Abstract Fabrication of graphene quantum dots (GQDs) often requires strong acids or organic solvents, and their green synthesises on sustainable routes still face challenges. Herein, an eco‐friendly synthetic process has been developed, in which the natural polymer cellulose has been utilized as a new precursor for the first time. The reaction system is only composed of cellulose and water, in absence of any other chemical reagents. Moreover, the products contain only GQDs, carbide precipitates, and water, leading to easy separation and avoiding complicated post‐processes. In addition, the synthetic mechanism is presented that the formation process of GQDs consists of the first hydrolyzation and the following cyclic condensation. With highly photoluminescent (PL) properties, favourable hydrophilicity, low cytotoxicity and excellent biocompatability, the as‐synthesized GQDs have been successfully applied in bioimaging. This work not only develops a sustainable route for the green synthesis of GQDs, but also finds a renewable resource as the raw material, which significantly facilitates the extensive applications of GQDs in biological fields.
With the development of science and technology, renewable energy for electricity plays an increasingly important role in people's lives. In order to provide users with high-quality services and environmentally friendly and energy-saving products, the use of Internet technology is particularly meanin
Using natural wattle bark tannin, a kind of stable, nontoxic, fluorescent carbon quantum dots (CQDs) was hydrothermally fabricated and applied as a multifunctional fluorescent nanomaterial for the determination of heavy metal ions (Cr6+ and Co2+), bio-imaging, and fluorescent ink applications. The CQDs could be assembled with polyvinyl alcohol (PVA) through hydrogen bonding to yield a composite fluorescent hydrogel that can be integrated with a smartphone to constitute a novel and convenient intelligent detection system for the rapid (10 s) real-time monitoring of Cr6+. Both the CQDs (with 1.37 μM of LOD (limit of detection)) and CQDs-PVA hydrogel (with 3.36 mg/L of LOD) sensing systems produced fast, sensitive, and selective response to Cr6+ based on the internal filtering effect and electron-transfer effect. The practicability of the CQDs-PVA fluorescence sensor was demonstrated by determining tap water and tanning wastewater samples. Based on their satisfactory fluorescence stability and solubility, the CQDs were further used for HeLa-cell imaging and as fluorescent ink for information encryption. When HeLa cells were incubated for 24 h in CQDs at a high concentration of 200 mg/L, the cell survival remained as high as 90%, and a clear fluorescence image was observed under a laser confocal fluorescence microscope. The CQD solution could be written directly as fluorescent ink on TLC (thin layer chromatography) paper, and the handwritings were invisible after drying, confirming their application potential in the field of information encryption. In summary, the present CQDs derived from wattle bark tannin exhibited excellent stability, sensitivity, and specificity in heavy metal ion sensing and also had great potential in bio-imaging and information encryption applications.
A simple hydrothermal method was conducted to transform chrome shavings (CS) into carbon quantum dots (CS-CQDs) that were then applied as supersensitive chemical sensors for the detection of Cr6+ (1.40 μM limit of detection (LOD)) and Fe3+ (1.67 μM LOD) ions. Meanwhile, most of the chromium in CS deposited in the resulting precipitate, realizing the separation and recovery of chromium. CS-CQDs were further used to prepare an "intelligent fluorescent switchable sensor" (IFSS) hydrogel with high sensitivity for the identification of Cr6+ in tannery wastewater (LOD of 45.59 μmol/L). Interestingly, the quenched IFSS-Cr6+ hydrogel system could be applied to determine ascorbic acid (AA) with a LOD of 21.33 μmol/L, owing to the reduction of Cr6+ into Cr3+ by AA and thus the IFSS's fluorescence regeneration. This ″fluorescent on/off″ effect could be recycled at least four times. IFSS hydrogel also could adsorb Cr6+ ions (13.50 mg/g) and is done so after the reduction by AA. The possible sensing mechanism to Cr6+ was confirmed to be the internal filtration effect and electron transfer. This work not only developed a feasible and clean recycling method of CS but also produced a smart functional material for the determination and separation of Cr6+, achieving "turning trash into treasure".
Mussel-inspired surface modification has received significant interest in recent years because of its simplicity and versatility. The deposition systems are still mainly limited to molecules with catechol chemical structures. In this paper, we report a novel deposition system based on a monophenol, vanillic acid (4-hydroxy-3-methoxybenzoic acid), to fabricate metal–phenolic network coatings on various substrates. The results of the water contact angle and zeta potential reveal that the modified polypropylene microfiltration membrane is underwater superhydrophobic and positively charged, showing applications in oil/water separation and dye removal. Furthermore, the single-face modified Janus membrane is promising in switchable oil/water separation. The results demonstrate a novel example of the metal–monophenolic deposition system, which expands the toolbox of surface coatings and facilitates the understanding of the deposition of phenols.
Double perovskite Cs 2 AgInCl 6 is a new direct band gap semiconductor material. Compared with traditional perovskite CsPbX 3 (X=Cl, Br, I), double perovskite Cs 2 AgInCl 6 has better stability and wider fluorescence half peak width. This study reports the mechanochemical synthesis, characterization and application of a lead-free double perovskite Cs 2 AgInCl 6 doped with Na and Bi ions. It was found that through a facile room temperature mechanical ball milling process, the double perovskite structure can be obtained within 30 minutes. Then, Na and Bi ions were used to dope to optimize its luminescence properties. By this synthesis method, the sample with the best doping ratio obtained in the experiment is Cs 2 Ag 0.7 Na 0.3 In 0.9 Bi 0.1 Cl 6 , whose photoluminescence quantum yield (PLQY) reaches 32.7%. The X-ray diffraction (XRD) and photoluminescence (PL) results show that Na and Bi ions can promote the crystallization and optimize the luminescence properties of Cs 2 AgInCl 6 . The theoretical calculation results show that both conduction band minimum (CBM) and vlance band maximum (VBM) of Cs 2 Ag 0.7 Na 0.3 In 0.9 Bi 0.1 Cl 6 are flat, which is favorable for the generation of self-trapped excitons. Packaging Cs 2 Ag 0.7 Na 0.3 In 0.9 Bi 0.1 Cl 6 sample on a UV LED chip, and a warm white LED with good performance can be obtained, which shows a bright potential application in the field of white LED.
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