Abstract
Carbon nanodots (C-dots) with sp2/sp3 framework and diameter of <10 nm contain abundant functional groups or polymers on their surface. C-dots have attracted immense attention because of their unique optical properties, excellent biocompatibility, facile preparation, and low cost. With these merits, C-dots have been used in a wide range of applications including sensing, bioimaging, catalysis, and light-emitting devices. C-dots exhibit good optical properties, such as tunable emission wavelength, good photostability, nonblinking, up-conversion emission, etc. Of note, C-dots show intrinsic pH-sensitive photoluminescence (PL), indicating their great potential for pH sensing, especially in biotic pH sensing. In this review, we systematically summarize the pH-sensitive PL properties and the pH-sensitive PL mechanism, as well as recent research progress of C-dots in pH sensing. The current challenges of pH-sensitive C-dots and their future research focus are also proposed here. We anticipate this review might be of great significance for understanding the characteristics of pH-sensitive C-dots and the development of photoluminescent nanomaterials with pH-sensitive properties.
Highlights
As a novel carbon nanomaterial, carbon nanodots (C-dots) have attracted extensive attentions because of their small particle size, wide source of raw materials, low cost, and excellent physical and chemical properties (Esteves da Silva and Gonçalves, 2011; Ding et al, 2014; Lim et al, 2015; Yuan et al, 2016; Liu et al, 2019)
Jin’s group (Sui et al, 2016) investigated ultrafast carrier relaxation dynamics in Carbon nanodots (C-dots) under different pH by femtosecond transient absorption spectra. They claimed that the distribution of π electron cloud density between the pH-Sensitive Photoluminescence of C-Dots carbon backbone and surface states would be changed by the deprotonation of carboxyl at higher pH
Shi et al (2016) prepared blue fluorescent C-dots with the PL intensity significantly increased as pH increased from 3 to 11. They believed that the increase of PL intensity of C-dots was induced by the deprotonation of carboxyl groups, which promoted the formation of delocalized π bonds and increase of n electrons
Summary
As a novel carbon nanomaterial, carbon nanodots (C-dots) have attracted extensive attentions because of their small particle size (generally
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