8 February 2023./  https://doi.org/10.1016/j.mtsust.2022.100305 
7. Yesica A., Castillo S., Luis Gonz´alez  Сhemically deposited PbS thin films by reaction media with glycine for use in photovoltaics https://doi.org/10.1016/j.mssp.2020.105405
8. Weyde M. M. ,  Yarema M. ,  Liu M. , Sargent E. , Wood V. / Nanocrystal Quantum Dot Devices: How the Lead Sulfide (PbS) System Teaches Us the Importance of Surfaces/ 852751 - Solution-Based Engineering of Nanodimensional Phase-Change Materials and Memory Devices (EC)/ https://doi.org/10.2533/chimia.2021.398
9. Jyothilakshmi V.P., Bhabhina N.M., Dharsana M.V., Sindhu Swaminathan/ Wet chemical synthesis of lead sulfide nanoparticles and its application as light harvester in photovoltaic cell/ Volume 33, Part 5, 2020, Pages 2125-2129/ https://doi.org/10.1016/j.matpr.2020.02.928