Fe and N co-doped carbon dots（Fe，N-CDs） were prepared by hydrothermal method using biomass（leaf of syngonium podophyllum schott）， ammonium ferric sulfate dodecahydrate and urea as raw materials， and their morphology and elemental composition were characterized by means of transmission electron micro-scopy（TEM） and X-ray photoelectron spectroscopy（XPS）. The obtained Fe，N-CDs possessed both peroxidase-like activity and strong fluorescence emission at 450 nm. A dual signal（colorimetry and ratio fluorimetry）
method<sup/>for the determination of H2O2was developed using Fe，N-CDs and o-phenylenediamine（OPD） as probe. When H2O2 was present， OPD was oxidized to 2，3-diaminophenazine（DAP） under the catalysis of Fe，N-CDs. DAP had a characteristic absorption peak at 420 nm. When excited at 360 nm， DAP had a strong fluorescence emission at 550 nm， quenching the fluorescence of Fe，N-CDs at 450 nm because of the inner filter effect. Results showed that the concentration of H2O2 could not only affect the color of the DAP but also the fluorescence intensity of DAP and Fe，N-CDs. Thus， the absorbance of DAP at 420 nm（A420） and fluorescence intensity ratio of DAP and Fe，N-CDs（I550/I450） could be used for the quantitative analysis of H2O2. Considering that glucose oxidase can catalyze glucose oxidation to produce H2O2， a colorimetric and ratio fluorescence dual-signal method for glucose detection was further developed. Under the conditions of pH 5.4， temperature 40 ℃， 1.75 mmol/L OPD and reaction time 25 min， A420 and I550/I450 showed good linear relationship with the glucose concentration in the range of 1.0—100 μmol/L， and the detection limits（LOD） for glucose were 0.8（colorimetry） and 0.6（ratio fluorimetry） μmol/L， respectively. This dual-signal method was applied to the determination of glucose in human serum with satisfactory results.
