Cooking Carbon Dots -- Making an Instant Neutrino Detector in Your Kitchen

Abstract

Liquid scintillators underpin a wide range of radiation detectors, including those used in neutrino physics, but typically rely on organic fluors dissolved in hazardous and costly solvents. Here, we show that carbon dots - nanoscale fluorescent carbon materials - synthesised from simple household ingredients using a microwave can function as water-based liquid scintillators. These carbon dots dispersed in water produce light yields up to 70 +/- 20 photons per MeV and enable the detection of atmospheric muons. This yield is sufficient to detect low-energy protons in water Cherenkov neutrino detectors, expanding their programs in both particle physics and astrophysics. These results establish an accessible, low-cost and environmentally benign route to scintillator development, opening new opportunities for large-scale radiation detection.

Figures (6)

• Figure 1: Artist's impression of carbon dots excited by an atmospheric muon emitting blue light.
• Figure 2: Left, ingredients of carbon dots: sugar, vinegar, and baking soda. Right, carbon dots are diluted in water until the blue emission becomes visibly the brightest.
• Figure 3: Left, absorbance measurements (dashed) used to normalize photoluminescence (solid) data (excitation wavelength = $340$ nm, vertical dashed line). Right, the hydrodynamic size of the three solutions measured with the dynamic light scattering method, in triplicate (solid, dashed, and dotted lines). Carbon dots sample 1 in red, Carbon dots sample 2 in blue, and a commercial carbon dots sample, in green.
• Figure 4: Left, schematics of the atmospheric muon response measurement. Muons were tagged by two plastic scintillators. After discrimination, a coincidence signal was produced to trigger the digitizer, and PMT responses were measured. Right, a photograph of the inside of the dark box. The carbon dots solution is illuminated by a UV torch.
• Figure 5: Left figure shows the two-dimensional histogram of the pulse peak height (mV) vs. peak pulse time (ns). Count is shown with color in logarithmic scale. Right, a typical pulse observed by a 3-inch PMT from the carbon dots muon response. Dashed line indicates the expected arriving time of the pulse from the known delays of cables and electronics. The pink region is used to calculate the baseline. The 100 ns green region is used to integrate the pulse to calculate the charge.