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

Abstract 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:NaYF 4 , and up to 673 K for microelectronic applications using Tm,Yb:GdVO 4 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:NaYF 4 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.