*3.1.3 Doped oxide nanomaterials*

*Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects*

*Electronic UV–vis (a) and photoluminescence (b) spectrum of Mn2+ doped CdSe QDs sample with and* 

UV light irradiation [44]. Here, the zinc blende crystal phase of ZnS was important for the efficient incorporation of Mn atoms. In the same year, Zhu *et al* reported the synthesis of of Mn-doped ZnS via green and rapid microwave-assisted approach and they also developed indapamide drug detector by recording room-temperature

*(a) Survey scan of the X-ray photoelectron spectrum of 2% Mn2+-doped CdSe QDs. (b, c) high-resolution spectrum of Cd 3d electrons depicting doublet splitting with binding energies separated by 6.9 eV and Se 3d, respectively. (d) the high-resolution spectrum of Mn 2p core electrons showing doublet splitting with binding* 

Later, Zhang *et al.* reported the aqueous synthesis of Mn and Cu doped ZnSe QDs by microwave radiation with higher quantum yields (QYs) and they have further extended this work to grow the white-light-emitting ZnSe/ZnS core/shell QDs via the co-doping of Mn and Cu [46]. Lead sulphide (PbS) QD are still emerging various applications in optoelectronics and its property was further tuned with a

phosphorescence (RTP) with that doped material [45].

**88**

**Figure 7.**

**Figure 6.**

*without microwave irradiation [17].*

*energy separated by 10.9 eV [17].*

Various metal oxides nanomaterials play a major role in the development of different novel daily life applications in the fields of display, sensors, medicine, biomedical devices, agriculture, information technology, optical, energy, electronics, and so on. Efforts are ongoing to tune their properties and applications further with incorporating impurity as dopants. For that reason, microwave heating based synthesis protocols is developing as a potential alternative to the conventional heating based growth process. Kar *et al.* developed a microwave synthesis of rare-earth element Eu3+ doped tin oxide (SnO2) to tune the optical and electrical properties of the host [49]. Jamatia *et al*. reported the microwave-assisted synthesis of Fe doped ZnO nanoparticles to show their application in polymer light-emitting diodes [50]. The wurtzite hexagonal crystal phase of ZnO nanoparticles and incorporation of the Fe dopant into the host ZnO crystal lattice was confirmed via X-ray diffraction analysis. This report claimed that the bandgap modification of ZnO via Fe doping is estimated from the Tauc plot without considering the influence of size. Similarly, many spinel structured metal oxides were also doped with different transition metal ions via microwave heating based synthesis technique with tunable structural, morphological, optical, vibrational, and magnetic properties and different potential applications like phosphor-based forensic testing and many more [51–54]. Interestingly, Er3+ doped α-Fe2O3 and Fe doped TiO2 nanoparticles were synthesized successfully with the help of microwave heating to study their crystal structure and optical properties [55, 56]. Recently, Yathisha *et al*. reported Zn2+ doped MgO nanoparticles utilizing microwave combustion route to study the influence on photovoltaic properties [57]. Therefore, microwave heating could explore further as a low-cost alternative synthesis protocol to design a new variant of nanomaterials.
