Microfluidic route for the synthesis of nanostructured materials offers several advantages over traditional synthetic pathways. However, the standard lithography techniques used for the fabrication of the microreactors are quite expensive, time taking and often requires sophisticated clean room fabrication facilities. Here, we have reported a simple, inexpensive yet highly efficient technique for the fabrication of Polydimethylsiloxane (PDMS) and Polymethyl methacrylate (PMMA) based microreactors. Using such PDMS based T-shaped fully circular cross-sectional microreactor, we have successfully synthesized spherical Ag3PO4 nanoparticles with narrow size distribution. We have also investigated the photocatalytic efficiency of these Ag3PO4 nanoparticles, embedded in the channels of a PMMA based photocatalytic microreactor for the visible light assisted degradation of Rhodamine B dye. We observed >97% degradation within just 15 min of irradiation. Greater photostability of the nanoparticles in the microreactor was experimentally confirmed by comparing the colour change in case of an aqueous solution of the material with that of the coated microreactor. These silver phosphate nanoparticles also demonstrated very high efficiency towards the inhibition of bacterial pathogens, Escherichia Coli even at a very low concentration.