Cold injury (CI) causes irreversible damage to tea plants, which results in decline in the quality of famous teas and huge economic loss. A new, quick, non-destructive method is provided to assess the CI of tea leaf based on terahertz (THz) spectroscopy. Absorbance of the samples was measured with THz spectroscopy in frequency bands from 0.1 to 1.6 THz under low temperature treatments of 4.0, 0, −2.5, −5.0, −7.5, and −10.0 °C. Fast Fourier transformation was explored to decompose the endpoint signal to improve the ratio of signal to air and convert the time-domain spectra to the corresponding frequency-domain spectra. To improve the separation of overlap signals caused by substantial scattering of injured cells in the leaf, two-dimensional correlation spectroscopy (2DCOS) and average intensity (AI) were introduced into the partial least squares regression (PLSR) to build 2DCOS–PLSR and AI–PLSR models. Quantitative assessments of the 2DCOS–PLSR and AI–PLSR models were conducted to evaluate the three models. The assessment results showed that the correlation coefficients of the 2DCOS–PLSR model (R_2D) were 0.7873, 0.8305, and 0.9103, respectively. The root mean square errors of the 2DCOS–PLSR model (RMSE_2D) were 0.6032, 0.5763, and 0.5221, respectively. For the AI–PLSR model, R_AI values were 0.7477, 0.7691, and 0.8974, respectively. RMSE_AI values were 0.6038, 0.5962, and 0.5797. The combination of THz spectroscopy with the 2DCOS–PLSR model provided a better benchmark for the input interval selection and improved the accuracy of cold-injury detection results.

In this work, novel biomass-derived carbon dots (CDs) with superior fluorescent properties were prepared from tomato straws. A selective, eco-friendly tetracycline (TC) sensor was fabricated by immobilizing a SiO₂ molecularly imprinted polymer (MIP) layer onto CDs, forming a CDs@SiO₂-MIP composite. This sensor combined highly selective adsorption properties with the sensitivity of fluorescence detection, with the sensing mechanism stemming from the off-fluorescent signal after molecular imprinting specifically recognizing the target substance. Under optimal conditions, the sensor exhibited a linear response to TC concentrations ranging from 1.00 × 10⁻⁷ to 5.00 × 10⁻⁴ mol/L, with fluorescence intensity decreasing as concentration increased. The detection limit of TC was 9.33 × 10⁻⁸ mol/L. This work provides novel biomass-derived CDs and a simple molecularly imprinted fluorescence sensing method for the detection of environmental organic pollutants.

In this work, a novel biomass derived carbon dots (CDs) with superior fluorescent properties were prepared by tomato straws. The selective, eco-friendly sensor for the detection of tetracycline (TC) was developed by grafting SiO2 molecular imprinted polymers onto the surface of CDs (CDs@SiO2-MIPs). This sensor combined the high selective adsorption property with the sensitivity of fluorescence detection, which sensing mechanism stems from the off fluorescent signal after the molecular imprinting specifically recognizing the target substance. Under optimal conditions, the fluorescence intensity of the sensor decreased linearly with increasing the concentration of TC from 1.00×10-7 to 5.00×10-4 mol/L. The detection limit of TC was 9.33 ×10-8 mol/L. This work provides a novel biomass derived CDs and a simple molecularly imprinted fluorescence sensing method for the detection of environmental organic pollutants.