Scrutiny Of Chemical Surfactants (n-Heptane, Polyimide, PVA, PVP, SDS) Based CdO Nanoparticles For The Application Of Solar Radiation Photocatalytic And Antimicrobial Activities


 The chemical surfactant-based synthesis route is the C-H-based aqueous method using to form the restrained shape of Cadmium Oxide (CdO) nanoparticles. The effect of different weight percentages of n-HEPTANE, POLYIMIDE, PVA, PVP, SDS in the preparation of CdO nanoparticles is studied. The surfactants are highly influenced by particle size variation and morphology gets changed. The role of surfactant is not produced any structural change apart from the particle size which is the advantageous part of the surfactant-based synthesis. The particle sizes from X-ray diffraction (XRD) analysis were found that there is a decrease in particle size from 54 to 92 nm when using the artificial chemical additives. The firmness of the CdO nanoparticles synthesized with help of chemical surfactants was characterized by UV-vis Diffused Reflectance Spectrometer (DRS), Fourier Transformer inferred (FT-IR), and photoluminescence studies. The photocatalytic activity and antimicrobial activity is investigated on using the chemical surfactant-based CdO nanoparticles as catalyst under Solar irradiation and zone inhibition method respectively.


Introduction
There are numerous numbers of attempts made on synthesizing nanostructured semiconductor materials. The semiconductor materials are becoming a pioneer in a large number of applications, like photonics, optoelectronics, photoluminescent devices, magnetic storage devices, photodetectors, chemical sensors, light-emitting diodes, logic gates, and electron transistors [6]. The optical and electrical properties of the semiconductor materials are supported for fabricating most of these devices. Also few of these materials possess photocatalytic activity [7,8]. The photocatalytic solution from water using a semiconductor material as a catalyst has been attracted researchers to give a solution for the global energy and environmental problems [9].
The outlet of nanomaterial synthesis with particular morphology and size is the great interest to the nanoworld [10]. This can be achieved by the researchers using polymeric materials in the synthesis. This preparation method helps to produce metal oxide nanoparticles with speci c properties. The synthesis of CdO nanoparticles with the help of surfactants can be reduced long reaction times and also enhance crystallinity [2]. In this aspect, the surfactant plays an important role in CdO nanoparticle preparation.

Experimental Details
The cadmium nitrate [Cd(NO3)2]. 6H2O, Ammonium hydroxide (NH4OH), n-heptane, and deionized water were chosen as raw materials for CdO nanoparticle preparation. 0.2 M of [Cd(NO3)2].6H2O was prepared by using 150 ml deionized water. The NH4OH solution was added drop by drop in the above precursor solution using a magnetic stirrer. This solution was stirred at 3hours. The pH was maintained at 8. Then separate beaker of 0.5 ml of n-heptane solution was made up into 10 ml using deionized water. This surfactant solution was added drop-wise into the above precursor solution using a burette. Then these two solutions were stirred at 2 hours at constant temperature for 80oC. The black-brown colored powder was obtained as the nal yield. This obtained yield was annealed at a constant temperature of 400 oC at 4 hours. A similar procedure was repeated for other polymeric surfactants for other four surfactants such as Polyimide, Poly Vinyl Alcohol, Poly Vinyl Pyrrolididone, and Sodium Dodecyl Sulfate in the preparation of CdO nanoparticles.  [3].The main peak of 33.1o of (111) crystallographic plane, which predominantly speci es the good crystalline nature for all the surfactant-based CdO nanoparticles. There are no additional diffraction peaks for representing other spices in the samples. It con rmed that these prepared cadmium oxide nanoparticles with the help of n-heptane, polyimide, PVA, PVP, and SDS are free from impurities.

