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A novel organic-inorganic nile-blue - CeO

A novel organic-inorganic nile-blue - CeO2 (CeO2/NB) nanohybrid has been synthesized by environmentally benign ultrasonic irradiation method for the selective determination of the environmental pollutant, carcinogenic hydrazine (HZ) in environmental water samples. Hydrophobic dyes have generally been as redox mediators in electrochemical sensors fabrication due to strong electron transfer capacity and they would allow the oxidation and reduction of the analytes at lower potentials. The CeO2 nanoparticles were initially synthesized by the ultrasonic irradiation of Ce(NO3)2, NH4OH and ethylene glycol mixture for 6 h using probe sonicator (20 kHz, 100 W) followed by calcination. The organic-dye NB was then added and ultrasonicated further 30 min for the formation of CeO2/NB nanohybrid material. Various spectroscopic and microscopic tools such as UV–vis and FT-IR spectroscopy, XRD, SEM and high-solution TEM and surface analysis tool Brunauer-Emmett-Teller (BET) confirm the formation of the nanohybrid. HR-TEM images showed the well-covered CeO2 on NB molecules and the average size of the nanohybrid is ~35 nm. For the fabrication of environmental pollutant electrochemical sensor, the prepared CeO2/NB nanohybrid was drop-casted on the electrode surface and utilized for the determination of HZ. The nanohybrid modified electrode exhibits higher electrocatalytic activity by showing enhanced oxidation current and less positive potential shift towards HZ oxidation than the bare and individual CeO2 and NB modified electrodes. The fabricated sensor with excellent reproducibility, repeatability, long-term storage stability and cyclic stability exhibited the sensational sensitivity (484.86 µA mM−1 cm−2) and specificity in the presence of 50-fold possible interfering agents with the lowest limit of detection of 57 nM (S/N = 3) against HZ. Utilization of the present sensor in environmental samples with excellent recovery proves it practicability in the determination of HZ in real-time application.

The present work describes the highly selective and sensitive determination of vitamin B1 (thiamine) using 4-amino-6-hydroxy-2-mercaptopyrimidine capped gold nanoparticles (AHMP-AuNPs) by spectrofluorimetry. The AHMP-AuNPs were synthesized by wet chemical method and were characterized by HR-TEM, XRD, UV-visible, zeta potential and spectrofluorimetry. They show emission maximum at 781 nm while exciting at 520 nm and a large stock shift (261 nm) with a narrow emission profile and good photostability. While adding 0.15 μM thiamine, the red color solution of AHMP-AuNPs changes to purple and the absorbance at 520 was decreased. This is due to the aggregation of AHMP-AuNPs and it was confirmed by HR-TEM. No change in absorbance was observed in the UV-visible spectra for AHMP-AuNPs in the presence of less than micromolar concentration of thiamine. On the other hand, the emission intensity of AHMP-AuNPs was enhanced even in the presence of picomolar concentration of thiamine. Based on the enhancement of emission intensity, the concentration of thiamine was determined. Interestingly, no change in the emission intensity was observed while adding even milli molar concentration of other vitamin B complexes. The present fluorophore showed an extreme selectivity towards the determination of thiamine in the presence of 10 000 fold common interferents including vitamin B2, B3, B6, B9 and vitamin C while the presence of cysteine and glutathionine interferes for the determination of thiamine. A good linearity was observed from 10 to 120 × 10−12 M thiamine and a detection limit was found to be 6.8 fM L−1 (S/N = 3). The present method was successfully used for the determination of thiamine in human blood serum samples.

Hydroquinone (HQ), a phenolic compound is expansively used in many industrial applications and due to the utilization of HQ, water pollution tragedies frequently found by the improper handling and accidental outflows. When HQ is adsorbed directly through the skin that create toxic effects to human by affecting kidney, liver, lungs, and urinary tract and hence, a highly selective and sensitive technique is required for its quantification. Herein, we have developed the ultrasonic synthesis of copper oxide nanoflakes (CuO-NFs) using ultrasonic bath (20 kHz, 100 W) and successfully employed for the sensitive detection of the environmental hazardous pollutant HQ. The formed CuO-NFs were confirmed by X-ray diffraction, field emission scanning electron microscopy (FE-SEM), FT-IR spectroscopy and UV–visible spectroscopy and fabricated with the screen-printed carbon electrode (SPCE). The SEM images exhibited the uniform CuO-NFs with an average width of 85 nm. The linker-free CuO-NFs fabricated electrode showed the appropriate wide range of concentrations from 0.1 to 1400 µM and the limit of detection was found to be 10.4 nM towards HQ. The fabricated sensor having long term stability and sensitivity was successfully applied for the environmental and commercial real sample analysis and exhibited good recovery percentage, implying that the SPCE/CuO-NFs is an economically viable and benign robust scaffold for the determination of HQ.