Measuring Nano-particle Fluorescence in Caramelized Sugar ... · Measuring Nano-particle...
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Measuring Nano-particle Fluorescence in Caramelized Sugar Glass RT Emission from Various LED Sources The Fluorescence Monitoring System William R. Heffner 1 and Donald Wright III 2 1 IMI-NFG, Lehigh University, Bethlehem, PA , 2 Oakwood University. Huntsville, AL Sugar Glass Preparation and the Excited Emission Fluorescence Decrease with Temperature Low Cost Approach for Investigation Increased Absorption with Caramelization Summary Cane sugar, corn syrup and water are heated to first dissolve all crystals and then remove most of the water. Boiling to ~ 150 °C leaves about 1-2% water and will make a glassy candy on cooling. 200 220 240 260 280 300 320 340 350 450 550 650 750 200 220 240 260 280 300 320 340 350 450 550 650 750 200 210 220 230 240 250 260 270 280 290 300 350 400 450 500 550 600 650 700 750 200 220 240 260 280 300 350 450 550 650 750 200 250 300 350 350 450 550 650 750 1. W. R. Heffner and H. Jain, “Building a Low Cost, Hands-on Learning Curriculum on Glass Science and Engineering using Candy Glass” in MRS Proceedings 1233 , Boston, 2009, (Materials Research Society, 2010). 2. W. R. Heffner and H Jain, “Low-Cost, Experimental Curriculum in Materials Science Using Candy Glass Part 2: Home-Built Apparatuses” in MRS Proceedings 1657, Boston, 2014, (Materials Research Society, 2014). 3. Y. Sun, et al., “Quantum-Sized Carbon Dots for Bright and Colorful Photoluminescence”, J. Am. Chem. Soc. 128, 7756 (2006),. 4. S. Yang, et al., "Carbon dots as nontoxic and high-performance fluorescence imaging agents." The Journal of Physical Chemistry C 113, 18110 (2009). 5. M. Sk, et al., "Presence of Amorphous Carbon Nanoparticles in Food Caramels." Scientific Reports 2, (2012), article 383. 200 210 220 230 240 250 260 270 280 290 300 350 450 550 650 750 Intensity Wavelength T0 T2 T3 T4 T5 T6 T7 RT 150 Gradual decrease of the fluorescence peak near 550 nm as the temperature increases from RT (T0) to T7 (near boiling). After heating the room temperature fluorescence has increased appreciably, associated with a deeper yellow color in the sample from caramelization. Blue /Gr LED (500 nm) Violet LED (397 nm) Yellow LED (594 nm) Red LED (627 nm) The luminescence is shown (yellow) on left, superimposed with the exciting LED light spectra. Note the strong dependence on source wavelength, with essentially no emission for yellow or red LEDs. Violet led provides the best separation between source and fluorescence. Radiation. For green, the overlapping excitation peak can be fit and removed (subtracted out) in Excel. Acknowledgement: This work has been supported by IMI-NFG, Lehigh University through National Science Foundations (NSF) Grant : DMR-0844014 www.lehigh.edu/imi International Materials Institute for New Functionality in Glass Sponsored by US National Science Foundation Abstract: Nano-particle fluorescence is a stimulating topic for introducing students to contemporary experimental physics. We present her the unexpected fluorescence observed in simple glasses made from sugars (hard candy), requiring only kitchen stove processing. The fluorescence is easy to see with UV or green laser pointer illumination. We characterize the observed emission using a home-built fluorescence monitoring system consisting of high intensity LEDs for the excitation and the student grade Ocean Optics Red Tide Spectrometer to resolve the emission. The fluorescence was found to span between about 470 nm and 650 nm with a marked dependence on excitation wavelength (WL). The fluorescence and absorption also increase as the glass caramelizes (browns) with further heat treatment (cooking). Recent literature has shown similar fluorescence in caramelized carbohydrates and sugars to be due to the production of carbon nanoparticles. We propose the experiment as a cross-disciplinary and open-ended investigation for an undergraduate lab in physics, chemistry or material science. This is part of a larger collection of experiments to explore glass and optical science through