Defect induced optical bandgap narrowing in undoped SnO2 nanocrystals

Abstract

Unusual optical bandgap narrowing is observed in undoped SnO2 nanoparticles synthesized by the solution combustion method. The estimated crystallite size is nearly 7 nm. Though the quantum confinement effect predicts a larger optical bandgap for materials with small crystallite size than the bulk, the optical bandgap in the as synthesized materials is found to be 2.9 eV compared to the reported value of 3.6 eV for bulk SnO2 particles. The yellow-green photoluminescence emissions and the observed narrowing of the bandgap can be attributed to the deep donor levels of oxygen vacancies, owing to the high exothermicity of the combustion reaction and the faster cooling rates involved in the process.

Variation in luminescence and bandgap of Zn-doped SnO2 nanoparticles with thermal decomposition

“…The peaks at 1384 and 1460 cm -1 of (SnO 2 :Zn) calcined at 400 and 600°C, respectively, and 1631 cm -1 for both samples are due to -OH and NH 3 vibration. The absorption peaks observed between 2300 and 2900 cm -1 are assigned to the CO 2 mode [16]. Peaks at 3430 and 3439 cm -1 of the (SnO 2 :Zn) calcined at 400 and 600°C respectively, corresponds to the OH vibrational mode [22].…”

“…Its n-type conductivity is because of presence of oxygen vacancies in its rutile structure. The properties which make it very much valuable according to technological point of view are its high conductivity, transparence in visible light, high infrared reflectance, abundance in nature, and absence of toxicity [14][15][16].…”

Analyzing the kinetic response of tin oxide-carbon and tin oxide-CNT composites gas sensors for alcohols detection

“…The details of preparation method can be found elsewhere. 20,21 Multiwalled carbon nanotubes (CNT) were synthesized by simple pyrolysis method using Benzene and ferrocene at 750 o C. 22 The as prepared CNTs were functionalized by treating with conc. HNO 3 .…”

Correlating defect induced ferromagnetism and gas sensing properties of undoped tin oxide sensors

“…The details of the synthesis can be found elsewhere. 17,18 The as-synthesized combustion product is named as "TO". (ii) The as-synthesized nanoparticles were further annealed at 800 C in a muffle furnace for 2 h in air atmosphere, and the final product is named as "TO800".…”

“…The combustion product shows fine crystallite size $7 nm, which undergoes grain growth ($25 nm) after annealing as expected, while the dried non-combustion SnO 2 (TOAm) shows highly broadened peaks due to inadequate grain growth ($3.5 nm) due to insufficient thermal energy which is also confirmed by transmission electron microscopy studies. 18 The room temperature (300 K) M-H curves of the different SnO 2 samples are studied and are shown in Fig. 2.…”