Yellow-emissive carbon dots as a fluorescent probe for chromium(VI).

The authors describe a one-step method for the preparation of yellow fluorescent carbon dots (CDs) starting from 4-aminoacetanilide hydrochloride and 4-acetamidobenzaldehyde. The CDs have excitation/emission peaks at 470/550 nm, good water solubility, salt-tolerance and photostability. Their fluorescence is quenched by hexavalent chromium [Cr(VI)] via static quenching. Fluorescence intensity drops linearly in the 1 to 400 µM Cr(VI) concentration range, and the limit of detection is 0.13 µM. This method is selective for Cr(VI) over potential metal ion interferences and was successfully applied to the detection of Cr(VI) in spiked water and biological tissue samples. Recoveries from spiked samples ranged from 97.7% to 103.8%. Graphical abstract Schematic presentation of (a) the preparation of the CD fluorescent probe and (b), the principle of Cr(VI) determination.

Synthesis of orange-red emissive carbon dots for fluorometric enzymatic determination of glucose.

The authors describe a method for the preparation of orange-red emissive carbon dots (CDs) with excitation/emission peaks at 520/582 nm. The CDs were hydrothermally prepared by a one-pot strategy from trimesic acid and 4-aminoacetanilide. The fluorescence of the CDs is strongly quenched by hydrogen peroxide. The oxidation of glucose by glucose oxidase (GOx) produces H2O2 that quenches the fluorescence via static quenching. Based on this phenomenon, a fluorometric method was established for the determination of glucose. Under the optimum conditions, response is linear in the 0.5 to 100 µM glucose concentration range, with a 0.33 µM limit of detection. The method is selective for glucose over its analogues and was successfully applied to the determination of glucose in diluted human serum and in urine from diabetics and healthy individuals. Recoveries from spiked samples range from 98.7 to 102.5%. Graphical abstract (a) One-step synthetic strategy of the CDs; (b) Schematic illustration of the CDs for glucose detection.

Target triggered fluorescence "turn-off" of silicon nanoparticles for cobalt detection and cell imaging with high sensitivity and selectivity.

Cobalt ions (Co2+) are among heavy metals ions which cause pollution in environment because of their toxicity and improper degradation. In this work, a new fluorescent approach based on silicon nanoparticles (Si NPs) was designed for Co2+ detection. The fluorescent Si NPs were prepared by mixing 3-aminopropyl trimethoxysilane (APTES) and basic fuchsin, and under the excitation of 400 nm, they emitted green fluorescence at 515 nm. The prepared Si NPs were highly soluble in water, stable to salt and pH, and their fluorescence emission was extremely constant, with the quantum yield of 2.28%. The detailed mechanism studies showed that Co2+ effectively quenched the fluorescence of Si NPs by forming static complex. After optimizing the reaction parameters, a good linear relationship for Co2+ was observed from 0.2 to 60 µM, and the limit of detection was 0.14 µM that is lower than the guideline announced by Department of Environmental Protection for drinking water (1.7 µM). The preparation method of Si NPs was cheap, rapid and simple, and the fluorescent approach was applied to determine Co2+ in Yellow river water, drinking water, and industrial wastewater. Moreover, the Si NPs has good response to exogenous Co2+ in HepG2 cell imaging.