In Situ Synthesis of Amino Acid Functionalized Carbon Dots with Tunable Properties and Their Biological Applications

Abstract

Emissive carbon dots (C-Dots) are known for displaying versatile properties, which have been widely utilized in many applications such as bioimaging, light-emitting devices, and photocatalysis. Further functionalization can tune their physical and chemical properties, which play the key role in many biologically and chemically relevant applications. Amino acids provide an attractive means for introducing functionality with a structural diversity. In this work, water-soluble emissive C-Dots were synthesized from pyrolysis of citric acid in the presence of various amino acids under hydrothermal conditions. We established that the diverse functionality-bearing polyamides and the polyester backbone of C-Dots are the origin of optical properties with a high quantum yield. The amino acid based C-Dots were systematically characterized using various analytical methods to confirm the core structure as well as the functionality. The results show that, depending on functionalization, the quantum yield can be varied and enhanced up to 62% and surface charge and hydrophobicity can be tuned. Most importantly, we observed a correlation between the quantum yield and properties of the side chain residue of amino acids such as hydrophobicity index and volume. Furthermore, it was found that the synthesized, diversely functionalized C-Dots exhibit no cellular toxicity and can be used for cell imaging. Due to variable surface functionality, we have also applied these C-Dots for array-based protein sensing. Overall, based on this reported method, we can easily tune the optical as well as surface properties of C-Dots, which will be suitable for many future applications.

Covalent Conjugation of Carbon Dots with Plasmid and DNA Condensation Thereafter: Realistic Insights into the Condensate Morphology, Energetics, and Photophysics

“…For the determination of quantum yield, a solution of quinine sulfate (QY = 0.55) in 0.5 M H 2 SO 4 was used as the standard. 35 The solutions of CD in water and quinine sulfate in H 2 SO 4 were prepared to have similar absorbance at the excitation wavelength. Quantum yield was calculated by using the following equation where subscript x and s denote the test and standard sample, respectively; Φ is the fluorescence quantum yield; I is the integrated fluorescence intensity; f is the absorption factor ( f = 1 – 10 – A , where A = absorbance); and η is the refractive index of the solvent.…”

Interface electron collaborative migration of Co–Co3O4/carbon dots: Boosting the hydrolytic dehydrogenation of ammonia borane

“…The synthesized CDs clearly contained abundant carboxyl and hydroxyl groups on the surface derived from the citric acid molecules. The presence of these oxygen-containing groups not only increased the water solubility of the as-prepared CDs but also caused their surfaces to exhibit a certain negative potential, which greatly promoted the complexation between them and metal cations [38] . In addition, the C-O-C/C-O stretching vibration peak observed at 1212 cm -1 indicates that before carbonization, dehydration and polymerization of several citric acid molecules occurred to form macromolecules during the hydrothermal process [39] .…”

Application of Zero-Dimensional Nanomaterials in Biosensing

“…Up to now, various 0D nanomaterials have been extensively explored. For instance, graphene quantum dots (GQDs) (Qian et al, 2014;Lu et al, 2018;Yan et al, 2019), carbon quantum dots (CQDs) (Zheng et al, 2015;Li et al, 2018b;Pandit et al, 2019), fullerenes (Barberis et al, 2015;, inorganic quantum dots (QDs) (Freeman et al, 2012;Li et al, 2018a;Robidillo et al, 2019), magnetic nanoparticles (MNPs) (Yu et al, 2017;Bragina et al, 2019), noble metal nanoparticles (Yang C. T. et al, 2016;Jain and Chauhan, 2017;Bagheri et al, 2018), upconversion nanoparticles (UCNPs) (Cheng Z. H. et al, 2019;Gu et al, 2019) and polymer dots (Pdots) (Ou et al, 2019; are all representative 0D nanomaterials with potential applications in materials science (Zhang X. et al, 2014), photovoltaic science (Guo et al, 2010), catalysis (Xu et al, 2015), energy (Guldi and Sgobba, 2011), sensing (Ramanathan et al, 2019), biomedicine (Yao et al, 2018) and nanodevices (Zhang Y. et al, 2014).…”