• Korean Journal of Medicinal Crop Science
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• v.21 no.3
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• pp.213-219
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• 2013

This study was carried out to find out the optimum method of preparation of indigo standard solution and its stability, and to investigate the indigo contents in Niram, blue dye extract, from a total of 7 indigo plants and 34 breeding lines of Persicaria tinctoria H. Gross. Proper solvent for indigo standard was dimethyl sulfoxide (DMSO), and appropriate concentration was 1 mg of indigo in 10 mL of DMSO. Absorbance value of UV/Vis Spectrophotometer at 620 nm of standard solution was changed decreasingly 12 hours after the preparation of standard solution irrespective of the storage conditions such as temperature and light. Average value of absorbance of 8-fold diluted standard solutions prepared daily during 16 days was $0.210{\pm}0.005$, indicating the powder of indigo compound was stable chemically. Calibration curve was made for quantitative analysis of indigo of 7 Niram samples, and indigo contents ranged from 0.69% to 18.76% showing relatively larger variation. Across all 34 breeding lines, the range of indigo content was from 7.9 mg to 56.4 mg per 100 g of fresh leaves, averaging 25.2 mg of indigo content and showing a 47.7% coefficient of variation.

• Fashion & Textile Research Journal
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• v.13 no.2
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• pp.263-268
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• 2011

One-step reduction/dyeing method was applied for ramie dyeing with natural indigo powder. The effect of reduction/dyeing conditions including the pH of bath, dye temperature and time, and concentration of indigo powder and reduction agent on dye uptake and color properties were investigated. Regardless of addition of alkali, the dyed fabrics appeared in the PB Munsell color range(${\lambda}_{max}$: 660 nm) and the dye uptake was much higher with no addition of sodium hydroxide. Dyeing was carried out through the use of only sodium hydrosulfite in the bath. The maximum dye uptake was obtained at 60 for 30min. Saturated dye uptake was obtained at 2 g/L of sodium hydrosulfite concentration up to 2 g/ L of indigo powder. Whereas, at higher indigo powder concentration (4 g/L), more than 3 g/L of reducing agent concentration was required for obtaining the saturated dye uptake. Color reproducibility was reliable with color difference in the range of 0.03~0.16. Regardless of color strength, fastness to rubbing was acceptable with a 3/4~4/5. Fastness to washing, dry cleaning, and light of samples with low color strength were poor. Whereas, fastness to washing, dry cleaning, and light of samples with high color strength were very good.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2093-2098
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• 2013

Density functional theory (DFT) was used to determine the ground state geometries of indigo and new design dyes (IM-Dye-1 IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. All the calculations were performed in both gas and solvent phase. The LUMO energies of all the dyes were above the conduction band of $TiO_2$, while the HOMOs were below the redox couple (except IM-Dye-3). The HOMO-LUMO energy gaps of new design dyes were smaller as compared to indigo. All new design dyes were strongly red shifted as compared to indigo. The improved light harvesting efficiency (LHE) and free energy change of electron injection ${\Delta}G^{inject}$ of new designed sensitizers revealed that these materials would be excellent sensitizers. The broken coplanarity between the benzene near anchoring group having LUMO and the last benzene attached to TPA unit in all new design dyes consequently would hamper the recombination reaction. This theoretical designing will the pave way for experimentalists to synthesize the efficient sensitizers for solar cells.

• Textile Coloration and Finishing
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• v.11 no.4
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• pp.24-30
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• 1999

Cotton fabric was dyed with indigo at different pHs, dye concentrations, and repeated dyeings. And the K/S value and dye uptake of the dyed materials at those conditions were determined. The decrease of pH during the reduction process of indigo stock solution was observed. As a result the decrease of pH of the dye stock solution depended on the dye concentration and initial pH. The highest K/S value was shown at fabric dyed at pH 11 and the relationship between K/S value and dye uptake depended on initial pH of reduction bath and the slope was lower as the pH increased to 13.

