Computer-Assisted Design of Environmentally Friendly and Light-Stable Fluorescent Dyes for Textile Applications

Five potentially environmentally friendly and light-stable hemicyanine dyes were designed based on integrated consideration of photo, environmental, and computational chemistry as well as textile applications. Two of them were synthesized and applied in dyeing polyacrylonitrile (PAN), cotton, and nylon fabrics, and demonstrated the desired properties speculated by the programs. The computer-assisted analytical processes includes estimation of the maximum absorption and emission wavelengths, aquatic environmental toxicity, affinity to fibers, and photo-stability. This procedure could effectively narrow down discovery of new potential dye structures, greatly reduce and prevent complex and expensive preparation processes, and significantly improve the development efficiency of novel environmentally friendly dyes.

. Geometry structures of the fluorescent dyes (Z1, Z2. Z3, Z4, Z5 and Z6) Compare the homo orbitals of the materials, it is easy to find that the five materials (A2,A3,A4,A5 and A6) have similar orbitals, indicating that they have similar chemical properties.
The LUMO orbitals of A3 in Figure S5 is similar to that of A1, especially for the shape and area of orbitals of the atoms. A3 could be similar to A1 in some properties, According to the following relationships (equations S1 and S2) between wavelength and frequency, the absorption and emission wavelengths of the N-methylacridinium chloride were calculated.
C:light speed; λN: wavelength of the light emitted or absorbed by Nmethylacridinium chloride; λR: wavelength of the light emitted or absorbed by -0.01823hartree -0.05457hartree -0.06118hartree -0.05859hartree -0.05875hartree -0.05604hartree Rhodamine B; νR: frequency of the light emitted or absorbed by Rhodamine B; νN: frequency of the light emitted or absorbed by N-methylacridinium chloride.
According to the reference [S1], frequencies of the maximum absorption and emission light of N-methylacridinium chloride in water were approximately 20×10 -3 cm -1 and 24×10 -3 cm -1 . The maximum emission wavelength of Rhodamine B (in ethanol) is about 570nm, and the emission frequency in the reference [S1] was about 17.5 x10 -3 cm -1 . So the calculated maximum absorption and emission wavelengths were 415nm and 498nm for N-methylacridinium chloride. Table S1. Absorption wavelength, emission wavelength, and oscillator strength (f) calculated by TD-DFT method for N-methylacridinium chloride. Molecules of triplet oxygen contain two unpaired electrons, making triplet oxygen an unusual example of a stable and commonly encountered diradical.

MO character MO coefficient Eexc (eV) Wavelength f
Superoxide(O2 -): A superoxide is a compound that contains the superoxide anion, which has the chemical formula O2 -. The systematic name of the anion is dioxide(-1).
The reactive oxygen anion superoxide is particularly important as the product of the one-electron reduction of oxygen molecule O2, which occurs widely in nature [S2] Figure S6. Numbered atoms of six dyes  The charges of the hydrogen atoms are not listed in Table S4 because that all the hydrogen atoms have positive charges, the atoms of dyes are numbered in Figure S6.
From Table S4 and Figure S6, it easy to notice that the carbon atoms in the bridge The Figure S7b shown the reflectivity of the PET fiber dyed by Rhodamine b, it's easy to find the absorption and emission peak in the curve even the intensity of the peak was weak, it could be illustrate that the Rhodamine B could dye PET fiber when the dyeing-temperature was 130°C, thus, the HSP distance would be credible to predict the dyeing properties of dyes. As shown in Figure Table S5, the different methods would give different results in varied error ranges. Compared with the experiment data in Figure S7, program mpw1pw91/6-311+G(d) produced better estimated results.  Figure S9. (a)Reflectance of the PET dyed by Z2 and Z5 at 130°C As shown in Figure S9, Z2 and Z5 dyeing PET at 130°C successfully-have obvious absorption an emission wavelength. dyeing properties of the fibers. The synthesized dyes and commercial dye Rhodamine B were used to dye PAN, celloluse and nylon following the Figure S10. The fabrics were dyed in an X-5 DYEING machine (Foshan HUANGJU, China), and the dye solutions were prepared with the required amount of each dye, sodium sulphate (3g/L) and a surfactant (0.5g/L). The pH of the dye bath was maintained at 4.5-5.0 by acetic acid-sodium acetate buffer solution. The liquor-to-goods ratio was kept at 50:1. After immersing the fabrics into the dye solutions at room temperature, the temperature was increased to 100℃ at the rate of 1℃/min and maintained at the temperature for 60 minutes, the dye solution was cooled to 70℃ at 1.25℃/min. At the end of the dyeing, the dyed fabric was rinsed thoroughly in distilled water and allowed to dry in the open air.
The synthesized dyes and commercial dye Rhodamine B were used to dye PET fabric following the Figure S11, The PET fabrics were dyed in an X-5 DYEING machine (Foshan HUANGJU, China), and the dye solutions were prepared with the required amount of each dye, and a dispersant NNO (0.5g/L). The liquor-to-goods ratio was kept at 50:1. After immersing the PET fabric into the dye solutions at room temperature, the temperature was increased to 130℃ at the rate of 2℃/min and maintained at the temperature for 60 minutes, the dye solution was cooled to 70℃ at 3℃/min. At the end of the dyeing, the dyed fabric was rinsed thoroughly in distilled water and allowed to dry in the open air. Figure S11. Dyeing process of PET fabric