Preparation of carbon quantum dot fluorescent probe from waste fruit peel and its use for the detection of dopamine.

Carbon quantum dots (CQDs), as a new type of fluorescent nanomaterial, are widely used in the detection of small molecules. Abnormal dopamine secretion can lead to diseases such as Parkinson's disease and schizophrenia. Therefore, it is highly significant to detect dopamine levels in the human body. Using discarded fruit peels to prepare carbon quantum dots can achieve the reuse of kitchen waste, reduce pollution, and create value. Nitrogen-doped carbon quantum dots (N-CQDs) were prepared using the hydrothermal method, with orange peel as the raw material. The fluorescence quantum yield of N-CQDs reached a high value of 35.37% after optimizing the temperature, reaction time, and ethylenediamine dosage. N-CQDs were characterized using various techniques, including ultraviolet visible (UV-vis) spectroscopy, fluorescence spectrophotometer (PL), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). These analyses confirmed the successful doping of nitrogen in the CQDs. The DA concentration ranged from 0 to 300 µmol L-1, and the linear equation for fluorescence quenching of N-CQDs was F/F0 = -0.0056c + 0.98647, with an R2 value of 0.99071. The detection limit was 0.168 µmol L-1. The recovery and precision of dopamine in rabbit serum were 98% to 103% and 2% to 6%, respectively. The prepared N-CQDs could be used as a fluorescent probe to effectively detect DA.

Study on Antioxidant Activity of Spearmint Essential Oil and Pure Dew.

Spearmint essential oil and pure dew were used as research objects, the antioxidant capacity of spearmint was evaluated by measuring the scavenging capacity of superoxide anion radical and hydroxyl radical, providing technical support for the subsequent development and utilization of spearmint truffle and essential oil. The results showed that when the volume fraction (V/V) of spearmint essential oil was 1%, its antioxidant capacity was the strongest, and its scavenging rates of superoxide anion radical and hydroxyl radical were 50.94% and 90.11% respectively; When the volume fraction (V/V) of spearmint hydrosol was 100%, its antioxidant capacity was the strongest, and its scavenging rates of superoxide anion radical and hydroxyl radical were 47.65% and 45.60%.