Fluorescent sensing system based on molecularly imprinted phase-change microcapsules and carbon quantum dots for high-efficient detection of tetracycline

Aiming at enhancing the detection efficiency and identification accuracy of tetracycline under a high-temperature condition, this study focuses on an innovative fluorescent sensing system (MIP@CQD-PCM) based on molecularly imprinted phase-change microcapsules along with the carbon quantum dots (CQDs) embedded in their shell. This system was fabricated by microencapsulating n-eicosane as a phase change material (PCM) core within a CQDs-embedded SiO₂ shell, followed by coating a tetracycline-templated molecularly imprinted polymer (MIP) layer onto the surface of the SiO₂ shell. The specific recognition sites to tetracycline molecules were finally achieved by removal of tetracycline template from the MIP layer. Comprehensive characterizations and investigations on the structure and performance of the fluorescent sensing system were given to confirm its successful fabrication in accordance to our design strategy. The resultant MIP@CQD-PCM exhibits a satisfactory thermal storage capacity and phase-change cycle stability for temperature regulation and thermal management applications under a phase-change enthalpy of over 162 J/g. Most of all, a typical fluorescence-quenching effect was obtained from the combination of the CQDs embedded in the SiO₂ shell and the tetracycline molecules adsorbed in the MIP layer. This makes the MIP@CQD-PCM achieve an enhanced capability for the fluorescence identification of tetracycline in a high-temperature environment through the in situ thermal management of its PCM core. The MIP@CQD-PCM also displays high selectivity and good reusability for tetracycline detection in industrial applications. This work provides a promising strategy for the design and development of fluorescent sensing systems with high recognition efficiency and identification accuracy in the detection of hazardous substances.

Hydrothermally Green Synthesized Nitrogen-Doped Carbon Dots from Phyllanthus emblica and Their Catalytic Ability in the Detoxification of Textile Effluents

A facile method for reduction of textile effluents (TEff) using fluorescent nitrogen-doped carbon dots (N-CDs) has been developed and reported here. The synthesis of N-CDs was done by a hydrothermal carbonization method using the aqueous extract of Phyllanthus emblica (P. emblica) fruit as a carbon source and aq NH3 as a nitrogen dopant. Various analytical techniques have been employed for the characterization of N-CDs. The size of the synthesized N-CDs was found to be 4.08 nm, which was confirmed by high-resolution transmission electron microscopy analysis. The graphitic character of the N-CDs was studied by using selected area energy diffraction pattern and Raman spectroscopy studies. Under the excitation of 320 nm, an intense blue fluorescence was emitted by N-CDs of around 400 nm. From the obtained results of energy-dispersive spectrometry, EDAX, and Fourier transform infrared studies, it was confirmed that nitrogen was doped over the N-CD surface. Finally, the catalytic ability of NaBH4 was found to be enhanced remarkably by the synthesized CDs in the detoxification of TEff.

Poly(pyrrole-co-o-toluidine) wrapped CoFe2O4/R(GO–OXSWCNTs) ternary composite material for Ga3+ sensing ability

A ternary P(Py-co-OT)/CF/R(GO–OXSWCNTs) nanocomposite has been fabricated as a novel conductive hybrid material with high stability and excellent electrochemical Ga³⁺ sensing ability.

Ultra-highly fluorescent N doped carbon dots-CdTe QDs nanohybrids with excitation-independent emission in the blue-violet region

Luminescent carbon dots (CDs) are of significant practical application interest such as in optoelectronic devices and sensitive probing in the life science and environment fields. In this study, N doped CDs-CdTe quantum dots (QDs) nanohybrids (CdTe/N-CDs) were synthesized by a plasma heating process using silk fibroin and CdTe QDs as precursors. The synthesis, doping, hybridizing and passivation of the CdTe/N-CDs were carried out in a single-step process. The as-synthesized CdTe/N-CDs dispersed in ethanol exhibited blue-violet photoluminescence with excitation-independent emission characteristics (strong emissions at 405 nm and 429 nm, and a weak emission at 456 nm). Additionally, the optimal excitation wavelength for the CdTe/N-CDs was found at 360–380 nm, which very closely matches the intrinsic wavelength of GaN-based LEDs. Furthermore, the obtained CdTe/N-CDs exhibited a very high quantum yield of ∼84%, showing great potential in developing chip-based high performance optoelectronics devices. The emission mechanism and emission enhancement by related factors including N-bonded configurations in the carbon base and the transfer of photo-excited electrons from the CdTe QDs to the N doped CDs were studied, as well.

The photoluminescence quantum yield of N-doped carbon dots was brought up to 84% by hybridizing with CdTe QDs.

Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells

Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells.

High-performance oxygen reduction catalyst derived from porous, nitrogen-doped carbon nanosheets

A facile, self-foaming strategy is reported to synthesize porous, nitrogen-doped carbon nanosheets (N-CNSs) as a metal-free electrocatalyst for oxygen reduction reaction (ORR). Benefiting from the synergistic functions of N-induced active sites, a highly specific surface area and continuous structure, the optimal N-CNS catalyst exhibits Pt-like ORR activity (positive onset potential of ∼0 V versus Ag/AgCl and limiting current density of 5 mA cm(-2)) through a four-electron transfer process in alkaline media with excellent cycle stability and methanol tolerance. This work not only provides a promising metal-free ORR catalyst but also opens up a new path for designing carbon-based materials towards broad applications.

A new turn on coumarin-based fluorescence probe for Ga(3+) detection in aqueous solution

The probe CT was synthesized and investigated as a novel label-free chemosensor for Ga(3+) detection in water. Probe CT showed remarkable selectivity and sensitivity for Ga(3+) in Tris-HCl aqueous buffer solution (pH7.0). The chemosensor responded rapidly to Ga(3+) with a 1:1 stoichiometry. Meanwhile, the unapparent changes of fluorescence lifetime decays suggest the turn-on process of probe CT by Ga(3+) which appears to be a static mechanism.