New Insight into the Concept of Carbonization Degree in Synthesis of Carbon Dots to Achieve Facile Smartphone Based Sensing Platform

Abstract

Direct pyrolysis of citric acid (CA) has been proved to be a facile bottom–up technique for making pristine carbon dots (CD) with homogenous size distribution. However, limited reports are available on systematic optimization of carbonization degree. In this investigation, pyrolysis temperatures between 160 °C and 220 °C were studied, based on CA thermal decomposition path, using various heating durations. The effect of the formation of more carbonized carbon particles (MCCPs), as the major byproduct of this method, on photoluminescence properties of CDs was also considered. The NaOH amount that neutralizes the solution and the effect of dilution on the emission intensity, were introduced as simple and accessible factors for monitoring carbonization degree, and an estimate of MCCP/CD ratio, respectively. The results show that the CDs fabricated at 160 °C, 50 minutes attain almost twice higher quantum yield (QY) of 29% than highest QY reported based on pyrolysis of CA. The so–prepared CDs can be employed as excellent candidates for turn–off sensing. As a proof of concept, detection limit of 50 nM for Hg2+ was achieved using a facile and inexpensive smartphone set–up that is able to quantify and compare fluorescent intensity in several samples simultaneously.

Synthesis and Characterization of Green Carbon Dots for Scavenging Radical Oxygen Species in Aqueous and Oil Samples

“…Also, in comparison with the spectral characteristics of GCDs, the maximum excitation of P2CDs shifted to the blue (318 nm) and the maximum emission wavelength was at 440 nm with a very weak fluorescence intensity. The synthesis procedure of P2CDs must be behind the poor photoluminescent behaviour of these nanoparticles, as proposed in different works [ 40 , 41 ]. Begheri et al [ 42 ] have suggested that during the thermal treatment, along with CDs more carbonized carbon particles (MCCPs) may also be formed as a major by-product, which have quenching effects on the photoluminescence of the CDs.…”

Effect of carbonization degree of carbon dots on cytotoxicity and photo-induced toxicity to cells

“…Variations in heating time and temperature have major effects on the formation and photoluminescence (PL) properties of CDs [35]. Therefore, we synthesized CDs under four different temperature-time conditions: 220-20, 200-30, 180-40, and 160-50.…”

“…The highest emission intensity was observed at 350 and 375 nm. Fourier transform infrared (FTIR) spectra in Figure 3c indicated absorption of stretching vibration O–H, C–H, and C–OH groups [35]. To determine the size distribution of CDs dynamic light scattering (DLS) was employed [37, 38, 39, 40].…”

Emerging Trends in Nanocarbon‐Based Cardiovascular Applications

“…A wide range of methods, such as laser radiation, [ 156 ] microwave energy, [ 157 ] hydrothermal/solvation techniques [ 158 ] and carbonization techniques, [ 159 ] have been used for the preparation of imaging and diagnostic agents, such as fluorescent aspirin‐based carbon dots (FACDs). [ 160 ] The novel FACDs showed 23% of quantum yield and a fluorescent lifetime of 3.82 ns.…”