Effect of Sodium Selenosulfate Concentration on Microstructural, Morphological, and Luminescence Characteristics of Cadmium Selenide Nanoparticles

Abstract

CBD-deposited cadmium selenide nanoparticles in acidic medium production at pH value of bath solution was stayed constant at 6.5 using EDTA as complexing agents; sodium selenosulfite acts as a source of Se^2- ion and cadmium acetate as source of Cd²⁺ ion. The nanoparticles of binary compound CdSe were also grown at different concentrations of sodium selenosulfite, and the influence of this parameter on the behaviours of the nanoparticles was studied. The as-synthesized cadmium selenide nanoparticles are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and PL absorption spectroscopy. Cadmium-selenide nanoparticles were produced using various concentrations as 10, 15, and 20 milliliters on a microscopic glass plate by chemical technique at a growth temperature of 90 degree Celsius. Microstructural constraints realized from the X-ray diffraction pattern decrease in grain size with an increase of concentration (8.25 nm–0.01 nm). It witnessed that the synthesized nanoparticle has a cubic crystal structure with favoured direction towards the (111) Miller indices’ plane. The oriented peak was investigated from the planes (311) and (111). From patterns of PL emissions, it was detected that in increasing concentration of sodium selenosulfate intensity, the nanoparticles with small crystal size could represent maximum luminescence intensity associated with the larger crystal size. This is due to the fact that the amount of ions on the nanoparticle surface rapidly increases as the crystal size of the nanoparticles reduces. Additionally, the transporter recombination ratio was increased as the size of the transporter reduces resulting in an increase in the overlap between the electron and hole wave functions. SEM inspection of produced nanoparticles reveals that the surface is free of cracks and that the grains are spherically formed. The surface is coated with granules of consistent size and shape. There are no fractures or holes visible inside the thin films under examination.

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction

The usage of nanostructure instruments for optoelectronic tools, containing light-emitting diodes, laser-diodes, photodetectors, and photovoltaic panels, has newly concerned significant attention because of their distinctive geometry. Nanostructures in narrow length could be effortlessly assimilated into numerous technological platforms, giving new physiological and chemical behaviours for maximum enactment of optoelectronic devices. The misuse of new nanostructures, as well as their optical and electrical characteristics, is important for their developing applied instrumental applications [1]. In recent years, CdSe nanoparticles have been very interesting in the study community with their maximum demands regarding their application in optical electronics. CdSe was a largely used semiconductor compound because of its direct bandgap (1.74 ev) at a normal temperature radius of 5.6 nm from Bohr’s theory [2, 3]. The size of cadmium selenide increased the volume ratio; so, it can be found vastly in different fields from light-emitting diode to photovoltaic cells. A lot of journalists are demanding to study different properties of CdSe, which is a kind of (II-VI) semiconductors in cost-effective ways [4]. CBD is a somewhat inexpensive method for the deposition of nanomaterials as it does not need extremely cultured materials. Cadmium selenide nanostructures have been produced by numerous scientists by using different methods such as microwave deposition, sputtering, precipitation, sonochemical, and solvothermal [4, 5]. In order to prepare for nanostructure temperatures of deposition, annealing and the volume ratio of source solution have a vital role in the behaviours of the samples to be produced [6]. The crystal size of the nanoparticle is once more solely relying on the nucleation hotness/coldness and the other listed factors. The previous ways of synthesizing CdSe nanoparticles cause pollution of the environment and can lead to greenhouse effect and drought except for chemical bath deposition techniques which are sometimes known as green synthesis.

It is a very difficult maximum quality production of CdSe nanoparticles by using basic chemical atmospheric infusion unless the problems of CdSe synthesization are overcome [7]. The influence of hydroxide is reduced when CdSe nanoparticles are prepared in an acidic medium. For most metal ions widely used in CBD, it is fair to conclude that no hydroxide is available under such conditions and also that deposition occurs through ion-by-ion processes [8]. The aim of this research was to look at CdSe nanoparticles grown under various concentrations for optoelectronic applications. Having this in consideration, we have deposited cadmium selenide nanoparticles with various concentrations of sodium selenosulfite via chemical bath deposition techniques.

During this work, we have a tendency to gift the result of bimetallic precursor concentration on morphological, structural, and optical properties of CdSe nanoparticles deposited from chemical containing Cd acetate, hydroxyl acid ammonia, and metallic element selenosulfite, at a temperature of 90°C and a pH of 6.5. To make our investigation effective, cadmium-acetate is often primarily used because of the supply of Cd ions in reaction with hydroxyl acid as a complexing agent for the deposition of Cd selenide films at a concentration of selenosulfite 10, 15, and 20 ml.

2. Experimental Details

2.1. Cleaning Materials

Cleaning laboratory instruments are a serious side that can give to nanoparticle observance. The microscopic glass plate, bath beaker, small beakers for measurements, and spoons were purified in weak acid over a day and successively put in ethanol for 40 min, at that moment; ultrasonically washed with deionized water; and got dehydrated underneath ambient temperatures before being used for the synthesis [9, 10].

