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In the present study, a food additive, tert-butylhydroquinone (TBHQ), was selectively and sensitively determined by both colorimetric and spectrofluorimetric methods using bovine serum albumin capped gold nanoclusters (BSA-AuNCs) for the first time. The AuNCs were synthesized by a one-pot method using BSA as a stabilizing agent in an alkaline medium at room temperature. The synthesized BSA-AuNCs were then confirmed by UV-vis spectroscopy, fluorimetry and HR-TEM. The absence of a surface plasmon resonance band and appearance of red luminescence in a UV chamber confirmed the formation of AuNCs. The HR-TEM images exhibited the average size of BSA-AuNCs as 1.8 nm. The BSA-AuNCs showed an emission maximum at 663 nm and were utilized for the colorimetric and fluorimetric detection of TBHQ. The addition of 50 μM TBHQ to the BSA-AuNCs leads to the disappearance of the red luminescence as well as the quenching of the emission at 663 nm. This is due to the strong electrostatic interaction between TBHQ and BSA-AuNCs and it was confirmed from the decrease in the zeta potential value from −43.7 to −0.9 mV. The emission intensity of the BSA-AuNCs does not change when adding higher concentrations of major interferents including propyl gallate, butyl hydroxyltoluene, butyl hydroxyanisole and metal ions. On the other hand, the emission intensity decreases when increasing the concentration of TBHQ from 2.5 to 50 μM and the limit of detection was found to be 72 nM (S/N = 3). The practical application of the BSA-AuNCs was determined in oil samples for determining TBHQ and the results were validated with the GC-MS method.

Herein, we present the electrochemical scaffold for the quantification of acetaminophen (ACAP) using a silver phosphate nanoparticle (Ag–P NP) fabricated screen-printed carbon electrode (SPCE). The...

An efficient electrochemical biosensor has been developed for the simultaneous evaluation of DNA bases using AgNPs-embedded covalent organic framework (COF). The COF (p-Phenylenediamine and terephthalaldehyde) was synthesized by reflux (DMF; 150 °C; 12 h) and the nanoparticles were embedded from the aqueous solutions of AgNO

In this study, controlled growth of Ni-MOF was decorated in amino acid-functionalized graphene nanoplatelets (FxGnP) by a solvothermal approach. The synthesized nanocomposite was characterized by various spectral, microscopic, and electrochemical techniques. FE-SEM and TEM image results exhibited the sheet-like structure of FxGnP and spherical-like Ni-MOF with an average size of 5.6 μm. Appreciably, the size of Ni-MOF was reduced to ∼2.3 μm while introducing the FxGnP. The presence of a large number of hydroxyl and epoxy functional groups of FxGnP acts as a nucleation center and restricted the uncontrolled growth of Ni-MOF. The FxGnP-Ni-MOF composite was modified on GCE and then utilized for the oxidation of bisphenol A (BPA). The nanocomposite material showed a sharp peak at +0.38 V vs. Ag/AgCl (saturated NaCl) with a stable response for BPA due to their less particle size with high electroactive surface area and higher electrical conductance, whereas bare GCE failed to the stable determination of BPA. The developed assay for determination of BPA exhibited a wide linear range from 2 × 10−9 M to 10 × 10−6 M, LOD 0.184 × 10−9 M and sensitivity of 247.65 μA mM−1 cm−2. The FxGnP-Ni-MOF/GCE showed good stability and reproducibility against BPA. Finally, the present electrocatalyst was effectively utilized for the quantitative determination of BPA in water samples and obtained results were validated with HPLC method.

Development of a facile method for the detection of nitrite ion is very important due to its huge impact on environment. In the present study, water soluble bovine serum albumin capped gold nanoparticles (BSA-AuNPs) were directly attached on glassy carbon (GC) electrode for the sensitive determination of nitrite ion. The BSA-AuNPs were synthesized and HR-TEM images showed that the average size was ~5 nm. The BSA-AuNPs were then directly attached on GC electrode without any external linker and confirmed by SEM, EDS, XPS, DRS and CV. The appearance of peak at 286 eV (C-N) in XPS confirmed that BSA-AuNPs were attached on GC substrate through Michaeli's nucleophilic addition. The GC/BSA-AuNPs electrode showed an excellent catalytic activity towards nitrite by not only shifting its oxidation potential towards less positive potential by 150 mV but also enhanced its oxidation current by 3-fold compared to bare GC electrode. The amperometric current was increased linearly while increasing nitrite concentration from 10 × 10−9 to 1 × 10−6 M (R2 = 0.9917) and the limit of detection (LOD) by amperometry was found to be 2 × 10−9 M (S/N = 3). The real-time application of the present electro-catalyst was evidenced by determining nitrite in water samples.

The present study describes the facile and fast growth of Ag–Cu dendritic nanostructures (D-AgCuNSs) via an environmentally benign electro–electroless deposition method and determination of hydrazine (HZ) in water samples using the resultant D-AgCuNSs-grown indium tin oxide (ITO) electrode. HZ was also successfully determined with the aid of Raman spectroscopy, in which the Raman signal was enhanced 15-fold at D-AgCuNSs in the presence of HZ, in contrast to bare ITO. Initially, CuNSs were grown on the ITO substrates at different applied potentials and the resultant substrates were used in the galvanic displacement reaction with Ag+ ions and thereby grown D-AgCuNSs on the ITO substrate. The growth of D-AgCuNSs was followed by scanning electron microscopy (SEM), with respect to time and Ag+ concentration. The D-AgCuNSs grown on ITO substrates were further characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive spectroscopy (EDS), cyclic voltammetry (CV), and elect...

Bimetallic nanoparticles (BMNPs) offer a novel vision for enhancing the electrocatalytic activity due to their promising synergetic effects. In this study, bimetallic Au-CuNPs were directly attached on electrode surface by electroless deposition for the first time. Initially, AuNPs were fabricated on glassy carbon (GC) electrode by the reduction of HAuCl4 by hydrazine hydrochloride besides catalyzed by the substrate. SEM studies showed that the size of the deposited AuNPs was found to be 40 nm. The CuNPs were then formed on the AuNPs fabricated electrode by immersing it into the solution containing CuSO4 and hydrazine and the former act as a nucleation centre. The growth of CuNPs on AuNPs follows the seeding mechanism and the growth was monitored by SEM with respect to deposition time. The deposited Au-CuNPs were isotropic and uniform. The X-ray photoelectron spectroscopic (XPS) results confirmed the zero valent nature of both Au and Cu in the Au-CuNPs assembly. The electrocatalytic activity of the GC/Au-CuNPs electrode was examined towards the reduction of dioxygen and hydrogen peroxide (HP). It was found that the GC/Au-CuNPs electrode exhibited higher electrocatalytic activity by not only enhancing the reduction current of dioxygen and HP but also decreased their reduction overpotentials. Moreover, the deposition time dependent electrocatalytic activity was studied at Au-CuNPs modified electrode and it was found that 4 h deposition of CuNPs on AuNPs showed higher electrocatalytic activity in contrast to other electrodes. The limit of detection was found to be 73 nM (S/N = 3) and the sensitivity was 941 μA mM−1 cm−2 for HP at Au-CuNPs modified electrode.

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.