Details

Autor(en) / Beteiligte

• Saravanan, R. Sakthi Sudar
• Pukazhselvan, D.
• Mahadevan, C.K.

Titel

Studies on the synthesis of cubic ZnS quantum dots, capping and optical–electrical characteristics

Ist Teil von

• Journal of alloys and compounds, 2012-03, Vol.517, p.139-148

Ort / Verlag

Kidlington: Elsevier B.V

Erscheinungsjahr

2012

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• [Display omitted] ► Zinc acetate and sodium sulphide as reactants. Cubic QDs of size ∼3nm in 1:3 reactant ratios with or without capping agent. ► At least 30 times smaller size while using microwave source instead of conventional heating source. ► Widening of band gap from 3.6eV to 3.94eV by reducing size of ZnS. ► Better conduction with lower activation energy in wide band gap ZnS. ► Thermionic emission mechanism for conduction phenomenon. This paper presents a comparative analysis of ZnS QDs synthesized by conventional and microwave heating techniques using zinc acetate and sodium sulphide reactants. The size of the quantum dots achieved by the latter technique (∼3nm) is at least 30 times smaller than the former technique. Incorporation of excess Na2S and microwave treatment are the important factors responsible for controlling the size of ZnS nanocrystals. Furthermore, the distribution of quantum dots is highly influenced by the addition of small amount of NaOH. The UV–vis analysis reveals that the band gap can be widened up to 3.94eV (correspond to ∼3nm ZnS) from 3.67eV (correspond to bulk ZnS). Surprisingly better conductivity is observed for the widest band gap ZnS of the present study; this could be due to defects/vacancies present in the system and its influence in the band structure. The higher conductivity value is supported by the smaller activation energy value, smaller dielectric constant and higher dielectric loss, etc. The conduction is further explained by thermionic emission mechanism.