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g-C3N4/ Bio–synthesized silver nanoparticle for fluorometric bio-sensing of acetylcholinesterase and malathion

Ali Abdu Hussen

Advances in Materials Science

2022

Vol. 22, nr 3(73)

23--40

Malathion is widely used in agriculture due to their high efficiency as insecticides. They are very toxic hazardous chemicals to both human health and environment even at low concentration. The detection of pesticides (malathion) at the low levels developed by the environmental protection agency (EPA) still remains a challenge. A highly efficient fluorescent biosensor based on g-C3N4/AgNPs for AChE and malathion detection is successfully developed by impregnation method. The structural and morphological properties of the nanocomposites were characterized by using powder X-ray diffraction (XRD), fourier- transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The analysis confirmed that there is a strong interfacial interaction between g-C3N4 and AgNPs. The fluorescent responses show an increase in intensity upon the additions of AChE which indicates that AChE as enzyme was hydrolyzing the substrate ACh, with the increase in oxidative electron as the preferred route of reaction. The developed OFF-ON sensor immobilizes by Actylcholestrase (AChE) and use as new probe for malathion detection. In the absence of malathion, AChE−g-C3N4/AgNCs exhibit high fluorescence intensity. However, the strong interaction of the basic sites to malathion, causes fluorescence quenching via static quenching and Ag form aggregation on the surface of g-C3N4. The experimental parameter such as pH of buffer (pH=6), concentration of acetylcholine (1 mM) and malathion (500 μM) were optimized. The sensor was also more sensitive with Stern-Volmer quenching constants (KSV) of 3.48x10 3 M -1. The practical use of this sensor for malathion determination in Khat was also demonstrated. The obtained amount of malathion in Khat is 168.8 μM.

Determination of manganese in food by polymer-phase fluorescence quenching method with eosin in the presence of phenanthroline

Jiang Z. T., Li R.

Chemia Analityczna

2008

Vol. 53, No. 5

659-671

A sensitive and selective polymer-phase fluorescence quenching method for determination of trace amounts of manganese in food samples has been developed. The method is based on the reaction between manganese and eosin in the presence of phenanthroline to form a weak-fluorescence compound at pH 8.2. The fluorescence intensity was measured in 5 mm quartz cells at excitation and emission wavelengths of 533 and 550 nm, respectively. There was a satisfactory linear relationship between the fluorescence quenching and concentration of manganese in the range 0.2-3.5 μg in 25 mL of sample solution (i.e. 8-140 μg L-1). Detection limit was 0.03 μg for 25 mL of sample solution and RSD was 1.9%. Coexisting ions did not interfere with the reaction of eosin with manganese. The proposed method was applied to the determination of trace amounts of manganese in millet, black rice, and tea with satisfactory results.

Opracowano czułą i selektywną metodę gaszenia fluorescencji w fazie polimerowej do oznaczania śladowych ilości manganu w żywności. W metodzie wykorzystano reakcję manganu z eozyną w obecności renantroliny. w wyniku której powstaje przy pH 8,2 słabo fluoryzujący związek. Intensywność fluorescencji mierzono w 5 mm komórce kwarcowej przy dł. fal wzbudzenia i emisji wynoszących odpowiednio 533 i 550 nm. Otrzymano dobrą zależność liniową między gaszeniem fluorescencji i stężeniem manganu w zakresie 0.2-3.5 μg w 25 mL roztworu próbki (czyli 8-140 μ g L-1).Wykrywalność wynosiła 0.03 μ g w 25 mL roztworu próbki, a względne odchylenie standardowe - l ,9%. Współ-występujące jony nie przeszkadzały w reakcji eozyny z manganem. Zaprapowaną metodę zastosowano do oznaczania śladowych ilości manganu w prosie, czarnym ryżu i w herbacie uzyskując dobre rezultaty.