sugar glass [1,2]. Carbon Quantum Dots In Caramelized Bread and Sugars Sk, et. al. 2012 [5] provide TEM analysis of carbon nano dots in caramelized foods and provide similar, yet more thorough, measurements of the excitation dependent fluorescence. For quantitative examination: Fluorescence monitoring system was assembled using the Ocean Optics Red Tide USB Spectrometer available in many high school and undergraduate labs. A nichrome wire was wrapped around an outer glass tube to provide a simple heater for temperature control. Transmission for sugar glass heated to increasingly higher temperatures from 160 to 200 ⁰C. The highly caramelized samples are quite absorbing in the blue, resulting in a reabsorption of any fluorescence. We provide a simple and highly accessible system to engage students in nano-particle optics within glassy materials. • The fluorescence arises from the formation of surface stabilized carbon nano- spheres in caramelized sugar glass • The fluorescence can be examined qualitatively with simple, LED multi wavelength sources or quantitatively with the addition of a low-cost student spectrometer. • Example of how exploring even common materials like candy, with some basic tools such as a simple student spectrometer, can bring the curious student to discovery of real, contemporary science. • Appropriate for the undergraduate lab and especially as an open-ended introductory research project. A gateway project. Excel scaled luminescence shows a distinct dependence of fluorescence peak on the excitation wavelength, characteristic of NP fluorescence. Results Experimental Carbon Nano-dot Fluorescence A half disc was molded for a Snell’s law demo; the yellowish scatter from green laser suggested something more interesting. Under UV (375 nm) light, the same candy glass sample emits blue. Certain semiconductor quantum dots are known to exhibit WL dependent fluorescence. Sun, et al. [3] was the first to observe bright visible photoluminescence from surface passivated carbon nano-particles (CNP) in 2006. These CNPs have generated considerable interest as environmentally friendly bio- compatible fluorescent probes[4]. In 2012 Sk, et al. [5] found that the same CNPs are produced during the caramelization of foods, establishing the CNP origin of our own observations. High brightness LEDs are used to obtain a range of excitation wavelength sources from UV (violet) to RED. LEDs alone are sufficient for qualitative observation of the WL dependence of the fluorescence. RT Blue LED (470 nm) References:
Transcript of Measuring Nano-particle Fluorescence in Caramelized Sugar ... · Measuring Nano-particle...
Measuring Nano-particle Fluorescence in Caramelized Sugar Glass
RT Emission from Various LED Sources
The Fluorescence Monitoring System
William R. Heffner1 and Donald Wright III2
1 IMI-NFG, Lehigh University, Bethlehem, PA , 2 Oakwood University. Huntsville, AL
Sugar Glass Preparation and the Excited Emission
Fluorescence Decrease with Temperature
Low Cost Approach for Investigation
Increased Absorption with Caramelization
Summary
Cane sugar, corn syrup and water are heated to first dissolve all crystals and then remove most of the water. Boiling to ~ 150 °C leaves about 1-2% water and will make a glassy candy on cooling.
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1. W. R. Heffner and H. Jain, “Building a Low Cost, Hands-on Learning Curriculum on Glass Science and Engineering using Candy Glass” in MRS Proceedings 1233 , Boston, 2009, (Materials Research Society, 2010).2. W. R. Heffner and H Jain, “Low-Cost, Experimental Curriculum in Materials Science Using Candy Glass Part 2: Home-Built Apparatuses” in MRS Proceedings 1657, Boston, 2014, (Materials Research Society, 2014).3. Y. Sun, et al., “Quantum-Sized Carbon Dots for Bright and Colorful Photoluminescence”, J. Am. Chem. Soc. 128, 7756 (2006),.4. S. Yang, et al., "Carbon dots as nontoxic and high-performance fluorescence imaging agents." The Journal of Physical Chemistry C 113, 18110 (2009).5. M. Sk, et al., "Presence of Amorphous Carbon Nanoparticles in Food Caramels." Scientific Reports 2, (2012), article 383.
