Flow synthesis and in-channel photocatalysis of antimicrobially active ZnS quantum dots using an efficient planar PMMA microreactor

We report a rapid, robust and efficient technique for the fabrication of poly(methyl methacrylate) based microreactors using laser engraver to synthesize ZnS quantum dots. We also present a comparative study of synthesis and photocatalytic activity of ZnS quantum dots by conventional beaker reactor and microfluidic route. The ZnS synthesized in a microfluidic reactor revealed the formation of well dispersed quantum dots with uniform size of 2.5 +/- 1 nm and higher band gap (4.12 eV) as compared to the quantum dots prepared by beaker reactor method. In comparison to the degradation profile in a conventional bulk reactor, a remarkable enhancement in the photocatalytic activity of ZnS quantum dots in microfluidic reactor has also been observed for degradation of organic dyes (Rhodamine B and Methyl orange) under UV irradiation. The degradation efficiency of ZnS can further be tuned by controlling flow rate of dyes through the photocatalyst coated micro-reactor. Instant degradation with efficiency of 93% and 99% for rhodamine B and methyl orange respectively, were achieved when the flow rate was maintained at 50 mu l min(-1). The microfluidic reactor also offers the prolonged photocatalyst stability, ensuring its reusability without significantly losing its efficiency. The ZnS quantum dots were also observed to have excellent antibacterial property thus inhibiting the growth of E. coli bacterial colonies even at a very low concentration of 10 mu g ml(-1).