Origami 3D-microfluidic paper-based analytical device for detecting carbaryl using mesoporous silica-platinum nanoparticles with a molecularly imprinted polymer shell

Herein, we present a novel Origami 3D-mu PAD for colorimetric carbaryl detection using a super-efficient catalyst, namely mesoporous silica-platinum nanoparticles coated with a molecularly imprinted polymer PtNPs@MIP). Morphological and structural characterization reveals that coating MIP on the MSN-PtNPs significantly increases the selective area, leading to larger numbers of imprinting sites for improved sensitivity and selectivity in determining carbaryl. The as-prepared MSN-PtNPs@MIP was used for catalytic oxidation 3,3 ',5,5 '-tetramethylbenzidine (TMB) by H2O2. Carbaryl selectively binds to the cavities embedded on the PtNPs surface and subsequently inhibits TMB oxidation leading the color to change to light blue. The change reaction color from dark blue to light blue depends on the concentration of carbaryl within the 3D-mu PAD detection zone. This design integrates the advantages of highly efficient sample delivery through micro channels (top layer) and efficient partition/separation paths (bottom layer) of the cellulose substrate to achieve improved detection sensitivity and selectivity. Assay on the Origami 3D-mu PAD can determine carbaryl by detection, over a dynamic range of 0.002-20.00 mg kg-1, with a very low limit of detection at 1.5 ng g-1. developed 3D-mu PAD exhibit high accuracy when applied to detect carbaryl in fruits, with satisfactory recoveries from 90.1% to 104.0% and relative differences from the reference HPLC values less than 5.0%. Furthermore, fabricated Origami 3D-mu PAD provides reliable durability and good reproducibility (3.19% RSD for devices).