Section
| HS Code | 129066 |
| Product Name | Rhodamine 6GDN |
| Common Synonyms | Rhodamine 6G; Basic Red 1; C.I. 45160 |
| Cas Number | 12224-98-5 |
| Einecs Number | 213-584-9 |
| Chemical Class | Xanthene cationic/basic dye |
| Color Index | C.I. 45160 |
| Molecular Formula | C28H31ClN2O3 |
| Molecular Weight | 479.01 g/mol |
| Appearance | Reddish-brown to dark red powder |
| Solubility | Soluble in water and ethanol |
| Fluorescence | Strong orange-red fluorescence |
| Absorption Maximum | Approximately 530 nm |
| Emission Maximum | Approximately 550-570 nm |
| Primary Uses | Fluorescent dye, laser dye, biological stain, textile/paper dye |
| Storage Conditions | Store sealed in a cool, dry, dark place |
As an accredited Rhodamine 6GDN factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Rhodamine 6GDN is packaged in a sealed 25 kg fiber drum with an inner polyethylene liner for safe storage and transport. |
| Container Loading (20′ FCL) | Rhodamine 6GDN is packed and loaded into a 20′ FCL container, securely stowed to ensure safe, dry, and stable transport. |
| Shipping | Rhodamine 6GDN is generally shipped as a non-hazardous solid in sealed, properly labeled containers at ambient temperature, protected from moisture and light. Always verify the current SDS and applicable regulations; if classified hazardous, use the required UN number, packing group, labels, and shipping documents. |
| Storage | Store Rhodamine 6GDN in a tightly closed, clearly labeled container in a cool, dry, well-ventilated area protected from light and moisture. Keep away from oxidizers, acids, bases, and ignition sources. Avoid dust generation, and use appropriate personal protective equipment. Follow the manufacturer’s safety data sheet and local regulations. |
| Shelf Life | Rhodamine 6GDN shelf life is typically several years when stored dry, sealed, and protected from light and moisture. |
Cationic xanthene dyestuff of the Rhodamine 6GDN grade is applied to polyacrylonitrile and modacrylic staple and tow in buffered aqueous exhaust. The dye is prepared as a 1.0–3.0 wt% stock solution at 60–70 °C and screened through a 50 µm filter before the addition tank. The exhaustion bath is set with 0.5 g/L acetic acid and 0.3–1.0 g/L sodium acetate to a pH of 4.5–5.0. A quaternary ammonium retarder is added at 0.3–1.0 wt% o.w.f. for pale depths and at 1.0–2.0 wt% o.w.f. for dye concentrations above 0.5 wt% o.w.f. The liquor ratio is held at 1:10–1:15 in a packed soft-flow rope machine with a circulation rate of 2–3 L/kg fibre·min. The temperature ramp is controlled from 70 °C to 98 °C at 0.7–1.0 °C/min; this ramp window is critical because the polyacrylonitrile fibre transition temperature is crossed at 85–95 °C, and dye uptake becomes rapid above that band. The hold time at 98 °C is 30–45 min; longer holds are used for navy and black formulations but not for fluorescent red shades because thermal dimerization of the xanthene skeleton can reduce emission intensity. After exhaustion, the bath is cooled at 1.0–1.5 °C/min to 65 °C before drain. The yarn or fabric is after-soaped with a non-ionic detergent at 80 °C for 20 min, then dried at air temperature not exceeding 110 °C to prevent dye migration. Fastness is evaluated with ISO 105-C10:2006 washing at 40 °C, ISO 105-X12:2016 rubbing, and ISO 105-B02:2014 xenon arc. The finished knitwear, blanket binding, and interior apparel accessories are acceptable only when the lightfastness rating is at least 4 on the blue scale; published data for this specific configuration is limited, so each batch requires a control dyeing against a reference standard.
