Subgram-Scale Synthesis of Biomass Waste-Derived Fluorescent Carbon Dots in Subcritical Water for Bioimaging, Sensing, and Solid-State Patterning

Abstract

Fluorescent carbon dots (FCDs) have received considerable attention because of the great potential for a wide range of applications, from bioimaging to optoelectronic devices. In this work, we reported the synthesis of nitrogen-doped FCDs with an average size of 2 nm in a subcritical water apparatus by using biomass waste (i.e., expired milk) as the precursor. The obtained FCDs were highly dispersed in aqueous solution because of the presence of O-containing functional groups on their surfaces. Under the excitation of ultraviolet and blue light, the FCDs exhibited excitation wavelength-dependent fluorescence in the emission range of 400–550 nm. The FCDs could be easily taken up by HeLa cells without additional surface functionalization, serving as fluorescent nanoprobes for bioimaging. The applications of FCDs as sensing agents for the detection of Fe3+, solid-state fluorescent patterning, and transparent hybrid films were also performed, demonstrating their potential for solid-state fluorescent sensing, security labeling, and wearable optoelectronics.

Preparation of Multifunctional N-Doped Carbon Quantum Dots from Citrus clementina Peel: Investigating Targeted Pharmacological Activities and the Potential Application for Fe3+ Sensing

“…Moreover, several studies have used biomass waste for obtaining CQDs, including citrus [ 8 , 9 ], kitchen waste [ 10 ], mango peel [ 11 ], banana peel [ 12 ], expired milk [ 13 ], egg shell [ 14 ], and agarose waste [ 15 ], all exhibiting good chemical and optical properties, and obtained carbon dots were applicable for the bioimaging, biosensing, and environmental monitoring. A significant challenge in the fabrication of biomass-derived CQDs represents obtaining CQDs with a high quantum yield.…”

An Overview of the Recent Developments in Carbon Quantum Dots—Promising Nanomaterials for Metal Ion Detection and (Bio)Molecule Sensing

“…The preparation of CQDs from low-value biomass, such as by-products and wastes, could be an example of efficient conversion of low-value products into valuable materials with a wide spectrum of possible applications. The literature data have shown that biomass has been widely used for the synthesis of efficient CQDs such as tomato [53,54], potato [55], expired milk [56] (Figure 2), and different plant material (Table 2); however, recently, the preparation of CQDs from waste of different origin (agricultural, industrial, domestic) covers more of this research topic and focuses also on the important concerns regarding the environmental impact and efficient waste management. It is interesting that biomass-derived CQDs can be used to detect metal ions and some molecules, and some selected examples are shown in Table 2.…”

“…Techniques such as X-ray photoelectron spectroscopy (XPS) are very useful for the elemental analysis of the synthesized sample, with the possibility of the oxygen quantification present on the CQDs surface in the form of carbon-oxygen bonding, as well as the quantification of heteroatoms such as sulfur, nitrogen, phosphorus, boron, etc. In the study by Su et al [56], nitrogen-doped carbon quantum dots (N-CQDs) were fabricated by using expired milk as a carbon and nitrogen precursor in a subcritical water reactor. Through the reactions of protein denaturation and Maillard reactions, N-CQDs were obtained with QY = 8.64% exhibiting also an excitation wavelength-dependent emission in the wavelength range of λ EM = 400-550 nm.…”

Preparation of carbon quantum dots from corn straw and their application in Cu2+ detection

“…Carbon quantum dots (CQDs) are one of the most attractive fluorescent nanomaterials, given they have the following advantages: low toxicity, high watersolubility, favorable biocompatibility, excellent electronic properties, high photostability, and easy surface functionalization (Xu et al 2015;Yu et al 2015;Su et al 2018;Xie et al 2019). For this reason, CQDs are successfully applied in many fields, including fluorescent ink (Li et al 2018), solar cells (Briscoe et al 2015), cell imaging (Huang et al 2019), sensors (Yang et al 2019), photocatalysis (Cao et al 2011), and drug delivery (Feng et al 2016).…”

“…In recent decades, biomass has been considered an important renewable resource and has been used to successfully prepare various materials. Several studies have employed biomass resources as starting materials to fabricate CQDs, e.g., highland barley (Xie et al 2019), milk (Su et al 2018), potatoes (Xu et al 2015), oatmeal (Yu et al 2015), hong cai tai (Li et al 2018), flowers (Huang et al 2019), plant leaves (Zhu et al 2013), soybeans (Hu et al 2019), and Dunaliella salina (Singh et al 2019). However, most of these CQDs were synthesized from edible and usable materials, causing a waste of resources.…”