# Upconversion Nanoparticle-Based Luminescence DNA Sensor on Porous Silicon Substrate

## TL;DR

A new DNA sensor using upconversion nanoparticles on porous silicon detects DNA with high sensitivity and low cost.

## Contribution

The first UCNPs-based biosensor on a PSi substrate for DNA detection is developed.

## Key findings

- The biosensor achieved a detection limit of 86 pM for target DNA.
- The method enables rapid and sensitive detection of DNA molecules.
- Porous silicon was successfully functionalized for DNA immobilization.

## Abstract

Rare-earth-doped upconversion nanoparticles (UCNPs) exhibit upconversion luminescence upon excitation with infrared light and have been extensively utilized in the field of biosensing. In this study, a UCNPs-based biosensor with porous silicon (PSi) as the substrate was developed for the first time, enabling the detection of target DNA molecule concentration. First, a PSi substrate was prepared via electrochemical etching and subsequently functionalized to enable target DNA molecules to immobilize onto the inner walls of the PSi substrate’s pores. Then, UCNPs-labeled probe DNA molecules hybridized with the target DNA molecules, enabling indirect attachment of UCNPs to the inner walls of the PSi substrate. Subsequently, the sample surface is irradiated with a 980 nm laser. Upconversion fluorescence images of the sample, both before and after the biological reaction, are captured using an image acquisition device. Image processing software is employed to calculate the average change in grayscale values, enabling the determination of the molecular concentration of target DNA. The limit of detection (LOD) of this method for target DNA molecular concentration is 86 pM, demonstrating that it enables low-cost, highly sensitive, rapid, and convenient biological detection of target DNA molecules.