A new route towards selective synthesis of supported Cu2O and CuO nanoparticles under extremely mild condition

• Cu0 nanoparticles are very prone towards oxidation in presence of oxygen.
• Small (<2 nm) Cu0 nanoparticles can be selectively oxidized to Cu2O in presence of air (22% O2) and to CuO by purging oxygen (100% O2).
• Halloysite clay nanotube (HNT) supported uniformly sized Cu2O and CuO nanoparticles were synthesized using this strategy.
• Both catalysts show good photocatalytic activity for degradation of organic dye in visible light conditions using H2O2 as oxidizing agent.

We find a new reactivity (oxidation) pattern of small Cu nanoparticles with varying oxygen concentration. Small Cu nanoparticles (<2 nm size) were exposed to air with the result of complete conversion to crystalline nanostructured Cu2O in 7 h. On the other hand, crystalline CuO was obtained by purging O2 through the same Cu nanoparticle solution in 30 min. These findings demonstrate that Cu2O or CuO nanostructures can be obtained with complete selectivity by just tuning oxygen flow rate to small Cu particles in water at room temperature. The strategy was successfully extended to synthesize Halloysite clay nanotube (HNT) supported uniform sized Cu2O and CuO nanoparticles with good catalytic activity towards photochemical degradation of organic dye.

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