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Uniform graphitic-carbon nitride quantum dots were fabricated through a combination of hydrothermal treatment, sintering and sonication methods and the production yield is up to 39 %. The obtained graphitic-carbon nitride quantum dots dry powder possesses outstanding redispersibility, stability and water solubility in deionized water. [Display omitted] • Mass production of g-C 3 N 4 quantum dots was achieved through an efficient method. • The production yield of g-C 3 N 4 quantum dots is up to 39 %. • The g-C 3 N 4 quantum dots have excellent redispersibility and stability and in deionized water. • The g-C 3 N 4 quantum dots exhibited high sensitivity and selectivity to Fe3+. • The g-C 3 N 4 quantum dots were subjected to the photocatalytic degradation of rhodamine B and methyl orange. Graphitic-carbon nitride quantum dots (gCNQDs) have various fascinating properties and potential applications, but the low yield production of gCNQDs by current synthetic methods severely limits to exploit their properties and large-scale applications. Here we report the large scale synthesis of uniform gCNQDs through a combination of hydrothermal treatment, sintering and sonication methods for the first time. The production yield is up to 39 %, and the obtained gCNQDs dry powder possesses outstanding redispersibility, stability and water solubility in deionized water. The gCNQDs aqueous suspensions emit bright blue luminescence under UV excitation and can be an effective fluorescence probe for Fe3+ detection with good selectivity, sensitivity and photostability. The fluorescent probe shows low cytotoxicity and good cell-permeability, and then being successfully applied for the fluorescence imaging of Fe3+ in living cells. Moreover, the gCNQDs show the improved photocatalytic activity, which was evaluated by degradation of Rhodamine B and Methyl Orange. The large scale synthesis of gCNQDs with outstanding fluorescent properties, biocompatibility and photocatalytic properties can effectively facilitate the applications of gCNQDs and gCNQDs based nanocomposites in various fields. [ABSTRACT FROM AUTHOR]

Liquid-phase exfoliation (LPE) is a widely used and promising method for the production of 2D nanomaterials because it can be scaled up relatively easily. Nevertheless, the yields achieved by this process are still low, ranging between 2% and 5%, which makes the large-scale production of these materials difficult. In this report, we investigate the cause of these low yields by examining the sonication-assisted LPE of graphene, boron nitride nanosheets (BNNSs), and molybdenum disulfide nanosheets (MoS2 NS). Our results show that the low yields are caused by an equilibrium that is formed between the exfoliated nanosheets and the flocculated ones during the sonication process. This study provides an understanding of this behaviour, which prevents further exfoliation of nanosheets. By avoiding this equilibrium, we were able to increase the total yields of graphene, BNNSs, and MoS2 NS up to 14%, 44%, and 29%, respectively. Here, we demonstrate a modified LPE process that leads to the high-yield production of 2D nanomaterials. [ABSTRACT FROM AUTHOR]