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Solvothermal Synthesis of Multicolor-Emitting Carbon Quantum Dots for White Light and Optoelectronic Applications
Kanagaraj Reivanth1, Arumugam Sangeetha1, Maheswari Palanivel1
1Quantum Materials & Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu 641 046, India.
None:
Carbon quantum dots (CQDs) were synthesized via a one-step solvothermal reaction of citric acid and urea in formamide. The CQDs display excitation-dependent photoluminescence tunable from blue to orange arising from multiple emissive surface states. Time-correlated single-photon counting (TCSPC) reveals triexponential decays with τ1 = 0.87 ns, τ2 = 3.25 ns, and τ3 = 7.0 ns, confirming coexisting fast and slow recombination pathways responsible for multicolor emission. In addition to that femtosecond TAS provides direct insight into core-to-surface relaxation pathways that underpin the broadband emission behavior. In dispersion, the CQDs emit cool-white light with CIE (0.27, 0.32), CCT ≈ 10 411 K, and CRI ≈ 82, while a flexible transparent CQD/PVA film produces white emission with CIE (0.27, 0.33), CCT ≈ 11,346 K, and CRI ≈ 79. A photodiode of configuration FTO/TiO2/CQDs/MoO3/Al exhibits wavelength-dependent photocurrent maximum under blue illumination (45 μA at 1 V) with an on/off response of ∼1.2 s correlating optical absorption with electrical behavior. The integration of one-step solvothermal prepared CQDs into both a flexible white-emitting film and a functional photodiode demonstrates their dual optoelectronic applicability.
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The Dot Product
Dot Product
In engineering, the dot product of any two vectors is the product of the magnitudes of the vectors and the cosine of the angle between them. It is denoted by a dot symbol between the two vectors.
Consider a vehicle pulling an object along the ground using a rope. If the rope makes an angle with the horizontal axis, the work done can be calculated using the dot product of the force applied and the object's displacement.
The dot...

