Different parameters such as pH and microwave (MW) irradiation time (in
MW-assisted synthesis methods) can affect the photo-physical properties of
nano-materials via tuning the size of nanocrystals. In this research work,
ZnSe semiconducting nanocrystals (NCs) were synthesized in aqueous medium
at different pH. Growth of NCs was done employing microwave irradiation
with the power of 1000 W at different irradiation times. According to the
results of x-ray diffraction (XRD), no displacement was seen in the x-ray
diffraction pattern peaks of ZnSe nanoparticles by altering the pH and microwave
irradiation time. Generally, UV–Visible absorption spectra of the
samples indicate that the increase of microwave irradiation time and the pH,
resulted in the red shift of the absorption edge. The exact amount of the
energy band gap of the nanoparticles was estimated by using the derivation of
absorption spectrum fitting method (abbreviated as DASF) which was within
the range of 3.488–3.721 eV depending on the pH and microwave irradiation
time. Also, for the present NCs, using the values of energy gap, the optical
charge carrier transition index (m) was evaluated, indicating crucially the
direct gap nature. Depending to the microwave irradiation time, the size of the
synthesized crystallites (obtained from XRD) were within the range of 1.74–
2.18 nm and no general certain trend was founded against pH; employing the
precise data of energy gap, effective mass approximation gives a reasonable
increasing trend of NCs size with increasing pH except for pH = 12.2 Other
purposes of this study are gaining the additional photo-physical properties of
Urbach energy (Etail), dielectric constant (e), and the refractive index (n).