Fabrication of Gd2O3 Nanosheet-Modified Glassy Carbon Electrode for Nonenzymatic Highly Selective Electrochemical Detection of Vitamin B2

Electrochemical nanosensors: Revolutionizing vitamin detection

Electrochemical nanosensors offer remarkable capabilities for precise and selective vitamin detection, with transformative implications for healthcare, nutrition, and food industry quality control. Nanotechnology advancements have facilitated the creation of nanoscale sensors with customized properties, enhancing the efficacy of detecting vitamins. Materials such as gold nanoparticles, carbon nanotubes, and quantum dots have been modified to display remarkable sensitivity and specificity for distinct vitamins. Integrating these materials with electrochemical techniques enables the translation of biochemical interactions into measurable electrical signals, achieving accurate and swift detection. Real-time monitoring of vitamin levels enables health optimization and improves quality control, nutritional label accuracy and supply chain monitoring in the food industry. This review comprehensively examines the electrochemical properties of sensors for vitamin analysis, highlighting modernization in the design of sensors, restyling nanomaterial-based sensor technologies and exploring their applications in food quality control while simultaneously addressing current challenges and future directions in the development of sensors.

B@LGTs of Nd, Eu, Er, and Yb lanthanides with physicochemical interfacing for enhanced photocatalytic reduction of fluorescent dyes, transition metal ions, and quinonoid phenolphthalein

In this work, lanthanide sulphide nanorods (LSNRs) of neodymium (Nd2S3), europium (Eu2S3), erbium (Er2S3), and ytterbium (Yb2S3) were prepared with a LnCl3·6H2O salt, sodium metal, and H2S gas through a crash reaction methodology (CRM) at NTP. The LSNRs were doped with gadolinium ions (Gd3+) and coated with graphene oxide (GO) to prepare bimetallic LSNRs (B@LSNRs) and GO templates (B@LGTs), respectively. LSNRs, B@LSNRs, and B@LGTs were characterised using XRD, FT-IR spectroscopy, BET analysis, UV/vis spectroscopy, HR-TEM, SEM, TGA/DTG, XPS, Raman spectroscopy, and elemental analysis. The B@LGTs as interstitial photocatalysts photocatalytically reduced the Coomassie brilliant blue red (BBR) dye, transition metal ions (TMIs), and quinonoid phenolphthalein (QHIn) in aqueous solutions under visible light. Experimental parameters including pollutant concentrations, B@LGT dosages, physicochemical properties (PCPs), and pH were optimized for achieving monodispersion and maximum PCR. The PCPs like density, viscosity, sound velocity, surface tension, friccohesity, and isentropic compressibility have predicted the spontaneity and sustainability at 288.15, 298.15, and 310.15 K with photocatalysing medium. B@Nd2S3:GO, B@Eu2S3:GO, B@Er2S3:GO, and B@Yb2S3:GO with 2.23, 2.28, 2.38, and 1.88 eV bandgaps (E g) and -670.14, -829.18, -767.39, and -925.57 J mol-1 activation energies (E a) having -0.9869, 0.8843, -1.4011, and -1.2102 J mol-1 entropies (ΔS) photocatalytically reduced a dye with 96.35, 96.67, 97.60, and 99.17% quantum yields (Φ), respectively. The above-mentioned data indicated that the B@LGTs are robust photocatalysts that photocatalytically reduce BBR in 48 and 30 times shorter duration than LSNRs and B@LSNRs, respectively. It was found that 0.01 g% B@LGTs photocatalytically reduced 40 ppm BBR and 20 ppm CrCl3, NiCl2, CuCl2, and QHIn in 30, 20, 40, 35, and 15 min, respectively. Kinetic rate constants of 3.25 × 10-2, 3.21 × 10-2, 3.18 × 10-2 and 3.15 × 10-2 min-1 for BBR were in the order of B@Nd2S3:GO > B@Er2S3:GO > B@Eu2S3:GO > B@Yb2S3:GO with 4f3e, 4f11e, 4f6e, and 4f13e electrons, respectively. This indicated first-order reaction similar to QHIn and TMIs. Furthermore, the B@LGTs exhibited favourable stabilities, with 58.1-68.05% PCR efficiencies after 10 cycles of reduction experiments.

