Novel low-cost, compact and fast signal processing sensor for ratiometric luminescent nanothermometry

- Compact, low-cost, non-invasive temperature sensor including RGB digital color sensor coupled to an optical focusing system.
- Use of luminescent nanoparticles emitting at least in two of the detection channels of the digital color sensor.
- Probed potentiality of this setup for luminescence thermometry in the biological range of temperatures using Er,Yb:NaYF4 NPs.
- Probed potentiality for luminescence thermometry up to 673 K for microelectronic applications using Tm,Yb:GdVO4 NPs.
- Developed luminescent nanoparticles/PDMS composites for luminescence thermometry in microfluidics.

We developed a new compact, low-cost and non-invasive temperature sensor based on a ratiometric luminescence technique. The setup included a commercial digital color sensor, which collects simultaneously signals in the blue, green and red regions of the electromagnetic spectrum, usually used to assess the quality of computer screens and used for the first time here as a sensor for luminescent thermometry, coupled to an optical system that focuses an excitation laser beam onto luminescent nanoparticles emitting at least in two of these electromagnetic regions, which simplifies considerably the design, alignment and measurement procedures of setups used up to now for the same purpose. The same optical system collects the emission arising from the luminescent nanoparticles and directs it towards the digital color sensor through a dichroic mirror. We probed the potentiality of this setup for luminescence thermometry in the biological range of temperatures using Er,Yb:NaYF4, and up to 673 K for microelectronic applications using Tm,Yb:GdVO4 up-converting nanoparticles. The thermal sensitivity obtained in both cases is similar to that previously reported for the same kinds of nanoparticles using conventional systems. This validates our setup for temperature measurements. Also, we developed new flexible and transparent polymer composites, in which we embedded upconversion luminescent nanoparticles of Er,Yb:NaYF4 in PDMS, a standard polymer for microfluidic devices used for biomedical studies, which allow fabricating thermometric microfluidic chips in which temperature can be determined using our setup. The thermal sensitivity for these composites is slightly smaller than that of the bare nanoparticles, bur still allowing for precise and fast temperature measurements.