| Process variable | Recommended window | Measurement point | Deviation consequence |
|---|---|---|---|
| Dye stock concentration | 1.0–3.0 wt% | Weighing and dissolution vessel at 60–70 °C | Undissolved xanthene crystals above 50 µm cause spotting |
| Exhaust bath pH | 4.5–5.0 | In-line pH electrode after salt addition | pH above 5.5 lowers exhaustion below 85% |
| Temperature ramp | 0.7–1.0 °C/min from 70 °C to 98 °C | PLC ramp profile | Ramp above 1.5 °C/min produces skittery dyeing at pale depths |
| Hold at 98 °C | 30–45 min | Batch timer and thermal probe | Hold below 30 min lowers wash fastness; hold beyond 60 min risks emission dulling |
| Drain temperature | 65 °C maximum | Thermocouple in main vessel | Draining above 85 °C causes fibre shock and rope creasing |
Chrome-tanned leather coloured with Rhodamine 6GDN is processed in the drum after neutralization to a cut pH of 5.0–5.5. The dyestuff is added at 0.4–2.0 wt% of wet-blue weight, preferably as a predissolved solution at 1.0–2.0 wt% concentration, into a float of 1:0.8–1:1.2 at 55–60 °C. Drum rotation is maintained at 8–12 rev/min for 60–90 min. Sulphited vegetable retanning agents and anionic fatliquors are not added simultaneously with this cationic dye; they are introduced in a separate retanning step or only in the final 20 min after the dye has penetrated the cross-section. Fixation is carried out with 0.5–1.0 wt% formic acid diluted 1:10 in water and added in two portions 10 min apart. The exhausted float should be nearly colourless; residual absorbance above 0.1 at 525 nm in a 10 mm cell is considered an indicator of incomplete fixation. Crust leather is tested under ISO 11640:2018 with 50 dry felt cycles, ISO 11641:2012 for perspiration, and ISO 105-B02:2014. Migration into flexible PVC contact layers is assessed by compression at 60 °C for 72 h; published data for this specific configuration is limited, and a factory-scale contact test is required before upholstery use. The colorant is retained for lining leather, bookbinding leather, and interior upholstery with limited direct UV exposure.
In non-potable hydrologic time-of-travel studies, Rhodamine 6GDN is injected as a concentrated aqueous stock at 50–250 g/L through a positive-displacement metering pump with a pulse dampener at 10–100 mL/min. The injection boom is placed downstream of a hydraulic structure that creates complete lateral and vertical mixing; a mixing length of at least 20–100 channel widths is preferred before the first fluorometer transect. Submersible fluorometers with excitation at 530 nm and emission at 555 nm are calibrated in the field with a serial dilution series from 0.01 µg/L to 100 µg/L prepared from the same dye lot. The calibration is repeated at the beginning and end of each day because the dye signal is quenched by temperature changes and by dissolved organic matter. Suspended sediment is the most serious interference; montmorillonite clay above 10 NTU adsorbs the cationic dye and can reduce mass recovery below 60%. The dye is not recommended for karst systems with high total organic carbon above 5 mg/L, where background fluorescence and quenching combine to raise the limit of detection above 0.05 µg/L. Data are processed with the one-dimensional advection-dispersion equation under ASTM D5613-94(2014), with the time to peak and the first-arrival time used for travel-time calculation. The tracer is restricted to non-potable water bodies; potable supply hydrogeology requires a fluorophore with different toxicological and regulatory clearance.
Gravure and flexographic security printing use solvent-borne nitrocellulose inks in which Rhodamine 6GDN is pre-dissolved at 0.3–1.0 wt% of the finished ink. The dye is first dissolved in ethanol at 40–50 °C under low-shear mixing for 60 min, then passed through a 5 µm absolute filter before addition to the vinyl and acrylic binder solution. A reference gravure formula contains 8–12 wt% nitrocellulose, 3–6 wt% polyurethane, 45–55 wt% ethyl acetate, 18–25 wt% ethanol, and 0.3–1.0 wt% antistatic additive. Print laydown is maintained at 0.8–1.2 g/m² on coated security paper and 1.5–2.0 g/m² on polypropylene film with an anilox volume of 6–8 cm³/m². The printed mark is checked at 365 nm UV with a photodiode or CCD line-scan sensor for emission intensity; a signal-to-noise ratio above 3:1 is typical for automatic sorting machines. Light fastness is tested by ISO 2836:2021 and water fastness by ISO 2837:2008; for tax-stamp and voucher applications the printed image is further evaluated for rub resistance under ISO 11640:2018 modified for paper and film. The dye is suitable for secondary fluorescent features on fiscal stamps, event tickets, and security labels, but it is not used as a primary covert feature where high solvent resistance is required, because the dye migrates in plasticizer-containing PVC sleeves under pressure at 40 °C.
