Chiang Mai Journal of Science

 This work presents a new method development using the gold nanoparticles (AuNPs)- bacterial cellulose (BC) nanopaper for the spectrophotometric determination of hydrogen peroxide (H₂O₂). The AuNPs were embedded in the BC nanopaper, where the nanopaper played two roles as both the reducing agent and the template for the as-prepared AuNPs. The preparation process was started by putting the wet bare BC nanopaper (Ø 30 mm and 3 mm thickness) into 0.75 mmol L^-1 HAuCl₄ (25.0 mL). This solution was vigorously and continuously stirred for 60 min at 90ºC. After the embedding process, color of the nanopaper was changed from milky-white to wine-red. The AuNPs-BC nanopaper was characterized by UV-visible spectrophotometer, FE-SEM and EDS. Absorption spectrum of the nanopaper showed the characteristic peak of Au⁰ at 525 nm. The amount of 97.3 weight % of Au⁰ was found. The spectrophotometric assay was carried out by dropping the aliquots of 100 μL of sample and 400 μL of 20 mmol L^-1 citrate buffer (pH 6.0) onto the AuNPs-BC nanopaper. The nanopaper was then kept in a plastic back for 10 min. In the presence of H₂O₂, the wine-red color of the AuNPs-BC nanopaper was turned to pale red accordingly to reduction of Au^o to Au(III) by H₂O₂. Decreasing in the absorbance of the nanopaper at 525 nm was monitored using UV-visible spectrophotometer. Detection limit (y_B + 3S_B) of 0.79 % (v/v) was observed and this value was enough sensitive for the determination of H₂O₂ in wound cleaner and hair dye samples. The H₂O₂ contents in all samples were agreed well with the label values. Good analytical recovery (88.8 to 97.2 %) with high precision (RSD: 3.3 %) were obtained. These results confirmed that the as-prepared nanopaper was successfully synthesized and was effectively applied as the two dimensional (2D)-microcuvette for the spectrophotometric determination of H₂O₂ in real samples.