Facile fabrication of a flexible laser induced gold nanoparticle/chitosan/ porous graphene electrode for uric acid detection.

We developed a simple, inexpensive, environmentally friendly one-step fabrication of a flexible laser induced graphene-chitosan-gold nanoparticles (LIG-CS-AuNPs) electrode. The fabrication was based on a laser treatment of polyimide (PI) film coated with CS solution containing gold ions (Au (III)). The AuNPs decorating the induced 3D graphene composite were uniformly distributed. The electrode exhibited good electrical conductivity and excellent electrocatalytic activity toward the oxidation of UA. To enable on-site monitoring of uric acid (UA) in blood serum by differential pulse adsorptive stripping voltammetry (DPAdSV), the electrode was coupled to a portable potentiostat connected to a cellphone to control and monitor analysis. The affecting parameters of DPAdSV were optimized. Under the optimal conditions for UA determination, the limit of detection of the developed sensor was 0.33 µmol L-1 and the limit of quantification 1.10 µmol L-1. Two linear ranges were produced: 1.0-30 µmol L-1 and 30-100 µmol L-1. The sensor was highly sensitive and demonstrated excellent reproducibility and selectivity, determining UA in blood serum with recoveries between 86.6 ± 0.6 and 94.7 ± 0.4%. The analysis results were in agreement with those of the hospital standard enzymatic method.

A portable electrochemical sensor for detection of the veterinary drug xylazine in beverage samples.

A portable electrochemical sensor was developed to determine xylazine in spiked beverages by adsorptive stripping voltammetry (AdSV). The sensor was based on a graphene nanoplatelets-modified screen-printed carbon electrode (GNPs/SPCE). The electrochemical behavior of xylazine at the GNPs/SPCE was an adsorption-controlled irreversible oxidation reaction. The loading of graphene nanoplatelets (GNPs) on the modified SPCE, electrolyte pH, and AdSV accumulation potential and time were optimized. Under optimal conditions, the GNPs/SPCE provided high sensitivity, linear ranges of 0.4-6.0 mg L-1 (r = 0.997) and 6.0-80.0 mg L-1 (r = 0.998) with a detection limit of 0.1 mg L-1 and a quantitation limit of 0.4 mg L-1. Repeatability was good. The accuracy of the proposed sensor was investigated by spiking six beverage samples at 1.0, 5.0, and 10.0 mg L-1. The recoveries from this method ranged from 80.8 ± 0.2-108.1 ± 0.3 %, indicating the good accuracy of the developed sensor. This portable electrochemical sensor can be used to screen for xylazine in beverage samples as evidence in cases of sexual assault or robbery.