All-Optical Thermometry with Nitrogen-Vacancy Centers in Nanodiamond-Embedded Polymer Films

Abstract

Fluorescent nanodiamonds (FNDs) containing negatively charged nitrogen-vacancy (NV–) centers are applicable for nanoscale temperature sensing in frontier areas of science and engineering. As researchers take advantage of the unique chemical and physical properties of this nanomaterial, many new innovations are emerging. Here, we show that FNDs can be readily embedded in poly­(2-hydroxyethyl methacrylate) (PHEMA) with a high density (1 × 1011 particles in a film of 10 × 10 × 0.1 mm3) and a high uniformity (intensity variation of ∼10% over a distance of 10 μm). The FND-embedded polymer films can be fabricated in large scale and are useful as all-optical thermometers for practical applications. This work made a comparative study on the temperature dependence of the peak positions and heights of the zero phonon line (ZPL) of NV– centers in these films from 35 to 120 °C. A measurement sensitivity of 0.46–1.1 and 0.15–0.62 K Hz–1/2 was achieved respectively for the ZPL shifts and height changes over this temperature range. The utility and versatility of this device were demonstrated with a study for the energy transfer kinetics of a resistively heated gold microwire embedded in the PHEMA film.

Preparation and Applications of Carbon‐Based Fluorescent Nanothermometers

“…The mechanism of the response of carbon‐based fluorescent nanomaterial thermometers to temperature has always been a research hotspot. [ 5–18 ] However, there is still no unified explanation for the fluorescence mechanism of temperature sensing. This is because various carbon‐based materials have been reported, including the aforementioned fluorescent NDs, P‐dots, GQDs, and CDs.…”

“…This is because various carbon‐based materials have been reported, including the aforementioned fluorescent NDs, P‐dots, GQDs, and CDs. [ 5–18 ] Their chemical structures are quite different, with a wide variety of the luminescent centers controlling the fluorescence. Nevertheless, as the temperature rises, the photoluminescence (PL) intensity of the most temperature‐sensitive carbon‐based materials changes, enabling temperature detection.…”

“…Accurately measuring the internal temperature of living organisms, as well as the gradient can promote the research on biology and biomedicine progress. [ 1–18 ] Up to now, a large number of macro‐ and micro‐sensors have been reported for the temperature sensing. [ 2–18 ] Among the utilized sensors, fluorescence‐based temperature sensors have shown great potential because they can be used as “non‐contact” tools for the dual functions of imaging and temperature sensing at molecular level synchronously.…”

“…[ 1–18 ] Up to now, a large number of macro‐ and micro‐sensors have been reported for the temperature sensing. [ 2–18 ] Among the utilized sensors, fluorescence‐based temperature sensors have shown great potential because they can be used as “non‐contact” tools for the dual functions of imaging and temperature sensing at molecular level synchronously. [ 5–18 ] For the last few decades, a series of fluorescent nanomaterials, such as semiconductor quantum dots, organic dyes, fluorescent polymers, and metal nanoclusters (NCs) have been developed as typical fluorescence‐based sensors for temperature detection.…”

“…They show the following advantages: high optical absorptivity, adjustable fluorescent emission, chemical stability, well biocompatibility, and low toxicity. [ 5–99 ] Given these superior properties, they have been extensively discussed in bioimaging devices, biosensors, catalysts, photovoltaic devices, as well as fluorescent nanothermometers for spatially resolved temperature ( Figure ). [ …”