Bleached kraft mills using Rhodamine 6GDN for wet-end addition dose the dyestuff after the alum or polyaluminium chloride addition and before the cationic polyacrylamide retention aid. The dye is applied at 0.05–0.30 wt% on dry fibre from a 0.1–0.5 wt% solution. The headbox pH is controlled at 4.5–6.0; a streaming current detector is used to keep the white water cationic demand below 10 µeq/L. The addition point is chosen to allow 15–25 s contact time before the fan pump, and the dye line is flushed with warm water to prevent precipitation from alum carryover. At the size press, the dye is carried in an oxidized starch solution of 4–8 wt% solids at 0.02–0.10 wt% of the starch solution, with a size-press pick-up of 1.5–2.5 g/m² per side. Colour strength and brightness are assessed by ISO 2470-1:2016 and by ISO 5631-1:2022 diffuse reflectance colour measurement. The dyed paper is directed to file folders, index cards, divider stock, and non-food gift wrap. Food-contact use requires migration testing under EU 1935/2004 and the applicable national paper and board recommendations; no direct food-contact clearance is inferred from the dyestuff availability alone.
| Application | Standard | Test condition | Typical control |
|---|---|---|---|
| Acrylic dyed knitwear | ISO 105-C10:2006 | 40 °C wash, 30 min | shade change ≥ 4 grey scale |
| Leather lining | ISO 11640:2018 | 50 dry felt cycles | ≥ 4 grey scale |
| Hydrological tracing | ASTM D5613-94(2014) | Calibration 0.01–100 µg/L | mass recovery 60–110% |
| Security gravure | ISO 2836:2021 | Xenon arc 72 h | density loss ≤ 20% |
| Paper surface | ISO 2470-1:2016 | Diffuse blue reflectance | brightness shift ≤ 2.0 points |
| Marker ink | EN 71-3:2019+A1:2021 | 0.07 mol/L HCl extraction | ICP-MS element migration acceptance limits |
Whiteboard marker and stamp-pad ink systems dissolve Rhodamine 6GDN in a low-viscosity oxygenated solvent blend. The dye concentration is 0.4–0.8 wt% in marker inks and 0.2–0.4 wt% in stamp-pad fluids, with a solvent blend containing 20–35 wt% ethanol, 15–25 wt% isopropanol, 30–45 wt% ethyl acetate, and 3–6 wt% glycol ether. The solution is stirred at 25 °C for 120 min and passed through a 5 µm polypropylene membrane; particle counts above 100 particles per mL in the 1–5 µm channel are cause for refiltration. Ink viscosity is adjusted to 3–6 mPa·s at 25 °C using a rotational viscometer at 100 s⁻¹. Capillary ink-feed systems with channel dimensions below 10 µm require surface tension of 28–32 mN/m and a re-dissolution test after 14 days at 50 °C to ensure no ring deposits. The finished writing instruments and stamp pads are checked against EN 71-3:2019+A1:2021 migration of elements in the toy category and against the relevant REACH limits for substances in inks. The dyestuff is not used in cosmetic eyeliner or tattoo inks at this grade; those applications require a purified analytical or cosmetic grade with separate microbiological and toxicological files.
Closed-pore hardwood pre-stains represent a separate solvent-borne application in which Rhodamine 6GDN is incorporated into nitrocellulose pre-stain at 0.2–0.6 wt%. The wet stain is sprayed at 15–25 g/m² through a gravity-feed spray gun with a 1.2–1.4 mm nozzle at 0.2–0.3 MPa air pressure. The solvent blend is adjusted to an evaporation half-time of 8–12 min at 20 °C and 50% RH to control dye penetration in maple and beech sapwood; faster evaporation leaves surface dye deposits that produce lap marks on panels wider than 600 mm. After 15–20 min flash-off, the panels are sealed with a two-component polyurethane or acid-curing topcoat. The unpigmented stain has limited lightfastness; CIELAB ΔE* greater than 3 is observed after 100 h xenon arc in clear topcoat systems, so exterior millwork and UV-exposed flooring are outside the recommended use boundary. Adhesion is tested by cross-hatch under ISO 2409:2020 and viscosity by ASTM D1200-10(2018). Typical finished articles are musical instrument edging, display plaques, and decorative furniture accent panels.
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For solution-phase dye laser oscillators, fluorescence lifetime calibration, and microscopy tracer applications, Rhodamine 6GDN is supplied as a chloride-salt xanthene chromophore with the molecular formula C28H31ClN2O3, CAS 989-38-8, and molar mass 479.02 g/mol. The 6GDN model designation denotes a laser-grade lot specified for reduced ash, controlled counterion stoichiometry, and reproducible spectral output in ethanol. In spectroscopic-grade ethanol at 25 °C, the absorption maximum is 530 nm, the fluorescence emission maximum is 552 nm, and the molar extinction coefficient at the absorption maximum is 1.16 × 105 L mol−1 cm−1. The Stokes shift is 22 nm, and the fluorescence quantum yield is approximately 0.95 when referenced against fluorescein in 0.1 M sodium hydroxide. Wavelength accuracy in lot-release spectroscopy is checked against NIST SRM 2034 holmium oxide solution, and spectrophotometer bandwidth is qualified in accordance with ASTM E275.
