A novel method for the rapid sensing of H2O2 using a colorimetric AuNP probe and its DFT study

Fabrication of Nitrogen-Doped Reduced Graphene Oxide Modified Screen Printed Carbon Electrode (N-rGO/SPCE) as Hydrogen Peroxide Sensor

In recent years, the electrochemical sensing approach has attracted electrochemists because of its excellent detection process, simplicity, high sensitivity, cost-effectiveness, and high selectivity. In this study, we prepared nitrogen doped reduced graphene oxide (N-rGO) and characterized it using various advanced techniques such as XRD, SEM, EDX, Raman, and XPS. Furthermore, we modified the active surface of a screen printed carbon electrode (SPCE) via the drop-casting of N-rGO. This modified electrode (N-rGO/SPCE) exhibited an excellent detection limit (LOD) of 0.83 µM with a decent sensitivity of 4.34 µAµM⁻¹cm⁻² for the detection of hydrogen peroxide (H₂O₂). In addition, N-rGO/SPCE also showed excellent selectivity, repeatability, and stability for the sensing of H₂O₂. Real sample investigations were also carried out that showed decent recovery.

Ultrasensitive Pd nano catalyst as peroxidase mimetics for colorimetric sensing and evaluation of antioxidants and total polyphenols in beverages and fruit juices

Herein, we developed a new Pd NP from the aq extract of Elsholtzia blanda Benth. flower that showed efficient peroxidase mimetic activity. The catalytic mechanism was confirmed through colorimetric analysis. The optimizations of temperature, concentration, P^H and time were done to find out the best procedure to implement the intrinsic catalytic activity in practical applications. Michaelis-Menten constants were evaluated for both TMB and H₂O₂ substrate to investigate the affinity of Pd NP towards them. K_m was observed to be 42.35 mM for H₂O₂ and 0.0076 mM for TMB. Antioxidants were sensed using the peroxidase mimetic property up to nanomolar levels with a LOD = 0.78 nM for Gallic acid 0.85 nM for Tannic acid. The method was further implemented in comparing the radical scavenging power of different phenolic compounds. Smart-phone based analysis was done for observing the change in colour which could further be utilized as an analytical tool for study the antioxidant activity. R-Square values of 0.97 and 0.96 for detection of gallic acid and tannic acid respectively suggest good linearity of the plot. Lastly, the system was utilized in the evaluation of total antioxidant capacity (TAC) and total phenolic content (TPC) in commercially available juices and beverages.

Dual colorimetric sensing of ascorbic acid and thyroxine using Ag-EGCG-CTAB via a DFT approach

In this work, a colorimetric approach for the detection of ascorbic acid (AA) and thyroxine (TH) was developed by synthesizing cost-effective silver nanoparticles (AgNPs) decorated with epigallocatechin gallate (EGCG) and CTAB. EGCG is the major bioactive chemical constituent that played a significant role in this study. The environment around the nanoparticle (NP) was controlled by adding CTAB surfactants. The synthesized NPs were characterized by different advanced techniques including XRD, XPS, SEM, and TEM. UV-visible spectra were thoroughly analyzed for sensing of AA and TH and the colour change of the solution can be visually monitored. The change in the localized surface plasmon resonance (LSPR) properties was used as an asset for the detection of AA and TH. A good linear relationship was obtained in both the sensing schemes with a limit of detection (LoD) of 0.67 μM and 0.33 μM for AA and TH respectively. Furthermore, the nanoparticles (NP) were implemented for real-sample analysis (pharmaceutical tablets). A cost-effective filter paper strip-based method coupled with smartphone scanning sensing was developed for the detection of AA. The interaction of AA and TH with the probe was depicted by a density functional theory (DFT) analysis. The synthesized NPs show tremendous selectivity towards AA and TH and excellent potential for practical applications.