Photoluminescent organosilane-functionalized carbon quantum dots (CQDs), 3.0–3.5 nm in diameter, were synthesized via a facile hydrothermal method using citric acid monohydrate as a precursor and N-(3-(trimethoxysilyl) propyl) ethylenediamine as a coordinating and passivation agent. The optical properties of the as-obtained CQDs were investigated in detail. The CQD aqueous solution emits bright blue-white light under ultraviolet (UV) illumination with a quantum yield of 57.3% and high red-green-blue (RGB) spectral composition of 60.1%, and in particular the CQDs exhibit excitation-independent photoluminescence. The CQDs have a narrow size distribution around 3.1 nm and good film-forming ability through simple heat-treatment. By virtue of these excellent optical characteristics and good film-forming ability, a white light-emitting device (LED) was fabricated by combining a UV-LED chip with a single CQD phosphor film, which exhibited cool white light with a CIE coordinate of (0.31, 0.36), a color rendering index of 84 and a correlated color temperature of 6282 K. In addition, the white LED exhibits good optical stability under various working currents and for different working time intervals. Moreover, the interaction between the carbogenic core and surface groups was discussed using the DMol³ program based on density functional theory. This research suggests the great potential of CQDs for solid-state lighting systems and reveals the effect of the surface state on the photoluminescent mechanism of CQDs.

Highly fluorescent water-soluble and nitrogen-doped carbon dots (NCDs) were synthesized by a simple one-pot hydrothermal method using citric acid as carbon source and urea as nitrogen source. Quantum yield of NCDs reaches 42.2%. As-obtained NCDs show a strong emission at 440 nm with an optimum excitation at 355 nm, and exhibit high photostability and excitation-independent photoluminescence (PL) behavior under excitation at 240–380 nm. However, such NCDs show excitation-dependent PL behavior under excitation of 380–480 nm. Because of the Hg²⁺-induced fluorescence quenching of carbon dots (CDs), such NCDs can be used as an effective fluorescent nanoprobe for highly selective and sensitive detection of Hg²⁺ in aqueous solution, with a limit of detection (LOD) as low as 2.91 nM in a linear range of 0–50 nM. The NCDs offer a rapid detection of Hg²⁺ with one-step rapid operation within 5 min. Further, as-prepared NCDs also exhibit high sensitivity towards Hg²⁺ in tap water and mineral water samples. The linear ranges of detection are both 0–50 nM. The LODs in tap water and mineral water samples are as low as 2.88 nM and 2.87 nM, respectively.

A one-pot microwave-assisted hydrothermal approach was developed to quickly synthesize organosilane-functionalized carbon dots (Si-CDs) within 5 minutes. With the assistance of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KH-792) as distance barrier chains, aggregation-caused quenching is suppressed successfully, which contributes to the emission of bright blue fluorescence by solid-state Si-CDs (λ_em ∼ 454 nm). The photoluminescence quantum yield of the as-prepared Si-CDs in the solid state reaches 65.8% with an optimized molar ratio of the reactant citric acid to KH-792 of 1 : 5 and a reaction temperature of 180 °C, which is 2.5-fold that of their solution. Together with their good film-forming ability and thermal stability, Si-CDs were applied to fabricate a white-light-emitting device with color coordinates of (0.32, 0.36) and a correlated color temperature of 6071 K. Our results indicate that the as-prepared Si-CDs are promising materials with efficient solid-state emission to be used in lighting, backlight displays and other optoelectronic devices.

Temperature and magnetism bi-responsive molecularly imprinted polymers (TMMIPs) based on Fe3O4-encapsulating carbon nanospheres were prepared by free radical polymerization, and applied to selective adsorption and controlled release of 5-fluorouracil (5-FU) from an aqueous solution. Characterization results show that the as-synthesized TMMIPs have an average diameter of about 150 nm with a typical core-shell structure, and the thickness of the coating layer is approximately 50 nm. TMMIPs also displayed obvious magnetic properties and thermo-sensitivity. The adsorption results show that the prepared TMMIPs exhibit good adsorption capacity (up to 96.53 mg/g at 25 °C) and recognition towards 5-FU. The studies on 5-FU loading and release in vitro suggest that the release rate increases with increasing temperature. Meanwhile, adsorption mechanisms were explored by using a computational analysis to simulate the imprinted site towards 5-FU. The interaction energy between the imprinted site and 5-FU is -112.24 kJ/mol, originating from a hydrogen bond, Van der Waals forces and a hydrophobic interaction between functional groups located on 5-FU and a NIPAM monomer. The electrostatic potential charges and population analysis results suggest that the imprinted site of 5-FU can be introduced on the surface of TMMIPs, confirming their selective adsorption behavior for 5-FU.