Because the molar extinction coefficient in ethanol is established, dilute fluorescence standards can be prepared by absorption. A 1 cm quartz cuvette with an absorbance of 0.1 at 530 nm corresponds to a concentration of approximately 8.6 × 10−7 mol/L. This relationship is used to check cuvette path length and to normalize emission measurements before absolute quantum-yield determination.
The optical density at the pump wavelength can be estimated from the Beer–Lambert relation. With ε at 530 nm of 1.16 × 105 L mol−1 cm−1, a concentration of 1 × 10−3 M, and a path length of 0.5 mm (0.05 cm), the calculated optical density is 5.8. This value corresponds to a transmittance below 0.001% at the absorption maximum. At 532 nm, the optical density is only slightly lower than at 530 nm; pump absorption therefore remains above 99% in a single pass.
In flowing dye cell service, the product is dissolved in ethanol or methanol at 1 × 10−3 mol/L. The solution is filtered through a 0.2 µm PTFE membrane and circulated through a 0.5 mm dye cell or jet stream at 1–3 L/min. Stainless-steel, PTFE, and borosilicate are preferred wetted materials. Prolonged contact with aluminium or unpassivated copper should be avoided because transition-metal ions released from these surfaces can quench the excited singlet state and form insoluble metal-dye deposits on dye cell windows.
Each lot is released against a spectrophotometric and chromatographic panel. Representative limits are shown below; the manufacturer’s certificate of analysis should be consulted for exact lot-specific values because process-scale crystallization can shift trace impurity profiles. The HPLC method uses a C18 column and diode-array detection at 530 nm, where the principal xanthene peak area is integrated against related dye impurities. The certificate of analysis is issued under a documented quality system consistent with ISO 9001:2015, and each batch is traceable to the vendor lot number.
| Parameter | Specification | Method/condition |
|---|---|---|
| HPLC purity | ≥99.0% area | C18 reversed-phase, diode array at 530 nm |
| Absorption maximum in ethanol | 530 ± 2 nm | Double-beam spectrophotometer, 1 nm bandwidth |
| Fluorescence emission maximum | 552 ± 3 nm | Corrected spectrofluorometer, 1 × 10−6 M ethanol solution |
| Molar extinction coefficient at λmax | ≥1.05 × 105 L mol−1 cm−1 | Ethanol, 25 °C |
| Water content | ≤0.5 wt% | Karl Fischer coulometry |
| Filtration test | Clear passage through 0.2 µm PTFE | 1 × 10−3 M ethanol solution |
| Storage | −20 °C to 4 °C, desiccated | Long-term; use working solution within 7 days |
In addition to these limits, visible insoluble matter is checked by filtration, because unfiltered aggregates can nucleate on dye cell windows and reduce cavity efficiency. The chloride salt form is selected when users cannot use perchlorate-containing laser dyes in facilities with strict oxidizer-management policies. However, the chloride salt is hygroscopic; repeated exposure to ambient air at relative humidity above 60% can increase water content and shift the ethanol absorption maximum by 1–2 nm.
Solubility in ethanol and methanol is sufficient for the 1 × 10−3 M working solution without heating. Ethylene glycol solutions require stirring at 25 °C for 30–60 min; dimethyl sulfoxide stock solutions should be protected from light and used fresh because photochemical side reactions are solvent-dependent. In water, the absorption maximum shifts to approximately 526 nm, the emission band broadens, and the fluorescence quantum yield is lower than in ethanol; published data for this chloride formulation in aqueous buffer systems is limited.
The Rhodamine 6G chromophore is shared across several salt forms, but the counterion changes handling, storage, and waste classification. Perchlorate salts introduce a strong oxidizer anion; if solvent recovery evaporators are used, dry perchlorate residues can become shock-sensitive. Tetrafluoroborate grades avoid perchlorate but can show slower dissolution in cold ethylene glycol at 10 °C. The 6GDN chloride form dissolves readily in ethanol and methanol without sonication and leaves no perchlorate residue in evaporation basins. The trade-off is hygroscopicity: the chloride salt gains mass in humid air more readily than the perchlorate salt, so storage should be in desiccated packaging.
| Form | Counterion | Absorbance/emission in ethanol | Handling constraint |
|---|---|---|---|
| Rhodamine 6GDN | Chloride | 530 nm/552 nm | Hygroscopic; store desiccated at −20 °C |
| Rhodamine 6G perchlorate | Perchlorate | 530 nm/552 nm | Oxidizer residue; not for evaporative drying |
| Rhodamine 6G tetrafluoroborate | Tetrafluoroborate | 530 nm/552 nm | Lower solubility in cold ethylene glycol; sonication may be needed |
The choice between salt forms also affects waste handling. Perchlorate-bearing materials may require oxidizer-contaminated waste classification under local regulations; the chloride form simplifies waste classification in many facilities. The solid and concentrated solutions should still be handled with nitrile gloves, and dust generation should be controlled when transferring quantities above 5 g. A fine-particulate respirator is recommended if local ventilation cannot keep dust below the occupational exposure limit.
