**5.3 Results and discussion**

Scanning electron microscope (SEM) and FESEM were used for topographical imaging of the nanoparticles, and to investigate the size, shape, impurities &

#### **Figure 8.**

*EDS spectrum confirming the presence of silver, carbon and oxygen.*

#### **Figure 9.**

*FTIR graph showing prominent peaks representing the unique fingerprint of AgNPs that was synthesized.*

stabilization of the particles, as shown in **Figure 5(a)** and **(b)**. The SEM image of the AgNPs shown in **Figure 5(a)** reveals a globular-shaped morphology, which was further confirmed by the FESEM image in **Figure 5(b)**. The FESEM confirmed the globular-cluster shaped morphology of the silver nanoparticles.

Interestingly, the HRTEM image in **Figure 6(a)** showed that the AgNPs are spherical at nano-range with spherically shaped internal structures. This is supported by the selected area diffraction structure (SAED) image in **Figure 6(b)**. HRTEM results also complement the SAXS results, which show that most of the particles are spherical or cuboidal in shape.

The SAXS analysis in **Figure 7** was used to investigate the internal structure of the nanoparticle, and it revealed that the AgNPs show lattice fringes, which confirms that the particles are crystalline. In addition, they exhibited a quarzispherically shaped internal structure as expected. **Figure 7(a)** shows the internal structure of the AgNPs, while **Figure 7(b)** shows their size distribution by number.

The elemental composition of the AgNPs was evaluated by energy dispersion x-ray spectroscopy (EDS) to find out the purity of the nanomaterials. From the layered images and the EDS spectrum analysis, we confirm the presence of silver, carbon and oxygen, as shown in **Figure 8**. The presence of carbon was due to the carbon tape used for coating the nanomaterial before the analysis.

The morphology is consistent with the expectation for silver nanoparticles, and we functionalized our silver with polyethylene glycol. The sizes (width and *Nanomaterial-Enhanced Receptor Technology for Silicon On-Chip Biosensing Application DOI: http://dx.doi.org/10.5772/intechopen.94249*

diameter) for the AgNPs could not be clearly determined due to agglomeration of the particles. In the FTIR analysis represented by the graph in **Figure 9**, prominent peaks were observed for different stretches of bonds. The peak at 3435 cm−1, representing N-H stretch, 3074 cm−1 assigned to C-H stretching vibrations, and 1593 cm−1 corresponding to stretching vibration of C=O bond. The peak at 1391 cm−1 corresponds to C-C and C-N stretching, while 1113 cm−1 assigned to –C = bond, and 908 cm−1 and 621 cm−1 are for C-H out-of-plane bend and CH bending vibrations, respectively. These peaks are comparable to [39].

UV Visible spectroscopy is one of the most important techniques which can confirm that the prepared material are nanoparticles [40]. **Figure 10** shows the plot of absorption spectrum obtained from the UV-Vis spectroscopic analysis of the AgNPs over a range of 200 to 800 nm. The exact peaks occurred at 310 and 400, which is indicative of the peak of silver nanoparticles [41, 42]. The bandgap from the Tauc plot in **Figure 10(b)** for the synthesized AgNPs is 3.26 eV, which implies that the nanomaterials will absorb in the UV-Vis range.
