Synthesis And Optical Properties Of Dual Emission Carbon Dots

As a new type of nano-fluorescent material,carbon dots(CDs)have broad application prospects in the fields of cell imaging,analysis and detection and optical catalysis due to their advantages such as strong fluorescence,adjustable emission wavelength,low cytotoxicity and stable luminescence performance.Aiming at the defects of traditional single emission CDs,In particular,blue light emission has defects such as optical damage to biological tissues.The development of a simple and one-step method for the synthesis of red CDs with dual emission characteristics has become a research hotspot.In this paper indole as carbon source,in alkali/ethanol system,using a simple,low cost of electrochemical method carbide step synthesis can launch a red and blue double launch CDs(emission peak λem = 460 nm and 610 um).And the conversion from single blue light emission CDs to dual emission can be realized by controlling the existence of base.The as synthesized CDs have been thoroughly characterized by different spectroscopic techniques.The origin of the red emission has been investigated by analysing the intermediate product of CDs using gas chromatography-mass spectrometry(GCMS),and the optical properties of CDs obtained from the precursor of 2-naphthalenamine and naphthalene have been compared.It is found that ⅰ)alkaline ethanol system played a pivotal role in structural transition from single emission to dual emission,because surface oxidation is caused by hydroxyl radicals produced in the alkaline system.Surface oxidation creates surface defects thereby giving rise to the surface-state-related red emission,ⅱ)2-naphthaleneamine,a dual emission CDs intermediate(B-R-CDs),also plays an important role for forming B-R-CDs which brings an extendedπ-conjugated system and heteroatom functional group,which are synergistically responsible for emission at longer wavelength.The red emission of B-R-CDs are found highly pH dependent which makes them a potential candidate for application in pH sensing.Moreover,as prepared B-R-CDs have been used in full color bio-imaging of HepG2 cells,and exhibit an accurate mitochondrial-targeting ability.In addition,benzimidazole and citric acid were used as carbon sources,formamide as solvent,hydrothermal method(180 ℃,12 h)preparation of blue light emission(λem= 465 nm)and red(λem= 588 nm)of the CDs.CDs has higher sensitivity to acid and base than blue light emission.The fluorescence of red light is stronger in alkaline medium than in acidic medium,showing potential pH sensing performance.This method is simple and provides a new way to realize mass synthesis of dual emission carbon dots.