Structural design of a high sensitivity biomass cellulose-based colorimetric sensor and its in situ visual recognition mechanism for Cu.

A novel biomass cellulose-based colorimetric sensor (DAC-PDH) was prepared by a Schiff base reaction between the aldehyde groups of dialdehyde cellulose (DAC) and the amino groups of 2,6-pyridine dihydrazide (PDH). The as-prepared sensor (DAC-PDH) showed selective recognition of Cu and a visual colour change from white to green. The visual limit of detection for Cu was 10 mol/L. Furthermore, DAC-PDH responded to Cu within 30 s by the method of dynamic condition. The sensor possessed the properties of a high density of functional groups (CO, NH, NH), a large external surface area, a short transit distance and flexibility; thus, Cu can be rapidly absorbed and enriched on the DAC-PDH through multi-dentate ligand chelation between Cu and the carbonyl groups (CO) and the amino groups (NH, NH) of DAC-PDH. The as-prepared DAC-PDH colorimetric sensor exhibits promising prospects for in situ identification of Cu.