• Journal of the Korean Society of Clothing and Textiles
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• v.37 no.6
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• pp.827-836
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• 2013

Indigotin, indirubin, berberine, palmatine, alizarin, and purpurin are major pigments of indigo plant, Phellodendron bark, and madder. The six pigments were examined using the HPLC-DAD-MS instrument for the purpose of the simultaneous detection of the pigments in a single sample run. The HPLC-DAD-MS method examined the individual pigment solutions in DMSO, a solution containing 6 pigments, and the DMSO extract of the silk dyed with a dye solution of 5 pigments excluding indirubin. The retention times of the HPLC chromatograms, ${\lambda}_{max}$ of the uv-vis absorption bands in the DAD analyses, and the molecular ions detected for the compound peaks in the MSD analyses were consistent throughout the analyses of individual pigment solutions, mixed pigment solutions, and dye extracted from silk dyeing. The developed instrumental method of the simultaneous detection of six pigments can identify dye in an exhumed textile if the textile is dyed using any one (or multiple) pigments of indigo, Phellodendron bark, or madder plant.

• Journal of the Korea Fashion and Costume Design Association
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• v.12 no.4
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• pp.149-157
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• 2010

After observing various changed colors by some dyeing conditions in case of the Indio and Indigo Pulberata Levis, we had below result. 1. Best reduction temperature for Indigo was $50^{\circ}C$, and the reduction temperature had an effect on level dyeing and dye-uptake. For the Indigo Pulberata Levis, best reduction temperature was $60^{\circ}C$, and best reduction time for Indigo was 20 minutes, for the Indigo Pulberata Levis was 30~40 minutes. 2. Both Indigo and Indigo Pulberata Levis showed high K/S without using alkali, but it was almost not possible to be dyed without reduction agent. The best amount of potassium carbonate concentration and soldium hydrosulfite concentration was $2{\sim}3g/{\ell}$ and $2g/{\ell}$ each for dyeing. 3. The best dyeing temperature for Indigo was $30^{\circ}C$ and $60^{\circ}C$ for Indigo Pulberata Levis. 4. In case of Indigo, K/S increased slightly at $5g/{\ell}$ concentration. Thus, $5g/{\ell}$ is efficient amount. However, it needed $50g/{\ell}$ to increase K/S for Indigo Pulberata Levis. It tells that we need a lot of Indigo Pulberata Levis for dyeing dark color. 5. Indigo dyed cotton looked more greener than silk. Since silk absorbs lots of red color, it looked strong red color. However, Indigo Pulberata Levis looked greenish on both cotton and silk. 6. Since the hue's range of Munsell's value was PB for both Indigo and Indigo Puberata Levis, we are able to know that red color's indirubin is contained as well as blue color's indigo.

• The Research Journal of the Costume Culture
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• v.20 no.4
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• pp.463-474
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• 2012

The purpose of this research was to find the suitable dyeing method for dyeing cotton fabric into indigo blue color using the raw indigo powder dyes sold in the Korean market. The research focused primarily on the comparison of the non-reduced dyeing method and the reduced dyeing method. The dyeing effects using different dyeing temperatures ($2{\sim}80^{\circ}C$) and different concentrations of reducing agent and alkali were also investigated. It was found that the reduced dyeing method must be used for dyeing cotton into indigo blue color using the commercial raw indigo powder dyes. The best result was obtained by $20^{\circ}C$ dyeing with the $40^{\circ}C$ dyeing giving a comparable result. The intensity of the blue color could be enhanced by increasing the alkali concentration. The non-reduced dyeing could not dye cotton fabric into indigo blue color at any given dyeing temperatures ($2{\sim}80^{\circ}C$). The reduce-dyed cotton fabrics showed a gradual color change upon repeated washing and extended sunlight exposure, the most color change occurring after the first two washing cycles and the first 5 hours of sunlight exposure. The standard tests of colorfastness showed that the reduce-dyed cotton fabrics had good to excellent colorfastness whereas the colorfastness of the non-reduce-dyed cotton fabrics were mostly poor.

