A method to form semiconductor quantum dot (QD) thin films by igniting a flame at air–liquid interface: CdS and WO3

• We report a method to grow thin films of CdS and WO3 materials consisting of 1–2.5 nm sized Quantum Dots (QDs).
• The synthesis takes place in a very short time (few seconds) at the air–liquid interface.
• No use of special conditions like use of inert atmosphere and high temperature.
• Use of layer by layer (LbL) growth so that good control over the film thickness.
• Possible mechanism of formation (QD) is discussed.

We reveal an easy, inexpensive, efficient one step flame synthesis of semiconductor/metal oxide thin films at air–liquid interface, subsequently, transferred on suitable substrate. The method has been illustrated by the formation of CdS and WO3 QDs thin films. The features of the present method are (1) Growth of thin films consisting of 0.5–2.0 nm sized Quantum Dots (QDs)/(ultra-small nanoparticles) in a short time, at the air–liquid interface which can be suitably transferred by a well-known Blodgett technique to an appropriate substrate, (2) The method is suitable to apply layer by layer (LbL) technique to increase the film thickness as well as forming various compositions as revealed by AFM measurements. The films are characterized for their structure (SAED), morphology (TEM), optical properties (UV–Vis.) and photoluminescence (PL). Possible mechanism of formation of QDs thin film and effect of capping in case of CdS QDs is discussed.

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