Recently, nanoparticles have been used for many biomedical applications such as drug delivery, antimicrobial agent, diagnosis, and cancer treatment, because of their outstanding characteristics. They have good optical, magnetic, electric, and photothermal properties, for instance. Certain nanoparticles, for example, gold and iron oxide nanoparticles, show an impressive light-to-heat conversion capability while being exposed to the light of a specific wavelength. However, this photo-induced ability has mainly focused on the field of cancer treatment. As thermochromic material completely changes color once activation temperature is reached, the color contrast is high. We took advantage of this effect to enhance optical signal of colorimetric assays. In this work, we aimed to exploit the photothermal properties of nanoparticle on a membrane in combination with thermo-sensitive paper to increase the optical signal (as shown in the diagram). The role of nanoparticle is to generate sufficient heat to activate a thermochromic sheet resulting in greater color contrast. Firstly, the heat generation of nanoparticles was determined. Different types and morphologies of photothermal nanoparticles were heated by a light-emitting diode. The degree of temperature change of nanoparticles was tracked by an infrared camera. Afterwards, thermochromic sheet with the most appropriated working temperature was selected for the next experiment. Then, nanoparticle-deposited membrane was exposed to a light-emitting diode which, in turn, triggers the color change of thermochromic paper underneath. Images of nanoparticle and activated thermochromic sheet were taken and converted into digital value for comparison. This study shows the potential of using photothermal nanoparticles with thermo-sensitive material as an optical readout. This can be a promising method to significantly improve colorimetric assay, even at a diluted concentration of analyses.

Enhancement of thermochromic signal from photothermal nanoparticles

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.