Blue Carbon Quantum Dots Research Articles

Synthesis of Red, Green, and Blue Carbon Quantum Dots and Construction of Multicolor Cellulose‐Based Light‐Emitting Diodes

Synthesis of Red, Green, and Blue Carbon Quantum Dots and Construction of Multicolor Cellulose‐Based Light‐Emitting Diodes

Synthesis of Red, Green, and Blue Carbon Quantum Dots and Construction of Multicolor Cellulose‐Based Light‐Emitting Diodes

Light‐emitting diodes (LEDs) are widely used in lighting and display applications. Carbon quantum dots (CQDs), which have high biocompatibility, high resistance to photobleaching, and full‐spectrum luminescence, have inherent advantages as fluorescent materials for LED devices. Herein, multicolor CQDs are prepared by a new reagent engineering strategy due to the difference of effective conjugate length and the surface electron‐withdrawing groups of CQDs. White CQDs are realized by mixing blue, green, and red CQDs proportionally. Then, the aggregation‐caused quenching phenomenon of CQDs is suppressed through the hydrogen‐bonding network of cellulose nanofibrils (CNFs). Multicolor fluorescent films are prepared from CQDs and CNFs by simple mixing and casting methods. Finally, thin‐film encapsulation based on the photosensitive resin ABPE‐10 coating can be realized and rapidly assembles into fluorescent films with different light‐emitting colors into LED devices, leading to have superior thermal performance compared with conventional LEDs. White LEDs have excellent white‐light illumination performance, with Commission Internationale de L’Eclairage color coordinates of (0.33, 0.37), a correlated color temperature of 5688 K, and a color rendering index of 86. This strategy provides a convenient and scalable pathway for low‐cost, environmentally friendly, and high‐performance CQDs‐based LEDs.

Dual-wavelength ratiometric immunosensor for Bacillus cereus: Oxidase-like MnO2-Au trigged “OFF-ON” detection strategy

As an opportunistic pathogen, Bacillus cereus (B. cereus) has caused increasing emetic and diarrheal food poisoning, even fulminant hepatic failure and death case. Herein, a mimetic oxidase-mediated ratiometric fluorescence enzyme-linked immunosorbent assay (ELISA) was developed to detect B. cereus. In this system, 3D MnO2-Au nanoflowers with layered crystalline structure can oxidize o-phenylenediamine (OPD) to generate a fluorescence peak at 570 nm (I570, response signal), while blue carbon quantum dots (bCDs) display a fluorescence peak at 455 nm (I455, reference signal). Under the effect of fluorescence resonance energy transfer (FRET), the response signal increased while the reference signal was weakened. By using MnO2-Au as the mimetic oxidase to replace the horseradish peroxidase and associate with antibody in traditional ELISA, a linear relationship was established between the ratiometric fluorescence signal (I570/I455) and the logarithm of B. cereus concentrations in the range from 1.7 × 102 to 3.3 × 106 CFU/mL. Comparing with conventional sandwich ELISA, the detection time was shortened by 43 min and the sensitivity was improved by 5-folds, indicating that the proposed ratiometric immunoassay holds great potential as a rapid and convenient tool for sensitive screening of B. cereus.

Sandwich Fluorescence Detection of Foodborne Pathogen Staphylococcus aureus with CD Fluorescence Signal Amplification in Food Samples.

Timely detection of Staphylococcus aureus (S. aureus) is critical because it can multiply to disease−causing levels in a matter of hours. Herein, a simple and sensitive DNA tetrahedral (Td) fluorescence signal amplifier with blue carbon quantum dots (bCDs) was prepared for sandwich detection of S. aureus. bCD was modified at the apex of Td, and an aptamer on Td was used to accurately identify and “adsorb” the amplifier to the surface of S. aureus. Atomic force microscopy (AFM) demonstrates the successful preparation of this signal amplifier. The fluorescence intensity emitted in this strategy increased 4.72 times. The strategy showed a stronger fluorescence intensity change, sensitivity (linear range of 7.22 × 100–1.44 × 109 CFU/mL with a LOD of 4 CFU/mL), and selectivity. The recovery rate in qualified pasteurized milk and drinking water samples was 96.54% to 104.72%. Compared with simple aptamer sandwich detection, these fluorescence signal amplifiers have improved fluorescence detection of S. aureus. Additionally, this fluorescent signal amplification strategy may be applied to the detection of other food pathogens or environmental microorganisms in the future.

Full color fluorescent carbon quantum dots synthesized from triammonium citrate for cell imaging and white LEDs

Multicolor fluorescent carbon quantum dots (CDs) exhibit prospective applications but the intrinsic reaction and luminescence mechanisms of CDs remain unclear. In this work, full color fluorescent CDs were synthesized through a facile solvothermal treatment with triammonium citrate as the carbon source. By adjusting the reaction temperature, the maximum emission wavelength is tuned from 440 nm for blue CDs (B-CDs) to 625 nm for red CDs (R-CDs), covering the whole visible spectrum range. The emission mechanism is proposed as surface-state-controlled, which results from different degrees of graphitization and increasing of functional groups on the surfaces. Three different surface states are derived from the overlap of the absorption and excitation spectra and the mechanism is established by XRD, Raman, XPS and UV–Vis absorption. The full-color luminescent CDs with high light and pH stability as well as good biocompatibility are successfully employed to image HeLa cells. White LED is fabricated by B-, G-, and R-CDs/polymer films with a near ultraviolet (NUV) semiconductor chip. The results of this research demonstrate that the synthesized CDs can be potentially applied in multi-color displays, white LEDs and biological imaging probes.

A simple method for the preparation of multi-color carbon quantum dots by using reversible regulatory color transformation.

It is known that polychromatic carbon quantum dots (CQDs) can be obtained by doping and surface modification. The layer-wise synthesis of blue and green emitting CQDs (with typical sizes between 3 and 6nm) is described here by adding oxalic acid and by introducing polycarboxy groups. By changing the external environment, the emission of CQDs can be adjusted in the blue-green spectral region (469-527nm) under photoexcitation at 405nm. The findings presented here provide new directions for the reversible regulatory transformation of polychromatic CQDs. The luminescence also is affected by a variety of conditions such as surface defects, degree of polymerization, polarity of external solutions, and hydrogen bonding which is studied in some detail. Graphical abstract Schematic presentation of the blue-green fluorescent transformation of the green carbon quantum dots(G-CQDs) to blue carbon quantum dots(B-CQDs).