Results And Discussion
The crystallinity level of CdO nanoparticles of chemical surfactant of n-heptane during the preparation is helped well to achieve good crystallinity in a curve (a) in Fig [1]. The in uence of the next surfactant of polyimide for the preparation of CdO nanoparticles is also analyzed from the XRD pattern and it is shown in the curve (b) of Fig. 1(b). The re ection peaks of polyimide-based CdO nanoparticles are observed as This change is occurred due to the in uence of chemical surfactants like n-heptane, polyimide, PVA, PVP, and SDS. These chemical surfactants are played as a capping agent [4] and decreased the grain size.
The addition of these chemical polymeric surfactants helps to give the con rmed environment for the nucleation of growth of particles. The sharp diffraction peaks at 33.1oand 38.4o indicated that the crystallite size of CdO nanoparticles is very small. The remaining diffraction peaks (55.4o, 66.0o, and 69.3o) indicate the high crystalline. The average particle size of the CdO nanoparticles is determined using Debye-Scherrer's formula [12]. The crystallite sizes are predicted as 70 nm for n-heptane based CdO nanoparticles, 84 nm for polyimide-based CdO nanoparticles, 89 nm for PVA-based CdO nanoparticles, 54 nm for PVP-based CdO nanoparticles, and 71 nm for SDS based CdO nanoparticles.
The usage of PVP as surfactant is well to form the less particle size than the other above-mentioned surfactants.
3.2 UV-Vis-DRS Spectra Figure 2(a-e) shows the UV absorption spectra of CdO nanoparticles prepared under four different surfactants such as n-heptane, polyimide, PVA, PVP, and SDS. The UV absorption spectrum of n-heptane based CdO nanoparticles shown a peak in the UV region but the absorption band edge was gradually decreased compared to other spectra. The surfactants like n-heptane, polyimide, PVA, PVP, and SDS in CdO nanoparticles formation have indicated the same band at 240 nm. This occurrence of absorption at 240 nm is due to the intrinsic bandgap absorption of CdO nanoparticles due to the electron transitions from the valence band to the conduction band (Cd3d -O2p) [5]. Further, the adding of chemical surfactant solutions of n-heptane, polyimide, PVA, PVP, and SDS possess a strong absorption band in the visible region at 516 nm within an absorption edge of 400-800 nm. The surfactants-based CdO nanoparticles lead to a gradual increase in absorption intensity. The various surfactants which obtaining the different absorption of the CdO nanoparticles are identi ed from these spectra. The re ectance (R) is taken from The bandgap energies of n-heptane, polyimide, PVA, PVP, and SDS-based CdO nanoparticles of samples are predicted from the DRS spectra and it is shown in Fig. 3(a-e). The optical bandgap energy value varies are 2.37 eV for n-heptane CdO nanoparticles 2.28 eV for polyimide CdO nanoparticles, 2.21 eV for PVA CdO nanoparticles, 2.39 eV for PVP CdO nanoparticles and 2.30 eV for SDS CdO nanoparticles respectively. A good agreement of the bandgap energy value with standard CdO nanoparticles is found for these samples [7]. This process of change in a bandgap due to chemical surfactants is happened because of surface modi cation of CdO nanoparticles. Thus, this difference in bandgap energy (Eg) value is caused only by various chemical surfactants. The increase in bandgap energy value for PVPbased CdO nanoparticles has also evidenced the decrease of particle size [21]. Figure 4(a-e) shows the PL spectra of CdO nanoparticles prepared under various surfactants such as nheptane, polyimide, PVA, PVP, and SDS. The n-heptane based CdO nanoparticles of luminescence spectrum of the curve (a) in Fig. 4 show (a) strong emission peak at 310 nm corresponding to the UV region of CdO nanoparticles. Similarly, luminance spectra of the curve (b-e) the polyimide, PVA, PVP, and SDS-based CdO nanoparticles showed in Fig. 4 (b-e). This spectrum shows the emission peak at 312 nm with