Compared with Rhodamine B, the absorption maximum of 6GDN is shorter by 13 nm and the fluorescence quantum yield in ethanol is higher, making it more compatible with 532 nm pumping. Compared with fluorescein, the emission is red-shifted and the Stokes shift is smaller; this reduces the separation between pump and signal in high-power dye amplifiers and requires a dichroic separator with a transition near 550 nm.
The strong S0→S1 absorption at 530 nm allows efficient excitation with the 532 nm second harmonic of Nd:YAG. In a grating-tuned Littman cavity, the gain bandwidth supports output from 570 nm to 610 nm, with the gain peak near 576 nm. The reported stimulated emission cross-section at the gain peak is approximately 1.2 × 10−16 cm2, and the singlet fluorescence lifetime in ethanol is approximately 3.9 ns. Intersystem crossing to the triplet manifold is non-negligible under pulses longer than 100 ns; the dye solution should therefore be circulated rapidly to refresh the excitation zone. Slope efficiency in a 532 nm-pumped dye oscillator is commonly reported in the 20% to 30% range for optimized cavity alignment, but published data for this exact 6GDN designation is limited.
In dye ring lasers, the dye jet is usually an ethylene glycol solution with a thickness of 0.2 mm to 0.3 mm. Ethylene glycol increases viscosity and reduces thermal-lens distortion relative to ethanol, but the dissolution time is longer; the solution should be filtered at a temperature not exceeding 40 °C to avoid solvent vaporisation. For 10 ns pump pulses at 532 nm, triplet-state losses are smaller than for microsecond-long pulses, but singlet oxygen suppression remains necessary.
At repetition rates of 10 Hz or higher, the dye cell window and pump mirror should be inspected after 105 pulses. A decrease in output energy greater than 10% without cavity misalignment typically indicates photobleaching or particulate deposition. The working solution is replaced, and the dye cell is flushed with spectroscopic-grade ethanol before reassembly.
When retrofitting a dye laser from Rhodamine B or fluorescein to 6GDN, the cavity mirrors and tuning element should be re-optimized. Output coupler reflectivity that maximizes output at 576 nm is usually 50% to 70%; higher reflectivity can increase circulating power but may reduce extraction efficiency. The grating or birefringent filter should be calibrated with a mercury or neon lamp, and a 0.5 nm bandpass is typical for spectral narrowing.
Dissolved oxygen is the principal photodegradation vector in ethanol solutions of Rhodamine 6GDN. The triplet state formed by intersystem crossing transfers energy to molecular oxygen, generating singlet oxygen that attacks the xanthene ring and forms non-fluorescent products. In sealed systems, the dye reservoir is blanketed with nitrogen to maintain dissolved oxygen below 1 ppm. In open systems, a continuous nitrogen purge is preferable to air exposure.
The operational pH in aqueous solution should remain between 4 and 9. Strong acids can protonate the ethylamino groups and alter the absorption spectrum; strong bases can hydrolyse the ethyl ester group. The dye is incompatible with strong oxidizers and should not be mixed with perchloric acid or nitrating agents, even though the 6GDN salt form is not perchlorate.
Long-term storage of the solid is recommended at −20 °C under desiccant. Working solutions in amber borosilicate vessels at 4 °C under nitrogen preserve output for approximately 7 days; frozen solutions can precipitate and may not fully redissolve, so freezing is not recommended.
For fluorescence microscopy and tracer applications, the dye stock solution is diluted to 1 × 10−6 M in ethanol or phosphate-buffered saline. Because the chromophore is cationic, it adsorbs to borosilicate glass and silica surfaces; cuvettes and cell windows should be rinsed with ethanol before filling. Particles and aggregates are removed by filtration through 0.2 µm PTFE; this step is required to avoid hot spots in laser cavities and fluorescent debris in microscopy. For polymer embedding and sol-gel work, the dye is dried before incorporation because residual water can interfere with hydrolysis-sensitive precursors. Aqueous working solutions should be prepared immediately before use because the quantum yield in water is lower than in ethanol and published data for this chloride formulation in complex biological buffers is limited.
