Carbon Dots: Diverse Preparation, Application, and Perspective in Surface Chemistry

Abstract

Carbon dots (CDs) are a novel class of nanoparticles with excellent properties. The development of CDs involves versatile synthesis, characterization, and various applications. However, the importance of surface chemistry of CDs, especially in applications, is often underestimated. In fact, the study of the surface chemistry of CDs is of great significance in the explanation of the unique properties of CDs as well as the pursuit of potential applications. In this feature article, we do not only introduce the development of CDs in our group but also highlight their applications where surface chemistry plays a critical role.

On the Emission Properties of Carbon Dots: Reviewing Data and Discussing Models

“…Since then, the research on this matter is exponentially increasing (according to Scopus, the search engine by Elsevier, more than 1900 search results for 2019 to date and even 28 already dated 2020), with thousands of papers published on the subject in the last few years [4]. Besides a high QY (even larger than 80% [5][6][7][8][9]), other appealing features of CDs are low toxicity, biocompatibility, and photo-and water stability [10][11][12], which make them suitable for applications in luminescence-related fields, such as bioimaging and sensing [13][14][15], photocatalysis [16,17], LED [18,19], lasing [20,21], printing, and cosmetics [22,23] or displays [24]. In addition, drug delivery applications were proposed, exploiting the easy surface functionalization of CDs' surface [23,25,26].…”

“…Besides a high QY (even larger than 80% [5][6][7][8][9]), other appealing features of CDs are low toxicity, biocompatibility, and photo-and water stability [10][11][12], which make them suitable for applications in luminescence-related fields, such as bioimaging and sensing [13][14][15], photocatalysis [16,17], LED [18,19], lasing [20,21], printing, and cosmetics [22,23] or displays [24]. In addition, drug delivery applications were proposed, exploiting the easy surface functionalization of CDs' surface [23,25,26]. All these applications take advantage of two quite unusual optical properties: a quite large Stokes shift (on average larger than 100 nm if we consider near UV excitation around 350 nm and the blue emission) and an excitation wavelength dependent peak position, allowing tuning of the emission from blue to red across the whole visible spectral range [4,27,28].…”

Study and Comparison on Purification Methods of Multicolor Emission Carbon Dots

“…So far, different methods have been employed for the purification of CDs, which includes precipitation method, dialysis, column chromatography, polyacrylamide gel electrophoresis, capillary electrophoresis, etc [13] . The precipitation method is to precipitate CDs by adding a poor solvent to the system, which is suitable for the large scale preparation of CDs.…”

“…When CDs are allowed to move through a column containing the gel, the small‐sized substances are able to penetrate into the gel particle pores while the large‐sized substances are excluded from the pores and pass directly through the column. Consequently, the largest sized substances elute first and the smallest sized substances elute last [13] . With the help of SEC, Messina and co‐workers obtained a type of CD with high fluorescence quantum yield, benefiting from the monodisperse size distribution and well‐controlled structure [19] .…”

Insight into the Multistate Emissive N, P‐doped Carbon Nano‐Onions: Emerging Visible‐Light Absorption for Photocatalysis

“…In recent years, carbon nanomaterials such as graphene, graphene oxide, nanodiamond, and their typical analogs in different dimensions (e. g.-carbon nanotubes, carbon dots, and carbon nano-onions), have drawn much attention from the scientific community due to their multimodal applicabilities in photonics, optoelectronics, catalytic and sensing devices. [1][2][3][4][5] Especially, carbon dots (CDs), are one kind of emerging carbonbased nanomaterials with excellent optical and fluorescence features with high quantum yield (QY) that have great potential in various applications including fluorescent probes, biological labeling, photocatalysis, and optoelectronic devices. [2][3][4]6] Furthermore, simple and low-cost preparation methods, high thermal and optical photostability, tunable excitation and emission features, easy surface functionalization, and environmental sustainability with high biocompatibility make them versatile materials in various fields.…”