88 CHAPTER 5 CHARACTERIZATION OF ZINC OXIDE NANO- PARTICLES 5.1 INTRODUCTION This chapter deals with the characterization of ZnO nano-particles using FTIR, XRD, PSA & SEM. The results analysis and interpretations of the various tests used to characterize the three types of ZnO nano-particles (Z 1, Z 2 & Z 3 ) synthesized as per the procedures IV, V & VI. The characterization of ZnO nano-particles has been carried out using Fourier Transform Infrared Spectroscopy (FTIR) for identifying the name of chemical groups and bonds, powder X-ray Diffraction (XRD) for studying the crystal structure of ZnO, Particle Size Analyzer (PSA) for measuring the range of size of nano-particles and Scanning Electron Microscopy (SEM) for capturing the images containing topological information of coated fabrics. 5.2 FOURIER TRANSFORM INFRARED SPECTROSCOPY In FTIR, the intensity-time output of the interferometer is subjected to a Fourier Transform to convert it to the families infra-red spectrum i.e., intensity frequency. The identification of the atomic arrangement and the concentrations of the chemical bonds present in the samples have been carried using Fourier Transform Infra-red Spectroscopy (FTIR), in which percentage transmission and wave number are the output. The FTIR spectrogram of control cotton fabric sample is shown in Figure 5.1.
89 Figures 5.2, 5.3 & 5.4 show the FTIR spectrogram of the fabric coated with ZnO nano-particles synthesized with Zinc acetate, Zinc chloride and Zinc nitrate ( particles designated as Z 1, Z 2, Z 3 ) adopting procedure IV, V & VI respectively. Figure 5.2 shows the FTIR spectrogram of the cotton fabric coated with ZnO nano-particles synthesized with water medium and Zinc acetate as precursor (Z 1 ). The spectrum of interference pattern obtained in Figure 5.2 clearly shown that the absorption band of ZnO is nearer to 440 cm -1. The peaks at 3,450 and 2,350 cm 1 indicate the presence of OH and C=O residues, probably due to atmospheric moisture and CO 2 respectively. Figure 5.3 shows the FTIR spectrogram of the fabric coated with ZnO nano-particles synthesized with water medium and Zinc chloride as precursor (Z 2 ). The spectrum of interference pattern obtained in Figure 5.3 clearly shows that the absorption band of ZnO nearer to 440 cm -1. The peaks at 3,450 and 2,350 cm 1 indicate the presence of OH and C=O residues, probably due to atmospheric moisture and CO 2 respectively. Figure 5.4 shows the FTIR spectrogram of the fabric coated with ZnO nano-particles synthesized with water medium and Zinc nitrate as precursor (Z 3 ). The spectrum of interference pattern obtained in Figure 5.4 clearly shows that the absorption band of ZnO nearer to 440 cm -1. The peaks at 3,450 and 2,350 cm 1 indicate the presence of OH and C=O residues, probably due to atmospheric moisture and CO 2 respectively.
Figure 5.1 FTIR Spectrogram of control cotton fabric sample 90
Figure 5.2 FTIR Spectrogram of ZnO (Z 1 ) nano-particles treated cotton fabric sample 91
Figure 5.3 FTIR Spectrogram of ZnO (Z 2 ) nano-particles treated cotton fabric sample 92
Figure 5.4 FTIR Spectrogram of ZnO (Z 3 ) nano-particles treated cotton fabric sample 93
94 5.3 X - RAY DIFFRACTROMETRY (XRD) STUDIES The XRD spectrogram of ZnO nano-particles synthesized with Zinc acetate, Zinc chloride & Zinc nitrate respectively (Z 1, Z 2, & Z 3 ) using procedures IV, V, VI are shown in Figures 5.5, 5.6 & 5.7 respectively. According to the spectrogram of the crystal structure, the well defined peaks typical of ZnO in the crystal structure of Zinc oxide are clearly noticed. This is in compliance with the reports of the norms of the joint committee on powder diffraction standard JCPDS card number 36-1451. The peaks are in well defined shape and form. This clearly indicates the crystallinity of the synthesized nano-particles. According to Jenkin et al 1996, the particle size affects the effect on broadening of the peaks in the XRD spectrogram. From the Scherer s equation the mean crystallite size of the sample is estimated from the full width at half maximum (FWHM) of the diffraction peak. Figure 5.5 XRD patterns of the ZnO (Z 1 ) nano-particles
95 The X-ray Diffraction (XRD) spectrogram of ZnO nanoparticles synthesized using Zinc acetate with water is shown in Figure 5.5. In the Figure 5.5 the distinctive ZnO peaks at 32.90, 34.5, 36.40, 47.50, 57.25, 63.62, 68.78, 72.52 and 82.2 respectively. Figure 5.5 exhibit peaks similar to those reported for ZnO which suggests the formation of ZnO nanoparticles in anatase form. The XRD pattern for ZnO nanoparticles obtained with water medium shows much sharper peaks. This means that the crystallinity is more for Z 1 nano-particles. Figure 5.6 XRD patterns of the ZnO (Z 2 ) nano-particles The X-ray Diffraction (XRD) spectrogram of ZnO nano-particles synthesized using Zinc chloride with water medium is shown in Figure 5.6. In the Figure 5.6 the distinctive ZnO peaks at 32.90, 34.5, 36.40, 47.62, 57.28, 68.78, 72.26 and 82.10 respectively. Figure 5.6 exhibit peaks similar to those reported for ZnO which suggests the formation of ZnO nano-particles in anatase form. The XRD pattern for ZnO nanoparticles obtained with water medium shows much sharper peaks. This means that the crystallinity is more for Z 2 nano-particles.
