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Natural indigo, the most widely produced and utilized natural dye, encounters quality challenges due to the lack of standardization in the natural dye industry. Rapid determination of natural indigo dye contents before the dyeing process appears extremely important. In this study, two prediction models for different concentrations were established using partial least squares in conjunction with near-infrared analysis quantitatively to analyze the natural indigo dye content. A total of 228 indigo samples were collected from 14 different dyestuffs across various regions, with concentrations ranging from 100 to 1000 mg/L and 10 to 100 mg/L, respectively. The spectral pre-processing methods of multiplicative scatter correction plus first-order derivative and Savitzky–Golay smoothing plus band normalization plus first-order derivative were selected to enhance the model prediction accuracy. The optimized model exhibited excellent prediction accuracy. Within the concentration range of 100–1000 mg/L, the model has an R 2 value of 0.9994, and a root mean square error of prediction value of 6.36 mg/L. In the concentration range of 10–100 mg/L, the model returned an R 2 value of 0.9907, and a root mean square error of prediction value of 2.80 mg/L. The model's detection limit stands at 49.2 mg/L. The results demonstrated that the near-infrared models developed in this study can be used rapidly and accurately for the quantitative determination of natural indigo dyes. [ABSTRACT FROM AUTHOR]

During the drafting process, the fiber acceleration motion contributes significantly to the sliver irregularity. In this study, the drafting simulation based on the improved model of fiber arrangement in the sliver was developed to analyze the sliver irregularity caused by the acceleration motion during the drafting process. The results indicated that the drafting simulation could provide an effective reference for the parameter optimization of the drafting process under the condition of saving raw material cost and time cost. The simulations and calculations denoted that a shorter gauge length and larger input sliver linear density by more concentrated accelerated motion could be conducive to more even slivers during the drafting process. In addition, in order to generate higher sliver evenness, in the double-zone drafting process, the draft ratio of the back drafting zone should be selected to be slightly greater than 1 so that the draft ratio of the front drafting zone would be relatively large when the total draft ratio is constant due to the trend of the additional irregularity caused by the acceleration motion increasing to a peak value firstly and then decreasing as the draft ratio grows. [ABSTRACT FROM AUTHOR]

Colloidal carbon dots (C‐dots) are considered as promising heavy‐metal‐free materials to achieve room‐temperature phosphorescence (RTP) properties for promising applications, such as photoelectronic devices, information encryption, and bio‐imaging. However, most of the current obtained RTP C‐dots have a short lifetime with a relatively low quantum yield (QY). In this work, the C‐dots large‐scale synthesized via a vacuum heating approach have multiple RTP emissions (blue, green, and yellow), a long RTP lifetime of as high as 1.92 s, and a high QY of 34.4% by selecting different types of precursors, which is superior to most of reported RTP C‐dots. The multiple atoms doping and strong bonding between neighbored C‐dots promoted by vacuum heating contributes to the excellent RTP properties. As a proof‐of‐concept, the as‐obtained RTP C‐dots are used as optical ink for flexible security codes, exhibiting a bright shape with a lifetime of 1.37 s. This work offers an efficient approach for producing large‐scale high‐quality RTP C‐dots, which can be applied to anti‐counterfeiting and information encryption systems. [ABSTRACT FROM AUTHOR]