Exploiting Chemical and Structural Tunability to Harness Temperature-Dependent Luminescence at the Nanoscale

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The accurate and precise determination of temperature is critical in diagnostic and therapeutic biosystems. Nanomaterials capable of serving as optical temperature sensors are uniquely suited for this task because they are able to operate in environments where contact thermometry cannot be implemented (e.g., cells and deep tissues). However, the vast majority of luminescent nanothermometers lack the required temperature sensitivity. New inorganic nanomaterials with temperature-dependent luminescence response will be discovered and developed in this research. Through a combination of synthesis and characterization studies the rules governing the temperature sensitivity of these phosphors are established. These rules are then used to design optical thermometers with targeted sensitivity within a given temperature window. In addition, this project provides opportunities for workforce development at both undergraduate and graduate levels and K-12 STEM outreach. Graduate and undergraduate students are trained in the synthesis and advanced characterization of luminescent nanomaterials. 6th through 9th grade students participating in the annual STEM Day hosted by Wayne State University are introduced to optical materials research through a hands-on activity based on photostimulable phosphors.The research aims to develop an understanding of how to tune the temperature sensitivity of luminescent nanothermometers by rationally matching hosts and activators. The chemical and structural tunability of a novel family of host materials is exploited to this end. The project can be divided into three thrust areas. The first area involves synthesis of a series of inorganic nanocrystals that incorporate divalent and trivalent metal dopants as luminescent centers. To this end, colloidal synthetic routes to heterocationic and heteroanionic nanocrystals are developed. The second thrust focuses on ascertaining the placement of the luminescent centers in the nanocrystalline hosts. This task involves interrogating the atomic arrangement in multiple length scales using element-specific spectroscopic probes. Finally, in the third thrust, the temperature-dependent luminescence response of the nanocrystals is systematically probed using steady-state and time-dependent spectrofluorometry. Composition–structure–luminescence relationships are then derived to reveal the fundamental chemical and structural principles governing the temperature sensitivity of the nanothermometers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.