Carbon quantum dots (CQDs) are attracting tremendous interest owing to their low toxicity, water dispersibility, biocompatibility, optical properties and wide applicability. Herein, CQDs with an average diameter of (4.0 ± 0.2) nm and high crystallinity were produced simply from the electrochemical oxidation of a graphite electrode in alkaline alcohols. The as-formed CQDs dispersion was colourless but the dispersion gradually changed to bright yellow when stored in ambient conditions. Based on UV-Vis absorption, fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM), this colour change appeared to be due to oxygenation of surface species over time. Furthermore, the CQDs were used in specific and sensitive detection of ferric ion (Fe(3+)) with broad linear ranges of 10-200 μM with a low limit of detection of 1.8 μM (S/N = 3). The application of the CQDs for Fe(3+) detection in tap water was demonstrated and the possible mechanism was also discussed. Finally, based on their good characteristics of low cytotoxicity and excellent biocompatibility, the CQDs were successfully applied to cell imaging.

such as layered transition metal dichalcogenides (TMDs), [2] hexagonal boron nitride (h-BN), [3] metal halides, [4] and black phosphorus, [5] which opened up a new horizon for a novel class of low-dimensional systems with superior properties for applications in optoelectronics, [6] energy conversion, [7] and catalysis. [8] Among these, h-BN nanosheet has its peculiar and fascinating properties such as good electrical insulation, [9] high-temperature stability, [10] high mechanical strength, [11] large thermal conductivity, [12] low toxicity and chemical stability, [13] leading to a variety of potential applications as both structural and electronic materials. [14] With further reducing the size of the layered BN sheets to less than 10 nm, 0D BN quantum dots (BNQDs) with excellent fluorescence properties and good dispersibility can be endowed due to the quantum confinement, edge effects, and defect centers. [13][14][15] Combining with the intrinsic properties of BN, BNQDs were supposed to be promising agents in biological and optoelectronic applications. [15b] However, compared with the widely studied 2D BN nanosheet, [9][10][11]16] BNQDs were much less reported than expected. [13][14][15] First, further exploration is required for the preparation of desired BNQDs products. BNQDs were initially prepared via high intensity ultrasound and subsequent refluxing. [14a] Allwood et al. have also successfully fabricated monolayer BNQDs via three steps of potassium-intercalation, deintercalation, and disintegration of BN edges, but only low quantum yield (QY) of 2.5% was achieved. [15a] Recently, sonication-solvothermal strategy was found to be a facile and universal method for the generation of BNQDs with relatively high QY of 8.6% or 19.5%. [13,15b] Although the filling factor of the autoclave, synthesis temperature and reaction time in the solvothermal process have been investigated, [13] little attention has been paid to how different solvents affect the properties of the BNQDs, which is usually an important parameter to influence the optical properties and QYs of the zero-dimensional QDs. [17] Second, besides the most frequently studied PL properties, electrochemiluminescence (ECL) is also an interesting characteristic Exploration of novel optical features, generation mechanisms, and versatile applicability of boron nitride quantum dots (BNQDs) is still in nascent stage. Herein, BNQDs are prepared using liquid exfoliation-solvothermal treatment of bulk BN in three different solvents. The photoluminescence of BNQDs is blue in ethanol (or N,N-dimethylformamide (DMF)) and green in N-methyl-2-pyrrolidone (NMP) under the same UV-irradiation, respectively.The quantum yields (QYs) and average lateral sizes of the BNQDs are 12.6% and 4.1 ± 0.2 nm, 16.4%, and 2.8 ± 0.3 nm, as well as 21.3% and 2.0 ± 0.2 nm in solvents of ethanol, DMF, NMP, respectively. The distinct sizes, QYs, and optical properties of the BNQDs are found to depend on the polarity of these solvents. Different BNQDs can be chosen on-demand for versatile...

Tungsten oxide (WO ), a new alternative to conventional semiconductor material, has attracted numerous attentions owning to its widespread potential applications. Various methods have been reported for the synthesis of WO nanostructures such as nanowires or nanodots. However, templates or surfactants are often required for the synthesis, which significantly complicate the process and hinder the broad applications. Herein, one-pot template/surfactant-free solvothermal method is proposed to synthesize the WO nanostructures including fluorescent quantum dots (QDs) and bundle-like nanowires simultaneously. The as-prepared WO QDs can be well dispersed in aqueous medium, exhibit excellent photoluminescent properties, and show an average size of 3.25 ± 0.25 nm as evidenced by transmission electron microscopy. Meanwhile, the diameter of the WO nanowires is found to be about 27.5 nm as manifested by the scanning electron microscope images. The generation mechanism for these two WO nanostructures are systematically studied and proposed. The WO QDs have been successfully applied in efficient fluorescent staining and specific ferric ion detection. Moreover, the WO nanowires can be utilized as effective dielectric materials for electromagnetic wave absorption.