2.2. Sample Preparation (Cadmium Selenide Nanoparticles)

In synthesization of cadmium selenide films, water bath was arranged by adding 20-milliliter (0.4) molarity of cadmium-acetate [Cd (CH₃COO)₂·2H₂O] deeds as cadmium ion bases; 10 ml (0.5 M) ethylenediamine (EDTA) acts as a complex agent, in a 150 ml beaker. To this, adding different one molarity of sodium selenosulfate (Na₂SeSO₃) was used for a source of selenide ion (Se-2) at ordinary temperature. The total volume was kept to be 70 milliliters by filling with distilled water. The pH value of the mixture solution was accustomed to be around 6.5 by using some droplets of sulfuric acid (H₂So₄), and the bath temperature adjusted to 313 Kelvin. Glass beaker was then set aside in a water bath. Then, a magnetic stirrer revolves at a continuous rate per second (rps). Likewise, the systems adjusted three times, keeping all parameter values the same and varying the volume of concentration of sodium selenosulfite as 10, 15, and 20 milliliters; this is to be done for the first time for 120 minutes without troubling. Finally, cadmium selenide nanofluids were deposited. After 120 min bath beaker was taken from the heater, by using a syringe, the bath solution was fetched gently, and nanofluid left on the bottom side of the beaker was transferred on a pure glass plate and dried in the warm air; finally, CdSe nanoparticles were kept in the oven for characterization.

3. Results and Discussion

The characterization of samples is an integrated process with nanoparticle deposition. Various methods were used for the characterization of the nanoparticles. The samples of CdSe nanoparticles were structurally characterized by using a Bruker D8 X-ray diffractometer functioning at 45 kV and 40 mA with Cu Kα monochromatic radiation ($\lambda =0.15406$ nm) in the Bragg-Brentano geometry [11].

Figure 1 shows the patterns for CdSe nanoparticles generated with varying concentrations of nonmetallic precursor values and deposited for 120 minutes; X-ray diffraction patterns were observed. Figure 1 demonstrates the XRD spectra of the CdSe nanoparticles deposited at different concentration values. Because of this, it can be concluded that the XRD phase of the CdSe nanoparticles as generated by the chemical bath deposition approach is polycrystalline in nature. According to the samples, the observed $d$-values and the corresponding noticeable peak that were obtained are in the best accord with the data [12]. This revealed that the synthesized nanoparticle has a cubic crystal structure with a favoured orientation towards the (111) Miller indices’ plane. The oriented peak was investigated from the planes (311) and (111) for the 20 ml of sodium selenosulfate concentration; other little intensity peak was performed at$2\theta =14$degrees. The angle of the diffraction peak in relation to the (400) plane is in good agreement with the permissible limit that was previously mentioned. Thus, it was determined that the CdSe nanoparticles generated from a 20 ml concentration exhibited good crystallite formation. In the diffraction phase, there have been no peaks associated with contaminants that could be detected. Raising the volume ratio of sodium selenosulfate did not alter the cubic structure of the produced cadmium selenide nanoparticles. Furthermore, the XRD results are in agreement with reported data [13].

[figure omitted; refer to PDF]

The crystalline size ($D$) was calculated from XRD data and calculated by using the Scherrer formula, given by $$\begin{array}{}\text{(1)}& D=\frac{0.9\lambda }{\beta \text{Cos}\theta },\end{array}$$where $\lambda$ is the wavelength and $\beta$ is denoted for FWHM in radian $\theta$ position angle of diffraction. Some parameters obtained from XRD are summarized in Table 1.

Table 1

Parameters obtained from XRD results.

Concentration (ml)	2 theta (degree)	FWMH (radians)	$D$ (nm)
10	53	107807	8.25
15	15	54626.62	0.18
20	14	-7862.93	0.01

The photoluminescence properties of the prepared nanoparticles are shown in Figure 2. From the patterns of photoluminescence emissions, it was detected that increasing concentration of sodium selenosulfate intensity of photoluminescence emission peaks was confirmed because of the wide area to volume ratio for the small-size crystals. Therefore, the nanoparticles having small crystal sizes can reflect the maximal luminescence intensity associated with the larger-crystal-size nanoparticles [12, 14]. This is due to the fact that the amount of ions on the nanoparticle surface rapidly increases as the crystal size of the nanoparticles reduces. Moreover, the transporter recombination ratio as high as the size of the transporter reduces due to the increase in the overlap between the electron and hole wave functions [12]. The external topography of deposited CdSe nanoparticles was characterized using a scanning electron microscope (SEM) since it substitutes an enormously authoritative attractiveness on the outcome of cell. SEM is a favourable and very important method to investigate and evaluate the surface morphology of nanoparticles. The SEM micrograph of cadmium selenide is depicted in Figure 3. This demonstrates that there are no fissures on the surface and that the grains are spherically formed. The surface was covered with granules of consistent size and shape. There have been no fractures or holes visible inside the thin films under examination. So as to supplementarily show the aspect and crystalline segment of the nanoparticle, image became taken and is represented in Figure 3. The obtained photograph of synthesized nanoparticles is composed of globular crystallites of approximately 60 nm. The grains were cumulative in formed clusters, and this agreed with previous report [15].

[figure omitted; refer to PDF][figure omitted; refer to PDF]

4. Conclusion

CdSe nanoparticles were deposited for the first time via low-cost chemical bath methods in the acidic bath at a pH value of 6.5. The influence of sodium selenosulfate concentrations on microstructural, surface morphology, and optical properties of prepared nanoparticles was studied. The XRD analyses revealed that the cubic structure could be found in all of the grown samples. With the rising of the concentration of nonmetallic precursors, the crystal size declined. The difference in the optical behaviour of cadmium selenide nanoparticles was caused by the quantum size effect, which could have occurred as a result of the concentration of selenide ions in the ion source. The scanning electron microscope micrographs revealed that surface morphology of nanoparticles was composed of nearly cubic formed grains via changed sizes. There were blue variations in the photoluminescence spectrum caused by the crystal size, and these shifts were noticeable. All of these findings supported studying the concentration of precursor deliveries for the production of high-quality cadmium selenide nanoparticles by chemical bath approach for the applications of nanotechnology.

Disclosure

This study was performed as a part of the employment of the authors.

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