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Inte
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Wavelength
T0
T2
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T6
T7
RT
150
Gradual decrease of the fluorescence peak near 550 nm as the temperature increases from RT (T0) to T7 (near boiling). After heating the room temperature fluorescence has increased appreciably, associated with a deeper yellow color in the sample from caramelization.
Blue /Gr LED (500 nm)
Violet LED (397 nm)
Yellow LED (594 nm)
Red LED (627 nm)
The luminescence is shown (yellow) on left, superimposed with the exciting LED light spectra. Note the strong dependence on source wavelength, with essentially no emission for yellow or red LEDs. Violet led provides the best separation between source and fluorescence. Radiation. For green, the overlapping excitation peak can be fit and removed (subtracted out) in Excel.
Acknowledgement: This work has been supported by IMI-NFG, Lehigh University through National Science Foundations (NSF) Grant : DMR-0844014
www.lehigh.edu/imiInternational Materials Institute for New Functionality in Glass
Sponsored by US National Science Foundation
Abstract: Nano-particle fluorescence is a stimulating topic for introducing students to contemporary experimental physics. We present her the unexpected fluorescence observed in simple glasses made
from sugars (hard candy), requiring only kitchen stove processing. The fluorescence is easy to see with UV or green laser pointer illumination. We characterize the observed emission using a home-built fluorescence monitoring system consisting of high intensity LEDs for the excitation and the student grade Ocean Optics Red Tide Spectrometer to resolve the emission. The fluorescence was found to span between about 470 nm and 650 nm with a marked dependence on excitation wavelength (WL). The fluorescence and absorption also increase as the glass caramelizes (browns) with further heat treatment (cooking). Recent literature has shown similar fluorescence in caramelized carbohydrates and sugars to be due to the production of carbon nanoparticles. We propose the experiment as a cross-disciplinary and open-ended investigation for an undergraduate lab in physics, chemistry or material science. This is part of a larger collection of experiments to explore glass and optical science through sugar glass [1,2].
Carbon Quantum Dots In Caramelized Bread and Sugars
Sk, et. al. 2012 [5] provide TEM analysis of carbon nano dots in caramelized foods and provide similar, yet more thorough, measurements of the excitation dependent fluorescence.
For quantitative examination:Fluorescence monitoring system was assembled using the Ocean Optics Red Tide USB Spectrometer available in many high school and undergraduate labs. A nichrome wire was wrapped around an outer glass tube to provide a simple heater for temperature control.
Transmission for sugar glass heated to increasingly higher temperatures from 160 to 200 ⁰C. The highly caramelized samples are quite absorbing in the blue, resulting in a reabsorption of any fluorescence.
We provide a simple and highly accessible system to engage students in nano-particle optics within glassy materials. • The fluorescence arises from the formation of surface stabilized carbon nano-
spheres in caramelized sugar glass• The fluorescence can be examined qualitatively with simple, LED multi
wavelength sources or quantitatively with the addition of a low-cost student spectrometer.
• Example of how exploring even common materials like candy, with some basic tools such as a simple student spectrometer, can bring the curious student to discovery of real, contemporary science.
• Appropriate for the undergraduate lab and especially as an open-ended introductory research project. A gateway project.
Excel scaled luminescence shows a distinct dependence of fluorescence peak on the excitation wavelength, characteristic of NP fluorescence.
ResultsExperimental
Carbon Nano-dot Fluorescence
A half disc was molded for a Snell’s law demo; the yellowish scatter from green laser suggested something more interesting. Under UV (375 nm) light, the same candy glass sample emits blue.
Certain semiconductor quantum dots are known to exhibit WL dependent fluorescence. Sun, et al. [3] was the first to observe bright visible photoluminescence from surface passivated carbon nano-particles (CNP) in 2006. These CNPs have generated considerable interest as environmentally friendly bio-compatible fluorescent probes[4]. In 2012 Sk, et al. [5] found that the same CNPs are produced during the caramelization of foods, establishing the CNP origin of our own observations.
High brightness LEDs are used to obtain a range of excitation wavelength sourcesfrom UV (violet) to RED.
LEDs alone are sufficient for qualitative observation of the WL dependence of the fluorescence.
RT
Blue LED (470 nm)
References:
