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Here we report on the first ultrabright fluorescent nanothermometers, ∼50 nm-size particles, capable of measuring temperature in 3D and down to the nanoscale. The temperature is measured through the recording of the ratio of fluorescence intensities of fluorescent dyes encapsulated inside the nanochannels of the silica matrix of each nanothermometer. The brightness of each particle excited at 488 nm is equivalent to the fluorescence coming from 150 molecules of rhodamine 6G and 1700 molecules of rhodamine B dyes. The fluorescence of both dyes is excited with a single wavelength due to the Förster resonance energy transfer (FRET). We demonstrate repeatable measurements of temperature with the uncertainty down to 0.4 K and a constant sensitivity of ∼1%/K in the range of 20–50 °C, which is of particular interest for biomedical applications. Due to the high fluorescence brightness, we demonstrate the possibility of measurement of accurate 3D temperature distributions in a hydrogel. The accuracy of the measurements is confirmed by numerical simulations. We further demonstrate the use of single nanothermometers to measure temperature. As an example, 5–8 nanothermometers are sufficient to measure temperature with an error of 2 K (with the measurement time of >0.7 s).
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Ultrabright Fluorescent Silica Nanoparticles for Dual pH and Temperature Measurements
The mesoporous nature of silica nanoparticles provides a novel platform for the development of ultrabright fluorescent particles, which have organic molecular fluorescent dyes physically encapsulated inside the silica pores. The close proximity of the dye molecules, which is possible without fluorescence quenching, gives an advantage of building sensors using FRET coupling between the encapsulated dye molecules. Here we present the use of this approach to demonstrate the assembly of ultrabright fluorescent ratiometric sensors capable of simultaneous acidity (pH) and temperature measurements. FRET pairs of the temperature-responsive, pH-sensitive and reference dyes are physically encapsulated inside the silica matrix of ~50 nm particles. We demonstrate that the particles can be used to measure both the temperature in the biologically relevant range (20 to 50 °C) and pH within 4 to 7 range with the error (mean absolute deviation) of 0.54 °C and 0.09, respectively. Stability of the sensor is demonstrated. The sensitivity of the sensor ranges within 0.2–3% °C−1 for the measurements of temperature and 2–6% pH−1 for acidity.
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- PAR ID:
- 10280906
- Date Published:
- Journal Name:
- Nanomaterials
- Volume:
- 11
- Issue:
- 6
- ISSN:
- 2079-4991
- Page Range / eLocation ID:
- 1524
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/nano11061524
