High-performance size exclusion chromatography with online fluorescence and multi-wavelength absorbance detection for isolation of high-purity carbon dots fractions, free of non-fluorescent material

Abstract

The carbon dots (CDs) from natural nanographite oxide mixture (NGO-MIX) and from its fraction NGO (3.5-10K) recovered after ultrafiltration and dialysis were analyzed by 2 3D-excitation/emission matrix and high-performance size exclusion chromatography (HPSEC) combined with online fluorescence and absorbance detections. HPSEC chromatograms obtained simultaneously with absorption within the wavelength range 200-500 nm and fluorescence detection at λ exc /λ em = 270/450 nm/nm showed that NGO-MIX sample is not homogeneous and consist of well resolved CDs fractions with different sizes, absorption spectra and distinct fluorescence and non-fluorescence properties. Despite the twice higher fluorescence intensity of fraction NGO (3.5-10K) compared to the NGO-MIX, some impurity of non-fluorescent components was detected by HPSEC. The absorbance spectra of chromatographic peaks, extracted from the data of multi-wavelength absorbance detector, demonstrated different combinations of absorbance maxima. It means that different chromatographic peaks correspond to sized and chemically different CDs fractions. This study demonstrated for the first time the possibility of separating oxidized nanographite into homogeneous free from non-fluorescent material CDs fractions with their simultaneous spectroscopic characterization.

Separation and purification of fluorescent carbon dots – an unmet challenge

“…8a). 119 The smaller particles or those with equal size to that of the pores in the packing materials infuse deep into the column, leading to a longer retention time. However, larger particles that diffuse freely and move along with the mobile phase are excluded and are first to elute.…”

“…8 (a) Schematic representation of particle size-based separation using SEC. 119 (b) Dialysis and subsequent SEC to obtain two CD fractions, which demonstrated characteristic emissions. 122 (c) Isolation of brighter CDs from an apparently low QY mixture using AE-HPLC 126 and (d) GC using a silica column to obtain a series of full-color light-emitting excitation-independent CDs with a surface-state-controlled luminescence mechanism.…”

“…Fig.8(a) Schematic representation of particle size-based separation using SEC 119. (b) Dialysis and subsequent SEC to obtain two CD fractions, which demonstrated characteristic emissions 122.…”

Rational design of large flat nitrogen-doped graphene oxide quantum dots with green-luminescence suitable for biomedical applications

“…48,49 Therefore, sophisticated purication techniques are required for GOQDs purication. 50 As an alternative to metal-containing oxidants, water solution of hydrogen peroxide was successfully texted in preparation of GOQDs from GO in the presence of iron ions. 51 Most likely, GOQDs formation emerges from the process of GO radical epoxidation with further hydrolysis of oxirane cycles.…”