A sensitive and facile electrochemical paper-based sensor for glucose detection in whole blood using the Pd/CB-Ni@rGO modified electrode.

We created novel Pd/CB-Ni@rGO nanomaterials for glucose detection. The as-synthesized nanomaterials were dropped on the electrode surface using the drop casting technique. The prepared electrode was then attached to a paper-based device containing the sample zone and the reaction zone, enabling plasma isolation and an enzymatic reaction for glucose detection in whole blood. The nanomaterials and surfaces of electrodes were characterized by FTIR, TEM, and SEM. The proposed approach is a disposable glucose detection method that is unaffected by protein fouling on the electrode, and it requires only one drop of human blood. Therefore, there is no need for extensive sample preparation, and there is less sample consumption. Under optimal conditions, Pd/CB-Ni@rGO can accurately measure blood glucose levels with a linear range of 7 to 7140 µM (R2 = 0.9986) and a low detection limit of 0.82 µM. Besides, the developed sensor shows excellent anti-interference capacity, stability, and satisfactory reproducibility and repeatability. Importantly, Pd/CB-Ni@rGO was successfully applied for glucose in whole blood from 4 volunteers, with results that correlated well with those obtained using an Accucheck glucometer at a 95% confidence level. Given its low cost, high accuracy, and ease of use, the blood glucose sensor holds significant potential for clinical use and broadens the area of future noninvasive sensor development.

Catalyst Composites of Palladium and N-Doped Carbon Quantum Dots-Decorated Silica and Reduced Graphene Oxide for Enhancement of Direct Formic Acid Fuel Cells.

Pd-based catalysts consisting of Pd nanoparticles on nitrogen-doped carbon quantum dots (N-CQDs) modified silica (SiO2) and reduced graphene oxide have been synthesized through reduction for use as catalysts for improved formic acid oxidation. The structure, morphology, chemical composition, functional groups, and porosity of the synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and Brunauer-Emmett-Teller (BET) spectroscopy, respectively. Their electrocatalytic activities were also evaluated by electrochemical measurements. The differences in the average particle sizes found for Pd/N-CQDs-SiO2-rGO, Pd/N-CQDs-rGO, and Pd/rGO were 4.81, 5.56, and 6.31 nm, respectively. It was also found that the Pd/xN-CQDs-SiO2-yrGO composite catalysts (where x and y is 1 to 4) can significantly improve the activity and stability toward formic acid electrooxidation compared with Pd/rGO and commercial Pt/C. The mass activities of Pd/N-CQDs-SiO2-rGO, Pd/N-CQDs-rGO, and Pd/rGO were 951.4, 607.8, and 157.6 mA g-1, respectively, which was ca. 6-7 times compared with Pd/rGO and approximately 3-4 times compared with commercial Pt/C. With low potential for CO oxidation and high current intensity, the composites of rGO, SiO2, and N-CQDs into Pd-based catalysts improved the catalytic activity of the prepared catalyst for the oxidation of formic acid in acidic media. The value of the Tafel slope designated that the chief path of the prepared catalysts is the dehydrogenation process. These prepared catalysts exhibit promise toward the development of high-performance Pd-based electrocatalysts for formic acid oxidation.

Distance-Based Paper Device Combined with Headspace Extraction for Determination of Cyanide.

We report for the first time a distance-based paper device based on gold/silver core shell nanoparticles (Au@Ag NPs) for a simple, inexpensive, instrument-free, and portable determination of cyanide by the naked eye. Au@Ag NPs immobilized on a paper channel were etched by cyanide ions so that a yellow color band length of Au@Ag NPs is proportional to a decrease in the cyanide concentration. Quantification is achieved by measuring color length, thus eliminating the need to differentiate hues and intensities by the user, and the processing data of each imaging device. Moreover, the paper-based headspace extraction was combined with the distance-based paper device to improve the sensitivity. The enrichment factor was found to be 30-fold and the linearity was found in the range 0.05-1 mg L-1. The naked eye detection limit was 10 µg L-1 where the World Health Organization (WHO) have regulated the maximum level of cyanide in drinking water as 70 µg L-1. Our proposed device also showed no interference from common cations and anions presenting in seawater and waste water including thiocyanate, chloride. Finally, our device has been successfully applied to determine cyanide ions in seawater, drinking water, tap water and wastewater providing satisfactory precision and accuracy.

Disposable Nonenzymatic Uric Acid and Creatinine Sensors Using µPAD Coupled with Screen-Printed Reduced Graphene Oxide-Gold Nanocomposites.

Uric acid (UA) and creatinine are the imperative biological substance for clinical monitoring and diagnosis. Measuring the ratio between uric acid and creatinine in urine helps differentiate acute uric acid nephropathy from the hyperuricemia that secondarily occurs to renal failure. In general, the ratio is greater than 0.9 in acute uric acid nephropathy and less than 0.7 in hyperuricemia. In this work, disposable nonenzymatic screen-printed reduced graphene oxide-gold nanocomposites electrodes were firstly developed for the quantitative analysis of uric acid. Our sensors were also coupled with the paper-based colorimetric sensor of the determination of creatinine. Hence, an alternative high-throughput screening test for the uric acid to creatinine ratio with high sensitivity, specificity, simplicity, and rapidity was developed. Under the optimum conditions, our disposable nonenzymatic screen-printed electrode for the determination of uric acid shows the acceptable analytical performance in a wide range of linearity (2.5-1,000 µM) with a low detection limit of 0.74 µM. Our electrodes also showed no interference from common physiologic compound in urine. The determination of creatinine has been developed using Jaffé reaction between the creatinine and picric acid in alkaline condition. The alkaline picrate color on µPAD changed from yellow to orange in the presence of creatinine and the orange intensity is directly proportional to the creatinine amount in a linearity range of 0.20-6.0 mM as a detection limit of 180 µM. Finally, our device has been utilized to determine uric acid and creatinine simultaneously in control urine samples with acceptable result.