96 Figure 5.7 XRD patterns of the ZnO (Z 3 ) nano-particles The X-ray Diffraction (XRD) spectrogram of ZnO nano-particles synthesized using Zinc nitrate with water medium is shown in Figure 5.7. The XRD patterns of these samples give seven distinctive ZnO peaks in the Figure 5.7 at 32.90, 34.5, 36.40, 47.50, 57.0, 62.50 and 68.72 respectively. Figure 5.7 exhibit peaks similar to those reported for ZnO which suggests the formation of ZnO nanoparticles in anatase form. The XRD pattern for ZnO nanoparticles obtained with water medium shows much sharper peaks. This means that the crystallinity is more for Z 3 nano-particles. 5.4 PARTICLE SIZE ANALYSIS (PSA) TESTING Particle Size Analysis (PSA) testing is essential to study the influence of nano-particle size on functional properties such as anti-bacterial activity, UV protection, soil release action and self cleaning action. The particle size distribution curve for ZnO nano-particles Z 1, Z 2 & Z 3 synthesized by procedures IV, V, VI with precursors such as Zinc acetate, Zinc chloride & Zinc nitrate are shown in Figures 5.8, 5.9 & 5.10 respectively.
97 Figure 5.8 Particle Size Analysis of Z 1 nano-particles The Figure 5.8 shows clearly that the average particles size is 9nm for ZnO nano-particles synthesized with Zinc acetate as precursor (particle designated as Z 1 by adopting procedure IV). Figure 5.9 Particle Size Analysis of Z 2 nano-particles The Figure 5.9 shows that the average particle size is 24nm for ZnO nano-particles synthesized with Zinc chloride as precursor (particle designated as Z 2 by adopting procedure V).
98 Figure 5.10 Particle Size Analysis of Z 3 nano-particles The Figure 5.10 shows clearly that the average particle size is 38nm for ZnO nano-particles synthesized with Zinc nitrate as precursor (particle designated as Z 3 by adopting procedure VI). Among the three different precursors used Zinc acetate yields the smallest size of ZnO nano-particles, Zinc nitrate yields the largest particle size of ZnO nano-particles while Zinc chloride yields intermediate size of the ZnO nano-particles. The following table 5.1 indicates the size of ZnO nano-particles synthesized with water medium: Table 5.1 Details for ZnO Nano-particles S.No Precursor & medium Nanoparticles Procedure Crystallite Diameter in nm 1 Zinc acetate Z 1 IV 9 2 Zinc chloride Z 2 V 24 3 Zinc nitrate Z 3 VI 38
99 The size of nano-particles has influence over the anti-bacterial activity, UV protection, soil release action and self cleaning action. It also influences the durability of coating after washing. 5.5 NANO-PARTICLES COATED SURFACE CHARACTERIZATION The Scanning Electron Microscope (SEM) Photomicrograph of control cotton fabric sample is shown in Figure 5.11. Figure 5.11 SEM analysis for un-treated cotton fabric The surface characteristics of the ZnO nano-particles coated cotton fabric were shown in Figures 5.12, 5.13, & 5.14 shows the SEM photomicrographs of ZnO coated fabrics (Z 1, Z 2, and Z 3 ) adopting procedures IV, V & VI with precursors Zinc acetate, Zinc chloride & Zinc nitrate respectively.
100 Figure 5.12 SEM analysis for ZnO treated cotton fabric for Z 1 nano particle (procedure IV) Figure 5.12 clearly shows that the nano-particles are well dispersed on the fibre surface. There are no agglomerates of nano-particles seen on the surface of the fabric. They are deeply embedded and finely dispersed without the formation of any agglomerate. The degree of adhesion of the nanoparticles on fabric surface is determined by the particle size. The particles size plays a primary role in determining their adhesion to the fibres. It is reasonable to expect that the larger particle agglomerates will be easily removed from the fibre surface, while the smaller particles will penetrate deeper and adhere strongly into the fabric matrix. Figure 5.12 shows the SEM photomicrograph of the ZnO coated fabric (Z 1 ) synthesized by procedure IV.
101 Figure 5.13 SEM analysis for ZnO treated cotton fabric for Z 2 nano particle (procedure V) Figure 5.13 shown the SEM photo micrograph of the ZnO coated fabric (Z 2 ) synthesized by procedure V. Figure 5.14 SEM analysis for ZnO treated cotton fabric for Z 3 nano particle (procedure VI) Figure 5.14 shown the SEM photo micrograph of the ZnO coated fabric (Z 3 ) synthesized by procedure VI.
102 5.6 CONCLUSION The characterization tests on three types of ZnO nano-particles Z 1, Z 2, and Z 3 synthesized with procedures IV, V & VI using precursors such as Zinc acetate, Zinc chloride and Zinc nitrate are carried out by various analytical tests such as FTIR, XRD, PSA and SEM. The FTIR analysis was carried out to analyse the presence of ZnO on the cotton fabric. In The FTIR spectrograms, the presences of an IR signature in the region 432 cm -1 in the finished product indicate the presence of ZnO in the treated fabric. The peaks at 3,450 and 2,350 cm 1 indicate the presence of OH and C=O residues, probably due to atmospheric moisture and CO 2 respectively. The XRD spectrogram of the ZnO nano-particles was analyzed and the presences of well defined peaks indicate the crystalline structure of the synthesized nano-particles. Particle size Analysis (PSA) testing results shows that the ZnO nanoparticles average particles a size were found to be 9 nm, 24 nm & 38 nm for precursors of Zinc acetate, Zinc chloride & Zinc nitrate respectively. The Scanning Electron Microscope (SEM) images clearly show the firm binding of the ZnO nano-particles onto the fabrics. The nano-particles are found to be well dispersed on the fibre surface with no agglomerations.