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A slight enhancement of the onset transition temperature Tc has been observed in quantum dots of the high-Tc superconductor yttrium–barium–copper oxide (Y1Ba2Cu3O7-δ). The dots were formed when YBCO particles (diameter ≤600 nm) were exposed to an RF plasma to produce a Coulomb crystal. The plasma damages the particles and causes 20–25 nm sized isolated islands of the correct 1-2-3 stoichiometry to segregate within each particle. We believe that quantum confinement of carriers within these islands leads to discretization of the quasi-particle density-of-states which can account for the slight increase in the transition temperature.