excitation of 250 nm and slight variation is observed in wavelength. A small shift appears for other surfactants such as PVA, PVB, and SDS than n-heptane. This shift can be revealed the change in surface morphology of CdO nanoparticles [8]. This emission is assigned to the transition between photogenerated holes and singly ionized oxygen vacancies [9]. The second prominent peak at 372 nm and 375 nm belongs to the violet region of curve (c) and curve (d). The prominent peak in the curve (b) and (e) is observed only for the polyimide and SDS-based CdO nanoparticles. These peaks reveal the smoothness of the surface of spherical particles with no crystal defects in the crystal lattice [10]. Figure 5(a-e) shows the FT-IR spectrum of CdO nanoparticles prepared under various surfactants such as n-heptane, polyimide, PVA, PVP, and SDS. These samples display prominent transmittance spectra with respective signi cant vibration bands in the IR region of 4000-1-400 cm-1. The curve shows strong and weak bands at 3782 cm-1, 2348 cm-1, 1590 cm-1, 1382 cm-1, and 433 cm-1 emerge all the samples. The strong band at 3782 cm-1 is O-H stretching vibration of the hydroxyl group is appeared in all these samples [11]. The presence of O-H vibration in the calcinated samples may be due to the adsorption of moisture in the atmosphere. The tiny bend at 2348 cm-1correspond to the O = C = O stretching vibrations of instrumental carbon-di-oxide [12]. The band located at 1590 cm-1 is represented as the C-C stretching vibration of aromatics in the chemical surfactants [13]. The sharp band at 1382 cm-1 is indicated surface coated carbon present in the annealed samples [14]. The trace of carbon is evidenced in the EDAX spectra. This carbon procedure is unavoidable while preparing surfactant-based nanoparticles [ 15]. The main metal band region at 433 cm-1 is indicating the vibration between cadmium (Cd) and oxygen (O) [15].       shows the FESEM image of PVA-based CdO nanoparticles. This image displays a conglomeration of bulk CdO nanoparticles with very few plate structures. Also, this image shows carbon presence as noticed from FT-IR with CdO nanoparticles. It is nothing but the trace of the surfactant even after annealing treatment. It also re ects the polymeric nature of PVA surfactant. Figure 6.3 (c2) shows the HRTEM image of CdO nanoparticles. This image reveals small spherical particles combined to form a DNA-like structure. nm. Figure 6.3 (c4) shows the SAED image of CdO nanoparticles. It also reveals that the polycrystalline of the CdO nanoparticles with simple cubic structure [17]. The bright dots over the circular ring indicate corresponding plane such as (110), (200), (220), (311), and (222) which is identi ed from XRD pattern sample C. the agglomeration is more between the spherical particles than other surfactants used here for the PVA is not much supported to prevent agglomeration like other chemical surfactants such as nheptane and polyimide. CdO nanoparticles. This image exhibits coral shape with embedded spherical particles of the average particle size of 78 nm. It creates a network of CdO spherical particles. Figure 6.4 (d3) shows the next magni cation of CdO nanoparticles which displays particles combines to another like chain pasted structure. This combination may be occurring due to PVP surfactant. Figure 6.4 (d4) shows the SAED pattern of dark and bright fringes circular rings indicated good polycrystalline nature. CdO nanoparticles. The size of particles is measured from this image is between 71 nm and 92 nm. Also, this image con rms less agglomeration. Figure 6.5 (e4) shows the next magni cation of the above image (e3). This image shows the hexagonal crystalline form with smooth cutting edges. Figure 6.5 (e4) shows the SAED pattern of CdO nanoparticles with signi cant polycrystalline nature. The bright spots representation in the pattern has good agreement with the crystallinity as recorded from XRD spectra.  Table 1.