• Textile Coloration and Finishing
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• v.22 no.2
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• pp.101-109
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• 2010

The objective of this study is to investigate the characteristics of natural indigo dyeing of cotton fabric. Reduction and dyeing were carried out by one-step process using an infrared dyeing machine at the liquor ratio of 1:100, and subsequently oxidation and washing in water were followed. Dye uptake was increased with the increase of indigo concentration. Over the full range of dyeing tests, the dyeing condition was optimized to $40^{\circ}C$ for 40min. For most of dye concentrations, the cotton fabrics showed mainly PB color. Maximum K/S value was shown at 4g/L of sodium hydrosulfite concentration and the color strength increased with the increase of dye concentration. Value(lightness) decreased with the increase of dye uptake irrespective of mercerization or reduction method, while the mercerized cotton showed two times higher dye uptake than the untreated cotton. Whereas hue of the untreated cotton showed large decrease of P character(5.6~3.5 PB) with the increase of dye uptake, that of the mercerized cotton increased P character(4.7~5.5 PB). Irrespective of mercerization, value and chroma decreased with the increased of dye uptake. In addition, the untreated showed lower chroma than the mercerized cotton. In the case of traditional reduction, hue of the untreated cotton was changed very little with the increase of dye uptake. For hydrosulfite reduction, P character decreased with the increase of dye uptake. The difference of hue value was small with the change of reduction method(hydrosulfite reduction or traditional fermentation). Color character was not influenced by the changed maximum absorption wavelength. Washing fastness showed 4~4/5 shade change rating without any staining. And dry rubbing fastness was good at low color strength. The bacterial reduction ratios of dyed cotton fabric were also increased.

• Journal of Sericultural and Entomological Science
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• v.44 no.2
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• pp.93-98
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• 2002

Effect of reducing agent sodium hydrosulfite on the natural indigo on the silk fabrics were examined to improve traditional dyeing method. K/S values of dyed fabrics was monitored with various dyeing temperature time, amount of dye and reducing agent. The dyeability of silk fabrics was improved by using reducing agent, sodium hydrosulfite; K/S value (7.20) was higher then that (1.09) of traditional method at the frist dyeing. Natural indigo dye extracted from dyed silk fabrics are composed of isomer, indigo (67.3%) and indirubin (32.5%). However, silk fabrics showed excellent anti-microbial activity regardless of the dyeing methods.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.48 no.3
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• pp.57-65
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• 2016

Indigo (Polygonum tinctorium L.) is a typical blue dye which had been used from ancient times. This study was going to shade the complicated traditional methods extracting indigo dye by the fermentation and producing as adsorbate on calcium hydroxide, which says so called as the 'Indigo lime'. Accordingly we were going to make indigo through the hydrolysis of the hot water extractives of indigo leaves simply. During hot-water extraction, ${\beta}$-glucosidase which required hydrolysis of the linkage between indigo and glucose was not activated. To achieve this goal, indican was acid-hydrolyzed to glucose and indigo. The acetic acid, citric acid, hydrochloric acid, and sulfuric acid were used for the hydrolysis of hot water extractives. The hydrolysis conditions of extractives performed in water bath at $80^{\circ}C$ for 120 minutes and in an autoclave for 120 minutes. In the acid hydrolysis of extracted indican by hot water, the indican yields of acetic acid and hydrochloric acid hydrolysis were higher than sulfuric acid in water bath. Also, the indican yield of hydrochloric acid hydrolysis was better than sulfuric acid in autoclave. The hot water extracted indican was confirmed by HPLC analysis and its structure was confirmed by UV-Vis and FT-IR spectroscopy, compared with isolated indigo and commercial synthesized indigo. This improved extraction and hydrolysis methods can be replace the traditional indigo making method.