One-step hydrothermal synthesis of fluorescent silicon nanoparticles for sensing sulfide ions and cell imaging

β-Galactosidase-triggered in situ synthesis of yellow emitting silicon nanoparticle and its application in visual detection of E. coli O157:H7 and drug susceptibility test

The sensitive detection of foodborne pathogenic and rapid antibiotic susceptibility testing (AST) is of great significance. This paper reports the enzyme-triggered in situ synthesis of yellow emitting silicon nanoparticles (SiNPs) and the detection of Escherichia coli (E. coli) O157:H7 in food samples and the rapid AST. The rapid counting of E. coli O157:H7 has been achieved through direct visual observation, equipment detection, and smartphone digitalization. A simple detection platform based on smartphone senses and cotton swabs has been established. Meanwhile, rapid AST based on enzyme-catalyzed SiNPs can intuitively obtain colorimetric samples. This paper established a system for bacterial enzyme-triggered in situ synthesis of SiNPs, with high responsiveness, luminescence ratio, and specificity. The detection limit for E. coli O157:H7 can reach 100 CFU/mL during 5 h, and the recovery efficiency ranges from 90.14% to 110.16%, which makes it a promising strategy for the rapid detection of E. coli O157:H7 and AST.

Simple fluorescence "turn-off" assay for Congo red using commercial 2-aminophthalic acid

In this work, the fluorescence properties of 2-aminophthalic acid (NH2-BDC) were studied. NH2-BDC possessed excellent optical properties including bright blue emission with maximum emission at 425 nm, a high quantum yield of 38.49% and excellent photostability. And the fluorescence of NH2-BDC could be selectively quenched by Congo red, which was ascribed to the inner filter effect. Accordingly, NH2-BDC was further employed for fluorescence "turn-off" assay of Congo red with a linear range of 0.05-50 μM and a limit of detection of 1.72 μM. And the sensor was used for the detection of Congo red in real water samples with acceptable results.

A photo-controlled fluorescent switching based on carbon dots and photochromic diarylethene for bioimaging

Carbon dots (CDs) as luminescent zero-dimensional carbon nanomaterials have good aqueous dissolution, photostability, high quantum yield, and tunability of emission color. It has great application potential in many fields, including bioimaging, labeling of biological species, drug delivery, and sensing in biomedical. However, controlling the fluorescence emission of carbon dots remains a formidable challenge. Herein, we designed and exploited a photo-controlled fluorescent switching based on photochromic diarylethene (DT) and CDs for bioimaging. It could be modulated reversibly between "ON" and "OFF" under UV/vis light exposure. The fluorescent modulation efficiency was as high as 95.3%. The fluorescent switching could be used to the bioimaging in HeLa cells with low cell toxicity. Therefore, this fluorescent switching could be a promising candidate in many potential application areas, especially in bioimaging.

Carbon quantum dots for fluorescent detection of nitrite: A review

NO₂^- is commonly found in foods and the environment, and excessive intake of NO₂^- poses serious hazards to human health. Thus, rapid and accurate assay of NO₂^- is of considerable significance. Traditional instrumental approaches for detection of NO₂^- faced with limitations of expensive instruments and complicated operations. Current gold standards for sensing NO₂^- are Griess assay and 2,3-diaminonaphthalene assay, which suffer from slow detection kinetics and bad water solubility. The newly emerged carbon quantum dots (CQDs) exhibit integrated merits including easy fabrication, low-cost, high quantum yield, excellent photostability, tunable emission behavior, good water solubility and low toxicity, which make CQDs be widely applied to fluorescent assay of NO₂^-. In this review, synthetic strategies of CQDs are briefly presented. Advances of CQDs for fluorescent detection of NO₂^- are systematically highlighted. Lastly, the challenges and perspectives in the field are discussed.

Facile one-pot synthesis of fluorescent aminoclay and the applications for fluorescence sensing Cr2 O7 2

Here, we developed a facile one-pot strategy for the fabrication of fluorescent aminoclay (F-AC) through in situ solvothermal treatment of 3-aminopropyltrimethoxysilane, MgCl2 , and sodium ascorbate at 180°C for 6 h. The obtained F-AC exhibited blue emission, good water solubility, and satisfactory photostability. It was observed that Cr2 O7 2- could selectively quench the fluorescence of F-AC through the inner filter effect and static quenching process. As a result, a novel fluorescent F-AC-based nanosensor was constructed with good linearity in the range 0.1-75 μM. The nanosensor was successfully applied in real water samples with satisfactory results. This work not only provides a novel nanosensor for Cr2 O7 2- , but also highlights the F-AC's promising applications in wider fields due to the versatility and simplicity of the preparation strategy.

Bifunctional Nitrogen and Fluorine Co-Doped Carbon Dots for Selective Detection of Copper and Sulfide Ions in Real Water Samples

Copper ions (Cu²⁺) and sulfur ions (S²⁻) are important elements widely used in industry. However, these ions have the risk of polluting the water environment. Therefore, rapid and quantitative detection methods for Cu²⁺ and S²⁻ are urgently required. Using 2,4-difluorobenzoic acid and L-lysine as precursors, nitrogen and fluorine co-doped dots (N, F-CDs) were synthesized in this study via a hydrothermal method. The aqueous N, F-CDs showed excellent stability, exhibited satisfactory selectivity and excellent anti-interference ability for Cu²⁺ detection. The N, F-CDs, based on the redox reactions for selective and quantitative detection of Cu²⁺, showed a wide linear range (0–200 μM) with a detection limit (215 nM). By forming the N, F-CDs@Cu²⁺ sensing platform and based on the high affinity of S²⁻ to Cu²⁺, the N, F-CDs@Cu²⁺ can specifically detect S²⁻ over a linear range of 0–200 μM with a detection limit of 347 nM. In addition, these fluorescent probes achieved good results when used for Cu²⁺ and S²⁻ detection in environmental water samples, implying the good potential for applications.