XPS Study of Grafting Paramagnetic Ions onto the Surface of Detonation Nanodiamonds

Grafting of paramagnetic transition and rare earth metal ions onto the surface of detonation nanodiamonds (DNDs) was successfully implemented in the recent decade and opened new opportunities in the biomedical application of these compounds, particularly as novel contrast agents for magnetic resonance imaging. The grafting was studied mainly using EPR, NMR, and magnetic measurements. Such a highly surface-sensitive, quantitative, chemical analytic technique as X-ray photoelectron spectroscopy (XPS) was very rarely used. In this paper, we report the XPS study of grafting transition and rare-earth metal ions (Cu2+, Co2+, Mn2+, and Gd3+) onto the surface of DNDs. Binding energies for metal, carbon, oxygen, and nitrogen atoms were determined and attributed to the corresponding ion states and atomic groups. Comparing XPS and EPR findings, we showed that the developed synthesis route resulted in almost complete grafting of manganese and gadolinium atoms in the form of paramagnetic ions Mn2+ and Gd3+ to the diamond surface, while only 30% of the copper atoms on the surface are in the paramagnetic state Cu2+, and the rest 70% are in the non-magnetic Cu+ state. It was not possible to draw a similar conclusion regarding Co2+ ions due to the lack of data on the amount of these paramagnetic ions on the DND surface.

Creative synthesis of pH-dependent nanoporous pectic acid grafted with acrylamide and acrylic acid copolymer as an ultrasensitive and selective riboflavin electrochemical sensor in real samples

In current research, an innovative pectic acid was grafted with poly (acrylamide-co-acrylic acid) [PA-g-poly (AAm-co-AA)] nanoporous membrane using a free radical-mediated grafting copolymerization process. The optimized parameters for the grafting copolymerization reaction such as initiator concentration, monomer concentrations, polymerization reaction time, and temperature were studied. Additionally, the solid content, graft percentage, and conversion were calculated. The unique polymeric membrane was characterized using Fourier-transform infrared spectroscopy (FT-IR), thermal gravimetry (TG), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) supported by energy dispersive X-ray spectroscopy (EDX). The formulated novel PA-g-poly (AAm-co-AA) had a nanoporous structure with a diameter of 113 nm. pH-dependent swelling and biodegradation measurements were also studied. The electrochemical characterizations of PA-g-poly (AAm-co-AA) were conducted through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Furthermore, the screen-printed electrode (SPE) was modified with pure PA and the new generation of its grafted polymeric nanoparticles to detect and quantify the concentration of riboflavin (RF) in real samples using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The modified electrode showed two linear concentration ranges from 0.01 - 2 nM and 2 - 90 nM with low detection limits (LODs) of 0.004 and 0.97 nM, respectively, demonstrating high sensitivity. Besides, the fabricated sensor exhibited more selectivity, simplicity, great reproducibility, repeatability, and good stability. Finally, the PA-g-poly (AAm-co-AA)-modified SPE based sensor was effectively used in real sample analysis of egg yolk, milk, and vitamin B2 drugs with good recovery rates.

Highly Specific Non-Enzymatic Electrochemical Sensor for the Detection of Uric Acid Using Carboxylated Multiwalled Carbon Nanotubes Intertwined with GdS-Gd2O3 Nanoplates in Human Urine and Serum

Herein, the electrochemical sensing efficacy of carboxylic acid functionalized multiwalled carbon nanotubes (C-MWCNT) intertwined with coexisting phases of gadolinium monosulfide (GdS) and gadolinium oxide (Gd2O3) nanosheets is explored for the first time. The nanocomposite demonstrated splendid specificity for nonenzymatic electrochemical detection of uric acid (UA) in biological samples. It was synthesized using the coprecipitation method and thoroughly characterized. The presence of functional groups and disorder in the as-synthesized nanocomposite are confirmed using Fourier transform infrared spectroscopy and Raman spectroscopy. Furthermore, field emission scanning electron microscopy, high-resolution transmission electron microscope, X-ray powder diffraction, and X-ray photoelectron spectroscopy provides a clear understanding of the morphology, coexisting phases, and elemental composition of the as-synthesized nanocomposites. The differential pulse voltammetry technique was utilized to elaborate the electrochemical sensing of UA using a GdS-Gd2O3/C-MWCNT modified glassy carbon electrode (GCE), The sensor showed an enhanced current response by more than 2-fold compared to bare GCE. Also, the sensor's performance was further improved by dispersing the nanocomposite in an ionic liquid with the exceptional reproducibility (SD = 0.0025, n = 3). The fabricated UA sensor GdS-Gd2O3/C-MWCNT/IL/GCE demonstrated a wide linear detection range from 0.5-30 μM and 30-2000 μM, effectively covering the entire physiological range of UA in biological fluids with a limit of detection (LOD) of 0.380 μM (+3SD of blank) and a sensitivity of 356.125 μA mM-1 cm-2. Moreover, the electrodes exhibited storage stability for 2 weeks with decrease in zero-day current by only 4.5%. The sensor was validated by quantifying UA in 12 unprocessed clinical human urine and serum samples, and its comparison with the gold standard test yielded remarkable results (p < 0.05). Hence, the proposed nonenzymatic electrochemical UA sensor is selective, sensitive, reproducible, and stable, making it reliable for point-of-care diagnostics.

