Nanozyme-immobilized cellulose membranes designed by a simple hydrogen bond-dominated for colorimetric detection of hydrogen peroxide and uric acid

Nanozymes are considered promising replacement materials for natural enzymes. The application limitations of nanozymes in separation and purification, quantitative utilization, and recycling can be solved by immobilization technology. Herein, a cellulose membrane-based nanozyme immobilization platform was designed and successfully applied for the colorimetric detection of hydrogen peroxide (H2O2) and uric acid (UA). Gold nanoclusters (AuNCs), which can mimic peroxidase and catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2, were immobilized on cellulose membranes (CMs) by hydrogen bonding to prepare AuNCs functionalized CMs (Au@CMs) with firm immobilization and uniform dispersion. TMB (colorless) in solution was oxidized to oxTMB (blue) after collision with hydroxyl radicals (∙OH) formed by H2O2 decomposition on the surface of Au@CMs. The oxTMB generated on Au@CMs was immediately in-situ immobilized under the combined action of cellulose hydroxyl groups and AuNCs. This enabled the dispersion of the colored molecules on the Au@CMs without diffusing into the solution, therefore the colorimetric response was retained to the maximum. Au@CMs were used to effectively colorimetric H2O2 with high selectivity and sensitivity, its visual limit of detection (VLOD) was 7 μM. Experiment results proved that Au@CMs were stable, convenient, and recyclable. It was worth noting that in the presence of uricase, the sensor could also be used for the colorimetric detection of UA, which had a gradient colorimetric response to UA in the concentration range of 50–500 μM. The design and preparation of Au@CMs provided an effective method for immobilizing nanozymes, promising for early-warning and semi-quantitative analysis.