# Multiplexed Fluorescent Microarrays on MIL‐101(Cr) Thin Films as Luminescent Probes for pH and Disease‐Associated Molecules

## TL;DR

This paper introduces a stable and cost-effective method for creating fluorescent microarrays on MOF thin films to detect pH and molecules like dopamine in fluid environments.

## Contribution

A new strategy using MOF thin films and scanning probe lithography for stable, multiplexed sensing of small molecules in solution.

## Key findings

- Dye@MOF microarrays show good pH sensitivity in the range of pH 5–9.
- Dopamine can be distinguished from other metabolites using combined dye signals and principal component analysis.
- The microarrays are stable in analyte solutions and suitable for fluid-based detection.

## Abstract

Recently, metal‐organic frameworks (MOFs) have shown high potential in the field of sensing. However, fluorescent‐based detection with MOFs in solution needs complex pre‐treatments and has stability issues, complicating measurements and handling for sensing applications. Here, an easy‐to‐handle and low‐cost strategy is introduced to convert MOF‐based sensing from solution to surface using scanning probe lithography. The MOF is immobilized on the surface by receding meniscus coating, and then fluorescent dyes are patterned on the MOF thin films through microchannel cantilever spotting to generate dye@MOF fluorescent microarrays, which are stable in analyte solutions. The dye@MOF fluorescent microarrays exhibit good pH sensitivity in the pH 5–9 range, and dopamine can be distinguished from three other metabolites in the solution by these microarrays when signals from different dyes are analyzed in combination with principal component analysis. This concept provides a new approach for stable microarray‐based detection of small molecule analytes from a fluid environment.

In this study, a receding meniscus coating method is proposed for the fabrication of MOF thin film with good morphology, and multiplexed fluorescent microarrays based on four common dyes are developed on MIL‐101 thin films. The multiplexed fluorescent microarrays exhibit good stability in solution, pH sensitivity, and potential for discriminating dopamine from other interferents.