3.1.3. X-ray Diffraction Spectroscopy

The XRD patterns varied in peak intensity and width according to the reducing/capping agent used. In general, the peak widening could be observed for all the six types of synthesized ZnNPs which represents the nano-scale crystalline size of the prepared ZnNPs. The XRD peaks obtained showed close agreement with the characteristic Bragg peaks of hexagonal ZnO zincite (pattern: PDF 00-036-1451), and hydro-zincite (pattern: PDF 01-072-1100). Mixed crystal phases including the simonkolleite (pattern: COD 9004683) along with zincite and hydro-zincite specific peaks can be identified in ZnNMs derived from ZnCl<sup>2</sup> salt as substrate (Figure 4). The use of starch as a reducing agent resulted in the formation of nanoscale hydrozincite crystals. While Starch (CA) ZnNPs had both zincite and hydrozincite as the predominant crystal phases. This variation may be attributed to the use of NaOH as a reducing agent during the synthesis of the Starch (CA) ZnNPs. Cellulose (CA) ZnNPs possessed a mixed crystal phase with simonkolleite as one among the predominant crystal structure. As indicated above, it can probably be due to the use of a high concentration of zinc chloride (65 wt %) as the precursor salt for the synthesis of ZnNPs.

**Figure 4.** X-ray diffraction spectroscopy of the synthesized ZnNPs depicting the formation of wurtzite hexagonal crystal structure zincite (ZnO) on the use of various reducing and capping/complexing agents i.e., Sodium hydroxide (RA), Thiourea (RA), Starch (RA), Bovine serum albumin (CA), Starch (CA), and Cellulose (CA).