Mini-Review: Electrochemical Sensors Used for the Determination of Water- and Fat-Soluble Vitamins: B, D, K

Vitamins are one of the most essential organic compounds that are necessary for the human body, in order to develop and grow in a healthy way. The aim of this mini-review is to bring together a series of electrochemical sensors (voltametric and amperometric) developed for the determination of vitamins from the families of B, D and K in biological, pharmaceutical or food-related samples. For this mini-review, 16 articles published between 2016 and 2021 were taken into consideration.

Impact of Co-Doping on the Visible Light-Driven Photocatalytic and Photoelectrochemical Activities of Eu(OH)3

The microwave-assisted synthesis approach was used to synthesize Eu(OH)3 and Co-Eu(OH)3 nanorods. Various techniques were used to investigate the structural, optical, and morphological features of the Eu(OH)3 and Co-Eu(OH)3 NRs. Both Eu(OH)3 and Co-Eu(OH)3 NRs were found to be hexagonal with crystallite sizes ranging from 21 to 35 nm. FT-IR and Raman spectra confirmed the formation of Eu(OH)3 and Co-Eu(OH)3. Rod-shaped Eu(OH)3 and Co-Eu(OH)3 with average lengths and diameters ranging from 27 to 50 nm and 8 to 12 nm, respectively, were confirmed by TEM. The addition of Co was found to increase the particle size. Furthermore, with increased Co doping, the band gap energies of Co-Eu(OH)3 NRs were lowered (3.80-2.49 eV) in comparison to Eu(OH)3, and the PL intensities with Co doping were quenched, suggesting the lessening of electron/hole recombination. The effect of these altered properties of Eu(OH)3 and Co-Eu(OH)3 was observed through the photocatalytic degradation of brilliant green dye (BG) and photoelectrochemical activity. In the photocatalytic degradation of BG, 5% Co-Eu(OH)3 had the highest response. However, photoelectrochemical experiments suggested that 10% Co-Eu(OH)3 NRs showed improved activity when exposed to visible light. As a result, Co-Eu(OH)3 NRs have the potential to be a promising visible-light active material for photocatalysis.

A Reversible Mechanochromic AIEgen Based on Triphenylamine for the Selective Detection of Vitamin B2 (Riboflavin) in Aqueous Media and Histotoxicity

(E)-Ethyl 2-cyano-3-(4'-(diphenyl amino)-[1,1'-biphenyl]-4-yl) acrylate (RSJ) is a novel luminogen based on triphenylamine. It has been fully synthesized and characterized, exhibiting an incredible photophysical phenomenon known as aggregation-induced emission (AIE). This work describes a fluorescent sensor that detects vitamin B2 in mixed aqueous media with high selectivity and a low limit of detection as well as a mechanism for reversible mechanochromic luminescence. Moreover, the molecule was validated for its nontoxicity in water using a histotoxicological study. Fish subjected to two different concentrations of the "novel luminogen" that displayed photophysical phenomena during sensing of vitamin B2 (riboflavin) in mixed aqueous media did not exhibit any significant differences in the structural makeup of their liver, kidney, gills, brain, and muscle tissues when compared with the control group.

A facile method for the fabrication of hierarchically structured Ni2CoS4 nanopetals on carbon nanofibers to enhance non-enzymatic glucose oxidation

Unique Ni₂CoS₄-carbon nanofiber (CNF) composite nanostructures were fabricated using a simple electrospinning-assisted hydrothermal route and used for the rapid and accurate electrochemical oxidation of glucose in real samples at the trace level. Electrochemical impedance spectroscopy and cyclic voltammetry of unmodified and modified electrodes revealed low charge-transfer resistance and the excellent electrocatalytic sensing of glucose when using the Ni₂CoS₄-CNF at a low potential due to the combined benefits of the highly conductive Ni₂Co₂S₄ anchored to the large surface area of the CNFs. Amperometric analysis of the fabricated sensor has shown an extremely low limit of detection (0.25 nM) and a large linear range (5-70 nM) for glucose at a working potential of 0.54 V (vs. Hg/HgO). The practicability of the Ni₂CoS₄-CNF for use in glucose determination was tested withl human saliva, blood plasma, and fruit juice samples. The Ni₂CoS₄-CNF/GCE showed acceptable recovery values for human saliva (99.1-100.8%), blood plasma (98.6-101.5%), and fruit juice (95.1-105.7%) samples. The proposed sensor also exhibited outstanding electroanalytical characteristics for glucose oxidation in these samples, including reusability, repeatability, and interference resistance, even in the presence of other biological substances and organic and inorganic metal ions.