Photocatalytic activity
The photocatalytic activity of various surfactants-based CdO nanoparticles was investigated for the aqueous solution of the chromophoric structure of MB dye under solar light irradiation. The characteristics absorption peak of MB dye at ~ 664 nm is xed to monitor the photo degeneration of dye molecules. Figure 9. This result con rms that the spherical-shaped morphology like polyimide and PVB based CdO nanoparticles have shown an enhancement in intrinsic photocatalytic activity under solar light irradiation of their CdO nanoparticles. The comparison of degradation e ciency was made by considering the almost similar intensity of solar radiation [20].

Antibacterial and Antifungal activities
The antimicrobial activity of various surfactants-based CdO nanoparticles was investigated for an antibacterial agent were tested for respective antibacterial towards both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The inhibition of CdO nanoparticles over the bacterial and fungal are discussed as follows. The gram-positive bacteria cell wall is a peptidoglycan molecule. The gram-positive bacteria cell consists of a thick wall. As the Cd2 + ions are positively charged and peptidoglycan is negatively charged. So there is an electrostatic [21] attraction between these positive and negative ions. So, more positive Cd2 + ions are interacting over the surface of the peptidoglycan. The more accumulation of Cd2 + ions over the surface damages the cell wall and diffuses into the cells. In this way, the cell wall or membrane gets damaged.  Table 2 summarizes the antibacterial activity of extracts-based CdO nanoparticles. Based on the zone of inhibition, polyimide-based CdO nanoparticles proved the highest antibacterial activity against Staphylococcus aureus and Escherichia coli. The result from the antibacterial activity is presumed from the inhibition as low activity over the bacterial medium. Thus, the zones around CdO nanoparticles are formed when the growth of the bacteria is stopped by CdO nanoparticles cogently [22]. Antifungal properties of surfactant-based CdO nanoparticles were also examined against selected fungal test pathogens such as Candida Albicans and Aspergillus niger are shown in Fig. 9. (A-D) shows the zone of inhibition of CdO nanoparticles concerning all pathogens are listed in Table 2. This test is proved that CdO nanoparticles possessed good antifungal activity towards Candida Albicans and Aspergillus niger is observed as n-heptane, polyimide, PVA, PVB, and SDS. The predominant zone inhibition due to CdO nanoparticles over the antifungal activity is observed. These results con rmed that the chemical surfactant-based CdO nanoparticles showed signi cant antibacterial capability against gram-positive and gram-negative bacteria as well as good antifungal activities. The negative strain of the Escherichia coli is the best inhibition of bacterial study. Also tested by the fungal organism Candida albicans is the best inhibition value compared to the other organism of Aspergillus niger.

Conclusion
The water-soluble chemical surfactants of n-heptane, polyimide, PVA, PVP, and SDS are found as a major role in the synthesis of CdO nanoparticles. The XRD spectra show the different surfactants produces different crystallite size within the nano range. PL spectra predict at 310 nm and 312 nm. The bandgap value also resembles the particle size variation of CdO nanoparticles due to surfactants. FESEM and HRTEM image shows the formation of nanowires, spherical shaped smooth particles, DNA structure, and square platelets. The role of surfactants causes more agglomeration. Thus the effect of size reduction of particles is sustainable for the surfactants n-heptane, polyimide, PVP, and SDS except for PVA. The morphologic changes from polymeric material have created evidence and support for the morphological change. The photocatalytic activities of CdO nanoparticles prepared by different surfactants were tested under solar irradiation for 120 min. The spherical-shaped morphology of the CdO nanoparticles shows the best performance in MB azo dye. In particular, n-heptane based CdO nanoparticles show only 95 % of degradation. The highest degradation level of the 95 % of polyimide and 90 % of PVB are the sphericalshaped morphology and ne smooth surfaces. This spherical-shaped morphology leads to the more O-H stretching vibration and easily breaks the azo group. Other morphology of nanorod and DNA structure should not break the azo dye. So the degradation percentage is very less. Also, the previous researchers are proved the spherical morphology of the semiconducting oxide materials to the higher performance of a photocatalytic activity. Indeed, the other morphology like nanorods, agglomerated spherical particles also exhibited signi cant degradation compared to the other morphologies. The antibacterial study was tested both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The effective inhibition is occurred in the Escherichia coli and Staphylococcus aureus of antibacterial as well as in Candida albicans and Aspergillus niger of antifungal organism in the antimicrobial study. The different surfactant-based CdO nanoparticles proved their potential on zone inhibition of chemical-based CdO nanoparticles.

Con ict of Interest
The author declared there is no con ict of interest.